High-Efficiency Silicon Carbide-Based Buck-Boost Converter in an Energy Storage System: Minimizing Complexity and Maximizing Efficiency
Zheyu Zhang, Hao Tu, Xu She, Tomas Sadilek, Ramanujam Ramabhadran, Huan Hu, William Earls
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.