JPH09247863A - Reactive power compensator for protecting system interconnection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely defect an islanding state without selecting a variation frequency for the reactive power unit or using an expensive transmission breaking device and realize reliable protective function without a decrease in detective sensitivity caused by mutual interference of a reactive power unit. SOLUTION: When an islanding state takes place, a change in frequency at linkage points is detected by control units 45 to 49, and a reactive power reference value is adjusted under control in such a way as to increase the frequency change. A reactive power compensating unit 40 generates reactive power to cause a hunting state, in which frequency at the linkage point fluctuates in a given frequency cycle near to a rated frequency. Under these conditions, protective operation can be carried out by opening breakers 6 and 63 between the linkage point and a non-utility generator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive power compensator used in a private power generation facility connected to a grid, and particularly when a power supply from the grid side is stopped, a breaker on the private power generation facility side is opened. The present invention relates to a system interconnection protection reactive power compensator for performing a protection operation.

[0002]

2. Description of the Related Art There is a case where a private power generation facility such as a garbage power generation system, a cogeneration system, a fuel cell, or a solar power generation system is operated in an interconnected manner. When a general consumer uses this type of private power generation equipment, a grid interconnection protection system as shown in FIG. 7 is used.

This conventional device shows an example of a private power generation facility using a turbine. An AC generator 7 is connected to a turbine 10 driven by a speed governor 11 at a constant speed (synchronous speed) to generate electric power. The output of the AC generator 7 is connected to the power supply system for the general consumers of the substation 39 via the circuit breaker 6. The substation 39 steps down the AC voltage of the grid 1 via the transformer 2 and feeds it to the power supply grid for general consumers via the circuit breaker 3.

The governor 11 controls the output of the turbine 11 so that the frequency of the AC voltage output from the AC generator 7 is synchronized with the frequency of the AC voltage of the grid 1, and an automatic voltage regulator (AVR) 9 Controls the exciting current supplied to the field winding 8 of the AC generator 7 so as to obtain a desired output voltage. When the abnormality detection circuit 13 detects an abnormality in the generator from the relationship between the output voltage of the AC generator 7 and the output current of the AC generator 7 detected via the current transformer 12, the abnormality detection circuit 13 outputs the abnormality trip circuit 20. To open the circuit breaker 6.

In addition to this, the output side of the circuit breaker 6 (substation side)
Current transformer 14, overcurrent relay (OC) for detecting overcurrent of
19, frequency lowering relay (U
F) 15, frequency rising relay (OF) 16, protective means such as overvoltage relay (OV) 17 for detecting voltage abnormality, undervoltage relay (UV) 18, etc., and when the system is abnormal, for example, the circuit breaker 3 is opened. When this occurs, it detects that the frequency or voltage output from the AC generator 7 becomes abnormal, and opens the circuit breaker 6 through the fault trip circuit 20 by these detection signals to protect the load 5 and shut it off. A protective action is made to enable reclosing of the device 3.

When the output power of the AC generator 7 and the power consumption of the load 5 are substantially equal to each other in active power and reactive power, when the circuit breaker 3 on the substation side is opened, the frequency and the voltage may hardly change. In some cases, none of the relays 15 to 19 operate, and the power generation equipment for private use continues to operate independently, so-called a phenomenon of islanding occurs, and the circuit breaker 3 is prevented from reclosing. In order to prevent such an islanding, when the circuit breaker 3 on the substation side is opened, a transfer circuit breaker that sends a cutoff signal from the substation side to the private power generation equipment side via a dedicated line to open the circuit breaker 6 In some cases, the method of providing 38 is adopted. However, the transfer blocking device 38 described above may be effective when the substation is distant or when there are many customers, but the cost is high for a small-to-medium-capacity private power generation facility with an output of several hundred KW. , There are few practical advantages due to grid interconnection.

