JP2009201238A - Instantaneous voltage drop compensation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a load voltage from rapidly lowering due to an instantaneous voltage drop during a period from the detection of the instantaneous voltage drop to the cutting-off of a high speed switch. <P>SOLUTION: A current control command part 210 outputs a current control command S10 that supplies a current for compensating for a distortion element of the load current caused by an instantaneous voltage drop. A voltage control command 220 outputs a voltage control command S20 to output a three-phase voltage that is a rated voltage to the load. The current control command S10 is output during the period from the detection of an instantaneous voltage drop to the cutting-off of the high speed switch to reduce a drop in the load current, thus preventing the load voltage from rapidly dropping due to an instantaneous voltage drop. After cutting off the high speed switch, the voltage control command S20 is output, and a rated voltage is supplied to the load. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a voltage sag compensator.

In an electric power system, an instantaneous voltage drop (hereinafter referred to as “instantaneous voltage drop”) may occur due to a sudden change in the amount of load connected to the system or a lightning strike on the system. .
On the other hand, in a load such as an IT-related device, when an instantaneous drop occurs in the power system, a failure such as a device stop or malfunction may occur.
For this reason, in order to prevent a load from being damaged due to a sag, a power system is generally provided with a parallel sag compensator.

This parallel type voltage sag compensator supplies power to the load from the system power supply via a high-speed switch during normal times (when no voltage sag occurs), and a DC charging unit (electric double layer capacitor, etc.) To store power.
When a voltage sag occurs, the parallel voltage sag compensator instantaneously disconnects the load from the power system, converts the DC power stored in the DC charging unit to AC power, and converts this AC power to the load. Supply in an uninterruptible state.

  In addition, there is a parallel type voltage sag compensator that has an active filter function in addition to the voltage sag compensator. This type of parallel voltage sag compensator suppresses the harmonic current generated from the load in normal times ( (Compensated) Outputs compensation current.

  Here, the circuit configuration of the parallel sag compensator having the active filter function will be described with reference to FIG.

  As shown in FIG. 8, a load 3 is connected to a power system L <b> 1 including a system power supply 1 via a high-speed switch 2. The high speed switch 2 is configured by, for example, an IGBT or the like.

The power converter 4 includes an inverter device that can perform a reverse conversion operation (inverter operation) and a forward conversion operation (converter operation).
An electric double layer capacitor (DC charging unit) 5 is connected to the DC side of the power converter 4.
Further, the AC side of the power converter 4 is connected to the load 3 via the power line L <b> 2, and the power converter 4 is connected in parallel to the load 3. The power line L2 is provided with an LC filter or an LCL filter as an AC filter.

The power converter 4 performs the following operation function according to a gate control signal G output from a PWM (Pulse Width Modulation) modulator 6 under the control of the control unit 100 described later.
(1) In normal operation, a forward conversion operation (converter operation) is performed to convert AC power obtained from the system power supply 1 into DC power, and the electric double layer capacitor 5 is charged with this DC power.
(2) In normal times, a compensation current having a polarity opposite to that of the harmonic current generated from the load 3 is output, and the harmonic current is canceled by this compensation current. That is, it functions as an active filter.
(3) When an instantaneous drop occurs, by performing an inverse conversion operation (inverter operation), the DC power charged in the electric double layer capacitor 5 is converted to AC power, and this AC power is sent to the load 3. That is, the operation function as a voltage sag compensator is achieved.

A voltage detector 11 and a current detector 12 are interposed in the power system L1, the voltage detector 11 outputs a system voltage signal VS indicating the detected system voltage value, and the current detector 12 detects the detected system current. A system current signal IS indicating the value is output.
Note that an ACL may be connected to the power system L1 on the system power supply 1 side as viewed from the high-speed switch 2.

  A voltage detector 13 and a current detector 14 are interposed between the high-speed switch 2 and the load 3 in the power system L1, and the voltage detector 13 generates a load voltage signal VL indicating the detected load voltage value. The current detector 14 outputs a load current signal IL indicating the detected load current value.

  A current detector 15 for detecting an AC output current (inverter output current) output from the power converter 4 is provided on the AC side of the power converter 4, and the current detector 15 detects the detected AC output current value ( An AC output current signal (inverter output current signal) Iinv indicating the inverter output current value) is output.

  The electric double layer capacitor 5 is provided with a voltage detector 16, and the voltage detector 16 outputs a charging voltage signal Vdc indicating a charging voltage value of the electric double layer capacitor 5.

The control unit 100 takes in the signals VS, VL, IS, IL, Iinv, and Vdc to determine the state of the power system L1, and changes the power converter 4 to the electric double layer according to the state of the power system L1. The operating state of the power converter 4 is controlled so as to operate as a charging device that charges the capacitor 5, as an active filter, or as a sag compensation device.
The control unit 100 controls the switching operation of the high speed switch 2. That is, the high-speed switch 2 is closed during normal times, and when the instantaneous drop occurs, the high-speed switch 2 is shut off instantaneously.

  In the parallel type voltage sag compensator having the configuration shown in FIG. 8, when the occurrence of a voltage sag is detected, the high speed switch 2 is turned off, and the DC power stored in the electric double layer capacitor 5 is AC converted by the power converter 4. This AC power is converted into electric power and supplied to the load 3.

