Hybrid space-vector pulse width modulation strategies for a four-level open-end winding induction motor drive with an improvised harmonic performance and balanced DC-link capacitors

Abstract

The four-level open-end winding induction motor (4-L OEWIM) drive is con stituted by two 2-level voltage source inverters (VSIs), wherein their DC-link voltages should be maintained in the ratio of 2:1. Owing to the unsymmetrical structure of the power circuit, the 4-L OEWIM drive is plagued with the draw back of capacitor voltage imbalance. The DC-link capacitor of one of the inverters, which is operated with the lower voltage level, that show the propen sity of getting charged up by its higher voltage counterpart, belonging to the other inverter. In this article, two variants of space-vector pulse width modula tion (SVPWM) schemes are suggested for the 4-L OEWIM drive. The suggested sample based SVPWM techniques achieve the voltage balancing of the DC-link capacitors, while improving the harmonic performance of the drive. Specifi cally, one of the two proposed PWM schemes manages to clamp one of the inverters in every sampling time interval. Hence this scheme results in lower ing the total harmonic distortion (THD) in the no-load current in most of the operating range of the drive, resulting in lower ripple in the motor phase cur rent, lower ohmic loss and reduced torque ripple. The performances of the pro posed PWM techniques are assessed with the aid of simulation studies and are validated with the experimentation.