Research On Power System Coordination Scheduling Model And Method For Large-scale Wind Power Accommodation

In recent years,renewable energy in China develops rapidly.The high renewable energy integration will be an inevitable trend and an important feature of China's power system.Large-scale wind power integration increases the operation uncertainty of the power grid.The uncertainty of wind power forecasting at different time scales increases the challenge to traditional scheduling mode.Meanwhile,the wind power resources of China are highly concentrated,large-scale and far from the load center.The reverse distribution of wind power and load leads to large-scale wind power difficult to be accommodated locally.The multi-area coordinated scheduling is an effective measure to improve this condition.Therefore,the evolution law of wind power uncertainty and the research on coordinated scheduling in different time scales should be carried out.The tie-line transmission power and local generation resources of the multi-area grid should also be coordinated to improve the wind power accommodation.Thus,how to establish the coordinated scheduling model and method has become a key issue in the dispatching of large-scale wind power integrated power systems.The main research contents of this paper are as follows:(1)A multi-time scale coordinated scheduling method for wind power integrated system is studied.Based on the fuzzy chance-constrained programming and credibility theory,the traditional deterministic system constraints are transformed into fuzzy chance constraints.Because the forecasting accuracy improves with the shortening of the forecasting time scale,and as time draws near,the dispatchers' expectation degree for reliability gradually increase.Therefore,this paper set the fuzzy confidence level as an incremental vector to reflect the change of forecast accuracy and dispatcher's expectation degree for the system operation reliability.Thus a multi-timescale coordinated scheduling model is established.The case study shows that the proposed method can effectively reduce the influence of prediction uncertainty and gradually adjust the scheduling plan,which can realize the accommodation of power deviation step by step.(2)The intraday two-stage rolling coordinated scheduling method for wind power integrated system is studied.Based on model predictive control,a two-stage rolling coordinated scheduling method,including the intraday rolling optimal scheme and the real-time rolling base point tracking scheme,is proposed.The output obtained from the intraday rolling scheme is used as the reference of the real-time rolling scheme.The real-time rolling base point tracking scheme is based on the model predictive control,including the advanced rolling optimization and the hysteretic feedback correction strategy.According to the latest thermal unit output,closed-loop optimization is formed to achieve the correction of power deviation.The index of expected up reserve shortage and expected down reserve shortage is proposed to evaluate the system risk level of spinning reserve.The case study verifies that the proposed method can gradually adjust the reserve capacity and scheduling plan,which can promote the wind power accommodation,then reduce the regulation pressure of dispatchers and AGC units.(3)The decentralized coordinated robust scheduling method for the multi-area system is studied.Based on the affinely adjustable robust optimization and the analytical target cascading technique,a decentralized coordinated and robust scheduling method for the multi-area system with large-scale wind power is established.The AGC correction control is used in the affinely adjustable robust optimization.It can effectively deal with the wind power uncertainty by simultaneously optimizing the AGC participation factor and the wind power interval that can be accepted by the cross-region system.Based on the analytical target cascading technique,a decentralized coordinated scheduling model is proposed,which is composed of the regional scheduling subproblems and the master problem to ensure the operational security of tie-lines.The case study shows that the proposed method can provide an accommodated wind power interval to ensure the safe operation,the overall operational economy and the maximization of wind power accommodation.Meanwhile,the proposed model can realize the decentralized autonomy of each regional grid and the privacy of scheduling information,which is under the operating philosophy of the electricity market.(4)The decentralized coordinated scheduling model for AC/DC power delivery system is studied.The flexible operation characteristics of the HVDC tie-line are finely modeled.The tie line transmission power and regional unit output are jointly optimized to promote large-scale wind power accommodation.Based on the improved analytical target cascading technique,the day-ahead security constrained unit commitment problem for AC/DC power delivery system is decomposed into the main problem of upper-level dispatch center and the sub-problems of lower-level dispatch center.The upper-level dispatch center is responsible for the coordinated optimization of the tie-line flow between the regional grids,and the lower-level dispatch centers can independently solve their scheduling problem in parallel.The case study shows that the proposed method is under the hierarchical and partitioned scheduling mode of China,which can promote the large-scale wind power accommodation,reduce the peaking pressure of the receiving-side system.The proposed scheduling model can provide the method support for the active power dispatching of hierarchical and partitioned AC/DC power delivery system in China.(5)The hierarchical robust coordinated scheduling model for the MTDC meshed AC/DC power delivery system with large-scale wind power is studied.According to the multi-level architecture of MTDC meshed AC/DC system,a hierarchical robust coordinated scheduling model is proposed.Based on the analytical target cascading technique,the day-ahead scheduling problem is decomposed into three levels.The lower layer is the two-stage robust security constrained unit commitment problem of the AC grid.The middle level is the VSC power control optimization problem,and the upper level is the multi-time optimal power flow problem of the DC grid.At the same time,the flexible operation model of VSC station is proposed to make full use of its flexible and controllable power regulation capability,which can promote large-scale wind power accommodation.The case study demonstrates that the proposed model can guarantee the decision independence of each scheduling entity,reduce the impact of wind power uncertainty on system operation.The proposed model has good scalability,which can provide an effective scheduling solution for the AC/DC hybrid system.