Load Restoration Flexible Optimization In Wind Power Integrated System Based On Conditional Value At Risk

With the increasing interconnection and higher permeability of renewable energy in power system,misconduct to partial failure may cause cascading failures,or even worse the occurrence of blackout.Therefore it's necessary to make up scientific and reasonable black start scheme in advance.Compared with conditional generation approach,wind power is advantageous for better cranking and adjusting efficiency,so it is a promising idea to take it into consideration to speed up system restoration.Aiming at load restoration optimization problem in wind power integrated system,in this paper,the influencing principles and major reflecting indices caused by wind power to the load restoration safety is analyzed firstly.Then the flexible constraints model of safety indices above is set up by CVaR(conditional value at risk)method and flexible optimization strategy of load restoration scheme is proposed based on the safety check of flexible constraints' border.Finally,the previous optimization problem is transformed into mixed integer linear programming problem by linearized method based on PQ decoupled theory and sensitivity analysis so that the calculation speed is improved.The effectiveness and advantages of the strategy proposed in this paper is confirmed in IEEE39-bus system and South Hebei Power Grid.First,aiming at the safety problem the power grid and wind parks may encounter in load restoration and the effect wind power may bring about,the effect principle brought by wind power to load restoration safety is analyzed theoretically,and the indices reflecting system safety are chosen to set up indices safety constraints.According to the black start safety guidance and relative wind park operation guidelines,the load restoration two-dimension safety constraints model is set up and it offers the theoretical basis for the later load restoration scheme flexible adjustment.Then,the flexible adjustment strategy of safety constraints is brought up.It adjusts constraints border at real time by CVaR method according to wind speed forecasting data and the relative prediction confidence level.The flexible optimization strategy of load restoration scheme is proposed by combining the flexible constraints and regular load restoration optimization,after the safety check to the constraints border according to the black start technical guidelines and other guiding papers.Traverse the integrated wind power amount under the limit and make flexible restoration schemes respectively,the optimal wind power penetration is acquired by compare the recovery speed of the schemes.To improve the calculation speed,the previous problem is transformed into mixed integer linear programming(MILP)problem by power flow linearized method based on PQ decoupled and power flow sensitivity analysis method,so that online decision could be made by scrolling call of the strategy.Finally,the confirmation of effectiveness of the load restoration flexible optimization strategy is performed in IEEE39 bus system.The optimization principle is further given in certain restoration step of scheme in previous system.The flexible restoration scheme has advantage of accelerating the load recovery process at the premise of system safety,compared with the traditional restoration scheme.Moreover,the safety of system indices such as voltage and frequency is confirmed by performing BPA simulation to flexible scheme,so that the scheme is proved safe.