Model reference neural network controller for induction motor speedcontrol

This paper proposes a novel robust speed control method for induction motor drives based on a two-layered neural network plant estimator (NNPE) and a two-layered neural network PI controller (NNPIC). The NNPE is used to provide a real-time adaptive estimation of the unknown motor dynamics. The widely used projection algorithm is used as the learning algorithm for these neural networks to automatically adjust the parameters of the NNPIC and to minimize the differences between the motor speed and the speed predicted by the NNPE. The simulation and experimental results demonstrate that the proposed robust control scheme can improve the performance of an induction motor drive and reduce its sensitivity to parameter variations and load disturbances     

A discrete adaptive induction position servo drive

A discrete adaptive induction position servo is designed and implemented. In the proposed servo system, the dynamic model of the indirect field-oriented induction motor is estimated from measurements using the stochastic approach. Based on this model, a PI speed controller and a P position controller are designed using pole-placement and root-locus techniques. In order to reduce the effects of machine and load parameter variations on the performance of the indirect field-oriented induction motor servo drive, an adaptive controller is augmented in which a reduced reference model, which defines the desired following control performance, is chosen and the adaptive control signal is synthesized. The proposed adaptive controller has the advantages of being easy to design and implement. Simulation and experimental results show that good following and regulating control performances are achieved. Moreover, the performances are rather insensitive to parameter variations     

A computer program to predict the performance of slip energyrecovery induction motor drives

Details are provided, in the form of a flowchart, to permit the reconstruction of a computer program to predict the transient and steady-state performance of slip energy recovery induction motor (IM) drives. Slip energy recovery IM drives are different from most other drives in that the inverter is generally connected only after the machine has reached a predetermined speed. The initial conditions of the inverter are therefore nonzero and difficult to obtain. Three techniques that can be used to calculate the initial conditions are discussed. Theoretical predictions are supported by practical results     

Compensation of magnetic saturation in maximum torque to current vector controlled synchronous reluctance motor drives

This paper investigates the influence of magnetic saturation in maximum torque to current vector controlled synchronous reluctance motor drives. A theoretical analysis is presented where a maximum torque to current condition that takes into account and compensates the effect of magnetic saturation in the synchronous reluctance motor drive performance is derived. The proposed controller does not affect the dynamic performance of the drive and is easily implemented, since an experimental procedure is used to determine its parameter. Therefore, the knowledge of the exact motor model is not required. Several experimental results are presented to validate the effectiveness of the proposed controlled scheme.     

Assessment of a fuzzy logic based MRAS observer used in a photovoltaic array supplied AC drive

In this paper a fuzzy logic (FL) based model reference adaptive system (MRAS) speed observer for high performance AC drives is proposed. The error vector computation is made based on the rotor-flux derived from the reference and the adaptive model of the induction motor. The error signal is processed in the proposed fuzzy logic controller (FLC) for speed adaptation. The drive employs an indirect vector control scheme for achieving a good closed loop speed control. For powering the drive system, a standalone photovoltaic (PV) energy source is used. To extract the maximum power from the PV source, a constant voltage controller (CVC) is also proposed. The complete drive system is modeled in MATLAB/Simulink and the performance is analyzed for different operating conditions.     

A generalized computer-aided formulation for the dynamic and steadystate analysis of induction machine inverter drive systems

A generalized formulation for the computer-aided analysis of induction machine drives including feedback controls is presented. A simple circuit model for the induction machine is developed to enhance the conventional drive formulation. This model eliminates a general difficulty encountered in the automatic formulation of machine dq -terminal constraints imposed by the drive operations. An efficient algorithm is proposed using a simple nodal approach for automatic formulation of power electronic circuits. This algorithm, combined with the proposed machine circuit model, can easily be used to simulate an arbitrarily configured drive system including the effects of control dynamics. A pulse-width-modulated current-source-inverter drive system is employed to demonstrate the efficiency of the proposed formulation. The dynamic and steady-state performance of this drive system including an effective harmonic control are simulated. The simulated results are experimentally verified     

A DC linear motor with a square armature

One of the advantages in using DC linear motors for low speed linear drives is that the position and speed of these motors can be precisely controlled with the help of a feedback circuit. In addition, linear motors get rid of the rotary-to-linear conversion mechanism, hence reduce the weight cost backlash and dynamic complexity which produces friction, and eventually minimizes the space required by the drive. The neodymium-iron-boron (NdFeB) permanent magnet with high energy product has been used as the field source of these motors thus reducing the size and weight of the motors further. This paper describes the analysis of flux and force in a DC linear stepping motor built with NdFeB magnets. In order to verify the experimental results obtained for determining the performance of the motor, a computational method has been employed to compute the flux distributions throughout the machine. The discrepancy between the measured and computed values of axial and radial flux at most points ranges between 8% and 16% while the discrepancy between the measured and computed values of starting thrust is in the range between 4% and 13%     

