Symmetrical DC-Link Capacitor Voltage for Multi Solar PV Array Fed CHBMLI in Standalone Application

Abstract

In this paper, a generalized algorithm is proposed to balance the DC-link (DCL) voltage across each power cell of n number of cascaded H-bridge multilevel inverter (CHBMLI), using dc-dc converter, fed from multi solar photovoltaic (SPV) array for standalone application under varying environmental conditions, i.e. variation in radiation and temperature. Due to variation in the environmental conditions, the power flow through each H-bridge modules changes and subsequently the DCL voltage might change. This leads to unequal DC levels in the pole voltage of the CHBMLI, which results in different switching stress of the power modules. Therefore, the life span of the switches will get reduced. To maintain equal switching stress on each H-bridge module, duty cycle of the boost DC to DC converters is varied according to the proposed algorithm. It maintains equal voltage at the output of the boost converter under uniform/non-uniform environmental conditions. To operate the CHBMLI, the triangular carrier phase-shifted modulation has been used. The proposed algorithm as well as performance of the multi-SPV fed CHBMLI is simulated using PSCAD/EMTDC software for three-bridge seven-level CHBMLI. The experimental results are obtained using E4360 Modular Solar Array Simulator and Spartan 3AN FPGA controller for two-bridge five-level CHBMLI.