JP2000308362A - Power system failure detecting method and system incorporating inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To momentarily detect a failure to control abnormal rise of incorporating point voltage in view of obtaining more safe system incorporating inverter, by detecting an incorporating point current in the primary side of a system switch and then determining generation of an accident in regard to the power system based on the result of detection of the incorporating point current. SOLUTION: A system incorporating inverter is provided with a current detector 16 for detecting an incorporating point current Iac, and a power system accident detecting circuit 17 for detecting an accident in regard to the power system 7 based on the result of detection of an incorporating point current Iac. Moreover, the power system accident detecting circuit 17 is connected to a gate block circuit 15. If an accident is generated in the power system 7, an incorporating point current Iac is detected with a current detector 16, an accident detecting circuit 17 such as an ammeter determines an accident of the power system 7 depending on the theory and an irregular signal is outputted to a gate block circuit 15 to immediately stop the operation of a power converter 2. Accordingly, the power converter 2 can be stopped within a short period of time without delay from generation of accident.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection inverter device for converting DC power of a DC power supply into AC power and supplying the AC power to a power system.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional system interconnection inverter device. In this figure, DC power generated from a DC power supply 1 such as a solar cell is converted into AC power by a power converter 2. The power converter 2 and the power system 7 are interconnected by the interconnection switch 6 via the reactor 4 and the capacitor 5.
Note that the output current Is of the power converter 2 is equal to the current detector 3
Is to be detected.

In such a circuit, various detectors are usually provided in addition to the current detector 3 described above. That is, a voltage detector 8 for detecting the output voltage Vdc of the DC power supply 1, a voltage detector 9 for detecting the system voltage Vs, a zero-cross detector 10 for detecting the system voltage phase θ, and the like.

The detectors 3, 8, 9, 10
In addition, a current command calculator 11 that calculates an AC current command value Is ^* from the voltage Vdc and the system voltage phase θ, and an error amount between the current command value Is ^* and the output current Is of the power converter 2 described above Current control circuit 1 for calculating command value to decrease
2 is provided, and a value output from the current control circuit 12 is subjected to PWM pulse modulation by the gate drive circuit 13 and transmitted to the power conversion device 2. Therefore, the power conversion device 2 is controlled so as to always perform proper conversion, and the DC power is converted into a desired AC power and output to the power system 7 by a series of operations of these devices. It has become.

By the way, assuming that a disconnection accident or the like occurs in the power system 7 during the interconnection operation of the above-structured interconnection inverter device, the interconnection switch 6 is opened in an electric circuit diagram. It is equal to that. Interconnection switch 6
Is in an open state, the output current Is of the power converter 2 sharply decreases. When Is decreases, the amount of error with the current command value Is ^* increases, so that the PWM pulse becomes a signal in the direction of increasing Is. Therefore, the interconnection point voltage of the system interconnection inverter device (primary voltage of interconnection switch 6; the same applies hereinafter)
Rises rapidly, increasing the likelihood of damage to equipment within the device.

In order to avoid such a situation, in a conventional example, as shown in FIG.
4 and a gate block circuit 15 for invalidating the PWM pulse signal of the gate drive circuit 13 in response to the abnormal signal generated by the circuit 14 (in the conventional apparatus, the system voltage abnormality detection circuit is used). In general, there are various abnormality detection circuits such as a current and a frequency other than 14, but their description is omitted for simplicity).

[0007] Then, the connection point voltage is constantly observed using the system voltage detector 9, and when the connection point voltage level reaches an abnormal overvoltage level, an abnormal signal is generated from the system voltage abnormality detection circuit 14 and the gate is detected. A method has been adopted in which the PWM pulse signal of the gate drive circuit 13 is invalidated by the block circuit 15 and the operation of the power conversion device 2 is stopped.

