Rearch On Transmission System Planning With Wind Farms Considering Demand-side Response

Faced with the growing energy demand and the shortage of global fossil energy, the development of wind power has raised increasing attention at home and abroad currently. As a kind of clean and renewable energy with mature technology, wind power has developed rapidly all over the world in recent years. However, the growing penetration of wind energy in power systems may bring about much more uncertainty to the planning and operation of power system, such as affecting the power grid voltage stability, frequency stability and the load flow distribution. Therefore, it is necessary to consider uncertainty of wind power in the transmission system planning. Based on studies on uncertainty of wind power output and the effects on the transmission system, a planning model for transmission systems which contain wind farms is put forward. Demand side response mechanism is adopted to improve the utilization of wind power while ensuring the system stability at the same time. The specific work mainly includes the following aspects:1) A mathematical model for transmission system planning is established, of which the objective function is minimum annual investment cost of the transmission lines construction, considering various system operation constraints under normal conditions and ‘N-1' accident conditions. Particle swarm optimization algorithm is studied, and improvement is proposed to ensure a reliable and fast solution of the transmission system planning problem.2) Considering that demand-side response(DR) mechanism can realize peak load shifting according to consumers' intention, optimize load flow distribution, improve the equipment utilization and finally reduce or postpone transmission system expansion. What's more, demand-side response helps to cope with uncertainty of wind power as an alternative of spare resource. So thus, introduction of incentive and interruptible load measures to the transmission system planning can increase the wind power utilization. A bi-level planning model for transmission system with wind farms considering demand-side response is presented, of which the objective is minimizing the sum cost of transmission expansion investment, demand-side response, as well as the punishment of wind curtailment. Multiple scenarios are set up based on the uncertainty of load and wind power output. The optimization of transmission system planning is conducted to improve the utilization of wind power and the efficiency and reliability of the transmission system, under the premise of satisfying the opration constraints under each scenario.3) A comprehensive evaluation index system as well as a comprehensive decision method based on combined weight and cloud model theory is established, to evaluate the economy, reliability, flexibility, and environmental impact of the selected plans. On the basis of the subjective weights calculated by analytic hierarchy process(AHP) and sequence relations method, as well as the objective weights calculated by entropy weight method and variation coefficient method, a combined weight of evaluation indices is obtained, which not only respects the experts' opinions, but also makes full use of the objectivity of index data information. Cloud model theory is introduced to the process of evaluation to enhance the objectivity and credibility of the comprehensive evaluation decision results, as cloud model can fully reflect the fuzziness and randomness of evaluation information.At last, the research works of this paper are summarized, and the problems that need further studied are pointed out.