EPE Association: EPE 1993 - 47 - Dialogue Session DS3.5: CONTROL: OBSERVERS, TRANSDUCERS, SIMULATION, MECHANICAL ASPECTS

EPE 1993 - 47 - Dialogue Session DS3.5: CONTROL: OBSERVERS, TRANSDUCERS, SIMULATION, MECHANICAL ASPECTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 47 - Dialogue Session DS3.5: CONTROL: OBSERVERS, TRANSDUCERS, SIMULATION, MECHANICAL ASPECTS

   [return to parent folder]

   DETERMINATION OF MECHANICAL RESONANCES IN INDUCTION MOTORS BY RANDOM MODULATION AND ACOUSTIC MEASUREMENT
By Frede Blaabjerg; John K Pedersen; Ewen Ritchie; Peter Nielsen [View]
[Download]

Abstract: Acoustic noise emission from PWM-VSI inverter driven induction motors is a well known problem. The generated noise depends mainly on two factors: The harmonic content of the supply voltage waveform and the mechanical resonance frequencies of the induction motor. lt is necessary to know the mechanical resonances to optimize the switching scheme of the inverter to reduce the noise emission. Measuring the resonance frequencies is normally a laborious process. This paper introduces a new method for estimating the mechanical resonances from acoustic noise measurements. By random modulation of the output voltage of the inverter, the voltage spectrum can be spread over a wide frequency range. By FFT-analyzing the measured acoustic noise, the resonances can easily be estimated as the dominant frequencies of the acoustic noise spectrum. The method is tested on a 2.2 kW induction motor at no load and full load. Some of the mechanical resonances of the motor at no load are calculated by the Holzer method. The calculations show some agreement with the sound measurements. The influence of the fan cowl is investigated and it is concluded that this can be an important factor in the acoustic noise emission. Finally, it is observed that new mechanical resonances appear at load operation when the induction motor is mounted on a pump system and they are estimated by the measurement technique.

   ON-LINE ESTIMATION OF INDUCTION MOTOR PARAMETERS BY EXTENDED KALMAN FILTER
By T. Kataoka; S. Toda; Y. Sato [View]
[Download]

Abstract: In variable speed ac drives it is often important to know the accurate values of motor parameters to realize high performance drive systems. In this paper on-line estimation of two parameters of an induction motor, the rotor resistance and magnetizing inductance, which are important in field-oriented control is investigated by using an extended Kalman filter. A continuous form Kalman filter is adapted to reduce the amount of calculation needed. An estimation system based on this Kalman filter algorithm is implemented employing a digital signal processor. Using this estimation system the influence of covariances of noises and initial setting of parameters on the estimation results is first investigated. The variations of rotor resistance with temperature and magnetizing inductance with flux level are then estimated. The influence of load torque variations on the estimated parameters are also shown. These experimental results confirm the usefulness of on-line parameter estimation using Kalman filter.

   REDUNDANT DRIVE CONTROL BY OBSERVERS
By Klaus Hofer [View]
[Download]

Abstract: An increasing level of automation (intelligence) of technical processes automatically implies an increasing number of electric propulsion drives (muscles). These drives provide the necessary motion and dynamic in production plants as well as within the products itself. Because the failure of one single electric drive can possibly lead to a breakdown of the total production process causing relevant losses of production and / or give rise to dangerous situations an increasing demand exists for electric propulsion drives with high operational safety. This can only be guaranteed by redundant data acquisition and processing because in case of a damaged component (e.g. sensors) its fuction will be taken over by another component without affecting the total function of the system. The following article will show that this is not only possible in process plants with high investment costs but also in the so-called LOW-COST automation.

