Real-Time Calculation Method for Single-Phase Cascaded H-Bridge Inverters Based on Phase-Shifted Carrier Pulsewidth Modulation

摘要

The time delay caused by the digital computation and the update of the duty cycle tend to worsen the dynamic performance of digitally controlled power converters. This paper proposes a real-time calculation method for single-phase cascaded H-bridge (CHB) inverters with the phase-shifted carrier pulsewidth modulation (PSC-PWM) to eliminate the time delay caused by the digital computation in the control loop without the loss of duty cycle. In the approach, a sampling method for the PSC-PWM applied in a single-phase CHB inverter is introduced, which samples the current and voltage at points of the intersection for triangular carriers of legs in all adjacent H-bridge cells. The sampling method is used alternately with the conventional regular sampling method by following a selection rule in order to avoid the loss of duty cycle. Experimental results verify that the proposed method effectively improves the transient performance of the current control loop and suppresses the effect of the distortion of the grid voltage on the line current.