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EPE 1995 - 30 - Dialogue Session DS2b: Control (II)
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	THEORY AND CHARACTERISTICS OF A NOVEL VARIABLE RELUCTANCE RESOLVER   By A. Ishizaki; K. Takasaki; S. Shimomura; K. Masaki; K. Kitazawa	[View]   [Download]
Abstract: Although brushless resolvers have been widely used as angular position transducers, they are expensive due to their intricate construction, having a rotary transformer which supplies current to the exciting coils wound on the rotor poles. The authors have shown theoretically in the present paper that a resolver without rotary transformer or brushes can be realized, by a simple construction which consists of a stator core with both 4-pole exciting windings and 2-pole output ones and the rotor core carrying no windings. In this resolver the rotor core has a minimum gap at one side and a maximum gap at the opposite side of the rotor cross-section, and is characterized by an outer surface form which makes the gap permeance vary in proportion to cos omega, where omega represents the angular position of a point in the air gap with respect to the origin on the rotor, the point of minimum air gap. A method for determining the rotor form that embodies this gap permeance variation is also shown. It was confirmed by simulation and experiment that the 2-phase output voltages of a model designed according to this theory have sinusoidal waveforms with very small harmonic contents. Moreover, the rotor position detected by processing the output voltages through a conventional resolver/digital converter was within acceptable engineering accuracy.
	AN OVERSAMPLED HIGH ACCURACY CURRENT TRANSDUCER FOR LOW FREQUENCY CURRENT MEASUREMENT   By C.P. Lewis; T.G. Hesketh; S.J. Crump	[View]   [Download]
Abstract: The control of heavy currents in the steering and accelerating magnets of atomic particle accelerators is considered. Particular attention being paid to a technique of current measurement of current in a suitable format for digital control.
	A DSP-BASED INTERFERENCE CURRENT FILTER FOR ASYNCHRONOUS TRACTION DRIVES   By A. Duym; E.K.H. van der Pols	[View]   [Download]
Abstract: This paper describes a newly developed DSP-based digital interference current filter, for use in asynchronous traction drive control systems. The filter suppresses interference currents generated by the drive system, that interfere with the signalling and train protection system of Dutch Railways. The filter is pin-compatible with a previously designed analog filter. Main problem of the design process was the phase-critical behaviour of the filter in the drive control system. Field tests proved that the digital filter meets its design specifications. It is currently applied in the new IRM-1 Electrical Multiple Units of Dutch Railways. Special attention was paid to the programming and simulation environment. The calculated transfer function can easily be implemented, resulting in a high degree of flexibility. Built-in self-testing facilities greatly reduce filter board production time.
	AC MOTOR DRIVE SYSTEM FOR COLD STRIP MILL   By F. Ben Ammar; H. Godfroid; J.C. Lebrun; J. Schwedt	[View]   [Download]
Abstract: This paper describes a new AC drive system for SENDZIMIR Cold rolling Mill. The roller, coiler and uncoiler ,are driven by induction motors supplied by three-level high-power GTO inverters with a common DC busbar. The drives are coupled mechanically by an elastic strip of metal. The AC variable speed drive of the high performance type is provided with the vector control and substitutes for the conventional DC variable speed drive. For the purpose of field-oriented control, Kalman filter algorithm is used to obtain the unmesurable rotor flux of a squirrel-cage induction motor. The relationship between motor drive performance, strip tension quality and strip thickness accuracy is investigated and verified through simulation.
	LEAST SQUARES HIGH-VOLTAGE MODULATION STRATEGY FOR PWM INVERTERS   By A. Dell'Aquila; V. Giliberti; E. Montaruli; P. Zanchetta	[View]   [Download]
Abstract: The most diffuse approach for providing high output voltages of a PWM inverter using carrier modulated techniques is to overmodulate the PWM waveform. In the paper we present a particular modulation strategy with reference to M>1 and for low frequency ratios R and use it together with suboptimal modulation to cover all the operative range of the inverter. The analytic form of the new modulating waveforms is found by use of a least squares approximation.
