JP6558690B2 - Isolated operation detection device, power conditioner, and isolated operation detection method - Google Patents

Description

The present invention relates generally to the isolated operation detecting apparatus, power conditioners, and to a method for detecting islanding. More specifically, power conditioner that can detect the islanding operation detecting apparatus, the isolated operation of the distributed power supplies power system and system interconnection for detecting islanding operation of a distributed power supplies electric power system and system interconnection and, The present invention relates to an isolated operation detection method .

  Conventionally, as a single operation detection device that detects a single operation of a distributed power source connected to a power system, a single operation detection device that injects reactive power into the power system and determines a single operation of the distributed power source is known. (For example, refer to Patent Document 1). The isolated operation detection device described in Patent Literature 1 includes a measurement unit, an injection unit, and a determination unit. The measurement unit measures the voltage of the power system and calculates the system frequency. The injection unit injects reactive power into the power system in order to cause power fluctuation in the power system. The isolated operation detection device causes the measurement unit to repeatedly measure the system frequency of the power system, and the invalidity to be injected into the power system based on the frequency deviation between the measured system frequency and the system frequency measured in the past from the measurement. Power is calculated and reactive power is injected into the power system. The determination unit determines whether or not the distributed power source is operating independently using the system frequency and the frequency threshold measured by the measurement unit.

  When the injection unit injects reactive power into the power system, a direct current component is generated in the power system.

JP 2014-207750 A

  The isolated operation detection device described in Patent Document 1 causes reactive power to be injected into the power system a plurality of times from the injection unit in order to determine whether or not the distributed power source is performing independent operation. When the number of times of injecting reactive power into the power system increases, the fluctuation of the DC component generated in the power system tends to increase according to the number of times.

The present invention has been made in view of the above problems, detectable independent operation detecting apparatus islanding operation of a distributed power supply while suppressing the fluctuation of the DC component occurring in the power system, power conditioners, and a method for detecting islanding The purpose is to provide.

  An isolated operation detection device of the present invention is an isolated operation detection device that detects isolated operation of a distributed power source that is grid-connected to an electric power system, the reactive power fluctuation unit that varies the reactive power of the electric power system, Reactive power for measuring the frequency of the AC voltage of the power system, and determining the amount of change in the frequency of the AC voltage from a plurality of measurement results of the measurement unit, and causing the reactive power fluctuation unit to vary based on the amount of change. A calculation unit for obtaining the magnitude of the power system, and causing the reactive power fluctuation unit to start changing the reactive power of the power system at a timing at which the AC voltage zero-crosses, and the power system to the magnitude of the reactive power obtained by the calculation unit A fluctuation control unit that controls the reactive power fluctuation unit so as to fluctuate the reactive power, and the calculation unit before and after the reactive power fluctuation unit varies the reactive power of the power system. Based on the amount of change in the frequency of the meta said AC voltage, characterized in that it comprises a said distributed power supply determination section whether or not the isolated operation.

The power conditioner of the present invention converts the DC power output from the distributed power source into AC power, outputs the AC power to the power system, and the invalidity that varies the reactive power of the AC power output from the inverter. A power fluctuation unit; a measurement unit that measures the frequency of the AC voltage of the power system; and a change amount of the frequency of the AC voltage obtained from a plurality of measurement results of the measurement unit, and the reactive power fluctuation based on the change amount A calculation unit for determining the magnitude of the reactive power to be varied by the unit, and causing the reactive power variation unit to start the variation of the reactive power of the power system at the timing when the AC voltage is zero-crossed, and the reactive power obtained by the calculation unit A fluctuation control unit that controls the reactive power fluctuation unit to vary the reactive power of the power system up to a magnitude of A determination unit that determines whether or not the distributed power source is operating independently based on the amount of change in the frequency of the AC voltage obtained by the calculation unit before and after the change It is characterized by.
The detection method for isolated operation of the present invention is a detection method for detecting isolated operation of a distributed power source that is grid-connected to an electric power system, and includes a reactive power fluctuation step for changing reactive power of the electric power system, and the electric power A measurement step for measuring the frequency of the AC voltage of the system, and a change amount of the frequency of the AC voltage is obtained from a plurality of measurement results of the measurement step, and the reactive power is changed in the reactive power fluctuation step based on the change amount. Based on the amount of change in the frequency of the AC voltage obtained in the calculation step before and after changing the reactive power of the power system in the reactive power fluctuation step in the calculation step for obtaining the magnitude, A determination step of determining whether or not the distributed power source is operating alone, and in the reactive power fluctuation step, a timing at which the AC voltage zero-crosses The initiates the variation of the reactive power of the power system, and is characterized by varying the reactive power of the to the size power system reactive power calculated by said calculating step.

  The isolated operation detection device of the present invention can detect the isolated operation of the distributed power supply while suppressing the fluctuation of the direct current generated in the power system.

The power conditioner and the independent operation detection method of the present invention can detect the isolated operation of the distributed power source while suppressing the fluctuation of the direct current generated in the power system.

1 is a schematic block diagram of an isolated operation detection device and a power conditioner according to Embodiment 1. FIG. FIG. 3 is a waveform diagram illustrating a direct current component generated in the power system according to the first embodiment. It is a figure explaining the timing which fluctuates the reactive power of the electric power grid | system which concerns on Embodiment 1. FIG. FIG. 5 is another waveform diagram for explaining a direct current component generated in the power system according to the first embodiment. It is a figure explaining the change timing of the reactive power which concerns on the comparative example of Embodiment 1. FIG. 6 is a flowchart for explaining an operation for determining a timing for changing reactive power of the power system according to the second embodiment. It is a figure explaining the timing which fluctuates the reactive power of the electric power grid | system which concerns on Embodiment 2. FIG.

(Embodiment 1)
Hereinafter, the detection method used by the isolated operation detection apparatus 1 of this embodiment, the power conditioner 10 using the same, and the isolated operation detection apparatus 1 is demonstrated with reference to FIGS.

  As shown in FIG. 1, the isolated operation detection device 1 includes a reactive power fluctuation unit 2, a measurement unit 3, a calculation unit 4, a fluctuation control unit 5, and a determination unit 6. The isolated operation detection device 1 detects the isolated operation of the distributed power supply 152 that is connected to the power system 151 including a commercial system power supply. The isolated operation detection apparatus 1 realizes the reactive power fluctuation unit 2, the calculation unit 4, the fluctuation control unit 5, and the determination unit 6 by the operation of one microcomputer. The isolated operation detection device 1 is not limited to using a microcomputer, and an IC (Integrated Circuit) for calculation may be used.

  The determination unit 6 of the isolated operation detection device 1 determines that “the distributed power supply 152 operates alone when the distributed power supply 152 supplies power to the power system 151 even though the power system 151 has failed. Is determined. When the isolated operation detection device 1 determines that the distributed power supply 152 is operating independently, it is preferable to electrically disconnect the distributed power supply 152 from the system power supply by controlling the circuit breaker 8 described later. The determination unit 6 determines whether or not the distributed power source 152 is operating independently based on the amount of change in the frequency F1 of the AC voltage V1, which is the AC voltage of the power system 151. The frequency F1 is obtained by the measurement unit 3. When the isolated operation detection device 1 determines that the distributed power source 152 is operating independently, it controls the circuit breaker 8 to electrically disconnect the distributed power source 152 from the system power supply. When the isolated operation detection device 1 enters a state in which the distributed power source 152 is operated independently from a state in which power is supplied from the power system 151, the frequency F1 of the AC voltage V1 changes. The isolated operation detection device 1 varies the reactive power of the power system 151 in order to determine whether or not the distributed power source 152 is operated alone.

