Rotor Flux Research Articles

Reactive Vortexes in a Naturally Activated Process: Non-Diffusive Rotational Fluxes at Transition State Uncovered by Persistent Homology.

The dynamics of reaction coordinates during barrier-crossing are key to understanding activated processes in complex systems such as proteins. The default assumption from Kramers' physical intuition is that of a diffusion process. However, the dynamics of barrier-crossing in natural complex molecules are largely unexplored. Here we investigate the transition dynamics of alanine dipeptide isomerization, the simplest complex system with a large number of non-reaction coordinates that can serve as an adequate thermal bath feeding energy into the reaction coordinates. We separate conformations along the time axis and construct the dynamic probability surface of reaction. We quantify its topological structure and rotational flux using persistent homology and differential form. Our results uncovered a region with a strong reactive vortex in the configuration-time space, where the highest probability peak and the transition state ensemble are located. This reactive region contains strong rotational fluxes: Most reactive trajectories swirl multiple times around this region in the subspace of the two most important reaction coordinates. Furthermore, the rotational fluxes result from cooperative movement along the isocommitter surfaces and orthogonal barrier-crossing. Overall, our findings offer a first glimpse into the reactive vortex regions that characterize the non-diffusive dynamics of barrier-crossing of a naturally occurring activation process.

Direct speed-flux vector control of induction motors: controller design and experimental robustness evaluation

The paper presents a general theoretical solution oftheinduction motor speed-fluxdirect vector control, which is based on the second Lyapunov method application. The structure of the direct vector control algorithm involves the use of anyasymptotic flux observer with exponential stability properties. Suchapproach led to improvement of the vector control system robustness properties. A constructive procedure for the designof correction termsof the rotor flux observer is proposed.Designed family of the flux ob-servers guarantees the exponential stability and robustification with respect ofparametric disturbances. It is shown that the proposedsolution guarantees: global exponential trackingof the speed-flux reference trajectories together with asymptotic field orientation, asymptotic exponential estimation of the rotor flux, as well as asymptotic decoupling of torque (speed) and flux control. Comparative experimental study shows that new controller providesstabilization of the control performancesas well as efficiency at nominal levelwhen the rotor active resistance changes. The proposed direct vector control structures can be used for the development of energy-efficient high performanceinduction motor drives for metalworking, packaging equipment, modern electric transport and special equipment.

Excitation control of variable speed pumped storage unit for electromechanical transient modeling

In this paper, a new excitation control of variable speed pumped storage unit (VSPS) for electromechanical transient modeling is presented. Compared with the traditional VSPS excitation control based on current source, the inner loop control of rotor current is retained. The new VSPS excitation control model considers the rotor flux dynamics and represents it as a second-order system. The effectiveness of the proposed excitation control model is verified by the comparison between electromagnetic transient simulation and electromechanical transient simulation. The electromechanical transient simulation of VSPS based on current source and VSPS based on voltage source is compared to verify the necessity of considering rotor flux dynamics. The proposed VSPS excitation control model reflects the characteristics of controllable voltage source and can provide more accurate reactive power and voltage simulation results in transient stability analysis.

A Combined Control Scheme of Direct Torque Control and Field-Oriented Control Algorithms for Three-Phase Induction Motor: Experimental Validation

In this paper, a combined structure of algorithms based on field-oriented control (FOC) and direct torque control (DTC) is proposed for improving the performance of a three-phase induction motor (IM) over a wide range of torque loads. The objective of this study is to investigate the state-of-the-art research performed on the resilient intersection control management between FOC and DTC algorithms for IM drive. Three algorithms are employed in the proposed scheme: Direct Torque Stator Flux Control (DTSFC), Direct Torque Rotor Flux Control (DTRFC), and the FOC algorithm. The main aim of the control law is to launch the drive system by selecting DTSFC or DTRFC during the transient state while FOC is switched smoothly to the steady-state. The proposed method had several advantages, including the ability to produce torque beyond the pull-out torque range at 340%, high torque dynamics during transient state within 0.5 ms, low chattering up to 0.05 N.m, and fixed frequency at steady-state operation. Furthermore, a comprehensive comparison study has been conducted, including the most recent research, to verify the effectiveness and superiority of the proposed technique. Results were obtained using both MATLAB/Simulink environment and also were experimentally performed by using a dSPACE DS1103 digital signal processing board to verify the concept of the proposed control scheme.

