Study On Nonlinear Dynamic Analysis And Control For Complex Power Systems

Power system,composed by the power generation system and loading system,is a complex nonlinear system with multi-variable and strong coupling characters.The construction of power system is increasing expansion due to the user and loading abruptly added into the power grid,which will change the natural stability structure.The recent investigations have primarily indicated that the power system can exhibit chaotic behaviors when systematic parameters falling into a certain area.Therefore,to design effective control strategies and utilize the coupling effect of complex network can suppress the chaotic behavior and enhance the synchronous ability of power system,which has a practical significance to study the synchronous stability in power generation systems and complex power systems.The research of power generation and loading system,at home and abroad,is mainly considered identical mathematics model to study the rich dynamic behavior and chaos control,but hardly discuss the different mathematics model.Based on the above,we select the permanent magnet synchronous generator(PMSG)of wind turbine,Kuramoto-like model and the permanent magnet synchronous motor(PMSM)as research object to establish different power system models,analyzing the nonlinear dynamics and the controlling strategies in multi power generation systems and complex power systems.Discovered through coupling interaction between diverse power system,the adjustment of coupling parameter not only can play a significant role in controlling the chaos of the overall power system,but also can affect the synchronous ability of power network.In this thesis,two proper and applicable controllers are researched to restraint chaos in PMSGs system.Besides,the Kuramoto-like model as a fundamental power system,the PMSM system as a practical inductive loading,together establish a power system model with inductive loading and utilize the coupling parameter among them to discuss the influence of synchronous ability of power network and the control of chaotic behavior of inductive loading.The main research work of this dissertation has five parts as follow:First,building the dynamics models of several power systems.We have confirmed the value of system parameters that make the PMSG,PMSM system generate chaotic behaviors and portrayed the chaotic phase diagram of system.To quantitatively characterize the degree of synchronization of the power grid,we introduce order parameter as synchronous indicator to measure the spatial order of network and make sure the threshold of order parameter.Second,based on time-weighted feedback control law is investigated to study the chaos in two PMSGs system.First,we unexpectedly found that the chaotic PMSGs system coupled through similar variables can implement synchronized chaos state,while the system to be coupled via dissimilar variables can immediately turn into the state of amplitude death.Then,the periodic time is spontaneously proposed to combine with the similar and dissimilar variables feedback control strategies to analyze the dynamic behaviors under different time-weighted.The numerical simulation results show that the PMSGs system is in desynchronized chaos(C),synchronized chaos(CS),and amplitude death(AD)because of the different combination of time fraction factor and the coupled parameter.Furthermore,the feedback control law based on time-weighted is simple and easy to be constructed with effective control property.Third,a direct and environmental coupling control method is presented,which eliminate the chaos of two uniform PMSGs system.We introduced the Lyapunov asymptotic stability theory to verify the value ranges of direct coupling parameter and environmental damping coefficient,which can induce rich dynamic behaviors in PMSGs system.Excepted for the information of system speed variable,the innovative point of this virtual control method is designing an over-damped dynamic system of one dimension to control the chaotic PMSGs system.The experiment simulation verified that chaos restraining of PMSGs with direct and environmental coupling,which increase the utilization of wind energy and maintain the secure and stable operation of electromechanical systems.Fourth,we structure a practical and significant complex power system model to discuss an issue about the synchronization and dispersion of power grid.A power system model with inductive loading is established by an inductive loading PMSM and the fundamental power system that is represented by the Kuramoto-like model.Here we introduced two indicators,the phase order parameter and the average frequency deviation,to measure the degree of synchronization of power system.It is unexpectedly found that the coupling coefficient among loading and fundamental power grid is increased,the phase order parameter become more and more closed to one and the average frequency deviation will verge on zero,which indicated that the power grid,coupled with an inductive loading PMSM system,is favor to achieve the complete synchronous state.Fifth,when the inductive loading PMSM is respectively received the global and partial coupling effect from the fundamental power grid,the stabilization of chaotic PMSM is studied.It has been discovered that the global and partial coupling effect both can attain a positive impact for eliminating the chaotic behavior of PMSM,which means that the PMSM system is being in stabilization.Furthermore,the time required to stable state of global coupling of the chaotic PMSM system is shorter than that of partial coupling.Thus,these research results supply a reference value about the stabilization of inductive loading PMSM and the stable operation of complex power grid.