EPE Association: EPE 1985 - 11 - Lecture Session 2.04: MICROPROCESSOR BASED PWM TECHNIQUES

EPE 1985 - 11 - Lecture Session 2.04: MICROPROCESSOR BASED PWM TECHNIQUES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 11 - Lecture Session 2.04: MICROPROCESSOR BASED PWM TECHNIQUES

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   SOFTWARE TESTING FOR THE MICROPROCESSOR CONTROL OF A PWM TRANSISTOR INVERTER
By M. Serbanescu; E. Pacuraru [View]
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Abstract: The microprocessor control of PWM inverters used for variable-speed induction motor drives offers new ways to obtain better performances. A low harmonics content of the inverter current over a wide range of frequencies, and a fast system response are the most important requirements to be met. The approach of this paper is based on uniform sampIing using both on-Iine calculations and look-up tables containing results of off-line calculations. An interrupt-driven multitasking software configuration is developed and tested. The software testing techniques used have been instrumental in choosing a better configuration for the real time control system. The microprocessor controlled PWM transistor inverter has a wide frequency range (0.5 Hz - 100 Hz) and the harmonics content of the output current is very satisfactory over the full range of operation.

   A NEW MICROCOMPUTER BASED A.C. TO A.C. DIRECT FREQUENCY CONVERSION METHOD
By M. Aktekin [View]
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Abstract: This paper proposes a new a.c. to a.c. direct frequency conversion method. The proposed method depends on a microcomputer based intelligent switching of the line phases. The method gives good harmonic suppression and very large frequency conversion range (e.g. 0 Hz. to 150Hz.) compared to the cycloconverters. The cycloconverters have a shortcome on their harmonic noise and conversion range. But, the method needs high frequency sampling from the three line phases with a complex phase selection algorithm. The method also requires fast and forced commutation circuits. Various phase selection algorithms have been tested by using an induction motor model in the simulation. The motor speed, torque and current waveforms and their harmonic analysis during start up time also are given for various conversion parameters.

   SURVEY OF PWM TECHNIQUES FOR SINGLE PHASE TRANSISTOR INVERTERS
By G. A. Capolino; O. Hasnaoui [View]
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Abstract: Several pulse-width modulation (PWM) strategies used to generate the control signal for a single phase transistor inverter are described such as optimum, natural, regular and current-hysteresis ("bang-bang") sampled with two levels (+E, -E) or three levels (+E, 0, -E) control. The performances of the control techniques are analysed by means of minicomputer in terms of voltage waveform, harmonic spectra and performance index. The simulation permits a comparative analysis between the different techniques and displays the principle advantages in order to improve the performances of the power converters.

   A MICROPROCESSOR-BASED IMPLEMENTATION OF REGULAR SAMPLED PWM SWITCHING STRATEGY
By E. S. Tez; D. Akhrib [View]
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Abstract: A simple way of implementing the regular-sampled symmetric PWM switching strategy by microprocessors is described for use in 3-phase induction motor drives. The requirement of maintaining the inverter output voltage-to-frequency (V/f) ratio constant, together with the synchronous nature of the modulation strategy, results in considerable simplification in the system software. The hardware and software details are presented along with the experimentally-obtained PWM switching waveforms. Besides the regular-sampled PWM strategy presented in this paper, it is hoped to report during the conference on a totally new digital pulse-width-modulation technique, which promises to outperform all the existing analog and digital techniques of PWM switching signal generation.

   MODULATEUR A HAUTES PERFORMANCES POUR ONDULEURS A TRANSITORS
By P. Mathys; J. Koulischer [View]
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Abstract: Recent developments in power semi-conductors have led to faster invertors, well-suited for PWM control of AC drives. The paper presents a high performance microprocessor based PWM modulator meeting the requirements of such inverters. It generates asynchronous PWM waves with great accuracy in the position of firing angles, even at high carrier frequencies.

   A NOVEL ANALYTICAL STUDY OF DISTORTION MINIMIZATION PWM
By M. G. Egan; J. M. D. Murphy [View]
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Abstract: In pulsewidth modulated inverters for induction motor drives it has been shown that the distortion minimization modulation strategy offers the possibility of optimum inverter and motor performance in the critical transition region up to the familiar six-step waveform. The study of this technique in general, however, relies upon complex and time-consuming multivariable search techniques and methods must be found to reduce the problem to a form which is more suited to computer analysis. In this paper a new, direct analytical approach to the distortion minimization strategy is presented, which greatly simplifies the evaluation of the optimum switching angles for any number of switchings per cycle and for a given value of fundamental voltage. Among the principal advantages of this technique are its simplicity, accuracy, ease of computer implementation and the fact that it does not require the evaluation of long Fourier series. It is also a purely analytical approach and it is directly applicable to both single-phase and three-phase systems. In the final part of this paper a digital modulator which is capable of implementing these optimum waveforms is presented. This modulator is designed to have very fast transient response with zero phase shift.

