Comprehensive Assessment Of Development Status And Fault Diagnosis Of Distribution Systems

With ever-increasing demand of energy and global environmental problems,active distribution systems(ADSs)have been paid much attention.In order to ensure secure operation and sustainable development of an ADS,comprehensive assessment of its development status is an important issue to be addressed.Besides,an effective fault diagnosis strategy for an ADS with high penetration of renewable energy sources(RESs)are highly demanded for helping system operators to locate faults and speed the restoration of power supply to the customers interrupted.Given aforementioned background,this thesis investigates the comprehensive assessment of development status and presents fault diagnosis methods of ADSs.Main contents are listed as follows:1)Literature review on comprehensive assessment and fault diagnosis methods of distribution systems is given in Chapter ?.First,the assessment indices and comprehensive assessment methods for distribution systems are introduced and concluded.Afterwards,several fault diagnosis methods for distribution systems are introduced and compared,and their advantages and disadvantages are concluded.Finally,available fault diagnosis methods for the communication networks in the smart substations are summarized and compared.2)A novel comprehensive assessment method for evaluating the development levels of distribution systems is developed in Chapter ?.First,considering that the assessment indices for a county distribution system are of the feature of multiple attributes,an object-based comprehensive assessment index system is first presented.Next,the weights of indices are determined by the combination weighting method and the adaptive variable weight mechanism,and according to the adaptive weight mechanism the final weights of indices are next modified.Finally,5 county distribution systems in a provincial power system are employed to demonstrate the developed method,and the well-known radar chart used to identify the weakness points of these networks.It is shown by simulation results that the proposed method can well evaluate the investment and development status of county distribution systems.3)A fault diagnosis method based on a Multi Agent System(MAS)is proposed for ADSs.The MAS framework is designed,the general agent model established and the MAS-based fault diagnosis strategy developed.In the designed MAS framework,each bus/node is equipped with an agent based on the analytical model of fault diagnosis and a correlation factor is employed to represent the coupling relationship between any two bus agents.The impact of information loss or information distortion on the accuracy of fault diagnosis is analyzed separately.The developed strategy adopts the communication and negotiation mechanism between agents to obtain the global optimal results of fault diagnosis.The simulation for a modified 32-bus test system demonstrates that,the proposed method can tolerate the loss or distortion of alarm information and evaluate the operating characteristics of protections and circuit-breakers.4)An analytic model of fault diagnosis for communication networks in a smart substation is developed.First,based on the communication network model,the packet transmission path is searched.Afterwards,the falut hypothesis are proposed with the packet information taking into virtual and real circuits account,and the fault diagnosis analytical model is proposed based on information difference.BBO-TS algorithm is employed to solve the proposed model to obtain the optimal fault hypothesis.Finally,A typical 110kV smart substation is employed to verify the effectiveness of the proposed method,and the accurate fault diagnosis results can be obtained in the scenarios of multiple single faults and complicated double faults.Finally,the research work presented in this thesis is summarized,and future research directions in relevant research fields highlighted.