EPE Association: EPE 1993 - 42 - Dialogue Session DS2.7: DRIVES: ANALYSIS, OBSERVERS, TESTING, MODELLING

EPE 1993 - 42 - Dialogue Session DS2.7: DRIVES: ANALYSIS, OBSERVERS, TESTING, MODELLING
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 42 - Dialogue Session DS2.7: DRIVES: ANALYSIS, OBSERVERS, TESTING, MODELLING

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   PRACTICAL FIELD-WEAKENING PERFORMANCE OF THE FIVE CLASSES OF BRUSHLESS SYNCHRONOUS AC MOTOR DRIVE
By W. L. Soong; T. J. E. Miller [View]
[Download]

Abstract: The effect of stator resistance, magnetic saturation and iron losses on the field-weakening performance of synchronous reluctance and surface permanent magnet motors is examined. It is shown that the constant power speed range is relatively unaffected by stator resistance and iron losses but is strongly influenced by saturation. Methods for estimating the reduction in constant power speed range are described. The results are validated by comparisons with experimental measurements for a surface permanent magnet motor and two axially-laminated synchronous reluctance motors.

   REAL-TIME ESTIMATION OF ROTOR POSITION IN PM MOTORS DURING TRANSIENT OPERATION
By N. Ertugrul; P. P. Acarnley; C. D. French [View]
[Download]

Abstract: The paper describes a modern solution to real-time rotor position estimation, which has been the subject of intense research activity for the last 15 years. The previously proposed position estimation scheme based on flux linkage and line current estimation, is implemented in real-time. The overall position estimation strategy is accomplished with a fast digital signal processor, DSP (TMS320C30). The drive, the position estimation model of the test motor, development of hardware, and basic operation of the DSP are discussed. It has been confirmed in experiments that the estimated position tracks the actual position in real-time. As well as eliminating the mechanical shaft position sensor, the investigated method can be used for high performance torque control of brushless PM motors.

   MIXED-FREQUENCY TESTING OF INDUCTION MACHINES USING INVERTERS
By I. Colak; S. Garvey; M. T. Wright [View]
[Download]

Abstract: An inverter can be used to supply a voltage waveform containing more than one frequency component to an induction machine in order to cause full-load currents to flow in the conductors of both the rotor and stator. Unlike the usual mixed-frequency test where (typically) a 0.1 p.u. sinusoidal voltage at 40 Hz is superimposed on a 1.0 p.u. sinusoidal voltage at 50 Hz to supply the machine, the use of an inverter allows the machine tester to have relatively comprehensive control over various quantities which determine the rate at which power is dissipated inside the induction machine. In particular, though conventional practice can cause the correct r.m.s. currents to flow in the stator conductors, it is not generally possible to also ensure that other losses are the same in the mixed-frequency test as they would be during full-load operation of the machine. This paper reports the use of a digital simulation of the induction machine and inverter system to investigate the effects of different possible forms of the mixed-frequency test using an inverter supply. The model used for the induction machine simulation is a phase equation model which has been accelerated by a method developed by the authors.

   IDENTIFICATION OF MACHINE PARAMETERS IN CONVERTER-FED SYNCHRONOUS MOTOR DRIVE SYSTEMS
By J. Faucher; A. P. Xhuvani; H. A. Anvari; S. De Lara [View]
[Download]

Abstract: The authors present a method of identification of machine parameters. They have applied the reference model method to a Iinear model of a permanent magnet motor drive fed by a PWM voltage source inverter. In all cases, the Marquardt method is used for minimising the error function based on the least square criterion. The existence of good concordance between the experimental and the model output (a difference about 2% between estimated and measured values) confirm the validity of the proposed identification method.

   A NEW METHOD OF IDENTIFICATION AND COMPENSATION OF FRICTION AND MACHINING FORCES IN POSITIONING SYSTEMS
By B. Singer [View]
[Download]

Abstract: In electromechanical positioning systems (e. g. machine tools) with high accuracy requirements machining forces and the friction forces in the sliding hearings have a strong effect on the achievable position control quality. In this contribution a new technique for on-line determination of these normally not measurable forces is presented, that gives exact information even at low speeds and standstill. A feedback compensation is described, that takes the identified force as an input and generates an additional input signal for the torque controller of the drive.