	A DSP CONTROL OF A SOFT SWITCHING INVERTER FOR AN ELECTROMAGNETIC DAMPER OF VIBRATIONS   By C. Lombard; M. Mazaudier; A. Berthon	[View]   [Download]
Abstract: This paper deals with the implementation of the identification and the optimal control of a mechanical unbalances compensator on a Digital Signal Processor (DSP). The plant, called EDV, results from a study proposed by GEC Alsthom Company. This is a special machine designed to create a radial synchronous force in opposition with some unbalanced behaviour of a solid rotor shaft (ie. a turbo generator). The principle of the system is given before dealing with the power converter structure. Considering the complexity of the supply, the problem is taken from a parametric point of view. Although the EDV has large pure delays, a state-space model without singular state matrix is proposed by the way of a digital technique we explain. The implemented optimal controller to the experimental compensator system gives results and validates the method used.
	A NEW METHOD OF STATOR RESISTANCE ESTIMATION FOR ENHANCED DYNAMIC PERFORMANCE OF SENSORLESS VECTOR CONTROL DRIVES   By R. Blasco-Gimenez; G. M. Asher; M. Sumner	[View]   [Download]
Abstract: This paper describes a new methodology to estimate the stator resistance of induction machines for enhanced performance of sensorless vector control drives. To achieve this, the effect of incorrect stator resistance on the performance of a sensorless drive during transients through or near zero speed is analyzed. It has been found that the use of an inaccurate stator resistance will cause the estimated machine flux to deviate from a circular trajectory centred at the origin. This deviation will in turn cause undesired oscillations on the estimated flux magnitude and flux angle. The aforementioned deviation is used to obtain an instantaneous estimation of the stator resistance. This deviation is corrected for and the dynamic performance of a sensorless vector control scheme based on these flux estimates is enhanced.
	VOLTAGE-SOURCE INVERTER FED ASYNCHRONOUS MACHINE WITH HYSTERESIS CONTROL OF RECTIFIED MOTOR CURRENTS   By C. Tuttas	[View]   [Download]
Abstract: Voltage-source inverters (VSI) are used for feeding speed variable asynchronous machines. By means of hysteresis controller the stator currents can be impressed into the machine. The control circuit is simple, robust and fast but has the the disadvantage of higher switching frequency, compared with feed forward PWM methods. If the motor currents are rectified before hysteresis control, the switching frequency of the VSI can be distinctly reduced.
	MEASUREMENT OF LOSSES OF FAST POWER SWITCHES. IMPACT OF TYPICAL CAUSES OF INACCURACY   By Y. Lembeye; J.P. Keradec; D. Lafore	[View]   [Download]
Abstract: Measurements of losses in power electronics switches raises great theoretical difficulties this paper investigates with a practical point of view. Measurements acquired, with a maximum of care, during a switch work are, after, considered as perfect. Starting with these measurements, various inaccuracy causes are successively simulated to evaluate their impact on waveforms and numerical results. Results are presented to allowed an engineer to determine necessary measurement equipment performances regarding the studied switch and the needed accuracy.
	MICROPROCESSOR BASED MATHEMATICAL AND LOGICAL RANDOM PWM METHODS FOR POWER INVERTERS   By S.Y.R. Hui; I. Oppermann; F. Pasalic; S. Sathiakumar	[View]   [Download]
Abstract: This paper presents an evaluation of two microprocessor-based random PWM (RPWM) methods. Based on the mathematical and logical approaches, the two RPWM schemes are implemented and analysed using the probability density functions. The spectral characteristics of both schemes are included and compared. General trends and characteristics of the RPWM schemes are described and the limitations of some RPWM schemes addressed.
	ELECTROVALVES DRIVER UNIT WITH INTEGRATED STATE MACHINE BASED CONTROL CIRCUIT   By R. Groppo; U. Panizza	[View]   [Download]
Abstract: This paper describes an Electronic Power Unit that drives hydraulic electrovalves belonging to the intake air valve circuit of a multi-valves multi-cylinder engine. The state machine based control circuit bas been integrated into a Field Programmable Gate Array, together with the self-protection circuits; the unit bas been tested and is currently used on a prototype engine.
