JP2004048938A - Voltage compensation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage compensation apparatus in which the capacity of a convertor is reduced as a countermeasure for dropping of a system voltage, for a smaller size and lower cost. <P>SOLUTION: The apparatus comprises a convertor for converting a DC voltage into an AC voltage, a serial transformer of which a primary coil is connected to an AC voltage side of the convertor while a secondary coil is serially connected to a system, an electric double layer capacitor connected to a DC voltage side of the convertor, a control means which calculates an output of the convertor to output a gate signal, outputs an AC voltage from the convertor, and convolutes the AC voltage to the system from the secondary coil of the serial transformer, and a gate circuit for switching a self-arc-extinguishing element in the convertor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a voltage compensator that maintains a load-side voltage within an appropriate voltage range when a power-supply-side voltage of a power system drops.
[0002]
[Prior art]
FIG. 6 is a schematic diagram of a power system using a conventional voltage compensating device. In the figure, 1 is a required system, 2 is a system power supply side, 3 is a system load side, 4 is a load device, 5 is a converter, 6 is an electric double layer capacitor, 7 is a reactor, 8 is system 1 and voltage compensation. A connection point with the system, 9 is an interconnection switch between the system 1 and the power supply 2, 10 is a first voltage detector that detects a voltage of the system power supply 2, and 11 is a first voltage detector that detects a voltage of the system load 3. Reference numeral 2 denotes a voltage detector, 12 denotes a third voltage detector for detecting a terminal voltage of the electric double layer capacitor, 13 denotes control means, and 14 denotes a gate circuit.
[0003]
The DC voltage side of converter 5 is connected to electric double layer capacitor 6, and the AC voltage side of converter 5 is connected to system 1 at connection point 8 via reactor 7.
[0004]
The interconnection switch 9 is provided on the system power supply side 2 of the connection point 8, and the load device 4 is connected to the system load side of the connection point 8.
[0005]
Next, the circuit operation will be described. The control means 13 detects the voltage on the system power supply side 2 by the first voltage detector 10, detects the voltage on the system load side 3 by the second voltage detector 11, and detects the electric voltage by the third voltage detector 12. The terminal voltage of the double layer capacitor 6 is detected.
[0006]
When the control means 13 determines that the state is the low voltage state from the voltage value of the first voltage detector 10, the control means 13 opens the interconnection switch 9 and outputs an AC voltage by the converter 5, The voltage is supplied to the load device 4. Further, the control means 13 detects the terminal voltage of the electric double layer capacitor 6 by the third voltage detector 12 so that the AC voltage which is the detection value of the second voltage detector 11 becomes a value within a specified voltage range. Then, a driving switching signal for the DC / AC converter 5 is calculated.
[0007]
Gate circuit 14 receives the calculated switching signal, and outputs a switching pulse to drive the self-extinguishing element in converter 5.
[0008]
If the control means 13 determines that the system voltage has returned from the voltage value of the first voltage detector 10, the control means 13 adjusts the voltage of the system power supply 2 and the voltage of the system The system switch 9 is turned on. Here, when the system voltage is within a predetermined value range, that is, normal, the control unit 13 causes the converter 5 to charge the electric double layer capacitor 6.
[0009]
In this manner, the conventional voltage compensator supplies the voltage to the load device even when the system voltage drops to a predetermined value or more, and continues the operation without stopping the load device.
[0010]
[Problems to be solved by the invention]
However, in the conventional voltage compensating device, since the interconnection switch is opened to disconnect the system power supply side and the load side in response to a decrease in system voltage, the converter can output a voltage equivalent to that of the system power supply side. Power supply capacity was required.
[0011]
Nevertheless, the instantaneous voltage drop that occurs in a short time of less than 1 second often results in the system voltage drop not reaching half of the system voltage, and in most cases, 50% or more of the AC voltage remains. Met.
