EPE Association: EPE 1993 - 39 - Dialogue Session DS2.4: GENERATION AND TRANSMISSION: UNITY PF SYSTEMS AND STATIC VAR COMPENSATION

EPE 1993 - 39 - Dialogue Session DS2.4: GENERATION AND TRANSMISSION: UNITY PF SYSTEMS AND STATIC VAR COMPENSATION
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 39 - Dialogue Session DS2.4: GENERATION AND TRANSMISSION: UNITY PF SYSTEMS AND STATIC VAR COMPENSATION

   [return to parent folder]

   A MICROPROCESSOR-BASED CONTROLLED BOOST CONVERTOR TO OBTAIN GOOD INPUT AND OUTPUT PERFORMANCE PARAMETERS
By J. A. A. Wijntjens; J. L. Duarte; J. Rozenboom [View]
[Download]

Abstract: A microprocessor-based controlled boost convertor makes it possible to exploit a single-phase AC-DC convertor with good input and output performance parameters. With regard to the input performance, this paper outlines two simple algorithms for a Digital Signal Processor (DSP) based control circuit of the boost switch. The first algorithm fulfils the requirements of the suppliers of electricity, namely an input current which is under all circumstances nearly sinusoidal, with a very low harmonic distortion. The second algorithm makes it possible to satisfy the demands of certain consumers of electricity namely a high power factor, so that the available maximum power of the grid is used. Both algorithms are implemented on the TMS320C25 processor and operate at a fixed frequency. Since, a high quality output voltage is usually of first importance in switched-mode power conversion, this output performance parameter is controlled by a PI-based output voltage regulator which is also implemented on the processor.

   TRANSIENT EFFECTS AND SUPPRESSION IN A COMPACT 2 KW POWER FACTOR CONDITIONER WITH WIDE INPUT VOLTAGE RANGE
By S. Y. R. Hui [View]
[Download]

Abstract: This paper describes some specific problems encountered in a 2kW compact single-phase boost-type power factor conditioner suitable for telecom and navigation applications. Due to the required wide input voltage range (from 170V to 300V), a high nominal d.c. output voltage of 450V is required. This high voltage requirement puts considerable constraints on the choice of power components. Transient effects such as excessive diode reverse-recovery current and induced voltage spikes are also observed in the compact system in which power electronics are kept close to the low-voltage control electronics. Measures have been developped to suppress these transient effects to satisfactory levels. Experimental results with and without such measures are included and discussed.

   SMART NON-ACTIVE POWER COMPENSATOR WITH NEURAL NETWORK CONTROL - AN EVALUATION
By G. Blajszczak; J. D. van Wyk; I. Shaw [View]
[Download]

Abstract: Distortion in power network - non-active power components can be eliminated by a compensator that consists of one or a few converters. To obtain cost-optimal compensation, a specific distortion should be eliminated by a compensator configuration with the lowest operational costs. In this paper a multi-converter compensator is proposed with neural network control and investigated by simulation. The neural network control system analyses the distortion components - non-active power and the losses in the converters of the compensator - and chooses this converter (or converters) and their working mode that ensures cost-optimal compensation.

   MULTIPLE APPLICATIONS CONTROL SYSTEM FOR THE PWM VOLTAGE CONVERTER CONNECTED TO THE AC MAINS
By P. Verdelho; G. D. Marques [View]
[Download]

Abstract: A decoupled current control circuit of the PWM voltage converter connected to the AC mains is presented. The two AC current Park's components can be controlled independently. Expressions for the controllers synthesis are derived. The system performance is studied with a simulation program that allows the integration of the model equations by the Euler-Forward or Euler-Backward methods. Several applications of the system with the control circuit presented are referred: AC/DC bi-directional converter in power supplies for electrical drives or in HVDC energy transmission, reactive power compensator and active power filter. The control circuit presented leads to the possibility of realize all the applications referred at the same time. The PWM voltage converter connected to the AC mains is then a multiple applications converter.

