Stable Output Control Of Hydrostatic Wind Turbine System With Energy Storage

With the development of human progress and society,the development and utilization of fossil energy have exceeded the load,and the living environment is gradually deteriorating.Clean energy has gradually attracted people’s attention.Unlike conventional fossil fuels,wind energy is clean,abundant energy that will be available for future generations.However,wind speed is a highly stochastic component which can deviate very quickly.Output power of the wind energy conversion system(WECS)is proportional to the cube of wind speed,which causes the output power fluctuation of the wind turbine.In order to reduce the power fluctuation,various approaches have been proposed in the last decades.Power smoothing methods of the WECS are primarily divided into two categories such as energy storage based power smoothing method and without energy storage based power smoothing method.The main objectives of this Paper are to introduce operating principles for different power smoothing methods.The energy storage based power smoothing method is effective but installation and maintenance costs of a storage device are very high.According to the literatures review,without energy storage based power smoothing method can reduce the cost of the WECS extensively.Control methods have been proposed to generate a smooth output power of the WECS without energy storage devices.In this paper,the energy storage hydraulic wind turbine is taken as the research object.The closed volume speed control loop of the quantitative pump-variable motor is the main hydraulic system.The variable motor is rigidly connected with the variable pump/motor and the generator coaxially.The variable pump/motor and the hydraulic accumulator constitute the energy storage device.The control method of steady power output with the energy storage device and without the energy storage device is studied.In this paper,the principle and characteristics of the energy storage hydraulic wind turbine are analyzed,the working principle of the energy storage hydraulic wind turbine,the mathematical model of the hydraulic main transmission system and the mathematical model of the energy storage system are expounded,and the variable pump horse of the wind turbine speed,the variable motor power of the main transmission system and the energy storage system is obtained with the wind speed as the input and the variable pump horse of the wind turbine speed,the variable motor power of the main transmission system and the energy storage system.The swing angle is the transfer function of the output.The filtering characteristics of the swing angle to the wind speed and the response characteristics of the energy storage system are analyzed.This paper studies the power smooth output control of wind turbine without energy storage system,establishes the mathematical model of the stable output control target,adopts the ADRC control strategy,takes the speed and torque as the control output,puts forward the power smooth control strategy,analyses the control effect under fluctuating wind speed,and carries on the energy consumption analysis to the control strategy,further optimizes the control rate.Relying on variable displacement pump/motor-hydraulic accumulator as energy storage system,the steady output of wind turbine power is studied.The energy storage characteristics of the energy storage device are analyzed.Taking the transmission power of the system as the control output,combining with the inherent characteristics of the system after the hydraulic wind turbine is connected to the grid,the feedback linearization control law is solved based on the system state space model,and the simulation platform is built based on MATLAB/Simulink.The control effect of the control law under step wind speed and random wind speed is analyzed,and the wind turbine is adjusted.Stability of power output.Finally,through the 30 kVA energy storage hydraulic wind power experimental platform of Yanshan University,the steady output effect of feedback linearization is experimentally validated in the case of step wind speed and random wind speed using energy storage system,and the validity of the proposed control law is verified by experiments.