Therefore, the oscillator 41 causes 0.2 to 1 Hz.
When the reactive power device 40 that supplies a predetermined reactive power that changes in a cycle of about a degree to the interconnection point of the private power generation equipment is connected and the islanding state is reached, the frequency is changed by the change of the reactive power and the frequency fluctuation When the fluctuation amount of the frequency detected by the detection circuit 42 exceeds a predetermined level, the level detector 43 detects the islanding state, outputs a trip signal, and outputs the trip signal to the circuit breaker 6 via the fault trip circuit 20.
Has been proposed so that the protection operation is performed without using the transfer blocking device 38.

[0008]

However, in the conventional method, since the detection sensitivity changes depending on the fluctuation frequency of the reactive power, it is necessary to perform the simulation to determine the optimum fluctuation frequency. When there are multiple private power generation facilities in the separated grid when the islanding state occurs, the effect should be canceled depending on the phase of the fluctuation frequency of the reactive power supplied from each reactive power device. Can be considered. The present invention has been made based on such a circumstance, and an object of the present invention is to provide an expensive transfer interruption device,
Moreover, it is not necessary to select the fluctuating frequency of the reactive power device, and there is no risk of detection sensitivity deterioration due to mutual interference of the reactive power devices, and it is possible to reliably detect the islanding state and perform highly reliable protection operation. An object is to provide a protective reactive power compensator.

[0009]

The reactive power compensator for grid interconnection protection of the present invention is connected to the interconnection point of a private power generation facility that is interconnected to the grid, and when the private power generation facility is disconnected from the grid. , A reactive power compensator for supplying reactive power so as to generate a hunting state in which the frequency of the voltage at the interconnection point increases and decreases at a predetermined cycle before and after the rated frequency, and based on this hunting state, the interconnection point and Protective action to open the circuit breaker between private power generation facilities. (Claim 1) Furthermore, a reactive power standard is corrected so as to promote the frequency change based on the frequency change at the interconnection point, and a control unit for controlling the reactive power based on the reactive power standard is provided, and private power generation is provided. When the equipment is disconnected from the grid, the reactive power causes the frequency control system to be in an unstable state and causes the hunting state. (Claim 2) Further, the control unit controls the reactive power compensator so as to increase the forward reactive power when the frequency change rate is positive and increase the delayed reactive power when the frequency change rate is negative. To do. (Claim 3) Furthermore, the said control part is provided with the function generation part which outputs a correction signal based on a frequency change rate, and corrects a reactive power reference | standard by adding this correction signal to the said reactive power reference | standard. (Claim 4) Further, the function generator outputs a correction signal proportional to the frequency change rate. (Claim 5) Further, the function generating section outputs a correction signal in which a constant bias having a polarity corresponding to the polarity of the frequency change rate is added to a value proportional to the frequency change rate. (Claim 6) Furthermore, when the frequency change rate exceeds a predetermined level, the control section outputs a signal for performing a protection operation.
A level detector is provided, and the frequency change rate is set to exceed a predetermined level in the hunting state. (Claim 7) Further, the control unit includes a second level detection unit that integrates the frequency change rate and outputs a signal for performing a protection operation when the integrated value exceeds a predetermined level, and the hunting state. At, the integrated value is set to exceed a predetermined level. (Claim 8) Further, the control unit outputs a correction signal based on a frequency change rate, a function unit that amplifies the correction signal and limits the maximum value thereof, and a voltage at the interconnection point. , A determination unit that estimates that the private power generation facility is disconnected from the grid from a change in frequency, corrects the reactive power reference based on a correction signal output from the calculation unit, and the determination unit is the private power generation. When it is estimated that the equipment is disconnected from the system, the amplification factor of the arithmetic unit is increased, or the value limiting the maximum value of the correction signal is increased, or the amplification factor of the arithmetic unit is increased and the maximum correction signal is increased. Increase the value to limit the value. (Claim 9) Furthermore, the control unit includes a frequency detection unit that detects a frequency at an interconnection point through a filter having a high gain characteristic in a predetermined frequency range including a rated frequency, and detects a detection sensitivity near the rated frequency. Increase. (Claim 10) Furthermore, the filter has a characteristic that the phase advances as the frequency increases in a predetermined frequency range including the rated frequency, and the phase delays as the frequency increases in a range other than the predetermined frequency range. The phase deviation between the voltage phase detected through the voltage phase and the voltage phase at the interconnection point is added to the frequency change rate detection value to increase the frequency change rate detection sensitivity in the vicinity of the rated frequency. (Claim 11)

