OPTIMAL SIZING OF SOLAR-ARRAY AND INVERTER IN GRID-CONNECTED PHOTOVOLTAIC SYSTEMS

A new analytical approach is presented for finding the optimum ratio of photovoltaic array capacity to rated inverter input capacity in grid-connected photovoltaic systems. At optimum, the sizing ratio ranges from close to 1 for high insolation sites to well above 2 for low insolation conditions depending also on inverter characteristics and component costs. The sizing is more critical in low insolation conditions and the improvement of the economic performance thus obtained may be up to 20% compared to an inverter capacity equal to the PV-array. The optimum region is quite flat and up to +/- 20% deviations from the optimum point typically cause less than 2% losses. The analytical method coincides well with detailed numerical simulations for several locations (latitudes 33-60 degrees N) and PV-array orientations used in the verification.