| Electric power industry is energy-intensive industry. In order to alleviate Chinese energy supply and improve the ecological environment, improving the energy efficiency of industrial electric power, changing energy use, and reducing carbon emissions are essential. Compared to conventional power systems, power system with renewable energy generation on the one hand improve the economics of power system operation, improve energy efficiency and conserve a non-renewable energy sources, on the other hand, it faces environmental change, with great uncertainty and risk of complex operating environment. Mainly due to:(1) The ever-increasing penetration of wind power has resulted in some new problems even challenges to the secure and economic operation of the power system concerned. Thus, in transmission system planning it is necessary to consider the capability of accommodating wind power as well as the risks caused by wind power.(2) Power transmission from west to east mainly with hydropower, is the dominant group and seasonal. In order to transmit more hydropower from the west, the thermal power units should balance the water and fire proportion. In premises of the safety and stability of power systems, reasonable operation mode of power systems should be considered.(3) Considering limitation of the transmission capacity of the lines, it is hard to get spare shared between regions. The thermal power units in Guangdong should maintain reasonable minimum operation mode to realize fast response and upgrade the ability of the electric power grid against the faults.Shortages of the existing methods and models of transmission system planning are:(i) existing methods of power system planning fail to keep balance between the acceptance of wind farms and the risk brought by the wind farms;(ii) existing methods have not considered on the impact of thermal power units upon the safety of power system and the low output of thermal power units upon the ability of the electric power grid against the faults.Given the background above, a bi-level transmission system planning model for this purpose is presented with transmission investment cost, load shedding punishment, abandoned wind power punishment, the comprehensive benefit of wind power as well as security constraints considered; a model of operation mode of hydro-thermal power system which is based on safety and economic operation and energy conservation is established, which gives the smallest output of thermal power units that can maintain the system security. Finally, some conclusions of the researches are accomplished as follows:(1) First, existing theories of transmission system planning and dispatching are introduced, based on that, basic aspects of transmission system planning are analyzed and summarized for modeling and simulation. These models are made up of single/multiple scenes and non-timing/timing scene, which are broadly applicable to different scenarios of transmission system planning.(2) In order to balance the acceptance of wind power and the risk brought by wind power, a bi-level transmission system planning model for this purpose is presented with transmission investment cost, load shedding punishment, abandoned wind power punishment, the comprehensive benefit of wind power as well as security constraints considered. The average levels and volatilities of load shedding punishment and abandoned wind punishment caused by uncertain factors are addressed. In the upper level, the objective is to maximize the generating quantity from wind farms by per unit transmission investment within a given time period, and the attained transmission planning scheme is then transferred to the lower level. In the lower level, the objective is to minimize the sum of shedding load energy and abandoned wind energy in a given time period, and the load shedding punishment, abandoned wind punishment and wind farm energy are then transferred to the upper model. 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 features of the developed model and adopted algorithms are demonstrated by modified18-bus and modified46-bus test systems.(3) In order to solve the problem of prosperity of hydropower in the west and maintain safety to the power supply, the thermal power units in West China should balance the water and fire proportion as well as Guangdong. A model of operation mode of thermal power units is developed, ILOG CPLEX MIP software is used to solve this problem.Finally, several conclusions are obtained based on the research outcomes, and directions for future research indicated. |
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