Dual Inverter Fed Adjustable Field IPMSM Using DC Zero-Sequence Current

This article proposes a dual inverter system for an adjustable field permanent magnet synchronous motor (PMSM). The adjustable field PMSM can control a field flux to achieve an expansive driving range. However, a new current is required for the field control in addition to the d- and q-axis currents. On the other hand, the dual inverter has the unique feature of being able to control a dc zero-sequence current by creating a current path between two dc buses. Therefore, by using the dc zero-sequence current as the field control current, it is possible to achieve a motor drive that combines the two advantages of dual inverters and adjustable field PMSMs. In this article, an actual adjustable field PMSM is fabricated, and the validity and superiority of the proposed motor drive system are verified through simulations and experiments. The results confirm that the proposed dual inverter system can achieve the same field controllability without an additional dc/dc converter as a conventional single inverter system while retaining the advantages, such as output voltage with low total harmonic distortion (THD) and low voltage fluctuation, which contribute to long insulation life. In addition, the prototype has an asymmetric PM arrangement based on Halbach array, and we will confirm that it can achieve a wider driving range than traditional constant field PMSM and a conventional adjustable field PMSM.