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an embodiment of a reactive power compensator for grid interconnection protection according to the present invention. In the figure, the reactive power detection circuit 45 detects the reactive power Q0 output from the reactive power device 40 from the voltage on the output side of the reactive power compensator 40 and the detected current of the current transformer 44. A reactive power controller (AQR) 46 compares the reactive power reference Q * with the reactive power Q0 detected by the reactive power detection circuit 45 and controls and outputs the reactive power device 40 so that the deviation becomes zero. The reactive power Q0 is controlled to a value corresponding to the reactive power reference Q *. The frequency change rate detector 47 detects the frequency change rate df / dt at the interconnection point. The level detector 48 outputs a trip signal for opening the circuit breaker 3 when the detection signal df / dt exceeds a predetermined value. Function generator 49
Is the correction signal ΔQ * based on the frequency change rate df / dt.
Is output, and the reactive power reference is Q in addition to the reactive power reference Q *.
Correct to * + ΔQ *. The absolute value detection unit 50 converts the frequency change rate df / dt into an absolute value, the integrator 51 integrates the converted signal, and the level detection unit 52 detects when the integrated value exceeds a predetermined value. The trip signal for opening the circuit breaker 3 is output. Others are the same as the conventional one (FIG. 7), and the same reference numerals are given to omit the description.

FIG. 2 shows an equivalent circuit of the above-mentioned structure when the private power generation equipment is interconnected. The load 5 is represented by a parallel circuit of a resistor R, an inductance L and a capacitor C, active power output from the AC generator 7 is P, reactive power is Q, reactive power output from the reactive power compensator 40 is Q0, load is Assuming that the active power supplied to 5 is PL and the reactive power is QL, the active power ΔP and the reactive power ΔQ flowing out to the grid 1 are respectively expressed as follows.

[0012]

[Formula 1] ΔP = P−PL ΔQ = Q + Q0−QL The generated power of the private power generation facility and the power supplied to the load 5 are balanced, and the power flowing to the grid 1 is almost zero, that is, ΔP = 0, ΔQ = When the circuit breaker 3 is opened during the interconnected operation in the state of 0, the voltage and the frequency hardly change, and only the private power generation equipment operates independently, and the islanding state occurs. If you continue driving in this state,
Since the synchronous control with the voltage of the grid 1 is not performed, there is a difference in the voltage phase of the private power generation equipment with respect to the voltage phase of the grid 1, the phase difference gradually expands, and the circuit breaker 3 on the substation side is turned on again. In this case, an overcurrent occurs due to the difference between the voltage of the grid 1 and the voltage of the private power generation equipment, resulting in a dangerous state that causes an accident. In the present embodiment, in order to prevent such a danger, a protection operation described later is performed in which the circuit breaker 6 on the private power generation facility side is opened early. When the private power generation facility is in the independent operation state, the relationship between the voltage V at the interconnection point and the active power P output by the AC generator 7 is determined by the resistance R of the load 5.

[0013]

## EQU2 ## P = V ² / R. The relationship between the voltage V at the interconnection point and the reactive power Q + Q0 output by the AC generator 7 and the reactive power compensator 40 is determined by the inductance L of the load 5, the capacitor C, and the frequency f.

[0014]

[Number 3] ^{Q + Q0 = (V 2 ωC} ) - the (V ² / ωL) However ω = 2πf.

