Sensorless Direct Torque Control Research Articles

Novel Speed Sensorless DTC Design for a Five-Phase Induction Motor with an Intelligent Fractional Order Controller Based-MRAS Estimator

Abstract This paper presents a fractional-order adaptive mechanism-based model reference adaptive system (MRAS) configuration for speed estimation of sensorless direct torque control (DTC) of a five-phase induction motor. In effect, the fractional-order proportional-integral (FOPI) controller parameters are obtained by the particle swarm optimisation (PSO) algorithm to enhance the MRAS observer response. Thus, the developed algorithm in the speed loop control of the DTC strategy to increase its robustness against disturbances. Moreover, a comparative study has been done of the proposed MRAS-PSO/FOPI speed estimator with the conventional MRAS-proportional-integral (PI) and the PSO-based MRAS-PI. Simulation results have carried out of the different controllers used in the adaptation mechanism of the MRAS estimator, to show the performance and robustness of the proposed MRAS-PSO/FOPI algorithm in use.

Implementation of a new flux rotor based on model reference adaptive system for sensorless direct torque control modified for induction motor

Introduction. In order to realize an efficient speed control of induction motor, speed sensors, such as encoder, resolver or tachometer may be utilized. However, some problems appear such as, need of shaft extension, which decreases the mechanical robustness of the drive, reduce the reliability, and increase in cost. Purpose. In order to eliminate of speed sensors without losing. Several solutions to solve this problem have been suggested. Based on the motor fundamental excitation model, high frequency signal injection methods. The necessity of external hardware for signal injection and the adverse influence of injecting signal on the motor performance do not constitute an advantage for this technique. Fundamental model-based strategies method using instantaneous values of stator voltages and currents to estimate the rotor speed has been investigate. Several other methods have been proposed, such as model reference adaptive system, sliding mode observers, Luenberger observer and Kalman filter. The novelty of the proposed work consists in presenting a model reference adaptive system based speed estimator for sensorless direct torque control modified for induction motor drive. The model reference adaptive system is formed with flux rotor and the estimated stator current vector. Methods. The reference model utilizes measured current vector. On the other hand, the adjustable model uses the estimated stator current vector. The current is estimated through the solution of machine state equations. Practical value. The merits of the proposed estimator are demonstrated experimentally through a test-rig realized via the dSPACE DS1104 card in various operating conditions. The experimental results show the efficiency of the proposed speed estimation technique. Experimental results show the effectiveness of the proposed speed estimation method at nominal speed regions and speed reversal, and good results with respect to measurement speed estimation errors obtained.

Sensorless DTC-SVM applied to an induction motor controlled by a three-level inverter using SMSFO

PurposeThe direct torque control (DTC) of induction motor (IM) drive is featured by high ripples in the electromagnetic torque and stator flux profiles because they are controlled by two hysteresis regulators. Furthermore, the machine flux is not directly measurable. Hence, it is better to reconstitute it from the instantaneous electrical equations of the machine. Once the stator flux is estimated, we can guarantee a reliable sensorless DTC control. Thus, the purpose of this research work is to ensure fast response and full reference tracking of the IM under sensorless DTC strategy with desired dynamic behavior and low ripple levels.Design/methodology/approachIn this work, an improved DTC strategy, which is DTC_SVM_3L, is suggested. The first step of the designed approach is to substitute the conventional inverter feeding the motor with a three-level inverter because it guarantees reduced switching losses, improved quality of voltage waveform and low-current total harmonic distortion rate. The second aim of this paper is to make the IM operate at a constant switching frequency by using the nearest three vectors-based space vector modulation (SVM) technique rather than hysteresis controllers. The third objective of this study is to conceive a sliding-mode stator flux observer, which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The stability of the proposed observer is demonstrated based on the Lyapunov theory. To overcome the load change disturbance in the proposed DTC control strategy, this paper exhibits a comparative assessment of four speed regulation methods: classical proportional and integral (PI) regulator, fuzzy logic PI controller, particle swarm optimization PI controller and backstepping regulator. The entire control algorithm was tested under different disturbances such as stator resistance and load torque variations.FindingsIt was ascertained that the IM, controlled with three-level inverter, exhibits good performances under the proposed DTC-SVM strategy based on a sliding-mode observer. The robustness of the suggested approach against parameter variations is also proved.Originality/valueThe theoretical development of the proposed control strategy is thoroughly described. Then, simulations using Matlab/Simulink software are launched to investigate the merits of the sensorless DTC-SVM command of three-level inverter-fed IM drive with different speed regulators.

