WO2015111319A1

WO2015111319A1 - Islanding operation detection device and power conditioner system

Info

Publication number: WO2015111319A1
Application number: PCT/JP2014/082753
Authority: WO
Inventors: 修一三角; 馬渕　雅夫; 康介森田
Original assignee: オムロン株式会社
Priority date: 2014-01-23
Filing date: 2014-12-10
Publication date: 2015-07-30
Also published as: JP2015139308A; JP6164100B2

Abstract

　It is difficult for a modularized islanding operation detection device to acquire the phase difference between the AC voltage of a system power supply and an AC signal outputted from a PLL. An islanding operation detection device, provided with: a frequency change amount acquisition unit for acquiring the amount of change in the frequency of the system voltage of a system power supply; a transfer function acquisition unit for acquiring a transfer function representing the response characteristics of a phase change in a reference AC signal of a power conditioner in response to a change in the frequency of the system voltage; a phase difference estimation unit for sequentially estimating the phase difference, which is the difference between the phase of the system voltage and the phase of the reference AC signal, from the acquired amount of change in frequency and the transfer function; a planned value calculation unit for calculating a planned value relating to new output power for reducing the error in the output power of the power conditioner based on the estimated phase difference; and an output unit for outputting the calculated planned value relating to the output power to the power conditioner.

Description

Independent operation detection device and power conditioner system

The present invention relates to an isolated operation detection device and a power conditioner system.

Patent Document 1 discloses that an isolated operation detection device that detects an isolated operation of a power conditioner linked to a system power supply has a phase difference between an AC voltage of the system power supply and an AC signal output from a PLL (Phase Locked Loop). Is disclosed to correct the reactive current command value.
Patent Document 1 Japanese Patent Application Laid-Open No. 2008-61356

When the isolated operation detection device is modularized separately from the control device that controls the power conditioner based on the AC signal output from the PLL, the isolated operation detection device is output from the AC voltage of the system power supply and the PLL. It is difficult to obtain the phase difference from the AC signal.

An isolated operation detection device according to an aspect of the present invention is an isolated operation detection device that is used by being connected to a power conditioner connected to a distributed DC power supply and a system power supply, and outputs to the system in the power conditioner. A power value acquisition unit that acquires a value of power that is planned to be performed, a frequency change amount acquisition unit that acquires a change in frequency of the system voltage of the system power supply, and a power conditioner for a change in frequency of the system voltage A transfer function acquisition unit that acquires a transfer function representing a response characteristic of the phase change of the reference AC signal, and a difference between the phase change of the system voltage and the phase of the reference AC signal from the obtained frequency change amount and transfer function. A phase difference estimator that sequentially estimates the phase difference, and a power condition for the power that is planned to be output to the system in the power conditioner due to the estimated phase difference. Comprising a planning value calculation unit for calculating a planned values for a new output power to reduce the error in ® Na output voltage, and an output unit for outputting the planned values for the calculated output power to the power conditioner.

In the above isolated operation detection device, the planned value calculation unit causes the power conditioner to output electric power that is rotated in a direction approaching the phase of the grid, the phase of the power that is planned to be output to the grid in the power conditioner. An error in output power may be reduced by calculating a planned value for a new output voltage.

In the isolated operation detection device, the power value acquisition unit acquires the active power value output by the power conditioner, and the plan value calculation unit is acquired by the phase difference and power value acquisition unit estimated by the phase difference estimation unit. A planned value related to a new reactive power value may be calculated based on the active power value.

A power conditioner according to an aspect of the present invention includes an active power value output unit that outputs an active power value to an isolated operation detection device, and a reactive power value input unit that inputs a reactive power value from the isolated operation detection device. A power conditioner provided, and the isolated operation detection device.

Note that the above summary of the invention does not enumerate all the features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows the system block diagram which shows an example of the whole structure of the power conditioner system which concerns on this embodiment. It is a figure for demonstrating the influence which the phase difference produced between the alternating voltage of a system power supply and a reference | standard alternating signal has on a reactive power value. It is a figure which shows an example of the functional block of an isolated operation detection apparatus. It is a figure which shows an example of the reactive power value q1-frequency deviation characteristic. It is a flowchart which shows an example of the procedure which derives | leads-out the transfer function for every elapsed time. It is a figure for demonstrating the frequency of an alternating voltage, a transfer function, and a phase difference. It is a flowchart which shows an example of the procedure which correct | amends a reactive power value with the change of the frequency of a system power supply. An example of the hardware constitutions of the independent operation detection apparatus which concerns on this embodiment is shown.

Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

FIG. 1 is a system configuration diagram showing an example of the overall configuration of a power conditioner system according to the present embodiment. The power conditioner system includes a solar cell array 200 and a power conditioner 10. In the solar cell array 200, a plurality of solar cell strings in which a plurality of solar cell modules are connected in series are connected in parallel. The solar cell array 200 is an example of a distributed power source. As the distributed power source, a gas engine, a gas turbine, a micro gas turbine, a fuel cell, a wind power generator, an electric vehicle, a power storage system, or the like may be used.

The power conditioner 10 interconnects the solar cell array 200 that is a distributed DC power supply and the system power supply 300 based on the reference AC signal. The power conditioner 10 boosts the DC voltage output from the solar cell array 200, converts the boosted DC voltage into an AC voltage, and outputs the AC voltage to the system power supply 300 side. The power conditioner 10 includes a capacitor C1, a booster circuit 20, a capacitor C2, an inverter 40, a coil L, a capacitor C3, a relay 50, a control device 100, and an isolated operation detection device 400. The isolated operation detection device 400 may be provided outside the power conditioner 10 without being incorporated in the power conditioner 10.

One end and the other end of the capacitor C1 are electrically connected to the positive electrode terminal and the negative electrode terminal of the solar cell array 200 to smooth the DC voltage output from the solar cell array 200. The booster circuit 20 may be a so-called chopper type switching regulator. The booster circuit 20 boosts the voltage from the solar cell array 200. The booster circuit 20 may be constituted by an insulating booster circuit having a transformer winding such as a half-bridge booster circuit or a full-bridge booster circuit.

The capacitor C2 smoothes the DC voltage output from the booster circuit 20. The inverter 40 includes a switch. When the switch is turned on / off, the inverter 40 converts the DC voltage output from the booster circuit 20 into an AC voltage and outputs the AC voltage to the system power supply 300 side. The inverter 40 may be constituted by, for example, a single-phase full-bridge PWM inverter that includes four semiconductor switches that are bridge-connected. Of the four semiconductor switches, one pair of semiconductor switches is connected in series. Of the four semiconductor switches, the other pair of semiconductor switches are connected in series and connected in parallel with the one pair of semiconductor switches.

Between the inverter 40 and the system power supply 300, a coil L and a capacitor C3 are provided. The coil L and the capacitor C3 remove noise from the AC voltage output from the inverter 40. A relay 50 is provided between the capacitor C3 and the system power supply 300. Relay 50 switches whether to electrically disconnect between inverter 40 and system power supply 300. When the relay 50 is turned on, the power conditioner 10 and the system power supply 300 are electrically connected. When the relay 50 is turned off, the power conditioner 10 and the system power supply 300 are electrically disconnected.

The power conditioner 10 further includes

voltage sensors

12, 16, and 17 and

current sensors

14, 18, and 19. The voltage sensor 12 detects a voltage V1 corresponding to a potential difference between both ends of the solar cell array 200. The voltage sensor 16 detects a voltage V2 corresponding to a potential difference between both ends on the output side of the booster circuit 20. The voltage sensor 17 detects a voltage value V3 corresponding to the potential difference between both ends on the output side of the inverter 40.

The current sensor 14 detects the current value I1 of the current output from the solar cell array 200 and flowing to the input side of the booster circuit 20. The current sensor 18 detects the current value I2 of the current output from the booster circuit 20. The current sensor 19 detects the current value I3 of the current output from the inverter 40.

Control device 100 includes voltage booster circuit 20 and an inverter based on the voltage and current detected by

voltage sensors

12, 16 and 17 and

current sensors

14, 18 and 19 so that the maximum power can be obtained from solar cell array 200. The switching operation of 40 is controlled, the DC voltage output from the solar cell array 200 is boosted, the boosted DC voltage is converted into an AC voltage, and output to the system power supply 300 side.

In the power conditioner 10 configured as described above, when the system power supply 300 is stopped, the relay 50 must be turned off to electrically disconnect the power conditioner 10 and the system power supply 300 from each other. Further, the power conditioner 10 must control the voltage so that the voltage output to the system power supply 300 does not exceed the upper limit voltage.