   DYNAMIC CONTROL OF SELF-COMMUTATED SYNCHRONOUS MOTOR (SCSM) IN FIELD CONSTANT AND FIELD WEAKENING RANGE
By Krzysztof Zawirski [View]
[Download]

Abstract: In the paper problems of dynamic control of self-commutated synchronous motor (SCSM) with wide speed control range on the base of computer simulation method were solved. Good dynamic motor performance requires quick motor torque control as well as efficient control of machine side converter (MSC), which provides safety commutation process in inverter mode operation. A new general criterion of MSC control - commutation margin flux, which is valid in both speed ranges (below and over rated value) was applied in an adaptive control algorithm construction. Due to this a safety MSC operation during rapid current changes, with minimum possible inverter delay angle was obtained. Introduction of forced commutation, used in torque reverse algorithm, gave good dynamic properties of motor operation. All analyzed and solved control problems are well illustrated by proper transient's diagrams.

   CALCULATION OF TEMPERATURE CONDITIONS IN SEMICONDUCTORS FOR VARIABLE SPEED INDUCTION MOTOR DRIVE
By O. Mo; M. Hernes; T. Rogne [View]
[Download]

Abstract: In a variable speed PWM induction motor drive the maximum allowed current will be limited by the maximum allowed temperature in the semiconductors. The losses, which causes the temperature rise, depends on the current and voltage wave-forms, which varies with applied load, speed and motor parameters. Thus it is a complicated maner to estimate accurate temperature conditions in the semiconductor devices of a PWM induction motor drive. One approach for calculation of losses is by detailed modelling of the switching waveform, from which the losses can be calculated directly (voltage multiplied with current). Such an approach requires a complicated mathematical model which again leads to laborious calculations during the simulation, especially if the switching frequency/fundamental frequency ratio is high. This paper describes an alternative method to be used in a simulation program applying ideal switch models. Instead of a detailed modelling of the switches, simple switch models are used in the simulation (low or high resistance, depending on the state of the device). This makes it possible to simulate several thousand switching intervals, which may very well be required because of the relative large time constants in the thermal calculation. The loss calculations are performed simultanous to the simulation. Each turn-on and turn-off of the device implies a given energy loss. The on-state losses are given by the instantaneous current and chip temperature. The dependency between current, temperature and losses are found from data-sheets and/or loss measurements on a single switch.

   A LINEAR BRUSHLESS DOUBLY-FED MACHINE DRIVE FOR TRACTION APPLICATIONS
By F. Saifkhani; A. K. Wallace [View]
[Download]

Abstract: This paper proposes a new form of traction drive for rapid transit applications and describes work currently undertaken to investigate its viability. A brief background description of linear induction motor propulsion systems and the problems and limitations experienced in their practical application is given. The principle is introduced of the adjustable-frequency self-cascaded induction machine, or brushless doubly-fed machine and its advantages of synchronous operation and significantly reduced converter rating are explained. The linear counterpart of the brushless doubly-fed machine is developed and its perceived advantages and disadvantages for traction application are discussed. The design, and testing to confirm design parameters, of a laboratory machine is described and discussed with respect to its intended application. Finally, predictions of the performance of the drive at speeds commensurate with a typical mass transit system are presented.

   A NEW SPEED OBSERVER FOR AN INDUCTION MOTOR USING THE SPEED ESTIMATION TECHNIQUE
By I. Miyashita; Y. Ohmori [View]
[Download]

Abstract: A new speed observing algorithm for vector controlled induction motor, especially suitable for low speed operation, is proposed. Pulse generator generates pulse trains of which frequency is proportional to the motor speed. However, in low speed, the time interval between pulses becomes too long to detect the actual speed between the pulses. A new speed observer to solve this problem is fundamentally composed by combining the conventional speed calculator and speed sensorless speed estimator. Although estimated speed signal involves the error caused by parameter miss-matching, it will be accurate enough to interporate between two pulses.The fundamental algorithm and experimental results of proposed new speed observer is shown in this paper.