A Modified Flux Observer for Sensorless Direct Torque Control of Dual Three-Phase PMSM Considering Open-Circuit Fault

This article proposes a modified flux observer for sensorless direct torque control (DTC) of the dual three-phase permanent-magnet synchronous motor. The proposed method can improve torque performance without a position sensor. The flux observer is proposed to obtain the stator fluxes and rotor fluxes. The stator fluxes can be utilized to calculate the amplitude of torque and flux for DTC system. Meanwhile, the position information can be detected from the rotor fluxes by using a normalized phase-locked loop. This new flux observer can overcome the disadvantages due to the dc bias, initial value, and harmonic components. The stability of the proposed observer is also analyzed in this article. In addition, a fault-tolerant DTC scheme for open-circuit fault is introduced. The performances of torque control and position estimation are evaluated under healthy, open-circuit fault, and fault-tolerant conditions. Simulation and experimental evaluation are carried out to confirm the effectiveness of the proposed sensorless DTC scheme.

A coordinated control method for static PV model fed pump motor system under rapid irradiation drop

AbstractPhotovoltaic (PV)‐fed motor pump system employs an advanced system that eliminates the need for batteries to reduce maintenance and equipment costs during the day in desert areas. Real‐time adjustment of the motor output speed stops the motor from drawing power from a storage capacitor in the DC link so that sensors and microcontrollers (MCU) do not lose power and restart. This paper proposes an extremum seeking control (ESC) to achieve high accuracy of the maximum power point tracking (MPPT) algorithm by improving the accuracy of current and voltage measurements. MPPT‐based motor speed vector control rule is proposed. A field‐oriented control (FOC) scheme and sensorless direct torque control (DTC) scheme are introduced for comparison. The control method and interior permanent magnet synchronous motor (IPMSM) are tested on the PV simulator and dynamometer experimental test‐rig. The test results show that the sensorless DTC can regulate the motor speed and torque to the desired value without system power failure. In contrast, the speed fluctuation of FOC control is lower than sensorless DTC. However, the system tuning time of DTC is faster and easy to support the whole system operation. The main technical contribution of this study is to provide a coordinated control method to maintain the continuous operation of the entire system during the daytime.

A new intelligent adaptation mechanism of MRAS based on a genetic algorithm applied to speed sensorless direct torque control for induction motor

A new intelligent adaptation mechanism of MRAS based on a genetic algorithm applied to speed sensorless direct torque control for induction motor

Sensorless Direct Torque Control of PMSM Based on Fuzzy Sliding Mode Control with Full Order Sliding Mode Observer

This paper presents an implementation of Fuzzy Sliding Mode Control for Sensorless Direct Torque Control (DTC) of a Permanent Magnets Synchronous Machine as a combination between the known performances of direct torque control on the one hand and the robustness of sliding mode control on the other hand. The fuzzy controller is introduced to reduce the effect of chattering phenomenon which is the major disadvantage of sliding mode control technique. The proposed controller is used to replace the conventional PI angular speed controller that generates the electromagnetic reference torque for DTC, in order to improve the dynamic and the permanent behaviors of the angular speed control response as well the electromagnetic torque. The proposed control technique is implemented without using speed or position sensors, where a Full Order Sliding Mode Observer is used. It is shown that the proposed control technique has given improved simulation results with different speed ranges and different load values.