   DEADBEAT FLUX LEVEL CONTROL OF DIRECT FIELD ORIENTED INDUCTION SERVO MOTOR USING ADAPTIVE ROTOR FLUX OBSERVER
By K. Matsuse; Y. Tadokoro [View]
[Download]

Abstract: A deadbeat flux level control system of direct field oriented induction servo motor drives by use of an adaptive rotor flux observer is proposed. In this system, the adaptive rotor flux observer of a full-order type is used to construct the direct field oriented controller and to keep good performance of deadheat controller in spite of parameter variations of the equivalent circuit of an induction servo motor. The stator and rotor resistances are identified on the basis of the adaptive control theory. The fundamental characteristics of the system are discussed on the basis of experimental and simulation results. In this paper, we will also discuss that the high horse-power induction servo motor driven by this proposed system has high efficiency and good dynamic response.

   DYNAMIC MODELLING OF SWITCHING SYSTEMS
By H. R. Visser; P. P. J. van den Bosch [View]
[Download]

Abstract: A generalized approach for obtaining a small-signal model of linear switching systems is described. Starting from a piece-wise constant linear description of the system, a concise, discrete-time model is obtained using the augmented state vector method. This model together with a generalized description of the transition conditions between the modes is used to obtain the cyclic state of the system. Linearization of both the model and the transition conditions yields a linear small-signal model, which is valid in the vicinity of an operating point. Due to the augmented state form of the system, this linearized model can easily be calculated. This method for obtaining a small-signal model is applicable to a large class of systems. As an example, the advantages of the method are shown in an experiment with a DC-motor drive.

   MULTILEVEL MODELING AND SIMULATION OF POWER ELECTRONIC SYSTEMS
By P. J. van Duijsen [View]
[Download]

Abstract: This paper introduces the program CASPOC for multilevel modeling and simulation of electric circuits and dynamic block diagram. Because of the multilevel approach it is possible to model the power converter, electric components and the control on different levels. These levels are combined into one multilevel model. lt combines the advantages of modeling with circuit elements, dynamic non-linear system blocks and modeling language. Using the program you can model power electronic converters and electric machines. You can also model an analog or digital control, like for example vector or fuzzy control, enabling the complete multilevel modeling and simulation of drive systems.

   CONTROL OF AN ELEVATOR DRIVE WITH A SINGLE-SIDED LINEAR INDUCTION MOTOR
By J. F. Gieras; P. D. Hartzenberg; I. J. Magura; M. Wing [View]
[Download]

Abstract: A new concept for the application of a linear induction motor (LIM) to passenger elevators is given. A programmable logic contoller (PLC) has been implemented to achieve a suitable control of the drive system. A laboratory-scale physical model has been built. To measure the drive performance, a PC based data acquisition system has been used. The experimental test results have been discussed.

   INFLUENCE OF CURRENT OBSERVERS ON THE PERFORMANCES OF A PMSM SUPPLIED BY HYSTERESIS CURRENT CONTROLLED VSI
By H. Bouzekri; F. Meibody Tabar; B. Davat; O. Gosselin [View]
[Download]

Abstract: The Permanent Magnet Synchronous Machines (PMSM) are becoming more and more attractive to be used as embarked actuators. In most industrial applications, PMSMs are supplied by trapezoidal phase current and driven by a six sector position sensor. Using classical current sensing modes, an over current can appears during the commutation of the switches. The demagnetization of the PMSM rotor magnets and the increase of the torque ripple can result under such circumstances. This paper presents an original means of phase current observing in a PMSM supplied by a trapezoidal hysteresis current controlled VSI. The efficiency of the proposed sensing mode has been tested by digital simulation and confirmed by experimental results.

   A New Torque Calculator for Axial Winders with AC Motor Drives
By U. Riefenstahl; S. Kühne; R. Kroll [View]
[Download]

Abstract: This work presents a new torque calculator for winders with AC motor. A precise torque with a defect lower than 1 % is often required for an axial winder in the paper or iron- and steel industry. These demands are hard to please and at the moment realised only with DC- drives. The reasons to use AC motors in winders are their higher qualities with respect to robustness and maintainance. The implementalion of an exactly torque computation for an AC motor is more difficult than for a DC motor because there exist more variablt machine parameters (inductances and resistances). This paper shows a torque calculator with a robust flux observer, which permits to compute the torque with a precise statical and good dynamical behavoir.

