Research On Dynamic Response Of Frequency Regulation Of Pumped Storage Unit Under Mixed Model

Under the background of low-carbon energy transition,pumped storage power stations(PSPs),by virtue of their self-regulated power reliability and stability,assume the important task of absorbing renewable energy such as electricity and photoelectric energy in the power system.Variable speed pumped storage unit can effectively reduce the system frequency fluctuation caused by new energy output fluctuation because of its advantages of variable speed constant frequency operation and quick power regulation.However,variable speed unit may threaten the stability of hydraulic system because of its speed of regulation.Therefore,on the basis of revealing the dynamic regulation law of variable speed units in the transition process of multi-machine system and exploring its comprehensive regulation capability in the wind power-pumping storage hybrid power generation system,this study focuses on analyzing the stability and frequency regulation performance of the water generator system in the mixed type pumped storage power station with different ratios of variable speed units.The research results of this paper are mainly divided into the following three aspects:(1)In order to overcome the limitations of traditional fixed-speed units,this paper takes one-tube two-machine system and multi-machine load system as the research object,introduces variable speed units into the model,establishes the model of water diversion system,surge chamber and pump turbine system by using characteristic line method,and deduces the control model of rotor side and grid side converters by using Park transform and inverse transformation.With the speed,opening,flow and water as the key variables,the hydraulic,mechanical and electrical systems were coupled together with the S function,and the simulation models of the one-pipe two-machine system in solitary network mode and the twopipe three-machine system with load were built respectively.The models can clearly reflect the dynamic evolution law of the indicators of the fixed and variable speed units in the hybrid pumped storage power station under the complex multi-machine system.(2)In this paper,based on the simulation model of a two-machine isolated network system,the key parameters such as controller parameters,running water head and initial power are selected to make a comparative study of the dynamic regulation rules and operational stability of the water machine system of the variable-speed generator under power generation conditions.In order to overcome the existing limitations of fixed-speed units,this paper takes the two-one-tube three-unit load system as the research object,and formulates four types of unit allocation schemes,and reveals the regulation law of the number of variable speed units on the dynamic performance of hybrid type pumped storage power station.The results show that the more variable speed units,the faster the system frequency adjustment rate,but will significantly increase the volute,tail water and surge chamber water level fluctuation amplitude,and the fixed speed and variable speed units combined operation can take into account the stability of the hydraulic system and the quality of frequency modulation.(3)Focusing on the important engineering requirements of the comprehensive regulation performance of variable speed units in the wind power-pumping and storage hybrid power generation system,this paper combines the two-one-pipe three-machine load system with the wind power generation module,and adopts the key indicators of frequency and power regulation characteristics according to three different wind power output scenarios.Quantitative evaluation of frequency stability and power compensation capability of hybrid power generation system under different fixed and variable speed unit distribution ratios.The results show that when the ratio of fixed and variable speed units is 1:2:2:1,the system frequency regulation quality is optimal,and good operation stability of the hydraulic system can be guaranteed.When the ratio of fixed and variable frequency units is 0:3:3:0,the difference and ratio of the maximum up and down deviation of the system frequency reach the maximum,which will significantly reduce the overall stability of the system.In addition,increasing the number of variable speed units can effectively improve the power regulation performance of constant speed units.