WO2018168948A1

WO2018168948A1 - Voltage compensation device

Info

Publication number: WO2018168948A1
Application number: PCT/JP2018/010024
Authority: WO
Inventors: 俊介玉田; 宏餅川; 渡邊　裕治
Original assignee: 株式会社東芝; 東芝エネルギーシステムズ株式会社
Priority date: 2017-03-17
Filing date: 2018-03-14
Publication date: 2018-09-20
Also published as: JP2018157703A

Abstract

A voltage compensation device according to one embodiment of the present invention is provided with: a power converter that supplies a compensation voltage for compensating for a phase voltage of a power system to a transformer connected in series to phases of the power system; and a control unit that outputs a control signal for controlling the power converter on the basis of the phase voltage and a preset target voltage of the power system. The control unit includes: a first computing unit that generates a command value for generating the compensation voltage on the basis of the phase voltage and the target voltage; and a determination circuit that compares the deviation between the command value and the target voltage with a preset minimum compensation voltage value, and outputs a stop signal for stopping at least a part of the control signal when the deviation is less than the minimum compensation voltage value.

Description

Voltage compensator

Embodiments described herein relate generally to a voltage compensation device.

In the power system, the power line impedance increases according to the distance from the substation. Therefore, at the end of the power system, the received voltage may decrease due to a voltage drop. In the electric power system, it is necessary to supply a voltage within a certain allowable range to consumers regardless of the distance from the substation.

In order to compensate the voltage of the electric power system, a voltage compensator inserted in series in the electric power system has been proposed. Such a voltage compensation device incorporates an inverter circuit that performs high-frequency switching operation, thereby enabling voltage compensation of the power system at high speed and continuously.

When it is detected that the voltage of the power system has deviated from a preset target value, the voltage compensator operates to match the voltage of the power system with the target voltage value. Since the voltage compensator performs a high-frequency switching operation, a switching loss and a conduction loss accompanying the switching operation occur during operation. The voltage of the power system constantly fluctuates, so that the voltage compensator is always operating and generates a constant operating loss.

The embodiment provides a high-efficiency voltage compensator with little operation loss over the entire operation period.

The voltage compensator according to the embodiment includes a power converter that supplies a compensation voltage for compensating a phase voltage of the power system to a transformer connected in series to each phase of the power system, and the phase voltage is set in advance. And a control unit that outputs a control signal for controlling the power converter based on the target voltage of the power system. The control unit includes a first arithmetic unit that generates a command value for generating the compensation voltage based on the phase voltage and the target voltage, and between the command value and the target voltage. And a determination circuit that outputs a stop signal for stopping at least a part of the control signal when the deviation is smaller than the minimum compensation voltage value. Including.

1 is a block diagram illustrating a voltage compensation device according to a first embodiment. FIG. 2A and FIG. 2B are block diagrams illustrating a part of the voltage compensator of the first embodiment. FIG. 3A to FIG. 3C are schematic diagrams for explaining the operation of the voltage compensator according to the first embodiment. It is a block diagram which illustrates the voltage compensation apparatus concerning a 2nd embodiment. It is a block diagram which illustrates some voltage compensation apparatuses of a 2nd embodiment. It is a block diagram which illustrates the voltage compensating device concerning a 3rd embodiment. It is a block diagram which illustrates the voltage compensating device concerning a 4th embodiment. It is a block diagram which illustrates a part of voltage compensation apparatus of 4th Embodiment. It is a block diagram which illustrates the voltage compensating device concerning a 5th embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
In the present specification and drawings, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

(First embodiment)
FIG. 1 is a block diagram illustrating a voltage compensator according to this embodiment.
A configuration of the voltage compensator 1 of the present embodiment will be described.
As shown in FIG. 1, the voltage compensation device 1 according to this embodiment includes a voltage compensation unit 10 and a control unit 80.

The voltage compensator 10 includes

series transformers

11, 13, 15, a first power converter 20, a second power converter 30,

parallel transformers

41, 42,

inductors

51, 52, and a current detector 61. , 62,

AC voltage detectors

63, 64, and a DC voltage detector 65. The voltage compensator 1 is connected in series to the power system by the voltage compensator 10. The power system is a three-phase AC distribution system composed of a U phase, a V phase, and a W phase.

The voltage compensation unit 10 includes terminals 2a to 2c and 3a to 3c. The voltage compensator 10 is connected to the upstream sides 6a to 6c of the power system via the terminals 2a to 2c. The voltage compensator 10 is connected to the downstream sides 7a to 7c of the power system via the terminals 3a to 3c. For example, the upstream side of the power system is the substation side, and the downstream side is the consumer side. Hereinafter, the phases of the power system on the upstream side 6a to 6c are referred to as U phase, V phase, and W phase, and the phases of the power system on the downstream side 7a to 7c are referred to as u phase, v phase, and w phase. Therefore, the terminal 2a is connected to the U phase, and the terminal 3a is connected to the u phase. The terminal 2b is connected to the V phase, and the terminal 3b is connected to the v phase. Terminal 2c is connected to the W phase, and terminal 3c is connected to the w phase.

The voltage compensator 1 detects a decrease or an increase in the voltage on the upstream side 6a to 6c of the power system with respect to the target value, and outputs a compensation voltage so that the voltages on the downstream side 7a to 7c coincide with the target voltage. The compensation voltage is added to the voltage on the upstream side 6a to 6c or subtracted from the voltage on the upstream side 6a to 6c. When subtracted from the voltages on the upstream sides 6a to 6c, a compensation voltage having a phase different from the phase of the power system by 180 ° is added to the voltages on the upstream sides 6a to 6c.

