JP2012055036A - Operation stabilization method of power conditioner at time of brownout recovery, power conditioner carrying out the same, and program for operation stabilization of power conditioner at time of brownout recovery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an output effective power recovered to a state just before occurrence of a brownout, promptly in the case where an electric power system is recovered normally from the brownout.SOLUTION: A power conditioner comprises: a brownout detection part 4 which monitors an internal DC voltage Vdc, and switches an operation mode to a brownout mode by deciding that a momentary voltage drop phenomenon of an electric power system 11 has occurred in the case where the voltage Vdc exceeds an upper limit set in advance, and returns the operation mode to a normal mode by deciding that the momentary voltage drop phenomenon has been restored to the normal state in the case where the voltage Vdc falls short of a lower limit set in advance; an inverter control part 9 which operates an inverter circuit 13 so that an output current iac is in agreement with a value just before the occurrence of the momentary voltage drop phenomenon or a movement average value thereof in the brownout mode; a boosting-up chopper control part 14 which changes a DC input current iin so that the voltage Vdc is in agreement with a target value set in advance in the brownout mode; and a maximum power following control part 6 which returns a current change command of the DC input current iin to a command just before the occurrence of the momentary voltage drop phenomenon in the case where the operation mode has been returned to the normal mode from the brownout mode.

Description

  The present invention relates to a method for stabilizing operation at the time of recovery of a power conditioner connected to a power system, for example, a distributed power source such as a solar cell, a power conditioner for implementing the method, and at the time of recovery from a power conditioner of a power conditioner. It relates to a program for stabilizing operation.

  FIG. 16 shows a conventional power conditioner. The main circuit 101 of the power conditioner includes a boost chopper unit 103 that adjusts the output voltage of the solar cell array 102 to a voltage that provides maximum output power, and an inverter unit that converts the DC power boosted by the boost chopper unit 103 into AC power. 104 and a filter unit 105. Further, the control circuit 106 of the main circuit 101 is supplied with a maximum power follow-up control unit 107 that detects a current value at which the output power of the solar cell array 102 becomes maximum and supplies a current change command of the DC input current iin. A DC input current control unit 108 that operates switching of the step-up chopper unit 103 based on a current change command of the DC input current iin, and an output power iac so that the internal DC voltage Vdc matches a preset DC voltage reference value. An internal DC voltage constant control unit 109 that determines a current change command and supplies it to the inverter / switching control unit 110; an inverter / switching control unit 110 that operates a switch of the inverter unit 104 based on the current change command of the output power iac; A PLL circuit 111 is provided that generates a reference waveform whose frequency and phase match the interconnection point voltage Vg.

  A voltage source current control system is adopted for controlling the power conditioner, and the output current iac is controlled so that the waveform of the output current iac matches the frequency and phase of the interconnection point voltage Vg. FIG. 16 shows an example of instantaneous current value control. The connection point voltage Vg is monitored, and a reference waveform whose frequency and phase match the connection point voltage Vg is generated by the PLL circuit 111 while referring to the monitoring.

  On the other hand, on the DC side, maximum power tracking control (MPPT) is adopted so that the maximum power is always extracted from the solar cell array 102 having the IV characteristics and the PV characteristics as shown in FIG. The maximum power tracking control unit 107 periodically changes the input current iin while monitoring the input power, and the DC input current control unit 108 causes the step-up chopper so that the operating point always coincides with the maximum point of the PV characteristic curve. The switching of the unit 103 is controlled to control the input current iin.

  Next, the input power iin is charged to the smoothing capacitor 112 on the primary side of the inverter circuit. The primary side circuit voltage (internal DC voltage Vdc) is controlled to a fixed reference voltage (DC voltage reference value) such as 350 V by the internal DC voltage constant control unit 109. That is, while the internal DC voltage constant control unit 109 monitors the internal DC voltage Vdc, the absolute value of the reference waveform generated by the PLL circuit 111 is controlled and used as a command waveform so that the voltage always matches the reference voltage. . Finally, the instantaneous value of the command waveform and the sawtooth carrier wave is compared to perform switching control (gate control). Also, the reference waveform generated by the PLL circuit 111 is multiplied by the current command value by the internal DC voltage constant control unit 109 to obtain a current command waveform, which is provided with an allowable width (hysteresis), and the output current iac is the upper limit or lower limit of the allowable width When the output current iac is reached, the switching is reversed to reverse the increase / decrease direction of the output current iac, and the output current iac is controlled so that the output current iac always falls within the allowable range.

  The principle is to continue operation as much as possible against transient fluctuations in the power system such as instantaneous drop and sudden phase change. However, if it is technically unavoidable, the gate block in the power conditioner (PCS) If the power system returns to normal, the grid operation is resumed.

Kobayashi, Ito, “Development of Transient Characteristics Analysis Model of Power Conditioner for Grid-connected Solar Power Generation”, Research Report (R07027), July 2008 Okada et al., "Development of Inverter Simulation Program (Part 2)-Verification of Analytical Accuracy by Measurement Comparison-", Research Report (R07016), 2008

  Examine the operation behavior of the inverter when an instantaneous voltage drop phenomenon (instantaneous voltage drop) occurs in the power system.

(1) At the time of voltage drop As shown in FIG. 18, when the voltage drop occurs, the interconnection point voltage Vg rapidly decreases stepwise. Generally, the instantaneous drop is caused by a short-circuit failure on the power system side due to lightning strikes, etc., and the system impedance as viewed from the power conditioner is reduced. For this reason, when an output current control measure against the instantaneous drop is not appropriate, there is a possibility that an overcurrent occurs instantaneously and the operation stops. Furthermore, in the case of a system-side short circuit accident, an excessive current flows from the other power supply to the transmission / distribution line, so a case where the voltage phase changes suddenly due to the line impedance is considered. As a result, unnecessary detection may be caused depending on an isolated operation detection method such as a phase jump detection method.

  When the operation is continued at the time of occurrence of a sag, the interconnection point voltage value Vg is lowered, so that the output power is generally lowered. At this time, depending on the design of the control system, if the inflow of current to the internal DC unit is continued by the boost chopper unit 103, the voltage of the smoothing capacitor 112 (internal DC voltage Vdc) increases. In this case, the upper limit of the device protection level is reached and the inverter is stopped.

(2) At the time of voltage recovery As shown in FIG. 18, since the interconnection point voltage Vg increases stepwise, if the output current is constant before and after, the output power rapidly increases stepwise.

  As a result, the discharge of the smoothing capacitor 112 becomes large, the voltage of the internal DC section temporarily decreases, and the power conditioner may be stopped due to fluctuations in the output current iac or a protection function. Further, the system phase changes (such as returning to the phase immediately before the instantaneous drop) as in the case of the voltage drop, which may cause unnecessary stop detection of the isolated operation detection function.

