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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]

Position sensorless control of interior permanent magnet synchronous motors (IPMSMs) is of great importance for the sake of the cost reduction and robustness improvement. An improved position sensorless method based on adjustable high-frequency (HF) square-wave voltage injection has been proposed for the IPMSM drive under zero- and low-speed regions. The general detection method of position from positive- and negative-sequence HF current response has been developed by the simple algebraic operations of data at some adjacent sampling instants. In addition, the proposed method not only can retain the advantage of the removal of low-pass filters in current feedback but also can increase the voltage margin of inverter with adjustable frequency setting of HF signal compared with existing square-wave voltage injection methods. Comprehensive experimental results have been given to verify the proposed theoretical analysis. [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]

Pulsewidth-modulated (PWM) current-source converters (CSCs) have the features of simple configuration, reliable short-circuit protection, and sinusoidal ac output voltages. The conventional space-vector modulation (SVM) scheme usually generates high-magnitude low-order harmonics in CSCs with low switching frequency. In this article, two modified SVM schemes, namely MSVM1 and MSVM2, are proposed to improve the harmonic performance for PWM CSCs in the high-power applications with low switching frequencies. The MSVM1 scheme focuses on eliminating the average dwell-time error of current vectors within each sampling period, while the MSVM2 scheme is targeted to achieve the accurate dwell time of current vectors as that of the natural sampling-based SVM scheme. The theoretical analysis and the calculation equations of dwell time are derived for both MSVM1 and MSVM2. The experiments are given to verify the effectiveness of the two modified SVM schemes in improving the harmonic performance of high-power CSCs with low switching frequencies. [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]

A feedback linearization based direct torque control (FL-DTC) scheme is designed for interior permanent magnet synchronous motors drives. Several main aspects related to FL are studied thoroughly. A proper choice of two new state variables (the torque and the squared amplitude of stator flux) yields the exact input–output linearization decoupling of the closed-loop system. The FL-DTC frame is obtained after finding a feasible diffeomorphism. For the partially linearized subsystem, i.e., the independent torque and flux loops, two FL-DTC-based controller design solutions are provided. The control problem of internal dynamics is converted to an absolute tracking problem of an equivalent Lur'e system. [ABSTRACT FROM AUTHOR]

The silicon carbide (SiC) devices have attracted more and more attention due to the capability of withstanding higher blocking voltage, higher switching frequency, and higher temperature. However, challenges for SiC devices applied in voltage-source-inverter fed motor drives such as electromagnetic interference (EMI) issues and limited over-current capability still limit the further application of SiC devices. In this article, a novel SiC devices based zero-voltage-switching (ZVS) current-source-inverter (CSI) is proposed for permanent-magnet synchronous motor (PMSM) drive. The key is to propose an auxiliary resonant circuit, which achieves ZVS conditions for all switches in power circuits and reduces the dv/dt of high speed SiC devices. The resonant capacitor in the auxiliary circuit can clamp overvoltage caused by possible open-circuit faults. To further reduce the EMI, the random switching frequency pulsewidth modulation is designed for the proposed CSI motor drive. The system configuration, working principle, circuit design, and control schemes are described in detail. Both simulations and experiments are presented to verify the effectiveness of the proposed ZVS-CSI fed PMSM drive system. [ABSTRACT FROM AUTHOR]

Aiming at tolerating common electric faults of multiphase motor drives comprehensively and minimizing the adverse impacts from the remedial scheme itself, a diagnosis-free self-healing scheme is put forward for the open-circuit faults of dual three-phase permanent-magnet synchronous motor (PMSM) drives. First, the self-healing mechanisms of dual three-phase PMSM drives are analyzed in detail. On the basis of theoretical analysis, the repressed self-healing capability of the dual three-phase PMSM drives is fully released by optimizing the current references on harmonic subspace. Since the diagnosis process is not required in the proposed self-healing scheme, the misdiagnosis problem and the prolonged damage caused by the additional time cost of diagnosis can be fundamentally avoided. The proposed self-healing scheme can be generally applied to open-switch faults, single open-phase faults, and multiple open-phase faults in the multiphase motor drives. No change is required for the machine model, modulation strategy, or control framework under different open-circuit faults. Thus, the complex transition strategies among different fault-tolerant control methods for different faults can be avoided, and the adverse impacts from the remedial scheme itself can be minimized. Experimental verification is presented to prove the validity of the proposed self-healing scheme. [ABSTRACT FROM AUTHOR]