As will be described in more detail later, the voltage compensator 1 of the present embodiment has a voltage range in which fluctuations are allowed in both positive and negative directions with the detected upstream side voltages 6a to 6c as the center value. The voltage compensator 1 performs a compensation operation when the target voltage deviates from the detected allowable range of the upstream side voltages 6a to 6c. When the target voltage is within the allowable range of the detected voltages on the upstream sides 6a to 6c, the compensation operation is stopped.

First, the configuration of the voltage compensation unit 10 will be described in detail.

Series transformers

11, 13, and 15 include

primary windings

11p, 13p, and 15p, and

secondary windings

11s, 13s, and 15s, respectively. The primary winding 11p of the series transformer 11 is connected between the terminal 2a and the terminal 3a, and is connected in series to the power system. The primary winding 13p of the series transformer 13 is connected between the terminal 2b and the terminal 3b, and is connected in series to the power system. The primary winding 15p of the series transformer 15 is connected between the terminal 2c and the terminal 3c, and is connected in series to the power system. That is, the

primary windings

11p, 13p, 15p of the three

series transformers

11, 13, 15 are connected in series to each phase of the power system.

The

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15 are delta-connected. That is, one terminal 12a of the secondary winding 11s is connected to the other terminal 14b of the secondary winding 13s. One terminal 14a of the secondary winding 13s is connected to the other terminal 16b of the secondary winding 15s. One terminal 16a of the secondary winding 15s is connected to the other terminal 12b of the secondary winding 11s. A connection node of the

terminals

12 a and 14 b is connected to the AC terminal 22 b of the first power converter 20. A connection node of the

terminals

14 a and 16 b is connected to the AC terminal 22 c of the first power converter 20. A connection node of the

terminals

16 a and 12 b is connected to the AC terminal 22 a of the first power converter 20.

In the voltage compensation device 1 of the present embodiment, the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15 are delta-connected and connected to the AC output of the first power converter 20. Therefore, it is possible to flow a return current in the secondary winding, and the voltage compensation device 1 is less likely to cause voltage distortion and can link high-quality power to the power system.

Note that the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15 are not limited to delta connections, and may be star connections. By making the secondary winding a star connection, since the return current cannot flow, the voltage distortion tends to increase, but there is an advantage that the connection work becomes easy.

The first power converter 20 is connected between the high voltage DC terminal 21a and the low voltage DC terminal 21b. A DC voltage is supplied to the high-voltage DC terminal 21 a and the low-voltage DC terminal 21 b via a DC link capacitor 24. The first power converter 20 includes

AC terminals

22a, 22b, and 22c that output a three-phase AC voltage. The

AC terminals

22a, 22b, and 22c are connected to the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15 through the filter 26. The first power converter 20 is an inverter device that converts a DC voltage applied between the high-voltage DC terminal 21a and the low-voltage DC terminal 21b into a three-phase AC voltage.

The first power converter 20 includes, for example, six switching elements 23a to 23f. The switching elements 23a to 23f are self-extinguishing type switching elements, such as MOSFET (Metal-Oxide-Semiconductor-Field-Effect-Transistor) and IGBT (Insulated-Gate Bipolar-Transistor). The switching elements are connected in series as a high side switch and a low side switch. Three legs having arms connected in series are connected in parallel to form a three-phase inverter circuit. The inverter circuit of the first power converter 20 is not limited to this circuit configuration as long as it can convert a DC voltage into an AC voltage having a frequency higher than the frequency of the power system. The inverter circuit may be, for example, a multilevel inverter circuit or a modification thereof.

A filter 26 is connected between the first power converter 20 and the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15. In this example, the filter 26 is a low-pass filter including an inductor connected in series to each phase and a capacitor connected between the lines. The filter 26 removes harmonics of a high-frequency switching waveform of about several kHz to several hundred kHz output from the first power converter 20, and outputs a voltage at the frequency of the power system. As the filter 26, an appropriate circuit can be used according to the frequency of the output of the first power converter 20, the modulation method, or the like.

The DC link capacitor 24 supplies DC power to the first power converter 20. The capacitor 24 supplies active power supplied from the second power converter 30 to the first power converter 20.

The second power converter 30 includes a high voltage DC terminal 31a and a low voltage DC terminal 31b. The high-voltage DC terminal 31a and the low-voltage DC terminal 31b are connected to both ends of the capacitor 24, respectively. The 2nd power converter 30 has a terminal which supplies alternating current power, and one end of inductor 51 is connected to one of them. One end of the inductor 52 is connected to the other terminal.

The second power converter 30 is a converter device that converts AC power into DC and supplies it to the capacitor 24 of the DC link. The second power converter 30 operates as an active smoothing filter and supplies active power to the first power converter 20 via the capacitor 24.

The second power converter 30 may be an inverter device having the same circuit configuration as that of the first power converter 20. Similar to the first power converter 20, the second power converter 30 includes six self-extinguishing switching elements. The switching elements are connected in series as a high side switch and a low side switch. Three legs having arms connected in series are connected in parallel to form an inverter circuit. The inverter circuit of the second power converter 30 is not limited to this configuration as long as it can mutually convert a DC voltage and an AC voltage having a frequency higher than the frequency of the power system. In this example, the configuration of the inverter circuit of the second power converter 30 is the same as the configuration of the inverter circuit of the first power converter 20, but may be a different configuration.

In the voltage compensator 1 of the present embodiment, the second power converter 30 may have another configuration as long as it can supply a DC voltage and active power to the first power converter 20.

