JP2005312108A - Excitation controller of synchronous machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the excitation controller of a synchronous machine in which damage on an overvoltage protector and deterioration of an AC circuit breaker can be prevented. <P>SOLUTION: An overvoltage protector 12 comprises a positive polarity overvoltage protection circuit 20 connected in parallel with a thyristor rectifier 16 and operating when the positive electrode side has an overvoltage in the plus direction, and a negative polarity overvoltage protection circuit 21 operating when the negative electrode side of the series circuit has an overvoltage in the plus direction. The positive polarity overvoltage protection circuit 20 and the negative polarity overvoltage protection circuit 21 comprise a series circuit of thyristors S1, S2 being tuned on when an overvoltage appears across the DC circuit and resistors R2, R3 for suppressing the applying voltage to the thyristors S1, S2, and gate trigger circuits 22, 23 for supplying a gate current continuously to the thyristors S1, S2 when an overvoltage appears across the DC circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an excitation control device for a synchronous machine that supplies a direct current to a field winding of the synchronous machine.

  A synchronous machine such as a synchronous generator or a synchronous motor is excited by supplying a direct current to a direct current circuit of a field winding by an excitation control device. Normally, the DC current supplied to the field winding is supplied by rectifying an AC excitation power source with, for example, a thyristor rectifier and blocking the field between the field winding and the thyristor rectifier to protect the field winding. A vessel is provided. Since this field breaker is a DC breaker and is large, in recent years, an AC breaker has been installed between the thyristor rectifier and the AC excitation power source instead of the DC breaker to reduce the size of the excitation control device. I try to plan.

  When an AC circuit breaker is used, an overvoltage protection device is provided in the DC circuit in order to protect the field winding from the field side overvoltage generated when the AC circuit breaker is opened. In other words, since the opening operation of the AC circuit breaker is performed mechanically, an arc is generated at the main pole of the AC circuit breaker during the opening operation, and this arc has almost no impedance in the field winding. Therefore, it acts to remarkably increase the impedance on the field side of the synchronous machine. Therefore, since the field side overvoltage is generated when the AC circuit breaker is opened, an overvoltage protection device is provided.

  As an excitation control device using an AC circuit breaker and having an overvoltage protection device, when the AC circuit breaker is opened, in order to appropriately suppress the field side overvoltage generated by the opening, the field side overvoltage is There is one in which an overvoltage protection device is operated at an early stage by an open command to an AC circuit breaker before the occurrence (see, for example, Patent Document 1).

  FIG. 18 is a circuit configuration diagram of a conventional synchronous machine excitation control device, and FIG. 19 is an operation explanatory diagram of an overvoltage protection device in the conventional synchronous machine excitation control device. An overvoltage protection device 12 is provided in a DC circuit that supplies a field current to the field winding 11 of the synchronous machine. A three-phase AC excitation power supply 13 is input to a thyristor rectifier 16 via an excitation transformer 14 and an AC circuit breaker 15, and the thyristor rectifier 16 operates by a gate signal from a gate pulse generator 17 to convert a three-phase AC to DC. To supply to the DC circuit.

  The overvoltage protection device 12 is responsible for the overvoltage protection of the DC circuit and the function of discharging the field current when the synchronous machine stops. In the DC circuit, normally, the positive electrode P has a positive voltage and the negative electrode N has a negative voltage. However, when the field current is discharged when the synchronous machine is stopped, the negative electrode N becomes a positive voltage and the positive voltage becomes a negative voltage. Will occur. Further, an arc generated when the AC circuit breaker 14 is opened causes an overvoltage in which the positive electrode P is a positive voltage and the negative electrode N is a negative voltage. Further, even during normal operation, an overvoltage occurs between the positive electrode P and the negative electrode N of the DC circuit due to some abnormality.

  The overvoltage protection device 12 suppresses an overvoltage generated between the positive electrode P and the negative electrode N of the DC circuit, and a solid line when an overvoltage is generated where the voltage of the positive electrode P is higher than the voltage of the negative electrode N (P> N direction). It operates in the direction indicated by the arrow, and when an overvoltage occurs where the voltage at the negative electrode N is higher than the voltage at the positive electrode P (P <N direction), the operation is performed in the direction indicated by the dashed arrow.

  The overvoltage is detected by the overvoltage break element 18, and the polarity of the overvoltage is determined by the diode bridge circuit 19. That is, the positive electrode P of the DC circuit and the diode bridge circuit 19 are connected via the diode D1 and the current suppression resistor R1, and are connected so that a gate signal is given from the diode bridge circuit 19 to the thyristor S1. Further, the negative electrode N of the DC circuit and the diode bridge circuit 19 are connected via a discharge resistor R2 and a diode D2, and are connected so that a gate signal is applied from the diode bridge circuit 19 to a thyristor S2 via a current suppression resistor R1. ing.

Now, as shown in FIG. 19, it is assumed that the voltage starts increasing in the P> N direction between the positive electrode P and the negative electrode N of the DC circuit at time t0. When the time t1 reaches a specific break voltage V _BO having an overvoltage break element 18, the direction of current solid arrow flows through the diode bridge circuit 19 and overvoltage break element 18 via the diode D1 and the current suppressing resistor R1, Furthermore, a current flows between the gate and the cathode of the thyristor S1 (hereinafter referred to as GK) and the normal path of the discharge resistor R2. Since a gate current flows through the thyristor S1, the thyristor S1 is electrically connected between the anode and the cathode (hereinafter referred to as AK). This conduction period is several μsec (Tw). Thereafter, the voltage between AKs becomes almost zero at time t2. Along with this, a voltage VR2 of the discharge resistor _R2 is generated.

