| The power system is a typical high-dimensional dynamic system,and its stable operation seriously affects the national economy.The transient stability analysis method based on energy function has been widely used in nonlinear theory because of its rigorous theoretical foundation and clear physical meaning.Power system stability analysis is designed to stabilize control and further improve system stability.On the other hand,the excitation saturation phenomenon is ubiquitous in the actual power sys-tem control,which affects the safe and stable operation of the power system.In recent decades,scholars have given extensive attention to excitation saturation control and systematically studied various problems such as global stabilization,semi-global stabi-lization and local stabilization and stabilization of saturated systems,and obtained very considerable research results.However,in the study of local stability and stabilization,there is still some degree of conservation in dealing with saturation functions and se-lecting Lyapunov functions.In order to reduce this conservation,it is necessary to fur-ther study the local stability of the saturated constrained control system.Based on the stabilization study of the general saturation system,the power system control problem under the excitation saturation constraint is proposed.The effects of excitation saturation constraints on transient stability of the system are analyzed by simulation examples.The idea of anti-windup design is put forward.The concept of system estimation of the domain of attraction is introduced.Three methods of saturation constraint processing are summarized:sectors-bounded method,diagonal matrix method and convex combination method,the auxiliary matrix is introduced into the quadratic Lyapunov function,and the structural condition of linear matrix inequality(LMI)is introduced.The maximum contractively invariant ellipsoid is obtained for the system to estimate the domain of Attraction.In addition,aiming at obtaining the largest possible contractively invariant ellipsoid,the corresponding anti-windup design com-pensation strategy is designed to improve the dynamic performance of the system.On the basis of the generator excitation controller,considering the influence of the excitation saturation,the domain of attraction is estimated.First,the sector-bounded method is used to process the excitation saturation constraint,and the LMI conditions are constructed;the contraction-invariant ellipsoid of the system is analyzed.The at-traction domain of the system is estimated,and the influence of different excitation top voltages on the contraction-invariant ellipsoid of the system is analyzed with the exam-ple.Combined with the linear optimal excitation control strategy,different control strat-egies are compared and analyzed.The anti-windup compensator based on the proposed excitation controller is designed to weaken the influence of the saturation nonlinearity on the system control.In addition,in the multi-machine power system,promotion is carried out.The simulation verifies the correctness and effectiveness of the proposed control strategy.Based on the excitation control strategy of excitation and valve opening adjust-ment based on system energy function,considering the excitation saturation,the non-linear sector method is used to process the saturation term,and the LMI convex opti-mization problem is constructed to obtain the contractively-invariant ellipsoid of the system under coordinated control.The linear matrix inequality is used to project the high-dimensional contractively-invariant ellipsoid in three dimensions,which more intuitively shows the volume of the contractively invariant ellipsoid.Finally,the system is implemented in a multi-machine structure retention system.The simulation results show that the proposed anti-windup coordinated control strategy effectively improves the dynamic performance of the system and achieves the expected results. |
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