A novel repetitive PD control strategy for single-phase 400 Hz CVCF inverters

In this paper a novel repetitive PD control strategy for single-phase 400 Hz CVCF inverters is presented. The performance of CVCF inverters is evaluated in terms of output voltage waveform distortion with linear or nonlinear loads and transient response due to sudden changes in the load. The repetitive controller is synthesizing to minimize low-order harmonic distortion in steady state. Since the ratio between the switching frequency and the fundamental output frequency of 400 Hz inverter is significantly decreased, the inverse of inverter under no load is used to attenuate the resonant peak resulting from the inverter in order to obtain stability and satisfactory harmonic rejection. On the other hand, PD control is used to improve transient performance. The PD controller is designed using direct digital approach base on the frequency response method in the w-plane. Thus, repetitive controller and the PD controller can be combined to take advantage of their positive attributes. The control scheme is implemented using a TI TMS320F240 DSP in a 400 Hz 5.5 kW prototype. Simulation and experimental results prove that the proposed control scheme can achieve not only low THD during steady-state operation but also fast transient response subject to load step change.