Research On Reactive Power Related Issues In Electricity Market Environment

The power industry restructuring breaks the vertically integrated monopoly of the tranditional power industry with the aim of introducing competition, improving efficiency, optimizing resource allocation and reducing power price. However, many new problems and challenges have emerged during the restructuring process. If these new problems are not properly solved, the emerging electricity market may not be able to grow healthily and even the security and stability of the power system associated operation could be endangered. This dissertation focuses on the study of reactive power related issues in the electricity market environment and some significant results are obtained.Reactive power support service is regarded as an important ancillary service. Its adequacy and proper geographical allocation have significant impacts on the power system operation and electricity market performance. Given this background, much effort has been made in addressing many reactive power related issues in the electricity market environment in recent years, and a brief but yet systematic survey is made in this dissertation. The following topics are covered: cost analysis, valuation, spot pricing, procurement as well as cost allocation of reactive power services. In addition to the survey, some comments are also made.Reactive power produced by differently located suppliers may have different effects on the system economics and security, and hence it is necessary to assess the value of reactive power support service so as to provide a solid foundation for reactive power pricing and guidance for reactive power planning and dispatching. Existing research work on this subject is mainly based on a deterministic operating scenario and cannot properly reflect the values of reactive power resources when many plausible system operation scenarios may occur. In order to make a comprehensive valuation for reactive power support service for such cases, a method based on voltage sensitivity is proposed from the perspective of voltage regulation. Many factors, such as system voltage profile, probability distribution of contingency, are taken into account.Using a market mechanism to procure reactive power can offer incents for reactive suppliers to provide adequate reactive power support and induce more reasonable reactive power investment. Based on the analysis of the cost of generators' reactive power production and the power grid connection policy, a segmented bidding model of generators' reactive power generation is proposed in this dissertation, with capacity bidding and energy bidding of reactive power included. This model can fully cover the cost of reactive power support service. Based on optimal power flow (OPF) four models of reactive power procurement with different aims are developed. The objective functions of these models are respectively net loss minimization, cost minimization, power quality optimization and system security optimization. Results from the above four reactive power procurement models are compared and discussed.Reactive power reserve is a key factor for maintaining the stability, especially voltage stability of the power system. In this dissertation a security-constraint reactive power procurement method is proposed. Using this method the system operator can procure enough reactive power reserve along with the steady-state reactive power. Consequently the system stability under some contingencies can be improved. During the process of reactive power procurement the total cost, including the cost of steady-state reactive power, the cost of reactive power reserve and the cost of net loss, is minimized.In recent years, much effort has been made for establishing a trading market for reactive power procurement at least in the academic circle, and several schemes already proposed. In these studies the reactive market power problem has been regarded as a vital issue which may have a serious negative effect on the efficient operation of the market. Given this background, a modified Herfindahl-Hirschman Index (HHI), with the characteristics of reactive power well taken into account, is proposed in this dissertation. Furthermore a method incorporating the modified HHI and the concept of electrial distance is proposed to evaluate the local reactive market power problem.