JP5611009B2 - Unbalance compensator - Google Patents

Description

  The present invention relates to an unbalance compensator suitable for compensating reverse-phase power with respect to three-phase unbalanced load power in a three-phase power supply system for supplying power to a load from a three-phase AC power supply. .

  A conventional power converter is presented in Non-Patent Document 1, for example. FIG. 7 is a diagram illustrating a configuration of a conventional power conversion device based on the configuration disclosed in Non-Patent Document 1. Referring to FIG. 7, the power converter is an unbalanced power compensator, and includes step-down transformer 8, capacitors 91 and 94, high impedance transformers 92 and 95, and thyristor power converters 93 and 96. .

  The unbalanced load 2 is connected to the three-phase AC power source 1 and has a Scott connection transformer 21 and single-phase loads 22 and 23. Single-phase loads 22 and 23 are trains, for example, and each consumes power independently. For this reason, an unbalanced current flows on the three-phase side.

  FIG. 8 is a diagram showing an example of the load current. Referring to FIG. 8, for example, when a load current having a power factor of 1 flows only in the T seat of Scott connection transformer 21, currents Iv, Iu, and Iw flow on the three-phase side as shown in FIG. That is, in the V phase, a current Iv having a power factor of 1 as viewed from the V phase voltage flows to the V phase. The current Iv is equally divided between the U phase and the W phase. That is, the magnitudes of U-phase current Iu and W-phase current Iw are ½ of the V-phase current. The U-phase current Iu is a lag phase when viewed from the U-phase voltage Vu, and the W-phase current Iw is a lead phase when viewed from the W-phase voltage. For this reason, a three-phase unbalanced current flows. When an unbalanced current flows, a large amount of current flows only in a certain phase, while the utilization rate of the power supply equipment decreases such that another phase has a margin. In addition, the negative phase power flows through the generator that sends the three-phase power, which causes a problem that the shaft of the generator causes torsional vibration and fatigue.

  FIG. 9 is a diagram showing the unbalanced current divided into a positive phase current and a negative phase current. (A) shows a positive phase current, and (B) shows a negative phase current. Referring to FIG. 9, V-phase current Iv is decomposed into positive-phase current Iv1 and reverse-phase current Iv2. Similarly, the U-phase current Iu is decomposed into a positive-phase current Iu1 and a reverse-phase current Iu2. W-phase current Iw is decomposed into positive-phase current Iw1 and reverse-phase current Iw2.

  In the V phase, the phases of the positive phase current Iv1 and the negative phase current Iv2 are the same. In the U phase and the W phase, the direction of the positive phase current vector and the direction of the negative phase current vector are different. The direction of the vector of the positive phase current Iu1 is the same as the vector of the U phase voltage Vu (vector of the direction from O to U). On the other hand, the reverse-phase current Iu2 is advanced in phase by 120 ° when viewed from the U-phase voltage Vu. The direction of the vector of the positive phase current Iw1 is the same as the vector of the W phase voltage Vw (vector of the direction from O to W), but the reverse phase current Iw2 has a 120 ° phase when viewed from the vector of the W phase voltage Vw. Running late.

  The positive phase power is supplied from the original power source. The reverse phase power does not become active power but becomes reactive power. Since this reactive power causes the above problem, it is necessary to compensate for this reactive power. Therefore, an unbalance compensator is connected to the three-phase AC power source 1 in parallel with the unbalanced load 2. When the unbalance compensator compensates the negative phase current due to the load, only the positive phase power flows when viewed from the three-phase AC power source 1.

  FIG. 10 is a diagram showing the reverse phase current Iv2 shown in FIG. 9B divided into two current vectors. Referring to FIG. 10, reverse phase current Iv2 is divided into current vector Iv2uv and Iv2vw. Since the current vector Iv2uv has the same magnitude as the reverse phase current vector Iu2 and the directions are opposite to each other, the sum of these current vectors becomes zero. Similarly, the current vector Iv2vw has the same magnitude as that of the reverse-phase current vector Iw2 and the directions thereof are opposite to each other, so that when these current vectors are added, they become zero.

