EPE Association: EPE 1993 - 54 - Dialogue Session DS4.3: POWER SUPPLIES: MODELLING AND CONTROL

EPE 1993 - 54 - Dialogue Session DS4.3: POWER SUPPLIES: MODELLING AND CONTROL
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 54 - Dialogue Session DS4.3: POWER SUPPLIES: MODELLING AND CONTROL

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   CONTROLLABLE AC-AC CONVERTER WITH SOFT-SWITCHING
By M. P. N. van Wesenbeeck; J. B. Klaassens [View]
[Download]

Abstract: The paper presents a multi-purpose AC-AC power converter with thyristors applying the principles of soft-switching. The proposed converter operates with a high-internal frequency of about 10 kHz applying low-cost and efficient thyristor switches. On objective is to improve the technology of polyphase AC converters with controllable four-quadrant operation. The main content is the control of the external waveforms by means of a non-uniform and a periodic sampling process. By simplifying the various modes of transfer of electrical energy through the converter, a simple and practical solution for the digital control electronics for a high-frequency AC-AC converter is realized. A resonant six-switch and twelve-switch DC-AC and AC-AC power converter topology is implemented. Results from simulation and experiment are presented.

   SERIES RESONANT CONVERTER CONTROL: STABILITY AND ROBUSTNESS INDUCED BY USING STANDARD REGULATORS
By C. Collomb; M. Fadel; Y. Chéron; J.C. Hapiot [View]
[Download]

Abstract: In this paper, the authors deal with the closed-loop behaviour of frequency controlled DC-DC series resonant converters using standard regulators. A preliminary study, using a small signal modelling method, pointed out that the dynamic behaviour of this converter strongly depends on the operating point. This work revealed different behaviour areas, whose boundaries are function of the ratio between the output filter and the resonant circuit capacitors. We propose to use these results to determine a control structure considering the type of specifications which implicitely precises the operation zone. A theoretical study allows to predict the evolution of the closed-loop performances in the presence of a varying operting point. In particular, the apparition of instabilities is explained. Thus, the robustness and the limits of this linear control are evaluated, yielding general rules to select the adapted regulator in view of the desired closed-loop performances. These theoritical results are compared to experimental results.

   A COMPLETE MODELLING OF THE SERIES-RESONANT CONVERTER IN Z.C.S. MODE
By P. Kuo-penq; Y. Chéron; H. Piquet [View]
[Download]

Abstract: In most cases, the series-resonant converter is equipped with snubbers to reduce switching losses. These auxiliary circuits, which lead to an increase of the circuit order, also fundamentally modify the operation and the characteristics of the series-resonant converter. This paper presents a complete modelling of non-reversible series-resonant converters operating in thyristor mode (Z.C.S.) equipped with snubbers both on the inverter side (inductors) and on the rectifier side (capacitors). Based on the representation of the state plane, this analytical study characterizes the steady state operation of the converter and determines the main component stresses. The results of these analytical studies are integrated into a software which constitutes a powerful tool to design the converter.

   THE AC/DC CONVERSION SYSTEM OF RFX FUSION EXPERIMENT: OPERATIONAL EXPERIENCE AND CONTROL OPTIMIZATION
By E. Gaio; R. Piovan; V. Toigo [View]
[Download]

Abstract: During the operation of the high power ac/dc conversion system of RFX, a fusion experiment, instabilities and anomalous behaviours were observed when fast response is required; the more critical conditions are related with parallel operation of converters. To derive criteria for control optimization, the converters feeding the RFX load have been analyzed, both analytically and with computer simulation. The paper reports, after a brief converter system description, the more interesting mis-operations and the results of the control analyses.

   AN OBSERVER-BASED CONTROL OF A THREE PHASE INVERTER
By D. Eckhardt [View]
[Download]

Abstract: An observer-based cascaded control of the inverter of a three phase UPS-system is presented. lnstead of measuring the currents of the filtering capacitors, these currents are now estimated by an observer. The assumptions for developing an appropriate mathematical model of the inverter are explained. On the basis of the mathematical model the design principles of the observer, the capacitor current controller and the voltage controller are described. Finally, experimental results are presented which are obtained from a realisation of the presented control concept in an UPS-system with an apparent power of 60 kVA.