  The present invention relates to a method for stabilizing operation at the time of recovery of an instantaneous drop of a power conditioner, a power conditioner, and a power conditioner capable of quickly returning to a state immediately before the occurrence of the instantaneous drop when the power system returns to normal from the instantaneous drop. The purpose is to provide a program for stabilizing the operation when recovering from an instantaneous drop.

  In order to achieve this object, the method of stabilizing operation of the power conditioner according to claim 1 during recovery from an instantaneous drop monitors the internal DC voltage Vdc, and the internal DC voltage Vdc exceeds a preset upper limit value. In this case, it is determined that the instantaneous voltage drop phenomenon of the power system has occurred, the operation mode is switched to the instantaneous voltage drop mode, and the instantaneous voltage drop phenomenon has converged when the internal DC voltage Vdc falls below a preset lower limit value. The operation mode is returned to the normal mode by operating the switch of the inverter circuit so that the output current iac matches the value immediately before the occurrence of the instantaneous voltage drop phenomenon or the moving average value in the sag mode. When the DC input current iin is changed so that the internal DC voltage Vdc matches a preset target value and the operation mode is returned from the sag mode to the normal mode, the DC input current iin It is intended to return the current change command on a command just before the occurrence of the instantaneous voltage drop phenomenon.

  The power conditioner according to claim 2 monitors the internal DC voltage Vdc and determines that an instantaneous voltage drop phenomenon of the power system has occurred when the internal DC voltage Vdc exceeds a preset upper limit value. A voltage sag detector that switches the operation mode to the sag mode and determines that the instantaneous voltage drop phenomenon has converged when the internal DC voltage Vdc falls below a preset lower limit value, and returns the operation mode to the normal mode; In the sag mode, the inverter control unit that operates the switch of the inverter circuit so that the output current iac matches the value immediately before the occurrence of the instantaneous voltage drop phenomenon or its moving average value, and in the sag mode, the internal DC voltage Vdc is A step-up chopper controller that changes the DC input current iin so that it matches the preset target value, and when the operation mode is returned from the sag mode to the normal mode, Those with a maximum power follow-up control unit to return the current change instruction of the input current iin of a command just before the occurrence of the instantaneous voltage drop phenomenon.

  Furthermore, the operation stabilization program at the time of recovery of the power conditioner from the power failure according to claim 3 monitors at least the internal DC voltage Vdc, and the power when the internal DC voltage Vdc exceeds a preset upper limit value. It is judged that the instantaneous voltage drop phenomenon of the system has occurred and the operation mode is switched to the instantaneous drop mode, and it is judged that the instantaneous voltage drop phenomenon has converged when the internal DC voltage Vdc falls below the preset lower limit value. An instantaneous voltage drop detecting means for returning the operation mode to the normal mode, and an inverter control for operating the switch of the inverter circuit so that the output current iac coincides with the value immediately before the occurrence of the instantaneous voltage drop phenomenon or the moving average value in the instantaneous voltage drop mode. And a step-up chopper control means for changing the DC input current iin so that the internal DC voltage Vdc coincides with a preset target value in the voltage sag mode When the operation mode is returned from the sag mode to the normal mode, the computer functions as a maximum power follow-up control unit that returns the current change command of the DC input current iin to the command immediately before the occurrence of the instantaneous voltage drop phenomenon. is there.

  Therefore, when the instantaneous voltage drop phenomenon of the power system is detected based on the internal DC voltage Vdc, the operation mode is switched from the normal mode to the instantaneous voltage drop mode. In the sag mode, the inverter circuit is controlled so that the output current iac becomes the value immediately before the occurrence of the sag, so that the output current iac can be maintained at the value immediately before the sag (output current). Constant control). Further, by maintaining the output current iac at a value immediately before the voltage sag, an excessive increase in the internal DC voltage Vdc is expected, but the boost chopper unit is adjusted so that the internal DC voltage Vdc becomes a preset target value. By operating and changing the DC input current iin, an excessive increase in the internal DC voltage Vdc can be suppressed (internal DC voltage Vdc constant control).

  When the convergence of the instantaneous voltage drop phenomenon is detected based on the internal DC voltage Vdc, the operation mode is returned from the instantaneous drop mode to the normal mode. As a result, the inverter circuit side cancels the constant output current control and returns to the control based on the internal DC voltage Vdc. Further, the boost chopper unit side is released from the constant control of the internal DC voltage Vdc and returns to the maximum power tracking control.

  According to a method for stabilizing operation when the power conditioner according to claim 1 recovers from a sag, a power conditioner according to claim 2, and a program for stabilizing operation when the power conditioner recovers from a sag. For example, since the output current iac can be maintained at the value immediately before the sag during the sag, the excessive fluctuation of the output current iac can be suppressed when the system voltage returns to normal from the sag. The active power can be quickly returned to the state immediately before the occurrence of the instantaneous drop.

