| With the deepening reform of energy structure in the direction of sustainable development,hydropower,as a low-cost,environmentally friendly renewable clean energy,plays an important role in China's energy development plan.Hydropower unit is an indispensable tool for peak and frequency regulation in power system stability control,because it is flexible in operation and strong in adjustment.The pumped storage units,as a special kind of hydropower units which can operate in both power generating and consuming state,provide more adjustment space for the power system,and further improve the status of the hydropower unit in the power system regulation.In recent years,the power quality and stability of the power grid have been seriously challenged with the penetration of the intermittence renewable energy like wind power and photovoltaic energy.As the main adjustment equipment of power grid,hydropower units play an important role in alleviating the fluctuation of power and frequency caused by the integration of renewable energy sources.Thus,the aggravation of fluctuation in power grid has put more pressure on the regulating performance of hydropower units.Governing system of hydro generating unit is a complex nonlinear system with non-minimum phase characteristics coupled by hydraulic,mechanical and electrical factors,which brings highly complex dynamic response characteristic in daily operation.In order to further improve the regulation ability of hydropower units and ensure the safe and stable operation of power system,it is significant to carry out the control optimization research on grid connected hydropower units.The high accuracy model is the foundation of research on hydropower governing system.Traditional modeling of hydropower governing system generally only considers the speed regulating system of the units and describes the power generator as a rigid body with a certain moment of inertia,which neglects the effect of electrical factors on the dynamic response of the unit.This kind of model can hardly describe the characteristics of the hydropower governing system,and brings a negative influence on the research of accurate modeling,parameter identification and control optimization.Thus,by taking the improvement of regulation performance of hydropower unit in grid connected operation as the target,the system identification,intelligent optimization and modern control theory as the tool,the governing system of hydropower unit as the pointcut,optimization of frequency adjustment performance of power system with hydropower units has been well studied.The main research achievement and novelty in this thesis are given in the following:(1)The structure of the regulating system of hydropower unit has been thoroughly studied,and the system is divided into six modules: hydro turbine,conduit system,speed governor,generator and excitation system.The operation mechanism,modeling method and application scope of the aforementioned six modules have been analyzed and summarized,and model of the regulating system of the hydropower unit,which includes the speed regulation and excitation system,is established.The modeling research work lays the basis for parameter identification and operation optimization of hydro turbine governing system in grid connected running condition.(2)In order to implement the parameter identification of the regulating system of hydropower unit in grid connected running condition,the grey wolf optimizer has been introduced to transform the parameter identification into the optimization problem on the basis of the established regulating system model of hydropower unit.By integrating the chaos search strategy,an improved grey wolf optimization algorithm,which possesses the better optimization ability comparing with the original algorithm,has been proposed,and the high precision parameter identification of the model has been achieved.(3)For the purpose of improving the control performance of the regulating system of the hydropower unit,the synergetic control theory has been introduced to design the speed control system of hydropower unit.Based on the principle and design method of the synergetic control theory and the model of speed governing system of hydropower unit with complex conduit system,the synergetic control law has been deduced.Furthermore,the speed governing and excitation synergetic controller has been designed for the regulating system of pumped storage unit on basis of the established system model.Several simulation experiments under different running conditions have been conducted in the single machine infinite bus system,and the effectiveness and superiority of the designed controllers have been verified through the experiments.(4)In view of the increasing penetration of wind power in the power grid,the structure and characteristics of wind power unit has been deeply studied.Based on the model of hydropower unit established in the previous research,a micro grid model containing the pumped storage unit and the wind power unit has been built,which provides a model foundation for the study of the interconnected operation of the hydropower and the wind power units.For the sake of improving the regulating ability of the pumped storage unit and the dynamic performance of power system,an adaptive fuzzy PID controller has been designed for the speed governing system of the pumped storage unit based on the fuzzy control theory.In addition,the control parameters of the adaptive fuzzy PID controller have been optimized by the improved grey wolf optimizer algorithm and the validity of the controller has been verified by simulation experiments.(5)Considering the importance of secondary frequency regulation in the power system,the method and target of the load frequency control of the power system have been studied and two area load frequency control model of hydro-thermal interconnected power system have been built in order to conduct the control optimization research of the power system.The synergetic control theory has been introduced to design the controller for system load frequency control and the integral component has been added into the controller to improve the ability of error elimination.Ultimately,the effectiveness and superiority of the designed controllers have been verified through several simulation experiments under load disturbance condition. |
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