The frequency f is generated by the independent operation of the private power generation equipment.
When the frequency change rate begins to change slightly, the frequency change rate detection section 47 outputs the frequency change rate df / dt.
The correction signal ΔQ * is output from the function generator 49 based on / dt. For example, the function generating section 49 uses the detection signal df /
A correction signal .DELTA.Q * proportional to dt is output, whereby the reactive power Q0 output from the reactive power compensator 40 is .DELTA.Q.
* Only changes. In this case, the function generator 49 determines the frequency f
When it changes in the increasing direction, a positive correction signal is output, and the reactive power Q0 output from the reactive power compensating device 40 advances and increases by the reactive power ΔQ *. Conversely, when the frequency f changes in the decreasing direction, it becomes negative. Output the correction signal of the reactive power Q
0 is increased by delayed reactive power ΔQ *.

Now, if the frequency f rises slightly,
The reactive power Q0 output from the reactive power compensator 40 advances and increases by the reactive power ΔQ *, resulting in an imbalance of ΔQ = ΔQ * with the reactive power QL absorbed by the load 5.
The lead reactive current i0 due to this lead reactive power ΔQ * flows into the AC generator side, and the inductance Lg of the AC generator side
Causes a voltage drop, and consequently lowers the voltage V at the interconnection point, shifts the phase of the current ig supplied from the AC generator 7 in the delay direction, and the reactive power Q supplied from the AC generator 7 is delayed. Is increased by the delayed reactive power ΔQ * to offset the inflowing advanced reactive current i0. This voltage V
Of the active power P (= V ² /
R) decreases, the load of the AC generator 7 decreases correspondingly, the load of the turbine 10 becomes lighter, and the rotation speed changes in the direction of increasing, and the change rate of the frequency f in the increasing direction increases, and It acts as a positive feedback that increases the reactive power of the lead, and acts to promote the rise of the frequency f.

Assuming that the frequency f drops slightly, the reactive power Q0 output from the reactive power compensator 40 is reduced.
Increases by the delay reactive power ΔQ *, changes the voltage V in the direction of increasing it, and acts to promote the decrease of the frequency f.

Since the speed governor 11 controls the output of the turbine 11 so that the output frequency of the AC generator 7 is constant, it will return to the original frequency when the control response time of the speed governing system elapses. When the frequency deviation Δf reaches a predetermined value, the polarity of the change rate df / dt is reversed, and the hunting phenomenon in which the frequency f of the voltage at the interconnection point increases / decreases (fluctuates) in a predetermined cycle before and after the rated frequency. appear.

FIG. 3 shows this hunting state, and the correction signal (1) shows the case where the correction signal ΔQ * output from the function generator 49 is proportional to the rate of change df / dt of the frequency f. It is a thing.

When such a hunting phenomenon occurs,
Frequency change rate d output from the frequency change rate detector 47
When f / dt exceeds a predetermined value, a trip signal is output from the level detector 52, and a protection operation for opening the circuit breaker 6 via the trip circuit 20 is performed.

When the private power generation facility is operated independently,
Considering the case where the frequency f hardly changes, the characteristic of the function generating section 49 can be set as follows. That is,
A value proportional to the frequency change rate df / dt is output as the correction signal ΔQ *, the polarity of the frequency change rate df / dt is discriminated at the level of the minimum detection resolution of the frequency change rate detection unit 47, and the polarity is positive or negative. Predetermined bias value ±
The characteristic is that ΔQb is added. With such a characteristic, even when the private power generation equipment is operated independently and the frequency f hardly changes, the frequency change rate df / dt is positive or negative at the level of the minimum detection resolution of the frequency change rate detection unit 47. It is possible to supply the reactive power of either the lead or the delay corresponding to the bias value ± ΔQb, and the hunting phenomenon can be caused in a short time. The correction signal (2) in FIG. 3 shows an example of the correction signal ΔQ * output from the function generator 49 when this embodiment is used. When this embodiment is used, the reactive power corresponding to the bias value ± ΔQb flows out as ΔQ when the system is connected to the grid, but by setting the value small, it will not adversely affect the system side. To do.