  The reactive power fluctuation unit 2 varies the reactive power of the power system 151. The reactive power fluctuation unit 2 varies the magnitude of the reactive power by changing the phase of the output current A1 with respect to the AC voltage V1 of the power system 151, for example. The reactive power fluctuation unit 2 will be described later.

  When the distributed power source 152 is not operating independently, the frequency F1 of the AC voltage V1 hardly changes even if the magnitude of the reactive power varies, and the variation amount of the frequency F1 is less than the reference value. However, when the distributed power source 152 is operating alone, the frequency F1 of the AC voltage V1 changes due to fluctuations in the magnitude of reactive power. The isolated operation detection device 1 repeatedly performs the operation of changing the reactive power of the power system 151 and the measurement of the frequency F1 of the AC voltage V1, and when the fluctuation amount of the frequency F1 exceeds the reference value, the distributed power source 152 performs the isolated operation. Determine that you are doing. Details of the operation of changing the reactive power of the power system 151 and the operation of measuring the frequency F1 of the AC voltage V1 will be described later.

  The power conditioner 10 includes an inverter 7, a reactive power fluctuation unit 2, a measurement unit 3, a calculation unit 4, a fluctuation control unit 5, and a determination unit 6. The power conditioner 10 of the present embodiment further includes a disconnector 8 (for example, a relay). The inverter 7 converts the DC power output from the distributed power source 152 into AC power and outputs the AC power to the power system 151. The disconnector 8 is provided between the inverter 7 and the power system 151 and disconnects the distributed power source 152 from the power system 151.

  When the isolated operation detection device 1 is used for the power conditioner 10, the power conditioner 10 includes the isolated operation detection device 1 and the inverter 7.

  The power conditioner 10 is electrically connected to the power system 151 and the distributed power source 152. The power conditioner 10 converts DC power from the distributed power source 152 into AC power and outputs the AC power to the power system 151 and the load 153. The power system 151 is, for example, a power distribution system that connects the power generation facility of the power company to the power conditioner 10. The distributed power source 152 is a DC power source composed of, for example, a solar cell, a fuel cell, or a secondary battery. The secondary battery is, for example, a nickel metal hydride storage battery or a lithium ion storage battery.

  The inverter 7 includes a pair of input ends and a pair of output ends. A distributed power source 152 made of a solar power generation device is electrically connected to a pair of input terminals of the inverter 7. A load 153 and a power system 151 are electrically connected to a pair of output terminals of the inverter 7. The load 153 is an electrical device that operates with AC power. The load 153 and the power system 151 are electrically connected to a pair of output terminals of the inverter 7 via, for example, a connection breaker provided in the distribution board. The inverter 7 converts the DC power input to the pair of input terminals into AC power and outputs the AC power from the pair of output terminals. That is, the inverter 7 converts the DC power input from the distributed power supply 152 into AC power, and outputs the AC power to the load 153 and the power system 151.

  The circuit breaker 8 is electrically connected between the pair of output terminals of the inverter 7 and the power system 151. When the disconnection signal from the determination unit 6 is input, the disconnector 8 electrically disconnects the inverter 7 and the power system 151.

  The reactive power fluctuation unit 2 directly varies the reactive power of the AC power output from the inverter 7 by changing the phase of the output current of the inverter 7 with respect to the phase of the AC voltage V1. Accordingly, the reactive power fluctuation unit 2 varies the reactive power of the power system 151. The reactive power fluctuation unit 2 outputs, for example, a PWM (Pulse Width Modulation) control signal to the inverter 7 and varies the phase of the current and voltage output from the inverter 7 to vary the magnitude of the reactive power.

  The measuring unit 3 includes a circuit that measures the frequency F1 of the AC voltage V1 of the power system 151. FIG. 2 shows the AC voltage V1 and the output current A1 in a state where the distributed power source 152 is connected to the power system 151. The measurement unit 3 periodically measures the voltage value of the AC voltage V1 and the current value of the output current A1 flowing through the power system 151, for example, at intervals of 5 milliseconds. The measuring unit 3 measures the period of the voltage waveform from the time difference between the two zero-cross timings when the AC voltage V1 is zero-crossed twice, and obtains the frequency F1 from the measured period. For example, the time difference between the timing t1 when the polarity of the AC voltage V1 is inverted from negative to positive (zero crossing) and the timing t3 when the polarity of the AC voltage V1 is inverted from positive to negative corresponds to a half cycle of the AC voltage V1. Based on this time difference, the measurement unit 3 obtains the frequency F1. The measurement unit 3 outputs the obtained frequency F1 to the calculation unit 4 and the determination unit 6. In FIG. 2, the measurement unit 3 measures the voltage value of the AC voltage V1 four times (timing t1, t2, t3, t4) from the timing t1 until the time corresponding to one cycle of the AC voltage V1 elapses.

  The calculation unit 4 includes a storage unit that stores a plurality of values of the frequency F1 input from the measurement unit 3. The calculation unit 4 obtains the fluctuation amount of the frequency F1 of the AC voltage V1 based on a plurality of frequencies F1 including the latest frequency F1 input from the measurement unit 3. Hereinafter, this fluctuation amount is referred to as a frequency deviation DF2. The calculation unit 4 obtains the magnitude of the reactive power of the power system 151 to be changed by the reactive power fluctuation unit 2 based on the frequency deviation DF2. The calculation unit 4 updates the magnitude of the reactive power of the power system 151 every time the value of the frequency F <b> 1 is input from the measurement unit 3, and causes the fluctuation control unit 5 to vary the reactive power of the power system 151. As an example, the calculation unit 4 obtains an average value f3 of the frequency F1 for eight times including the latest measurement result from the measurement unit 3. Moreover, the calculation part 4 calculates | requires the average value f4 of the frequency F1 for 16 times measured before 200 milliseconds before the measurement part 3 measured the newest frequency F1. The calculating unit 4 obtains the result of subtracting the average value f3 from the average value f4 as the frequency deviation DF2. Expressed as a mathematical formula, DF2 = f4-f3. The calculation unit 4 obtains the magnitude of reactive power to be injected from the reactive power fluctuation unit 2 into the power system 151 according to the frequency deviation DF2. The calculating unit 4 changes the reactive power of the power system 151 to a delayed phase or a leading phase, for example, according to the sign of the frequency deviation DF2. The calculation unit 4 obtains the reactive power phase (advanced phase or delayed phase) and the reactive power magnitude so that the absolute value of the frequency deviation DF2 increases (that is, the fluctuation amount of the frequency F1 increases). The magnitude of reactive power is calculated, for example, so as to increase in proportion to the absolute value of frequency deviation DF2 (the amount of fluctuation of frequency F1).

  The calculation unit 4 obtains a frequency threshold value F5 that serves as a reference for determining whether or not the distributed power source 152 is operating alone. The frequency threshold F5 is calculated so as to change according to the magnitude of the reactive power of the power system 151 that is changed by the reactive power changing unit 2. The sign of the frequency threshold F5 is determined according to the sign of the frequency deviation DF2. The absolute value of the frequency threshold F5 is calculated so as to increase in proportion to the magnitude of the reactive power, for example. The calculation unit 4 calculates a frequency threshold value F5 and outputs it to the determination unit 6 every time the frequency F1 is measured by the measurement unit 3.

  The fluctuation control unit 5 adjusts the magnitude of the reactive power that is varied by the reactive power fluctuation unit 2 every time the magnitude of the reactive power obtained by the calculation unit 4 is input from the calculation unit 4. The variation control unit 5 of the present embodiment has a timer, and measures the passage of time using the timer. The fluctuation control unit 5 determines the reactive power fluctuation amount and fluctuation timing of the power system 151 based on the input from the calculation unit 4 and the elapsed time measured by the timer. The variation control unit 5 controls the variation control unit 5 so that the reactive power of the power system 151 varies at the determined variation timing.