   MEASUREMENT OF NON-ACTIVE POWER COMPENSATOR EFFECTIVENESS
By G. Blajszczak; M. J. Case; W. J. van der Merwe [View]
[Download]

Abstract: The evaluation of the effectiveness of an in situ power compensator is not an obvious process. The guidelines available refer to complicated analysis and measurement by power analyzers and other expensive apparatus. This paper describes an economical microprocessor-based instrument that evaluates any power compensator; a numerical figure of merit is presented. The results of measurements obtained from a few typical compensator configurations are presented.

   POWER CONDITIONING VARIANTS FOR PHOTOVOLTAIC SYSTEMS
By J. Sachau [View]
[Download]

Abstract: For widespread application of photovoltaic power supply systems, it will be of basic importance to achieve cost reductions as well as reliability increases for the whole systems as this is the case for the PV-modules themselves. Here, the main emphasis is on the converter technology in combination with the current concentration. As the specific properties of the PV-generation are quite different from contemporary power systems, the basic power conditioning variants are compared.

   NONLINEAR THYRISTOR-CONTROLLED STATIC VAR COMPENSATION
By Y. H. Song; A. T. Johns; R. K. Aggarwal [View]
[Download]

Abstract: Power systems must be carefully controlled in order to maintain an acceptable power supply quality. Advances in power electronics and control technology have introduced powerful tools to power utilities, and more recently, the concept of flexible ac transmission systems (FACTS) has evolved. One of the major component of the latter is the thyristor-controlled static var compensator (SVC). In this paper, a nonlinear feedback method based on differential geometry theory is employed to derive a novel control approach for Static Var Compensation (SVC)'s. The paper first constructs the nonlinear model for the power system with SVC control. Special emphasis is placed on the modelling of the thyristor-controlled devices such as the thyristor controlled reactor (TRC). The conditions to algebraically transform the nonlinear model to linear system are then verified. The linearized model is obtained by feedback linearization, and optimal SVC control laws are then derived for power system stability improvements. The paper concludes with presenting some interesting simulation results.

   DEVELOPMENT AND LABORATORY VALIDATION OF OPTIMAL AND ADAPTIVE METHODS OF CO-ORDINATED AC/DC SYSTEM CONTROL
By K. W. V. To; A. K. David [View]
[Download]

Abstract: Characteristics of both optimal and adaptive multi-input/multi-output control techniques are discussed in this paper with particular emphasis on their applications to AC/DC power systems. Comparative studies of the optimal control strategy and the adaptive control technique for large disturbance show that the latter provides better damping in the system under study. This paper also reports on the establishment of a hardware laboratory facility including a scaled down AC/DC model and its use in the validation of controls.

   ON THE WAY TO REAL TIME FUZZY CONTROL OF A PWM SOURCE INVERTER WITH NONLINEAR LOADS
By P. Maussion; M. Grandpierre; J. Faucher [View]
[Download]

Abstract: This paper presents a new approach for PWM Voltage Source lnverter Real Time Control, based on Fuzzy Logic. The special case of non linear loads is studied. From error and error variation measurements, a new control law is proposed to reduce the harmonic distorsion and to provide a good fundamental regulation. The system architecture is described and the fuzzy control algorithm is implemented by off-line calculated look-up tables in ordec to minimize time response.The simulation results are compared to other classical approaches in terms of static and dynamic performances. It will show good results in spite of the coarse definition of the plant.

   MATCHING SITE AND POWER SYSTEM REQUIREMENTS DESIGN OF THE TWO PELHAM SVCS
By H. Tyll; G. Thumm; R. Stöber; M. Winfield [View]
[Download]

Abstract: This paper describes the design and layout for the two SVCs installed in the Pelham substation, north of London. Both SVCs of equal size and design have a nominal rating of -75 MVAr to 150 MVAr and are connected to the National Grid 400 kV system. The specified system requirements on operating range, harmonic performance and loss considerations led to an SVC configuration which contains one TSC branch, one TCR branch for continuous reactive power control and a single tuned filter branch for harmonic limitation. The system voltage of the SVC secondary side was optimised to 14 kV based on thyristor equipment capabilities. The paper shows the voltage and current stresses of the thyristor valves taking into account system faults for the TCR branch and misfiring effects for the TSC branch. The approach to filter design considering the harmonic performance requirements is described. The Pelham SVCs commenced commercial operation in summer 1992.

