CN111987705A - Direct current energy consumption system, electric power system and energy consumption method - Google Patents

Abstract

The present disclosure relates to DC energy consumption systems and power systems. Provided is a DC energy consumption system, comprising: an energy consumption part, which includes an energy consumption device; and a switch part connected in series with the energy consumption part, the switch part includes at least one switch module, and the switch module includes: a first node and a second node; a switch branch and a buffer branch connected in parallel between the first node and the second node, wherein the switch branch includes a power electronic switch, and the buffer branch includes at least a capacitor and a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent.

Description

DC energy consumption system, power system and energy consumption method

technical field

The present disclosure relates to a DC energy consumption system and a power system, and an energy consumption method for the power system.

Background technique

In recent years, HVDC technology has developed rapidly. On the other hand, there is a growing demand for clean energy. Wind farms (also called wind farms) are being used more and more widely for grid-connected flexible direct current transmission systems (VSC-HVDC, voltage source converter-based high voltage direct current transmission).

When VSC-HVDC is in normal operation, the energy generated by the wind turbine connected in an island mode is in balance with the energy consumed by the AC grid at the receiving end. When the AC power grid at the receiving end fails, the energy it can consume is reduced, and the ability to receive power is limited. However, since the wind farm at the sending end cannot directly obtain the frequency and voltage information of the AC grid, the voltage and frequency will not change in a short period of time. This causes energy to accumulate on the DC line, and the surplus power flows into the modular multilevel converter (MMC), which causes the converter sub-module capacitors to be charged and the voltage rises, which indirectly causes the DC line voltage to rise. If the control of the DC line by the receiving-end converter station fails, it will cause the line to trip in severe cases.

Accordingly, there is a need for improved DC energy consumption systems, power systems, and energy consumption methods.

SUMMARY OF THE INVENTION

According to one aspect of the present disclosure, there is provided a DC energy consumption system, comprising: an energy consumption part including an energy consumption device; and a switch part connected in series with the energy consumption part, the switch part including at least one switch module , the switch module includes: a first node and a second node; a switch branch and a buffer branch connected in parallel between the first node and the second node, wherein the switch branch includes a power electronic switch, so The buffer branch includes at least a capacitor; and a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent.

According to one aspect of the present disclosure, there is provided a DC energy consumption system, comprising: an energy consumption part including an energy consumption device; and a switch part connected in series with the energy consumption part, the switch part including at least one switch module , the switch module comprises: a first node and a second node; a switch branch connected between the first node and the second node, the switch branch comprising a power electronic switch; a protection module configured for protecting the power electronic switch from overvoltage and/or overcurrent; and a reverse current protection branch connected in anti-parallel with the switch branch between the first node and the second node to prevent A reverse current flows through the switch branch.

In some embodiments, the at least one switch module includes a plurality of the switch modules in series with each other.

In some embodiments, the snubber branch is configured to buffer voltages on the switch branch or switches in the switch branch without passing direct current from the buffer branch.

In some embodiments, an end of the switching portion remote from the energy consuming portion is adapted to be connected to a DC transmission line, and the energy consuming portion is configured to receive power from the DC transmission line via the switching portion.

In some embodiments, the protection module is connected in parallel with the switch branch between the first node and the second node.

In some embodiments, the protection module includes a metal oxide arrester (MOV).

In some embodiments, of the plurality of switch modules, a second node of a switch module that is upstream is coupled to a first node of a downstream switch module that is immediately adjacent thereto.

In some embodiments, the energy dissipating device is a centralized resistive energy dissipating device, the energy dissipating portion is configured to be remote from the switching portion such that the heat generated by the energy dissipating portion does not affect the switching portion .

In some embodiments, the power electronic switch comprises a fully controlled power electronic switch.

In some embodiments, the power electronic switch includes any one or more of the following: IGBT, IGET, IGCT.

In some embodiments, each switch module further includes: a reverse current protection branch connected in anti-parallel with the switch branch between the first node and the second node to prevent reverse current from flowing through the switch branch.

In some embodiments, each switch module further includes a bypass branch connected in parallel with the switch branch, the bypass branch includes a bypass switch, the bypass branch is configured to operate in the bypass circuit An on switch is turned on so that current flows therethrough and not through the switch branch.

