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Reliability Assessment Based On Bayesian Networks For Rural Active Distribution Systems

Posted on:2019-10-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:L A GaoFull Text:PDF
GTID:1362330596457939Subject:Agricultural mechanization project
Abstract/Summary:PDF Full Text Request
Due to the energy crisis and environmental constraints,distributed generation will become a strong supplement and effective support for rural distribution network,which is the development trend of rural distribution systems in the future.With the increasing penetration of distributed power supply,distributed energy storage device,controllable load and all kinds of energy in the power grid,the distribution systems change from the traditional passive network to active network,the network structure and operation mode of the systems become more complex,and the reliability evaluation method of the distribution systems will also change.In view of this,based on the research results of reliability evaluation of traditional power distribution systems,this paper conducts research on reliability assessment models and methods of rural active distribution systems.The main contents are as following:1.According to the change of power flow direction and the network structure of distributed generation which connected to the distribution system,based on the fault mode consequence impact analysis method and conditional probability algorithm,through the power flow calculation,the logical relationship between various components in the system is analyzed,and the Bayesian network is established in graphical form.A reliability evaluation method of distribution system including distributed generation based on Bayesian network is proposed,which evaluates the reliability of distribution system from three aspects,such as availability,position and capacity of distributed generation,and calculation of the influence of each component on the system reliability.The contribution rate index is used to represent the specific improvement degree of the reliability of distributed generation which accessed to the distribution system from different aspects.2.In view of the uncertainty of the output power of the distributed generation and the time-varying characteristics of the load when the microgrid is connecting to the distribution system,the reliability index of the distribution system with microgrid is solved by the timevarying method.In view of the different logic combination states of distributed generation and energy storage components in the isolated operation mode of microgrid,the equivalent power(power supply)node is set,and a dynamic supply logic model of power-load node in microgrid is proposed.The Bayesian network of microgrid and distribution system is established,and the reliability of power distribution system with microgrid is evaluated by the Bayesian network time sequence simulation reasoning algorithm.With the help of Bayesian network diagnostic reasoning,the key factors affecting the power supply reliability of the system or important load points can be solved,and the weak links of the system reliability can be identified.The example shows the effectiveness of the model and the algorithm.3.In order to make quantitative analysis of the influence of meteorological factors on the number of photovoltaic module fault repairing,the grey relational degree analysis method is adopted to build the relational degree model between the number of photovoltaic module fault repairing and meteorological factors.In view of the stratification of photovoltaic module EVA,meteorological factors that have significant influence on this kind of fault are extracted.The climatic conditions at different time and in different regions are considered,the correlation degree between the number of faults repairing and meteorological factors of photovoltaic modules is analyzed respectively from the time scale and space scale to explore the causes of high fault repairing quantity.The analysis results can be used as the operation and maintenance plan corresponding to the weather,which makes the photovoltaic module more directional and accurate in design and maintenance.For photovoltaic component failures have strong correlation with meteorological factors,the meteorological factors have strong time-varying,and the influence of different meteorological factors are planned to the photovoltaic component failure rate,the time-variant failure rate model based on photovoltaic modules of photovoltaic power system reliability assessment method is proposed in this paper.According to different time scales of failure rate of system reliability assessment respectively,the example shows the effectiveness of the model and the algorithm.4.Based on the uncertainty of output power of energy conversion components of distributed integrated energy system and the time-varying characteristics of load,a multienergy-dynamic-supply logic model of energy supply and load in distributed comprehensive energy system is established which is suitable for distributed comprehensive energy system.Based on the Bayesian network of the energy hub and distributed integrated energy system,the Bayesian network time sequence simulation reasoning algorithm is used to solve various load points and system reliability indexes respectively.At the same time,the fault sensitivity of the system and energy conversion components of each load point and system is reflected by the diagnostic reasoning,the example shows the effectiveness of the model and the algorithm.
Keywords/Search Tags:active distribution system, reliability assessment, Bayesian networks, grey correlation, distributed integrated energy system
PDF Full Text Request
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