Sensorless direct torque control based on seven-level torque hysteresis controller for five-phase IPMSM using a sliding-mode observer

This paper proposes sensorless control of the seven-level torque hysteresis controller (7LTHC) in the direct torque control (DTC) method for five-phase interior permanent magnet synchronous motor (IPMSM). Both torque response and torque ripples of the machine are directly related to the amplitude and location of voltage vectors in the hysteresis DTC method. Additionally, different level torque hysteresis controllers are used to configure a variety of voltage vectors. In this paper, 7LTHC is compared with three-level hysteresis torque controllers (3LTHCs) by using different amplitude voltage vectors to validate the DTC based on the proposed 7LTHC method in Matlab/Simulink environment. Dynamic torque response in the transient operation and low torque ripple and low stator current harmonics in the steady-state operation can be achieved by using the proposed 7LTHC. Furthermore, the speed of IPMSM which is controlled by the DTC based on the proposed 7LTHC is estimated using a sliding-mode observer (SMO) based on sigmoid function and the speed performance is enhanced by combining angle tracking observer (ATO) with the SMO. The simulation results confirm the performance of DTC based on the proposed 7LTHC using the structure of hysteresis DTC and the mathematical model of five-phase IPMSM which uses an SMO for sensorless speed control.

Sensorless Direct Torque Control of the Six-Phase Induction Motor by Fast Reduced Order Extended Kalman Filter

In this paper, a simple extended Kalman Filter (EKF) controller for direct torque control (DTC) of a six-phase induction machine in all speed ranges is proposed. The aim of this paper is to decrease the execution time of EKF modeling of a six-phase induction motor. The proposed method is fast and can operate online. If the machine parameters are changed during the operation, the EKF algorithm is activated to find parameters used for controlling the motor. In low speed, not only the motor speed measurement but also the DTC of machine is difficult. The EKF model can estimate speed, flux, load torque, and stator resistance in low speed; thus, optimization can be performed in all loads and speed range. The proposed method increases the accuracy of DTC of the six-phase induction machine and decreases the computation cost of the system using the simplified algorithm. The simulation and experimental results verify the effectiveness and the robustness of the proposed method against parameter variations.

Sensorless direct torque control based on nonlinear integral sliding mode controllers for an induction motor drive: Experimental verification

In this article, a novel sliding mode adaptation mechanism of a model reference adaptive system speed estimator and a modified sliding mode speed controller are proposed to replace the proportional-integral controller used in the adaptation mechanism of the model reference adaptive system and the proportional-integral speed controller, respectively. The suggested control strategy is designed by sensorless direct torque control with space vector modulation based on a sliding mode speed controller and a model reference adaptive system sliding mode speed estimator. The contribution of this work is the development of one control law based on a modified nonlinear component to overcome the first-order sliding mode control limitations, such as the chattering phenomenon. The performance of the suggested controller-based direct torque control with space vector modulation is verified by digital simulation with different operation conditions, like the abrupt variations in the load torque and the reference speed, using the MATLAB/SIMULINK environment. In fact, such simulation results are experimentally checked utilizing a dSPACE-1104.

Second-order sliding mode-direct torque control and load torque estimation for sensorless model reference adaptive system–based induction machine

In this article, an improved sensorless direct flux and torque control is presented for high-performance induction motor drive. This algorithm integrates the super twisting control approach with direct torque control and model reference adaptive system. The super twisting algorithm is a second-order sliding mode approach that uses a continuous control law in order solves the problems of chattering and enhances control robustness against various uncertainties. Besides, a load torque observer design bed on super twisting–based design is presented to improve the speed regulation loop and to increase its rejection ability of load disturbances. Furthermore, the stator flux model reference adaptive system is used as a sensorless algorithm for rotor speed reconstruction. The association of dual estimators can increase the control system’s reliability and reduce its cost. The effectiveness of the proposed control algorithm has been verified through simulation and experimental work using MATLAB/Simulink software and dSpace 1104 implementation board, respectively.

