Research On Flexibility Evaluation Method Of Power Distribution Grids With High Penetration Renewable Energy

Integrating high proportion of distributed renewable energy will be a basic feature of future smart distribution grids.Due to the variability and uncertainty of renewable energy,the operation modes of distribution grids are to be more complex.Therefore,distribution grids need to have sufficient flexibility to cope with the variability and uncertainty of renewable energy to ensure its secure operation.This thesis focuses on the scientific issues of evaluating and improving the flexibility of power distribution grids with high proportion integration of renewable energy generation.The main contributions of this thesis are as follows:First,the principle of power adjustment capability and network reconfiguration to improve the flexibility of distribution grids is analyzed.Taking power adjustment capability and network reconfiguration as measures of flexibility improvement,a two-stage robust optimization model for improving flexibility of distribution grids is proposed considering the variability and uncertainty characteristics of renewable energy.The first step determines network reconfiguration scheme and the flexible scheduling scheme,and the second step determines flexible adjustment scheme based on the flexible scheduling scheme.Second,a set of flexibility indexes are proposed to quantitatively evaluate the flexibility of distribution grids from the perspective of each period and scheduling horizon,including insufficient upward flexibility and insufficient downward flexibility at each period,the expectations of insufficient upward flexibility,the expectations of insufficient downward flexibility,the proportion of time with insufficient upward and downward flexibility during the evaluation cycle.The analysis of several distribution grids shows that the flexibility evaluation and optimization method proposed in this thesis can provide an important auxiliary tool for the quantitative evaluation and improvement of the flexibility of distribution grids.