   S.C.O.S.: A STATE SPACE, TIME-VARYING TOPOLOGY SIMULATOR FOR THE ANALYSIS OF CONTROLLED SWITCHING CONVERTERS
By L. Fratelli; A. M. Luciano; O. Marandola; A. G. M. Strollo [View]
[Download]

Abstract: A simulator for controlled switching circuits, based on the approach of time-varying topology, is presented. State-space equations of the circuit are formulated, and updated at each switch commutation, through a suitable linear transformation. An ideal model is used for switches, avoiding the numerical stiffness due to the insertion of fictitious impedances in the circuit. The feedback control system is modelled in terms of poles and zeros and by using user-defined functions to describe the control law of the switches. The simulator is suitable for application on personal computer since a minimum-size equations set has to be resolved and good numerical stability is exhibited. Simulations of a regulated Buck converter, including soft-start and over-current protection, and of a novel high quality AC-DC PWM converter are reported.

   NEW IMPROVED PHASE-SHIFT CONTROLLED H-BRIDGE CONVERTER
By R. J. Cliffe; C. D. Manning [View]
[Download]

Abstract: Techniques are presented to improve the performance of the phase-shift controlled H-bridge converter. Methods of avoiding hard switching or its effects at low load currents are compared, and one combination of techniques is proposed as the best solution. One of these techniques allows operation of the converter down to no load without increased switching noise due to hard switching, and without extra circuitry or increased component ratings.

   THE CONTROL OF QUASI-RESONANT CONVERTERS
By B. Baha [View]
[Download]

Abstract: In this paper, the small-signal transfer functions of the Buck QRC have been derived. The derived small-signal transfer functions have been used to design the control circuit for this converter. Based on the small signal analysis, the control circuit has been designed (using multiloop control), simulated, built and tested with the converter. By using this control scheme, the converter provides very good transient response and a stable system. The same technique can be used to design the control circuit for other quasi-resonant converters.

   A Smart-Lighting Emergency System for Fluorescent Lamps
By J. M. Alonso; J. Díaz; C. Blanco; P. J. Villegas; M. Rico [View]
[Download]

Abstract: In the traditional emergency lighting systems the internal damages must be detected and repaired by specialist workers. Since this occurs normally after a line voltage failure, the installations have a low security level. In this paper a new emergency ballast for fluorescent lamps with high operation reliability is presented. The system has the capability of testing itself, checking its functional state and displaying its internal damages. The fundamental block is the control circuit based on a microcontroller that performs the supervision and control function, achieving an increase in the installation security. High frequency electronics techniques are used to implement the battery charger and the lamp driver, with high power factor in the first and high luminous efficacy in the second. In this way, sizes and weights have been minimized for all the system. Following this way of conceiving lighting systems we are at this moment studying the possibility of extending this concept to a non-emergency systems. The results will be presented in a new work.

   A UNIVERSAL POWER CONVERTER
By M. J. Case; J. J. Schoeman; J. D. van Wyk [View]
[Download]

Abstract: This paper presents a variable transformer that operates over a wide frequency range. The circuit topology consists in essence of an inverter coupled to a synchronous rectifier. Bidirectional current flow is obtained by using field-effect transistors operating in the third quadrant as switching elements. Input/output phase modulation gives variation in transformer ratio.

   OPERATION MODES OF SERIES INVERTER 400 KHZ FOR INDUCTION HEATING
By G. Fischer; H.-C. Doht; B. Hemmer [View]
[Download]

Abstract: A series inverter for induction heating applications working with MOSFET is presented. Two different operation modes of a MOSFET inverter are discussed. The presented concepts are verified with measurements resulting from a prototype inverter running at 10 kW / 400 kHz. In the operation above the resonance frequency of the series load circuit it is important to protect the switches for overvoltage stress. This paper identifies the cause of the stress and works out options to tackle the overvoltage amplitude. It will be shown that the parasitics of the MOSFET with a suitable gate drive may be utilized to aid loss-less turn off. In operation below resonance high switching speed imposes heavy stress on the MOSFETs. For this operation mode a novel gate drive circuit is presented that dynamically enables switching in this mode.

