Abstract
Series connection of multiple transistors is an attractive solution to achieve higher voltage capability. However, the voltage imbalance among the series-connected devices is a critical issue caused by mismatches of device characteristics and gate signals. To prevent the failure of devices from the voltage imbalance, voltage balancing control (VBC) is required. In this work, an active VBC for series-connected silicon carbide (SiC) mosfet submodules is proposed with a pulsewidth modulation (PWM) method. A submodule consists of two switches and one shunt capacitor, and the PWM method actively controls the capacitor voltages for balancing. The proposed VBC is simulated in MATLAB/Simulink and experimentally verified with six series-connected SiC mosfet submodules at up to 150 kHz. The voltage balancing is achieved within 3.9% of the targeted balanced voltage.
Highlights
Silicon (Si)-based power devices, such as insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs), have been widely adopted in power electronics applications over several decades
digital signal processor (DSP) was used as a central controller, and it directly controlled the pulsewidth modulation (PWM) signals without additional analog control circuits
The proposed voltage balancing control (VBC) was simulated in MATLAB/Simulink and was experimentally validated with four series-connected silicon carbide (SiC) MOSFET submodules
Summary
Silicon (Si)-based power devices, such as insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOSFETs), have been widely adopted in power electronics applications over several decades. Extensive studies have been proposed for voltage balancing of series-connected devices, such as passive snubber circuit, active gate control, and capacitive coupling method. Snubber capacitor technique was studied for eight series connected SiC MOSFETs in a dc/dc converter and achieved accurate voltage balancing [25]. The switching frequency is less than 50 kHz in most cases, much lower than the switching frequency capability of SiC MOSFETs. In this paper, a VBC for series-connected SiC MOSFET submodules is proposed with PWM method to efficiently balance the device voltages. In the RC snubber circuit, the device voltage rising speed is determined by the capacitor charging speed as dVS1,n/dt = i/Csnb since the initial voltage of Csnb is zero during turn-off transient of S1,n.
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