Transient Characteristics Analysis And Control Optimization Of Large Fluctuation Transient Process For A Pumped Storage Unit With One Pipe And Three Units

Pumped storage generating units play a vital role in China’s power system,undertaking the tasks of peak and valley regulation,energy storage and phase regulation,and accident backup,etc.Their safe and stable operation determines the balance between supply and demand in the power system and the quality of power generation.At the same time,as more pumped storage units in the form of "one pipe,many machines" are being built,the hydraulic,mechanical and electrical characteristics of the units will change after being disturbed due to the hydraulic connection between the units and their interference with each other.Therefore,it is very necessary to carry out research on pumped storage units with "one tube,multiple machines" arrangement,analyze the transient characteristics of the units in the transition process,further optimize the control parameters and operation strategies,and provide theoretical basis and technical support for improving the operational stability and power generation quality of the units.To this end,this paper relies on the operational data of Jiangxi Hongping Pumped Storage Power Station to build a refined numerical simulation model of large pumped storage generating units under integration into the infinite power grid,and selects the hydraulic disturbance conditions that occur more frequently during the operation of the power station and the successive load shedding conditions that are more threatening to the operation of the power station.The control parameters are used to investigate the transient response characteristics of the one-tube-three-machine pumped storage unit under the complex water diversion system arrangement,and to try to optimize the control parameters of the unit.(1)Establishing a nonlinear hydro-mechanical coupling model for pumped storage units.The pumped storage hydroelectric power generation system with one tube and three machines is selected as the research object,and the improved Suter transform method is introduced to process the full characteristic curve of the pump turbine and establish the full characteristic curve model of the unit;based on the characteristic line method,the boundary conditions of the upstream and downstream reservoirs,the converging bifurcation tube and the regulating chamber are considered,and the nonlinear model in the generator and the governor are also considered,and finally the one-tube multi-machine pumped storage Nonlinear watermechanical coupling model.Relying on the Jiangxi Hongping pumped storage power plant load dumping test and the hydropower station regulation guarantee calculation standard,the simulation results are compared with the test results to verify the correctness and reasonableness of the simulation model.(2)Research on dynamic characteristics of pumped storage unit operation under hydraulic disturbance conditions and parameter optimization.For the unit with one tube and multiple machines,the hydraulic disturbance conditions caused by frequent start-up and shutdown during the operation of the pumped storage power plant are selected,and the effects of different "power plant structure-initial conditions-control parameters" on the transient characteristics of the hydraulic disturbance conditions are quantitatively analyzed.The control parameters are optimized by introducing multi-objective particle swarm optimization algorithm,and the optimized control strategy can effectively reconcile the conflicts between the operating safety of the disturbed unit and the power generation quality of the disturbed unit.(3)Analysis of dynamic characteristics of pumped storage unit operation under successive load shedding conditions.For pumped storage units with one tube and multiple machines,successive load shedding may cause the tail pipe to drop sharply,seriously threatening the safe and stable operation of the hydropower plant.For successive load shedding conditions,based on the mechanism of interaction between the three load shedding units,the impact of different power station structures and load shedding action strategies on the vacuum level of the tail pipe is studied.The results show that the vacuum level of the tailpipe of the post-dumping unit under forked pipe form 3 reaches 32.2m,and the air cushion type pressure regulating chamber can effectively improve the transition process of successive load shedding;the interval time,the successive load shedding scheme and the guide vane closing rule all have an impact on the transition process of successive load shedding,providing a theoretical basis for improving the vacuum level of the tailpipe caused by extreme working conditions.