In this article, the switching strategy and the remedial control scheme are studied for the cascaded current-source converters (CSCs) fed dual three-phase permanent-magnet synchronous motor (PMSM) variable-speed drives. An optimized space vector modulation (SVM) strategy is proposed to reduce the DC-link current ripple for the proposed drives system. In particular, this switching strategy can work effectively for motor drives under low speed with low back EMF, where there exists a large voltage difference between peak voltage values on the grid side and the motor side. Apart from that, a hybrid fault-tolerant control scheme is also designed for the open-phase fault in dual three-phase PMSM drives system, aiming at achieving small DC-link current ripple and torque ripple, low copper loss, and machine-friendly waveform quality. With the proposed optimized SVM and the hybrid fault-tolerant control strategy, the DC-link current ripple of the cascaded CSCs system can be effectively reduced and good operational performance can be obtained under both normal operation condition and open-phase fault condition. Experimental results are provided to verify the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

The problem of leakage-inductor parameter in paralleled current-fed isolated dc/dc system has not been solved. Aiming at solving that problem, a leakage-inductor parameter compensation method is proposed without an additional sensor. It provides tunable reflected voltage for parameter difference individually and compensation loops for parameter uncertainty. Thus, the circulating current and the current stress are minimized, and the voltage spike is avoided. The experimental results are given to validate the effectiveness of the method. [ABSTRACT FROM AUTHOR]

In this paper, diagnosis and tolerant control schemes have been studied for common electrical faults in T-type three-level inverter fed dual-three phase permanent magnet synchronous motor (PMSM) drives for safety-critical applications. Based on vector space decomposition and double three-phase space vector modulation, diagnostic and tolerant control methods have been developed comprehensively for open-phase faults, open-switch faults, and short-switch faults in T-type three-level inverter fed dual-three-phase PMSM drives, in such way that misdiagnosis of different faults sharing similar faulty features can be avoided. In particular, a two-step diagnostic scheme is proposed in order to simplify the diagnostic process. The first step is to identify the faulty phase and fault category by analyzing current trajectories on harmonic subspace, and the second step is to determine the specific fault type in a small fault-searching area obtained from the first step. In the aspect of fault-tolerant control, a novel current compensation method is proposed for open-phase fault without changing the machine model, space vector diagram, and control framework. Open-switch faults and short-switch faults are tolerated by making full use of the remaining vectors after faults. The validity of the proposed fault diagnosis and tolerance schemes has been verified by experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a novel nonlinear optimization-based sensorless control scheme for surface-mounted permanent magnet synchronous motors (SPMSM) over wide speed range operations. Two algebraic constraints derived from the voltage equations and the flux equations of the SPMSM system are fundamental to the establishment of the proposed scheme. The position estimation algorithm generates the rotor position estimate via the stator flux estimates obtained by minimizing an equality constrained scalar function. Specifically, the flux information is extracted both from the voltage-based flux model and the current-based flux model, which contributes to its robustness against the inherent weakness of the pure integrator to dc offsets. Meanwhile, a nonlinear observer, based on the standard gradient search, is constructed for speed estimation. The proposed method is unique because the position estimation and the speed estimation are achieved independently; thus, the complexity associated with the speed dependence in position estimation is eliminated. Further, it is simple to implement. The feasibility and effectiveness of the proposed position algorithm and the speed observer have been verified by experiments under different operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, fault diagnosis and fault-tolerant control strategies have been studied comprehensively for dual three-phase permanent-magnet synchronous motor (PMSM) drives to improve the reliability. Based on direct torque control (DTC) with space vector modulation, a series of diagnostic and tolerant control methods have been proposed for five types of faults, namely, speed-sensor fault, dc-link voltage-sensor fault, current-sensor fault, open-phase fault, and open-switch fault. First, diagnosis and tolerant schemes are proposed for speed-sensor fault by estimating the rotor angle speed with the rotating speed of stator flux. Second, diagnosis and tolerant schemes are proposed for dc-link voltage-sensor fault by combining the current model based stator flux observer with the voltage model based stator flux observer. Third, a three-step method is designed to diagnose three types of faults related to current signals, namely, current-sensor fault, open-phase fault, and open-switch fault simultaneously. A vector space decomposition based current estimation method is proposed to achieve fault-tolerant control for the current-sensor fault, and the voltage compensation based fault-tolerant control is presented for both open-phase and open-switch faults. The experiments have been taken on a laboratory prototype to verify the effectiveness of the proposed fault diagnosis and fault-tolerant schemes. [ABSTRACT FROM AUTHOR]