  The determination unit 6 determines whether or not the distributed power source 152 is operating independently based on the frequency F <b> 1 measured by the measurement unit 3. The determination unit 6 is based on the frequency deviation DF2 obtained by using the frequency F1 measured by the measurement unit 3 after the reactive power variation unit 2 varies the reactive power of the power system 151, and the frequency threshold F5. It is determined whether the mold power source 152 is operating alone.

  The determination unit 6 determines whether or not the absolute value of the frequency deviation DF2 exceeds the absolute value of the frequency threshold F5. Specifically, when the frequency deviation DF2 calculated by the calculation unit 4 exceeds the frequency range determined by the frequency threshold value F5 continuously for a predetermined number of times (for example, four times), the determination unit 6 determines that the distributed power source 152 is It is determined that a single operation is being performed. If the determination unit 6 determines that the distributed power source 152 is operating alone, the determination unit 6 outputs a disconnection signal to the disconnector 8. When the disconnection signal from the determination unit 6 is input, the disconnector 8 electrically disconnects the inverter 7 and the power system 151.

  Here, the DC component D1 generated when the isolated operation detecting device 1 changes the reactive power of the power system 151 will be described with reference to FIG. Thereafter, the AC output current A1 flows through the power system 151 before the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151, and the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151. Assume that an AC output current A2 flows immediately after the generation.

  The fluctuation control unit 5 does not vary the reactive power when the frequency F1 (of the AC voltage V1) obtained by the measurement unit 3 is not fluctuated, but when the frequency F1 fluctuates, the distributed power source 152 operates alone. In order to determine whether or not there is, the reactive power fluctuation section 2 is caused to vary the reactive power. For example, when the frequency F1 fluctuates so that the frequency F1 becomes low (that is, the time (1 / F1) for one cycle becomes long), the fluctuation control unit 5 supplies the reactive power of the power system 151 to the reactive power fluctuation unit 2 at timing t1. Fluctuate so that the lead phase is reached. Further, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power so as to be “the magnitude of the reactive power obtained by the calculation unit 4”. “The magnitude of the reactive power obtained by the calculation unit 4” is determined to be a magnitude of the reactive power such that the frequency F1 of the AC voltage V1 hardly changes when power is supplied to the power system 151. Yes.

  For example, when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start fluctuation of the reactive power output from the inverter 7 at timing t1, the fluctuation control unit 5 supplies power to the reactive power fluctuation unit 2 at least until a certain time T1 elapses from timing t1. The reactive power of the system 151 is changed. In FIG. 2, as an example, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 between timings t1 to t5. In the present embodiment, the fixed time T1 is set to, for example, 5 milliseconds, but is not limited to this number of seconds.

  In FIG. 2, the fluctuation control unit 5 controls the reactive power fluctuation unit 2 so that the phase of the reactive power is advanced at the timing t1. For example, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power so that the phase of the output current A2 advances with respect to the AC voltage V1. The reactive power fluctuation unit 2 gradually advances the phase of the output current A2 with respect to the phase of the output current A1 from timing t1 to timing t5. When power is supplied from the power system 151, the phase of the output current A2 advances (deviates) from the phase of the output current A1, but the phase of the AC voltage V1 hardly changes. That is, when power is supplied from the power system 151, it can be considered that the frequency F1 of the AC voltage V1 is not substantially changed even if the reactive power fluctuates. In other words, when the distributed power source 152 is not operating alone, the absolute value of the frequency deviation DF2 is less than or equal to the absolute value of the frequency threshold F5 even if the reactive power phase is changed to the advanced phase. The determination unit 6 determines that is not operating alone.

  On the other hand, if the phase of the reactive power is changed to a leading phase when the power system 151 is out of power, the phase of the output current A2 of the power system 151 is changed to the phase of the output current A1 before the phase of the reactive power is changed. Proceeds (shifts). The phase of the AC voltage V1 advances (shifts) in accordance with the phase of the output current A2. That is, the phase of the AC voltage V1 changes according to the change in the phase of the reactive power, and the frequency F1 of the AC voltage V1 changes. Then, when the absolute value of the frequency deviation DF2 continuously exceeds the absolute value of the frequency threshold F5 a predetermined number of times (four times), the determination unit 6 determines that the distributed power source 152 is operating alone.

  When the reactive power fluctuates, a direct current component D1 is generated in the power system 151 at a timing t5 when a time (1 / F1 in a mathematical expression) of one cycle of the alternating voltage V1 has elapsed from the timing t1. In the present embodiment, the time (1 / F1) for one cycle is set to 20 milliseconds, for example, but is not limited to this number of seconds.

  The DC component D1 periodically changes at a period determined by the frequency F1 of the AC voltage V1, the type of the load 153, and the power supplied to the distributed power source 152. For example, the DC component D1 may fluctuate with a period (for example, 500 milliseconds) longer than the period of the frequency F1 (20 milliseconds). The magnitude of the fluctuation of the direct current component D1 tends to increase as the reactive power fluctuation section 2 rapidly changes the reactive power in a short time.

  By the way, the AC voltage V1 may fluctuate due to the operating state of the system power supply (for example, the operating state of the power generation facility and the substation facility) or the fluctuation of power demand. For example, the phase of the AC voltage V1 may fluctuate alternately between a lead phase and a delay phase. The isolated operation detection device 1 performs an operation of changing the reactive power of the power system 151 so as to further promote the change of the frequency F1, and thus the phase of the reactive power is changed alternately between the advanced phase and the delayed phase. . When the reactive power phase is changed alternately between the advance phase and the delay phase, the fluctuation of the DC component D1 becomes larger than when the reactive power is changed only in the advance phase (or only in the delay phase). In order to link the distributed power source 152 to the power system 151, the magnitude of the DC component D1 must be smaller than a predetermined value. For this reason, there has been a desire to suppress fluctuations in the magnitude of the DC component D1 that occurs when the reactive power phase is continuously changed between the advance phase and the delay phase.

  Here, an isolated operation detection device of a comparative example having the same basic configuration as that of the isolated operation detection device 1 of the present embodiment and different in the operation of the variation control unit 5 will be described with reference to FIG. In the comparative example, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151, for example, every 5 milliseconds elapses. In FIG. 5, the periods T21 to T28 each indicate a period of 5 milliseconds. Further, in FIG. 5, for easy understanding, the AC voltage V1 in which the phase angle of the AC voltage V1 is about 30 degrees at the start of the period T21 is illustrated. The maximum value of the alternating voltage V1 at the start of each of the periods T21 to T28 is referred to as voltage values V21 to V28. It is assumed that one cycle of the AC voltage V1 is 20 milliseconds.

