Design and calculation of positive equivalent reactance for the intermediate winding of three-winding transformer

Three-winding transformer can be used for certain harmonic filtering when the intermediate winding is connected to a tuned filter branch. The design of positive equivalent reactance of the intermediate winding is proposed in this paper, to reduce the external tuned reactor of the filter branch, which improves the integration of transformer and filter device. The positive equivalent reactance of the intermediate winding can be realized by reducing the axial height of the intermediate winding. Calculate the leakage reactance between windings using the leakage reluctance method, or simulate the inductance using the finite element method to solve the equivalent reactance of the intermediate winding; Finally, the filter system with positive equivalent reactance and the filter system with external reactor are compared and analyzed by simulation, and the engineering prototype of the three-winding transformer and filter is tested, the results of simulation and test verify the correctness of the positive equivalent reactance design and the effectiveness of filtering.