Electricity Exchange between Control Areas Due to Tie Line Expansion and Demand Shifting Using Unit Commitment in Japan

Amid the growing concerns over global warming, Japan has set a goal to become carbon neutral by 2050. According to the long-term policy for a wide-area grid in the large scale introduction of renewable energy (RE) announced by the organization for Cross-regional Coordination of Transmission Operators (OCCTO) in March 2023, the construction cost is expected to be approximately 7 trillion JPY, half of which is for expanding tie lines between Hokkaido and Tohoku areas and between Tohoku and Tokyo areas using high-voltage direct-current submarine cables. Power demand shifting is one of the alternatives to the costly and time-consuming expansion of tie lines. In this study, the unit commitment simulation analysis is performed using the Japanese power system in 2050 for the electricity demand shift and expansion of tie lines, which have similar operational costs and RE output curtailment. The results of the analysis indicate that in the case of electricity demand shift, the amount of RE output curtailment decreases the most in Hokkaido area, where demand growth is small. Meanwhile, in the expansion of tie lines, the utilization between Tokyo and Chubu areas, where no expansion was implemented, increased.