Study On Charging And Discharging Control Of Flywheel Energy Storage System Applied In Wind Farm

In recent years,our country’s clean energy industry has continued to grow and develop.Especially with the ’carbon peak’ and ’carbon neutral’ targets proposed,the proportion of solar power and wind power in the power grid will become higher and higher.This puts forward higher requirements for the flexibility of the grid.As a flexible power source,the energy storage system has received widespread attention in the industry and has become a research hotspot for improving the performance of the power grid.Among the various forms of energy storage,flywheel energy storage is considered to be a promising energy storage technology due to its high energy storage density,high power density,fast response speed,high cycle times,long service life,and pollution-free recycling.This paper takes the AC bus-parallel flywheel energy storage unit and its array system as the object to study the control problems in its charging and discharging operation and its application in wind farms.The main work is as follows:(1)Motor control is the basis of the charge and discharge power control of the flywheel energy storage unit.Two power conversion strategies in motor control in flywheel energy storage units are analyzed,among which flywheel motors are more suitable for the strategy of converting power to torque;the voltage decoupling method in asynchronous motor control is analyzed,and a torque-based state is proposed.The decoupling method of equations is simpler and more feasible through simulation;a simulation model of asynchronous motor control is established,and the simulation verifies that the motor can accurately follow the given power for speed-up and speed-down operation in the full speed range,and it can also be fast switch between charge and discharge.(2)Analyze the grid-side circuit model of the flywheel energy storage unit,establish the model and perform power control simulation;analyze the relationship between the DC bus voltage and the grid-side and machine-side currents,and use the motor model,the grid-side circuit model and the Based on the DC capacitor model,establish the overall control model of the flywheel energy storage unit,simulate the charge and discharge power control of the flywheel energy storage unit and the DC bus voltage control to verify the feasibility of the control strategy used.Finally compare the charge and discharge response speed of this flywheel energy storage unit and the lithium battery arrays at the same power.The simulation results show that the flywheel energy storage unit is faster.(3)Introduce the power allocation strategy of the flywheel energy storage array,analyze the existing problems,make corresponding improvements,and simulate to verify the feasibility of the improved power allocation strategy;introduce the application advantages and connection forms of energy storage in wind farms,select 8 flywheel energy storage units forms a flywheel energy storage array to smooth the output power of wind power.The simulation results show that it can effectively smooth the rapid fluctuation of wind power.