JP2005020878A - System linkage protection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system linkage protection device that can surely and easily detect and protect the single operation of a regular use generating set during system linkage at the side of the regular use generating set, without the need for arranging an expensive transfer breaker. <P>SOLUTION: The voltage of a synchronous motor 10 is largely changed by changing an output voltage downward when the rate of the frequency change of the synchronous motor 10 is positive, and changing the output voltage upward when the rate of the frequency change is negative, thus determining the single operation when the polarity of a voltage change rate and the polarity of a voltage oscillation signal coincide with each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grid interconnection protection device applied to a power generation device having a typical power generation device such as a garbage power generation system and cogeneration as a typical example.
[0002]
[Prior art]
Patent Document 1, Patent Document 2, and Patent Document 3 are known as devices for interconnecting and protecting a regular power generation device such as a garbage power generation system and cogeneration and an AC power system.
[0003]
A conventional example of such a grid interconnection protection device will be described with reference to FIG.
[0004]
In FIG. 5, in the upper substation 4 that is an AC power system, the voltage of the system power supply 1 is stepped down via the transformer 2, and the electric power from the upper substation 4 side is distributed to consumers through the circuit breaker 3. Electric power is supplied to the general consumer 7 by the electric wire 26. The general consumer 7 consumes electric power with the load 6B through the circuit breaker 5B.
[0005]
On the other hand, in the distributed power supply installation customer 9 in which the common power generator and the grid connection protection device 20 are installed, the output of the synchronous generator 10 driven by the prime mover 24 as the regular power generator is supplied to the circuit breaker 28 and the circuit breaker 12. It is connected to the upper substation 4 via
[0006]
Control of the output voltage of the synchronous generator 10 is performed by controlling the voltage of the field winding 23 of the synchronous generator 10 by means of an automatic voltage regulator (AVR) 22, and the control of the output frequency of the synchronous generator 10 is as follows: This is done by controlling the power of the prime mover 24 with a speed governor (not shown) of the prime mover 24 that drives the synchronous generator 10.
[0007]
In addition, the distributed power supply installation customer 9 receives power from the upper substation 4 via the circuit breaker 12 and the circuit breaker 5A, and receives power from the synchronous generator 10 via the circuit breaker 28 and the circuit breaker 5A. Receiving and loading (in-house load) 6A.
[0008]
On the other hand, the grid connection protection device 20 is provided with a current transformer 14 on the output side (substation side) of the circuit breaker 28 and an overcurrent detector that detects an overcurrent based on the output current of the current transformer 14. From the imbalance between the output power of the synchronous generator 10 and the load power of the load 6A when the (OC) 15 and the system power supply 1 are abnormal, especially when the system power supply 1 is interrupted by, for example, releasing the circuit breaker 3 And a voltage lowering relay (UF) 16, a frequency increasing relay (OF) 17, an overvoltage relay (OV) 18, and an undervoltage relay (UV) 19 for detecting that the voltage becomes abnormal. The fault trip circuit 13 is operated based on the detection signal, and a trip signal is output to release the circuit breaker 12 so that the circuit breaker 3 can be closed again.
[0009]
In addition to this, a current transformer 11 for detecting the output current is provided on the output side of the synchronous generator 10 as protection means for the generator, and based on the output current of the current transformer 11, the synchronous generator 10 An overcurrent relay (OC) 51 that detects an overcurrent, an overvoltage detector (OV) 52 and an undervoltage relay (UV) 53 that detect an output voltage abnormality of the synchronous generator 10, and a reverse power of the synchronous generator 10 A reverse power relay (RPR) 54 for detection is provided, and the fault trip circuit 27 is operated based on the detection signals of these protection relays to output a trip signal and release the circuit breaker 28.
[0010]
By the way, in such a grid connection protection device, for example, when an abnormality occurs in the system power supply 1 and the circuit breaker 3 is opened, the output power of the synchronous generator 10 and the required power of the loads 6A and 6B are: If both the effective part and the ineffective part are substantially equal, neither the frequency nor the voltage changes, so that none of the protective relays 15 to 19 operate and the operation is continued. This is a phenomenon called so-called islanding (islanding), which causes a problem of preventing reclosing of the circuit breaker 3.
