A Module-Based Self-Balancing Series Connection for IGBTs

This article presents a self-balancing technique for voltage sharing of series-connected insulated gate bipolar transistors (IGBTs). Each series IGBT is augmented with an auxiliary switch, which operates in complementary to the main one, and a capacitor in series. When gate signal delays, based on the capacitor voltage feedbacks, are applied to the series modules, the voltage sharing can be balanced. The delays are generated with local controllers without DSP/field-programmable gate array, regardless of the parasitic element distribution, thermal characteristics of the devices, or current amplitudes. Since there is no resistive element in the auxiliary branch, the balancing circuit is low loss. The circuit and the operation modes are provided in detail and illustrated with simulation models. Experimental results with ten series modules at different voltage levels are presented to demonstrate the principle of control, and the performance of the proposed technique.