   DESIGNING LIGHT SOURCES FOR SOLAR-POWERED SYSTEMS
By J. L. Duarte; J. A. A. Wijntjens; J. Rozenboom [View]
[Download]

Abstract: The design of a fluorescent lamp power circuit for (portable) light sources, using a photovoltaic-supplied battery as intermediate energy buffer, is documented. The described driver circuit, which is based on a class-E resonant inverter, operates on a high frequency (125 kHz), requires low-cost components and simple design and exhibit a high efficiency (over 85%). The circuit provides resonance ignition, sinusoidal lamp current and illumination intensity control. These operating conditions are optimal, and they yield a long tube life. Experimental results from a 7W-lamp are included.

   TESTING OF A NEW D.C.-D.C. CONVERTER TOPOLOGY FOR INTEGRATED WIND-PHOTOVOLTAIC GENERATING SYSTEMS
By F. Caricchi; F. Crescimbini; A. Di Napoli; O. Honorati; E. Santini [View]
[Download]

Abstract: This paper presents a d.c.-to-d.c. converter topology which can find application in the development of small-size integrated wind and photovoltaic energy generating systems. The converter layout is the result of the connection in series of two switch-mode d.c.-to-d.c. step-up converter stages, so that the overall converter is able to operate as a double input - single output power electronics interface between the system generating units and the utility circuit. The paper discusses the converter modes of operation and reports experimental results taken from an IGBTs converter prototype.

   A DC/DC CONVERTER WITH TWO-SWITCH STRUCTURE FOR EFFICIENCY IMPROVEMENT AND INTEGRATED POWER SUPPLY
By B. Hauck [View]
[Download]

Abstract: Photovoltaic systems need an actuating element for the adaption of the generator to the back-up battery or the d.c. link. Further especially for these systems a high efficiency is desired. The d.c./d.c. converter with the two-switch structure improves a high efficiency and it has an integrated power supply for the controlling unit, the data acquisition and the basic current for the main transistor. By switching off the main transistor of the converter the current commutates to the auxiliary transistor and the integrated power supply will be loaded. lf its voltage is high enough, the auxiliary transistor switches off the current. The converter works on the effect, that the auxiliary transistor (MOSFET) operates much faster than the main transistor (bipolar). For the dimensioning of the reactor a new method, the so-called core distinctive number method is used. The measurements show, that the efficiency especially in the range less than 1/3 of the maximum power is better than for usual converters.

   CAD PROGRAMS HELP TO DESIGN RELIABLE CONTROLLER FOR POWER PHOTOVOLTAIC SYSTEMS
By L. Lori; P. Redi [View]
[Download]

Abstract: The design of a battery charge regulator for high power photovoltaic plants is obtained thank to Spice simulation program. The highest reliability is reached by controlling the switching components with an 8-bit microcontroller.

   A SINEWAVE INTERFACE FOR VARIABLE-SPEED WIND TURBINES
By G. A. Smith; R. G. Stephens; P. Marshall; M. Kansara [View]
[Download]

Abstract: There are a number of major benefits from operating wind turbines at variable-speed including improved energy capture, reduced mechanical stress and lower levels of audible noise in light winds. A number of variable-speed systems have been operated with varying degrees of success. These include ac-dc-ac link inverters for synchronous or capacitor excited asynchronous generators and also slip-recovery schemes with cycloconverters. The latter has the disadvantage of slip-rings whilst the former recover energy through Line Commutated Inverters (LCI's) with variable power factor and poor current waveform. The IGBT may be used to provide a power interface that can synthesise good quality current waveforms in both generator and the power network. In this solution a generator side step-up converter produces a constant dc link voltage from the variable frequency and voltage generator. This is then inverted through a high-frequency interface to produce near sinusoidal current at unity power factor. Results show overall efficiencies around 90% with total harmonic distortion as a % of fundamental not exceeding 10%.