Fault characteristics analysis of DFIGWT in whole LVRT process considering control strategy switching between RSC and Crowbar

In order to address the relaying protection issues of the full renewable energy grid, the fault characteristics of the DFIGWT in whole LVRT process should be studied. Currently, researches on fault characteristics of DFIGWT considering crowbar generally assume that crowbar is activated at the moment of fault. However, in fact, the DFIGWT’s fault current characteristics are mainly affected by both (rotor-side converter) RSC and crowbar. The crowbar does not act instantaneously at the moment of fault due to the control system. The DFIGWT is mainly controlled by the RSC before the crowbar is activated. In this paper, the fault process was divided into two stages, namely RSC control stage and crowbar activating stage. The fault characteristics of DFIGWT were analyzed at RSC control stage. Then, the activation time of crowbar was obtained, especially the activation of crowbar due to over-voltage of DC bus was considered. The last values of stator and rotor flux linkages at the first stage were calculated and used as the initial values of the stator and rotor flux linkages at the second stage. Then, the analytical expressions of rotor flux linkage were deduced by Laplace and inverse Laplace transformations. Based on this, the fault mechanism of DFIGWT is resolved and analytical expression of DFIGWT’s short circuit characteristics considering whole LVRT process was proposed. The expression of DFIGWT’s fault current characteristics was verified by the simulation results.The research results are helpful to the construction of relaying protection system for a full-renewable-based system.

Finite element level validation of an anisotropic hysteresis model for non-oriented electrical steel sheets

This paper presents the finite element level validation of the anisotropic Jiles–Atherton hysteresis model. Numerical analysis of a round rotational single sheet tester is performed using the 2D finite element method. Anisotropic extension of the Jiles–Atherton hysteresis model is coupled with the 2D finite element method. The finite element simulations are performed for the cases when the magnetic field alternates and rotates in the lamination plane. The simulated results for alternating and rotational flux density excitations agree with the measured data. The measured data used in this paper corresponds to the M400-50A nonoriented silicon steel.

Rotational flux influenced cusp entrainment in a viscous pool

Evolution of entrained gaseous cusp in a viscous liquid pool caused by a fully immersed horizontal revolving circular drum is elucidated thoroughly. Finite volume-based open source Gerris is employed to carry out the numerical simulations. Length θs* and width (H*) of the cusp are characterized thoroughly by varying the strength of rotational flux (measured by the capillary number, Ca) and depth of immersion (submersion height to roller diameter ratio, h/D) of the spinning roller. Locus and travel rate of cusp tip are also elaborated from origination to attainment of steady state with the progress of time for different combinations of Ca and h/D. We have also reported the bubble ejection mechanism from the advancing end of the cusp after achieving macroscopic steady length. Bubbling frequency and volume accumulation of detached bubbles show strong dependency on Ca or h/D. Entrainment patterns are also observed by investigating the effect of gravitational pull (measured by employing the Archimedes number, Ar) and viscous drag (specified by using the Morton number, Mo). Correlations are developed to estimate the cusp width (H*) at different angular locations and steady length of gaseous cusp θs*, which show satisfactory agreement within ±6%. Finally, an analytical model is proposed to determine the cusp width by using the relevant influencing forces acting on the cusp. A satisfactory agreement is obtained between the analytical solutions and computational results.

A new simplified sensorless direct stator field-oriented control of induction motor drives

A field-orientation scheme is a typical control technique of induction motors to obtain sophisticated performance. The stator field-oriented control is less sensitive to parameter variations than the rotor field-oriented control. In addition, the estimation of the stator flux is more accurate than that of the rotor flux. Therefore, the stator flux system is considered a good choice for variable speed drives. However, the traditional configuration of the system includes four PI controllers which need effort in tuning. In this article, simple calculations are proposed such that the configuration and performance of the stator field-oriented control systems are improved by including only two PI controllers. In addition, with the aid of the machine phase axes, a simple procedure for the speed estimation target is suggested to effectively estimate the rotor speed of the machine with a direct estimation without any need for a PI controller or additional observers in the speed observer procedure. The obtained results confirm the effectiveness of the proposed control scheme.