[0008]

However, in such a method, even if a disconnection accident or the like occurs in the power system 7, there is a time delay before the interconnection point voltage reaches an abnormal level. The power converter 2 cannot be stopped immediately,
Meanwhile, the interconnecting switch 6 is open (equivalent to being open)
In some situations, normal operation was performed. In such a case, even if the power conversion device 2 is stopped when the interconnection point voltage reaches an abnormal level, the interconnection point voltage is reduced by the electric power stored in the reactor 4 and the capacitor 5 during the above-described delay time. There is a problem that the breakdown voltage may exceed the abnormal level and exceed the breakdown voltage of the device. That is, there is a high possibility that an abnormal rise of the interconnection point voltage during the delay time is caused, and there is a great possibility that the equipment and load of the device are adversely affected.

The present invention has been made in view of the above circumstances, and an object thereof is to detect an accident occurring in an electric power system instantaneously, suppress an abnormal rise of an interconnection point voltage, and achieve a more secure operation. It is to provide a simple system interconnection inverter device.

[0010]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the power system accident detection method according to claim 1 converts a DC power generated from a DC power supply into an AC power and outputs the AC power to a power system via a connection switch. The present invention is characterized in that a connection point current on the primary side of the connection switch is detected, and based on a detection result of the connection point current, it is determined whether or not an accident has occurred in the power system.

According to this, in the electric power system, for example, when an accident such as disconnection occurs, the event that the link point current stops flowing is used. In other words, if the detection result of the link point current Iac is Iac = 0, it is known that an accident of the power system has occurred indirectly, and appropriate measures (for example, suspension of power conversion) are performed based on the fact. Becomes possible. Incidentally, it is needless to say that the present invention is not limited to the above-described example, and is applicable to, for example, a case where an abnormal current value that cannot be normally seen is observed.

A power system fault detection method according to a second aspect is characterized in that, in the first aspect, the detection of the link point current is performed in synchronization with a PWM control cycle.

According to this, the detection of the link point current can be performed "instantly". That is, the above “appropriate treatment” can be performed instantaneously.

According to a third aspect of the present invention, there is provided a power system fault detection method according to the first or second aspect, wherein when the detected value of the link point current continuously falls below a certain value for a certain period of time. And determining that an accident relating to the power system has occurred.

According to this, when an accident such as a disconnection occurs in the electric power system, the state in which the link point current becomes 0 generally continues. In view of the above, the fact that such an event is detected and the occurrence of an accident in the power system can be considered logically. It is possible to carry out various measures.

In addition, the power system fault detection method according to claim 4 is the method according to any one of claims 1 to 3, wherein the detection of the connection point current, its level and cycle, the predetermined period, It is characterized in that the constant values are variable from time to time and are determined automatically.

According to this, it is possible to appropriately set the detection mode of the link point current to contribute to the determination as to whether or not an accident has occurred in the power system. For example, when the state in which the link point current is 0 according to the above example is continued for a certain period of time, if the accident is determined to be “occurred”, the method may convert the DC power into the AC power in the first place. Considering that there is always a moment when the AC power becomes 0 when viewed along time in the AC power, it should be noted that the above-mentioned "certain period" must be determined with due consideration. According to the invention, this "appropriate consideration" is meant to be made automatically.

Finally, the grid-connected inverter device according to claim 5 converts DC power generated from a DC power supply into AC power by a power converter, and converts the AC power to a power system via a connection switch. In the output system interconnection inverter device, a current detector for detecting an interconnection point current on the primary side of the interconnection switch, and determining whether or not an accident has occurred in the power system based on the detection result of the interconnection point current. A power system fault detection circuit; and a gate block circuit that stops operation of the power conversion device when a signal indicating that the fault has occurred is output from the power system fault detection circuit. .

This device can be said to be a system interconnection inverter device that is the most suitable form for realizing the power system fault detection method according to any one of the first to fourth aspects.
Note that the present device is provided with a gate block circuit that stops the operation of the power conversion device when the power system fault detection circuit determines that a fault has occurred. In other words, "appropriate measures" in the operations described in claims 1 to 4 means "stopping the power conversion device" in the case of the present invention.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a preferred embodiment of a system interconnection inverter device according to the present invention. In the following description, the same reference numerals will be used for the same reference numerals in the drawings (FIG. 2) referred to in the description of the conventional example and the same reference numerals in the drawings referred to in the present embodiment. The description will be made with reference to FIG.

