Fractional Order Identification And Analysis Of Nonlinear Model For Doubly Fed Variable Speed Pumped Storage Units

With the rise of new energy,the intermittency and instability of new energy power generation have a great impact on the stabil ity of the power grid.The emergence of variable speed pumped storage units with their excellent regulation ability has largely solved these problems.Therefore,research on variable speed pumped storage units is extremely necessary and important.At present,the full characteristic curve model of water pump turbine is an effective model for expressing the water pump turbine system,but it is not easy to study its stability and control strategy.Therefore,an analytical mathematical model based on the full characteristic curve can be established for relevant research.This article focuses on the study of the working condition model of the variable speed pumping and storage unit,and combines fractional calculus,parameter identification,and T-S fuzzy to establish an analytical mathematical model for the working condition of the pumping and storage unit.This provides a solution for studying the control and nonlinear characteristics analysis of the variable speed pumping and storage unit.On the basis of the traditional doubly fed pumping and storage unit model,this article focuses on refined modeling of the full characteristic curve model of the pump turbine.The paper determined the fractional order model structure,selected 8 operating points for dividing the operating conditions,and used PSO algorithm for parameter identification of each operating point to obtain the fractional order transfer function model of the selected operating points.The obtained model was compared with the original characteristic curve model through time-domain simulation.The results showed that the identification results were basically consistent with the original model simulation results under the corresponding operating points,This indicates that the identified linear model is very close to the full characteristic curve model under the same operating conditions,and can represent the characteristics of the unit under corresponding operating conditions.For the fractional order model under multiple operating conditions,the paper uses T-S fuzzy method to establish the nonlinear model of pump turbine operating conditions.This method converts the identified transfer function model into the state space equation,establishes the relevant fuzzy rules of three operating conditions,obtains the nonlinear fractional order model of three operating conditions through fuzzy logic,and conducts fuzzy reasoning on the model,Extend it to a nonlinear mathematical model of the entire pump turbine operating condition.The simulation comparison between the established fractional order model and the full characteristic curve model shows that the simulation results of both models are basically consistent under the same operating conditions,with small errors,both below 0.03pu.Prove that the obtained nonlinear mathematical model can to a certain extent represent the dynamic characteristics of pump turbine turbine operating conditions.Finally,a simulation comparison was conducted between the doubly fed pumping and storage unit model under this model and the doubly fed unit under the full characteristic curve.The error of some key parameters of the doubly fed motor was compared,and the results showed that the simulation error of the two on the key parameters of the doubly fed motor was relatively small.Therefore,the nonlinear model obtained in this article can be used in conjunction with the doubly fed motor to conduct a more in-depth and comprehensive study of the entire doubly fed unit.