Modified Winding Function Analysis of Synchronous Reluctance Motor for Design Iteration Purposes

This article proposes a hybrid analytical modeling procedure for the performance parameter estimation of synchronous reluctance machine, including its operation in the region of magnetic saturation. The proposed model better estimated the torque profile through improved translation and stepped transition of rotor flux barriers. The non-linear operation is simulated by considering the global saturation and estimating the machine’s operating point on the magnetization curve of the core material. The procedure formulation focuses on improving the accuracy and rapidness of the iterative design process. The obtained results are validated against an already established design analysis technique, finite-element analysis, and the frequency spectrum analysis of practical machine results. With the improved accuracy and the least requirement of simulation runtime and computational resources, the modeling procedure can be utilized as an initial design iteration tool.

Study on the Flow Boiling Heat Transfer Characteristics of the Liquid Film in a Rotating Pipe

A three-dimensional numerical model is established to study the flow boiling heat transfer characteristics of the liquid film in a rotating pipe, and the effectiveness of the model is verified by a comparison between the numerical results and the experimental results. The effects of rotational speed, heat flux, and Coriolis force on the characteristics of heat transfer of the rotating liquid film are investigated. The conclusions are drawn as follows: (1) The convection of the rotating liquid film is enhanced while the nucleate boiling in the rotating liquid film is inhibited by the increase in the rotational speed; (2) With the influence of these two factors, the heat transfer coefficient increases with centrifugal acceleration increasing from 20 g to 40 g, then decreases with centrifugal acceleration increasing from 40 g to 120 g; (3) The turbulent intensity of the flow with Coriolis force is obviously increased compared to that without Coriolis force when the centrifugal acceleration ranges from 20 g to 80 g, which shows no increase at higher centrifugal accelerations when the turbulence is sufficiently strong. The Coriolis force also has an impact on the heat transfer coefficient of the liquid film, which should not be ignored when studying the boiling heat transfer of a rotating liquid film.

Pengaturan Torsi Motor Induksi 3 Phasa Menggunakan Direct Torque Control

The three-phase induction motor is the most widely used drive in the industry due to its sturdy construction and relatively affordable price. However, there is a disadvantage that it is difficult to control torque and speed dynamically and separately. The torque and speed characteristics of the three-phase induction motor are a couple and are nonlinear. So it is difficult to be able to control torque and speed separately. To overcome these problems, there is a decoupling control method that will separate the control between torque and speed using DTC (Direct Torque Control) by setting the value of the stator flux as a sector selector switching. DCT is a form of vector control. The least square estimation method is used for speed forecasting on induction motors through measurement data of stator flux and rotor flux which are regressed into non-linear form to monitor motor speed. Based on tests using simulations, the results show that when an induction motor is given a torque load, the torque response changes (tracking) the torque response of the induction motor can follow these changes. Where the characteristic value of the response transient , time constant (?) is 0.082 seconds, the rise time (T R ) is 0.242 seconds and the settling time (T S ) is 0.246 seconds.

An Integral Sliding Mode Stator Current Control for Industrial Induction Motor

An integral sliding mode control (ISMC) for stator currents of the induction motor (IM) is developed in this work. The proposed controller is developed in the d-q synchronous reference frame, by using the indirect field-oriented control (FOC) method. Robust asymptotic tracking of stator current components in the presence of model uncertainties and current coupling disturbance terms has been guaranteed by using an enhanced ISMC surface. More precisely, the stationary error of stator currents has been eliminated, and the accuracy of the regulators has been enhanced. According to the Lyapunov approach, it has been proven that the stator currents tracking happens asymptotically, and consequently, the stability of each loop has been demonstrated. Simulation and experimental results show the capability of the new controller in diminishing system chattering and increasing the robustness of the designed scheme, considering the variation of the plant parameters and current disturbance terms. It has been illustrated that compared with the conventional ISMC and PI regulators, the proposed current controllers provide smoother control actions and excellent dynamics. In addition, because of the precise control over the rotor flux, the rotor flux weakening method is employed to run the motor at a higher speed than the rated value.

Analysis of the operating principle of a dual-armature consequent-pole bearingless flux reversal permanent magnet machine

This paper proposes a new type of dual-armature alternating pole bearingless magnetic flux reverse permanent magnet machine, which combines the advantages of the alternating pole structure and the dual-armature structure. This machine shows the advantages of high torque density and good fault tolerance, which can not only reduce the number of permanent magnets but also further improve the machine’s torque. It is suitable for use in wind power, aerospace, and other applications. The dual-armature alternating pole bearingless magnetic flux reverse permanent magnet machine is used to improve the torque performance and suspension force. Based on the dual-armature alternating pole magnetic flux reverse machine, by adding an additional set of stator teeth to suspended windings, a new type of dual-armature alternating pole bearingless magnetic flux reverse permanent magnet machine is obtained. The number of permanent magnets is halved, and each permanent magnet has the same polarity. The ferromagnetic pole piece next to the permanent magnet automatically acts as the other pole. Based on the introduction of its related structure, the stator flux, rotor flux, stator back electromotive force, cogging torque, electromagnetic torque, etc., are analyzed. This new machine can reduce the number of permanent magnets and has a higher torque conferring advantages of output capacity and low torque ripple.

