JP4037380B2 - Voltage compensator - Google Patents

Description

  The present invention relates to a voltage compensation device that compensates for a voltage drop by superimposing a compensation voltage on a power supply voltage when the power supply voltage supplied to a load drops.

The voltage of the electric power system is instantaneously reduced by lightning, etc., and precision equipment such as factories malfunctions or is temporarily stopped, which can cause great damage on the production line. In order to prevent such damage, a voltage fluctuation compensator that monitors voltage fluctuations such as an instantaneous voltage drop (hereinafter referred to as a momentary voltage drop) of the power system and compensates for the voltage drop is used.
A conventional voltage fluctuation compensator is configured by a plurality of voltage compensation circuits that are connected in series to a power system and output a compensation voltage with either positive or negative polarity. Each voltage compensation circuit is provided with a full bridge inverter composed of four semiconductor switching elements with diodes connected in antiparallel, and a charging capacitor, which converts the DC voltage of the charging capacitor into AC and outputs it. In addition, a high-speed mechanical steady short-circuit switch is provided in parallel at the output terminal of each voltage compensation circuit. The charging capacitors in each voltage compensation circuit are charged with different voltages by the charging diode and the charging transformer, and the voltage ratio is set to a power ratio of about 2.

  Constantly, current flows through a steady short circuit switch. In addition, when a voltage drop occurs instantaneously in the system voltage, the voltage drop is detected by a detection unit that monitors voltage fluctuation, and a steady short-circuit switch is opened by power supply control based on the voltage drop, and a plurality of voltage drops depending on the error voltage. A desired combination is selected from the voltage compensation circuit, and the voltage drop of the power system is compensated by the sum of the output voltages (see, for example, Patent Document 1).

JP 2002-359929 A

  In the conventional voltage compensator as described above, the voltage drop is compensated by superimposing the compensation voltage on the system voltage at the time when the system voltage is suddenly reduced. Then, the compensation voltage of 100% of the shortage is generated and supplied to the load side. When the breaker provided upstream of the voltage compensator is turned off for some reason, the detection unit monitoring the voltage fluctuation on the power supply side of the voltage compensator determines that the power supply voltage has dropped to 0 V, and the shortage 100% compensation voltage is generated to try to supply voltage to the load side. Since the upstream breaker is off, the voltage detected on the power supply side fluctuates due to the generation of the compensation voltage, and there is a problem that an unnecessary compensation operation for further compensating for the fluctuation is performed.

  In addition, power supply control is performed by generating a control signal in the control unit based on the detection of the voltage drop, but the power supply circuit for operating the control unit has both a start-up and a power supply voltage drop. In order to supply voltage, the power supply circuit is connected to both terminals on the power supply side and the load side so that the voltage is supplied through the noise filter. This hinders simplification of the device configuration.

The present invention has been made to solve the above-described problems, and when a breaker provided upstream of the voltage compensator is turned off, it can quickly detect and perform unnecessary voltage compensation operation. The first purpose is to stop the operation.
It is a second object of the present invention to provide a small and inexpensive device configuration by simplifying a circuit configuration for supplying a voltage to a power supply circuit for operating a control unit.

The voltage compensator according to the present invention has an energy storage means, and a compensation circuit for converting the DC voltage stored in the energy storage means into an alternating current and outputting it is connected in series to an AC power supply and connected in parallel to the power supply voltage. voltage detection unit for monitoring a power supply voltage is, and a control unit that performs power supply control based on the power supply voltage, when detecting the power supply voltage drop at the voltage detecting unit, the compensation voltage output by the compensation circuit This is a device configuration that compensates for a drop in the voltage supplied to the load superimposed on the power supply voltage. The voltage detection unit includes phase detection means for detecting a voltage at both ends of the voltage detection unit as the power supply voltage and detecting a phase fluctuation exceeding a predetermined amount from a reference phase of the power supply voltage, and the compensation circuit includes the compensation voltage. When the phase detection unit detects a phase fluctuation of the power supply voltage during the compensation operation for outputting the compensation voltage, a compensation operation termination unit is provided for stopping the output of the compensation voltage from the compensation circuit . When the AC power supply is shut off, the compensation circuit outputs a compensation voltage, and the voltage detection unit bypasses the AC power supply, and is a closed circuit that connects the compensation circuit, the load, and the voltage detection unit. The phase detection means detects the fluctuation of the power supply voltage phase, and the compensation operation end means stops the output of the compensation voltage from the compensation circuit.