It is a block diagram which shows an example of embodiment of the power conditioner of this invention. It is a flowchart which shows an example of embodiment of the driving | running stabilization method at the time of the sag recovery of the power conditioner of this invention, and shows switching of an operation mode. It is a flowchart which shows the driving | operation in normal mode. It is a flowchart which shows the driving | operation in a sag mode. The simulation result of the driving | running stabilization method at the time of the sag recovery of the power conditioner of this invention is shown, (a) is a figure which shows the time change of output current iac, (b) is a figure which shows the time change of output active power, (C) is a figure which shows the time change of DC input current iin, (d) is a figure which shows the time change of internal DC voltage Vdc. It is a block diagram of a current control system and a gate output unit. It is a block diagram of an effective current control part. It is a block diagram of the reactive current control part. It is a control block diagram of a step-up chopper. Operation characteristics of the power conditioner at the time of a sag when the operation stabilization method at the time of the sag recovery of the present invention is not implemented (simulation result, sag mode is not applied, voltage drop rate: 30%, sag duration: 500 ms (A) is a diagram showing a time change of the system voltage, (b) is a diagram showing a time change of the output current, (c) is a diagram showing a time change of the output power, and (d) is a DC input voltage. The figure which shows the time change of (2), (e) is a figure which shows the time change of DC input current, (f) is a figure which shows the time change of internal DC voltage. The operation characteristics (test result, model H, voltage drop rate: 30%, voltage sag duration: 500 ms) of the conventional power conditioner at the time of a sag are shown, (a) is a diagram showing the time change of the system voltage ( FIG. 4B is a diagram showing the time change of the output current, FIG. 4C is a diagram showing the time change of the output power, and FIG. 4D is a diagram showing the time change of the DC voltage. Driving characteristics of the power conditioner at the time of a voltage drop when the operation stabilization method at the time of a voltage drop recovery of the present invention is implemented (simulation results, voltage drop rate: 30%, voltage drop duration: 500 ms when the voltage drop mode is applied) (A) is a diagram showing a time change of the system voltage, (b) is a diagram showing a time change of the output current, (c) is a diagram showing a time change of the output power, and (d) is a DC input voltage. The figure which shows the time change of (2), (e) is a figure which shows the time change of DC input current, (f) is a figure which shows the time change of internal DC voltage. Driving characteristics of the power conditioner at the time of a voltage sag when the method for stabilizing operation at the time of the sag recovery of the present invention is implemented (simulation results, voltage drop rate: 80%, voltage sag duration: 500 ms when the voltage sag mode is applied) (A) is a diagram showing a time change of the system voltage, (b) is a diagram showing a time change of the output current, (c) is a diagram showing a time change of the output power, and (d) is a DC input voltage. The figure which shows the time change of (2), (e) is a figure which shows the time change of DC input current, (f) is a figure which shows the time change of internal DC voltage. Operation characteristics of the power conditioner at the time of a voltage sag when the method for stabilizing operation at the time of the sag recovery of the present invention is carried out (simulation results, voltage drop rate: 30%, voltage sag duration: 40 ms when the voltage sag mode is applied (A) is a diagram showing a time change of the system voltage, (b) is a diagram showing a time change of the output current, (c) is a diagram showing a time change of the output power, and (d) is a DC input voltage. The figure which shows the time change of (2), (e) is a figure which shows the time change of DC input current, (f) is a figure which shows the time change of internal DC voltage. Driving characteristics of the power conditioner at the time of a voltage sag when the operation stabilization method at the time of the sag recovery of the present invention is implemented (simulation result, voltage drop rate: 80%, voltage sag duration: 40 ms when the voltage sag mode is applied) (A) is a diagram showing a time change of the system voltage, (b) is a diagram showing a time change of the output current, (c) is a diagram showing a time change of the output power, and (d) is a DC input voltage. The figure which shows the time change of (2), (e) is a figure which shows the time change of DC input current, (f) is a figure which shows the time change of internal DC voltage. It is a block diagram which shows the conventional power conditioner. It is a figure for demonstrating the IV characteristic and PV characteristic of a solar cell. It is a figure which shows the characteristic (voltage drop rate: 40%, duration: 300 ms) of the connection point voltage at the time of a sag occurrence.

  Hereinafter, the configuration of the present invention will be described in detail based on the form shown in the drawings.

  FIG. 1 shows an example of an embodiment of a power conditioner of the present invention. The power conditioner 1 is for connecting, for example, a solar cell as a distributed power source 2 to a consumer's load and power system, and the power conditioner 1 of the present embodiment arranges the solar cells in an array. A solar cell array (hereinafter referred to as a solar cell array 2) is connected to a consumer's load and power system. However, the distributed power source 2 is not necessarily limited to the solar cell array, and may be a single solar cell.

  The power conditioner 1 monitors the internal DC voltage Vdc, and when the internal DC voltage Vdc exceeds a preset upper limit value, it is determined that an instantaneous voltage drop phenomenon of the power system 11 has occurred, and the operation mode is instantaneously reduced. In addition to switching to the mode, the instantaneous voltage drop detecting unit 4 that determines that the instantaneous voltage drop phenomenon has converged when the internal DC voltage Vdc falls below a preset lower limit value and returns the operation mode to the normal mode, The inverter control unit 9 that operates the switch of the inverter circuit 13 so that the output current iac coincides with the value immediately before the occurrence of the instantaneous voltage drop phenomenon or the moving average value thereof, and the internal DC voltage Vdc is preset in the sag mode. The step-up chopper controller 14 that changes the DC input current iin so as to match the set target value, and the DC when the operation mode is returned from the sag mode to the normal mode. And a maximum power follow-up control unit 6 to return the current change command forces the current iin to a command just before the occurrence of the instantaneous voltage drop phenomenon.

  The control circuit 3 of the power conditioner 1 can also be realized by executing on the computer an operation stabilization program when the power conditioner 1 of the present invention recovers from an instantaneous drop. In the present embodiment, a case where an operation stabilization program (hereinafter simply referred to as an operation stabilization program) when the power conditioner 1 recovers from an instantaneous drop will be described as an example.

  FIG. 1 shows a power conditioner 1 of this embodiment for executing an operation stabilization program. The power conditioner 1 includes a main circuit 10, a control circuit 3, and a storage unit 12, and the main circuit 10 includes a boost chopper unit 15 that raises the voltage of DC power supplied from a solar cell array that is a distributed power source 2; The inverter unit 13 converts DC power into AC power and the filter unit 16 absorbs harmonic current. Further, the inverter unit 13 is provided with a smoothing capacitor 17.

  The control circuit 3 includes a voltage sag detector (instantaneous voltage sag detector) 4, an inverter controller 9, a step-up chopper controller 14, a maximum power follow-up controller 6, and a PLL circuit (not shown).

  Here, the DC input current iin is a DC input current to the power conditioner 1. The DC input voltage value Vin is a DC input voltage to the power conditioner 1. The internal DC voltage Vdc is a terminal voltage of the smoothing capacitor 17. The output current iac is an AC output current of the power conditioner 1.

  The control circuit 3 controls the main circuit 10 in accordance with an operation stabilization program stored in the storage unit 12, and is a CPU (Central Processing Unit), for example. The control circuit 3 executes the operation stabilization program, thereby causing the above-described instantaneous voltage drop detection unit (instantaneous voltage drop detection unit) 4, inverter control unit (inverter control unit) 9, boost chopper control unit (boost chopper control unit). ) 14, a maximum power tracking control unit (maximum power tracking control means) 6, and a PLL circuit are configured.

  An internal DC voltage Vdc is supplied to the voltage sag detector 4. The instantaneous drop detection unit 4 constantly monitors the internal DC voltage Vdc and compares it with the upper limit value and the lower limit value stored in advance in the storage unit 12. When the internal DC voltage Vdc exceeds the upper limit value, it is determined that an instantaneous voltage drop phenomenon has occurred in the power system 11, and the operation mode is switched to the instantaneous voltage drop mode. On the other hand, when the internal DC voltage Vdc falls below the lower limit value, it is determined that the instantaneous voltage drop phenomenon has converged, and the operation mode is returned to the normal mode. The operation mode switching command is transmitted to the output current command unit 19 of the inverter control unit 9, the internal DC voltage constant control unit 7 of the boost chopper control unit 14, and the maximum power tracking control unit 6.

