Power Converter for Dual-Power PV-Grid Energy System Utilizing Cascaded Multilevel Inverter

Abstract

The dual-power PV-grid system was introduced to manipulate the lower tariff rate at off-peak period and to reduce the capital installation cost of PV energy system. The power converter in the PV energy system is used to process solar energy captured by PV modules into usable electrical energy. In the dual-power PV-grid system, the power converter component is consists of a boost regulator to boost and regulate PV outputs to fixed voltage of 240V, 50Hz, a maximum power point tracker (MPPT) to derive maximum power from PV panels and a three operation modes of the battery converter to regulate charging current/discharging current under various PV output and load variation. In this project, a reduced switch and increased level of cascaded H-bridge multilevel inverter was introduced to convert the direct current (DC) output of the solar energy to alternating current (AC) signal to supply an AC load or to be integrated to the grid system. By adapting selective harmonic elimination (SHE) switching strategy, the inverter produces 21 levels of stepped sinusoidal output signal with resultant total harmonics distortion (THD) of 3.90%.