Control strategy of power converter system in the dual-power PV-grid system energy utilizing cascaded multilevel inverter

摘要

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 system consists of a boost regulator to boost and regulate PV outputs to fixed voltage of 240V, 50Hz, a maximum power point tracking (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. The system utilizes 25 levels of cascaded multilevel inverter to invert DC voltage from solar panel to AC voltage. The operation and the synchronization of the power converter system was digitally controlled to ensure the system works at maximum captured power, fast switching with minimum losses, and produces fixed 240 V, 50Hz power supply in variation of environmental conditions. In this paper, the control strategy implemented in the power converter system in the dual-power PV-grid energy system are described and discussed.