The QSS (Quasi Steady State) model of converter which neglects the negative impedance of DC system will bring some errors when unbalancedfault occurs in AC system.
The experiment result shows that the time-frequency method based on EMD can effectively extract the feature of unbalancedfault signal and is proper for non-frequency modulation signal procession.
In this program the voltage and current of simultaneous faults or unbalanced power system are calculated by solving the simultaneous equations of multi-port network and of the fault boundary.