Torque Control Of Induction Motor Research Articles

Optimized Anti-Windup Coordinating Strategy for Torque-Maximized High-Speed Flux-Weakening Operation of Constrained Induction Motor Drives

Due to the contradiction between torque-maximized requirements and limited voltage and current constraints, voltage closed-loop flux-weakening strategy is developed to circumvent the saturation problem for maximum torque control of induction motor when the accelerating speed enters high-speed region. At the same time, since voltage inconsistency caused by the saturation is employed to construct flux-weakening controller (FC), anti-windup (AW) item in current regulator needs to be cut off to avoid the conflict. However, the replacement discards part of AWs utility and results in the distortion of command voltage, thus compromising system’s dynamic performance and making the tuning process of proportional-integral controller (PI)-based FC much trickier. To address this issue, an equivalent saturation model is presented. An optimized AW coordinating strategy is proposed, combining a novel structure, so-called virtual voltage buffer, with FC. Through an equivalent proof, it can be transformed into over-modulation block for a convenient implementation. Through its compensation in the transient period, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis current can be quickly and smoothly manipulated in a more concise tuning process. As a result, the overall system possesses a fast acceleration capability with maximum torque and a wide speed range, while retaining a desirable system response. Simulation and experimental results verify the effectiveness of proposed method.

Fuzzy-based estimation of reference flux, reference torque and sector rotation for performance improvement of DTC-IM drive

In this study, the fuzzy-based reference flux estimator (RFE), reference torque estimator (RTE) and sector rotation strategy called fuzzy logic estimator are proposed to direct torque control of induction motor (DTC-IM) drive for performance improvement. The basic DTC-IM drive with conventional RFE, RTE and sector division causes large torque ripple, variable switching frequency and uneven voltage vector contribution in stator flux. The torque and speed responses of the proposed system are investigated with load variations. The simulation results of the proposed DTC-IM drive are compared with the basic DTC-IM drive. The assessment of the proposed system shows improved performance. A hardware is developed using Xilinx Spartan-6XC6SLX45-Field Programmable Gate Array (FPGA) Kit for experimental verification of the results. Moreover, sinusoidal pulse width modulation and space vector pulse width modulation techniques are applied to reduce the torque ripples. The performance of the drive is investigated for various speed ranges. The comparison of the simulated and experimental results proves that the proposed fuzzy-based DTC-IM drive provides better performance than the basic DTC-IM drive.

Sliding Model-Based Predictive Torque Control of Induction Motor for Electric Vehicle

This article presents a sliding model-based predictive torque control (S-PTC) of an induction motor for the electric vehicle application. In this work, a battery-operated bidirectional converter fed induction machine-driven power train system is considered. In the conventional predictive torque control (C-PTC), only the machine model is used for the prediction of stator flux, current, and electromagnetic torque. Unlike the C-PTC, the presented control scheme offers a nonlinear switching feedback term in the prediction equation to overcome the model uncertainties, disturbances, and variation in motor parameters. The gains of the feedback terms are selected based on the Lyapunov stability criterion. Adaptive full order observer is used for the estimation of speed and rotor flux. This method is implemented and the speed response and torque ripple of the motor are analyzed for various operating modes of the vehicle. The robustness of the control is verified for variation in motor parameters and a comparison is shown to justify the achievement of objectives through S-PTC than with C-PTC. The control algorithm for the developed system is verified experimentally through the laboratory prototype.

Improved Direct Torque Control of Induction Motor for Torque Ripple Minimization

A new direct torque control (DTC) method of an induction motor (IM) which minimizes torque ripple <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\left ({T_{ripp} }\right)$ </tex-math></inline-formula> while preserving all the conventional DTC advantages is presented in this paper. Large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{ripp}$ </tex-math></inline-formula> and current ripple are the main drawbacks of the conventional DTC. To address this problem, this paper gives a qualitative analysis of the main <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{ripp}$ </tex-math></inline-formula> sources of the conventional DTC. A novel strategy to reduce <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{ripp}$ </tex-math></inline-formula> in the constant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T$ </tex-math></inline-formula> and in the field weakening (FW) regions is proposed. The performance of the proposed method is evaluated and compared with a recently published method that aims for the same goals that are pursued in this paper, as well as with the conventional DTC. The analysis has been carried out on the basis of the results obtained by theoretical analysis and hardware implementation.