[0012]
Therefore, the voltage compensator of the present invention compensates for the voltage drop by using a series transformer when the power supply side voltage of the system drops to a predetermined value or more, and maintains the load side voltage within an appropriate voltage range. Accordingly, an object of the present invention is to provide a voltage compensating device that can reduce the capacity of a converter, and as a result, can reduce the size and cost.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a voltage compensator according to claim 1 includes a converter for converting a DC voltage into an AC voltage, a primary winding connected to an AC voltage side of the converter, and a secondary winding. A series transformer having a line connected in series with the grid, an electric double layer capacitor connected to the DC voltage side of the converter, a first voltage detector for detecting a power supply side voltage of the grid, and an AC voltage of the converter. And output signals from a third voltage detector for detecting the DC voltage of the electric double layer capacitor, and calculating the output of the converter to output a gate signal, The converter charges the electric double layer capacitor when the voltage on the power supply side of the system is within the specified value range, and discharges the electric double layer capacitor when the voltage on the power supply side of the system falls below the predetermined value. To output an AC voltage from the converter. Control means for superimposing on the system from the secondary winding of the series transformer, and a gate circuit for inputting a gate signal and outputting a gate pulse for switching a self-extinguishing element in the converter are provided. And
[0014]
As a result, the compensation voltage generated in the secondary winding of the transformer can be reduced only by the voltage drop of the system voltage, and the capacity of the converter and the electric double layer capacitor can be reduced. The size and cost can be reduced.
[0015]
A voltage compensation device according to claim 2, wherein the converter converts a DC voltage to an AC voltage,
A primary winding is connected to the AC voltage side of the converter, a secondary winding is connected in series with the system, a series transformer, and a capacitor connected to the DC voltage side of the converter to suppress ripple. Charge and discharge the electric double layer capacitor together with the DC voltage side of the converter and the electric double layer capacitor connected via a capacitor and a buck-boost chopper to accumulate the power at the time of voltage compensation, and the DC voltage side of the converter. Step-up / step-down chopper, a first voltage detector for detecting a power supply side voltage of the system, a second voltage detector for detecting an AC voltage of the converter, and a third voltage detector for detecting a DC voltage of the converter And a fourth voltage detector for detecting the DC voltage of the electric double layer capacitor, inputting the output signal of the converter, outputting the gate signal by calculating the output of the converter, and setting the power supply side voltage of the system to a predetermined value. Is within the range The electric double layer capacitor is charged from the converter and the buck-boost chopper, and when the power supply side voltage of the system drops to a predetermined value or more, the electric double layer capacitor is discharged to output an AC voltage from the converter, Control means for superimposing a voltage on a system from a secondary winding of a series transformer, and a gate circuit for inputting a gate signal and outputting a gate pulse for switching a self-extinguishing element in the converter. It is characterized by.
[0016]
As a result, even when the required capacity of the electric double-layer capacitor is small and the rated voltage of the electric double-layer capacitor is smaller than the operating voltage of the converter, the compensation voltage is boosted by the buck-boost chopper to the operating voltage of the converter, and the compensation voltage is increased. And voltage compensation can be performed.
[0017]
The voltage compensating device according to claim 3 is the voltage compensating device according to claim 1 or 2, wherein the converter that converts the DC voltage to the AC voltage outputs three phases of single-phase AC voltages, and , Characterized by being connected to the primary winding of a single-layer series transformer for three phases.
[0018]
Thus, even if a three-phase imbalance occurs in the three-phase system in which the voltage of one or two phases decreases, the voltage of the load device is made three-phase balanced by outputting the compensation voltage by the present voltage compensator. be able to.
[0019]
A voltage compensating device according to a fourth aspect of the present invention is the voltage compensating device according to any one of the first to third aspects, further comprising a bypass switch connected in parallel to the series transformer. When the power supply side voltage of the system is within a predetermined value range, a bypass switch is turned on to gate-block the converter and stop, and when the power supply side voltage of the system falls to a predetermined value or more, the bypass The switch is turned off, and the compensation voltage is output by the converter.
[0020]
Thus, when the system power supply has the proper voltage, the voltage compensator can be stopped, so that the loss of the converter itself can be reduced.
[0021]
The same effect can be obtained by connecting the bypass switch in parallel with the primary winding of the series transformer.
[0022]
The voltage compensator according to claim 5 is the voltage compensator according to claim 4, further comprising a charging circuit connected in parallel with the electric double layer capacitor and charging the electric double layer capacitor. Features.
