Main Article Content
Renewable energy sources (RESs) are connected one way or the other to the grid through power electronic devices. The SC current of these RES plants exhibits characteristics such as limited amplitude, controlled phase angle which may lead to the malfunction of the RES side distance protection on the transmission line.
A distance protection method based on high frequency fault component is proposed in order to overcome this problem. The voltage drop caused by the fault has a full frequency component and this can be extracted by wavelet transform. After that, the high frequency impedance models of the inverter-interfaced renewable energy generator (IIREG) and the doubly-fed induction generator (DFIG) are established and the frequency selection principle that makes them have the stable phase angle is determined. Based on this the internal and external faults can be determined by comparing the high frequency voltage at the fault point and the magnitude of high frequency operating voltage. This method eliminates the influence of frequency offset and week feed of RESS using high frequency signals and it can also tolerate some noise. At the same time, due to the larger radius of Impedance circle at the high-frequency range, this method has a strong ability to withstand the fault resistance.
A distance protection method based on power electronic method using pwm controller is used in this project along with an algorithm & photovoltaic array protection as an extension to the previous method.