An Improved 3-D Space Vector Modulation Strategy for Three-Phase Series-End Winding PMSMs

The series-end winding motors provides a path for zero-sequence current, thereby increasing the degree of freedom of the current. However, the presence of zero-sequence current also causes the voltage vector to be distributed in an irregular 3-D space, making the space vector pulse width modulation (SVPWM) very complex and nonintuitive. Moreover, zero-sequence current also leads to distortion of the phase currents. Existing methods, such as SVPWM based on virtual vectors, provide a relatively small 3-D modulation region and are unable to effectively suppress zero-sequence current in the overmodulation region. To address this, this article proposes an improved 3-D space vector modulation (3D-SVM) with an extended linear modulation region. A novel concept of space slicing is introduced to decompose the synthesis of the 3-D desired voltage vector. Consequently, 3D-SVM can be implemented simply and intuitively in a 2-D plane. Moreover, due to the dimensionality reduction, the precise 3-D linear modulation region can be obtained. Intuitive 3-D overmodulation is also being investigated. Experimental results verify the effectiveness of the proposed 3D-SVM in suppressing the zero-sequence current.