Title: Soft-Switching Solid-State Transformer With Reduced Conduction Loss

Journal Article · · IEEE Transactions on Power Electronics
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]
  1. Georgia Inst. of Technology, Atlanta, GA (United States). School of Electrical and Computer Engineering; Georgia Inst. of Technology, Atlanta, GA (United States)
  2. Georgia Inst. of Technology, Atlanta, GA (United States). School of Electrical and Computer Engineering
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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 are typically three-stage, i.e., hard-switching cascaded multilevel rectifiers and inverters with dual active bridge (DAB) converters, which leads to bulky passives, low efficiency, and high electromagnetic interference (EMI). This article proposes a new soft-switching solid-state transformer (S4T). The S4T has full-range zero-voltage switching (ZVS), electrolytic capacitor-less dc link, and controlled dv/dt, which reduces EMI. The S4T comprises two reverse-blocking current-source inverter (CSI) bridges, auxiliary branches for ZVS, and transformer magnetizing inductor as a reduced dc link with 60% ripple. Compared with the prior S4T, an effective change on the leakage inductance diode is made to reduce the number of the devices on the main power path by 20% for significant conduction loss saving and retain the same functionality of damping the resonance between the leakage and resonant capacitors and recycling trapped leakage energy. The conduction loss saving is crucial, being the dominating loss mechanism in SSTs. Importantly, the proposed single-stage SST not only holds the potential for high power density and high efficiency but also has full functionality, e.g., multiport dc loads integration, voltage regulation, and reactive power compensation, unlike the traditional single-stage matrix SST. The S4T can achieve single-stage isolated bidirectional dc–dc, ac–dc, dc–ac, or ac–ac conversion. It can also be configured input-series output-parallel (ISOP) in a modular way for medium-voltage (MV) grids. Hence, the S4T is a promising candidate for the SST. The full functionality, e.g., voltage buck–boost, multiport, etc., and the universality of the S4T for the dc–dc, dc–ac, and ac–ac conversion are verified through the simulations and experiments of two-port and three-port MV prototypes based on 3.3 kV SiC MOSFETs in dc–dc, dc–ac, and ac–ac modes at 2 kV.

Research Organization:
Georgia Inst. of Technology, Atlanta, GA (United States); Georgia Institute of Technology, Atlanta, GA (United States)
Sponsoring Organization:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Grant/Contract Number:
AR0000899
OSTI ID:
1848302
Journal Information:
IEEE Transactions on Power Electronics, Journal Name: IEEE Transactions on Power Electronics Journal Issue: 5 Vol. 36; ISSN 0885-8993
Publisher:
IEEECopyright Statement
Country of Publication:
United States
Language:
English

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14 SOLAR ENERGY
17 WIND ENERGY
24 POWER TRANSMISSION AND DISTRIBUTION
25 ENERGY STORAGE
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
42 ENGINEERING
MVDC
current-source converter (CSC)
dc transformer (DCT)
distributed renewable energy resource (DER)
engineering
high-frequency link (HFL)
power electronic transformer (PET)
smart grid
soft-switching solid-state transformer (S4T)
solid-state transformer (SST)