Fault-Tolerant Control of Dual Three-Phase Permanent Magnet Synchronous Motor Under Two-Phase Open Faults

This article proposes a fault-tolerant control (FTC) method under a two-phase open fault for a dual-three phase permanent magnet synchronous motor (DTP-PMSM) with separated neutral points. The two-phase open faults are classified into the two-phase orthogonal (TPO) mode, which indicates that the two open fault phases have a phase difference of 90°, and the two-phase nonorthogonal (TPN) mode, which indicates that the two open fault phases have a phase difference of 30° or 150°. For both cases, the phase currents for FTC were mathematically derived based on balanced magneto-motive force theory. To improve FTC performance even at high speed, a novel coordinate transformation is proposed to control the DTP-PMSM under TPO mode with dc references, instead of ac references. Similarly, a novel ellipse-circle linear transformation is proposed to control <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i>-axes of the DTP-PMSM with the same value as the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i>-axes in TPN mode. By using the proposed coordinate transformation, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i>- and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xy</i>-axes can be controlled with the same dc value, thereby improving controllability at high speed. The validity of the proposed FTC under two-phase open fault is verified through experiments.