  The inverter control unit 9 includes an inverter switching operation unit 18, an output current command unit 19, and an internal DC voltage constant control unit 7. The internal DC voltage constant control unit 7 is also a constituent element of the boost chopper control unit 14.

  The inverter switching operation unit 18 refers to a reference current waveform supplied from a PLL (Phase Locked Loop) circuit (not shown) in the voltage sag mode, and converts the DC current / voltage boosted by the boost chopper unit 15 to the same frequency as that of the power system. The AC current / voltage is converted into the same phase AC current / voltage, and the output current iac of the main circuit 10 is set to the value immediately before the occurrence of the instantaneous drop or the moving average value based on the current change command of the output current iac from the output current command unit 19. The switch of the inverter circuit 13 is operated so as to match. For example, when the current change command of the output current iac is to increase the output current iac, the period during which the switch of the inverter circuit 13 is turned on is lengthened and decreased. Shorten the period during which the switch is on.

  The output current command unit 19 stores the output current iac immediately before the occurrence of the sag in the normal mode or the moving average value thereof as the output current command value It, and after the transition to the sag mode, the output current iac immediately before the transition is output. A current change command of the output current iac is supplied to the inverter switching operation unit 18 so as to coincide with the value It. For example, when the output current iac is larger than the output current command value It, that is, when the value of the output current iac is lowered, a current change command for decreasing the output current iac is supplied, and the output current iac is larger than the output current command value It. When the output current iac is small, ie, when the value of the output current iac is increased, a current change command for increasing the output current iac is supplied. An output current iac is supplied to the output current command unit 19.

  In the present embodiment, the output current iac is set as the output current command value It. That is, in the normal mode before the instantaneous drop is detected by the instantaneous drop detection unit 4, the output current iac at that time is stored as the output current command value It at a predetermined cycle. The memory is overwritten. Therefore, the stored output current command value It is always updated to a new value (output current iac). Then, when receiving a switching command for switching the operation mode to the sag mode from the sag detecting unit 4, the output current command unit 19 stops the periodic overwriting of the output current command value It. Therefore, in the voltage sag mode, the output current iac immediately before the occurrence of the voltage sag is stored and stored as the output current command value It. The period for overwriting the output current command value It is, for example, about 0.5 seconds or less, and preferably 0.1 seconds or less.

  In the above description, the output current iac is used as the output current command value It. However, the present invention is not limited to this. For example, a moving average value of the output current iac may be used as the output current command value It. That is, when storing the output current iac at that time in a predetermined cycle, the output current iac for several cycles is stored, and the oldest value is overwritten with the newest value and replaced. Then, a moving average value of the stored output current iac for several cycles may be obtained and used as the output current command value It. Here, the number of samples for obtaining the moving average value is not particularly limited, but, for example, about 5 (for 5 cycles) is preferable.

  The inverter switching operation unit 18 receives a current change command of the output current iac from the output current command unit 19 in the sag mode, but receives a current change command of the output current iac from the internal DC voltage constant control unit 7 in the normal mode. Then, the switch of the inverter circuit 13 is operated.

  In the normal mode, the inverter switching operation unit 18 receives the current change command of the output current iac from the internal DC voltage constant control unit 7 and operates the switch of the inverter circuit 13 itself. Although it is the same as the switching operation unit, the inverter switching operation unit 18 of the present invention is different in that the switch of the inverter circuit 13 is operated in response to a current change command of the output current iac from the output current command unit 19 in the sag mode. Yes.

  The step-up chopper controller 14 includes an internal DC voltage constant controller 7 and a DC input current controller 8.

  The internal DC voltage constant control unit 7 constantly monitors the internal DC voltage Vdc in the sag mode, and inputs a current change command of the DC input current iin so that the internal DC voltage Vdc matches a preset target value. The current is supplied to the current controller 8 (DC-AVR function: Direct Current-Automatic Voltage Regulator). For example, when the internal DC voltage Vdc is larger than the target value, that is, when the internal DC voltage Vdc is lowered, a current change command for decreasing the DC input current iin is supplied, and when the internal DC voltage Vdc is smaller than the target value, that is, internal When the DC voltage Vdc is increased, a current change command for increasing the DC input current iin is supplied. The internal DC voltage constant control unit 7 is supplied with an internal DC voltage Vdc.

  In the normal mode, the internal DC voltage constant controller 7 constantly monitors the internal DC voltage Vdc, and issues a current change command for the output current iac so that the internal DC voltage Vdc matches a preset DC voltage reference value. This is supplied to the inverter switching operation unit 18. For example, when the internal DC voltage Vdc is larger than the target value, that is, when the internal DC voltage Vdc is lowered, a current change command for increasing the output current iac is supplied, and when the internal DC voltage Vdc is smaller than the target value, that is, the internal DC voltage When the voltage Vdc is increased, a current change command for decreasing the output current iac is supplied.

The constant internal DC voltage control unit 7 performs control so that the internal DC voltage Vdc matches a preset value (DC-AVR function) itself. Although it is the same as the control unit, the internal DC voltage constant control unit 7 of the present invention is different in that a current change command of the DC input current iin is supplied to the DC input current control unit 8 in the sag mode.

  The DC input current control unit 8 operates the gate switch of the step-up chopper unit 15 in accordance with the current change command of the DC input current iin supplied from the internal DC voltage constant control unit 7 in the sag mode, and sets the DC input current iin. Increase / decrease (DC-ACR function: Direct Current-Automatic Current Regulator, DC current adjustment function) (PWM control). For example, when the current change command of the DC input current iin is to reduce the DC input current iin, the gate switch ON / OFF frequency is decreased and when the DC input current iin is increased, the gate switch is turned on / off. Increase frequency.

  In the normal mode, the DC input current control unit 8 operates the gate switch of the step-up chopper unit 15 according to the current change command of the DC input current iin supplied from the maximum power tracking control unit 6 to increase or decrease the DC input current iin. To do.

  The DC input current control unit 8 operates the gate switch of the step-up chopper unit 15 in accordance with the current change command of the DC input current iin to increase or decrease the DC input current iin (DC-ACR function) itself. The DC input current control unit 8 of the present invention is the same as the DC input current control unit of the inverter, but the DC input current control unit 8 of the present invention is a current change command for the DC input current iin supplied from the internal DC voltage constant control unit 7 in the sag mode. Is different in that the operation is performed according to.

