Abstract: We describe a system for controlling very large numbers of power semiconductor switching devices (132) to switch in synchronisation. The devices are high power devices, for example carrying hundreds of amps and/or voltages of the order of kilovolts. In outline the system comprises a coordinating control system (110, 120), which communicates with a plurality of switching device controllers (130) to control the devices into a plurality of states including a fully-off state, a saturated-on state, and at least one intermediate state between the fully-off and saturated-on states, synchronising the devices in the at least one intermediate state during switching.

Abstract: This invention generally relates to voltage balancing among series-connected power switching devices comprising one or more insulated gate bipolar transistor (IGBT), and more particularly to a method controlling sharing of voltage among series-connected power switching devices, wherein at least one said device is an insulated gate bipolar transistor (IGBT), the method comprising: controlling the IGBT dependent on a reference signal and collector or emitter voltage of the IGBT such that during an off period of said IGBT said reference signal limits an absolute value of collector-emitter voltage of said IGBT to be within a range; and control to temporarily change during said limiting said reference signal from an initial value to a temporary clamp value to reduce said range, said change when each of said devices is in a substantially non-conducting state.