Utility friendly three-level neutral point clamped converter-fed high-performance induction motor drive

In this study, a two back-to-back three-level neutral point clamped (TLNPC) converter system is presented for industrial and traction applications. The front-end TLNPC ac-dc converter draws sinusoidal ac current from the supply and the current remains in phase with the supply phase voltage leading to unity input power factor. The front-end TLNPC ac-dc converter also keeps the total dc-link voltage constant. Hysteresis current control is used for the control of front-end TLNPC ac-dc converter. The load-end TLNPC dc-ac converter is used for driving an induction motor operating under direct torque control (DTC) scheme. The proposed control technique ensures constant stator flux control for forward motoring and reverse motoring. The DTC principle is applied to the entire speed range. The front-end converter and load-end converter are controlled independently. A two-quadrant chopper circuit is employed to equalise the capacitor voltages. The experimental results of the complete drive system are presented here for both forward and reverse motoring operations with regeneration capability. The experimental results show the effectiveness of the proposed system.