  In this case, the voltage waveform of the load 3 is abrupt for a moment because of the time taken from the momentary drop occurrence to the interruption of the high-speed switch 2 or the occurrence of a surge when the high-speed switch 2 is interrupted. Depression occurs.

  In order to prevent this sudden drop in the load voltage waveform (a momentary drop in voltage), Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-187089) devised the control unit 100.

Therefore, details of the control unit 100 shown in Patent Document 1 will be described with reference to FIG.
As shown in FIG. 9, the control unit 100 includes a voltage sag detection unit 101, a cutoff control unit 102, a reference voltage generation unit 103, an addition unit 104, a harmonic compensation command unit 110, and a current control command unit 120. And a voltage control command unit 130 and a selection / output command unit 140.
In FIG. 9, a charge command control system for creating a charge command for charging the electric double layer capacitor 5 is not shown.

  The voltage drop detection unit 101 monitors the system voltage signal VS, and determines that an instantaneous voltage drop has occurred when the system voltage signal VS falls below a preset threshold value. In addition, since it takes time to perform the detection operation in the voltage sag detector 101, there is a slight time lag between the time when the voltage sag actually occurs and the time when the voltage sag is detected.

  When the sag detecting unit 101 detects the occurrence of a sag, the severance control unit 102 outputs the severing signal Sh when a preset time (for example, several tens of μS) elapses from the momentary sag detection time. When this shut-off signal Sh is input to the high speed switch 2, the high speed switch 2 is immediately shut off.

  The reference voltage generation unit 103 takes in the system voltage signal VS, performs a PLL operation or the like to calculate the phase of the system voltage, and the like, and supplies a three-phase voltage (not including a harmonic component and a phase) A reference voltage signal Vref indicating the voltage value and phase of the three-phase voltage without deviation) is output.

The harmonic compensation command unit 110 includes a harmonic extraction unit 111, a subtraction unit 112, and a current control unit 113.
Then, the harmonic extraction unit 111 extracts a load harmonic component from the load current signal IL, and the subtraction unit 112 obtains a deviation between the load harmonic component and the AC output current signal (inverter output current signal) Iinv. The harmonic compensation command S1 is obtained by performing a proportional / integral (PI) calculation by the current control unit 113 on the deviation.
The harmonic compensation command S1 is a command for causing the power converter 4 to output a compensation current so as to suppress (cancel) harmonics generated from the load 3.

The current control command unit 120 includes a subtraction unit 121 and a current control unit 122.
Then, the subtracting unit 121 obtains a deviation between the load current signal IL and the AC output current signal (inverter output current signal) Iinv, and performs a proportional / integral (PI) operation on the deviation by the current control unit 122 to obtain a current control command. S2 is obtained.
The current control command S2 is a command for operating the power converter 4 so that the power converter 4 supplies a necessary current to the load 3.
As described above, when the power converter 4 supplies the necessary current to the load 3, the supply of the current flowing from the system power supply 1 to the load 3 via the high-speed switch 2 is stopped. As a result, the current flowing through the high-speed switch 2 is reduced. Can be zero.

The voltage control command unit 130 includes a subtraction unit 131 and a voltage control unit 132.
Then, the subtractor 131 obtains a deviation between the load voltage signal VL and the reference voltage signal Vref, and obtains a voltage control command S3 by performing a proportional / integral (PI) operation on the deviation by the voltage controller 132.
This voltage control command S3 operates the power converter 4 (inverter operation) so that the power converter 4 supplies the load 3 with a three-phase voltage having a rated voltage (a voltage equal to the rated voltage of the system power supply 1). ) Command.

The selection / output command unit 140 includes a gain signal output unit 141, multiplication units 142, 143, 144, and addition units 145, 146.
The gain signal output unit 141 outputs gain signals g1, g2, and g3, and the values of the gain signals g1, g2, and g3 are set to values between 0 and 1 depending on the situation of the power system L1. To change.
The operation of the selection / output command unit 140 will be described later with reference to FIG. 10, and a command output from the selection / output command unit 140 is referred to as a selection / output command S0.

  The adding unit 104 adds the reference voltage signal Vref to the selection / output command S0 to obtain the final command SS, and the final command SS is output. The final command SS is PWM-modulated by the PWM modulator 6 to become a gate control signal G, and the gate control of the power converter 4 is performed by the gate control signal G (PWM-modulated final command SS).

  Here, with reference to FIG. 10, the operation of the selection / output command unit 140 and the operation of the parallel sag compensator will be described.

In FIG. 10, the gain signal output unit 141 outputs only the gain signal g <b> 1 having a value of 1 in the period T <b> 0, that is, the period before the time t <b> 2 when the instantaneous drop is detected by the instantaneous drop detection unit 101. The gain signals g2 and g3 are not output (the values of the gain signals g2 and g3 are set to 0, respectively).
Therefore, the selection / output command S0 output from the selection / output command unit 140 includes only the harmonic compensation command S1. Therefore, the final command SS also has only the harmonic compensation command S1, and the power converter 4 is operated by the gate control signal G obtained by PWM-modulating the final command SS (= harmonic compensation command S1). Compensator 4 outputs a compensation current that suppresses (cancels) harmonics generated from load 3 and performs harmonic compensation operation as an active filter.

