IMPROVED SEPIC-ZETA CONVERTER FOR PHOTOVOLTAIC SYSTEMS

Abstract: A Bidirectional Single-Stage Grid-connected inverter (BSG inverter) for the battery energy storage system in EV applications using SEPIC-ZETA converter is proposed. The proposed BSG-inverter is composed of Bidirectional SEPIC- ZETA type DC–DC converters (BSZS) and a DC–AC unfolder. The circuit diagram of the proposed BSG- inverter which is composed of distributed SEPIC-ZETA type DC–DC converters and a DC–AC unfolder. BBC consists of two switches, two diodes, and one inductor. It can convert the DC current generated by the battery module into a high frequency pulsating DC current. This high frequency pulsating output current of the BBCs will be converted into sinusoidal one with utility line frequency by the DC–AC unfolder of four active switches operated at low switching frequency and an LC filter. The proposed BSG-inverter will comply with the power commands which is coming from the central control unit of the BMS tocharge or discharge the battery modules. The power flow from each battery module is transferred to the AC mains by means of single-stage power conversion. Also the BBCs can be operated with interleaving to reduce the current ripple of the output inductor. This proposed method is implemented using MATLAB simulation and hardware is developed with DSPIC30F4011controller.

Keywords: SEPIC-ZETA Converter, BSG inverter, AC grid, Photovoltaic.