[0011]
Therefore, conventionally, for the purpose of preventing such an isolated operation, a method of providing a transfer interruption device 8 connected by a dedicated line from the substation 4 and carrying out transfer interruption for the circuit breaker 12 has been adopted. There is something.
[0012]
That is, the transfer interrupting device 8 opens the circuit breaker 12 by sending a circuit breaker signal to the circuit breaker 12 when detecting the signal that the circuit breaker 3 of the upper substation 4 is opened.
[0013]
As an invention related to the transfer blocking device 8, there is, for example, Patent Document 4 shown below.
[0014]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-281673
[Patent Document 2]
[Patent Document 1] Japanese Patent Laid-Open No. 2002-281654
[Patent Document 3]
Japanese Patent Laid-Open No. 2002-291158
[Patent Document 4]
JP-A-7-59250 [0018]
[Problems to be solved by the invention]
However, this type of transfer interrupting device 8 is very expensive for a medium and small capacity utility power generator having an output of several hundred kW, and it is necessary to install transmission means and a transmission path. The merit of energy cost reduction by installing the power generation device cannot be obtained.
[0019]
An object of the present invention is to provide a grid interconnection capable of reliably and easily detecting and protecting a single operation of a regular power generator in a grid interconnection without providing an expensive transfer interruption device. It is to provide a protective device.
[0020]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the present invention provides a common system interconnection protection device for a regular power generator that is linked to an AC power system via a circuit breaker.
A frequency detector for detecting the frequency of the AC power system;
A frequency change rate detector for calculating a change rate of the frequency detected by the frequency detector;
Based on the frequency change rate, when the frequency change rate is positive, the output voltage of the common power generator is decreased, and when the frequency change rate is negative, the voltage fluctuation is increased to increase the output voltage of the common power generator. A voltage fluctuation signal calculation unit for outputting a dynamic signal;
A plurality of threshold values according to the frequency change rate, and a gain switching means for switching the gain of the voltage fluctuation signal every time each threshold value is exceeded;
A voltage change rate detector for detecting the change rate of the output voltage of the regular power generator;
When the voltage fluctuation signal calculated by the voltage fluctuation signal calculation unit is applied to an automatic voltage regulator provided in the normal power generator, the voltage change rate of the normal power generator exceeds a predetermined value, and the voltage fluctuation signal And a protection means for releasing the circuit breaker and disconnecting the common power generator from the AC power system when the polarity of the voltage change rate is the same.
[0021]
In the grid interconnection protection device according to the present invention, the frequency change rate of the common power generator is detected, and when the frequency change rate is positive, the output voltage of the common power generator is changed in the downward direction, and the frequency change rate is negative. In this case, the voltage of the common power generator is changed in the upward direction. When the voltage of the generator changes greatly and the polarity of the voltage change rate and the polarity of the voltage fluctuation signal are the same, it is determined that the operation is independent. Without the need for an expensive transfer interruption device as in the past, it is possible to reliably and easily detect the independent operation of the utility power generator in the grid connection on the utility power generator side, and disconnect the utility power generator. It becomes possible to protect.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment, corresponding to claims 1 and 2)
Hereinafter, an embodiment corresponding to claim 1 of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 is a diagram illustrating a configuration example of a grid interconnection protection device according to the present embodiment. The same parts as those in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted. Only different parts will be described here.
[0024]
As shown in FIG. 1, the distributed power supply installation customer 9 ′ of this embodiment includes a grid interconnection protection device 29. The system interconnection protection device 29 is different from the conventional system interconnection protection device shown in FIG. 5 in that the expensive transfer cut-off device 8 described above is omitted and the frequency for detecting the frequency from the output of the synchronous generator 10 is detected. A detector 41, a frequency change rate detector 42, a change rate excess first determination unit 43 that detects a change rate of the frequency output from the frequency detector 41, and a voltage fluctuation signal that is a voltage fluctuation signal generating means. The calculation unit 44, the voltage change rate detector 48, and the change rate excessive second determination unit 49 are newly provided.