  In FIG. 10, when a voltage sag occurs at time t1, the voltage sag detector 101 detects that a voltage sag has occurred at time t2 that is delayed in time from time t1.

When the voltage drop detecting unit 101 detects a voltage drop, the gain signal output unit 141 outputs only the gain signal g2 having a value of 1, and does not output the gain signals g1 and g3 (the gain signals g1 and g3). Each value is 0).
Therefore, the selection / output command S0 output from the selection / output command unit 140 has only the current control command S2, and the gate control signal G obtained by PWM-modulating the final command SS (= current control command S2) The power converter 4 operates, and the load 3 supplies a necessary current from the power converter 4 to the load 3.
For this reason, the supply of current flowing from the system power supply 1 to the load 3 via the high-speed switch 2 is stopped, and as a result, the current flowing through the high-speed switch 2 can be reduced to 0 in a very short time.

  Moreover, the interruption | blocking control part 102 outputs the interruption | blocking signal Sh at the time t3 when the preset time (for example, several dozen microseconds) T1 passed from the time t2 when the instantaneous voltage drop detection part 101 detected generation | occurrence | production of the instantaneous voltage drop. When this shut-off signal Sh is input to the high speed switch 2, the high speed switch 2 is immediately shut off.

In FIG. 10, when time t3, that is, when the high speed switch 2 is cut off, the gain signal output unit 141 gradually decreases the value of the gain signal g2 from 1 in the period T2 (period from time t3 to time t4). In addition to 0, the value of the gain signal g3 is gradually increased from 0 to 1, and the gain signal g1 is not output (the value of the gain signal g1 is set to 0).
Therefore, in the selection / output command S0 output from the selection / output command unit 140, the current control command S2 gradually decreases and the voltage control command S3 gradually increases.
When the voltage control command S3 increases, the power converter 4 is operated by the gate control signal G obtained by PWM modulating the voltage control command S3, and the rated voltage ( A three-phase voltage that is equal to the voltage of the system power supply 1 is supplied. For this reason, even if the high-speed switch 2 is cut off, three-phase power can be supplied to the load 3.

  9 and 10, the current control command unit 120 performs current control such that the inverter output current command Iinv and the load current command IL become equal after the instantaneous voltage drop is detected. Since the command S2 is output, the system current is quickly set to 0, and then the high-speed switch 2 is shut off, the time from the instantaneous voltage drop detection to the switch shut-off (period T1) can be shortened, and the occurrence of surge is suppressed and caused by the surge. Voltage fluctuation is suppressed.

JP 2006-187089

As explained based on FIG. 9 and FIG. 10, in the conventional technique shown in Patent Document 1 and the like, from the power converter 4 using the current control command S <b> 2 output from the current control command unit 120 when the instantaneous drop is detected. By supplying the load 3 with the necessary current, the supply of current flowing from the system power supply 1 to the load 3 via the high-speed switch 2 is stopped, and the current flowing through the high-speed switch 2 is quickly reduced to 0. After this, the high-speed switch 2 is shut off.
In this way, since the high-speed switch 2 can be shut off when no current is flowing, the occurrence of surge can be suppressed, and voltage fluctuations (caused by surge) supplied from the power converter 2 to the load 3 can be suppressed. (Voltage fluctuation) can be suppressed, and the time (period T1) from the momentary drop detection to the switch cutoff can be shortened.

  However, in FIG. 10, there is a problem that the voltage waveform of the load 2 suddenly drops due to the instantaneous drop in the period T1 from the time t2 when the instantaneous drop is detected to the time t3 when the switch is shut off.

  In order to reduce this sudden drop in the load voltage, a circuit system such as inserting a reactor on the system power supply 1 side of the power system L1 of the parallel type voltage sag compensator can be considered, but that alone completely eliminates the voltage drop. It is not possible.

  In order to completely prevent a voltage drop on the load side, it is necessary to perform control such as reducing a sudden drop in the load voltage due to a voltage drop during the period from the time when the voltage drop is detected to the time when the high-speed switch is shut off. However, this technology has not been developed in the past.

  An object of the present invention is to provide a voltage sag compensator that can suppress a decrease in load voltage caused by a voltage sag even when a voltage sag occurs.

The configuration of the present invention for solving the above problems is as follows.
A switch interposed in the power system connecting the load and the system power supply,
A power converter capable of performing reverse conversion operation and forward conversion operation, with an alternating current side connected to the load and a direct current charging unit connected to the direct current side,
When an instantaneous drop occurs in the power system, the switch is controlled to be cut off, and the power converter is controlled to supply power from the power converter to the load by performing an inverse conversion operation of the power converter. In a voltage sag compensator having a control unit,
The controller is
A voltage sag detector that detects whether a voltage sag has occurred in the power system;
After detecting a voltage sag by the voltage sag detector, a shut-off controller that shuts off the switch when a preset time has elapsed,
A voltage control command for generating a voltage control command for controlling the power converter so that the power converter supplies power to the load and applies a rated voltage to the load from a deviation between a load voltage and a reference voltage And
In order to extract a distortion component corresponding to a drop in the load current due to a momentary drop from the load current, the power converter supplies power to the load and compensates the distortion component to supply the load with a compensation current. A current control command unit for generating a current control command for controlling the power converter;
A selection / output command unit that selects and outputs the current control command when the voltage drop is detected by the voltage drop detection unit, and selects and outputs the voltage control command when the switch is cut off by the cut-off control unit. When,
A modulator that sends a gate control signal for controlling the power converter to the power converter to supply power to the load from the power converter based on a control command output from the selection / output command unit; It is characterized by having.