The direct torque control (DTC) is widely used in motion control of electric drives, especially for the switching table based direct torque control (ST-DTC) and the space vector modulation (SVM) based DTC (SVM-DTC). The classical ST-DTC schemes can achieve fast dynamic response but may suffer from distinct torque and flux ripples in steady-state operation. On the other hand, the classical SVM-DTC schemes have lower ripples in torque and flux, but the methods slow down dynamic response of DTC. Different from them, a novel hybrid DTC scheme is proposed for dual three-phase permanent-magnet synchronous motor (PMSM) drives in this paper, which can achieve fast dynamic response of classical ST-DTC scheme and good steady-state performance of classical SVM-DTC scheme simultaneously. The key of the proposed scheme is to implement different torque control methods under dynamic operation mode and steady-state operation mode, respectively. A switching method has been designed to guarantee smooth transition between the two operation modes. Besides, the decoupling control of torque and stator flux is maintained with the proposed control scheme, and the stator flux is controlled stably all along. By experiments on a laboratory prototype, it has been verified that the proposed scheme can achieve both good steady-state and transient performance compared to other control methods for dual three-phase PMSM drives. [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]

In this paper, three control schemes with variable switching frequencies are proposed and analyzed for the paralleled voltage source inverters (VSIs) fed permanent magnet synchronous motor (PMSM) drive. The proposed schemes could be applied in the low-speed operation region of high-power drive system, where the frequency modulation index is high. First, the field-oriented control (FOC) with phase-shifted chaotic space vector modulation (SVM) under synchronous frame and the FOC with phase-shifted chaotic sinusoidal pulse width modulation under stationary frame is proposed for the paralleled VSIs fed PMSM drive. The proposed phase-shifted chaotic PWM schemes not only eliminate specific switching harmonics completely but also suppress all remaining switching harmonic peaks in the spectrum. The avoidance of inherent circulating current is also considered in designing these two schemes. Second, the direct torque control (DTC) for the paralleled VSIs fed PMSM drive is proposed with circulating current suppression. Besides inheriting the advantages of DTC, the output currents of paralleled VSIs are kept balanced. The working principles of these three methods are presented in detail. Experimental results on a laboratory prototype are given to verify the validity of the three proposed control schemes for the paralleled VSIs fed PMSM with variable switching frequencies. [ABSTRACT FROM PUBLISHER]

In this paper, a hybrid pulsewidth modulation (PWM) scheme is proposed to suppress the LC resonance for the high-power current-source inverter (CSI) fed drives with low switching frequency. In CSI drive systems, the selective harmonic elimination (SHE) is selected due to the better performance of harmonics, but the LC resonance cannot be effectively damped due to the lack of control flexibility of SHE. In this paper, SHE is only used for the steady-state operation. The modulation scheme is then switched to space vector modulation with dynamic capacitor voltage control when the transient event occurs. The smoothed transitions between different modulation schemes are proposed. The proposed hybrid method effectively solves the resonant issues in CSI drives, while maintaining the power quality. Both simulation and experiments verify the performance of the proposed hybrid PWM scheme. [ABSTRACT FROM AUTHOR]

