JPH09252540A - Singles operation detector for distributed power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single operation detector which detects that a distributed power source composed of an induction motor and a synchronous motor breaks its parallel operation during linking in the system and becomes single operation. SOLUTION: This distributed of power source looses the balance when the power source composed of an induction motor 21 and a synchronous motor 23 breaks the parallel operation during its linking, and this detector detects a single operation, by connecting a reactive power adjuster 51 to the output end of an induction motor 21, and equipping this with a ripple signal generator 53 which gives periodic small ripple to the reactive power setter of the reactive power adjuster 41, and a single operation generating circuit 54 which monitors the output of the frequency detector 41 connected to the system of the side 20 of a consumer and outputs a single operation signal when this output deviates from the tolerable lower value of the reference frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed power source in which a synchronous generator and an induction generator operate in parallel to supply power to a load, and the distributed power source and the power system are connected to each other when the distributed power source is connected. The present invention relates to an islanding operation detection device that detects when the mold power source is disconnected and the islanding mode is activated.

[0002]

2. Description of the Related Art Conventionally, this type of isolated operation detecting device has detected the isolated operation of a distributed power source by using a transfer interruption method or a method of monitoring voltage or frequency. These methods will be described with reference to FIG. FIG.
FIG. 7 is a block diagram showing a configuration of a conventional islanding operation detection device. In FIG. 8, reference numeral 10 indicates the commercial system side, and the infinite bus 11 and the power transmission line 12 on the commercial system side 10
Is connected to the customer side 20 via the system breaker 13.

An induction generator 21 on the customer side 20 is connected to the commercial system side 10 via an induction generator breaker 22 and a detector side breaker 25, and similarly, a synchronous generator 23 is a synchronous generator breaker 24. And, it is connected through the circuit breaker 25 on the detection device side and is interconnected with the power system. The synchronous generator 23 and the induction generator 21 are operated in parallel by a well-known technique to form a distributed power source. The induction generator-side internal load 30 on the customer side 20 is connected to the internal load circuit breaker 31 and the detection device side disconnection. It is connected to the commercial system side 10 via the switch 25 and is also connected to the induction generator 21 via the internal load circuit breaker 31 and the induction generator circuit breaker 22. Similarly, the synchronous generator side of the consumer side 20 is connected. The in-house load 32 is connected to the commercial system side 10 via the in-house load circuit breaker 33 and the detection device side circuit breaker 25, and to the synchronous generator 23 via the in-house load circuit breaker 33 and the synchronous generator circuit breaker 24. Is also connected.

The external load 34 on the customer side 20 is connected to the commercial system side 10 via an external load side breaker 35, and the detector breaker 25 and the induction generator breaker 2 are connected.
2 via the induction generator 21 and the synchronous generator side circuit breaker 2
4 to each of the synchronous generators 23. In this way, the induction generator 21 and the synchronous generator 2 on the customer side 20 that are connected to the commercial power system side 10 and operate in parallel with the power system
In the device for detecting the islanding operation in No. 3, the islanding breaker 13 on the commercial system side 10 shuts off, and the induction generator 21 and the synchronous generator 23 on the consumer side 20 detect the islanding operation by the transfer cutoff method. A method of disconnecting the detection device side circuit breaker 25 and the external load side circuit breaker 35 on the customer side 20 by a transfer cutoff signal 14 from the commercial system side 10 when the system is disconnected from the system side and in an isolated operation state Is.

Further, in the method of monitoring voltage and frequency,
As shown in FIG. 8, the voltage and frequency detected by the voltage detector 40 and the frequency detector 41 connected to the system on the customer side 20 are input to the islanding operation detection circuit 42. That is, the method of monitoring the voltage or frequency is based on this islanding operation detection circuit 4
This is a method of passively detecting the islanding operation by monitoring changes in the voltage and frequency of the system on the customer side 20 according to 2.

[0006]

However, in the above-described conventional islanding operation detection device, the method of detecting the islanding operation by the transfer interruption method requires the use of a dedicated line for transmission of the transfer interruption signal 14, and in the future. However, when the number of distributed power sources increases, it is necessary to increase the capacity of the dedicated line. In addition, the transfer cutoff signal 14
It is impractical and economically problematic to use a shared line or wireless for the transmission of data.

Further, in the method of detecting the islanding operation by the method of monitoring the voltage and the frequency, the capacity of the load on the customer side 20 (external load 34, internal load on the induction generator side 30 and internal load on the synchronous generator side 32) Then, there is a problem that the total amount of power generation of the induction generator 21 and the synchronous generator 23 is balanced, and detection is impossible in a state where there is no tidal current between the commercial system side 10 and the customer side 20. .

