JP4935376B2 - Isolated operation detection method, isolated operation detection device, and power line conditioner - Google Patents

Description

  The present invention relates to an isolated operation detection method for detecting whether or not a distributed power source is disconnected from an electric power system and operated independently, an isolated operation detection device for detecting an isolated operation, and a power line conditioner.

  Independent operation is a state in which a distributed power source supplies power to a local system load when the power system is stopped due to an accident or other circumstances. A distributed power source can generate power by installing a power source at or near a demand location. There are various types of distributed power sources such as an engine generator, a turbine generator, a power storage device, a fuel cell, a solar cell and the like that are linked to a power system. In addition, in order to use such a distributed power supply in conjunction with system power, many power conditioners that adapt the frequency and voltage to the power system have been proposed.

  In the isolated operation detection device that detects the isolated operation of the distributed power source described above, the detection method of the isolated operation includes, for example, active disturbance such as reactive power fluctuation, active power fluctuation, frequency shift, or harmonic injection. Inject signal, inject disturbance signal included in power system line between power system and distributed power source, detect system fluctuation due to injection, and detect isolated operation of distributed power source based on this detection result A power fluctuation method has already been proposed.

  In such an isolated operation detection by the power fluctuation method, if a large number of isolated operation detection devices irregularly inject a disturbance signal into the power system, the disturbance signals may cancel each other out in the power system. Yes, it affects the isolated operation detection.

  Therefore, there is a system in which a disturbance signal is injected into a power system all at once in synchronization with a standard time radio signal or the like in a large number of single operation detection devices.

  However, the above synchronization method requires equipment for receiving radio signals from radio clocks and the like, which increases costs, and excessive injection of disturbance signals causes a load connected to the power system, such as a fluorescent lamp. There is a risk of flickering causing flickering, malfunction of the microcomputer, and inability to control the rotation of the motor. The following are representatives of patent documents relating to isolated operation.

FIG. 9 shows an image diagram of a multi-unit interconnection of distributed power sources. The independent operation detection time of the inverter is 0.5 to 1.0 seconds in the active method. This is a characteristic that assumes (i) isolated operation in units of houses, and there was no problem at the stage of the spread of distributed power sources in small quantities. Recently, however, distributed power sources are in the period of popularization, and a multi-unit interconnection as shown in FIG. 9 has been implemented. In this case, there is a possibility of independent operation in units of (ii) pole transformers, (iii) units of section switches, and (iv) units of circuit breakers. When these high-pressure systems are included, it is necessary to detect an isolated operation assuming a high-low pressure mixed accident.

  The problem to be solved by the present invention is not based on a method of injecting a disturbance signal that causes power fluctuations in the power system for the purpose of detecting whether or not a single unit of a single operation detection device irregularly operates alone in the power system, In addition, independent operation of distributed power sources can be reliably detected regardless of the method of injecting disturbance signals from multiple independent operation detection devices all at once in synchronization with radio signals from radio clocks, etc. It is.

  (1) The isolated operation detection method according to the present invention is a method for detecting whether or not a distributed power source is disconnected from an electric power system and is operating independently, and a measurement step for measuring a system frequency, and the measured system frequency includes: A disturbance signal injection step of injecting a disturbance signal for causing power fluctuations in the power system line when the state of staying within a certain minute frequency range continues for a predetermined number of cycles. is there.

  The fixed minute frequency range is not particularly limited, but is, for example, a range of ± 0.001 Hz, and this range can be determined because it is smaller than a normal system frequency fluctuation.

  The predetermined number of cycles is one cycle or a plurality of cycles, and can be appropriately determined by experiments or the like, but a preferable cycle number range is 2 to 3 cycles.

  In the case of a method of injecting a disturbance signal for causing power fluctuation in the power system line, if a disturbance signal is injected into the power system line irregularly from a number of isolated operation detection devices, the isolated operation occurs. Nevertheless, the disturbance signals may cancel each other out, and there may occur a situation in which the system frequency changes and it becomes impossible to detect an isolated operation. On the other hand, the measured system frequency may occur in less than a predetermined number of cycles due to another factor that is not an isolated operation.

  Therefore, in the present invention, the disturbance signal is injected into the power system line when the system frequency stays within a certain minute frequency range for the predetermined number of cycles or more. The single operation detection can be reliably performed based on the injection.