  In this case, the selection / output command unit may gradually reduce the current control command and gradually increase the voltage command when the switch is cut off by the cutoff control unit.

The configuration of the present invention is as follows.
A switch interposed in the power system connecting the load and the system power supply,
A power converter capable of performing reverse conversion operation and forward conversion operation, with an alternating current side connected to the load and a direct current charging unit connected to the direct current side,
When an instantaneous drop occurs in the power system, the switch is controlled to be cut off, and the power converter is controlled to supply power from the power converter to the load by performing an inverse conversion operation of the power converter. In a voltage sag compensator having a control unit,
The controller is
A voltage sag detector that detects whether a voltage sag has occurred in the power system;
After detecting a voltage sag by the voltage sag detector, a shut-off controller that shuts off the switch when a preset time has elapsed,
A voltage control command for generating a voltage control command for controlling the power converter so that the power converter supplies power to the load and applies a rated voltage to the load from a deviation between a load voltage and a reference voltage And
In order to extract a distortion component corresponding to a drop in the load current due to a momentary drop from the load current, the power converter supplies power to the load and compensates the distortion component to supply the load with a compensation current. A distortion component compensation command for controlling the power converter is generated, and from a deviation between a load current and an AC output current output by the power converter, the power converter supplies power to the load to the load. A current control command unit for generating a system current zero command for controlling the power converter in order to supply a rated current;
When a voltage sag is detected by the voltage sag detector, the distortion component compensation command and the grid current zero command are selected and output.When the switch is shut off by the shut-off controller, the voltage control command is selected. Select / output command section to output,
A modulator that sends a gate control signal for controlling the power converter to the power converter to supply power to the load from the power converter based on a control command output from the selection / output command unit; It is characterized by having.

  In this case, the selection / output command unit may gradually reduce the distortion component compensation command and gradually increase the voltage command when the voltage sag detecting unit detects a voltage sag.

According to the present invention, in the period from the time when the instantaneous drop is detected to the time when the high-speed switch is shut off, the current that compensates for the distortion component of the load current caused by the instantaneous drop from the power converter to the load, that is, A compensation current having a phase and frequency equal to each other and a magnitude multiplied by −1 with respect to a distortion component of the load current is supplied from the power converter to the load.
For this reason, it is possible to reduce the drop in the load current. As a result, even if a sudden drop in the load voltage occurs due to the instantaneous drop, the drop can be reduced.

  Furthermore, by supplying a current corresponding to the load current from the power converter to the load during the period from when the instantaneous drop is detected to when the high-speed switch is shut off, the current flowing through the high-speed switch (system current) Since the high-speed switch can be shut off in the state of 0, the occurrence of surge can be suppressed, voltage fluctuation caused by the surge can be suppressed, and the period from the momentary voltage drop detection to the switch cutoff can be reduced. It can be shortened.

  The best mode for carrying out the present invention will be described below in detail based on examples.

FIG. 1 shows a controller 200 used in the voltage sag compensator according to the first embodiment of the present invention. This control unit 200 is used in place of the conventional control unit 100 shown in FIG. 8, and controls the operation of the parallel type sag compensation device.
In FIG. 1, harmonic compensation for generating a charging command control system for generating a charging command for charging the electric double layer capacitor 5, and for generating a harmonic compensation command for performing an active filter operation by outputting a compensation current from the power converter 4. The command unit is not shown.

  As shown in FIG. 1, the control unit 200 includes a voltage sag detection unit 201, a cutoff control unit 202, a reference voltage generation unit 203, an addition unit 204, a current control command unit 210, and a voltage control command unit 220. And a selection / output command unit 230.

  The voltage drop detection unit 201 monitors the system voltage signal VS, and determines that an instantaneous voltage drop has occurred when the system voltage signal VS falls below a preset threshold value. In addition, since it takes time to perform the detection operation in the voltage sag detector 201, there is a slight time lag between the time when the voltage sag actually occurs and the time when the voltage sag is detected.

  The interruption control unit 202 outputs the interruption signal Sh after the instantaneous voltage drop detection unit 101 detects the occurrence of an instantaneous voltage drop. When this shut-off signal Sh is input to the high speed switch 2, the high speed switch 2 is immediately shut off.

  The reference voltage generation unit 203 takes in the system voltage signal VS, performs a PLL operation or the like to calculate the phase of the system voltage, and the like, and thereby supplies a three-phase voltage (not including a harmonic component and a phase) A reference voltage signal Vref indicating the voltage value and phase of the three-phase voltage without deviation) is output.