[0025]
Now, assuming that the active power of the output from the synchronous generator 10 is P, the reactive power is Q, the active power required by the loads 6A and 6B is PL, and the reactive power is QL, the active power ΔP flowing out to the system power supply 1 and The reactive power ΔQ is expressed as follows, respectively.
[0026]
ΔP = P-PL
ΔQ = Q-QL
Here, the voltages of the loads 6A and 6B are V and the frequency is f.
[0027]
Then, in the normal case, the voltage V and the frequency f of the loads 6A and 6B hardly change even when the circuit breaker 3 is opened in a state close to ΔP≈0 and ΔQ≈0. The protective relays 15 to 19 cannot detect the single operation of the synchronous generator 10 and continue the single operation.
[0028]
On the other hand, in this embodiment, the independent operation of the synchronous generator 10 can be detected by adding the detectors 41 to 49 without the transfer blocking device.
[0029]
FIG. 2 is a simplified diagram based on FIG. 1, and the same components as those in FIG. The load 6 is a load obtained by combining the load 6A and the load 6B, and represents the entire load existing in the distribution system. Therefore, PL and QL are electric power consumed by the load 6.
[0030]
In FIG. 2, the active power PL of the load 6 is PL = V2 / R (1)
(V: Voltage, R: Resistance value)
It is represented by
[0031]
The voltage fluctuation signal calculation unit 44 incorporates a function as shown in FIGS. 3A and 3B as an example. Based on the frequency change rate detected by the frequency change rate detector 42, The voltage fluctuation signal is calculated so as to promote the change, and the voltage fluctuation signal is given to the automatic voltage regulator 22 of the synchronous generator 10. (ΔV *: voltage fluctuation signal, df / dt: frequency change rate)
The voltage fluctuation signal calculation unit 44 initially determines a voltage fluctuation signal to be given to the automatic voltage regulator 22 according to the frequency change rate by the function of FIG.
[0032]
Here, a case where the frequency slightly decreases during the independent operation of the synchronous generator 10 is considered. The frequency change rate is a negative number and a very small value.
[0033]
At this time, the voltage fluctuation signal calculation unit 44 outputs a voltage fluctuation signal so that the voltage of the synchronous generator 10 is slightly increased. The voltage rises by the action of the automatic voltage regulator 22.
[0034]
Then, since the active power PL of the load represented by the above equation (1) increases, the torque of the load increases and acts on the rotational speed of the synchronous generator 10, that is, the frequency decreases. A positive feedback action of lowering is formed, increasing the frequency variation.
[0035]
The frequency fluctuation due to the voltage fluctuation signal increases as the voltage fluctuation signal increases.
[0036]
In order to determine whether the distributed power supply is operating alone or in a grid connection, it is preferable to provide a voltage fluctuation signal that causes sufficient frequency fluctuations when the system is operated independently. There is a concern that giving a large voltage fluctuation signal becomes a factor causing disturbance to the system.
[0037]
Therefore, at first, as an example, as shown in FIG. 3A, a voltage fluctuation signal having a small level that does not adversely affect the system is used.
[0038]
When the frequency change rate reaches a certain level and the frequency change rate excess is detected by the first change rate excess first determination unit 43, the voltage fluctuation signal calculation unit 44 determines whether the automatic voltage regulator 22 is in accordance with the frequency change rate. Is switched to a voltage fluctuation signal based on a function as shown in FIG. This acts as a means for switching the gain of the voltage fluctuation signal with respect to the frequency change rate. When the frequency change rate increases, the voltage fluctuation signal is increased to increase the voltage and frequency fluctuations quickly.
[0039]
The voltage change rate detector 48 calculates the change rate dv / dt of the generator voltage. The change rate excessive second determination unit 49 receives the change rate dv / dt of the generator voltage and the voltage fluctuation signal ΔV *, and the absolute value of dv / dt is equal to or greater than a predetermined set value dv1. When the polarities of dt and ΔV * are the same, it is determined that the single operation is performed.