  As a result of the above, in the present invention, in a plurality of single operation detection devices, there is a problem of mutual cancellation of disturbance signals that may occur in the case of a method of injecting disturbance signals irregularly, and a standard obtained from a radio timepiece or the like It is possible to solve problems such as an increase in equipment cost in the method of injecting disturbance signals in synchronism with time radio signals and the like and the occurrence of flicker.

  (2) According to a preferred aspect of the present invention, when the system frequency measured in the measurement step is changed, the system step includes an operation step of performing feedback operation of the system frequency in a direction to further increase the change, and the system frequency is a minute frequency with a constant system frequency. When the state of staying within the range continues for a predetermined number of cycles or more, it is a step of injecting a disturbance signal for causing power fluctuation in the power system line in order to determine whether or not it is an independent operation. .

  In this aspect, when the measured system frequency changes, the system frequency is feedback-operated in a direction to further increase the change, and the distributed power source is used alone based on the system frequency change according to the system frequency feedback operation. Since there is a step to determine whether or not the system is operating, if the system frequency change is a change due to system frequency measurement error, system frequency minute fluctuations, etc. and is not isolated operation, increase the system frequency change Even if the feedback operation is performed in the direction to be changed, the system frequency change does not change in the increasing direction. On the other hand, in the case of single operation, if the feedback operation is performed in the direction to increase the system frequency change, the system frequency change is increased. By changing the direction, it is possible to reliably detect the isolated operation of the distributed power supply That.

  Further, in this aspect, when the state where the system frequency does not change and remains within a certain minute frequency range is continued for a predetermined number of cycles or more, a disturbance signal is injected in the same direction. Since this disturbance signal does not cancel out between the detectors, the generated power and load power are perfectly balanced, and the system frequency can be changed even in the case of isolated operation where the system frequency does not vary at all. Can be reliably detected.

 (3) An isolated operation detection apparatus for a distributed power source according to the present invention includes a microcomputer having a software program for executing the isolated operation detection method. The isolated operation detection device is not limited to a name, and includes a case where it is referred to as a power conditioner or other names.

  According to the present invention, independent operation of a distributed power source can be reliably detected regardless of the power fluctuation method.

  Hereinafter, an isolated operation detection method, its control device, an isolated operation detection device, and a distributed power supply according to embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a configuration of a power control system including a distributed power source (including a power conditioner) and an isolated operation detection device. Referring to FIG. 1, 10 is a distributed power source such as a solar cell or a fuel cell, 20 is an isolated operation detection device, and 30 is a power system.

  The isolated operation detection device 20 includes an interconnection relay 21, a control device 22, an inverter control unit 23, an inverter 24, an interconnection relay 25, and a current detector 26. The interconnection relay 21 is interposed in a power line 40 between the distributed power source 10 and the power system 30.

  The control device 22 is mainly composed of a microcomputer. According to the software program, the control device 22 measures the system frequency, and when the measured system frequency changes, the system frequency is increased in the direction of increasing the change. And determining whether or not the distributed power source is in a single operation based on an operation step for feedback operation and a change in the system frequency according to the feedback operation of the system frequency, while the system frequency does not change and is constant. A disturbance signal injection step of injecting a disturbance signal into the power system line 40 to determine whether or not the operation is independent when the state of staying in the minute frequency range continues for a predetermined number of cycles or more. Is. Examples of the disturbance signal include active signals such as reactive power fluctuation, active power fluctuation, frequency shift, and harmonic injection.

  The microcomputer can execute at least the above steps. The microcomputer has a CPU, a memory, an interface, and the like. The software program is stored in the memory. The CPU executes various calculations based on the system voltage, system current, system power, etc. input through the interface, and opens and closes the interconnection relays 21 and 25 through the interface from the execution result. Commands and various commands to the inverter control unit 23 are input.

  The control device 22 can also be configured by hardware other than the microcomputer. In the embodiment, for the purpose of understanding the explanation, it is shown in FIG. 2 which is a functional diagram which incorporates a microcomputer and is executed by a software program of the microcomputer. Since it is a functional diagram, the microcomputer does not include the configuration illustrated in FIG. 2 as hardware, but may be described in the same manner as hardware.

In FIG. 2, 22a is a system frequency measurement unit, 22b is a frequency feedback unit, 22c is an isolated operation determination unit, 22d is a system frequency coincidence determination unit, and 22e is a power fluctuation injection command unit.

  The system frequency measuring unit 22a is connected to the power system line 40 of the power system 30 and takes in the system voltage and the like from the power system line 40 and measures the system frequency of the power system from the acquired system voltage and the like.

