SU479212A1 - Device for controlling the excitation of a synchronous generator - Google Patents

Description

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This invention relates to devices for automatically controlling the excitation of synchronous machines.

The known device that performs excitation control based on deviation and derived mode parameters, includes a voltage block, a frequency block, a current block, differentiators, frequency and current signal converters, a logical amplifier consisting of two parallel branches of transistors of different conductivity, each of which two consecutive transistors of the same conductivity and an adder, while the signal converters are connected to the outputs of each of the bases of two transistors of different conductivity a logic amplifier, and the output of the logic amplifier is connected to the input of the adder.

A disadvantage of the frequency deviation and its first derivative stabilization is the excitation of the generator instead of the necessary formation in transient conditions associated with a decrease in the frequency of the generators while simultaneously increasing the transmission angle. Correction of action of ARV is based on a comparison of the signs of the frequency change and the first Derivative of the generator current.

The disadvantage of the correction is an increase in the generator excitation with different signs of the compared signals and the absence

the need for forming (for example, when the load is disconnected in the power system)

In addition, the magnitude of the voltage applied to the input of the ARV during correction is limited by possible overshoots, since in interrupt modes accompanied by a decrease in frequency, these signals can be input to the APB repeatedly.

In most cases, to ensure the stability of the power system in case of load surges or disconnections of the generated power, a relatively large additional voltage is not required, which can cause overshoot. However, there may be such modes (for example, in the case of power transmission operation near the static stability limit) when a relatively large excitation rise is required to prevent buckling.

In order to increase the excitation in transient conditions while decreasing the frequency and simultaneously increasing the generator current, the device is equipped with a blocking relay, the winding of which is connected to the output of the signal converter through the rectifier to the frequency, a, n. about. a relay contact shunts the output of a logic amplifier.

The drawing shows a schematic diagram of a device for controlling the excitation of synchronous generators. The circuit contains voltage block i, frequency block 2, current block 3, differentiators 4, 5, converters 6, 7, respectively, of frequency and current signals, block 8 of automatic blocking, force device 9 and adder 10. Signal converters 6, 7 are made on transistors Ti and T according to the scheme with diode limitation. Transducers amplify small input signals, while signals greater than 0.5 volts transform into square voltage. G1A input of one of the converters through the capacitor Ci receives a signal proportional to the first derivative of the generator current, and to the input of the second converter through the capacitor C and a resistor - a signal proportional to the frequency change. A signal proportional to the first derivative of the frequency is also fed through the capacitor C3 to the converter input. This signal allows the commutation of hint caused by the inertia of both the frequency block itself and the filter at its output. Logic amplifier 11 is made of forward and reverse conduction transistors. It has two parallel branches with a shared load for them. In each parallel branch there are two transistors Tz, T and Tb, TS of the same conductivity, connected in series. The output of the logic amplifier (points a and b) is connected either directly to the input of the adder or to the relay coil Pi, the contacts of which connect a signal supply circuit to increase the excitation to the adder 10. The output of the logic amplifier 11 is connected n.o. PZ relay contacts of selective blocking, the winding of which is connected via rectifier 12, zener diode 13 and separation capacitor C with the output of converter 6 of signals in frequency. The device works as follows. In transient conditions associated with a decrease in frequency while simultaneously increasing the generator current, as is the case when the load is increased or the generated power in the power system is disconnected, a positive signal is fed to the input of one of the converters 7 and 6, and a negative signal is fed to the other. This leads to the closure of one transistor in each of the parallel branches of the logic amplifier 11 and, consequently, an increase in voltage between points a and b. As a result, an additional adjustment signal is applied to the input of summatr 10, causing a significant increase in excitation. Further, when the frequency was reduced to a selected value determined by the threshold of the Zener diode 13, the relay blocked its contacts by shunting the output of the logic amplifier, eliminating the signal to increase the excitation in the course of the generator oscillations. The lock is automatically released at the end of the transient mode. In all modes associated with an increase in the oscillator frequency, the output of the logic amplifier I is bridged, since in order for the blocking relay to operate in these cases, the change in voltage at the output of the signal converter over the frequency of just about 2 volts is sufficient. The subject of the invention. A device for controlling the excitation of a synchronous generator, regulating the deviation and the derived mode parameters, comprising a voltage block, a frequency block, a current block, differentiators, frequency and current signal converters, a logical amplifier consisting of two parallel transistors of different conductivity. , each of which has two series-connected transistors of the same conductivity and an adder, with the signal converters being connected to each output with the bases of two transistors of different conductivity of the logic amplifier, and the output of the logic amplifier is connected to the input of the adder, characterized in that, in order to increase the excitation in transient conditions at a lower frequency and simultaneously increase the generator current, it is provided with a locking relay, which is wired through a straightener connected with the output of the converter ignited in frequency, and n. a relay contact bypasses the output of a logic amplifier.