An enhanced control strategy based imaginary swapping instant for induction motor drives

<p>The main aim of this paper is to present a novel control approach of an induction machine (IM) using an improved space vector modulation based direct torque control (SVM-DTC) on the basis of imaginary swapping instant technique. The improved control strategy is presented to surmount the drawbacks of the classical direct torque control (DTC) and to enhance the dynamic performance of the induction motor. This method requires neither angle identification nor sector determination; the imaginary swapping instant vector is used to fix the effective period in which the power is transferred to the IM. Both the classical DTC method and the suggested adaptive DTC techniques have been carried out in MATLAB/SimulinkTM. Simulation results shows the effectiveness of the enhanced control strategy and demonstrate that torque and flux ripples are massively diminished compared to the conventional DTC (CDTC) which gives a better performance. Finally, the system will also be tested for its robustness against variations in the IM parameters.</p>

Performance Entitlement by Using Novel High Strength Electrical Steels and Copper Alloys for High-Speed Laminated Rotor Induction Machines

The laminated rotor Induction Machine (IM), with its simple construction and manufacturing, robustness, ease of control and comparatively lower cost remains by far the most utilized electromechanical energy converter. At very high speeds, traditionally its use is considered to be limited to the previously established operational limits of 2.5 × 105 rpm√kW, beyond which the surface Permanent Magnet (PM) Machine and the solid rotor Induction Machine become the machines available for consideration. The aforesaid limits are derived from the use of classic materials. This paper reviews the recent developments in electrical steels and copper alloys and translates these into the resulting performance entitlement and operational limits through a case study involving a marine application, for which an existing rare-earth PM machine is in use. It is concluded that with novel materials, laminated rotor induction machines can be operated up to 6 × 105 rpm√kW, thus opening the use of the rare-earth free Induction Machine for a wider application range previously limited to PM machines.

Simulation of iron losses in induction machines using an iron loss model for rotating magnetization loci in no electrical steel

Purpose Various iron loss models can be used for the simulation of electrical machines. In particular, the effect of rotating magnetic flux density at certain geometric locations in a machine is often neglected by conventional iron loss models. The purpose of this paper is to compare the adapted IEM loss model for rotational magnetization that is developed within the context of this work with other existing models in the framework of a finite element simulation of an exemplary induction machine. Design/methodology/approach In this paper, an adapted IEM loss model for rotational magnetization, developed within the context of the paper, is implemented in a finite element method simulation and used to calculate the iron losses of an exemplary induction machine. The resulting iron losses are compared with the iron losses simulated using three other already existing iron loss models that do not consider the effects of rotational flux densities. The used iron loss models are the modified Bertotti model, the IEM-5 parameter model and a dynamic core loss model. For the analysis, different operating points and different locations within the machine are examined, leading to the analysis of different shapes and amplitudes of the flux density curves. Findings The modified Bertotti model, the IEM-5 parameter model and the dynamic core loss model underestimate the hysteresis and excess losses in locations of rotational magnetizations and low-flux densities, while they overestimate the losses for rotational magnetization and high-flux densities. The error is reduced by the adapted IEM loss model for rotational magnetization. Furthermore, it is shown that the dynamic core loss model results in significant higher hysteresis losses for magnetizations with a high amount of harmonics. Originality/value The simulation results show that the adapted IEM loss model for rotational magnetization provides very similar results to existing iron loss models in the case of unidirectional magnetization. Furthermore, it is able to reproduce the effects of rotational flux densities on iron losses within a machine simulation.