The islanding detection device 400 causes the control device 100 to adjust the phase difference between the phase of the current output from the inverter 40 and the phase of the voltage, and the amplitude of the current output from the inverter 40, thereby adjusting the power condition. The reactive power is output to the na 10. The isolated operation detection device 400 detects the frequency fluctuation of the voltage of the system power supply 300 accompanying the supply of reactive power, thereby detecting that the system power supply 300 is stopped, that is, the power conditioner 10 is operating independently. To do.

In addition, the isolated operation detection device 400 has a phase difference between the phase of the current output from the inverter 40 and the phase of the voltage when the voltage output from the power conditioner 10 exceeds the upper limit voltage, and By causing the control device 100 to adjust the amplitude of the current output from the inverter 40, the reactive power supplied to the system power supply 300 side in the power conditioner 10 is increased. By increasing the reactive power, the voltage of the system power supply 300 decreases. Accordingly, the control device 100 can control the voltage output from the power conditioner 10 to be smaller than the upper limit voltage. The upper limit voltage may be a value based on an upper limit value defined by the grid connection regulations.

In this embodiment, the control device 100 and the isolated operation detection device 400 are configured as individual modules, and the control device 100 and the isolated operation detection device 400 are connected via a transmission cable 60. The control device 100 and the isolated operation detection device 400 are each configured by a substrate and a microcomputer provided on the substrate. The substrate of the control device 100 and the substrate of the isolated operation detection device 400 have connectors, and the respective connectors are connected via the transmission cable 60. Note that the control device 100 and the isolated operation detection device 400 have a wireless communication function, and the control device 100 and the isolated operation detection device 400 may exchange signals with each other by wireless communication.

The control device 100 includes a PLL (Phase Locked Loop) 102, an active power value output unit 104, and a reactive power value input unit 106. The PLL 102 outputs a reference AC signal synchronized with the AC voltage of the system power supply 300. The control device 100 controls the power output from the power conditioner 10 based on the reference AC signal output from the PLL 102. The active power value output unit 104 derives the active power value P output from the power conditioner 10 and outputs it to the isolated operation detection device 400 via the transmission cable 60. The active power value output unit 104 may derive the active power value P output from the power conditioner 10 from the voltage value V3 detected by the voltage sensor 17 and the current value I3 detected by the current sensor 19. . The reactive power value input unit 106 inputs a planned value related to output power including the reactive power value to be output from the power conditioner 10 from the isolated operation detection device 400 via the transmission cable 60.

When the AC voltage of the system power supply 300 changes abruptly, the PLL 102 cannot follow the rapid change of the AC voltage of the system power supply 300, and a large phase difference occurs between the AC voltage of the system power supply 300 and the reference AC signal. Sometimes. When such a phase difference occurs, the control device 100 may not be able to output reactive power to be output from the power conditioner 10. When the reactive power to be output cannot be output from the power conditioner 10, the isolated operation detection device 400 may not be able to immediately detect the isolated operation of the power conditioner 10.

FIG. 2 is a diagram for explaining the influence of the phase difference generated between the AC voltage of the system power supply 300 and the reference AC signal on the reactive power value. The first X axis (X1) and the first Y axis (Y1) represent the first XY coordinates for indicating the relationship between the active power and the reactive power in the system power supply 300, and the second X axis (X2) and the second Y axis (Y2). Represents a second XY coordinate for indicating a relationship between active power and reactive power recognized by the control device 100. For example, the isolated operation detection device 400 derives the reactive power value Q1 and the active power value P1 on the assumption that no phase difference is generated between the AC voltage of the system power supply 300 and the reference AC signal. In other words, the isolated operation detection device 400 derives the reactive power value Q1 and the active power value P1, assuming that the first XY coordinate and the second XY coordinate coincide. Here, when there is a phase difference θ between the AC voltage of the system power supply 300 and the reference AC signal, the power actually output from the power conditioner 10 is the reactive power value Q1 and the active power value P1. The power corresponding to the apparent power value W2 including the reactive power value Q2 (Q2 = Q1 × cos θ) and the active power value P2 (P2 = P1 × sin θ) shifted by the phase difference θ from the apparent power value W1 included. . Accordingly, the reactive power to be output from the power conditioner 10 cannot be output unless the rotation correction for canceling the phase difference θ with respect to the apparent power value W2 is performed. May not be detected immediately.

