Three-Phase Low-Harmonic Rectifier Based on Third Harmonic Current Injection with Passive Circuit

Study to use passive approach to reduce input current´s harmonics of three-phase diode rectifier based on injection of third harmonic current is performed in this paper. Compared with the popular star/delta transformer, a set of star-connected capacitors are used as injection circuit. The circuit operates at third serial resonant state and therefore enhances the amplitude of circulating third current. Principle and characteristics of the injection circuit are analyzed in details, which including the condition of optimal injection, the effect of component parameters´ deviation and the load varying range with optimal component parameters. This approach has better harmonic suppression performance than passive filter´s and more simple and reliable than active power filters. Results of simulation and experiments validate the feasibility of the method and analysis.