Operating within dynamic voltage limits during magnetization state increases in variable flux PM synchronous machines

This paper examines the issue of staying within the voltage capacity of a fixed bus voltage inverter during increasing magnetization state (MS) of variable flux permanent magnet synchronous machines (VF-PMSMs). MS manipulation using a fast stator i_d pulse is shown to induce a large voltage even at low speeds. In order to utilize the power conversion capability and improved efficiency regions of VF machines, MS should be manipulated over a wide speed range. Therefore, reaching the voltage capacity of the inverter when increasing MS is a significant dynamic voltage limitation for the existing methods. A reverse rotating current vector trajectory (RRCVT) method is proposed in this paper to mitigate the dynamic voltage limitation. The RRCVT method is a partial inverse model solution, where the current vector trajectory causes the contributing voltage components to partially cancel each other. The RRCVT method allows for MS to be increased at significantly higher speeds before reaching the voltage capability of the inverter.