SU892639A1 - Device for limiting minimum excitation of synchronous generator excitation - Google Patents

Description

(54) DEVICE FOR LIMITING A MINIMUM EXCITATION OF A SYNCHRONOUS GENERATOR The invention relates to the regulation of the reactive power of energy systems, in particular, to the control of the excitation of synchronous generators operating with the consumption of reactive power. Devices are known to limit the minimum excitation of a synchronous generator operating in the mode of consumption of reactive power 1 and 2. However, these devices are complex, have non-universal characteristics and, due to the small output signal, have been used only with excitation taps, which have a high force factor. The closest to the technical essence of the proposed device is a device for limiting the minimum excitation of a synchronous generator, containing a phase-rotation unit, the input of which serves to connect to the voltage transformer of the synchronous generator, the current sensors of the stator of the generator and the key circuit 3. The lack of equipment oystva is a linear characteristic, making it difficult to use the device for generators operating in the consumption of reactive power mode. In order to more fully use the generator in the mode of reactive power consumption, the device for limiting the minimum excitation of a synchronous generator containing a phase rotation unit, the input of which serves to connect a synchronous generator voltage to the voltage transformer, current generator stator sensors and the key circuit, is equipped with a second key phase rotation block a circuit, a matching unit with pulse generators phase voltage sensors, the inputs of which are connected to the outputs of the phase shifters, and the output to the control inputs of the key circuits, the power inputs of the key circuits are connected to the generator's stator current sensor, the power input of one of the key circuits connected to the stator current sensor via an additional adjustable resistor, and the second power input to the postal circuit is connected to the engine of the same resistor, and the outputs of the key circuits are connected by matching the block with the clips to the connection to the exciter generator.

FIG. Figures 1 and 2 show variants of the device circuits for limiting the minimum excitation of a synchronous generator; Fig, 3 shows the characteristics of the device

The device for limiting the minimum generator excitations includes phase shifting units 1 and 1 which are connected to the stator winding of the synchronous generator through a voltage transformer 2, a stator current sensor 3 connected to the current transformer 4, key circuits 5 and 5 acting as exciter control systems 6 , performed, for example, on thyristors, the inputs of which are connected to you: sensors of sensors 7 and 7 of the generator voltage and stator current sensor 3, and the output is connected to the exciter b via matching unit 8, which For example, a potentiometric bridge with a stabilized emf (Fig. 1), a zener diode with an isolation diode (Fig. 2), or an amplifier of direct current can be used.

Phase-turn units are used to set the starting angles of the Key schemes of the corresponding active interval, generator power, above which it is necessary to regulate the rotor PCs in the mode of consumption of reactive power.

The initial angles are set by changing the phase of the voltage supplied from transformers 2 relative to the voltage from current sensor 3, so that the key circuits 5 and 5 receive pulses from sensors 7 and coincide in time with the positive half-wave sinusoid of the stator current.

From the output of the phase rotation unit, the voltage with the installed phase is applied to the input of the phase voltage sensor of the generator 6. The sensor zener diode forgates almost rectangular pulses.

The pulses are applied to the control inputs of the key circuits 5 and 5 by opening them depending on the voltage difference between the stator current generator and the internal angle of the generator. With an increase in the reactive power consumed by the generator, the signal at the output of the key circuits 5 and 5 decreases. The matching unit 8, which is a nonlinear Zener diode bridge, converts the output characteristic to a more convenient form for realization (Fig. 3).

For all values of the angle (G less than permissible for the first circuit, the pulses of positive polarity from the sensors arriving at the input of the first key circuit; coincide in time with the positive half-wave sinusoidal voltage supplied

to the second input of circuit 5 from phase shifter 1. At the same time, the input voltage of the key circuits is the maximum voltage of the control current of the exciter at the output of the matching unit

When the generator reactive load increases in the consumption mode and, accordingly, the angle cG, the pulses from the sensors 7 and 7 arrive at the control inputs of the key circuits shifted along the time axis in the direction of decreasing the period of operation of the key circuit according to the deviation of the angle cG. The voltage at the output of the key circuits decreases, but increases at the output of the matching unit 8 and a current appears in the control circuit of the exciter, the magnitude of which depends linearly on the stator current and the cosine law on the angle between this current and the generator voltage. The control unit of the exciter increases the excitation of the generator and prevents further growth of the consumed reactive power. When changing (f to the value of cfj, the second key circuit is disconnected, connected to higher voltages of the current sensor, and the coefficient of proportionality of the characteristic changes.

The use of the device provides the characteristic of limiting the minimum excitation of the generator, which coincides with the characteristic of the permissible modes of the generator in the modes of consumption of reactive power, reliability of the device, due to the use of elements of the key type that are not affected by the environment.

High noise immunity, as there are no circuits with low signals.

Claims (3)

1. USSR author's certificate number 538468, cl. H 02 R 9/14, 1972. 2. Authors certificate of the USSR 575794, cl. H 02 R 9/14, 1973. 3. USSR author's certificate number 58583, cl. H 02 R 9/14, 1976.