   REDUCTION OF ACOUSTICAL NOISE EMISSION IN AC-MACHINES BY INTELLIGENT DISTRIBUTED RANDOM MODULATION
By John K. Pedersen; Frede Blaabjerg; Per S. Frederiksen [View]
[Download]

Abstract: AC-machines driven by PWM-VSI inverters emit acoustical noise. The dominating frequencies in the acoustical noise emission spectra are placed around the switching frequency of the inverter and multiples of this. To reduce the emitted noise a quasi random modulation strategy is proposed. Quasi random modulation means that the switching frequency is varied within a prespecified frequency band. The modulation gives the emitted noise a more "acceptable" sound for the human ear due to the distinct tones are less significant. The modulation strategy is improved in order to distribute the output voltage spectra more uniform. Measurements show an almost uniform distribution of the voltage spectra when a special weight function of the distribution of the random modulation frequency is used. Further improvements can be done by considering the mechanical resonance frequencies of the AC-machine. Test on a pump system shows that omitting the switching frequencies around estimated mechanical resonance frequencies of the AC-machine and Ioad reduces the emitted acoustical noise significantly. It is concluded that an almost silent AC-machine is obtained even at low switching frequencies.

   THE OPTIMIZATION PARAMETERS OF SPACE VECTOR MODULATION
By F. Jenni; D. Wueest [View]
[Download]

Abstract: The principal advantage of space vector modulation is its aptitude for easy microprocessor implementation. Most of today's realizations use that principle in its most simple form, being identical to a regular sampled carrier based PWM. A thorough analysis and discussion of all degrees of freedom, together with simulation results, reveals that this implementation is nearly optimal in a wide range of operation. An additional reduction of the distortion currents is possible for a high modulation index.

   Modelling and Control of a Cycloconverter with Permanent Magnet Generator
By N. H. M. Hofmeester; L. J. J. Offringa; H. Polinder; P. P. J. van den Bosch [View]
[Download]

Abstract: A 6-pulse noncirculating current cycloconverter is used as frequency changer for a high-frequency permanent magnet generator. A high-efficiency, high-speed gasturbine in the power range of 250 kW to 870 kW, drives the generator-converter unit. This system is intended for use in total energy systems or hybrid systems in vehicles and high speed vessels. The cycloconverter is designed for three-phase 833 Hz to 50 Hz applications. A new vector control like digital control strategy and a special discrete Fourier filter (DFT), intended for use with a one-phase version of the cycloconvcrter, are described. Both are implemented in a multi-processor digital controller used for feedback control and pulse-pattern generation. Simulation results and measurements of a laboratory one-phase version of the converter and a dummy-generator, using this digital control strategy and DFT, are given.

   Speedcontrol of a continuous casting machine using a street of coupled DC-motors at Hoogovens IJmuiden
By H. G. Jeursen; H. Mijnarends [View]
[Download]

Abstract: Out of ironore Hoogovens makes fluid steel. Continuous casting, in which slabs are cast direct from molten metal, replaces the traditional method of pouring molten steel into a mould to produce ingots which, when solidified, are reheated and rolled into slabs. Continuous casting not only saves time and energy, but also improves the quality of the steel and increases the yield. Moreover, the process is more controllable. At the moment a continuous slab casting machine is used with a street of coupled DC-motors.