  In the comparative example, the variation control unit 5 varies the reactive power of the power system 151 every time the periods T21 to T28 of 5 milliseconds elapse. Therefore, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power regardless of the magnitude (instantaneous value) of the AC voltage V1 at the time when each of the periods T21 to T28 has elapsed. As the magnitude of the AC voltage V1 at the time when the reactive power is changed in the reactive power fluctuation unit 2, the fluctuation of the DC component D1 that occurs after the reactive power of the power system 151 fluctuates increases. Specifically, when the reactive power fluctuation unit 2 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 at the start timing of the period T21, the magnitude of the AC voltage V1 is equal to the voltage value V21. Yes, it is about half the maximum value of the AC voltage V1. When reactive power fluctuation unit 2 causes reactive power fluctuation unit 2 to vary reactive power of power system 151 at the start timing of period T22, the magnitude of AC voltage V1 is the magnitude of voltage value V22, and AC voltage V1. It is about 0.86 times larger than the maximum value of. Since the voltage value V22 is larger than the voltage value V21, the reactive power is changed at the start timing of the period T22 rather than changing the reactive power of the power system 151 at the start timing of the period T21. The fluctuation of the DC component D1 becomes large. The magnitudes of the voltage values V23, V25, V27 of the AC voltage V1 at the start timing of the periods T23, T25, T27 are substantially equal to the magnitude of the voltage value V21. The magnitudes of the voltage values V24, V26, V28 of the AC voltage V1 at the start timing of each of the periods T24, T26, T28 are substantially equal to the magnitude of the voltage value V22. The reactive power fluctuation unit 2 is invalid at the start timing of each of the periods T24, T26, and T28, rather than causing the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 at the start timing of each of the periods T23, T25, and T27. The fluctuation of the DC component D1 becomes larger when the electric power is changed. Therefore, in the comparative example, when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 depending on the magnitude of the voltage values V21 to V28 of the power system 151 with respect to the start timing of the periods T21 to T28. There is a case where the fluctuation of the direct current component D1 generated in is increased.

  On the other hand, in the present embodiment, as shown in FIG. 3, the fluctuation control unit 5 causes the reactive power of the power system 151 at each of timings t31 to t35 at which the magnitude (instantaneous value) of the AC voltage V1 becomes almost zero. The reactive power fluctuation unit 2 is controlled so as to fluctuate. The fluctuation control unit 5 predicts the timing at which the AC voltage V1 zero-crosses based on the change in the voltage value of the AC voltage V1 measured by the measurement unit 3. For example, the fluctuation control unit 5 predicts the next and subsequent zero cross timings including the following based on the frequency F1 obtained by the measurement unit 3 and the latest zero cross timing measured by the measurement unit 3. For example, the reactive power fluctuation unit 2 predicts a zero-cross timing after a half cycle and a zero-cross timing after one cycle by calculation using a calculation function such as a microcomputer or a calculation IC. The fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 when the predicted zero cross timing is reached. Thereby, the fluctuation | variation control part 5 fluctuates the reactive power of the electric power grid | system 151 to the reactive power fluctuation | variation part 2 at the timing substantially the same as the timing when the alternating voltage V1 is zero loss. When the frequency of the AC voltage V1 slightly changes immediately after the latest measurement result measured by the measurement unit 3, the reactive power fluctuation unit 2 varies the reactive power with respect to the timing at which the AC voltage V1 actually crosses zero. The timing may be slightly shifted. However, since the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151 at a timing when the voltage value of the AC voltage V1 is smaller than that of the comparative example, fluctuations in the magnitude of the DC component D1 are suppressed as compared with the comparative example.

  Here, the difference in operation between the isolated operation detection device 1 of the present embodiment and the isolated operation detection device of the comparative example will be described with reference to FIG.

  A direct current component D1 shown in FIG. 4 shows a waveform of a direct current component that is generated when the fluctuation control unit 5 of the isolated operation detection device of the comparative example causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151. On the other hand, the direct current component D2 shows a waveform of the direct current component that is generated when the variation control unit 5 of the isolated operation detection device 1 of the present embodiment causes the reactive power variation unit 2 to vary the reactive power of the power system 151. The DC components D1 and D2 are measured so as to periodically change due to the influence of the frequency F1 of the AC voltage V1, the type of the load 153, the power supplied to the distributed power source 152, and the like. FIG. 4 shows a case where the DC components D1 and D2 change in the same cycle as the AC voltage V1. When the fluctuation of the DC component D1 is not suppressed, the maximum value of the varying DC component D1 is substantially constant during the illustrated period. On the other hand, when the fluctuation of the direct current component D2 is suppressed, the maximum value of the varying direct current component D2 decreases with time. For example, the maximum value D22 of the DC component D2 at the timing t42 after the timing t41 is smaller than the maximum value D21 of the DC component D2 at the timing t41 (D22 <D21). That is, by suppressing the fluctuation of the direct current component D1, the magnitude of the direct current component generated in the power system 151 can be reduced.

  As described above, the isolated operation detection device 1 of the present embodiment detects an isolated operation of the distributed power source 152 that is connected to the power system 151. The isolated operation detection device 1 includes a reactive power fluctuation unit 2, a measurement unit 3, a calculation unit 4, a fluctuation control unit 5, and a determination unit 6. The reactive power fluctuation unit 2 varies the reactive power of the power system 151. Measuring unit 3 measures the frequency of AC voltage V <b> 1 of power system 151. The calculation unit 4 obtains a change amount (frequency deviation DF2 in this embodiment) of the frequency of the AC voltage V1 from a plurality of measurement results of the measurement unit 3, and the reactive power fluctuation unit 2 based on the change amount (frequency deviation DF2). Find the amount of reactive power to be varied. The fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the timing when the AC voltage V1 crosses zero, and the reactive power of the power system 151 reaches the magnitude of the reactive power obtained by the calculation unit 4. The reactive power fluctuation unit 2 is controlled so as to fluctuate. The determination unit 6 is based on the amount of change in frequency (frequency deviation DF2) of the AC voltage V1 obtained by the calculation unit 4 before and after the reactive power variation unit 2 varies the reactive power of the power system 151. It is determined whether or not the distributed power source 152 is operating alone.

  According to the above configuration, the measurement unit 3 measures the frequency F1 of the AC voltage V1 of the power system 151. The calculation unit 4 obtains a change amount (frequency deviation DF2) of the frequency F1 of the AC voltage V1 from a plurality of measurement results of the measurement unit 3. The determination unit 6 determines whether or not the distributed power source 152 is operating independently based on the amount of change in the frequency F1 (frequency deviation DF2) of the AC voltage V1 of the power system 151. The fluctuation control unit 5 controls the reactive power fluctuation unit 2 so as to vary the reactive power at the timing when the AC voltage V1 of the power system 151 crosses zero. Since the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power at the timing when the AC voltage V1 crosses zero, the fluctuation of the reactive power compared to the case where the reactive power is varied at a timing when the AC voltage V1 is not zero. The DC component D1 generated by the above can be reduced. In other words, the isolated operation detection device 1 can detect the isolated operation of the distributed power source 152 while suppressing the fluctuation of the DC component D1 generated in the power system 151.

  The isolated operation detection device 1 according to the present embodiment predicts the zero-cross timing after the half cycle and the zero-cross timing after one cycle of the AC voltage V1 based on the latest zero-cross timing measured by the measuring unit 3. The reactive power of the system 151 is varied. Therefore, the reactive power can be varied at substantially the same timing as the timing at which the AC voltage V1 actually zero-crosses.

  The power conditioner 10 of the present embodiment includes an inverter 7, a reactive power fluctuation unit 2, a measurement unit 3, a calculation unit 4, a fluctuation control unit 5, and a determination unit 6. The inverter 7 converts the DC power output from the distributed power source 152 into AC power and outputs the AC power to the power system 151. The reactive power fluctuation unit 2 varies the reactive power of the AC power output from the inverter 7. Measuring unit 3 measures the frequency of AC voltage V <b> 1 of power system 151. The calculation unit 4 obtains a change amount (frequency deviation DF2 in this embodiment) of the frequency F1 of the AC voltage V1 from a plurality of measurement results of the measurement unit 3, and based on the change amount (frequency deviation DF2), the reactive power fluctuation unit 2 Find the amount of reactive power that fluctuates in. The fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the timing when the AC voltage V1 crosses zero, and the reactive power of the power system 151 reaches the magnitude of the reactive power obtained by the calculation unit 4. The reactive power fluctuation unit 2 is controlled so as to fluctuate. The determination unit 6 is based on the change amount (frequency deviation DF2) of the frequency F1 of the AC voltage V1 obtained by the calculation unit 4 before and after the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151. Then, it is determined whether or not the distributed power source 152 is operating alone.

