Direct Field-oriented Control Research Articles

Rapid Prototyping and Hardware-In-the-Loop Verification of Enhanced Sliding Mode Control of an Asynchronous Machine Using a Xilinx System Generator and an FPGA-Zynq Board

This article describes rapid prototyping using the Xilinx system generator (XSG) of a direct field oriented control (DFOC) strategy based on improved super twisting sliding mode controllers (ISTSMCs) of an asynchronous machine to succeed a hardware implementation on a field programmable gate array (FPGA) board. The main goal is to enhance regulation loops governing rotor speed, rotor flux, and stator current components within the classical DFOC structure. These ISTSMCs replace integral proportional controllers, resulting in improved system dynamics, faster speed and torque responses, and heightened robustness against load and rotor resistance variations, surpassing other control methods. Additionally, the article aims to implement this DFOC-ISTSMC method on an FPGA board to reduce control system sampling time and loop delays, leveraging the FPGA’s parallel processing capabilities. The hardware architecture is designed using XSG in the MATLAB/Simulink environment, enabling effective simulation, testing, discrete algorithm creation, and VHDL code generation for FPGA implementation via the hardware-in-the-loop (HIL) process. Assessment involves digital simulation studies and HIL processes using XSG with a Xilinx FPGA Zynq 7000 under MATLAB/Simulink, demonstrating improved system performance, reduced time delays, and efficient FPGA utilization. This approach validates the effectiveness of the proposed DFOC-ISTSMC algorithm in enhancing control strategy for asynchronous machines.

Direct Field-Oriented Control of Induction Motor with Discrete Full-Order Flux Observer

Direct Field-Oriented Control of Induction Motor with Discrete Full-Order Flux Observer

Implementation of Indirect Field Oriented Control Using Space Vector Pulse Width Modulation for the Control of Induction Motor

For the efficient speed control of three phase Induction motor, the Vector control or Field oriented control (FOC) technique is used for the Voltage source inverter. In implementing FOC the angular position of the rotor flux vector is to be determined. There are two methods (direct and indirect) of vector control for the evaluation of rotor angle. In an Indirect field-oriented control (IFOC) method rotor angle is estimated from slip frequency and rotor frequency without using a sensor (sensors are used in direct FOC) which are achieved in a synchronously rotating frame. IFOC produces high performance in induction motor drives by decoupling rotor flux and torque, so it can be separately controlled by stator direct-axis current and quadrature-axis current respectively, like in a DC motor. The rotor flux orientation method is used for incorporating PI control system using the Space Vector Pulse Width Modulation (SVPWM) technique. The Induction motor drive control generally involves three different PI controllers for torque, speed, and flux respectively. Through the simulation result, varying the load torque, and reference speed is achieved within a few milliseconds, and the behavior of the separately excited DC motor is observed.

A novel control method for improving reliability of 3‐phase induction motor drives under the stator winding open‐circuit fault

AbstractPost‐fault control of a 3‐phase Induction Motor (IM) drive under the Stator winding Open‐Circuit Fault (SOCF) has gained significant importance in recent years especially for safety‐critical industrial applications. Nevertheless, most of proposed schemes suffer from low accuracy or high complexity. In this research, a novel control scheme for improving reliability of wye‐connected 3‐phase IM drives under the SOCF according to Direct Field‐Oriented Control (DFOC) is proposed and evaluated. In the proposed system, different transformations are presented and employed to control the faulty system. The controller is achieved by minor modifications in the traditional control scheme structure. In the proposed system, an Extended Kalman Filter (EKF) is also used to estimate the rotor flux. The designed EKF‐based DFOC (DFOCEKF) is verified using simulations and experimental tests conducted on a 0.75 kW 3‐phase IM drive. Based on the results it can be calculated that the torque ripple is decreased clearly after the proposed fault‐tolerant control approach is applied. The DFOCEKFstrategy can control the faulty motor accurately, which can further improve the reliability of IM drive systems. The results also confirmed that the proposed controller after the SOCF has faster dynamic response and higher accuracy compared to previous published papers.

