Fault-tolerant Permanent Magnet Synchronous Motor Research Articles

Design and Analysis of a Five-phase Flux-Intensifying Fault-Tolerant Permanent-Magnet Motor With Active Sensorless Strategy Under Multimode Operation

In this paper, a new flux-intensifying fault-tolerant permanent magnet synchronous motor (FI-FTPMSM) is proposed to improve sensorless operating capacity under multimode operation including fault conditions. Most previous studies regarding fault-tolerant motors aim to improve fault-tolerant capability but suffer the saliency characteristic problem, which is unfavorable for sensorless control. In this study, an active sensorless strategy is developed by considering the sensorless operating capability under multimode operation in the motor design stage. Based on this novel idea, a new FI-FTPMSM with a high inverse saliency ratio is designed. By carefully choosing slot-pole combination, subtly setting <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis magnetic barrier shape, and improving air gap waveform, the superior inverse saliency characteristic is obtained, which effectively improves the dynamic and steady-state sensorless operating performance. Through simulation analysis and experimental tests, the rationality and validity of the proposed strategy are verified.

PWM Harmonic-Current-Based Interturn Short-Circuit Fault Diagnosis for the Aerospace FTPMSM System Even in the Fault-Tolerant Operation Condition

This paper proposes a new PWM harmonic current based diagnostic method for the interturn short-circuit fault (ITSCF) of fault tolerant permanent magnet synchronous motor (FTPMSM) drives, which is able to detect and locate the fault phase for the system even in fault tolerant operation (FTO) condition. The ITSCF model for the H-bridge drive based FTPMSM system is firstly proposed, while the high-frequency (HF) harmonic current component and impedance are analyzed both in normal and ITSCF conditions. The PWM harmonic current based fault diagnostic approach is then proposed to confirm the fault phase, which consists of the band-pass filter, the periodic root mean square (RMS) calculator and the fault identification. The resulting fault diagnostic method has simple structure, fast fault detection, good robustness and low computational burden, which can achieve the ITSCF for the FTPMSM system both under normal and FTO conditions. The effectiveness of the ITSCF diagnostic method is verified via the six-phase FTPMSM experimental platform, which can provide a guideline for the ITSCF mitigation and FTO of the FTPMSM system.

A Novel Dual-Redundancy Permanent Magnet Synchronous Motor With Small Teeth

A novel dual-redundancy permanent magnet synchronous motor (DRPMSM) with small teeth is proposed, which combines the advantages of fault-tolerant permanent magnet synchronous motor (PMSM) and multi-phase PMSM. When fractional slot concentrated winding (FSCW) is used in PMSM, no electromagnetic coupling can be realized by selecting a reasonable slot-pole (SP) combination and using single-layer (SL) winding. However, the goal of no electromagnetic coupling can also be achieved by adding small teeth in the common slot center between two adjacent phase windings under appropriate SP combination and double layer (DL) winding. Compared with the former method, the latter has smaller eddy current loss and a lower saturation level of the magnetic field caused by lower-order harmonics. In addition, the influence of small teeth on electromagnetic properties is analyzed. The correctness of the theoretical derivation is verified by simulation and experiment.

Fault-Tolerant Current Control of Six-Phase Permanent Magnet Motor With Multifrequency Quasi-Proportional-Resonant Control and Feedforward Compensation for Aerospace Drives

To improve the current tracking performance, this article proposes a new fault-tolerant current control for the six-phase fault-tolerant permanent magnet synchronous motor (FTPMSM) system with multifrequency quasi-proportional-resonant (QPR) control and back electromotive force (EMF) feedforward compensation, which can track the time-varying sinusoidal and nonsinusoidal reference currents in the stationary reference frame (SRF) under normal and fault conditions. First, the multifrequency QPR current controller with shunt topology is proposed to track the time-varying reference current in SRF, which can guarantee the current control performance regardless of the motor speed variation and the load torque change. Second, the optimized feedforward compensation method for the back EMF is proposed to further reduce the steady-state current tracking error, which takes the time delay of the digital implementation into consideration. Finally, the effectiveness of the proposed approach is verified on a 3 kW six-phase FTPMSM platform. The resulting six-phase FTPMSM system with the proposed current control has great current tracking performance, strong robustness to various external/internal disturbance, as well as low computational burden, which can guarantee the multiphase FTPMSM system performance in normal and fault conditions.