The primary winding 41p of the parallel transformer 41 is connected between the u-phase and v-phase lines on the downstream side 7a to 7c of the series transformer. The primary winding 42p of the parallel transformer 42 is connected between the v-phase and w-phase lines on the downstream sides 7a to 7c of the

series transformers

11, 13, and 15. One of the secondary windings 41 s of the parallel transformer 41 is connected to the other end of the inductor 51, and the other is connected to a terminal of the second power converter 30. The secondary winding 42 s of the parallel transformer 42 is connected to the other end of the inductor 52, and the other is connected to a terminal of the second power converter 30. The

secondary windings

41 s and 42 s of the

parallel transformers

41 and 42 are V-connected to the terminals of the second power converter 30 via the

inductors

51 and 52.

The current detector 61 is connected in series between the AC terminal of the second power converter 30 and the secondary winding 41 s of the parallel transformer 41. The current detector 62 is connected in series between the other AC terminal of the second power converter 30 and the secondary winding 42 s of the parallel transformer 42. That is, the

current detectors

61 and 62 detect the respective alternating currents flowing through the

inductors

51 and 52, and output current data IL1 and IL2.

AC voltage detectors

63 and 64 are connected to upstream sides 6a to 6c of

series transformers

11, 13, and 15. The AC voltage detector 63 is connected between the U-phase and V-phase lines, and detects the line voltage between UV. The AC voltage detector 64 is connected between the lines of the V phase and the W phase, and detects the line voltage between the VWs. The

AC voltage detectors

63 and 64 include, for example, an instrument transformer and a transducer that converts the output of the instrument transformer to an appropriate voltage level. The

AC voltage detectors

63 and 64 detect the line voltages on the upstream sides 6a to 6c, step down the voltage with an instrument transformer, and generate AC voltage data VAC1 and VAC2 that are signals that can be input to the control unit 80 by the transducer. Convert and output.

The DC voltage detector 65 detects the DC voltage across the capacitor 24, outputs DC voltage data VDC, and supplies it to the control unit 80.

The controller 80 receives the AC voltage data VAC1, VAC2, the current data IL1, IL2, and the DC voltage data VDC, generates gate signals (control signals) Vg1, Vg2 based on these, and generates the first power converter 20 and The switching element of the second power converter 30 is driven.

The control unit 80 includes a first control circuit 81 and a second control circuit 82. The first control circuit 81 supplies a gate signal Vg <b> 1 for controlling the operation of the first power converter 20 to the first power converter 20. The second control circuit 82 supplies a gate drive signal Vg <b> 2 for controlling the operation of the second power converter 30 to the second power converter 30.

The first control circuit 81 includes an arithmetic unit 91 that calculates a compensation value Vc * of the series voltage, an operation determination circuit 92, and a gate signal generation circuit 93.

The value calculator (first calculator) 91 detects the respective phase voltages on the upstream sides 6a to 6c based on the AC voltage data VAC1 and VAC2. The calculator 91 outputs a command value Vc * for series voltage compensation generated based on the deviation between each phase voltage and the target value VL of the load voltage. The command value Vc * is a command value corresponding to the compensation voltage of each phase.

The output of the calculator 91 is connected to the gate signal generation circuit 93. The gate signal generation circuit 93 generates the gate signal Vg1 of the switching element based on the command value Vc * output from the calculator 91.

The operation determination circuit (determination circuit) 92 is connected to the output of the arithmetic unit 91. The operation determination circuit 92 receives the minimum compensation voltage value Vc (min). The minimum compensation voltage value Vc (min) is set in advance according to the allowable voltage range of the upstream sides 6a to 6c. For example, the minimum compensation voltage value Vc (min) is set to 1% or the like with respect to the target value VL. When the target value VL is 6600V, the minimum compensation voltage value Vc (min) is 66V. The output of the operation determination circuit 92 is connected to the gate signal generation circuit 93.

The operation determination circuit 92 supplies the gate block signal GB to the gate signal generation circuit 93 so as to stop the gate signal Vg1 when the magnitude of the command value Vc * is smaller than the minimum compensation voltage value Vc (min). . For example, when the gate block signal GB is at a high level, the gate signal generation circuit 93 stops outputting. Therefore, the first power converter 20 stops the switching operation.

The operation determination circuit 92 supplies the gate block signal GB to the gate signal generation circuit 93 so that the gate signal Vg1 is continuously output when the magnitude of the command value Vc * is equal to or greater than the minimum compensation voltage value Vc (min). To do. For example, when the gate block signal GB is at a low level, the gate signal generation circuit 93 outputs the gate signal Vg1 corresponding to the command value Vc *, and the first power converter 20 performs a switching operation.

FIG. 2A and FIG. 2B are block diagrams illustrating a part of the voltage compensator of this embodiment.
2A and 2B show specific configuration examples of the operation determination circuit 92 of the first control circuit 81. FIG.
As shown in FIG. 2A, the operation determination circuit 92 includes determination units 92a to 92c and an AND circuit 92d. The determination units 92a to 92c receive the command values Vc1 * to Vc3 * of the respective phases of the calculator 91. The determination units 92a to 92c receive the minimum compensation voltage value Vc (min). The outputs of the determination units 92a to 92c are input to the AND circuit 92d. The AND circuit 92 d supplies the gate block signal GB to the gate signal generation circuit 93.

As shown in FIG. 2B, the determination units 92a to 92c have the same configuration. Hereinafter, one determination unit 92a will be described.

The determination unit 92a includes an arithmetic unit 101 that calculates an absolute value,

comparators

102 and 103, a coefficient unit 104, and an RS flip-flop 105.

The computing unit 101 is connected to the output of the computing unit 91. The arithmetic unit 101 receives the command value Vc * 1 output from the arithmetic unit 91, calculates the absolute value | Vc1 * |, and outputs it.