On the other hand, when the voltage starts to abnormally large at P <N direction between the positive electrode P and a negative electrode N of the DC circuit reaches the specific break voltage V _BO having an overvoltage break element 18 at time t1, the discharge resistor A current flows in the direction of the diode bridge circuit 19 and the overvoltage break element 18 via R2 and the diode D2, and further a current flows in a normal path between the current suppression resistor R1 and GK of the thyristor S2. When a gate current is injected into the thyristor S2, the AK becomes conductive, and the voltage between the AKs becomes almost zero at time t2 after several μsec (Tw).

  Note that the P <N direction overvoltage protection circuit composed of the discharge resistor R2, the diode D2, the diode bridge circuit 19, the overvoltage break element 18, the current suppression resistor R1, and the diode D1 is a field for emergency stop of the synchronous machine. It is also used as a current discharge circuit.

In the case of an emergency stop of the synchronous machine, the AC circuit breaker 15 is cut off while a field current is flowing. At this time, since the field winding 11 of the synchronous machine has a large reactor L, the current cannot be instantaneously zero, and therefore, L between the PN of the DC circuit of the field winding 11 is L. A large voltage in the P <N direction is generated at di / dt. Therefore, the gap between the breaking contacts of the AC circuit breaker 15 cannot be cut off instantaneously but is connected by an arc. In this case, if a voltage higher than the break voltage V _BO of the overvoltage break element 18 is generated between P and N, the field current bypasses the route between the discharge resistor R2 and the thyristor S2 by the overvoltage protection operation, and the AC is cut off. The device 15 is shut off.
JP 2003-229398 A

  However, in such a conventional excitation control device, since the supply time Tw of the gate current to the thyristors S1 and S2 of the overvoltage protection device 12 is extremely short, the thyristors S1 and S2 may be broken, and the synchronous machine During an emergency stop, an excessive load is applied to the AC circuit breaker 15, and the life of the AC circuit breaker 15 may be greatly consumed or damaged.

That is, when the voltage between the positive electrode P and a negative electrode N of the DC circuit exceeds the break voltage V _BO of the overvoltage break element 18, thyristors S1, S2 is conductive in accordance with their polarity, substantially zero AK voltage is several μsec After that, most of the voltage between the positive electrode P and the negative electrode N of the DC circuit is loaded on the discharge resistor R2. Therefore, the time for the current to flow through the current suppressing resistor R1 is several μsec. For this reason, the thyristors S1 and S2 cannot be sufficiently diffused in the thyristors S1 and S2, and the current flows in a narrow range rather than the entire joint surface, and the thyristors S1 and S2 may be damaged by overheating of this portion.

When the AC circuit breaker 15 is urgently shut off in a state where a field current is flowing through the field winding 11 due to an emergency stop of the synchronous machine, the voltage generated between the breaking poles of the AC circuit breaker 15 is the overvoltage break element 18. The break voltage V _BO is exceeded and the P <N direction overvoltage protection circuit operates to expect the field current to be bypassed to the discharge resistor R2 and the thyristor S2, but the break voltage V _BO continues to operate. The voltage is much larger than the voltage that can be normally generated including the required transient time, and is larger than the voltage that can be easily generated between the breaking poles of the AC breaker 15. When a voltage larger than the break voltage V _BO is not generated between the breaker poles of the AC breaker 15, the breaker electrode is interrupted until the field current is gradually attenuated to a value that can be interrupted by the AC breaker 15 by connecting the breaker poles with an arc. Can not. In this case, the AC circuit breaker 15 greatly consumes its life or is worst damaged.

  An object of the present invention is to provide an excitation control device for a synchronous machine that can prevent damage to an overvoltage protection device and deterioration of an AC circuit breaker.

  An excitation control device for a synchronous machine of the present invention includes an overvoltage protection device in a DC circuit that supplies a field current to a field winding of the synchronous machine, and an AC excitation power input through an AC circuit breaker is a thyristor rectifier. In the synchronous machine excitation control device that converts to DC and supplies to the DC circuit, the overvoltage protection device is connected in parallel with the thyristor rectifier and operates when the positive side of the DC circuit becomes overvoltage in the positive direction. And a negative polarity overvoltage protection circuit that is connected in parallel with the thyristor rectifier and the positive polarity overvoltage protection circuit and that operates when the negative side of the series circuit becomes an overvoltage in the positive direction, the positive polarity overvoltage protection circuit and the negative polarity overvoltage protection circuit Is a series circuit of a thyristor that turns on when the voltage across the DC circuit becomes an overvoltage and a resistor that suppresses the voltage applied to the thyristor, Characterized in that it consists of a gate Torigga circuit supplies to continue gate current to the thyristor when an overvoltage across the DC circuit voltage across the road is applied occurs.

  Further, the excitation control device for a synchronous machine according to the present invention converts an AC excitation power input through an AC circuit breaker into a DC by a thyristor rectifier to a DC circuit that supplies a field current to the field winding of the synchronous machine. A thyristor rectifier that rectifies the three phases of the AC excitation power source by sequentially connecting the two arms and receiving the three phases of the AC excitation power source. A gate pulse generator that sequentially outputs a gate signal to two of the six arms of the rectifier, and the gate pulse generator 3 of the AC excitation power source that is applied to the thyristor rectifier by an external gate pulse stop signal. The gate pulse to two sets of four arms connected to any two phases of the phases is stopped, and conduction of the two arms connected to the remaining one phase is maintained.

