Research Article Open Access

A GSA Based Generalised Formulation of SHE-PWM Problem of Multilevel Inverter for Both Equal and Unequal Source Voltages

Abstract

A generalised formulation of SHE-PWM technique applicable for high power voltage source cascaded multilevel inverter used in constant frequency utility applications has been discussed in this paper. The SHE-PWM scheme features a broad solution space. This paper aims at to eliminate low order dominant harmonics and at the same time maintaining fundamental also. Since SHE equations are non-linear transcendental in nature , to solve these equations a new artificial intelligence technique called Gravitational Search Algorithm has been implemented to find out switching angles with faster and guaranteed convergence. To illustrate the effectiveness of the proposed method, a 3-phase five level voltage source inverter has been considered with six no. of switching per quarter cycle. Since for a 3- phase balanced system all the triplen harmonics are absent in the line, thus in this case with six no of switching per quarter cycle, five dominant non-triplen harmonics (5th to 17th) was possible to eliminate using SHE-PWM technique for both equal and unequal source voltages for a wide range of modulation index and voltage ratio. Then the output voltage THD obtained using this approach is compared with another approach for minimum system voltage THD.

Sayanti Ray, Pradip Kumar Saha, Goutam Kumar Panda