[0023]
This eliminates the need to drive the converter with the charging of the electric double-phase capacitor, and maintains the terminal voltage of the electric double-phase capacitor at the proper system voltage at an appropriate voltage even when the converter is not driven. Therefore, the loss caused by driving the converter can be significantly reduced.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment: Corresponding to Claim 1)
FIG. 1 is a diagram showing a circuit configuration according to the first embodiment. In FIG. 1, 1 to 14 have been described in the related art, and a description thereof will be omitted.
[0025]
In the figure, 15 is a series transformer, and 16 is a fourth voltage detector for detecting the AC voltage of the converter 5.
[0026]
The DC voltage side of converter 5 is connected to electric double layer capacitor 6, and the AC voltage side is connected to the primary winding of series transformer 15.
[0027]
The secondary winding of the series transformer 15 is connected in series with the system, and maintains the voltage on the load side within a specified voltage range by superimposing an AC voltage on the voltage drop on the system power supply side 2.
[0028]
The control means 13 detects the voltage of the system power supply 2 by the first voltage detector 10, detects the terminal voltage of the electric double layer capacitor 6 by the third voltage detector 12, To detect the secondary voltage of the series transformer.
[0029]
If it is determined from the voltage value of the first voltage detector 10 that it is in the low voltage state, the control means 13 performs the third voltage detection so that the input voltage of the load device 4 falls within the specified voltage range. The terminal voltage of the electric double layer capacitor, which is the detection value of the converter 12, is taken in, and a switching signal for the converter 5 is calculated.
[0030]
Gate circuit 13 receives this switching signal and outputs a switching pulse to drive the self-extinguishing element of converter 5.
[0031]
As a result, the converter 5 outputs the compensation source voltage, and the secondary winding of the series transformer 16 generates the compensation voltage.
[0032]
When it is determined from the voltage value of the first voltage detector 10 that the system voltage has returned, the control unit 13 starts control so that the converter 5 charges the electric double layer capacitor 6.
[0033]
When the control means 13 determines from the voltage value of the third voltage detector 12 that the electric double layer capacitor 6 is fully charged, the control means 13 stops the charging operation by the converter 5. Further, the control means 13 calculates the amount of current from the amount of increase or decrease in the voltage detection value of the third voltage detector 12 and controls the converter 5 so that the charging current of the electric double layer capacitor 6 becomes a target current value. To charge.
[0034]
According to the first embodiment, the compensation voltage generated in the secondary winding of the series transformer need only be the voltage drop of the system voltage. The capacity of the electric double layer capacitor can be reduced, and as a result, the size and cost of the device can be reduced.
[0035]
In FIG. 1, the DC / AC converter 5 is described using a three-phase bridge converter, but an NPC (Neutral Point Clamped) converter can also be applied. The voltage compensation may be performed not only for the three-phase system but also for a single-phase system.
[0036]
(Second embodiment: corresponds to claim 2)
FIG. 2 is a diagram showing a circuit configuration according to the second embodiment, in which 17 is a capacitor, 18 is a step-up / step-down chopper, and 19 is a fifth voltage for detecting a DC voltage of the converter 5. It is a detector.
[0037]
The DC voltage side of the DC / AC converter 5 is connected to the capacitor 17, and the capacitor 17 is connected to the electric double layer capacitor 6 via the step-up / step-down chopper 18.
[0038]
When it is determined from the voltage value of the first voltage detector 10 that it is in the low voltage state, the control unit 13 sets the fifth voltage detector so that the input voltage of the load device 4 falls within the specified voltage range. The capacitor voltage which is the detected value of 19 is taken in, and the switching signal of the converter 5 is calculated. Gate circuit 13 receives this switching signal and outputs a switching pulse to drive the self-extinguishing element of converter 5. Converter 5 outputs a compensation source voltage to generate a compensation voltage in the secondary winding of series transformer 16. Further, the control means 13 controls the step-up / step-down chopper 18 to discharge the electric double layer capacitor 6 while maintaining the voltage of the capacitor 17 at the target voltage.