  According to the present invention, the gate current is continuously supplied to the thyristor of the overvoltage protection device when an overvoltage occurs at both ends of the DC circuit of the field winding of the synchronous machine. Diffusion is performed properly and destruction of the thyristor of the overvoltage protection device can be prevented. In addition, when an AC circuit breaker shut-off command is issued, the pulse generator of the overvoltage prevention device supplies a continuous pulse having a frequency several times larger than the frequency of the AC excitation power source to the thyristor gate to intermittently turn on the thyristor. Therefore, when the AC circuit breaker is interrupted, the voltage generated between the interrupting poles can be lowered, and the arcs between the interrupting poles can be prevented. Further, when the AC circuit breaker is instructed to shut off, the arm connected to the two phases of the thyristor rectifier is made non-conductive, and the two arms connected to the remaining one phase are kept conductive. The voltage generated between the breaking poles can be lowered, and the breaking poles can be prevented from being connected by an arc.

  Embodiments of the present invention will be described below. FIG. 1 is a circuit configuration diagram of an excitation control device for a synchronous machine according to the first embodiment of the present invention, and FIG. 2 is a diagram of an overvoltage protection device in the excitation control device for the synchronous machine according to the first embodiment of the present invention. It is operation | movement explanatory drawing. In FIG. 1, a three-phase AC excitation power supply 13 is input to a thyristor rectifier 16 via an excitation transformer 14 and an AC circuit breaker 15, and the thyristor rectifier 16 operates by a gate signal from a gate pulse generator 17 and operates as a three-phase AC. Is converted to a direct current and supplied to a DC circuit for supplying a field current to the field winding 11 of the synchronous machine. As the AC circuit breaker 15, an air circuit breaker ACB or a vacuum circuit breaker VCB is used.

  The overvoltage protection device 12 is connected in parallel to the thyristor rectifier 16 to a DC circuit that supplies a field current, and operates when a positive side of the DC circuit becomes overvoltage in the positive direction, and a series circuit It comprises a negative polarity overvoltage protection circuit 21 that operates when the negative side becomes an overvoltage in the positive direction.

  The positive overvoltage protection circuit 20 includes a series circuit of a thyristor S1 that is turned on when the voltage across the positive electrode P and the negative electrode N of the DC circuit becomes an overvoltage, and a resistor R3 that suppresses the voltage applied to the thyristor S1. A gate trigger circuit 22 that is connected and continuously supplies a gate current to the thyristor S1 when an overvoltage occurs at both ends of the DC circuit is connected via a diode D2 for reverse overvoltage protection between the gate and the cathode of the thyristor S1. Connected to both ends of the DC circuit.

  Similarly, the negative overvoltage protection circuit 21 also has a thyristor S2 that turns on when the voltage across the positive electrode P and negative electrode N of the DC circuit becomes an overvoltage, and a resistor R2 that suppresses the voltage applied to the thyristor S2. In addition, a gate trigger circuit 23 that continuously supplies a gate current to the thyristor S2 when an overvoltage is generated at both ends of the DC circuit is connected to a reverse overvoltage protection between the gate and the cathode of the thyristor S2. It is connected to both ends of the DC circuit via a diode D1.

  Further, the gate trigger circuits 22 and 23 are formed of series circuits of reverse blocking diodes D3 and D4, current suppression resistors R4 and R5, and overvoltage break elements B1 and B2, respectively. The positive overvoltage protection circuit 20 and the negative overvoltage protection circuit 21 are formed independently without supplying circuit elements.

Now, as shown in FIG. 2, at time t0, the voltage starts to increase between the positive electrode P and the negative electrode N of the DC circuit in the direction of P> N. In this case, the positive overvoltage protection circuit 20 of the overvoltage protection device 12 operates. In other words, reaches the specific break voltage V _BO voltage having an overvoltage break element B1 gate Torigga circuit 22 at time t1 between the positive electrode P and a negative electrode N of the DC circuit, through the current suppressing resistor R4, the diode D3 A gate current flows between GK of the thyristor S1, and AK of the thyristor S1 becomes conductive.

In this case, the voltage between the AKs of the thyristor S1 becomes substantially zero at time t2 after several μsec (Tw), but the voltage of the series circuit of the thyristor S1 and the resistor R3 is caused by the resistor R3 to the positive electrode P and the negative electrode N of the DC circuit. It is maintained in the voltage _{V PN} between PN. In addition, the voltage V _PN between the positive electrode P and the negative electrode N of the DC circuit continues in the gate current supply circuit configured between the GK of the overvoltage break element B1, the current suppressing resistor R4, the diode D3, and the thyristor S1. A sufficient gate current is continuously injected into the thyristor S1. Therefore, the thyristor S1 is sufficiently diffused in electric charge, and the current flows on the entire junction surface on average, and the possibility of damage due to partial overheating is eliminated.

  On the other hand, when the voltage is abnormally increased in the P <N direction between the positive electrode P and the negative electrode N of the DC circuit, the same operation is performed, and the thyristor S2 is not likely to be damaged due to partial overheating.

  Although the case where the AC circuit breaker 15 is provided between the excitation transformer 14 and the thyristor rectifier 16 has been described above, the AC circuit breaker 15 is provided between the three-phase AC excitation power supply 13 and the excitation transformer 14. May be provided. Preferably, the AC circuit breaker 15 provided between the excitation transformer 14 and the thyristor rectifier 16 is an air circuit breaker ACB, and the AC circuit breaker 15 provided between the three-phase AC excitation power supply 13 and the excitation transformer 14 is The vacuum circuit breaker VCB.

