Application of Semiconductor Excitation Regulator for Diesel Generator

The current diesel generator regulator can comprehensively reflect a variety of control signals, including voltage deviation signals, for excitation regulation, so it is called excitation regulator. Obviously, the excitation regulator includes the function of voltage regulator. The semiconductor excitation regulator of diesel generator is briefly introduced below.

Excitation control system: the excitation system is an important part of the AC synchronous diesel generator, which controls the voltage and reactive power of the synchronous diesel generator. In addition, the speed governing system controls the speed (frequency) and active power of the prime mover and diesel generator. The two are the main control systems of diesel generators. Excitation control system is a feedback control system composed of synchronous diesel generator and its excitation system.

The excitation regulator is the main part of the excitation control system. Generally, it senses the change of diesel generator voltage, and then controls the excitation power unit. Before the excitation regulator changes the given control command, the excitation power unit will not change its output excitation voltage.

Requirements for excitation regulator: the excitation regulator shall have high reliability and stable operation. Corresponding measures should be taken in circuit design, component selection and assembly process. The excitation regulator shall have good steady-state and dynamic characteristics. The time constant of the excitation regulator shall be as small as possible. The excitation regulator shall be simple in structure, easy to repair and maintain, and be systematic, standardized and universal gradually.

Composition of excitation regulator: The semiconductor excitation regulator is mainly composed of three basic units: measurement comparison, comprehensive amplification and phase shifting trigger, and each unit is composed of several links.

Measurement and comparison unit The measurement and comparison unit consists of voltage measurement, comparison setting and difference adjustment. The voltage measurement link includes measurement rectifier and filter circuit, and some have positive sequence voltage filter. The measurement comparison unit is used to measure the converted DC voltage proportional to the terminal voltage of the diesel generator, and compare it with the reference voltage corresponding to the rated voltage of the diesel generator to obtain the deviation between the terminal voltage of the diesel generator and its given value. The voltage deviation signal is input to the comprehensive amplification unit. The positive sequence voltage filter can improve the accuracy of the regulator when the diesel generator is operating asymmetrically, and can improve the forced excitation capability when the asymmetric short circuit occurs. The function of the difference adjustment link is to change the difference adjustment coefficient of the regulator to ensure the stable and reasonable distribution of reactive power among parallel operating units.

Comprehensive amplification unit The comprehensive amplification unit synthesizes and amplifies signals such as measurements. In order to obtain good static and dynamic characteristics of the regulating system and meet the operation requirements, in addition to the voltage deviation signal from the basic device, it is sometimes necessary to synthesize other signals such as stability signal, limit signal, compensation signal, etc. from the auxiliary device as required. The integrated amplified control signal is input to the phase-shifting trigger unit.

Phase-shifting trigger unit phase-shifting trigger unit includes synchronization, phase-shifting, pulse formation and pulse amplification. The phase-shifting trigger unit changes the phase of the trigger pulse output to the thyristor according to the change of the input control signal, that is, changes the control angle (or called phase-shifting angle), so as to control the output voltage of the thyristor rectifier circuit to regulate the excitation current of the diesel generator. In order to trigger thyristor reliably with trigger pulse, it is often necessary to use pulse amplifier to amplify power. The synchronization signal is taken from the main circuit of the thyristor rectifier to ensure that the trigger pulse is sent out when the anode voltage of the thyristor is in the positive half cycle, so that the trigger pulse is synchronized with the main circuit.

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