SIMULATION OF IGBTS FOR SERIAL CONNECTIONS USING ACTIVE VOLTAGE BALANCING CONTROL

Abstract

For high-voltage or high-power applications, it may be necessary to realize a logical switch by connecting smaller units in parallel and series to achieve high availability, high-frequency operation, and low cost due to build-in redundancy, reduced dynamic losses, and modular use of standardized units, respectively. IGBTs are very convenient to realize such units, because of quasi-linear controllability via a gate terminal. This thesis investigates control methodologies for power MOS semiconductor switches with focus on series connection of IGBT modules. It is proposed to provide each IGBT with primary local control to monitor and adjust the IGBT's static and dynamic behavior. That is, the entire system is manageable by the local gate drive circuitry. A simple auxiliary circuit has been proposed for high voltage IGBTs connected in series so as to realize a voltage balancing at both static and dynamic states and allow series operation of an almost unlimited number of devices. The simulations were performed in PSPICE using models of ST-Microelectronics and Infineon to verify the circuit by applying intentional delay differences in gate circuits The results show that transient voltage of switches when the auxiliary circuit is included is almost same even though there was some intentional delay between the two gate signals.