Experimental Validation of Fault Identification in VSC-Based DC Grid System

DC system has come a long way to shift the direction of power transmission in future. With respect to that, the protection is still one of the hot topics that need to be addressed, particularly the dc fault detection method. This paper presents methods to robustly differentiate between load change and dc fault in a two terminal dc system connected to passive load. In the first method, wavelet transform is used to determine the wavelet coefficient for the system dc line current. The performance of wavelet transform is compared with the rate of change of current (di/dt) method. Details regarding synchronous reference frame dq current controller at source terminal, root mean square method controller at load terminal are discussed. Simulation studies are carried out on MATLAB/Simulink model and the corresponding steady state, load change, and fault studies results are presented. Experimental validation of wavelet fault detection method is performed on the developed laboratory dc grid setup interfaced to dSPACE 1103 controller through MATLAB real time toolbox.