JP4357556B2 - Switching controller for three-phase AC phase advance capacitor - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a switching control device for a three-phase AC phase advance capacitor, and in particular, a switching control device for a three-phase AC phase advance capacitor that connects high-speed capacitors suitable for improving the power factor of a three-phase AC generator at high speed. About.

  In a three-phase AC generator, the power factor reduction associated with reactive power must be improved. Conventionally, various reactive power compensations for generators have been proposed. A typical load device of a three-phase AC generator is a three-phase AC motor. To reduce or cancel the reactive power, it is possible to compensate for reactive power by providing a phase advance capacitor on the three-phase AC line. Are known.

JP 2006-109649 A JP 2006-311686 A

  The reactive power compensation described in Patent Document 1 determines the actual capacity of each phase-advancing capacitor based on the voltage and frequency of each line of a three-phase AC line flowing to a load device such as a three-phase AC motor, By controlling the phase of the energized current, the power factor accompanying the capacitance change of the phase advance capacitor is improved.

  The reactive power compensation described in Patent Literature 2 is turned on / off so that the capacity of the phase advance capacitor becomes appropriate according to the amount of reactive power by the induction motor, thereby improving the power factor.

  Both the reactive power compensation of Patent Document 1 and the reactive power compensation of Patent Document 2 contribute to the improvement of the power factor. However, if there is a time delay in connecting a phase advance capacitor having an appropriate capacity to each three-phase AC line, the effect of power factor improvement is delayed with the delay. None of the devices described in Patent Document 1 and Patent Document 2 deal with such high-speed connection of the phase advance capacitor.

  Generally, a switching control device for a three-phase AC phase advance capacitor is connected to or disconnected from a phase advance capacitor arranged in each phase line of the three-phase AC and each phase line and each phase advance capacitor. And a controller that sends an ON signal to each of the switch circuits. Each of the switch circuits includes a pair of thyristors connected in antiparallel, and is turned on and off by a zero crossing (so-called zero crossing) in which the voltage across the thyristor becomes zero.

  When the thyristor is shut off, the timing at which the thyristor current becomes zero differs for each phase line due to a phase shift in the three-phase phase line. Therefore, when the current of any phase line becomes zero, the thyristor on that phase line is turned off and cut off. At this time, since the current of the turned off phase line is advanced by 60 degrees from the voltage, 86% of the voltage peak value is applied to the phase advance capacitor. Further, current continues to flow in another phase line whose phase is delayed. Therefore, the capacitor of the phase line that has been turned off is further charged, resulting in a phenomenon that exceeds the peak value of the power supply voltage. Since the phase of the capacitor current is advanced by 90 degrees from the voltage, the capacitor current is turned off when charged to the maximum value of the power supply voltage. When a series reactor is inserted to prevent harmonics in this capacitor connection, the phase advance capacitor of the phase line that was initially turned off is charged to a voltage much higher than the power supply voltage, and it is between the cathode and anode of the thyristor. Is not zero level (ie, 0 volts) in a short time. Therefore, in the general zero-cross control system, the switch circuit is not turned on until the phase advance capacitor is discharged below the power supply voltage by a discharge reactor or the like, and the next quick connection operation cannot be achieved.

  An object of the present invention is to provide a switching control device for a three-phase AC phase advance capacitor that can connect the phase advance capacitor at high speed.

In order to achieve the above object, according to the present invention, a phase advance capacitor is arranged in each phase line of the three-phase alternating current, and at least two phase lines include each of the phase lines. A switch circuit is provided for connection or disconnection with the phase advance capacitor, and each of the switch circuits has a controller that sends an ON signal to put the switch circuit in a connected state. A phase capacitor switching control device, wherein each of the switch circuits includes a pair of thyristors connected in antiparallel, and each of the switch circuits detects a voltage across the thyristor; and In response to a signal from the detecting means, it is determined that the voltage is higher than zero level and lower than a predetermined value, and further, the voltage falls below the predetermined value. Means for determining an ascending point that turns from rising to rising, and a trigger signal that generates a trigger signal at the rising point and sends the trigger signal to the gate of the thyristor when the on signal is sent from the controller Generating means, wherein the determining means receives the signal from the detecting means, and determines that the voltage is lower than a predetermined value that is higher than the zero level but close to the zero level; And a voltage increase determination means for determining an increase point at which the voltage equal to or lower than the predetermined value decreases from the predetermined value to the increase. The voltage increase determination means changes from the state at which the voltage decreases below the predetermined value to the increase. When the ascending point is determined, an ascending point determination signal is sent to the trigger signal generating means, and the trigger signal generating means Generates a trigger signal to the thyristor sent to the thyristor, the voltage of the thyristor both ends to ON operation of the thyristor before the zero crossing, there is provided a switching control device, characterized in that.