   ECONOMICAL COMPARISON OF HIGH POWER STATIC VAR COMPENSATORS
By G. Blajszczak; I. Boake; J. D. van Wyk [View]
[Download]

Abstract: The fundamental reactive power can be compensated by line or force commutated compensators. Installation costs, operational losses and harmonic pollution of these compensators are compared in a power range from 20kVAr up to 100MVAr. The detailed analysis shows that the widely applied line commutated compensator is less cost-effective than a force commutated compensator.

   ESTIMATION OF ENERGETIC FACTORS IN POWER ELECTRONICS SUPPLY SYSTEMS
By Y. Stabulnieks; Y. Shinka [View]
[Download]

Abstract: Conventional calculation methods of electric power and its components as orthogonal, integral, symbolic, systems equivalence, etc., applied to nonsinusoidal system analysis bring to different and sometimes to inexplicable results. Obtained in such a way reactive and apparent power have no physical interpretation and have only an arbitrary mathematical implication. Therefore, currently accepted definitions of electric power components are reviewed and their limitations in systems with converters are analyzed. In terms of instantaneous power a number of energy flow and power components such as active, external, input, reverse, resonant, storage, oscillation, etc... have been determined. These components can be used to determine new energetic factors: the system energy utilization factor, consumer energy utilization factor, power oscillation factor, etc... They may be applied for the power system optimization, reactive and active compensation, harmonic suppression. The application of the theory developed is illustrated by a typical example. The proposed power and energy components can be directly measured by means of digital electronic instruments.

   THE APPLICATION OF TRANSPUTERS FOR DIGITAL CONTROL OF STATIC VAR COMPENSATORS
By M. Davies; D. A. Picken [View]
[Download]

Abstract: This paper discusses the advantages of using digital control systems for Static Var Compensators (SVC) and describes the implementation of such a digital control system using transputer technology. The application of digital controls to SVC is demanding in terms of system hardware and software, particularly the processing power and intersystem communications required to achieve a performance equivalent to the latest analogue controllers. One approach in adopting a digital solution for an SVC controller is by the use of concurrent processing. This can be implemented by the INMOS family of transputers, which are particularly suitable. A description of some aspects of the digital design is given and also test results taken from comparative studies on the performance of analogue and digital SVC controls. These studies were performed on a real time analogue simulator model and show that the digital implementation has been successful in reproducing a performance equivalent to an analogue control.

   STATE OF THE ART IN SOLID STATE POWER CONTROLLER FOR AERONAUTICAL APPLICATION
By J. J. Simon [View]
[Download]

Abstract: Recent breakthrouqh in power transistors technoloqy enables speedinq up the development of HVDC for aeronautical applications. Concerning the power distribution, Solid State Power Controller (SSPC) are proving now to be a mature product, in a wide ranqe of current, from 1 to 60 Amp. However , dependinq of their implementation in the electrical power network, as well as of the loads they control, their features widely differ. This topic is aimed at describing the main features required and the corresponding technical and technoloqical innovative solutions for achieving them. Low current devices must comply with the most general requirements as low ON resistance, hiqh side and low side switching capabilities, short-circuit and overload protection, while high current devices incorporate more specific features like very low ON status drop out, active current limitinq for large capacitive loads, fault tolerance capability, internal DC/DC converter supplied by the power network.

   RESIDENTIAL SOLAR-POWERED AIR CONDITIONER
By K. Tanaka; E. Sakoguchi; Y. Fukuda; A. Takeoka; H. Tokizaki [View]
[Download]

Abstract: Sanyo has been developinq two types of residential solar-powered air conditioners. One is a uni-directional system, and the other is a bi-directional system. When usinq a 600 Wp photovoltaic (PV) array for the uni-directional system, we confirmed that the system can supply 50% of the power consumed by an air conditioner in summer. We also confirmed that the bi-directional system can feed surplus power back to the commercial power supply from PV, and suppress the input current distortion of the air conditioner. There is little doubt that the introduction and widespread use of these systems will play an important role in reducing the peak power energy requirements in summer and the generation of carbon dioxide.

