Fractional Phase Lead Compensation RC for an Inverter: Analysis, Design, and Verification

Repetitive control (RC) can offer a promising accurate voltage control scheme for constant-voltage constant-frequency (CVCF) pulse width modulation (PWM) inverters to compensate the harmonic distortion caused by nonlinear loads. However, limited by digital sampling, conventional RC with integer phase lead compensation cannot exactly compensate the system phase lag, which may result in instability in the case of low sampling frequency. In this paper, a fractional phase lead compensation RC (FPLC-RC) scheme is proposed to enable the phase lead step to be fractional, which can enlarge the stability region and improve the tracking accuracy. A newly devised finite-impulse response fractional lead filter based on Lagrange interpolation is applied to approximate the fractional lead items. Meanwhile, the synthesis and analysis of fractional phase lead RC for a single PWM inverter are given. Furthermore, simulations and experiments are provided to demonstrate the validity of the proposed FPLC-RC scheme.