Soft-Switching Solid-State Transformer With Reduced Conduction Loss

Solid-state transformers (SSTs) are a promising solution photovoltaic (PV), wind, traction, data center, battery energy storage system (BESS), and fast charging electric vehicle (EV) applications. The traditional SSTs typically three-stage, i.e., hard-switching cascaded multilevel rectifiers inverters with dual active bridge (DAB) converters, which leads to bulky passives, low efficiency, high electromagnetic interference (EMI). This article proposes new soft-switching solid-state transformer (S4T). S4T has full-range zero-voltage switching (ZVS), electrolytic capacitor-less dc link, controlled dv/dt, reduces EMI. comprises two reverse-blocking current-source inverter (CSI) bridges, auxiliary branches for ZVS, magnetizing inductor as reduced link 60% ripple. Compared the prior S4T, an effective change on leakage inductance diode is made reduce number of devices main power path by 20% significant conduction loss saving retain same functionality damping resonance between resonant capacitors recycling trapped energy. crucial, being dominating mechanism in SSTs. Importantly, proposed single-stage SST not only holds potential density efficiency but also full functionality, e.g., multiport loads integration, voltage regulation, reactive compensation, unlike matrix SST. can achieve isolated bidirectional dc-dc, ac-dc, dc-ac, or ac-ac conversion. It be configured input-series output-parallel (ISOP) modular way medium-voltage (MV) grids. Hence, candidate buck-boost, multiport, etc., universality conversion verified through simulations experiments two-port three-port MV prototypes based 3.3 kV SiC mosfets modes at 2 kV.