  The maximum power tracking control unit 6 has a maximum power tracking function (MPPT: Maximum Power Point Tracking), detects a current value at which the output power of the solar cell array becomes maximum in the normal mode, A current change command for the DC input current iin is supplied to the DC input current controller 8 so that the DC input current iin matches. The maximum power tracking control unit 6 is supplied with a DC input current iin and a DC input voltage value Vin. The maximum power follow-up control unit 6 detects a current value Imax that maximizes the output power based on the solar cell output power Pin determined by the product of the DC input current iin and the DC input voltage value Vin. For example, the solar cell output power Pin is monitored while a current increase signal (or current decrease signal) is supplied to the DC input current control unit 8 as a current change command of the DC input current iin, and the solar cell output power Pin increases. During this time, a current increase signal (or a current decrease signal) is continuously supplied to the DC input current control unit 8. Next, if the current increase signal is supplied when the solar cell output power Pin starts to decrease, the current decrease signal is supplied (if the current decrease signal is supplied, the current increase signal is supplied). . While Pin is increasing in this supply state, a current decrease signal (or current increase signal) is continuously supplied to the DC input current control unit 8. When Pin starts to decrease again, if the current decrease signal is supplied, the current increase signal is supplied again (if the current increase signal is supplied, the current decrease signal is supplied again). By repeating the above, ine necessarily exists in the vicinity of Imax where the maximum output Pmax is obtained. Whenever Imax changes due to a change in weather or the like, iin automatically moves to the vicinity of the new Imax by repeating the above procedure. As described above, a current change command for the DC input current iin is supplied to the DC input current control unit 8 so that the output power is always maximized.

  The maximum power follow-up control unit 6 stores a current change command for the DC input current iin immediately before the occurrence of the instantaneous voltage drop phenomenon. That is, in the normal mode, a current change command of the DC input current iin at that time is stored in a predetermined cycle. The memory is overwritten. Therefore, the stored current change command is always updated to a new command. Then, when receiving a switching command for switching the operation mode from the voltage drop detection unit 4 to the voltage drop mode, the maximum power follow-up control unit 6 stops periodic overwriting of the current change command. Therefore, in the sag mode, the current change command immediately before the occurrence of the sag is stored and saved. The period for overwriting the current change command is, for example, about 0.5 seconds or less, and preferably 0.1 seconds or less.

  Moreover, in the sag mode, the maximum power follow-up control unit 6 is in a pause state, and the detection of the current value Imax that maximizes the output power of the solar cell array 2 is paused.

  The maximum power follow-up control unit 6 detects the current value at which the output power of the solar cell array becomes maximum, and the DC input current control unit 6 determines the current of the DC input current iin so that the DC input current iin matches this current value. The supply of the change command itself is the same as the maximum power follow-up control unit of a power conditioner that is already on the market, but the maximum power follow-up control unit 6 of the present invention is in a sleep state in the sag mode. The current change command of the DC input current iin immediately before the occurrence of the voltage drop phenomenon is memorized, and the current change command memorized when the operation mode returns from the voltage sag mode to the normal mode after the sag convergence is obtained. It differs in that it is supplied to the control unit 8.

  The storage unit 12 can store at least data and programs, and is, for example, a hard disk.

  The storage unit 12 uses an upper limit value and a lower limit value that are threshold values of the internal DC voltage Vdc for determining occurrence and convergence of the instantaneous voltage drop, a target value of the internal DC voltage Vdc used in the instantaneous voltage drop mode, and a normal mode. A DC voltage reference value for the internal DC voltage Vdc is stored in advance. Here, the DC voltage reference value is a value designed so that the internal DC voltage Vdc becomes the value during operation in the normal mode. For example, when the internal DC voltage Vdc is designed to be 350 V during operation in the normal mode, 350 V is the DC voltage reference value.

  The magnitude relationship between the target value, upper limit value, and lower limit value is upper limit value> target value> lower limit value. The target value is the value of internal DC voltage Vdc when there is no instantaneous drop, and the upper limit value is The lower limit value is set to the value that the internal DC voltage Vdc that has risen due to the occurrence of the instantaneous drop decreases and reaches the value that has reached the convergence due to the instantaneous drop. Yes. The target value, the upper limit value, and the lower limit value are obtained experimentally, for example. In the present embodiment, the target value, the upper limit value, and the lower limit value are determined as follows. That is, it is conceivable that the target value is set to the same value as the DC voltage reference value, and the upper limit value and the lower limit value are set to the target value ± α% with the target value (= DC voltage reference value) interposed therebetween. However, in this case, the internal DC voltage Vdc decreases and reaches the lower limit value when the system voltage recovers after the voltage sag has converged. There will be a difference from the reference value. As a result, the control works so that the internal DC voltage Vdc matches the target value, and as a result, the output current iac may change greatly. For this reason, in this embodiment, the lower limit value is set to a DC voltage reference value or a value slightly higher than the DC voltage reference value. Then, the target value and the upper limit value are set based on the lower limit value. For example, the upper limit value and the lower limit value are set to be the target value ± α%. Here, α% is a few percent of the target value, for example, 5%. However, it is not limited to 5%. The upper limit value is set so as not to cause unnecessary operation due to voltage fluctuation (for example, about 10 V at the maximum in a low voltage 100V system) accompanying ON / OFF of the load of the customer during operation in the normal mode.

  However, when the large change in the output current iac as described above is not a problem, the target value is set to the same value as the DC voltage reference value, and the upper limit value and the lower limit value are set to the target value ± α across the target value. % May be set. Here, α% is a few percent of the target value, for example, 5%. However, it is not limited to 5%.

  Next, based on FIG. 2 to FIG. 4, an operation stabilization method when the power conditioner 1 recovers from an instantaneous drop (hereinafter, simply referred to as an instantaneous drop recovery operation stabilization method) will be described. The instantaneous drop recovery operation stabilization method monitors the internal DC voltage Vdc and determines that an instantaneous voltage drop phenomenon of the power system 11 has occurred when the internal DC voltage Vdc exceeds a preset upper limit value. Is switched to the instantaneous drop mode (step S31 in FIG. 2), and when the internal DC voltage Vdc falls below a preset lower limit value, it is determined that the instantaneous voltage drop phenomenon has converged and the operation mode is returned to the normal mode. (Step S32 in FIG. 2). In the instantaneous voltage drop mode, the switch of the inverter circuit 13 is controlled so that the output current iac matches the value immediately before the occurrence of the instantaneous voltage drop phenomenon or its moving average value (step S52 in FIG. 4), and the internal DC voltage The DC input current iin is changed so that Vdc matches the preset target value (steps S53 and S54 in FIG. 4), and the current change of the DC input current iin is returned when the operation mode is returned from the sag mode to the normal mode. The command is returned to the command immediately before the occurrence of the instantaneous voltage drop phenomenon (step S55 in FIG. 4).

