A Compensation Winding Structure for Balanced Three-phase Coupled Inductor

Inductors and transformers are widely used in three-phase power conversion systems. Integrated or coupled structure is often adopted to reduce the size of the bulky magnetic components. However, these structures could bring the unbalance problem in three-phase power system or motor drive system, and this unbalance issue will impact the system's performance. In order to get a balanced performance in threephase system, special structure of three-limb E cores or separated cores should be applied in inductor design. This paper proposes a balanced three-phase coupled inductor which can be used with any E cores by applying additional compensation windings to the three phases. Then, a design guideline for balanced three-phase coupled inductor is suggested based on core geometry. Moreover, this coupled structure improves the phase inductance with coupling effects resulting in a reduction of the total inductor's volume compared with separated inductors. A finite element analysis (FEA) simulation and experiment results verify the proposed structure. A prototype of proposed inductor is built and shows a much better balanced performance compared with conventional design.