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

This paper proposes a new bidirectional buck–boost converter, which is a key component in a photovoltaic and energy storage system (ESS). Conventional bidirectional buck–boost converters for ESSs operate in discontinuous conduction mode (DCM) to achieve zero-voltage switching turn-<sc>on</sc> for switches. However, operation in DCM causes high ripples in the output voltage and current, as well as low power-conversion efficiency. To improve the performance of the conventional converter, the proposed converter has a 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 and the efficiency is increased. A prototype was built and tested to verify the effectiveness of the converter. The proposed converter has a maximum efficiency of 98%, less than <inline-formula><tex-math notation="LaTeX">${\text{5.14}}{\ \text{V}}_{{\text{p.p}}}$</tex-math></inline-formula> of output voltage ripple, and less than <inline-formula><tex-math notation="LaTeX">${\text{7.12}}{\ \text{A}}_{{\text{p.p}}}$</tex-math></inline-formula> of output current ripple. These results were obtained at an input voltage of 160 V, switching frequency of 45 kHz, output voltage of 80–320 V, and output power of 16–160 W. The experimental results show that the proposed converter has improved performance compared to the conventional converter.