The grid-connected inverter device according to the present embodiment includes a DC power supply 1 such as a solar cell, a power converter 2 for converting DC power generated from the DC power supply 1 into AC power,
The power conversion device 2 and the power system 7 are completely the same as the conventional example in that the power conversion device 2 is provided with a connection switch 6 that links the power conversion device 2 and the power system 7 via the reactor 4 and the capacitor 5.

A current detector 3 for detecting the output current Is of the power converter 2, a voltage detector 8 for detecting the output voltage Vdc of the DC power supply 1, and a voltage detector 9 for detecting the system voltage Vs , A zero-cross detector 10 for detecting the system voltage phase θ, etc., and a current command calculator 11 for calculating an AC current command value Is ^* from the voltage Vdc and the system voltage phase θ. Current control circuit 1 for calculating a command value such that an error amount between current command value Is ^* and output current Is of power conversion device 2 described above is reduced.
2. A point that a gate drive circuit 13 for PWM-modulating a value output from the current control circuit 12 and transmitting the value to the power conversion device 2 is provided, and a system voltage abnormality detection circuit 14
The same applies to the point that a gate block circuit 15 for invalidating the PWM pulse signal of the gate drive circuit 13 in response to the abnormal signal generated from the circuit 14 is provided.

The system interconnection inverter device according to the present embodiment has the following characteristic components in addition to the above components. First, as shown in FIG. 1, a current detector 16 for detecting a connection point current Iac is provided.
Further, based on the detection result of the interconnection point current Iac, the power system
A power system fault detection circuit 17 for detecting a fault related to the power system is also provided. Then, the power system accident detection circuit 17
Are connected to the gate block circuit 15 described above. Note that the “coupling point” here means “primary side as viewed from the interconnection switch 6”. For this reason, in the present embodiment, the term “coupling point current” or the like naturally refers to the “primary voltage of the interconnection switch 6” or the like.

Hereinafter, the operation and effect of the system interconnection inverter device of the present embodiment having the above configuration will be described. Normally, the various detectors 3, 8, 9, and 10, the current command calculator 11, the current control circuit 12, and the gate drive circuit 13
For example, the power converter 2 is controlled so as to always perform proper conversion, and the DC power generated from the DC power supply 1 is converted into a desired AC power and output to the power system 7. Further, at this time, since an AC current synchronized with the system voltage Vs flows through the interconnection point, a current value near 0 A is not continuously detected.

Here, if a disconnection accident or the like occurs in the electric power system 7 (equivalent to a state in which the interconnection switch 6 is open in terms of an electric circuit), the interconnection point current I
ac becomes 0A instantaneously, and the state continues. Therefore, if the interconnection point current Iac is sampled at a very high speed by the current detector 16, if the resulting sampled value is continuously within a certain level range for a certain period, an accident may occur in the power system 7. Can be considered as having occurred.

The power system fault detection circuit 17 determines whether or not a fault has occurred in the power system 7 according to the above logic, and outputs an abnormal signal to the gate block circuit 15 if it is determined that a fault has occurred. To immediately stop the operation of the power converter 2. Note that the sampling cycle that requires a certain period of time to determine a system fault is very short because it is synchronized with the PWM control cycle of 50 μs.
c is detected “instantly”, and therefore, when an abnormality occurs, the power converter 2 can be stopped “instantly”.

Incidentally, the zero cross of the normal alternating current is
In order to prevent erroneous detection of an accident in the power system 7, control for automatically changing a certain period and a detection level for the accident detection based on the output of the inverter device can be performed.

As described above, according to the system interconnection inverter device of the present invention, it is possible to detect the occurrence of a system failure without delay and stop the power conversion device 2 in a short time after the occurrence of the failure. Will be possible. As a result, a voltage increase of the interconnection point voltage can be suppressed, and more secure interconnection operation can be performed.

[0029]

As described above, the method for detecting a power system fault according to claim 1 detects a connection point current at the primary side of the connection switch, and based on the detection result, detects a fault in the power system. Judgment is made as to whether or not a fault has occurred.If, for example, a fault such as a disconnection occurs and the detection result of the link point current is continuously 0, a fault in the power system occurs indirectly from this fact. I understand that
Based on this, it is possible to perform an appropriate action (for example, stop power conversion). In addition, the link between the link point current and the occurrence of an accident relating to the power system realizes not only that an appropriate judgment can be made but also quick judgment when considering that the latter change is directly reflected in the former. be able to.