Sliding mode approach applied to sensorless direct torque control of cage asynchronous motor via multi-level inverter

To improve the robustness and performance of the dynamic response of a cage asynchronous motor, a direct torque control (DTC) based on sliding mode control (SMC) is adopted to replace traditional proportional-integral (PI) and hysteresis comparators. The combination of the proposed strategy with sinusoidal pulse width modulation (SPWM) applied to a three-level neutral point clamped (NPC) inverter brings many advantages such as a reduction in harmonics, and precise and rapid tracking of the references. Simulations are performed for a three-level inverter with SM-DTC, a two-level inverter with SM-DTC and the three-level inverter with PI-DTC-SPWM. The results show that the SM-DTC method achieves better performance in terms of reference tracking, while adoption of the three-level inverter topology can effectively reduce the ripples. Applying the SM-DTC to the three-level inverter presents the best solution for achieving efficient and robust control. In addition, the use of a sliding mode speed estimator eliminates the mechanical sensor and this increases the reliability of the system.

Stator Resistance Compensator Based on Model Reference Adaptive System Scheme for Sensor-Less Direct Torque Control of an Open End-Winding Induction Motor with First Coil Faults

Stator Resistance Compensator Based on Model Reference Adaptive System Scheme for Sensor-Less Direct Torque Control of an Open End-Winding Induction Motor with First Coil Faults

Performances of a Fractional-Slot Concentrated-Winding Permanent Magnet Synchronous Machine Under Position Sensorless Control in Deep Flux-Weakening Region

In recent time, the use of fractional-slot concentrated-winding (FSCW) stator has made it possible to drive the interior permanent magnet synchronous motors in very deep flux-weakening speed range. Many of such motors can operate along the maximum torque per voltage (MTPV) trajectory during the deep flux-weakening operation. Performances of the FSCW interior permanent magnet synchronous machine (IPMSM) while operating along the MTPV trajectory in the deep flux-weakening region under sensorless direct torque and flux control are yet to be investigated thoroughly. A 14-pole/18-slot FSCW IPMSM, which has a flux-weakening speed range of 9:1, was investigated in this paper. The position and speed were estimated using a sliding mode observer. Experimental results showed that satisfactory dynamic operation was possible during deep flux weakening only when a voltage compensation technique was integrated. This paper attempts to investigate the underlying reasons behind the requirement of the additional voltage compensation during deep flux weakening in the FSCW IPMSM.

An Improved Sensorless DTC Technique for Two/Three-Level Inverter Fed Asynchronous Motor

The Direct Torque Control (DTC) technique was designed to provide high performance for a three-phase asynchronous motor’s behavior by accurately controlling the flux and torque of the latter. However, this conventional DTC generates strong ripples at the level of flux and torque and a variation of the switching frequency since it uses hysteresis comparators, for this reason, the sine-triangle pulse width modulation (SPWM) has been proposed to improve it. The use of Integral Proportional Regulators (PI) allows the generation of the voltage direct and quadrature components that serve as inputs for the SPWM. The technique thus presented provides a fixed switching frequency and lower undulations at the torque and the stator flux. The objective of this work is to apply the improved DTC technique for the control of a cage asynchronous motor that will be powered by two inverters of different topologies; the first is the two-level and the second is the three-level of Neutral point clamped NPC structure. In addition, the control strategy uses a speed estimator that allows the elimination of the mechanical sensor, which greatly increases the reliability of the system. To evaluate the performance and efficiency of the proposed method, a simulation using the MATLAB / SIMULINK software and a fair comparison between the results of the two inverters will be made.

Design of Adaptive Fuzzy PI Controller for Electric Vehicle with BLDC Drives

Electric vehicles in concern with its innumerable advantages, replaces the internal combustion engine vehicles (ICEV). The efficiency and performance of the Electric Vehicle (EV) depends mainly on the electric motor and its control technique. The Brushless DC (BLDC) Motor is used as the electric motor in the EV as it has high efficiency and high starting torque. The sensorless direct torque control technique is used to enhance the performance of the EV. The Adaptive Fuzzy PI (AFPI) Controller is the proposed controller in the EV. The comparison of reference torque and actual torque produce the error. It is applied to the AFPI controller which produces an output of reference torque. The EV with stationary reference frame theory of direct torque control with AFPI controller is simulated using MATLAB/SIMULINK.