EPE 1993 - 39 - Dialogue Session DS2.4: GENERATION AND TRANSMISSION: UNITY PF SYSTEMS AND STATIC VAR COMPENSATION
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 39 - Dialogue Session DS2.4: GENERATION AND TRANSMISSION: UNITY PF SYSTEMS AND STATIC VAR COMPENSATION
	[return to parent folder]

	A MICROPROCESSOR-BASED CONTROLLED BOOST CONVERTOR TO OBTAIN GOOD INPUT AND OUTPUT PERFORMANCE PARAMETERS By J. A. A. Wijntjens; J. L. Duarte; J. Rozenboom	[View] [Download]
Abstract: A microprocessor-based controlled boost convertor makes it possible to exploit a single-phase AC-DC convertor with good input and output performance parameters. With regard to the input performance, this paper outlines two simple algorithms for a Digital Signal Processor (DSP) based control circuit of the boost switch. The first algorithm fulfils the requirements of the suppliers of electricity, namely an input current which is under all circumstances nearly sinusoidal, with a very low harmonic distortion. The second algorithm makes it possible to satisfy the demands of certain consumers of electricity namely a high power factor, so that the available maximum power of the grid is used. Both algorithms are implemented on the TMS320C25 processor and operate at a fixed frequency. Since, a high quality output voltage is usually of first importance in switched-mode power conversion, this output performance parameter is controlled by a PI-based output voltage regulator which is also implemented on the processor.

	TRANSIENT EFFECTS AND SUPPRESSION IN A COMPACT 2 KW POWER FACTOR CONDITIONER WITH WIDE INPUT VOLTAGE RANGE By S. Y. R. Hui	[View] [Download]
Abstract: This paper describes some specific problems encountered in a 2kW compact single-phase boost-type power factor conditioner suitable for telecom and navigation applications. Due to the required wide input voltage range (from 170V to 300V), a high nominal d.c. output voltage of 450V is required. This high voltage requirement puts considerable constraints on the choice of power components. Transient effects such as excessive diode reverse-recovery current and induced voltage spikes are also observed in the compact system in which power electronics are kept close to the low-voltage control electronics. Measures have been developped to suppress these transient effects to satisfactory levels. Experimental results with and without such measures are included and discussed.

	SMART NON-ACTIVE POWER COMPENSATOR WITH NEURAL NETWORK CONTROL - AN EVALUATION By G. Blajszczak; J. D. van Wyk; I. Shaw	[View] [Download]
Abstract: Distortion in power network - non-active power components can be eliminated by a compensator that consists of one or a few converters. To obtain cost-optimal compensation, a specific distortion should be eliminated by a compensator configuration with the lowest operational costs. In this paper a multi-converter compensator is proposed with neural network control and investigated by simulation. The neural network control system analyses the distortion components - non-active power and the losses in the converters of the compensator - and chooses this converter (or converters) and their working mode that ensures cost-optimal compensation.

	MULTIPLE APPLICATIONS CONTROL SYSTEM FOR THE PWM VOLTAGE CONVERTER CONNECTED TO THE AC MAINS By P. Verdelho; G. D. Marques	[View] [Download]
Abstract: A decoupled current control circuit of the PWM voltage converter connected to the AC mains is presented. The two AC current Park's components can be controlled independently. Expressions for the controllers synthesis are derived. The system performance is studied with a simulation program that allows the integration of the model equations by the Euler-Forward or Euler-Backward methods. Several applications of the system with the control circuit presented are referred: AC/DC bi-directional converter in power supplies for electrical drives or in HVDC energy transmission, reactive power compensator and active power filter. The control circuit presented leads to the possibility of realize all the applications referred at the same time. The PWM voltage converter connected to the AC mains is then a multiple applications converter.

