Nonlinear Adaptive Backstepping Control For Power Generation Units Considering Generation-Grid Coordination

Promoted by the rapid growth of the national economy,the electric power industry of China has developed rapidly,and with it,some new challenges and opportunities have arisen.On the power supply side,with the rapid development of large-capacity thermal power units and the large-scale access of various emerging clean energy sources,large-capacity thermal power units that acted as the backbone of China’s power grid,are facing greater adjustment pressure in balancing the contradiction between power supply and demand and ensuring the stable operation of the power grid.On the power grid side,with the continuous construction of large interconnected power grids,the stability of power system is becoming more and more prominent as the increasingly complex system structure and operating environment.Moreover,with the scale development of power supply side and power grid side and the increasing complexity of system operation state,it is of great significance for the security and stability of power system to study the integrated control strategy of power generation units on the basis of considering the comprehensive coordination of power supply and power grid to ensure the stable,safe and controllable power supply.In order to improve the stability and control quality of power system,several new control system design schemes are proposed based on the comprehensive study of each link of power production.The contents and achievements of this paper are mainly shown in the following aspects.(1)The development history and research status of related control systems are summarized from the power supply side and the power grid side respectively.From the perspective of source-grid coordination,the current research on power system stability and coordinated control of power generation unit are discussed respectively.The possible problems caused by the incomplete consideration of the dynamic characteristics of boiler,steam turbine and generator further illustrate the significance of power generation unit control considering the comprehensive coordination between the power supply and power grid.(2)A nonlinear adaptive backstepping excitation control system is designed for the excitation control in multi-machine power system.In order to improve the robustness of excitation control and avoid the influence of unmodeled dynamics on the performance of the designed controller,a high-order power system model considering both the high-order two-axis model of generator and the dynamic characteristics of typical excitation system is adopted,and the effects of model uncertainties and external disturbances on the stability of the power system are analyzed.Combined with Lyapunov stability method,the adaptive updating laws for unknown system parameters are designed,which can achieve the real-time and on-line dynamic estimation of unknown system parameters.Moreover,the influence of external disturbance on the control performance of the system is accurately compensated by adding a damping term in the control law.The simulation results of multi-machine power system show that the designed excitation control system has good anti-interference ability and strong adaptability.(3)In order to further improve the stability performance of multi-machine power system and ensure the power quality of power generation units,a coordinated excitation-valving opening control strategy is proposed lor the multi-machine power system model,which considering the dynamic characteristics of both generator and steam turbine governing systems,and taking into account the uncertain parameters of the system and external disturbances.Firstly,the excitation controller and the valve opening controller are designed by using the robust adaptive backstepping method.Then,the coordination strategy between the two controllers is proposed under different system operation cases.The influence of uncertain factors on the controller performance is solved by designing the adaptive law of uncertain parameters and introducing corresponding robust terms.The simulation results of multi-machine power system show that the proposed robust adaptive backstepping coordinated control scheme can effectively improve the stability and control performance,and has good anti-interference ability and strong adaptability.(4)In order to improve the dynamic performance of large-scale power generation unit in the process of wide-range load change,a robust adaptive backstepping coordinated control system for the boiler-turbine unit is designed,which can overcome the influence of strong nonlinearity and uncertainty of the power generation unit on the controller performance.Firstly,the non-linear model of boiler-turbine unit considering both parameter uncertainties and external disturbances is decomposed into two subsystems by model preprocessing.Then,the main steam valve controller and fuel controller are designed respectively by using robust adaptive backstepping method.In order to avoid the parameter drift of uncertain system parameters,an adaptive law of parameters is designed by introducing a sufficiently smooth projection operator,and a damping term is set in the control law to compensate for the influence of external disturbances.Furthermore,the implementation steps of the coordinated control system and the actual control input law of the unit are summarized to facilitate the engineering implementation.The simulation results show that the designed coordinated control system has good load command tracking performance,anti-interference ability and robustness.(5)With regard to the nonlinear power generation unit modeling fully illustrating the dynamic characteristics of boiler,steam turbine and generator,a nonlinear integrated control strategy is proposed based on robust adaptive backstepping method and coordinated passivity theory,which considering the uncertainties of system parameters and external disturbances.Firstly,the whole high-order model of the power generation unit is decomposed into three low-order subsystems,and then the main steam valve opening controller,excitation controller and fuel controller are designed respectively.In order to efficiently improve the excitation voltage level and fully develop the reactive power reserve capacity of power generator,the excitation controller is optimized by means of reactive current compensation aiming at high voltage side.With the purpose of overcoming the system uncertainties,a robust term is added to the control law,and the related parameter adaptive law is constructed by using a fully smooth projection operator.The parameter setting law of the designed control system is summarized to ensure the regulation quality of the control strategy in engineering application.The simulation results show that the designed integrated control system not only optimizes the active power response of the power generation unit,but also effectively improves the reactive power response characteristics of the system,and has good anti-interference performance and robustness.