Optimized Kalman filters for sensorless vector control induction motor drives

<span lang="EN-US">This paper presents the comparison between optimized unscented Kalman filter (UKF) and optimized extended Kalman filter (EKF) for sensorless direct field orientation control induction motor (DFOCIM) drive. The high performance of UKF and EKF depends on the accurate selection of state and noise covariance matrices. For this goal, multi objective function genetic algorithm is used to find the optimal values of state and noise covariance matrices. The main objectives of genetic algorithm to be minimized are the mean square errors (MSE) between actual and estimation of speed, current, and flux. Simulation results show the optimal state and noise covariance matrices can improve the estimation of speed, current, torque, and flux in sensorless DFOCIM drive. Furthermore, optimized UKF present higher performance of state estimation than optimized EKF under different motor operating conditions.</span>

Analysis of the Drive of the Electric Vehicle with Six-Phase Induction Motor

Abstract The article presents the analysis of the drive system of the electric vehicle with a six-phase induction motor. The mathematical models of the six-phase induction motor and model reference adaptive system (MRASF) estimator are presented, and the description of the voltage source inverter, space vector modulator and bidirectional buck–boost converter is shown. The direct field-oriented control (DFOC) system and the direct torque control with space vector modulation (DTC-SVM) system are analysed. Results of simulation studies of these control methods and comparative analysis are shown. The DTC-SVM method is selected as the method with the best properties, and a full model of the electric vehicle drive system is built using this method. The detailed description of the drive system of the electric vehicle with a six-phase induction motor and DTC-SVM control system and the results of simulation tests for this drive system are presented. The aim of the authors and an element of novelty is to develop and test a drive system for an electric vehicle with a six-phase induction motor, adaptive speed estimator and extensive space vector modulator.

Induction Generator with Direct Control and a Limited Number of Measurements on the Side of the Converter Connected to the Power Grid

The article presents an induction generator connected to the power grid using the AC/DC/AC converter and LCL coupling filter. Three-level inverters were used in the converter, both from the generator side and the power grid side. The algorithm realizing Pulse Width Modulation (PWM) in inverters has been simplified to the maximum. Control of the induction generator was based on the Direct Field-Oriented Control (DFOC) method. At the same time, voltage control has been used for this solution. The MPPT algorithm has been extended to include the variable pitch range of wind turbine blades. The active voltage balancing circuit has been used in the inverter DC voltage circuit. In the control system of the grid converter with an LCL filter, the number of measurements was limited to the measurement of power grid currents and voltages. Synchronization of control from the power grid side is ensured by the use of a PLL loop with the system of preliminary suppression of undesired harmonics.

Direct Field Orientation Control Based on H∞ Method of Wind Turbine Based on DFIG

This study aims to propose the direct field orientation control based on the H-infinity method (DFOC_ H∞) scheme for controlling the stator power (active/ reactive) of a direct drive vertical axis wind turbine power system based on a doubly fed induction generator (DFIG). the sensitivity to parameters uncertainty of the machine presents the major drawback of the PI controller, in order to cope with this problem; the H-infinity method was used to solve it. The proposed controller H∞ is evaluated with Matlab/Simulink. Simulation results showed that the suggested H∞ controller has a good performance in terms of enhancing the quality of energy provided to the power network. Even in the presence of DFIG parameter variation.