 The frequency feedback unit 22b stores the system frequency (previous measurement system frequency) previously measured by the system frequency measurement unit 22a, and the previous measurement system frequency and the system frequency measured this time (current measurement system frequency) and And a system frequency feedback operation is performed in accordance with the calculated deviation. The previous measurement is a measurement in the past of one cycle or a plurality of cycles from the current measurement.

  The system frequency coincidence determination unit 22d determines whether or not a state where the system frequency does not change and remains within a certain minute frequency range continues for a predetermined number of cycles. Input to the power fluctuation injection command section.

The feedback operation output of the frequency feedback section 22b, is input to the power fluctuation injected command section 22e of the coincidence determination section 22d of the system frequency, the sum of two by the power fluctuation injected command unit 22e, the sum combined power variation command value This is given to the inverter control unit 23. The inverter control unit 23 controls the inverter 24 in response to the power fluctuation command value, whereby the inverter 24 injects a disturbance signal having a magnitude corresponding to the power fluctuation command value into the power system line 40.

  The system frequency changes due to the injection of the disturbance signal into the power system line 40. This system frequency is measured by the system frequency measuring unit 22a.

  During normal operation that is not isolated operation, the system frequency does not substantially change due to a measurement error. Therefore, the frequency feedback unit 22b inputs a feedback operation output corresponding to the change in the system frequency to the inverter control unit 23, and as a result, the inverter 24 The amount of disturbance signal injection is very small. Moreover, since the system frequency coincidence determination unit 22d determines that the system frequency does not change and remains within a certain micro frequency range, the micro frequency range is set smaller than the normal system frequency fluctuation. There is no disturbance signal from the frequency coincidence determination unit 22d.

  On the other hand, in the case of isolated operation, the system frequency changes exceeding the measurement error, and this system frequency is measured by the system frequency measurement unit 22a. Based on the measured system frequency, the frequency feedback unit 22b detects the isolated operation. The inverter control unit 23 is provided with a feedback operation output necessary for detecting an isolated operation. The inverter control unit 23 controls the inverter 24 so as to inject a disturbance signal corresponding to the frequency feedback operation into the power system line 40. As a result, a disturbance signal capable of detecting an isolated operation is injected into the power system line 40.

  In the case of isolated operation, the system frequency changes corresponding to the disturbance signal injection. In the case of non-independent operation, the system frequency does not change corresponding to the disturbance signal injection. This change is measured by the system frequency measuring unit 22a and input to the frequency feedback unit 22b. The frequency feedback unit 22b inputs the frequency feedback operation output to the inverter control unit 23 in the direction of changing the system frequency more in the case of single operation as the measurement from the system frequency measurement unit 22a is input for each system cycle. To do.

  As a result, the system frequency changes in a direction of increasing or decreasing in the case of an isolated operation, and does not change when not in an isolated operation.

   In this case, this is a rare example, but the generated power and the load power are completely balanced and remain within a certain minute frequency range, which matches the reference frequency of 50 Hz in the embodiment. A condition that stays in frequency can occur.

 When this state continues for a predetermined number of cycles (for example, 4 cycles) or more, the system frequency coincidence determination unit 22d sends a disturbance signal command to the inverter control unit 23 via the power fluctuation injection command unit 22e. input. In response to the disturbance signal correction command, the inverter control unit 23 controls the inverter 24.

With this control, the system frequency measured by the system frequency measuring unit 22a changes according to the injection disturbance signal from the state where it is stopped at a constant frequency if it is an isolated operation. The measured system frequency does not change from the state where it stays at a constant frequency.

  If it is a single operation, the system frequency measured by the system frequency measuring unit 22a changes corresponding to the injection disturbance signal from the state where it is stopped at a constant frequency. The frequency feedback unit 22b operates to further increase the change in the system frequency. It is determined whether or not the distributed power source 10 is operating alone by capturing the frequency change caused by these.

  When the isolated operation determination unit 22c determines that the operation is performed independently, the isolated operation determination unit 22c controls the interconnection relays 21 and 25 to be turned off and inputs an inverter stop control command to the inverter control unit 23 to stop the inverter 24. Let

FIG. 3 is a time chart showing the behavior leading to the isolated operation detection when there is a slight imbalance between the generated power and the reactive power of the load power. Single operation occurs at time t1. Due to this occurrence, the reactive power of the generated power and the load power is slightly unbalanced, so that the system frequency is slightly changed. Taking this slightly changed system frequency into account, frequency feedback starts to operate at time t3. By this frequency feedback operation, power fluctuation is injected in the direction in which the system frequency change is amplified.
The system frequency changes rapidly due to the fluctuation of the injected power. Then, the isolated operation is determined from the rapidly changed system frequency.

