Abstract
With the enlarging scale of doubly-fed induction generators (DFIGs) connected to power systems, it is important to analyze the influence of a short-circuit current to system relay protection. Due to the correct evaluation of the protection operation characteristics, the DFIG short-circuit current needs to be calculated accurately. But the current research on the short-circuit current of DFIG is based on the following assumption: the rotor excitation current is zero after the rotor crowbar is put, and the influence of its dynamic process is ignored. This will bring errors to the calculation results. This paper takes into account the influence of rotor current dynamics by studying the mechanism of the potential transient change of DFIG. The stator rotor flux linkage of DFIG in the event of a three-phase short-circuit is accurately calculated, and an improved RMS calculation method of doubly-fed wind turbine short circuit current is proposed. A physical experiment platform with an actual controller of a doubly-fed fan is established, based on RTDS. It can be seen from the experiment that the short-circuit current calculation method proposed in this paper is more accurate than those methods that ignore the rotor dynamic process. This study lays a foundation for further study of the influence of DFIG on the protection operation characteristics.
Highlights
In recent years, the wind power in the world has developed rapidly
The accuracy of the proposed method in this paper is improved by 4.6%, especially from the 0.5 s to the 0.55 s(short circuit current attenuation process)
In order to correctly evaluate the protective action characteristics of the large-scale doubly-fed induction generators (DFIGs) accessing to the grid, the influence of the dynamic process of rotor current is taken into account in short-circuit current calculation
Summary
The wind power in the world has developed rapidly. In Inner Mongolia, Gansu, and Liaoning Province, wind power has developed rapidly. Large-scale wind power access to the power grid has made a great influence, and the impact of grid-connected wind power on relay protection has become a major concern in the current power system field. With the increase of DFIG, the influence of the transient process of DFIG on the short-circuit current calculation cannot be ignored. Inaccurate calculation of the short-circuit current will cause deviation in the protection setting, affect the accuracy of the protection, and even cause the phenomenon of protection rejection or mis-operation in severe cases. In order to improve the accuracy of the protection action, it is necessary to study the methods of short-circuit current calculation of DFIG thoroughly
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