Control Strategy of a Five-Phase Induction Machine Supplied by the Current Source Inverter With the Third Harmonic Injection

In the five-phase induction machine (IM), it is possible to better use the electromagnetic circuit than in the three-phase IM. This requires the use of an adequate converter system which will be supplied by an induction machine. The electric drive system described, in this article, includes the five-phase induction machine supplied by the current source inverter (CSI). The proposed novelty—not presented previously—is the control system structures for the five-phase IM, which is supplied by CSI. The proposed control systems allow for independent control of IM state variables in the first and the second system plane to inject the third harmonic. However, the third harmonic must be suitably associated with the fundamental harmonic. In the proposed solution, the machine vector model is not transformed into the ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d–q</i> ) coordinate system that is connected to the rotor flux vector but utilizes the stationary system ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α–β</i> ). The nonlinear model linearization is based on the demonstrated nonlinear variables transformation for i-orthogonal ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α–β</i> ) (i) planes. Voltage control is applied to the control system structure. The control variables of the five-phase IM are the voltage in the dc link and the angular speed of the output current vector. In the control strategy, the control variables are determined for both system planes. Therefore, the transformation of these control variables to the dc link of CSI is proposed. The proposed control structure allows for independent control of variables in the first and second system planes. It leads to the possibility to increase the value of electromagnetic torque up to 12% for the five-phase IM, which has not been used before in the case of the machine supplied by the CSI. All theoretical issues are confirmed by experimental tests in the 5.5 kW five-phase IM.

Significance of nanoparticles aggregation and Coriolis force on the dynamics of Prandtl nanofluid: The case of rotating flow

A comparative study is provided by this article with rotational Prandtl host fluid flux of aggregated nano particles and non aggregated nano particles on linear stretching surface. Along with the chemical species diffusion, Arrhenius activation energy is examined. The nano particles thats are playing vital role in modern technology like heat exchange, electronics and material sciences are incorporated because of enhancing heat transmission. The current analysis has significant applications in rolling and manufacturing of polymer sheet, lubrication processes, crystal growing, polymer industry, biomedical and polymer industry. By applying similarity transformation to mathematical formulation based upon conservation laws yielded a related set of differential equations. For obtaining the numerical solution of non linear problem, Runge Kutta technique is employed and listed in platform of MATLAB. The goal of this study is to illustrate the comprehensive analysis of repercussions of parameters on heat, velocity and nanoparticles concentration via graphical and numerical outcomes is computed. Both velocities (f1′ and f2) reduced against amplified value of β, λ and Fr but, have increasing behavior for α1 and α2. Heat distribution is rise with growing values of Fr and λ but, reduce in case of α1 (Prandtl fluid parameter) and α2 (elastic parameter) and concentration of nano particles is higher for λ and E but, lessen for δ. It is observed that the increment and decrement in values of f1′, f2, θ, ϕ by impact of variation in values of parameters is slightly fast in non aggregated phase as compared to aggregated phase. On linearly extending surface, Nu and friction factor variational patterns are numerically calculated.

Performance Enhancement of Doubly Fed Induction Generator–Based Wind Farms With STATCOM in Faulty HVDC Grids

In this study, an investigation of different faults for a wind turbine–based doubly fed induction generator (DFIG) system is studied and the performance using a static compensator (STATCOM) is observed. The DFIG network is connected to a voltage source converter high-voltage dc link with a fault occurring near the wind generator network. The ride through capability of DFIG is promising with STATCOM using the proposed control strategy. The ac and dc voltage and torque oscillations are damped effectively, and improved power flow is observed. The low voltage AC grid fault occurs for an HVDC transmission, and the DFIG performance without and with STATCOM is compared, where the DFIG converter control schemes are developed using the proposed improved field-oriented control (IFOC) method. In this, the reference rotor flux value alters to a new synchronous speed value or a slighter value or a standstill depending on the stator voltage dip due to grid disturbance. This speed variation leads to introducing rotor current at that new rotor slip frequency as there is a change in the rotor speed because of the fault, which further decreases the stator flux dc component. Hence, this dc-offset constituent in the stator flux is alleviated and decays rapidly in scheming the divergence of the speed of the rotor to a new orientation speed with decay in the rotor flux. This operation is done in the inner control scheme of the rotor converter, which is quicker in response to the faults. Apart from this, the stator’s real and reactive power also changes accordingly based on the lookup table mechanism–based closed-loop control action of the pulse generator, and this power change is done in the outer loop. The analysis for DFIG and HVDC operation is verified under different faults without and with STATCOM.

