Proposal of a new soft switching system for three-phase voltage source inverters

The paper presents a new soft switching system in three-phase voltage source inverters. In the majority of existing soft switching systems, there is a risk of damaging main or auxiliary transistors in the case of disturbances in the control system due to capacitors that are connected in parallel to the main transistors and due to resonant inductors which are connected in series to the auxiliary transistors. In the proposed new soft switching system, a danger of an abrupt discharge of capacitors through a conductive transistor does not occur and there is no risk of the interruption of the inductor current which usually causes damage to transistors. The paper describes the operation principles and the control algorithm of the presented solution, which is much simpler with respect to the control methods in soft switching systems applied by now. The method of the selection of the soft switching system's elements is also briefly described. The operation correctness of the presented system has been confirmed by laboratory research, and attention has been paid to certain limitations of the control system.