  FIG. 4 shows the behavior leading to the isolated operation detection in a state where the generated power and the reactive power of the load power are perfectly balanced (the system frequency does not change at all). Single operation occurs at time t1. Since the reactive power of the generated power and load power is perfectly balanced, the system frequency does not change.

  When the state in which the system frequency does not change continues for several periods (four periods in FIG. 4), the system frequency coincidence determination unit operates at time t2 to inject power fluctuations to break the complete balance state.

  The system frequency changes due to the injected power fluctuation.

  Then, the frequency feedback starts to operate at time t3 by capturing the changed system frequency.

  Thus, power fluctuation is injected in the direction in which the system frequency change is amplified by the operation of the frequency feedback.

  The system frequency changes rapidly due to the fluctuation of the injected power.

  The isolated operation is determined from the rapidly changed system frequency.

  On the other hand, the isolated operation determination unit 22c of the control device 22 creates a change curve of the system frequency based on the deviation between the current system frequency and the previous system frequency corresponding to the predetermined system period, and the pattern of the created change curve The single operation may be determined based on the above.

  The system frequency this time is not limited to the system frequency of one cycle, but may be an average system frequency of a plurality of cycles. The previous system frequency is not limited to one system frequency, and may be an average system frequency of a plurality of periods. In this case, a moving average of a plurality of system frequencies may be used.

  When the single operation determination unit 22c of the control device 22 determines that the single operation is performed, as described above, the interconnection relays 21 and 25 are turned off, and an inverter stop control command is input to the inverter control unit 23 to stop the inverter 24. Let

  FIG. 5 shows a power conditioner incorporating a stand-alone operation detection device. This distributed power source includes a power source body 50 such as a solar cell or a fuel cell, and a power conditioner 60. The power conditioner 60 includes an inverter 61, a current detector 62, an interconnection relay 63, an inverter control unit 64, and a control device 65.

  The control device 65 is composed of a microcomputer as in the control device 22 of the above embodiment, and has functional blocks shown in FIG.

  In the above configuration, in the power conditioner 60, a control command for causing a power fluctuation in the power system is input from the control device 65 to the inverter control unit 64 in order to detect an isolated operation. As a result, the inverter control unit 64 drives the inverter 61, and a disturbance signal for causing power fluctuation is injected from the inverter 61 to the power line 66. Note that the interconnection relay 63 is closed by the control device 65.

  The control device 65 measures the system frequency from the voltage waveform from the power line 66. The control device 65 performs control according to FIG. 3 and FIG. 4 by the occurrence of the isolated operation, and the measured system frequency does not change after the isolated operation occurrence time t1 in FIG. In the embodiment, if the state where the frequency stays at the frequency that matches the reference frequency is continued for, for example, four periods (n1-n4 in FIG. 4), an electric power fluctuation injection command is issued at time t2 that has continued for the four periods. Thus, the system frequency changes after time t2. Similarly to the above, when the system frequency measured this time increases from the previous system frequency, the disturbance increases in the direction in which the system frequency increases, and when it decreases, the disturbance in the direction in which the system frequency further decreases. Correct and control signal injection. Therefore, the correction control command is input to the inverter control unit 64. The inverter control unit 64 drives the inverter 61 in response to the correction control command, whereby a corrected disturbance signal is injected into the power line 66.

  On the other hand, the control device 65 may create a change curve of the system frequency based on the deviation between the current system frequency and the previous system frequency, and may determine the isolated operation from the pattern of the change curve. .

  When the control device 65 determines that the operation is independent, it controls the interconnection relay 63 to be turned off and inputs an inverter stop control command to the inverter control unit 64 to stop the inverter 61.

  FIG. 6 shows a distributed power source to which an isolated operation detection device is externally attached. The islanding detection device 80 is externally attached to the distributed power source 70. The isolated operation detection device 80 includes an interconnection relay 81, an isolated operation detection determination unit 82, an isolated operation high speed control unit 83, an inverter control unit 84, an inverter 85, and a current detector 86.

  In the above configuration, in the isolated operation detection device 80, the isolated operation detection determination unit 82 corresponds to a normal isolated operation detection device. The isolated operation detection device 80 corresponds to the control device of the embodiment.

