Fractional delay repetitive control of three-phase PWM inverters

Repetitive control (RC), when the exponent of delay links is an integer with the sampling frequency being an integer multiple of the control signal frequency, can achieve high-precision output waveform control of power electronic converters. However, it would severely limit the system performance of classical RC, whose exponent is often fractional in real applications. In this paper, a fractional delay repetitive control (FDRC) scheme for pulse-width-modulated (PWM) inverters is proposed to deal with the case of non-integral delay links at a fixed sampling frequency, where a finite impulse response (FIR) filter was introduced to approximate it. Experimental results on a three-phase PWM inverter are provided to demonstrate the effectiveness of the proposed control scheme.