Rotor Flux Research Articles

Effective predictive current control for a sensorless five-phase induction motor drive

The paper aims to develop an effective predictive current control (PCC) procedure for a sensorless five-phase induction motor (IM) drive. The proposed PCC considers the discrete behaviour of the voltage source inverter (VSI) and provides the voltage vectors utilising the finite control set (FCS) principle, thus, there is no need for using the pulse width modulation (PWM) techniques. A combined sliding mode-Luenberger observer is used to estimate the motor speed, stator current, rotor flux, load torque, and stator and rotor resistances. An effective pole placement procedure is proposed for selecting the most appropriate gains of the observer to enhance the estimation process and to improve the observer's robustness against uncertainties in the system. The drive performance has been tested for a wide range of speed changes. The obtained results demonstrate the effectiveness of proposed PCC in obtaining high dynamic performance from the drive. Moreover, the proposed sensorless procedure has confirmed its validity to estimate precisely the required control variables.

Permanent magnet synchronous motor sensorless control based on rotor flux observer with low-pass filter adaptation

This paper presents a strategy for a permanent magnet synchronous motor sensorless vector control based on rotor flux estimation considering a rotor saliency. The integration problem in the stator flux estimation was solved by replacing the integrator with a low-pass filter. The low-pass filter parametric adaptation algorithm with phase delay compensation, based on Bode diagrams was designed for the rotor angular position estimation accuracy improving. The proposed adaption algorithm allowed to expand a stable motor control with a high accuracy in the rotor position estimation down to 15 rpm. Also the developed rotor angular position estimation algorithm together with adaptive field weakening algorithm provides a sable motor operation with a high accuracy in the rotor position estimation at the high speed.

Sliding Mode Observer for Speed Sensorless Linear Induction Motor Drives

In this paper, a sliding mode observer (SMO) for the speed-sensorless direct torque vector control of linear induction motor(LIM) is proposed, considering the influence of dynamic end effects. The proposed SMO estimate the motor speed, the rotor flux, the angular position of the rotor flux, and the speed dependent parameter w, only by using the measured stator voltages and stator currents. The nonlinear sliding mode technique guarantees very good performance for different situations of motor speed. The proposed SMO does not use complicated observer gains and robust to the parameter variation over the full-speed range. Moreover, the convergence of SMO is proven by using the Lyapunov theory. Furthermore, LIM Drive state observability is presented with detailed analysis. The performance of the proposed SMO is verified by hardware-in-the-loop test (HIL) system. Furthermore, a comparative study with and Luenberger observer(LO) and model reference adaptive system(MRAS) is presented.

A Novel Sensorless Predictive Voltage Control for an Induction Motor Drive Based on a Back-Stepping Observer-Experimental Validation

The current paper presents a novel predictive voltage control (PVC) for an induction motor (IM) without using a speed sensor. The proposed PVC is formulated using the model predictive control principle in which the stator voltages are directly controlled rather than regulating the flux and torque as in traditional MP DTC. The advantages of the proposed PVC over the commonly used MP DTC scheme are the reduced calculation time, the reduced ripples and the fast dynamic. To realize the sensorless operation of the IM, a robust observer is used to estimate the speed, rotor flux, stator current and stator and rotor resistances. The observer is constructed based on the back-stepping theory. Testing the validness of the proposed sensorless PVC technique is performed in a form of comparison between the PVC and MP DTC procedures. The tests are firstly accomplished using the Matlab/Simulink software; then, a dSPACE 1104 test board is utilized for the experimental validation. The simulation and experimental results show that the IM dynamics are effectively enhanced when applying the proposed PVC in comparison with the MP DTC performance. The back-stepping observer (BSO) also proved its ability to estimate the specified variables for different operating speeds and under parameters variation as well.