[0040]
If the voltage command to the automatic voltage regulator 22 is fluctuated during grid connection, the voltage is maintained by the system power source 1 so that the generator voltage does not fluctuate very much. The generator voltage fluctuates greatly in the opposite direction. This makes it possible to determine the isolated operation.
[0041]
If it is determined that the vehicle is operating alone, an abnormal signal V31 is output.
[0042]
In the fault trip circuit 13, the circuit breaker 12 is operated to be disconnected by the abnormal signal V31, and the synchronous generator 10 is disconnected.
[0043]
This makes it possible to detect an isolated operation on the side of the regular power generation device without using the transfer interruption device 8 that has been used conventionally.
[0044]
As described above, in the grid interconnection protection device according to the present embodiment, the frequency change rate df / dt of the synchronous generator 10 of the regular power generator is detected, and when the frequency change rate is positive, the synchronous generator 10 When the frequency change rate is negative, the voltage of the synchronous generator 10 is changed in the upward direction, the generator voltage changes greatly, and the polarity of the voltage change rate Since it is determined that the operation is independent when the polarity of the voltage fluctuation signal is the same, the independent operation of the common power generator in the grid connection is not provided without providing the expensive transfer interruption device 8 as in the conventional case. Can be detected reliably and easily on the side of the common power generator, and the synchronous generator 10 can be disconnected and protected.
[0045]
(Second embodiment, corresponding to claim 3)
FIG. 4 is a diagram illustrating a configuration example of the grid interconnection protection device according to the present embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. Only different parts will be described here.
[0046]
As shown in FIG. 4, the distributed power supply installation customer 9 ″ of this embodiment includes a grid interconnection protection device 29 ′. This grid connection protection device 29 ′ is newly provided with a change rate excess third determination unit 50 and a logical product calculation unit 47.
[0047]
The excessive change rate third determiner 50 determines whether or not the absolute value of the change rate df / dt of the generator frequency is equal to or greater than a predetermined set value D2, and outputs V03 if it seems to be an isolated operation if the condition is satisfied. To do.
[0048]
The change rate excessive second determination unit 49 receives the change rate dv / dt of the generator voltage and the voltage fluctuation signal ΔV *, and the absolute value of dv / dt is equal to or greater than a predetermined set value dv1. It is determined whether or not the polarities of dt and ΔV * are the same, and if the condition is satisfied, V02 is output because it seems to be an independent operation. Here, D2 is set to a value larger than D1, which is the threshold value of the change rate excess first determination unit 43.
[0049]
The logical product calculator 47 calculates the logical product of V02, which is the estimated output of the isolated operation as seen from the rate of change of the generator voltage, and V03, which is the estimated output of the isolated operation as seen from the rate of change of the generator frequency. Here, each of V02 and V03 is an estimated output alone, but by taking the logical product of the two estimated outputs, it is possible to obtain an almost deterministic determination result that exceeds the estimation for the determination of the isolated operation. Based on the above, the AND operator 47 outputs an abnormal signal V31.
[0050]
In the fault trip circuit 13, the circuit breaker 12 is operated to be disconnected by the abnormal signal V31, and the synchronous generator 10 is disconnected.
[0051]
This makes it possible to detect an isolated operation on the side of the regular power generation device without using the transfer interruption device 8 that has been used conventionally.
[0052]
As described above, in the grid interconnection protection device according to the present embodiment, the frequency change rate df / dt of the synchronous generator 10 of the regular power generator is detected, and when the frequency change rate is positive, the synchronous generator 10 When the frequency change rate is negative, the voltage of the synchronous generator 10 is changed in the upward direction. The voltage change rate of the generator is greater than a predetermined value, and the voltage change rate is And the polarity of the voltage fluctuation signal are the same, and the frequency change rate becomes larger than a predetermined value, it is determined that the single operation is performed. Without the provision, it is possible to reliably and easily detect the independent operation of the common power generator in the grid connection on the side of the common power generator and to disconnect and protect the synchronous generator 10.
