Modeling Of Distribution Network With Wind Power And Study On Its Protection

Wind power generation is a development form of new energy, which is environmentally friendly and has mature technology, high conversion efficiency and significant economies of scale. Thus, it develops very rapidly. However, it is greatly influenced by wind resources. For one thing, its output power is random and fluctuant because of the impact of wind speed, so as not to be controlled as conventional thermal power units. For another, wind farms often exist in remote areas, where the power grid is relatively weak. Therefore, the impact of wind power integration on the power grid can not be ignored.Firstly, different characteristics of various wind power generators in practical application of engineering were introduced and then the widely used double-fed induction generator (DFIG) was selected for study in this paper. Then, it analyzed the structure and working principle of DFIG, obtained the mathematical model of DFIG in two-phase rotating coordinate system by coordinate transformation. On basis of that, the vector control strategies using to control the two converter of double-fed wind generator were researched. Then the simulation model of double-fed wind generator was established using Real Time Digital Simulator (RTDS) and the operating characteristics and fault response characteristics of DFIG were studied by dynamic real-time digital simulation. Simulation results showed that this model was able to control the output active and reactive power independently. Besides, steady and transient characteristics were consistent with the theoretical analysis, which verified the correctness and validity of this model.Meanwhile, this paper further studied the impact of wind farm on the relay protection of distribution network based on the study of modeling and fault response characteristics of double-fed wind generator in different situations. First of all, the problems of protection and their causes were analyzed in theory. Then, two simulation models of distribution network in which wind farm was nearly conneted to line in the form of T and distribution network in which wind farm was connected to regional substation were build using RTDS. Based on setting calculation for protectin of original grid without wind farm, this paper studied the influence of short-circuit current provided by wind farm on the sensitivity and reliability of current protection in distribution network by simulation. The results showed that different capacity of the wind farms, different wind speeds, different reactive power status and different fault locations can cause different effect on protection.Finally, the paper summarized the countermeasures to reduce the impact of wind farm on protection of distribution network and analyzed the principle and setting calculation method of adaptive current protection. At the same time, the paper focused on the problems when traditional adaptive current protection applied in distribution network with wind farms and made targeted improvement for it. Its protective effect was evaluated by the method of combinating RTDS simulation and MATLAB programming. The results confirmed that the improved adaptive current protection can automatically adjust its setting value according to different operation status and have good sensitivity and reliability, reducing the impact of wind farm on protection of distribution network.