EPE Association: EPE 1991 - 32 - Session 3.10: FIELD ORIENTED CONTROL 1

EPE 1991 - 32 - Session 3.10: FIELD ORIENTED CONTROL 1
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   Experiments for teaching on current-source inverter-fed induction motors with indirect field oriented control
By Ph. Lataire; H. Van Muylem; G. Maggetto [View]
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Abstract: The experiments presented are done on a test set-up designed for educational purposes around a current source inverter-fed induction motor. These experiments are intended for under-graduate students who have choosen their specialisation in the field of electric power engineering, for graduate students in the same field and for interested industry staff members in the frame of special training programs. Besides illustrating the fundamental operation of the induction motor drive, the experiments emphasize the dynamic properties of the drive, the control schemes, the controllers tunings and the parametric sensitivity. The controller can be tuned either as a programmed flux controller or as a field oriented controller based on the induction machine's current model. The paper also shows a particular stabilizing effect of the field oriented controller in the case of large phase lags between the inverter's thyristor firing pulses and the induction motor stator currents.

   EFFECTS OF MAIN FLUX SATURATION ON BEHAVIOR OF A STATOR AND AIRGAP FLUX ORIENTED INDUCTION MACHINE
By E. Levi; V. Vuckovic [View]
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Abstract: Application of decoupling circuits is mandatory, if a high performance induction motor drive with field orientation along stator or airgap flux is to be realized. Decoupler equations are derived from constant parameter induction machine model. However, actual machine parameters are subject to variation. As a consequence, deterioration of drive performance from expected may occur. One of the sources of parameter variations is the main flux saturation. This paper discusses effects of main flux saturation on behavior of a vector controlled, current-fed, induction machine with orientation along stator and airgap flux. Constant parameter decouplers are employed in conjunction with appropriate model of saturated induction machine and simulation study is carried out for a number of different operating conditions. At first, it is assumed that the value of the magnetizing inductance in the decoupler is set to correct value which corresponds to rated operating point. The second part of the simulation study deals with effects of application of detuned magnetizing inductance value in decoupler equations. It is shown that orientation along stator flux exhibits higher degree of sensitivity to saturation level change in the machine, compared to airgap flux orientation.

   ANALYTICAL PARAMETER SENSITIVITY EXPRESSIONS FOR A FIELD ORIENTED INDUCTION MOTOR DRIVE
By T. Du; M. A. Brdys; J. A. Taufiq [View]
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Abstract: It is known that under certain conditions the Indirect Field Orientation Control (IFOC) is equivalent to the Field Acceleration Current Control (CFAM). Based on this fact a new approach to the analysis of parameter sensitivity of an induction motor IFOC drive is presented . The consequence of the motor parameter variation on the rotor flux and electrical torque performance is thoroughly investigated by means of the analytical sensitivity expressions derived not only for the steady state but also for transients. Some new results are demonstrated, among them the conclusion that not all the parameter variations work against the speed of the torque response. This may disagree to some extent with the common expectation.

   THE APPLICATION OF FIELD ORIENTED CONTROL TO THE BRUSHLESS DC MACHINE
By M. T. Wishart; R. G. Harley; G. Diana [View]
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Abstract: The brushless DC machine (BDCM) is similar in structure to the permanent magnet synchranous machine (PMSM) except that its windings and magnets are arranged in a way which produces a trapezoidally shaped back emf rather than a sinusoidally shaped back emf. This paper considers the effect of applying field oriented control (FOC) to the trapezoidally excited brushless DC machine (BDCM). The mathematical model of the BDCM and its inverter is presented and its FOC theory is briefly described. The practical system, built to implement this type of control, is described in detail and simulation studies are conducted. Practical results captured from the physical system are presented for both speed and position control applications agree well with the simulated results. For both speed and position control applications the responses are linear and show no sign of torque oscillations. Although this system would not usually be used for speed control applications (due to economic considerations) it provides a viable alternative to conventional techniques for position control applications.

   SPEED AND POSITION AC-SERVO DRIVE BASED ON CURRENT VECTOR CONTROL
By Poul Erik Nielsen; Kurt Moller; Soren Vammen [View]
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Abstract: This paper describes an AC-servo drive which can be controlled in different speed and position control modes. The drive is adapted to a cost efficient modified standard induction motor with an integrated encoder. The current vector control algorithm is derived from the steady-state solution of the well-known dq-dynamic model. This control method has proven to be very robust to changes in motor temperature. A signal processor is used to run all the control algorithms, and a μ-controller is used for parameter setting and bus control. An ASIC has been developed for encoder signal processing. The results prove that servo performance have been achieved.

   Indirect Phase Current Detection for Field Oriented Control of a Permanent Magnet Synchronous Motor Drive
By J. F. Moynihan; R. C. Kavanagh; M. G. Egan; J. M. D. Murphy [View]
[Download]

Abstract: The field oriented control of a permanent magnet synchronous motor with feedback derived from the dc link current of the inverter is investigated. The derived current signals are updated at the switching frequency of the PWM inverter. The current control algorithm is based on a model of the machine in the rotor reference frame. A space vector modulation strategy is used to determine the switching instants of the voltage source inverter. It is shown that the inverter states in each modulation cycle are such that the values of each of the phase currents can be obtained. Under certain operating conditions, some adjustment of the space vector is required to ensure that reliable samples of the dc link current are acquired. Two such adjustment mechanisms are proposed. Detailed simulations of both strategies are carried out to assess their suitability and accuracy.