  The power conditioner 1 has two modes of operation modes: a normal mode when no sag occurs and a sag mode when a sag occurs. The voltage sag detector 4 constantly monitors the internal DC voltage Vdc in both the normal mode and the voltage sag mode.

  First, the normal mode will be described. In the normal mode, which is a normal operation mode, the DC input current control unit 8 changes the switch frequency of the step-up chopper unit 15 in accordance with the current change command of the DC input current iin supplied from the maximum power tracking control unit 6 (FIG. 3). Step S41). Thus, the DC input current iin is operated so as to coincide with the current value Imax that maximizes the output power, and the internal capacitor (smoothing capacitor 17) is efficiently charged. Further, the internal DC voltage constant control unit 7 refers to the DC voltage reference value stored in the storage unit 12, and performs an inverter switching operation on a current change command of the output current iac so that the internal DC voltage Vdc matches the DC voltage reference value. It supplies to the part 18 (step S42). The inverter switching operation unit 18 performs on / off control (PWM control) of the switch (switching element) of the inverter circuit 13 based on the received current change command (step S43). Thereby, the solar cell array 2 is operated to follow the maximum output.

  The instantaneous voltage drop detection unit 4 constantly monitors the internal DC voltage Vdc. When a voltage drop occurs in the power system 11 and the internal DC voltage Vdc of the power conditioner 1 increases and exceeds the upper limit value, the voltage drop detection unit 4 that detects this switches the operation mode to the voltage drop mode, The switching command is supplied to the output current command unit 19 of the inverter control unit 9, the internal DC voltage constant control unit 7 of the boost chopper control unit 14, and the maximum power tracking control unit 6 (step S31 in FIG. 2).

  The output current command unit 19 of the inverter control unit 9 that has received the switching command to the sag mode stops the update of the output current command value It and stores the value It immediately before receiving the mode switching command (step of FIG. 4). S51). Then, a current change command for the output current iac is supplied to the inverter switching operation unit 18 so that the output current iac matches the stored output current command value It. The inverter switching control unit 18 operates the switch of the inverter circuit 13 in accordance with the current change command of the output current iac (step S52). As a result, an excessive change in the output current iac due to the instantaneous drop can be suppressed (constant control of the output current iac).

  Further, the maximum power follow-up control unit 6 that has received the switching command to the instantaneous voltage drop mode enters a halt state, stops updating the current change command of the DC input current iin, and stores the current change command immediately before receiving the mode switching command. (Step S51).

  Further, the internal DC voltage constant control unit 7 that has received the switching command to the instantaneous drop mode switches the value used for the control from the DC voltage reference value to the target value (validation of the target value, step S51). Then, the internal DC voltage constant control unit 7 supplies a current change command of the DC input current iin to the DC input current control unit 8 so that the internal DC voltage Vdc matches the target value (step S53), and the DC input current control is performed. The unit 8 controls the switch frequency of the step-up chopper unit 15 to make the DC input current iin coincide with the target value (step S54). As a result, it is possible to suppress an excessive increase in the internal DC voltage Vdc associated with the switching of the output current iac to constant control.

  When the voltage drop of the power system 11 recovers and the internal DC voltage Vdc of the power conditioner 1 decreases and falls below the lower limit value, the voltage drop detection unit 4 detects this and the operation mode is changed. The mode is returned from the sag mode to the normal mode (step S32 in FIG. 2). The voltage drop detection unit 4 supplies a command for switching to the normal mode to the output current command unit 19 of the inverter control unit 9, the internal DC voltage constant control unit 7 of the boost chopper control unit 14, and the maximum power tracking control unit 6. As a result, the operation is performed in the normal mode (step S55 in FIG. 4).

  In response to the command for switching to the normal mode, the maximum power follow-up control unit 6 in the resting state uses the DC input current control unit 8 of the step-up chopper control unit 14 to send the current change command of the DC input current iin stored immediately before the occurrence of the instantaneous drop. To resume operation. The DC input current control unit 8 operates the boost chopper unit 15 based on the current change command of the DC input current iin supplied from the maximum power follow-up control unit 6.

  Also, the internal DC voltage constant control unit 7 that has received the command to switch to the normal mode switches the value used for control from the target value to the DC voltage reference value, and sends the current change command of the DC input current iin to the DC input current control unit 8. And the current change command of the output current iac is supplied to the inverter switching operation unit 18.

  Further, the output current command unit 19 resumes the update of the output current command value It.

  FIG. 5 shows output current iac (a), output active power (b), DC input current iin (c), and internal DC voltage Vdc (d) when the method for stabilizing operation during recovery from a sag is performed according to the present invention. The state of change is shown. FIG. 5 shows the simulation results when the voltage drop rate is 80% and the instantaneous drop duration is 0.5 seconds (occurrence: 0.2 seconds, recovery: 0.7 seconds). The horizontal axis represents the elapsed time from the start of the simulation, and the vertical axis represents the respective numerical values.

  The operation mode is switched from the normal mode to the sag mode due to the occurrence of the sag, and the inverter control unit 9 controls the switch of the inverter circuit 13 so that the output current iac matches the output current command value It immediately before the occurrence of the sag. Therefore, as shown in FIG. 5A, the output current iac remains almost unchanged after the occurrence of the sag and before the occurrence of the sag. For this reason, even after the system voltage is recovered due to the instantaneous low convergence, the output current iac can be made to be substantially constant without greatly fluctuating. In addition, by controlling the output current iac to coincide with the output current command value It immediately before the occurrence of the sag during the sag period, the output active power decreases during the sag period (see FIG. b)) Since the output current iac can be made to be substantially constant after the system voltage is recovered by the sag convergence, the output active power after the sag converges stably at almost the same value as before the sag. In other words, the vehicle is stably operated even after the instantaneous drop recovery.

  Note that, as shown in FIG. 5C, by performing control so that the internal DC voltage Vdc coincides with the target value during the voltage sag period, the DC input current iin greatly decreases during the voltage sag period. When the maximum power follow-up control unit 6 resumes operation due to the convergence of the sag, the current change command of the DC input current iin immediately before the occurrence of the sag is supplied to the DC input current control unit 8. Since the maximum power tracking control is resumed, the DC input current iin quickly recovers to a value that maximizes the output power after the instantaneous drop convergence.

  Further, as shown in FIG. 4D, the internal DC voltage Vdc increases with the occurrence of a sag, but immediately switches to the sag mode, and the internal DC voltage Vdc due to the decrease of the DC input current iin is the target at the time of the sag. It keeps constant to match the value. The smoothing capacitor 17 is kept below the upper limit voltage (400 V in the figure) in a range where the smoothing capacitor 17 is not damaged. At the time of instantaneous convergence, the internal DC voltage Vdc decreases as the output active power rapidly increases as shown in FIG. 5B, but immediately switches to the normal mode, and an excessive decrease is prevented by the increase of the DC input current iin. I'm back.

