Optimization Methods Of Power System Relay Protection Coordination

Relay protection devices are important guarantees for power system security and stability.To meet the requirements of the power system operation and give full play to the effectiveness of relay protection devices,the settings of the devices must be accurately and reasonably calculated.With the continuous development of UHV technology,China has gradually formed a large-scale cross-regional complex interconnected power system,which sets a higher standard for the relay coordination system in terms of the calculation scale,efficiency,the level of automation,etc.This dissertation devotes to the optimization methods of power system relay protection coordination,including the research on opening all of the directional loops in the complex interconnected power network,the research on mutual inductance branch building method of Y-matrix and Z-matrix,and the research on the integration of setting calculation data.The major works and achievements of this thesis are summarized as follows.An improved biogeography-based optimization algorithm to determine minimum break point set of directional protection for multi-loop networks is proposed.Determination of minimum break point set(MBPS)is the key procedure during setting and calculation of directional protections in multi-loop power networks.This method improves the mathematical model for determining MBPS by handling constraint based on protection incidence matrix.Additionally,a method based on improved biogeography optimization(IBBO)is proposed to solve the model effectively.Simulations reflect that the proposed method can reduce the MBPS dimension compared with the traditional graph theory based methods and relay dependency function based methods,and the proposed algorithm has faster global convergence,stronger robustness and higher convergence precision when applied to practical complex networks.A new method for coordination of directional relays based on minimum break protection dependency set(MBPDS)is proposed.In order to solve the problem that the existing method based on MBPS leads to large amounts of broken relay dependency relations,this method establishes a mathematical model that aims at minimizing the number of protection dependency relations that need to be disconnected.A method based on self-adaptive biogeography-based optimization(SaBBO)is proposed to effectively solve the model.To improve the performance of the SaBBO algorithm,four strategies,i.e.,cosine migration model,self-adaptive migration operator,self-adaptive differential mutation operator,and diversity mechanism are embedded.Case studies on various test systems verify the feasibility and efficiency of the proposed approach,and compared with other three kinds of algorithm,the simulation results show that the SaBBO algorithm has faster convergence speed,stronger robustness,and higher convergence precision in determining the MBPDS.A method for updating minimum break relay dependency set which can apply to arbitrary topology changing has been proposed.This method deduces the evolution rule of MBPDS after the line adding and breaking or bus-tie switch opening and closing.Based on the equivalence relation between the protection incidence matrix and the simple loop matrix,the evolution rule can be transformed to the correlation calculation of the protection incidence matrix which can achieve a fast update of MBPDS.The calculation results demonstrate that the proposed methodology can evidently reduce the acquisition time of MBPDS in the case of topology change,and so that it can be applied to online verification,early warning and calculation of relay protection settings.A novel method of building Y-matrix and Z-matrix based on branch groups is proposed.In the process of building Y-matrix and Z-matrix by traditional adding branches method,the additional of mutual inductance lines is more complex than non-mutual inductance lines.This method divides the mutual inductance lines into three types:tree branch group,chain branch group,and mixed branch group.Then,the calculation formula of adding this three types to the Y-matrix and the Z-matrix is deduced.This method can be used to unify the computing method of mutual inductance lines and non-mutual inductance lines,reduce the amount of computation and improve the computational efficiency.The simulation results show that the novel algorithm is effective and universal.In order to solve the problem that the existing equivalent data interaction method is more and more complex and cannot meet the power system needs,a graphical and data integration method for power system relay protection coordination is proposed.And,the relay protection coordination framework and merging scheme are presented.The integrated platform of relay protection coordination based on the proposed method has been put into operation in electric power dispatch centers of the State Grid,the Southern Power Grid,the Central China Grid,and the Northeast Power Grid.This method realizes the distribution maintenance and centralized sharing of the data for relay protection coordination.So the power system practitioners can grasp the more comprehensive network parameters and relay protection coordination.The effectiveness of this method is verified by the merging of the Southern Power Grid and the Guangdong Power Grid.