JP6574742B2 - Voltage compensator - Google Patents

Description

  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, so that the received voltage may decrease due to the voltage drop at the end. In the electric power system, it is necessary to be able to use a voltage within a certain allowable range regardless of the distance from the substation.

Yuji Sasaki, Takahiko Yoshida, Nagataka Seki, Toshiyuki Watanabe, Yuji Saito, “TVRs enabling high-speed response and their verification tests”, IEEJ Transactions B, Vol. 123 (2003)

  The embodiment provides a voltage compensator that compensates a voltage of a power system to an appropriate value continuously at high speed.

The voltage compensator according to the embodiment is inserted in series in the power system to compensate for the voltage of the power system. The voltage compensator includes a first terminal, a second terminal, and a third terminal connected to one of the inserted power systems, and a fourth terminal, a fifth terminal, and a sixth terminal connected to the other of the power systems. A first transformer having a primary side connected in series between the first terminal and the fourth terminal; and a second transformer having a primary side connected in series between the second terminal and the fifth terminal. A transformer, a third transformer having a primary side connected in series between the third terminal and the sixth terminal, and a self-extinguishing type switching element, the frequency being higher than the frequency of the power system A first power converter including an output connected to a secondary side of each of the first transformer, the second transformer, and the third transformer, and the first terminal. The first voltage or the fourth terminal which is the voltage of the power system on the side of Comprising a second voltage is a voltage of the electric power system in the side, and the target voltage is a voltage which is a target, based on, and a control unit for generating a driving signal for driving the switching element. The control unit inputs one of the first voltage and the second voltage according to a selection signal, and converts the one voltage into rotational coordinates in synchronization with the phase of the one voltage. A first coordinate converter that outputs a first component and a second component orthogonal to the first component, and a first value of the first component and a target value of the first component set according to the target voltage A second coordinate conversion unit that inputs a deviation and a second deviation between the second component and the target value of the second component and reversely converts the rotation coordinate in synchronization with the phase of the one voltage; Including. The control unit generates the selection signal based on the first deviation and the second deviation .

1 is a block diagram illustrating a voltage compensation device according to a first embodiment. It is a block diagram which illustrates a part of voltage compensating device of a 1st embodiment. It is a block diagram which illustrates a part of voltage compensating device of a 1st embodiment. It is a block diagram which illustrates the voltage compensating device concerning a comparative example. It is a block diagram which illustrates the voltage compensating device concerning the modification of a 1st embodiment. It is a block diagram which illustrates a part of voltage compensating device concerning a 2nd embodiment. FIG. 7A to FIG. 7D are conceptual diagrams for explaining an operation example of the voltage compensator of the second embodiment. FIG. 8A and FIG. 8B are conceptual diagrams for explaining an operation example of the voltage compensator of the second embodiment. FIG. 9A to FIG. 9D are conceptual diagrams for explaining an operation example of the voltage compensator of the second embodiment. It is a block diagram which illustrates some voltage compensation apparatuses of a 3rd embodiment. It is a block diagram which illustrates a part of voltage compensation apparatus of 4th Embodiment. FIG. 12A and FIG. 12B are conceptual diagrams for explaining the operation of the voltage compensator of the fourth embodiment. FIG. 13A and FIG. 13B are conceptual diagrams for explaining the operation of the voltage compensator of the fourth embodiment. It is a block diagram which illustrates the voltage compensating device concerning a 5th embodiment. It is a block diagram which illustrates some voltage compensation apparatuses of a 5th embodiment. It is a conceptual diagram for demonstrating operation | movement of the voltage compensation apparatus of 5th Embodiment. It is a block diagram which illustrates a part of voltage compensation apparatus of the modification of 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.
2 and 3 are block diagrams illustrating a control unit that is a part of the voltage compensator of 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 71 to 74, and a DC voltage detector 75. 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.

  Hereinafter, when viewed from the voltage compensator 1 connected in series to the power system, one side is referred to as a temporary power supply terminal 6 and the other side is referred to as a temporary load terminal 7. For convenience, the phases of the temporary power supply terminal 6 are referred to as the U phase, the V phase, and the W phase, and the phases of the temporary load terminal 7 are referred to as the u phase, the v phase, and the w phase. In the power system, the U phase and the u phase are the same phase, the V phase and the v phase are the same phase, and the W phase and the w phase are the same phase. In the temporary power supply terminal 6, the voltage compensation device 1 is connected to the U phase via the terminal 2a, connected to the V phase via the terminal 2b, and connected to the W phase via the terminal 2c. The voltage compensator 1 is connected to the u phase at the terminal 3a, connected to the v phase at the terminal 3b, and connected to the w phase at the terminal 3c at the temporary load end 7.

  In the present embodiment, after determining one of the temporary power supply terminal 6 and the temporary load terminal 7 in the direction of the substation, the voltage compensator 1 compensates the voltage of each phase. When the temporary power supply terminal 6 is in the substation direction, the voltage compensator 1 detects how high or low the voltage of the temporary power supply terminal 6 is relative to the target value or the target range. The voltage at the load end 7 is compensated so as to be within the target value or the target range. When the temporary load terminal 7 is in the substation direction, the voltage compensator 1 detects how high or low the voltage at the temporary load terminal 7 is relative to the target value or the target range. Compensation is performed so that the voltage at the power supply terminal 6 is within the target value or the target range.

  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 connected to each other through one terminal 12a, 14a, and 16a, and the other terminal 12b, 14b, and 16b are connected to the first power converter. It is connected to each AC terminal 22a, 22b, 22c of the vessel 20. That is, the secondary windings 11 s, 13 s, and 15 s of the series transformers 11, 13, and 15 are star-connected and connected to the output of the first power converter 20.

  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 switching elements such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The switching elements are connected in series as a high side switch and a low side switch. Three arms connected in series are connected in parallel to form an 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 includes inductors Lu, Lv, and Lw connected in series to each phase, and capacitors Ca, Cb, and Cc connected between the lines. The filter 26 is a low-pass filter that converts a high-frequency switching waveform of about several kHz to several hundred kHz output from the first power converter 20 into a 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. Note that the capacitor 24 may exchange reactive power with the power system side via the second power converter 30 as in other embodiments described later.

  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 second power converter 30 includes AC terminals 32a, 32b, and 32c. One end of the inductor 51 is connected to any one of the AC terminals 32a, 32b, and 32c, in this example, the AC terminal 32a. One end of the inductor 52 is connected to the other one of the AC terminals 32b and 32c, in this example, the AC terminal 32c.

  The second power converter 30 is a converter device that converts AC power input to the AC terminals 32a, 32b, and 32c into DC and supplies the DC power to the capacitor 24 of the DC link. More specifically, 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 33 a to 33 f. The switching elements 33a to 33f are connected in series as a high side switch and a low side switch. Three 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 41 p of the parallel transformer 41 is connected between the U-phase and V-phase lines at the temporary load end 7. The primary winding 42 p of the parallel transformer 42 is connected between the V-phase and W-phase lines at the temporary load end 7. 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 the AC terminal 32 b 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 the AC terminal 32 b of the second power converter 30. Secondary windings 41 s and 42 s of parallel transformers 41 and 42 are V-connected to AC terminals 32 a to 32 c of second power converter 30 through inductors 51 and 52.

  The current detector 61 is connected in series between the AC terminal 32 a 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 AC terminal 32 c 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.

  The AC voltage detectors 71 and 72 are connected to the temporary power supply terminal 6 side. The AC voltage detector 71 is connected between the U-phase and V-phase lines, and detects the line voltage between UV. The AC voltage detector 72 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 73 and 74 are connected to the temporary load end 7 side. The AC voltage detector 73 is connected between the u-phase and v-phase lines and detects the line voltage between uv. The AC voltage detector 74 is connected between the lines of the v phase and the w phase, and detects the line voltage between the vw. AC voltage detectors 71-74 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 71 to 74 are signals that can detect the line voltages of the temporary power supply terminal 6 and the temporary load terminal 7, step down the voltage with an instrument transformer, and can be input to the control unit 80 by a transducer. It converts into some AC voltage data VAC1-VAC4, and outputs.

  DC voltage detector 75 detects the DC voltage across capacitor 24 and outputs DC voltage data VDC.

  The controller 80 receives the AC voltage data VAC1 to VAC4, the current data IL1 and IL2, and the DC voltage data VDC, generates the gate drive signals Vg1 and Vg2 based on these, and generates the first power converter 20 and the second power. The switching element of the converter 30 is driven.

  As will be described in detail later, the control unit 80 inputs the substation direction signal Dss so that either the temporary power supply terminal 6 or the temporary load terminal 7 is connected to the actual substation.

  As shown in FIG. 2, the control unit 80 includes a first control circuit 81 and a second control circuit 82. The first control circuit 81 supplies the first power converter 20 with a gate drive signal Vg1 for controlling the operation of 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 three-phase voltage detection circuits 91 and 92, a switch 93, an abc-dq conversion circuit 94, a PLL 95, adders / subtractors 96 and 97, a dq-abc conversion circuit 98, and a gate signal generation. Circuit 99.

  The first control circuit 81 inputs the alternating voltage data VAC1 and VAC2 of the temporary power supply terminal 6 or the alternating voltage data VAC3 and VAC4 of the temporary load terminal 7 by inputting the substation direction signal Dss. Select. In the present embodiment, it is assumed that either the temporary power supply terminal 6 or the temporary load terminal 7 side is known in advance to be in the substation direction.

  The first control circuit 81 generates a compensation voltage command corresponding to the compensation voltage for each phase based on the selected AC voltage data VAC1, VAC2 or AC voltage data VAC3, VAC4, and based on the generated compensation voltage command. The gate drive signal Vg1 is generated. The generated gate drive signal Vg1 drives the switching elements 23a to 23f of the first power converter 20.