The output of the computing unit 101 is connected to one input of the

comparators

102 and 103, respectively. The minimum compensation voltage value Vc (min) is input to the other input of the comparator 102. The comparator 102 compares the absolute value | Vc1 * | of the command value Vc1 * with the minimum compensation voltage value Vc (min). When the absolute value | Vc1 * | is smaller than the minimum compensation voltage value Vc (min), the comparator 102 outputs a high-level signal (for example, a logical value “1”). When the absolute value | Vc1 * | is equal to or greater than the minimum compensation voltage value Vc (min), the comparator 102 outputs a low-level signal (for example, a logical value “0”).

The minimum compensation voltage value Vc (min) is input to the other input of the comparator 103 via the coefficient unit 104. The coefficient unit 104 multiplies the amplitude of the input signal by a preset coefficient value and outputs the result. The coefficient k of the coefficient unit 104 is a positive number larger than 1. The coefficient k is, for example, 1.2. The minimum compensation voltage value Vc (min) is multiplied by, for example, 1.2 and input to the comparator 103.

The comparator 103 compares the absolute value | Vc1 * | with the output k × Vc (min) of the coefficient unit 104. The comparator 103 outputs a high level signal when the absolute value | Vc1 * | is equal to or greater than k × Vc (min). The comparator 103 outputs a low-level signal when the absolute value | Vc1 * | is smaller than k × Vc (min).

In the RS flip-flop 105, when the reset input R is at a low level and the set input S is inverted to a high level, the output signal GB1 transitions to a high level.

In the RS flip-flop 105, when the reset input R is inverted to a high level when the set input S is at a low level, the output signal GB1 transitions to a low level.

That is, when the absolute value | Vc1 * | decreases, when the comparator 102 detects that the absolute value | Vc1 * | is smaller than the minimum compensation voltage value Vc (min), the operation determination circuit 92 outputs a high level signal GB1.

When the absolute value | Vc1 * | increases, when the comparator 103 detects that the absolute value | Vc1 * | is equal to or greater than k × Vc (min), the operation determination circuit 92 outputs the signal GB1. Invert to low level.

The coefficient unit 104 is provided for setting hysteresis to the threshold value. When the absolute value | Vc1 * | becomes close to the minimum compensation voltage value Vc (min) by providing hysteresis to the minimum compensation voltage value Vc (min), which is the threshold value, the outputs of the

comparators

102 and 103 It is possible to prevent the operation determination circuit 92 from malfunctioning due to oscillation.

Other determination units

92b and 92c operate in the same manner. Signals GB1 to GB3 output from determination units 92a to 92c are input to AND circuit 92d. The AND circuit 92d supplies a high level signal to the gate signal generation circuit 93 as the gate block signal GB when all the signals GB1 to GB3 are at the high level. The gate signal generation circuit 93 stops the switching operation of the switching element by the high level gate block signal GB.

When at least one of the signals GB1 to GB3 output from the determination units 92a to 92c becomes low level, the low level gate block signal GB is supplied to the gate signal generation circuit 93. The gate signal generation circuit 93 generates a gate signal according to the command values Vc1 * to Vc3 * without being affected by the low-level gate block signal GB, and supplies it to the switching element.

The configuration of the operation determination circuit 92 is not limited to the above. In the above description, the description is mainly based on the positive logic, but the operation determination circuit 92 may be configured with negative logic. Further, the operation determination circuit 92 may be constituted by other logic circuits.

Returning to FIG. 1, the description will be continued.
The second control circuit 82 includes a controller 95 for DC voltage control, a controller 96 for AC current control, and a gate signal generation circuit 97. The second control circuit 82 receives current data IL1 and IL2 from the

current detectors

61 and 62 and DC voltage data VDC from the DC voltage detector 65. The second control circuit 82 generates a gate signal Vg2 based on the current data IL1 and IL2 and the DC voltage data VDC and supplies it to the second power converter 30.

The controller 95 generates an active current command value based on the input DC voltage data VDC and the DC voltage command value set internally.

The controller 96 calculates the effective current that the second power converter 30 supplies to the first power converter 20 via the capacitor 24 based on the current data IL1 and IL2 and the effective current command value, and the command value for that purpose. Is generated.

The gate signal generation circuit 97 generates the gate signal Vg2 based on the active current command value supplied from the controller 96.

The operation of the voltage compensator 1 of this embodiment will be described.
FIG. 3A to FIG. 3C are schematic diagrams for explaining the operation of the voltage compensator according to the first embodiment.
FIG. 3A shows a simplified configuration of the voltage compensator 1 of the present embodiment. As shown to Fig.3 (a), the voltage compensation apparatus 1 is inserted in series in an electric power system (three-phase power distribution system). The voltage compensator 1 detects the upstream voltage (the installation point voltage Vs of the voltage compensator 1) and compensates so that the downstream voltage (load voltage) becomes the target value VL.

The first power converter 20 receives a supply of active power from the second power converter 30 connected via the capacitor 24 and performs a compensation operation. The second power converter 30 operates by inputting AC power from the three-phase power distribution system via the

parallel transformers

41 and 42.

FIG. 3B shows the change over time of the voltage Vs at the installation point of the voltage compensator 1 of FIG. 3A together with the target value VL.

As shown in FIG. 3B, in the voltage compensator 1 of this embodiment, the voltage Vs at the installation point has a range. This range is set by the minimum compensation voltage value Vc (min). A range of Vc (min) is provided in the positive direction and a range of −Vc (min) is provided in the negative direction with respect to the voltage Vs at the installation point detected by the voltage compensator 1. ± Vc (min) (= | Vc (min) | represents the range in which the variation of the voltage Vs at the installation point is allowed. The target value VL is within the allowable range of the voltage Vs at the installation point that changes over time. In some cases, the voltage compensator 1 does not perform the compensation operation, and during the period when the compensation operation is not performed, the first power converter 20 of the voltage compensator 1 stops the switching operation, and thus accompanies the switching operation. Loss can be reduced.