   CONSIDERATION TO THE OPERATION LIMIT OF A FIELD-WEAKENING SPEED CONTROL SYSTEM FOR A SELF-CONTROLLED SYNCHRONOUS MOTOR
By S. Nishikata; W. Takanami; T. Kataoka; A. Ishizaki [View]
[Download]

Abstract: The operation limit as well as the dynamic performance of a field-weakening speed control system for a self-controlled synchronous motor with constant margin angle of commutation is discussed in this paper. The steady-state characteristics of the motor are first shown for both field-weakening control and dc input voltage control regions. It is shown that the experimental value of margin angle in the field-weakening region was reduced as motor speed increased. A simple and effective method to keep the margin angle constant based on correcting the subtransient inductance of the motor in accordance with the air-gap flux is then proposed. This method is useful not only in the steady state, but also in the transient state when the speed reference is changed. Finally the dynamic responses and the operation limit of the field-weakening speed control system when the speed reference is stepped up greatly are clarified for a motor having average constants. It is shown that a large operation range with field-weakening is obtained for a large value of margin angle, and that a large value of short-circuit ratio of the motor widens the operation limit.

   MINIMIZING ELECTROMECHANICAL OSCILLATIONS IN THE DRIVES WITH RESILIENT COUPLINGS BY MEANS OF STATE AND DISTURBANCE OBSERVERS
By M. S. Tondos [View]
[Download]

Abstract: The paper presents the principles of estimating non-measurable state variables and external torque load in the drives with elastic motor shaft (two mass system). In many drive systems resilient couplings between the motor and processing machine, caused by elastic shafts and gears are often unavoidable. General rules of state and disturbance observers design are given. Besides, they have been applied to the drive system with elastic shaft. It is only the possibility of electromechanic torque generated by the motor and speed of motor shaft measurements that is discussed. Schematic diagrams of the drives system with elastic shaft and appropiate diagrams of state and disturbance (i.e. external torque load) observers are shown. The proposed observer could be used for correcting drive control to minimize electromechanical oscillations in a variable-speed drive system, which are caused by elasticity of mechanical connection.

EPE 1993 - 42 - Dialogue Session DS2.7: DRIVES: ANALYSIS, OBSERVERS, TESTING, MODELLING
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 42 - Dialogue Session DS2.7: DRIVES: ANALYSIS, OBSERVERS, TESTING, MODELLING
	[return to parent folder]

	PRACTICAL FIELD-WEAKENING PERFORMANCE OF THE FIVE CLASSES OF BRUSHLESS SYNCHRONOUS AC MOTOR DRIVE By W. L. Soong; T. J. E. Miller	[View] [Download]
Abstract: The effect of stator resistance, magnetic saturation and iron losses on the field-weakening performance of synchronous reluctance and surface permanent magnet motors is examined. It is shown that the constant power speed range is relatively unaffected by stator resistance and iron losses but is strongly influenced by saturation. Methods for estimating the reduction in constant power speed range are described. The results are validated by comparisons with experimental measurements for a surface permanent magnet motor and two axially-laminated synchronous reluctance motors.

	REAL-TIME ESTIMATION OF ROTOR POSITION IN PM MOTORS DURING TRANSIENT OPERATION By N. Ertugrul; P. P. Acarnley; C. D. French	[View] [Download]
Abstract: The paper describes a modern solution to real-time rotor position estimation, which has been the subject of intense research activity for the last 15 years. The previously proposed position estimation scheme based on flux linkage and line current estimation, is implemented in real-time. The overall position estimation strategy is accomplished with a fast digital signal processor, DSP (TMS320C30). The drive, the position estimation model of the test motor, development of hardware, and basic operation of the DSP are discussed. It has been confirmed in experiments that the estimated position tracks the actual position in real-time. As well as eliminating the mechanical shaft position sensor, the investigated method can be used for high performance torque control of brushless PM motors.