   SELF-TUNING STATE CONTROL FOR A POORLY DAMPED MECHANICAL SYSTEM
By N. Klaassen [View]
[Download]

Abstract: As compared to the tuning of a PI-controller, the commissioning of a state controller requires exact knowledge of the plant' s dynamics and is not easily done by hand. To facilitate tuning of a state controller, an automatic plant identification and controller optimization procedure has been developed . The identification algorithm is based on the common extended least squares algorithm. Some modifications improve the robustness of the algorithm against deterministic disturbances. The controller optimization is done by an improved vector optimization method. Fuzzy reasoning is employed to make the optimization easily configurable. Results show the great reliability of the identification and the excellent performance of the optimized controller.

   ONE METHOD FOR INDIRECT SPEED ESTIMATION IN VECTOR CONTROLLED INDUCTION MACHINE DRIVE
By J. Zdenkovic; Z. Kuljic; S. Canic; M. Perkovac [View]
[Download]

Abstract: In order to improve the robustness of vector controlled induction machine drive, the direct speed measurement should not be applied. One method for indirect speed estimation, which permits speed estimation from stator voltage equation in field coordinates is introduced. Presumptions that rotor flux vector modulus is held constant and total leakage factor considered to be zero are used. Speed estimator is applied to the indirect field orientation control structure. Simulation results and experimental verification on real 4kW drive show that good behaviour is obtained in static conditions under variable load and in dynamic conditions under stepwise speed reference changes. The dynamic and static performances are still acceptable even if error in assumed values for stator and rotor resistance exists. Control unit contains two digital signal processors in parallel work. lnverter is realized with IGBTs.

   PERFORMANCE BENEFITS OF RESOLVING CURRENT IN OPEN-LOOP AC DRIVES
By P. P. Waite; G. Pace [View]
[Download]

Abstract: This paper describes the use of the simple mathemetical techniques of high bandwidth resolving of the three phase output currents of an AC drive into active and reactive components. The system feedbacks that may be derived from this, and the performance improvements (compared with traditional current feedback techniques) that may be achieved by this method are also described. These include: fast current limit; ability to handle shock loads; high starting torque with low ripple (achieved by accurate dead-time compensation); stabilisation of unstable motors; handling of overhauling loads; and fast synchronisation to a rotating motor. Practical measurements of the improvements are presented. The methods and features described are implemented in volume manufactured drives.

EPE 1993 - 47 - Dialogue Session DS3.5: CONTROL: OBSERVERS, TRANSDUCERS, SIMULATION, MECHANICAL ASPECTS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 47 - Dialogue Session DS3.5: CONTROL: OBSERVERS, TRANSDUCERS, SIMULATION, MECHANICAL ASPECTS
	[return to parent folder]

	DETERMINATION OF MECHANICAL RESONANCES IN INDUCTION MOTORS BY RANDOM MODULATION AND ACOUSTIC MEASUREMENT By Frede Blaabjerg; John K Pedersen; Ewen Ritchie; Peter Nielsen	[View] [Download]
Abstract: Acoustic noise emission from PWM-VSI inverter driven induction motors is a well known problem. The generated noise depends mainly on two factors: The harmonic content of the supply voltage waveform and the mechanical resonance frequencies of the induction motor. lt is necessary to know the mechanical resonances to optimize the switching scheme of the inverter to reduce the noise emission. Measuring the resonance frequencies is normally a laborious process. This paper introduces a new method for estimating the mechanical resonances from acoustic noise measurements. By random modulation of the output voltage of the inverter, the voltage spectrum can be spread over a wide frequency range. By FFT-analyzing the measured acoustic noise, the resonances can easily be estimated as the dominant frequencies of the acoustic noise spectrum. The method is tested on a 2.2 kW induction motor at no load and full load. Some of the mechanical resonances of the motor at no load are calculated by the Holzer method. The calculations show some agreement with the sound measurements. The influence of the fan cowl is investigated and it is concluded that this can be an important factor in the acoustic noise emission. Finally, it is observed that new mechanical resonances appear at load operation when the induction motor is mounted on a pump system and they are estimated by the measurement technique.

