CN106918737A

CN106918737A - A kind of method and reactive power detection device for detecting power network dynamic reactive power

Info

Publication number: CN106918737A
Application number: CN201510998926.9A
Authority: CN
Inventors: 曾晓生; 郭海滨; 辛凯
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2015-12-28
Filing date: 2015-12-28
Publication date: 2017-07-04
Also published as: WO2017113754A1

Abstract

The embodiment of the invention discloses a method for detecting dynamic reactive power of a grid and a reactive power detection device, which are used for detecting reactive power demand in the grid, and can avoid inaccurate data due to communication delay. The method includes: the reactive power detection device obtains the impedance of the access line in the last detection cycle, and the last detection cycle refers to a detection cycle before the current detection cycle; the reactive power detection device Acquiring the voltage, current and phase difference of the inverter in the current detection cycle; the reactive power detection device according to the impedance of the access line in the current detection cycle and the inverter in the current detection cycle Periodic voltage, current and phase difference to calculate the voltage, current and phase difference of the power grid; the reactive power detection device calculates the reactive power of the power grid according to the calculated voltage, current and phase difference of the power grid work power.

Description

Method for detecting dynamic reactive power of power grid and reactive power detection device

Technical Field

The invention relates to the field of strong electricity, in particular to a method for detecting dynamic reactive power of a power grid and a reactive power detection device.

Background

The reactive power compensation plays a role in improving the power factor of a power grid in an electric power supply system, reduces the loss of a power supply transformer and a transmission line, improves the power supply efficiency and improves the power supply environment, so that the reactive power compensation device is in an indispensable and very important position in the electric power supply system.

The compensation device is reasonably selected, so that the loss of the power grid can be reduced to the maximum extent, and the quality of the power grid is improved. Conversely, improper selection or use may cause many factors such as power supply system, voltage fluctuation, harmonic increase, and the like. In the traditional application, a special reactive compensation device is adopted for reactive compensation of a power grid, however, after a grid-connected inverter, particularly a photovoltaic grid-connected inverter, is connected to the power grid in a large quantity, the inverter can serve as the reactive compensation device to provide reactive power for the power grid.

The method for detecting the reactive power requirement of the power grid is that the information such as voltage, current, phase or active power, reactive power and the like of the power grid is directly collected and calculated to obtain the requirement, regardless of a traditional reactive compensation device or a grid-connected inverter with a reactive compensation function.

When the voltage, current, phase or active power, reactive power and other information of the power grid are transmitted to the grid-connected inverter and the grid-connected inverter calculates the reactive power according to the data, the information cannot be accurately used as the reactive power requirement of the current detection period due to the delay of the communication line.

Disclosure of Invention

The embodiment of the invention provides a method for detecting the dynamic reactive power of a power grid and a reactive power detection device, which are used for detecting the reactive power requirement in the power grid, can avoid inaccurate data generated by communication delay and improve the accuracy of reactive power detection.

In view of the above, a first aspect of the embodiments of the present invention provides a method for detecting dynamic reactive power of a power grid, the method being applied to a power grid system, the power grid system including a power grid and an inverter connected to the power grid through an access line, the inverter converting direct current into alternating current, the inverter being incorporated into the power grid through the access line, the method including: acquiring the impedance of the access line in a last detection period, wherein the last detection period refers to a detection period before the current detection period; acquiring the voltage, the current and the phase difference of the inverter in the current detection period; calculating the voltage, the current and the phase difference of the power grid according to the impedance of the access line in the last detection period and the voltage, the current and the phase difference of the inverter in the current detection period; and calculating the reactive power of the power grid according to the calculated voltage, current and phase difference of the power grid. According to the embodiment of the invention, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data acquisition is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

With reference to the first aspect of the embodiment of the present invention, in a first implementation manner of the first aspect of the embodiment of the present invention, the obtaining an impedance of the access line in a last detection period includes: acquiring the voltage, the current and the phase difference of the access line in the last detection period; and calculating the impedance of the access line according to the voltage, the current and the phase difference of the access line in the last detection period.

With reference to the first specific implementation manner of the first aspect of the embodiment of the present invention, in a second specific implementation manner of the first aspect of the embodiment of the present invention, the access line includes a plurality of series-connected transformers; obtaining the voltage, the current and the phase difference of the access line in the last detection period, including: acquiring the voltage, the current and the phase difference of each stage of transformer in the multi-stage transformer in the last detection period; calculating the impedance of the access line according to the voltage, the current and the phase difference of the access line in the last detection period, wherein the method comprises the following steps: calculating the impedance of each transformer according to the voltage, current and phase difference of each transformer in the last detection period, and summing the impedances of each transformer to obtain the impedance of the access line, specifically, calculating the impedance of each transformer according to the phase difference θ of each transformer in the last detection period as the impedance angle of the transformer, and adopting the following formula:

in the above formula, Z is the impedance of the stage transformer, U is the voltage effective value of the stage transformer, I is the current effective value of the stage transformer, and θ is the impedance angle of the stage transformer. And the reactive power detection device sums the impedances of the multistage transformers to obtain the impedance of the access line. In the invention, the access line is regarded as being composed of the transformers connected in series, so that the impedance of the access line can be regarded as the sum of the impedances of all the transformers connected in series in the access line, and the accurate impedance data of the access line can be directly obtained by directly calculating the sum of the multi-stage transformers connected in series.

With reference to the first aspect of the embodiment of the present invention, in a third implementation manner of the first aspect of the embodiment of the present invention, the obtaining an impedance of the access line in a last detection period includes: obtaining the impedance of the access line in the last detection period includes: acquiring the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period; and calculating the impedance of the access line according to the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period.

With reference to the third specific implementation manner of the first aspect of the present embodiments, in a fourth specific implementation manner of the first aspect of the present embodiments, the method includes: calculating the impedance of the access line according to the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period, and calculating the impedance of the access line by adopting the following formula:

in the above-mentioned formula,in order to switch in the voltage of the line,for current of the incoming line, Z_lineIn order to be able to access the impedance of the line,is the current of the power grid and is,for an inverterThe voltage of (c). And the reactive power detection device indicates the inverter to control the voltage and the current in the electric signal according to the calculated reactive power of the power grid in the current detection period, so that the power grid obtains the reactive power as reactive compensation. Because the dynamic reactive power is used for dynamic reactive power compensation, the reactive power detection device can provide proper and accurate reactive power for the power grid in the current detection period in time. Because the impedance of the access line is calculated according to the data of the power grid and the inverter, rather than the data of the transformer, the number of the transformers is large, the used data is large, the data calculation using the inverter and the power grid is simpler and more convenient, the used data is less, and the processing burden of the reactive power detection device is reduced.