Postfault Direct Field-Oriented Control of Induction Motor Drive Using Adaptive Virtual Current Sensor

Electric drives immune to failures of selected elements of the power system or measuring sensors have been the subject of research in recent years, due to the growing interest in systems with an increased level of safety. This article concerns the analysis of the direct field-oriented control induction motor drive after the failure of all stator current sensors. An adaptive virtual current sensor (AVCS) was used to estimate the stator current, based on the measurement of the motor angular velocity and the voltage in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{DC}\ (u_{\text{DC}})$</tex-math></inline-formula> of the voltage-source inverter. This article presents the possibility of improving the accuracy of stator current estimation using the original approximation of changes in rotor resistance depending on the drive operating point when the measurement information about the stator current has been lost. This approximation was determined experimentally during the normal operation of the drive using a rotor resistance estimator. The determined approximate lookup functions were used to adapt the rotor resistance in the AVCS during the drive system operation in a postfault mode. This approach has made it possible to significantly improve the accuracy of the stator current reconstruction, especially under low speeds and load torques, which was demonstrated in experimental studies <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</b>

Influence of Selected Non-Ideal Aspects on Active and Reactive Power MRAS for Stator and Rotor Resistance Estimation

Mathematical models of induction motor (IM) used in direct field-oriented control (DFOC) strategies are characterized by parametrization resulting from the IM equivalent circuit and model-type selection. The parameter inaccuracy causes DFOC detuning, which deteriorates the drive performance. Therefore, many methods for parameter adaptation were developed in the literature. One class of algorithms, popular due to their simplicity, includes estimators based on the model reference adaptive system (MRAS). Their main disadvantage is the dependence on other machines’ parameters. However, although typically not considered in the respective literature, there are other aspects that impair the performance of the MRAS estimators. These include, but are not limited to, the nonlinear phenomenon of iron losses, the effect of necessary discretization of the algorithms and selection of the sampling time, and the influence of the supply inverter nonlinear behavior. Therefore, this paper aims to study the effect of the above-mentioned negative aspects on the performance of selected MRAS estimators: active and reactive power MRAS for the stator and rotor resistance estimation. Furthermore, improved reduced-order models and MRAS estimators that consider the iron loss phenomenon are also presented to examine the iron loss influence. Another merit of this paper is that it shows clearly and in one place how DFOC, with the included effect of iron losses and inverter nonlinearities, can be modeled using simulation tools. The modeling of the IM and DFOC takes place in MATLAB/Simulink environment.

Third-Order Sliding Mode Applied to the Direct Field-Oriented Control of the Asynchronous Generator for Variable-Speed Contra-Rotating Wind Turbine Generation Systems

Traditional direct field-oriented control (DFOC) techniques with integral-proportional (PI) controllers have undesirable effects on the power quality and performance of variable speed contra-rotating wind power (CRWP) plants based on asynchronous generators (ASGs). In this work, a commanding technique based on the DFOC technique for ASG is presented on variable speed conditions to minimize the output power ripples and the total harmonic distortion (THD) of the grid current. A new DFOC strategy was designed based on third-order sliding mode (TOSM) control to minimize oscillations and the THD value of the current and active power of the ASG; the designed technique decreases the current THD from ASG and does not impose any additional undulations in different parts of ASG. The designed technique is simply implemented on traditional DFOC techniques in variable speed DRWP systems to ameliorate its effectiveness. Also, the results show that by using the designed TOSM controllers, in addition to regulating the active and reactive powers of the ASG-based variable speed CRWP system, the THD current and active power undulations of the traditional inverters can be minimized simultaneously, and the stator current became more like a sinusoidal form.

Measures and Simulations of Induction Machines Flux Linkage Characteristics Based on Rotor Field Orientation

The focus of this work is on the experimental measurement and the proper finite-element prediction of stator and rotor flux linkages for induction machines. The purpose is to characterize the stator and rotor flux linkages adopting a rotor field-oriented reference frame. The proper basic set of equations is inspired by the direct field-oriented control approach, in order to indirectly derive the rotor flux linkage from the measurement of the stator flux. The proposed method requires a small set of preliminarily known parameters, such as the stator resistance and the overall leakage inductance. Moreover, the only measured quantities are voltages and currents, from which the flux linkages are derived. The adopted strategy also allows to estimate electromagnetic torque and rotor resistance, using the rotor field-oriented model equations. A complete finite-element validation reported for comparison.