Processor in the Loop Comparative Study of Indirect Rotor Field Oriented Control, Direct Self Control, Direct Torque Control and Space Vector Modulation Based Direct Torque Control for Induction Motor Drives

This work proposes a design and implementation, using Processor In the Loop technique, of several control strategies of the induction motor. Therefore, this paper offers a validation, by experimentation, of Direct Self Control, Direct Torque Control and its variants, Space Vector Modulation based Direct Torque Control and Indirect Rotor Field Oriented Control. These control strategies are also compared by waveforms quality, switching frequency and complexity of the algorithms running in an actual Digital Signal Processor. For code generation and algorithm validation, MATLAB/Simulink R2017b and Code Composer Studio are used. For implementation, LAUNCHXL-F28069M development board, based on TMS320F28069 from Texas instruments, is chosen. Results of this comparative study, using Processor In the Loop technique, show that Space Vector Modulation based Direct Torque Control strategy offers the best performances compared to the other Direct Torque Control strategies; and it is, in addition, less complex than the Indirect Rotor Field Oriented Control strategy.

Influence of the stator current reconstruction method on direct torque control of induction motor drive in current sensor postfault operation

Influence of the stator current reconstruction method on direct torque control of induction motor drive in current sensor postfault operation

Direct torque control of induction motor with different energy storage for electrical vehicle (EV) application

Energy demand worldwide is rising at an unprecedented pace. This has already shown its impact on the depletion of energy sources and environmental issues (global warming and the weakening of the ozone layer). This growing pattern of energy insufficiency will, of course, intensify in the future. Referring to the literature, significant energy savings can be achieved by controlling the speed of the electric motor system using variable frequency drives (VFDs). Efficient control of induction motor drives provides an excellent opportunity for energy savings. As a result, research into the optimal operation of induction motor drives is escalating and mainly focuses on the Direct Torque Control (DTC) control technique on improving the dynamic operation of torque control. However, the study on the type of energies on improving the dynamic response is least reported. This paper will study the effect of different energy supplies on the dynamic response of torque performance. The standard DC battery and supercapacitor will be used to energize the induction motor through the three-phase inverter and controlled with the DTC control scheme. The results are validated through MATLAB Simulink and it shows the supercapacitor has the better dynamic response in torque response compared to the standard DC battery. The comparative results are presented in a proper mannered way.

Direct Torque Control of Induction Motor Based on Particle Swarm Optimization

Induction Motor (IM) is most commonly used in different industrial applications, that require fast dynamic response and accurate control over wide speed ranges. Therefore, this paper proposes high performance Direct Torque Control (DTC), which is closed loop control system to improve the dynamic performance of IM. The main objective of this work is to improve the speed response of IM during different load and speed conditions. Proportional-Integral (PI) controller based on Particle Swarm Optimization (PSO) technique is used for optimal gains tuning. The results show the improvement in the speed response of DTC using PSO technique when compared with conventional PI and the conventional DTC (without PI), in terms of reducing steady state error, settling time, overshoot and ripple reduction which make this controller more robust to variation in load and speed. The simulation of the overall drive system is performed using MATLAB/Simulink program version 7.10 (R2010a).Keywords: Induction Motor (IM), Direct torque control, PI controller and Particle Swarm Optimization (PSO).

Sensorless fuzzy direct torque control of induction motor with sliding mode speed controller

In this work, a fuzzy direct torque control (DTC) is developed for asynchronous motor drive powered by two-level inverter. The main objective is to enhance the system performance by reducing electromagnetic torque and stator flux ripples while improving stator current waveforms. The hysteresis comparators and voltage vector switching table of classic DTC are replaced by fuzzy logic block to ensure robust control against various disturbances. The outer speed loop is initially executed by PI regulator and secondly by sliding mode controller, for both systems stator flux MRAS estimator is adopted. A critical and comparative study between the DTC based on fuzzy logic and non-linear sliding mode DTC was done under MATLAB/SIMULINK. The performance analysis was carried out under different operating conditions such as steady and transient states, low , medium and high speeds, speed reversal and application of two different loads at various times.