  According to the above configuration, the measurement unit 3 measures the frequency F1 of the AC voltage V1 of the power system 151. The calculation unit 4 obtains a change amount (frequency deviation DF2) of the frequency F1 of the AC voltage V1 from a plurality of measurement results of the measurement unit 3. The determination unit 6 determines whether or not the distributed power source 152 is operating independently based on the amount of change in the frequency F1 (frequency deviation DF2) of the AC voltage V1 of the power system 151. The fluctuation control unit 5 controls the reactive power fluctuation unit 2 so as to vary the reactive power at the timing when the AC voltage V1 of the power system 151 crosses zero. Since the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power at the timing when the AC voltage V1 crosses zero, the fluctuation of the reactive power compared to the case where the reactive power is varied at a timing when the AC voltage V1 is not zero. The DC component D1 generated by the above can be reduced. In other words, the power conditioner 10 can detect the independent operation of the distributed power source 152 while suppressing the fluctuation of the DC component D1 generated in the power system 151.

  The reactive power changing unit 2 is configured to change the magnitude of the reactive power by changing the phase of the output current A1 with respect to the AC voltage V1, but is not limited to this configuration. For example, the reactive power fluctuation unit 2 may be configured to vary the magnitude of reactive power by injecting an output current having a phase different from that of the output current A1 into the power system 151.

  The fluctuation control unit 5 is not limited to predicting the zero cross timing of the AC voltage V1 by calculation, and may be configured to predict the zero cross timing of the AC voltage V1 with reference to, for example, an information table. The information table is composed of, for example, a part of a memory included in a microcomputer or IC. In the information table, for example, voltage value information for each millisecond in the AC voltage V1 corresponding to the frequency F1 is stored for one cycle of the AC voltage V1. The fluctuation control unit 5 predicts the zero-cross timing after the half cycle and one cycle of the AC voltage V1 with reference to the information table based on the frequency F1 and the latest zero-cross timing acquired by the measurement unit 3. Can do. The information table stores voltage value information related to a plurality of AC voltages V1 having different frequencies F1. Therefore, even when the frequency F1 of the AC voltage V1 changes slightly, the fluctuation control unit 5 can predict voltage value information for one cycle of the AC voltage V1 with reference to the information table.

  Although the fluctuation control unit 5 of the present embodiment predicts each of the zero-cross timing after the half cycle and one cycle of the AC voltage V1 based on the latest measurement result measured by the measurement unit 3, for example, 1 Only the timing of the zero cross after the cycle may be predicted. In addition, for example, the fluctuation control unit 5 is not limited to the configuration that predicts the timing at which the AC voltage V1 of the power system 151 crosses zero, but after detecting that the AC voltage V1 has zero-crossed based on the measurement result of the measurement unit 3 The reactive power fluctuation unit 2 may be controlled. In this case, the fluctuation control unit 5 measures the AC voltage V1 of the power system 151 at a cycle shorter than, for example, 5 milliseconds (for example, 1 millisecond). The fluctuation control unit 5 may determine that the AC voltage V1 has zero-crossed when the sign of the AC voltage V1 is reversed and cause the reactive power fluctuation unit 2 to vary the reactive power of the power system 151. In this case, between the time when the fluctuation control unit 5 detects the zero cross of the AC voltage V1 and the time when the reactive power fluctuation unit 2 causes the reactive power of the power system 151 to fluctuate, the zero cross detection determination process and the reactive power fluctuation unit 2 are performed. It takes a little time for the signal output processing. This time is, for example, about several milliseconds although it depends on the processing speed of the microcomputer or the IC for calculation. Therefore, the timing at which the reactive power changing unit 2 changes the reactive power is slightly shifted from the zero-cross timing of the AC voltage V1. However, when the AC voltage V1 slightly deviates from the actual zero cross timing, the magnitude of the AC voltage V1 when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 (instantaneous) Value) is close to zero. Therefore, compared with the case where the fluctuation control unit 5 of the isolated operation detection device of the comparative example causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151, the isolated operation detection device 1 of the present embodiment has a direct current component D1. It is possible to suppress variation in size.

  The reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151 by changing the phase of the output current A1 output from the inverter 7. For example, the reactive power fluctuation unit 2 converts AC current having a phase different from the AC voltage V1 to the power system. The reactive power may be varied by injecting at 151.

  The disconnector 8 electrically disconnects the inverter 7 and the power system 151 in accordance with the disconnection signal from the determination unit 6, but the transmission source of the disconnection signal is not limited to the determination unit 6. . For example, the power conditioner 10 may include a control unit that controls opening and closing of the disconnector 8. As an example in that case, the determination unit 6 outputs the determination result of the isolated operation to the control unit, and the control unit is configured to control the opening / closing operation of the disconnector 8 according to the determination result of the determination unit 6. .

  Although the variation control unit 5 has a timer, the variation control unit 5 is not limited to having a timer. For example, the variation control unit 5 may use a timer included in a microcomputer.

(Embodiment 2)
The basic configurations of the isolated operation detection device 1 and the power conditioner 10 of the present embodiment are the same as those of the first embodiment, and only the operation of the fluctuation control unit 5 is different from that of the first embodiment. Hereinafter, the operation of the variation control unit 5 in the present embodiment will be described with reference to FIGS. 6 and 7. In addition, about the structure similar to Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The fluctuation control unit 5 starts measuring a predetermined time shorter than the half cycle T10 of the AC voltage V1 before starting the control of the reactive power fluctuation unit 2. The fluctuation control unit 5 sets the predetermined time to 6 milliseconds. The variation control unit 5 measures the predetermined time by measuring the elapsed time from the start timing of the predetermined time to the end timing. The variation control unit 5 starts measuring the next predetermined time every time the predetermined time being measured reaches the end timing. Hereinafter, the predetermined time measured by the variation control unit 5 is referred to as “current predetermined time”, and the predetermined time measured next to the current predetermined time is referred to as “next predetermined time”. In other words, the fluctuation control unit 5 repeats time measurement for the current predetermined time and the next predetermined time using a timer.

  Although the cycle of the AC voltage V1 slightly changes according to the interconnection state of the power system 151, the load 153, and the distributed power source 152, the AC voltage V1 of this embodiment has a half cycle T10 of 10 milliseconds and one cycle. Assume 20 milliseconds.

  The fluctuation control unit 5 determines the end timing of the predetermined time from the start timing of the next predetermined time every time the predetermined time elapses.

  The fluctuation control unit 5 sets the reactive power of the power system 151 at a timing at which the absolute value of the AC voltage V1 (the magnitude of the AC voltage V1) is minimized from the time when the start timing of the predetermined time is reached to the time when the end timing is reached. The reactive power fluctuation unit 2 is controlled so as to start fluctuation. The fluctuation control unit 5 selectively selects either the start timing of the predetermined time, the end timing of the predetermined time, or the timing at which the AC voltage V1 zero-crosses according to the absolute value of the AC voltage V1. The reactive power fluctuation of the power system 151 is started at the timing. Below, the operation | movement which the fluctuation | variation control part 5 determines the timing which starts the fluctuation | variation of the reactive power of the electric power grid | system 151 according to the absolute value of the alternating voltage V1 in the following predetermined time is demonstrated with reference to FIG. The absolute value of the AC voltage V1 at the start timing of the predetermined time is called a voltage value VS, and the absolute value of the AC voltage V1 at the end timing of the predetermined time is called a voltage value VE.