Real-Time Implementation of Extended Kalman Filter Observer With Improved Speed Estimation for Sensorless Control

This work presents an investigation on Improved Extended Kalman Filter (IEKF) performance for induction motor drive without a speed sensor. The performance of a direct sensorless vector-controlled system through simulation and experimental work is tested. The proposed observer focuses on estimating rotor flux and mechanical speed of rotor from the stationary axis components. Extended Kalman Filters’ estimation performance depends on the system matrix’s proper value ( $Q$ ) and measurement error matrix ( $R$ ). These matrices are assumed to be persistent and are calculated by the trial-and-error method. But, the operating environment affects these matrix values. They must be updated based on the prevailing operating conditions to get high speed and accurate estimates. The values of Q and R in the Improved EKF (IEKF) algorithm are obtained using the genetic algorithm. Besides, IEKF is incorporated to reduce in computational burden for real-time applications.

Advanced speed sensorless control strategy for induction machine based on neuro-MRAS observer

High-performance field-oriented motor control requires accurate knowledge of flux and speed information. Furthermore, the elimination of sensors leads to reduced overall cost and size of the electric drive system and subsequently improving its reliability. So far, Speed sensorless control of induction motors has been faced with various techniques of speed estimation. However, the main drawbacks of these models are their insufficient performance at low speeds, along with sensitivity to parameters variation, which engenders an unsteady drive system. This paper proposes an effective sensorless indirect Field Oriented control scheme for an induction motor drive. The proposed speed observer combines artificial intelligence and model reference adaptive system (MRAS). This observer is associated with the control scheme as sensorless algorithms for rotor speed and flux estimation. This conjunction is intended to enhance the conventional MRAS performance especially in low-speed regions and reduce its sensitivity to noise and system uncertainties as well. Otherwise, the effectiveness of the proposed speed estimator is tested in simulation using Matlab/Simulink software environment. The control structure is checked in the low speed with load variation.

Frequency Control of the Dynamic State of an Induction Motor Based on Forecasting

The problem of frequency control of the dynamic state of an induction motor (IM) is considered on the basis of predicting its state. The significance of L. Euler's method of the first order in the numerical solution of ordi-nary differential equations as a predictor - a tool for the formation of predicted values of control actions in de-termining the analytical designs of electric drive control systems based on IM, built using algorithms of the classical theory of the calculus of variations - is noted. It is proposed to use a digital dynamic model of IM, which is implemented on the basis of numerical methods for solving ordinary differential equations as a model that predicts the behavior of real IM. It has been established that the possible found solutions of the optimal problem of frequency control of the IM state in the form of analytical connections of control actions (frequency, voltage) with the parameters of the state estimation of the model - the IM predictor (electromagnetic torque, ro-tor speed, stator (rotor) flux linkage, etc.) can be used as predictors for real control.

Open-Loop Self-Calibration of Position Sensor Offset in SM-PMSM Drive Systems

Field-oriented control (FOC) or vector control is a formidable control strategy for permanent magnet synchronous machines (PMSMs) due to high dynamic torque response. However, FOC requires rotor flux orientation information, typically obtained using a position sensor mounted on the motor. The relative displacement between the position sensor and the rotor zero location is a key calibration required to properly orient the stator field based on the rotor magnetic field. A method is proposed herewith that enables the calibration of this relative offset between the position sensor and the rotor zero that reduces the overall manufacturing floor space and manufacturing time. The proposed scheme exploits hardware and software components that are readily available on the motor-drive system for FOC control. The self-calibration scheme generates a slowly rotating stator flux vector to rotate the motor rotor under the no-load condition to collect information about the position sensor alignment. Lack of a need for specialized measurement in comparison to conventional methods saves and space while reducing the calibration time. The novelty lies in the ability to self-calibrate and, in doing so, reduces resource utilization. Analysis, simulation, and experimental results are provided to validate the proposed methodology.

