INPUT FILTER DESIGN FOR PWM CURRENT-SOURCE RECTIFIERS

Pulse-width modulated (PWM) rectifiers are increasingly used because they allow the elimination of low-order harmonics, and therefore a reduction in input filter components. Filtering requirements for PWM current-source rectifiers are usually satisfied through the use of low-pass LC input filters. This paper offers a systematic and user-friendly approach to choosing the filter components. Design of LC filters involves the positioning of the resonant frequency to meet the harmonic attenuation requirements (THD), and introducing damping at the resonant frequency to avoid amplification of residual harmonies. The problem is further complicated by considerations related to cost, power factor, voltage attenuation, system efficiency, and filter parameter variation. The systematic approach proposed in this paper focuses on PWM rectifiers, but can easily be extended to other classes of converters. Practical design considerations are detailed and design equations derived. Simulated results are presented to validate the design approach.