  The current vector Iv2uv and the negative phase current vector Iu2 are orthogonal to the UV phase line voltage Vuv. For this reason, when viewed from the line voltage Vuv, the current vector Iv2uv and the reverse phase current Iu2 become single-phase reactive power. Similarly, since current vector Iv2vw and reverse phase power Iw2 are orthogonal to the VW phase line voltage, when viewed from line voltage Vvw, current vector Iv2vw and reverse phase current Iw2 are single-phase reactive power. In other words, by disposing a reactive current generating source capable of flowing the currents Iv2uv and Iu2 in the UV phase line voltage and similarly arranging a reactive power generating source capable of flowing the currents Iv2vw and Iw2 in the VW phase line voltage. Thus, it is possible to compensate for the reverse phase currents Iu2, Iv2, and Iw2. Thereby, it can suppress that a negative phase electric current flows into the three-phase alternating current power supply 1 side.

  Returning to FIG. 7, the capacitor 91 is a capacitor that advances between UV rays and supplies reactive power. The high impedance transformer 92 and the thyristor power converter 93 constitute a thyristor-controlled reactor that turns on and off the secondary terminal of the high impedance transformer 92 to supply delayed reactive power. When the thyristor power converter 93 is turned off by the capacitor 91 and the thyristor-controlled reactor (92, 93), the advance reactive power by the capacitor 91 flows between the UV rays. On the other hand, when the thyristor is turned on, reactive power by the high-impedance transformer 92 flows, canceling forward reactive power by the capacitor 91 and flowing delayed reactive power between the UV rays. By controlling the timing by turning the thyristor on and off during one AC cycle, it is possible to continuously control from the reactive power that is flowing between the UV rays to the delayed reactive power. Similarly, the reactive power flowing between the VW lines can be continuously controlled from the advanced reactive power to the delayed reactive power by the capacitor 94, the high impedance transformer 95, and the thyristor power converter 96.

  Therefore, when a load current as shown in FIG. 8 flows, the thyristor power converter 93 is controlled so that the current vector Iu2 in the opposite phase component (see FIG. 9B) flows between the UV rays, and the current vector When the thyristor power converter 96 is controlled so that Iw2 flows between the VW lines, a current Iv2 obtained by synthesizing the current vector Iv2uv and the current vector Iv2vw can be supplied to the V phase. That is, since the negative phase currents Iu2, Iv2, and Iw2 flow, only the positive phase currents Iu1, Iv1, and Iw1 flow on the three-phase AC power supply 1 side, and the negative phase power compensation is achieved.

“Railway and Electrical Technology” August 1996, VOL. 7 No. 8 “Application and Maintenance of Power Electronics (6) Static Unbalanced Power Compensator (SUC)”

  The conventional power conversion device is configured as described above, and by disposing the single-phase reactive power compensator between the line voltage UV phase and the line voltage VW phase, the negative phase power generated by the load is compensated. It was. However, a load current having a power factor different from 1 flows depending on the L component of the transmission line. Therefore, there arises a problem that all the negative phase power cannot be compensated.

  That is, the conventional power conversion apparatus is effective for a load in which the negative phase power vector is orthogonal to the line voltage UV phase and the VW phase as shown in FIG. 8, but the direction of the load current vector is different. That is, there is a problem that all the negative phase power cannot be compensated for a load having a power factor different from 1.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an unbalance compensator that can compensate for reverse phase power regardless of the power factor of the load current.

An unbalance compensator according to the present invention is connected to a three-phase power supply system that supplies power to a load from a three-phase AC power source through first to third wirings, and flows to the first to third wirings. This is an unbalance compensator that compensates for a balanced current. The imbalance compensation device includes a first to third primary-side terminal for receiving three-phase AC voltage, and first and second secondary terminals receiving the two single-phase AC voltage, first to 3 of the primary-side terminal and the first to third Scott connection transformer that will be connected to the wiring, their AC output terminal connected to the first and second secondary-side terminal, its these DC By controlling the currents of the first and second single-phase inverters whose input terminals are connected to each other and the first and second single-phase inverters, the first to third currents flowing in the first to third wirings, respectively. And a control circuit for adjusting a compensation current for compensating the negative phase current of the control circuit.

