A MODIFIED PWM SCHEME TO IMPROVE AC POWER QUALITY FOR MLIS USING PV SOURCE

A. Rakesh Kumar, Deepa Thangavelusamy, Sanjeevikumar Padmanaban, and Dwarkadas P. Kothari

Keywords

Multilevel inverter, PV, total harmonics distortion, nearest levelmodulation, power qualityList of AbbreviationsCCS MLI cross-connected sources-basedmultilevel inverterIGBT insulated gate bipolar transistorMLDCLI multilevel DC-link inverterMLI multilevel inverter∗ School of Electrical Engineering, Vellore Institute of Technol-ogy, Chennai, India; e-mail: rakesh9490@gmail.com, Deepa.t@vit.ac.in∗∗ Department of Energy Technology, Aalborg University,Aalborg, Denmark; e-mail:

Abstract

A low-switching frequency PWM scheme offers numerous advantages over high-frequency PWM schemes for multilevel inverters (MLIs). The paper demonstrates the implementation of a modified low- switching frequency PWM scheme on MLIs with photovoltaic system as input source. The proposed modulation scheme is an improvement over the conventional nearest level modulation scheme. A multilevel DC-link inverter topology of symmetric configuration is used to test the proposed modulation scheme. An algorithm for the same is also designed which enables the proposed modulation scheme to be implemented on any MLI. The simulation is carried out using Matlab/Simulink and extended to an experimental setup. The effectiveness of modified nearest level modulation can be observed in terms of reduced voltage total harmonics distortion (THD) and current THD at the MLI output. Because of the reduced THD, the RMS voltage, RMS current and output power have increased considerably.

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