An object of the present invention is to provide an islanding machine for a synchronous generator which solves the above problems.

[0009]

The first aspect of the present invention is a distributed power source in which a synchronous generator and an induction generator operate in parallel to supply power to a load, and the distributed power source and the power system are connected to each other. In an islanding operation detection device for detecting that the distributed power source is disconnected in the system to be in an islanding operation, a reactive power adjusting device connected to the induction generator end, and a reactive power setting of the reactive power adjusting device. Signal generator that gives a periodic minute fluctuation to the power supply unit, a frequency detector that detects the frequency of the power receiving point or the distributed power source, and a small change in the reactive power at the power receiving point by the fluctuation signal generator. An islanding operation signal generating circuit for generating an islanding operation signal when the deviation between the output of the frequency detector and a predetermined reference frequency becomes a certain value or more.

According to a second aspect of the present invention, in the islanding operation detection device, a fluctuation signal that gives a minute periodic fluctuation to a reactive power adjusting device connected to the end of the induction generator and a reactive power setting device of the reactive power adjusting device. A generator, a frequency detector that detects the frequency of the power receiving point or the distributed power supply, and monitors minute fluctuations in the output of the frequency detector, and when the output value deviates from a predetermined upper limit value or lower limit value. , An amplifier circuit for amplifying the amplitude of the output of the fluctuation signal generator for a predetermined minute time, and a minute change in the reactive power of the power receiving point is always given by the amplifier circuit and the fluctuation signal generator. An islanding operation signal generating circuit for generating an islanding operation signal when the deviation between the output and a predetermined reference frequency exceeds a certain value.

According to a third aspect of the present invention, in the islanding operation detection device, a fluctuation signal that gives a minute periodic fluctuation to a reactive power adjusting device connected to the end of the induction generator and a reactive power setting device of the reactive power adjusting device. A generator, a frequency detector that detects the frequency of the power receiving point or the distributed power supply, and monitors minute fluctuations in the output of the frequency detector, and when the output value deviates from a predetermined upper limit value or lower limit value. Start the timer,
A delay amplifier circuit that amplifies the amplitude of the output of the fluctuation signal generator for a predetermined minute time when the timer has passed a predetermined time, and a power receiving point reactive power by the delay amplifier circuit and the fluctuation signal generator. And an isolated operation signal generating circuit for generating an isolated operation signal when the deviation between the output of the frequency detector and a predetermined reference frequency becomes a certain value or more.

A fourth aspect of the present invention is the distributed power source islanding operation detecting apparatus according to any one of the first to third aspects of the present invention, wherein a static var compensator is provided as the reactive power adjusting device. A fifth aspect of the present invention is the distributed power source islanding operation detection apparatus according to any one of the first to third aspects, wherein an active filter device is provided as the reactive power adjusting device.

According to a sixth aspect of the present invention, in the islanding operation detecting apparatus, a fluctuation signal generator that gives a periodic minute fluctuation to the reactive power setting device of the phase adjusting equipment of the distributed power supply, and a frequency of the power receiving point or the distributed power supply. A frequency detector that detects the frequency and the fluctuation signal generator constantly gives a small change to the reactive power at the receiving point, and when the deviation between the output of the frequency detector and a predetermined reference frequency exceeds a certain value, And an independent operation signal generating circuit for generating an operation signal.

According to a seventh aspect of the present invention, in the islanding operation detecting device, a fluctuation signal generator for giving a minute periodic fluctuation to a reactive power setting device of the phase adjusting equipment of the distributed power source, and a power receiving point or the distributed power source. A frequency detector for detecting the frequency,
An amplifier circuit for monitoring minute fluctuations in the output of the frequency detector, and amplifying the amplitude of the output of the fluctuation signal generator for a predetermined minute time when the output value deviates from a predetermined upper limit value or lower limit value; , An independent operation signal when the amplifier circuit and the fluctuation signal generator constantly give a small change to the reactive power at the receiving point, and the deviation between the output of the frequency detector and a predetermined reference frequency becomes a certain value or more. And an isolated operation signal generation circuit for generating

According to an eighth aspect of the present invention, in the islanding operation detecting apparatus, a fluctuation signal generator that gives a periodic minute fluctuation to the reactive power setting device of the phase adjusting equipment of the distributed power supply, and a frequency of the power receiving point or the distributed power supply. A frequency detector that detects a frequency change and a minute change in the output of the frequency detector, and starts a timer when the output value deviates from a predetermined upper limit value or a lower limit value, and the timer passes a predetermined time. In doing so, a delay amplifier circuit that amplifies the amplitude of the output of the fluctuation signal generator for a predetermined minute time, and a small change is always given to the reactive power of the receiving point by the delay amplifier circuit and the fluctuation signal generator, An islanding operation signal generating circuit for generating an islanding operation signal when a deviation between the output of the frequency detector and a predetermined reference frequency becomes a predetermined value or more.