The current control command unit 210 includes a strain component extraction unit 211, a multiplication unit 212 that multiplies by −1, a subtraction unit 213, and a current control unit 214.
The distortion component extraction unit 211 extracts a distortion component signal ILh corresponding to the drop in the load current due to the instantaneous drop from the load current signal IL, and the multiplication unit 212 sets −1 to the distortion component signal ILh in order to compensate the distortion component. The multiplication and subtraction unit 213 obtains a deviation between the distortion component signal ILh multiplied by −1 and the AC output current signal (inverter output current signal) Iinv, and the current control unit 214 calculates the deviation by the proportional / integral (PI) calculation. Thus, the current control command S10 is obtained.
Various types of strain component extraction unit 211 can be used, and an example of the circuit configuration will be described later.

The voltage control command unit 220 includes a subtraction unit 221 and a voltage control unit 222.
The subtracting unit 221 calculates a deviation between the load voltage signal VL and the reference voltage signal Vref, and calculates a voltage control command S20 by performing a proportional / differential (PD) operation on the deviation by the voltage control unit 222.
The voltage control command S20 is such that the power converter 4 supplies power to the load 3 and outputs a three-phase voltage having a rated voltage (a voltage equal to the rated voltage of the system power supply 1) to the load 3. This is a command for operating the power converter 4 (inverter operation).

The selection / output command unit 230 includes a gain signal output unit 231, multiplication units 232 and 233, and an addition unit 234.
The gain signal output unit 231 outputs the gain signals g11 and g12, and the values of the gain signals g11 and g12 are changed to a value between 0 and 1 depending on the situation of the power system L1. ing.
The operation of the selection / output command unit 230 will be described later with reference to FIG. 2, and a command output from the selection / output command unit 230 is referred to as a selection / output command S0.

  The adder 204 adds the reference voltage signal Vref to the selection / output command S0 to obtain the final command SS. This final command SS is PWM-modulated by the PWM modulator 6 to become a gate control signal G, and the gate control of the power converter 4 is performed by the gate control signal G (PWM-modulated final command SS).

  Next, the operation of the selection / output command unit 230 and the operation of the parallel type voltage sag compensator will be described with reference to FIG.

In FIG. 2, the gain signal output unit 231 does not output the gain signals g11 and g12 (gain signals g11 and g12) in the period T10, that is, the period before the time t12 when the instantaneous drop is detected by the instantaneous drop detection unit 201. Is set to 0).
For this reason, the current control command S10 and the voltage control command S20 are not output from the selection / output command unit 230. That is, it is in a standby state.

  In FIG. 2, when a sag occurs at time t11, the sag detector 201 detects that a sag has occurred at time t12 that is delayed in time from time t11 (period T11 has elapsed).

When the voltage drop detecting unit 201 detects a voltage drop, the gain signal output unit 231 outputs only the gain signal g11 having a value of 1, and does not output the gain signal g12 (the value of the gain signal g12 is set to 0). To do).
For this reason, the selection / output command S0 output from the selection / output command unit 230 has only the current control command S10, and the PWM modulator 6 PWM-modulates the final command SS (= current control command S10). The power converter 4 is activated by the gate control signal G, and supplies a current that compensates for a distortion component of the load current caused by the instantaneous drop from the power converter 4 to the load 3. That is, a compensation current having the same phase and frequency and -1 times the magnitude of the distortion component of the load current is supplied from the power converter 4 to the load 3.

  In this way, since the compensation current having the same phase and frequency and -1 times the magnitude with respect to the distortion component of the load current is supplied from the power converter 4 to the load 3, the drop in the load current is reduced. As a result, even if an abrupt drop in the load voltage occurs due to an instantaneous drop, this drop can be reduced.

  The interruption control unit 202 outputs the interruption signal Sh at a time point t13 when a preset period T12 has elapsed from the time point t12 when the instantaneous voltage drop detection unit 201 detects the occurrence of an instantaneous voltage drop. When this shut-off signal Sh is input to the high speed switch 2, the high speed switch 2 is immediately shut off.

In FIG. 2, when the cutoff signal Sh is output from time t13, that is, the cutoff control unit 202, the gain signal output unit 231 outputs only the gain signal g12 having a value of 1, and does not output the gain signal g11 ( The value of the gain signal g11 is set to 0).
For this reason, the selection / output command S0 output from the selection / output command unit 230 has only the voltage control command S20, and the PWM modulator 6 performs PWM modulation on the final command SS (= voltage control command S20). In response to the gate control signal G, the power converter 4 operates to supply a three-phase voltage having a rated voltage (a voltage equal to the voltage of the system power supply 1) from the power converter 4 to the load 3. For this reason, even if the high-speed switch 2 is cut off, three-phase power can be supplied to the load 3.

After all, in the control unit 200 of the voltage sag compensator according to the first embodiment, the gate control signal G based on the current control command S10 is used in the period T12 from the time t12 when the voltage sag is detected to the time t13 when the high speed switch 2 is shut off. By operating the power converter 4, the phase and frequency of the current from the power converter 4 to the load 3 are compensated for the distortion component of the load current caused by the instantaneous drop, that is, the distortion component of the load current. A compensation current which is equal and has a magnitude multiplied by −1 is supplied from the power converter 4 to the load 3.
For this reason, it is possible to reduce the drop in the load current. As a result, even if a sudden drop in the load voltage occurs due to the instantaneous drop, the drop can be reduced.