Feedback linearization based sensorless direct torque control using stator flux MRAS-sliding mode observer for induction motor drive

The high-performance Direct Torque Control (DTC) 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. This paper proposes an effective sensorless direct torque control scheme for induction motor drive. The proposed scheme consists of enhancing the decoupling structure and variable estimation as well. Therefore, an enhanced direct flux and torque control based on feedback linearization is implemented in one hand. This allows obtaining a linear decoupled control together with minimized flux and torque ripples. In another hand, a combined sliding mode observer and model reference adaptive system is associated with the control scheme as sensorless algorithms for rotor speed and flux estimation. This conjunction is intended to enhance the sliding mode observer performances especially at low speed operations and reduce its sensitivity to noise and system uncertainties as well. The effectiveness of the proposed control algorithm has been verified through simulation and experimental work using MATLAB/Simulink software and dSpace 1104 implementation board respectively.

Reduced-Sensor-Based PV Array-Fed Direct Torque Control Induction Motor Drive for Water Pumping

This paper aims at the design, control, and implementation of a solar photovoltaic (PV) array-fed speed sensorless direct torque control of an induction motor drive (IMD) for water pumping in a standalone as well as battery-connected hybrid mode. This stator flux estimated by the proposed flux observer is used for speed estimation. A dc-link current sensor is used to reconstruct the motor phase currents by modified active voltage vector. One voltage sensor for dc-link voltage sensing and only one current sensor for dc-link current sensing are used in this system for standalone operation of the system. All other required quantities are estimated through these two sensed signals. The IMD is energized by a PV array, which is operated at maximum power point (MPP). A perturb and observe control algorithm with additional flow rate controller is proposed for MPP, which tracks MPP throughout the operating range and provides the facility to control the flow rate. The suitability of the system is judged through simulated results in MATLAB/Simulink as well as test results obtained on a prototype developed in the laboratory.

Position sensorless direct torque control for six‐phase permanent magnet synchronous motor under two‐phase open circuit

A position sensor is usually required in the existing fault-tolerant direct torque control (FT-DTC) system for the multiphase permanent magnet synchronous motor (PMSM). Thus, the volume, weight, and cost of the system is increased, and the reliability is decreased. The conventional high-performance position sensorless strategies for the multiphase motor under fault-free condition cannot be directly applied to FT-DTC system. To improve this situation, a high-speed position sensorless FT-DTC strategy for a six-phase symmetrical winding PMSM with two opened phases is proposed in this study. Firstly, modified variables and a new rotating coordinate system are defined to achieve the symmetrical and decoupled mathematical model. Secondly, a stator flux observer based on the modified variables and a new coordinate system is proposed. According to the current model of modified stator flux, the estimated modified stator current can be achieved. Then, the estimated error of the modified stator current is sent to the integrator of the modified stator flux observer to correct the voltage model. Finally, the proposed stator flux observer is applied in FT-DTC for six-phase PMSM with two opened phases to realize the position sensorless operation at high speed. The experimental results verify the feasibility and effectiveness of the proposed strategy.

Sensorless DTC of BDFRG using LMS algorithm for wind energy conversion systems

This paper presents a new sensorless speed and secondary winding resistance estimation technique for brushless doubly fed reluctance generator (BDFRG) using least mean square (LMS) algorithm. Detailed mathematical derivation of the algorithm is explained and simulation results in MATLAB Simulink are shown for sensorless direct torque control (DTC) of BDFRG using LMS algorithm. A comparison to traditional speed estimation technique for BDFRG using primary winding flux linkage formula in stationary frame is then held to show the advantages of this proposed technique over the traditional method of speed estimation. Power electronics of the drive system is also simulated to consider effect of harmonics injected by electronic switches on both algorithms.