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The supply current required by non-linear loads, like power electronic devices, is characterised by presence of harmonic and non-active components. A solid state compensator can supply the distorting current and, hence, solves the related problems. Referring to a single phase rectifier system with variable active load in the DC side, an adaptive solid state compensator is presented in the paper. The control system operates the real time identification of the DC load equivalent resistance, basis on the model reference adaptive control system theory.

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 linear oscillating reluctance drive is presented in the paper. The actuator is a prototype of a high anisotropy linear motor supplied by a simple PWM converter. It is controlled by an analog control system provided with a current loop and a position loop. The strong oscillating operation mode is induced by decreasing the feedback gain of the current loop. Computer simulation results of the drive nonlinear behaviour are presented and discussed. Comparison between computed and experimental results is finally presented A linear oscillating reluctance drive is presented in the paper. The actuator is a prototype of a high anisotropy linear motor supplied by a simple PWM converter. It is controlled by an analog control system provided with a current loop and a position loop. The strong oscillating operation mode is induced by decreasing the feedback gain of the current loop. Computer simulation results of the drive nonlinear behaviour are presented and discussed. Comparison between computed and experimental results is finally 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.

A model reference approach to control induction motor drives is proposed. The robustness, against rotor time constant variation, is also assured. Reference is made to CRPWM inverter supply. Thus, a simple linear, time invariant and decoupled reference model is assumed. A non-linear controller which takes into account rotor time constant variation is synthesized resorting to the Lyapunov stability theory. Field oriented control is imposed to the reference model expressed in stator coordinates and computer simulation results are reported. The reference model and its control system has been implemented using operational amplifiers and integrated-circuits chips for generating special functions. The test results of the circuit are finally reported

Espoo-Helsinki (Finland)

In the paper an interleaved soft switching dc-dc converter for applications in electric vehicle is proposed. The used topology raises the efficiency and the power density of the dc/dc converter minimizing switching losses by adopting a simple auxiliary active clamping circuit. Such auxiliary circuit is operational regardless of boost or buck mode of operation. The configuration guarantees fixed switching frequency, active clamped zero voltage switching operations of the main switches and bidirectional power flow. ZVS operations are guaranteed with wide load range. In the paper the operating principle, soft-switching conditions and steady state analysis are presented. A 27 kW prototype is designed and simulation results to verify the theoretical analysis are provided.

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

In this paper, the problem of applying H_infinity 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_infinty 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 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

A linear reluctance motor with strong magnetic anisotropy is considered in the paper. High thrust densities can be obtained by exploiting the axial arrangement of the iron lamination sheets on the induced machine element. A mathematical model of this linear motor is briefly summarized with reference to different level of simplifications in the air-gap magnetic permeance evaluation. A method for optimizing the thrust density of the motor is presented. This method takes into account the direct and quadrature air-gap inductances and allows to obtain the optimum value of the ratio between lamination and insulation thickness. Results are synthetized in some diagrams of general use.

The model reference-based field oriented control of the induction motor drive is presented in the paper. The main feature of the proposed control system is the absence of coordinate transformations. The synthesis procedure, basis on the Lyapunov stability theory, is briefly resumed. The simplification introduced by this control technique should allow to implement the control algorithm on a single low cost DSP or on a microcontroller. The time delays due to the D/A A/D converter and to the microprocessors computing time has been taken into account. The analysis evidences the system stability in a wide range of delay values and the robust stability against rotor time constant variation. Computer simulation results of the controlled drive are presented to highlight the goodness of the proposed control strategy.

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.

NAGASAKI - JAPAN.