DSP-based multiple-loop control strategy for single-phase inverters used in AC power sources

This paper presents a fully digital multiple-loop control scheme for the regulation of the PWM inverters used in AC power sources. The proposed digital control scheme incorporates an inner current loop with an outer voltage loop to regulate the output voltage of the PWM inverter. The digital controller is designed through deadbeat theory so that the inverter can achieve fast dynamic response. To enhance the robustness of the PWM inverter concerned, an output voltage decoupling mechanism is added to improve the performance of the inner current loop. Besides, a load disturbance compensation scheme is also developed to remedy the voltage distortion caused by load variation. Both the frequency-domain and time-domain behavior of the proposed control scheme have been examined in this paper. A PWM inverter control system based on DSP TMS320C14 was constructed to verify the control law. The results show that the output voltage of the controlled PWM inverter has little distortion even under rough load conditions.