A current controlled near unity power factor three-phase PWM buck rectifier without passive damping requirements

Abstract

Three-phase current source PWM rectifier (also known as three-phase buck rectifier) is often used as the front-end in utility interfaced systems. An input LC filter is required to suppress the current harmonics injected into AC mains. The input filter affects the input displacement factor (IDF) of the system, which varies with the rectifier operating point and may result in unacceptable low values. In this paper, closed-loop control of the input line currents is proposed to achieve near unity IDF independent of the load conditions. The current reference template is generated from the filter capacitor voltages, the need for damping resistors is eliminated and efficiency is increased. The output DC current is regulated by varying the amplitudes of the current references. The proposed scheme features good steady state results, fast transient response and higher efficiency. The paper includes analysis, a design example and simulation results for steady state and transient conditions.