	PWM VOLTAGE VECTOR CONTROL WITH PREDICTIVE PULSE GENERATION FOR LOW-SWITCHING INVERTERS   By W. Hofmann	[View]   [Download]
Abstract: A new method for control of a pwm inverter is presented, what makes it possible to compensate static and transient deviations of the output current and to measure the controlled variables without distortion at the sampling instants. This treated problem will get some importance if the pulse-frequency is set in the lower range about few hundred hertz and the voltage vector control should be applied in field-oriented control systems. The control laws will be given and the results of simulation and experiments as voltage transfer factor and the harmonic contents of the output current will be discussed.
	POSITION DETECTION FOR CYLINDRICAL LINEAR SWITCHED-RELUCTANCE ACTUATOR   By J. Corda; J. Breiland; P. Slater	[View]   [Download]
Abstract: The paper presents a position transducer intended for use in the linear switched reluctance actuator having cylindrical form. The transducer incorporates only fixed sensors of 'variable-reluctance, differential transformer type, connected to a signal processing unit. It does not require any additional element on the actuator's mover, i.e. the original saliences of the mover are used for electromagnetic sensing of position. The transducer enables identification of the discrete positions which are required for position feedback switching (energization) of the actuator's phases, and also continuous position sensing in the form of a voltage signal proportional to position within an interval of the mover pitch.
	VECTOR PWM MODULATOR WITH CONTINUOUS TRANSITION TO THE SIX-STEP MODE   By A. Haras; D. Roye	[View]   [Download]
Abstract: Full output voltage range of a voltage source PWM inverter is achieved vvith a special overmodulation strategy. The aim of control is to establish a linear relation between desired and real fundamental of output voltage including the overmodulation region. Gate pulse minimal time is considered as an important parameter of an inverter. Space vector strategy is used to cover full range of inverter output voltage up to the six-step mode. Three general commutation rhythms are presented: called three-phase, two-phase and one-phase vector modulation. Two algorithms enabling the choice of the commutation rhythm vvith pulse minimal time control are presented. A practical implementation and experimental results are shown.
	COMBINED SPEED AND TEMPERATURE ESTIMATION IN BRUSHED DC DRIVES   By P.P. Acarnley; J.K. Al-Tayie	[View]   [Download]
Abstract: An observer for the real-time estimation of rotor speed and armature temperature in a brushed dc drive is formulated using electrical, mechanical and thermal models of the motor. The observer is implemented using a TMS 320C31 digital signal processor system. A range of experimental results, demonstrating the observer's steady-state and transient performance, are presented for a 3kW machine supplied from a phase-controlled rectifier.
	A SPEED SENSORLESS DIGITALLY CONTROLLED INDUCTION MOTOR DRIVE ESTIMATING ROTOR RESISTANCE VARIATION   By C. Attaianese; I. Marongiu; A. Perfetto	[View]   [Download]
Abstract: An algorithm suitable for the simultaneous estimation both of the velocity and of the rotor time constant of a digitally controlled induction motor drive, is proposed in the paper. It is based on a full order flux observer structure and on an adequate arrangement of the error system. In comparison with other solutions of the same problem presented in previous papers, the considerable difference and contribution is that the numerical derivative of the stator current error is not required, thanks to an adequate approximated analytical solution of the error system. The results obtained by means of a numerical simulation are presented in order to verify the performances of the proposed algorithm. They shows a very fast drive response at the same time as an high accuracy of the estimation of the motor state and of the rotor resistance variations.
	MOS GATE DRIVER CIRCUIT WITH EXTREMELY HIGH GALVANIC ISOLATION   By Michael A. E. Andersen	[View]   [Download]
Abstract: This paper describes how to make a MOS gate driver circuit that isolates power electronics from control electronics and computers. An extremely high galvanic isolation has been achieved using optical plastic fibre to send signal to the driver and using a special current transformer to send power to the driver.