An Improved ADRC with RLS for Torque Control of Permanent Magnet Starter

Abstract This paper investigates an improved active disturbance rejection torque controller for the permanent magnet starter of micro gas turbine engine. Based on the motivation of decreasing the workload of the extended state observer and realizing the better control performance, the system disturbance is modeled in advance, and it is compensated actively in the closed-loop system. The following works have been carried out. First, in order to model the system disturbance, we identify the stator resistance, inductance and rotor flux linkage online by the recursive least square with forgetting factors method. Then, we describe the structure of the improved active disturbance rejection controller in detail and the stability of the improved extended state observer is proved. Finally, we verify the proposed controller on the Matlab/Simulink environment, and the tuning rules of different controllers are given. Simulation results illustrate that the parameters can be online identified accurately and the system disturbance can be well modeled. The speed and torque responses of the permanent magnet starter have better control performance and stronger robustness with the investigated controller, compared with the conventional active disturbance rejection controller.

Field Oriented Control of Doubly Fed Induction Motor using Speed Sliding Mode Controller

This article presents a modeling and control of the Doubly Fed Induction Motor (DFIM), associated with two inverters controlled through the Pulse Width Modulation technique (PWM), the control of the DFIM is carried out by the approach of Rotor Flux Oriented Control (RFOC) according to the direct axis. In this approach, regulation is done by classic PI regulators, the latter having undesirable overruns and static errors in non-linear systems, for that the introduction of the control by sliding mode in place of the classic PI speed regulator, that is in the form of a control law based on this type of controller since it is invariant to the non-linearity of the system and precise, stable, simple and has a good response time, in order to validate the objectives of improving the DFIM behavior in front of the reference parameters, such as the speed and the torque imposed on the machine. The results of the proposed approach are validated by its implementation on the Matlab/Simulink environment.

Sensorless Field-Oriented Control for Open-End Winding Five-Phase Induction Motor With Parameters Estimation

This paper proposes a sensorless field-oriented control (FOC) of an open-end stator winding five-phase induction motor (OESW-FPIM). The FOC technique used is associated with dual Space Vector Modulation (SVM) to provide a constant switching frequency and lower harmonics distortion. Furthermore, a simple hybrid observer is proposed which combines a model reference adaptive system (MRAS) and a sliding mode (SM) observer. The examined observer is designed for the estimation of the rotor flux and rotational speed as well as for the estimation of the load torque disturbances. Lyapunov theorem is used in this paper to prove the observer's stability. The work presented in this paper aims to enhance the researched motor's sensorless control and its robustness against external load disturbances and parameters variation. In the proposed MRAS-SM observer, the reference model is replaced by a SM model which uses a sigmoid function as a switching function to overcome the chattering problem. This combination is intended to make use of the advantages of both strategies. At the same time, to preserve the high-level performance of the sensorless FOC technique and to reduce system uncertainties, an estimation algorithm is developed to identify the rotor resistance and the stator resistance simultaneously during motor operation. The parameter estimation algorithm is combined with the proposed control to improve the speed estimation and control accuracy, particularly at low-speed operation. Finally, the effectiveness of the proposed control is validated in real-time by utilizing a hardware-in-the-loop (HIL) platform.

A Modified FOC Strategy With Optimal Rotor Flux for FTC of Star-Connected TPIMDs Against Single-Phase Open Fault

In this research, a modified field-oriented control (MFOC) strategy with optimal rotor flux for fault-tolerant control (FTC) of star-connected three-phase induction machine drives (TPIMDs) against single-phase open fault (SPOF) is proposed. First, an FTC scheme based on using an unbalanced transformation matrix (TM) for stator current components in order to control the TPIMD during SPOF is presented. Then, the model of the losses based on the extended mathematical model of the machine in the rotational reference frame is calculated. The minimum losses of the drive system are determined by the calculation of optimal flux at any operating condition. The optimal flux is then used as the reference flux in the presented FTC system. The introduced strategy with some changes can be used during normal and SPOF conditions. Simulation and experimental results are given to confirm this new FTC approach. It will be shown that the introduced method gives good results both in normal and SPOF operations.