EPE 1985 - 11 - Lecture Session 2.04: MICROPROCESSOR BASED PWM TECHNIQUES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 11 - Lecture Session 2.04: MICROPROCESSOR BASED PWM TECHNIQUES
	[return to parent folder]

	SOFTWARE TESTING FOR THE MICROPROCESSOR CONTROL OF A PWM TRANSISTOR INVERTER By M. Serbanescu; E. Pacuraru	[View] [Download]
Abstract: The microprocessor control of PWM inverters used for variable-speed induction motor drives offers new ways to obtain better performances. A low harmonics content of the inverter current over a wide range of frequencies, and a fast system response are the most important requirements to be met. The approach of this paper is based on uniform sampIing using both on-Iine calculations and look-up tables containing results of off-line calculations. An interrupt-driven multitasking software configuration is developed and tested. The software testing techniques used have been instrumental in choosing a better configuration for the real time control system. The microprocessor controlled PWM transistor inverter has a wide frequency range (0.5 Hz - 100 Hz) and the harmonics content of the output current is very satisfactory over the full range of operation.

	A NEW MICROCOMPUTER BASED A.C. TO A.C. DIRECT FREQUENCY CONVERSION METHOD By M. Aktekin	[View] [Download]
Abstract: This paper proposes a new a.c. to a.c. direct frequency conversion method. The proposed method depends on a microcomputer based intelligent switching of the line phases. The method gives good harmonic suppression and very large frequency conversion range (e.g. 0 Hz. to 150Hz.) compared to the cycloconverters. The cycloconverters have a shortcome on their harmonic noise and conversion range. But, the method needs high frequency sampling from the three line phases with a complex phase selection algorithm. The method also requires fast and forced commutation circuits. Various phase selection algorithms have been tested by using an induction motor model in the simulation. The motor speed, torque and current waveforms and their harmonic analysis during start up time also are given for various conversion parameters.

	SURVEY OF PWM TECHNIQUES FOR SINGLE PHASE TRANSISTOR INVERTERS By G. A. Capolino; O. Hasnaoui	[View] [Download]
Abstract: Several pulse-width modulation (PWM) strategies used to generate the control signal for a single phase transistor inverter are described such as optimum, natural, regular and current-hysteresis ("bang-bang") sampled with two levels (+E, -E) or three levels (+E, 0, -E) control. The performances of the control techniques are analysed by means of minicomputer in terms of voltage waveform, harmonic spectra and performance index. The simulation permits a comparative analysis between the different techniques and displays the principle advantages in order to improve the performances of the power converters.

	A MICROPROCESSOR-BASED IMPLEMENTATION OF REGULAR SAMPLED PWM SWITCHING STRATEGY By E. S. Tez; D. Akhrib	[View] [Download]
Abstract: A simple way of implementing the regular-sampled symmetric PWM switching strategy by microprocessors is described for use in 3-phase induction motor drives. The requirement of maintaining the inverter output voltage-to-frequency (V/f) ratio constant, together with the synchronous nature of the modulation strategy, results in considerable simplification in the system software. The hardware and software details are presented along with the experimentally-obtained PWM switching waveforms. Besides the regular-sampled PWM strategy presented in this paper, it is hoped to report during the conference on a totally new digital pulse-width-modulation technique, which promises to outperform all the existing analog and digital techniques of PWM switching signal generation.

	MODULATEUR A HAUTES PERFORMANCES POUR ONDULEURS A TRANSITORS By P. Mathys; J. Koulischer	[View] [Download]
Abstract: Recent developments in power semi-conductors have led to faster invertors, well-suited for PWM control of AC drives. The paper presents a high performance microprocessor based PWM modulator meeting the requirements of such inverters. It generates asynchronous PWM waves with great accuracy in the position of firing angles, even at high carrier frequencies.

	A NOVEL ANALYTICAL STUDY OF DISTORTION MINIMIZATION PWM By M. G. Egan; J. M. D. Murphy	[View] [Download]
Abstract: In pulsewidth modulated inverters for induction motor drives it has been shown that the distortion minimization modulation strategy offers the possibility of optimum inverter and motor performance in the critical transition region up to the familiar six-step waveform. The study of this technique in general, however, relies upon complex and time-consuming multivariable search techniques and methods must be found to reduce the problem to a form which is more suited to computer analysis. In this paper a new, direct analytical approach to the distortion minimization strategy is presented, which greatly simplifies the evaluation of the optimum switching angles for any number of switchings per cycle and for a given value of fundamental voltage. Among the principal advantages of this technique are its simplicity, accuracy, ease of computer implementation and the fact that it does not require the evaluation of long Fourier series. It is also a purely analytical approach and it is directly applicable to both single-phase and three-phase systems. In the final part of this paper a digital modulator which is capable of implementing these optimum waveforms is presented. This modulator is designed to have very fast transient response with zero phase shift.