EPE Association: EPE 1993 - 30 - Dialogue Session DS1.6: POWER SUPPLIES: HARMONICS

EPE 1993 - 30 - Dialogue Session DS1.6: POWER SUPPLIES: HARMONICS
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   HOW TO AVOID FILTERS IN OFF-LINE POWER SUPPLIES
By M. Albach [View]
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Abstract: In ac-dc switched mode power supplies high frequency filter components are necessary to bring the conducted emissions within the limits of the specifications VDE 0871/5. As these power line filters considerably contribute to total size, weight and cost of the power supply, any improvement is highly desirable. In this paper a new operation mode is presented, which offers the possibility to reduce the filter in the power range below 100 w or even to completely avoid the additional filter components as demonstrated with a 10 w supply for a rechargeable shaver. This new method is based on the effect, that the conducted emissions are transferred to the mains impedance only during the recharging time of the storage capacitor, this means when the rectifier brigde is conducting. During the non-conducting phase the diodes are nearly perfect filter components. Utilizing this different behaviour gives a tremendous benefit for the size and cost of the power supplies. Possible applications are in audio/video, household equipment or in the telecommunication area.

   IMPROVED DOUBLE CONNECTED INVERTER FOR REDUCING OUTPUT VOLTAGE HARMONICS
By S. Iida; S. Masukawa [View]
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Abstract: In this paper, we propose a new method for reducing harmonic components involved in output voltages of the doubIe connected inverter. By adding four auxiliary switching devices and an interphase transformer with secondary winding into the input dc side of the usual 12-step inverter, the proposed circuit can decrease the output voltage harmonics no less than the conventional 36-step inverter. Basic theories are discussed by analyzing the output voltage waveforms, and optimum parameters are derived. Then, We can recognize the effects of harmonic reductions by both theoretical and experimental results. Moreover, we try to suppress surge voltages impressed to switching devices by stray inductances on the equipment wirings in the input dc sides. By applying auxiliary suppressive circuits similar to the usual snubber circuit, we confirm by experiments that they can be enough restrained.

   NONCHARACTERISTIC LINE CURRENT HARMONICS IN DIODE RECTIFIER BRIDGES PRODUCED BY NETWORK ASYMMETRIES
By M. Grötzbach; J. Xu [View]
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Abstract: In case of an asymmetric network, i.e. unbalanced three-phase voltages or/and different line reactances, noncharacteristic harmonics appear in the line current of diode rectifiers. To investigate the basic mechanism of the generation of these noncharacteristics, a discrete small-signal modeling is proposed consisting of difference equations of the dc current and firing angle determinations. Thereby, the influence of network asymmetries is described analytically taking into account commutation process and dc current ripple effects. With this, basic dependencies can be investigated and an effective evaluation of the noncharacteristics is obtained. The results drawn as locis in the complex plane lead to a compact and userfriendly representation. Thereby, arbitrary network asymmetries can be considered easily by corresponding phasor additions, especially for the estimation of the maximum values. Comparing digital simulation studies confirm the validity of small-signal modeling in the practical range of network asymmetries.

   THREE- TO SINGLE-PHASE CONVERTERS WITH A SWITCH-CONTROLLED INTERPHASE TRANSFORMER FOR LOW-DISTORTED SUPPLY OF RESISTIVE LOADS
By V. Sarv; J. Soojarv; A. Tuisk [View]
[Download]

Abstract: Comparative evaluation of three- to single-phase converters with a switch-controlled interphase transformer is given. Design and optimization principles of the phase converters both with the close to rectangular and sinusoidal output voltage waveforms have been analyzed and experimentally evaluated. In case of a single-phase resistive load and rectangular output voltage, the conversion can be carried out using only a properly controlled time-variable transtormer. For a complex load and/or sinusoidal output voltage in addition to the time-variable transformer, a controlled energy storing element is required. Performance characteristics of three 12-pulse converters with a switch-controlled interphase transformer have been described.