High-Frequency Square-Wave Signal Injection Based Sensorless Fault Tolerant Control for Aerospace FTPMSM System in Fault Condition

To enhance position detection reliability, this article proposes a new high-frequency square-wave signal injection (HFSWSI) based sensorless control for aerospace fault tolerant permanent magnet synchronous motor (FTPMSM) drives, which can be configured as the nonsimilar redundancy for a physical sensor. The novel sensorless control scheme with HFSWSI in two nonfault windings is first proposed for the FTPMSM system under each phase current independent control frame, which is free of the coordinate transformation. The HFSWSI-based position detection is then proposed for rotor position estimation via HF response currents even in phase open-circuit fault (OCF) and short-circuit fault (SCF) conditions. To enhance the dynamic performance, a novel dual-output filter is proposed for the fundamental and HF response current component extractions with almost no phase lag. To guarantee the fault tolerant performance, the optimal torque control (OTC) is utilized to ensure that the FTPMSM system generates the ripple-free torque even in fault condition. The resulting sensorless FTPMSM system has outstanding low-speed sensorless control performance both in normal and fault conditions, which is also experimentally validated on a six-phase FTPMSM platform.

Sensorless Fault-Tolerant Control via High-Frequency Signal Injection for Aerospace FTPMSM Drives With Phase Open- and Short-Circuit Faults

The high-frequency (HF) signal injection methods have been widely used for the low-speed sensorless control of permanent magnet motors under the vector control framework. However, for the fault-tolerant permanent magnet synchronous motor (FTPMSM) system under fault conditions, the fault-tolerant control is usually based on independent control of each phase current, rather than the vector control, which prevents the existing sensorless control from being directly applied. To cope with this issue, this article proposes a novel sensorless control by HF signal injection in any nonfault two-phase windings for the FTPMSM system with no coordinate transformation, which can ensure the low- and zero-speed sensorless control performance both in fault-free and fault-tolerant operation conditions. This sensorless control scheme is based on an independent control framework of each phase current, which consists of the real-time inductance observer, the nonorthogonal phase-locked loop (NPLL), the notch filter, and the polarity discrimination of the magnet pole. The real-time inductance observer is proposed to estimate the differential mode inductances of two nonfault phases. The NPLL is proposed to achieve the rotor position and speed estimation based on the obtained two-phase inductances. To enhance the sensorless control performance, a new notch filter is proposed to filter out the injected HF response component in phase current. The proposed sensorless FTPMSM system has preeminent low-speed control performance and robustness in the nonfault and fault-tolerant operation process, which is also verified via experiments on a six-phase FTPMSM platform.

A Novel Diagnostic Method for Single and Dual Power Switch Open-Circuit Faults of Six-Phase FTPMSM System Even in Fault Tolerant Operation

This article proposes a new diagnostic method based on average current Park vector (ACPV) for single and dual power switch open-circuit faults of six-phase fault-tolerant permanent magnet synchronous motor (FTPMSM) system, which can be applied for the system both in nonfault and fault tolerant operation conditions. The fault diagnosis structure is composed of two parts: the ACPV moduli-based fault detection and the ACPV polarity-based fault location. By analyzing the ACPV before and after the fault, the normalized ACPV moduli-based fault detection is proposed by using the ACPV components in three orthogonal subspaces, which has good robustness to the speed and load changes. The ACPV polarity-based fault location is then proposed to locate the faulted power switches of the FTPMSM system. Finally, the effectiveness of the proposed fault diagnosis method is validated by a six-phase FTPMSM experimental platform. The fault diagnosis approach has the advantageous features of simple implementation, good robustness to various disturbances, no requirement of the extra sensors, and low computational burden, which can achieve single and dual power switch open-circuit fault diagnosis for the FTPMSM system both in normal and fault tolerant operation conditions.

Research on Fault-Tolerant Field-Oriented Control of a Five-Phase Permanent Magnet Motor Based on Disturbance Adaption

To ensure the high-quality output performance of the five-phase fault-tolerant permanent magnet synchronous motor (FTPMSM) drive system under normal and open-circuit faults and achieve the minimal reconfiguration of the FTPMSM control drive system under various open-circuit faults, in this paper, a fault-tolerant field-oriented control (FOC) strategy based on disturbance adaption is proposed. The speed-loop and current-loop steady-healthy controllers are designed to effectively suppress the torque ripples caused by open-circuit faults and improve the robustness of the drive system to load disturbance and motor parameter variation under fault operation. Moreover, the additional zero-sequence current controller can be omitted. In addition, the modified reduced-order coordinate transformation matrices are proposed to weaken the influence of oscillating neutral. Finally, the fault-tolerant FOC system of the FTPMSM is established, and its experiment is conducted. The experimental results verify the feasibility and effectiveness of the proposed control strategy.