  According to the first embodiment, the positive polarity overvoltage protection circuit 20 and the negative polarity overvoltage protection circuit 21 of the overvoltage protection device 12 are formed independently without supplying circuit elements, and the field windings of the synchronous machine are formed. When an overvoltage occurs at both ends of the DC circuit, the positive polarity overvoltage protection circuit 20 and the negative polarity overvoltage protection circuit 21 of the overvoltage protection device 12 each independently supply a gate current to the thyristors S1 and S2. Therefore, the charge diffusion is appropriately performed in the thyristors S1 and S2 of the overvoltage protection device 12, and the destruction of the thyristors S1 and S2 of the overvoltage protection device 12 can be prevented.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a circuit configuration diagram of an excitation control device for a synchronous machine according to the second embodiment of the present invention. In the second embodiment, a continuous pulse generator 24 is added to the negative polarity overvoltage protection circuit 21 of the overvoltage protection device 12 with respect to the first embodiment shown in FIG. The same elements as those in the first embodiment shown in FIG.

The continuous pulse generator 24 supplies a continuous pulse having a frequency several times larger than the frequency of the AC excitation power supply 13 to the gate of the thyristor S2 when the AC breaker 15 is instructed to cut off, thereby turning on the thyristor S2 intermittently. . That is, as shown in FIG. 4, the continuous pulse generator 24 outputs a continuous pulse between the gate and the cathode of the thyristor S2 when there is a cutoff command output to the AC circuit breaker 15 to stop the synchronous machine. Apply. Thereby, the thyristor S2 can be turned on before the voltage generated between the positive electrode P and the negative electrode N of the DC circuit becomes the break voltage V _BO of the overvoltage break element B2 of the gate trigger circuit 23, and the positive electrode of the DC circuit An overvoltage generated between P and the negative electrode N is prevented.

  FIG. 5 is a characteristic diagram of the input / output voltage of the thyristor rectifier 16 when the continuous pulse generator 24 is not provided, and FIG. 6 is a thyristor according to the second embodiment of the present invention in which the continuous pulse generator 24 is provided. 6 is a characteristic diagram of input / output voltages of the rectifier 16. FIG.

  When stopping the synchronous machine, a cutoff command is output to the AC circuit breaker 15 and a gate pulse stop command is output to the thyristor rectifier 16. There is a time delay after the interruption command to the AC circuit breaker 15 is output until the AC circuit breaker 15 actually starts the interruption. Similarly, after the gate pulse stop instruction to the thyristor rectifier 16 is output. Actually, there is a time delay until the thyristor rectifier 16 stops generating the gate pulse.

  When the AC circuit breaker is interrupted without the continuous pulse generator 24, the characteristics shown in FIG. 5 are obtained. In FIG. 5, it is assumed that the generation of the gate pulse is actually stopped at time t0 and the AC circuit breaker 15 actually starts breaking at time t1. In this case, as the generation of the gate pulse is stopped, the DC voltage that is the output of the thyristor rectifier 16 becomes a single-phase AC voltage through the two arms of the thyristor rectifier 16 that has been conducted before the gate pulse is stopped, and is several Negative voltage within msec. And even if the AC circuit breaker 15 starts breaking at time t1, it cannot be easily broken because it is the field winding 11 of the synchronous machine having a large reactor.

On the DC circuit side that is the load side, a large negative voltage is generated at L · di / dt because the current tends to decrease. Accordingly, a state in which a large voltage is applied between the breaker poles of the AC breaker 15 while being connected by an arc continues. When the voltage across the DC circuit becomes equal to or higher than the break voltage V _BO of the gate trigger circuit 21 at time t2, the thyristor S2 is finally turned on to form a field current discharge bypass, and the output of the thyristor rectifier 16 When the voltage becomes small, the AC circuit breaker 15 is cut off.

The break voltage V _BO of the gate trigger circuit 21 takes into consideration the difference between the effective value and the instantaneous value, commutation surge at the time of arm commutation, short-time allowable overvoltage of the synchronous machine, variation of the overvoltage break element B2, etc. The voltage is set to be considerably larger than the AC voltage effective value. Therefore, while the voltage across the DC circuit becomes equal to or higher than the break voltage V _BO of the gate trigger circuit 21, the breaking electrode contact of the AC circuit breaker 15 is severely worn.

Therefore, in the second embodiment, the continuous pulse generator 24 is provided, and when there is a cutoff command output to the AC circuit breaker 15, a continuous pulse is applied between the gate and the cathode of the thyristor S2, and the thyristor S2 intermittently to conduct, thereby turning on the positive electrode P and a previously thyristor S2, will break the voltage V _BO of the overvoltage break element B2 gate Torigga circuit 23 is a voltage generated between the negative electrode N of the DC circuit.

  In FIG. 6, when there is a cutoff command to the AC breaker 15 at time t0, the continuous pulse generator 24 generates a pulse and applies a continuous pulse between the gate and the cathode of the thyristor S2. As a result, the thyristor S2 is intermittently conducted.

  Then, when the gate pulse of the thyristor rectifier 16 stops at time t1 and the DC circuit shifts to a negative voltage, since the continuous pulse is applied to the thyristor S2, the thyristor S2 is immediately turned on and the field current discharge bypass path Can do. Therefore, when the AC circuit breaker 15 starts breaking at time t2, the voltage across the DC circuit has a small value, so that the AC circuit breaker 15 is easily cut off and the contact life of the contact of the breaker pole is reduced. There is no burden that can be consumed greatly.