With reference to the first aspect of the embodiment of the present invention, in a fifth specific implementation manner of the first aspect of the embodiment of the present invention, the method includes: calculating the voltage, the current and the phase difference of the power grid according to the impedance of the access line in the last detection period and the voltage, the current and the phase difference of the inverter in the current detection period, wherein the calculation comprises the following steps: calculating the voltage, the current and the phase difference of the power grid by adopting the following formulas;

θ_grid＝θ_live+θ_inv，

in the above-mentioned formula,is the voltage of the electricity network and,is the voltage of the inverter, Z_lineIs thatThe impedance of the access line is such that,is the current of the electricity network and is,is the current of the inverter, theta_gridIs the phase difference between the voltage and the current of the network, theta_invIs the phase difference between the inverter voltage and current, theta_lineIs Z_lineThe impedance angle of (c).

With reference to the first aspect of the embodiment of the present invention, in a sixth specific implementation manner of the first aspect of the embodiment of the present invention, the method includes: calculating the reactive power of the power grid according to the calculated voltage, current and phase difference of the power grid, and the method comprises the following steps: calculating the effective voltage value of the power grid according to the voltage of the power grid, calculating the effective current value of the power grid according to the current of the power grid, and calculating the reactive power of the power grid by adopting the following formula:

Q_grid＝U_grid×I_grid×sinθ_grid，

in the above formula, Q_gridFor dynamic reactive power, U, of the grid in the current detection cycle_gridIs the effective value of the voltage of the power grid, I_gridIs the effective value of the current of the power grid, theta_gridIs the phase difference of the voltage and current of the grid.

It should be understood that, according to different specific embodiments of the above method, the last detection period refers to a previous detection period adjacent to the current detection period, or any detection period within a preset time range before the current detection period, or a certain detection period established before the current detection period, and is not limited.

According to the technical scheme, the embodiment of the invention has the following advantages:

the reactive power detection device obtains the impedance of the access line and the voltage and the current of the inverter in the current detection period, and uses the obtained impedance and the current in the current detection period to calculate the reactive power of the power grid in the current detection period. According to the embodiment of the invention, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data acquisition is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

A second aspect of an embodiment of the present invention provides a reactive power detection apparatus for a power grid system, the power grid system including a power grid and an inverter connected to the power grid through an access line, the inverter converting direct current into alternating current, the inverter being incorporated into the power grid through the access line, the apparatus including: a first obtaining module, configured to obtain an impedance of the access line in a previous detection period, where the previous detection period is a detection period before a current detection period; the second acquisition module is used for acquiring the voltage, the current and the phase difference of the inverter in the current detection period; the first calculation module is used for calculating the voltage, the current and the phase difference of the power grid according to the impedance of the access line in the last detection period acquired by the first acquisition module and the voltage, the current and the phase difference of the inverter in the current detection period acquired by the second acquisition module; and the second calculation module is used for calculating the reactive power of the power grid according to the voltage, the current and the phase difference of the power grid calculated by the calculation module.

According to the embodiment of the invention, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data acquisition is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

With reference to the second aspect of the embodiment of the present invention, in a first implementation manner of the second aspect of the embodiment of the present invention, the first obtaining module includes: the first acquisition unit is used for acquiring the voltage, the current and the phase difference of the access line in the last detection period; and the first calculating unit is used for calculating the impedance of the access line according to the voltage, the current and the phase difference of the access line acquired by the first acquiring unit in the last detection period.

In combination with the first specific implementation manner of the second aspect of the embodiment of the present invention, in the second specific implementation manner of the second aspect of the embodiment of the present invention, the method includes: the first obtaining unit is specifically configured to obtain a voltage, a current and a phase difference of each stage of the transformer in the multi-stage transformer in a previous detection period; the first calculating unit is specifically configured to calculate an impedance of each transformer according to the voltage, the current, and the phase difference of each transformer obtained by the first obtaining unit in the last detection period, and sum the impedances of each transformer to obtain an impedance of the access line, specifically, calculate an impedance of each transformer according to a phase difference θ of each transformer in the last detection period as an impedance angle of the transformer, and by using the following formula:

With reference to the second aspect of the embodiment of the present invention, in a third implementation manner of the second aspect of the embodiment of the present invention, the first obtaining module includes: the first acquisition unit is used for acquiring the voltage, the current and the phase difference of the access line in the last detection period; and the first calculating unit is used for calculating the impedance of the access line according to the voltage, the current and the phase difference of the access line acquired by the first acquiring unit in the last detection period.

With reference to the third specific implementation manner of the second aspect of the embodiment of the present invention, in a fourth specific implementation manner of the second aspect of the embodiment of the present invention, the first obtaining module includes: the second acquisition unit is used for acquiring the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period; a second calculating unit, configured to calculate an impedance of the access line according to the voltage and the current of the power grid and the voltage and the current of the inverter in the previous detection period, which are acquired by the second acquiring unit, and calculate the impedance of the access line by using the following formula:

in the above-mentioned formula,in order to switch in the voltage of the line,for current of the incoming line, Z_lineIn order to be able to access the impedance of the line,for an electric networkThe current of (a) is measured,is the voltage of the inverter. And the reactive power detection device indicates the inverter to control the voltage and the current in the electric signal according to the calculated reactive power of the power grid in the current detection period, so that the power grid obtains the reactive power as reactive compensation. Because the dynamic reactive power is used for dynamic reactive power compensation, the reactive power detection device can provide proper and accurate reactive power for the power grid in the current detection period in time. Because the impedance of the access line is calculated according to the data of the power grid and the inverter, rather than the data of the transformer, the number of the transformers is large, the used data is large, the data calculation using the inverter and the power grid is simpler and more convenient, the used data is less, and the processing burden of the reactive power detection device is reduced.