   DUAL ACTIVE BRIDGE CONVERTER WITH LARGE SOFT-SWITCHING RANGE
By Knut Vangen; Terje Melaa; Alf Kare Adnanes; Per Even Kristiansen [View]
[Download]

Abstract: A direct DC/Low Frequency AC Dual-Active-Bridge (DAB) converter with Zero Voltage Switching, Resonant Transition (ZVS-RT) has been tested at 75 kHz at power levels up to 23 kW. lt has dual angle, constant frequency phase shift control, and is soft-switched with high efficiency in a large part of the output V-I-plane. There is an optimum set of control angles for each operating point. Efficiency up to 93,3% has been measured at DC output, and 89% at AC output. IGBT dynamic saturation at turn-on from zero current into a positive di/dt is shown to be an important loss factor, together with the diode forward recovery voltage spike. Experiments show the influence of package stray inductance on voltage wave forms and efficiency. The resonant transition is disturbed by semiconductor and stray component effects.

   DESIGN AND IMPLEMENTATION OF A MICROPROCESSOR BASED HIGH FREQUENCY SWITCHING MODE POWER SUPPLY
By Z. Sari; K. Amgoud; M. Ait-Bouabdallah [View]
[Download]

Abstract: This work presents a new version of a microprocessor based high frequency switching mode power supply. The system, that is designed to be used in computer systems as main and standby power supply, is controlled by a microprocessor card constructed around the MC6802 microprocessor. The system is composed of two controllable converters and two uncontrollable converters:
- A step down chopper used as a power supply of the standby battery.
- A single phase voltage source inverter used to supply the high frequency transformer.
- A single phase diode bridge rectifier used as the input of the power supply.
- A centre taped two way rectifier fed to the output of the high frequency transformer.
The system possesses, in addition to a high quality output voltage regulation, some protection from over-voltages and over-current.

   SPACE VECTOR BASED POWER FACTOR CONTROL OF RESONANT CONVERTERS
By P. Bauer; J. B. Klaassens [View]
[Download]

Abstract: Soft switching resonant converters utilize pulse frequency modulation techniques in order to synthesize a low frequency behaviour. In this paper pulse modulation techniques are analyzed. A novel control approach based on space vector dynamical equation is suggested. The obtained equations prescribes the dynamics of the entire converter including the filters. The modulator designed on their base can solve drawbacks of pulse modulation techniques. The sliding mode control is considered in order to control the power factor of the pulse modulated converter.

EPE 1993 - 54 - Dialogue Session DS4.3: POWER SUPPLIES: MODELLING AND CONTROL
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 54 - Dialogue Session DS4.3: POWER SUPPLIES: MODELLING AND CONTROL
	[return to parent folder]

	CONTROLLABLE AC-AC CONVERTER WITH SOFT-SWITCHING By M. P. N. van Wesenbeeck; J. B. Klaassens	[View] [Download]
Abstract: The paper presents a multi-purpose AC-AC power converter with thyristors applying the principles of soft-switching. The proposed converter operates with a high-internal frequency of about 10 kHz applying low-cost and efficient thyristor switches. On objective is to improve the technology of polyphase AC converters with controllable four-quadrant operation. The main content is the control of the external waveforms by means of a non-uniform and a periodic sampling process. By simplifying the various modes of transfer of electrical energy through the converter, a simple and practical solution for the digital control electronics for a high-frequency AC-AC converter is realized. A resonant six-switch and twelve-switch DC-AC and AC-AC power converter topology is implemented. Results from simulation and experiment are presented.

	SERIES RESONANT CONVERTER CONTROL: STABILITY AND ROBUSTNESS INDUCED BY USING STANDARD REGULATORS By C. Collomb; M. Fadel; Y. Chéron; J.C. Hapiot	[View] [Download]
Abstract: In this paper, the authors deal with the closed-loop behaviour of frequency controlled DC-DC series resonant converters using standard regulators. A preliminary study, using a small signal modelling method, pointed out that the dynamic behaviour of this converter strongly depends on the operating point. This work revealed different behaviour areas, whose boundaries are function of the ratio between the output filter and the resonant circuit capacitors. We propose to use these results to determine a control structure considering the type of specifications which implicitely precises the operation zone. A theoretical study allows to predict the evolution of the closed-loop performances in the presence of a varying operting point. In particular, the apparition of instabilities is explained. Thus, the robustness and the limits of this linear control are evaluated, yielding general rules to select the adapted regulator in view of the desired closed-loop performances. These theoritical results are compared to experimental results.