	ON-LINE ESTIMATION OF INDUCTION MOTOR PARAMETERS BY EXTENDED KALMAN FILTER By T. Kataoka; S. Toda; Y. Sato	[View] [Download]
Abstract: In variable speed ac drives it is often important to know the accurate values of motor parameters to realize high performance drive systems. In this paper on-line estimation of two parameters of an induction motor, the rotor resistance and magnetizing inductance, which are important in field-oriented control is investigated by using an extended Kalman filter. A continuous form Kalman filter is adapted to reduce the amount of calculation needed. An estimation system based on this Kalman filter algorithm is implemented employing a digital signal processor. Using this estimation system the influence of covariances of noises and initial setting of parameters on the estimation results is first investigated. The variations of rotor resistance with temperature and magnetizing inductance with flux level are then estimated. The influence of load torque variations on the estimated parameters are also shown. These experimental results confirm the usefulness of on-line parameter estimation using Kalman filter.

	REDUNDANT DRIVE CONTROL BY OBSERVERS By Klaus Hofer	[View] [Download]
Abstract: An increasing level of automation (intelligence) of technical processes automatically implies an increasing number of electric propulsion drives (muscles). These drives provide the necessary motion and dynamic in production plants as well as within the products itself. Because the failure of one single electric drive can possibly lead to a breakdown of the total production process causing relevant losses of production and / or give rise to dangerous situations an increasing demand exists for electric propulsion drives with high operational safety. This can only be guaranteed by redundant data acquisition and processing because in case of a damaged component (e.g. sensors) its fuction will be taken over by another component without affecting the total function of the system. The following article will show that this is not only possible in process plants with high investment costs but also in the so-called LOW-COST automation.

	DEADBEAT FLUX LEVEL CONTROL OF DIRECT FIELD ORIENTED INDUCTION SERVO MOTOR USING ADAPTIVE ROTOR FLUX OBSERVER By K. Matsuse; Y. Tadokoro	[View] [Download]
Abstract: A deadbeat flux level control system of direct field oriented induction servo motor drives by use of an adaptive rotor flux observer is proposed. In this system, the adaptive rotor flux observer of a full-order type is used to construct the direct field oriented controller and to keep good performance of deadheat controller in spite of parameter variations of the equivalent circuit of an induction servo motor. The stator and rotor resistances are identified on the basis of the adaptive control theory. The fundamental characteristics of the system are discussed on the basis of experimental and simulation results. In this paper, we will also discuss that the high horse-power induction servo motor driven by this proposed system has high efficiency and good dynamic response.

	DYNAMIC MODELLING OF SWITCHING SYSTEMS By H. R. Visser; P. P. J. van den Bosch	[View] [Download]
Abstract: A generalized approach for obtaining a small-signal model of linear switching systems is described. Starting from a piece-wise constant linear description of the system, a concise, discrete-time model is obtained using the augmented state vector method. This model together with a generalized description of the transition conditions between the modes is used to obtain the cyclic state of the system. Linearization of both the model and the transition conditions yields a linear small-signal model, which is valid in the vicinity of an operating point. Due to the augmented state form of the system, this linearized model can easily be calculated. This method for obtaining a small-signal model is applicable to a large class of systems. As an example, the advantages of the method are shown in an experiment with a DC-motor drive.

	MULTILEVEL MODELING AND SIMULATION OF POWER ELECTRONIC SYSTEMS By P. J. van Duijsen	[View] [Download]
Abstract: This paper introduces the program CASPOC for multilevel modeling and simulation of electric circuits and dynamic block diagram. Because of the multilevel approach it is possible to model the power converter, electric components and the control on different levels. These levels are combined into one multilevel model. lt combines the advantages of modeling with circuit elements, dynamic non-linear system blocks and modeling language. Using the program you can model power electronic converters and electric machines. You can also model an analog or digital control, like for example vector or fuzzy control, enabling the complete multilevel modeling and simulation of drive systems.

