Study On Fine Dispatching Of Southwest China’s Hydropower In Response To The Flexibility Peak Shaving Demand Of Power Grids

With the rapid development of China’s economy,power grids are generally facing severe peak shaving problems.The promotion of the carbon peaking and carbon neutrality goals and large-scale connection of renewable energy into the power grid have further exacerbated the difficulty of peak shaving and also brought new scheduling problems to the power grid and hydropower dispatching.It is necessary to take the impact of unit maintenance,backwater jacking,and renewable power generation on hydropower peak shaving capacity into consideration fine when hydropower responds to the peak shaving demand of the power grid.Therefore,in combination with the actual problems in the China Southwest Power Grid and cascade hydropower dispatching,take improve the refinement level of hydropower peak shaving as the mainline,the research has been carried out on the joint dispatching of unit maintenance and generation scheduling of cascade hydropower before flood season,the coordinated multi-objective dispatching of short-term between cascade hydropower and the power grid under backwater,the joint peak shaving operation of hydrothermal in flood season and the ultra-short-term joint dispatching of hydro and wind power.The research contents and results are as follows:(1)To address the poor flexibility of peak shaving caused by the interaction between unit maintenance and generation plan of cascade hydropower plants before flood season,a joint optimization model of unit maintenance and power generation for cascade hydropower plants considering peak shaving demand of the power grid is constructed.The daily peak shaving demand of the power grid before flood season is considered in the model,and a variety of typical inflow scenarios of cascade hydropower plants before flood season are constructed by using the improved k-means clustering method to characterize the randomness of inflow before flood season,which avoids the insufficient output regulation capacity caused by unreasonable maintenance of units,and reasonably plans the unit maintenance plan and peak shaving capacity of hydropower before flood season.The feasibility and practicability of the generation plan before flood season are guaranteed through the control constraints of reservoir pre-flood water level falling and long-term contract electricity.The application in Beipan cascaded,Guizhou shows that the proposed model can satisfy the peak shaving demand of the power grid before flood season,ensure the water level falling stable of the large hydropower plant,and achieve the bi-level optimization of the unit maintenance and the generation plan.(2)To deal with the contradictory demand of peak shaving and generation benefits between hydropower plants and the power grid in the made of daily generation plan of cascade hydropower plants caused by the decline of regulation ability under backwater jacking,a coordinated multi-objective dispatching model for short-term peak shaving and generation between cascade hydropower plants and power grid under backwater jacking is proposed.The influence of backwater is fully considered in the model,and the accurate calculation of output regulation capacity of hydropower plants is realized.The model takes the units of hydropower as the dispatching unit and considers the complex constraints.The difficulty of modeling and solving is lowered by the comprehensive feasible operation area which couples the irregular vibration of the unit and the limit of output constraints and realizes the fine production of the power generation plan.Based on the multi-objective model of minimum residual load peak valley difference and maximum power generation,the effective coordination between peak shaving and generation benefits is effectively realized.A case study of cascade hydropower in Hongshui River,Guangxi,shows that the model can achieve the coordination between peak shaving and generation plan of cascade hydropower in daily generation making under the influence of backwater jacking.(3)To handle the problem of the peak shaving contradiction between hydropower and thermal when the hydropower output is output blocked in flood season,which leads to the difficulty of making generation plan and the poor calculation accuracy of abandoned electricity,a short-term combined dispatching model of hydrothermal in flood season considering abandoned hydro power caused by peak shaving is proposed.This paper fully considers the block of hydropower output in flood season,the deep peak shaving of thermal power,and the demand of power grid reserve capacity.In this model,an integrated hydrothermal generation plan-making method coupled with the calculation of abandoned hydropower is constructed,which simplifies the making process of the power generation plan in flood season and improves the accuracy of the plan.A case study in a large-scale hydrothermal system in Guangxi shows that the abandoned hydro power is more accurate.The introduction of the value of abandoned hydro power can coordinate the operation of hydrothermal in flood season.The joint dispatching mode can achieve the efficient utilization of clean energy,reduce the operation cost of thermal power,and is conducive to the energy-saving dispatching of the power grid.(4)To modify hydropower generation plan reasonably and efficiently when using cascade hydropower to stabilize the output fluctuation of wind power under complex regulation and management is a challenge in ultra-short-term hydropower scheduling,an ultra-short-term dispatching model for cascade hydropower regulated by multilevel dispatch centers to suppress wind power volatility is proposed.The rationality and generation fairness of output adjustment of cascade hydropower plants with multilevel regulation is guaranteed by the novel objective function,the coordination strategy containing the minimum increment and load rate ranking constraint.The constraint aggregation technology and improved three-direction SOS2 linearization method can improve the calculation accuracy effectively and meets the requirements of ultra-short-term scheduling for efficiency and accuracy.A case study in Bei Pan cascaded hydropower shows that the proposed model can stabilize the output deviation caused by the wind power by cascade hydropower,guarantee the fairness and stability of cascade hydropower output adjustment,and ensure the timeliness and accuracy of the ultra-short-term calculation.