According to the present invention, the period is transmitted to the reactive power adjusting device newly installed at the induction generator end of the distributed power source connected to the grid or to the reactive power setting device of the phase adjusting equipment of the distributed power source connected to the grid. It is possible to detect the isolated operation of these distributed power sources by periodically changing the reactive power at the power receiving point by monitoring the change in the frequency of the power receiving point or the distributed power source. That is, the islanding operation detecting device for a distributed power source of the present invention detects the islanding operation by actively breaking the equilibrium state by giving periodic minute fluctuations to the reactive power output of the distributed power source.

[0017]

1 is a block diagram of a distributed power source islanding operation detecting apparatus according to a first embodiment of the present invention. The configuration of the conventional islanding operation detecting apparatus shown in FIG. Components having the same functions as those in the block diagram shown are designated by the same reference numerals, and detailed description thereof will be omitted. That is, in FIG. 1, the isolated operation detection device 50 of the distributed power source including the induction generator 21 and the synchronous generator 23 includes a static var compensator, an active filter device, or the like. A reactive power adjusting device 51 connected to the output end of the device via a reactive power adjusting device breaker 52,
The output of the fluctuation signal generator 53 that gives a small periodic fluctuation to the reactive power setting device of the reactive power adjusting device 51 and the output of the frequency detector 41 connected to the system on the customer side 20 are monitored, and this output is set to the reference frequency ( f ₀ ), which is 50 Hz or 60 Hz, and a stand-alone operation signal generation circuit 54 including a comparator for detecting deviation from the lower limit (f ₀ ± Δf ₁ hertz) and an OR element. ing.

The isolated operation detecting apparatus of the present invention shown in FIG.
50 detection operation, refer to the operation waveform diagram shown in FIG.
One will be described below. In FIG. 2, an induction generator 21 and
The amount of power generated from the synchronous generator 23 and the induction generator
Side load 30 and synchronous generator Side load 32 and external load
34 and the amount of power consumed by the balance
At time t shown in FIG.₀And the commercial system side 10 things
Therefore, the commercial system side 10 is disconnected by the system breaker 13
Then, it is composed of an induction generator 21 and a synchronous generator 23.
The distributed power supply is put into an isolated operation state. Like this
In the state of change, the fluctuation signal generator 53 and the reactive power adjusting device 51
The reactive power fluctuation is given by and as shown in FIG.
Fluctuation is (+) polarity and reactive power is supplied to the customer side 20 system.
The force adjusting device 51 gives a more delayed lag reactive power fluctuation,
Reactive power adjustment for the grid on the consumer side 20 with (-) polarity
Device 51 is set to give more advanced phase reactive power fluctuation
2B, the time t ₀~ T
₁A frequency fluctuation like that between occurs and time t₁At
The islanding signal generation circuit 54 operates to output the islanding signal.
Force (see FIG. 2 (C)).

FIG. 3 is a block diagram of an isolated operation detecting apparatus for a distributed power source showing a second embodiment of the present invention.
The components having the same functions as those in the block diagram showing the configuration of the islanding operation detection device 50 shown in FIG. That is, in FIG. 3, a frequency detector 41, a reactive power adjusting device 51, a reactive power adjusting device circuit breaker 52, a fluctuation are included in an isolated operation detection device 60 of a distributed power source including an induction generator 21 and a synchronous generator 23. When the outputs of the signal generator 53, the islanding operation signal generation circuit 54, and the frequency detector 41 are monitored and the outputs deviate from predetermined upper and lower limits (f ₀ ± Δf ₂ hertz, Δf ₁ > Δf ₂ ). An amplifier circuit 6 including a comparator, an OR element, an amplifier, etc., for increasing the amplitude of the output of the fluctuation signal generator 53.
1 is provided.

