Minimal circuit for power system conditioning

This paper introduces a new circuit, intended for use in the elimination of current harmonics in power systems. The essential characteristics of the system are a three phase supply with series inductance and a load, a substantial part of which is one or more uncontrolled rectifiers feeding into DC voltage buses to which DC loads are connected. The new circuitry consists of a set of three switches connected in either delta or star at the AC terminals of the rectifiers. No reactive elements are required except for snubbing circuits. The switches are fully controlled and must be capable of blocking voltage in either direction and of conducting current in either direction. Such a switch can be realised by a series/parallel connection of two transistors and two diodes. The circuit is analysed and control strategies are specified. Results showing good current shaping are presented from both simulation and a low power circuit