With reference to the second aspect of the embodiment of the present invention, in a fifth specific implementation manner of the second aspect of the embodiment of the present invention, the first calculating module is specifically configured to calculate the voltage, the current, and the phase difference of the power grid by using the following formulas:

θ_grid＝θ_live+θ_liv，

With reference to the second aspect of the embodiment of the present invention, in a sixth specific implementation manner of the second aspect of the embodiment of the present invention, the second calculating module is specifically configured to calculate a voltage effective value of the grid according to the voltage of the grid, calculate a current effective value of the grid according to the current of the grid, and calculate the reactive power of the grid by using the following formula:

Q_grid＝U_grid×I_grid×sinθ_grid，

A third aspect of the embodiments of the present invention provides a reactive power detection apparatus for a power grid system, where the power grid system includes a power grid and an inverter connected to the power grid through an access line, and the inverter converts direct current into alternating current and is incorporated into the power grid through the access line; the reactive power detection device comprises

A processing unit and a collector; the collector is used for acquiring the voltage, the current and the phase difference of the inverter in the current detection period; the processing unit is used for calculating the voltage, the current and the phase difference of the power grid according to the impedance of the access line in the last detection period and the voltage, the current and the phase difference of the inverter in the current detection period; and calculating the reactive power of the power grid according to the calculated voltage, current and phase difference of the power grid.

With reference to the third aspect of the embodiments of the present invention, the impedance of the access line is obtained according to different manners of obtaining the impedance of the access line by the reactive power detection device, where in the first implementation manner of the third aspect of the embodiments of the present invention, the collector is further configured to obtain the voltage, the current, and the phase difference of the access line in the last detection period; the processing unit is further used for calculating the impedance of the access line in the last detection period according to the voltage, the current and the phase difference of the access line in the last detection period.

In a second implementation manner of the third aspect of the embodiment of the present invention, the collector is further configured to obtain a voltage and a current of the power grid in a previous detection period and a voltage and a current of the inverter in the previous detection period; the processing unit is further used for calculating the impedance of the access line in the last detection period according to the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period.

In the reactive power detection device provided by the third aspect of the embodiment of the present invention, the impedance of the current detection period of the access line is similar to the impedance of the previous detection period, and the voltage and the current at the inverter end of the current detection period are obtained in time, so that the influence of the communication delay on the data acquisition is avoided, and therefore, the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

A fourth aspect of the embodiments of the present invention provides an inverter for a power grid system, the power grid system including a power grid and an inverter connected to the power grid through an access line, the inverter converting direct current into alternating current, the alternating current being incorporated into the power grid through the access line; the inverter includes: the reactive power detection module and the current conversion module; the current conversion module is used for converting the input direct current into alternating current and outputting the alternating current; the reactive power detection module adopts the same structure as the reactive power detection device provided by the third aspect of the embodiment of the invention, and executes the same function. According to the inverter of the fourth aspect of the present invention, the reactive power detection module is integrated into the conventional inverter, thereby simplifying the system structure.

With reference to the fourth aspect of the embodiment of the present invention, in another implementation manner of the fourth aspect of the embodiment of the present invention, the reactive power detection module of the inverter further includes a communication unit, configured to receive data of the remotely acquired circuit parameter, and supply the data to the processing unit in the reactive power detection module for use. According to the inverter in the embodiment, further, the operation is more convenient by receiving the circuit parameter data acquired remotely.

Drawings

Fig. 1 is a schematic diagram of an architecture of a power grid system according to an embodiment of the present invention;

fig. 2 is a schematic flow chart of an embodiment of a method for detecting dynamic reactive power of a power grid according to the present invention;

fig. 3 is a schematic flow chart of another embodiment of a method for detecting dynamic reactive power of a power grid according to an embodiment of the present invention;

fig. 4 is a schematic flow chart of another embodiment of a method for detecting dynamic reactive power of a power grid according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of an embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of another embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of another embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of another embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of another embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of another embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram of another embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 12 is a schematic circuit diagram of an embodiment of a reactive power detection apparatus according to an embodiment of the present invention;

fig. 13 is a schematic circuit diagram of another embodiment of the reactive power detection apparatus according to the embodiment of the present invention.

Detailed Description

The embodiment of the invention discloses a method for detecting dynamic reactive power of a power grid and a reactive power detection device, which are used for detecting reactive power requirements in the power grid.

In order to make the technical solutions of the embodiments of the present invention better understood, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims, as well as in the drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Fig. 1 is a schematic diagram of a power grid system, which includes a power grid and an inverter connected to the power grid through an access line, wherein the inverter converts direct current into alternating current and the alternating current is merged into the power grid through the access line; the access line typically includes a multi-stage transformer. The power grid system further includes a reactive power detection device, which may be a component mounted on the inverter, the inverter itself, or a detection device connected in series with the inverter, and is not limited herein. The reactive power detection device is respectively connected with the inverter, the power grid and each stage of transformer, and can acquire electric signals of the inverter, the power grid and each stage of transformer, such as voltage, current and phase difference. Throughout the present specification, the term "phase difference" refers to a phase difference of a voltage and a current. The power grid, the multi-stage transformer and the inverter can form a reactive power compensation system, the inverter can obtain data information of the inverter, the transformer and the power grid in the reactive power compensation system, and reactive power required by the power grid is obtained through calculation.

Reactive power compensation, called reactive compensation for short, plays a role in improving the power factor of a power grid in an electric power supply system, reduces the loss of a power supply transformer and a transmission line, improves the power supply efficiency and improves the power supply environment. The reactive power compensation device is in an indispensable and very important place in the power supply system. The compensation device is reasonably selected, so that the loss of the power grid can be reduced to the maximum extent, and the quality of the power grid is improved. Conversely, improper selection or use may cause many factors such as power supply system, voltage fluctuation, harmonic increase, and the like.

From the application market, the reactive power compensation device industry is rapidly developed at home and abroad, has penetrated into each link of generation, transmission, distribution and application of electric energy, is widely applied to industrial systems, electric power systems, traffic systems, communication systems, computer systems, new energy systems and daily life, and is a basic technology of all other industries using electric energy. In the traditional application, a special reactive power compensation device is adopted to perform reactive power compensation on a power grid.

However, after the grid-connected inverter, especially the photovoltaic grid-connected inverter, is connected to the grid in a large number, the inverter can be used as a reactive power compensation device to provide reactive power for the grid. The grid-connected power generation work operation of the photovoltaic grid-connected system with the reactive compensation function can not only effectively provide the active electric energy of the power grid, but also compensate the required reactive power in the power grid, and is beneficial to further improving the power supply capacity and quality of the power grid.