The voltage compensation device 1 performs a compensation operation when the target value VL exceeds the allowable range of fluctuation of the installation point voltage Vs.

More specifically, during the period from time t0 to t1, the target value VL is within the allowable range of the installation point voltage Vs. Therefore, the voltage compensator 1 stops operating.

During the period from time t1 to t2, the target value VL is higher than the allowable range of the installation point voltage Vs. Therefore, the voltage compensation device 1 performs a compensation operation for outputting a positive compensation voltage so that the load voltage becomes equal to the target value VL.

During the period from time t2 to t3, the target value VL is within the allowable range of the installation point voltage Vs. Therefore, the voltage compensator 1 stops operating.

During the period from time t3 to t4, the target value VL exceeds the allowable range of the installation point voltage Vs. Therefore, the voltage compensation device 1 performs a compensation operation for outputting a negative compensation voltage so that the load voltage becomes equal to the target value VL.

Whether or not the power system voltage compensation operation is to be performed is determined by the control unit 80. The calculator 91 of the first control circuit 81 generates a command value Vc * based on the deviation between the installation point voltage Vs and the target value VL. Command value Vc * corresponds to the compensation voltage output by first power converter 20.

The operation determination circuit 92 determines whether or not the compensation voltage is within a range of ± Vc (min). More specifically, the operation determination circuit 92 compares the absolute value | Vc * | of the command value Vc * corresponding to the compensation voltage with the minimum compensation voltage value Vc (min). When the absolute value | Vc * | is lower than the minimum compensation voltage value Vc (min), the operation determination circuit 92 stops the gate signal Vg1 by the gate block signal GB. Therefore, the first power converter 20 can stop the switching operation. Therefore, the voltage compensation apparatus 1 can reduce the loss accompanying the switching operation of the first power converter 20, and can improve the efficiency over the entire operation period.

FIG. 3C shows an operation when the first control circuit 81 does not have the operation determination circuit 92.
As shown in FIG. 3C, when the operation determination circuit 92 is not provided, the voltage compensator calculates the difference between the installation point voltage Vs and the target value VL when the installation point voltage Vs does not match the target value VL. Output compensation voltage to compensate for the difference. In the example of this figure, since the voltage Vs at the installation point does not coincide with the target value VL except for times t11, t12, and t13, a compensation voltage is output. As apparent from the comparison with the case of FIG. 3B, the voltage compensator in the case of FIG. 3C performs the compensation operation over almost all periods. Therefore, the first power converter 20 performs a switching operation over almost all the period, and a loss due to the switching operation occurs.

The effect of the voltage compensator of this embodiment will be described.
As described in the above description of the operation, the voltage compensation device 1 of the present embodiment includes the operation determination circuit 92. Therefore, the target value VL is within the voltage range of the installation point (minimum compensation voltage value Vc (min)). ), The compensation operation can be stopped.

Since the voltage compensator 1 according to the present embodiment includes the first power converter 20 that performs a high-frequency switching operation, the voltage of the power system can be compensated at high speed almost continuously. On the other hand, when the first power converter 20 performs a high-frequency switching operation, a switching loss or a conduction loss occurs in the switching element or the like. In particular, since the switching loss occurs depending on the switching frequency of the switching element, a certain loss occurs even when the value of the passing power is small.

In power systems where various loads and various reverse power flow devices are interconnected, it has become difficult to maintain the voltage value at the target value. The demand to do is strong. On the other hand, if the voltage compensator is inserted into the system, it is difficult to finely stabilize the system by introducing a large number of voltage compensators so as to affect the power transmission efficiency.

According to the voltage compensator of the present embodiment, if the voltage fluctuation range at the point where the voltage compensator is installed is within a predetermined range, the voltage compensator stops operating, and thus the loss caused by the voltage compensator. Hardly occurs. Therefore, a large number of voltage compensation devices can be introduced into the power system, which can contribute to the stabilization of the power system.

(Second Embodiment)
FIG. 4 is a block diagram illustrating a voltage compensator according to this embodiment.
As shown in FIG. 4, the voltage compensation device 1a of the present embodiment is partially different from that of the first embodiment in the configuration of the control unit 80a. The control unit 80a includes a first control circuit 81a. The first control circuit 81a includes a selection unit 94. Other points are the same as those of the first embodiment, and the same components are denoted by the same reference numerals and detailed description thereof is omitted as appropriate.

FIG. 5 is a block diagram illustrating a part of the voltage compensator of this embodiment.
FIG. 5 is a block diagram illustrating the first control circuit 81a of the voltage compensation device 1a.
As shown in FIG. 5, the first control circuit 81a includes a selection unit 94, and the selection unit 94 includes a high side selection unit 94H and a low side selection unit 94L.

The high side selector 94H is connected to the outputs for the switching elements 23a to 23c of the first power converter 20 among the outputs of the gate signal generation circuit 93. The output of the high side selector 94H is connected to the gate terminals of the switching elements 23a to 23c and supplies the gate signal Vg1H.

The output of the operation determination circuit 92 is connected to the high side selection unit 94H. The high side selection unit 94H inputs from the operation determination circuit 92 a signal HLT indicating that the absolute value | Vc * | is detected to be lower than the minimum compensation voltage value Vc (min). In that case, the high side selection unit 94H turns on the switching elements 23a to 23c on the high side of the first power converter 20.

The low side selection unit 94L is connected to the outputs for the switching elements 23d to 23f of the first power converter 20 among the outputs of the gate signal generation circuit 93. The output of the low side selector 94L is connected to the gate terminals of the switching elements 23d to 23f and supplies the gate signal Vg1L.

