Transmission System Planning And Reliability Evaluation Considering Integration Of Intermittent Generation Sources

The penetration level of intermittent generation sources has been increasing in some actual power systems, and hence has introduced some new problems and even challenges for transmission system planning and reliability evaluation. Given this background, the relevant concepts, procedures and methods are comprehensively presented and prospected in this thesis. The mathematical models of transmission system are particularly described. The methods for power system reliability evaluation are summarized and classified.Aiming at transmission system planning, a bi-level transmission system planning model is presented with transmission investment costs, load shedding costs, abandoned wind power costs as well as relevant operating constraints considered. In the upper level, the objective is to minimize the sum of annual investment cost and the expected value of annual economic loss of shedding load and wind energy abandoned for given scenarios. In the lower level, the objective is to minimize the sum of economic loss of shedding load energy and wind energy abandoned for each scenario. These two levels are implemented interactively and iteratively, and the optimal transmission system planning scheme will ultimately be attained. The upper level model is described as a mixed-integer optimization problem, and solved by the well-established particle swarm optimization algorithm; the lower level model is formulated as a linear programming problem, and solved by the linear programming solver ILOG CPLEX. Finally, the essential characteristics of the proposed models and adopted algorithms are demonstrated by a modified 18-bus sample power system.Aiming at reliability evaluation of power systems, the Monte Carlo simulation method is proposed considering integration of intermittent generation sources. Two reliability evaluation indices are introduced to show the influence of integration of intermittent generation sources to the power system reliability:the contributing coefficient of intermittent generation sources for energy not supplied NEENS, and the contributing coefficient of intermittent generation sources for period of energy not fully supplied NT. Mathematical models of wind power generation and photovoltaic power generation are established using probability distribution function. The minimum load shedding model is introduced to evaluate the power system reliability. Finally, the proposed indices and models are used in the Monte Carlo simulation method, and this method is applied to the reliability evaluation of a 56-bus power system.A Markov process based reliability evaluation method considering condition based maintenance is next proposed. The impacting factors on power system reliability are divided into three kinds:outside destroying, aging of equipment and equipment maintenance. With these impacting factors considered, the changes of power equipment states are described as a non-aftereffect Markov process with five equipment state levels included. The equipment state transition models are respectively established next for the scenarios with and without maintenance. Then, the system reliability is evaluated using the well-established Monte Carlo simulation method and one of the widely used reliability indices, i.e. Expected Energy Not Supplied (EENS) calculated. The results indicate that the equipment quality and work environment have significant impacts on the system reliability. Hence, improving equipment quality and work environment is the first option to enhance the system reliability.