When the voltage, current, phase or active power, reactive power and other information of the power grid are transmitted to the grid-connected inverter and the grid-connected inverter calculates the reactive power according to the data, the phase difference of the lines changes at the moment due to the delay of the communication lines, so that the obtained reactive power demand cannot be accurately used as the reactive power demand of the current detection period. Therefore, the grid reactive power requirement acquired by the grid-connected inverter in the mode is only suitable for static reactive power compensation and is not suitable for dynamic reactive power compensation.

In the embodiment of the invention, the reactive power detection device obtains the impedance of the access line and the voltage, the current and the phase difference of the inverter in the current detection period, and uses the impedance, the current and the phase difference to calculate the reactive power of the power grid in the current detection period. According to the embodiment of the invention, the impedance of the current detection period of the access line is similar to the impedance of the previous detection period, and the voltage, the current and the phase difference of the current detection period of the inverter are obtained and used without causing communication delay, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

The core idea of the embodiment of the invention is that the impedance of the access line is obtained by obtaining the data stored in the previous detection period and calculating to be used as the impedance of the current detection period, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, and the reactive power is calculated by the impedance and the information of the inverter in the current detection period.

For convenience of understanding, a specific flow in the embodiment of the present invention is described below, and referring to fig. 2, an embodiment of the method for detecting a dynamic reactive power of a power grid in the embodiment of the present invention includes:

201. the reactive power detection device acquires the impedance of the access line in the last detection period.

The reactive power detection device may be an element mounted on the inverter, may be the inverter itself, or may be one detection device connected in series with the inverter, and is not limited herein, but in the present embodiment, the reactive power detection device is described as an example of the inverter itself.

The impedance of the access line in the last detection period is obtained and is taken as the core point of the embodiment of the invention, and the impedance of the access line in the last detection period is approximate to the impedance of the access line in the last detection period, so that the impedance of the access line in the last detection period can be regarded as the impedance of the access line in the current detection period, and the obtained reactive power can be calculated accurately and timely. According to different specific embodiments, the previous detection period refers to a previous detection period adjacent to the current detection period, or any detection period within a preset time range before the current detection period, or a certain detection period established before the current detection period, which is not limited.

202. The reactive power detection device acquires the voltage, the current and the phase difference of the inverter in the current detection period.

The current detection period is a detection period requiring reactive power demand for compensation.

Since the voltage, the current and the phase difference of the inverter are different in each detection period, when the voltage or the current of the inverter needs to be used in each detection, the voltage and the current data of the inverter in the current detection period need to be acquired again as the voltage, the current and the phase difference used in the current detection period.

In the embodiment of the present invention, the phase difference refers to a phase difference between a voltage and a current. The voltage, current and phase difference of the inverter are the voltage of the inverter, the current of the inverter and the phase difference of the voltage and the current of the inverter. The voltage, current and phase difference of the power grid are the voltage of the power grid, the current of the inverter and the phase difference of the voltage and the current of the inverter. Similarly, the voltage, the current and the phase difference of the transformer are the voltage of the transformer, the current of the transformer and the phase difference of the voltage and the current of the transformer.

The specific method for acquiring the voltage, the current and the phase difference of the inverter in the current detection period by the reactive power detection device is to calculate the voltage and the current by detecting the amplitude of the voltage and the current of the inverter and the phase difference of the voltage and the current and by the amplitude of the voltage and the current and the phase difference of the voltage and the current. The specific method for detecting the amplitudes and phase differences of the voltage and the current is common knowledge and will not be described herein.

It should be noted that step 202 and step 201 have no time series relationship, that is, step 202 may occur before step 201 or after step 201, and is not limited herein.

Since the information of the inverter can be regarded as being obtained instantly, the reactive power detection device obtains the data of the inverter without causing a delay in communication, and therefore, the accuracy of the calculated reactive power is not affected by using the data of the inverter as a reference.

203. And the reactive power detection device calculates the voltage, the current and the phase difference of the power grid in the current detection period according to the impedance of the access line and the voltage, the current and the phase difference of the inverter in the current detection period.

The reactive power detection device calculates the voltage and the current of the power grid by adopting the following formulas:

θ_grid＝θ_live+θ_inv，

wherein,is the voltage of the electricity network and,is the voltage of the inverter, Z_lineIn order to be able to access the impedance of the line,is the current of the power grid and is,is the current of the inverter, theta_gridIs the phase difference between the voltage and the current of the network, theta_invIs the phase difference between the voltage and the current of the inverter, theta_lineIs Z_lineThe impedance angle of (c).

Since the inverter, each stage of transformer, and the grid are connected in series, the current of the inverter may be regarded as the current of the grid, or as the current of the incoming line. Therefore, the product of the current of the inverter and the impedance of the access line is the product of the current of the access line and the impedance of the access line, and the voltage of the access line is obtained.

Because the inverter, the transformers at all levels and the power grid are in a series connection relationship, one path of voltage of the inverter is divided by the transformers at all levels through the transformers, and therefore the voltage of the power grid is obtained by subtracting the voltage of the access line from the voltage of the inverter.

Thus, the voltage, the current and the phase difference of the power grid are obtained.

204. The reactive power detection device calculates the dynamic reactive power of the power grid in the current detection period according to the calculated voltage, current and phase difference of the power grid;

the reactive power detection device in the embodiment of the invention uses the data without communication delay to carry out reactive power detection, so that the dynamic reactive power can be calculated for the power grid in time, and the power grid can carry out proper reactive power compensation according to the dynamic reactive power.

The reactive power detection device adopts the following formula to calculate the dynamic reactive power of the power grid in the current detection period:

Q_grid＝U_grid×I_grid×sinθ_grid，

wherein Q is_gridFor dynamic reactive power, U, of the grid in the current detection cycle_gridIs the effective value of the voltage of the power grid, I_gridIs the effective value of the current of the power grid, theta_gridIs the phase difference of the voltage and current of the grid.

And the reactive power detection device indicates the inverter to control the voltage and the current in the electric signal according to the calculated reactive power of the power grid in the current detection period, so that the power grid obtains the reactive power as reactive compensation.

