7.2 kV Three-Port SiC Single-Stage Current-Source Solid-State Transformer With 90 kV Lightning Protection
- Georgia Inst. of Technology, Atlanta, GA (United States)
- Tesla, Palo Alto, CA (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
This article proposes a multiport modular single-stage current-source solid-state transformer (SST) for applications like photovoltaic, energy storage integration, electric vehicle fast charging, data center, etc. The 7.2 kV 50 kVA current-source SST consists of five input-series output-parallel modules, each based on 3.3 kV SiC reverse-blocking MOSFET-plus-diode modules. The proposed SST has some unique features. First, compared to the voltage-source or matrix converter-based SSTs, the current-source SST has a unique advantage of single-stage isolated AC/DC or AC/AC conversion with an inductive DC link, but no medium-voltage (MV) AC experiments have been reported. This article for the first time demonstrates MV AC current-source SST up to 7.5 kV peak. Second, the multiport SST has a buffer port for active power decoupling (APD) or energy storage integration. The double-line-frequency power ripple from single-phase AC grid normally results in a large capacitor size in MV SSTs. The APD scheme is proposed in MV applications for the first time to enable a reduced DC link and the electrolytic capacitor-less SST with high reliability. Third, as a direct grid-connected converter without line-frequency transformer, insulation and protection are critical. A medium-frequency transformer design passes 55 kV basic-insulation level (BIL) and 60 kV high potential dielectrics withstand test with only 0.09% leakage inductance. Importantly, a lightning protection scheme is presented to protect the SST itself from 90 kV BIL impulse. Fourth, the proposed current-source SST topology is a modular soft-switching solid-state transformer (M-S4T) with full-range zero-voltage switching and controlled dv/dt for low electromagnetic interference. Furthermore, these concepts are verified in a three-port M-S4T prototype with forced oil cooling under single-module, stacked-module, steady-state, and dynamic operations.
- Research Organization:
- Georgia Institute of Technology, Atlanta, GA (United States)
- Sponsoring Organization:
- USDOE Advanced Research Projects Agency - Energy (ARPA-E)
- Grant/Contract Number:
- AR0000899
- OSTI ID:
- 1892474
- Journal Information:
- IEEE Transactions on Power Electronics, Vol. 37, Issue 10; ISSN 0885-8993
- Publisher:
- IEEECopyright Statement
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
14 SOLAR ENERGY
17 WIND ENERGY
24 POWER TRANSMISSION AND DISTRIBUTION
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
42 ENGINEERING
Solid-state transformer (SST)
current-source inverter (CSI)
current-source converter (CSC)
high-frequency link (HFL)
input-series output-parallel (ISOP)
ZVS
medium-frequency transformer (MFT)
cascaded multilevel power electronic transformer (PET).