  The three-phase voltage detection circuit 91 receives the AC voltage data VAC1 and VAC2 of the temporary power supply terminal 6 and detects each phase voltage of the power system. The output of the three-phase voltage detection circuit 91 is supplied to the abc-dq conversion circuit 94.

  The three-phase voltage detection circuit 92 receives the AC voltage data VAC3 and VAC4 of the temporary load terminal 7 and detects each phase voltage of the power system. The output of the three-phase voltage detection circuit 91 is supplied to the abc-dq conversion circuit 94.

  The switch 93 selects one of the three-phase voltage detection circuits 91 and 92 based on the substation direction signal Dss. One of the selected voltages is the system voltage supplied from the substation. This voltage is also referred to as a substation connection end system voltage Vsst. The substation connection end system voltage Vsst is input to the abc-dq conversion circuit 94. For example, when the substation direction signal Dss has a logical value “1”, the three-phase voltage detection circuit 91 connects the system voltage Vsst at the substation connection end to the abc-dq conversion circuit 94. When the substation direction signal Dss has a logical value “0”, the three-phase voltage detection circuit 92 connects the system voltage Vsst at the substation connection end to the abc-dq conversion circuit 94.

  The abc-dq conversion circuit 94 inputs three-phase AC phase voltages and converts the rotational coordinates. The abc-dq conversion circuit 94 is a dq conversion circuit including Clark conversion and Park conversion, and converts each phase voltage into dq according to Expression (1). In Expression (1), ω is an angular frequency of the substation connection end system voltage Vsst, and is, for example, 2π × 50 [rad / s] or 2π × 60 [rad / s].

  The abc-dq conversion circuit 94 outputs a system voltage d-axis component d1 and a system voltage q-axis component q1. These components d1 and q1 are vector quantities orthogonal to each other.

  The output system voltage d-axis component d1 is input to the adder / subtractor 96 together with the load voltage d-axis target value d1 *. The adder / subtractor 96 outputs the deviation Δd1 (= d1 * −d1) and inputs it to the dq-abc conversion circuit 98.

  The output system voltage q-axis component q1 is input to the adder / subtractor 97 together with the load voltage q-axis target value q1 *. The adder / subtractor 97 outputs the deviation Δq 1 (= q 1 * −q 1) and inputs it to the dq-abc conversion circuit 98.

  In the present embodiment, the “system voltage” d-axis component and the “system voltage” q-axis component are generated based on AC voltage data connected in the substation direction. The “load voltage” d-axis target value and the “load voltage” q-axis target value are set based on the range of the target voltage output to the actual load end.

  These deviations Δd1 and Δq1 correspond to compensation voltages for the respective phase voltages, and are hereinafter referred to as compensation amounts Δd1 and Δq1.

  The dq-abc conversion circuit 98 is an inverse dq conversion circuit including an inverse park conversion and an inverse Clark conversion. Each of the dq-abc conversion circuit 98 receives the d-axis compensation amount Δd1 and the q-axis compensation amount Δq1 according to Equation (2), Generates and outputs a voltage compensation voltage command.

  The compensation voltage command for each phase output from the dq-abc conversion circuit 98 is supplied to the gate signal generation circuit 99. The gate signal generation circuit 99 includes a PWM circuit and the like, and generates the gate drive signal Vg1 based on the compensation voltage command for each phase.

  As shown in FIG. 3, the PLL 95 includes an adder / subtractor 95a, a PI compensator 95b, an adder 95c, and an integrator 95d. The adder / subtractor 95a inputs the reference voltage value 0 and the voltage value Vq1 of the system voltage q-axis component q1, and outputs these deviations. The deviation is outputted by the PI compensator 95b after proportional-integral calculation so that the deviation becomes zero. The output of the PI compensator 95b is added to the power supply angular frequency ω0 by the adder 95c, and then output as angle (phase) data θ by the integrator 95d. Here, the power supply angular frequency ω0 is the angular frequency of the voltage in the true substation direction selected by the substation direction signal Dss.

  The PLL 95 generates and outputs phase θ data as a synchronization signal so that the magnitude of the system voltage q-axis component q1 becomes zero. The output of the PLL 95 is supplied to an abc-dq conversion circuit 94 and a dq-abc conversion circuit 98. The abc-dq conversion circuit 94 and the dq-abc conversion circuit 98 are operated by the PLL 95 in synchronization with the phase θ of the system voltage Vsst at the substation connection end. The PLL 95 can output data on the angular velocity ω based on the phase θ that is a synchronization signal.

  The voltage compensation direction determination circuit 105 receives the substation direction signal Dss. The voltage compensation direction determination circuit 105 outputs a signal for switching the polarity of the voltage to be compensated according to the actual substation direction. For example, when the substation direction signal Dss is a logical value “1”, “1” is output. When the substation direction signal Dss is a logical value “0”, “−1” is output.

  The output of the voltage compensation direction determination circuit 105 is connected to the multiplier 106. Multiplier 106 inputs a compensation voltage command corresponding to each phase. For example, the multiplier 106 multiplies the compensation voltage command for each phase by “1” and outputs it. When the polarity of the compensation voltage command is reversed according to the actual substation direction, it is multiplied by “−1” and output. The multiplier 106 supplies a voltage compensation command including the polarity of each phase to the gate signal generation circuit 99.

  Second control circuit 82 includes an alternating current control circuit 100, for example. AC current control circuit 100 generates an effective current command value based on, for example, the difference between DC voltage data VDC and a preset DC voltage command value VDC * and current data IL1 and IL2. The alternating current control circuit 100 controls the alternating current of the second power converter 30 according to the generated effective current command value, and generates a command value for operating the power flowing into the capacitor 24. The gate signal generation circuit 101 generates a gate drive signal Vg2 according to the generated command value.

The operation of the voltage compensator 1 of this embodiment will be described.
In the voltage compensator 1 of this embodiment, one of the temporary power supply terminal 6 and the temporary load terminal 7 is set in the substation direction. Since the substation that supplies power behaves as a voltage source with low impedance, when viewed from the voltage compensator 1, the impedance on the substation side is sufficiently lower than the impedance on the load side. The voltage compensator 1 compensates the voltage on the load side with reference to the voltage on the substation side.

  In this embodiment, since the substation direction is known in advance, the substation direction signal Dss is supplied in accordance with the direction. For example, when the temporary power supply terminal 6 is in the substation direction, the substation direction signal Dss is set to the logical value “1”, and the output of the three-phase voltage detection circuit 91 is selected by the switch 93. The voltage compensator 1 compensates the voltage at the temporary load end 7 using the AC voltage data VAC1 and VAC2.

  When the voltage at the temporary power supply terminal 6 is lower than a target value or a target voltage range (hereinafter referred to as a target value), the voltage compensator 1 determines that the voltage at the temporary load terminal 7 is the target value or the like. Thus, the compensation voltage is added to the voltage of the temporary power supply terminal 6 through the series transformer. In the voltage compensation device 1 of the present embodiment, the first power converter 20 adds a compensation voltage to each phase voltage of the power system via the series transformers 11, 13, and 15.

  When the voltage of the temporary power supply terminal 6 is higher than the target value or the like, the voltage compensation device 1 uses the series transformer so that the voltage of the temporary load terminal 7 becomes the target value or the like. The compensation voltage is subtracted from the voltage at the power supply terminal 6. Subtracting the compensation voltage means adding a compensation voltage having a phase that is 180 ° different from the voltage of the temporary power supply terminal 6. In addition, the set value of the above-mentioned substation direction signal Dss is an example. Different logical values may be assigned, and of course, analog values may be set instead of logical values.

  When the temporary load terminal 7 is in the substation direction, the substation direction signal Dss is set to a logical value “0”, and the output of the three-phase voltage detection circuit 92 is selected by the switch 93. The voltage compensator 1 compensates the voltage of the temporary power supply terminal 6 using the AC voltage data VAC3 and VAC4 detected by the AC voltage detectors 73 and 74.

  When the voltage at the temporary load terminal 7 is lower than the target value or the like, the voltage compensation device 1 causes the temporary load terminal to pass through the series transformer so that the voltage at the temporary power supply terminal 6 becomes the target value or the like. 7 is added to the compensation voltage.

  When the voltage at the temporary load terminal 7 is higher than the target value or the like, the voltage compensation device 1 causes the temporary load via the series transformer so that the voltage at the temporary power supply terminal 6 becomes the target value or the like. A compensation voltage that is 180 ° out of phase with the voltage at the temporary load end 7 is added to the voltage at the end 7.

The generation of the compensation voltage will be described in more detail.
The voltage in the substation direction output from one of the three-phase voltage detection circuits 91 and 92 is input to the abc-dq conversion circuit 94. The abc-dq conversion circuit 94 outputs a system voltage d-axis component d1 and a system voltage q-axis component q1.

  The system voltage d-axis component d1 is input to the adder / subtractor 96 together with the load voltage d-axis target value d1 *. The adder / subtractor 96 outputs a compensation amount Δd1 which is a deviation between the system voltage d-axis component d1 and the load voltage d-axis target value d1 *.

  The system voltage q-axis component q1 is input to the adder / subtractor 97 together with the load voltage q-axis target value q1 *. The adder / subtractor 97 outputs a compensation amount Δq1 that is a deviation between the system voltage q-axis component q1 and the load voltage q-axis target value q1 *.

  When the three-phase voltage is dq converted, the q-axis component is generated as a voltage component orthogonal to the d-axis component. In this embodiment, since the substation direction is known in advance, the system voltage q-axis target value q1 * may be zero. Since the abc-dq conversion circuit 94 and the dq-abc conversion circuit 98 operate synchronously so that q1 = 0 by the PLL 95, the output of the adder / subtractor 97 is also 0 when q1 * = 0. .

  In addition, by setting the system voltage q-axis target value q1 * to a value other than 0, in other embodiments described later, the substation direction is determined including the case where the voltage in the substation direction is at the target value or the like. be able to.