	SPEED SENSORLESS DRIVE WITH INDUCTION MACHINE BASED ON NATURAL FIELD ORIENTATION   By J. Zdenkovic; Z. Kuljic; N. Pasalic	[View]   [Download]
Abstract: The speed sensorless drive in indirect vector control scheme with acting on stator voltage vector is realized by excluding the speed sensor and including the current measurement. The decoupling circuit and the speed estimator are based on Natural Field Orientation presumptions: the rotor flux vector modulus is held constant and the total leakage factor is zero. The sensorless drive is tested on laboratory set up where another induction machine operating in torque control mode is used for loading. Steady state characteristics are presented together with system responses to speed reference reversing under no load condition and system responses during stepwise loading processes. Influence of the machine stator and rotor resistance thermal changes, and changes in the main machine inductance during machine operation on the behaviour of the proposed control structure is discussed. Simplicity of the proposed control algorithms allows implementation in low cost microcontroller hardware.
	THE INFLUENCE OF OPTIMAL PROGRAMMED PULSE WIDTH MODULATION ON THE STATIC AND DYNAMIC OUTPUT BEHAVIOUR OF A DIGITAL CONTROLLED DC/DC-CONVERTER   By S. Huth	[View]   [Download]
Abstract: A method to suppress conducted EMI at the input of a DC/DC-converter called Programmed Pulse Width Modulation (pPWM) is discussed in this paper. Function principle and theoretical aspects are described. Further the influence of this method on the static and dynamic output behaviour is investigated. Concerning this, simulation results are shown and have been verified by practical measurements. Finally a full digital implementation of the pPWM waveform generator is given.
	THE PARALLEL RESONANT CONVERTER - A DYNAMICAL SYSTEM APPROACH   By Enric Fossas; Robert Pique	[View]   [Download]
Abstract: This paper introduces a complete circuital model for the parallel-loaded resonant converter (PRC). From this model the PRC is studied as a discontinuous dynamical system providing new perspectives for the resonant converter modelization (SRC, PRC, LCC,...). Furthermore, by application of duality rules to the model, other converter topologies can be derived. Experimental results are in perfect agreement with the theoretical predictions of the model.
	MODELLING OF VOLTAGE AND CURRENT MODE CONTROLLED PWM CONVERTERS USING SIMULINK   By P.R. Holme; C.D. Manning	[View]   [Download]
Abstract: A state space averaged/sampled data Simulink model is presented for voltage and current mode controlled PWM converters. This enables the effects to be studied of changing power and control circuit parameters on the main converter transfer functions. An example is given of a peak current mode controlled buck converter.
	Prototype Drive and Modulation Concepts for DSP-Controlled Ultrasonic Motors powered by Resonant Converters   By J. Maas; N. Fröhleke; P. Krafka; H. Grotstollen	[View]   [Download]
Abstract: The driving principle of travelling wave ultrasonic motors (USM) is basically different from those of electromagnetic motors and requires thus tailored control schemes. This paper deals with newly developed analog and digital modulation concepts to drive a two-phase resonant converter, allowing a feeding of the USM with variable frequency, amplitudes and phase. A flexible experimental set-up for ultrasonic drives controlled by a DSP is presented including a suitable digital measuring system in order to realize efficiently control algorithms for the high level prototype drive.
	AN OBJECT-ORIENTED APPROACH TO COMPUTER AIDED ANALYSIS OF POWER ELECTRONICS SYSTEMS   By A. Mendez; J. Bordonau; J. Peracaula	[View]   [Download]
Abstract: An object-oriented approach to Computer Aided Analysis in Power Electronics is presented. This method provides the simulation efficiency of high-level language-based tools and a degree of user-friendly features as in specific-purpose simulation programs. The method is based on the use of different objects: subcircuits and high-level control descriptions. Subcircuits model the behaviour of the hardware of the system: input filter, converter, output filter and load, while high-level control descriptions are used for the software of the converter. Subsequently, analysis of complete systems is allowed, including converter, control subsystem, input and output filters and load. An example of the approach is given, comparing this approach for the case of a single-phase inverter, when simulated with well-known techniques such as SPICE.