	MEASUREMENT OF NON-ACTIVE POWER COMPENSATOR EFFECTIVENESS By G. Blajszczak; M. J. Case; W. J. van der Merwe	[View] [Download]
Abstract: The evaluation of the effectiveness of an in situ power compensator is not an obvious process. The guidelines available refer to complicated analysis and measurement by power analyzers and other expensive apparatus. This paper describes an economical microprocessor-based instrument that evaluates any power compensator; a numerical figure of merit is presented. The results of measurements obtained from a few typical compensator configurations are presented.

	POWER CONDITIONING VARIANTS FOR PHOTOVOLTAIC SYSTEMS By J. Sachau	[View] [Download]
Abstract: For widespread application of photovoltaic power supply systems, it will be of basic importance to achieve cost reductions as well as reliability increases for the whole systems as this is the case for the PV-modules themselves. Here, the main emphasis is on the converter technology in combination with the current concentration. As the specific properties of the PV-generation are quite different from contemporary power systems, the basic power conditioning variants are compared.

	NONLINEAR THYRISTOR-CONTROLLED STATIC VAR COMPENSATION By Y. H. Song; A. T. Johns; R. K. Aggarwal	[View] [Download]
Abstract: Power systems must be carefully controlled in order to maintain an acceptable power supply quality. Advances in power electronics and control technology have introduced powerful tools to power utilities, and more recently, the concept of flexible ac transmission systems (FACTS) has evolved. One of the major component of the latter is the thyristor-controlled static var compensator (SVC). In this paper, a nonlinear feedback method based on differential geometry theory is employed to derive a novel control approach for Static Var Compensation (SVC)'s. The paper first constructs the nonlinear model for the power system with SVC control. Special emphasis is placed on the modelling of the thyristor-controlled devices such as the thyristor controlled reactor (TRC). The conditions to algebraically transform the nonlinear model to linear system are then verified. The linearized model is obtained by feedback linearization, and optimal SVC control laws are then derived for power system stability improvements. The paper concludes with presenting some interesting simulation results.

	DEVELOPMENT AND LABORATORY VALIDATION OF OPTIMAL AND ADAPTIVE METHODS OF CO-ORDINATED AC/DC SYSTEM CONTROL By K. W. V. To; A. K. David	[View] [Download]
Abstract: Characteristics of both optimal and adaptive multi-input/multi-output control techniques are discussed in this paper with particular emphasis on their applications to AC/DC power systems. Comparative studies of the optimal control strategy and the adaptive control technique for large disturbance show that the latter provides better damping in the system under study. This paper also reports on the establishment of a hardware laboratory facility including a scaled down AC/DC model and its use in the validation of controls.

	ON THE WAY TO REAL TIME FUZZY CONTROL OF A PWM SOURCE INVERTER WITH NONLINEAR LOADS By P. Maussion; M. Grandpierre; J. Faucher	[View] [Download]
Abstract: This paper presents a new approach for PWM Voltage Source lnverter Real Time Control, based on Fuzzy Logic. The special case of non linear loads is studied. From error and error variation measurements, a new control law is proposed to reduce the harmonic distorsion and to provide a good fundamental regulation. The system architecture is described and the fuzzy control algorithm is implemented by off-line calculated look-up tables in ordec to minimize time response.The simulation results are compared to other classical approaches in terms of static and dynamic performances. It will show good results in spite of the coarse definition of the plant.

	MATCHING SITE AND POWER SYSTEM REQUIREMENTS DESIGN OF THE TWO PELHAM SVCS By H. Tyll; G. Thumm; R. Stöber; M. Winfield	[View] [Download]
Abstract: This paper describes the design and layout for the two SVCs installed in the Pelham substation, north of London. Both SVCs of equal size and design have a nominal rating of -75 MVAr to 150 MVAr and are connected to the National Grid 400 kV system. The specified system requirements on operating range, harmonic performance and loss considerations led to an SVC configuration which contains one TSC branch, one TCR branch for continuous reactive power control and a single tuned filter branch for harmonic limitation. The system voltage of the SVC secondary side was optimised to 14 kV based on thyristor equipment capabilities. The paper shows the voltage and current stresses of the thyristor valves taking into account system faults for the TCR branch and misfiring effects for the TSC branch. The approach to filter design considering the harmonic performance requirements is described. The Pelham SVCs commenced commercial operation in summer 1992.

