Local Grid Dynamic Equivalent Model and Improvement of Equivalent Method

To simplify the analysis of the large-scale ultra-high voltage interconnected local grid,a series of power grid equivalent methods have been proposed in recent years,but the unreasonable equivalent methods could cause a decline in the accuracy of the power grid data.To address the problem,this paper,through analysis of the commonly used equivalent method process,identifies the error source,and then puts forward a new improvement scheme.By this scheme,under the condition of the invariable static boundary tide of the equivalent,grounding impedances and equivalent adjusting power loads are hung on the equivalent border to ensure the power injection of the external grid into the internal grid to remain unchanged in dynamic situations.In the end,the method is used in the software PSASP of an 8-machine and 36-node system,the simulation results show that the method is both simple and practical.