Analysis And Control Of Power System Security Based On Complex Network Theory

With the development of China’s economy,the scale of power grid is increasing.The interconnection between regions has become the trend of power grid development.Modern power system has become a complex and diverse complex network.With the continuous complexity of power grid,new security problems appear.The existing methods to analyze the security of power grid are mainly based on the reductionism,which can’t analyze the security of system from a holistic perspective.Thus,it has certain limitations.However,the complex network theory can analyze and study the structural and dynamic characteristics of network from a holistic perspective,which can make up for the lack of existing methods to analyze the security of power grid.Thus,based on the knowledge of complex network theory,this disstertation mainly focuses on the two major issues of "identification of key links" and "frequency synchronization control of system",mainly including the following aspects:In order to identify accurately the key nodes of power communication network,an analysis method based on the importance of power business is proposed.Firstly,a multi-layer evaluation model and quantitative rules of indicators are established by analyzing the requirements of power businesses on the power communication network and the influence of power businesses on power network.On this basis,the subjective weight and objective weight of power business are obtained based on the improved AHP and entropy weight method.Secondly,defining the comprehensive evaluation index to get the comprehensive importance of power business.Finally,combined with the actual power business distribution and the power communication network structure,the key nodes of network are identified based on the improved weight reduction method.In order to identify accurately the key nodes of the power system,a dentification method of key nodes based on the improved Page Rank algorithm is proposed.Firstly,the sensitivity matrix of voltage reactive power and the sensitivity matrix of phase angle active power are obtained based on Jacobi matrix to define the link matrices under different indices of system.Secondly,considering the influence of power communication system on power system,the derived networks and matrix of system are defined based on the node contraction principle.Finally,the weight of nodes are obtained based on the improved PageRank algorithm,which is used to identify the key nodes of power grid.In order to identify accurately the key transmission lines of the power system,a identification method of key transmission lines based on cloud model is proposed.Firstly,based on the isophase angle theory,the phase angle partition area is defined,and on this basis,the transmission lines are grouped.The generalized entropy index of power flow growth rate is defined to measure the equilibrium degree of power flow impact distribution based on the theory of generalized entropy index.Secondly,based on RPCA model,the redundancy index is defined to evaluate the system’s resistance to power flow impact.And the Katz-Bonacich centrality index is defined to evaluate the importance of transmission line location based on the Katz-Bonacich centrality model.Finally,based on the principle of cloud model,the evaluation indexes are transformed.And the evaluation results are presented in the form of cloud maps,which used to identify the key transmission lines.In order to realize the synchronization of system,a control method based on dynamic compensation LMI sliding mode control is proposed to realize the frequency synchronization of synchronous generators.Firstly,the synchronization error is obtained by defining the synchronization state of system.The synchronization controller is designed based on the sliding mode function with dynamic compensation component and the pinning control model.Secondly,based on the state equation of hydroelectric generator,the control model of generator is constructed.Finally,in order to be more close to the actual situation of power grid,based on the principle of successive expansion loop method,the flow direction of power,the branch weight and the ability of node to receive signals,the external coupling relationship matrix between the generators is formed.And the frequency synchronization between the synchronous generators is realized by the designed synchronous controller.In order to realize synchronization of system with uncertain disturbances,a sliding mode global synchronization control method is proposed based on extended observer theory and sliding mode control theory.Firstly,the extended observer is used to observe the variables of system,and the sliding mode function is selected to design the global synchronization controller.Secondly,based on the state equation of synchronous generator,the global synchronous control model of power system is constructed.Finally,based on the designed global synchronization controller,the frequency synchronization control of power system with uncertain disturbance is realized.