  As described above, since the thyristor is turned on before the voltage across the thyristor crosses zero, the phase-advancing capacitor can be connected at high speed. Therefore, the effect of improving the power factor is not delayed.

In the above device, the phase advance capacitor is delta-connected to the three-phase AC line, and the two phase lines are connected to the connection point of the phase advance capacitor via the switch circuit, respectively. One phase line is directly connected to the connection point of the phase advance capacitor. The phase line of the three-phase AC is connected to each of the three-phase outputs of the three-phase AC generator, and a load device such as an electric motor is connected to the three-phase AC generator. A phase capacitor is used to offset or reduce reactive power associated with the load equipment connected to the generator to improve power factor.
The ON signal of the controller is an instruction signal for setting the switch circuit in a connected state, and the stop of the output of the ON signal is an instruction signal for setting the switch circuit in a cutoff state. ON signal of the controller, that has been entered in the trigger generation means. Before SL voltage rise judgment means judges, in order to prevent errors, multiple, an increase in the voltage.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments according to the present invention and reference embodiments for understanding the present invention will be described with reference to the drawings. In FIG. 1, a load device 2 such as an electric motor is connected to a three-phase AC generator 1. The phase advance capacitors 3, 4 and 5 are connected to the phase lines R, S and T of the three-phase AC of the three-phase AC generator in a delta connection form. Between the phase lines R, S, T and the phase advance capacitors 3, 4, 5, a three-phase AC phase advance capacitor switching control device 6 is provided. The switching control device 6 for a three-phase AC phase advance capacitor cancels or reduces the reactive power generated in the phase lines R, S, T of the three-phase AC, for example, with the operation of the load device 2 such as an electric motor. Capacitors 3, 4 and 5 are properly connected or the connection is cut off.

  The three-phase AC phase advance capacitor capacity switching control device 6 is provided between the connection points 7 and 9 of the phase advance capacitors 3, 4, 5 connected in delta to the two phase lines R and T for connection or disconnection. The first switch circuit 10 and the second switch 11, and the controller 12 that sends an ON signal to each of the switch circuits 10 and 11. Furthermore, the control device 6 includes a power measuring unit 13 that receives power and current from the power transformer PT and current transformer CT provided in the phase lines R, S, and T of the generator 1 and measures power and the like. The output of the power measuring unit 13 is input to the controller 12. The power measuring unit 13 measures power, current, voltage, and frequency in the three-phase AC phase lines R, S, and T. As shown in the figure, the first switch circuit 10 is provided in the phase line R, and the output of the first switch circuit 10 is connected to the connection point 7 of the phase advance capacitor. The second switch circuit 11 is provided in the phase line T, and the output of the second switch circuit 11 is connected to the phase advance capacitor connection point 9. The phase line S is not provided with a switch circuit, and the phase line S is directly connected to the connection point 8.

  The phase advance capacitors 3, 4, 5 are delta connected by connection points 7, 8, 9. Reactors (coils) 14 and 15 are provided in series on the input side of the connection points 7 and 9 in order to suppress rush currents and prevent harmonics. The resistor 16 provided in parallel between the connection points 7 and 8 and the resistor 17 provided in parallel between the connection points 8 and 9 are discharge resistors for the phase-advancing capacitors 3, 4, and 5. In general, it is built in a storage box (not shown) for the phase-advancing capacitors 3, 4, and 5.

  The controller 12 receives various signals after measurement of apparent power, reactive power, active power, current, voltage, frequency, and the like, measured by the power measuring unit 13. Note that reactive power is related to the control of the present invention. When the controller 12 receives the reactive power signal, the first switch circuit 10 and the second switch so as to effectively input the delta-connected phase advance capacitors 3, 4, and 5 to the phase lines R, S, and T. An ON signal is input to the circuit 11 via the line 18. The ON signal is a connection command, that is, a connection instruction signal for setting the switch circuit in a connected state, and the stop of the output of the ON signal is a disconnection command, that is, a disconnection instruction signal for setting the switch circuit in a disconnected state.