	A NEURAL FUZZY CONTROL WITH STATOR RESISTANCE ESTIMATOR FOR IM DRIVE WITH DSC   By B. Dobrucky; F. Chaloupka; P. Kucer; V. Racek	[View]   [Download]
Abstract: The paper deals with direct self control, a variation of field oriented control, that uses only stator resistance in its calculations making the controller less sensitive to parameter changes. Some problems emerge in the case that value of stator resistance differs from value used by controller (it is given e.g. by change in stator temperature). Therefore the stator resistance estimator was developed to match the actual machine resistance. The function of this estimator is based on difference between the actual magnitude of stator current and magnitude calculated from desired values of stator flux and electromagnetic torque. The difference between above mentioned magnitude of current replies to error in stator resistance. The stator resistance estimator is based on fuzzy set theory a neural network theory - neural fuzzy resistance estimator. The description of learning process for stator resistance estimator is also done in the paper.
	PULSE WIDTH MODULATION WITH EXTENDED MODULATION DEPTH RANGE FOR THREE-PHASE VOLTAGE CONVERTERS   By N. Pop; A. Kelemen	[View]   [Download]
Abstract: The minimum and maximum values of the modulation depth which observe the minimum switching state time of the converter valves are computed for different modulation methods already known from the technical literature. A new modulation method is proposed, suitable for ac-dc converters operating at high modulation depth and zero phase displacement between phase voltage and current, which increases the allowed maximum modulation depth. Finally, the influence of the new modulation method on line current harmonics is analyzed.
	CURRENT TRANSFORMER PERFORMANCE ON ASYMMETRICAL TRIGGERED THYRISTORIZED CIRCUIT   By L. Pierrat; T. Tran-Quoc	[View]   [Download]
Abstract: This paper presents a computed method of current transformer (CT) steady-state performance including core hysteresis in circuits with symmetrically triggered rectifiers or triacs. The distortion (instantaneous magnitude and phase) in the secondary current of current transformer due to saturation and hysteresis is investigated. Influences of degree of asymmetry (delta-alpha) and firing angle (alpha) upon current transformer accuracy are studied.
	COMPARISON OF A SPACE-VECTOR MODULATION STRATEGY FOR A THREE PHASE STANDARD AND A COMPONENT MINIMIZED VOLTAGE SOURCE INVERTER   By Frede Blaabjerg; Sigurour Freysson; Hans Henrik Hansen; Soren Hansen	[View]   [Download]
Abstract: This paper compares space-vector modulation strategies for a standard and a component minimized VSI-inverter where the input is a single phase rectifier. Two component minimized systems are compared with a traditional inverter with six transistors. Space vector modulation strategies are proposed for the three inverters. The modulation strategies are explained and a comparison is done both by simulation and measurement. A detailed description of the implementation is done. It is concluded that a component minimized VSI-inverter can almost get the same performance as a traditional VSI-inverter if the DC-link voltage can be controlled between the input line voltage and twice the input line voltage and the switching frequency is increased by a factor of two. Otherwise the component minimized inverter has a poorer characteristic, but at least two active power components are saved.
	STANDSTILL ESTIMATION OF ELECTRICAL PARAMETERS IN INDUCTION MOTORS USING AN OPTIMAL INPUT SIGNAL   By H. Borsting; M. Knudsen; P. Vadstrup	[View]   [Download]
Abstract: The paper suggests a simple off-line method to obtain accurate estimates of the resistances and inductances of the induction motor. The method is based on a non recursive prediction error method to estimate the physical parameters directly from a continuous time model description of the motor. To obtain accurate estimates a multi-sinusoid has been optimized based on a sensitivity analysis. All measurements are performed at stand-still and the motor is excited by a single-phase multi-sinusoid.
