High-Efficiency Bidirectional Buck–Boost Converter for Photovoltaic and Energy Storage Systems in a Smart Grid

Abstract

This paper proposes a new bidirectional buck-boost converter, which is a key component in the photovoltaic and energy storage system (PV-ESS) for smart grid. The conventional bidirectional buck-boost converters for ESS operate in discontinuous conduction mode (DCM) to achieve zero-voltage-switching turn-on for switches. However, the operation in DCM causes a high output voltage/current ripples and a low power-conversion efficiency. To improve the performance of the conventional converter, the proposed converter has the new combined structure of a cascaded buck-boost converter and an auxiliary capacitor. The combined structure of the proposed converter reduces the output current ripple by providing a current path. Therefore, the output voltage ripple is reduced and the efficiency is increased. To verify the effectiveness of the proposed converter, a prototype was built and tested. The proposed converter with a maximum efficiency of 98% had an output voltage ripple of less than 5.14 V $_{p.p}$ , and an output current ripple of less than 7.12 A $_{p.p}$ at input voltage of 160 V, switching frequency of 45 kHz, output voltage of 80 ~ 320 V, and output power of 16 ~ 160 W. These experimental results showed that the proposed converter improved the performance of the conventional converter.