Modeling and Control of Three-Level Boost Rectifier Based Medium-Voltage Solid-State Transformer for DC Fast Charger Application

摘要: This paper presents modeling, control, and system design of three-level boost (TLB) rectifier based medium-voltage (MV) solid-state transformer (SST) for dc fast charger application. In order to operate at MV with 1.2-kV SiC devices, the target is configured by input-series output-parallel (ISOP) multimodule structure. Each module adopts TLB front-end stacked half-bridge LLCs back-end isolated dc–dc converters. Operation principles LLC converters are analyzed derive an equivalent model entire system. Based on detailed derivation, this aims achieve three performance criteria, including bus voltage regulation, input current balancing. Basic feedback control loops designed TLB’s output in average manner, derived model. Then, ideal duty-ratios both continuous/discontinuous conduction modes duty-ratio feedforward proposed improve low quality due inherent limitations. For balancing, approaches used SST prototype. With design, a prototype four-module-stacked was built tested up 3.8-kVrms 16-kW conditions.