Model reference adaptive backstepping control of double star induction machine with extended Kalman sensorless control

Introduction. Newly, the design of a controller for speed control of double star induction motor as a research focus. Consequently, backstepping technique is used to recursively construct a stable control law for speed and flux. Nevertheless, this control law coming from backstepping requires the knowledge of speed and flux values; in practice the measurement sensors are expensive and fragile. The novelty of this work consists to propose a control strategy which based on accurate Kalman filter observer that estimates speed, flux and torque. This extended Kalman filter is an optimal state estimator and is usually applied to a dynamic system that involves a random noise environment. Purpose. Apply a backstepping control of double star induction motor based on principle of rotor flux orientation. This approach consists in finding a Lyapunov function that allows deducing a control law and a modified adaptation rule is referred and sufficient conditions for the stability of the command-observer, in contrast to other techniques who use nonlinear principle. Results. The simulation results are shown to illustrate the performance of the proposed scheme under parametric uncertainties by simulation on MATLAB. The obtained results showed the robustness of the sensorless control in front of load and parameters variation of double stator induction motor. The research directions of the model were determined for the subsequent implementation of results with simulation samples.

A Quick Dynamic Torque Control for an Induction-Machine-Based Traction Drive During Square-Wave Mode of Operation

In high power traction drives using induction motors, during operation above the base speed, it is generally preferred to drive the machine in the square-wave mode since it offers maximum DC-bus utilization and reduced switching loss. However, the conventional field oriented control method cannot control the drive effectively in square-wave mode since independent control of torque and flux is difficult to achieve due to stator voltage saturation. This paper proposes a new technique to control the drive in the square-wave mode where only one degree of freedom is available for control. In the square-wave mode, the proposed method controls the torque of the machine by directly varying the stator voltage angle with respect to the rotor flux axis. The flux of the machine is kept at a required value below the saturation limit by appropriate selection of the operating point. The proposed control strategy also offers good torque dynamics in the square wave operating mode. The control algorithm is experimentally verified on a 5.5 kW induction machine drive and the experimental results are presented.

Asynchronous Machine with Wind Turbine IRFO Control

The paper deals with a squirrel cage induction generator connected to the grid through a back-to-back converter driven by vector control. The stator-side converter controls the generator torque by means of an indirect vector control scheme. In order to reduce the system dependence from the mechanical system behavior, a torque loop is used in the current reference calculations. The battery energy storage system (BESS) plays a fundamental role in controlling and improving the efficiency of renewable energy sources. Stochasticity of wind speed and reliability of the main system components are considered. The grid-side converter controls the DC bus voltage and the reactive power in order to accomplish the grid codes. Speed control using flow directional control, indirect conventionally uses proportional integral (PI) type current regulators, which achieve satisfactory objectives on torque and flow dynamics. The objective of this article is to present an indirect vector control strategy with oriented rotor flux using current regulators of the proportional integral (PI) type, applied to an asynchronous machine supplied by a voltage inverter, capable of supplying during restrictive stresses, more satisfactory torque and flux responses. The obtained simulation results upon simulation tests of the global system are developed under the MATLAB / Simulink environment and are satisfactory.

Sensorless Control of Induction Motor Based on Differential Flatness Theory and Reduced MRAS Observer

In this paper, we propose a hybrid sensorless control method of IM, This method consists of using the differential flatness theory and reduced MRAS observer. The control design proceeds by showing that each input of the motor model stands for a differentially flat system, where the flat output is chosen to be the associated state variable. Next for each regulation loop is a virtual control input is computed, that can invert the loop’s dynamics and can eliminate the system’s tracking error. The reduced MRAS observer is used to estimate the rotor speed and flux. Simulation and experimental results are presented to illustrate the effectiveness of the proposed approach for sensorless control of induction motor.