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The fault-tolerant control method of dual three-phase permanent-magnet synchronous motor (PMSM) drives has gained more and more attention in some applications, such as aircraft system and offshore wind energy system. In this letter, the reason for the torque ripple caused by the standard control method has been investigated in view of the frequency domain after the occurrence of a single open-phase fault. Based on the theoretical analysis, a universal control scheme has been proposed for the dual three-phase PMSM drives with two isolated neutral points, which can be implemented under either healthy condition or fault condition. The key is to modify with a closed-loop controller on harmonic subspace with the notch filter. The proposed method not only realizes the seamless transition between two operation conditions without fault diagnosis but also avoids the reconfiguration of the control structure. Moreover, the system optimization of the minimum copper loss under postfault condition has been integrated into the proposed method. The experimental results are presented to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Inthis article, a half-centralized open-winding primary permanent-magnet linear motor (HCOW-PPMLM) drives system is proposed, in which two independent voltage-source-inverters (VSIs) and one common VSI are required to supply two open-winding movers. Compared to the traditional open winding motor topology, the proposed topology requires less half-conductor switches, which can reduce the construction cost, system volume, system weight, operation and maintenance cost, and failure rate. To achieve high-performance operation, a collaborative control is proposed for the proposed topology. Based on the principle that minimizes maximum voltage of VSIs, the voltage distributor in the proposed collaborative control is designed to maximize the dc bus voltage utilization. The effectiveness of the proposed topology and the proposed collaborative control have been verified by experimental results. The proposed topology is also compared with conventional open-winding PPMLM topology by variable speed and load experiments. [ABSTRACT FROM AUTHOR]

In this article, a minimum-copper-loss fault-tolerant control scheme is proposed for open-phase fault and open-switch fault of dual three-phase permanent magnet synchronous motor (DT-PMSM) drives. Both the winding configurations of isolated neutral points and connected neutral points are studied in this article. In conventional minimum-copper-loss fault-tolerant control schemes, the constraints of sinusoidal phase currents result in insufficient copper-loss reduction. Different from them, the current references with the theoretically lowest copper losses are first derived and applied for different fault cases of DT-PMSM drives without using any unnecessary constraints in the proposed fault-tolerant control scheme. Thus, all phase currents in the proposed minimum-copper-loss fault-tolerant control scheme are optimized to be nonsinusoidal waveforms. Besides, the copper losses are further reduced by fully utilizing the remaining healthy switch in the faulty inverter leg for the open-switch fault of DT-PMSM drives with the proposed scheme. It has been theoretically and experimentally proved that the proposed fault-tolerant control scheme can reduce copper losses than all existing fault-tolerant schemes for both open-phase fault and open-switch fault in typical two-level voltage-source-inverter-fed DT-PMSM drives. [ABSTRACT FROM AUTHOR]

In this article, the control strategy is studied for the neutral-point-clamped three-level inverter-fed dual three-phase permanent-magnet synchronous motor (PMSM) drive with low switching frequencies. An interleaved finite-control-set model predictive control (MPC) scheme is proposed, where a two-layer MPC is designed to solve the multiobjective optimization problem. The two sets of windings in PMSM are sampled and controlled in an interleaved way so that the control delay and the prediction horizon of the drive system are reduced by half. Moreover, the proposed interleaved control scheme increases the equivalent sampling and control frequency from the perspective of the whole drive system, and thus provides better steady-state performance and dynamic performance. With the switching states of one inverter remaining unchanged, the cross traversal of vector candidate sets between two sets of windings is avoided, and the computational burden can be reduced effectively. Experimental results are given to verify the validity and effectiveness of the proposed interleaved control scheme. [ABSTRACT FROM AUTHOR]

The rotor flux linkage of permanent-magnet synchronous motor (PMSM) is of great importance for monitoring and high-performance control. However, most of the existing online estimation methods need prior knowledge of other PMSM parameters such as stator resistance and dq axis inductance, which are difficult to realize in the rank-deficient models of electrical machines. This article proposes a simple online estimation method of rotor flux linkage for the dual three-phase surface-mounted PMSM (SPMSM) drives with the assistance of injected position offset. The independent estimation model has been developed for the rotor flux linkage by appropriate setting of positon offset between two sets of three-phase windings of dual three-phase SPMSM drives. The proposed method not only has little influence on the output torque and high signal-to-noise ratio for observation, but also offers the superior performance in estimation accuracy irrespective of the influence of VSI nonlinearity. In addition, the proposed position-offset-based method is suitable for the full-speed region including the field-weakening operation. Finally, comprehensive experimental results are presented to verify validity of the proposed method under different working conditions. [ABSTRACT FROM AUTHOR]