  When the microcomputer of the isolated operation detection device 1 starts operating, the variation control unit 5 sets 0 milliseconds for the waiting time TZ2. The “waiting time TZ2” is a waiting time from the time when the start timing of the next predetermined time is reached to the time when the timing of starting the reactive power fluctuation of the power system 151 is reached within the next predetermined time. That is, the fluctuation control unit 5 determines 0 milliseconds as the initial value of the waiting time TZ2 at the start of operation (S1).

  The fluctuation control unit 5 determines the value of the waiting time TZ2 for the waiting time TZ1 (S2). The waiting time TZ1 is a waiting time from the time when the current predetermined time start timing is reached to the time when the reactive power fluctuation of the power system 151 is started. When the fluctuation control unit 5 reaches the start timing of the current predetermined time, it starts counting the elapsed time TS (S3). In other words, the variation control unit 5 measures the time elapsed from the start timing of the current predetermined time by measuring the elapsed time TS.

  The variation control unit 5 determines the start timing and end timing of the next predetermined time based on the start timing of the current predetermined time and the required time of the predetermined time (6 milliseconds in the present embodiment) (S4). The fluctuation control unit 5 predicts the AC voltage V1 within the next predetermined time by calculation (S5). The fluctuation control unit 5 predicts whether or not the AC voltage V1 crosses zero within the next predetermined time (S6). If the fluctuation control unit 5 predicts that the AC voltage V1 will zero-cross within the next predetermined time (S6: Yes), it calculates the waiting time TZ2 by calculation. For example, the fluctuation control unit 5 determines the time from the start timing of the next predetermined time to the timing at which the AC voltage V1 zero-crosses as the waiting time TZ2 (S7).

  If the fluctuation control unit 5 predicts that the AC voltage V1 does not zero-cross within the next predetermined time (S6: No), the absolute value of the AC voltage V1 at the start timing of the next predetermined time and the AC voltage at the end timing are calculated. The absolute values of V1 are compared (S8). That is, the fluctuation control unit 5 compares the voltage value VS with the voltage value VE. If it is predicted that the voltage value VS is smaller than the voltage value VE (S8: Yes), the waiting time TZ2 is set to 0 milliseconds (S9). By setting the waiting time TZ2 to 0 milliseconds, the variation control unit 5 determines the start timing of the next predetermined time as the timing to start the variation of the reactive power of the power system 151.

  When the fluctuation control unit 5 predicts that the voltage value VS is equal to or higher than the voltage value VE (S8: No), the fluctuation control unit 5 sets the waiting time TZ2 to 6 milliseconds, which is a predetermined time length (S10). By setting the waiting time TZ2 to 6 milliseconds, the variation control unit 5 determines the end timing of the next predetermined time as the timing for starting the variation of the reactive power of the power system 151.

  The fluctuation control unit 5 determines whether or not the elapsed time TS of the current predetermined time has reached 6 milliseconds (S11). When the elapsed time TS has not reached 6 milliseconds (S11: No), the fluctuation control unit 5 determines whether or not the elapsed time TS has reached the waiting time TZ1 (S12). When the elapsed time TS has not reached the waiting time TZ1 (S12: No), the variation control unit 5 continues to count the elapsed time TS. When the fluctuation control unit 5 determines that the elapsed time TS has reached the waiting time TZ1 (S12: Yes), the fluctuation control unit 5 controls the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 (S13). As an example, when it takes 1 millisecond from the time when the fluctuation control unit 5 outputs the control signal to the reactive power fluctuation unit 2 to the time when the reactive power fluctuation of the power system 151 starts, the fluctuation control unit 5 uses the AC voltage V1. A control signal is output one millisecond before the timing at which zero crosses. Note that the time required from when the fluctuation control unit 5 outputs a control signal to the reactive power fluctuation unit 2 until the reactive power fluctuation unit 2 starts changing the reactive power of the power system 151 is an example. It is not intended to be limited.

  If the fluctuation control unit 5 determines that the elapsed time TS has reached 6 milliseconds (S11: Yes), it resets the elapsed time TS to 0 milliseconds (S14) and returns to the step of S2. Thereafter, the variation control unit 5 repeats steps S2 to S14.

  As described above, the fluctuation control unit 5 determines whether or not the timing for causing the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 is reached within the current predetermined time (S12). Further, the fluctuation control unit 5 predicts the timing at which the absolute value of the AC voltage V1 (the magnitude of the AC voltage V1) within the next predetermined time is minimized (S6, S8).

  Next, an operation for determining the timing at which the fluctuation control unit 5 starts the fluctuation of the reactive power of the power system 151 based on the above operation will be described. Hereinafter, in order to describe the operation of the fluctuation control unit 5, the predetermined time for 10 cycles is referred to as periods T11 to T20 (see FIG. 7). The variation control unit 5 determines that the end timing of the current predetermined time and the start timing of the next predetermined time are the same timing. For example, the variation control unit 5 determines that the end timing of the period T11 and the start timing of the period T12 are the same timing.

  Before the start timing of the period T11, the variation control unit 5 determines 0 milliseconds for the waiting time TZ2 (S1). When the fluctuation control unit 5 reaches the start timing of the period T11, it causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 (S12, S13). The start timing of the period T11 is substantially the same as the zero-cross timing of the AC voltage V1. Therefore, the voltage value V11 of the AC voltage V1 at the start timing of the period T11 is almost zero. In FIG. 7, the timing at which the AC voltage V1 zero-crosses is indicated by a circle.

  The fluctuation control unit 5 predicts the timing at which the absolute value of the AC voltage V1 in the period T12 is minimized until the end timing of the period T11 is reached (S5). The fluctuation control unit 5 predicts that the AC voltage V1 is zero-crossed during the period T12 (S6: Yes), and predicts the timing at which the AC voltage V1 is zero-crossed (S7). The fluctuation control unit 5 predicts the waiting time TZ2 from the start timing of the period T12 to the time point when the AC voltage V1 zero-crosses (S7).

  When 6 milliseconds have elapsed from the start timing of the period T11 (S11: Yes), the variation control unit 5 determines that the end timing of the period T11 has been reached, and resets the elapsed time TS (S14). The variation control unit 5 determines the value of the waiting time TZ2 for the waiting time TZ1 (S2), changes the current predetermined time from the period T11 to the period T12, and starts measuring the time period T12 (S3). The fluctuation control unit 5 compares the waiting time TZ1 with the elapsed time TS to determine whether or not the timing for causing the reactive power fluctuation unit 2 to start reactive power fluctuation of the power system 151 has been reached in the period T12. (S12).

  The fluctuation control unit 5 predicts the timing at which the absolute value of the AC voltage V1 within the period T13 is minimized (S5). If it is predicted that the AC voltage V1 does not zero-cross within the period T13 (S6: No), the fluctuation control unit 5 compares the voltage value VS with the voltage value VE (S8). The fluctuation control unit 5 predicts that the voltage value VS in the period T13 is smaller than the voltage value VE (S8: Yes), and sets the waiting time TZ2 to 0 milliseconds (S9).

  In the period T12, the waiting time TZ1 is set to a timing at which the AC voltage V1 crosses zero. Therefore, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the timing when the elapsed time TS reaches the waiting time TZ1 and the AC voltage V1 zero-crosses (S13). During the period T12, the voltage value V12 of the AC voltage V1 when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 is substantially zero.

  When the elapsed time TS reaches 6 milliseconds and reaches the end timing of the period T12 (S11: Yes), the variation control unit 5 determines the value of the waiting time TZ2 for the waiting time TZ1 (S2). The variation control unit 5 changes the current predetermined time from the period T12 to the period T13, and starts measuring the period T13 (S3). Since the waiting time TZ1 in the period T13 is set to 0 milliseconds, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the start timing of the period T13 (S13). The magnitude of the voltage value V13 of the AC voltage V1 at the start timing of the period T13 is smaller than the magnitude of the AC voltage V1 at the end timing of the period T13. In FIG. 7, when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 at the start timing of a predetermined time, the timing is indicated by a triangle mark.

