Design and Optimization for IGBT On-state Voltage Monitoring Circuit in Hybrid DC Circuit Breaker

The high-power press-pack insulated gate bipolar transistor (IGBT) is widely used in flexible direct current (DC) transmission system equipment, such as converter valves and DC circuit breakers. As a key performance parameter, the on-state voltage drop (uce) of IGBTs is of great significance to the reliability of the equipment and online monitoring. Research on online monitoring circuits for IGBT on-state voltage drop primarily focuses on converter applications. However, studies addressing DC circuit breaker conditions remain rare. The IGBTs in the communication branch of the hybrid DC circuit breaker handle the critical tasks of fault current transfer and interruption. Their real-time operating state requires close attention to ensure reliable performance. This paper designs and tests an online monitoring circuit for the IGBTs for on-state voltage drop in the communication branch of the hybrid DC circuit breaker. This process reveals a serious transient voltage overshoot issue caused by the unique operating conditions of the DC circuit breaker. The overvoltage directly impacts the circuit and can damage the operational amplifier. To solve this problem, this paper emphatically models the transient voltage during the IGBT switch. This study analyzes the influence of parasitic capacitance in semiconductor devices on transient voltage overshoot. It clarifies how parasitic capacitance contributes to the overvoltage phenomenon under specific operating conditions. Then, a voltage overshoot suppressing method is proposed and further verified through experiments. This approach offers significant potential for practical applications in DC circuit breakers.