  The first switch circuit 10 and the second switch circuit 11 are each composed of the same circuit. Each switch circuit includes a pair of thyristors SCR1 and SCR2 connected in antiparallel. The thyristors SCR1 and SCR2 are turned on when a trigger signal (ON signal) is applied to the gate while a forward voltage is applied between the anode and the cathode, and the voltage between the anode and the cathode crosses the zero level and is reversed. It turns off when a directional voltage is applied. Since a three-phase AC voltage is applied between the phase lines R-S and T-S, the thyristors SCR1 and SCR2 connected in parallel in the reverse direction are alternately turned on if a trigger signal is input to the gate. As long as the trigger signal is in the on state, the switch circuit 10 or 11 remains on as a whole, and the phase lines R and S are connected to the cut points 7 and 9 of the phase advance capacitors 3 to 5, respectively. Is done.

  Here, the operation of a general zero-crossing type three-phase AC phase advance capacitor switching control apparatus will be described with reference to the apparatus of FIG. 1 and with reference to the waveform diagrams of FIGS. The power measurement unit 13 starts by measuring reactive power. Initially, since the phase advance capacitors 3 to 5 are not turned on, the power measuring unit 13 measures reactive power associated with the load device 2 connected to the generator 1. When the load device 2 is activated, reactive power is observed and the power measuring unit 13 sends a signal to the controller 12. From the controller 12, a corresponding ON signal for turning on the phase advance capacitors 3 to 5 is sent to the first switch circuit 10 and the second switch circuit 11. Accordingly, in order to improve the power factor, the phase-advancing capacitors 3 to 5 are connected to the phase lines R to T of the three-phase alternating current to try to reduce or cancel the reactive power.

  Next, when the connection of the connected phase advance capacitors 3 to 5 is to be interrupted, the ON signal is disconnected from the controller 12 to the first switch circuit 10 and the second switch circuit 11, which is a disconnect command. It becomes. For example, in the case of the first switch circuit FIG. 10, in the waveform diagram of FIG. 2A, when a disconnection command (stop of on signal) is output from the controller 12 to the thyristors SCR1 and SCR2 at time t0, the phase line R At the time when the R phase current of t1 becomes t1, the current becomes 0, and first, the thyristors SCR1 and SCR2 of the first switch circuit 10 connected to the phase line R are turned off (cut off). At this time, the R-S voltage on the phase advance capacitor side does not exceed the voltage on the power supply side, but the thyristors SCR1 and SCR2 of the second switch circuit 11 connected to the phase line T are still in the on (connected) state. Therefore, the phase advance capacitor side voltage rises exceeding the power supply side voltage. This increase continues in the waveform diagrams of FIGS. 2A and 2B until the thyristors SCR1 and SCR2 connected to the phase line T are turned off at the time t2, and at the time t2, the power supply side The voltage will be exceeded.

  Since the phase line R side is cut first, the phase line T side has a single-phase connection current waveform, and the R-S voltage on the phase advance capacitor side is the peak value of the R-S voltage on the power supply side. The fluctuation ends when the battery is charged. When all of the first switch circuit 10 and the second switch circuit 11 are turned off, the respective phase advance capacitors 3 to 5 are discharged by the built-in discharge resistors 16 and 17, but the discharge resistors 16 and 17 and the phase advance capacitors 3 to 3 are discharged. Since the time constant with 5 is about 1 minute, the R-S voltage on the phase advance capacitor side does not immediately become lower than the voltage on the power supply side. 3A to 3C, the R-S voltage on the power supply side (FIG. 3A), the R-S voltage on the phase advance capacitor side (FIG. 3B), and the thyristor The voltage between the anode and the cathode of SCR1 and SCR2 (= RS voltage on the power supply side−RS voltage on the phase advance capacitor side: (FIG. 3C)) is shown. As shown in FIG. 4, since the voltage between R and S on the phase advance capacitor side does not immediately become lower than the voltage on the power source side, the next time the controller 12 sends an ON signal (that is, a connection command) The voltage between the anode and cathode of the thyristor SCR1 (or SCR2) of the first switch circuit 10 connected to the phase line R does not become zero, and when the discharging means is only the resistor 16, the time of several tens of seconds or more elapses. If there is no voltage, the voltage between R and S on the phase advance capacitor side is less than the voltage on the power source side. The Nariezu, that period would not be connected by zero crossing (zero crossing) is.

It is the switching control device for a three-phase AC phase advance capacitor according to the present invention that eliminates the problems in the above-described zero-crossing type three-phase AC phase-advanced capacitor switching control device. In the present invention, without using a thyristor connected by zero crossing (cross), the voltage of the power supply side, below a certain value (but not at the zero level) when Tsu arrives, the trigger command in minimum value of the half-wave By sending out and causing the thyristor to perform the connection operation, the connection operation is performed at high speed.