  The fluctuation control unit 5 predicts the timing at which the absolute value of the AC voltage V1 within the period T14 is minimized. If the fluctuation control unit 5 predicts that the AC voltage V1 is zero-crossed within the period T14, the fluctuation control unit 5 predicts a waiting time TZ2 from the start timing of the period T14 to the time when the AC voltage V1 crosses zero. The fluctuation control unit 5 determines that the end timing of the period T13 has been reached when 6 milliseconds have elapsed from the start timing of the period T13, and resets the elapsed time TS.

  The variation control unit 5 changes the current predetermined time from the period T13 to the period T14, and starts measuring the period T14. The fluctuation control unit 5 determines the value of the waiting time TZ2 for the waiting time TZ1, and compares the waiting time TZ1 with the elapsed time TS, thereby causing the reactive power fluctuation unit 2 to change the reactive power fluctuation of the power system 151 in the period T14. It is determined whether or not the timing to start is reached.

  The fluctuation control unit 5 predicts the timing at which the absolute value of the AC voltage V1 within the period T15 is minimized. If the fluctuation control unit 5 predicts that the AC voltage V1 does not zero-cross within the period T15, the fluctuation control unit 5 compares the voltage value VS with the voltage value VE. The fluctuation control unit 5 predicts that the voltage value VS in the period T15 is larger than the voltage value VE, and sets the waiting time TZ2 to 6 milliseconds.

  In the period T14, the waiting time TZ1 is set to a timing at which the AC voltage V1 crosses zero. Therefore, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the timing when the AC voltage V1 crosses zero. In the period T14, the voltage value V14 of the AC voltage V1 when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 is substantially zero.

  When the elapsed time TS reaches 6 milliseconds and reaches the end timing of the period T14 (S11: Yes), the fluctuation control unit 5 changes the current predetermined time from the period T14 to the period T15 and starts measuring the period T15. To do. Further, the fluctuation control unit 5 determines the value of the waiting time TZ2 for the waiting time TZ1. Since the waiting time TZ1 in the period T15 is set to 6 milliseconds, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power in the power system 151 at the end timing of the period T15. The magnitude of the voltage value V15 of the AC voltage V1 at the end timing of the period T15 is smaller than the magnitude of the AC voltage V1 at the start timing of the period T15. In FIG. 7, when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 at the end timing of the predetermined time, the timing is illustrated by square marks.

  Thereafter, the fluctuation control unit 5 determines the timing at which the reactive power fluctuation unit 2 starts the fluctuation of the reactive power of the power system 151 based on the elapsed time TS and the waiting time TZ1, and the AC voltage V1 at the next predetermined time. The operation of predicting the timing when becomes the minimum value is repeated. For example, when the current predetermined time is the periods T16, T18, T19, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the timing when the AC voltage V1 crosses zero. In each of the periods T16, T18, and T19, the voltage values V16, V18, and V19 of the AC voltage V1 when the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 are substantially zero.

  In addition, for example, when the current predetermined time is the period T17, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the end timing of the period T17. When the current predetermined time is the period T20, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the start timing of the period T20. The magnitude of the voltage value V17 of the AC voltage V1 at the end timing of the period T17 is smaller than the magnitude of the AC voltage V1 at the start timing of the period T17.

  As described above, the fluctuation control unit 5 of the present embodiment repeatedly determines a predetermined time of 6 milliseconds shorter than the half cycle T10 of the AC voltage V1, and reacts to the reactive power fluctuation unit until the predetermined time elapses. 2 starts the reactive power fluctuation of the power system 151. The fluctuation control unit 5 of the first embodiment causes the reactive power fluctuation unit 2 to start changing the reactive power of the power system 151 at the timing when the AC voltage V1 crosses zero, so that the reactive power fluctuation unit 2 varies the reactive power four times. The time required for this varies depending on the frequency F1 of the AC voltage V1. On the other hand, the fluctuation control unit 5 according to the present embodiment causes the reactive power fluctuation unit 2 to change the reactive power once until the time when 6 milliseconds of the predetermined time elapses, so that regardless of the frequency F1 of the AC voltage V1. The reactive power can be varied four times during 24 milliseconds. In addition, the fluctuation control unit 5 in the present embodiment starts the reactive power fluctuation of the power system 151 in the reactive power fluctuation unit 2 at the timing when the AC voltage V1 is zero-crossed or at the timing when the AC voltage V1 is minimized within a predetermined time. Let The magnitude of the fluctuation of the DC component D1 due to the fluctuation of the reactive power tends to increase according to the absolute value of the AC voltage V1 when the reactive power fluctuates. The fluctuation control unit 5 controls the reactive power fluctuation unit 2 to cause the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 at the timing at which the AC voltage V1 becomes the minimum. It can suppress that the fluctuation | variation of the part D1 becomes large.

  As described above, in the isolated operation detection device 1 of the present embodiment, the fluctuation control unit 5 performs the half cycle T10 (10 milliseconds in the present embodiment) of the AC voltage V1 before starting the control of the reactive power fluctuation unit 2. ) Is started for a predetermined time (6 milliseconds in this embodiment) shorter than (). The variation control unit 5 repeatedly determines the predetermined time (periods T12 to T20) each time a predetermined time (periods T11 to T19 in the present embodiment) elapses. The fluctuation control unit 5 supplies power to the reactive power fluctuation unit 2 at a timing at which the magnitude (absolute value) of the AC voltage V1 is minimum between the start timing of the predetermined time (periods T11 to T20) and the end timing of the predetermined time. The fluctuation of the reactive power of the system 151 is started.

  According to the above configuration, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 at a timing at which the magnitude (absolute value) of the AC voltage V1 is minimized within a predetermined time. As a result, it is possible to suppress an increase in fluctuation of the DC component D1 due to fluctuations in reactive power.

  The fluctuation control unit 5 of the present embodiment can cause the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 within a predetermined time (periods T11 to T20). Therefore, the determination unit 6 determines whether or not the distributed power source 152 is operating independently for a predetermined time (approximately 24 milliseconds in the present embodiment) regardless of the frequency F1 of the AC voltage V1. Can do. In addition, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to vary the reactive power of the power system 151 at a timing at which the AC voltage V1 is minimized in each of the predetermined times (periods T11 to T20). Can be suppressed.

  In the power conditioner 10 of the present embodiment, the fluctuation control unit 5 starts measuring a predetermined time shorter than the half cycle of the AC voltage V1 before starting the control of the reactive power fluctuation unit 2. The variation control unit 5 repeatedly determines the predetermined time every time the predetermined time elapses. The fluctuation control unit 5 sends the reactive power of the power system 151 to the reactive power fluctuation unit 2 at a timing at which the magnitude (absolute value) of the AC voltage V1 is minimum between the start timing of the predetermined time and the end timing of the predetermined time. Start the change.

  According to the above configuration, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to start the fluctuation of the reactive power of the power system 151 at a timing at which the magnitude (absolute value) of the AC voltage V1 is minimized within a predetermined time. As a result, it is possible to suppress an increase in fluctuation of the DC component D1 due to fluctuations in reactive power.

  In this embodiment, the half cycle T10 of the AC voltage V1 is 10 milliseconds, and the fluctuation control unit 5 repeatedly determines a predetermined time in which the required time is set to 6 milliseconds. The length of time is an example, and is not limited to this value. For example, the length of the predetermined time (required time) may be set to a length shorter than the half cycle T10 of the AC voltage V1.