	A COMPLETE MODELLING OF THE SERIES-RESONANT CONVERTER IN Z.C.S. MODE By P. Kuo-penq; Y. Chéron; H. Piquet	[View] [Download]
Abstract: In most cases, the series-resonant converter is equipped with snubbers to reduce switching losses. These auxiliary circuits, which lead to an increase of the circuit order, also fundamentally modify the operation and the characteristics of the series-resonant converter. This paper presents a complete modelling of non-reversible series-resonant converters operating in thyristor mode (Z.C.S.) equipped with snubbers both on the inverter side (inductors) and on the rectifier side (capacitors). Based on the representation of the state plane, this analytical study characterizes the steady state operation of the converter and determines the main component stresses. The results of these analytical studies are integrated into a software which constitutes a powerful tool to design the converter.

	THE AC/DC CONVERSION SYSTEM OF RFX FUSION EXPERIMENT: OPERATIONAL EXPERIENCE AND CONTROL OPTIMIZATION By E. Gaio; R. Piovan; V. Toigo	[View] [Download]
Abstract: During the operation of the high power ac/dc conversion system of RFX, a fusion experiment, instabilities and anomalous behaviours were observed when fast response is required; the more critical conditions are related with parallel operation of converters. To derive criteria for control optimization, the converters feeding the RFX load have been analyzed, both analytically and with computer simulation. The paper reports, after a brief converter system description, the more interesting mis-operations and the results of the control analyses.

	AN OBSERVER-BASED CONTROL OF A THREE PHASE INVERTER By D. Eckhardt	[View] [Download]
Abstract: An observer-based cascaded control of the inverter of a three phase UPS-system is presented. lnstead of measuring the currents of the filtering capacitors, these currents are now estimated by an observer. The assumptions for developing an appropriate mathematical model of the inverter are explained. On the basis of the mathematical model the design principles of the observer, the capacitor current controller and the voltage controller are described. Finally, experimental results are presented which are obtained from a realisation of the presented control concept in an UPS-system with an apparent power of 60 kVA.

	S.C.O.S.: A STATE SPACE, TIME-VARYING TOPOLOGY SIMULATOR FOR THE ANALYSIS OF CONTROLLED SWITCHING CONVERTERS By L. Fratelli; A. M. Luciano; O. Marandola; A. G. M. Strollo	[View] [Download]
Abstract: A simulator for controlled switching circuits, based on the approach of time-varying topology, is presented. State-space equations of the circuit are formulated, and updated at each switch commutation, through a suitable linear transformation. An ideal model is used for switches, avoiding the numerical stiffness due to the insertion of fictitious impedances in the circuit. The feedback control system is modelled in terms of poles and zeros and by using user-defined functions to describe the control law of the switches. The simulator is suitable for application on personal computer since a minimum-size equations set has to be resolved and good numerical stability is exhibited. Simulations of a regulated Buck converter, including soft-start and over-current protection, and of a novel high quality AC-DC PWM converter are reported.

	NEW IMPROVED PHASE-SHIFT CONTROLLED H-BRIDGE CONVERTER By R. J. Cliffe; C. D. Manning	[View] [Download]
Abstract: Techniques are presented to improve the performance of the phase-shift controlled H-bridge converter. Methods of avoiding hard switching or its effects at low load currents are compared, and one combination of techniques is proposed as the best solution. One of these techniques allows operation of the converter down to no load without increased switching noise due to hard switching, and without extra circuitry or increased component ratings.

	THE CONTROL OF QUASI-RESONANT CONVERTERS By B. Baha	[View] [Download]
Abstract: In this paper, the small-signal transfer functions of the Buck QRC have been derived. The derived small-signal transfer functions have been used to design the control circuit for this converter. Based on the small signal analysis, the control circuit has been designed (using multiloop control), simulated, built and tested with the converter. By using this control scheme, the converter provides very good transient response and a stable system. The same technique can be used to design the control circuit for other quasi-resonant converters.

