Optimal design of voltage regulators for static excitation system in synchronous generator to reduce shaft-induced voltage

Authors: MAHMOUD SAMIEIMOGHADDAM, MOHAMMAD TAVAKOLI BINA, MASOUD ALIAKBAR GOLKAR, SHOKROLLAH SHOKRIKOJOORI

Abstract: Long-term shaft-induced voltage could harm synchronous generators, specifically their bearings and insulators. This paper investigates the reduction of shaft-induced voltage using both a passive filter and an active voltage regulator. An RLC circuit is used as a passive filter, and a DC-DC buck converter is used as an active voltage regulator. As a result, they remove high-frequency spikes, leading to the reduction of shaft-induced voltage. Buck converters show minimum-phase behavior and can pose as stable-casual converters. A 5 kW synchronous generator was considered for the laboratory setup in which a static excitation system using a 6-pulse thyristor rectifier supplies the rotor winding. Active and passive filters were placed between the rectifier and the excitation winding of the synchronous generator. Both simulations and experiments show that the suggested filters are capable of efficiently removing the parasitic capacitance, significantly mitigating shaft-induced voltage. However, the active voltage regulator performs better than the passive filter in reducing shaft-induced voltage. This reduction can increase the lifespan of bearings in a generator.

Keywords: Bearing current, active voltage regulator, shaft-induced voltage, passive filter, static excitation system

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