  The switch circuit 10 (or 11) according to the present invention will be described with reference to FIGS. In FIG. 4, the switch circuit 10 (or 11) receives a voltage detection means 20 for detecting a voltage difference between both ends A and B of the pair of thyristors SCR1 and SCR2 cut in antiparallel, and a signal from the voltage detection means 20. The voltage level determination means 21 for determining that the voltages at both ends A and B are higher than the zero level and lower than the predetermined value, and the rise in which the voltages at both ends A and B are lowered from the predetermined value to rise. A voltage increase determination unit 22 for determining a point and a trigger signal generation unit 23 for generating a trigger signal at the determined increase point are provided. An ON signal output from the controller 12 (see FIG. 1) is sent to the trigger signal generation means 23. The trigger signal generation means 23 receives the rising point signal sent from the voltage rise determination means 22 and generates a trigger signal when the ON signal is sent from the controller 12 and sends the trigger signal to the lines 24 and 25. To the gates of thyristors SCR1 and SCR2. As a result, the thyristor SCR1 or SCR2 is turned on before the voltage across the thyristor crosses zero. The voltage level determination means 21, the voltage rise determination means 22, and the trigger signal generation means 23 may be configured as a single circuit by a processor such as an ASIC. Further, the voltage detection means 20 may be provided with an AD converter to convert an analog value into a digital value.

  The operation of the controller 12 and the switch circuit 10 (or 11) of FIG. 4 will be described with reference to FIG. In step S01, the controller 12 determines in accordance with the signal from the power measuring unit 13 whether the phase advance capacitors 3 to 5 should be connected to the phase lines R to T, that is, whether or not the on command should be issued. If the ON command should not be issued (No), in step S02, the ON signal is not output to the thyristor of the switch circuit (OFF command). When the ON command is to be issued (Yes), the voltage detection means 20 measures the voltages at both ends A and B of the thyristor in step S03. This voltage measurement value signal is sent to the voltage level determination means 21 to determine whether it is equal to or lower than a specified voltage (predetermined value) (step S04). The predetermined value of the specified voltage is set higher than the zero level. In the waveform diagram of the anode-cathode voltage of the thyristor in FIG. 3C, a voltage level V0 higher than 0 volts is selected. If it is not less than the specified voltage (No), the process returns to step S03 and the determination in step S04 is repeated. This determination is made by the voltage level determination means 21.

  When the voltage is less than the specified voltage (Yes), the measured values of the voltages at both ends A and B of the thyristor are read again (step S05), and the rising point at which the voltage starts to rise from the state where the voltage has dropped from the predetermined value is determined. (Steps S06 to S08). The rising point is indicated by a point P in the waveform diagram of FIG. If the voltage has not increased (No in step S06), the determination of the voltage increase is repeated as shown in step S09 (steps S05 and 06). Further, in order to avoid the determination in step S06 from malfunctioning, the increase determination is performed up to a specified number (step S07), and it is determined whether the number of increases is a specified value (step S08). If the number of rises has not reached the specified value (No), the process returns to step S05 to continue the determination. It is the voltage increase determination means 23 that determines the increase point.

  In step S08, when the number of rise determinations is a specified value (Yes), the trigger signal generation unit 23 generates a trigger signal and sends the trigger signal to the gates of the thyristors SCR1 and SCR2 via the lines 24 and 25 ( Step S10). The trigger signal is generated as an ON signal having a specified time width according to the period of the ON signal generated by the controller 12. Therefore, in step S11, the apparatus waits for the specified time of the ON signal. Thereafter, the ON signal is terminated, and the connection of the phase advance capacitors 3 to 5 is disconnected. In step S12, since the switch circuit 10 (or 11) is in the off state, it is determined whether or not the voltage between the both ends A and B of the thyristors SCR1 and SCR2 decreases. If the voltage has decreased (Yes), the operation is normal, and the process returns to the first step S01. If the voltage has not decreased (No), it is determined that there is a failure in step S13, and a failure indication of the circuit is displayed on, for example, a controller panel (not shown).

  As described above, in the embodiment of the present invention, by using the switch circuit of FIG. 4 and performing the operation of FIG. 5, the rising point P in the waveform diagram of FIG. 3C is found, and the thyristors SCR1 and SCR2 are detected. Before the anode-cathode voltage drops to zero volts, a trigger signal is generated to prevent delay in connection of the phase-advancing capacitors 3-5. Therefore, since the thyristor is turned on before the voltage across the thyristor crosses zero, the phase-advancing capacitor can be connected at high speed, and the effect of improving the power factor is not delayed.