In some embodiments, one end of the switch part away from the energy consumption part is adapted to be connected to a high-potential DC transmission line in the DC transmission line, and one end of the energy consumption part away from the switch part is adapted to be connected to the DC transmission line. a low-potential DC transmission line of the DC transmission lines, the DC transmission line being adapted to be connected to an AC power system, the DC energy consuming system further comprising a control portion configured to generate a voltage based on the DC transmission line A control signal for the switch branch of each of the switch modules to control the opening of the switch branch of each of the switch modules, so that current passes through the energy consumption device for energy consumption.

In some embodiments, the at least one switch module includes a plurality of the switch modules connected in series with each other, and the DC energy consumption system further includes an additional energy consumption device configured with the plurality of energy consumption devices. One or more of the switch modules are connected in parallel.

In some embodiments, the additional energy dissipating device includes a metal oxide arrester.

In some embodiments, the switch module further includes an energy dissipating branch connected between the first node and the second node, the energy dissipating branch including an energy dissipating device and a power electronic switch connected in series with each other.

According to one aspect of the present disclosure, there is provided a power system comprising: a DC subsystem including a DC transmission line; and the DC energy consumption system according to any embodiment, connected to the DC transmission line, Wherein, one end of the switch part away from the energy consumption part is connected to a high potential transmission line in the DC transmission line, and one end of the energy consumption part away from the switch part is connected to a low potential in the DC transmission line Transmission line.

In some embodiments, the power system further includes an AC subsystem that receives power from the DC transmission line and converts it into AC power, the AC subsystem including a DC-AC conversion device.

In some embodiments, the power system further includes a power generation or conversion system configured to provide DC power to the DC transmission line.

In some embodiments, the power generation or conversion system includes one of: a direct current power generation system; and an alternating current power generation system and an AC-DC conversion device connected between the alternating current power generation system and the direct current transmission line.

In some embodiments, the alternating current power generation system includes a wind farm.

According to one aspect of the present disclosure, an energy consumption method of a power system is provided. The power system may include: a DC subsystem, the DC subsystem including a DC transmission line; and the DC energy consumption system according to any embodiment, connected to the DC transmission line, wherein the switch portion is remote from the DC transmission line. One end of the energy consumption part is connected to a high potential transmission line in the DC transmission line, and one end of the energy consumption part away from the switch part is connected to a low potential transmission line in the DC transmission line; and an AC subsystem, the The AC subsystem receives power from the DC transmission line and converts it to AC power. The method includes: determining whether the voltage on the DC transmission line exceeds a threshold; if the voltage on the DC transmission line exceeds the threshold, based on the active power on the DC transmission line and the active power consumed by the AC subsystem The power difference between the powers is used to generate a control signal for the switching branch of each of the switch modules; based on the control signal, the opening of the switch branch of each of the switch modules is controlled, so that the current passes through the energy consuming device to consume energy.

In some embodiments, generating the control signal for the switching branch of each of the switching modules includes generating the said threshold based on the power difference and based on a comparison between the voltage on the DC transmission line and the threshold control signal.

In some embodiments, generating the control signal for the switch branch of each of the switch modules includes: scaling the power difference based on the parameters of each switch module and the per-unit value of the power difference to obtain a proportional the processed power difference; based on the proportionally processed power difference, and the comparison between the voltage on the DC transmission line and the threshold value, determine the duty cycle of the control signal for the switching branch of each of the switching modules; based on The duty cycle generates a pulse signal as the control signal for the switching branch of each of the switching modules.

In some embodiments, the method further includes: controlling switching off of the switching branches of each of the switching modules based on the control signal.

Description of drawings

The accompanying drawings, which constitute a part of this specification, illustrate exemplary embodiments of the present disclosure, and together with the description serve to explain the principles of the invention, in which:

Figure 1 shows a schematic diagram of a power system;

FIG. 2 shows a schematic diagram of the power flow of the power system shown in FIG. 1 and the situation of a fault;

3 shows a schematic diagram of an energy consumption system and a power system incorporating the energy consumption system according to one embodiment of the present disclosure;

FIG. 4 shows a schematic diagram of a specific implementation of an energy consumption system according to an embodiment of the present disclosure;

FIG. 5 shows a flowchart of an energy consumption method for a power system according to an embodiment of the present disclosure;

FIG. 6 shows a specific example of a step of generating a control signal in an energy consumption method according to an embodiment of the present disclosure;

FIG. 7 shows a schematic diagram of a control unit for an energy consumption system or a power system including an energy consumption system and a control process thereof according to an embodiment of the present disclosure; and

8-12 illustrate some variations of modules of switches according to embodiments of the present disclosure.

