Torque Control Of Induction Machine Research Articles

Predictive Control of an Induction Machine Fed by a Matrix Converter With Increased Efficiency and Reduced Common-Mode Voltage

Predictive control represents an optimization-oriented alternative for the control of power converters and drives. Predictive torque control of induction machines has been shown to achieve excellent initial results. The objective of this paper is to help develop this promising control approach by introducing new elements to improve its performance. The resulting algorithm improves the efficiency of the converter from 91.1% to 92.6% and achieves a common-mode voltage mitigation of 50%, compared to the basic control method. A tradeoff is observed in the power quality. The algorithm gives the designer the ability to select the best operating point for each particular application and to optimize the converter's performance. Experimental results are presented to validate the proposals.

Encoderless Finite-State Predictive Torque Control for Induction Machine With a Compensated MRAS

An encoderless predictive torque control (PTC) is proposed in this paper. By using a rotor flux model reference adaptive system (MRAS) estimation method to PTC, the system has the virtue of low cost due to the absence of PWM and speed measurement components. PTC requires not only estimated speed but also estimated stator and rotor flux. In implementation, a compensated MRAS is considered for obtaining good flux estimations. The experimental results confirm that this control strategy has very fast dynamics, can adapt a very wide speed range, and shows good performance both at transient and steady states.

Comments on “Predictive Torque Control of Induction Machines Based on State-Space Models”

In the paper “Predictive torque control of induction machines based on state-space models” by Miranda et al. (IEEE Trans. Ind. Electron., vol. 56, no. 6, pp. 1916-1924, Jun. 2009), a discrete-time model for an induction machine with time-varying components was proposed to improve the accuracy of the model predictive control strategy. In this letter, we clarify that the sampled model proposed by Miranda et al. is not exact, but rather an accurate approximation. Finally, its accuracy is analyzed and compared to using the simple Euler discretization.

DTC-SVM Based on PI Torque and PI Flux Controllers to Achieve High Performance of Induction Motor

The fundamental idea of direct torque control of induction machines is investigated in order to emphasize the property produced by a given voltage vector on stator flux and torque variations. The proposed control system is based on Space Vector Modulation (SVM) of electrical machines, Improvement model reference adaptive system, real time of stator resistance and estimation of stator flux. The purpose of this control is to minimize electromagnetic torque and flux ripple and minimizing distortion of stator current. In this proposed method, PI torque and PI flux controller are designed to achieve estimated torque and flux with good tracking and fast response with reference torque and there is no steady state error. In addition, design of PI torque and PI flux controller are used to optimize voltages in d-q reference frame that applied to SVM. The simulation Results of proposed DTC-SVM have complete excellent performance in steady and transient states as compared with classical DTC-SVM.

IM Torque Control Schemes Based on Stator Current Vector

This paper proposes an induction machine torque control derived from the model in the stator current vector reference frame. The required torque is produced by simultaneously manipulating the magnitude and the rotation speed of the stator current vector, thus forcing the rotor flux linkage vector to change implicitly in such a way that overall stability is preserved. Additional control features include maximal torque-per-ampere ratio in steady state and almost perfect command tracking even if the machine is magnetically saturated. The control adopts a cascaded structure and is based on a partial dynamic inversion of the reduced model that assures existence and uniqueness of the inverse mapping between the required torque, the rotor flux linkage vector, and the stator current vector. Singularity at zero rotor flux linkage represents no restriction for the control performance in the admissible machine operating range. The implementation of the proposed control requires the estimation of the torque-producing rotor flux component and cascaded stator current controllers. Experimental results confirm the key expectations and show the potential and benefits of the proposed control schemes.

An Improved FPGA Implementation of Direct Torque Control for Induction Machines

This paper presents a novel direct torque control (DTC) approach for induction machines, based on an improved torque and stator flux estimator and its implementation using field-programmable gate arrays (FPGA). The DTC performance is significantly improved by the use of FPGA, which can execute the DTC algorithm at higher sampling frequency. This leads to the reduction of the torque ripple and improved flux and torque estimations. The main achievements are: 1) calculating a discrete integration operation of stator flux using backward Euler approach; 2) modifying a so called nonrestoring method in calculating the complicated square root operation in stator flux estimator; 3) introducing a new flux sector determination method; 4) increasing the sampling frequency to 200 kHz such that the digital computation will perform similar to that of the analog operation; and 5) using two's complement fixed-point format approach to minimize calculation errors and the hardware resource usage in all operations. The design was achieved in VHDL, based on a Matlab/Simulink simulation model. The Hardware-in-the-Loop method is used to verify the functionality of the FPGA estimator. The simulation results are validated experimentally. Thus, it is demonstrated that FPGA implementation of DTC drives can achieve excellent performance at high sampling frequency.