The reactive power detection device obtains the information of the access line, obtains the voltage and the current of the inverter in the current detection period, calculates the impedance of the access line through the first calculation module, and further calculates to obtain the reactive power of the power grid in the current detection period. The impedance of the current detection period of the access line is similar to the impedance of the last detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data obtaining is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

In this embodiment, obtaining the impedance of the access line in the last detection period may calculate the impedance of the access line according to the voltage, the current, and the phase difference of the access line in the last detection period, or may calculate the impedance of the access line according to the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period, specifically referring to fig. 3, another embodiment of the method for detecting the dynamic reactive power of the power grid in the embodiment of the present invention includes:

firstly, calculating the impedance of the access line in the last detection period by acquiring the data of the access line, and taking the impedance of the access line in the current detection period as follows:

301. the reactive power detection device acquires the voltage and current of each stage of transformer in an access line in the last detection period;

in the embodiment of the invention, the impedance of the access line is calculated according to the voltage, the current and the phase difference acquired in the last detection period of the access line.

The last detection period refers to a latest detection period in which the reactive power detection device obtains information such as voltage, current, phase, active power, reactive power, and the like of the power grid, the transformer, and the inverter, and may be a last detection period closest to a current detection period, an earlier detection period when information related to the last detection period has not yet arrived due to communication delay, or a specified earlier detection period, which is not limited herein.

Here, the voltage is a voltage vector, and is distinguished from a voltage effective value described later; similarly, the current here is a current vector and is distinguished from an effective current value described below. The voltage, current, phase, active power, reactive power and the like acquired by the reactive power detection device are all information data of the device, but not the voltage, current, phase, active power, reactive power and the like. The voltage effective value and the current effective value are common knowledge and will not be described herein.

When the inverter works, an electric signal is transmitted from the inverter to a power grid through the access line, and data of voltage and current generated by each stage of transformer, the inverter and the power grid in the access line are collected by the reactive power detection device and stored in a storage module of the reactive power detection device, and are used as updated data to replace original data, wherein the data of the last detection period refers to the latest updated data. When the reactive power detection device needs to use the stored current and voltage related data in any detection period, the data are obtained from the storage module.

302. The reactive power detection device calculates the impedance of each stage of transformer according to the voltage and current of each stage of transformer in the last detection period;

firstly, calculating the phase difference theta between the voltage and the current of each stage of transformer in the last detection period as the impedance angle of the stage of transformer, and then calculating the impedance of the stage of transformer by adopting the following formula:

wherein, Z is the impedance of the stage transformer, U is the effective voltage value of the stage transformer, I is the effective current value of the stage transformer, and θ is the impedance angle of the stage transformer.

The data of the impedance of each stage of the transformer, which is obtained by each calculation of the inverter, is stored in a storage module of the reactive power detection device by the reactive power detection device and is used as updated data to replace the original data. When the reactive power detection device needs to use the impedance of the transformer of a certain stage stored in the storage module in any detection period, the impedance is obtained from the storage module. Since the impedance of the transformer can be regarded as data that is constant for a certain time, the data used for several detection cycles thereafter can be regarded as accurate data.

In this case, the other element connected in series with the transformer may be regarded as one transformer in the incoming line, and the present embodiment is not limited to this, but the example in which only the transformer is present in the incoming line will be described. However, the impedance of the wire in the access line is too small to be ignored, and therefore is not considered in the embodiment of the present invention.

303. The reactive power detection device sums the impedances of the multi-stage transformers to obtain the impedance of the access line in the last detection period, and the impedance is used as the impedance of the access line in the current detection period;

since the impedance of the electric wire in the access line is ignored in this embodiment, the impedance of the access line can be regarded as the sum of the impedances of the multi-stage transformers, and therefore the impedance of the access line is obtained by adding the impedances of the multi-stage transformers in the access line, and is used as the impedance of the access line in the current detection period.

The impedance obtained by each calculation of the inverter is stored in a storage module of the reactive power detection device by the reactive power detection device and is used as updated data to replace the original data. When the reactive power detection device needs to use the stored impedance in any detection period, the impedance is obtained from the storage module. Since the impedance can be regarded as data that is constant for a certain time, the data used for several detection cycles thereafter can be regarded as accurate data.

304. The reactive power detection device acquires the voltage, the current and the phase difference of the inverter in the current detection period;

305. the reactive power detection device calculates the voltage, the current and the phase difference of the power grid in the current detection period according to the impedance of the access line and the voltage, the current and the phase difference of the inverter in the current detection period;

306. the reactive power detection device calculates the dynamic reactive power of the power grid in the current detection period according to the calculated voltage, current and phase difference of the power grid;

step 304 to step 306 in this embodiment are the same as step 202 to step 204 in the above embodiment, and are not described herein again.

In the embodiment of the invention, the access line is regarded as being composed of the transformers connected in series, so that the impedance of the access line can be regarded as the sum of the impedances of all the transformers connected in series in the access line, and the accurate impedance data of the access line can be directly obtained by directly calculating the sum of the multi-stage transformers connected in series.

Secondly, calculating to obtain the impedance of the access line in the last detection period by obtaining the data of the power grid and the inverter in the last detection period, and taking the impedance of the access line in the current detection period as follows:

401. the reactive power detection device acquires the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period;

when the inverter is in operation, an electrical signal is transmitted from the inverter to the grid through the access line, and corresponding voltage and current are generated in the inverter and the grid. The data of current and voltage generated by the inverter and the power grid each time are collected by the reactive power detection device, stored in a storage module of the reactive power detection device and used as updated data to replace the original data. When the reactive power detection device needs to use the stored current and voltage related data in any detection period, the data are obtained from the storage module.

402. Calculating the impedance of the access line in the last detection period according to the voltage and the current of the power grid in the last detection period and the voltage and the current of the inverter in the last detection period, and calculating the impedance of the access line in the last detection period by adopting the following formula:

wherein,in order to switch in the voltage of the line,for current of the incoming line, Z_lineIn order to be able to access the impedance of the line,is the current of the power grid and is,is the voltage of the inverter.

The data of the impedance of each stage of the transformer, which is obtained by each calculation of the inverter, is stored in a storage module of the reactive power detection device by the reactive power detection device and is used as updated data to replace the original data. When the reactive power detection device needs to use the impedance of the transformer of a certain stage stored in the storage module in any detection period, the impedance is obtained from the storage module.

It should be noted that the reactive power detection apparatus may also obtain the data of the impedance through obtaining the stored reactive power or active power in the previous detection period, the voltage of the inverter in the previous detection period, and the current calculation, as long as the latest data of the impedance of the power grid can be calculated through the stored data of the previous detection period, which is not limited herein.

