High-performance programmable AC power source with low harmonic distortion using DSP-based repetitive control technique

This paper proposes a new control scheme based on a two-layer control structure to improve both the transient and steady-state responses of a closed-loop regulated pulse-width-modulated (PWM) inverter for high-quality sinusoidal AC voltage regulation. The proposed two-layer controller consists of a tracking controller and a repetitive controller. Pole assignment with state feedback has been employed in designing the tracking controller for transient response improvement, and a repetitive control scheme was developed in synthesizing the repetitive controller for steady-state response improvement. A design procedure is given for synthesizing the repetitive controller for PWM inverters to minimize periodic errors induced by rectifier-type nonlinear loads. The proposed control scheme has been realized using a single-chip digital signal processor (DSP) TMS320C14 from Texas Instruments. A 2-kVA PWM inverter has been constructed to verify the proposed control scheme. Total harmonic distortion (THD) below 1.4% for a 60-Hz output voltage under a bridge-rectifier RC load with a current crest factor of 3 has been obtained. Simulation and experimental results show that the DSP-based fully digital-controlled PWM inverter can achieve both good dynamic response and low harmonics distortion.