  The compensation amount Δd1 output from the adder / subtractor 96 represents the deviation of the voltage in the substation direction from the target value, and the first control circuit 81 generates a compensation voltage command based on the compensation amount Δd1, and sets the compensation amount Δd1 to the compensation amount Δd1. A gate drive signal Vg1 is generated so as to output a corresponding compensation voltage.

The effect of the voltage compensation apparatus 1 of this embodiment is demonstrated comparing with the voltage compensation apparatus 200 of a comparative example.
FIG. 4 is a block diagram illustrating a voltage compensation device of a comparative example.
As shown in FIG. 4, the voltage compensator 200 of the comparative example includes series transformers 211, 213, and 215, tap switching circuits 220 a and 220 b, parallel transformers 241 and 242, and AC voltage detectors 271 to 274. And a control unit 280.

  In the voltage compensator 200 of the comparative example, the primary windings of the series transformers 211, 213, and 215 are connected in series to each phase of the power system. One ends of the secondary windings of the series transformers 211, 213, and 215 are connected to each other. The other end of the secondary winding of the series transformer 211 is connected to one terminal of the tap switching circuit 220a. The other end of the secondary winding of the series transformer 213 is connected to the other terminal of the tap switching circuit 220a. The other end of the secondary winding of the series transformer 213 is also connected to one terminal of the tap switching circuit 220b. The other end of the secondary winding of the series transformer 215 is connected to the other terminal of the tap switching circuit 220b.

  The tap switching circuit 220a includes switch circuits 222a to 222f corresponding to the number of taps on the secondary side of the parallel transformer 241. The switch circuits 222a to 222f are bidirectional switch circuits in which thyristors are connected in antiparallel. The switch circuits 222a and 222d are connected in series. The switch circuits 222c and 222e are connected in series. The switch circuits 222c and 222f are connected in series. The secondary side of the parallel transformer 241 is connected to the connection node of the bidirectional switch circuit connected in series.

  The tap switching circuit 220b has the same circuit configuration as the tap switching circuit 220a. In the switch circuits 222g to 222m, bidirectional switch circuits in which thyristors are connected in antiparallel are connected in series, and the number of bidirectional switch circuits connected in series is connected to the secondary side of the parallel transformer 242. Yes.

  The primary winding of the parallel transformer 241 is connected between the downstream of the U phase (u phase) and the downstream of the V phase (v phase). The primary winding of the parallel transformer 242 is connected between the downstream of the V phase (v phase) and the downstream of the W phase (w phase). Each tap of each secondary winding of the parallel transformers 241 and 242 is connected to a series connection node of the bidirectional switch.

  The AC voltage detectors 271 to 274 are connected in the same manner as the AC voltage detectors 71 to 74 of the voltage compensator 1 of the present embodiment.

  Control unit 280 has an upper limit value and a lower limit value of the target voltage of the power system voltage. The detection result of the AC voltage detectors 271 to 274 is compared with the upper limit value and the lower limit value of the target voltage, and a signal for firing the gate of the thyristor is generated.

  The contactors 291 and 292 are connected to both ends of the tap switching circuits 220a and 220b. The contactors 291 and 292 operate to protect the tap switching circuits 220a and 220b when an accident such as a ground fault occurs in the power system.

  In the voltage compensator 200 of the comparative example, the secondary windings of the series transformers 211, 213, and 215 and the secondary windings of the parallel transformers 241 and 242 are connected by bidirectional switches 222a to 222m using thyristors. Yes. Control unit 280 compares the detection results of AC voltage detectors 271 to 274 with the upper limit value and lower limit value of the target voltage set in advance. Then, when the voltage of each phase is lower than the lower limit value of the target value, the control unit 280 is connected to the tap that outputs a higher voltage so that the voltage of the primary winding of the series transformer becomes higher. Control the direction switch.

  For example, when the voltage downstream of the U phase is low, control unit 280 generates a gate drive signal so as to turn on bidirectional switches 222c and 222d. The bidirectional switches 222c and 220d are connected to a tap that generates the highest voltage among the taps of the parallel transformer 241. When the voltage downstream of the U phase is high, control unit 280 generates a gate drive signal to turn on bidirectional switches 222a and 222f. The bidirectional switches 222a and 222f are connected to a tap that generates the highest voltage among the taps of the parallel transformer 241, and the voltage of the connected tap is applied in an opposite phase to the U-phase voltage.

  In such a voltage compensator 200 of the comparative example, assuming that the substation is connected to the U-phase, V-phase, and W-phase sides, the respective phase voltages of the downstream u-phase, v-phase, and w-phase are obtained. We are going to compensate. For this reason, when the connection of the substation is changed by switching the power transmission network or the like, the voltage compensation device 200 cannot perform the voltage compensation operation. When the connection direction of the substation is changed, in the voltage compensator of the comparative example, it is necessary to switch the upstream and downstream connections, and power transmission is interrupted for a long time.

  In the voltage compensator 200 of the comparative example, the voltage of the series transformers 211, 213, and 215 is compensated by switching the taps provided in the parallel transformers 241 and 242. Therefore, the set value of the compensation voltage is set to the number of taps. It depends on discrete values. In the voltage compensator 200 of the comparative example, since the compensation voltage is discrete, additional equipment such as a reactive power compensator is further provided downstream of the power system, which complicates the system and increases the cost.

  In the voltage compensator 200 of the comparative example, since the compensation voltage can be set only discretely, it is difficult to set the voltage for each phase and compensate the unbalanced voltage. Therefore, when an unbalanced load is connected downstream of the power system, the unbalanced load may also be affected upstream of the power system.

  In the bidirectional switch using the thyristor of the voltage compensator 200 of the comparative example, when switching the taps of the parallel transformers 241 and 242, a time corresponding to ½ period of the voltage of each phase of the power system is required. Therefore, the response time of the voltage compensation device 200 is limited by the cycle of the power system.

  In contrast to the voltage compensator 200 of the comparative example, the voltage compensator 1 of the present embodiment can set the substation direction appropriately and appropriately by inputting the substation direction signal Dss. Therefore, the voltage compensation device 1 can output an appropriate compensation voltage according to the switching of the power transmission network, not only when the voltage compensation device 1 is installed.

  In the first power converter 20, the detected voltage data and compensation amount are generated as substantially continuous data in the first control circuit 81. For example, since the values of the AC voltage data VAC1 to VAC4 are read by an analog-digital converter (AD converter), the accuracy of these data is increased to the extent determined by the resolution of the AD converter. Therefore, a compensation voltage having a substantially continuous value can be set. In the power system using the voltage compensator 1 of the present embodiment, an apparatus or system that increases the accuracy of the compensation voltage is not required, so that the entire system of the system can be simplified and costs can be reduced. .

  Further, as described above, in the voltage compensator 1 of the present embodiment, the compensation voltage can be set independently for each phase, so that the unbalanced voltage can also be compensated. Therefore, it is possible to effectively prevent the upstream unbalanced state from being exerted downstream.

  Furthermore, in the voltage compensation device 1 of the present embodiment, voltage compensation is performed by a power converter using a self-extinguishing type switching element, so that voltage compensation operation can be performed at high speed regardless of the period of the power system. .

  Conventionally, a device for compensating the voltage has been devised in a place where a decrease in the voltage of the power system is expected according to the distance from the substation. For example, the tap position is set to a high voltage in advance at the system end where the voltage drop of the pole transformer is expected. Further, a phase advance capacitor that supports a voltage by injecting a reactive power with respect to the system impedance is also used. However, these measures are based on the premise that each consumer consumes electric power, and there is a problem that the system voltage is unnecessarily increased when the electric power demand decreases at night.

  In order to cope with these problems, a TVR (Thyristor Voltage Regulator) like the voltage compensation device 200 of the comparative example has been proposed. As described above, the TVR has a function of varying the compensation voltage in accordance with the system voltage, so that it can cope with a power reduction during the daytime when power demand is large and can also cope with a voltage rise at nighttime. .

  However, TVR uses a thyristor to switch parallel transformer taps and manipulates the voltage applied to the series transformer to perform voltage compensation operation. Therefore, the response time is slow, and the compensation voltage depends on the transformer tap, so discontinuous voltage compensation. With the widespread use of household photovoltaic power generation, there is a situation where voltage abnormalities cannot be fully compensated for in recent power systems where reverse power flow has increased.

  In the voltage compensation device 1 of the present embodiment, not only continuous voltage compensation is possible, but also voltage compensation independent of each phase is enabled, so that the voltage compensation of the recently complicated power system can be performed at high speed. Can be done effectively.

(Modification of the first embodiment)
FIG. 5 is a block diagram illustrating a voltage compensator 1a according to this modification.
The secondary windings 11s, 13s, and 15s of the series transformers 11, 13, and 15 are star-connected. The secondary windings 11s, 13s, and 15s are not limited to the star connection, and may be a delta connection.
The voltage compensator 1a of the present modification is the same as the voltage compensator 1 of the first embodiment except for the connection of the secondary windings 11s, 13s, 15s of the series transformers 11, 13, 15 and Constituent elements are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 5, in the voltage compensator 1a of the present modification, the secondary winding 11s of the series transformer 11 of the voltage compensator 10a includes terminals 12a and 12b. The secondary winding 13s of the series transformer 13 includes terminals 14a and 14b. Secondary winding 15s of series transformer 15 includes terminals 16a and 16b. One terminal 12a, 14a, 16a of each secondary winding 11s, 13s, 15s is the start of winding, and the other terminal 12b, 14b, 16b is the end of winding. One terminal 12a is connected to the other terminal 14b, one terminal 14a is connected to the other terminal 16b, and one terminal 16a is connected to the other terminal 12b. 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. That is, the secondary windings 11 s, 13 s, and 15 s of the series transformers 11, 13, and 15 are delta-connected and connected to the AC terminals 22 a, 22 b, and 22 c of the first power converter 20 through the filter 26. Has been.

  The voltage compensator 1a of the present modification operates in the same manner as the voltage compensator 1 of the first embodiment.