In the power system fault detection method according to the second aspect, the detection of the link point current is performed in synchronization with a PWM control cycle, so that the detection of the link point current can be performed “instantly”. As a result, the above “appropriate treatment” is also performed instantaneously. In other words, the determination of the presence or absence of an accident is higher than in the case of "swiftly" and is performed instantaneously, so that an event such as an abnormal rise of the link point voltage is generated as in the related art. The danger can be almost completely eliminated.

According to a third aspect of the present invention, in the method for detecting a power system fault, when the detected value of the link point current continuously falls below a certain value for a certain period of time, it is determined that an accident concerning the power system has occurred. From the judgment, when an accident such as disconnection occurs in the power system, it is usually said that such an event is detected in consideration of the fact that the state where the link point current becomes 0 continues, and The occurrence of an accident may be logically linked, and it is possible to judge the presence or absence of an appropriate occurrence of an accident, and to carry out the above-described appropriate measures accordingly.

[0032] A method for detecting a power system accident according to claim 4 is as follows.
The detection of the connection point current, its level and cycle, the certain period, the certain value is variable at any time, and these are automatically determined, so that it is possible to contribute to the determination as to whether or not an accident has occurred in the power system. Detection mode of the connection point current
It can be set to a suitable state as appropriate. For example, a situation in which 0 detection inevitably observed in AC power is erroneously determined as an “occurrence” of a power system accident is avoided.

The system interconnection inverter device according to claim 5 can be said to be a device most suitable for realizing the power system accident detection method according to any one of claims 1 to 4. In this device, when the power system fault detection circuit determines that a fault has occurred, the power converter is stopped by the operation of the gate block circuit.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a grid interconnection inverter device according to the present invention.

FIG. 2 is an explanatory diagram showing an outline of a conventional system interconnection inverter device.

[Explanation of symbols]

 Reference Signs List 1 DC power supply 2 Power conversion device 3 Current detector (for detecting output current Is) 4 Reactor 5 Capacitor 6 Interconnection switch 7 Power system 8 Voltage detector (for detecting output voltage Vdc of DC power supply 1) 9 Voltage detector ( System voltage Vs detection) 10 Zero cross detector 11 Current command calculator 12 Current control circuit 13 Gate drive circuit 14 System voltage abnormality detection circuit 15 Gate block circuit 16 Current detector (for detection of connection point current Iac) 17 Power system accident detection circuit

Continuation of the front page (72) Inventor Satoshi Matsuda 1 Takamichi, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi F-term in Nagoya Machinery Works, Mitsubishi Heavy Industries, Ltd. F-term (reference) 5H007 AA06 AA17 CA01 CB04 CC03 CC32 DB01 DC02 DC04 EA02 FA14 FA19 GA08

Claims (5)

[Claims] 1. A system interconnection inverter device that converts DC power generated from a DC power supply into AC power and outputs the AC power to a power system via an interconnection switch. Detect the interconnection point current on the primary side,
A method for detecting a power system fault, comprising determining whether or not a fault has occurred in the power system based on a detection result of the link point current. 2. The method according to claim 1, wherein the detection of the link point current is performed in synchronization with a PWM control cycle. 3. The method according to claim 1, wherein the detected value of the link point current is a predetermined period,
The power system fault detection method according to claim 1 or 2, wherein it is determined that an accident related to the power system has occurred when the power system continuously falls below a certain value. 4. The method according to claim 1, wherein the detection of the connection point current, its level and cycle, the constant period, and the constant value are variable at any time and are automatically determined. The power system accident detection method described in 5. A system interconnection inverter device which converts DC power generated from a DC power supply into AC power by a power converter and outputs the AC power to a power system via a connection switch. A current detector for detecting a connection point current on the primary side of the power supply, a power system fault detection circuit for determining whether or not a fault has occurred in the power system based on the detection result of the connection point current; and the power system fault detection circuit. And a gate block circuit for stopping the operation of the power conversion device when a signal indicating that the accident has occurred is output from the system.