EPE 1991 - 32 - Session 3.10: FIELD ORIENTED CONTROL 1
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 32 - Session 3.10: FIELD ORIENTED CONTROL 1
	[return to parent folder]

	Experiments for teaching on current-source inverter-fed induction motors with indirect field oriented control By Ph. Lataire; H. Van Muylem; G. Maggetto	[View] [Download]
Abstract: The experiments presented are done on a test set-up designed for educational purposes around a current source inverter-fed induction motor. These experiments are intended for under-graduate students who have choosen their specialisation in the field of electric power engineering, for graduate students in the same field and for interested industry staff members in the frame of special training programs. Besides illustrating the fundamental operation of the induction motor drive, the experiments emphasize the dynamic properties of the drive, the control schemes, the controllers tunings and the parametric sensitivity. The controller can be tuned either as a programmed flux controller or as a field oriented controller based on the induction machine's current model. The paper also shows a particular stabilizing effect of the field oriented controller in the case of large phase lags between the inverter's thyristor firing pulses and the induction motor stator currents.

	EFFECTS OF MAIN FLUX SATURATION ON BEHAVIOR OF A STATOR AND AIRGAP FLUX ORIENTED INDUCTION MACHINE By E. Levi; V. Vuckovic	[View] [Download]
Abstract: Application of decoupling circuits is mandatory, if a high performance induction motor drive with field orientation along stator or airgap flux is to be realized. Decoupler equations are derived from constant parameter induction machine model. However, actual machine parameters are subject to variation. As a consequence, deterioration of drive performance from expected may occur. One of the sources of parameter variations is the main flux saturation. This paper discusses effects of main flux saturation on behavior of a vector controlled, current-fed, induction machine with orientation along stator and airgap flux. Constant parameter decouplers are employed in conjunction with appropriate model of saturated induction machine and simulation study is carried out for a number of different operating conditions. At first, it is assumed that the value of the magnetizing inductance in the decoupler is set to correct value which corresponds to rated operating point. The second part of the simulation study deals with effects of application of detuned magnetizing inductance value in decoupler equations. It is shown that orientation along stator flux exhibits higher degree of sensitivity to saturation level change in the machine, compared to airgap flux orientation.

	ANALYTICAL PARAMETER SENSITIVITY EXPRESSIONS FOR A FIELD ORIENTED INDUCTION MOTOR DRIVE By T. Du; M. A. Brdys; J. A. Taufiq	[View] [Download]
Abstract: It is known that under certain conditions the Indirect Field Orientation Control (IFOC) is equivalent to the Field Acceleration Current Control (CFAM). Based on this fact a new approach to the analysis of parameter sensitivity of an induction motor IFOC drive is presented . The consequence of the motor parameter variation on the rotor flux and electrical torque performance is thoroughly investigated by means of the analytical sensitivity expressions derived not only for the steady state but also for transients. Some new results are demonstrated, among them the conclusion that not all the parameter variations work against the speed of the torque response. This may disagree to some extent with the common expectation.

	THE APPLICATION OF FIELD ORIENTED CONTROL TO THE BRUSHLESS DC MACHINE By M. T. Wishart; R. G. Harley; G. Diana	[View] [Download]
Abstract: The brushless DC machine (BDCM) is similar in structure to the permanent magnet synchranous machine (PMSM) except that its windings and magnets are arranged in a way which produces a trapezoidally shaped back emf rather than a sinusoidally shaped back emf. This paper considers the effect of applying field oriented control (FOC) to the trapezoidally excited brushless DC machine (BDCM). The mathematical model of the BDCM and its inverter is presented and its FOC theory is briefly described. The practical system, built to implement this type of control, is described in detail and simulation studies are conducted. Practical results captured from the physical system are presented for both speed and position control applications agree well with the simulated results. For both speed and position control applications the responses are linear and show no sign of torque oscillations. Although this system would not usually be used for speed control applications (due to economic considerations) it provides a viable alternative to conventional techniques for position control applications.

	SPEED AND POSITION AC-SERVO DRIVE BASED ON CURRENT VECTOR CONTROL By Poul Erik Nielsen; Kurt Moller; Soren Vammen	[View] [Download]
Abstract: This paper describes an AC-servo drive which can be controlled in different speed and position control modes. The drive is adapted to a cost efficient modified standard induction motor with an integrated encoder. The current vector control algorithm is derived from the steady-state solution of the well-known dq-dynamic model. This control method has proven to be very robust to changes in motor temperature. A signal processor is used to run all the control algorithms, and a μ-controller is used for parameter setting and bus control. An ASIC has been developed for encoder signal processing. The results prove that servo performance have been achieved.

	Indirect Phase Current Detection for Field Oriented Control of a Permanent Magnet Synchronous Motor Drive By J. F. Moynihan; R. C. Kavanagh; M. G. Egan; J. M. D. Murphy	[View] [Download]
Abstract: The field oriented control of a permanent magnet synchronous motor with feedback derived from the dc link current of the inverter is investigated. The derived current signals are updated at the switching frequency of the PWM inverter. The current control algorithm is based on a model of the machine in the rotor reference frame. A space vector modulation strategy is used to determine the switching instants of the voltage source inverter. It is shown that the inverter states in each modulation cycle are such that the values of each of the phase currents can be obtained. Under certain operating conditions, some adjustment of the space vector is required to ensure that reliable samples of the dc link current are acquired. Two such adjustment mechanisms are proposed. Detailed simulations of both strategies are carried out to assess their suitability and accuracy.