In this article, a fault diagnosis method is proposed to detect current sensor faults for the studied primary permanent-magnet linear motor (PPMLM) traction system, in which only two current sensors are required, and the gain fault and zero-offset fault can be distinguished. In this proposed fault diagnosis method, synchronous currents are estimated by the PPMLM model. By comparing the estimated and measured synchronous currents, estimation errors are calculated, and ac components can be extracted by corresponding filters. In the synchronous frame, the zero-offset fault and the gain fault can be detected by the single-frequency and double-frequency components, respectively. Furthermore, the fault phase also can be located. Compared with conventional fault diagnosis methods, the proposed one can distinguish gain fault and zero-offset fault but only two current sensors are required. Simulation and experimental results verify the effectiveness of the proposed fault diagnosis method. [ABSTRACT FROM AUTHOR]

The magnetic circuit has been a popular and powerful tool to analyze the magnetic field in electromagnetic devices for a long history. However, in the conventional magnetic circuit there is only one kind of component namely reluctance, which cannot analyze the phase shift or the amplitude attenuation of the alternating flux in electromagnetic devices. In this article, a new physical concept of magnetic-inductance is proposed, based on which the alternating-flux magnetic circuit theory including two kinds of components namely reluctance and magnetic-inductance has been developed. Furthermore, the virtual magnetic power is defined as the analogue of electric power, and the magnetoelectric power law is derived for magnetic circuits. Using the proposed magnetic circuit theory with magnetic-inductance, the relationship between the electric power and the virtual magnetic power is revealed and the long-lasting confusions in previous magnetic circuit methods, i.e., power calculation and phase shifts of magnetic variables, are clarified. By experiments, the magnetic-inductance and the magnetoelectric power law are validated, and their applications in eddy current loss analysis and B-H curve estimation in magnetic materials are demonstrated. [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 dual-vector located model predictive control (DL-MPC) method based on a single dc-link current sensor is proposed for the permanent-magnet linear motor drive system. In DL-MPC, the phase currents are reconstructed by sampled dc-link current and selected active voltage vector (VV). Meanwhile, the sunk number of phase current is defined to evaluate the accuracy of current reconstruction. The first-optimal and second-optimal VVs are determined by dual-vector location. The second-optimal VV is selected for the voltage source inverter when the sunk number exceeds the threshold. Compared with traditional MPC schemes, DL-MPC has smaller current tracking error and better dynamic performance. Meanwhile, DL-MPC has more accurate current reconstruction and lower computation burden than that of the traditional MPC. The effectiveness of DL-MPC is verified by both theoretical analysis and experimental results. [ABSTRACT FROM AUTHOR]

This letter proposes a fast current control scheme for ac drives by minimizing the latency from current sampling to the updation of a pulsewidth-modulation (PWM) command. By reconstructing the architecture of a linear controller, the minimal necessary steps to obtain the output voltage are deduced as the primary calculation, and the other computation work of the current loop is done in the postcalculation after updating the PWM command. With the proposed method, the computational delay is reduced with negligible loss in the available modulation index, and a higher stability margin or system bandwidth is realized. Also, the developed controller structure exhibits inherited antiwindup characteristics. The technique has been validated by experimental investigations on a permanent magnet synchronous motor. [ABSTRACT FROM AUTHOR]

The half-bridge (HB) submodule (SM) based MMC requires a large number of sensors to measure capacitor voltages. In this letter, a double half-bridge (DHB) SM-based MMC is proposed, where each SM consists of two HBs. But only one voltage sensor is equipped in each DHB-SM for the capacitor voltage estimation, which is connected between the positive poles of two capacitors in the DHB-SM. A capacitor voltage estimation method is also proposed, which can estimate capacitor voltages in the proposed MMC with only a half number of voltage sensors in comparison with HB-SM-based MMCs. A DHB-SM-based three-phase MMC is simulated with power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC) and a DHB-SM-based single-phase MMC prototype is built in the laboratory. Both the simulation and experimental results confirm the effectiveness of the proposed method. [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 article, a coupled fault-tolerant control (C-FTC) is proposed for primary permanent-magnet linear motor traction system in subway applications. By coupling the faulty mover with a healthy mover, the proposed C-FTC can achieve continuous operation of the faulty mover, in which one or more current sensors fail. A healthy mover is determined as the reference mover. The switch-states of the reference mover are also applied to its mathematical model. As a result, synchronous currents of the reference mover are also estimated from its mathematical model, and they are treated as the reference currents of the mathematical model of the faulty mover. Hence, the switch-states of the faulty mover can be determined. Therefore, the faulty mover can be controlled without any current sensors. The key of C-FTC is to compensate the parameter variations and the nonlinear effects of the faulty mover drive system with those of a healthy mover drive system, which is the main contribution of this article. Comparing with the conventional current-sensorless control, C-FTC has stronger robustness to the parameter variations and the nonlinear effects. The effectiveness and robustness of the proposed C-FTC are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