Predictive torque control of induction motor drive with reduction of torque and flux ripple

Predictive torque control of induction motor drive with reduction of torque and flux ripple

Direct Torque Control of Induction Motors using Speed Estimator

A new approach to Direct torque control of induction motor is presented in this paper.A ripple in torque of the induction motor is a very common problem and it is to bereduced. In conventionalDTCmethodstheinverter has constant switching frequency and is dramatically increased. In proposed DTC based induction motor drive, an improved space vector modulation technique is applied to inverter control, therefore reducingthe torque/speed ripples. As the proposed approach does not include any dead beat control or hysteresis control, it automatically reduces computational calculations. Simulation results of proposed DTC based induction motor drive technique is validated using MATLAB/SIMULINK environment

Induction motor drive based on direct torque controlled used multi-pulse AC-DC rectifier

This paper presents the direct torque-controlled induction motor drives (DTCIMDs) based on a retrofit 44-pulse rectifier (44PR). A 22-phase polygon autotransformer (PA) is designed to supply the rectifiers. The above structure improves the power quality standards in the power grid and complies with the requirements of the IEEE-519 standard for different loads. Besides, a power factor close to one is obtained for a wide range of DTCIMD performance. The results show that the total harmonic distortion (THD) of the input current under variable loads for 44PR is less than 3%.

Accurate Torque Control for Induction Motors by Utilizing a Globally Optimized Flux Observer

High-precision torque estimation and control of induction motor drives is an important research field due to the extensive use of these motors in torque controlled applications, for example, in electric vehicles. The open-loop torque control performance depends strongly on the accuracy of both the motor model and the flux estimation. To address this appropriately, an adaptive Kalman filter with offline parameter and observer design optimization is proposed in this article. Thereby, the basic induction motor model is extended by magnetic saturation, iron losses, and skin effect influences. All uncertain motor model and observer configuration parameters are offline identified by a global optimization technique, namely particle swarm optimization. The identification utilizes a comprehensive data set consisting of test bench measurements and leads to an optimized observer enabling precise torque estimation and control. In experimental validation, for both torque estimation and control, the root-mean-square error is below 1 % of the nominal torque over the entire operating range. With the help of an accurate gray-box inverter model for phase voltage estimation and a speed-adaptive Kalman filter tuning scheme, the proposed observer is able to operate also at slow speeds including standstill.

Modified model predictive torque control for induction motors with improved robustness against mutual inductance mismatching

This article proposes a new model predictive torque control (MPTC) for induction motors to improve its robustness against parameter mismatching when current model (CM) for flux estimation is employed. The main advantages of the proposed method are the improved range of stable operation during the occurrence of mutual inductance Lm, mismatched value, lower computational burden, and reduced switching losses. The improvement in robustness is achieved via adaptation of direct torque control (DTC) features thus eliminating any additional parameter estimation mechanism. Reference transformation is used to remove torque error from the cost function to achieve weighting-factor-free MPTC formulation. Then, based on the estimated and reference stator flux vector positions, it is established that flux positional error is directly proportional to the torque error. The positional error is then employed to reduce the admissible voltage vectors, which decreases parameter dependence of MPTC. The simulation results are compared to two other well-established MPTC techniques and based on the results, it is concluded that the proposed MPTC without parameter estimation and compensation technique have a wider tolerability of 56% for Lm mismatching.

Improved Performance of Direct Torque Control with PMSM compared to DTC with Induction Motor

For induction motor torque control, direct torque control is becoming the industry standard. This paper proposes a switching loss minimization technique for improved Direct Torque Control (DTC) of permanent magnet synchronous motors in order to increase the drive system's steady-state and dynamic results. Direct torque control (DTC) of a voltage source inverter-supplied PMSM is a simple scheme that requires little computation time, can be implemented without speed sensors, and is unaffected by parameter variations. In theory, the motor terminal voltages and currents are used to calculate the flux and torque of the motor. A voltage vector is chosen to restrict the flux and torque errors within their flux and torque hysteresis bands based on the instantaneous torque and stator flux magnitude errors, as well as estimates of the flux position. The electromagnetic torque, rotor speed, and stator current of DTC with PMSM and DTC with IM were successfully calculated using Total Harmonic Distortion (THD) in this article. As compared to DTC with IM, DTC with PMSM reduced THD by 12 percent in torque, speed, and stator current [21]. Switching Losses Minimization Technique by THD Minimization is used in this article. Since transistors are only switched when necessary to maintain torque and flux within their hysteresis limits, switching losses are minimised, resulting in increased efficiency and lower losses. Matlab SIMULINK has experimentally confirmed direct torque regulation with PMSM and IM.

