Eliminating output distortion in four-switch inverters with three-phase loads

A new space vector switching strategy for four-switch inverters driving three-phase induction motors is described. The technique allows a full range of operation, compensating for both DC link ripple and imbalance to eliminate torque and speed pulsations under all operating conditions, while allowing the largest possible voltages to be produced. The paper presents theoretical expectations and compares these with measured values obtained from an inverter operating off a single phase AC supply corresponding to worst case conditions.