High performance repetitive control for three-phase CVCF PWM inverter using a 4th-order linear phase IIR filter

This paper presents a high performance repetitive controller (RC) for three-phase constant-voltage constant-frequency (CVCF) pulse width modulated inverters. The proposed control algorithm can eliminate all the periodic distortions and guarantees a high quality sinusoidal output voltage under unknown and severely distorted loads. Distinguished from existing repetitive control schemes, the proposed approach incorporates a 4^th-order linear phase infinite-impulse-response (IIR) filter Q(z) in the RC instead of commonly used low order FIR filters. Benefiting from the great pass band flatness and sharp high frequency attenuation rate of Q(z), the proposed controller is capable of compensating harmonic distortions up to the 19^th order. In addition, the proposed RC exhibits very good stability margin, indicating a strong tolerance to the system parameter drifting and a good robustness. The voltage reference feed forward and load disturbance decoupling feed forward are added to boost up the controller dynamic response. Experimental results are provided to verify the performance of the proposed repetitive controller. Very low THD (0.98%~1.73%) and good transient responses are demonstrated.