FPGA in-the-loop implementation of direct torque control for induction motor

In this study, the hysteresis based direct torque control (DTC) of a three-phase induction motor was carried out experimentally. The DTC algorithm was also modelled in the hardware environment by using FPGA’s in-the-loop feature. The dSPACE DS1103 controller board was used in the experimental study and Altera DE2-115 model development board was used in the hardware modelling. Both applications had the same sample time and all of the DTC algorithm was tested within the FPGA. The hardware simulation study conducted in FPGA environment was carried out in MATLAB/Simulink environment. The experimental results were compared with the hardware simulation results obtained from FPGA. As a result of the comparison, it was shown that DTC algorithm could be realized easily in FPGA environment without experimental installation, and the obtained current, voltage and velocity graphs were similar.

Model Predictive Based Direct Torque Control for Induction Motor Drives by Sole-Evaluation of Two Parameter Independence Duty Ratios for Each Voltage Vector

Due to importance of duty cycle based model predictive torque control (MPTC), it has been accepted as an effective and common alternative control strategy for industry. Since its major drawback is great dependency on duty ratio parameter, the robustness and the complexity of control system has been respectively decreased and increased. A duty-ratio set considering limited members can be replaced with continuous and dependent parameters form duty cycle relationship. Hence, this paper proposes a new and applicable discrete duty cycle control strategy to reduce both the torque and flux ripples appeared in MPTC method. In the proposed method, after preselecting around half of all admissible voltage vectors based on the torque sign or speed variation and the stator flux position, two duty ratios have just been selected for the preselected active voltage vectors. These two duty ratios are achieved based on the equivalent voltage concept with independent motor parameter. Then, the model predictive control method is employed to select the optimum active voltage vector and its relevant duty ratio among the reduced feasible voltage vectors which reduces both the flux and torque ripples, especially in low speed ranges. The simulation results have confirmed the performance of the proposed method in order to reduce the torque and flux ripples, and the experimental results have accordingly validated its performance. Since the number of voltage vectors and duty ratios is significantly decreased, the execution time of the proposed method is further reduced, and virtually worked with a constant switching frequency for all speed ranges.

Enhanced Finite-State Predictive Torque Control of Induction Motor Using Space Vector Modulation

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Current Ripple Reduction of Predictive Torque-Controlled Induction Motor Drive Using Delta-Star Switchover

The current and torque ripple of inverter-fed induction motor drives is an inherent problem of control strategies working with switching frequencies in the range of multiple kilohertz, such as direct torque and, more recently, predictive torque control. If the drive operates in a wide-speed and wide-torque range and is equipped with a machine with an accessible terminal block whose winding is nominally connected in delta, then the current and torque ripple can be reduced by utilizing the delta-star winding changeover technique. When the winding configuration is switched from delta to star, the instantaneous motor phase voltage peak is lowered, and its total harmonic distortion is reduced. However, the control strategy must be adjusted according to the actual winding topology, mainly due to the difference in the coordinate transformations of the measured currents and the difference between the phase voltage vectors obtained from the inverter. This paper proposes a predictive torque control of an induction motor drive with a switchable delta-star winding configuration. The paper is supported by theoretical background, and the key idea is verified by simulations in MATLAB/Simulink and experiments conducted on a dSPACE-controlled 5.5-kW laboratory drive. The simulations validated the presented equations and show the effects of not respecting the actual winding topology. The experiments mainly focused on analyzing the total harmonic distortion of the currents and consumed electrical power in multiple operating points.

Computationally efficient predictive torque control for induction motor drives based on flux positional errors and extended Kalman filter

This paper proposes an improved model based predictive torque control (MPTC) method based on positional error between reference and estimated stator flux vectors. The main advantages of the proposed method are: the improved computational efficiency which requires minimum hardware resources and weighting-factor-free cost function. Weighting factor is removed by using modified reference transformation, which converts torque reference into equivalent stator flux reference. Improvement in computational performance is achieved by using decreased number of voltage vectors for prediction. An admissibility criterion based on flux positional errors is introduced to reduce the number of voltage vectors. The computational time saved is utilised to incorporate extended Kalman filter for better estimation of flux and torque. The validity of the proposed method is tested on a two-level three-phase inverter fed induction motor drive with dSpace DS1104 as controller board. The dynamic response and computational cost of the proposed method is compared to other established MPTC methods. The superiority of the proposed technique is confirmed by experimental results, which show an average of 32% reduction in computational time when compared to conventional MPTC while comparable dynamic response in terms of torque ripple, flux ripple and load current harmonics, is also maintained.