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Ralph Kennel - One of the best experts on this subject based on the ideXlab platform.

  • finite control set model predictive torque control of induction machine with a robust adaptive observer
    IEEE Transactions on Industrial Electronics, 2017
    Co-Authors: Fengxiang Wang, Davood Arab Khaburi, Alireza S Davari, Zhe Chen, Zhenbin Zhang, Jose Rodrieguez, Ralph Kennel
    Abstract:

    This paper proposes a finite control set model predictive torque control (PTC) of induction machine with an adaptive observer. Model reference adaptive system (MRAS) can accurately estimate the rotor speed. However, the encoderless PTC method requires not only the estimated rotor speed but also the estimated fluxes. A sliding mode Stator Voltage model observer is applied as the reference model in the MRAS. Although sliding mode method has chattering problem, it can be largely reduced by optimizing the sliding function and by proper sliding gains designed with H infinity method. The proposed encoderless PTC is experimentally verified in this work. The results show that the method is stable in a wide speed range and has good performance over load disturbance. Moreover, the proposed encoderless strategy has the merits of predictive control: fast dynamics, straightforward structure, and easy implementation for constraints’ inclusion.

  • sensorless control of synchronous machines based on direct speed and position estimation in polar Stator current coordinates
    IEEE Transactions on Power Electronics, 2013
    Co-Authors: Dirk Paulus, Jeanfrancois Stumper, Ralph Kennel
    Abstract:

    This paper proposes a sensorless control scheme for a surface-mounted permanent-magnet synchronous machine (PMSM) based on the back-electromotive force Voltage. It is a direct estimation method, meaning the rotor position is directly calculated based on Stator-current measurements and the Stator Voltage commands as well as on the knowledge of Stator resistance and Stator inductance, but without the use of an asymptotic observer or integration of speed, respectively, flux. The estimated angle is filtered and used directly for sensorless field-oriented current and torque control. Analogously, the rotor speed is also directly calculated and used for sensorless speed control. A polar Stator-current coordinate representation is chosen for the Stator currents such that the scheme is easily extendable with filters to cope with measurement noise. A comparison to a reduced-order observer highlights the robustness advantage. Experimental results confirm good dynamical performance, even at low speeds.

  • a nonlinear estimator for dynamical and robust sensorless control of permanent magnet synchronous machines
    Conference on Decision and Control, 2011
    Co-Authors: Jeanfrancois Stumper, Dirk Paulus, Ralph Kennel
    Abstract:

    This paper proposes an angular position and speed estimation scheme that is based on a direct evaluation of the angle of the Voltage induced by the spinning rotor (back-EMF) of a permanent-magnet synchronous motor (PMSM). It is an inverse parallel-model estimation method, meaning the rotor position and speed are directly calculated based on Stator current measurements and the Stator Voltage commands. In contrast to existing schemes, no observer, no integration and no speed or flux estimation is necessary. The estimators are extended with filters to cope with measurement noise, and directly used for field-oriented control. It is shown algebraically and experimentally that parametric robustness is outstanding. The resulting estimated angle is driftless even under uncertainties. The scheme is suitable for encoderless control of a PMSM at high and low speeds. The performance of the scheme is confirmed by experimental results.

Heng Nian - One of the best experts on this subject based on the ideXlab platform.

  • A Simplified Stator Frequency and Power Control Method of DFIG-DC System Without Stator Voltage and Current Sensors
    IEEE Transactions on Power Electronics, 2020
    Co-Authors: Chao Wu, Heng Nian, Yingzong Jiao, Frede Blaabjerg
    Abstract:

    The primary objective of the grid connected DFIG-DC system is to achieve the accurate control of Stator frequency and active power. In this letter, a simplified power control method is proposed by just controlling the magnitude of the rotor current vector, which can avoid the Stator Voltage and current sensors. The Stator active power is calculated by the product of dc Voltage and dc current. The Stator frequency is simply controlled by the rotating speed of the rotor current vector, which is achieved through a given rotating frame. Furthermore, the parameter dependence and dc sampling offset problems can be eliminated because the Voltage model or current model, which are usually used for acquiring Stator frequency and Stator flux angle, can be avoided. Therefore, the robustness and stability of the Stator frequency and power control can be improved. Finally, experiments based on a 1 kW DFIG-DC setup are carried out to verify the proposed method.

  • Sinusoidal Current Operation of a DFIG-DC System Without Stator Voltage Sensors
    IEEE Transactions on Industrial Electronics, 2018
    Co-Authors: Chao Wu, Heng Nian
    Abstract:

    This paper presents a sinusoidal current control scheme for the doubly fed induction generator (DFIG)-DC system to reduce the harmonic current losses of the Stator and rotor windings. The DFIG-DC system can be controlled as an open-winding system if the DFIG is equivalent in the Γ circuit. The Stator is connected to the dc link through the diode bridge and the rotor is connected to the same dc link through the rotor-side converter. A phase-locked loop based on Stator flux is applied for estimating not only the Stator frequency but also the angle of Stator flux linkage. The sinusoidal Stator current can be achieved by injecting appropriate harmonic Voltages to the rotor side. The rotor harmonic Voltages are produced by applying the Stator Voltage directly without employing a series of resonant controllers. Since the Voltage of the diode bridge depends on the direction of the flowing current, the Stator Voltage of DFIG can be expressed by the Stator current avoiding the Stator Voltage sensors. In this way, the harmonic current losses of the Stator and rotor windings can be greatly reduced, which is beneficial for system efficiency. Furthermore, the torque ripple and power ripple can also be reduced, which is a good operation condition of the DFIG-DC system. The proposed control method is validated through experiments.

