An Engineering Approach for Short-Circuit Current Calculation Considering WTG Integrated

Abstract

With the ever-increasing scale of wind power, the fault characteristics of power grids have changed dramatically, and the existing relay setting calculation approaches can no longer meet the requirements of modeling. The wind turbine generator (WTG) is usually treated as constant current source or set to zero to adapt to the traditional short-circuit current calculation software. This method does not consider the fault characteristics of the WTG, so the calculation accuracy is lower than that of iteration. However, the iterative algorithm also has problems, such as non-convergence or too many iterations leading to long computation time. Therefore, a calculation method of short-circuit current considering WTG integrated is proposed in this paper, which can solve the problem of iteration non-convergence while ensuring accuracy within the allowable range of engineering. Firstly, the WTG short-circuit current models considering converter control strategy and fault characteristics are established. Then, the branches with WTG are converted into "constant potential source + equivalent impedance" to facilitate WTG embedding in the relay protection setting calculation software and maintain consistency with the traditional synchronous generator equivalent mode. In addition, the calculation formula of equivalent impedance is deduced, and the modified voltage is also proposed to improve the accuracy. Finally, a simulation is performed in GIRGE B4-39 and part of actual power grids structures in a province to verify engineering practical value of the proposed method.