	DESIGNING LIGHT SOURCES FOR SOLAR-POWERED SYSTEMS By J. L. Duarte; J. A. A. Wijntjens; J. Rozenboom	[View] [Download]
Abstract: The design of a fluorescent lamp power circuit for (portable) light sources, using a photovoltaic-supplied battery as intermediate energy buffer, is documented. The described driver circuit, which is based on a class-E resonant inverter, operates on a high frequency (125 kHz), requires low-cost components and simple design and exhibit a high efficiency (over 85%). The circuit provides resonance ignition, sinusoidal lamp current and illumination intensity control. These operating conditions are optimal, and they yield a long tube life. Experimental results from a 7W-lamp are included.

	TESTING OF A NEW D.C.-D.C. CONVERTER TOPOLOGY FOR INTEGRATED WIND-PHOTOVOLTAIC GENERATING SYSTEMS By F. Caricchi; F. Crescimbini; A. Di Napoli; O. Honorati; E. Santini	[View] [Download]
Abstract: This paper presents a d.c.-to-d.c. converter topology which can find application in the development of small-size integrated wind and photovoltaic energy generating systems. The converter layout is the result of the connection in series of two switch-mode d.c.-to-d.c. step-up converter stages, so that the overall converter is able to operate as a double input - single output power electronics interface between the system generating units and the utility circuit. The paper discusses the converter modes of operation and reports experimental results taken from an IGBTs converter prototype.

	A DC/DC CONVERTER WITH TWO-SWITCH STRUCTURE FOR EFFICIENCY IMPROVEMENT AND INTEGRATED POWER SUPPLY By B. Hauck	[View] [Download]
Abstract: Photovoltaic systems need an actuating element for the adaption of the generator to the back-up battery or the d.c. link. Further especially for these systems a high efficiency is desired. The d.c./d.c. converter with the two-switch structure improves a high efficiency and it has an integrated power supply for the controlling unit, the data acquisition and the basic current for the main transistor. By switching off the main transistor of the converter the current commutates to the auxiliary transistor and the integrated power supply will be loaded. lf its voltage is high enough, the auxiliary transistor switches off the current. The converter works on the effect, that the auxiliary transistor (MOSFET) operates much faster than the main transistor (bipolar). For the dimensioning of the reactor a new method, the so-called core distinctive number method is used. The measurements show, that the efficiency especially in the range less than 1/3 of the maximum power is better than for usual converters.

	CAD PROGRAMS HELP TO DESIGN RELIABLE CONTROLLER FOR POWER PHOTOVOLTAIC SYSTEMS By L. Lori; P. Redi	[View] [Download]
Abstract: The design of a battery charge regulator for high power photovoltaic plants is obtained thank to Spice simulation program. The highest reliability is reached by controlling the switching components with an 8-bit microcontroller.

	A SINEWAVE INTERFACE FOR VARIABLE-SPEED WIND TURBINES By G. A. Smith; R. G. Stephens; P. Marshall; M. Kansara	[View] [Download]
Abstract: There are a number of major benefits from operating wind turbines at variable-speed including improved energy capture, reduced mechanical stress and lower levels of audible noise in light winds. A number of variable-speed systems have been operated with varying degrees of success. These include ac-dc-ac link inverters for synchronous or capacitor excited asynchronous generators and also slip-recovery schemes with cycloconverters. The latter has the disadvantage of slip-rings whilst the former recover energy through Line Commutated Inverters (LCI's) with variable power factor and poor current waveform. The IGBT may be used to provide a power interface that can synthesise good quality current waveforms in both generator and the power network. In this solution a generator side step-up converter produces a constant dc link voltage from the variable frequency and voltage generator. This is then inverted through a high-frequency interface to produce near sinusoidal current at unity power factor. Results show overall efficiencies around 90% with total harmonic distortion as a % of fundamental not exceeding 10%.