  The voltage compensator according to the present invention comprises a mechanical short-circuit switch for bypassing the compensation circuit in parallel with the compensation circuit, and the control circuit controls the short-circuit switch when the power supply voltage is steady. Closes and bypasses the compensation circuit. When the power supply voltage drops, the short-circuit switch is opened to compensate for the power supply voltage drop by the compensation voltage output from the compensation circuit. A control power supply circuit is provided. The control power supply circuit is connected to the load side terminal of the compensation circuit, and is connected to the power supply side terminal of the compensation circuit with a switching means. When a voltage is supplied from the side terminal and the short-circuit switch is closed by starting the apparatus, the switching means cuts off the voltage supply from the power supply side terminal and switches to the voltage supply from the load side terminal.

  In the voltage compensator according to the present invention, during the compensation operation, it is detected that the power supply voltage phase has changed by more than a predetermined amount from the reference phase, and the compensation operation is stopped by stopping the output of the compensation voltage from the compensation circuit. When the breaker provided upstream of the voltage compensation device is turned off, it is possible to quickly detect and stop unnecessary voltage compensation operation.

  In the voltage compensator according to the present invention, the control power supply circuit is supplied with a voltage from the power supply side terminal at the time of starting the device, and when the short circuit switch is closed by the start of the device, the voltage supply from the power supply side terminal is cut off. Switching to voltage supply from the terminal eliminates the need for a voltage supply from the power supply side terminal via a noise filter, simplifying the circuit configuration for supplying voltage and providing a small and inexpensive device configuration.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below. 1 is a schematic configuration diagram of a voltage compensator according to Embodiment 1 of the present invention.
As shown in FIG. 1, a compensation circuit 2 that is a voltage generator is connected in series to an AC power source 1, and the compensation circuit 2 outputs a compensation voltage, and this compensation voltage is superimposed on the power source voltage to vary the voltage of the load 3. To compensate. A shorting switch 4 for bypassing the compensation circuit 2 is connected in parallel to the compensation circuit 2. Furthermore, based on the information of the voltage detection unit 5 that monitors the power supply voltage, the control unit 6 generates a control signal and controls the short-circuit switch 4 and the switching element in the compensation circuit 2 to perform power feeding control. A breaker 7 is provided upstream (on the power supply side) from the connection position of the power supply terminal of the compensation circuit 2 and the voltage detection unit 5.

  Further, the voltage detector 5 not only detects the voltage value of the power supply voltage but also has phase detection means for detecting the phase thereof. When the voltage detection unit 5 detects that the power supply voltage phase has greatly changed from the phase of the reference voltage by a predetermined amount, the control unit 6 generates a control signal in the compensation circuit 2. The generation of the compensation voltage is stopped and the compensation operation is finished.

  When the power supply voltage is steady, the short circuit switch 4 is closed and the compensation circuit 2 is bypassed. When the voltage detector 5 detects a drop in the power supply voltage, the controller 6 opens the short-circuit switch 4 and switches to power supply via the compensation circuit 2. The compensation circuit 2 outputs a compensation voltage, and superimposes this compensation voltage on the power supply voltage and supplies it to the load 3.

When the upstream breaker 7 is turned off, the voltage detection unit 5 determines that the power supply voltage is 0 V, opens the short-circuit switch 4, generates a deficient 100% compensation voltage, and performs a compensation operation. At this time, a circuit as shown in FIG. 2 is formed. Here, V1 is a power supply voltage detected by the voltage detection unit 5, V2 is a compensation voltage output from the compensation circuit 2, V3 is a supply voltage to the load 3, R1 is an input impedance 5a of the voltage detection unit 5, and Rload is a load 3 Impedance.
At this time, V1 + V2 = V3
Considering V2 as a power supply, V1: -V3 = R1: Rload
As a result, V1 = (− R1 / Rload) V3
It becomes. The compensation voltage V2 output from the compensation circuit 2 is output so that the supply voltage V3 to the load 3 becomes the power supply voltage Vt at the normal time.
V1 = (− R1 / Rload) Vt
Thus, the power supply voltage V1 detected by the voltage detector 5 has an opposite phase that is approximately 180 degrees out of phase with the normal power supply voltage Vt. At this time, the compensation voltage V2 output from the compensation circuit 2 is
V2 = Vt−V1 = ((Rload + R1) / Rload) Vt
It becomes.