The reactive power output from the private power generation equipment and the reactive power supplied to the load 5 are balanced, the active power output from the private power generation equipment and the active power supplied to the load 5 are unbalanced, and ΔQ = 0, When the circuit breaker 3 is opened to operate independently when operating in the condition of ΔP ≠ 0, in the conventional case, as shown in f1 and f2 of FIG. 4 (a), the frequency immediately changes depending on whether the ΔP is positive or negative. The f approaches the stable point while f changing upward or downward. In the case of the present embodiment, when such a state occurs, the reactive power ΔQ is increased based on the frequency change rate df / dt so as to promote the frequency change rate as described above.
Is supplied, the frequency f is not stable as shown by f1 'and f2' in FIG. 4 (b), the amplitude of frequency fluctuation gradually increases, and the hunting phenomenon starts. Therefore, the conventional protective relay 15-
At 19, it is possible to easily detect the islanding operation and perform the protective operation. In FIG. 4B, f1 'shows the case where .DELTA.P is positive, and f2' shows the case where .DELTA.P is negative.

As described above, when the private power generation facility is in the independent operation and actively causes hunting to change the frequency, it may be necessary to elapse time until the frequency fluctuation at the level for detecting the independent operation is reached. Even in such a case, since the isolated operation is detected within the predetermined time, the following protection operation is performed.

When the frequency f fluctuates as indicated by f1 'and f2' in FIG. 4 (b), the absolute value conversion section 50 uses the frequency change rate df / dt detected by the frequency change rate detection section 47 as an absolute value. The value is converted into a value A (ABS (df / dt)), and the part (ABS (d
f / dt) -α0) is integrated, and the integrated value B
When exceeds the predetermined detection level β, the level detection unit 52 outputs a trip signal. According to this embodiment, the frequency change rate df / dt can be detected at the time t1 earlier than the time t2 when the level detection unit 48 reaches the detection level α1, and the islanding operation can be detected in a short time.

In the above description, as a private power generation facility,
Although the case where only the AC generator 7 is connected has been described, the power supplied from the battery 61 is converted into AC power by the inverter 62, and the inverter 62 is connected via the breaker 63.
In some cases, the output of is connected to the interconnection point. The inverter performs constant P, Q control or current phase control at high speed, and since the frequency control system has no mechanical inertia, it is easier for the frequency to fluctuate than in the case of only the AC generator.

According to this embodiment, by controlling the reactive power in the direction of promoting the frequency change based on the frequency change rate at the interconnection point, different types of power generation equipment such as generators and inverters are interconnected. Even if there is, the islanding operation can be reliably detected.

Another embodiment of the present invention is shown in FIG. In FIG. 5, the filter 53 operates as a bandpass filter having a high gain around the rated frequency f0, and the frequency detection circuit 54 detects the frequency f at the interconnection point via the filter 53. The determination unit 57 determines the frequency f of the interconnection point detected by the frequency detection circuit 54, the frequency change rate df / dt detected by the frequency change rate detection unit 47, and the voltage of the interconnection point detected by the voltage detection circuit 55. Since the values of V, the voltage change rate dV / dt, etc. detected by the voltage change rate detecting unit 56 are different from the normal values, the eyelanding state is determined (estimated) with a sensitivity higher than the detection level of the protection operation described above. , And outputs signals M1 and M2 for changing the control parameters. Amplifier 58
Changes the amplification factor according to the signal M1, and the signal limiter 59 changes the value for limiting the maximum value of the correction signal according to the signal M1.

The characteristic of the filter 53 used in this embodiment is, as shown in FIG. 6, a characteristic in which the phase advances as the frequency f increases in the range of frequencies f2 to f1 before and after the rated frequency f0, and a characteristic of emphasizing a change in frequency. In the range lower than f2 or in the range higher than f1, the phase is delayed as the frequency f rises, and the characteristic is to suppress the frequency change.
With such a characteristic, a large frequency fluctuation is detected near the rated frequency f0, and a small frequency fluctuation is detected outside the range of f2 to f1.