Detailed ways

Specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood, however, that the descriptions of the embodiments are merely illustrative and are not intended to limit the invention claimed in this application in any sense. The relative arrangement of components and steps, expressions, numerical values, etc. in the exemplary embodiments are not intended to limit the invention claimed by this application unless otherwise specifically stated or indicated or implied by context or its principles.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. As used herein, the singular forms "a" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It is also to be understood that the word "comprising" when used herein indicates the presence of the indicated features, integers, steps, operations, units and/or components, but does not preclude the presence or addition of one or more other features, Entities, steps, operations, units and/or components and/or combinations thereof. In addition, "coupled/connected" mentioned in this application includes both direct coupling and indirect coupling; in other words, "A is coupled/connected to B" or "A is coupled/connected to B" includes A and B are directly coupled/connected, and A and B are indirectly coupled/connected and other intermediate elements may exist between A and B.

Herein, semiconductor-based power switching devices are also referred to as power electronic switching devices or power switching devices (or power devices).

Figure 1 shows a schematic diagram of a power system. As shown in FIG. 1 , the power system 100 may include a wind farm (or wind power plant) 101 . The alternating current generated by the wind farm 101 is converted into direct current (eg, high voltage direct current) through the converter 105 (MMC1 ), and is transmitted to the receiving end through the direct current transmission line 107 . At the receiving end, the DC power is converted into AC power by the converter 109 (MMC2) and supplied to the subsequent AC power grid 113 .

Optionally, the electronic system 100 may further include AC-AC conversion devices 103 and 111 to convert the AC power.

FIG. 2 shows a schematic diagram of the power flow of the power system shown in FIG. 1 and a fault condition. As shown in FIG. 2 , the power (eg, active power) generated by the wind farm 101 is P _wind . A small portion of the power P _wind generated by the wind farm 101 is consumed by transmission equipment such as MMCs 105 and 109 , eg _PMMC1 and _PMMC2 , and the rest is supplied to the AC grid (P _{ac_rev} ) for consumption by the AC grid. Under normal operation, the energy emitted by the wind farm 101 is basically balanced with the energy consumed by the AC power grid at the receiving end.

However, when the receiving-side AC grid fails (as indicated by reference numeral 201 in FIG. 2 ), the energy that the AC grid can consume is reduced, and the ability to receive power is limited. However, since the wind farm at the sending end cannot directly obtain the frequency and voltage information of the AC grid, the voltage and frequency will not change in a short period of time. This causes energy to build up on the DC line, and the surplus power flows into the modular multilevel converters (MMC1 and/or MMC2), causing the converter sub-module capacitors to be charged and the voltage to rise, indirectly causing the DC line voltage to rise. If the control of the DC line by the receiving-end converter station fails, it will cause the line to trip in severe cases.

In order to avoid failures, it is necessary to apply the DC energy consumption device to consume the surplus power by means of energy consumption. For example, the power consumption can be controlled by a chopper circuit to achieve power balance.

At present, there are mainly two schemes for DC energy consumption devices. One solution is a modular distributed resistance DC energy consumption device, which adopts a modular design to reduce current fluctuations and better achieve dynamic and static voltage equalization; however, this solution requires the use of many high-rated semiconductor devices, and the circuit cost Tall and bulky. In addition, for the distributed resistance type DC energy consumption device, the distributed resistance must be arranged in the module, that is, the distributed resistance must be arranged around the switching device. Therefore, when the DC energy consumption device is running, the high temperature of the distributed resistance will cause the switching device to fail to work normally. , must use a high-power water cooling system to dissipate its heat. This increases cost and reduces the reliability and lifetime of switching devices.

Another solution is a centralized resistor chopping energy dissipation device. However, due to the use of the switch series connection technology in this solution, it is difficult to realize the dynamic and static voltage equalization of the direct series of switching devices, and the performance requirements of the devices are very high.

Due to the capacity limitation of a single switching device, in the case of high-power conversion, such as DC transmission, the DC side voltage often reaches tens or hundreds of kV. However, the current commercial IGBT and IGCT with the highest voltage level are only 6.5kV. In this case, dozens or hundreds of switching devices need to be connected in series to share this higher voltage. When the switching devices are used in direct series, due to their fast switching speed, which is basically completed within a few microseconds, it is inevitable that some of the switching devices will be turned on or off first, and some of the switching devices will be turned on later. or after shutdown. This makes it very likely that the voltage on each switching device will exceed its rated voltage, resulting in damage to the switching device.

In view of one or more of the above-mentioned problems, the inventors of the present application have proposed novel technologies to provide improved DC energy consumption systems, power systems, and related methods and the like.