On the other hand, when the control device 100 and the isolated operation detection device 400 are modularized separately, the isolated operation detection device 400 can immediately and accurately receive the reference AC signal from the PLL 102 unless it has a special function such as high-speed communication. Cannot be received. When the reference AC signal received from the PLL 102 is delayed, the isolated operation detection device 400 cannot immediately and accurately grasp the phase difference between the AC voltage of the system power supply 300 and the reference AC signal.

Therefore, in this embodiment, the isolated operation detection device 400 estimates the phase difference between the AC voltage of the system power supply 300 and the reference AC signal without receiving the reference AC signal output from the PLL 102 from the control device 100. .

FIG. 3 is a diagram illustrating an example of a functional block of the isolated operation detection device 400. The isolated operation detection apparatus 400 includes a frequency measurement unit 402, a moving average value derivation unit 404, a frequency deviation derivation unit 406, an output voltage value acquisition unit 410, a frequency change amount acquisition unit 430, a plan value calculation unit 500, and a phase difference estimation unit 440. , A transfer function acquisition unit 441, a transfer function holding unit 442, an active power value acquisition unit 446, an output unit 450, and an isolated operation detection unit 460.

The planned value calculation unit 500 calculates a planned value related to the output power that the power conditioner 10 should output. The planned value calculation unit 500 includes a first reactive power value deriving unit 502, a second reactive power value deriving unit 504, a reactive power value adding unit 506, and a reactive power value correcting unit 510.

The frequency measuring unit 402 acquires the voltage of the system power supply 300 via the voltage sensor 17 and measures the system frequency indicating the frequency of the system power supply 300 from the acquired voltage. The frequency measuring unit 402 measures, for example, a time difference between the intermediate value between the falling and rising edges of the voltage signal detected from the voltage sensor 17 and the next falling and rising intermediate value as one cycle. When the system frequency of the system power supply 300 is 50 Hz (one system period is 20 milliseconds), the measurement period may be 1/3 or less of the system period, for example, 5 milliseconds.

The moving average value deriving unit 404 sequentially derives the moving average value of the system frequency for a predetermined moving average time based on the system frequency measured by the frequency measuring unit 402. The moving average time may be longer than one period of the system frequency, for example, 20 ms, and may be equal to or shorter than the time allowed until the isolated operation state is detected after the isolated operation state is detected. The moving average time may be, for example, shorter than 100 milliseconds, and the moving average time may be, for example, 40 milliseconds.

The frequency deviation deriving unit 406 calculates a difference between the latest moving average value derived by the moving average value deriving unit 404 and a past moving average value before a predetermined time, for example, 200 ms before the latest moving average value. Is derived as a frequency deviation. The frequency deviation deriving unit 406 may derive the frequency deviation at the same period as the system frequency measurement period, for example, every 5 milliseconds.

The first reactive power value deriving unit 502 derives the reactive power value q1 based on the frequency deviation of the system power supply 300. The first reactive power value deriving unit 502 may derive the reactive power value q1 so that the reactive power value q1 increases in proportion to the frequency deviation of the system power supply 300. For example, the first reactive power value deriving unit 502 may derive the reactive power value q1 corresponding to the frequency deviation by referring to the reactive power value q1−frequency deviation characteristic as shown in FIG.

The output voltage value acquisition unit 410 acquires a voltage value V3 corresponding to the voltage of the system power supply 300 detected by the voltage sensor 17. The second reactive power value deriving unit 504 determines whether or not the acquired voltage value V3 is greater than or equal to a predetermined upper limit voltage value Vth. When the voltage value V3 is equal to or higher than the upper limit voltage value Vth, the second reactive power value deriving unit 504 increases the reactive power to be supplied to the system power supply 300 side and suppresses an increase in the output voltage of the power conditioner 10. Therefore, the reactive power value q2 is derived.

The reactive power value adding unit 506 adds the reactive power value q1 derived by the first reactive power value deriving unit 502 and the reactive power value q2 derived by the second reactive power value deriving unit 504, thereby invalidating the reactive power value q1. A power value Q is derived.

Here, the reactive power value Q output from the reactive power value addition unit 506 takes into account the phase difference between the AC voltage of the system power supply 300 and the reference AC signal output from the PLL 102 used in the control device 100. Absent. Accordingly, the reactive power value correcting unit 510 corrects the reactive power value Q output from the reactive power value adding unit 506 in consideration of the phase difference, and derives the corrected reactive power value Q ′.

