Space vector based hybrid PWM for VSI fed variable speed induction motor drives

The space vector approach in real time PWM offers a variety of switching patterns for effective control of induction motor drives. The flexibility of placing zero vector results various advanced bus clamping PWM like continuous or discontinuous SVPWM. The performance of different PWM strategies subject to maximum switching frequency of inverter is analysed in terms of the Total Harmonic Distortion (THD) of no load current. An IGBT based 5 kVA voltage source inverter with a dc bus voltage of 540 V is designed and vector control is implemented by floating point DSP processor (TMS320F28335). The various PWM strategies are experimentally verified on 415 V, 3 hp, 50 Hz three phase induction motor. The simulated and experimental performance analysis reveals that these strategies perform better at different operating conditions. In this paper a hybrid PWM algorithm is proposed, which uses different PWM strategies at different pulse numbers for the various operating conditions for lowest harmonic distortion in the line current. The experimental results of IM drive strongly favor the effectiveness of the proposed hybrid PWM algorithm.