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Precise output torque control is often required in applications using synchronous reluctance machines. Direct measurement of torque has drawbacks due to both cost and reliability issues. To overcome these limitations, the development of torque estimation methods has received significant research attention. Most of the exiting torque estimation methods require knowledge of machine parameters, suffering, therefore, from parameter sensitivity. Load and saturation are recognized as the primary source of parameter variation. This article proposes the use of a high-frequency signal injection for the online estimation of the machine parameters required for torque estimation. The improvement in the torque estimation will be especially relevant in deep-saturation regions. The method operates without interfering with the normal operation of the machine. [ABSTRACT FROM AUTHOR]

Torque measurement/estimation in permanent magnet synchronous machines (PMSMs) is required in a large variety of applications. Direct torque measurement by means of torque transducers is typically limited to laboratory applications due to cost, reliability, and room concerns. Alternatively, torque can be estimated. Torque estimation methods require accurate knowledge of machine parameters. Injection of a high frequency (HF) signal in the stator via inverter has been shown to be a viable option for online machine parameters identification in PMSMs. However, this introduces concerns on the performance of the machine due to the noise, vibration, and additional losses produced by the HF signal. This article proposes a torque estimation method for PMSMs using low cost Hall-effect sensors. The method is based on the dependency of the leakage flux complex vector due to interaction between permanent magnet flux and stator coil flux and does not interfere with the drive operation of the machine. [ABSTRACT FROM AUTHOR]

Torque pulsations are one of the major concerns in permanent magnet synchronous machines (PMSMs). Torque pulsations can be mitigated by proper machine design and/or by control. Independently of the means being used, precise measurement of torque pulsation is highly desirable for the validation and improvement of machine designs and control strategies. This article proposes a non-invasive, wireless vibration measurement system aimed to provide precise estimates of torque pulsations. The system is mounted on the rotor shaft of the PMSM, i.e., there is no mechanical coupling, and allows on-line measurement without interfering with the normal operation of the machine. [ABSTRACT FROM AUTHOR]

Torque measurement/estimation in surface permanent magnet synchronous machines (SPMSMs) is needed in many applications. Torque measurement systems are expensive, require extra room, add weight, can introduce resonances into the system, and their performance can be compromised due to electromagnetic interference. Alternatively, torque can be estimated, accurate knowledge of machine parameters being critical in this case. Injection of a high-frequency (HF) signal in the stator via an inverter has been shown to be a viable option for online identification of machine parameters identification required by torque estimation methods for interior PMSMs. However, the reported methods require the use of two pulsating HF currents, which introduces concerns both on the adverse effects on machine's performance (additional noise, vibration, losses, etc.) as well as to the additional computational burden, as HF current controllers are required. This article proposes a torque estimation method for SPMSMs using a single HF signal; furthermore, a HF voltage signal can be used, avoiding the use of HF current controllers, and therefore simplifying the implementation. [ABSTRACT FROM AUTHOR]

Torque estimation in permanent-magnet synchronous machines is highly desirable in many applications. Torque produced by a permanent-magnet synchronous machine depends on the permanent-magnets’ flux and dq-axes inductances. Consequently, precise knowledge of these parameters is required for proper torque estimation. This article proposes the use of a high-frequency signal for both PM flux and dq-axes inductances estimation. The high-frequency signals will be injected in the stator via an inverter superposed on top of the fundamental excitation. The proposed method can be used without interfering with the normal operation of the machine, the results being highly insensitive from machine's working condition. [ABSTRACT FROM AUTHOR]

Torque production capability of permanent magnet synchronous machines (PMSMs) depends on the magnetization state of the permanent magnets (PMs). Electrical stress, thermal stress, or the combined effect of both can produce demagnetization of the PMs, which eventually can result in several adverse effects including decrease in the motor torque and efficiency and increase of the torque ripple and vibration, eventually degrading the performance and reliability of the motor and drive system. A number of approaches have been proposed for detecting PM demagnetization using model-based flux estimation, signal injection, and spectrum analysis of current/back electromotive force; however, all these methods show limitations in terms of invasiveness, implementation cost, and/or reliability of the diagnosis. In this paper, accurate PM demagnetization detection based on measurements from Hall-effect sensors is proposed. Such sensors are often mounted in commercial PMSMs; the proposed method can, therefore, be implemented at practically no cost. [ABSTRACT FROM AUTHOR]