When the phase difference between the AC voltage of the system power supply 300 and the reference AC signal is θ, and the active power value of the active power output from the power conditioner 10 is P, the reactive power value correcting unit 510 is represented by the following formula ( Based on 1), the reactive power value Q ′ obtained by rotationally correcting the phase difference θ may be derived.
Q ′ = Q × cos θ−P × sin θ (1)

The active power value acquisition unit 446 acquires the value of power planned to be output to the system in the power conditioner 10. The active power value acquisition unit 446 may acquire the active power value P from the control device 100.

The frequency change amount acquisition unit 430 acquires the frequency change amount Δf per unit time of the AC voltage output from the system power supply 300. The frequency change amount acquisition unit 430 may acquire the frequency change amount Δf by deriving the frequency change amount Δf per unit time based on the frequency measured by the frequency measurement unit 402. The frequency change amount acquisition unit 430 may acquire the frequency change amount Δf from the control device 100.

Here, there is a proportional relationship between the frequency change amount Δf and the phase difference θ between the reference AC signal and the AC voltage of the system power supply 300. Therefore, a correspondence relationship between the phase difference between the reference AC signal and the AC voltage of the system power supply 300 and the frequency change amount Δf of the AC voltage of the system power supply 300 is specified in advance by experiment or simulation. Thereby, the isolated operation detection device 400 estimates the phase difference θ from the frequency change amount Δf by using the correspondence relationship without receiving the phase difference θ from the control device 100.

When the frequency change amount Δf acquired by the frequency change amount acquisition unit 430 is equal to or larger than the reference change amount, the phase difference estimation unit 440 determines the phase difference between the reference AC signal and the AC voltage of the system power supply 300, and the system power supply 300. The phase difference θ corresponding to the frequency change amount Δf acquired by the frequency change amount acquisition unit 430 is estimated based on a predetermined correspondence relationship with the frequency change amount Δf of the AC voltage.

The transfer function holding unit 442 holds the correspondence for each elapsed time after the frequency change amount Δf changes to the reference change amount or more. The transfer function holding unit 442 uses the transfer function indicating the relationship between the frequency change amount Δf of the AC voltage of the system power supply 300 and the phase difference θ between the reference AC signal and the AC voltage as a correspondence relationship, and the frequency change amount Δf is You may hold | maintain for every elapsed time after changing beyond a reference | standard change amount. The transfer function represents the response characteristic of the phase change of the reference AC signal of the power conditioner 10 to the change in the frequency of the system voltage. The transfer function holding unit 442 transfers the transfer function (θn = F (Δf)) at every elapsed time Tn (n ≧ 1, n is a positive integer) after the frequency change amount Δf changes to the reference change amount or more. May be held. The transfer function holding unit 442 may hold a table in which the frequency change amount Δf of the AC voltage of the system power supply 300 is associated with the phase difference θ between the reference AC signal and the AC voltage as a transfer function. The transfer function acquisition unit 441 acquires the transfer function held in the transfer function holding unit 442. The phase difference estimation unit 440 uses the frequency change amount Δf acquired by the frequency change amount acquisition unit 430 and the transfer function acquired by the transfer function acquisition unit 441 to the phase of the system voltage of the system power supply 300 and the phase of the reference AC signal. Are sequentially estimated.

The plan value calculation unit 500 calculates a plan value relating to a new output power for reducing an error in the output power of the power conditioner 10 based on the phase difference estimated by the phase difference estimation unit 440. The planned value calculation unit 500 causes the power conditioner 10 to output the power that is rotated in the direction in which the phase of the power planned to be output to the system power supply 300 in the power conditioner 10 approaches the phase of the system power supply 300. An error in output power may be reduced by calculating a planned value for a new output voltage. The plan value calculation unit 500 may calculate a plan value related to a new reactive power value based on the phase difference estimated by the phase difference estimation unit 440 and the active power value P acquired by the active power value acquisition unit 446. . The reactive power value correction unit 510 rotationally corrects the reactive power value Q output from the reactive power value addition unit 506 based on the phase difference θ estimated by the phase difference estimation unit 440 and outputs the corrected power value Q to the power conditioner 10. The reactive power value Q ′ to be derived is derived.