The operation and effect of the voltage compensator 1a of this embodiment will be described.
When a star-connected series transformer is connected to the output of the first power converter 20, one terminal of the secondary winding is connected to the output of the first power converter 20, so that the wiring work is facilitated. There are advantages. On the other hand, in the star connection, the other terminals of the secondary winding are connected to each other as a neutral point, but the neutral point is not connected to the other, and voltage distortion occurs due to the nonlinearity of the transformer, etc. Sometimes, it is difficult to eliminate the voltage distortion phenomenon because the current cannot flow elsewhere.

  When a series transformer of delta connection is connected to the output of the first power converter 20, the connection work becomes complicated by connecting the secondary windings of each phase to each other, but in the secondary winding. A reflux current can flow. Therefore, the voltage compensation device 1a is less likely to cause voltage distortion and can link high-quality power to the power system.

  In the voltage compensator 1a of the present embodiment, since the secondary windings 11s, 13s, 15s of the series transformers 11, 13, 15 connected to the output of the first power converter 20 are delta-connected, voltage distortion High-quality power connection with less power is possible.

  The secondary windings 11 s, 13 s, and 15 s of the series transformers 11, 13, and 15 can employ either star connection or delta connection in other embodiments described below.

(Second Embodiment)
FIG. 6 is a block diagram illustrating a part of the voltage compensation apparatus of this embodiment.
FIG. 6 shows an example of a block diagram of the first control circuit 81b in the case of the present embodiment. In the case of the present embodiment, the voltage compensator detects the substation direction itself and generates a substation direction signal Dss indicating the detected substation direction. Then, the voltage compensator inputs the AC voltage data on the substation side by the substation direction signal Dss generated by itself, and compensates the voltage on the load side.

  The first control circuit 81b includes a substation direction signal generation circuit 110. The substation direction signal generation circuit 110 receives the compensation amounts Δd1 and Δq1, detects the substation direction based on these, and generates a substation direction signal Dss indicating the detected substation direction. One of the temporary power supply terminal 6 and the temporary load terminal 7 is selected by the generated substation direction signal Dss, and the voltage compensator determines the actual load based on the AC voltage data on the selected side. Compensate the voltage on the side.

  The substation direction signal generation circuit 110 includes a determination circuit 111 and an initial value setting unit 112. The discrimination circuit 111 is connected to the outputs of the adder / subtracters 96 and 97. The determination circuit 111 receives the compensation amounts Δd1 and Δq1 from the adders / subtractors 96 and 97, determines the substation direction based on these, and generates the substation direction signal Dss.

  The output of the initial value setting unit 112 is connected to the determination circuit 111. The initial value setting unit 112 is set with an initial value of the substation direction signal Dss. The initial value of the substation direction signal Dss sets the substation direction signal Dss when the voltage compensator is activated. For example, at the first startup, the initial value setting unit 112 sets the determination circuit 111 so as to generate the substation direction signal Dss for inputting the AC voltage data VAC1 and VAC2 of the temporary power supply terminal 6. The initial value of the initial value setting unit 112 can be arbitrarily set. Of course, the AC voltage data VAC3, VAC4 of the temporary load end 7 may be used at the first startup of the voltage compensator. The initial value setting unit 112 may be rewritten at an arbitrary time. For example, when the voltage compensator is started for the second time or later, the substation direction determined last time may be set as the initial value.

An operation for detecting the direction of the substation and compensating the voltage in the present embodiment will be described.
FIG. 7A to FIG. 9D are conceptual diagrams illustrating an operation example of the voltage compensator of this embodiment.
In the example described here, it is assumed that the temporary power supply terminal 6 is set in the substation direction by the initial value setting unit 112. That is, the determination circuit 111 outputs the substation direction signal Dss so that the three-phase voltage detected by the AC voltage data VAC1 and VAC2 of the temporary power supply terminal 6 is input to the abc-dq conversion circuit 94. When the temporary power supply terminal 6 is in the true substation direction, the substation direction signal Dss is maintained. When the temporary power supply terminal 6 is not in the true substation direction, the substation direction signal Dss is switched.

  FIGS. 7A to 7D show voltage compensation operations when the voltage Vss in the substation direction is lower or higher than a target value or the like. 8 and 9 show the voltage compensation operation when the voltage Vss in the substation direction is at the target value or the like.

  In the method for determining the substation direction of the voltage compensator according to the present embodiment, the impedance on the substation SS side as viewed from the voltage compensator 1b is sufficiently lower than that on the load DE side. Even if the operation is performed, the fact that the voltage on the substation SS side does not change is utilized. When the compensation operation was performed on the voltage on either the temporary power supply end 6 side or the temporary load end 7 side, the voltage compensation device was able to compensate the voltage because the side where voltage compensation was not possible was the substation direction. It is determined that the side is connected to the actual load.

  More specifically, in this embodiment, when the substation direction signal generation circuit 110 tries to voltage compensate the voltage on the actual load side, the compensation amount Δd1 converges to a constant value, and the substation side signal generation circuit 110 converges to the substation side. When voltage compensation is attempted, it is detected that the compensation amount Δd1 ′ does not converge to a constant value but diverges and is saturated at the maximum value.

  First, the case shown in FIGS. 7A and 7B will be described. As shown in FIG. 7A, the voltage compensation device 1b is connected to the substation SS via terminals 2a to 2c of the temporary power supply terminal 6, and is loaded via terminals 3a to 3c of the temporary load terminal 7. Connected to DE. That is, the temporary power supply terminal 6 is the true substation direction.

  Data of the voltage Vss supplied from the substation SS and applied to the terminals 2a to 2c is input to the abc-dq conversion circuit 94 of the first control circuit 81b. The abc-dq conversion circuit 94 performs dq conversion on the data of the voltage Vss, and outputs a system voltage d-axis component d1 and a system voltage q-axis component q1. Here, the system voltage q-axis component q 1 is controlled to 0 by the PLL 95. That is, the abc-dq conversion circuit 94 performs dq conversion in synchronization with the phase of the voltage Vss, and the dq-abc conversion circuit 98 performs inverse dq conversion in synchronization with the phase of the voltage Vss.

  The adder / subtractor 96 outputs the deviation between the system voltage d-axis component d1 and the load voltage d-axis target value d1 * as the compensation amount Δd1. The load voltage d-axis target value d1 * corresponds to the target system voltage range and is set based on this range. Here, the voltage corresponding to the load voltage d-axis target value d1 * is set as the target voltage Vref.

  In the case of “system voltage” d-axis component and “system voltage” q-axis component, “system voltage” means the voltage of the temporary power supply terminal 6, and in the example described below, in the example described below, the actual system voltage ( May not always match the true voltage on the substation side). Also, in the case of “load voltage” d-axis target value and “load voltage” q-axis target value, “load voltage” means the voltage of the temporary load terminal 7 and does not necessarily match the actual load voltage. There is a case.

  In the example of FIGS. 7A to 7D, it is assumed that the load voltage q-axis target value q1 * is 0 in order to explain the principle of substation direction detection. Therefore, the q-axis compensation amount Δq1 is always zero. In general, as will be described later, the load voltage q-axis target value q1 * is sufficiently smaller than the load voltage d-axis target value d1 * and is set to a value other than zero.

  As shown in FIG. 7B, when the voltage Vss is lower than the target voltage Vref, the system voltage d-axis component d1 corresponding to the voltage Vss is the load voltage d-axis target value d1 corresponding to the target voltage Vref. * Smaller than. Therefore, the compensation amount Δd1 has a positive value. The voltage compensation device 1b outputs a positive compensation voltage Vc with respect to the voltage Vss according to the compensation amount Δd1. The voltage VDE on the load DE side is expressed as follows.

  VDE = Vss + Vc, Vc> 0 (3)

  When voltage Vss exceeds target voltage Vref, system voltage d-axis component d1 is larger than load voltage d-axis target value d1 *. Therefore, the compensation amount Δd1 has a negative value. The voltage compensation device 1b outputs a compensation voltage −Vc for the voltage Vss according to the compensation amount Δd1 having a positive value. The compensation voltage Vc has a negative value. The load voltage VDE is expressed as follows.

  VDE = Vss + Vc, Vc <0

  The compensation voltage Vc can be set to a negative value by generating a compensation voltage Vc that is 180 ° out of phase with the voltage Vss on the substation SS side and adding it to the voltage Vss.

  Next, the case shown in FIGS. 7C and 7D will be described. As shown in FIG. 7C, the voltage compensating device 1b is connected to the load DE via the terminals 2a to 2c of the temporary power supply terminal 6, and via the terminals 3a to 3c of the temporary load terminal 7. Connected to substation SS. That is, the temporary load end 7 is in the true substation direction.

  Since the substation direction signal Dss is set to an initial value, the abc-dq conversion circuit 94 receives data of the voltage VDE transmitted from the substation SS and appearing in the load DE via the voltage compensator 1b. Entered.

  The abc-dq conversion circuit 94 performs dq conversion on the data of the voltage VDE of the load DE, and outputs the result as a system voltage d-axis component d1 'and a system voltage q-axis component q1'. It is the voltage VDE of the load DE that actually performs the dq conversion. The system voltage q-axis component q <b> 1 ′ is controlled to 0 by the PLL 95. That is, the abc-dq conversion circuit 94 performs dq conversion in synchronization with the phase of the voltage VDE, and the dq-abc conversion circuit 98 performs inverse dq conversion in synchronization with the phase of the voltage VDE. In the following description, as described above, the voltage compensator operates with the connection end opposite to the connection end to which the substation is actually connected as the power supply end, and the voltage compensation device misidentifies the substation direction. There are things like that.

  As shown in FIG. 7D, when the voltage VDE is lower than the target voltage Vref, the system voltage d-axis component d1 ′ corresponding to the voltage VDE is the load voltage d-axis target value corresponding to the target voltage Vref. It is smaller than d1 *. Therefore, the compensation amount Δd1 ′ has a positive value. The voltage compensation device 1b outputs a positive compensation voltage Vc 'with respect to the voltage VDE according to the compensation amount Δd1'.

