JPH0477560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation control device for a synchronous machine, and particularly to an excitation control device that calculates the deviation between the output voltage of the synchronous machine and a voltage setting value, and keeps the output voltage of the synchronous machine constant based on this deviation. The present invention relates to an excitation control device for a synchronous machine that supplies voltage to a field coil of the synchronous machine.

Conventional excitation control devices for synchronous machines of this type input the output voltage of the synchronous machine into a deviation signal amplifier, compare it with the voltage setting value set by the voltage setting device, calculate the deviation, and control the synchronous machine based on this deviation. A typical configuration is such that the output from an excitation voltage forming circuit that forms an excitation voltage such that the output voltage of the synchronous machine is constant is supplied to the field coil of the synchronous machine via a field switch or disconnector. be. Further, as is well known, the synchronous machine controlled by the excitation control device has its output circuit connected to the grid via an AC switch or disconnector.

By the way, the synchronous machine and the above-mentioned excitation control device are operated in such a manner that when the synchronous machine is stopped, the AC switch or disconnector of the output circuit of the synchronous machine is opened, and then the field is turned on or the disconnector is opened. However, in general, an AC switch or disconnector is placed as a high-voltage circuit device, whereas a field switch or disconnector is often installed as part of an excitation device near a synchronous machine, and the tripping power source for the switch or disconnector is It was often divided. For this reason, if the cable for the power supply, etc., is disconnected or, in the worst case scenario, the cable is burnt out, the field or disconnector cannot be opened, even if the AC or disconnector can be opened. A phenomenon occurred.

In such a case, when the synchronous machine is disconnected from the power grid, stopped, and its speed decreases, the automatic voltage adjustment function, which acts as the deviation signal amplifier, will work to control the output voltage of the synchronous machine to a constant level. This had the disadvantage of causing low-frequency overexcitation, which could damage the transformer connected to the synchronous machine output circuit.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, apply reverse conversion control of a thyristor exciter, reduce the field current of a synchronous machine, and prevent low-frequency overexcitation for a synchronous machine. To provide an excitation control device.

In order to achieve the above object, the present invention monitors the control voltage of the field generator and disconnector trip circuit, and reduces the control voltage of the field generator and disconnector trip circuit when the synchronous machine is disconnected from the power system. is detected, and based on the detection result, phase-back control of the excitation voltage forming circuit is performed to reduce the current in the synchronous machine field coil, thereby preventing low frequency overexcitation of the synchronous machine.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the overall configuration of a synchronous machine to which an embodiment of the excitation control device according to the present invention is applied.

In the figure, a synchronous machine 1 has its output circuit connected to a system 3 via an AC disconnector 2. The field coil 1L of this synchronous machine 1 is supplied with an output voltage 100 from an excitation voltage forming circuit 4 that forms an excitation voltage that makes the output voltage of the synchronous machine 1 constant via a field coil and disconnector 5. It is becoming more and more common. This excitation voltage forming circuit 4 has an output voltage 11 of the synchronous machine 1.
0 is taken into the deviation signal amplifier 7 via the voltage transformer 6 and compared with the voltage setting value 120 from the voltage setting device 8 to form a deviation signal 130 and supplied to the control circuit 9. This control circuit 9 is
During normal operation, the deviation signal 130 is supplied to the excitation voltage forming circuit 4, and in the event of an abnormality such as when the synchronous machine 1 is disconnected from the system 3, the control voltage of the trip circuit of the field switch and disconnector 5 is detected. This circuit performs phase-back control on the excitation voltage control device 4 based on this detection result, or when either one of the detection result and the activation of the synchronous trip interlock is satisfied. . The excitation voltage forming circuit 4 also receives a signal 14 from the control circuit 9.
a gate pulse phase shifter 10 that takes in 0 and forms a gate pulse signal 150, a thyristor exciter 11 that generates a predetermined excitation voltage 100 by the gate pulse signal 150 from the gate pulse phase shifter 10, and a synchronous machine 1. a control power transformer 13 to which the excitation power transformer 12 is connected; and a gate pulse phase shifter 1 that converts the power from the transformer 13 into DC.
0, and a power supply device 14 that supplies power to

The operation of the device having such a configuration will be briefly explained below.