  Next, a second embodiment of the present invention will be described. In the second embodiment, the configuration of the control unit 200 is the same as that in the first embodiment, but the output states of the gain signals g11 and g12 are partially changed. The output state of the gain signals g11 and g12 will be described with reference to FIG.

  As shown in FIG. 3, the operation up to time t13 is the same as that in the first embodiment.

In the second embodiment, in FIG. 3, when the time t13, that is, when the high speed switch 2 is cut off, the gain signal output unit 231 sets the value of the gain signal g11 in a preset period T13 (period from time t13 to time t14). Is gradually decreased from 1 to 0, and the value of the gain signal g12 is gradually increased from 0.
For this reason, in the selection / output command S0 output from the selection / output command unit 240, the current control command S10 gradually decreases and the voltage control command S20 increases gradually.

  Since the current control command S10 gradually decreases and the voltage control command S20 increases gradually in this way, the transition from the current control state that reduces the drop in the load current to the voltage control state that maintains the load voltage at the rated voltage. Can be reduced, the rate of change of voltage fluctuation after the high-speed switch 2 is cut off can be reduced, and the occurrence of voltage oscillation can be suppressed.

  Next, a control unit 200A used in the voltage sag compensator according to the third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as the control part 200 concerning Example 1 shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  The control unit 200A of the third embodiment includes a current control command unit 300 and a selection / output command unit 310, and other parts are the same as those of the first embodiment shown in FIG.

  The current control command unit 300 includes a distortion component extraction unit 301, a first multiplication unit 302 that multiplies by -1, a second multiplication unit 303, a third multiplication unit 304, an addition unit 305, and a subtraction unit. 306 and a current control unit 307.

The distortion component extraction unit 301 extracts a distortion component signal ILh corresponding to the drop in the load current due to the instantaneous drop from the load current signal IL, and the multiplication unit 302 sets −1 to the distortion component signal ILh in order to compensate for the distortion component. Multiply.
The distortion component signal ILh multiplied by −1 is further multiplied by the gain signal g11a by the multiplier 303, the load current signal IL is multiplied by the gain signal g11b by the multiplier 304, and both signals are added by the adder 305. The The subtracting unit 306 calculates a deviation of the added signal from the AC output current signal (inverter output current signal) Iinv, and the current control unit 307 calculates a deviation / proportional / integral (PI) calculation to thereby control the current control command. S30 is obtained.

This current control command S30 is:
(1) A distortion component compensation command S31 for preventing a drop in the load current by supplying a current for compensating for a distortion component of the load current due to the instantaneous drop from the power converter 4 to the load 3,
(2) A current (system current) that flows through the high-speed switch 2 by supplying a current corresponding to the load current from the power converter 4 to the load 3 by performing current control to match the load current and the inverter current. And a system current zero command S32 for setting 0 to zero.

The distortion component compensation command S31 is obtained by subtracting the AC output current signal (inverter output current signal) Iinv from the value obtained by multiplying the gain component g11a by the distortion component signal ILh multiplied by −1, and subtracting the subtraction value [(−ILh × g11a) −Iinv] is obtained by proportional / integral (PI) calculation.
The system current zero command S32 subtracts the AC output current signal (inverter output current signal) Iinv from the value obtained by multiplying the load current signal IL by the gain signal g11b, and the subtraction value [(IL × g11b) −Iinv] is proportional. -Integration (PI) calculation.

  Various types of strain component extraction unit 301 can be used, and an example of the circuit configuration will be described later.

The selection / output command unit 310 includes a gain signal output unit 311, a multiplication unit 312, and an addition unit 313.
The gain signal output unit 311 outputs gain signals g11a, g11b, and g12. The values of the gain signals g11a, g11b, and g12 are set to values between 0 and 1 depending on the situation of the power system L1. To change.
The operation of the selection / output command unit 310 will be described later with reference to FIG. 5, and a command output from the selection / output command unit 310 is referred to as a selection / output command S0.

  Next, the operation of the selection / output command unit 310 and the operation of the parallel sag compensator will be described with reference to FIG.

In FIG. 5, the gain signal output unit 311 does not output the gain signals g11a, g11b, and g12 in the period T10, that is, the period before the time t12 when the instantaneous drop is detected by the instantaneous drop detection unit 201 (gain signal g11a). , G11b, and g12 are set to 0).
For this reason, the current control command S30 and the voltage control command S20 are not output from the selection / output command unit 310. That is, it is in a standby state.

  In FIG. 5, when a sag occurs at time t11, the sag detector 201 detects that a sag has occurred at time t12 that is delayed in time from time t11 (period T11 has elapsed).

When the voltage drop detecting unit 201 detects a voltage drop, the gain signal output unit 311 outputs gain signals g11a and g11b having a value of 1, and does not output the gain signal g12 (the value of the gain signal g12 is set to 0). And).
Therefore, the selection / output command S0 output from the selection / output command unit 310 has only the current control command S30 (= S31 + S31), and the final command SS (= current control command S30) is sent to the PWM modulator 6. The power converter 4 is operated by the PWM-modulated gate control signal G.

