Discrete Duty Cycle Control for Single-Phase Voltage Source Inverter

Since steady-state error exists in the output voltage of a proportional-integral (PI) controlled single-phase voltage source inverter (SP-VSI), the bandwidth of the PI controller is usually set as low as 10% of the switching frequency to improve the control accuracy. However, a small bandwidth results in a slow transient response against load variations. This paper presents a new discrete duty cycle (DDC) control method based on pulse train modulation (PTM). Different from the conventional PI control, the proposed DDC control method adjusts the output voltage by generating high and low power control pulses with discrete duty cycles and fitting a target duty cycle, which corresponds to the sinusoidal output voltage of SP-VSI. The DDC controller can achieve both zero output voltage steady-state error and fast transient response without compensation circuits. Experimental results from a 200Vdc-1l0Vrms, 50Hz, 240W SP-VSI are presented to validate the proposed DDC control method and its superiority over conventional PI controllers.