求解二维Euler方程的旋转通量混合格式

To improve the resolution of the numerical results for the 2D Euler equations, a hybrid scheme of rotational flux was proposed. The algorithm was built under the quasi-1D idea of the rotational flux method, and the flux function was given in the form of a hybrid scheme coupling the entropy stable numerical flux satisfying the 2nd law of thermodynamics with the HLL numerical flux of good robustness. The time was advanced with the 3rd-order strongly stable Runge-Kutta method. The hybrid scheme of rotational flux has the advantages of simple structure and high resolution. Numerical results show good characteristics of the algorithm.

The Design of Low-Cost Synchronous Reluctance Motor with a Surrogate-Assisted Optimization Technique

This paper presents the performance of centrifugal pump coupled with synchronous reluctance motor of 24kW. The 4-pole 36 slots induction motor stator has been used for the prototype. The reduction of torque ripple and power losses is the main aim of research. Different arrangement of rotor flux barrier shapes has been tested through finite element analysis method. The rotor optimization carried out by varying different barrier edge angle, width of flux carriers, flux barriers and shaft diameter. The method of particle swarm optimization has been used by generating samples with surrogate assisted optimization technique for performance improvement of the motor. Distinct flux barrier shapes and designs have been checked through simulation. For the prototype development, final V-shaped best model is chosen. The proposed rotor shows the excellent performance in terms of reduced torque ripple and improved average torque in experimental results. The suggested design also has good thermal and mechanical performances with the capability to use in various industrial applications.

Nonlinear Current-Mode Control of SCIG Wind Turbines

In this paper, a nonlinear controller is proposed to manage the rotational speed of a full-variable Squirrel Cage Induction Generator wind turbine. This control scheme improves upon tractional vector controllers by removing the need for a rotor flux observer. Additionally, the proposed controller manages the performance through turbulent wind conditions by accounting for unmeasurable wind torque dynamics. This model-based approach utilizes a current-based control in place of traditional voltage-mode control and is validated using a Lyapunov-based stability analysis. The proposed scheme is compared to a linear vector controller through simulation results. These results demonstrate that the proposed controller is far more robust to wind turbulence than traditional control schemes.

Enhanced Low-Frequency Ride-Through for Speed-Sensorless Induction Motor Drives With Adaptive Observable Margin

For speed-sensorless induction motor (IM) drives, the observability of rotor speed is still a challenging problem under steady-state operations at low synchronous frequencies. To cope with this problem, an enhanced magnetizing current-oriented low-frequency ride-through method is proposed for adaptive full-order observers to ensure the observability of rotor speed. The adaptive changes of magnetizing current reference are generated to maintain the speed observable margin near zero synchronous frequency. Compared with existing methods, it avoids the noises caused by direct rotor flux reference calculation. In addition, the feedback matrix is employed to narrow the unstable regenerating region, and enlarge the observable margin. Addressing the detailed implementation, the analyses are provided with respect to output torque constraint, magnetizing current selection, and observability. Finally, the effectiveness of proposed method is validated on a 2.2 kW IM experimental bench during low-frequency ride-through.

Rotor Design and Optimization of a Three-Phase Line-Start Synchronous Reluctance Motor

Three-phase line-start synchronous reluctance motor (LS-SynRM) is started by asynchronous torque generated by the rotor conductor bars, and runs synchronously by reluctance torque generated by the inductance difference. In this article, the rotor structure of an LS-SynRM is designed and optimized, based on the theory and characteristics of LS-SynRMs during starting and steady-state operation. First, the influence of the number of rotor flux barriers and the flux barriers ratio on the dq-axis inductance is simulated, and a better structure of rotor flux barriers is obtained. Second, according to the transient theory, a method of separating each torque during the starting process of LS-SynRMs is proposed, and the main reason for the poor starting ability of the initial LS-SynRM is analyzed. Based on the optimized structure of rotor flux barriers, the influence of the area and distribution of the rotor conductor bars on the starting ability of the LS-SynRM is studied, and the structure of rotor conductor bars under the condition of starting with heavy load (constant load) is determined. Finally, through the prototype test, the rated efficiency of the LS-SynRM is 2.8% higher than that of the SCIM is replaced by three phase squirrel cage induction motor (SCIM), which verifies the accuracy of the simulated results. At the same time, the starting current and the pull-in torque under a specific inertia are tested, and the improved effect of the synchronization ability of the improved LS-SynRM was verified.

