Abstract: Compared with the DC bus access mode of energy storage battery combined with bidirectional DC/DC Converter, the multiplex Four-Switch Buck-Boost converter (FSBB) is used as the front stage converter of industrial and commercial optical storage converter, which can reduce the number of inductors and equipment volume. And achieve a wide range of photovoltaic voltage input. Aiming at the problems of multi-mode hard switching, low accuracy of traditional control methods and poor robustness of energy storage conditions in multi-mode FSBB, carrier cascade modulation is adopted to realize smooth switching between Buck, Buck-Boost and Boost modes, and a unified equation of state under the three modes of single FSBB converter is established. In addition, a super spiral sliding mode control method is designed to control the multiplex FSBB converter on the photovoltaic side, and the maximum power fast tracking is realized. The simulation model of the optical storage converter is built on MATLAB/Simulink. The simulation results show that ST-SMC can better improve the stability and dynamic performance of the photovoltaic energy storage system compared with the traditional proportional integration and sliding mode control methods.