  Therefore, a current that compensates for the distortion component of the load current caused by the instantaneous drop is supplied from the power converter 4 to the load 3 by the distortion component compensation command S31 of the current control command S30. That is, a compensation current having the same phase and frequency and -1 times the magnitude of the distortion component of the load current is supplied from the power converter 4 to the load 3.

  In this way, since the compensation current having the same phase and frequency and -1 times the magnitude with respect to the distortion component of the load current is supplied from the power converter 4 to the load 3, the drop in the load current is reduced. As a result, even if an abrupt drop in the load voltage occurs due to an instantaneous drop, this drop can be reduced.

  Further, by supplying a current corresponding to the load current from the power converter 4 to the load 3 by the system current zero command S32 in the current control command S30, the current (system current) flowing through the high-speed switch 2 is reduced to zero. can do.

  The interruption control unit 202 outputs the interruption signal Sh at a time point t13 when a preset period T12 has elapsed from the time point t12 when the instantaneous voltage drop detection unit 201 detects the occurrence of an instantaneous voltage drop. When this shut-off signal Sh is input to the high speed switch 2, the high speed switch 2 is immediately shut off.

  In this case, by supplying a current corresponding to the load current from the power converter 4 to the load 3 in accordance with the system current zero command S32, the current (system current) flowing through the high-speed switch 2 is set to 0 in a high-speed state. Since the switch 2 can be cut off, the occurrence of surge can be suppressed, voltage fluctuation caused by the surge can be suppressed, and the period T12 from the momentary voltage drop detection to the switch cutoff can be shortened. .

In FIG. 5, at time t13, that is, when the cutoff signal Sh is output from the cutoff control unit 202, the gain signal output unit 311 outputs only the gain signal g12 having a value of 1, and the gain signals g11a and g11b are output. No (the values of the gain signals g11a and g11b are set to 0).
For this reason, the selection / output command S0 output from the selection / output command unit 310 has only the voltage control command S20, and the PWM modulator 6 PWM-modulates the final command SS (= voltage control command S20). In response to the gate control signal G, the power converter 4 operates to supply a three-phase voltage having a rated voltage (a voltage equal to the voltage of the system power supply 1) from the power converter 4 to the load 3. For this reason, even if the high-speed switch 2 is cut off, three-phase power can be supplied to the load 3.

Eventually, in the control unit 200A of the voltage sag compensator according to the third embodiment, the distortion component compensation command in the current control command S30 in the period T12 from the time t12 when the voltage sag is detected to the time t13 when the high speed switch 2 is shut off. The power converter 4 is operated by the gate control signal G based on S31, and the current from the power converter 4 to the load 3 is compensated for the distortion component of the load current caused by the instantaneous drop, that is, the distortion component of the load current. In contrast, a compensation current having the same phase and frequency and a magnitude multiplied by −1 is supplied from the power converter 4 to the load 3.
For this reason, it is possible to reduce the drop in the load current. As a result, even if a sudden drop in the load voltage occurs due to the instantaneous drop, the drop can be reduced.

  Further, in the control unit 200A of the voltage sag compensator according to the third embodiment, the system current zero command in the current control command S30 in the period T12 from the time t12 when the voltage sag is detected to the time t13 when the high speed switch 2 is shut off. By supplying a current corresponding to the load current from the power converter 4 to the load 3 through S32, the high-speed switch 2 can be shut off while the current (system current) flowing through the high-speed switch 2 is set to zero. Therefore, the occurrence of surge can be suppressed, voltage fluctuation caused by the surge can be suppressed, and the period T12 from the momentary voltage drop detection to the switch cutoff can be shortened.

  Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the configuration of the control unit 200A is the same as that of the third embodiment, but the output states of the gain signals g11a and g11b are partially changed. The output state of the gain signals g11a and g11b will be described with reference to FIG.

As shown in FIG. 6, the gain signal output unit 311 gradually increases the value of the gain signal g11a from 1 during a predetermined period α (where α <T12) from the time point t12 when the detection unit 201 detects the instantaneous drop. The gain signal g11b is gradually increased from zero.
Therefore, in the period α, the selection / output command S0 (= current control command S30) output from the selection / output command unit 310 is such that the distortion component compensation command S31 gradually decreases and the system current zero command S32 gradually increases. To increase.

  Since the distortion component compensation command S31 gradually decreases and the system current zero command S32 gradually increases in this way, the load current and the inverter current are made to coincide from the current control state that reduces the drop in the load current due to the instantaneous drop. The switching to the current control state in which the current (system current) flowing through the high-speed switch 2 is set to 0 can be moderated, and the voltage step change and the voltage fluctuation due to the voltage step change can be suppressed.

[Example of configuration of strain component extraction unit]
Next, a strain component extraction unit 400 that can be used as the strain component extraction unit 211 shown in FIG. 1 or the strain component extraction unit 301 shown in FIG. 4 will be described with reference to FIG.

