High-Efficiency Silicon Carbide-Based Buck-Boost Converter in an Energy Storage System: Minimizing Complexity and Maximizing Efficiency

Abstract

Energy storage (es) systems are key enablers for the high penetration of renewables. The buck-boost converter in a dc-coupled architecture for integrated photovoltaic (PV) and ES systems shows promising performance with a lower cost and higher efficiency. Silicon carbide (SiC) devices can benefit ES converters as well as the whole ES system. This article focuses on the development of a high-efficiency, SiC-based buck-boost converter in an ES system while emphasizing its unique design considerations. First, the topologies of the buck-boost converter, considering system requirements and device rating/availability, are discussed. A two-level voltage source converter (VSC) with paralleled discrete SiC devices in mature packages (e.g., TO-247) is selected because of its smaller converter complexity and better device availability. Then, the gate drive and layout design for current sharing between paralleled devices are presented. The impact of a device parameter mismatch (e.g., threshold voltage) on switching loss is also evaluated. Moreover, control and protection schemes for the buck-boost converter are discussed. Finally, a 60-kW ES converter with four 1,700-V SiC MOSFETs is prototyped and experimentally demonstrates up to 99.48% efficiency and satisfactory short circuit performance.