A Synergetic Sliding Mode Controller Applied to Direct Field-Oriented Control of Induction Generator-Based Variable Speed Dual-Rotor Wind Turbines

A synergetic sliding mode (SSM) approach is designed to address the drawbacks of the direct field-oriented control (DFOC) of the induction generators (IGs) integrated into variable speed dual-rotor wind power (DRWP) systems with the maximum power point tracking (MPPT) technique. Using SSM controllers in the DFOC strategy, the active power, electromagnetic torque, and reactive power ripples are reduced compared to traditional DFOC using proportional-integral (PI) controllers. This proposed strategy, associated with SSM controllers, produces efficient state estimation. The effectiveness of the designed DFOC strategy has been evaluated on variable speed DRWP systems with the MPPT technique.

A Novel Flux State-based Control Method for Improved Dynamic Performance of Induction Motor

ABSTRACT Induction machine (IM) is widely used in industries because of certain advantages. In previous research studies, investigations were completed to analyze the machine flux behavior in different reference frames such as Stationary and Park’s, however, the analysis and comparison for the wide-ranging machine flux behavior, in synchronously rotating stator field-oriented, and rotor-oriented reference frames, is not offered particularly during transients. In addition, the dynamically accurate torque and flux control is an essential requirement for high-performance induction motor drive. A number of techniques, including direct and indirect field-oriented control, direct torque and direct power control techniques, have been developed; however, most of them apply certain approximation criteria to optimize the linear system. It results in inaccurate tuning of respective current, torque and flux controllers, which deteriorates the dynamic performance. In this paper, a novel flux state-based nonlinear control method is presented which results in improved dynamic performance of induction motor drive. The proposed control method is simulated in the MATLAB/Simulink environment and experimentally validated on a 0.75 kW IM. The obtained results show the effectiveness of the proposed flux state-based control method for improved dynamic performance of induction motor drive.

Self-Tuning Observer for Sensor Fault-Tolerant Control of Induction Motor Drive

This paper introduces a new solution for the speed and current sensor fault-tolerant direct field-oriented control of induction motor drives. Two self-adjusting observers derived from a modified current-based model reference adaptive system (CB-MRAS) are presented. Finally, the recursive least squares method was used to estimate the parameters of the used observers. The method, in the proposed solution, provides a very fast and accurate finding of the observer parameters while maintaining relative simplicity and ease of implementation. The presented algorithm eliminates the CB-MRAS observer dependence on the induction motor parameters and also compensates for the inaccuracies in the evaluation of the stator voltage vector. The proposed fault-tolerant control offers the drive operation while either a speed sensor or one/two current sensors fault occurs. The drive still works with the direct field-oriented control even when no current sensors are healthy. The proposed scheme was simulated in the MATLAB/Simulink software environment. Then the algorithm was implemented in a floating-point digital signal controller (DSC) TMS320F28335 and tested on an induction motor drive prototype of rated power of 2.2 kW to validate the proposed schemes.

A novel direct field‐oriented control strategy for fault‐tolerant control of induction machine drives based on EKF

AbstractThis article presents a novel Direct Field‐Oriented Control (DFOC) strategy for Fault‐Tolerant Control (FTC) of wye‐connected 3‐Phase Induction Machine (3‐PIM) drives under the stator winding open‐phase failure. In the proposed control strategy, instead of flux measurement, an Extended Kalman Filter (EKF) for flux estimation is used. The introduced controller with minor modifications can be used during normal and stator winding open‐phase failure conditions. With the proposed DFOC system, the speed and torque pulsations that normally happen during the open‐phase failure can be reduced. The performances of the proposed EKF‐based DFOC strategy and the conventional control strategy for a faulted machine using simulations and experiments under different operation conditions are compared. Simulation and experimental results demonstrated an important improvement in speed and torque pulsations through this type of fault. Results also confirmed the superiority of the proposed EKF‐based DFOC scheme over the conventional control scheme to balance the faulted machine phase currents.