Performance improvement of DTC for induction motor-fed by three-level inverter with an uncertainty observer using RBFN

A stable sensorless controller for DTC of induction motor fed by three-level inverter using the Radial Basis Function Network (RBFN) is presented in this paper. The torque ripple can be drastically reduced and low speed performance can be obtained in the DTC system for high performance induction motor drives. However, speed control performance is still influenced by the lumped uncertainties of the system such as parameter variations, external load disturbances, and unmodeled dynamics which make it difficult to obtain an exact mathematical model. In this paper, the lumped uncertainties are estimated on-line by the RBFN. Simulations as well as experimental results are shown to illustrate the performance of the proposed system.     

A novel approach to speed and parameters estimation in inductionmotor drives

With reference to speed controlled induction motor drives, an algorithm which allows the on-line estimation either of the speed and one motor parameter or, alternatively, of two motor parameters, is presented in the paper. The results obtained by simulation fully confirm the validity of the proposed algorithm. Finally, the problems arising from the implementation of the proposed algorithm on a DSP-based control hardware are analysed     

A hysteresis current-regulated control for multi-level drives

Most multi-level converters are controlled through the use of voltage-source based control techniques such as space-vector modulation or multi-level sine-triangle modulation. However, in many applications such as field oriented drives, a high bandwidth current-source inverter based control is more desirable. In this paper, the concept of a multi-level hysteresis current-source control is set forth. The new control is experimentally verified using a four-level converter/induction motor drive system and the results are compared to a space vector modulation controller. A dynamic study involving a step change in current command demonstrates the controls high bandwidth     

Improved sensorless vector control for induction motor drives fed by a matrix converter using nonlinear modeling and disturbance observer

This paper presents a new sensorless vector control system for high performance induction motor drives fed by a matrix converter with nonlinearity compensation and disturbance observer. The nonlinear voltage distortion that is caused by commutation delay and on-state voltage drop in switching device is corrected by a new matrix converter modeling. The lumped disturbances such as parameter variation and load disturbance of the system are estimated by the radial basis function network (RBFN). An adaptive observer is also employed to bring better responses at the low speed operation. Experimental results are shown to illustrate the performance of the proposed system.     

Efficiency testing of motors powered from pulse-width modulatedadjustable speed drives

This is a report of efficiency testing of an induction motor powered from three different pulse width modulated adjustable speed drives. The motor was operated at a range of speeds and torques, and each drive was operated at the highest, lowest, and an in-between carrier frequency. The motor was a typical NEMA design B motor, and the drives were typical, industrial scalar drives using the default volts/Hz setting. The testing showed that the drive efficiencies remained above 90% until torque was lowered to below 20% of rated torque. Combined motor and drive efficiencies remained above 80% until speeds or horsepower loads were lowered to below 20% of rated torque. The test was performed using a unique data acquisition scheme that permitted acquisition of a large number of torque settings for each speed selection     

Simple Power Control for Sensorless Induction Motor Drives Fed by a Matrix Converter

This paper presents a new and simple method for sensorless control of matrix converter drives using a power flowing to the motor. The proposed control algorithm is based on controlling the instantaneous real and imaginary powers into the induction motor. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-on and turn- off times of switching devices, and on -state switching device voltage drop are modeled using a PQ power transformation and compensated using a reference power control scheme. The proposed sensorless control method is applied for the induction motor drive using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.      

Cancellation of common-mode Voltages for induction motor drives using active method

This paper presents a theoretical analysis for canceling common-mode (CM) voltages for induction motor (IM) drives using a CM transformer with active circuitry. The design methodology and the practical implementation are presented for motor drives rated 460 V or higher. To verify the design approach, an implementation example and experimental results for a 460-V motor drive system are presented.     

