A Hybrid Si/GaN-Based Quasi-Single-Stage Converter for Microgrid Applications with Simplified Space-Vector Modulation

In low-voltage energy storage microgird systems, the quasi-single-stage architecture is a promising alternative to improve the efficiency, which contains a direct power flow path from the battery to the inverter, resulting in reduced power losses by dc/dc converter. However, the unbalanced dc-link voltage of two ports certainly generates asymmetric space vectors. Thus, how to design the modulation strategy under this scenario is the major challenge. Meanwhile, the power losses are not only determined by the topology, but the device material such as gallium nitride (GaN) also has a significant impact on it. Therefore, a novel hybrid Si/GaN-based quasi-single-stage converter (HSG-QSSC) is proposed in this paper. Furthermore, a simplified space-vector modulation (SVM) scheme is presented to concentrate all the high-frequency switching events on the GaN HEMTs while the Si IGBTs operate with low frequency and avoid complicated triangle functions. As a result, the total power losses are reduced due to the decoupled frequency switching, and the high efficiency of calculation is achieved. Islanded microgrid experimental results with a hybrid Si/GaN active-neutral-point converter (ANPC) prototype are provided to verify the feasibility and effectiveness of the presented modulation scheme.