In this embodiment, when the eye landing state is reached, the determining unit 57 first determines the frequency f and the frequency change rate df.
/ Dt, voltage V, voltage change rate dV / dt, etc., determine (estimate) disconnection from the system, and signal M1
Is output to increase the gain of the amplifier 58, and at the same time, the signal M2 is output to switch the limit value of the correction signal ΔQ * of the signal limiter 59 to a large value to increase the fluctuation range of the reactive power, thereby ensuring the hunting state. I am trying to raise it.

According to this embodiment, the reactive power flowing to the grid during normal interconnection operation can be suppressed to a small level, and when the landing state is reached, the hunting state is surely generated and the protection operation is performed. You can

In this embodiment, the gain of the amplifier 58 may be increased, the limit value of the correction signal ΔQ * of the signal limiter 59 may be switched to a large value, or only one of the signals M1 and M2 may be used. . The filter 53 and the frequency detector 54 used in this embodiment can also be applied to the embodiment of FIG. 1, and the phase between the voltage phase detected through the filter 53 and the voltage phase at the interconnection point. The deviation can be added to the frequency change rate df / dt to increase the frequency change rate detection sensitivity in the vicinity of the rated frequency.

[0032]

According to the present invention, when the private power generation facility is disconnected from the grid and is in an independent operation state, reactive power is supplied so as to generate a hunting state in which the frequency increases and decreases within a predetermined frequency fluctuation range. It is possible to reliably detect the islanding state in a short time without using a transfer interruption device and perform a protective operation even when operating in a state where the output power of the private power generation equipment is equal to the power consumption of the load, which is reliable. It is possible to provide a reactive power compensator for system interconnection protection, which has improved efficiency and economy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a reactive power compensator for grid interconnection protection of the present invention.

FIG. 2 is an equivalent circuit diagram for explaining the operation of the above embodiment.

FIG. 3 is a waveform diagram for explaining the operation of the above embodiment.

FIG. 4A is a waveform diagram for explaining the operation of the conventional device, and FIG. 4B is a waveform diagram for explaining the operation of the above embodiment.

FIG. 5 is a configuration diagram of another embodiment of the reactive power compensator for grid interconnection protection of the present invention.

FIG. 6 is a characteristic diagram of the filter 53 shown in the above embodiment.

[Fig. 7] Configuration diagram of a conventional system interconnection protection system

[Explanation of symbols]

1 ... System power supply 2 ... Transformer 3, 6, 63 ... Circuit breaker 5 ... Load 7 ... AC generator 8 ... Field winding 9 ... Automatic voltage regulator (AVR) 10 ... Turbine engine 11 ... Governor 12, 14 ... Current transformer 13 ... Abnormality detection circuit 15 ... Frequency lowering relay (UF) 16 ... Frequency rising relay (OF) 17 ... Overvoltage relay (OV) 18 ... Undervoltage relay (UV) 19 ... Overcurrent relay (OC) 20 ... Fault trip circuit 39 ... High-order substation 40 ... Reactive power compensator 41 ... Transmitter 42 ... Frequency fluctuation detection circuit 43, 48, 52 ... Level detection unit 44 ... Current transformer 45 ... Reactive power detection circuit 46 ... Reactive power control Unit (AQR) 47 ... Frequency change rate detection unit 49 ... Function generation unit 50 ... Absolute value conversion unit 51 ... Integrator 53 ... Filter 54 ... Frequency detection unit 55 ... Voltage detection circuit 56 ... Voltage change rate detection 57 ... judging unit 58 ... amplifier section 59 ... signal limiting unit 61 ... battery 62 ... Inverter

Claims (11)