  Although the fluctuation control unit 5 predicts the reactive power fluctuation timing within the next predetermined time with respect to the current predetermined time, it is not limited to this operation. For example, the fluctuation control unit 5 may predict the fluctuation timing of reactive power within a predetermined time after two cycles after the current predetermined time for a predetermined time that is repeatedly determined. By setting the predetermined time predicted by the fluctuation control unit 5 within a predetermined time after two cycles, the period from the start timing of the current predetermined time to the start of fluctuations in reactive power of the power system 151 is further increased. Can be determined. For example, it is assumed that the total time of the time required for the determination operation of the fluctuation control unit 5 and the time until the reactive power fluctuation unit 2 starts the fluctuation of the reactive power of the power system 151 is longer than the predetermined time for one cycle. To do. In this case, by setting the fluctuation timing of the reactive power of the power system 151 within a predetermined time after two cycles after the predetermined time, the fluctuation control unit 5 causes the reactive power fluctuation unit 2 to react with the reactive power of the power system 151 at the predicted timing. Fluctuations can be started.

  The fluctuation control unit 5 predicts the timing at which the absolute value of the AC voltage V1 at the next predetermined time is minimized by calculation, but is not limited to the calculation, and stores, for example, the voltage value of the AC voltage V1. The timing may be predicted with reference to the information table.

  In addition, for example, the fluctuation control unit 5 may predict the timing at which the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151 for each predetermined time after two cycles. For example, when the fluctuation control unit 5 predicts the timing at which the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151 at a predetermined time one cycle ahead and a predetermined time two cycles ahead, the fluctuation control unit 5 The timing for changing the reactive power in time is predicted twice. The fluctuation control unit 5 may determine the average value of the two prediction timings as the timing at which the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151 at each predetermined time. In this case, the prediction accuracy can be improved as compared with the case where the fluctuation control unit 5 predicts the timing at which the reactive power fluctuation unit 2 fluctuates the reactive power of the power system 151 at each predetermined time.

  Although the fluctuation control unit 5 of the present embodiment measures the elapsed time TS using the timer of the fluctuation control unit 5, the fluctuation control unit 5 is not limited to having the timer, and the microcomputer timer of the independent operation detection device 1 is used. May be used.

DESCRIPTION OF SYMBOLS 1 Isolated operation detection apparatus 10 Power conditioner 2 Reactive power fluctuation | variation part 3 Measurement part 4 Calculation part 5 Fluctuation control part 6 Judgment part 7 Inverter 151 Electric power system 152 Distributed power supply V1 AC voltage T11-T20 Period (predetermined time)
T10 half cycle (half cycle of AC voltage)

Claims (5)

An isolated operation detection device for detecting isolated operation of a distributed power source connected to an electric power system,
A reactive power fluctuation unit that varies the reactive power of the power system;
A measuring unit for measuring the frequency of the AC voltage of the power system;
A calculation unit for obtaining a change amount of the frequency of the AC voltage from a plurality of measurement results of the measurement unit, and obtaining a magnitude of the reactive power to be varied in the reactive power fluctuation unit based on the change amount;
The reactive power fluctuation unit starts to change the reactive power of the power system at the timing when the AC voltage crosses zero, and the reactive power of the power system is changed to the magnitude of the reactive power obtained by the calculation unit. A fluctuation control section for controlling the reactive power fluctuation section;
Based on the amount of change in the frequency of the AC voltage obtained by the calculation unit before and after the reactive power variation unit varies the reactive power of the power system, the distributed power source is operated independently. An independent operation detection device comprising: a determination unit that determines whether or not there is. An isolated operation detection device for detecting isolated operation of a distributed power source connected to an electric power system,
A reactive power fluctuation unit that varies the reactive power of the power system;
A measuring unit for measuring the frequency of the AC voltage of the power system;
A calculation unit for obtaining a change amount of the frequency of the AC voltage from a plurality of measurement results of the measurement unit, and obtaining a magnitude of the reactive power to be varied in the reactive power fluctuation unit based on the change amount;
The reactive power fluctuation unit starts to change the reactive power of the power system at the timing when the AC voltage crosses zero, and the reactive power of the power system is changed to the magnitude of the reactive power obtained by the calculation unit. A fluctuation control section for controlling the reactive power fluctuation section;
Based on the amount of change in the frequency of the AC voltage obtained by the calculation unit before and after the reactive power variation unit varies the reactive power of the power system, the distributed power source is operated independently. A determination unit for determining whether or not
With
The variation controller, and when repeatedly set shorter predetermined time than the half period of the previous Ki交 current voltage, the magnitude of the AC voltage during the period until the start timing or et termination timing of the predetermined time Min alone operation detecting apparatus you characterized in that to start the change of reactive power of the power system to the reactive power fluctuation portion in comprising timing. An inverter that converts the DC power output from the distributed power source into AC power and outputs the AC power to the power system;
A reactive power variation unit that varies the reactive power of the AC power output from the inverter;
A measuring unit for measuring the frequency of the AC voltage of the power system;
A calculation unit for obtaining a change amount of the frequency of the AC voltage from a plurality of measurement results of the measurement unit, and obtaining a magnitude of the reactive power to be varied in the reactive power fluctuation unit based on the change amount;
The reactive power fluctuation unit starts to change the reactive power of the power system at the timing when the AC voltage crosses zero, and the reactive power of the power system is changed to the magnitude of the reactive power obtained by the calculation unit. A fluctuation control section for controlling the reactive power fluctuation section;
Based on the amount of change in the frequency of the AC voltage obtained by the calculation unit before and after the reactive power variation unit varies the reactive power of the power system, the distributed power source is operated independently. A power conditioner comprising: a determination unit that determines whether or not there is. An inverter that converts the DC power output from the distributed power source into AC power and outputs the AC power to the power system;
A reactive power variation unit that varies the reactive power of the AC power output from the inverter;
A measuring unit for measuring the frequency of the AC voltage of the power system;
A calculation unit for obtaining a change amount of the frequency of the AC voltage from a plurality of measurement results of the measurement unit, and obtaining a magnitude of the reactive power to be varied in the reactive power fluctuation unit based on the change amount;
The reactive power fluctuation unit starts to change the reactive power of the power system at the timing when the AC voltage crosses zero, and the reactive power of the power system is changed to the magnitude of the reactive power obtained by the calculation unit. A fluctuation control section for controlling the reactive power fluctuation section;
Based on the amount of change in the frequency of the AC voltage obtained by the calculation unit before and after the reactive power variation unit varies the reactive power of the power system, the distributed power source is operated independently. A determination unit for determining whether or not
With
The variation controller, and when repeatedly set shorter predetermined time than the half period of the previous Ki交 current voltage, the magnitude of the AC voltage during the period until the start timing or et termination timing of the predetermined time Min features and to Rupa word conditioner that starts the change of reactive power of the power system to the reactive power fluctuation portion in comprising timing.   A detection method for detecting isolated operation of a distributed power source connected to a power system,
  A reactive power fluctuation step for changing the reactive power of the power system;
  A measurement step of measuring the frequency of the AC voltage of the power system;
  A calculation step of obtaining a change amount of the frequency of the AC voltage from a plurality of measurement results of the measurement step, and obtaining a magnitude of the reactive power to be varied in the reactive power fluctuation step based on the change amount;
  Based on the amount of change in the frequency of the AC voltage obtained in the calculation step before and after changing the reactive power of the power system in the reactive power fluctuation step, the distributed power source is operated independently. A determination step for determining whether or not
  Including
  In the reactive power fluctuation step, the reactive power of the power system is started to change at the timing when the AC voltage crosses zero, and the reactive power of the power system is changed to the magnitude of the reactive power obtained in the calculation step.
  An isolated operation detection method characterized by the above.

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