Research On Multi-scale Wind-PV-hydro Power Complementary Operation And Flexibility For Clean Energy Base Of Yalong River

The low-carbon transformation of the energy structure has become an inevitable choice to deal with energy shortage,climate change and environmental issues.With the formulation of national carbon reduction targets all over the world,the development and utilization of clean and renewable energy have increased rapidly around the world.However,the new energy(including wind power and photovoltaic),characterized by randomness,intermittency and volatility,largescale new energy connected to the power grid would lead to frequent new energy curtailment.Cascade hydropower stations,characterized by the advantages of rapid response,flexible regulation and cost economy,has become a key clean energy to promote the consumption of new energy.Therefore,adding large-scale wind and PV power stations in the existing hydropower base,the integrated wind-PV-hydro power output is sent to the load demand center by the original transmission channel of the hydropower base to build the watershed-type wind-PV-hydro multienergy complementary bases(WMCB),to help achieving the targets of carbon emission peak and carbon neutrality of China.The original theories and methods of power system planning and operation cannot meet the needs of the integration development modes.In this context,it is urgent to conduct in-depth research on the key theories and methods for the the WMCB.Taking the WMCB in the downstream Yalong River basin as the object,focusing on the key problems in the planning and operation of the WMCB,and along the main line of "resource characteristic analysis-optimal scheduling and production simulation-flexibility evaluation and improvement",this paper carries out the multi-scale coupling operation and flexibility researching of hybrid power system for the planning and operation of the WMCB.Firstly,the characteristics of wind and PV power output and its temporal and spatial distribution are analyzed;Secondly,carry out the short-term complementary optimal operation of hybrid system and the long-term optimal operation coupled with short-term demand,and reveal the relationship between hydropower peak shaving and new energy consumption;Finally,the flexibility margin of hybrid power system of the WMCB is evaluated by fully considering the uncertainty of new energy prediction,and the appropriate development scale of new energy and the flexible operation strategy of cascade hydropower stations in the WMCB are studied.The main research contents and achievements are as follows:(1)To accurately simulate the large-scale wind-PV power output in the WMCB,based on the output characteristics and spatial-temporal distribution rules of regional wind and PV power,this paper proposes a wind-PV output scenario simulation method with the clustering characteristics of power stations and the correlation between clusters.The result shows that the 65 wind farms and 19 PV power stations in the downstream Yalong River basin are divided into 6 wind clusters and 3 PV clusters by GA-Kmeans method.And the clusters accord with the temporal and spatial distribution law of wind-PV power.Then,based on the Copula joint distribution,combined with Markov chain Monte Carlo sampling method(MCMC),the scene set with correlation can be effectively simulated,and the accuracy of large-scale wind-PV power cluster simulation can be significantly improved.Through the synchronous back-reduction method,a large number of redundant information in multi-scene sets can be effectively removed and typical scenes can be extracted from the scene set.(2)Focusing on the short-term operation of integrated energy bases,the short-term complementary optimal operation model of WMCB aiming at the maximum power generation of wind-PV-hydro hybrid power system is constructed.Combined with the compensation principles of each power source and the peak regulation and compensation index of hydropower,a hydropower compensation calculation method based on the balance of power and electricity is proposed.The result shows that the short-term operation model of the WMCB adapts to different new energy power output processes in different seasons,and the decision space pre-screening technology can significantly improve the solution efficiency of the optimal model.The calculation results reveal the short-term operation law of the cascade hydropower in downstream Yalong River under different inflow conditions.Through the joint scheduling of Jinping I and Ertan,the short-term power output of the cascade has high stability and controllability,and the cascade hydropower can stabilize the power output fluctuation of new energy in the WMCB.In addition,the response relationship between the discharge of the leading hydropower station and the compensation peak-shaving regulation capacity of the cascade hydropower stations can be described quantitatively by using the hydropower compensation calculation method.(3)Focusing on the long-term operation of integrated energy bases,a long-term hydropower peak-shaving maximum benefit model coupling with the short-term complementary characteristics of wind-PV-hydro hybrid power system is constructed.The result shows that the scheduling pattern coupling long and short term based on typical scenarios is an important way to solve the hydropower long-term peak shaving of problem,especially for the WMCB.In this model,the hydropower compensation calculation method based on electric power balance can quickly and accurately calculate the short-term compensation peak-shaving coefficient of hydropower in each operation period,and then reflect whether the water level and discharge process of long-term dispatching decision meets the short-term needs.The maximum benefit model of long-term hydropower peak-shaving coupled with short-term characteristics only lost 0.09%to 2.14%of hydropower generation,increased about 12.2%of new energy consumption,increased the overall benefit of WMCB,and realized the reasonable connection of multi-scale operation process.(4)Aiming at the problems of the system flexibility evaluation and different energy capacity configuration in integrated energy base,this paper proposes a wind-PV-hydro hybrid power system flexibility evaluation method for WMCB planning stage.The result shows that the proposed flexibility supply and demand calculating method could reasonably determine the probability distribution of system flexibility supply,demand and margin.Then the accurate values of lack of flexibility probability(LOFP),the loss of flexibility expectation(LOFE),flexibility resource deficit(FDS)indices are calculated by the flexibility probability distribution.By calculating the flexibility indices and the risk expectation of load loss or new energy curtailment under different new energy installed capacity,the relationship between the flexibility margin and the new energy development scales is described.For the WMCB of downstream Yalong River,if only relying on cascade hydropower to provide system flexibility supply,the new energy development scale of the WMCB should be controlled below 12.7 GW.If 1600 MW upward flexibility resources and 850 MW downward flexibility resources are configured in WMCB,the development potential of new energy will reach 22.0 GW.(5)Aiming at the problem of flexibility power generation planning of integrated energy bases under the influence of new energy uncertainty,this paper constructs a short-term stochastic optimal model of WMCB considering the flexibility of wind-PV-hydro system.And a new energy predicted deviation calculating method based on GAMLSS-GLO distribution model is proposed.The result shows that the GAMLSS-GLO model could fit the overall characteristics of new energy predicted deviation comprehensively,and describe the variation law of the deviation distribution of new energy with the predicted value accurately.In addition,the GAMLSS model constructed by selecting GLO-V could adapt to the positive and negative biased samples.The stochastic optimal operation model considering the system flexibility can greatly reduce the expectations and risks of insufficient flexibility of the WMCB of downstream Yalong River.And it also improves the ability of the hybrid power system to resist the deep damage of minimal probability,and then work out a flexible power generation plan with both safety,reliability and economy.