Chao Wu - One of the best experts on this subject based on the ideXlab platform.

  • A Simplified Stator Frequency and Power Control Method of DFIG-DC System Without Stator Voltage and Current Sensors
    IEEE Transactions on Power Electronics, 2020
    Co-Authors: Chao Wu, Heng Nian, Yingzong Jiao, Frede Blaabjerg
    Abstract:

    The primary objective of the grid connected DFIG-DC system is to achieve the accurate control of Stator frequency and active power. In this letter, a simplified power control method is proposed by just controlling the magnitude of the rotor current vector, which can avoid the Stator Voltage and current sensors. The Stator active power is calculated by the product of dc Voltage and dc current. The Stator frequency is simply controlled by the rotating speed of the rotor current vector, which is achieved through a given rotating frame. Furthermore, the parameter dependence and dc sampling offset problems can be eliminated because the Voltage model or current model, which are usually used for acquiring Stator frequency and Stator flux angle, can be avoided. Therefore, the robustness and stability of the Stator frequency and power control can be improved. Finally, experiments based on a 1 kW DFIG-DC setup are carried out to verify the proposed method.

  • Sinusoidal Current Operation of a DFIG-DC System Without Stator Voltage Sensors
    IEEE Transactions on Industrial Electronics, 2018
    Co-Authors: Chao Wu, Heng Nian
    Abstract:

    This paper presents a sinusoidal current control scheme for the doubly fed induction generator (DFIG)-DC system to reduce the harmonic current losses of the Stator and rotor windings. The DFIG-DC system can be controlled as an open-winding system if the DFIG is equivalent in the Γ circuit. The Stator is connected to the dc link through the diode bridge and the rotor is connected to the same dc link through the rotor-side converter. A phase-locked loop based on Stator flux is applied for estimating not only the Stator frequency but also the angle of Stator flux linkage. The sinusoidal Stator current can be achieved by injecting appropriate harmonic Voltages to the rotor side. The rotor harmonic Voltages are produced by applying the Stator Voltage directly without employing a series of resonant controllers. Since the Voltage of the diode bridge depends on the direction of the flowing current, the Stator Voltage of DFIG can be expressed by the Stator current avoiding the Stator Voltage sensors. In this way, the harmonic current losses of the Stator and rotor windings can be greatly reduced, which is beneficial for system efficiency. Furthermore, the torque ripple and power ripple can also be reduced, which is a good operation condition of the DFIG-DC system. The proposed control method is validated through experiments.

Frede Blaabjerg - One of the best experts on this subject based on the ideXlab platform.

  • A Simplified Stator Frequency and Power Control Method of DFIG-DC System Without Stator Voltage and Current Sensors
    IEEE Transactions on Power Electronics, 2020
    Co-Authors: Chao Wu, Heng Nian, Yingzong Jiao, Frede Blaabjerg
    Abstract:

    The primary objective of the grid connected DFIG-DC system is to achieve the accurate control of Stator frequency and active power. In this letter, a simplified power control method is proposed by just controlling the magnitude of the rotor current vector, which can avoid the Stator Voltage and current sensors. The Stator active power is calculated by the product of dc Voltage and dc current. The Stator frequency is simply controlled by the rotating speed of the rotor current vector, which is achieved through a given rotating frame. Furthermore, the parameter dependence and dc sampling offset problems can be eliminated because the Voltage model or current model, which are usually used for acquiring Stator frequency and Stator flux angle, can be avoided. Therefore, the robustness and stability of the Stator frequency and power control can be improved. Finally, experiments based on a 1 kW DFIG-DC setup are carried out to verify the proposed method.

Xi Xiao - One of the best experts on this subject based on the ideXlab platform.

  • torque ripple reduction of the torque predictive control scheme for permanent magnet synchronous motors
    IEEE Transactions on Industrial Electronics, 2012
    Co-Authors: Hao Zhu, Xi Xiao
    Abstract:

    The direct torque control (DTC) technique of permanent-magnet synchronous motors (PMSMs) receives increasing attention due to its advantages in eliminating the current controllers and quicker dynamic response, compared with other motor control algorithms. However, high torque and Stator flux ripples remain in the system when using DTC technologies. This means large Stator Voltage and current harmonic contents exist in the PM motors. Since the variation of motor electromagnetic torque is related to the Voltages that are applied to the motor, by analyzing the relationships between Stator flux, torque, and Voltages, a PMSM torque predictive control scheme is proposed in this paper. In each digital signal processor cycle, the optimized Voltage is utilized to reduce torque ripple, and the Voltage vector angle is determined by the output of torque and flux hysteresis controllers. The proposed scheme is simulated and experimentally verified. Both simulation and experimental results have shown that low torque ripple and reduced Stator current harmonics are achieved by using the proposed scheme.