  In the present invention, the instantaneous voltage drop mode can be added to the operation mode in addition to the normal mode by changing the software to the existing power conditioner. For this reason, it is possible to easily and inexpensively stabilize the operation at the time of instantaneous recovery.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

  For example, in the above description, the internal DC voltage Vdc is constantly monitored and the occurrence and convergence of a sag are detected based on the change in the internal DC voltage Vdc. However, the present invention is not limited to this. In addition to detection by monitoring the voltage Vdc, or instead of detection by monitoring the internal DC voltage Vdc, the effective value of the power at the connection point with the power system 11 is monitored, and the effective value exceeds a predetermined upper limit value. In this case, the occurrence of a sag may be detected, and the convergence of the sag may be detected when it falls below a predetermined lower limit.

  In order to confirm the effect of the present invention, the XTAP (eXpandable Transient Analysis Program: an electrical circuit transient analysis program currently under development at our office, “Development of an instantaneous power system analysis program (Part 1) —Basic structure—” PCS dynamic characteristics simulation at the time of a sag is carried out according to the report of the Denki Research Institute, H06002, (2007-3)).

(1 setting model and analysis evaluation method)
The PCS used in the experiment is a commercial product, and detailed design specifications such as control constants are not available due to the confidentiality of the manufacturer. Development (Part 2)-Verification of analysis accuracy by actual measurement comparison ", Research Report (R07016), 2008), based on the PCS used in this experiment, it is relatively resistant to sag. The setting was made with reference to the test results of two models considered to be high.

The basic specifications of the set inverter model are shown below.
・ Inverter method: Voltage type current control ・ Power control method: Maximum power tracking control (normal)
・ Rated capacity: 4kW
・ Interconnection point voltage: Single phase 200V
・ Internal DC voltage (smoothing capacitor): 350V
・ DC input voltage: 250V (during MPPT control)
・ Inverter switching frequency: 18Hz
・ Driving power factor: 1.0

  The set main circuit model conformed to FIG. 6 to 9 and Table 1 show the control system model including the sag mode and the set parameter values.

  FIG. 6 is a block diagram showing in detail a function current control system and a gate output unit included in the inverter switching operation unit 18 of the inverter control unit 9. The effective current command value output from the control block of FIG. 7 (in FIG. 1, the output current command from the internal DC voltage constant control unit 7 or the output current command unit 19 to the inverter switching operation unit 18), and the control block of FIG. The inverter switching reference carriers (instantaneous command values) V_INV_U and V_INV_V are generated on the basis of the reactive power command value output from the inverter and the phase value of the system voltage output from the PLL circuit. Each reference carrier and the peak value of a triangular carrier wave generated by a separate transmitter are sequentially compared, the gate drive voltage of each switch of the inverter is determined based on the magnitude relationship, and the on / off control of each switch is performed. .

  FIG. 7 is a block diagram showing in detail the effective current control part of the internal DC voltage constant control part 7 (left part in FIG. 7) and the output current command part 19 (upper right part in FIG. 7). In the normal mode, the internal DC voltage measurement value of the smoothing capacitor 17 and the same command value (DC voltage reference value) are sequentially compared, and if there is a difference, the PI controller (parallel connection circuit of the proportional and integrator) is used. Thus, the effective current command value (in FIG. 1, the output current command from the internal DC voltage constant control unit 7 to the inverter switching operation unit 18) is changed. For example, if the measured value is larger, the active power command value is increased. When a voltage sag occurs, the stored output current value immediately before the voltage sag is changed to the effective current command value (in FIG. 1, from the output current command unit 19 to the inverter switching operation unit 18 by switching each flag on / off). Output current command).

  FIG. 8 is a block diagram showing in detail the reactive current control portion of the function included in the inverter switching operation unit 18. As a control function, a reactive power constant control function for sequentially comparing a preset reactive power command value and a measured reactive power value and outputting the difference as a reactive current index value via a PI controller, and a preset AC voltage command It has two functions of constant AC voltage control function that sequentially compares the measured value with the measured value of AC voltage and outputs the difference as a reactive current index value via the PI controller. Can be done. In this verification, both were invalid.

  9 shows an internal DC voltage constant control unit 7 (left part in FIG. 9), a maximum power tracking control unit 6 (upper right part in FIG. 9), and a DC input current control unit 8 (lower right part in FIG. 9). FIG. 2 is a control block diagram showing the details. In the normal mode, only the MPPT control on the right side is enabled by the flag, the DC input power and the DC input current are sequentially compared with the values before t seconds respectively, and the current of the boost chopper is determined based on the positive / negative condition of the product of each difference value. Adjust and change the command value. For example, in the case of positive, the current command value is increased. Next, it sequentially compares with a separately generated sawtooth wave, and outputs a gate signal for switching the step-up chopper according to the magnitude relationship. In the sag mode, the MPPT function is disabled and the DC-AVR function is enabled by switching the flag. The DC voltage command value and the measured value are sequentially compared, and the current command value is changed according to the difference.

Table 1 shows set constant values of the control system.

  The output power of the PCS (power conditioner) in the normal state was set to 90% (3.6 kW) of the rating. In addition, a limiter was set so that the output current was limited to 1.2 times the rating (20 A) even in modes other than the instantaneous drop mode. Furthermore, the system voltage phase angle at the time of the occurrence of a sag is set to 0 degree, which mainly focuses on confirming the controllability of the electrical energy inside the PCS at the time of sag, and other transient phenomena are unlikely to occur. Set.

  As for the voltage sag condition, the voltage drop rate was changed from 30% to 90%, and the duration was changed from 0.04 seconds to 0.5 seconds.

  In each of these cases, the voltage, current, and power characteristics of each part of the PCS were simulated, and changes in the characteristics of the internal DC voltage, output current, and output power were evaluated.

(2 Simulation results)
(1) Results when the present invention is not adopted First, in order to confirm the validity of the setting model, the results when the present invention is not adopted are shown in FIG. The voltage sag condition has a duration of 0.5 seconds and a voltage drop rate of 30%, and is generated 0.2 seconds after the start of calculation.

  As shown in FIG. 10, after the occurrence of a sag, the output current value increases at the time of sag and returns to the value before the sag again after the system voltage is restored. The internal DC voltage increases to about 370 V when an instantaneous drop occurs, but returns to the target value of 350 V after about 0.2 seconds by the internal DC voltage constant control unit 7. After the system voltage is recovered, the voltage temporarily decreases, but returns to the target value again after 0.15 seconds. The output power shows a transitional change in the occurrence of a sag and the system voltage recovery time. When the system voltage is recovered, the output power increases up to about 130% of the value immediately before the sag. FIG. 11 shows the characteristics test result at the time of a voltage sag under the same conditions of the model H or the like used as a reference for model setting. The characteristics are similar and the model can be said to be appropriate.

