Analysis on output LC filters for PWM inverters

The cutoff frequency of output LC filters of PWM inverters limits the control bandwidth of the converter system while it attenuates voltage ripples caused from the inverter switching. For a selected cutoff frequency of an output LC filter, infinite number of L-C combinations is possible. This paper analyses the characteristics of output LC filters for PWM inverters in the view of L-C combinations. Practical circuit conditions such as no-loads, full resistive-loads, and inductive-loads are considered in the analysis. This paper proposes a design criterion and a design example for the L-C filter combination considering both the control performance and the size of PWM inverters. An experimental PWM inverter system based on the proposed output LC filter design guideline is built and tested.