The output unit 450 outputs the plan value related to the output power calculated by the plan value calculation unit 500 to the power conditioner 10. The output unit 450 outputs to the power conditioner 10 a planned value for causing the power conditioner 10 to output power corresponding to the reactive power value Q ′ derived by the reactive power value correcting unit 510. The output unit 450 outputs an instruction signal indicating the current value of the current to be output by the power conditioner 10 whose phase or amplitude is determined based on the reactive power value Q ′ to the control device 100, so that the reactive power value Q ′. May be output from the power conditioner 10. The output unit 450 causes the power conditioner 10 to output power corresponding to the reactive power value Q ′ by outputting to the control device 100 an instruction signal indicating the reactive power value Q ′ to be output by the power conditioner 10. Good.

When detecting a change in the voltage or frequency of the system power supply 300, the islanding operation detection unit 460 determines that the system power supply 300 is stopped and the power conditioner 10 is operating independently, and causes the control device 100 to A stop signal is transmitted to stop the controller 10. In response to the stop signal, the control device 100 may open the relay 50 and electrically disconnect between the inverter 40 and the system power supply 300.

FIG. 5 is a flowchart showing an example of a procedure for deriving a transfer function (θn = F (Δf)) for each elapsed time.

First, the power conditioner 10 to be measured is connected not to the system power supply 300 but to a simulated system power supply capable of arbitrarily changing the output voltage. Further, a measuring device capable of controlling the power conditioner 10 and the simulated system power supply is connected to the power conditioner 10 and the simulated system power supply. The measuring device stops the output of reactive power from the power conditioner 10 (S100). Next, the frequency of the alternating voltage of the simulated system power supply is changed by Δf to be measured (S102), and the phase difference φ between the current and voltage output from the power conditioner 10 is acquired (S104). The measuring device detects the current and voltage output from the power conditioner 10 via the current sensor and the voltage sensor, and derives the interval between the detected zero cross point of the current and the zero cross point of the voltage. You may acquire phase difference (phi) of an electric current and a voltage.

The phase difference φ between the acquired current and voltage is a phase difference that occurs even though the measuring apparatus instructs the power conditioner 10 to stop the output of reactive power. This phase difference φ corresponds to the phase difference θ between the reference AC signal output from the PLL generated by changing the frequency by Δf and the AC voltage output from the simulated system power supply. Therefore, the measuring apparatus stores the phase difference φ in the memory as the phase difference θ in association with the elapsed time after changing the frequency of the alternating voltage of the simulated system power supply by Δf, and Δf.

When the acquired phase difference is greater than or equal to the reference phase difference (S106), the measuring apparatus returns to step S104 and acquires the phase difference φ between the current and voltage output from the power conditioner 10 again. When the phase difference becomes smaller than the reference phase difference, the measurement apparatus determines whether there is another Δf to be measured (S108). If there is another Δf to be measured, the assumed apparatus repeats the processing from step S102 to step S106 for the other Δf.

When the phase difference for each elapsed time is acquired for Δf to be measured, the measuring device derives a transfer function (θ = F (Δf)) for each elapsed time for each Δf (S110).

As described above, the measuring device derives, for each elapsed time, a transfer function indicating the correspondence between Δf and the phase difference θ for each Δf to be measured. Each derived transfer function is registered in the transfer function holding unit 442 of the isolated operation detection device 400.

FIG. 6 is a diagram for explaining the frequency, transfer function, and phase difference of the AC voltage. The frequency change of the AC voltage starts at time T0, the frequency of the AC voltage changes by Δf1 from time T0 to time T1, and the frequency of the AC voltage changes by Δf2 from time T1 to time T2. Assume that the frequency of the AC voltage changes by Δf3 from time T2 to time T3, and the frequency of the AC voltage changes by Δf4 from time T3 to time T4. Then, a transfer function ph1 is derived for Δf1. Similarly, a transfer function ph2 is derived for Δf2, a transfer function ph3 is derived for Δf3, and a transfer function ph4 is derived for Δf4. Thus, the transfer functions ph1 to ph4 derived for each elapsed time include a time component. Therefore, the phase difference used for the correction of the reactive power value Q is the total sum of the phase differences derived according to the transfer function for each elapsed time.