Non-Holonomy in Induction Machine Torque Control

In this brief, induction machine (IM) torque control is studied as an example of a 3-D non-holonomic integrator including drift terms. By expanding Brockett's controller derived for the driftless systems, a control structure is proposed that provides simultaneous modulation of both the amplitude and the frequency of the sinusoidal stator current vector. Although not explicitly controlled or programmed, the rotor flux linkage vector is implicitly forced to track natural periodic orbits satisfying non-holonomic constraints of the IM. The proposed control assures high dynamics in the torque response, maximal torque per amp ratio during transients and in steady-state and global asymptotic stability. The overall IM control scheme includes cascaded high-gain current controllers based on measured electrical and mechanical quantities together with rotor flux linkage vector estimator. Simulation and experimental results illustrate the main characteristics of the proposed control.

Voltage angle direct torque control of induction machine in field-weakening regime

This study presents a novel algorithm for the induction motor torque control in field-weakening region. The proposed method insures maximum DC bus utilisation and extends the torque–speed curve up to the system limits. Controller is based on the stator voltage angle control. It provides full DC-link disturbance rejection and offers the torque response time sufficient for most applications. The algorithm is simple, without neither the outer flux loop nor the inner current loop. Dynamic response is preserved over wide speed range by means of gain-scheduling. Simulations and experiments prove an ease of implementation and the robustness of the proposed solution. This study comprises analytical considerations, simulation results, a detailed description of implementation steps and extensive experimental results.

Direct Torque Control of Induction Machine based on Intelligent Techniques

Induction machine drive based on Direct Torque Control (DTC) allows high dynamic performance with very simple hysteresis control scheme. Conventional Direct Torque Control (CDTC) suffers from some drawbacks such as high current, flux and torque ripple, difficulties in torque as well as flux control at very low speed. In this paper, we propose two intelligent approaches to improve the direct torque control of induction machine; fuzzy logic control and artificial neural networks control. We carry out a detailed comparison study between direct torque fuzzy control (DTFC), direct torque neural networks control (DTNNC) and CDTC applied to switching select voltage vector. The theoretical foundation principle, the numerical simulation procedure and the performances of both methods are also presented.

STATCOM-Based Indirect Torque Control of Induction Machines During Voltage Recovery After Grid Faults

This paper proposes a control method for limiting the torque of grid-connected cage induction machines during the recovery process after grid faults, by using a static synchronous compensator (STATCOM) connected at the machine terminals. When a STATCOM is used for transient stability improvement, common practice is to design the control system to keep reactive current at maximum level until the voltage has returned to its initial value. This will result in high torques during the recovery process after grid faults. The control method proposed in this paper is intended to limit such torque transients by temporarily defining a new voltage reference for the STATCOM control system. As torque is controlled through the voltage reference of the STATCOM, the method is labeled indirect torque control (ITC). The presented concept is a model-based approach derived from a quasi-static equivalent circuit of the induction machine, the STATCOM and a The?venin representation of the power system. For illustration and verification, time-domain simulations of a wind power generation system with a STATCOM at the terminals of an induction generator, are provided. As the objective of limiting the torque of the induction machine is achieved, the derivation of the concept proves to be reasonable. The approach is presented in its most general form, oriented to torque limitation of induction machines both in generating and motoring mode, and is not restricted to the presented example.

A Direct Torque-Controlled Induction Machine Bidirectional Power Architecture for More Electric Aircraft

A Direct Torque-Controlled Induction Machine Bidirectional Power Architecture for More Electric Aircraft

Predictive Torque Control of Induction Machines Based on State-Space Models

In this paper, we present a predictive control algorithm that uses a state-space model. Based on classical control theory, an exact discrete-time model of an induction machine with time-varying components is developed improving the accuracy of state prediction. A torque and stator flux magnitude control algorithm evaluates a cost function for each switching state available in a two-level inverter. The voltage vector with the lowest torque and stator flux magnitude errors is selected to be applied in the next sampling interval. A high degree of flexibility is obtained with the proposed control technique due to the online optimization algorithm, where system nonlinearities and restrictions can be included. Experimental results for a 4-kW induction machine are presented to validate the proposed state-space model and control algorithm.

