Improved Nonlinear Excitation Control Research Based On Differential Geometry

To improve and enhance the stability of the power system is a pressing and arduoustask, the generator excitation control is an important and cost-effective measure ofimproving the stability. The generator excitation control can not only improve staticstability and transient stability, stabilize the terminal voltage, suppress low-frequencyoscillation, but also have obvious advantages on efficiency investments and being easy toimplement. Power system is a strongly nonlinear system, when the actual state is faraway from the particular state, the mathematical model of approximate linearization inthe particular state can not accurately represent the actual control system. Therefore,studying nonlinear excitation control of power system is of great theoretical and practicalsignificance.Based on the differential geometry theory, this paper puts forward an improvednonlinear excitation control law by modifying the objective functions and quadraticperformance index, allowing the system to have the better dynamic qualities andmulti-objective optimization, and introduces extended state observer theory, makes thecontroller easy to design and have better robust. The research contents are divided intotwo parts:Combining differential geometry theory, extended state observer theory and variablestructure theory, this paper proposes a design method of nonlinear variable structureexcitation control based on differential geometric and extended state observer. Thesimulation results show that in mechanical power disturbance, three-phase short circuitfault, parameter disturbance cases, excitation controller that this paper designs has bettercontrol effect, can improve regulation precision of the terminal voltage, enhance thestability of the system. At the same time, using extended state observer to estimate theunknown parameters and nonlinear models, reduces the complexity of the controller, hasbetter robustness of the system uncertainty.Then, this paper combines objective holographic feedbacks with extended stateobserver, proposes an excitation control based on objective holographic feedbacks andextended state observer, selects a practical indicator of more interest as the state variablesto achieve a coordinated control of system performance, and has the advantage ofextended state observer. The simulation results show that the controller is capable of stabilizing the terminal voltage and enhancing the stability of the system.