Soft-stall control of small wind turbines is a method to protect the generation system and/or load from excessive wind speeds and wind gusts without discontinuing power generation. Soft-stall can be activated due to an excess of the power and/or torque/current. This paper proposes a method to improve the existing soft-stall methods for over torque/current protection using a turbine torque estimator. In addition, this paper also proposes two methods to emulate the wind turbine inertia without communications between the load drive (wind turbine emulator) and the generation system controller. This will allow the evaluation of the proposed methods in working conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a new soft-stalling control strategy for grid-connected small wind turbines operating in the high and very high wind speed conditions. The proposed method is driven by the rated current/torque limits of the electrical machine and/or the power converter, instead of the rated power of the connected load, which is the limiting factor in other methods. The developed strategy additionally deals with the problem of system startup preventing the generator from accelerating to an uncontrollable operating point under a high wind speed situation. This is accomplished using only voltage and current sensors, not being required direct measurements of the wind speed nor the generator speed. The proposed method is applied to a small wind turbine system consisting of a permanent magnet synchronous generator (PMSG) and a simple power converter topology. Simulation and experimental results are included to demonstrate the performance of the proposed method. The paper also shows the limitations of using the stator back electromotive force to estimate the rotor speed in PMSG connected to a rectifier, due to significant $d$-axis current at high load. [ABSTRACT FROM AUTHOR]

This paper focuses on dynamic control, under loaded conditions, of the magnetization state of suitably designed variable-flux (VF) permanent-magnet (PM) machines. Such VF-PM machines have been shown to achieve low loss operation over a wide range of load and speed. For this type of machine, the PM flux linkage varies during the magnetization manipulation process. Published magnetization techniques have occurred at zero load conditions and thus did not generate torque pulsations. However, under loaded conditions, the existing methods would produce unwanted torque pulsation. This paper proposes a parameter insensitive method to solve this issue. This method generates a decoupling current command that is calculated from accurately estimated stator flux linkage. Accurate flux estimation, i.e., insensitive to inductance saturation and PM flux linkage variation (e.g., temperature or magnetization level) is achieved by using the voltage disturbance estimated by a closed-loop stator current vector observer. In both simulations and experiments, it is shown that even during magnetization processes under loaded conditions, the flux can be estimated correctly, and smooth torque output can be achieved. [ABSTRACT FROM AUTHOR]

This paper proposes a new rotor design for flux-intensifying interior permanent magnet synchronous machine (FI-IPM SM) that is more suitable for self-sensing control at zero/very low speed based on saliency-tracking methods and retains acceptable power conversion capability as compared to a traditional flux-weakening IPM SM (FW-IPM SM). Design steps for the rotor structure of the new machine are laid out and discussed to emphasize key design challenges. The proposed FI-IPM SM and a conventional FW-IPM SM with similar torque-speed capability are made to evaluate performances in power conversion as well as self-sensing capability at very low speed. Finite-element analysis (FEA) is used to evaluate each machine's performance. The proposed FI-IPM SM shows less variation in the saliency when the machine is loaded, leading to a possibility of better self-sensing performance at very low speed as compared to the traditional FW-IPM SM. Experimental results on the efficiency and self-sensing performance of these two machines are presented to verify the design methodology. [ABSTRACT FROM AUTHOR]

Torque estimation in permanent magnet synchronous machines and synchronous reluctance machines is required in many applications. Torque produced by a permanent magnet synchronous machine depends on the permanent magnets' flux and d q -axes inductances, whereas torque in synchronous reluctance machines depends on the d q -axes inductances. Consequently, precise knowledge of these parameters is required for proper torque estimation. The use of high frequency signal both for permanent magnets' flux and d q -axes inductances estimation has been recently shown to be a viable option. This paper reviews the physical principles, implementation and performance of high-frequency signal injection based torque estimation for permanent magnet synchronous machines and synchronous reluctance machines. [ABSTRACT FROM AUTHOR]