Analysis of Six Pulse Modulation High Frequency Three Phase Inverter

Abstract

Fuel cells have achieved global attention as alternative power sources due to the environmentalconcerns. The prime focus of this paper is to design a three phase inverter fed with hybrid modulationtechnique suitable for fuel cell applications. Hybrid modulation technique comprises two differentmodulation schemes. Unlike conventional sinusoidal pulse width modulated inverter this inverter needsonly one third modulation of switching devices reducing the switching losses.It reduces the control complexity owing to single-reference three-phase modulation as compared to conventional three-reference three-phase SPWM. In addition, it relives the necessity of dc-link capacitor reducing the cost and volume. Eliminating dc link capacitor helps in retaining the modulated information at the input of the three-phase inverter. At any instant of line cycle, only two switches are required to switch at HF and remaining switches retain their unique state of either ON or OFF. At the same time inverter devices are not commutated when the current through them is at its peak value. Drop in switching loss is very high in comparison with a standard voltage source inverter (VSI) employing standard three-phase sine pulse width modulation. This proposed work explains operation and analysis of the HF two-stage inverter modulated by the proposed modulation scheme. MATLAB 7.1 software is used for the analysis of the system.