Implementation of SOLM as an Extended SVPWM for Variable Six Pulse DC-Bus Electrolytic Capacitor-Less VSI Based Constant V/f Induction Motor Drive

Synchronous one-leg modulation (SOLM) technique has been used for six-pulse dc-bus electrolytic capacitor-less voltage source inverter (VSI) considering reduced switching loss compared to space vector pulsewidth modulation (SVPWM). The existing method for generating the modulating signal in SOLM technique utilizes a sector identification-based approach. This work demonstrates, through both mathematical analysis and hardware results, that despite differences in the dc-bus voltage, modulating signal and instantaneous pole voltage waveforms between SVPWM and SOLM techniques, their average pole voltages are identical. Based on this understanding, this work proposes implementing the SOLM technique as an extension of SVPWM technique without requiring sector identification. A comparison between the proposed and the existing implementations of SOLM shows reduction in computational effort. A 1.25-kVA hardware prototype was developed for open-loop V/f control of a 1-hp induction motor. A comparison has been made between SVPWM with fixed dc-bus voltage, SVPWM with variable dc-bus voltage and SOLM with variable six-pulse dc-bus voltage. VSI efficiency with SOLM was in the range of 98.4%–99.1% at different operating conditions. Operation of the converter was successfully demonstrated under motor acceleration, steady-state operation as well as during deceleration.