Analysis On External Connected Switching Power Of Regional Grid With Wind-farms

The distribution of energy resources and load center is not balanced, which has caused a large scale of power flow in the whole country. It is needed to build large capacity and long distance transmission channels to realize the intensive development of energy resources and optimize the allocation of resources around the country. Therefore, the construction of UHV AC/DC and regional power grid interconnection will be a major trend in the future and it has been put on agenda. After the regional power grid interconnection, how to determine the switching power of tie lines according to reliability standard is a difficult problem in network planning:the one question is that in order to avoid the high operational risk caused by not-planned outage of large capacity generators in regional power grid, the switching power should be larger than one limit value, which is the demand of connected switching power; the other question is that in order to assure that the transmission and distribution network relative to regional interconnecting points can meet the static security cheek-level, the switching power should be smaller than another limit value, which is called the scale of connected switching power. For this purpose, this paper makes a further study on the external connected switching power of regional grid with wind-farms, and the main work is as follows:Firstly, the paper puts forward an analysis method about external power demand of regional power system and the specific evaluation process, which is based on generation reliability assessment. This paper has formed a system model suitable for the demand analysis on switching power and introduced three reliability assessment methods of power generation system. And through bringing the external power and wind power output into the reliability indexes, the power demand can be calculated according to the given grid reliability criteria. For the wind-farm modeling, this paper has put forward a more accurate multi-period and multi-state wind power output model, which is combined with the load model to form a wind power-load probabilistic distribution. And for the algorithm, this paper has proposed two improved algorithm used by power demand analysis, respectively, the capacity differential interval method and probability interval differential method. This paper has also deduced the relationship between interval number and calculation deviation, in order to improve the calculation speed under the guaranteed calculation accuracy.Then, this paper proposes a analysis method about the scale of connected switching power of regional power network and the specific evaluation process, which is based on static security checking. The paper has formed a system model suitable for the scale analysis and put forward a static security assessment index system. Through the coordination adjustment of load and external power, the maximum external power could be calculated, which can meet the security check indexes. For the wind-farm output, a model with strong adaptability in the scale analysis based on the average output coefficient is proposed. For static security check index system, this paper has formed a single check-index system on trend function and comprehensive check-index on the analytic hierarchy process, which lays the foundation for the network security quantitative analysis.Finally, according to analysis theory above, this paper takes one of North-China, East-China and Central-China regional grid plans as an example, and has calculated the demand and scale of external switching power, and analyzed the results to validate the practicality of proposed methods.