1.State Key Laboratory of Power System Operation and Control (Tsinghua University), Beijing 100084, China;2.Economic and Technological Research Institute of State Grid Gansu Electric Power Company, Lanzhou 730030, China;3.Laboratory of Carbon Energy, Tsinghua University, Beijing 100084, China

With the high proportion of renewable energy, extreme weather events bring great risks and challenges to power production. Among these extreme weather events, extreme steady weather, as a special atmospheric feature, usually tends to result in continuous low renewable energy output for days, which greatly impacts the long-term supply-demand balance of new power systems. Aiming at the risk of long-term supply-demand imbalance caused by extreme steady weather, a quantitative risk assessment and control method is proposed from the perspective of optimal planning. Firstly, the extreme steady weather for power security is defined, and extreme scenarios are identified and extracted. Then, based on the extracted scenarios, the power production simulation is carried out, and the evaluation index system of long-term power supply-demand imbalance is constructed. On this basis, a risk assessment model of long-term supply-demand imbalance in extreme steady weather based on chance constraints is proposed. Finally, the above-mentioned model is embedded into the traditional power planning model to realize the optimal allocation of long-term flexible resources for the risk management of long-term supply-demand imbalance. Based on the IEEE RTS-79 case analysis, the effectiveness of the proposed method is demonstrated, and the role of long-term energy storage in the risk management of long-term supply-demand imbalance in extreme steady weather is explored.