Short-circuit model of the DFIG considering coordinated control strategy of grid- and rotor-side converters

Abstract

The short-circuit current calculation is of vital importance for the power system. With a high proportion of new energy sources, the setting of relay protection and the selection of electrical equipment have been severely degraded. An accurate short-circuit current calculation model of new energy source is necessary for the short-circuit calculation of power grid with new energy sources. However, due to the DFIG’s control system is a ”black box”, and an accurate fault characteristics and short-circuit current calculation models of DFIG is difficult to obtained. Currently, for the fault current of the DFIG, lots of research works is carried out under symmetrical fault or the crowbar protection is activated condition. However, under crowbar protection is not activated and unsymmetrical fault condition, there are no unified short-circuit calculation models of DFIG. In this paper, the transient process of DFIG under those condition is analyzed, and mathematical expressions are derived. Moreover, the comprehensive and unified short-circuit calculation models of DFIG have established under different low voltage ride through control conditions. The influence of GSC and slip rate of DFIGs can be considered. The test results show that the LVRT control strategies, the GSC and slip have an important influence on the DFIG’s short-circuit calculation model. The quantitative research results are of important significance for relay protection setting calculation, grid operation and control, and the selection of electrical equipment of power grid with DFIGs.