  This distortion component extraction unit 400 includes a three-phase / two-phase converter 401 and a band pass filter (BPS) whose band pass frequency is designed so as to extract a distortion component corresponding to a drop in load current due to an instantaneous drop. ) 402 and 403, and a two-phase / three-phase converter 404.

  The load current signal IL is three-phase / two-phase converted by a three-phase / two-phase converter 401 and converted into a dq coordinate component of a rotating coordinate system synchronized with the frequency of the system power supply 1. Then, the d-axis component and the q-axis component are filtered through the band pass filters 402 and 403, and the filtered d-axis component and the q-axis component are subjected to inverse dq conversion by the two-phase / three-phase converter 404. The distortion component signal ILh corresponding to the drop in the load current due to the instantaneous drop can be obtained.

It is a block block diagram which shows the control part of the voltage drop compensation apparatus based on Example 1 of this invention. FIG. 6 is an explanatory diagram illustrating an operation state of the first embodiment. FIG. 6 is an explanatory diagram illustrating an operation state of the second embodiment. It is a block block diagram which shows the control part of the voltage drop compensation apparatus based on Example 3 of this invention. FIG. 10 is an explanatory diagram illustrating an operation state of the third embodiment. FIG. 10 is an explanatory diagram illustrating an operation state of the fourth embodiment. It is a block diagram which shows an example of a distortion component extraction part. It is a block diagram which shows the control part of the sag compensation apparatus based on a prior art. It is a block block diagram which shows the conventional control part. It is explanatory drawing which shows the operation state of the conventional control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 System power supply 2 High speed switch 3 Load 4 Power converter 5 Electric double layer capacitor 6 PWM modulator 100,200,200A Control part 201 Instantaneous voltage drop detection part 202 Shutdown control part 203 Reference voltage generation part 204 Addition part 210,300 Current control Command unit 220 Voltage control command unit 230, 310 Select / output command unit

Claims (4)

A switch interposed in the power system connecting the load and the system power supply,
A power converter capable of performing reverse conversion operation and forward conversion operation, with an alternating current side connected to the load and a direct current charging unit connected to the direct current side,
When an instantaneous drop occurs in the power system, the switch is controlled to be cut off, and the power converter is controlled to supply power from the power converter to the load by performing an inverse conversion operation of the power converter. In a voltage sag compensator having a control unit,
The controller is
A voltage sag detector that detects whether a voltage sag has occurred in the power system;
After detecting a voltage sag by the voltage sag detector, a shut-off controller that shuts off the switch when a preset time has elapsed,
A voltage control command for generating a voltage control command for controlling the power converter so that the power converter supplies power to the load and applies a rated voltage to the load from a deviation between a load voltage and a reference voltage And
In order to extract a distortion component corresponding to a drop in the load current due to a momentary drop from the load current, the power converter supplies power to the load and compensates the distortion component to supply the load with a compensation current. A current control command unit for generating a current control command for controlling the power converter;
A selection / output command unit that selects and outputs the current control command when the voltage drop is detected by the voltage drop detection unit, and selects and outputs the voltage control command when the switch is cut off by the cut-off control unit. When,
Based on a control command output from the selection / output command unit, a modulator that sends a gate control signal for controlling the power converter to supply power to the load from the power converter to the power converter;
A voltage sag compensator characterized by comprising: In claim 1,
The selection / output command unit, when the switch is cut off by the cut-off control unit, gradually reduces the current control command and gradually increases the voltage command. A switch interposed in the power system connecting the load and the system power supply,
A power converter capable of performing reverse conversion operation and forward conversion operation, with an alternating current side connected to the load and a direct current charging unit connected to the direct current side,
When an instantaneous drop occurs in the power system, the switch is controlled to be cut off, and the power converter is controlled to supply power from the power converter to the load by performing an inverse conversion operation of the power converter. In a voltage sag compensator having a control unit,
The controller is
A voltage sag detector that detects whether a voltage sag has occurred in the power system;
After detecting a voltage sag by the voltage sag detector, a shut-off controller that shuts off the switch when a preset time has elapsed,
A voltage control command for generating a voltage control command for controlling the power converter so that the power converter supplies power to the load and applies a rated voltage to the load from a deviation between a load voltage and a reference voltage And
In order to extract a distortion component corresponding to a drop in the load current due to a momentary drop from the load current, the power converter supplies power to the load and compensates the distortion component to supply the load with a compensation current. A distortion component compensation command for controlling the power converter is generated, and from a deviation between a load current and an AC output current output by the power converter, the power converter supplies power to the load to the load. A current control command unit for generating a system current zero command for controlling the power converter in order to supply a rated current;
When a voltage sag is detected by the voltage sag detector, the distortion component compensation command and the grid current zero command are selected and output.When the switch is shut off by the shut-off controller, the voltage control command is selected. Select / output command section to output,
Based on a control command output from the selection / output command unit, a modulator that sends a gate control signal for controlling the power converter to supply power to the load from the power converter to the power converter;
A voltage sag compensator characterized by comprising: In claim 1,
The selection / output command unit, when the voltage drop detection unit detects a voltage drop, gradually reduces the distortion component compensation command and gradually increases the voltage command.

Images