[Claims] 1. When the private power generation equipment connected to the grid is connected to the grid and the private power generation equipment is disconnected from the grid, the frequency of the voltage at the grid is a predetermined cycle before and after the rated frequency. A grid interconnection system characterized by having a reactive power compensator that supplies reactive power so as to generate a hunting state that increases and decreases with, and opens the circuit breaker between the interconnection point and private power generation equipment based on this hunting state. Protective reactive power compensator. 2. The reactive power compensator for grid interconnection protection according to claim 1, wherein the reactive power reference is corrected so as to promote the frequency change based on the frequency change at the interconnection point, and the reactive power reference is set. A control unit that controls the reactive power based on
A reactive power compensator for grid interconnection protection, characterized in that, when the private power generation facility is disconnected from the grid, the reactive power causes the frequency control system to be in an unstable state and the hunting state to occur. 3. The reactive power compensator for grid interconnection protection according to claim 2, wherein the control unit advances the reactive power when the frequency change rate is positive and increases the reactive power when the frequency change rate is negative. A reactive power compensator for grid interconnection protection, characterized in that the reactive power compensator is controlled so as to increase delayed reactive power. 4. The reactive power compensator for grid interconnection protection according to claim 2, wherein the control unit includes a function generation unit that outputs a correction signal based on a frequency change rate, and the correction signal is used as the invalid signal. A reactive power compensator for grid interconnection protection characterized by correcting a reactive power standard in addition to a power standard. 5. The reactive power compensator for grid interconnection protection according to claim 4, wherein the function generator outputs a correction signal proportional to the frequency change rate. Power compensator. 6. The reactive power compensator for grid interconnection protection according to claim 4, wherein the function generating unit has a value proportional to the frequency change rate and a predetermined bias having a polarity corresponding to the polarity of the frequency change rate. A reactive power compensator for grid interconnection protection, which is characterized by outputting a correction signal to which is added. 7. The reactive power compensator for grid interconnection protection according to claim 2, wherein the control section outputs a signal for performing a protection operation when the frequency change rate exceeds a predetermined level. A reactive power compensator for grid interconnection protection, comprising: a level detector, wherein the frequency change rate is set to exceed a predetermined level in the hunting state. 8. The reactive power compensator for grid interconnection protection according to claim 2, wherein the control unit integrates the frequency change rate and performs a protection operation when the integrated value exceeds a predetermined level. A reactive power compensator for grid interconnection protection, comprising: a second level detecting section for outputting a signal, wherein the integrated value is set to exceed a predetermined level in the hunting state. 9. The reactive power compensator for grid interconnection protection according to claim 2, wherein the control unit amplifies the correction signal with a function generation unit that outputs a correction signal based on a frequency change rate. A calculation unit that limits the maximum value and a determination unit that estimates that the private power generation equipment has been disconnected from the grid based on the voltage at the interconnection point and the change in frequency are provided, and based on the correction signal output from the calculation unit. Correct the reactive power standard, when the determination unit estimates that the private power generation equipment is disconnected from the grid, increase the amplification factor of the arithmetic unit, or increase the value limiting the maximum value of the correction signal,
Alternatively, the reactive power compensator for grid interconnection protection is characterized in that the amplification factor of the arithmetic unit is increased and the maximum value of the correction signal is increased. 10. The reactive power compensator for grid interconnection protection according to claim 2 or claim 9, wherein the control unit is interconnected via a filter having a high gain characteristic in a predetermined frequency range including a rated frequency. A reactive power compensator for system interconnection protection, comprising a frequency detection unit for detecting a frequency at a point, and enhancing detection sensitivity in the vicinity of a rated frequency. 11. The reactive power compensator for grid interconnection protection according to claim 10, wherein the filter has a phase that changes in an advance direction as the frequency rises in a predetermined frequency range including a rated frequency, and In a frequency range other than the frequency range, the characteristic is such that the phase changes in the delay direction as the frequency rises, and the phase deviation between the voltage phase detected through the filter and the voltage phase at the interconnection point is added to the frequency change rate detection value. A reactive power compensator for system interconnection protection, which is characterized by increasing the detection sensitivity of the frequency change rate near the rated frequency.