Hybrid switching sequences for harmonic distribution in voltage source inverter [articol]

Abstract

This paper analyzes the harmonic distribution in the voltage and current of the voltage source inverter (VSI) through adjusting randomize the inactive vectors operating period of the space vector modulation (SVM) for different sequence inside the sector. Initially the range of inactive vector operating period is analyzed for different sequence is studied with respect to harmonics distribution. Degree of randomization inside the sector is analyzed in terms of sequences which is decide means of modulation index as well as selection of inactive vectors. Based on the selection of inactive vectors randomization, five different inactive vector timing is proposed namely null active T0>T7, full inactive T0<T7, alternate null full, alternate with fixed random T0 dominant and alternate with fixed random T7 dominant. These randomized operating times is implemented in the zone wise sequence which results in harmonic spreading in the output voltage. Additionally, the zonal distribution of T0 & T7 inactive vector operating timings is make significant effect in the current ripple. The randomization of inactive operating time is analyzed in terms of d-q axis and RMS current ripple expression which is suitable for motor fed drive. Advantage of the proposed scheme is reducing the switching loss than existing schemes with superior harmonics distribution. Effectiveness of the proposed scheme is analyzed through harmonic spreading factor, harmonic distortion in the output voltage and current. Practical implementation of new scheme is through the dead time showing the effectiveness of the study. The simulation and experimental results showing the effectiveness of the mathematical concepts proposed.