The determination of induction motor losses in steel taking into account its saturation

Purpose This paper aims to work out a method for calculating losses in induction motor steel taking into account its saturation. Design/methodology/approach The theory of electric machines is applied during the analysis of induction motor equivalent circuits. The theory of Fourier series is used to determine the harmonic components of voltage, current and power. Instantaneous power theory and trigonometric transformations are used to solve algebraic and differential equations and their systems. The methods of approximation and interpolation are applied to obtain analytical expressions from the experimental data. Experimental research was carried out to verify the reliability of theoretical provisions and research results. Findings A method for assessing an induction machine steel as a function of the generalized electromotive force has been proposed. It allows taking into account higher harmonics of the current, which are caused by the presence of nonlinearity of an induction motor magnetic circuit. Practical implications The obtained results can be used in calculating the energy characteristics and operating modes of an induction motor, as well as in the construction of control systems. Originality/value A method for determining the losses in the stator steel of an induction motor, using a generalized electromotive force, has been proposed for the first time. It enables taking into account the currents flowing both in the stator circuit and in the rotor circuit.

Sensorless Speed Contorl of Doubly-Fed Induction Machine Using Reactive Power Based MRAS

A sensorless speed control method for doubly-fed induction machine (DFIM) operating with constant frequency but in variable speed mode is presented in this project work. The control method is based on rotor speed estimation technique by a reactive power model reference adaptive system (MRAS) observer. The presented technique does not depend on any kind of flux evaluation and also independent to the resistance variation of either stator or rotor. The MRAS observer has a capacity for speed catching operation. PI controller is designed and also optimized using algorithm for better dynamic behaviour of the machine. MATLAB Simulink model and the simulation results are shown to check the effectiveness of the observer and also of the controller.

MODELING A DC BUS CHARGE CONTROL SYSTEM IGBT INVERTER FOR TWO PHASE LINEAR INDUCTION MACHINE

The problems of modeling in the Matlab environment the modes of the MHD-stirring of aluminum melt in furnaces, taking into account the distribution network. It is noted that the operation of frequency inverters of the power supply system sharply complicates the electromagnetic environment in a network of limited power. It is proposed to apply a complex of models to assess the possibility of reducing the distortion of the network currents by modifying the rectifier control algorithms, while maintaining the stability of the DC bus of the frequency converter.

An Analytical Prediction Model of Balanced and Unbalanced Faults in Doubly-Fed Induction Machines

This paper presents the exact transient solution to the unbalanced and balanced faults in the doubly-fed induction machine (DFIM). Stator currents, rotor currents, and stator fluxes have been validated using simulation and experiment. The work is meant to strengthen and fasten the predictability of large DFIMs in the design stage to comply with mechanical constraints or grid fault issues. Moreover, the analytical approach reduces the computational costs of large-scale stability studies and is especially suited to the initial phase where a plethora design computations must be carried out for the DFIM before it is checked for its transient interaction with the power system. The possibility to dynamically estimate DFIM performance is simplified by original equations derived from first principles. First, a case study of a large 265.50 MVA DFIM is used to verify the proposed "large machine approximation" using simulation, achieving an exact match. Then, laboratory measurements were conducted on a 10.96 kVA and a 1.94 kVA DFIM to validate the transient current peaks predicted in the proposed analytic expressions for two-phase and three-phase faults, respectively.

An Analytical Prediction Model of Balanced and Unbalanced Faults in Doubly-Fed Induction Machines

This paper presents the exact transient solution to the unbalanced and balanced faults in the doubly-fed induction machine (DFIM). Stator currents, rotor currents, and stator fluxes have been validated using simulation and experiment. The work is meant to strengthen and fasten the predictability of large DFIMs in the design stage to comply with mechanical constraints or grid fault issues. Moreover, the analytical approach reduces the computational costs of large-scale stability studies and is especially suited to the initial phase where a plethora design computations must be carried out for the DFIM before it is checked for its transient interaction with the power system. The possibility to dynamically estimate DFIM performance is simplified by original equations derived from first principles. First, a case study of a large 265.50 MVA DFIM is used to verify the proposed "large machine approximation" using simulation, achieving an exact match. Then, laboratory measurements were conducted on a 10.96 kVA and a 1.94 kVA DFIM to validate the transient current peaks predicted in the proposed analytic expressions for two-phase and three-phase faults, respectively.