Power System Reliability Assessment Methodology Improvement And Its Application

Safety and reliability of electric power system are of great importance on the development of national economy.In recent years,the rapidly increasing of load demand and the widespread application of noval techniques challenge the reliable operation of power system.Therefore,it is necessary to assess the reliability of power system for planners and operators to make appropriate decisions.This thesis will focus on the improvement and application of power system reliability assessment approaches.The main work can be summarized as follows:1.An impact increment-based state enumeration(IISE)reliability assessment approach is proposed.Firstly,the reliability index calculation formula of the traditional state enumeration technique is transformed into an impact increment-based formation.With the derived formula,the calculation of state probability is simplified and the weight of low order contingency states is increased.Moreover,it is proved that the impact increment of the mutually independent high order contingency state,whose outage components are far away from each other,can be eliminated.Due to this fact,the impact calculation of this kind of high order contingencies can be omitted without decreasing the precision of reliability indices.2.A continuous time Markov chain(CTMC)based sequential analytical reliability assessment approach is developed for composite generation and transmission systems.The basic idea is to construct a CTMC model for the composite system.Based on this model,sequential analyses are performed.Various kinds of reliability indices can be obtained,including expectation,variance,frequency,duration and probability distribution.In order to reduce the dimension of the state space,traditional CTMC modeling approach is modified by merging all high order contingencies into a single state,which can be calculated by Monte Carlo simulation(MCS).Then a state mergence technique is developed to integrate all normal states to further reduce the dimension of the CTMC model.Moreover,a time discretization method is presented for the CTMC model calculation.3.A Markov chain based hierarchical risk assessment approach is proposed for scheduling operations.The characteristics of two major influence factors of scheduling operations,which are operation result of each step and facility failures,are decoupled and analyzed with hierarchical method.In the external layer,Markov chain is used to simulate the evaluation of system topologies during scheduling operations and achieve their probability distributions.In the internal layer,analytical method is used to calculate risk indices of each system topology.By calculating the weighted sum of all system topologies according to the probability distribution of each operation step,final indices of scheduling operations will be obtained.4.Reliability of the integrated transportation and electrical power system(ITES)is studied in detail.A bidirectional EV charging control strategy is first demonstrated to model the interaction between the two systems.Thereafter,a simplified transportation system model is developed,whose high efficiency makes the reliability assessment of the ITES realizable with an acceptable accuracy.Novel transportation system reliability indices are then defined from the view point of EV's driver.Based on the charging control model and the transportation simulation method,a quasi Monte Carlo simulation based reliability assessment method is proposed for the ITES system.5.With the increasing utilization of combined heat and power plants(CHP),electrical,gas,and thermal systems are becoming tightly integrated in the urban energy system(UES).However,these three systems are usually planned and operated separately,ignoring their interactions and coordination.To address this issue,the coupling point of different systems in the UES is described by the energy hub model.With this model,an integrated load curtailment method is proposed for the UES.Then a Monte Carlo simulation based approach is developed to assess the reliability of the coordinated energy supply systems.Based on this approach,a reliability-optimal energy hub planning method is proposed to accommodate higher renewable energy penetration.