A new optimized space vector modulation strategy for a component minimized voltage source inverter

This paper presents a new space vector modulation strategy suitable for a low cost PWM-VSI inverter employing only four switches, four diodes and a split capacitor bank in the DC-link. The work is motivated by the need of an efficient and flexible modulation method, which is optimized with respect to minimum machine torque ripple. The modulation strategy is named Space Vector Modulation for Four Switch Inverter (SVMFSI) and is realized by planning the switching patterns between four active voltage vectors on the basis of a desired flux trajectory for the stator flux vector in the AC-machine (variable speed induction motor drive). The strategy is implemented in a single 8-bit microcontroller as a double sided modulation strategy. Simulations of the motor torque ripple are performed at a switching frequency of 4 kHz and indicate a torque ripple of 14% at nominal load. Finally, selected results are verified experimentally on a 1.5 kVA prototype B4 inverter. The test results indicate high quality output voltage spectra with no low-order voltage harmonics and a harmonic loss factor (HLF) of 1.12% at unity modulation index