The total phase difference PH indicates a change in the total sum of the phase differences (PH = ph1 + ph2 + ph3 + ph4) derived according to the transfer functions ph1 to ph4 for each elapsed time. As indicated by the total phase difference PH, the phase difference θ gradually increases until a change in the frequency of the AC voltage ends after the change in the frequency of the AC voltage, and gradually after the change in the frequency of the AC voltage ends. Reduce to converge. The reactive power value correction unit 510 starts correcting the reactive power value Q based on the phase difference θ after the change in the frequency of the AC voltage, and after the change in the frequency of the AC voltage is completed, until the phase difference θ converges. Then, the reactive power value Q is corrected based on the phase difference θ.

FIG. 7 is a flowchart showing an example of a procedure for correcting the reactive power value with a change in the frequency of the system power supply 300.

The frequency change amount acquisition unit 430 acquires the frequency of the AC voltage of the system power supply 300 measured by the frequency measurement unit 402 for each unit time, and compares the previous frequency with the current frequency for each unit time. A frequency change amount is acquired (S200). When the frequency change amount acquired by the frequency change amount acquisition unit 430 is larger than the reference change amount (S202), the phase difference estimation unit 440 determines that a change has occurred in the frequency of the AC voltage of the system power supply 300. The reference change amount may be a value of 0 or more. The phase difference estimation unit 440 obtains a transfer function corresponding to the elapsed time from the detection of the frequency change from the transfer function holding unit 442 (S204).

Next, the phase difference estimation unit 440 estimates a phase difference corresponding to the acquired frequency change amount based on the acquired transfer function (S206). Furthermore, if there is another phase difference estimated up to the present time after detecting the change in the frequency, the phase difference estimation unit 440 adds the respective phase differences estimated up to the present time (S208). The reactive power value correction unit 510 receives provision of the added phase difference from the phase difference estimation unit 440. Further, the reactive power value correction unit 510 receives provision of the active power value P output from the power conditioner 10 from the active power value acquisition unit 446. Then, the reactive power value correcting unit 510 corrects the reactive power value Q provided from the reactive power value adding unit 506 according to the equation (1) using the phase difference and the active power value P, and the reactive power value Q ′ is corrected. Derived (S210).

The output unit 450 instructs the control device 100 to output the power corresponding to the derived reactive power value Q ′ from the power conditioner 10. The output unit 450 causes the power conditioner 10 to output power corresponding to the reactive power value Q ′ by outputting to the control device 100 an instruction signal indicating the reactive power value Q ′ to be output by the power conditioner 10. Good.

Next, the frequency change amount acquisition unit 430 again acquires the frequency change amount of the frequency of the AC voltage of the system power supply 300 (S214). If the phase difference after addition is larger than the reference phase difference (S216), the isolated operation is detected. The apparatus 400 repeats the processing from step S204 to step S214. On the other hand, if the phase difference after addition is equal to or smaller than the reference phase difference, the process of correcting the reactive power value is terminated.

As described above, according to the isolated operation detection device 400 according to the present embodiment, the phase difference between the AC voltage of the system power supply 300 and the reference AC signal is estimated based on the frequency change amount of the AC voltage of the system power supply 300. To do. Therefore, the isolated operation detection device 400 can grasp the phase difference between the AC voltage of the system power supply 300 and the reference AC signal without receiving the reference AC signal output from the control device 100 by the PLL 102. Even when the isolated operation detection device 400 is modularized so as to be separate from the control device 100, the phase difference between the AC voltage of the system power supply 300 and the reference AC signal can be grasped. Therefore, the isolated operation detection device 400 can derive the reactive power value to be output from the power conditioner 10 in consideration of the phase difference. Even if the phase difference occurs, the isolated operation detection device 400 can output the desired reactive power from the power conditioner 10, so that the isolated operation of the power conditioner 10 can be detected immediately.

Each unit included in the isolated operation detection device 400 according to the present embodiment installs a program recorded on a computer-readable recording medium that performs various processes related to the isolated operation detection of the power conditioner 10, and installs the program on the computer. You may comprise by making it perform. That is, even if the isolated operation detecting device 400 is configured by causing the computer to execute programs that perform various processes related to the isolated operation detection of the power conditioner 10, the computer functions as each unit included in the isolated operation detecting device 400. Good.

FIG. 8 shows an example of the hardware configuration of the isolated operation detection apparatus 400 according to the present embodiment. The isolated operation detection apparatus 400 according to the present embodiment includes a CPU peripheral unit having a CPU 904 and a RAM 906 connected to each other by a host controller 902, a ROM 910 connected to the host controller 902 by an input / output controller 908, and a communication interface 912. Prepare.

