Studies On Static Equivalent Of Power System And Its Evaluation Method

With appearance of combined power system, especially interconnection of the large scaled power grid, the calculation of power system planning and operation in the calculation method becomes very complicated. Because the running of power system control and management is a layered distribution, we calculated the power system analysis which we are interested in (the internal system), and did the offline and online analysis. However, the operation of external systems also play an important role in the analysis of the internal systems, and so we need to do the equivalent of external system, and get a reasonable model which could be used to directly simulate the whole network model. By analysis and calculation, the analysis of interconnected power system will become easy and convenient calculation when it was approximate to the origin model.Equivalent model can impact directly on a lot of network analysis results obtained from software. In this paper, we study in the static equivalent of the Ward equivalent method. The basic Ward equivalent have been widely used. By utilizing the analysis of the basic Ward equivalent, we know that for different power grid prototypes, this equivalent network approach has different problems. Therefore, based on the analysis of the basic Ward equivalent, we obtained some improved Ward equivalent methods.There are many algorithms to calculate the external equivalent at home and abroad, and we know that the method of equivalent power system plays an important role on both offline and online analysis of power system. Therefore, to evaluate the effect of an equivalent method, a systematic evaluation of the merits of the standard equivalent method, it is valuable for further research and development of the equivalent method and how we choose the equivalent method on different grids. This paper proposes a method from four aspects of evaluation:power balance analysis, voltage stability analysis, transient stability analysis and short circuit current analysis. In this paper, calculations are based on the results of power flow achieved by computing engine, and the results can be easily obtained.In this paper, the basic Ward equivalent method has been used to establish a static external network equivalent model. Also Shandong Power Grid and the actual network data have been adopted to do the applied research. In the end, the evaluation comparison of the reasonableness of the equivalent model is given according to the above four aspects of the whole network and the calculation of the equivalent network.