Nonlinear flux observer-based feedback linearisation control of IM drives with ANN speed and flux controller

ABSTRACT In this paper, ANN speed and flux controller for feedback linearisation control (FLC) IM drive with nonlinear flux observers are proposed to achieve an accurate and fast dynamic response over a wide operating range. Because of the nonlinearity in IM, a linear PI controller with direct field oriented control (DFOC) IM drive, gives the poor performance, longer convergence time and limited disturbance capability. Therefore, a nonlinear flux observer is developed for intelligent FLC using a modified LPF to reduce the dc offset, which minimises torque ripple, flux ripple and also reduces current THDs. Dynamic performances are simulated in MATLAB/Simulink environment and simulation results are validated experimentally. A relative comparative analysis is also carried out between classical field-oriented controlled induction motor drive and the proposed method. From the results obtained, it is observed that the proposed method is superior to FOC IM drive in terms of fast dynamic response, better speed tracking dynamics and reduction of, current THDs, torque and flux ripples.

Direct field-oriented control strategy for fault-tolerant control of induction machine drives based on EKF

This study presents a novel direct field-oriented control (DFOC) strategy for fault-tolerant control of wye-connected three-phase induction machine drives under the stator winding open-phase failure. In the proposed control strategy, instead of flux measurement, an extended Kalman filter (EKF) for flux estimation is used. The introduced controller with minor modifications can be used during normal and stator winding open-phase failure conditions. With the proposed DFOC system, the speed and torque pulsations that normally happen during open-phase failure can be reduced. The performances of the proposed EKF-based DFOC strategy and the conventional control strategy for a faulted machine using simulations and experiments under different operation conditions are compared. Simulation and experimental results demonstrated an important improvement in speed and torque pulsations through this type of fault. Results also confirmed superiority of the proposed EKF-based DFOC scheme over the conventional control scheme to balance the faulted machine phase currents.

Model Predictive Base Direct Speed Control of Induction Motor Drive—Continuous and Finite Set Approaches

In the paper a comparative study of the two control structures based on MPC (Model Predictive Control) for an electrical drive system with an induction motor are presented. As opposed to the classical approach, in which DFOC (Direct Field Oriented Control) with four controllers is considered, in the current study only one MPC controller is utilized. The proposed control structures have a cascade free structure that consists of a vector of electromagnetic (torque, flux) and mechanical (speed) states of the system. The first investigated framework is based on the finite-set MPC. A short horizon predictive window is selected. The continuous set MPC is used in the second framework. In this case the predictive horizon contains several samples. The computational complexity of the algorithm is reduced by applying its explicit version. Different implementation aspects of both MPC structures, for instance the model used in prediction, complexity of the control algorithms, and their properties together with the noise level are analyzed. The effectiveness of the proposed approach is validated by some experimental tests.

Torque ripple mitigation in FCS-MPDTC of PMSM Drive using an Adaptive Fuzzy Logic Modulator

This paper presents the use of the fuzzy logic duty cycle concept in the finite-control-set model predictive direct torque control (FCS-MPDTC) strategy to mitigate the torque ripples of a surface-mounted permanent magnet synchronous motor (PMSM) drive. In fact, MPDTC is a simple and powerful tool to overcome the main drawbacks associated with the commonly used control strategies like direct torque control (DTC) and field-oriented control (FOC). However, the conventional-MPDTC selects only one voltage vector (VV) per sampling period and this procedure leads to increase relatively the torque ripple. In order to further improve the torque control performance, an adaptive fuzzy logic-based duty cycle modulation is utilised and two VV's instead of single VV are applied during the whole control cycle. The performances of the proposed control scheme are simulated and compared to those obtained with conventional-MPDTC. The simulation results show that the proposed AFLM-MPDTC can effectively mitigate the torque ripples, even under severe operating conditions.