[0053]
The second embodiment is different from the first embodiment in that the frequency change rate is larger than a predetermined value in addition to the voltage change rate, which is added to the determination condition for the isolated operation. There is an advantage that false detections are reduced by the increase of the determination condition from one to two.
[0054]
In each embodiment mentioned above, although the synchronous generator driven by the motor | power_engine in a refuse power generation system, cogeneration, etc. was illustrated as a regular power generator, it is not limited to this.
[0055]
Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention at the stage of implementation. In addition, the embodiments may be appropriately combined as much as possible, and in that case, combined effects can be obtained. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, when an invention is extracted by omitting some constituent elements from all the constituent elements shown in the embodiment, when the extracted invention is implemented, the omitted part is appropriately supplemented by a well-known common technique. It is what is said.
[0056]
【The invention's effect】
As described above, according to the grid interconnection protection device of the present invention, it is possible to reliably detect the single operation of the regular power generation device in the grid interconnection on the regular power generation device side without providing an expensive transfer cutoff device, The generator can be quickly disconnected from the grid and protected.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a system interconnection protection device according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining an operation in the grid interconnection protection device according to the first embodiment;
FIG. 3 is a diagram showing an example of a function for determining a voltage fluctuation signal in the system interconnection protection device according to the first embodiment;
FIG. 4 is a configuration diagram showing a system interconnection protection device according to a second embodiment of the present invention.
FIG. 5 is a configuration diagram of a conventional grid connection protection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... System power supply, 2 ... Transformer, 3, 5A, 5B, 12, 28 ... Circuit breaker, 4 ... Upper substation, 6, 6A, 6B ... Load, 7 ... General customer, 8 ... Transfer interruption device, 9 ... distributed power installation customers, 10 ... synchronous generators, 11, 14 ... current transformers, 13, 27 ... fault trip circuits, 15, 51 ... overcurrent relays, 16 ... frequency drop relays, 17 ... frequency boost relays, 18 , 52 ... Overvoltage relay, 19, 53 ... Undervoltage relay, 20, 29 ... Grid connection protection device, 22 ... Automatic voltage regulator, 23 ... Field winding, 24 ... Motor, 26 ... Distribution line, 41 ... Frequency Detector: 42 ... Frequency change rate detector, 43 ... Change rate excessive first determination unit, 44 ... Voltage fluctuation signal calculation unit, 47 ... Logical product calculator, 48 ... Voltage change rate detector, 49 ... Change rate excessive Second decision unit, 50 ... third rate decision unit with excessive change rate, 54 ... reverse power relay .

Claims (3)

In the regular system interconnection protection device of the regular power generator connected to the AC power system through the circuit breaker,
A frequency detector for detecting the frequency of the AC power system;
A frequency change rate detector for calculating a change rate of the frequency detected by the frequency detector;
Based on the frequency change rate, when the frequency change rate is positive, the output voltage of the common power generator is decreased, and when the frequency change rate is negative, the voltage fluctuation is increased to increase the output voltage of the common power generator. A voltage fluctuation signal calculation unit for outputting a dynamic signal;
A plurality of threshold values according to the frequency change rate, and a gain switching means for switching the gain of the voltage fluctuation signal every time each threshold value is exceeded;
A voltage change rate detector for detecting the change rate of the output voltage of the regular power generator;
When the voltage fluctuation signal calculated by the voltage fluctuation signal calculation unit is applied to an automatic voltage regulator provided in the normal power generator, the voltage change rate of the normal power generator exceeds a predetermined value, and the voltage fluctuation signal And a protection means for releasing the circuit breaker and disconnecting the common power generator from the AC power system when the polarity of the voltage change rate is the same. The grid connection protection device according to claim 1, wherein the regular power generation device includes a synchronous generator driven by a prime mover. When the voltage change rate exceeds a predetermined value, the polarity of the voltage fluctuation signal and the voltage change rate are the same, and based on the frequency change rate, the frequency change rate exceeds a predetermined threshold, The system interconnection protection device according to claim 1, further comprising a protection unit that releases the circuit breaker and disconnects the common power generator from the AC power system.

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