  Since the voltage compensation device 1b misidentifies the temporary power supply terminal 6 as the direction of the substation, the voltage compensation device 1b generates the compensation voltage Vc 'to be added to the initial voltage VDE as indicated by the broken line arrow in the figure. The voltage Vss of the temporary load terminal 7 is expressed as follows.

  Vss = VDE + Vc ′, Vc ′> 0

  In the above equation, since Vss is constant, even if the compensation voltage Vc ′ is added to the voltage VDE on the actual load DE side, it cannot be made equal to the target voltage Vref (> Vss).

  Since the voltage Vss does not increase even when the compensation voltage Vc ′ is added, the voltage compensation device 1b generates a larger compensation amount Δd1 ′ to increase the compensation voltage Vc ′. Thus, when the voltage compensator 1b performs a positive feedback operation, the compensation amount Δd1 ′ does not converge to a constant value. The compensation amount Δd1 ′ diverges by the positive feedback operation, reaches a value corresponding to the maximum value of the compensation voltage Vc ′, and is saturated. The maximum values of the compensation amounts Δd1, Δd1 ′ and the compensation voltages Vc, Vc ′ are set by the maximum voltage that the first power converter 20 can output.

  The determination circuit 111 can detect that the compensation amount Δd1 ′ has reached the maximum value, and can determine that the current connection state misidentifies the substation direction. That is, the determination circuit 111 can detect that the substation SS is connected to the terminals 3 a to 3 c of the temporary load end 7. The determination circuit 111 generates a substation direction signal Dss for switching the switch 93 so that the AC voltage data VAC3 and VAC4 of the temporary load end 7 are used.

  When the voltage Vss is lower than the target voltage Vref, the compensation amount Δd1 has a positive value. The voltage compensation device 1b outputs a compensation voltage Vc 'with respect to the voltage Vss so as to cancel the compensation amount Δd1 having a positive value. The compensation voltage Vc ′ has a negative value. The load voltage VDE is expressed as follows.

  VDE = Vss + Vc ′, Vc ′ <0

  As in the case of Vc> 0, the voltage compensation device 1b generates a compensation amount Δd1 ′ having a larger absolute value in order to compensate for the voltage Vss that cannot be compensated. The compensation amount Δd1 ′ reaches the maximum value by the positive feedback operation. The determination circuit 111 determines that the substation direction is misidentified, and generates a substation direction signal Dss for switching the switch 93.

  In the above description, the case where the voltage of the power system is lower or higher than the target value has been described. However, when the voltage of the power system is at the target value or the like, the compensation amount Δd1 is 0, so the voltage compensator does not perform voltage compensation and cannot determine the substation direction. Even in such a case, the voltage compensator of this embodiment uses the load voltage q-axis target value q1 * to determine the substation direction.

  First, as shown in FIG. 7A, the case where the temporary power supply end 6 and the actual substation direction coincide will be described. As shown in FIG. 8A, when the magnitude of the target voltage Vref and the voltage Vss on the substation SS coincide, the compensation amount Δd1 is zero.

  The first control circuit 81b generates the compensation amount Δq1 by subtracting the system voltage q-axis component q1 output from the abc-dq conversion circuit 94 from the load voltage q-axis target value q1 *. Since the system voltage q-axis component q1 is controlled to 0 by the PLL 95, the compensation amount Δq1 is q1 *.

  When the compensation voltage corresponding to the compensation amount Δd1 is Vc, the compensation amount Δq1 corresponds to the voltage Vcq orthogonal to the compensation voltage Vc. Therefore, when the voltages in equation (3) are vectors, equation (4) is obtained. In this example, Vc = 0, but more generally, Vc as a vector may be added to the right side of Equation (4).

  FIG. 8B shows the relationship between the voltage vectors of the respective parts after the load voltage q-axis target value q1 * is injected. As shown in FIG. 8B, the voltage VDE on the load DE side can be obtained by vector addition of the compensation voltage Vcq to the voltage Vss (= Vref) in the substation direction. By adding the compensation voltage Vcq, the voltage VDE has a phase difference δ with respect to the voltage Vss, and the magnitude of the voltage VDE becomes larger than the magnitude of the voltage Vss on the substation SS side.

  In this case, the compensation amounts Δd1 and Δq1 are both constant. Specifically, the compensation amount Δd1 is 0, which is smaller than the maximum value. Therefore, the discrimination circuit 111 recognizes the correct substation direction and maintains this substation direction signal Dss.

  Next, as shown in FIG. 7C, a case where the temporary power supply terminal 6 does not coincide with the actual substation direction and the temporary load terminal 7 is in the true substation direction will be described. As shown in FIG. 9 (a), when the target voltage Vref and the voltage VDE on the load DE side coincide with each other on the d axis, the corresponding compensation amount Δd1 ′ is zero.

  FIGS. 9B to 9D show the relationship between the voltage vectors of the respective parts after the load voltage q-axis target value q1 * is injected. Also, in FIGS. 9B to 9D, the solid coordinate axis relates to the temporary load end 7, that is, the voltage Vss in the substation direction. The coordinate line of the alternate long and short dash line relates to the temporary power supply terminal 6, that is, the voltage VDE on the load DE side in practice. By injecting the load voltage q-axis target value q1 *, it is indicated that the coordinate axis on the load DE side is rotated according to the load voltage q-axis target value q1 *. A partial circle of the broken line is a locus of the d-axis target voltage (target value) of the voltage VDE on the load DE side.

  As shown in FIG. 9B, when the load voltage q-axis target value q1 * is input, the voltage compensator 1b outputs a compensation voltage Vcq 'corresponding to q1 *. However, when the voltage compensation device 1b tries to match the voltage Vss on the substation SS side by adding the compensation voltage Vcq ′ to the voltage VDE on the load DE side, the voltage Vss is constant. As a result, the d-axis value decreases. Therefore, a compensation amount Δd1 ′ that should not be generated is generated, and the voltage compensation device 1b outputs a compensation voltage Vc ′ corresponding to the compensation amount Δd1 ′. The voltage compensation device 1b tries to generate a larger compensation voltage Vc 'in order to eliminate the compensation amount Δd1' (FIG. 9 (c)). The compensation amount Δd1 ′ further increases due to the positive feedback, and operates until reaching the maximum value of the compensation voltage Vc ′ and saturating (FIG. 9D).

  Therefore, when the magnitude of the compensation amount Δd1 ′ reaches the maximum value, the substation direction signal generation circuit 110 determines that the substation direction is not the temporary power supply end 6 but the temporary load end 7. . The determination circuit 111 generates the substation direction signal Dss so as to switch the switch 93 so that the AC voltage data VAC3 and VAC4 are input to the abc-dq conversion circuit 94.

  In the above description, for the sake of convenience of explanation, the voltage Vss in the substation direction or the voltage VDE on the load DE side is distinguished depending on whether or not it is equal to the target voltage Vref (or within the target voltage range). In any case, the voltage compensator 1b of the present embodiment detects the substation direction by inputting the target values d1 * and q1 * and determining the magnitude of the compensation amount Δd1. The voltage on the load DE side can be appropriately compensated with reference to the voltage in the direction of the substation.

  Further, in the voltage compensator 1b of the present embodiment, the phase difference δ is generated between the voltage at the temporary power supply terminal 6 and the voltage at the temporary load terminal 7 by injecting the load voltage q-axis target value q1 *. Can be made. Therefore, as will be described in the effect described later, the substation direction can be accurately detected even when the power conditioner with the output limiting function is connected to the temporary load end 7.

The operation and effect of the voltage compensator of this embodiment will be described.
The voltage compensator 1b is inserted between the substation and the load at a place where the voltage is reduced. For example, when the voltage compensator 1b is first installed, the substation direction is often known, and the side instructed in the substation direction by a work instruction or the like is referred to as the temporary power supply terminal 6. There is nothing wrong with doing. In such a case, the operator can set the substation direction signal in accordance with the work instruction as in the voltage compensation device 1 of the first embodiment.

  In recent years, the transmission grid of the power system may be configured in a complicated manner, and the transmission network may be switched appropriately according to the power demand on the consumer side or in response to an upstream system failure or the like. . For example, there is a case where power is transmitted from one substation of the transmission line provided with the voltage compensation device 1b, and there is a case where power is transmitted by switching to the other substation for the above-described reason. It is necessary to cope with either case.

  Although it is possible to switch the substation direction signal Dss of the voltage compensator according to the state of the power transmission network by wire or wireless using a power network control system etc., there are many targets for switching control, and in order to make it practical in a wide range There are also difficulties. Since the voltage compensation device 1b according to the present embodiment includes the substation direction signal generation circuit 110, the voltage compensation device 1b itself can monitor the direction of the substation SS constantly or in a timely manner. It can be automatically identified and connected properly. Therefore, an appropriate connection can be easily obtained without introducing a special power network control system and the like, and the power system can be simplified and reduced in cost.

  In recent years, it has become prominent that a device that reversely flows into a system such as a photovoltaic power generation system is linked to a consumer side of the power system. Even in such a case, the voltage compensator 1b of the present embodiment can determine the substation direction by itself by injecting the load voltage q-axis target value q1 *, and can connect to the appropriate direction.

  In a power system in which a power conditioner (PCS) of a solar power generation system is connected, the system voltage increases as the reverse power flow increases. Many PCSs have an output limiting function. The output limiting function of the PCS limits the output and reduces the reverse power flow when the system voltage reaches a preset voltage so that the system voltage does not rise above a certain level.