  According to the present invention, reverse phase power can be compensated regardless of the power factor of the load current.

It is a schematic block diagram of the unbalance compensation apparatus which concerns on embodiment of this invention. 4 is a vector diagram of the reverse phase currents Iu2, Iv2, Iw2 and the secondary side M phase and T phase of the Scott connection transformer 3. FIG. It is a vector diagram showing a load current when the power factor changes from 1. FIG. 4 is a vector diagram showing a normal phase component and a negative phase component of the load current shown in FIG. 3. It is the figure which showed the reverse phase electric current Iv2 shown in FIG.4 (B) with two electric current vectors. It is the exploded view which showed the reverse phase current shown to FIG. 4 (B) in the M phase and the T phase. It is a figure which shows the structure of the conventional power converter device based on the structure disclosed by the nonpatent literature 1. It is the figure which showed an example of load current. It is the figure which divided and expressed the unbalanced current into the positive phase current and the negative phase current. FIG. 10 is a diagram showing the reverse phase current Iv2 shown in FIG. 9B divided into two current vectors.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram of an unbalance compensator according to an embodiment of the present invention. Referring to FIG. 1, the unbalance compensation device is connected to a three-phase power supply system that supplies power from a three-phase AC power source 1 to an unbalanced load 2. The unbalance compensator 100 compensates for an unbalanced current caused by the unbalanced load 2. The unbalanced load 2 includes a Scott connection transformer 21 and single-phase loads 22 and 23. The single-phase loads 22 and 23 are trains, for example, and each consumes power independently.

  The unbalance compensation device 100 includes a Scott connection transformer 3, single-phase inverters 31 and 32, and a control circuit 6. The Scott connection transformer 3 converts the three-phase alternating current from the three-phase alternating current power source 1 into two single-phase alternating currents. The Scott connection transformer 3 is connected to single-phase inverters 31 and 32 whose DC sides are connected to each other. Single-phase inverters 31 and 32 are self-excited inverters. The single-phase inverters 31 and 32 allow electric power to be exchanged from the T seat to the M seat or from the M seat to the T seat of the Scott connection transformer 3. Since the single-phase inverters 31 and 32 are self-excited inverters, reactive power can be compensated for in each phase.

  The control circuit 6 adjusts the compensation current for compensating for the negative phase component of the load current by controlling the current of the single-phase inverters 31 and 32. The compensation current is adjusted based on, for example, detection values of the U-phase current sensor 41, the V-phase current sensor 42, the UV line voltage sensor 51, and the VW line voltage sensor 52.

  Next, the operation of the unbalance compensation apparatus 100 according to the embodiment of the present invention will be described in the case of a load current similar to the load current shown in FIG.

  FIG. 2 is a vector diagram of the reverse phase currents Iu2, Iv2, Iw2 and the secondary side M phase and T phase of the Scott connection transformer 3. Referring to FIG. 2, when viewed from the T phase of the Scott connection transformer 3, the reverse phase current Iv <b> 2 of the V phase is the same phase as the T phase and is in the same direction. That is, active power is consumed on the T-phase voltage axis.

  The reverse phase current Iu2 is decomposed into a current component Iu2m parallel to the UW phase line voltage, that is, the M phase voltage, and a component Iu2v orthogonal to the M phase voltage. Similarly, the reverse phase current Iw2 is also decomposed into a UW phase line voltage, that is, a component Iw2m parallel to the M phase voltage and a component Iw2v orthogonal to the M phase voltage. The U-phase current component Iu2v and the W-phase current component Iw2v orthogonal to the M-phase voltage are components that the V-phase reverse-phase current Iv2 is shunted through the U-phase and the W-phase. The U-phase current component Iu2m flows in the direction opposite to the direction of the UW line voltage, and the W-phase current component Iw2m flows in the direction opposite to the direction of the WU line voltage, thereby regenerating active power.