The amplification circuit 61 of the islanding operation detection device 60 in FIG. 3 makes it possible to quickly detect the islanding operation. The detection operation of the islanding operation detection system 60 of the present invention shown in FIG. 3 will be described below with reference to the operation waveform diagram shown in FIG. In FIG. 4, the induction generator 21
4 in a state in which the amount of electric power supplied from the internal generator 30 and the synchronous generator 23 is balanced with the amount of electric power consumed by the induction generator side internal load 30, the synchronous generator side internal load 32, and the external load 34. As shown in (B), when the commercial system side 10 is disconnected by the system breaker 13 due to an accident on the commercial system side 10 at time t ₀ , the distributed power source including the induction generator 21 and the synchronous generator 23 becomes It becomes the independent operation state. In such a state, when the fluctuation of the reactive power is given by the fluctuation signal generator 53, the amplifier circuit 61, and the reactive power adjusting device 51, and the polarity of the fluctuation of the reactive power is the same as in FIG. 2, it is shown in FIG. ,
Frequency fluctuations such as between time t _{0 and} t ₁ occur and
_{At 1} , the amplifier circuit 61 operates and the fluctuation signal generator 5
3 increases the amplitude of the output, and as a result, the fluctuation of the reactive power also increases as shown in FIG. 4 (A), and at time t ₂ ,
The isolated operation signal generation circuit 54 operates to output an isolated operation signal (see FIG. 4C).

FIG. 5 is a block diagram of an isolated operation detecting apparatus for a distributed power source showing a third embodiment of the present invention.
The components having the same functions as those in the block diagram showing the configuration of the islanding operation detection device 50 shown in FIG. That is, in FIG. 5, a frequency detector 41, a reactive power adjusting device 51, a reactive power adjusting device circuit breaker 52, a fluctuation are included in an isolated operation detection device 60 of a distributed power source including an induction generator 21 and a synchronous generator 23. When the outputs of the signal generator 53, the islanding operation signal generation circuit 54, and the frequency detector 41 are monitored and the outputs deviate from predetermined upper and lower limits (f ₀ ± Δf ₂ hertz, Δf ₁ > Δf ₂ ). A delay amplifying circuit 71 including a comparator, an OR element, a timer, an amplifier, etc., which starts a timer and increases the amplitude of the output of the fluctuation signal generator 53 when the timer elapses a predetermined time (T ₀ ). It has and.

The delay amplifying circuit 71 of the islanding operation detecting device 70 in FIG. 5 prevents the above-mentioned malfunction of the islanding operation detection and enables quick detection. The detection operation of the islanding operation detection device 70 of the present invention shown in FIG.
This will be described below with reference to the operation waveform diagram shown in FIG. FIG.
, The amount of power supplied from the induction generator 21 and the synchronous generator 23 is balanced with the amount of power consumed by the induction generator-side internal load 30, the synchronous generator-side internal load 32, and the external load 34. 6B, the time t shown in FIG.
_{When the} commercial system side 10 is disconnected by the system breaker 13 due to an accident on the commercial system side 10 at ₀ , the distributed power source including the induction generator 21 and the synchronous generator 23 is in an independent operation state. In such a state, the fluctuation signal generator 53
When the reactive power fluctuation is given by the delay amplification circuit 71 and the reactive power adjusting device 51 and the polarity of the reactive power fluctuation is the same as that in FIG. 2, the time t _{0 to} t ₁ shown in FIG. 6B is obtained. When a frequency fluctuation occurs, the timer of the delay amplification circuit 61 operates at time t ₁ , and this timer increases the amplitude of the output of the fluctuation signal generator 53 at time t ₂ when the time limit T ₀ has elapsed, and as a result, As shown in FIG. 6A, the fluctuation of the reactive power also increases, and at time t ₃ , the islanding operation signal generation circuit 5
4 operates and outputs an isolated operation signal (see FIG. 6C).

FIG. 7 is a block diagram of an isolated operation detecting apparatus for a distributed power source showing a fourth embodiment of the present invention.
The components having the same functions as those in the block diagram showing the configuration of the islanding operation detection device 70 shown in FIG. That is, in FIG. 7, a phase modifying equipment 26 such as a synchronous phase modulator or a reactive power compensator is connected to the system on the customer side 20 via a phase modifying equipment circuit breaker 27 and connected to the system on the customer side. When used for improving the power factor, improving the stability of the synchronous generator, etc., the reactive power setting device of the phase adjusting equipment 26 is subjected to periodic minute fluctuations so as to be composed of the induction generator 21 and the synchronous generator 23. Operation detection device for detecting isolated operation of distributed power source
0 is provided.