	NONLINEAR FIELD ORIENTED CONTROL IN A ROTOR REFERENCE FRAME   By P. J. Coussens; A. P. Van den Bossche; J. A. Melkebeek	[View]   [Download]
Abstract: Field oriented control for a squirrel cage motor can be implemented, in many different ways. Most systems employ a reference frame fixed to the estimated flux (e.g. rotor flux). However, for an indirect rotor flux based system a reference frame fixed to the rotor has a lot of advantages. By this approach the calculations for the vector rotations can be performed. in hardware. This frees up calculation capacity on the controlling microprocessor which can then be used to implement a nonlinear motor model. This paper describes the actual implementation of a field oriented control in a reference frame fixed to the rotor. The rotor flux is estimated using a nonlinear approximation. The performance has been verified by measurements and simulations. The proposed method has possibilities for on-line rotor resistance estimation.
	AVERAGED MODELLING FOR AC CONVERTERS WORKING UNDER DISCONTINUOUS CONDUCTION MODE - APPLICATION TO THYRISTORS CONTROLLED SERIES COMPENSATORS   By S. Bacha; J.P. Rognon; N. Hadj Said	[View]   [Download]
Abstract: In this paper, the authors present a dynamic modelling method for AC power electronic static converters working under discontinuous conduction mode. It is based on an harmonic development. First, the basic element is modelled separately for various loads. Finally, a complete structure which represents a Thyristors Controlled Series Compensator (TCSC) is modelled. The simulation of the model and its corresponding structure is achieved in order to validate the method.
	IMPROVING IGBT BEHAVIOUR ON SHORT CIRCUIT CONDITION   By A. S. Carvalho; A. P. Martins; A. S. Araujo	[View]   [Download]
Abstract: The short circuit clearance in IGBT based power converters must be done with gate control such that the maximum current and voltage ratings are not exceeded. Conventional drives, using normal off commutation circuit, usually react fastly to the fault with current commutation time optimised for the normal working frequency of the converter. For inverters in the power range of several tens of kVA the physical disposition of the semiconductors does not allow to continuously reduce the leakage inductance. So this commutation time causes the overdimensioning of the capacitor of the turn off aid circuit, derating the commutation frequency. If the short circuit current is shared between the limiter and the power semiconductor the overvoltage may be reduced enabling the use of a smaller capacitor that benefits the duties and working frequency. This paper presents a drive circuit ruling these characteristics.
	INDIRECT SENSORS FOR ELECTRIC DRIVES   By M. Jufer	[View]   [Download]
Abstract: Any electric motor has intrinsic feed-backs, depending on the movement or on the load. These behaviors can be systematically used in order to create indirect sensors or observers, using PC-board or integrated electronics. The main possibilities are : dynamic position and speed sensors using a direct or indirect measurement of the back-EMF, the third harmonic of thf) back EMF or the current analysis; static position sensors using the PM saturation effect or the variable reluctance; torque sensors using the current and voltage measurements in order to determine the load behaviour. These techniques can be mainly applied to EC motors as the brushless DC motor or the switched reluctance motor. A comparative analysis of the main solutions is presented and summarized in a table, proposing the best choices according to specific applications.
	CHARACTERISTICS OF ELECTRIC DRIVE WITH THREE PHASE ASYNCHRONONS MOTOR OPERATED FROM ONE-PHASE SUPPLY LINE VIA THYRISTOR SWITCH IN FREQUENCY-STEP MODE   By A. L. Pisarev; Yu. T. Portnoy	[View]   [Download]
Abstract: The new method of control of electric drive with three-phase asynchronous motor (AM) operated from one-phase sypply line via thyristor switch (TS) is given in account. The method is named the frequency-step one. Application: supplied from one-phase main electrical drive with control speed and position (robots, medicine and domestic equipment). It is shown characteristics of drive with AM and TS are better than characteristics of drive with step motor. It is given PC-simulation and experimental data.