Research on magnetizing inrush current of microgrid based on Grey identification

Abstract

With the large-scale access of wind and light energy, the power system is gradually developing towards the micro grid with low inertia. AC microgrid often uses multiple parallel transformers to supply power to the load at the same time. In case of power failure due to a fault or maintenance, the parallel transformer needs to be powered on and closed without load to restore power supply. The parallel transformer is easier to saturate, the core remanence is higher, and the peak value of inrush current is larger, which has an impact on the stability of microgrid. It will also lead to misoperation of transformer differential protection and affect the safe and stable operation of power system. Therefore, a switching method of parallel transformer based on Grey recognition is proposed. Firstly, the generation mechanism of inrush current is analyzed theoretically, and then the waveform shape characteristics are analyzed. The grey whitening weight clustering method is used to identify the feature set to complete the magnetizing inrush current locking and ensure that the protection does not misoperate. Finally, the PSCAD simulation model is established to simulate the AC microgrid to verify the feasibility of this method.