3 shows a schematic diagram of an energy consuming system and a power system incorporating the energy consuming system according to one embodiment of the present disclosure. FIG. 4 shows a schematic diagram of a specific implementation of an energy consumption system according to an embodiment of the present disclosure. The following description will be made with reference to FIG. 3 and FIG. 4 .

As shown in FIG. 3, power system 300 may include a DC subsystem. The DC subsystem may include a DC transmission line 107 . In some examples, power system 300 may also include a power generation or conversion system. A power generation or conversion system may be configured to provide DC power to the DC transmission line. Power generation or conversion systems may include, but are not limited to: direct current power generation systems; and/or alternating current power generation systems and combinations thereof. For example, the DC power generation system may include a DC power generation device such as a solar farm. For example, the AC power generation system may include a wind farm (such as an offshore or land-based wind farm), a thermal power plant (such as a geothermal or molten salt power plant, etc.), and the like. The AC-DC conversion device may be configured to connect between the AC power generation system and the DC transmission line to provide DC power to the DC transmission line.

In the example shown in FIG. 3 , a wind farm is used as an example for illustration and description. The power system 300 shown in FIG. 3 may further include an AC-AC conversion device 103 , an MMC 105 , and a wind farm 101 . It should be understood that the present disclosure is not limited to this embodiment, and the DC subsystem only needs to include a DC transmission line, or may also include one or more other components.

Here, in the context of the present application, the term high voltage refers to voltages of 10 kV or above, thus also covering ultra-high voltages and ultra-high voltages. Although the technology disclosed in this application is particularly suitable for high voltage power transmission, it should be understood that this application is not so limited.

Power system 300 may also include an AC subsystem. The AC subsystem can receive power from the DC transmission line and convert it into AC power. In some embodiments, the AC subsystem may include a DC-AC conversion device, such as a DC-AC conversion device 109 (MMC2). In other embodiments, the AC subsystem may further include an AC-AC conversion device 111 . The AC subsystem may also include the AC grid 113 . Here, the AC grid 103 is used to denote any equipment, device or facility connected downstream that receives AC power.

As shown in FIG. 3, the power system 300 also includes a DC energy consumption system connected to the DC transmission line. As shown in FIG. 3 , the DC energy consumption system may include an energy consumption part 301 , which includes an energy consumption device (in the figure, the resistance Ri is used as a schematic diagram of the energy consumption device). The DC energy consumption system further includes a switch unit 303 connected in series with the energy consumption unit 301 . In some embodiments, one end of the switch part 303 is connected to the energy consumption part 301 , and one end of the switch part far from the energy consumption part can be connected to one of the DC transmission lines, such as a high potential transmission line. One end of the energy consuming part 301 away from the switching part may be connected to another one of the DC transmission lines, eg, a low-potential transmission line. The energy consuming part 301 can receive power from the DC transmission line via the switching part 303 .

As shown in FIG. 4 , the switch part may include at least one switch module 410 . In the embodiment shown in FIG. 4 , the switch section may include a plurality of switch modules 410 connected in series with each other, such as switch modules SM1 . . . SMn.

The switch module may include a first node 401 and a second node 403 . The switch module may further include a switch branch 411 and a buffer branch 413 , which are connected in parallel with each other between the first node 401 and the second node 403 .

The switch branch 411 is configured to be able to be turned on or off (disconnected) according to a control signal. The switch branch 411 may comprise a power electronic switch T. Preferably the power electronic switch may comprise eg a fully controlled power electronic switch. In some embodiments, the power electronic switch may comprise any one or more of the following: IGBT, IGET, IGCT. It should be understood here that although in the embodiment shown in FIG. 4 , the switch branch 411 is shown as including only one power electronic switch T, the present disclosure is not limited thereto. In other embodiments, the switch branch 411 may also include multiple power electronic switches or a combination thereof. Incidentally, in the context of this application, "plurality" means more than one, ie, there may be two or more.

The buffer branch 413 may include at least the capacitor C. A snubber branch is provided to buffer the voltage on the switch branch (or switches therein) to slow down the rate of voltage rise. The buffer branch 413 is configured not to pass direct current. In some embodiments, as shown in FIG. 4 , the buffer branch 413 may further include a resistor R. As shown in FIG. Resistor R can be used to limit the charging and discharging current to the capacitor. It should be understood that the configuration of the buffer branch is not limited to the embodiment shown in FIG. 4 , and may have various forms as long as it can buffer the voltage on the switch branch (or the switch therein).

