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To address the contradiction between dynamic performance and robustness of the enhanced linear active disturbance rejection control (ELADRC) method, a fuzzy-ELADRC method for a bearingless induction motor (BIM) is proposed. First, based on the air-gap flux oriented control, the first-order and second-order ELADRC are designed for the torque system and the suspension system of the BIM, respectively. Second, a fuzzy controller is introduced to adjust the controller bandwidth and observer bandwidth of ELADRC online. The fuzzy rules are established by analyzing the influence of ELADRC with different bandwidths on the BIM system, and adaptive initial bandwidth is adopted to improve the variable speed performance of the BIM. Finally, the simulation and experimental comparisons of the PID control method, the ELADRC method, and the fuzzy-ELADRC method are carried out. The results show that the proposed method not only realizes the rapid and stable suspension of the rotor, but also effectively improves the starting performance, variable speed performance, and antidisturbance performance of the BIM system. [ABSTRACT FROM AUTHOR]

This article presents a novel power-angle control method of the doubly fed induction generator dc system based on regulating the air gap flux vector. The relationship between the angle of air gap electromotive force (EMF) vector and the stator output power is revealed in this article, which can be used for controlling the output power directly. Since the stator frequency is determined by the rotating speed of air gap flux vector and the output power is determined by the angle of air gap EMF vector, the stator frequency can be generated by the power control loop that can avoid the classical voltage model or current model and reduce the parameter dependence. The stator frequency can be regulated through the d-axis rotor current since the product of the stator frequency and the d-axis rotor current is constant. Furthermore, the improved direct resonant control for torque ripple and harmonic current mitigation can still be applied in this novel control method because air gap flux orientation is achieved through controlling the q-axis air gap flux to be zero. Finally, the experimental results are presented to validate the proposed control method. [ABSTRACT FROM AUTHOR]

The proposed technique focuses on the nonsinusoidal power supply control strategy aiming to obtain the optimal air gap flux density distribution. The electrical constraints for the alignment between rotated fundamental and harmonic air gap flux are illustrated in detail. The supporting simulation is performed to analyze the misaligned angles between fundamental and harmonic air gap flux for the traditional methods. Different from traditional flux-oriented methods, the improved algorithm for harmonic currents injection is designed based on rotor flux orientated control in fundamental plane and air gap flux orientated control in harmonic planes. The synchronous and aligned control of the fundamental and harmonic air gap flux is achieved regardless of load condition. The experimental verification is implemented based on a multiphase driving platform using a seven-phase induction machine as prototype. Various scenarios are provided for the proposed control strategy comparing with the traditional ones in terms of induced electromotive force waveforms, harmonic currents, and advance angles of air gap flux. The simulated and experimental results validate the theoretical assumption and the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Dual stator winding induction machines (DSWIMs), which have two sets of three-phase windings with unequal pole pairs in their stator and a standard squirrel cage rotor, have overcame the narrow speed operation region and circulating current problems exists in other types of dual winding machines. These advantages are resulted from the independent operation of their winding sets. The independent operation of winding sets will be guaranteed if the flux saturation is avoided. This letter proposes a novel reference frame angle determination technique that not only guarantees the flux saturation avoidance but also results in flux optimization in DSWIMs. Despite pervious methods, the proposed method does not require position or speed sensor and it is easily applicable in various control schemes and in different reference frames. This method is implemented in a flux and torque vector control system for driving a 3.3 kW DSWIM. The experimental results confirm the effectiveness of the proposed method. Moreover, by implementing the proposed method, the torque sharing between the two winding sets is properly done according to the power rating of each of them. [ABSTRACT FROM AUTHOR]

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]

A comprehensive literature review shows that transformer-based solutions are superior for the mitigation of inrush currents than external (to the transformer) solutions. The use of air gaps and low-permeability (iron) materials are known techniques for this purpose. This paper investigates the effectiveness of these approaches for reducing inrush and phase-hop currents. Studies are carried out on toroidal transformers, due to their broad application in power electronics devices. Contrary to common belief, this paper demonstrates that air gaps do not reduce the inrush currents when a transformer is fully demagnetized. However, inrush currents can be mitigated by the use of low-permeability iron materials. It is also demonstrated that air-gaps significantly reduce inrush currents when transformers have residual flux, e.g., for phase-hop conditions. Analytical expressions are derived to compute the mitigation factor for a specific gap length. The results and formulae presented in this paper are verified with laboratory experiments, transient simulations with validated circuit models, and 2-D finite element simulations. [ABSTRACT FROM AUTHOR]

This paper presents an indirect vector control scheme with an improved flux pattern using third harmonic injection. The control objective is to independently control both flux and torque and to generate a nearly rectangular air-gap flux, resulting in improved machine power density. If there is a proportional relation between the third harmonic and fundamental plane currents, variable misalignment between fundamental and third air-gap flux components occurs with varying mechanical loading. Due to this misalignment, saturation may take place. Accordingly, the total flux is saturated and iron loss increases. Hence, coupling results between different sequence planes. Instead of a proportional relation between the current components, direct and quadrature current components of the injected third harmonic current reference are a function of the fundamental direct and quadrature reference current components, respectively. These functions ensure that the air-gap flux is near rectangular with a maximum value of 1 p.u. from no load to full load. Moreover, this controller guarantees complete decoupling between the sequence planes. An eleven-phase induction machine is used to validate the proposed controller experimentally, while supporting simulation results and theoretical analysis use both MATLAB and finite element platforms. [ABSTRACT FROM AUTHOR]