Design of the active voltage controller for series IGBTs

This paper presents an investigation into the stability and performacc of the Active Voltage Control (AVC) method of gate drive applied to Insulated Gate Bipolar Transistors (IGBTs). The analysis is performed using standard control theory methods. Various parameters that affect the stability of the feedback system are investigated using root locus plots. It will be shown that the bandwidths of various elements of the controller and the stray inductances in the gate-emitter circuitry are influential. This sets the design guidelines for improving the performance of the gate drives and for designing the compensating controller. Finally, experimental switching results from an IGBT switched with AVC using an optimised controller will be given and conclusions drawn.