The output of the operation determination circuit 92 is connected to the low side selection unit 94L. The low-side selection unit 94L inputs a signal HLT indicating that the absolute value | Vc * | is lower than the minimum compensation voltage value Vc (min) from the operation determination circuit 92 via the NOT circuit 94N. In that case, the low side selector 94L turns off the switching elements 23d to 23e on the low side of the first power converter 20.

That is, when the target value VL is within the voltage range of the upstream side 6a to 6c, the high side selection unit 94H turns on the switching elements 23a to 23c, and at the same time, the low side selection unit 94L sets the switching elements 23d to 23d to 23f is turned off.

The operation of the voltage compensator 1a of this embodiment will be described.
In the voltage compensator 1a of the present embodiment, the operation determination circuit 92 compares the deviation (command value Vc *) between the target value VL and the upstream side voltages 6a to 6c with the minimum compensation voltage value Vc (min). To do. When the absolute value of the command value Vc * is smaller than the minimum compensation voltage value Vc (min), the operation determination circuit 92 operates the high side selection unit 94H and the low side selection unit 94L. The high side selection unit 94H turns on the switching elements 23a to 23c, and the low side selection unit 94L turns off the switching elements 23d to 23f.

When the switching operation of the first power converter 20 is stopped by the operation determination circuit 92, the current flowing through the power system is upstream through the

primary windings

11p, 13p, and 15p of the

series transformers

11, 13, and 15. Flow from the sides 6a to 6c to the downstream sides 7a to 7c (solid arrows). At this time, a current is induced in the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15. Since diodes are connected in antiparallel to the switching elements 23a to 23f of the first power converter 20, a current path is formed together with the

secondary windings

11s, 13s, and 15s. How the current flows is determined by the impedance of the wiring or the like, and depending on the path and magnitude of the flowing current, there is a possibility that a problem may occur in the components of the first power converter 20.

In the voltage compensation device 1a of the present embodiment, the switching element on the high side of the first power converter 20 is turned on and the switching element on the low side is turned off when the switching operation is stopped. Therefore, the path of the current flowing through the

secondary windings

11s, 13s, and 15s is determined as indicated by the broken-line arrows in FIG. Therefore, even when the operation of the voltage compensator 1a is stopped, it is possible to prevent a current that causes a problem in the components of the first power converter 20 from flowing, and to stably maintain the stopped state. .

(Third embodiment)
FIG. 6 is a block diagram illustrating a voltage compensator according to this embodiment.
In the voltage compensator of this embodiment, another induced current path that flows when the switching operation of the first power converter 20 is stopped is set.
As shown in FIG. 6, the voltage compensation device 1b of the present embodiment includes a voltage compensation unit 10b and a control unit 80b, which are different from those in the other embodiments described above. In the voltage compensation device 1b of the present embodiment, the other components are the same as those in the first embodiment described above, and the same components are denoted by the same reference numerals and detailed description thereof is omitted as appropriate. To do.

The voltage compensation unit 10b includes a bypass circuit 70. The bypass circuit 70 includes thyristor switches 71 and 72. The thyristor switches 71 and 72 each have two SCRs (Silicon Controlled Rectifiers), and the two SCRs are connected in antiparallel to each other. Therefore, the thyristor switches 71 and 72 can pass an alternating current. The thyristor switch 71 is connected between the terminal 12b of the secondary winding 11s and the secondary winding 13s terminal 14b. The thyristor switch 72 is connected between the terminal 14b of the secondary winding 13s and the terminal 16b of the secondary winding 15s.

The control unit 80b includes a first control circuit 81b. The first control circuit 81b outputs a bypass signal Vb1 that triggers the bypass circuit 70. The bypass signal Vb1 is supplied to the bypass circuit 70 and turns on the two

thyristor switches

71 and 72.

In the first control circuit 81b, the gate block signal GB output from the operation determination circuit 92 is supplied to the gate signal generation circuit 93 and also supplied to the bypass circuit 70 as the bypass signal Vb1.

In this example, the bypass signal Vb1 is generated and output with the same logic as the gate block signal GB. Therefore, the operation determination circuit 92 stops the switching operation of the first power converter 20 and outputs the bypass signal Vb1 at the same time when the target value VL is within the upstream voltage range, and the thyristor switches 71 and 72 are output. Turn on.

When the thyristor switches 71 and 72 are turned on, a path through which an induced current flows is formed as indicated by a broken arrow in FIG. Therefore, there is no possibility of causing a problem in the components of the first power converter 20 or the like due to the induced current to the secondary winding of the current flowing through the power system while the first power converter 20 is stopped.

The bypass circuit 70 can also be used to protect the first power converter 20 when a part of the power system is grounded and an abnormal current flows through the power system. In that case, the voltage compensator 10 b further includes

current detectors

66 and 67, and the controller 80 b has an abnormal current detection circuit 83.

The abnormal current detection circuit 83 compares the current data IL3 and IL4 supplied from the

current detectors

66 and 67 with a preset threshold value, and when the current data IL3 and IL4 exceed the threshold value, Outputs a bypass signal.

The control unit 80b has an OR circuit 111 for taking the logical sum of the output of the operation determination circuit 92 and the output of the abnormal current detection circuit 83 and outputting the bypass signal Vb1.

The effect of the voltage compensator 1b of this embodiment will be described.
In the voltage compensation device 1b of the present embodiment, the voltage compensation unit 10b has a bypass circuit 70, and the control unit 80b outputs a bypass signal Vb1 that triggers the bypass circuit 70. Therefore, even if the first power converter 20 stops the switching operation by the gate block signal GB, the induced current flowing in the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15 is bypass circuit 70. Can be shed. Therefore, the voltage compensation device 1b can operate safely over all periods during the switching operation and the stop of the first power converter 20.