  A control command for performing an operation that causes power fluctuation in the power system is detected from the isolated operation high-speed control unit 83 to the inverter control unit 84 to detect the isolated operation. Thereby, the inverter control unit 84 drives the inverter 85, and a disturbance signal is injected from the inverter 85 into the power line 87.

  The isolated operation high speed control unit 83 measures the system frequency from the voltage waveform from the power line 87. The isolated operation high-speed control unit 83 performs control according to FIGS. 3 and 4 by the occurrence of isolated operation, and the measured system frequency does not change after the isolated operation generation time t1 along FIG. Within the range, in the embodiment, when the state that stops at the frequency that matches the reference frequency is continued for, for example, four periods (n1-n4 in FIG. 4), the power fluctuation injection command is inverter-controlled at time t2 that continues for the four periods. This is output to the unit 23, whereby the system frequency changes after time t2. As described above, when the system frequency measured this time is higher than the previous system frequency, the disturbance frequency is increased in the direction in which the system frequency is increased. Compensate and control injection. Therefore, the correction control command is input to the inverter control unit 84. The inverter control unit 84 drives the inverter 85 in response to the correction control command, whereby a corrected disturbance signal is injected into the power line 87.

  On the other hand, the isolated operation high speed control unit 83 creates a change curve of the system frequency based on the deviation between the current system frequency and the previous system frequency, and determines the isolated operation based on the pattern of the change curve. You may do it. If the single operation high speed control unit 83 determines that the single operation is performed, the inverter control unit 84 inputs an inverter stop control command to stop the inverter 85.

  FIG. 7 shows a distributed power source to which an isolated operation detection device is externally attached. The isolated operation detection device 100 is externally attached to the distributed power source 90. The distributed power source 90 includes an inverter control unit 91, an inverter (not shown) controlled by the inverter control unit 91, and an interconnection relay 92. The isolated operation detection device 100 includes an isolated operation detection determination unit 102 and an isolated operation high speed control unit 101. The isolated operation detection determination unit 102 and the isolated operation high-speed control unit 101 constitute the control device of the embodiment.

  In the isolated operation detection device 100 configured as described above, the isolated operation high speed control unit 101 inputs a control command for performing an operation causing power fluctuation in the power system to the inverter control unit 91 for the purpose of detecting the isolated operation. As a result, the inverter control unit 91 drives the inverter to inject a disturbance signal into the power line 93.

  The isolated operation high speed control unit 101 measures the system frequency from the voltage waveform from the power line 93. The isolated operation high speed control unit 101 performs control according to FIG. 3 and FIG. 4 by the occurrence of isolated operation, and the measured system frequency does not change after the isolated operation occurrence time t1 according to FIG. Within the range, in the embodiment, when the state that stops at the frequency that matches the reference frequency is continued for, for example, four periods (n1-n4 in FIG. 4), the power fluctuation injection command is inverter-controlled at time t2 that continues for the four periods. This is output to the unit 23, whereby the system frequency changes after time t2. As described above, when the system frequency measured this time is higher than the previous system frequency, the disturbance frequency is increased in the direction in which the system frequency is increased. Compensate and control injection. Therefore, the correction control command is input to the inverter control unit 91. Inverter control unit 91 drives an inverter (not shown) in response to the correction control command, whereby a corrected disturbance signal is injected into power line 93. When the isolated operation detection determination unit 102 determines the isolated operation, the isolated operation high speed control unit 101 receives the determination and inputs an inverter stop control command to the inverter control unit 91 to stop the inverter.

  FIG. 8 shows a distributed power source to which an isolated operation detection device is externally attached. The islanding detection device 120 is externally attached to the distributed power source 110. The distributed power source 110 includes an inverter control unit 111, an inverter (not shown) controlled by the inverter control unit 111, an interconnection relay 113, and an isolated operation high-speed control unit 112 corresponding to the control device of the embodiment. The isolated operation detection device 120 includes an isolated operation detection determination unit 121 that is a normal isolated operation detection device.

  In the above configuration, the isolated operation high speed control unit 112 inputs a control command for performing an operation causing power fluctuation in the power system to the inverter control unit 111 for the isolated operation detection. As a result, the inverter control unit 111 drives the inverter to inject a disturbance signal into the power line 114.