A Third Harmonic Current Elimination Strategy for Symmetrical Six-Phase Permanent Magnet Synchronous Motor

This paper mainly focuses on the third harmonic current suppression for symmetrical six-phase fault-tolerant permanent magnet synchronous motor drives. First, a brief motor model is established to analyze the source of the third harmonic current. Resonant controller is always appreciated in terms of harmonic current suppression. However, its performance is highly depended on the precise of the motor speed, which makes it not really suit for variable-speed applications. Fortunately, adaptive filter can skip this problem. Then a current controller based on the adaptive filter is designed to eliminate the third harmonic current. However, the dynamic response of the controller designed is unsatisfactory. Besides, the steady edge of the controller is rather narrow, which limits the operation range of motor. Then some improvements are made to the structure of the controller as well as the adaptive algorithm. Finally, several groups of experiments are conducted to compare both steady performance and dynamic performance of the controller based on adaptive filter and the improved controller. The experiments results coincide with the analysis and several conclusions are drawn. Besides, the proposed controller also applies to the elimination of other harmonic current.

Power Switch Open-Circuit Fault Diagnosis of Six-Phase Fault Tolerant Permanent Magnet Synchronous Motor System Under Normal and Fault-Tolerant Operation Conditions Using the Average Current Park's Vector Approach

In this article, a new power switch open-circuit fault diagnosis approach is proposed for the six-phase fault-tolerant permanent magnet synchronous motor (FTPMSM) system based on average current Park's vector (ACPV), which can detect the fault power switch for the FTPMSM system in both normal and phase open-circuit/short-circuit fault-tolerant operation conditions. To detect the power switch open-circuit fault, the fault detection approach based on the moduli of the ACPV in two orthogonal subspaces is first proposed for the six-phase FTPMSM system even in phase open-circuit and short-circuit fault-tolerant operation. Then, the ACPV-based fault location approach is proposed, which can identify the fault power switch according to the sign symbol of the ACPV. The resulting fault diagnosis approach has a simple structure and low computation burden, which can detect the power switch open-circuit fault online for the FTPMSM system in both normal and fault-tolerant operation conditions. Finally, the effectiveness of the proposed fault diagnosis approach is demonstrated by a six-phase FTPMSM system experimental platform.

Sensorless Fault-Tolerant Control With Phase Delay Compensation for Aerospace FTPMSM Drives With Phase Open-Circuit and Short-Circuit Faults

To enhance the reliability of fault-tolerant permanent-magnet synchronous motor (FTPMSM) drives, a new sensorless control based on the robust observer, nonorthogonal phase-locked loop (PLL), and variable phase delay compensation is proposed, which can guarantee the medium- and high-speed sensorless control performance for the FTPMSM even in the phase open-circuit and short-circuit fault conditions. A robust observer is proposed to achieve any two healthy phase back electromotive force (EMF) estimation, regardless of the parameter variation, external disturbance, and the phase fault. The nonorthogonal PLL is presented to extract the information of the rotor position from the observed two nonorthogonal phase back-EMFs. To enhance the estimation accuracy of the rotor position as the speed changes, the variable cut-off frequency low-pass filter (VLPF) is proposed to eliminate the high-frequency noises of the observed phase back-EMFs, while a phase delay compensation is presented to compensate for the estimation deviation caused by the VLPF. The resulting sensorless FTPMSM system has excellent speed control performance both in normal and fault conditions, which is also demonstrated by a six-phase FTPMSM system experimental platform.

Finite-Control-Set MPC for Open-Phase Fault-Tolerant Control of PM Synchronous Motor Drives

A fault-tolerant permanent magnet synchronous motor drive is proposed in this article. The strategy is based on finite-control-set model-predictive control that is easy to implement and replaces the conventional proportional-integral controllers and pulsewidth modulators. A three-phase four-wire converter topology is used, which connects the neutral of the motor to the middle of the dc link in a capacitive divider. The main contribution of the proposed strategy relies on the fact that no reconfigurations or modifications of the converter topology and the controller strategy are required from normal operation to postfault operation. As a result, the transition from healthy to faulty state is smooth and not noticeable in the torque waveform. In addition, a simple fault detection method is derived by using the predicted variables. Experimental results, obtained from a laboratory prototype, validate the practical feasibility of the proposed strategy and show a pulsation-free torque on fault operation.

