Research On Frequency Modulation Of Pumped Storage Energy Assisted By Flywheel Energy Storage

In recent years,with the promotion of the double-carbon strategy,the proportion of renewable energy in our energy structure has been increasing continuously.In the power industry,due to the randomness and volatility of renewable energy generation itself,the increase in the proportion of renewable energy generation affects the frequency security of the power grid,so the generator set is required to improve the frequency modulation ability to maintain the frequency stability of the power grid.Pumped storage unit is a kind of high quality frequency modulation power supply.However,due to the limitation of structure,in the whole operation cycle,the frequency modulation capacity of hydraulic turbine is better,while the frequency modulation capacity of pump is worse.Therefore,it is of engineering significance to upgrade the frequency modulation capacity of pumped storage unit.Flywheel energy storage is a kind of mechanical energy storage technology,which is characterized by fast load response,high energy conversion rate,many times of charge and discharge,and long life.In principle,it is suitable to assist pumped storage unit in frequency modulation operation.This paper firstly analyzes the feasibility of frequency modulation operation of the pumped storage unit assisted by flywheel energy storage,then introduces the frequency modulation principle of the generator unit and the common frequency control model,and constructs the mathematical model of the thermal power unit and the pumped storage unit,as well as the two regional frequency control models including the pumped storage unit.This paper analyzes the frequency improvement of the single power generation network by the addition of pumped storage units and the frequency modulation performance of pumped storage units under different working conditions.Then the frequency modulation process of the pumped storage unit assisted by the flywheel energy storage unit is studied.According to the principle of flywheel energy storage,the mathematical model of flywheel energy storage device is constructed,and different load distribution strategies are formulated according to different working conditions of pumped storage unit.According to the above research content,the corresponding simulation model is built in the Matlab/Simulink simulation platform and the simulation experiment is carried out.The simulation results show that the pumped storage unit has good frequency modulation ability under the turbine condition,but no frequency modulation ability under the pump condition.The addition of the flywheel energy storage device enables the pumped storage unit under the pump condition to perform frequency modulation.At the same time,since the frequency characteristics of the flywheel energy storage device is better than that of the pumped storage unit under the hydraulic turbine condition,the frequency modulation capacity of the pumped storage unit under the hydraulic turbine condition has also been improved to some extent.In order to solve the problem that overcharge and discharge of flywheel energy storage device may affect the service life and operation safety of the device in actual operation,fuzzy control based on the state of charge of flywheel energy storage device is used to distribute the load.Simulation model is established and simulation experiment is carried out to verify the effect of fuzzy control load distribution rules.The results show that the fuzzy control load distribution rule can improve the output of the flywheel energy storage device.When the state of charge approaches the safety threshold,the load assigned to the flywheel energy storage device can be adjusted to avoid exceeding the safe operating interval,so as to ensure the equipment safety and operation safety of the flywheel energy storage device.