Integration of Solar Photovoltaic (PV) Systems with CCM Inverters into VCM Droop-Controlled Islanded AC Microgrids

Abstract

Nowadays, photovoltaic (PV) systems and microgrids are two of the main technologies in electrical engineering researches. Both are important to realize different types of energy management, feeding islanded loads with high reliability, efficiency, social benefits, low cost and environmental impact. This paper assess the possibility of connecting a PV system to a droop-controlled islanded AC microgrid without modified advanced controls, additional components or the use of batteries in a way that only simple standard commercial equipment are used. Two inverters operating with Voltage Control Mode (VCM) employing the droop control method to form an islanded AC microgrid is approached. These inverters function as grid forming converters giving voltage references in order to integrate them with a conventional solar PV system in Current Control Mode (CCM), consolidated technologies which are easily found on the market, since they are used for grid-tie. The proposed complete system is analysed for a typical day, with real measured variations of irradiance and temperature. The computational results of the VCM and CCM inverters integrated is exposed, showing its feasibility and its limitations.