Robust Floating Capacitor Voltage Control of Dual Inverter Drive for Open-Ended Winding Induction Motor

A robust control scheme for the dual inverter drive using a floating capacitor bridge is proposed which allows decoupled control of the motor and the capacitor voltage. Indirect vector control is implemented in the rotor flux reference frame and the voltage references generated are then converted into the stator current reference frame. This allows for simpler assignment of inverter voltage references and eliminates the need for a dedicated PI controller to operate the main bridge at unity power factor. Feed forwarding of the stator current is also introduced which makes the capacitor voltage immune to any changes in the stator current. This allows the capacitor to be sized taking into consideration only the voltage ripple due to switching effects. These claims have been demonstrated both through simulation and experimentation. The effect of switching frequency and capacitance on the voltage ripple has also been studied.