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Direct-drive wind turbines often require full size converters, especially for latest offshore 10 MW units. This paper contributes to the evaluation of 10 MW, 600 poles, doubly fed induction generators, possibly enabling to reduce the converter size. The work relies on a lumped parameters design procedure and on finite elements mechanical and magnetic verifications, which seem to confirm the technical feasibility of the machine.

In the paper, an intelligent set-up for PWM rectifiers is proposed. It is based on a predictive estimation control algorithm which guarantees the imposed value of the dc link output voltage and, at the same time, a unity power factor behaviour at the mains. Besides, a particular blank time free digital space vector modulator is described which eliminates the drop voltage due to the dead time effect and, also, avoids the current zero clamping phenomenon. Improvements on the AC source current waveforms and dc bus voltage are achieved with the proposed system, as shown in the experimental analysis.

In the paper, the H∞ control theory is used in order to design a state feedback controller for field oriented speed control of an induction motor. In particular, the problem of finding an optimal H∞ controller has been considered. The performances of the proposed controller are numerically analyzed and experimentally verified. The results confirm that good dynamic performances and high robustness to variations of a system's parameter can be achieved

An adaptive speed sensorless fourth order observer for online estimating rotor flux and speed in induction motor drives is presented in the paper. The synthesis procedure of the adaptive observer is based on the hyper-stability theory. Assuming the speed as unknown parameter of the rotor flux observer, the online identification process of its value has been set-up. The adaptation mechanism of the rotor speed and the gain matrix of the observer have been chosen so that stable operation is assured. The stability is tested using the hyperstability theory. The parameter (speed) convergence is assured thanks to the persistent exciting propriety of the input vector. Simulation tests conducted on the observer and on a field oriented controlled drive, using the proposed adaptive observer, show the convergent trajectories of the speed and of the state error vector under various significant steady state and transient operating conditions and for different values of the adaptation gains. The results show the satisfactory behaviour of the proposed adaptive observer

The problem of applying H∞ optimization synthesis to design a position controller for DC drives is considered. Robust stability, low sensitivity both to system parameter variations and exogenous disturbances, robust tracking property without steady-state error are expected to be achieved by means of H∞ control theory. Firstly a simulation and then an experiment have been set up and tested by controlling the position of an unstable mechanical system represented by an inverted pendulum. The results obtained fully confirm the validity of the design procedure and the robustness of the proposed controller

The today widespread use of power electronic supplies gives rise to a number of problems concerning the presence of strong distortion and non-active components in the currents required to the main supply. The solid state compensator can be used for compensating these undesirable effects. Referring to the three phase rectifier system, a method of controlling such a solid state compensator, capable of operating under load variation, is presented in the paper. The method is based on the real time identification of the equivalent resistance of the DC load which is obtained using the model reference adaptive control theory. The DC equivalent resistance allows to determine the reference current of the compensator.

A prototype of a digital controller for induction motor drive is presented in the paper. The single board microprocessor based on the TMS320C30 Digital Signal Processor is developed and programmed using C language. The software is elaborated for performing the full digital control of the induction motor drive. The control algorithm is determined using the MRAS technique which allows to implement the field oriented control of the motor in the stator coordinates. The inverter control is performed using a predictive technique which avoids to implement analog current loops. Experimental test results of the prototype behaviour are presented.

In order to highlight the possibilities of an induction motor drive to be competitive with respect to a permanent-magnet one, the paper analyzes and compares the dynamic performances of both speed-controlled drives. A microprocessor-based closed-loop control scheme is considered. Proper feeding algorithms are implemented either for induction or PM-brushless drives. As well as with classical hysteresis current regulators of VSI, the dynamic behaviour of the drives is analyzed also with reference to specific predictive control techniques. Even if more sophisticated, these digital control algorithms allow a reduction of the ripples in the currents and torque waveforms. Finally, comparative remarks are deduced from a series of numerical results obtained by means of a digital simulation of overall closed-loop drives with regard to some meaningful transient operations.

The authors design a variable reluctance motor to perform the rotation of clawed-pole rotors. Starting from this singular problem and encouraged by the good practical results they obtained, they have investigated the structure in terms of motor performances for application in variable speed drives. The paper refers to a particular electromagnetic structure of a VR brushless motor with sectorized stator, operating in open loop without position control. A simple mathematical model is presented and motor performances are investigated for transient operations with electronic supply.