Study On Parameter Identification Method And Control Strategy Of Hydraulic Turbine Governing System

With the increasing proportion of hydropower unit capacity,the tasks of peak modulation,frequency modulation and voltage modulation become more arduous,and the requirement of operation stability and governing quality of the hydropower unit becomes stricter.Because the hydraulic turbine governing system is a nonlinear,non-minimum phase and complicated closed system which is influenced by hydraulic,mechanical,electrical equiment and other factors,it is relatively difficult to model and control the system.It has always been the research hotspot and difficulty point of this field.Under this background,the analysis of the operating mechanism of system,the modeling simulations of various parts of system and the study of advanced identification method and control strategy have very important theoretical significance and engineering application value for the safe and stable operation of hydropower units.This paper firstly thoroughly analyses the operating mechanism and chatacteristics of various parts in the hydraulic turbine governing system.The models of each part are summarized respectively,and the different models of hydraulic turbine governing system are set up with the system structure characteristics,various operation conditions and objects.On this basis,with the subspace identification theory and the advanced intelligent algorithm,the hydraulic turbine governing system parameter identification is studied.This paper designs and proposes high-performance hydraulic turbine controller and parameter optimiztion method using the multi-objective optimization method,fractional order control theory and stability region analysis method.The main work results and research innovations of the paper are as follows:(1)The linear and nonlindear mathematical models are summerized according to the operation mechanism and characteristics of earch modula in the hydraulic turbine governing system.And the applicable conditions of different models are summerized.On this basis,considering the system structure characteristics,various operation conditions and so on,four common mathematical model of hydraulic turbine governing system are established.The above work provides a basis for the research on system parameter identification and control strategy.(2)Focusing on the issue that the noise has great influence on closed-loop identification,the model of hydraulic turbine governing closed-loop nonlinear system with frequency noise is studied and established.The subspace identification theory is introduced,and the parsimonious subspace identification method in predictor form based particle swarm parameter optimization is proposed.The simulation results of no-load operation verify the proposed method’s feasibility and superiority in the parameter identification of hydropower unit system with frequency noise;the accuracy of parameters is the prerequisite and basis of hydraulic turbine governing system simulation reliability.Therefore,a high-accuracy improved ant lion optimization algorithm is put forward to identify the sixth-order state space equation model parameter of hydraulic turbine governing system.The simulation results of different operations show that the proposed method can overcome the shortcoming of local optimization.This method can effectively identify the hydraulic turbine governing system parameters and has high identification accuracy;in order to achieve the high effcient identification of hydraulic turbine no-load model parameter,an improved whale optimization algorithm is present in this parper.With taking Unit 4 of a hydropower station in Hubei province as an example,the hydraulic turbine governing system simulation model under no-load condition is established.The effiecient and fast identification of hydraulic turbine no-load model parameter based on the improved whale optimization algorithm is achieved by the measured data;finally,PARSIM-K-PSO,IALO and IWOA are compared and analyzed in terms of the identification object,identification result accuracy,identification speed and so on.And the application scope of each approach is discussed.(3)With the control performance requirements of hydropower unit continue to increase,it is necessary to develop the new control strategies based on the traditional PID controller.Therefore,with combination of PID plus second order derivative controller and fractional order theory,a novel fractional order PID plus second order derivative controller is proposed in this paper.The multi-objective evolutionary method based on a hybrid mutation operator is used to optimize the hydropower unit governor parameter.The simulations verify the effectiveness and superiority of the designed controller.(4)Considering the hydraulic turbine governing system requirement for robustness,the stability regions of hydraulic turbine controller parameters are studied.The fractional order model has better performance than the integer order model.With taking advantage of the fractional order model’s benefit and introducing parameter uncertainty and time delay terms,the hydraulic turbine fractional order interval parameter system with time delay is given.The parameter stability regions of PID,fractional order PID,double differential PID and double differential fractional order PID controllers based on this system model are studied.With the edge theorem and D decomposition method,the problem of system stability domain determination of different controllers and the change rules of system stability with various controller parameters are studied.The results show that the fractional order PID plus second order derivative controller has the greatest stability region and best robust stability.