	MIXED-FREQUENCY TESTING OF INDUCTION MACHINES USING INVERTERS By I. Colak; S. Garvey; M. T. Wright	[View] [Download]
Abstract: An inverter can be used to supply a voltage waveform containing more than one frequency component to an induction machine in order to cause full-load currents to flow in the conductors of both the rotor and stator. Unlike the usual mixed-frequency test where (typically) a 0.1 p.u. sinusoidal voltage at 40 Hz is superimposed on a 1.0 p.u. sinusoidal voltage at 50 Hz to supply the machine, the use of an inverter allows the machine tester to have relatively comprehensive control over various quantities which determine the rate at which power is dissipated inside the induction machine. In particular, though conventional practice can cause the correct r.m.s. currents to flow in the stator conductors, it is not generally possible to also ensure that other losses are the same in the mixed-frequency test as they would be during full-load operation of the machine. This paper reports the use of a digital simulation of the induction machine and inverter system to investigate the effects of different possible forms of the mixed-frequency test using an inverter supply. The model used for the induction machine simulation is a phase equation model which has been accelerated by a method developed by the authors.

	IDENTIFICATION OF MACHINE PARAMETERS IN CONVERTER-FED SYNCHRONOUS MOTOR DRIVE SYSTEMS By J. Faucher; A. P. Xhuvani; H. A. Anvari; S. De Lara	[View] [Download]
Abstract: The authors present a method of identification of machine parameters. They have applied the reference model method to a Iinear model of a permanent magnet motor drive fed by a PWM voltage source inverter. In all cases, the Marquardt method is used for minimising the error function based on the least square criterion. The existence of good concordance between the experimental and the model output (a difference about 2% between estimated and measured values) confirm the validity of the proposed identification method.

	A NEW METHOD OF IDENTIFICATION AND COMPENSATION OF FRICTION AND MACHINING FORCES IN POSITIONING SYSTEMS By B. Singer	[View] [Download]
Abstract: In electromechanical positioning systems (e. g. machine tools) with high accuracy requirements machining forces and the friction forces in the sliding hearings have a strong effect on the achievable position control quality. In this contribution a new technique for on-line determination of these normally not measurable forces is presented, that gives exact information even at low speeds and standstill. A feedback compensation is described, that takes the identified force as an input and generates an additional input signal for the torque controller of the drive.

	DYNAMIC CONTROL OF SELF-COMMUTATED SYNCHRONOUS MOTOR (SCSM) IN FIELD CONSTANT AND FIELD WEAKENING RANGE By Krzysztof Zawirski	[View] [Download]
Abstract: In the paper problems of dynamic control of self-commutated synchronous motor (SCSM) with wide speed control range on the base of computer simulation method were solved. Good dynamic motor performance requires quick motor torque control as well as efficient control of machine side converter (MSC), which provides safety commutation process in inverter mode operation. A new general criterion of MSC control - commutation margin flux, which is valid in both speed ranges (below and over rated value) was applied in an adaptive control algorithm construction. Due to this a safety MSC operation during rapid current changes, with minimum possible inverter delay angle was obtained. Introduction of forced commutation, used in torque reverse algorithm, gave good dynamic properties of motor operation. All analyzed and solved control problems are well illustrated by proper transient's diagrams.

	CALCULATION OF TEMPERATURE CONDITIONS IN SEMICONDUCTORS FOR VARIABLE SPEED INDUCTION MOTOR DRIVE By O. Mo; M. Hernes; T. Rogne	[View] [Download]
Abstract: In a variable speed PWM induction motor drive the maximum allowed current will be limited by the maximum allowed temperature in the semiconductors. The losses, which causes the temperature rise, depends on the current and voltage wave-forms, which varies with applied load, speed and motor parameters. Thus it is a complicated maner to estimate accurate temperature conditions in the semiconductor devices of a PWM induction motor drive. One approach for calculation of losses is by detailed modelling of the switching waveform, from which the losses can be calculated directly (voltage multiplied with current). Such an approach requires a complicated mathematical model which again leads to laborious calculations during the simulation, especially if the switching frequency/fundamental frequency ratio is high. This paper describes an alternative method to be used in a simulation program applying ideal switch models. Instead of a detailed modelling of the switches, simple switch models are used in the simulation (low or high resistance, depending on the state of the device). This makes it possible to simulate several thousand switching intervals, which may very well be required because of the relative large time constants in the thermal calculation. The loss calculations are performed simultanous to the simulation. Each turn-on and turn-off of the device implies a given energy loss. The on-state losses are given by the instantaneous current and chip temperature. The dependency between current, temperature and losses are found from data-sheets and/or loss measurements on a single switch.