  In the method of detecting the true substation direction by operating one of the voltage on the substation side and the voltage on the load side to detect whether the voltage changes, the PCS having an output limiting function is connected to the load DE. When connected to the side, the substation direction cannot be detected. Specifically, when the reverse power flow of the PCS is increased and the output limiting function is operating, if the voltage compensation operation is performed so that the voltage compensator reduces the voltage, the PCS is considered to have a reduced system voltage. Judge and release the output restriction function. For this reason, the reverse flow rate by the PCS increases, and the voltage on the load DE side increases. That is, the power system voltage does not change due to the operation and release of the PCS output restriction function.

  In the voltage compensator 1b of the present embodiment, the load voltage q-axis target value q1 * is injected, so that a phase difference can be generated in the voltage on the load DE side with respect to the voltage on the substation side. That is, the voltage compensator 1b can change the magnitude of the voltage VDE by changing the phase on the load DE side. Since the PCS having the output limiting function cannot control the voltage VDE causing the phase difference δ, even if the PCS having the output limiting function is connected to the load DE side, the voltage compensator 1b is connected to the substation. The direction can be accurately determined.

(Third embodiment)
FIG. 10 is a block diagram illustrating a part of the voltage compensator of this embodiment.
In the voltage compensator of this embodiment, the configuration of the substation direction signal generation circuit 310 is different from that of the second embodiment. The first control circuit 81 c includes a substation direction signal generation circuit 310. Substation direction signal generation circuit 310 includes a switch 311, an abc-dq conversion circuit 313, a load voltage phase calculation circuit 314, a determination circuit 315, and an initial value setting unit 316.

  The switch 311 selects one of the three-phase voltage detection circuits 91 and 92 and connects it to the abc-dq conversion circuit 313. The switch 311 operates complementarily with the switch 93. In this example, the substation direction signal Dss is input via the inverter 312. That is, when the switch 93 selects the three-phase voltage detection circuit 91, the switch 311 selects the three-phase voltage detection circuit 92. When the switch 93 selects the three-phase voltage detection circuit 92, the switch 311 selects the three-phase voltage detection circuit 91.

  The abc-dq conversion circuit 313 receives the output of any of the three-phase voltage detection circuits 91 and 92 and performs dq conversion. The abc-dq conversion circuit 313 is phase-synchronized by the PLL 95.

  The load voltage phase calculation circuit 314 receives the d-axis component and the q-axis component from the abc-dq conversion circuit 313, respectively. The load voltage phase calculation circuit 314 calculates whether or not a phase difference has occurred between the input d-axis component and q-axis component. The calculated result is input to the determination circuit 315 to determine whether or not the temporary power supply terminal 6 is in the true substation direction. The initial value setting unit 316 sets the initial value in the substation direction as in the case of the second embodiment.

The operation of the voltage compensator of this embodiment will be described.
The abc-dq conversion circuit 313 of the substation direction signal generation circuit 310 of the voltage compensator according to the present embodiment has a load side voltage when the true substation direction voltage is input to the abc-dq conversion circuit 94. Entered. At this time, the abc-dq conversion circuit 313 outputs the in-phase component of the voltage on the load side and the quadrature component of the voltage. The abc-dq conversion circuit 313 operates in synchronization with the phase of the voltage in the substation direction. Therefore, the common-mode voltage on the load side generates a phase difference δ generated by the compensation amount Δq1 from the voltage in the substation direction.

  The load voltage phase calculation circuit 314 calculates whether the phase of the voltage on the load side includes the phase difference δ generated by the compensation amount Δq1. When the phase difference δ can be extracted from the phase of the voltage on the load side, a signal indicating that the correct phase difference has been detected is output.

  The determination circuit 315 determines that the signal is connected in the true substation direction by inputting a signal indicating that the phase difference is correct, and generates a signal for maintaining the connection to the switches 93 and 311.

  On the other hand, when the voltage compensator misidentifies the substation direction, the load side voltage is input to the abc-dq conversion circuit 94, and the abc-dq conversion circuit 313 of the substation direction signal generation circuit 310 is input to the abc-dq conversion circuit 313. The voltage in the direction of the substation is input. As in the case of the first embodiment, the voltage in the substation direction does not vary depending on the voltage on the load side and does not cause a phase difference due to the voltage on the load side. Therefore, the phase of the voltage output from the abc-dq conversion circuit 313 is not equal to the phase difference δ generated by the compensation amounts Δd1 and Δq1. Therefore, the load voltage phase calculation circuit 314 outputs a signal indicating that the phase difference is not correct.

  The determination circuit 315 generates a signal for switching connection to the switches 93 and 311 based on a signal indicating that the phase difference is not correct. When the connection of the switches 93 and 311 is switched, the voltage in the true substation direction is input to the abc-dq conversion circuit 94 and operates according to the above-described operation.

The effect of the voltage compensator of this embodiment will be described.
The voltage compensation device according to the present embodiment produces the same effects as those of the other embodiments described above. Even when a PCS with an output limiting function is connected to the load side, the true substation is detected by detecting the phase difference δ of the load voltage in-phase component and the load voltage quadrature component with respect to the voltage on the substation side. The direction can be accurately detected. In the voltage compensation device of the present embodiment, it is not necessary to detect output saturation, so the substation direction can be determined more quickly.

(Fourth embodiment)
FIG. 11 is a block diagram illustrating a part of the voltage compensator of this embodiment.
In the case of this embodiment, a frequency change of the power source is detected for connection determination.
As shown in FIG. 11, the first control circuit 81 d includes a substation direction signal generation circuit 410. In the voltage compensator of this embodiment, the configuration of the substation direction signal generation circuit 410 is different from that of the other embodiments. In the case of this embodiment, the substation direction signal generation circuit 410 is different from the case of the third embodiment in that it includes a PLL 414 and differentiators 415 and 416. The same constituent elements as those of the other embodiments are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

  The switch 311, the inverter 312 and the abc-dq conversion circuit 313 are the same as those in the third embodiment. However, the abc-dq conversion circuit 313 operates in synchronization with the phase θ2 output from the PLL 414 connected to the output. The abc-dq conversion circuit 94 operates in synchronization with the phase θ1 output from the PLL 95 connected to the output. That is, the abc-dq conversion circuit 313 of the substation direction signal generation circuit 410 operates in synchronization with the load-side voltage when the voltage compensator is connected in the true substation direction. The abc-dq conversion circuit 313 of the substation direction signal generation circuit 410 operates in synchronization with the phase of the voltage in the substation direction when the voltage compensator is connected to the load side.

  The PLL 414 is connected to the output on the orthogonal component side of the abc-dq conversion circuit 313. That is, the PLL 414 operates so that the abc-dq conversion circuit 313 sets the output on the orthogonal component side to zero.

  The PLLs 95 and 414 have the configuration shown in FIG. The PLLs 95 and 414 can output angular velocity data together with angle (phase) data. The data output of the angular velocity data ω 1 of the PLL 95 is connected to the differentiator 415. The data output of the angular velocity ω 2 of the PLL 414 is connected to the differentiator 416. That is, the data of the angular velocities ω1 and ω2 output from the PLLs 95 and 414 are differentiated by the differentiators 415 and 416 and input to the determination circuit 417.

The operation of the voltage compensator of this embodiment will be described.
FIG. 12A to FIG. 13B are conceptual diagrams for explaining the operation of the voltage compensator of this embodiment.
FIG. 12A and FIG. 12B show an example where the voltage compensator correctly recognizes the substation direction. FIG. 13A and FIG. 13B show a case where the voltage compensator incorrectly recognizes the substation direction. Hereinafter, in each case, the voltage Vss in the substation direction is within the allowable range, but the case where the voltage Vss is outside the allowable range is the same as that described in the case of the second embodiment. is there.

First, a case where the voltage compensator correctly recognizes the substation direction will be described.
As shown in FIG. 12A, when the voltage Vss in the substation direction is within the allowable range, voltage compensation is not performed for the positive phase voltage component.

  As shown in FIG. 12B, the phase of the voltage VDE on the load DE side changes by injecting the target value q1 * of the q-axis component on the load DE side. For this reason, the PLL 414 operates so as to set the orthogonal component output of the abc-dq conversion circuit 313 to 0. Therefore, the PLL 414 that was initially operating at the angular velocity ω1 (= 1 / angular frequency) of the voltage Vss on the substation SS side. The voltage VDE on the load DE side is made to coincide with the angular velocity ω2. That is, the frequency of the voltage on the load DE side changes.

  The determination circuit 417 receives the frequency change of the voltage Vss on the substation SS side and the frequency change of the voltage VDE on the load DE side, and when the frequency change of the voltage VDE is larger than the frequency change of the voltage Vss, the substation Judge that the direction is correctly recognized.

A case where the voltage compensator does not correctly recognize the substation direction will be described.
As shown in FIG. 13A, when the voltage on the load DE side recognized as the direction of the substation SS is within the allowable range, voltage compensation is not performed with the positive phase voltage component.

  As shown in FIG. 13B, when the target value q1 * is injected into the q axis, the side where the target value q1 * is injected is actually the substation SS side, so that a phase change may occur. Absent. On the other hand, on the load DE side where the target value q1 * is injected, a phase change is caused by the target value q1 *.

  For this reason, the component output from the PLL 95 connected to the abc-dq conversion circuit 94 causes a frequency change.

  Therefore, when the frequency change of the signal output from the PLL 95 on the abc-dq conversion circuit 94 side is larger than the frequency change of the signal output from the PLL 414 on the abc-dq conversion circuit 313 side, the substation direction is misidentified. Can be determined.

The effect of the voltage compensator of this embodiment will be described.
The voltage compensation device according to the present embodiment has the following effects in addition to the same effects as those of the above-described embodiments. That is, in the voltage compensator of this embodiment, the frequency of the voltages Vss and VDE on both the substation SS side and the load DE side can be detected, and the true substation direction can be determined according to the frequency change. . Therefore, the true substation direction can be correctly determined even if phase, frequency disturbance, or the like occurs in the power system.

  In the case of this embodiment, since the substation direction is determined in a transient state after the injection of the q-axis target value, a quick determination result can be obtained.

