Technology-Oriented Analysis of Active Thermal Control in Si-IGBT and SiC-MOSFET During LVRT Events

Abstract

Low Voltage Ride Through (LVRT) requirements impose short-time overcurrent operation in grid-connected converters, directly stressing the thermal limits of power semiconductor devices. Conventional solutions based on current limitation or stage oversizing either compromise grid support capability or increase cost and volume. Active Thermal Control (ATC) has emerged as a control-oriented alternative to dynamically manage junction temperature during fault events. However, its effectiveness strongly depends on the underlying semiconductor technology. This paper presents a technology-oriented analysis of three ATC strategies during LVRT operation: gate voltage $\left(V_{\mathbf{G}}\right)$ increase, switching frequency $\left(f_{\text{sw }}\right)$ reduction, and discontinuous PWM (DPWM3), applied to both a Si-IGBT module and a SiC-MOSFET module under identical grid-support conditions. A unified electrothermal framework with temperature feedback and current- and gate-voltage-dependent loss modelling is employed. For the Si-IGBT module, reducing the switching frequency to $0.6 f_{\text{sw }}$ decreases the maximum transistor junction temperature from 159.0 °C to 120.3 °C, corresponding to a 24% reduction. For the SiC-MOSFET module, increasing the gate voltage to 20 V reduces the maximum junction temperature from 169.6 °C to 130.8 °C, achieving a 23% reduction. The results demonstrate that ATC effectiveness is technology dependent: switching-loss-oriented strategies are more beneficial for IGBTs, while conduction-oriented strategies are more effective for SiC devices.