[0039]
When it is determined from the voltage value of the first voltage detector 10 that the system voltage has returned, the control unit 13 starts controlling the step-up / step-down chopper 18 to charge the electric double layer capacitor 6. Further, the converter 5 is operated so that the terminal voltage of the capacitor 17 is maintained at the target voltage.
[0040]
On the other hand, when it is determined from the voltage detection value of the third voltage detector 12 that the electric double layer capacitor 6 is fully charged, the control means 13 stops the charging operation by the step-up / step-down chopper 18. Further, the control means 13 calculates a current amount from an increase / decrease change amount of the voltage detection value of the third voltage detector 12, and controls the step-up / step-down chopper 18 so that the charging current of the electric double layer capacitor 6 becomes a target current value. Control and charge.
[0041]
According to the second embodiment, even when the required capacity of the electric double layer capacitor is small and the rated voltage of the electric double layer capacitor is smaller than the operating voltage of the converter, the voltage is raised by the buck-boost chopper to the operating voltage of the converter. Thus, the compensation source voltage can be supplied to the series transformer, and the compensation voltage can be output from the series transformer.
[0042]
(Third Embodiment: Corresponding to Claim 3)
FIG. 3 is a diagram showing a circuit configuration according to the third embodiment. In FIG. 3, a converter 5 is configured by parallelizing three sets of single-phase bridge converters. The AC voltage side is connected to the primary winding of each phase series transformer.
[0043]
If it is determined from the voltage value of the first voltage detector 10 that it is in the low voltage state, the control unit 13 determines the low voltage of the system voltage phase from the secondary winding of the series transformer. A compensation voltage is output to set the input voltage of the load device 4 within a specified voltage range.
[0044]
According to the third embodiment, even when a three-phase imbalance occurs in which a voltage of one or two phases decreases in a three-phase system, a compensation voltage is output for each phase, so that the voltage of the load device is reduced. Can be brought into a three-phase equilibrium.
[0045]
(Fourth Embodiment: Corresponding to Claim 4)
FIG. 4 is a diagram showing a circuit configuration according to the fourth embodiment, in which 20 is a bypass switch.
[0046]
The bypass switch 20 is connected in parallel with the secondary winding of the series transformer 15, and when the system power supply voltage is at an appropriate voltage, the control unit 13 turns on the bypass switch 20, and from the system power supply side via the bypass switch. Power to the system load side while the converter 5 is stopped. When the system power supply side voltage is low, the control unit 13 turns off the bypass switch 20, supplies the compensation source voltage from the converter 5, and outputs the compensation voltage from the series transformer 15, thereby controlling the system load side voltage. Within an appropriate voltage range.
[0047]
According to the fourth embodiment, when the system power supply has an appropriate voltage, the present voltage compensator can be stopped, so that the loss caused by the converter can be reduced.
[0048]
Note that the same effect can be obtained by connecting the bypass switch 20 in parallel with the primary winding of the series transformer.
[0049]
(Fifth embodiment: corresponds to claim 5)
FIG. 5 is a diagram showing a circuit configuration according to the fifth embodiment. In FIG. 5, a charging circuit 21 is added to the circuit configuration according to the fourth embodiment.
[0050]
When it is determined that the system power supply side voltage is an appropriate voltage, the control means 13 turns on the bypass switch 20 and gates the converter 5 to stop the voltage compensation operation. 6 is in an open state, and the voltage is reduced by the self-discharge operation.
[0051]
In order to obtain a sufficient voltage compensation effect by the voltage compensator, it is necessary to always maintain the terminal voltage of the electric double-phase capacitor 6 at an appropriate voltage. For this purpose, a small-capacity charging circuit 21 is connected in parallel with the electric double-phase capacitor 6, and the electric double-phase capacitor 6 is appropriately charged.
[0052]
According to the fifth embodiment, since the electric double-phase capacitor 6 is not charged by the converter 5, the loss generated by the converter can be reduced, and the electric double-phase capacitor when the system voltage is normal can be reduced. Can be prepared for the voltage compensation operation by maintaining the terminal voltage at the appropriate voltage.
