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Power imbalances such as power shortfalls and photovoltaic (PV) curtailments have become a major problem in conventional power systems due to the introduction of renewable energy sources. There can be large power shortfalls and PV curtailments because of PV forecasting errors. These imbalances might increase when installed PV capacity increases. This study proposes a new scheduling method to reduce power shortfalls and PV curtailments in a PV integrated large power system with a battery energy storage system (BESS). The model of the Kanto area, which is about 30% of Japan’s power usage with 60 GW grid capacity, is used in simulations. The effect of large PV power integration of 50 GW and 100 GW together with large BESS capacity of 100 GWh and 200 GWh has been studied. Mixed integer linear programming technique is used to calculate generator unit commitment and BESS charging and discharging schedules. The simulation results are shown for two months with high and low solar irradiance, which include days with large PV over forecast and under forecast errors. The results reveal that the proposed method eliminates power shortfalls by 100% with the BESS and reduce the PV curtailments by 69.5% and 95.2% for the months with high and low solar irradiance, respectively, when 200 GWh BESS and 100 GW PV power generation are installed.

During cold-air outbreaks in winter, a thick cloud band frequently appears over the northern Sea of Japan and produces localized heavy snowfall in the western coastal region of Hokkaido Island, northern part of Japan. The formation mechanism of this thick cloud band is investigated through a series of nonhydrostatic numerical simulations with a horizontal grid spacing of 5 km. The control simulation well reproduces the characteristics of an observed cloud band. The cloud band forms between relatively warm north-northwesterly winds on the northeast side and relatively cold northwesterly winds on the southwest side. Sensitivity experiments in which upstream topography is modified indicate that the formation and intensification of the cloud band depend on the following two e¤ects; one is the e¤ect of a specific mountain located near the coastline in the middle part of Russia's Sikhote-Alin mountain range (SAMR), and the other is the e¤ect of large-scale topography along the SAMR on synoptic-scale low-level cold northwesterlies.The specific mountain deflects the cold airflow and immediately a convergence zone forms downstream of the specific mountain, where the cloud band is initiated. On the northeastern side of this mountain, the Froude number is estimated to be about 0.4 from relatively high topography (@1.2 km), stable stratification (@0.02 s À1 ), and synoptic-scale wind speed of 10 m s À1 . Thus, the relatively high topography strongly blocks a low-level cold air, whereas an upper air with high potential temperature flows downward over the sea. In contrast, on the southwestern side of the mountain, a low-level cold air can pass over the topography, because the Froude number is estimated to be about 1.6 from relatively low topography (@0.8 km) and weak stable stratification (@0.008 s À1 ). These two airs with di¤erent potential temperature create a mesoscale frontal zone over the sea, which causes the further development of the thick cloud band initiated by the coastal specific mountain in the SAMR.