The host controller 902 connects the RAM 906 and the CPU 904 that accesses the RAM 906 at a high transfer rate. The CPU 904 operates based on programs stored in the ROM 910 and the RAM 906 to control each unit. The input / output controller 908 connects the host controller 902, the communication interface 912 that is a relatively high-speed input / output device, and the ROM 910.

The communication interface 912 communicates with the control device 100 via the communication interface 912 and the transmission cable 60. The ROM 910 stores programs and data used by the CPU 904 in the isolated operation detection device 400. In addition, the ROM 910 stores a boot program that the isolated operation detection device 400 executes at startup, a program that depends on the hardware of the isolated operation detection device 400, and the like.

The program provided to the ROM 910 via the RAM 906 is stored in a computer-readable recording medium such as a CD-ROM or USB memory and provided by the user. The program is read from the recording medium, installed in the ROM 910 in the isolated operation detection device 400 via the RAM 906, and executed by the CPU 904.

The program installed and executed in the isolated operation detection device 400 works on the CPU 904 or the like to make the isolated operation detection device 400 the frequency measurement unit 402, the moving average value derivation unit 404, the frequency deviation described with reference to FIGS. Deriving unit 406, output voltage value acquiring unit 410, frequency change amount acquiring unit 430, plan value calculating unit 500, phase difference estimating unit 440, transfer function acquiring unit 441, transfer function holding unit 442, active power value acquiring unit 446, output Unit 450 and single operation detection unit 460.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

The execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior”. It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for the sake of convenience, it means that it is essential to carry out in this order. is not.

DESCRIPTION OF SYMBOLS 10 Power conditioner 20 Booster circuit 40 Inverter 50 Relay 60 Transmission cable 100 Control apparatus 102 PLL
104 Active power value output unit 106 Reactive power value input unit 200 Solar cell array 300 System power supply 400 Independent operation detection device 402 Frequency measurement unit 404 Moving average value derivation unit 406 Frequency deviation derivation unit 410 Output voltage value acquisition unit 430 Frequency change amount acquisition Unit 440 phase difference estimation unit 441 transfer function acquisition unit 442 transfer function holding unit 446 active power value acquisition unit 450 output unit 460 isolated operation detection unit 500 plan value calculation unit 502 first reactive power value derivation unit 504 second reactive power value derivation Unit 506 reactive power value addition unit 510 reactive power value correction unit

Claims

An isolated operation detection device used by being connected to a power conditioner connected to a distributed DC power supply and a system power supply,
A power value acquisition unit for acquiring a value of power planned to be output to the grid in the power conditioner;
A frequency change amount acquisition unit for acquiring a change amount of a frequency of the system voltage of the system power supply;
A transfer function acquisition unit that acquires a transfer function representing a response characteristic of a phase change of a reference AC signal of the power conditioner with respect to a change in frequency of the system voltage;
A phase difference estimator that sequentially estimates a phase difference that is a difference between the phase of the grid voltage and the phase of the reference AC signal from the obtained change in frequency and the transfer function;
Calculate a planned value for new output power to reduce an error in the output voltage of the power conditioner with respect to the power planned to be output to the grid in the power conditioner due to the estimated phase difference A planned value calculation unit to
An isolated operation detection device comprising: an output unit that outputs the calculated planned value related to the output power to the power conditioner.
The planned value calculation unit is a new output for causing the power conditioner to output electric power obtained by rotating the phase of the electric power that is planned to be output to the grid in the power conditioner in a direction approaching the phase of the grid. The isolated operation detection device according to claim 1, wherein an error in output power is reduced by calculating a planned value related to voltage.
The power value acquisition unit acquires an active power value output by the power conditioner,
The plan value calculation unit calculates a plan value related to a new reactive power value based on the phase difference estimated by the phase difference estimation unit and the active power value acquired by the power value acquisition unit. The isolated operation detection device according to 1 or 2.
An active power value output unit that outputs the active power value to the isolated operation detection device;
A reactive power value input unit that inputs the reactive power value from the isolated operation detection device;
A power conditioner comprising:
A power conditioner system comprising the isolated operation detection device according to claim 3.
A program for causing a computer to function as the isolated operation detection device according to any one of claims 1 to 3.