[0053]
【The invention's effect】
As described above, according to the present invention, it is possible to compensate for the voltage drop of the system voltage by the series transformer connected in series to the system and maintain the load voltage within an appropriate voltage range. it can. As a result, the capacity of the converter can be reduced, and the size and cost of the voltage compensator can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram according to a first embodiment of the present invention; FIG. 2 is a circuit diagram according to a second embodiment of the present invention; FIG. 3 is a circuit diagram according to a third embodiment of the present invention; FIG. 4 is a circuit configuration diagram according to a fourth embodiment of the present invention. FIG. 5 is a circuit configuration diagram according to a fifth embodiment of the present invention. Circuit configuration diagram [Description of symbols]
DESCRIPTION OF SYMBOLS 1 ... System, 2 ... System power supply side, 3 ... System load side, 4 ... Load device, 5 ... Converter, 6 ... Electric double phase capacitor, 7 ... Reactor, 8 ... Connection point between this device and system, 9 ... Connection switch, 10 ... First voltage detector, 11 ... Second voltage detector, 12 ... 3 voltage detector, 13 control means, 14 gate circuit, 15 series transformer, 16 fourth voltage detector, 17 capacitor, 18 up / down Pressure chopper, 19: fifth voltage detector, 20: bypass switch, 21: charging circuit

Claims (5)

A converter for converting a DC voltage to an AC voltage,
A series transformer in which a primary winding is connected to the AC voltage side of the converter, and a secondary winding is connected in series with the system;
An electric double layer capacitor connected to the DC voltage side of the converter,
A first voltage detector for detecting a power supply side voltage of the system, a second voltage detector for detecting an AC voltage of the converter, and a third voltage detector for detecting a DC voltage of the electric double layer capacitor. And outputs the gate signal by calculating the output of the AC / DC converter, and when the power supply side voltage of the system is within a predetermined value range, the converter outputs the electric power. When the multilayer capacitor is charged and the power supply side voltage of the system drops to a predetermined value or more, the electric double layer capacitor is discharged to output an AC voltage from the converter, and the AC voltage is converted to the series transformer. Control means for superimposing on the system from the secondary winding of
And a gate circuit for receiving the gate signal and outputting a gate pulse for switching a self-extinguishing element in the AC / DC converter. A converter for converting a DC voltage to an AC voltage,
A series transformer in which a primary winding is connected to the AC voltage side of the converter, and a secondary winding is connected in series with the system;
A capacitor connected on the DC voltage side of the converter to suppress ripple,
An electric double layer capacitor connected to the DC voltage side of the AC / DC converter and the capacitor and the buck-boost chopper to store power at the time of voltage compensation;
A buck-boost chopper for charging and discharging the electric double layer capacitor together with the DC voltage side of the converter,
A first voltage detector for detecting a power supply side voltage of the system, a second voltage detector for detecting an AC voltage of the converter, a third voltage detector for detecting a DC voltage of the converter, An output signal from a fourth voltage detector for detecting a DC voltage of the double-layer capacitor is input, an output of the converter is calculated, a gate signal is output, and a power supply side voltage of the system is a predetermined value. When the voltage is within the range, the electric double layer capacitor is charged from the converter and the buck-boost chopper, and when the power supply side voltage of the system is reduced to a predetermined value or more, the electric double layer capacitor is discharged to discharge the electric double layer capacitor. Control means for outputting an AC voltage from the AC / DC converter and superimposing the AC voltage on the system from the secondary winding of the series transformer;
A voltage compensator comprising: a gate circuit that receives the gate signal and outputs a gate pulse for switching a self-extinguishing element in the converter. The converter for converting a DC voltage into an AC voltage outputs three-phase single-phase AC voltage and is connected to a primary winding of a three-phase single-layer series transformer. The voltage compensator according to claim 1 or 2. The power supply further comprises a bypass switch connected in parallel with the series transformer, wherein the control unit turns on the bypass switch to gate the converter when the power supply side voltage of the system is within a predetermined value range. 4. The method according to claim 1, wherein when the power supply side voltage of the system drops to a predetermined value or more, the bypass switch is turned off and a compensation voltage is output by the converter. 5. A voltage compensator according to any one of the preceding claims. The voltage compensator according to claim 4, further comprising a charging circuit connected in parallel with the electric double layer capacitor and charging the electric double layer capacitor.

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