Study on Protection Principle of Novel Filtering Transformer Based on Coupled Inductance

In view of the increasingly severe power quality problems, this paper studies a novel filtering transformer with four windings. It has a specially designed filtering winding and has a good multi-port harmonic suppression function. Based on the coupled inductance parameters and the transformer model, this paper reveals the special connection of the coupling inductor of the novel filtering transformer. By establishing the voltage-current conversion relationship equation of the novel filtering transformer, the protection principle applicable to the novel transformer is expounded. Furthermore, the protection action equation of the novel filtering transformer is derived, and then the internal fault identification criterion is proposed. The protection principle is based on the corresponding relationship between the internal structure of the transformer and the coupled inductance parameters. Combined with the characteristics of the coupled inductor, it can identify internal faults and at the same time avoid the external fault of the transformer. Finally, the correctness and reliability of the protection principle are verified by building a MATLAB simulation model.