(2) Results when the present invention is adopted Simulation results in typical cases are shown in FIGS. Of these, FIGS. 12 and 13 show cases where the sag time is relatively long, each case having a duration of 0.5 seconds, and FIGS. 14 and 15 show cases where the sag time is short, and the duration 0 Each case of .04 seconds is shown. Regarding the voltage drop rate, two cases of a voltage drop rate of 30% are shown as small cases and a case of a voltage drop rate of 80% as large cases, respectively. Furthermore, Table 2 (rate of change of output current after system voltage recovery (maximum value, ratio to value immediately before voltage sag)) is the value of output power immediately before system voltage sag during system voltage recovery after voltage sag, which is an important evaluation item. Table 3 (Internal DC voltage (maximum value) at the time of instantaneous drop) shows the maximum value of the internal DC voltage (smoothing capacitor voltage) during the instantaneous drop.

  These results are summarized as follows.

  Taking the result of the voltage drop rate of 30% and the instantaneous drop duration of 0.5 seconds in FIG. 12 as an example, the internal DC voltage Vdc starts to rise immediately after the occurrence of the instantaneous drop and reaches the upper limit value of 370 V. The direct current input current Iin is rapidly decreasing. In addition, the output current increases in a period of about one cycle after the occurrence of the sag, but immediately returns to a value almost immediately before the sag and maintains a constant value during the sag. The increase in the internal DC voltage Vdc is eliminated by the decrease in the DC input current Iin, and is maintained at about 380V. From these, it can be seen that switching to the set instantaneous drop mode is performed as designed.

  When the system voltage is restored, the internal DC voltage Vdc drops below the lower limit value: 355 V (normal mode switching voltage), and then returns to the normal 350 V value just before the voltage sag as the DC input current Iin increases. . Although the output current slightly decreases, it is maintained at a value almost immediately after the instantaneous drop. It can be seen that the output power temporarily increases immediately after the recovery from the sag, but immediately returns to a stable value immediately before the occurrence of the sag. The increase rate immediately after the recovery from the voltage drop is about 13% of the value immediately before the voltage drop, and the result is suppressed to less than half of the increase rate when the present invention is not adopted as shown in (1).

  The above operating characteristics are almost the same in the other voltage sag cases of FIGS. 13 to 15, and the change in the output current does not depend on the voltage sag duration even in the case of a large voltage drop rate of 80%. Including almost the same. As a result, the increase rate of the output power value after the recovery from the instantaneous drop is suppressed to be relatively small.

  Table 2 and Table 3 show, as a summary of the results, the rate of increase of the output power after the recovery from the sag in each case from the value immediately before the sag and the maximum value during the sag of the internal DC voltage.

  From these results, the increase rate of the output power is about 13% at the maximum when the voltage drop rate is 30%, and at other voltage drop rates, it is suppressed to about 10% or less regardless of the sag duration. It became clear that Moreover, although the internal DC voltage tends to increase with the voltage drop rate, it has become clear that the target voltage of 400 V or less can be maintained at the maximum. From the above, it was confirmed that the operation at the time of voltage recovery due to instantaneous drop convergence can be stabilized by the present invention.

1 Power conditioner 2 Distributed power supply 4 Voltage drop detection unit (voltage drop detection means)
6 Maximum power tracking control unit (maximum power tracking control means)
9 Inverter control unit (inverter control means)
11 Power System 13 Inverter Circuit 14 Boost Chopper Control Unit (Boost Chopper Control Unit)

Claims (3)

  The internal DC voltage Vdc is monitored, and when the internal DC voltage Vdc exceeds a preset upper limit value, it is determined that the instantaneous voltage drop phenomenon of the power system has occurred, and the operation mode is switched to the instantaneous voltage drop mode. When the internal DC voltage Vdc falls below a preset lower limit value, the instantaneous voltage drop phenomenon is judged to have converged, and the operation mode is returned to the normal mode. In the instantaneous voltage drop mode, the output current iac Operating the switch of the inverter circuit so as to match the value immediately before the occurrence of the instantaneous voltage drop phenomenon or its moving average value, and the DC input so that the internal DC voltage Vdc matches the preset target value. When the current iin is changed and the operation mode is returned from the voltage sag mode to the normal mode, a current change command of the DC input current iin is generated by the instantaneous voltage drop phenomenon. Operation method for stabilizing during sag recovery power conditioner and returning to the previous command.   The internal DC voltage Vdc is monitored, and when the internal DC voltage Vdc exceeds a preset upper limit value, it is determined that the instantaneous voltage drop phenomenon of the power system has occurred, and the operation mode is switched to the instantaneous voltage drop mode. When the internal DC voltage Vdc falls below a preset lower limit value, it is determined that the instantaneous voltage drop phenomenon has converged, and a voltage sag detector that returns the operation mode to the normal mode; In the inverter control unit that operates the switch of the inverter circuit so that the current iac matches the value immediately before the occurrence of the instantaneous voltage drop phenomenon or the moving average value thereof, and the internal DC voltage Vdc is preset in the instantaneous voltage drop mode. The step-up chopper controller that changes the DC input current iin so as to match the target value, and the operation mode is returned from the instantaneous drop mode to the normal mode. Power conditioner characterized in that it comprises a maximum power follow-up control unit to return the current change instruction of the DC input current iin the instruction immediately before the occurrence of the instantaneous voltage drop phenomenon when.   At least the internal DC voltage Vdc is monitored, and when the internal DC voltage Vdc exceeds a preset upper limit value, it is determined that an instantaneous voltage drop phenomenon of the power system has occurred, and the operation mode is switched to the instantaneous low mode. A voltage sag detecting means for determining that the instantaneous voltage drop phenomenon has converged when the internal DC voltage Vdc falls below a preset lower limit value and returning the operation mode to the normal mode; and in the voltage sag mode, In the inverter control means for operating the switch of the inverter circuit so that the output current iac coincides with the value immediately before the occurrence of the instantaneous voltage drop phenomenon or the moving average value thereof, the internal DC voltage Vdc A step-up chopper control means for changing the DC input current iin so as to coincide with a set target value; and When the power conditioner recovers from a dip in the power conditioner for causing the computer to function as a maximum power tracking control means for returning the current change command of the DC input current iin to the command immediately before the occurrence of the instantaneous voltage drop phenomenon when the normal mode is restored. Program for stabilization of driving.