Influence of forecast accuracy of photovoltaic power output on capacity optimization of microgrid composition under 30-minute power balancing control

Abstract

A microgrid (MG) is one of the measures for enhancing the high penetration of renewable energy (RE)-based distributed generators (DGs). If a number of MGs are controlled to maintain the predetermined electricity demand including RE-based DGs as negative demand, they would contribute to supply-demand balancing of the whole electric power system. For constructing an MG economically, capacity optimization of controllable DGs against RE-based DGs is essential. Using a numerical simulation model developed on the basis of a demonstrative study on an MG using PAFC and NaS battery as controllable DGs and photovoltaic power generation system (PVS) as an RE-based DG, this study discusses the influence of the forecast accuracy of PVS output on capacity optimization. Three forecast cases with different accuracy are compared. The main results are as follows. Even with no forecast error during every 30-minute period, the ideal forecast method, the required capacity of NaS batteries reaches about 40% of the PVS capacity for mitigating the instantaneous forecast error within 30 minutes. The required capacity to compensate for forecast error is doubled under the actual forecast method. The influence of forecast error can be reduced by adjusting the scheduled power output of controllable DGs according to weather forecasts. Besides, the required capacity can be reduced significantly if the error of balancing control in an MG is acceptable for a few percent of periods, because the total periods of large forecast error are not frequent. © 2012 Wiley Periodicals, Inc.