  The isolated operation high speed control unit 112 measures the system frequency from the voltage waveform from the power line 114. The isolated operation high-speed control unit 112 performs the control according to FIGS. 3 and 4 by the occurrence of the isolated operation, and the measured system frequency does not change after the isolated operation occurrence time t1 according to FIG. Within the range, in the embodiment, when the state that stops at the frequency that matches the reference frequency is continued for, for example, four periods (n1-n4 in FIG. 4), the power fluctuation injection command is inverter-controlled at time t2 that continues for the four periods. This is output to the unit 23, whereby the system frequency changes after time t2. As described above, when the system frequency measured this time is higher than the previous system frequency, the disturbance frequency is increased in the direction in which the system frequency is increased. Compensate and control injection. Therefore, the correction control command is input to the inverter control unit 111. The inverter control unit 111 drives an inverter (not shown) in response to the correction control command, and thereby a corrected disturbance signal is injected into the power line 114. When the isolated operation high speed control unit 112 detects the isolated operation, the inverter operation unit 111 inputs an inverter stop control command to stop the inverter.

  As described above, in the islanding operation detection method according to the embodiment, when the change in the system frequency is a change due to a measurement error of the system frequency, a slight fluctuation in the system frequency, and the like, and is not an islanding operation, the system frequency is increased. The system frequency does not change in the increasing direction even if the feedback operation is performed in the direction in which the system frequency is increased. On the other hand, in the case of single operation, if the feedback operation is performed in the direction in which the system frequency is increased, the system frequency changes in the increasing direction. By doing so, it becomes possible to reliably detect the isolated operation of the distributed power source.

  Further, in the embodiment, when the state where the system frequency does not change and stays within a certain minute frequency range continues for a predetermined number of cycles or more, it is determined whether or not the system is in isolated operation. Since the signals are injected in the same direction, the isolated operation can be reliably detected without canceling the disturbance signal due to interference between the multiple isolated operation detecting devices.

  Further, in the embodiment, in order to eliminate mutual cancellation of disturbance signals, a method of performing an operation to cause disturbance signals to the power system simultaneously in synchronization with a standard time radio wave signal etc. in a plurality of single operation detection devices Therefore, it is possible to suppress the equipment cost increase and the occurrence of flicker, which are problems due to the synchronization method.

  The present invention is not limited to the above-described embodiment, and includes various changes or modifications within the scope described in the claims.

FIG. 1 is a diagram illustrating a configuration of a power control system including a distributed power source and an isolated operation detection device to which an isolated operation detection method according to an embodiment of the present invention is applied. FIG. 2 is a functional block diagram of the control device of FIG. FIG. 3 is a diagram used for explaining the frequency feedback operation when the generated power and the load power are unbalanced in the isolated operation detection device of FIG. 1. FIG. 4 is a diagram used for explaining the frequency feedback operation in the case where the generated power and the load power are perfectly balanced in the isolated operation detection device of FIG. FIG. 5 is a diagram illustrating another configuration example of the power control system including the distributed power source and the isolated operation detection device to which the isolated operation detection method according to the embodiment of the present invention is applied. FIG. 6 is a diagram showing still another configuration example of a power control system including a distributed power source and an isolated operation detection device to which the isolated operation detection method according to the embodiment of the present invention is applied. FIG. 7 is a diagram showing still another configuration example of a power control system including a distributed power source and an isolated operation detection device to which the isolated operation detection method according to the embodiment of the present invention is applied. FIG. 8 is a diagram illustrating still another configuration example of the power control system including the distributed power source and the isolated operation detection device to which the isolated operation detection method according to the embodiment of the present invention is applied. FIG. 9 is an image diagram of a multi-unit interconnection of distributed power sources.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Distributed type power supply 20 Isolated operation detection apparatus 30

Claims (4)

In a method for detecting whether a distributed power source is disconnected from a power system and is operating independently,
A measurement step for measuring the system frequency;
When the state where the measured system frequency remains within a certain minute frequency range continues for a predetermined number of cycles or more, in order to determine whether or not it is a single operation, in order to cause power fluctuations in the power system line A disturbance signal injection step for injecting a disturbance signal;
An islanding operation detection method comprising:   2. The islanding operation detection method according to claim 1, further comprising an operation step of performing feedback operation of the system frequency in a direction to further increase the change when the system frequency measured in the measurement step is changed.   An isolated operation detection device for detecting whether or not a distributed power source is disconnected from an electric power system and operating independently, comprising a microcomputer having a software program for executing the method according to claim 1 or 2. An isolated operation detection device characterized by   An isolated operation detection device for detecting whether or not a distributed power source is disconnected from an electric power system and operating independently, comprising a microcomputer having a software program for executing the method according to claim 1 or 2. A power line conditioner characterized by that.

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