Digital Implementation of Stator and Rotor Flux-Linkage Observers and a Stator-Current Observer for Deadbeat Direct Torque Control of Induction Machines

Properly formed discrete-time recursive models of a stator and rotor flux-linkage observer are presented. A model delay in the flux-linkage observer, which hindered previous work, is identified. To remove this delay, a new stationary frame current observer is developed and experimentally verified. With this new observer system, the flux linkages are properly estimated for the next sample instant, thus removing the computational delay. The improved and the delayed flux observer are evaluated in a deadbeat direct torque control algorithm.

Predictive Current Control of an Induction Machine Fed by a Matrix Converter With Reactive Power Control

A different approach to perform the control of an induction machine fed by a matrix converter (MC) is presented in this paper. The proposed technique is based on predictive control and effectively controls input and output variables to the power converter, as expected from an MC. The method allows the use of all valid switching states, including rotating vectors that are not considered in most control techniques, as space vector modulation or direct torque control for induction machines fed by MCs. Experimental results show the excellent performance of the proposed approach, with low-distortion input currents, adjustable power factor, sinusoidal output currents with smooth frequency transitions, and good speed control in motoring and regeneration conditions, even working under an unbalanced power supply. The implementation and comprehension of the method should be considered simple compared to other control strategies with similar features. The high computational effort required should not be a problem considering recent progresses in digital signal processors-and even less in years to come.

Formal Derivation of Direct Torque Control for Induction Machines

Direct torque control (DTC) is an induction motor control technique that has been successful because it explicitly considers the inverter stage and uses few machine parameters, while being more robust to parameter uncertainty than field-oriented control (FOC). This paper presents a formal derivation of DTC based on singular perturbation and nonlinear control tools. The derivation elaborates an explicit relationship between DTC performance and machine characteristics; low-leakage machines are expected to perform better under DTC. It is shown that DTC is a special case of a sliding-mode controller based on the multiple time-scale properties of the induction machine. The known troublesome machine operating regimes are predicted and justified. Explicit conditions to guarantee stability are presented. DTC is shown to be a suboptimal controller because it uses more control effort than is required for flux regulation. Finally, compensation strategies that extend DTC are discussed. The derivation does not require space vector concepts thus, it is established that the traditional link between DTC and space vectors is not fundamental

Speed-Sensorless Torque Control of Induction Machine Based on Carrier Signal Injection and Smooth-Air-Gap Induction Machine Model

A speed-estimation technique for induction machines, based on carrier signal injection and the standard two-axis smooth-air-gap induction machine model, is presented. The proposed speed-estimation technique can work over a wide range of operating points, including fundamental dc excitation. The stability of the algorithm is analyzed using a two-time-scale approach. Based on the estimated rotor speed, a torque controller is designed. Experimental results are presented confirming the validity of this approach. A method to reduce torque ripple generated by the injected carrier signals is also introduced

A New Torque and Flux Controller for Direct Torque Control of Induction Machines

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents the implementation of a high-performance direct torque control (DTC) of induction machines drive. DTC has two major problems, namely, high torque ripple and variable switching frequency. In order to solve these problems, this paper proposed a pair of torque and flux controllers to replace the hysteresis-based controllers. The design of these controllers is fully discussed and a set of numerical values of the parameters for the proposed controllers is given. The simulation of the proposed controllers applied to the DTC drive is presented. The simulation results are then verified by experimental results. The hardware implementation is mainly constructed by using DSP TMS320C31 and Altera field-programmable gate array devices. The results prove that a significant torque and stator flux ripples reduction is achieved. Likewise, the switching frequency is fixed at 10.4 kHz and a more sinusoidal phase current is obtained. </para>

Direct Torque Control of Induction Machines With Constant Switching Frequency and Reduced Torque Ripple

Direct torque control (DTC) of induction machines is known to have a simple control structure with comparable performance to that of the field-oriented control technique. Two major problems that are usually associated with DTC drives are: switching frequency that varies with operating conditions and high torque ripple. To solve these problems, and at the same time retain the simple control structure of DTC, a constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller. In this paper, the modeling, averaging, and linearization of the torque loop containing the proposed controller followed by simulation and experimental results are presented. The proposed controller is shown to be capable of reducing the torque ripple and maintaining a constant switching frequency.

Simple direct torque control of induction machine using space vector modulation

A new method for direct torque control (DTC) based on load angle control is developed. The use of simple equations to obtain the control algorithm makes it easier to understand and implement. Fixed switching frequency and low torque ripple are obtained using space vector modulation, overcoming the most important drawbacks of classic DTC.

유도전동기의 직접토크제어 시스템에서 출력전압벡터선정을 위한 시간지연의 보상

유도전동기의 직접토크제어 시스템에서 출력전압벡터선정을 위한 시간지연의 보상