Control of an open-ended induction machine using a dual inverter system with a floating capacitor bridge

A speed control scheme is proposed for a 3-phase induction motor that uses an open-ended stator winding fed by a dual inverter system with a floating bridge. The floating bridge has a voltage boosting function that extends the constant power high-speed range of the induction machine and operates the main inverter bridge at unity power factor. The proposed control scheme coordinates the two inverters that supply the motor, regulates the dc-link voltage of the floating bridge and boosts the machine terminal voltage at high speed. Simulation results are used to clarify the motor-drive torque capability in the high speed region. Experimental results show that a significant power improvement is achievable in the field weakening region.