Bidirectional Grid-Connected Single-Stage Converter with Unfolding Circuit

In this paper, a bidirectional grid-connected single-stage converter is proposed which consists of a power conversion stage that is a bidirectional DC-DC converter along with an unfolding circuit. By adjusting the Pulse Width Modulation (PWM) of the DC-DC converter the low DC voltage is converted into a rectified sinusoidal voltage. The unfolding circuit, which operates at the grid frequency, unfolds/folds the rectified sinusoidal waveform and provides a current pathway to the grid. Because of its low switching loss, it is not respected as a power conversion stage. The computer simulations are done in MATLAB/Simulink environment to verify the mathematical analysis. The proposed converter has below 1% output current ripple. Compared to a state of art converter, with a similar principle, the proposed converter achieved a 12% higher switch utilization factor.