  That is, the V phase consumes power, but the U phase and W phase regenerate power. Overall, the amount of power consumed and the amount of power regenerated are balanced. Therefore, the control circuit 6 takes out electric power from the M phase by the single phase inverter 31 connected to the M phase among the single phase inverters 31 and 32 so that the electric power is supplied from the single phase inverter 32 to the T phase. The current flowing through the single-phase inverters 31 and 32 is adjusted. The electric power taken out by the single-phase inverter 31 is sent to the single-phase inverter 32 via the direct current side, and the single-phase inverter 32 supplies the electric power to the T-phase. In this case, since the V-phase current Iv2 flows in the same direction as the T-phase current IT, power is consumed in the T-phase. The same power (= IM × VM) as the consumed power (= IT × VT) is regenerated (consolidated) from the M phase.

  Therefore, according to the embodiment of the present invention, since the unbalance compensation device 100 can supply power corresponding to the negative phase power of the load, the negative phase power compensation can be achieved.

  The U-phase current component Iu2v and the W-phase current component Iw2v that are orthogonal to the M-phase voltage are the reverse-phase current that flows in the V-phase because the reverse-phase current Iv2 that flows in the V-phase is divided into the U-phase and the W-phase. Can be compensated by compensating for

  Furthermore, according to the embodiment of the present invention, it is possible to compensate the negative phase power even for an unbalanced load whose power factor has changed as compared with the case shown in FIG. FIG. 3 is a vector diagram showing the load current when the power factor changes from 1.

  Referring to FIG. 3, current vector Iv is inclined from the direction of voltage Vv (the direction from O to V). Similarly, the currents Iu and Iw are inclined in the direction opposite to the current Iv from the direction shown in FIG.

  FIG. 4 is a vector diagram showing a normal phase component and a negative phase component of the load current shown in FIG. (A) shows the positive phase component of the load current shown in FIG. (B) shows the negative phase component of the load current shown in FIG. FIG. 5 is a diagram showing the reverse phase current Iv2 shown in FIG. 4B with two current vectors. First, as shown in FIG. 5, the reverse-phase current Iv2 can be expressed by two current vectors Iv2uv and Iv2vw. However, the current vector Iv2uv is not orthogonal to the line voltage Vuv between the UV phases. For this reason, in the conventional technology, only the component orthogonal to the reverse phase current Iu2 when viewed from the line voltage between the UV phases can be compensated. The same applies to the reverse phase current Iw2.

  Referring to FIG. 4, positive phase currents Iu1, Iv1, Iw1 are tilted from the direction shown in FIG. The positive phase component flows as it is.

  FIG. 6 is an exploded view showing the reverse-phase current shown in FIG. 4B in the M-phase and the T-phase. Referring to FIGS. 4 and 6, the current to be compensated for in the T phase is a V phase reverse phase current Iv2. On the other hand, the currents to be compensated for in the M phase are the currents Iu2m and Iw2m obtained by subtracting the U-phase inflows Iu2v and Iw2v of the V-phase reverse-phase current Iv2 from the U-phase reverse-phase current Iu2 and W-phase reverse-phase current Iw2, respectively. It is. The current vectors Iu2v and Iw2v have a magnitude that is ½ of the magnitude of the reverse phase current Iv2, and the direction thereof is opposite to the direction of the vector of the reverse phase current Iv2. The current vectors Iu2v and Iw2v are components that are inevitably generated when the reverse-phase current Iv2 flows. That is, by compensating Iv2, the current vectors Iu2v and Iw2v are compensated (removed).

  Therefore, the currents Iu2m and Iw2m are to be compensated for in the M phase. When viewed from the M phase, these become the M phase current IM. As a result, the phase of the M-phase current IT and the T-phase current IM is always shifted by 90 °. The magnitudes of the M-phase current IT and the T-phase current IM are the same.

