An Integrated Approach for Reliability Evaluation of Electric Power Systems Considering Natural Gas Network Reliability

Abstract

With the rapid increase of demand for electric power and the growing complexity of the electric system, the reliable operation of electric systems is facing new challenges. Meanwhile, natural gas has been widely used in transportation, electricity generation, and heating. In addition, gas-fired turbines play a growing vital role in the generation of electricity. However, all the facilities in a natural gas network are subject to failures. The operation of gas-fired turbines will be affected by the status of natural gas network, and the insufficient supply of natural gas may cause the output of gas turbine units to reduce to zero. This power decrease may further influence the operation of power systems. Therefore, it is quite urgent to quantify the influence of natural gas networks on the power system reliability. A deep understanding of the operation of natural gas network is needed to quantify the impact that natural gas networks will bring to the power system reliability. The main facilities in a natural gas network are natural gas pipelines, compressor stations and natural gas sources. Additionally, the mathematical failure models have been developed for these facilities to build a reliability analysis framework for the gas network. The mass flow of natural gas at different failure conditions is analyzed by the maximum flow algorithm. Case studies are conducted on a modified Europe Belgium natural gas network to analyze the influences of different failures on the maximum flow of natural gas. The main problem discussed in this thesis is related to how the natural gas network operation status influences the reliability of power system. The coupling unit is the gas-fired turbine between and electric and gas infrastructures, while the simplified gas-fired turbine model used in this work shows a linear relation among the power generation and the mass flow of natural gas. In this thesis, reliability evaluation is performed based on the hierarchical level II which contains the generation system and the transmission system. The optimal power flow analysis has been conducted for the reliability evaluation. Based on the results of power flow, the status of load shedding can be obtained in a power system. Then, system reliability states can be determined. Failure statuses of both the natural gas network and electric system are simulated by Monte Carlo Simulation. Case studies are conducted on the RTS-79 system and the modified Europe Belgium natural gas network by using MATLAB and IBM CPLEX. The results indicate that the reliability of system decreases.