EPE 1993 - 30 - Dialogue Session DS1.6: POWER SUPPLIES: HARMONICS
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 30 - Dialogue Session DS1.6: POWER SUPPLIES: HARMONICS
	[return to parent folder]

	HOW TO AVOID FILTERS IN OFF-LINE POWER SUPPLIES By M. Albach	[View] [Download]
Abstract: In ac-dc switched mode power supplies high frequency filter components are necessary to bring the conducted emissions within the limits of the specifications VDE 0871/5. As these power line filters considerably contribute to total size, weight and cost of the power supply, any improvement is highly desirable. In this paper a new operation mode is presented, which offers the possibility to reduce the filter in the power range below 100 w or even to completely avoid the additional filter components as demonstrated with a 10 w supply for a rechargeable shaver. This new method is based on the effect, that the conducted emissions are transferred to the mains impedance only during the recharging time of the storage capacitor, this means when the rectifier brigde is conducting. During the non-conducting phase the diodes are nearly perfect filter components. Utilizing this different behaviour gives a tremendous benefit for the size and cost of the power supplies. Possible applications are in audio/video, household equipment or in the telecommunication area.

	IMPROVED DOUBLE CONNECTED INVERTER FOR REDUCING OUTPUT VOLTAGE HARMONICS By S. Iida; S. Masukawa	[View] [Download]
Abstract: In this paper, we propose a new method for reducing harmonic components involved in output voltages of the doubIe connected inverter. By adding four auxiliary switching devices and an interphase transformer with secondary winding into the input dc side of the usual 12-step inverter, the proposed circuit can decrease the output voltage harmonics no less than the conventional 36-step inverter. Basic theories are discussed by analyzing the output voltage waveforms, and optimum parameters are derived. Then, We can recognize the effects of harmonic reductions by both theoretical and experimental results. Moreover, we try to suppress surge voltages impressed to switching devices by stray inductances on the equipment wirings in the input dc sides. By applying auxiliary suppressive circuits similar to the usual snubber circuit, we confirm by experiments that they can be enough restrained.

	NONCHARACTERISTIC LINE CURRENT HARMONICS IN DIODE RECTIFIER BRIDGES PRODUCED BY NETWORK ASYMMETRIES By M. Grötzbach; J. Xu	[View] [Download]
Abstract: In case of an asymmetric network, i.e. unbalanced three-phase voltages or/and different line reactances, noncharacteristic harmonics appear in the line current of diode rectifiers. To investigate the basic mechanism of the generation of these noncharacteristics, a discrete small-signal modeling is proposed consisting of difference equations of the dc current and firing angle determinations. Thereby, the influence of network asymmetries is described analytically taking into account commutation process and dc current ripple effects. With this, basic dependencies can be investigated and an effective evaluation of the noncharacteristics is obtained. The results drawn as locis in the complex plane lead to a compact and userfriendly representation. Thereby, arbitrary network asymmetries can be considered easily by corresponding phasor additions, especially for the estimation of the maximum values. Comparing digital simulation studies confirm the validity of small-signal modeling in the practical range of network asymmetries.

	THREE- TO SINGLE-PHASE CONVERTERS WITH A SWITCH-CONTROLLED INTERPHASE TRANSFORMER FOR LOW-DISTORTED SUPPLY OF RESISTIVE LOADS By V. Sarv; J. Soojarv; A. Tuisk	[View] [Download]
Abstract: Comparative evaluation of three- to single-phase converters with a switch-controlled interphase transformer is given. Design and optimization principles of the phase converters both with the close to rectangular and sinusoidal output voltage waveforms have been analyzed and experimentally evaluated. In case of a single-phase resistive load and rectangular output voltage, the conversion can be carried out using only a properly controlled time-variable transtormer. For a complex load and/or sinusoidal output voltage in addition to the time-variable transformer, a controlled energy storing element is required. Performance characteristics of three 12-pulse converters with a switch-controlled interphase transformer have been described.