In this way, for example, the rising speed of the voltage of the switching devices when turned off can be slowed down, thereby reducing the dynamic voltage difference between the switching devices.

In some embodiments, the switch module 410 may also include a protection module (represented by an MOV) configured to protect the power electronic switches of the switch branch from overstress, such as overvoltage and/or overcurrent. In some embodiments, the protection module may include a surge arrester or a varistor or the like, such as a metal oxide surge arrester (MOV). Here, the protection modules are collectively indicated by MOV. In the embodiment shown in FIG. 4 , the protection module is implemented as a branch 415 connected in parallel with the switching branch between the first node and the second node; however, the present disclosure is not limited thereto. For example, in other embodiments, lightning arresters (MOVs) may also be placed in parallel with the power electronic switches in the switch branch rather than in parallel with the entire switch branch.

By providing the protection module MOV, the voltage across the switching branch or the switching device therein can be stabilized, and overvoltage and overcurrent protection can be provided for it. When the voltage value reaches the operating voltage at both ends of the arrester, the resistance of the arrester is greatly reduced due to the nonlinear resistance effect, and the arrester will flow charge, limit the amplitude of the overvoltage, and release the overvoltage energy; at the same time, the arrester can cut off the freewheeling current. Thus, overvoltage and overcurrent protection are realized. According to the embodiments of the present application, the reliability of the switching device can be improved, and the redundancy can be increased.

In some embodiments, among the plurality of switch modules, the second node (low potential node) 403 of the switch module on the upstream side (eg, the high potential side, or the side away from the energy consuming device Ri) may be coupled to the first node (high potential node) 401 of the immediately adjacent downstream switch module.

In embodiments of the present disclosure, the energy consumers 303 (Ri) may be centralized resistive energy consumers. The energy consumption part 303 may be arranged away from the switch part 301 . For example, a plurality of resistors or resistive devices for dissipating energy may be relatively concentrated in one place, while the switch portion is remote from the dissipating portion. Thus, the switching portion can be substantially unaffected by the heat generated by the energy consuming portion. Moreover, since the switch part and the energy dissipation part are separated, the heat dissipated by the two will not be superimposed. Therefore, instead of using a high-power water-cooling system to dissipate heat for the energy-consuming part and the switch part, only an air-cooling system or natural cooling can be used. In this way, the reliability of the equipment can be improved and the cost can be significantly reduced.

In some embodiments, the switch module may further include a reverse current protection branch 417 connected in anti-parallel with the switch branch between the first node and the second node to prevent reverse current from flowing through the switch branch. In some embodiments, reverse current protection branch 417 may include diode D, as shown in FIG. 4 . The current direction of diode D is configured to be opposite to the current direction in the switching branch.

In some embodiments, the switch module may further include a bypass branch 419 connected in parallel with the switch branch, and the bypass branch may include a bypass switch S. The bypass branch is configured to pass current therethrough without passing through the switch branch when the bypass switch is turned on. Thus, when a switch module fails, it can be bypassed.

According to some embodiments of the present disclosure, the energy consumption system may further include a control part. The control section may be configured to generate a control signal for the switch branch of each switch module based on the voltage on the DC transmission line, to control the opening of the switch branch of each switch module to allow current to pass through the energy consuming device for energy consumption .

So far, it should be understood that the present disclosure also provides a power system, which may include: a DC subsystem including a DC transmission line; and a DC energy consumption system according to any embodiment of the present disclosure, which is connected to The DC transmission line, wherein one end of the switch part away from the energy consumption part is connected to one of the DC transmission lines, and one end of the energy consumption part away from the switch part is connected to the DC transmission line another transmission line.

In some embodiments, the power system further includes an AC subsystem that receives power from the DC transmission line and converts it to AC power. The AC subsystem may include a DC-AC conversion device.

In some embodiments, the power system further includes a power generation or conversion system configured to provide DC power to the DC transmission line. In some embodiments, the power generation or conversion system includes one of: a direct current power generation system; and an alternating current power generation system and an AC-DC conversion device connected between the alternating current power generation system and the direct current transmission line. In some embodiments, the alternating current power generation system includes a wind farm.

FIG. 5 shows a flowchart of an energy consumption method according to an embodiment of the present disclosure. FIG. 6 shows a specific example of a step of generating a control signal in an energy consumption method according to an embodiment of the present disclosure. FIG. 7 shows a schematic diagram of a control unit and a control process thereof for an energy consumption system or a power system including an energy consumption system according to an embodiment of the present disclosure. The following description will be made with reference to Figures 5-7.