  Although the case where the AC circuit breaker 15 is provided between the excitation transformer 14 and the thyristor rectifier 16 has been described above, the AC circuit breaker 15 is provided between the three-phase AC excitation power supply 13 and the excitation transformer 14. May be provided. Preferably, the AC circuit breaker 15 provided between the excitation transformer 14 and the thyristor rectifier 16 is an air circuit breaker ACB, and the AC circuit breaker 15 provided between the three-phase AC excitation power supply 13 and the excitation transformer 14 is The vacuum circuit breaker VCB.

  According to the second embodiment, the pulse generator of the overvoltage prevention device supplies a continuous pulse having a frequency several times larger than the frequency of the AC excitation power source to the thyristor gate when an AC circuit breaker cutoff command is issued. As the DC circuit shifts to a negative voltage, the thyristor S2 is immediately turned on, and the voltage generated between the breaking electrodes can be lowered when the AC circuit breaker is cut off. It is possible to prevent connection by arc.

  Next, a third embodiment of the present invention will be described. FIG. 7 is a circuit configuration diagram of the negative polarity overvoltage protection circuit 21 of the overvoltage protection device 12 in the excitation control device of the synchronous machine according to the third embodiment of the present invention. This third embodiment is different from the first embodiment shown in FIG. 1 in that a plurality of overvoltage break elements B21 to B2n are connected in series instead of the overvoltage break element B2 of the gate trigger circuit 23. An overvoltage break circuit 25 is provided. The same elements as those in the gate trigger circuit 23 of FIG.

In FIG. 7, an overvoltage break circuit 25 incorporated in the gate trigger circuit 23 is configured by connecting a plurality of overvoltage break elements B21 to B2n in series. Each overvoltage break elements B21~B2n has a specific break voltage _V BO21 _{~V BO2n,} total overall overvoltage break circuit 25 of the break voltage _V BO21 _{~V BO2n} of plural overvoltage break element B21~B2n Break voltage _VBO .

FIG. 8 is a characteristic diagram of voltage / current of the overvoltage break elements B21 to B2n. The voltage applied to the overvoltage break element B21~B2n is started with short operation Kosu break voltage V _BO, continues the short circuit condition if the current holding current I _H or more. Since the overvoltage break elements B21 to B2n having such current-voltage characteristics are connected in series, the break voltage V _{BO of the} entire overvoltage break circuit 25 is set to the break voltages V _{BO21 to} VBO of the plurality of overvoltage break elements B21 to _{B2n. This is} the sum of _BO2n . As the overvoltage break elements B21 to B2n, for example, Sidac (registered trademark) made by Shindengen Electric Industry Co., Ltd., which has a thyristor structure having two bidirectional terminals, is used.

The According to the third embodiment, by selecting the serial number of the overvoltage break elements B21~B2n commensurate with the break voltage V _BO required for overvoltage protector 12 of the excitation controller for a synchronous machine, the break voltage Can be set.

  Next, a fourth embodiment of the present invention will be described. FIG. 9 is a circuit configuration diagram of an excitation control device for a synchronous machine according to the fourth embodiment of the present invention. This fourth embodiment is different from the third embodiment shown in FIG. 7 in that the overvoltage break circuit 25 of the gate trigger circuit 23 includes one or more of a plurality of overvoltage break elements B21 to B2n. When the AC breaker 15 is instructed to shut off, the contact 26 is turned on to reduce the break voltage value of the overvoltage break circuit 23. The same elements as those in FIG. 1 and FIG.

  The overvoltage break circuit 23 of the reverse polarity overvoltage protection circuit 21 includes a series circuit of a plurality of overvoltage break elements B21 to B2n and a contact 26. The contact 26 is a plurality of overvoltage break elements B21 during a discharge operation at the time of field interruption. The operation of reducing the break voltage value of the entire overvoltage break circuit 23 is performed by bridging one or some of the plurality of overvoltage break elements B in .about.B2n.

FIG. 10 is a diagram for explaining the operation of the overvoltage break circuit 23. Before the time t0 when the interruption command to the AC circuit breaker 15 is output, the overvoltage protection operation is not caused by the bypass discharge of the field current due to the interruption of the AC circuit breaker 15, so the entire overvoltage break circuit 23 is The break voltage _VBO is set large. As a result, a protection operation against overvoltage during normal operation is performed. On the other hand, after the time point t0 when the interruption command to the AC circuit breaker 15 is output, the break voltage V _BO of the overvoltage break circuit 23 as a whole is set small in order to quickly eliminate the arc discharge of the AC circuit breaker 15. That is, the contact 26 is turned on to bridge one or some of the plurality of overvoltage break elements B21 to B2n, thereby reducing the break voltage V _{BO of the} entire overvoltage break circuit 23.

  Although the case where the AC circuit breaker 15 is provided between the excitation transformer 14 and the thyristor rectifier 16 has been described above, the AC circuit breaker 15 is provided between the three-phase AC excitation power supply 13 and the excitation transformer 14. May be provided. Preferably, the AC circuit breaker 15 provided between the excitation transformer 14 and the thyristor rectifier 16 is an air circuit breaker ACB, and the AC circuit breaker 15 provided between the three-phase AC excitation power supply 13 and the excitation transformer 14 is The vacuum circuit breaker VCB.

  According to the fourth embodiment, the overvoltage protection operation not caused by the bypass discharge of the field current due to the interruption of the AC breaker 15 and the overvoltage caused by the bypass discharge of the field current caused by the interruption of the AC breaker 15 Since the break voltage of the negative polarity overvoltage protection circuit 21 of the overvoltage protection device 12 is switched by the protection, it is possible to properly protect the overvoltage during normal operation, and arc discharge of the AC circuit breaker 15 when the AC circuit breaker 15 is cut off. Can be resolved quickly.