Further, since the bypass circuit 70 can also be used for protection when an abnormal current occurs due to a power system accident or the like, the voltage compensator 1b can operate more safely.

(Fourth embodiment)
FIG. 7 is a block diagram illustrating a voltage compensator according to this embodiment.
In the voltage compensator of this embodiment, the third embodiment further includes a second bypass circuit 120, and the control unit 80c outputs a signal for controlling the second bypass circuit 120. The voltage compensation device of this embodiment is otherwise the same as that of the third embodiment, and the same components are denoted by the same reference numerals and detailed description thereof is omitted as appropriate.

As shown in FIG. 7, the voltage compensation device 1c of the present embodiment includes a voltage compensation unit 10c and a control unit 80c.

The voltage compensation unit 10 c includes a second bypass circuit 120. The second bypass circuit 120 is connected between the

terminals

12b, 14b, 16b of the

secondary windings

11s, 13s, 15s and the capacitor 24.

The second bypass circuit 120 includes a diode bridge 121, a short-circuit switch 122, and a backflow prevention diode 123.

The diode bridge 121 includes diodes 122a to 122f. The diodes 122a to 122f are connected to flow current from the

terminals

12b, 14b, and 16b of the

secondary windings

11s, 13s, and 15s toward the high-voltage DC input terminal 21a of the first power converter 20. The diodes 122a to 122f are connected so that a current flows from the low-voltage DC input terminal 21b toward the

terminals

12b, 14b, and 16b.

The diodes 122a to 122f are, for example, semiconductor rectifier elements. The diode bridge 121 provides a path through which a current induced in the

secondary windings

11s, 13s, and 15s flows in the event of an accident such as a ground fault in the power system.

The short-circuit switch 122 is connected to both ends of the DC voltage output terminal of the diode bridge 121. A control terminal of the short-circuit switch 122 is connected to a terminal that outputs a gate block signal GB output from the first control circuit 81c. The short-circuit switch 122 is turned on when the gate block signal GB becomes high level to short-circuit both ends of the DC voltage output terminal of the diode bridge 121. The short-circuit switch 122 is, for example, an IGBT.

The backflow prevention diode 123 is connected in a direction in which a current for charging the capacitor 24 flows from the diode bridge 121. The backflow prevention diode 123 is provided so that current does not flow back from the capacitor 24 to the diode bridge 121 when the short-circuit switch 122 is turned on.

FIG. 8 is a block diagram illustrating a part of the voltage compensator of this embodiment.
As shown in FIG. 8, the first control circuit 81c outputs the gate block signal GB generated by the operation determination circuit 92 as a bypass signal Vb2. The bypass signal Vb2 is supplied to the control terminal of the short-circuit switch 122. A drive circuit may be provided so that the control terminal of the short-circuit switch 123 can be driven by the bypass signal Vb2.

In the voltage compensator 1c of this embodiment, when the operation determination circuit 92 detects that the target value VL is within the upstream voltage range, the gate block signal GB is supplied to the control terminal of the short-circuit switch 122. . The short-circuit switch 122 is turned on to form a path of current induced in the

secondary windings

11s, 13s, and 15s of the

series transformers

11, 13, and 15 (broken arrows in FIG. 7).

In the case of an accident such as a ground fault in the power system, the abnormal current is detected by the

current detectors

66 and 67, and the abnormal current detection circuit 83 generates the bypass signal Vb1. The bypass signal Vb1 turns on the thyristor switches 71 and 72 of the bypass circuit 70.

Here, since the SCR of the thyristor switches 71 and 72 has a turn-on time of several μs to several tens of μs, an abnormal current is induced in the

secondary windings

11 s, 13 s, and 15 s until the SCR is turned on. Therefore, the diode bridge 121 forms a path through which an abnormal current flows. At the time of detecting an abnormal current, the short-circuit switch 122 may be on or off.

In the voltage compensator 1c of the present embodiment, in the event of an accident such as a ground fault in the power system, the bypass path when the abnormal current is induced in the

secondary windings

11s, 13s, and 15s is divided into the two

bypass circuits

70 and 120. Formed by. Then, by using the

bypass circuits

70 and 120 provided in the event of an accident, a path for the induced current of the

secondary windings

11s, 13s, and 15s in which the first power converter 20 stops the switching operation is used. Can be formed.

(Fifth embodiment)
FIG. 9 is a block diagram illustrating a voltage compensator according to this embodiment.
As shown in FIG. 9, the voltage compensation device 1d of the present embodiment includes a voltage compensation unit 10d. The voltage compensator 1d includes the same components as those of the third embodiment, except for the configuration of the voltage compensator 10d. Omitted.

The voltage compensation unit 10d includes a bypass circuit 70d. The bypass circuit 70 d includes thyristor switches 71 and 72 and

electromagnetic contactors

73 and 74.

The electromagnetic contactor 73 is connected between the

terminals

12b and 14b. That is, the electromagnetic contactor 73 is connected in parallel with the thyristor switch 71. The magnetic contactor 74 is connected between the

terminals

14b and 16b. That is, the electromagnetic contactor 74 is connected in parallel with the thyristor switch 72.

The

electromagnetic contactors

73 and 74 are turned on by a drive signal supplied from a drive circuit (not shown) that receives the bypass signal Vb1 and generates a conduction signal.

The

electromagnetic contactors

73 and 74 have a longer delay time until they are turned on than the thyristor switches 71 and 72, but the DC resistance value when turned on is lower than the resistance value when the thyristor switches 71 and 72 are turned on. Therefore, the

magnetic contactors

73 and 74 can pass a larger current than the thyristor switches 71 and 72 over a long period of time. The

magnetic contactors

73 and 74 bypass the current flowing through the thyristor switches 71 and 72 after being turned on behind the thyristor switches 71 and 72.

