The current error is hard to avoid for finite control set model predictive current control (FCS-MPCC) in nine-phase open-end winding permanent magnet synchronous motors. To overcome this problem, an online virtual voltage vector (V $^{3}$ ) synthesis strategy is proposed in this article. First, a group of V $^{3}$ s without harmonic voltage components are designed as the basic vectors for online synthesis. Then, two adjacent basic V $^{3}$ s and a zero vector are used to synthesize a new V $^{3}$ , which can output arbitrary amplitude and phase angle in the fundamental space. The two basic V $^{3}$ s are directly selected from the located sector of the predicted reference voltage vector (RVV), and their duration ratio can be simply calculated according to the angle of the RVV in the sector. In this way, the zero error is realized between the new V $^{3}$ and RVV. Moreover, an online pulse generation algorithm corresponding to the new V $^{3}$ is proposed, which can calculate the symmetrical pulse sequences in real-time for the multiphase OW drive system without the space vector modulator. Finally, experimental results have verified the effectiveness and superiority of the proposed strategy, in comparison to existing FCS-MPCC in multiphase OW motor drive systems.

The heavy computational burden and the complexity in pulse generation based on multivector synthesis represent serious challenges for applying finite control set model-predictive control (FCS-MPC) in multiphase open-end winding (OW) drive systems. In this article, a low-complexity model-predictive control with dead-time compensation is proposed for the nine-phase OW permanent magnet synchronous machine drive system. First, to simultaneously eliminate voltage vectors on the third, fifth, and seventh harmonic planes, three vectors in the same direction are selected to synthesize the virtual vector (VV). In addition, a multivector synthesis algorithm is designed to generate a symmetrical pulse sequence. Then, in order to suppress the harmonic voltage vector caused by the dead time, an additional voltage vector was added to the VV. Finally, the deadbeat principle was introduced to calculate the reference voltage vector, and the optimal voltage vector is determined according to the position of the reference voltage vector, which reduces the computational burden successfully. The proposed method is studied and compared with traditional FCS-MPC schemes. Simulation and experimental results have verified the effectiveness of the proposed method, which reduces the computational burden and complexity and enables the use of FCS-MPC for multiphase OW drive systems.

Surface-mounted permanent magnet (SPM) motors with shaped magnets and a quasi-regular polygon rotor core (QPRC) are challenging to analyze in terms of accuracy and speed because of the special structure. This article proposes a new technique for the subdomain method which can accurately predict the electromagnetic performance of this kind of motor. The proposed new technique deals with the shaped magnet based on the method of magnet symmetrical segmentation, and it can solve the magnetic field generated by a pair of symmetrical segments together at each time. Especially, for the QPRC, the idea of variable rotor core radius is used in the new technique to analyze different segments. Furthermore, the new technique adopts a periodic boundary condition, which can quickly predict the electromagnetic performance of the motor, such as air-gap flux density, cogging torque, no-load back-EMF, winding inductance, electromagnetic torque and unbalanced magnetic force (UMF). This proposed new technique is applied to a 12-pole/3-phase SPM motor with shaped magnets and a QPRC, and its correctness is verified by finite-element analysis and experiment. The new technique can analyze the motor accurately, and its calculation speed is two orders of magnitude faster than that of the finite-element method.

The current sensor faults (CSFs) and open-circuited faults (OCFs) are common for multiphase permanent magnet synchronous motor (PMSM) drives with open-end stator winding. Different faults often induce similar current characteristics, which increases the fault diagnosis difficulty. In this article, a new current signal-based fault diagnose method is proposed to detect all kinds of CSFs and OCFs for multiphase PMSM drives, especially the faults with similar current characteristics. First, the influence of the CSFs and OCFs on multiphase current signals are analyzed and compared. Second, a new current-based fault diagnosis method is proposed and the steps of its judgement criterion are illustrated. Furthermore, an adaptive algorithm is proposed, which can quantitatively describe the level of the faults. Finally, experimental results have verified the effectiveness and robustness of the proposed method, which accurately detects and locates all kinds of CSFs and OCFs for multiphase open-end winding PMSM drives.

For the open-phase fault (OPF) tolerant operation of multi-phase motors based on model predictive current control (MPCC), the fault diagnosis and control scheme reconfiguration are difficult to avoid, which leads to the increase of control complexity. A natural fault-tolerant (NFT) MPCC method based on virtual voltage vectors (V3) can simplify this procedure and realize the fault-tolerant operation by using a unified control algorithm during pre- and post-faults. However, there is no effective control scheme to deal with the V3 shifting after the fault, which will lead to the control errors. To overcome this problem, an enhanced NFT-MPCC strategy is proposed in this paper. Firstly, this paper analyzes the causes of the control error in NFT, and elaborates the influence of V3 shifting on the current tracking performance. Then, a duty ratio optimization based on an PI regulator is proposed for the first time. After the fault occurs, the PI regulator automatically corrects the duty ratio calculation result to eliminate the control error caused by vector shifting, and the proposed method is versatile to different OPF scenarios. Compared with existing NFT-MPCC technologies, the experimental results show that the proposed method significantly suppresses the torque ripple in post-fault, and provides a satisfactory control performance before and after fault without the need of software reconfiguration.

In this article, permanent magnet (PM) machines with irregular rotor cores, mainly including surface-mounted PM (SMPM) machines and surface-inset PM (SIPM) machines, are analyzed by an enhanced conformal mapping (CM) model. The three special issues have been addressed. The irregular boundary in the rotor core is divided into several segments, and the enhanced CM model can be used to deal with PM machines with irregular rotor cores conveniently. Then, the proposed equivalent-current model converts various shaped PMs into current sheets, and the actual permeability of PMs can be considered by constructing the model of modified equivalent currents to improve the accuracy of the PM equivalent-current method. Furthermore, the enhanced model can also consider the magnetic-saturation effect of machines. Finally, the electromagnetic performances of machines, such as air-gap magnetic density and back-EMF, can be predicted accurately. PM machines with various rotor core structures and PM shapes are modeled by the enhanced CM model, and the finite-element model and experiments are used to verify its universality and correctness. This model has high universality, accuracy and speed, which is of great help to the initial design and optimization of PM machines.