Impact of stray load losses on vector control accuracy in current-fed induction motor drives

Vector control accuracy of induction motor drives is affected by variations of motor parameters that are treated in the control algorithm as constant values, and by the phenomena that are not modeled at all and are therefore unaccounted for in the controller. Detuning sources of the first type include variations of rotor and stator resistance, mutual inductance, and leakage inductances, while the second category includes stator iron (core) losses. All these sources of detuned operation have been studied in a considerable depth in the past. It appears that the only potential source of detuned operation, which has never been studied before, is the stray load loss (SLL), which belongs to the category of unmodeled phenomena. This paper develops an analytical model that characterizes detuning due to SLLs in indirect rotor-flux-oriented (RFO) current-fed induction motor drives in steady-state operation by means of the orientation angle error, actual to reference rotor-flux ratio, and actual to reference-torque ratio. A quantitative assessment of the impact of SLL on accuracy of rotor-flux-oriented control is performed, with the necessary motor parameters obtained from IEEE 112-B standard measurements and subsequent equivalent circuit parameter fitting. Detuning is also examined in transient operation. It is shown that, although SLLs are comparable to the iron losses in the studied machine (of approximately the same value in the rated operating point), their impact on accuracy of vector control is much smaller when compared to the iron loss induced detuning.     

A fixed structure discrete-time sliding mode controller forinduction motor drives

In this paper, discrete-time sliding mode control is proposed for implementing an induction motor drive without varying the system structure. Very simple constant gain reaching control and sliding control are obtained to eliminate the chattering phenomenon and steady state error as well as to achieve robustness and minimized computation. For integration of the whole system, a simple field acceleration control algorithm is also derived to coordinate with the sliding mode control such that a simple 8 bit microcomputer can be used to implement a high performance induction motor drive     

An induction machine model for predicting inverter-machineinteraction

The conventional qd induction motor model typically used in drive simulations is very inaccurate in predicting machine performance, except perhaps for the fundamental component of the current and the average torque near rated operating conditions. Predictions of current and torque ripple are often in error by a factor of two to five. This work sets forth an induction machine model specifically designed for use with inverter models to study machine-inverter interaction. Key features include stator and rotor leakage saturation as a function of current and magnetizing flux, distributed effects in the rotor circuits, and a highly computationally efficient implementation. The model is considerably more accurate than the traditional qd model, particularly in its ability to predict switching frequency phenomena. The predictions of the proposed model are compared with those of the standard qd model and to experimental measurements on a 37 W induction motor drive     

Machine modeling and universal controller for vector-controlled induction motor drives

Developments of machine model and a universal controller for vector-controlled induction motor drives are presented in this paper. The machine representations associated with vector-control methods referring to various frames, including stator, rotor, and air-gap flux frames, can be derived simply by selecting different state variables; thereby clearly identifying the relationship between machine modeling and vector control. Moreover, a universal vector controller for induction motor drives fed by a voltage-controlled voltage source inverter is presented. It is shown in this paper that various vector controllers, including rotor flux-oriented controller, stator flux-oriented controller and air-gap flux-oriented controller, can be realized by simply changing few parameters. It is demonstrated by experimental results that the developed universal vector controller for various vector-control approaches can be implemented using the same hardware with a minor change to software associated with parameters; and thereby confirming the theoretical analysis.     

Transient Modeling and Parameter Estimation of Field Aligned Starting

Field aligned starting (FAS) is a new technique for starting three-phase cage induction motors on single-phase supply lines with minimal inrush currents. It uses a simple energy storage system to generate a very high impulsive torque by which the motor is started before being connected to the mains supply. The spinning motor can then be connected to the mains to operate in a standard Steinmetz connection without incurring high inrush currents, if the moment of mains connection is properly timed. This paper presents a transient model and an accompanying parameter estimation method through which the transient behavior of three-phase induction motors operated with FAS can be analyzed. The proposed model is based on instantaneous symmetrical components and is used to investigate a 3 kW motor started under various operating conditions. The proposed parameter estimation method and the developed transient model are both validated by experimental results.     

Development of a novel wind turbine simulator for wind energy conversion systems using an inverter-controlled induction motor

A wind turbine simulator for wind energy conversion systems has been developed with a view to design, evaluate, and test of actual wind turbine drive trains including generators, transmissions, power-electronic converters and controllers. The simulator consists of a 10-hp induction motor (IM) which drives a generator and is driven by a 10-kW variable speed drive inverter and real-time control software. In this simulator, a microcontroller, a PC interfaced to LAB Windows I/O board, and an IGBT inverter-controlled induction motor are used instead of a real wind turbine to supply shaft torque. A control program based on C language is developed that obtains wind profiles and, by using turbine characteristics and rotation speed of IM, calculates the theoretical shaft torque of a real wind turbine. Comparing with this torque value, the shaft torque of the IM is regulated accordingly by controlling stator current demand and frequency demand of the inverter. In this way, the inverter driven induction motor acts like a real wind turbine to the energy conversion system. The drive is controlled using the measured shaft torque directly, instead of estimating it as conventional drives do. The experimental results of the proposed simulator show that this scheme is viable and accurate. This paper reports the operating principles, theoretical analyses, and test results of this wind turbine simulator.