403. The reactive power detection device acquires the voltage, the current and the phase difference of the inverter in the current detection period;

404. the reactive power detection device calculates the voltage, the current and the phase difference of the power grid in the current detection period according to the impedance of the access line and the voltage, the current and the phase difference of the inverter in the current detection period;

405. the reactive power detection device calculates the dynamic reactive power of the power grid in the current detection period according to the calculated voltage, current and phase difference of the power grid;

steps 403 to 405 in this embodiment are the same as steps 202 to 204 in the above embodiment, and are not described again here.

In the embodiment, the impedance of the access line is calculated according to the data of the power grid and the inverter, but not according to the data of the transformer, the number of the transformers is large, the used data is large, the data calculation using the inverter and the power grid is simpler and more convenient, the used data is less, and the processing burden of the reactive power detection device is reduced.

However, in the embodiment of the present invention, not only the two ways of obtaining the impedance of the access line, such as obtaining the impedance by a third-party device, may also be used, and is not limited herein.

The method for detecting the dynamic reactive power of the power grid in the embodiment of the invention is described above, the reactive power detection device in the embodiment of the invention is described below,

referring to fig. 5, an embodiment of the present invention further provides a reactive power detection apparatus 500 for a power grid system, where the power grid system includes a power grid and an inverter connected to the power grid through an access line, and the inverter converts direct current into alternating current and is incorporated into the power grid through the access line;

this reactive power detection device includes:

a first obtaining module 501, configured to obtain an impedance of the access line in a last detection period; according to different specific embodiments, the previous detection cycle refers to a previous detection cycle adjacent to the current detection cycle, or any detection cycle within a preset time range before the current detection cycle, or a certain detection cycle established before the current detection cycle, without limitation;

a second obtaining module 502, configured to obtain a voltage, a current, and a phase difference of the inverter in a current detection period;

a first calculating module 503, configured to calculate, in the current detection period, the voltage, the current, and the phase difference of the power grid according to the impedance of the access line in the current detection period, which is obtained by the first obtaining module 501, and the voltage, the current, and the phase difference of the inverter in the current detection period, which are obtained by the second module 502;

a second calculating module 504, configured to calculate a dynamic reactive power of the power grid in the current detection period according to the voltage, the current, and the phase difference of the power grid calculated by the first calculating module 503.

The reactive power detection device obtains information of an access line through a first obtaining module 501, obtains voltage and current of the inverter in a current detection period through a second obtaining module 502, calculates impedance of the access line through a first calculating module 503, and calculates and obtains reactive power of a power grid in the current detection period through a second calculating module 504. According to the embodiment of the invention, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data acquisition is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

Referring to fig. 6, in some embodiments, the first obtaining module 501 includes:

a first obtaining unit 5011, configured to obtain a voltage, a current, and a phase difference of the access line in the previous detection period;

the first calculating unit 5012 is configured to calculate the impedance of the access line according to the voltage, the current, and the phase difference of the access line obtained by the first obtaining unit in the previous detection period.

Referring to fig. 6, in some embodiments, the access circuit includes a plurality of series-connected transformers;

the first obtaining unit 5011 is specifically configured to obtain a voltage, a current, and a phase difference of each stage of the multi-stage transformer in the previous detection period;

the first calculating unit 5012 is specifically configured to calculate impedances of each transformer according to the voltage, the current, and the phase difference of each transformer in the previous detection period, which are acquired by the first acquiring unit, and sum the impedances of the transformers to obtain an impedance of the access line.

Referring to fig. 7, in some embodiments, the first calculating unit 5012 is specifically configured to calculate the impedance of the transformer stage according to the phase difference θ of the transformer stage in the last detection period acquired by the first acquiring unit as the impedance angle of the transformer stage by using the following formula:

wherein, Z is the impedance of the stage transformer, U is the effective voltage value of the stage transformer, I is the effective current value of the stage transformer, and θ is the impedance angle of the stage transformer, and the impedances of the multi-stage transformers are summed to obtain the impedance of the access line as the impedance of the access line in the current detection period.

Referring to fig. 8, in some embodiments, the first obtaining module 501 includes:

a second obtaining unit 5013, configured to obtain a voltage and a current of the grid in the previous detection period and a voltage and a current of the inverter in the previous detection period;

the second calculating unit 5014 is configured to calculate the impedance of the access line according to the voltage and the current of the power grid in the previous detection period acquired by the second acquiring unit and the voltage and the current of the inverter in the previous detection period.

Referring to fig. 9, in some embodiments, the second calculating unit 5014 is specifically configured to calculate the impedance of the access line by using the following formula:

Referring to fig. 10, in some embodiments, the first calculating module 503 is specifically configured to calculate the voltage, the current and the phase difference of the power grid by using the following formulas;

θ_grid＝θ_live+θ_inv，

Because the impedance of the access line obtained by calculation according to the data of the power grid and the inverter is taken as the impedance of the access line in the current detection period, rather than the impedance calculated according to the data of the transformer, the number of the transformers is large, the used data is large, the data calculation using the inverter and the power grid is simpler and more convenient, the used data is less, and the processing burden of the reactive power detection device is reduced.

Referring to fig. 10, in some embodiments, the second calculating module 504 is specifically configured to calculate the dynamic reactive power of the grid in the current detection period by using the following formula:

Q_grid＝U_grid×I_grid×sinθ_grid，

In the above, the network device in the embodiment of the present invention is described from the perspective of the modular functional entity, and in the following, the reactive power detection apparatus in the embodiment of the present invention is described from the perspective of the hardware processing, please refer to fig. 11, an embodiment of the present invention provides a reactive power detection apparatus for a power grid system, the power grid system includes a power grid and an inverter connected to the power grid through an access line, the inverter converts direct current into alternating current, and the alternating current is merged into the power grid through the access line;

this reactive power detection device includes:

a collector 601 and a processing unit 602;

the collector 601 and the processing unit 602 are connected through a line;

the collector 601 is used for acquiring voltage, current and phase difference of the inverter in the current detection period;

the processing unit 602 is configured to calculate a voltage, a current, and a phase difference of the power grid according to an impedance of the access line in a last detection period and a voltage, a current, and a phase difference of the inverter in the current detection period; and calculating the reactive power of the power grid according to the calculated voltage, current and phase difference of the power grid.

