Research On Nonlinear Coordinated Control Of Power System With Renewable Energy Generation

Power is the basic energy related to the national economy and people’s livelihood.In order to deal with the problems of fossil energy depletion and environmental pollution,new energy power is being developed on a large scale.With the wide application of new energy power access and supporting power electronic equipment,the problem of power system stability is increasingly prominent.As the power output of new energy generation is intermittent and fluctuant,the grid connection of large capacity,cross regional and long-distance new energy generation not only tests the strength of the power system,but also easily results in the inter-area oscillation between regional power grids and the disconnection of new energy generation,which will increase the risk of safe operation of the power grid.This paper took the power system with new energy as the research object,studied its structure and dynamic characteristics,established the differential dynamic system model and differential algebraic system model which can reflect the dynamic of the system.Combined the wide area information of the power system with the advanced control theory,and put forward the corresponding wide area multi-objective nonlinear control method,robust control method and the design method of the corresponding controller.Main work and contributions:1.A wide area multi-objective nonlinear control method based on differential dynamic system model has been proposed.Based on the mathematical analysis method of differential geometry,the precise feedback linearization of differential system,the introduction of wide area measurement information and local target in the multi-objective output function,the construction of wide area multi-objective output equation,the derivation of performance indicators including wide area output equation,the impact of the target on system performance,and the establishment of wide area control model of multi machine power system were given.The matching controller design method was verified by simulation analysis and theory.2.A wide area multi-objective nonlinear control method based on differential algebraic system was proposed,which considered the influence of algebraic constraints in the system model on the dynamic stability of the system.By using the nonlinear transformation method of differential algebraic system,the preliminary design of the system control was realized,and the law of the influence of the multi-objective output equation of differential algebraic system on the system performance index was clarified.The dynamic model of integrated coordinated control of power system and the differential algebraic system model composed of network power flow constraint equation were presented.3.The nonlinear robust control method of holographic feedback and the design method of matching single-input multi-output and multi-input multi-output models were proposed to solve the key problem of uncertain input interference in nonlinear control system.A three-mass model with blade dynamics was established,and a nonlinear robust controller with holography feedback was designed,which can simultaneously suppress the system shafting oscillation and ensure the output power stability.The effectiveness of the control strategy was verified by simulation.4.A multi-objective coordinated control strategy based on the differential algebraic model was proposed for the excitation of photovoltaic energy storage power station and generator.The design method of the coordinated controller for the excitation of conventional synchronous generator and photovoltaic energy storage power station with photovoltaic energy storage power system was presented,which improved the coordinated control level of photovoltaic energy storage power station and conventional synchronous generator.It provided the key technology to ensure the safe and stable operation of photovoltaic energy storage power station under the condition of voltage fluctuation of power system.Main conclusion:(1)The wide area multi-objective nonlinear control method and wide area multi-objective output equation based on the differential dynamic system model were proposed,which not only introduced the performance index of wide area output equation,but also reflected the influence of its objective on the system performance.The design method of its matching controller was given,which can realize the damping and voltage regulation of the system inter-area oscillation and improve the transient stability control of the system,and its control effect.The simulation analysis and theoretical verification were obtained.(2)This paper presented a wide area multi-objective nonlinear control method based on a differential algebraic system,which solved the key problem of control under differential algebraic system composed of differential dynamic equation and algebraic constraint equation.The wide area nonlinear coordinated control strategy of the multi machine power system of the differential algebraic system not only realized the effective coordinated control of the turbine valve regulation and the synchronous generator excitation,but also avoided the regulation limitation when the excitation control acted alone and the mismatched between the two controllers.(3)The nonlinear robust controller with target holographic feedback was designed to suppress the system shafting oscillation and ensure the output power stability at the same time.It can effectively suppress the uncertain disturbance in the system,enhance the stability of the wind turbine when the wind speed fluctuates and the voltage drops,and improve the stability control level of the wind turbine.Based on the two-mass shafting model of the wind turbine,this paper proposed a nonlinear robust controller with blade.The dynamic three-mass model,considering the non-linear coordinated control of pitch control and rotor current,was in line with the actual effect of blade dynamics on the shafting oscillation.It provided a simple and applicable method for the effective control of doubly fed wind turbine in new energy generation.(4)The proposed multi-objective coordinated control strategy based on differential algebraic model was practical.The design method of the coordinated controller for the excitation of the conventional synchronous generator and the photovoltaic energy storage power station in the power system with photovoltaic energy storage was given,which can enhance the anti-interference ability of the power system,and avoid the interaction effect caused by the design of the two controllers and the safe operation risk caused by the regulation mismatch.(5)Based on the security and stability of the traditional power grid,taking the system dynamic control as the key,this paper gave full play to the potential of the stability regulation of the traditional power grid,preliminarily solved the related scientific and technical problems of the stability of the power system including new energy generation,and provided the technology and method for the effective coordination and control of the traditional power grid and new energy generation.