  Next, a fifth embodiment of the present invention will be described. FIG. 11 is a circuit configuration diagram of an excitation control device for a synchronous machine according to the fifth embodiment of the present invention. The fifth embodiment is different from the second embodiment shown in FIG. 3 in that the continuous pulse generator 24 has a timer circuit 27 for counting time from an external pulse generation start command a, and interrupts AC. When a shut-off command for the device 15 is received, supply of continuous pulses to the gate of the thyristor S2 is started with a time delay set in the timer circuit 27. The same elements as those in FIG. 3 are denoted by the same reference numerals, and redundant description is omitted.

  The continuous pulse generator 24 includes a timer 27 and a pulse generator 28. When a pulse generation start command a is received from the outside, the continuous pulse generator 24 generates a continuous pulse with a delay set by the timer 27.

  FIG. 12 is a characteristic diagram when the continuous pulse generator 24 does not have the timer 27, and shows a case where the generation of the continuous pulse is earlier than the stop of the gate pulse to the thyristor rectifier 16. In FIG. 12, time t0 is the time of the interruption command to the AC circuit breaker 15 and the gate pulse stop command to the thyristor rectifier 16, time t1 is the time when the thyristor rectifier 16 stops generating the gate pulse, and time t2 is the field current. The time point t3 is the time point when the AC circuit breaker 15 has started to break.

  When there is a cutoff command to the AC circuit breaker 15 and a gate pulse stop command to the thyristor rectifier 16 at time t0, the continuous pulse generator 24 generates a pulse and applies a continuous pulse between the gate and the cathode of the thyristor S2. . In this case, there is a possibility that the gate pulse is applied while the voltage applied to the anode and cathode of the thyristor S2 is negative during this period. Alternatively, there may be a state in which a gate pulse is applied in the forward direction and is once turned on, and then turned off again by a reverse voltage from the thyristor rectifier 16. If the secondary voltage of the excitation transformer 14 is very large, the occurrence of such a state may not be preferable for the thyristor S2.

  Therefore, the start of continuous pulse generation by the timer 27 of the continuous pulse generator 24 is set immediately after the gate pulse of the thyristor rectifier 16 is stopped. FIG. 13 is a characteristic diagram when the continuous pulse generator 24 has a timer 27. In FIG. 13, time t1 is the time when the thyristor rectifier 16 stops generating the gate pulse, time t2 is the time when the timer circuit 27 permits the output of the continuous pulse signal, and time t3 is the time when the AC circuit breaker 15 starts breaking. is there. By starting the continuous pulse generation immediately after the gate pulse of the thyristor rectifier 16 is stopped by the timer 27 of the continuous pulse generator 24, the thyristor S2 is surely turned on when it is in the forward direction to form a field current bypass circuit, Immediately thereafter, the AC circuit breaker 15 can be easily disconnected.

  Although the case where the AC circuit breaker 15 is provided between the excitation transformer 14 and the thyristor rectifier 16 has been described above, the AC circuit breaker 15 is provided between the three-phase AC excitation power supply 13 and the excitation transformer 14. May be provided. Preferably, the AC circuit breaker 15 provided between the excitation transformer 14 and the thyristor rectifier 16 is an air circuit breaker ACB, and the AC circuit breaker 15 provided between the three-phase AC excitation power supply 13 and the excitation transformer 14 is The vacuum circuit breaker VCB.

  According to the fifth embodiment, when the thyristor S2 in the discharge direction is ignited with a continuous pulse, the timer circuit 27 of the continuous pulse generator 24 sets the generation time of the continuous pulse to the thyristor rectifier 16 with better timing. Therefore, it is possible to prevent the gate pulse from being applied when the voltage applied to the anode and cathode of the thyristor S2 is negative. It is also possible to prevent a state in which the gate pulse is applied in the forward direction and once turned on, and then turned off again by the reverse voltage from the thyristor rectifier 16.

  Next, a sixth embodiment of the present invention will be described. FIG. 14 is a circuit configuration diagram of an excitation control device for a synchronous machine according to the sixth embodiment of the present invention. In the sixth embodiment, the AC / DC conversion thyristor rectifier 16 is used as a field current discharge bypass circuit when the field is cut off.

  The three-phase voltage of the AC excitation power supply 13 is input via an excitation transformer 14 and an AC circuit breaker 15 to a thyristor rectifier 16 configured by a 6-arm Gretz connection of UVW and XYZ. The thyristor rectifier 16 rectifies the three phases of the AC excitation power supply 13 by sequentially turning on two of the six arms of UVW and XYZ by the gate signal from the gate pulse generator 17.

  The gate pulse generator 17 is connected to two sets of four arms connected to any two phases of the three phases of the AC excitation power supply 13 applied to the thyristor rectifier 16 by an external gate pulse stop signal GR. , And the conduction of the two arms connected to the remaining one phase is maintained.

  That is, the gate pulse generator 17 includes a U arm pulse generator 17U, an X arm pulse generator 17X, a V arm pulse generator 17V, a Y arm pulse generator 17Y, a W arm pulse generator 17W, and a Z arm pulse generator 17Z. The gate pulse generation of two sets of arms connected to any two phases (for example, VY and WZ arms) can be stopped by an external gate pulse stop signal GR.