The islanding operation detecting device 80 shown in FIG.
The frequency detector 41, the fluctuation signal generator 81, the isolated operation signal generation circuit 54, the frequency detector 41, and the delay amplification circuit 71 are provided.
This is the same as the islanding operation detection device 70 shown in FIG.

[0025]

According to the present invention, a reactive adjusting device newly installed at the end of an induction generator of a distributed power source connected to a grid or a reactive power setting device of a phase adjusting facility of a distributed power source connected to a grid is provided. A periodic minute fluctuation is applied to the power supply, and the reactive power at the power receiving point is changed periodically to actively break the equilibrium state and detect the isolated operation, which can improve the operation reliability. It does not require transmission equipment such as a dedicated line for the cutoff signal, which was necessary in the transfer cutoff method, and balances the load capacity and the power generation of the distributed power supply, which were not possible with conventional voltage and frequency monitoring methods. Even when there is no power flow, it is possible to reliably detect the isolated operation of the distributed power source including the induction generator and the synchronous generator.

Further, according to the present invention, since it is not necessary to modify the control device of the existing distributed power source induction generator or synchronous generator, it is effective in improving the isolated operation detection function of the existing distributed power source. It becomes an effective means.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an isolated-operation detection device for a distributed power source showing a first embodiment of the present invention.

FIG. 2 is a waveform chart illustrating the operation of FIG.

FIG. 3 is a block diagram of an islanding operation detection device for a distributed power source showing a second embodiment of the present invention.

FIG. 4 is a waveform chart for explaining the operation of FIG. 3;

FIG. 5 is a configuration diagram of an islanding operation detection device for a distributed power source showing a third embodiment of the present invention.

6 is a waveform diagram illustrating the operation of FIG.

FIG. 7 is a configuration diagram of an isolated-operation detection device for a distributed power source showing a fourth embodiment of the present invention.

FIG. 8 is a block diagram of an isolated operation detection device for a distributed power source showing a conventional example.

[Explanation of symbols]

10 ... Commercial system side, 11 ... Infinity bus, 12 ... Transmission line,
13 ... System breaker, 14 ... Transfer cutoff signal, 20 ... Customer side, 21 ... Induction generator, 22 ... Induction generator breaker, 23
... Synchronous generator, 24 ... Synchronous generator side circuit breaker, 25 ... Detection device side circuit breaker, 26 ... Phase adjusting equipment, 27 ... Phase adjusting equipment circuit breaker, 30 ... Induction generator side internal load, 31 ... Internal load cut-off 32, ... Synchronous generator side internal load, 33 ... Internal load circuit breaker, 34 ... External load, 35 ... External load circuit breaker, 40 ... Voltage detector, 41 ... Frequency detector, 42 ... Single operation detection circuit, 50 , 60, 70, 80 ... Islanding operation detection device, 51
… Reactive power adjusting device, 52… Reactive power adjusting device circuit breaker,
53, 81 ... Fluctuating signal generating circuit, 54 ... Single operation signal generating circuit, 61 ... Amplifying circuit, 71 ... Delay amplifying circuit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shinji Nakazawa 1-1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (8)