  As described above, when the voltage detection unit 5 detects that the power supply voltage phase has greatly fluctuated beyond a predetermined amount from the phase of the reference voltage (normal power supply voltage Vt), the control unit 6 performs compensation operation. End. For this reason, when the power supply voltage V1 detected by the voltage detection unit 5 is in an opposite phase that is approximately 180 degrees out of phase with the normal power supply voltage Vt, the voltage detection unit 5 has detected that it has exceeded a predetermined amount. Then, the compensation circuit 2 stops generating the compensation voltage and finishes the compensation operation.

  In this embodiment, it is detected that the power supply voltage phase detected by the voltage detector 5 has greatly fluctuated from the reference voltage phase, and it is detected that the upstream breaker 7 has been turned off. Since the compensation operation is immediately terminated, unnecessary compensation operation is not continued. For this reason, reliable operation control of the voltage compensator can be performed.

  In normal phase fluctuations, fluctuations exceeding 60 degrees are not observed. Therefore, for example, when phase fluctuations exceeding 60 degrees are detected at a voltage exceeding 30 V, which is a safety voltage, it is determined that the breaker 7 is turned off. Immediately finish the compensation operation.

An example of the compensation circuit 2 in the first embodiment will be described below with reference to FIG.
As shown in the figure, the compensation circuit 2 includes a full-bridge single-phase inverter 8 composed of semiconductor switching elements such as four IGBTs (T1 to T4) in which diodes D1 to D4 are connected in antiparallel, and energy storage means. And a capacitor 9 that outputs a compensation voltage with either positive or negative polarity and superimposes it on the power supply voltage to compensate for a drop in the voltage supplied to the load 3.
Further, a plurality of compensation circuits 2 having such a configuration may be provided, and the AC side of each single-phase inverter 8 may be connected in series. In this case, the output voltage generated from each single-phase inverter 8 can be used. Multi-stage compensation voltage is output by summation, and high-precision voltage compensation is possible.

Embodiment 2. FIG.
Next, the power supply of the control unit 6 that controls the short-circuit switch 4 and the switching elements in the compensation circuit 2 in the voltage compensation device shown in the first embodiment will be described below.
FIG. 4 is a configuration diagram of a voltage compensation apparatus according to Embodiment 2 of the present invention.
As shown in the figure, a control power supply circuit 10 for operating the control unit 6 is connected to the control unit 6, and the control power supply circuit 10 is connected to the power supply side terminal 11a and the load side terminal 11b of the compensation circuit 2, respectively. The Also, a constant voltage means 12 is inserted between the control power supply circuit 10 and the power supply side terminal 11a of the compensation circuit 2 as an impedance that is energized when the voltage between the two electrodes exceeds a predetermined voltage. Further, a rectifier circuit 13 is provided in the front stage of the control power circuit 10, and the potential on the control power circuit side of the diode (in the rectifier circuit 13) at the rear stage of the constant voltage means 12 is input from the load side terminal 11b of the compensation circuit 2. Configure. A voltage is supplied from the power supply side terminal 11a of the compensation circuit 2 to the control power supply circuit 10 via the constant voltage means 12 and the rectifier circuit 13, and a noise filter 14 is provided from the load side terminal 11b to provide the filter 14 and the rectifier circuit. The voltage is supplied to the control power supply circuit 10 through 13.

When the voltage compensator is started, the short-circuit switch 4 is in an open state, and the short-circuit switch 4 is closed by starting the device. When the voltage compensation device is activated with the short-circuit switch 4 open, a voltage is supplied from the power supply side terminal 11a to the control power supply circuit 10 through the constant voltage means 12, and when the short-circuit switch 4 is closed by the activation of the device, the constant voltage The diode in the subsequent stage of the means 12 is cut off, and the constant voltage means 12 is cut off. At this time, since power is supplied to the load 3 via the short-circuit switch 4, the voltage is switched from the load-side terminal 11b to the control power supply circuit 10. The constant voltage means 12 is configured so that the power supply voltage at startup can be used with any polarity.
Further, in this embodiment, the voltage supply to the control power supply circuit 10 is surely switched by using the constant voltage means 12 as the impedance inserted between the control power supply circuit 10 and the power supply side terminal 11a of the compensation circuit 2. However, the present invention is not limited to this. For example, a resistor may be used as the impedance.