This letter proposes a four-leg current-source inverter (CSI) fed three-phase motor drive. Different from the previous four-leg CSI inverter, the proposed configuration introduces the fourth leg in CSI, which connects to the neutral point of the motor through an extra output filter capacitor. Therefore, the proposed configuration can not only reduce the common-mode voltage (CMV) under the normal condition, but also provide the fault-tolerant operation ability under open-circuit faults in windings and switches. The dedicated space vector modulation (SVM) strategies have been designed. Compared with prior research on CMV reduction, the four-leg method has the full range of modulation index and will not increase any harmonics in the currents. Meanwhile, the fault-tolerant ability is offered, which can further enhance the reliability of the motor drive. A laboratory prototype has been built to experimentally verify the effectiveness of the proposed motor drive topology and the control schemes. [ABSTRACT FROM AUTHOR]

When the permanent magnet synchronous machine (PMSM) based electric vehicles (EV) are in the postcrash situations, the dc-bus capacitor voltage requires to be reduced quickly for the sake of electric shock risk prevention. Currently, due to the advantages of low cost, compact structure, and high reliability, the pure-winding-based discharge strategies are attracting increasing attentions. However, there are no theoretical criteria for judging whether a pure-winding-based method is suitable for bleeding a particular PMSM-based EV drive, not to mention the rules for opting for an effective discharge strategy among the instant nonzero d-axis, zero q-axis (NDZQ), long-cycle NDZQ, and the nonzero d-axis, nonzero q-axis (NDNQ) current control techniques. This article discusses the applicable occasions of the instant NDZQ, long-cycle NDZQ, and NDNQ discharge methods based on parametric analysis. On this ground the principles for determining whether an EV drive can adopt a pure-winding-based method for discharge are given. Meanwhile, the implementation procedures of the proposed criteria are detailed clearly. Finally, the proposed selection criteria are used for evaluating five different EV drives so as to select the corresponding winding-based discharge strategy for each system, and the effectiveness is verified by simulation or experiments. [ABSTRACT FROM AUTHOR]

In this paper, a novel space vector modulation (SVM) strategy is proposed and designed for dual three-phase three-level motor drives based on vector space decomposition (VSD), which could be applied for high-power and high-reliability applications. The key of the proposed method is to design two decoupled groups of voltage vector candidates for synthesis on α − β subspace and x − y subspace, respectively. The two decoupled groups of voltage vectors will synthesize respective voltage references on α − β subspace and x − y subspace, while having no impact on each other. The redundant small voltage vectors and zero-sequence voltage vectors are utilized to mitigate voltage oscillation in midpoint of dc link and suppress zero-sequence current component for dual three-phase windings with a common neutral. For comparison, another VSD-SVM strategy is designed based on traditional solution, which cannot offer closed-loop control on x − y subspace. Both simulation and experiments have been given to verify that the proposed decoupled VSD-SVM can suppress harmonic components on x − y subspace besides tracking torque components on α − β subspace. Furthermore, the harmonic performance of the proposed decoupled VSD-SVM has been compared with the traditional VSD-SVM strategy and the carrier disposition based pulsewidth modulation. [ABSTRACT FROM AUTHOR]

This paper studies and proposes the vector space decomposition-based direct torque control (DTC) scheme for the T-type neutral-point-clamping (T-NPC) three-level inverters-fed double-stator-winding permanent magnet synchronous machine (PMSM) drive, which provides an effective solution for high-power high-reliability applications. The key is to propose a simple but effective space vector modulation (SVM) for DTC of T-NPC double-stator-winding drives-based two-step voltage vector synthesis, in such a way that good dynamic response and harmonic performance are obtained. The closed-loop controllers on harmonic subspace are incorporated to suppress the possible harmonics induced from back electromotive force and unbalanced parameters in phase windings of electrical machine. Furthermore, a hybrid current control is proposed for fault-tolerant operation of the T-NPC double-stator-winding PMSM drives under one-phase open-circuit conditions. In the hybrid current controller, the healthy winding still uses the SVM-DTC control while the faulty winding uses the closed-loop current controller to track the optimized current references. Both simulation and experimental results are presented to verify the performance of the proposed switching strategies and control schemes. [ABSTRACT FROM AUTHOR]