	ECONOMICAL COMPARISON OF HIGH POWER STATIC VAR COMPENSATORS By G. Blajszczak; I. Boake; J. D. van Wyk	[View] [Download]
Abstract: The fundamental reactive power can be compensated by line or force commutated compensators. Installation costs, operational losses and harmonic pollution of these compensators are compared in a power range from 20kVAr up to 100MVAr. The detailed analysis shows that the widely applied line commutated compensator is less cost-effective than a force commutated compensator.

	ESTIMATION OF ENERGETIC FACTORS IN POWER ELECTRONICS SUPPLY SYSTEMS By Y. Stabulnieks; Y. Shinka	[View] [Download]
Abstract: Conventional calculation methods of electric power and its components as orthogonal, integral, symbolic, systems equivalence, etc., applied to nonsinusoidal system analysis bring to different and sometimes to inexplicable results. Obtained in such a way reactive and apparent power have no physical interpretation and have only an arbitrary mathematical implication. Therefore, currently accepted definitions of electric power components are reviewed and their limitations in systems with converters are analyzed. In terms of instantaneous power a number of energy flow and power components such as active, external, input, reverse, resonant, storage, oscillation, etc... have been determined. These components can be used to determine new energetic factors: the system energy utilization factor, consumer energy utilization factor, power oscillation factor, etc... They may be applied for the power system optimization, reactive and active compensation, harmonic suppression. The application of the theory developed is illustrated by a typical example. The proposed power and energy components can be directly measured by means of digital electronic instruments.

	THE APPLICATION OF TRANSPUTERS FOR DIGITAL CONTROL OF STATIC VAR COMPENSATORS By M. Davies; D. A. Picken	[View] [Download]
Abstract: This paper discusses the advantages of using digital control systems for Static Var Compensators (SVC) and describes the implementation of such a digital control system using transputer technology. The application of digital controls to SVC is demanding in terms of system hardware and software, particularly the processing power and intersystem communications required to achieve a performance equivalent to the latest analogue controllers. One approach in adopting a digital solution for an SVC controller is by the use of concurrent processing. This can be implemented by the INMOS family of transputers, which are particularly suitable. A description of some aspects of the digital design is given and also test results taken from comparative studies on the performance of analogue and digital SVC controls. These studies were performed on a real time analogue simulator model and show that the digital implementation has been successful in reproducing a performance equivalent to an analogue control.

	STATE OF THE ART IN SOLID STATE POWER CONTROLLER FOR AERONAUTICAL APPLICATION By J. J. Simon	[View] [Download]
Abstract: Recent breakthrouqh in power transistors technoloqy enables speedinq up the development of HVDC for aeronautical applications. Concerning the power distribution, Solid State Power Controller (SSPC) are proving now to be a mature product, in a wide ranqe of current, from 1 to 60 Amp. However , dependinq of their implementation in the electrical power network, as well as of the loads they control, their features widely differ. This topic is aimed at describing the main features required and the corresponding technical and technoloqical innovative solutions for achieving them. Low current devices must comply with the most general requirements as low ON resistance, hiqh side and low side switching capabilities, short-circuit and overload protection, while high current devices incorporate more specific features like very low ON status drop out, active current limitinq for large capacitive loads, fault tolerance capability, internal DC/DC converter supplied by the power network.

	RESIDENTIAL SOLAR-POWERED AIR CONDITIONER By K. Tanaka; E. Sakoguchi; Y. Fukuda; A. Takeoka; H. Tokizaki	[View] [Download]
Abstract: Sanyo has been developinq two types of residential solar-powered air conditioners. One is a uni-directional system, and the other is a bi-directional system. When usinq a 600 Wp photovoltaic (PV) array for the uni-directional system, we confirmed that the system can supply 50% of the power consumed by an air conditioner in summer. We also confirmed that the bi-directional system can feed surplus power back to the commercial power supply from PV, and suppress the input current distortion of the air conditioner. There is little doubt that the introduction and widespread use of these systems will play an important role in reducing the peak power energy requirements in summer and the generation of carbon dioxide.