A Robust Observer and Nonorthogonal PLL-Based Sensorless Control for Fault-Tolerant Permanent Magnet Motor With Guaranteed Postfault Performance

This article proposes a robust observer and nonorthogonal phase-locked loop (PLL)-based sensorless control for the fault-tolerant permanent magnet synchronous motor (FTPMSM) in medium- and high-speed ranges to improve the position estimation reliability of the system, which can be applied for the sensorless control of the FTPMSM system in both normal and fault conditions. Due to the unsymmetric state of the FTPMSM under fault condition, a new sensorless control scheme based on the back electromotive force (EMF) of nonfault two-phase windings is proposed, in which the reference frame transformation is not necessary. The robust observer is proposed to accurately estimate the back EMF of the nonfault two-phase windings, which can guarantee the uniform boundedness and uniform ultimate boundedness of the system regardless of various uncertainties, including external disturbance, parameter variation, and phase winding fault. The nonorthogonal PLL is proposed to calculate the rotor position and speed of the FTPMSM by using the estimated two-phase back EMFs. The simulation and experimental results show that the FTPMSM system with the proposed sensorless control has excellent speed control performance, accurate rotor position/speed estimation, and great system robustness in the presence of various uncertainties, which is able to guarantee the system performance both in normal condition and in fault condition.

Design and Analysis of a Five-Phase Fault-Tolerant Permanent Magnet Synchronous Motor for Aerospace Starter-Generator System

In this paper, a novel five-phase fault-tolerant permanent magnet synchronous motor (FTPMSM) is designed for aerospace starter-generator (SG) system. Small teeth are placed at the center of the slots, in which the two coils belong to different phases, and on both sides of the small teeth, thermal insulation materials are placed. In this way, the motor owns low thermal coupling and no electromagnetic coupling among different windings. By optimizing the stator size and rotor structure, the short-circuit current is limited to a low level and thus the motor has strong fault-tolerant capability under short-circuit fault. The finite element analysis (FEA) model of the five-phase FTPMSM is established, by which no-load characteristic, load characteristic, and fault-tolerant capability of the motor are analyzed. The simulation results show that the mutual inductance of different phase windings are almost zero, and the motor has good fault-tolerant capability. Finally, the prototype of the proposed five-phase FTPMSM is built to verify the design and simulation results.

Robust Control of Fault-Tolerant Permanent-Magnet Synchronous Motor for Aerospace Application With Guaranteed Fault Switch Process

This paper proposes a novel ten-phase fault-tolerant permanent-magnet synchronous motor (FTPMSM) with two stators and two rotors on the same shaft. Furthermore, a concentrated, single-layer, and alternate-teeth-wound winding is adopted to enhance the fault isolation capacity of the motor. In addition, we propose a new approach to the speed control of the developed motor, which takes the electromagnetic torque ripple in the fault switch process into account. The control can guarantee the uniform boundedness and uniform ultimate boundedness of the system regardless of the load disturbance and the parameter variation, particularly for the fault switch process after a fault occurrence before the fault-tolerant control can take effect. Moreover, an optimal torque control is adopted to further improve the fault-tolerant performance, which enables a ripple-free torque operation under open-circuit and short-circuit fault conditions. Simulation and experimental results show that the FTPMSM system with the proposed control strategy has excellent fault-tolerant performance and good robustness. This paper provides an innovative approach by employing a robust control for a speed loop to guarantee the fault-tolerant performance of the proposed motor system under normal and fault conditions, even in the fault switch process.

Study on inverter fault-tolerant operation of PMSM DTC

This paper presents an investigation of inverter fault-tolerant operation for a permanent magnet synchronous motor (PMSM) direct torque control (DTC) system under various inverter faults. The performance of a faulty standard 6-switch inverter driven PMSM DTC system is analyzed. To avoid the loss or even disaster caused by the inverter faults, a topology-modified inverter with fault-tolerant capability is introduced, which is reconfigured as a 3-phase 4-switch inverter. The modeling of the 4-switch inverter is then analyzed and a novel DTC strategy with a unique nonlinear perpendicular flux observer and feedback compensation scheme is proposed for obtaining a continuous, disturbance-free drive system. The simulation and experimental results demonstrate that the proposed inverter fault-tolerant PMSM DTC system is able to operate stably and continuously with acceptable static and pretty good dynamic performance.