Performance Analyzing of Stand-Alone PV Hybrid Mini-Grid System with PV at DC and AC Coupling

Abstract

Stand-alone PV system has been originally developed to feed solar energy produced by PV modules into the system by using solar charger controller at DC bus called “DC Coupling” for long time. In Late 1990 there is a new concept of feeding solar energy to the PV system at AC bus called “AC Coupling”. The AC coupling system uses grid connected inverter to convert energy produced by PV modules and synchronize output to AC distribution line. In mini grid system the common AC output of Bi-directional inverters or diesel generators performs as grid forming device to supply distribution line. Since 1990 there are stand-alone PV systems designed by using DC coupling or AC coupling which each type of PV coupling system highlight their advantage over the other. The work in this document presents a comparison of the efficiency of DC coupling and AC coupling PV system design in a hybrid mini-grid and finally proposes the alternative PV system design by using the “Dual DC and AC coupling” PV system in a hybrid mini-grid design. The HOMER Pro micro-grid analysis tool which can simulate DC and AC coupling PV system is used to compare leverage cost of energy (LCOE) of different type of PV hybrid mini-grid system. The simulation software which can do performance analyzing metric according to IEC 61724 and IEA-PVPS T2 is created in this study in order to simulate system operation and performance using DC, AC and dual DC and AC coupling PV system. The conclusion can clearly identify the best PV system in hybrid mini-grid in terms of LCOE and system performance.