	CONTROL OF AN ELEVATOR DRIVE WITH A SINGLE-SIDED LINEAR INDUCTION MOTOR By J. F. Gieras; P. D. Hartzenberg; I. J. Magura; M. Wing	[View] [Download]
Abstract: A new concept for the application of a linear induction motor (LIM) to passenger elevators is given. A programmable logic contoller (PLC) has been implemented to achieve a suitable control of the drive system. A laboratory-scale physical model has been built. To measure the drive performance, a PC based data acquisition system has been used. The experimental test results have been discussed.

	INFLUENCE OF CURRENT OBSERVERS ON THE PERFORMANCES OF A PMSM SUPPLIED BY HYSTERESIS CURRENT CONTROLLED VSI By H. Bouzekri; F. Meibody Tabar; B. Davat; O. Gosselin	[View] [Download]
Abstract: The Permanent Magnet Synchronous Machines (PMSM) are becoming more and more attractive to be used as embarked actuators. In most industrial applications, PMSMs are supplied by trapezoidal phase current and driven by a six sector position sensor. Using classical current sensing modes, an over current can appears during the commutation of the switches. The demagnetization of the PMSM rotor magnets and the increase of the torque ripple can result under such circumstances. This paper presents an original means of phase current observing in a PMSM supplied by a trapezoidal hysteresis current controlled VSI. The efficiency of the proposed sensing mode has been tested by digital simulation and confirmed by experimental results.

	A New Torque Calculator for Axial Winders with AC Motor Drives By U. Riefenstahl; S. Kühne; R. Kroll	[View] [Download]
Abstract: This work presents a new torque calculator for winders with AC motor. A precise torque with a defect lower than 1 % is often required for an axial winder in the paper or iron- and steel industry. These demands are hard to please and at the moment realised only with DC- drives. The reasons to use AC motors in winders are their higher qualities with respect to robustness and maintainance. The implementalion of an exactly torque computation for an AC motor is more difficult than for a DC motor because there exist more variablt machine parameters (inductances and resistances). This paper shows a torque calculator with a robust flux observer, which permits to compute the torque with a precise statical and good dynamical behavoir.

	REDUCTION OF ACOUSTICAL NOISE EMISSION IN AC-MACHINES BY INTELLIGENT DISTRIBUTED RANDOM MODULATION By John K. Pedersen; Frede Blaabjerg; Per S. Frederiksen	[View] [Download]
Abstract: AC-machines driven by PWM-VSI inverters emit acoustical noise. The dominating frequencies in the acoustical noise emission spectra are placed around the switching frequency of the inverter and multiples of this. To reduce the emitted noise a quasi random modulation strategy is proposed. Quasi random modulation means that the switching frequency is varied within a prespecified frequency band. The modulation gives the emitted noise a more "acceptable" sound for the human ear due to the distinct tones are less significant. The modulation strategy is improved in order to distribute the output voltage spectra more uniform. Measurements show an almost uniform distribution of the voltage spectra when a special weight function of the distribution of the random modulation frequency is used. Further improvements can be done by considering the mechanical resonance frequencies of the AC-machine. Test on a pump system shows that omitting the switching frequencies around estimated mechanical resonance frequencies of the AC-machine and Ioad reduces the emitted acoustical noise significantly. It is concluded that an almost silent AC-machine is obtained even at low switching frequencies.

	THE OPTIMIZATION PARAMETERS OF SPACE VECTOR MODULATION By F. Jenni; D. Wueest	[View] [Download]
Abstract: The principal advantage of space vector modulation is its aptitude for easy microprocessor implementation. Most of today's realizations use that principle in its most simple form, being identical to a regular sampled carrier based PWM. A thorough analysis and discussion of all degrees of freedom, together with simulation results, reveals that this implementation is nearly optimal in a wide range of operation. An additional reduction of the distortion currents is possible for a high modulation index.

