Space Vector Methods for AC Drives to Achieve High Efficiency and Superior Waveform Quality

摘要

Space vector approach to pulse width modulation offers several advantages over the traditional triangle comparison methods, which are not fully exploited by conventional space vector PWM (SVPWM). New sequences, which divide the active vector duration, offer additional degrees of freedom that are not possible in triangle comparison approach. The objectives of this research are to identify% all such new sequences and develop new PWM techniques that reduce distortion and switching loss. Four new sequences involving active state division are introduced. The concept of stator flux ripple is used to design THD-optimized PWM techniques. By applying different sequences within a sector based on above techniques, THD can be reduced by 47% compared to conventional SVPWM. The effects of sequences on inverter switching loss are analyzed to design a new hybrid PWM that reduces switching loss by 30%. This involves using sequences that clamp the phase with the highest current, and double switch the phase with lowest current. Finally, a combined hybrid PWM technique that simultaneously reduces THD by over 30% and switching loss by 20%, under nominal conditions is developed. The new techniques have been implemented in a 2kW induction motor drive controlled by a DSP - TMS320F243. THD reduction of 38% in the THD-optimized PWM and switching loss reduction of 30% in the loss-optimized PWM are demonstrated. Future work in this area may focus on extending the concept to multi-level inverters.