The impedance of the access line in the last detection period can be obtained in various ways, and in a specific embodiment, the collector 601 is configured to obtain the voltage, the current and the phase difference of the access line in the last detection period; the processing unit 602 is configured to calculate an impedance of the access line in a previous detection period according to a voltage, a current, and a phase difference of the access line in the previous detection period; a circuit structure corresponding to the present embodiment is shown in fig. 12, wherein the collector 601 specifically includes an ammeter 603 and a voltmeter 604, and is used to obtain circuit parameter data such as current, voltage, and phase difference. In another specific embodiment, the collector 601 is configured to obtain a voltage and a current of a power grid in a previous detection period and a voltage and a current of an inverter in the previous detection period; the processing unit 602 is configured to calculate an impedance of the access line in a previous detection period according to a voltage and a current of the power grid in the previous detection period and a voltage and a current of the inverter in the previous detection period; a circuit structure corresponding to the present embodiment is shown in fig. 13, wherein the collector 601 specifically includes an ammeter 603 and a voltmeter 604, and is used to obtain circuit parameter data such as current, voltage, and phase difference.

It should be understood that the collector 601 may include one or more combinations of a voltmeter, an ammeter, an impedance meter, a current-voltage sensing module, and the like, and the measuring device or the sensor for measuring the circuit parameters of the circuit, such as the voltage, the current, the impedance, the phase difference, and the like, is not limited in the present invention, and may be an electronic instrument or a mechanical instrument, and is not limited in the present invention.

It should be understood that the processing unit 602 may include, without limitation, various instruments or chips for processing the data of the circuit physical quantity parameter collected by the collector, such as a processor, a calculator, a memory, and the like.

The reactive power detection device obtains the information of the access line, obtains the voltage and the current of the inverter in the current detection period, calculates the impedance of the access line through the first calculation module, and uses the impedance as the impedance of the access line in the current detection period, so as to calculate the reactive power of the power grid in the current detection period. According to the embodiment of the invention, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data acquisition is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid.

The embodiment of the invention provides an inverter for a power grid system, wherein the power grid system comprises a power grid and an inverter accessed to the power grid through an access line, and the inverter converts direct current into alternating current and is incorporated into the power grid through the access line; the inverter includes: the reactive power detection module and the current conversion module; the current conversion module is used for converting the input direct current into alternating current and outputting the alternating current; the reactive power detection module has the same structure as the reactive power detection device shown in fig. 11 and performs the same function.

In a specific implementation manner, in combination with the above embodiment of the present invention, the reactive power detection module of the inverter further includes a communication unit, configured to receive data of the remotely acquired circuit parameters, and supply the data to a processing unit in the reactive power detection module for use.

According to the embodiment of the invention, the impedance of the current detection period of the access line is approximate to the impedance of the previous detection period, the voltage and the current of the inverter end of the current detection period are obtained in time, and the influence of communication delay on data acquisition is avoided, so that the reactive power requirement calculated by the reactive power detection device through the data can be accurately used as the reactive power requirement of the current detection period of the power grid. Meanwhile, the reactive power detection module is integrated in the traditional inverter, so that the structure of the system is simplified. Furthermore, the operation is more convenient by receiving the circuit parameter data acquired remotely.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the unit is only one logical functional division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting dynamic reactive power of a grid, characterized in that the method is used in a grid system, and the grid system includes a grid and an inverter connected to the grid through an access line, and the inverter The converter converts direct current into alternating current and merges it into the power grid through the access line;

The methods include:

Obtaining the impedance of the access line in a previous detection cycle, where the last detection cycle refers to a detection cycle before the current detection cycle;

Obtain the voltage, current and phase difference of the inverter in the current detection cycle; according to the impedance of the access line in the previous detection cycle and the voltage, current and phase difference of the inverter in the current detection cycle phase difference, calculating the voltage, current and phase difference of the grid; and

calculating the reactive power of the grid according to the calculated voltage, current and phase difference of the grid.

2 . The method for detecting dynamic reactive power of a power grid according to claim 1 , wherein the last detection cycle refers to a previous detection cycle adjacent to the current detection cycle. 3 .

3 . The method for detecting dynamic reactive power of a power grid according to claim 1 , wherein the last detection cycle refers to any detection cycle within a preset time range before the current detection cycle. 4 .

4. The method for detecting the dynamic reactive power of the power grid according to any one of claims 1-3, wherein said acquiring the impedance of said access line in a previous detection period comprises:

Obtaining the voltage, current and phase difference of the access line in the last detection cycle;

Calculate the impedance of the access line according to the voltage, current and phase difference of the access line in the last detection period.

5. the method for detecting grid dynamic reactive power according to claim 4, is characterized in that, described access circuit comprises the multistage transformer of series connection;

The acquiring the voltage, current and phase difference of the access line in the last detection cycle includes:

Obtaining the voltage, current and phase difference of each stage of transformer in the multi-stage transformer in the last detection cycle;

The calculating the impedance of the access line according to the voltage, current and phase difference of the access line in the last detection cycle includes:

According to the voltage, current and phase difference of the transformers of each stage in the last detection cycle, calculate the impedance of the transformers of each stage, and sum the impedances of the transformers of each stage to obtain the access The impedance of the line.

6. The method for detecting the dynamic reactive power of the power grid according to claim 5, characterized in that, according to the voltage, current and phase difference of each stage transformer in the last detection cycle, calculate the The impedance of the stage transformer, and the impedance of each stage transformer is summed to obtain the impedance of the access line, including:

According to the phase difference θ of the transformer of each stage in the last detection cycle, as the impedance angle of the transformer of this stage, and adopt the following formula to calculate the impedance of the transformer of this stage:

Z Z = = \frac{U u}{I I} c c o o s the s θ θ + + i i ((\frac{U u}{I I} s the s i i n no θ θ)),,

Wherein, Z is the impedance of the transformer of this stage, U is the effective value of the voltage of the transformer of this stage, and I is the effective value of the current of the transformer of this stage, and the impedance of each stage of transformer is summed to obtain the input line impedance.

7. The method for detecting the dynamic reactive power of the power grid according to any one of claims 1-3, wherein said obtaining the impedance of said access line in the last detection period comprises:

Obtaining the voltage and current of the power grid in the last detection cycle and the voltage and current of the inverter in the last detection cycle;

Calculate the impedance of the access line according to the voltage and current of the power grid in the last detection cycle and the voltage and current of the inverter in the last detection cycle.

8. The method for detecting the dynamic reactive power of the grid according to claim 7, characterized in that, according to the voltage and current of the grid in the last detection cycle and the inverter in the last detection cycle Periodic voltage and current, calculating the impedance of the access line, including:

Calculate the impedance of the access line using the following formula:

in, is the voltage of the access line, is the current of the access line, Z _line is the impedance of the access line, is the grid current, is the inverter voltage.