  FIG. 15 is a characteristic diagram of the voltage waveform of the thyristor rectifier 16 in the sixth embodiment of the present invention. If the AC circuit breaker 15 is interrupted at time t0, the gate pulse stop signal GR is output simultaneously with the interrupt command, and V and Y connected to the V phase and W phase of the AC input of the thyristor rectifier 16 are output. , The gate pulses to the W and Z arm thyristors are stopped. As a result, at time t1, the U arm and the X arm are conducted to form a field current discharging circuit. At this time, the breaking pole of the AC breaker 15 can be cut off.

  Although the case where the AC circuit breaker 15 is provided between the excitation transformer 14 and the thyristor rectifier 16 has been described above, the AC circuit breaker 15 is provided between the three-phase AC excitation power supply 13 and the excitation transformer 14. May be provided. Preferably, the AC circuit breaker 15 provided between the excitation transformer 14 and the thyristor rectifier 16 is an air circuit breaker ACB, and the AC circuit breaker 15 provided between the three-phase AC excitation power supply 13 and the excitation transformer 14 is The vacuum circuit breaker VCB.

  According to the sixth embodiment, the arm connected to the two phases of the thyristor rectifier is made non-conductive when the AC circuit breaker cutoff command is issued, and the conduction of the two arms connected to the remaining one phase is maintained. Therefore, it is possible to reduce the voltage generated between the breaking electrodes when the AC circuit breaker is broken, and to prevent the breaking electrodes from being connected by an arc.

  Next, a seventh embodiment of the present invention will be described. FIG. 16 is a circuit configuration diagram of an excitation control device for a synchronous machine according to the seventh embodiment of the present invention. The seventh embodiment is different from the sixth embodiment shown in FIG. 14 in that the gate pulse generator 17 receives the UVW and thyristor rectifier circuit 16 when an external gate pulse stop signal GR is input. Of the six arms of XYZ, the conduction of the two arms that are conducted next to the two arms that are in the conducting state is maintained, and the gate pulse to the other four arms is stopped.

  As shown in FIG. 16, the gate pulse generator 17 includes a U arm pulse generator 17U, an X arm pulse generator 17X, a V arm pulse generator 17V, a Y arm pulse generator 17Y, a W arm pulse generator 17W and a Z arm. It has a pulse generator 17Z and three gate pulse stop circuits GR1, GR2, GR3.

  The gate pulse stop circuit GR1 includes an OR circuit 29UX and an AND circuit 30UX. The U arm, the X arm, the W arm, and the AND gate are generated according to the AND condition between the U arm or X arm pulse generation and the external gate pulse stop signal GR. Stops Z-arm gate pulse generation.

  Similarly, the gate pulse stop circuit GR2 has an OR circuit 29VY and an AND circuit 30VY. Depending on the AND condition between the pulse generation of the V arm or the Y arm and the gate pulse stop signal GR from the outside, the V arm, the Y arm, Stops U-arm and X-arm gate pulse generation.

  The gate pulse stop circuit GR3 includes an OR circuit 29WZ and an AND circuit 30WZ. Depending on the AND condition between the W arm or Z arm pulse generation and the external gate pulse stop signal GR, the W arm, Z arm, V Stops the gate pulse generation of the arm and Y arm. Here, the OR circuit of the output pulses of UX, VY and WZ in the gate pulse stop circuits GR1, GR2 and GR3 has a timed function which continues until the next pulse is generated.

  FIG. 17 is a characteristic diagram of the voltage waveform of the thyristor rectifier 16 in the seventh embodiment of the present invention. If the AC breaker 15 is interrupted at time t0, the gate pulse stop signal GR is generated simultaneously with the interrupt command, and the timing is immediately after the generation of the V arm pulse, so that the positive electrode P side commutates from V to W. At that time, the pair of WZ is turned on to form a field current discharging circuit. At this time, the breaker pole of the AC breaker 15 can be easily cut off.

  Although the case where the AC circuit breaker 15 is provided between the excitation transformer 14 and the thyristor rectifier 16 has been described above, the AC circuit breaker 15 is provided between the three-phase AC excitation power supply 13 and the excitation transformer 14. May be provided. Preferably, the AC circuit breaker 15 provided between the excitation transformer 14 and the thyristor rectifier 16 is an air circuit breaker ACB, and the AC circuit breaker 15 provided between the three-phase AC excitation power supply 13 and the excitation transformer 14 is The vacuum circuit breaker VCB.

  According to the seventh embodiment, when an external gate pulse stop signal GR is input, two arms that are conductive next to two arms that are in the conductive state among the six arms of UVW and XYZ of the thyristor rectifier circuit 16 Since the gate pulse to the other 4 arms is stopped, the voltage generated between the breaking poles can be reduced when the AC breaker is cut off, and the breaking poles can be connected by an arc. Can be prevented.