The output voltage 100 of the excitation voltage forming circuit 4 is applied to the field coil 1L of the synchronous machine 1 connected to the system 3 via the AC shield breaker 2 through the field shield breaker 5. The output voltage of this excitation voltage forming circuit 4 is 100
In normal operation, the output voltage of the synchronous machine 1 is controlled by the deviation signal amplifier 7 and the gate pulse phase shifter 10 so as to be constant.

By the way, in the first embodiment of the present invention, the condition for performing the phase-back control in FIG. 1 is that the voltage of the field trip circuit becomes below the specified value, ,
This also applies to the configurations shown in FIGS. 3 and 4. FIG. 2A is a circuit diagram showing a trip circuit of the AC shunt breaker 2, and FIG. 2B is a circuit diagram showing a trip circuit of the field shunt breaker 5. In the figure A, it is connected in series with the auxiliary switch 52a of the AC cutter 2 and between the control power terminals _P1 and _N1 . This switch 52a is a switch that is interlocked with the operation of the AC breaker 2, and is turned on when the breaker 2 is turned on.

In addition, in FIG. B, the trip coil 41T of the field magnet and disconnector 5 is
, an auxiliary switch 52b that is interlocked with the AC switch breaker 2 and opened when the switch breaker 2 is turned on, and an auxiliary switch 52b that is linked with the field switch breaker 5 and opened when the switch breaker 2 is turned on. 41a and is connected in series to the control power supply terminals P ₂ and N ₂ of the field trip circuit.
Further, a voltage detection relay A is connected to these terminals P ₂ and N ₂ , and the control circuit 9 shown in FIG. 1 is controlled based on the contacts of this voltage relay A.

Further, FIG. 3 is a circuit diagram showing the configuration of the control circuit 9. As shown in FIG. In this figure, since the control circuit 9 normally has the contact 33b closed and the contact 33a open, the control circuit 9 receives the deviation signal 13 from the deviation amplifier 7.
0 is supplied to the excitation voltage forming circuit 4 as the output signal 140, and in the event of an abnormality, the contact 33b is opened and the contact 33a is closed, so that the phase back signal from the phase back signal generator 32 is is supplied to the excitation voltage forming circuit 4 as an output signal 140.

As shown in FIG. 4, the phase back interlock relay 33 as a circuit for opening and closing the contacts 33 is connected to the voltage relay A shown in FIG. 2B.
Auxiliary switch 5 of normally closed contact A _b and AC circuit breaker 2
Control power terminal P ₄₈ and
Connected to _N48 . At this time, terminal P ₄₈ and
N ₄₈ is preferably connected to the positive and negative terminals of the control power supply 14.

The operation of the first embodiment of the present invention constructed in this way will be explained below with reference to FIGS. 1 to 4.

