Title:
7.2 kV Three-Port SiC Single-Stage Current-Source Solid-State Transformer with 90 kV Lightning Protection
7.2 kV Three-Port SiC Single-Stage Current-Source Solid-State Transformer with 90 kV Lightning Protection
Author(s)
Zheng, Liran
Han, Xiangyu
Xu, Chunmeng
Kandula, Rajendra Prasad
Graber, Lukas
Saeedifard, Maryam
Divan, Deepakraj M.
Han, Xiangyu
Xu, Chunmeng
Kandula, Rajendra Prasad
Graber, Lukas
Saeedifard, Maryam
Divan, Deepakraj M.
Advisor(s)
Editor(s)
Collections
Supplementary to
Permanent Link
Abstract
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. 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.
Sponsor
This work was supported in part by ARPA-E under DE-AR0000899 and in part by the Center for Distributed Energy, Georgia Institute of Technology.
Date Issued
2022-05
Extent
Resource Type
Text
Resource Subtype
Post-print