Implementation of Hybrid Filter for 12-Pulse Thyristor Rectifier Supplying High-Current Variable-Voltage DC Load

This paper presents a parallel combination of a shunt-connected passive filter and a distribution static compensator (DSTATCOM) for a 12-pulse thyristor rectifier feeding a high-current variable-voltage electrolyzer load. Since the process requires variation of voltage and current over a wide range, the reactive power consumed by the thyristor rectifier also varies enormously. As the passive filter is only able to provide a fixed compensation, the DSTATCOM is used to meet variable reactive power demand to keep the input power factor high even at partial load. In order to keep the DSTATCOM rating small, the bulk of reactive power is supplied by the dominant harmonic passive filter. Moreover, DSTATCOM does not provide any harmonic compensation, which is also taken care by the passive filter. Design and control of this system are discussed briefly, and more emphasis is laid on the implementation of the hybrid filter. An experimental system is tested rigorously, and detailed results are presented.