	A LINEAR BRUSHLESS DOUBLY-FED MACHINE DRIVE FOR TRACTION APPLICATIONS By F. Saifkhani; A. K. Wallace	[View] [Download]
Abstract: This paper proposes a new form of traction drive for rapid transit applications and describes work currently undertaken to investigate its viability. A brief background description of linear induction motor propulsion systems and the problems and limitations experienced in their practical application is given. The principle is introduced of the adjustable-frequency self-cascaded induction machine, or brushless doubly-fed machine and its advantages of synchronous operation and significantly reduced converter rating are explained. The linear counterpart of the brushless doubly-fed machine is developed and its perceived advantages and disadvantages for traction application are discussed. The design, and testing to confirm design parameters, of a laboratory machine is described and discussed with respect to its intended application. Finally, predictions of the performance of the drive at speeds commensurate with a typical mass transit system are presented.

	A NEW SPEED OBSERVER FOR AN INDUCTION MOTOR USING THE SPEED ESTIMATION TECHNIQUE By I. Miyashita; Y. Ohmori	[View] [Download]
Abstract: A new speed observing algorithm for vector controlled induction motor, especially suitable for low speed operation, is proposed. Pulse generator generates pulse trains of which frequency is proportional to the motor speed. However, in low speed, the time interval between pulses becomes too long to detect the actual speed between the pulses. A new speed observer to solve this problem is fundamentally composed by combining the conventional speed calculator and speed sensorless speed estimator. Although estimated speed signal involves the error caused by parameter miss-matching, it will be accurate enough to interporate between two pulses.The fundamental algorithm and experimental results of proposed new speed observer is shown in this paper.

	CONSIDERATION TO THE OPERATION LIMIT OF A FIELD-WEAKENING SPEED CONTROL SYSTEM FOR A SELF-CONTROLLED SYNCHRONOUS MOTOR By S. Nishikata; W. Takanami; T. Kataoka; A. Ishizaki	[View] [Download]
Abstract: The operation limit as well as the dynamic performance of a field-weakening speed control system for a self-controlled synchronous motor with constant margin angle of commutation is discussed in this paper. The steady-state characteristics of the motor are first shown for both field-weakening control and dc input voltage control regions. It is shown that the experimental value of margin angle in the field-weakening region was reduced as motor speed increased. A simple and effective method to keep the margin angle constant based on correcting the subtransient inductance of the motor in accordance with the air-gap flux is then proposed. This method is useful not only in the steady state, but also in the transient state when the speed reference is changed. Finally the dynamic responses and the operation limit of the field-weakening speed control system when the speed reference is stepped up greatly are clarified for a motor having average constants. It is shown that a large operation range with field-weakening is obtained for a large value of margin angle, and that a large value of short-circuit ratio of the motor widens the operation limit.

	MINIMIZING ELECTROMECHANICAL OSCILLATIONS IN THE DRIVES WITH RESILIENT COUPLINGS BY MEANS OF STATE AND DISTURBANCE OBSERVERS By M. S. Tondos	[View] [Download]
Abstract: The paper presents the principles of estimating non-measurable state variables and external torque load in the drives with elastic motor shaft (two mass system). In many drive systems resilient couplings between the motor and processing machine, caused by elastic shafts and gears are often unavoidable. General rules of state and disturbance observers design are given. Besides, they have been applied to the drive system with elastic shaft. It is only the possibility of electromechanic torque generated by the motor and speed of motor shaft measurements that is discussed. Schematic diagrams of the drives system with elastic shaft and appropiate diagrams of state and disturbance (i.e. external torque load) observers are shown. The proposed observer could be used for correcting drive control to minimize electromechanical oscillations in a variable-speed drive system, which are caused by elasticity of mechanical connection.