9. The method for detecting the dynamic reactive power of the power grid according to any one of claims 1-8, characterized in that, according to the impedance of the access line in the last detection period and the inverter in the The voltage, current and phase difference of the current detection cycle are calculated to calculate the voltage, current and phase difference of the power grid, including:

The voltage, current and phase difference of the power grid are calculated by the following formula;

θ _grid = θ _line + θ _inv ,

in, is the grid voltage, is the voltage of the inverter, Z _line is the impedance of the access line, is the grid current, is the current of the inverter, θ _grid is the phase difference between the voltage and current of the grid, θ _inv is the phase difference between the voltage and current of the inverter, and θ _line is the impedance angle of the Z _line .

10. The method for detecting the dynamic reactive power of the power grid according to any one of claims 1-9, wherein the voltage, current and phase difference of the power grid obtained according to the calculation are used to calculate the power of the power grid Reactive power, including:

Calculate the effective value of the voltage of the grid according to the voltage of the grid, calculate the effective value of the current of the grid according to the current of the grid, and calculate the reactive power of the grid by using the following formula:

Q _grid ＝ U _grid × I _grid × sinθ _grid ,

Wherein, Q _grid is the dynamic reactive power of the grid, U _grid is the voltage effective value of the grid, I _grid is the current effective value of the grid, and θ _grid is the phase difference between the voltage and current of the grid.

11. A reactive power detection device, characterized in that it is used in a grid system, the grid system includes a grid and an inverter connected to the grid through an access line, and the inverter converts direct current into alternating current integrated into the grid through the access line;

The reactive power detection device includes:

A first acquisition module, configured to acquire the impedance of the access line in a previous detection cycle, where the last detection cycle refers to a detection cycle before the current detection cycle;

The second obtaining module is used to obtain the voltage, current and phase difference of the inverter in the current detection cycle;

A first calculation module, configured to obtain the impedance of the access line in the last detection period obtained by the first acquisition module and the inverter in the current detection period obtained by the second acquisition module Calculate the voltage, current and phase difference of the grid;

The second calculation module is configured to calculate the reactive power of the grid according to the voltage, current and phase difference of the grid calculated by the calculation module.

12 . The reactive power detection device according to claim 11 , wherein the last detection cycle refers to a previous detection cycle adjacent to the current detection cycle. 13 .

13. The reactive power detection device according to claim 11, wherein the last detection cycle refers to any detection cycle within a preset time range before the current detection cycle.

14. The reactive power detection device according to any one of claims 11-13, wherein the first acquisition module comprises:

a first acquisition unit, configured to acquire the voltage, current and phase difference of the access line in the last detection cycle;

A first calculation unit, configured to calculate the impedance of the access line according to the voltage, current and phase difference of the access line acquired by the first acquisition unit in the last detection cycle.

15. The reactive power detection device according to claim 14, wherein the access line comprises a series connected multi-stage transformer;

The first obtaining unit is specifically configured to obtain the voltage, current and phase difference of each stage of the multi-stage transformer in the last detection cycle;

The first calculating unit is specifically configured to calculate the impedance of each level of transformer according to the voltage, current and phase difference of each level of transformer acquired by the first acquisition unit in the last detection cycle, And summing the impedances of the transformers at each stage to obtain the impedance of the access line.

16. The reactive power detection device according to claim 15, wherein the first calculation unit is specifically configured to obtain the phase difference of each stage of the transformer in the last detection cycle according to the first acquisition unit θ, as the impedance angle of the transformer of this stage, and use the following formula to calculate the impedance of the transformer of this stage:

Z Z = = \frac{U u}{I I} c c o o s the s θ θ + + i i ((\frac{U u}{I I} s the s i i n no θ θ)),,

Wherein, Z is the impedance of the transformer of this stage, U is the effective value of the voltage of the transformer of this stage, and I is the effective value of the current of the transformer of this stage, and the impedance of each stage of transformer is summed to obtain the input line The impedance is used as the impedance of the access line in the current detection period.

17. The reactive power detection device according to any one of claims 11-13, wherein the first acquisition module comprises:

A second acquisition unit, configured to acquire the voltage and current of the power grid in the last detection cycle and the voltage and current of the inverter in the last detection cycle;

The second calculation unit is configured to calculate the voltage and current of the power grid in the last detection cycle acquired by the second acquisition unit and the voltage and current of the inverter in the last detection cycle. The impedance of the access line is described.

18. The reactive power detection device according to claim 17, wherein the second calculation unit is specifically configured to calculate the impedance of the access line using the following formula:

19. The reactive power detection device according to any one of claims 11-18, wherein the first calculation module is specifically configured to calculate the voltage, current and phase difference of the grid by using the following formula;

θ _grid = θ _line + θ _inv ,

20. The reactive power detection device according to any one of claims 11-19, wherein the second calculation module is specifically configured to calculate the effective voltage value of the power grid according to the voltage of the power grid, according to the Calculate the effective value of the current of the grid according to the current of the grid, and use the following formula to calculate the reactive power of the grid:

Q _grid ＝ U _grid × I _grid × sinθ _grid ,

21. A reactive power detection device, characterized in that it is used in a grid system, the grid system includes a grid and an inverter connected to the grid through an access line, and the inverter converts direct current into alternating current integrated into the grid through the access line;

The reactive power detection device includes:

processing unit and collector;

The collector is used to obtain the voltage, current and phase difference of the inverter in the current detection cycle;

The processing unit is configured to calculate the voltage, current and phase of the grid according to the impedance of the access line in the last detection cycle and the voltage, current and phase difference of the inverter in the current detection cycle difference; and calculate the reactive power of the grid according to the calculated voltage, current and phase difference of the grid.

22. The reactive power detection device according to claim 21, characterized in that,

The collector is also used to obtain the voltage, current and phase difference of the access line in the last detection cycle;

The processing unit is further configured to calculate the impedance of the access line in the last detection period according to the voltage, current and phase difference of the access line in the last detection period.

23. The reactive power detection device according to claim 21, characterized in that,

The collector is also used to obtain the voltage and current of the power grid in the last detection cycle and the voltage and current of the inverter in the last detection cycle;

The processing unit is further configured to calculate the current detection time of the access line according to the voltage and current of the power grid in the last detection cycle and the voltage and current of the inverter in the last detection cycle. cycle resistance.