Evaluation of Power Surpluses and Shortfalls Due to Error in Forecasting of Photovoltaic Generation Output

The 2011 Tohoku earthquake had a great impact on Japanese energy policy. It is expected that nuclear power plants will be phased out and a large amount of generation from renewable energy sources will be installed. Attention is particularly focused on photovoltaic (PV) generation, technology in which Japan is superior, and a high price is set in the feed-in tariff policy, which started in 2012. However, large integration of PV into power grids may cause imbalances between power supply and demand. It will be indispensable to use PV power generation forecasts in economic-load dispatching control (EDC), so that the economics and reliability of power systems networks can be maintained. Thus, in the previous study, we proposed an EDC method with unit commitment (UC) based on the results provided by a day-ahead PV forecast. In this study, we evaluate the frequency and trend of shortfalls and surpluses of power due to error in forecasting PV power generation by numerical simulations using the power system model of the Kanto area in Japan. The results showed that shortfalls or surplus power occur not only due to overestimations or underestimations of PV power, but also due to the operating conditions of the power systems.