PWM Inverter Output Filter Cost-to-Losses Tradeoff and Optimal Design

This paper describes how to design the output filter of a pulsewidth-modulation inverter used in an uninterruptible power supply. Several constraints apply to this design: physical limitations of all material and components, output waveform quality, losses, cost, etc. All models used in the design process are described: semiconductor, inductor and capacitor losses, cost, total harmonic distortion, short-circuit behavior, etc. Input parameters are control law, switching frequency, inductor design parameters (number of turns and magnetic circuit), and capacitor values. Based on these design models, optimization is carried out, and cost-losses tradeoff curves are deduced. Two power levels (30 and 300 kVA) are taken as design example, with the same models, in order to show the robustness of the method.