In power systems with high penetration renewable energy

the contradiction between the reduced conventional flexible generation resource and the increased flexibility demand is becoming increasingly serious. According to the flexibility balance principle

the concept of generalized flexibility is proposed and the bi-level optimal planning model including investment decision and production simulation verification is developed. Then the convexity of the planning model is proved and a two stage algorithm proposed based on the maximum net benefit/increment ratio. Finally

through the actual data of a large wind power base in north China

the benchmark scenario is evaluated

and the problem of system flexibility deficiency is analyzed. Meanwhile

the optimal planning for generation-load-storage source is implemented by the proposed model

and the sensitivity analysis for storage and demand response is discussed. The case study indicates that the proposed method can integrate the flexibility assessment in power system planning

which can also quickly conduct the sensitivity analysis to improve the robustness and applicability.