Jun. 21, 2022
1. Requirements for the excitation regulator
1) High reliability and stable operation. Corresponding measures should be taken in circuit design, component selection and assembly process.
2) Good steady state and dynamic characteristics.
3) The time constant of the excitation regulator should be as small as possible.
4) The structure is simple, the maintenance and repair is convenient, and gradually achieves systemization, standardization and generalization.
2. Composition of the excitation regulator
Generator semiconductor excitation regulator is mainly composed of three basic units: measurement comparison, comprehensive amplification and phase shift trigger. Each unit is composed of several links.
1) The measurement comparison unit consists of voltage measurement, comparison setting and adjustment. The voltage measurement section includes measuring rectification and filtering circuit, and some have positive sequence voltage filters. The measurement comparison unit is configured to measure the converted DC voltage proportional to the generator terminal voltage and compare it with a reference voltage corresponding to the rated voltage of the generator to obtain a deviation of the generator terminal voltage from its given value. The voltage deviation signal is input to the integrated amplifier unit, and the positive sequence voltage filter can improve the accuracy of the regulator when the generator is running asymmetrically, and can improve the excitation capability when asymmetric short circuit occurs. The function of the adjustment link is to change the adjustment coefficient of the regulator to ensure stable and reasonable distribution of reactive power between the gensets in parallel operation.
2) The comprehensive amplification unit synthesizes and amplifies the measurement signal, in order to obtain the good static and dynamic characteristics of the adjustment system and meet the operation requirements, in addition to the voltage deviation signal from the basic device, sometimes it is necessary to synthesize other signals such as stable signals, limit signals, and compensation signals from auxiliary device according to requirements. The integrated amplified control signal is input to the phase shifting trigger unit.
3) The phase shifting trigger unit includes synchronization, phase shifting, pulse formation, and pulse amplification. According to the change of the input control signal, the phase shifting trigger unit changes the phase of the trigger pulse output to the thyristor, that is, changes the control angle (or phase shift angle), so as to control the output voltage of the thyristor rectifier circuit to adjust the excitation current of the generator. In order to trigger the pulse to touch off the thyristor reliably, it is often necessary to use the pulse amplification link for power amplification.
The synchronization signal is taken from the main loop of the thyristor rectifier, ensuring that the trigger pulse is emitted when the thyristor anode voltage is in the positive half cycle, so that the trigger pulse is synchronized with the main loop.
There is usually a manual part in the excitation system. When the automatic part of the excitation regulator fails, it can be switched to the manual mode.
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Aug. 12, 2022
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