(Fifth embodiment)
FIG. 14 is a block diagram illustrating a voltage compensator according to this embodiment.
FIG. 15 is a block diagram illustrating a part of the voltage compensator of this embodiment.
In the voltage compensator of this embodiment, the substation direction is determined by operating the second power converter 30 as a reactive power compensator and detecting the direction in which reactive power is injected. The substation behaves as a constant voltage power supply, so the impedance is low. Therefore, current based on reactive power injected into the power system (hereinafter also referred to as reactive current) flows in the direction of the substation. In this embodiment, the voltage on the substation side injects reactive power and detects the substation direction by detecting the presence or absence of a change in the current flowing through the power system.

  In the case of this embodiment, the respective voltages on the temporary power supply end 6 side and the temporary load end 7 side are assumed to be at a target value or the like.

  As shown in FIG. 14, the voltage compensation device 1e of the present embodiment includes a voltage compensation unit 10e. The voltage compensator 10e includes current detectors 63 and 64. The current detector 63 is connected between the series transformer 11 and the terminal 3 a of the temporary load end 7. The current detector 64 is connected between the series transformer 15 and the terminal 3 c of the temporary load end 7. In this example, the current detectors 63 and 64 are connected so as to detect the U-phase and W-phase line currents of the power system.

  In the voltage compensator 1e of this embodiment, the reactive power calculated based on the current detected by the current detectors 63 and 64 when the second power converter 30 is operated to inject reactive power into the power system. The true substation direction is determined by detecting whether or not has changed due to reactive power injection.

  The voltage compensation device 1e includes a control unit 80e. As shown in FIG. 15, the control unit 80e includes a first control circuit 81e and a second control circuit 82e.

  FIG. 15 is a block diagram illustrating the control unit 80e, and is a block diagram illustrating a detailed configuration of the second control circuit 82e. In FIG. 15, a part of the first control circuit 81e is shown. Since the outputs of the abc-dq conversion circuit 94 and the abc-dq conversion circuit 94 shown in FIG. 15 are the same as those in the other embodiments described above, illustration is omitted.

  Second control circuit 82e includes a substation direction signal generation circuit 510 and an alternating current control circuit 550.

  Substation direction signal generation circuit 510 includes a three-phase current detection circuit 511, switches 516a, 516b, 519a, and 519b, reactive power calculation circuits 520 and 521, a determination circuit 522, and an initial value setting unit 523. .

  First, the configuration of the alternating current control circuit 550 will be described. The AC current control circuit 550 includes a three-phase voltage detection circuit 551, a coefficient unit 552, an abc-dq conversion circuit 553, a PLL 554, adders 555, 556, a dq-abc conversion circuit 557, and a gate signal generation circuit. 558, a three-phase current detection circuit 559, an abc-dq conversion circuit 560, adders / subtractors 561, 562, and PI compensators 563, 564.

  The AC current control circuit 550 is an active power that is injected into the power system based on the voltage on the secondary side of the parallel transformers 41 and 42, the line current of each phase, the active current command value Ip * and the reactive current command value Iq *. The gate drive signal Vg2 for controlling the reactive current is generated.

  The three-phase voltage detection circuit 551 receives AC voltage data VAC3 and VAC4 on the temporary load end 7 side, and detects each phase voltage. The detected phase voltages are input to the abc-dq conversion circuit 553 via the coefficient unit 552. The coefficient of the coefficient unit 552 is set to 1 / N. Here, N is the turn ratio of the parallel transformers 41 and 42. The abc-dq conversion circuit 553 dq converts and outputs the AC voltage of each secondary side of the parallel transformers 41 and 42. The q-axis component output from the abc-dq conversion circuit 553 is input to the PLL 554, and the PLL operates to make the q-axis component zero. That is, the abc-dq conversion circuit 553 operates by the PLL 554 in synchronization with the voltage phase on the temporary load end 7 side. The dq-abc conversion circuit 557 is also operated by the PLL 554 in synchronization with the phase of the voltage on the temporary load end 7 side.

  The three-phase current detection circuit 559 receives current data IL1 and IL2 of the current flowing through the inductors 51 and 52 detected by the current detectors 61 and 62, and calculates the line current on the secondary side of the parallel transformers 41 and 42. To detect. The detected line current of each phase is input to the abc-dq conversion circuit 560.

  The abc-dq conversion circuit 560 performs dq conversion on the secondary side line current of the parallel transformers 41 and 42 and outputs the result. The d-axis component after the dq conversion is input to the adder / subtractor 561 together with the effective current command value Ip *. The q-axis component after the dq conversion is input to the adder / subtractor 562 together with the reactive current command value Iq *. The adders / subtracters 561 and 562 output the deviations of the d-axis component and the q-axis component, respectively.

  The respective deviations of the d-axis component and the q-axis component are input to the PI compensators 563 and 564, and the PI compensators 563 and 564 perform proportional-integral calculations on the respective deviations so that the respective deviations are based on zero. Output the compensation amount.

  The compensation amounts output from the PI compensators 563 and 564 are added to the d-axis component and the q-axis component of each phase voltage on the secondary side of the parallel transformers 41 and 42 by the adders 555 and 556, and dq-abc It is input to the conversion circuit 557. The dq-abc conversion circuit 557 generates command values for active power and reactive power and supplies them to the gate signal generation circuit 558.

  The above-described AC current control circuit 550 has a well-known configuration for reactive power compensation, and is not limited to the above-described configuration, and may be another known configuration.

  Next, a detailed configuration of the substation direction signal generation circuit 510 will be described. Three-phase current detection circuit 511 receives current data IL3 and IL4 of U-phase and W-phase line currents of the power system. The three-phase current detection circuit 511 detects the value of the alternating current of each phase of the power system based on the data of the U-phase and W-phase line currents.

  The data I0 of each line current detected by the three-phase current detection circuit 511 is divided into four and connected to each input of the switches 516a and 516b.

  Data I0 of the first current of each line current is input to the adder / subtracter 513. The output of the three-phase current detection circuit 559 of the alternating current control circuit 550 is connected to the input of the adder / subtractor 513 via the coefficient unit 512. In the coefficient unit 512, 1 / N is set as a coefficient. In other words, the primary side current data Iq 0 of the parallel transformers 41 and 42 is input to the adder / subtractor 513. The current data I1, which is the difference between the current data I1 and Iq0, is input to one input terminal of the switch 516a by the adder / subtractor 515. The current data I1 represents the current flowing from the temporary power supply terminal 6 toward the temporary load terminal 7 on the temporary power supply terminal 6 side.

  The second data I0 of each line current is input to the other input terminal of the switch 516a via the coefficient unit 514. The coefficient of the coefficient unit 514 is set to -1. That is, the current data I2 output from the coefficient unit 514 is −1 × I0. The current data I <b> 2 represents the current flowing from the temporary load terminal 7 toward the temporary power supply terminal 6 on the temporary load terminal 7 side.

  The third data I0 of each line current is input to one input terminal of the switch 516b as current data I3. The current data I <b> 3 represents a current flowing from the temporary power supply terminal 6 toward the temporary load terminal 7 on the temporary load terminal 7 side.

  The fourth data I0 of each line current is input to the coefficient unit 526. The coefficient of the coefficient unit 526 is set to -1. The current data (−) I 0 output from the coefficient unit 526 is input to the adder / subtractor 515. The adder / subtractor 515 receives the current data Iq0. The difference between the current data (−) I0 and Iq0 is input as current data I4 by the adder / subtractor 515 to the other input terminal of the switch 516b. The current data I <b> 4 represents the current flowing from the temporary load terminal 7 toward the temporary power supply terminal 6 on the temporary power supply terminal 6 side.

  The switches 516a and 516b switch inputs almost simultaneously by the substation direction signal Dss. When the switch 516a selects the current data I1 by the substation direction signal Dss, the switch 516b selects the current data I3. When the switch 516a selects the current data I2 based on the substation direction signal Dss, the switch 516b selects to output the current data I4. When the current data I1 and I3 are selected, the current data I1 and I3 are supplied to the reactive power calculation circuits 520 and 521, respectively. When the current data I2 and I4 are selected, the current data I2 and I4 are supplied to the reactive current calculation circuits 520 and 521, respectively.

  The output of the three-phase voltage detection circuit 517 is connected to one input terminal of the switch 519a. The output of the three-phase voltage detection circuit 518 is connected to the other input terminal of the switch 519a. The output terminal of the switch 519a is connected to the reactive power calculation circuit 520. The output of the three-phase voltage detection circuit 517 is connected to one input terminal of the switch 519b. The output of the three-phase voltage detection circuit 518 is connected to the other input terminal of the switch 519b. The output terminal of the switch 519b is connected to the reactive power calculation circuit 521.

  The switches 519a and 519b operate almost simultaneously in conjunction with the switches 516a and 516b. When the current data I1 is input to the reactive power calculation circuit 520 through the switch 516a, the voltage data V1 output from the three-phase voltage detection circuit 517 is input through the switch 519a. Reactive power calculation circuit 520 calculates and outputs reactive power Q1 based on current data I1 and voltage data V1.

  The reactive power calculation circuit 521 receives the voltage data V2 output from the three-phase voltage detection circuit 518 through the switch 519b when the current data I3 is input through the switch 516b. The reactive power calculation circuit 521 calculates and outputs the reactive power Q2 based on the current data I3 and the voltage data V2.

  When the current data I2 is input to the reactive power calculation circuit 520 through the switch 516a, the voltage data V2 is input through the switch 519a. Reactive power calculation circuit 520 calculates and outputs reactive power Q1 based on current data I2 and voltage data V2.

  When the current data I4 is input by the switch 516b, the reactive power calculation circuit 521 receives the voltage data V1 by the switch 519b. The reactive power calculation circuit 521 calculates and outputs the reactive power Q2 based on the current data I4 and the voltage data V1.

