Three Phase Space Vector PWM Based Multilevel Inverter for Pumping Applications

Abstract

This paper presents a three phase modular multilevel inverter (MMLI) topology with reduced number of sources, switches and eliminates the need of flying capacitors and its associated problems like capacitor unbalancing, capacitor overcharging bulky size, cost etc. The switching pulses for the MMLI are generated through space vector modulation (SVM) algorithm for reduced harmonic distortion (HD) in output voltage and current. The MMLI consists of basic three phase two level inverter with additional bidirectional modules in each phase. The bidirectional module consists of four diodes and a switch that can conduct in both directions. This topology can be easily extended for higher output levels with appropriate number of modules in each phase. Theoretical description is given for five level MMLI and results are presented for 11- level MMLI feeding an induction motor suitable for pumping applications. Also, the reliability of the inverter is tested for two conditions open circuit and short circuit of a phase in a module.
Keywords: MMLI; Space vector PWM; Pumping applications.