	Modelling and Control of a Cycloconverter with Permanent Magnet Generator By N. H. M. Hofmeester; L. J. J. Offringa; H. Polinder; P. P. J. van den Bosch	[View] [Download]
Abstract: A 6-pulse noncirculating current cycloconverter is used as frequency changer for a high-frequency permanent magnet generator. A high-efficiency, high-speed gasturbine in the power range of 250 kW to 870 kW, drives the generator-converter unit. This system is intended for use in total energy systems or hybrid systems in vehicles and high speed vessels. The cycloconverter is designed for three-phase 833 Hz to 50 Hz applications. A new vector control like digital control strategy and a special discrete Fourier filter (DFT), intended for use with a one-phase version of the cycloconvcrter, are described. Both are implemented in a multi-processor digital controller used for feedback control and pulse-pattern generation. Simulation results and measurements of a laboratory one-phase version of the converter and a dummy-generator, using this digital control strategy and DFT, are given.

	Speedcontrol of a continuous casting machine using a street of coupled DC-motors at Hoogovens IJmuiden By H. G. Jeursen; H. Mijnarends	[View] [Download]
Abstract: Out of ironore Hoogovens makes fluid steel. Continuous casting, in which slabs are cast direct from molten metal, replaces the traditional method of pouring molten steel into a mould to produce ingots which, when solidified, are reheated and rolled into slabs. Continuous casting not only saves time and energy, but also improves the quality of the steel and increases the yield. Moreover, the process is more controllable. At the moment a continuous slab casting machine is used with a street of coupled DC-motors.

	SELF-TUNING STATE CONTROL FOR A POORLY DAMPED MECHANICAL SYSTEM By N. Klaassen	[View] [Download]
Abstract: As compared to the tuning of a PI-controller, the commissioning of a state controller requires exact knowledge of the plant' s dynamics and is not easily done by hand. To facilitate tuning of a state controller, an automatic plant identification and controller optimization procedure has been developed . The identification algorithm is based on the common extended least squares algorithm. Some modifications improve the robustness of the algorithm against deterministic disturbances. The controller optimization is done by an improved vector optimization method. Fuzzy reasoning is employed to make the optimization easily configurable. Results show the great reliability of the identification and the excellent performance of the optimized controller.

	ONE METHOD FOR INDIRECT SPEED ESTIMATION IN VECTOR CONTROLLED INDUCTION MACHINE DRIVE By J. Zdenkovic; Z. Kuljic; S. Canic; M. Perkovac	[View] [Download]
Abstract: In order to improve the robustness of vector controlled induction machine drive, the direct speed measurement should not be applied. One method for indirect speed estimation, which permits speed estimation from stator voltage equation in field coordinates is introduced. Presumptions that rotor flux vector modulus is held constant and total leakage factor considered to be zero are used. Speed estimator is applied to the indirect field orientation control structure. Simulation results and experimental verification on real 4kW drive show that good behaviour is obtained in static conditions under variable load and in dynamic conditions under stepwise speed reference changes. The dynamic and static performances are still acceptable even if error in assumed values for stator and rotor resistance exists. Control unit contains two digital signal processors in parallel work. lnverter is realized with IGBTs.

	PERFORMANCE BENEFITS OF RESOLVING CURRENT IN OPEN-LOOP AC DRIVES By P. P. Waite; G. Pace	[View] [Download]
Abstract: This paper describes the use of the simple mathemetical techniques of high bandwidth resolving of the three phase output currents of an AC drive into active and reactive components. The system feedbacks that may be derived from this, and the performance improvements (compared with traditional current feedback techniques) that may be achieved by this method are also described. These include: fast current limit; ability to handle shock loads; high starting torque with low ripple (achieved by accurate dead-time compensation); stabilisation of unstable motors; handling of overhauling loads; and fast synchronisation to a rotating motor. Practical measurements of the improvements are presented. The methods and features described are implemented in volume manufactured drives.