  The determination circuit 522 compares the reactive powers Q1 and Q2 calculated by the reactive power calculation circuits 520 and 521, respectively, and generates a substation direction signal Dss based on the comparison result. In this example, the substation direction is correctly determined when Q1 <Q2, and it is determined that the substation direction is misidentified when Q1> Q2.

  When Q1 = Q2, it may be determined that the determination is impossible, and it may wait until Q1 <Q2 or Q1> Q2, or the substation direction signal Dss May be switched to repeatedly perform the discrimination operation. The output of the switch 519a selected by the substation direction signal Dss is input to the abc-dq conversion circuit 94 of the first control circuit 81e.

The operation of the voltage compensator of this embodiment will be described.
FIG. 16A and FIG. 16B are conceptual diagrams for explaining the operation of the voltage compensator of this embodiment.
The current flowing through the power system flows from the substation SS side to the load DE side. In the power system, since the impedance on the side to which the substation SS is connected is lower than the impedance on the side to which the load DE is connected, the reactive current injected by the second power converter 30 is converted into the parallel transformers 41 and 42. To the substation SS side. Therefore, the current flowing through the power system changes from the parallel transformers 41 and 42 on the side of the substation SS, and the reactive power based on the current changes. Since the current does not change on the load DE side as seen from the parallel transformers 41 and 42, the reactive power also does not change.

  In the example of FIG. 16A, the substation SS is connected to the terminals 2 a to 2 c of the temporary power supply terminal 6, and the load DE is connected to the terminals 3 a to 3 c of the temporary load terminal 7. The current data I1 represents the current flowing through the temporary power supply terminal 6 side, and the data I3 represents the current flowing through the temporary load terminal 7 side.

  The reactive power calculation circuit 520 calculates the reactive power Q1 based on the current data I1 and the voltage data V1 on the temporary power supply terminal 6 side. The reactive power calculation circuit 521 calculates the reactive power Q2 based on the current data I3 and the voltage data V2 on the temporary load terminal 7 side.

  When the substation SS is connected to the temporary power supply terminal 6 side and the load DE is connected to the temporary load terminal 7 side, since Q1 <Q2 because I1 <I3, the determination circuit 522 It can be determined that the true substation direction is selected by the connection.

  In the example of FIG. 16B, the substation SS is connected to the terminals 3 a to 3 c of the temporary load end 7, and the load DE is connected to the terminals 2 a to 2 c of the temporary power supply end 6. The current data I2 represents the current flowing through the temporary power supply terminal 6, and the current data I4 represents the current flowing through the temporary load terminal.

  The reactive power calculation circuit 520 calculates the reactive power Q1 based on the current data I2 and the voltage data V1. The reactive power calculation circuit 521 calculates the reactive power Q2 based on the current data I4 and the voltage data V2.

  In this case, since | I2 |> | I4 |, Q1> Q2. Therefore, the determination circuit 522 can determine that the temporary load end 7 side is in the true substation direction.

  In the voltage compensator of this embodiment, the substation direction can be determined by injecting reactive current into the power system, so the substation direction can be determined without changing the voltage of the power system in the voltage compensation operation. can do.

  In the above description, the reactive power on the temporary power supply end 6 side and the temporary load end 7 side is calculated, and the substation direction is determined by comparing the magnitude relationship. After obtaining the current on the temporary power supply end 6 side and the temporary load end 7 side, after performing the process of taking the absolute value of the current, the direction of the substation can also be determined by comparing the magnitude of the current Can do.

(Modification of the fifth embodiment)
FIG. 17 is a block diagram illustrating a part of the voltage compensator of this modification.
In the above-described embodiment, the power supply direction is determined from the relationship between the reactive current on the substation side, the reactive current on the load side, and the reactive current injected from the second power converter 30. On the other hand, since the reactive current flowing to the load side changes from moment to moment depending on the connection state of the load, it may be difficult to determine the substation direction by comparing the reactive currents described above. Therefore, in this modification, the direction of the substation is determined by determining the time variation of the reactive current on the substation side and the load side.

  In this modification, differentiators 524 and 525 are connected to the outputs of the reactive power calculation circuits 520 and 521, respectively. The outputs of the differentiators 524 and 525 are supplied to the discrimination circuit 522.

  When reactive current injection is not performed from the second power converter 30, the reactive power on the substation side and the load side of the voltage compensator are equal, and the amount of change is also equal. Here, when the reactive power is supplied from the second power converter 30 to the power system, the reactive power change amount on the substation side of the voltage compensator is larger than the reactive power change amount on the load side.

  If the substation direction is misidentified, the amount of change in reactive power on the load side seen from the voltage compensator increases, so it can be determined that the substation direction is misidentified, and the true substation direction is Can be determined.

  Even when the reactive power of the load changes, the direction of the substation can be easily determined by comparing the magnitudes of the changes.

  Each above-mentioned embodiment and modification can be implemented by combining one or two or more. For example, the first control circuit of the third embodiment may be combined with the first control circuit of the second embodiment, and further the second control circuit of the fifth embodiment may be combined.

  The control unit of the voltage compensation device of each embodiment described above may include, for example, a calculation unit and a storage unit. The arithmetic unit may include a circuit that operates in accordance with each step of a program such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The program is stored in the storage unit, for example. A part or all of each circuit and each part of the control unit may be replaced with a program stored in a storage unit or the like.

  According to the embodiment described above, it is possible to realize a voltage compensator that compensates the voltage of the power system to an appropriate value continuously at high speed.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of 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.

  DESCRIPTION OF SYMBOLS 1,1a-1c Voltage compensation apparatus, 2a-2c terminal, 3a-3c terminal, 6 Temporary power supply terminal, 7 Temporary load terminal, 10, 10a Voltage compensation part, 11, 13, 15 Series transformer, 12a, 12b , 14a, 14b, 16a, 16b terminal, 20 first power converter, 21a high voltage DC terminal, 21b low voltage DC terminal, 22a-22c AC terminal, 23a-23f switching element, 24 capacitor, 26 filter, 30 second power conversion 31a High voltage DC terminal, 31b Low voltage DC terminal, 32a to 32c AC terminal, 33a to 33f Switching element, 41 and 42 Parallel transformer, 51 and 52 Inductor, 61 to 64 Current detector, 71 to 74 AC voltage detector , 75 DC voltage detector, 80 control unit, 81 first control circuit, 82 second control circuit, 91, 92 three-phase Voltage detection circuit, 93 switch, 94 abc-dq conversion circuit, 95 PLL, 96, 97 adder / subtractor, 98 dq-abc conversion circuit, 99 gate signal generation circuit, 100 AC current control circuit, 101 gate signal generation circuit, 105 voltage Compensation direction determination circuit, 106 multiplier, 110 substation direction signal generation circuit, 111 discrimination circuit, 112 initial value setting unit, 310 substation direction signal generation circuit, 311 switch, 312 inverter, 313 abc-dq conversion circuit, 314 load Voltage phase calculation circuit, 315 discrimination circuit, 316 initial value setting unit, 410 substation direction signal generation circuit, 414 PLL, 415, 416 differentiator, 417 discrimination circuit, 418 initial value setting unit, 510 substation direction signal generation circuit, 511 three-phase current detection circuit, 512, 514 coefficient unit, 13,515 subtracter, 516a, 516b, 519a, 519b switches, 517 and 518 three-phase voltage detecting circuit, 520, 521 reactive power calculating circuit, 522 discriminating circuit, 523 an initial value setting unit, 524 and 525 differentiator

Claims (5)

A voltage compensator that is inserted in series in a power system and compensates the voltage of the power system,
A first terminal, a second terminal and a third terminal connected to one of the inserted electric power systems;
A fourth terminal, a fifth terminal and a sixth terminal connected to the other of the power system;
A first transformer having a primary side connected in series between the first terminal and the fourth terminal;
A second transformer having a primary side connected in series between the second terminal and the fifth terminal;
A third transformer having a primary side connected in series between the third terminal and the sixth terminal;
A power conversion circuit having a self-extinguishing type switching element and performing a switching operation at a frequency higher than the frequency of the power system, and each of the first transformer, the second transformer, and the third transformer A first power converter having an output connected to the secondary side;
Based on the first voltage that is the voltage of the power system on the first terminal side or the second voltage that is the voltage of the power system on the fourth terminal side, and the target voltage that is the target voltage. A control unit for generating a drive signal for driving the switching element;
With
The controller is
One of the first voltage and the second voltage is input according to a selection signal, the one voltage is subjected to rotational coordinate conversion in synchronization with the phase of the one voltage, and the first component and A first coordinate converter that outputs a second component orthogonal to the first component;
The first deviation between the first component and the target value of the first component set according to the target voltage, and the second deviation between the second component and the target value of the second component are respectively input. A second coordinate conversion unit that performs reverse rotation coordinate conversion in synchronization with the phase of the one voltage,
Only including,
The control unit is a voltage compensation device that generates the selection signal based on the first deviation and the second deviation . The controller is
A third coordinate converter that inputs the other voltage different from the one voltage, performs rotational coordinate conversion, and outputs a third component and a fourth component orthogonal to the third component;
An arithmetic unit that outputs the selection signal based on the third component and the fourth component;
Voltage compensation device according to claim 1 Symbol mounting including. Before and after inputting the target value of the second component, the control unit changes the time of the frequency of the one voltage measured based on the phase of the one voltage and the other voltage different from the one voltage. The voltage compensator according to claim 1 or 2 , wherein the selection signal is generated based on a time change of the frequency of the other voltage measured based on the phase of the other voltage. A second power converter connected between the fourth terminal and the first power converter;
A first current detector for detecting an alternating current flowing through the second power converter;
A second current detector for detecting a line current of the power system;
Further comprising
Wherein the control unit is configured based on the line current detected by the first current detected by the detector the said alternating current and said second current detector, it claims 1-3 for generating the selection signal The voltage compensator according to one. Said first transformer secondary winding, said second transformer secondary winding, and the third transformer secondary windings, claims 1-4 are either star connection or delta connection The voltage compensator according to any one of the above.

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