In the voltage compensator that generates the gate block signal GB by the operation determination circuit 92 and selectively stops the switching operation of the first power converter 20, the stop period of the first power converter 20 is long and the entire operation is performed. It can also be assumed that it occupies most of the period. In order to minimize loss due to the current flowing in the path of the current induced in the secondary winding while the first power converter 20 is stopped, including such a case, the switch elements forming the path include It is preferable to use one having a small conduction loss.

In the voltage compensator 1d of the present embodiment, since the

electromagnetic contactors

73 and 74 are arranged in the path of the induced current when the first power converter 20 is stopped, the voltage compensator 1d is inserted into the power system. This makes it possible to further reduce the loss that occurs, and to realize a highly efficient power transmission / distribution system.

In the case of the above-described embodiment, the bypass circuit 120 in the case of the fourth embodiment may be combined. Further, the bypass circuit may be realized by an electromagnetic contactor by removing the thyristor switch, and a second bypass circuit by a diode bridge may be added thereto.

In each embodiment and each modification described above, the

control units

80, 80a, 80b, and 80c may include devices that sequentially execute programs such as a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit). Each part, each arithmetic unit, etc. which comprise

control part

80, 80a, 80b, 80c may be implement | achieved by performing the 1 or several step which comprises a program.

According to the embodiment described above, it is possible to realize a high-efficiency voltage compensator with little operation loss over the entire operation period.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

Claims

A power converter for supplying a compensation voltage for compensating a phase voltage of the power system to a transformer connected in series to each phase of the power system;
A control unit that outputs a control signal for controlling the power converter based on the phase voltage and a preset target voltage of the power system;
With
The controller is
A first computing unit that generates a command value for generating the compensation voltage based on the phase voltage and the target voltage;
When the deviation between the command value and the target voltage is compared with a preset minimum compensation voltage value and the deviation is smaller than the minimum compensation voltage value, at least a part of the control signal is obtained. A determination circuit that outputs a stop signal to stop;
A voltage compensation device including:
The power converter is
A high potential DC terminal to which a DC voltage is input;
A low potential DC terminal to which a DC voltage having a lower potential than the high potential DC terminal is input;
An upper arm connected between the high potential DC terminal and the low potential DC terminal;
A lower arm connected between the upper arm and the low potential DC terminal;
Including
The voltage compensator according to claim 1, wherein the determination circuit blocks conduction of the upper arm and the lower arm by the stop signal.
Further comprising a bypass circuit connected between the lines of each secondary winding of the transformer;
The voltage compensation device according to claim 2, wherein the operation determination circuit makes the bypass circuit conductive by the stop signal.
The bypass circuit includes a thyristor,
The voltage compensation device according to claim 3, wherein the thyristor is ignited by the stop signal.
The bypass circuit includes an electromagnetic contactor;
The voltage compensator according to claim 3, wherein the electromagnetic contactor is ignited by the stop signal.
The bypass circuit includes an electromagnetic contactor;
The voltage compensator according to claim 4, wherein the electromagnetic contactor is ignited by the stop signal.
A diode bridge connected between a first potential side and a second potential side lower than the potential on the first potential side;
A switch element connected in series between the first potential side and the second potential side;
Further comprising
The AC node of the diode bridge is
Connected to the connection node to which the AC terminal of the power converter and the secondary winding of the transformer are connected, respectively.
The voltage compensator according to claim 2, wherein the operation determination circuit makes the switch element conductive by the stop signal.
A diode bridge connected between a first potential side and a second potential side lower than the potential on the first potential side;
A switch element connected in series between the first potential side and the second potential side;
Further comprising
The AC node of the diode bridge is
Connected to the connection node to which the AC terminal of the power converter and the secondary winding of the transformer are connected, respectively.
The voltage compensator according to claim 3, wherein the operation determination circuit makes the switch element conductive by the stop signal.
A diode bridge connected between a first potential side and a second potential side lower than the potential on the first potential side;
A switch element connected in series between the first potential side and the second potential side;
Further comprising
The AC node of the diode bridge is
Connected to the connection node to which the AC terminal of the power converter and the secondary winding of the transformer are connected, respectively.
The voltage compensator according to claim 4, wherein the operation determination circuit makes the switch element conductive by the stop signal.
A diode bridge connected between a first potential side and a second potential side lower than the potential on the first potential side;
A switch element connected in series between the first potential side and the second potential side;
Further comprising
The AC node of the diode bridge is
Connected to the connection node to which the AC terminal of the power converter and the secondary winding of the transformer are connected, respectively.
The voltage compensator according to claim 5, wherein the operation determination circuit makes the switch element conductive by the stop signal.
A diode bridge connected between a first potential side and a second potential side lower than the potential on the first potential side;
A switch element connected in series between the first potential side and the second potential side;
Further comprising
The AC node of the diode bridge is
Connected to the connection node to which the AC terminal of the power converter and the secondary winding of the transformer are connected, respectively.
The voltage compensator according to claim 6, wherein the operation determination circuit makes the switch element conductive by the stop signal.
The power converter is
A high potential DC terminal to which a DC voltage is input;
A low potential DC terminal to which a DC voltage having a lower potential than the high potential DC terminal is input;
An upper arm connected between the high potential DC terminal and the low potential DC terminal;
A lower arm connected between the upper arm and the low potential DC terminal;
Including
The voltage compensator according to claim 1, wherein the determination circuit makes the upper arm conductive and interrupts the lower arm conductive by the stop signal.