The Fast Reliability Evaluation Method in Transmission Grid Expansion Project Based on Power Flow Tracing and Ward Equivalent Method

The computational complexity of bulk power system reliability evaluation has become the main obstacle for its application in actual projects. Considering the limit influence of transmission grid expansion project to the whole system, this paper proposes a fast reliability evaluation method based on power flow tracing and ward equivalent method. The power flow tracing method is applied to select the small region that influenced significantly by the new project, while the ward equivalent method is used to solve the equality problem in the boundary of the small region. A modified load shedding model is proposed for the reliability evaluation of the selected grid. Finally, the method proposed in this paper is applied in a provincial power grid in China. The case studies indicate that the method can effectively select the influenced region by the new projects. The effect of boundary equivalent by Ward method is satisfied. By comparing the reliability evaluation results between the equivalent power grid and the whole grid, it can be seen that the computational accuracy is high and the computation speed is fast.