Research On Power Control System Of Hybrid Energy Storage Device For Wind Power

Wind power features intermittent,fluctuation,the seasons variation,meanwhile,the deviation between power generation and load,together with the frequency instability,are caused by the large-scale centralized grid.The grid friendliness of wind power generation can be effectively improved and the harm effects on the grid can be reduced by energy storage technology.The virtual inertia method of dynamic compensation wind farm in large-scale energy storage system is researched in this thesis,and the method of smooth wind power in hybrid energy storage system of wind farm is also studied.Furthermore,the optimization of the battery charge state is focused on through the power control strategy,which improves the life of battery.The main researches of this thesis are as follows:(1)The hybrid energy storage system,composed of vanadium flow battery and lithium battery,is studied,as well as its structure and mechanism,moreover,the energy flow relation of the hybrid energy storage system is analyzed.Then,the mechanism and structure of lithium battery and vanadium flow battery are respectively modeled and analyzed,and the significant parameters of the model are elaborated.Finally,the charge and discharge characteristics of lithium battery and vanadium redox flow battery are analyzed emphatically,combined with the advantages of those,the principle of power distribution on hybrid energy storage equipment is put forward,and the advantages of hybrid energy storage device in compensating virtual inertia of wind farm are summarized.(2)To the problem that the variable-speed constant-frequency wind turbine makes no contribution to the inertia of power system,on the basis of the SOC feedback regulation of the energy storage device,a variable parameter wind turbine virtual inertia compensation control strategy is presented in this thesis.According to the SOC and grid frequency change rate of the energy storage device,the fuzzy inertia compensation parameters are dynamically adjusted by controlling the fuzzy controller to control the virtual inertia of wind farm.The control strategy can effectively optimize the SOC of the energy storage device while satisfying the inertia response of the wind farm and prevent the overshoot of the battery,accordingly,prolong the life of the energy storage system.(3)In order to improve the service life of the energy storage on the premise of ensuring the smoothing effect of wind power,a power smoothing control strategy for the hybrid power plant based on the double-loop SOC regulation is proposed in this thesis.The current charge state and the estimated fluctuated wind power are employed in the control strategy.The output power of the energy storage is dominated by the fuzzy controller,the actual output power of lithium battery and liquid flow battery is reasonably distributed,and the hybrid energy storage state is updated in real-time.The smooth power of the wind power is achieved through the control strategy,the purpose of protecting the battery can be effectively realized finally.A simulation model is built in Matlab/Simulink to verify the effectiveness of the proposed hybrid energy storage system control method.The simulation results show that the control strategy proposed in this thesis can achieve the smooth control on fluctuation of output power and maintain the total hybrid energy storage system together with the state of charge in storage equipment in a reasonable range.Furthermore,the frequency of the power system is adjusted effectively by the vanadium redox flow battery to avoid the incident ratio of overcharge and over discharge phenomenon and to prolong its life.