Based on the model predictive current control (MPCC), a dual-level located feedforward control (DLFC) is proposed for the five-leg dual-mover primary permanent-magnet linear motor traction system, in which, two three-phase movers are fed by one five-leg voltage-source inverter (VSI). In the proposed DLFC, the studied traction system is divided into dual-level subsystems, including mover level and system level. In the mover level, it is assumed that one mover is fed by one three-leg VSI. The reference synchronous currents are replaced by the reference static voltages, and the model current predictions are eliminated by the discrete mover voltage vectors (MVVs). Furthermore, the global optimal MVVs are determined by the mover-level geometrical location. If the implementation conflicts between two global optimal MVVs, two local optimal MVVs will be determined by the system-level geometrical location to replace one former global optimal MVV. Compared with MPCC, the computation burden of DLFC can be significantly reduced. If both control methods use the same sampling period, they have the same performances. On the other hand, DLFC can use shorter sampling period, and it can perform better than MPCC. All the theoretical analyses are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is an attractive option for high-voltage and high-power applications. Fault localization is one of the most important challenges for the MMC consisting of a large number of power electronic switches. Existing literature has not provided a complete fault localization strategy for the MMC under submodule (SM) lower switch open-circuit fault, which only considers the MMC in inverter mode and neglects the MMC in rectifier mode. This article proposes a fault localization strategy for the MMC under SM lower switch open-circuit fault, which is suitable for the MMC not only in inverter mode but also in rectifier mode. This article analyzes the MMC fault characteristics under SM lower switch open-circuit fault, which considers the MMC in inverter and rectifier mode, respectively. Based on two modes’ common fault characteristic that the capacitor is charged all the time during the period when the arm current is positive, the faulty SM can be effectively located by the proposed fault localization strategy. The proposed strategy is not only implemented in simulation with professional tool PSCAD/EMTDC but also verified with a downscale MMC prototype in the laboratory. The results confirm the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Because both magnets and windings can be mounted in the mover, the primary permanent-magnet linear motor (PPMLM) has a low-cost advantage for subway applications. In this paper, a novel direct thrust force control (DTFC) with single dc-link current sensor is proposed for PPMLM traction system in subway applications. The first phase current is directly measured by the dc-link current sensor. The second phase current is sensed with a limited delay, which is strictly limited by the limited measurement delay principle. The third phase current is calculated based on the condition that the summation of the three phase currents is zero. During the current reconstruction, no motor parameters are required. Because PPMLM may sink in the same phase for a long time and affect the current reconstruction accuracy, the single optimal target is proposed to re-select the original voltage vector. Compared with the conventional DTFC scheme, the proposed one has nearly the same performances; especially, the maximum speed and response time remain nearly unchanged. The effectiveness of the proposed DTFC scheme is verified by experimental results. [ABSTRACT FROM AUTHOR]

Because both magnets and windings can be mounted in the mover, the primary permanent-magnet linear motor (PPMLM) has a low-cost advantage for subway applications. In this paper, a fault-tolerant control (FTC) with single phase current sensor is proposed for PPMLM traction system in subway applications. In the proposed FTC, d- and q-axis currents are estimated from the reference synchronous currents and the surviving measured phase current. The estimation is robust since no machine parameters are required. In steady-state operation, the estimated current errors are half the actual ones. As a result, the current response is slowed but the current command can be achieved. However, the achievement of control target depends on the current tracking accuracy, which is enhanced by the voltage decoupler. Compared with existed FTC schemes, the proposed one is robust and has better transient-state performances. The effectiveness of the proposed FTC is verified by theoretical analysis and experimental results. [ABSTRACT FROM AUTHOR]