  The T-phase current is decomposed into an active power component parallel to the T-phase voltage and a reactive power component orthogonal to the T-phase voltage. Similarly, the M-phase current is decomposed into an active power component parallel to the M-phase voltage and a reactive power component orthogonal to the M-phase voltage. Here, the M-phase active power component is regenerative and the T-phase active power component is power running (consumption), and thus, by the single-phase inverter 31 connected to the M-phase of the Scott connection transformer 3 as in the above case. The electric power is taken out from the M phase, and the electric power is sent to the single phase inverter 32 through the direct current of the single phase inverters 31 and 32, and the electric power is supplied from the single phase inverter 32 to the T phase.

  That is, by interchanging power between the M phase and the T phase, it is possible to compensate for the M phase active power component and the T phase active power component among the antiphase power components. Moreover, since the single-phase inverters 31 and 32 are self-excited inverters, the M-phase reactive power component and the T-phase reactive power component can also be compensated. As a result, it is possible to compensate for negative phase power. Furthermore, even if the phase of the reverse-phase current changes variously according to the power factor, the active power component can be compensated by accommodating power between the M phase and the T phase. Further, each of single-phase inverters 31 and 32 can compensate for the M-phase reactive power component and the T-phase reactive component.

  As described above, according to the present invention, two single-phase inverters connected to each other on the DC side are connected to the secondary-side (M-phase and T-phase) windings of the Scott connection transformer, and a three-phase load current is obtained. Are separated into an M-phase component and a T-phase component. Then, the currents of the M-phase and T-phase single-phase inverters (31, 32) are controlled according to the M-phase component and the T-phase component. As a result, the three-phase reverse phase current can be compensated.

  In the above embodiment, the reverse phase current of the load is decomposed into the M phase and the T phase to control the M phase and T phase inverters. However, since the M-phase component and the T-phase component of the reverse-phase current are orthogonal to each other and have the same magnitude, if one of the M-phase current and the T-phase current is detected, the phase is 90 °. The other current can be detected by shifting. Therefore, it is possible to control the current of the M-phase and T-phase single-phase inverters.

  Further, the M phase component and the T phase component of the negative phase current are orthogonal to each other and have the same magnitude, and the T phase current is in the same direction as the V phase negative phase current. Therefore, the T-phase current is calculated, and then the M-phase current is calculated by shifting the phase of the T-phase current by 90 °, and the currents of the M-phase and T-phase single-phase inverters according to the T-phase current and M-phase current. May be controlled. Thereby, the configuration of the control circuit can be simplified.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 Three-phase AC power supply, 2 Unbalanced load, 3,21 Scott connection transformer, 6 Control circuit, 8 Step-down transformer, 22, 23 Single-phase load, 31, 32 Single-phase inverter, 41 U-phase current sensor, 42 V Phase current sensor, 51 UV line voltage sensor, 52 VW line voltage sensor, 91,94 capacitor, 92,95 high impedance transformer, 93,96 thyristor power converter, 100 unbalance compensator.

Claims (4)

An unbalance compensator that is connected to a three-phase power supply system that supplies power from a three-phase AC power source to the load via the first to third wirings and compensates for the unbalanced current flowing through the first to third wirings. Because
The first to third primary-side terminal for receiving three-phase AC voltage, and a first and second secondary terminals receiving the two single-phase AC voltage, the first to third primary-side a Scott connection transformer terminal Ru is connected to the first to third wirings,
These AC output terminal connected to said first and second secondary-side terminal, its first and second single-phase inverters these DC input terminals are connected to each other,
A control circuit for adjusting a compensation current for compensating the first to third reverse-phase currents flowing in the first to third wirings by controlling the currents of the first and second single-phase inverters , respectively. An unbalance compensation device comprising: The unbalance compensation apparatus according to claim 1, wherein the control circuit calculates the compensation current by decomposing each of the first to third negative-phase currents into an M-phase component and a T-phase component.   The unbalance compensation apparatus according to claim 2, wherein the first and second single-phase inverters are self-excited inverters. And first and second current sensors for detecting currents flowing through the first and second wirings, respectively.
A first voltage sensor for detecting a voltage between the first and second wirings;
A second voltage sensor for detecting a voltage between the second and third wirings,
The control circuit controls currents of the first and second single-phase inverters based on detection results of the first and second current sensors and the first and second voltage sensors. The unbalance compensator according to any one of claims 3 to 4.

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