Design and Development of Digital Control Strategy for Solar Photovoltaic Inverter to Improve Power Quality

Abstract

The design and development of control circuit for a solar fed cascaded multilevel inverter is postulated in this paper. The control circuit based on logic operations reduces the semiconductor switches required for the multilevel inverter. In addition to the reduction of switches, it also improves the quality of the output power by minimizing the Total Harmonic Distortion (THD). The proposed design achieves the maximum output voltage levels without the requirement of detailed look up table, boost converters and output transformers. The implementation of multilevel inverter is carriedout with asymmetrical DC sources from solar photovoltaics to achieve 2^ns+1-1 and 3^ns levels, where ns is the number of individual inverter stages. Based on the proposed design 12 switches are required to achieve 15 and 27 levels respectively, whereas the conventional inverter can able to produce only 7 levels. MATLAB/Simulink is used for the simulation of the system. The modelling of solar panel which adheres to the experimental setup is developed. A 3kWp solar plant is taken into consideration for the implementation of the proposed control design and the performance parameters are measured using power quality analyser. The results are compared with the conventional inverter which shows that the proposed inverter is much suitable for both standalone and grid connected systems.