Abstract: Since the switching frequency of power devices is limited, the drive systems for large capacity or high speed motors usually require low carrier ratio operation. For interior permanent magnet synchronous motor (IPMSM), its asymmetric dq-axis parameters complicate the mathematic model. Furthermore, under low carrier ratio, the current feedback decoupling is incomplete, perplexing the controller optimization. Therefore, a modeling method based on normal canonical form is proposed. Though non-singular linear transformation, the asymmetric system is equivalently transformed into symmetric system, which is further simplified as a single-input single-output system through complex vector modeling and thus facilitates controller optimization. Furthermore, the complex PI controller applicable for asymmetric system is derived based on the proposed normal canonical form modeling method. The simulation and experimental results demonstrate that the proposed modeling method does not introduce extra errors and the derived complex PI controller achieves dq-axis decoupling control, faster dynamic response and much larger phase margin compared with standard PI controller.