It is a block diagram of a switching device for a three-phase AC phase advance capacitor. (A) is a current waveform diagram in each phase line at the time of disconnection command, (B) is a waveform diagram of the phase voltage on the phase advance capacitor side. (A) is a waveform diagram of the voltage between the phase lines R-S on the power supply side, (B) is a waveform diagram of the voltage between the phase lines R-S on the phase advance capacitor side when the switch is disconnected, and (C) is a switch disconnection. It is a waveform diagram of the voltage across the thyristor at the time. It is a block diagram of a 1st switch circuit or a 2nd switch circuit. 5 is a flowchart of the operation of the switch circuit of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase AC generator 2 Load apparatus 3-5 Phase advance capacitor 6 Three-phase AC phase advance capacitor switching device 7-9 Connection point 10 of phase advance capacitor 1st switch circuit 11 2nd switch circuit 12 Controller 13 Power measurement part 14, 15 Reactors 16, 17 Resistance 20 Voltage detection means 21 Voltage level determination means 22 Voltage rise determination means 23 Trigger signal generation means 26 Trigger signal generation section

Claims (9)

A phase advance capacitor is arranged in each phase line of the three-phase alternating current, and at least two phase lines are connected or disconnected between each of the phase lines and the phase advance capacitor. A switching circuit for a three-phase AC phase-advanced capacitor having a controller for sending an ON signal to each of the switch circuits to put the switch circuit in a connected state,
Each of the switch circuits includes a pair of thyristors connected in antiparallel,
Further, each of the switch circuits detects a voltage across the thyristor, and determines that the voltage is higher than a zero level and lower than a predetermined value in response to a signal from the detection means, Means for determining an ascending point when the voltage falls below the predetermined value and generating a trigger signal at the ascending point, and when the ON signal is sent from the controller, the gate of the thyristor Trigger signal generating means for sending the trigger signal to,
The determining means receives a signal from the detecting means, determines that the voltage is lower than a predetermined value that is higher than the zero level but close to the zero level, and a voltage level that is lower than the predetermined value. A voltage increase determination means for determining an increase point at which the voltage falls from the predetermined value to an increase; and when the voltage increase determination means determines an increase point at which the voltage decreases from the predetermined value The trigger signal generation means sends a rising point determination signal, and the trigger signal generation means generates a trigger signal to the thyristor upon receiving the rising point determination signal and sends the trigger signal to the thyristor. The thyristor is turned on before the zero crossing,
A switching control device.   2. The apparatus according to claim 1, wherein the phase advance capacitor is delta connected to the phase line of the three-phase alternating current, and each of the two phase lines is connected to the phase advance capacitor via the switch circuit. And the other phase line is directly connected to the connection point of the phase advance capacitor.   The apparatus according to claim 1 or 2, wherein the three-phase alternating current phase line is connected to each of the three-phase output lines of the three-phase alternating current generator, and the three-phase alternating current generator includes an electric motor or the like. A load device is connected, and the phase advance capacitor is used to improve the power factor by canceling or reducing the reactive power accompanying the load device connected to the generator. Device to do.   4. The device according to claim 1, wherein the ON signal of the controller is an instruction signal for setting the switch circuit in a connected state, and stopping the output of the ON signal interrupts the switch circuit. A device characterized by being an instruction signal for setting a state.   The apparatus according to claim 1, wherein an ON signal of the controller is input to the trigger generation unit. 6. The apparatus according to claim 1, wherein the voltage rise determination means determines the voltage rise a plurality of times and the number of times of the voltage rise is a predetermined value to prevent an error. A device characterized by determining whether or not 7. The apparatus according to claim 6, wherein the voltage increase determination unit sends the increase point determination signal to the trigger signal generation unit when it is determined that the number of times of the voltage increase has reached the specified value. A device characterized by. 8. The apparatus according to claim 6, wherein the on signal of the controller is input to the trigger signal generating unit, and the trigger signal generating unit determines the period of the on operation of the thyristor. A time width of a signal is determined by a period of the on signal. 9. The apparatus according to claim 8, wherein the controller determines whether or not a voltage across the thyristor decreases after the end of the time width of the trigger signal from the trigger signal generation unit. An apparatus characterized in that a failure is determined when there is no decrease in the number.

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