Distance protection method applicable to renewable energy grid-connected systems

To further improve the performance of distance protection in renewable energy systems,a distance protection method is proposed,which considers the effects of control system and the distributed capacitance effect of the line. When an asymmetric fault occurs in the system,combined with the control characteristics of the converter,the sequence impedance characteristics of the grid and the pure resistive feature of the fault resistance,three unknowns in the fault loop equation can be eliminated,and the solution of the fault distance can be solved in the R-L model. Then,the setting point is set based on the calculation results in the R-L model,and the real electrical quantity at the setting point can be deduced by the calculation formula in Bergeron model. Finally,the equation from the setting point to the fault point is simultaneously solved to reduce the distributed capacitance effect on the distance protection. The simulation results testify that the method is less influenced by the fault features of the converter and fault resistance. It still has good performance in long line.