EPE Association: EPE 1985 - 09 - Lecture Session 2.02: HARMONICS AND DISTORTION

EPE 1985 - 09 - Lecture Session 2.02: HARMONICS AND DISTORTION
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   DETECTING CROSSOVER MOMENTS OF ALTERNATING VOLTAGES
By R. Kennel [View]
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Abstract: Controlling converters it is often necessary to synchronize the control circuits with a line voltage or a load voltage - especially in the case of line commutated or load commutated converters. Normally this synchronization signal is noisy. The noise, which is mostly produced by the controlled converter itself or by other converters, leads to disturbances of circuits detecting the crossover moments of the synchronization signal. The application of filters has the effect of a detecting delay, which should be avoided to utilize the full range of the converter. In this paper a non-linear crossover detection circuit is proposed which eliminates disturbances without delaying the detected signal. This type of detection circuit is qualified for synchronizing microcomputers in real-time converter control applications.

   A HARMONlC CONTROL SCHEME FOR THE ACTlVE POWER FILTER
By E. Masada; K. Hayafune; Y. Ogihara [View]
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Abstract: In order to compensate the harmonics current in the power line, a novel control scheme for the active power filter using the current-fed inverter is proposed. This control principle is based on the numerical signal processing and easily realized with the microcomputer software. The output current waveform of the inverter is precisely determined to cancel specified harmonic components in the load current. Measurement of harmonic components and generation of pulse pattern are carried out with a microcomputer. This control scheme is verified by a model active filter experimentally under various harmonics and parallel load conditions. The results show better compensating ability especially for lower frequency harmonics than other types of active filters.

   A NEW DIGITAL SYSTEM FOR SIGNAL PROCESSING ON INVERTER-FED INDUCTION MOTORS
By A. Dell'Aquila; V. Di Lecce; L. Salvatore; M. Savino [View]
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Abstract: The paper describes a digital system for measuring harmonic voltages and currents for analysis of inverter-fed induction motors. The new system allows high accuracy measurements by using the Fast Fourier Transform in combination with suitable windows and interpolation algorithms in order to eliminate the spectral leakage errors. The system permits also accurate on-line measurements of power input and calculation of harmonic impedances so that a suitable motor model is obtainable.

   CURRENT UNBALANCE IN HIGH PULSE CONVERTERS
By F. Kehtari [View]
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Abstract: Industrial expansion of the power electronic installations shifts some design criterias of converters from the converters as separate devices to their AC network power supply. However, the exact confiquration of the AC network is generally unknown, and it changes in accordance with the active load or the adjunction of new installations. Of course, for a large majority of implementations, the influence of the AC network can be ignored, as far as the average performances of the converters are concerned. Hence in some couplings, the confiquration of the AC network may cause surprising effects. For applications requiring smooth DC voltage or low harmonics distorsion high pulse converters are more preferably decided. A typical solution to obtain a high pulse number of rectification, is the use of several converters in parallel. Under certain circumstances, such solutions lead to a current unbalance function of the converters. The analysis of the phenomenon, as detailed in this paper, denotes important aspects for the design of such converters.

EPE 1985 - 09 - Lecture Session 2.02: HARMONICS AND DISTORTION
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1985 - Conference > EPE 1985 - 09 - Lecture Session 2.02: HARMONICS AND DISTORTION
	[return to parent folder]

	DETECTING CROSSOVER MOMENTS OF ALTERNATING VOLTAGES By R. Kennel	[View] [Download]
Abstract: Controlling converters it is often necessary to synchronize the control circuits with a line voltage or a load voltage - especially in the case of line commutated or load commutated converters. Normally this synchronization signal is noisy. The noise, which is mostly produced by the controlled converter itself or by other converters, leads to disturbances of circuits detecting the crossover moments of the synchronization signal. The application of filters has the effect of a detecting delay, which should be avoided to utilize the full range of the converter. In this paper a non-linear crossover detection circuit is proposed which eliminates disturbances without delaying the detected signal. This type of detection circuit is qualified for synchronizing microcomputers in real-time converter control applications.

	A HARMONlC CONTROL SCHEME FOR THE ACTlVE POWER FILTER By E. Masada; K. Hayafune; Y. Ogihara	[View] [Download]
Abstract: In order to compensate the harmonics current in the power line, a novel control scheme for the active power filter using the current-fed inverter is proposed. This control principle is based on the numerical signal processing and easily realized with the microcomputer software. The output current waveform of the inverter is precisely determined to cancel specified harmonic components in the load current. Measurement of harmonic components and generation of pulse pattern are carried out with a microcomputer. This control scheme is verified by a model active filter experimentally under various harmonics and parallel load conditions. The results show better compensating ability especially for lower frequency harmonics than other types of active filters.

	A NEW DIGITAL SYSTEM FOR SIGNAL PROCESSING ON INVERTER-FED INDUCTION MOTORS By A. Dell'Aquila; V. Di Lecce; L. Salvatore; M. Savino	[View] [Download]
Abstract: The paper describes a digital system for measuring harmonic voltages and currents for analysis of inverter-fed induction motors. The new system allows high accuracy measurements by using the Fast Fourier Transform in combination with suitable windows and interpolation algorithms in order to eliminate the spectral leakage errors. The system permits also accurate on-line measurements of power input and calculation of harmonic impedances so that a suitable motor model is obtainable.

	CURRENT UNBALANCE IN HIGH PULSE CONVERTERS By F. Kehtari	[View] [Download]
Abstract: Industrial expansion of the power electronic installations shifts some design criterias of converters from the converters as separate devices to their AC network power supply. However, the exact confiquration of the AC network is generally unknown, and it changes in accordance with the active load or the adjunction of new installations. Of course, for a large majority of implementations, the influence of the AC network can be ignored, as far as the average performances of the converters are concerned. Hence in some couplings, the confiquration of the AC network may cause surprising effects. For applications requiring smooth DC voltage or low harmonics distorsion high pulse converters are more preferably decided. A typical solution to obtain a high pulse number of rectification, is the use of several converters in parallel. Under certain circumstances, such solutions lead to a current unbalance function of the converters. The analysis of the phenomenon, as detailed in this paper, denotes important aspects for the design of such converters.