According to some embodiments of the present disclosure, an energy consumption method of a power system is also provided, as shown in FIG. 5 , which may include the following steps.

At step 501: Determine whether the voltage on the DC transmission line exceeds a threshold. According to the energy consumption system (and the power system) of the present disclosure, the DC line voltage can be monitored in real time during the operation of the system. When the DC voltage exceeds the set threshold, the energy dissipation system (also called the unloading circuit) is triggered to work to consume the surplus energy.

In step 503, in the case where the voltage on the DC transmission line exceeds the threshold, based on the power difference between the active power on the DC transmission line and the active power consumed by the AC subsystem, generate a control for the switching branch of each switching module Signal.

For example, the power difference that should be consumed by the DC unloading circuit can be obtained by measuring the active power input to the DC line of the wind farm and the active power consumed by the receiving end grid (AC side). The DC input power of the power generation side (or DC grid side) converter station (eg, 103 ) can be represented by Pin_G, and the AC side output power is represented by Pout_G, as shown in FIG. 7 . The difference between the two is the power difference that the DC unloading circuit should consume. Control signals for the switching branches of the respective switching modules can thus be generated based on this power difference.

In some embodiments, the control signal may be generated based on this power difference and based on a comparison between the voltage on the DC transmission line and a threshold, as shown in FIG. 7 and described in more detail later.

In step 505, the switching branches of each switch module are controlled to be turned on based on the control signal, so that the current passes through the energy consumption device for energy consumption.

Optionally, the method may further include step 507, in which step, the switch branches of each switch module are controlled to be turned off based on the control signal. For example, the control signal may be a pulse signal, and the pulse signal may have a duty cycle to control the on or off of the switch branch of each switch module, so as to consume surplus power as required.

In some embodiments, as shown in FIG. 6 , generating control signals for the switch branches of each switch module includes the following steps.

In step 601, the power difference is proportionally processed based on the parameters of each switch module and the per-unit value of the power difference to obtain a proportionally processed power difference. The per unit value can be the ratio of the power deficit to the system's rated transmit power. The parameters of each switch module may include, for example, parameters of the power electronic switch, such as rated voltage, rated current, maximum average current, switching frequency, and the like.

At step 603, the duty cycle of the control signal for the switching branch of each switching module is determined based on the ratioed power difference and the comparison between the voltage on the DC transmission line and the threshold.

At step 605, a pulse signal is generated based on the duty cycle as a control signal for the switching branch of each switching module.

In one embodiment, as shown in FIG. 7, a control part 700 is also provided. The control part 700 may be configured to generate a control signal for the switch branch of each switch module based on the voltage on the DC transmission line, to control the opening of the switch branch of each switch module, so that the current passes through the energy consuming device for consumption. can. It should be understood that the control unit may be provided in the energy consumption system; or may also be provided in the power system including the energy consumption system, for example, integrated with other control systems of the electronic system.

The control part 700 may include a power difference determination module 701 that receives the value of the DC input power Pin_G and the value of the AC side output power Pout_G of the power generation side (or DC grid side) converter station (eg, 103 ) to determine the power difference. The power determination module 701 may be implemented by, for example, an adder; however, the present disclosure is not limited thereto. Those skilled in the art will understand that a subtractor is essentially an adder with a negative coefficient.

The control part 700 may also include a proportional module 703 . The scaling module is configured to scale the power difference. The proportional processing parameter of the proportional module can be determined by the per unit value of the power difference. Alternatively, the proportional processing parameters of the proportional module may be designed by the per-unit value of the power differential and based on the design values of the switching module (eg, rated voltage, rated current, maximum average current, switching frequency, etc.), and the like. For example, in some embodiments, the per-unit value may be configured as the ratio of the power difference to the system's rated transmit power.

In some embodiments, the control part 700 may further include a comparator 513 for comparing the measured voltage Edc on the DC transmission line (eg, 107 ) with a reference voltage Edc_ref to determine whether the voltage Edc on the DC transmission line is higher than the reference voltage Edc_ref. If the output of the comparator is 0, that is, the DC line voltage is less than the reference voltage, the DC energy consumption device is not activated at this time. If the output of the comparator is 1, that is, the DC line voltage is greater than the reference voltage, that is, the DC line generates a power surplus, at this time, the DC energy consumption device is activated to consume energy.