Generally, when the synchronous machine 1 is stopped, the AC breaker 2 is tripped by energizing the trip coil 52T by the trip interlock 21, and subsequently the field breaker 5 is tripped by energizing the trip coil 41T. Ru. In the present invention, the control voltage of the field switch/breaker trip coil 41T is detected by the voltage detection relay A, and when the control voltage decreases, the contact A _b of the voltage relay and the condition 52b for opening the AC switch/breaker 2 The phaseback interlock relay 33 is operated according to the AND condition with the trip interlock 21, and the control circuit 9 locks the output deviation signal 130 of the deviation signal amplifier 7, and excites the output of the phaseback signal generator 32. The gate pulse is applied to the phase shifter 10 of the voltage forming circuit 4. This phase back is achieved by setting the firing angle of the thyristor of the thyristor exciter 11 to π/2 or more in the pure bridge system of the thyristor, so that the output voltage of the thyristor exciter 11 becomes negative, and the exciter 11 of the excitation voltage forming circuit 4 The energy supplied to the synchronous machine field coil is reversely converted to the alternating current side of the thyristor exciter 11. Alternatively, the field current can be reduced by shifting the firing angle of the thyristor back to around π/2. Note that this phase back interlock relay 33 is connected to a power source different from the control power source (terminals P ₂ and N ₂ ) of the trip coil 41T of the field cutter 5, such as the output voltage of the control power source 14 of the excitation control device. _P48 , _N48
By using the above, it is possible to perform phaseback control reliably even when the field is turned off due to control power cut-off or when the disconnector 5 cannot be tripped, and it is possible to prevent low frequency overexcitation when the synchronous machine 1 is stopped. There is. Furthermore, the first
3 and 3 show a system in which the field coil 1L of the synchronous machine 1 is directly controlled by the output of the thyristor converter 11, but the output of the thyristor converter 11 is used to control the field of the rotary exciter Similar control is also possible in a system in which the synchronous machine field is controlled by the output of the exciter.

In the second embodiment of the present invention, the voltage of the trip circuit of the field cutter 5 is monitored by the voltage relay A, and the trip interlock 21 is included in the monitoring conditions, as shown in FIG. Figures 2 and 3
It consists of Fig. 5 and Fig. 5.

FIG. 5 shows an interlock circuit used in another embodiment of the invention. Contact point A _b of the voltage detection relay A of the trip coil control power supply of the aforementioned field switch and disconnector 5, and the trip interlock 21,
The trip coil 41T of the field disconnector 5 is
The thyristor phase back interlock relay 33 is activated even in the event of a wire breakage or a trip mechanism failure. This control reduces the field current in the synchronous machine field coil, thereby making it possible to prevent low frequency overexcitation of the synchronous machine.

According to the present invention, the field current of the synchronous machine is reduced by reverse operation of the thyristor converter using a pure bridge circuit system or by phase-backing the firing angle of the thyristor to around π/2 even when the field is turned on or the disconnector cannot be opened. This has the effect of preventing low frequency overexcitation of the synchronous machine.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the control circuit of a synchronous machine using an excitation control device, Figure 2A is a circuit diagram showing the trip sequence for AC disconnection, and Figure 2B is a circuit diagram for field excitation and disconnection. FIG. 3 is a block circuit diagram for explaining the operating principle of the present invention; FIG. 4 is a circuit diagram showing an interlock for the first embodiment of the present invention; and FIG. The figure is a circuit diagram showing an interlock for a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Synchronous machine, 2...AC line breaker, 4...Excitation voltage forming circuit, 5...Field line breaker, 7...Difference amplifier, 9...Control circuit, 10...Gate pulse Phase shifter, 11... Thyristor exciter, A... Voltage detection relay, 21... Trip interlock, 32... Phase back signal generator, 33...
...Phaseback interlock relay.

Claims (1)

[Scope of Claims] 1. Deviation signal creation means 7 that captures the output voltage of the synchronous machine and creates a deviation signal from the voltage setting value, and controls the firing phase of the exciter 11 based on the deviation signal, and It has an excitation voltage formation circuit 4 that forms an excitation voltage such that the output voltage of the excitation voltage is constant, and the output of the excitation voltage formation circuit is connected directly to a DC field or via a disconnector 5 or to a rotary exciter. In the excitation control device for a synchronous machine, which is supplied to the field coil 1L of the synchronous machine through A signal generator 32 that generates
and control voltage detection means A for detecting that the control voltage of the trip circuits 21, 52b, 41T, and 41a that trip the DC field magnets and circuit breakers has fallen below a specified value, and The deviation signal generating means and the excitation voltage forming means, on the condition that the alternating current switch or disconnector installed between them is opened, and the control voltage detecting means detects that the control voltage has become below a specified value. An excitation control device for a synchronous machine, comprising switching means 33b and 33a for switching the connection with the circuit to the connection between the signal generator and the excitation voltage forming circuit.