	A Smart-Lighting Emergency System for Fluorescent Lamps By J. M. Alonso; J. Díaz; C. Blanco; P. J. Villegas; M. Rico	[View] [Download]
Abstract: In the traditional emergency lighting systems the internal damages must be detected and repaired by specialist workers. Since this occurs normally after a line voltage failure, the installations have a low security level. In this paper a new emergency ballast for fluorescent lamps with high operation reliability is presented. The system has the capability of testing itself, checking its functional state and displaying its internal damages. The fundamental block is the control circuit based on a microcontroller that performs the supervision and control function, achieving an increase in the installation security. High frequency electronics techniques are used to implement the battery charger and the lamp driver, with high power factor in the first and high luminous efficacy in the second. In this way, sizes and weights have been minimized for all the system. Following this way of conceiving lighting systems we are at this moment studying the possibility of extending this concept to a non-emergency systems. The results will be presented in a new work.

	A UNIVERSAL POWER CONVERTER By M. J. Case; J. J. Schoeman; J. D. van Wyk	[View] [Download]
Abstract: This paper presents a variable transformer that operates over a wide frequency range. The circuit topology consists in essence of an inverter coupled to a synchronous rectifier. Bidirectional current flow is obtained by using field-effect transistors operating in the third quadrant as switching elements. Input/output phase modulation gives variation in transformer ratio.

	OPERATION MODES OF SERIES INVERTER 400 KHZ FOR INDUCTION HEATING By G. Fischer; H.-C. Doht; B. Hemmer	[View] [Download]
Abstract: A series inverter for induction heating applications working with MOSFET is presented. Two different operation modes of a MOSFET inverter are discussed. The presented concepts are verified with measurements resulting from a prototype inverter running at 10 kW / 400 kHz. In the operation above the resonance frequency of the series load circuit it is important to protect the switches for overvoltage stress. This paper identifies the cause of the stress and works out options to tackle the overvoltage amplitude. It will be shown that the parasitics of the MOSFET with a suitable gate drive may be utilized to aid loss-less turn off. In operation below resonance high switching speed imposes heavy stress on the MOSFETs. For this operation mode a novel gate drive circuit is presented that dynamically enables switching in this mode.

	DUAL ACTIVE BRIDGE CONVERTER WITH LARGE SOFT-SWITCHING RANGE By Knut Vangen; Terje Melaa; Alf Kare Adnanes; Per Even Kristiansen	[View] [Download]
Abstract: A direct DC/Low Frequency AC Dual-Active-Bridge (DAB) converter with Zero Voltage Switching, Resonant Transition (ZVS-RT) has been tested at 75 kHz at power levels up to 23 kW. lt has dual angle, constant frequency phase shift control, and is soft-switched with high efficiency in a large part of the output V-I-plane. There is an optimum set of control angles for each operating point. Efficiency up to 93,3% has been measured at DC output, and 89% at AC output. IGBT dynamic saturation at turn-on from zero current into a positive di/dt is shown to be an important loss factor, together with the diode forward recovery voltage spike. Experiments show the influence of package stray inductance on voltage wave forms and efficiency. The resonant transition is disturbed by semiconductor and stray component effects.

	DESIGN AND IMPLEMENTATION OF A MICROPROCESSOR BASED HIGH FREQUENCY SWITCHING MODE POWER SUPPLY By Z. Sari; K. Amgoud; M. Ait-Bouabdallah	[View] [Download]
Abstract: This work presents a new version of a microprocessor based high frequency switching mode power supply. The system, that is designed to be used in computer systems as main and standby power supply, is controlled by a microprocessor card constructed around the MC6802 microprocessor. The system is composed of two controllable converters and two uncontrollable converters: - A step down chopper used as a power supply of the standby battery. - A single phase voltage source inverter used to supply the high frequency transformer. - A single phase diode bridge rectifier used as the input of the power supply. - A centre taped two way rectifier fed to the output of the high frequency transformer. The system possesses, in addition to a high quality output voltage regulation, some protection from over-voltages and over-current.

	SPACE VECTOR BASED POWER FACTOR CONTROL OF RESONANT CONVERTERS By P. Bauer; J. B. Klaassens	[View] [Download]
Abstract: Soft switching resonant converters utilize pulse frequency modulation techniques in order to synthesize a low frequency behaviour. In this paper pulse modulation techniques are analyzed. A novel control approach based on space vector dynamical equation is suggested. The obtained equations prescribes the dynamics of the entire converter including the filters. The modulator designed on their base can solve drawbacks of pulse modulation techniques. The sliding mode control is considered in order to control the power factor of the pulse modulated converter.