Design and operation of an OCC-based scheme for a stand-alone PV system powering DC loads

Distributed energy resources such as stand-alone photovoltaic (PV) systems have been widely used in electric systems in the last decades due to the increase in global energy demand, and the concern about the environmental problems caused by fossil fuels power generation. Owing to the fast growing of direct current (DC) microgrids and electronic devices, such as their current compatibility nature in relation to primary sources, a small-scale stand-alone PV system with battery storage for DC applications is proposed in this work. The system consists of three DC-DC converters which operate according to the PV panel power and the main bus load demand. The control of these converters considers the quality in power supply ensuring safety to the loads and batteries of the system. Thus, this study proposes the implementation of the control units through the use of one-cycle control (OCC) which allows fast response to transient conditions, great accuracy of convergence and has low-cost analogue implementation. In this study, one-cycle controllers' waveforms are analysed in steady-state conditions and its duty cycles are compared with the expected in relation to the system operation. Simulations of transition conditions were performed through real situations such as cloud-edge effects, slow passing clouds and absence of sunlight.