The control part 700 may further include a trigger module 705 . The triggering module 705 can trigger (or start) related processing for controlling or starting the energy consuming part (energy consuming device) according to the comparison result of the comparator 705 . In some embodiments, trigger module 705 may include multiplier 705 . Multiplier 705 multiplies the scaled power difference by the output of the comparator. If the output of the comparator is 0, the output of the multiplier is 0, that is, the energy consumption device is not activated to consume energy. If the output of the comparator is 1, the proportionally processed power difference is output by the multiplier; in this case, the subsequent processing is appropriately initiated based on this power difference (and optionally other parameters, such as the design value of the switch module, etc.) DC energy consumption device for energy consumption.

In some embodiments, optionally, the control unit 700 may further include a clipping module 707 to clip the result of the proportional processing. In the previous stage (proportional module), the power difference has been converted into a ratio through the per-unit value, but the per-unit value is based on the rated power, and in practical applications, it may occur that the power sent by the wind farm exceeds its rated power for a short time. power situation. In this case, the ratio will appear with a value greater than 1. Therefore, it can be limited between 0-1 by the clipping module to determine the duty cycle of the signal used to control the switching device. The duty cycle 709 of the signal for controlling the switching device is obtained through the limiting module, and the duty cycle is limited between 0 and 1.

Afterwards, a pulse signal with a desired duty cycle 709 can be generated using the carrier signal as the control signal for the switching branch (or its switching device) of the switching module. In some implementations, the carrier signal may be a frequency-adjustable triangular carrier signal. In the embodiment shown in FIG. 7 , the control part 700 includes a comparator 711 to use the comparator 711 to generate a pulse signal with a desired duty cycle using a triangular carrier signal with adjustable frequency. Here, those skilled in the art will easily understand that the triangular carrier signal is a carrier signal with a triangular waveform, as shown in FIG. 7 .

8-12 illustrate some variations of modules of switches according to embodiments of the present disclosure.

In some embodiments, the bypass branch may be omitted from the switch module. For example, compared to the embodiment shown in FIG. 4 , in the embodiment shown in FIG. 8 , the bypass branch is omitted in the switch module.

The inventors of the present application also realized that, generally, the failure of the power device IGBT is an open circuit, and the failure of the power device IGCT and IEGT is a short circuit. Therefore, when IGCT and IEGT are used for the switch branch, the bypass switch S can be omitted.

In some embodiments, the buffer branch may be omitted in the switch module. For example, compared to the embodiment shown in FIG. 4 or FIG. 8 , in the embodiment shown in FIG. 9 , the snubber branch (RC snubber branch) is omitted in the switch module.

In some embodiments, the buffer branch may be omitted in the switch module. For example, compared to the embodiment shown in FIG. 4 , in the embodiment shown in FIG. 10 , the reverse current protection branch (eg, the anti-parallel connection with the switch T in FIGS. 8 and 9 ) can be omitted in the switch module diode D).

FIG. 11 shows a schematic diagram of a DC energy consumption system according to an embodiment of the present disclosure. In this embodiment, all switch modules are divided into several groups, for example, i groups, wherein SM ₁₁ -SM _1n are one group, . . . SM _i1 -SM _in is one group. One or more metal oxide arresters MOV ₁ ... MOV _i can be connected in parallel for each group of switches. In this embodiment, in addition to using the concentrated energy dissipation resistor Ri to dissipate energy, one or more of MOV ₁ . . . MOV _i can also be used to dissipate energy. For example, several levels can be set according to the power difference that needs to be absorbed, and the corresponding switches can be switched on (that is, turned on) or switched off (that is, turned off) in groups, and the corresponding MOVs in MOV ₁ . . . MOV _i are connected for power consumption. can. For example, when the power difference that needs to be absorbed needs to be dissipated in addition to the concentrated energy dissipating resistor Ri, the MOV1 also needs to be put in to dissipate energy, then the first group of switches SM ₁₁ -SM _1n is put in (ie, turned off), and connected to MOV ₁ in parallel with the first set of switches for power dissipation.

FIG. 12 shows a schematic diagram of an energy consumption system according to another embodiment of the present disclosure. In this example, the switch module may further include an energy dissipating branch connected between the first node and the second node. In the example shown in Figure 12, the energy dissipating branch may comprise an energy dissipating device Rii and a power electronic switch TR connected in series with each other. The dissipating branch is configured in parallel with the switching branch. In some implementations, the power electronic switch TR may be a thyristor. The energy dissipating device Rii may be an energy dissipating resistor. One or more dissipating resistors Rii may be provided in each switch module. Therefore, the dissipation resistance Rii is distributed.

