Research On SOFC System Modeling And Power Control For Wind Farm

With the development of a large amount of fossil energy,the problem of greenhouse effect and environmental pollution is prominent.Wind energy,as a kind of renewable energy,has been developed in a large scale,and the wind power industry has developed rapidly in our country.However,due to the indirectness and randomness of wind,the voltage stability of the grid will be affected or the power quality will be decreased.To solve this problem,a hybrid energy storage system composed of energy type(SOFC/SOEC hydrogen energy storage)and power type(flywheel energy storage unit)can be adopted to stabilize the wind power output.Solid oxide fuel cell is a device that converts hydrogen gas into electricity.Solid oxide fuel cells have high efficiency,no pollution and rich application scenarios,and have a good prospect in the field of large-scale energy storage.Therefore,it is particularly important to study the effect of SOFC/SOEC hydrogen energy-storage and flywheel hybrid energy storage system on wind farm output power fluctuation.In this paper,1MW/150kWh flywheel energy storage unit is used to suppress the high-frequency part of wind power fluctuations and SOFC power generation system discharge is used to supplement the low-frequency part of wind power fluctuations.First of all,according to the laws of electrochemical reaction,conservation of mass and conservation of thermodynamics,this paper carries SOFC reactor mechanism model under the environment of SIMULINK.In order to ensure the accuracy of the model,we use experimental data to verify the model.The polarization curve of the simulation model fits the experimental data well.The polynomial temperature module of SOFC system is established according to the experimental data.The I-V and I-P curves of SOFC at different temperatures are simulated.The results show that the SOFC mechanism model can better reflect the operating characteristics of SOFC,which ensures the effectiveness of the research work in this paper.SOFC is a strong nonlinear and complex system.In order to solve the problem that PID control parameters cannot be adjusted quickly and accurately by empirical method,Ziegler-Nichols method is adopted to adjust PID controller parameters,and single neuron network PID controller and BP neural network PID controller models are established.The response effect of three controllers is compared and analyzed.The response time of SOFC reaches minute level is taken as reference.After parameter optimization,the PID control parameters are determined.Finally,the power control of SOFC power generation system is realized.The output power of wind power generation is decomposed by the method of ensemble empirical mode decomposition,aiming to meet the power fluctuation of wind farm grid-connected power.By decomposing the output power of wind farm,the power meeting the power fluctuation index is the grid-connected reference power.Then,according to the quantity and power,the charge and discharge instructions of hydrogen energy charging and releasing-flywheel hybrid energy storage system are obtained.Finally,based on the historical operating data of a wind farm with a rated installed capacity of 15MW,the discharge order following effect of SOFC power generation system is simulated and verified.The average absolute percentage error is 1.28%.