The circuit block diagram of the excitation control apparatus of the synchronous machine concerning the 1st Embodiment of this invention. Operation | movement explanatory drawing of the overvoltage protection apparatus in the excitation control apparatus of the synchronous machine concerning the 1st Embodiment of this invention. The circuit block diagram of the excitation control apparatus of the synchronous machine concerning the 2nd Embodiment of this invention. The operation | movement explanatory drawing of the continuous pulse generator in the 2nd Embodiment of this invention. The characteristic diagram of the input-output voltage of a thyristor rectifier when not having the continuous pulse generator in the 2nd Embodiment of this invention. The characteristic diagram of the input-output voltage of a thyristor rectifier at the time of having the continuous pulse generator in the 2nd Embodiment of this invention. The circuit block diagram of the negative polarity overvoltage protection circuit 21 of the overvoltage protection apparatus in the excitation control apparatus of the synchronous machine concerning the 3rd Embodiment of this invention. The characteristic diagram of the voltage current of the overvoltage break element in the 3rd embodiment of the present invention. The circuit block diagram of the excitation control apparatus of the synchronous machine concerning the 4th Embodiment of this invention. Operation | movement explanatory drawing of the overvoltage break circuit in the 4th Embodiment of this invention. The circuit block diagram of the excitation control apparatus of the synchronous machine concerning the 5th Embodiment of this invention. The characteristic view in case the timer is not provided in the continuous pulse generator in the 5th Embodiment of this invention. The characteristic view in case the continuous pulse generator in the 5th Embodiment of this invention has a timer. The circuit block diagram of the excitation control apparatus of the synchronous machine concerning the 6th Embodiment of this invention. The characteristic figure of the voltage waveform of the thyristor rectifier in the 6th Embodiment of this invention. The circuit block diagram of the excitation control apparatus of the synchronous machine concerning the 7th Embodiment of this invention. The characteristic figure of the voltage waveform of the thyristor rectifier in the 7th Embodiment of this invention. The circuit block diagram of the excitation control apparatus of the conventional synchronous machine. Operation | movement explanatory drawing of the overvoltage protection apparatus in the excitation control apparatus of the conventional synchronous machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Field winding, 12 ... Overvoltage protection device, 13 ... AC excitation power supply, 14 ... Excitation transformer, 15 ... AC circuit breaker, 16 ... Thyristor rectifier, 17 ... Gate pulse generator, 18 ... Overvoltage break element, 19 DESCRIPTION OF SYMBOLS ... Diode bridge circuit, 20 ... Positive polarity overvoltage protection circuit, 21 ... Negative polarity overvoltage protection circuit, 22 ... Gate trigger circuit, 23 ... Gate trigger circuit, 24 ... Continuous pulse generator, 25 ... Overvoltage break circuit, 26 ... Contact, 27 ... Timer circuit, 28 ... Pulse generator, 29 ... OR circuit, 30 ... AND circuit

Claims (8)

A DC circuit that supplies a field current to the field winding of the synchronous machine is equipped with an overvoltage protection device, and an AC excitation power input through an AC circuit breaker is converted to DC by a thyristor rectifier and supplied to the DC circuit. In the excitation control device of the machine, the overvoltage protection device is connected in parallel with the thyristor rectifier and operates when a positive side of the DC circuit becomes an overvoltage in a positive direction, the thyristor rectifier and the thyristor rectifier A negative polarity overvoltage protection circuit connected in parallel with a positive polarity overvoltage protection circuit and operating when the negative side of the series circuit is overvoltage in the positive direction, the positive polarity overvoltage protection circuit and the negative polarity overvoltage protection circuit, A series circuit of a thyristor that turns on when the voltage across the DC circuit becomes an overvoltage and a resistor that suppresses the voltage applied to the thyristor And a gate trigger circuit that continuously supplies a gate current to the thyristor when a voltage is applied across the DC circuit and an overvoltage occurs across the DC circuit. Control device. In the negative overvoltage protection circuit, a series circuit of a thyristor that is turned on when a voltage across the DC circuit becomes an overvoltage and a resistor that suppresses a voltage applied to the thyristor, and a voltage across the DC circuit are applied. A gate trigger circuit that continuously supplies a gate current to the thyristor when an overvoltage occurs at both ends of the DC circuit, and a frequency several times larger than the frequency of the AC excitation power supply when the AC circuit breaker is instructed to shut down. 2. A synchronous machine excitation control apparatus according to claim 1, further comprising a continuous pulse generator for supplying a continuous pulse to the gate of the thyristor. The overvoltage break circuit incorporated in the gate trigger circuit for detecting that the voltage across the DC circuit is overvoltage is configured by connecting a plurality of overvoltage break elements in series. 3. An excitation control device for a synchronous machine according to 1 or 2. The gate trigger circuit has a contact for short-circuiting one or more of the plurality of overvoltage break elements of the overvoltage break circuit, and turns on the contact when the AC circuit breaker is instructed to shut down. 4. The synchronous machine excitation control device according to claim 3, wherein a break voltage value of the overvoltage break circuit is reduced. The continuous pulse generator has a timer circuit for counting time from an external pulse generation start command, and when there is a command to shut off the AC circuit breaker, a continuous pulse is sent to the thyristor with a time delay set in the timer circuit. 3. The excitation control device for a synchronous machine according to claim 2, wherein supply to the gate is started. In the excitation control device for a synchronous machine that supplies a DC circuit that supplies a field current to a field winding of the synchronous machine by converting an AC excitation power input via an AC circuit breaker into a direct current using a thyristor rectifier. A thyristor rectifier configured with 6-arm Gretz connection using three phases of the AC excitation power supply as input, and sequentially rectifying the three phases of the AC excitation power supply by conducting two arms sequentially, and two of the six arms of the thyristor rectifier A gate pulse generator that sequentially outputs a gate signal, and the gate pulse generator is one of the three phases of the AC excitation power source that is applied to the thyristor rectifier by an external gate pulse stop signal. Stopping the gate pulse to two sets of four arms connected to two phases and maintaining conduction of the two arms connected to the remaining one phase The control device. The gate pulse generator maintains the conduction of the two arms that are conducted next to the two arms that are in the conduction state among the six arms when an external gate pulse stop signal is input, and gates to the other four arms The excitation control device for a synchronous machine according to claim 6, wherein the pulse is stopped. 8. The excitation control apparatus for a synchronous machine according to claim 1, wherein the AC circuit breaker is an air circuit breaker or a vacuum circuit breaker.

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