Analysis of reducing total harmonic distortion in a PV integrated micro inverter

Abstract

The significant growth in photovoltaic (PV) energy is experienced in the last decade because of price reduction of PV modules and the revolution of PV micro inverters. High performance and reliability are the key merit to match the life time of PV and micro inverter. Multilevel micro inverters are mostly used for DC to AC power conversion, and they are divided into two types: current source inverters (CSI) and voltage source inverters (VSI). In the power industry, voltage source micro inverters are much more commonly used to convert lower DC voltages to higher AC voltages. The frequently used pulse width modulated (PWM) switching technology of DC sources introduces harmonics into the inverter output voltage during conversion. Total harmonic distortion (THD) is a measure of harmonic pollution in the power system, and it has been discovered that THD of inverter output voltage is affected by fluctuations in both DC voltages and switching angles of inverters. This study covers inverters with unequal DC sources, which is a reasonable and practical assumption. Evolutionary analysis is used to find the best DC voltages and switching angles for minimizing THD. This paper proposed a reliability and performance enhancement of micro inverter and new design has been proposed in single level and cascaded multilevel micro inverter for full irradiance and partial shading conditions. Design analysis with mathematical modeling is presented for the analysis of voltage and current ripples as well as for total harmonic distortion (THD). Two different scenarios are presented for simulations using MATLAB as tool. Results reveal that partial shading does increase the 44.01 % harmonics with cascaded inverters; however, the impact is limited as compared to single level micro inverter.