  In this way, the voltage supply to the control power supply circuit 10 for operating the control unit 6 is supplied from the power supply side only at the time of starting the apparatus, and is supplied from the load side during the subsequent operation of the apparatus. It is not necessary to use a filter in the voltage supply path from the circuit, and the circuit configuration can be simplified. For this reason, a small and inexpensive voltage compensator having a device configuration can be obtained.

It is a schematic block diagram of the voltage compensation apparatus by Embodiment 1 of this invention. It is a circuit diagram explaining operation | movement of the voltage compensation apparatus by Embodiment 1 of this invention. 1 is a circuit diagram of a compensation circuit according to a first embodiment of the present invention. It is a block diagram of the voltage compensation apparatus by Embodiment 2 of this invention.

Explanation of symbols

1 AC power supply 2 Compensation circuit 3 Load 4 Short-circuit switch 5 Voltage detector
6 control unit, 9 capacitor as energy storage means, 10 control power supply circuit,
11a Power supply side terminal, 11b Load side terminal, 12 constant voltage means, 14 filter.

Claims (5)

A voltage having an energy storage means and converting a DC voltage stored in the energy storage means into an alternating current and outputting it in series with an AC power supply and connected in parallel to the power supply voltage to monitor the power supply voltage And a control unit that performs power supply control based on the power supply voltage. When the voltage detection unit detects a decrease in the power supply voltage, the compensation voltage output by the compensation circuit is superimposed on the power supply voltage and applied to the load. In a voltage compensator that compensates for a drop in the supplied voltage,
The voltage detection unit has a phase detection unit that detects a voltage fluctuation exceeding a predetermined amount from a reference phase of the power supply voltage, while detecting a voltage at both ends of the voltage detection unit as the power supply voltage.
Compensation operation end means for stopping the output of the compensation voltage from the compensation circuit when the phase detection means detects a phase fluctuation of the power supply voltage during the compensation operation in which the compensation circuit outputs the compensation voltage ,
When the AC power supply is shut off, the compensation circuit outputs a compensation voltage, and the voltage detection unit forms a path that bypasses the AC power supply, thereby forming a closed circuit that connects the compensation circuit, the load, and the voltage detection unit. And the phase detection means detects the fluctuation of the power supply voltage phase, and the compensation operation end means stops the output of the compensation voltage from the compensation circuit . Phase variation of the supply voltage the phase detection means detects the voltage compensation device according to claim 1, wherein the at voltage exceeding the predetermined voltage is a variation of greater than about 60 degrees than the reference phase. A mechanical short-circuit switch for bypassing the compensation circuit is provided in parallel with the compensation circuit, and the control unit controls to close the short-circuit switch and bypass the compensation circuit when the power supply voltage is steady. When the power supply voltage drops, the short-circuit switch is opened to compensate for the power supply voltage drop by the compensation voltage output from the compensation circuit.
A control power supply circuit for operating the control unit;
The control power supply circuit is connected to the load side terminal of the compensation circuit, and is connected to the power supply side terminal of the compensation circuit with a switching means. A voltage is supplied from a side terminal, and when the short-circuit switch is closed by starting the device, the switching means cuts off the voltage supply from the power supply side terminal and switches to the voltage supply from the load side terminal. Item 3. The voltage compensation device according to Item 1 or 2. The switching means is configured by a predetermined impedance inserted between the control power supply circuit and the power supply side terminal of the compensation circuit, and the potential on the control power supply circuit side of the impedance is input from the load side terminal of the compensation circuit. 4. The voltage compensation device according to claim 3, wherein when the short-circuit switch is closed by starting the device, the current supply with the impedance is cut off. 5. A filter is provided between the control power supply circuit and a load side terminal of the compensation circuit, and a voltage is supplied from the load side terminal to the control power supply circuit via the filter. Voltage compensation device.

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