Integrated Transmission System Planning Considering Accommodation Of Intermittent Generation Sources

The integration of large-scale intermittent generation sources confronts the traditional power system with a highly uncertain, risky and complex operating environment. It is of great significance that how to provide guidance, coordination and support for the power system to enhance its capability to accommodate the intermittent power, as far as transmission system planning, which is a major concern of system planners at home and aboard. Shortages of the existing methods and models of transmission system planning are:(i) lack of comprehensive technical and economic evaluation and methods which is adapted to transmission system planning with high penetration of intermittent generation sources;(ii) existing methods of power system planning fail to keep balance between accommodating capability of the power system and required reliability level during operation;(iii) existing methods are uncapable to condiser the change of available transmission capacity of the transmission system brought by the intermittent power sources; et al.Given the background above, in-depth analysis is performed of the characteristics of intermittent generation output and the interaction disciplines with the power system, which bases on existing models and methods of transmission system planning. Afterwards, new indicators for comprehensive evaluation are introduced, a more flexible model of transmission system planning is established, and a coordinated decision-making method is developed for risk managemen. Finally, some conclusions of the researches are accomplished as follows:(1) First, existing theories of transmission system planning are introduced. Based on that, basic aspects of transmission system planning are analyzed and summarized for modeling and simulation, while considering accommodatinog intermittent generations. These models is of broad applicability to different scenarios of transmission system planning with high penetrating intermittent power, including non-timing/timing scene, single/multiple scenes.(2) A more comprehensive evaluation system is proposed to make up for the deficiencies of the existing one of transmission system planning considering accommodationg of intermittent sources. First, investigation and summarization of relevant international experience is conducted. Then, with domestic specific characteristics taken into account, new types of indicators are introduced, such an at-risk, maximum accommodating capability, pollutant reduction, et al. With such indicators, characteristics of economics, reliability, flexibility, environmental-friendness of the power system, which accommodating large-scale intermittent sources, are able to be evalutated qualitatively or quantitatively as fully as possible. The introduced evaluation index system can effectively distinguish obtained planning schemes and provide support for decision-making.(3) In order to solve the contradiction between requirements of economics as well as and accommodationg of intermittent generation sources, a bi-level programming model is developed for transmission system planning with the capability of accommodating high penetration of intermittent renewable generation taken into account. The upper-level and lower-level model respectively aims at minimizing the investment cost associated with transmission planning and the sum of the penalties for abandoning wind and for load shedding, meanwhile combined with check of security constraints under kinds of uncertainties, which ensure the adaptability of transmission planning schemes. Finally, a modified Brazilian southern46-bus system with three wind farms is served for demonstrating the essential features of the developed model and employed algorithm. Simulation results show that appropriate trade-off should be made between enhancing accommodating capalibility and economics of operation in the power system with a high penetration of intermittent renewable energy, and thus reasonablely balancing transmission investments and reliability of system operation.(4) A multi-objective Pareto optimal theory is introduced to solve the coordinated determination problem of available transmission capacity (ATC) of interconnected system with large-scale intermittent generation sources. First, sources of uncertainties are modeled with specific methods. Then, non-sequential Monte Carlo simulation is employed to obtain the marginal probability density distribution of ATC of each sub-region. Later, coordination for decision-making model is developed with an objective of maximizing the risk-benefit of ATC. The solution to the developed model is achieved by the fast non-dominated sorting (NSGA-II) algorithm, which could decrease the risk caused by uncertainties while coordinating the ATCs of different areas. Finally, the IEEE118-bus test system is served for demonstrating the applicability to regional synchronous coordination problems while taking risk caused by uncertainties into account. Simulation results show that the uncertainties associated with power system operation and the relative importance degrees among different regions have impacts on the risk of the multi-area ATC decision-making. Hence, it is of practical significance to coordinately and optimally determine the ATC among multiple areas.Finally, several conclusions are obtained based on the research outcomes, and directions for future research indicated.