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This paper proposes a d–q cross-coupling current controller for permanent magnet synchronous motor (PMSM) drives. Slotting and cross-coupling effects in PMSMs cause the effective air-gap length to vary with the rotor angle and distort the distribution of the air-gap flux. Such distortions have a significant influence on the current control by changing the relationship between the stator currents and voltages. To investigate their effects, a d–q model is established in this paper, which is suitable for describing the voltage characteristics of the actual PMSMs. The model contains the angle-dependent parameters, the cross-coupling inductance between d–q axes, and the q-axis permanent magnet flux linkage, unlike the ideal d–q model. The transfer function matrix from the d–q currents to d–q voltages of PMSM is newly derived from the model. Based on that, the current controller with the feedback and feedforward terms of 2-by-2 matrix is proposed. It is designed so that the independent gains are in low-pass filter forms and the coupling control gains are zero with eliminating interference between d–q axes. The proposed controller contributes to providing the stable control performance by canceling the slotting and cross-coupling effects. The performance of the proposed current controller is verified by experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a fault diagnosis technique for high-resistance connection (HRC) in a nine-phase flux-switching permanent-magnet (FSPM) machine based on zero-sequence voltage components (ZSVC), where the neutral-point connection mode is considered. A nine-phase FSPM machine topology is first introduced and no-load back electromotive force waveforms are analyzed. Moreover, the topologies of the nine-phase FSPM drive with different neutral-point connection modes are studied. Then, the mathematical model of a nine-phase FSPM machine with HRC is established with the consideration of the neutral-point connection mode and then the influence of the HRC on the ZSVC is analyzed based on the established model. It is shown that the HRC may be diagnosed by monitoring the change of the spectral contents of the ZSVC. Furthermore, this paper focuses on the situation of the nine-phase FSPM machine with one neutral point. In this case, to remove the influence of the FSPM machine operating point, an effective fault indicator is defined and used for HRC fault detection. Finally, the simulation and the experiment are carried out to validate the proposed method. Both the results show that the proposed method can be applied for the HRC fault diagnosis in a nine-phase FSPM machine. [ABSTRACT FROM AUTHOR]

This paper proposes a dc-flux-injection method for fault diagnosis of high-resistance connection (HRC) in a direct-torque-controlled permanent magnet synchronous machine (PMSM) drive system. In this method, the flux linkage bias is superimposed in the flux control loop of the direct torque control system, and then the dc current offset is excited in the stator windings. By superimposing two different pairs of flux linkage biases, a binary linear equation group about the resistance deviations can be established based on the stator currents and zero-sequence voltage component. By solving the equation group, the resistance deviations can be calculated for the HRC fault detection, faulty phase location, and fault severity estimation. Both the simulation and experimental results validate the effectiveness of the proposed method. In addition, the proposed method is immune to the symmetrical variations of stator resistance and interturn fault of the PMSM. [ABSTRACT FROM AUTHOR]

High-resistance connection (HRC) is a common electrical fault for the electric machine drive system. This fault can lead to the increased power loss and heat, thus possibly causing the damage of the electric machine drive system due to the excessive temperature. Hence, this paper first proposes a vector control strategy of the surface-mounted permanent magnet synchronous machine (PMSM) drive system with the HRC fault to minimize the copper loss. The mathematical model of the PMSM with the HRC is presented in abc stationary frame. The function relationship between the copper loss and the direct axis current, quadrature axis current, stator resistance, and the additional resistance due to the HRC is established and analyzed. The expression of the direct axis current, which minimizes the copper loss, is deduced under the condition of the HRC in one phase and two phases. Consequently, the proposed vector control strategy for the surface-mounted PMSM driving system is achieved. Both the simulation and experimental results show that the proposed method not only preserves the performance of the conventional vector control method, but also can effectively reduce the copper loss, thus protecting the PMSM from the damage due to the increased temperature possibly caused by the HRC fault. [ABSTRACT FROM AUTHOR]

The linear vernier permanent magnet (LVPM) motor incorporates the merits of high efficiency, simple mechanism, and low cost, which have a bright future in urban rail transportation. This paper proposes a new sensorless direct thrust force control (DTFC) for the LVPM motor. The novelty is the introduction of a modified flux linkage observer, which has strong robustness against the interferences, no phase lag, and no attenuation. Compared with conventional flux linkage calculation methods, the proposed observer can provide desirable flux linkages, which increases the robustness of the sensorless DTFC system. Simulation and experimental results based on an LVPM motor drive demonstrate the accuracy and robustness. The validations in the aspect of the robustness to parameter errors, measurement errors, and noise show the superiorities of the modified flux linkage observer. [ABSTRACT FROM AUTHOR]

This paper proposes a novel drive method for interior permanent magnet machines (IPMMs). In the proposed system, a two-phase IPMM is fed from a single-phase H-bridge inverter for low-cost applications. Its main winding in d -axis is connected to the inverter and the auxiliary winding in q-axis is inherently short circuited. This configuration enables the motor to operate in a wider speed range with higher energy efficiency than most other single-phase drive systems. Also, its torque capability in the high-speed range is as high as that of the three-phase IPMM drive despite the reduced power devices, drivers, and current sensors. Accordingly, the proposed system has benefits such as simple structure, low cost, high-power density, and improved efficiency. In this paper, the system is modeled with an equivalent three-phase machine. Based on the model, its torque characteristics and operating areas are analyzed and compared to those of the conventional IPMM drives. A speed control algorithm is also developed. It includes a maximum torque per ampere control to improve drive efficiency and a flux-weakening control to maximize the feasible inverter output voltage. The proposed system and control algorithm are verified by experimental results. [ABSTRACT FROM PUBLISHER]