In this example, the Ri concentrated energy dissipation resistor is also connected in parallel with the bypass switch S. Whether or not Ri is connected to the circuit can be controlled through the bypass switch S.

According to this embodiment, the energy dissipation can be shared by the Ri concentrated energy dissipation resistor and the Rii distributed energy dissipation resistor. Energy consumption can also be performed by controlling the power device T and thyristor TR of each switch module to control the input of one or more distributed energy dissipation resistors Rii and/or centralized energy dissipation resistors Ri according to the power difference to be absorbed.

According to the DC energy consumption device of the embodiment of the present disclosure, the switch part thereof includes at least one switch module connected in series with each other. According to some embodiments of the present disclosure, a parallel snubber circuit (eg, a resistor-capacitor snubber circuit) is used in the switch module to slow down the rising speed of the voltage of the switching device during turn-off and reduce the dynamic voltage difference.

According to some embodiments of the present disclosure, the use of a surge arrester MOV in the switch module can limit the voltage value across the switching device, thereby effectively limiting the overvoltage and ensuring the voltage equalization effect. Therefore, the safety of the switching device can be improved.

Furthermore, the voltage of each module can be controlled by the combined switching module including the protection module MOV, thus increasing the redundancy of the DC energy consumers. According to the embodiments of the present disclosure, even if one or some of the switch modules in the switch part fail, the system can still work normally.

According to the embodiments of the present disclosure, dynamic and static voltage equalization of switching devices can be realized, and the technical problem of series voltage equalization is solved. In addition, according to the embodiments of the present disclosure, an expensive high-power water cooling system is not required, and the occupation and cost are low. In addition, the energy consumption system according to the embodiment of the present disclosure is simple to control, has high reliability, and is easy to be incorporated into an existing power system.

Various embodiments of the present disclosure have been described above, but the above description is exemplary only, not exhaustive, and the invention is not limited to the various disclosed embodiments. The various embodiments disclosed herein and their features may be combined in any combination without departing from the spirit and scope of the present invention. Numerous modifications and variations of the invention will readily occur to those skilled in the relevant art from the teachings herein of the invention, which are also encompassed within the spirit and scope of the invention.

Claims (10)

1. A direct current energy dissipation system, comprising:

an energy consuming part comprising an energy consuming device; and

with power consumption portion series connection's switch portion, switch portion includes at least one switch module, switch module includes:

a first node and a second node;

A switching branch and a snubber branch connected in parallel between the first and second nodes, wherein the switching branch comprises a power electronic switch and the snubber branch comprises at least a capacitor; and

a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent.

2. A direct current energy dissipation system, comprising:

an energy consuming part comprising an energy consuming device; and

with power consumption portion series connection's switch portion, switch portion includes at least one switch module, switch module includes:

a first node and a second node;

a switching leg connected between the first node and a second node, the switching leg including a power electronic switch;

a protection module configured to protect the power electronic switch from overvoltage and/or overcurrent; and

a reverse current protection branch connected between the first node and the second node in anti-parallel with the switching branch to prevent reverse current from flowing through the switching branch.

3. The dc energy consuming system of claim 1 or 2, wherein the at least one switch module comprises a plurality of the switch modules connected in series with each other.

4. The direct current energy consuming system of claim 1 or 2, wherein the snubber branch is configured to snubber the voltage across the switch branch or across the switch in the switch branch and not pass direct current from the snubber branch.

5. The direct current energy consumption system of claim 1 or 2, wherein:

an end of the switching section remote from the energy consuming section is adapted to be connected to a direct current transmission line, and

the energy consuming part is configured to receive power from the direct current transmission line via the switching part.

6. The dc energy consuming system of claim 1 or 2, wherein the protection module is connected in parallel with the switching leg between the first node and the second node.

7. The direct current energy consumption system of claim 1 or 2, wherein the protection module comprises a metal oxide arrester (MOV).

8. The dc energy consuming system of claim 3, wherein, in the plurality of switch modules, the second node of an upstream switch module is coupled to the first node of a downstream switch module immediately adjacent thereto.

9. The direct current energy consumption system of claim 1 or 2, wherein:

the energy consuming device is a centralized resistive energy consuming device,

The energy consuming part is configured to be distant from the switching part so that heat generated from the energy consuming part does not affect the switching part.

10. The dc energy consuming system of any of claims 1-9, wherein the power electronic switch comprises a fully-controlled power electronic switch.

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