Modified Soft-Switching System With Safe Connections of Capacitors and Inductors in Three-Phase Voltage Source Inverter

This article presents a modified soft-switching system for three-phase voltage source inverters. Similar to the basic soft-switching system, capacitors are not connected in parallel to the main transistors, and inductors are not connected in series with the auxiliary transistors. These connections protect the inverter from damage when disturbances occur in the control system. Unlike the basic version, the modified soft-switching system does not allow resonant processes to affect the voltage waveform on the load, and the modified system features a simpler control algorithm for the main and auxiliary transistors. The structure and operating principles of the modified soft-switching solution are comprehensively described herein. Additionally, the principles for selecting the elements of the modified soft-switching system are discussed. The system's operation is validated through laboratory tests using a three-phase voltage source inverter (10 kW, 400 V) to supply a squirrel-cage induction motor, whereas numerical calculations are performed for inverters with higher rated power. The switching losses of the inverter operating under the modified soft-switching solution are compared with those of an inverter operating under the hard-switching technique. Results show that the proposed modified soft-switching system increases inverter efficiency .