Direct torque control of induction motor using three-level diode clamped inverter with DC-link capacitors voltage balancing

A simple switching table-based direct torque control of induction motor using three-level diode clamped inverter with DC-link capacitor voltage balancing is proposed in this paper. This scheme effectively utilises redundant states of small voltage vectors for charging and discharging of DC-link capacitors. The capacitor voltage balancing of the inverter is incorporated in the switching table of direct torque control. The switching table employed in this scheme balances the capacitor voltages for all operating conditions and it does not require any additional circuitry. To validate this scheme, extensive simulations are carried out for different load conditions. The steady state and transient operations of drive are investigated. The dynamics of DC-capacitor voltages are also tested. The results show that the proposed scheme provides capacitor voltage balancing and reduces neutral point drift voltage. The proposed scheme can be considered for medium and low voltage industrial drive applications.