Active Gate Voltage Control of Bidirectional Switches used in AC-AC Converters

Abstract

Active gate voltage control (AGVC) consists in introducing an intermediate voltage level into the control voltage of isolated gate transistors at turn-on: it allows to force the rate- of-rise of current through the switched-on device to a fixed value [1]. In the case of AC-AC converter (alternative chopper), it is then possible to set the amplitude and duration of this intermediate voltage level so that each device switching may be achieved under reduced overcurrent and overvoltage conditions, simultaneously. In this paper, switching operation analysis and experimental results are presented, for antiseries association of diodes and IGBTs (series-connected current bidirectional switches). A closed-loop active gate voltage control is applied to control short-circuit current into the 2 bidirectional switch cell. Such a complete and safe control allows to avoid overvoltage across switching devices.