An Adaptive Identification of Rotor Time Constant for Speed-Sensorless Induction Motor Drives: A Case Study for Six-Phase Induction Machine

Accurate rotor time constant ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> ) value is necessary to ensure an acceptable performance of the indirect field-oriented control (IFOC) strategy, where a detuned <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> affects rotor flux orientation and, in turn, results in poor dynamic and steady-state response of torque. The problems associated with detuned <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> will be exacerbated in sensorless drives when a model-based speed estimation algorithm is employed. This article investigates the problem of simultaneous identification of the rotor time constant and rotor speed for sensorless IFOC of six-phase induction motor (6PIM) drives. First, an adaptive observer is proposed for online detection of the low-frequency sinusoidal signal, which is intentionally injected into the rotor flux command. Then, a novel model reference adaptive system (MRAS)-based <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> estimator is proposed using the detected signal. The Lyapunov stability theorem is used to ensure the asymptotic stability of the proposed identification system. The proposed method is based on the induction machine (IM) model in primary subspace, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> subspace. Hence, it is usable for other multiphase IM (three phases and higher). Nevertheless, the 6PIM is adopted here as a case study. The simulation and experimental results clarify the effectiveness of the proposed parallel estimation system.

Equivalent calculation of aperiodic component of thermal effect of DFIG with short circuit fault

The temperature rise caused by three-phase short current at stator side of doubly fed induction generator (DFIG) may damage DFIG and its adjacent electrical equipment. By using the step-by-step integration, the thermal effect may be quantified, but the contribution of periodic component and aperiodic component of thermal effect cannot be distinguished, and the amount of calculation is large. In this paper, the steady-state component of rotor flux is considered to reduce the error of analytical expression of short current. The components of short current are decomposed and the square of the short current is integrated. The calculation method of equivalent duration of aperiodic component of thermal effect is proposed, and the effect of equivalent duration on different crowbar resistance and stator voltage drop ratio is quantified. The simulation results are provided to validate the accuracy of the proposed models.

SPEED OBSERVER FOR SENSORLESS ENERGY GENERATION SYSTEMS BASED ON FIELD ORIENTED INDUCTION GENERATOR

The paper presents a novel adaptive speed – rotor flux linkage observer for sensorless field oriented control of induction generators. The proposed solution is based on Matsuse observer structure to- gether with specially designed correction terms and utilize current measurement and calculated stator volt- ages for real-time flux and speed reconstruction. A special coordinate transformation is used to avoid non- linear parametrization in the right side of flux linkages differential equations. Adaptive observer is designed in two steps: at the first step nonadaptive flux linkage observer is designed under condition of speed meas- urement; at the second step adaptive to rotor speed version of the flux linkage observer is designed. Infor- mation about rotor speed for adaptive flux observer is calculated by developed speed observer. A second Lyapunov’s method together with adaptive control theory are utilized for observer’s correction terms synthe- sis and stability proof. Designed adaptive observer under persistence of excitation conditions guarantees local exponential estimation of constant rotor speed and flux linkage vector components of induction ma- chine. From the practical point of view persistency excitation conditions are met if rotor flux linkages are nonzero. Proposed solution investigated by simulations. It is shown, that developed adaptive speed observer provides asymptotic estimation of induction motor currents, speed and flux linkage components under con- stant speed conditions. For varying speed proposed observer provides estimation of required variables with a small dynamic error. Proposed observer can be used in energy generation systems based on induction generators as well as in sensorless induction motor-based drive systems with constant or slowly varying ro- tor speed.