[Claims] 1. A distributed power source in which a synchronous generator and an induction generator are operated in parallel to supply power to a load, and the distributed power source is disconnected during the interconnection of the distributed power source and the power system. In the islanding operation detecting device for detecting the independent operation as a whole, a fluctuation signal generating a periodic minute fluctuation in the reactive power adjusting device connected to the end of the induction generator and the reactive power setting device of the reactive power adjusting device is generated. And a frequency detector that detects the frequency of the power receiving point or the distributed power source, and always gives a small change to the reactive power of the power receiving point by the fluctuation signal generator, and the output of the frequency detector and a predetermined reference frequency. And an isolated operation signal generating circuit that generates an isolated operation signal when the deviation of the isolated value exceeds a certain value. 2. A distributed power source in which a synchronous generator and an induction generator are operated in parallel to feed a load, and the distributed power source is disconnected during the interconnection of the distributed power source and the power system. In the islanding operation detecting device for detecting the independent operation as a whole, a fluctuation signal generating a periodic minute fluctuation in the reactive power adjusting device connected to the end of the induction generator and the reactive power setting device of the reactive power adjusting device is generated. And a frequency detector that detects the frequency of the power receiving point or the distributed power source, and monitors minute fluctuations in the output of the frequency detector, and when the output value deviates from a predetermined upper limit value or lower limit value, An amplifier circuit that amplifies the amplitude of the output of the fluctuation signal generator for a predetermined minute time, and a minute change in the reactive power of the receiving point is always given by the amplifier circuit and the fluctuation signal generator, and the output of the frequency detector And the predetermined reference frequency Distributed power islanding detection apparatus characterized by comprising a single operating signal generating circuit for generating a single operation signal when the difference is a certain value or more. 3. A distributed power source in which a synchronous generator and an induction generator are operated in parallel to feed a load, and the distributed power source is disconnected during the interconnection of the distributed power source and the power system. In the islanding operation detecting device for detecting the independent operation as a whole, a fluctuation signal generating a periodic minute fluctuation in the reactive power adjusting device connected to the end of the induction generator and the reactive power setting device of the reactive power adjusting device is generated. And a frequency detector that detects the frequency of the power receiving point or the distributed power source, and a timer that monitors minute fluctuations in the output of the frequency detector and when the output value deviates from a predetermined upper limit value or lower limit value. And a delay amplification circuit for amplifying the amplitude of the output of the fluctuation signal generator for a predetermined minute time when the timer has passed a predetermined time, and the delay amplification circuit and the fluctuation signal generator. Receiving point reactive power is always small And a discrete operation signal generating circuit that generates an independent operation signal when the deviation between the output of the frequency detector and a predetermined reference frequency exceeds a certain value. Power supply islanding detection device. 4. The islanding operation detection device for a distributed power source according to claim 1, wherein a static var compensator is provided as the reactive power adjusting device. An isolated operation detection device for distributed power sources. 5. The islanding operation detection device for a distributed power supply according to claim 1, further comprising an active filter device as the reactive power adjusting device. Islanding detection device. 6. A distributed power source in which a synchronous generator and an induction generator are operated in parallel to feed a load, and the distributed power source is disconnected during interconnection of the distributed power source and a power system. In the isolated operation detection device for detecting that the isolated operation is performed, the fluctuation signal generator that gives periodic minute fluctuations to the reactive power setting device of the phase adjusting equipment of the distributed power supply, and the frequency of the power receiving point or the distributed power supply A frequency detector for detection and a small change in the reactive power at the receiving point by the fluctuation signal generator, and when the deviation between the output of the frequency detector and a predetermined reference frequency exceeds a certain value, it operates independently. An isolated operation detection device for a distributed power supply, comprising: an isolated operation signal generation circuit for generating a signal. 7. A distributed power source in which a synchronous generator and an induction generator are operated in parallel to feed a load, and the distributed power source is disconnected during the interconnection of the distributed power source and the power system. In the isolated operation detecting device for detecting that the isolated operation is performed, a fluctuation signal generator that gives periodic minute fluctuations to the reactive power setting device of the phase adjusting equipment of the distributed power supply, and a power receiving point or the frequency of the distributed power supply. A frequency detector for detecting a small fluctuation of the output of the frequency detector, and when the output value deviates from a predetermined upper limit value or a lower limit value, the amplitude of the output of the fluctuation signal generator is set to a predetermined value. An amplifier circuit that amplifies only for a minute time, and a minute change is always given to the reactive power at the receiving point by the amplifier circuit and the fluctuation signal generator, and the deviation between the output of the frequency detector and a predetermined reference frequency is a certain value or more. When it becomes An isolated operation detection device for a distributed power supply, comprising: an isolated operation signal generating circuit for generating the isolated operation signal. 8. A distributed power source in which a synchronous generator and an induction generator are operated in parallel to feed a load, and the distributed power source is disconnected during interconnection of the distributed power source and the power system. In the isolated operation detection device for detecting that the isolated operation is performed, the fluctuation signal generator that gives periodic minute fluctuations to the reactive power setting device of the phase adjusting equipment of the distributed power supply, and the frequency of the power receiving point or the distributed power supply The frequency detector to detect and the minute fluctuation of the output of the frequency detector are monitored, and when the output value deviates from a predetermined upper limit value or a lower limit value, a timer is started, and the timer has passed a predetermined time. Sometimes, a delay amplifier circuit that amplifies the amplitude of the output of the fluctuation signal generator for a predetermined minute time, and a small change is always given to the reactive power of the receiving point by the delay amplifier circuit and the fluctuation signal generator, Frequency detector output and predetermined An isolated operation detection device for a distributed power supply, comprising: an isolated operation signal generation circuit that generates an isolated operation signal when a deviation from a quasi-frequency exceeds a certain value.