This paper explores the use of speed harmonic for accurate and fast maximum-torque-per-ampere (MTPA) control of interior permanent magnet synchronous machines (IPMSMs). A novel MTPA angle calculation approach is proposed, in which the MTPA angle is directly calculated from the phase angle of the speed harmonic that is induced by an injected harmonic current. At first, the relation between the speed harmonic and machine parameters is derived from the IPMSM model, which shows that the phase angle of the induced speed harmonic can be utilized to cancel the machine parameters in existing MTPA equation. Thus, a new MTPA equation is derived, which does not involve machine parameters for MTPA angle calculation. Compared with existing methods, the proposed approach is independent from the machine and drive nonlinearities. Moreover, the MTPA angle is directly calculated from the derived MTPA equation, so the proposed approach is fast and computationally efficient. Thus, the proposed approach is suitable for both on-line applications and building off-line lookup tables of MTPA angles for IPMSMs. The proposed approach is experimentally evaluated on a laboratory IPMSM drive system. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid excited generator, which is suitable for a variable-speed wind power generation system. Two sets of excitation sources are employed, which are permanent magnets (PMs) on the rotor and the field windings on the stator. The rotor is design with PM-iron structure, namely the PMs and iron poles are alternatively located in rotor, which can provide PM excitation and flux modulating simultaneously. Meanwhile, the adjacent stator teeth are designed with different height, which enables the stator with flux modulating effect, and, therefore, bidirectional flux modulating can be achieved. Some specific harmonics excited by the rotor PMs can be effectively adjusted by the field current, and the back electromotive force and electromagnetic torque can be regulated accordingly. Therefore, the proposed generator can achieve constant voltage control and maximum power point tracking control by controlling the field current. The design considerations and field regulating principle are analytically investigated. An improved Tabu search algorithm is used to optimize the proposed generator, and finite-element method is used to realize preliminary study of the electromagnetic performances. A prototype is manufactured and experimental tests are conducted to verify the theoretical analysis and control strategies. [ABSTRACT FROM PUBLISHER]

Hybrid-excitation switched reluctance motors (HESRMs) have attracted considerable attention for various drive applications due to their simple structure, low cost, and high-torque/power capabilities. This paper comprehensively evaluates and compares a high-torque segmented-stator HESRM drive with a conventional SRM drive in terms of static magnetic and dynamic performances. The stator of the segmented HESRM consists of six individual U-shaped segments; each one has two teeth associated with a permanent magnet (PM) installed between them. The static magnetic characteristics of a segmented HESRM and a conventional SRM, including flux distribution, phase flux linkage, electromagnetic torque, are analyzed and compared. The total fluxes created by the PM and by the excited current are strongly coupled. The details of mathematical model as well as dynamic performances of the segmented HESRM is derived and compared with the conventional SRM. Finally, a segmented HESRM and a conventional SRM of the same size are prototyped for experimental verification. From the comparative study, it is indicated that the segmented HESRM has better characteristics than the conventional SRM, such as less iron consumption, higher static and dynamic average torque production, lower torque ripple, higher power and torque densities, higher efficiency, and stronger starting capability. The measured results of static magnetic characteristic, steady-state and transient performances, and torque–speed characteristic of two SRM drives verify the finite-element analysis, modeling, and corresponding predictions. [ABSTRACT FROM PUBLISHER]

This paper proposes a method for online diagnosis and localization of high-resistance connection (HRC) in permanent magnet synchronous machine (PMSM) with an improved fault indicator. In the proposed method, the amplitude and initial phase angle of zero-sequence voltage component are both analyzed. Based on the analysis, the fault indicator with angle difference is defined for fault diagnosis and localization. It is shown that not only the HRC can be detected, but also the fault severity can be assessed and the faulty phases can be identified in this method. The simulation and experiment are carried out to verify the theoretical analysis. Both the results show that the proposed method can be effectively applied for online detection and identification of the HRC in the PMSM. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive evaluation of several direct torque control (DTC) strategies for permanent magnet synchronous machines (PMSMs), namely DTC, model predictive DTC, and duty ratio modulated DTC. Moreover, field-oriented control is also included in this study. The aforementioned control strategies are reviewed and their control performances are analyzed and compared. The comparison is carried out through simulation, finite-element analysis, and experimental results of a PMSM fed by a two-level voltage source inverter. With the intent to fully reveal the advantages and disadvantages of each control strategy, critical evaluation has been conducted on the basis of several criteria: Torque ripple, stator flux ripple, switching frequency of inverter, steady-state control performance, dynamic response, machine losses, parameter sensitivity, algorithm complexity, and stator current total harmonic distortion. [ABSTRACT FROM PUBLISHER]

This paper develops an online interturn fault diagnosis method for permanent magnet synchronous machine (PMSM). The mathematical model of the PMSM with interturn fault is established. The zero-sequence voltage component and zero-sequence current component are analyzed in the PMSM, respectively. Then, the new fault indicators are defined to remove the influence of the variation of the rotor speed and an effective frequency tracking algorithm is presented to extract fault indicators. In this proposed method, not only the interturn fault can be effectively detected, but also the phase in which this fault occurs can be accurately identified. The experiments are carried out and the experiment results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]