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EPE 1991 - 07 - Session 1.7: HVDC, HARMONICS AND RENEWABLE ENERGY SOURCES
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - Conference > EPE 1991 - 07 - Session 1.7: HVDC, HARMONICS AND RENEWABLE ENERGY SOURCES
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	HARMONICS PRODUCED BY LARGE CONVERTER SYSTEMS   By Albert Kloss	[View]   [Download]
Abstract: General view on harmonic problems In power-electronic systems, large frequency converters and large rectifiers. Some new questions like non-whole multiple and non-stable harmonics are discussed. A.C. Filters for interharmonics are mentioned.
	HARMONICS: THE NEED OF A METHODOLOGICAL APPROACH   By José R. Ramos; Mauro Loggini	[View]   [Download]
Abstract: This paper evaluates the performance (in presence of harmonics) of a typical electrical plant. All of the possible scenarios are analyzed in order to provide (practical) design criteria from a user point-of-view.
	DYNAMIC BEHAVIOR OF HVDC SYSTEM USING FORCED COMMUTATION CONVERTER IN AC SYSTEM FAULT   By N. Kimura; M. Kishimoto; K. Matsu-ura	[View]   [Download]
Abstract: This paper shows the dynamic behavior of the HVdc system which uses forced commutation converter when an ac fault occurs in it. The model HVdc system is unidirectional transmission into a load system without any ac voltage source. Computer simulation program using transient analysis has been developed to perform many runs changing several parameters. First, the results of computer simulation when load impedance changes in the receiving system are shown and they indicate the superiority of voltage-source converter in dynamic behavior. Then, the results of computer simulation when an ac fault occurs in the receiving system are shown. Simulated ac faults are 1 Line-to-Ground (1LG), 2 Line-Short-Circuit (2LS) and 3 Line-to-Ground (3LG). The results of computer simulation indicate that the voltage source converter must be turned off quickly to protect the switching devices while the current-source converter has no severe problem in the ac fault condition. The overcurrent and overvoltage for the voltage-source converter are shown with the parameters of ac reactance and turn-off delay.
	HARMONIC EVALUATION IN ELECTRICAL PLANTS SUPPLYING 6-PULSE AC/DC CONVERTERS   By A. Cavallini; M. Loggini; G.C. Montanari	[View]   [Download]
Abstract: In the paper, harmonic pollution in electrical plants supplying 6-pulse converters is evaluated by analytical procedures, with particular attemption to the influence of plant parameters on harmonic content of AC current. In particular, amplitude and phase of harmonic currents injected by converters are studied with reference to load and plant parameters, like e.m.f., DC reactance and resistance, protection and supply reactances. It is shown that, dependently on plant parameters and e.m.f. values, some harmonic currents could become negligible or take values higher than those expected from the ideal case of rectangular current waveform, which is often considered the 'worst' case for harmonic current amplitudes.
	ELIMINATION OF CURRENT HARMONICS IN DIRECT AC-AC CONVERTER   By R. Badarou; C. Jaunay; G. A. Capolino; C. Glaize	[View]   [Download]
Abstract: The problems of harmonic effects generated by AC-AC converters directly connected to the mains have been clearly set by several authors. This paper deals with harmonic elimination in single phase AC-AC converter with interest in load and source currents. The first part of the paper presents the computation method based on optimum determination of switching angles to minimize the selected harmonics. This technique is presented for several switching patterns in term of displacement factor and distorsion factor. The last part of the paper is dedicated to hardware implementation of the proposed technique with comparison between simulation and measurement.
	CONTROL OF THYRISTOR CONTROLLED REACTORS FOR OPTIMAL FLICKER REDUCTION   By W. Hörger; D. Schröder	[View]   [Download]
Abstract: Voltage ftuctuations on powerlines caused by consumers with rapid fluctuating load are reduced by dynamic VAR compensators like thyristor controlled reactors (TCR). Delays in the signal processing due to the definition of power and the compensator itself result in poor reduction ratios of the fticker. This paper presents a new control strategy which is fitted to the human eye sensitivity curve for flicker. This, contrary to previous compensation methods, not only voltage fluctuations with low frequencies are reduced. Fast adaptive algorithms, applicated in communication engineering (e.g. adaptive channel equalisation, waveform coding, ...) up to now, enable optimal flicker reduction in the frequency range of human eye sensitivity. The reduction of faster voltage fluctuations requires a refined understanding of the relation between flicker and measured power, however. Reduction ratios of disturbing flicker up to factor 30 in the deterministic case can be achieved.
	HARMONIC INSTABILITY IN CHANNEL INDUCTION FURNACES INDUCED BY STATIC CONVERTERS   By W. Kaiser; W. Komatsu; W. Pó	[View]   [Download]
Abstract: This paper presents the analysis and proposed solution of a harmonic instability problem in a casting plant. Current harmonics, qenerated by the rectifier of a coreless induction furnace, cause disturbances in a channel induction furnace (CIF) circuit. A system analysis has been done, based on a model developed for the system, through digital simulation of a dedicated program. The results were further compared to the measurements obtained from the plant. A simple and economic solution is proposed consisting in the inclusion of inductors in the capacitive branches of the channel induction furnace circuit. When this solution was implemented, system behavior and measurements showed that the solution was effective.
	HVDC TAPPING STATION: POWER TAPPING FROM A DC TRANSMISSION LINE TO A LOCAL AC NETWORK   By P. Lamell; A. Ekström	[View]   [Download]
Abstract: A new type of tapping station for HVDC will be presented in this paper. A small amount of power will be tapped off from a high voltage direct current (HVDC) transmission to a local ac-network in two steps. The tapping station is built up of a current-source line-commutated converter connected in series in the dc transmission, and two converters of the voltage-source forced-commutated converter type. The basic function of the tapping station will be described and illustrated by the result from simulations with the EMTP program.
	Development of a Remote-controlled Continuous Observation System of Harmonics in Power Distribution Lines   By M. Kaneko; M. Yamada; F. Kohno; K. Ishihara; Y. Tanahashi	[View]   [Download]
Abstract: A continuous harmonic observation system has been developed which can continuously observe harmonics superposed in power distribution lines and be remotely controlled. The system consists of a fixed key station, movable terminal stations and communication lines connecting both kinds of stations and one key station can remotely control maximum five terminal stations so that the harmonics at multiple points can simultaneously be observed. There are two observation modes, one being a periodical observation mode and the other a continuous observation mode, and three types of observations are further prepared in the latter mode. The continuous observation mode is formed so that the maximum value data including the maximum value of a designated harmonic content, which can not be picked up in the conventional single-shot observation method, may reliably be sampled, This point is the most remarkable feature of the present system. The system can be utilized also as a support system for exploring the cause of harmonics generation by analyzing how harmonics in distribution lines are superposed at the spots of the terminal stations and in the period of observation.
	FIELD EVALUATION OF A NOVEL MAXIMUM POWER POINT TRACKING REGULATOR IN PV INSTALLATIONS   By J. H. R. Enslin; D. B. Snyman	[View]   [Download]
Abstract: A Maximum Power Point Tracking (MPPT) converter based on a novel Parallel Power Conversion Technique (PPCT), to enhance the converter efficiency, is evaluated under laboratory and field conditions. The converter is controlled to track the maximum power point of the input photovoltaic (PV) source, under varying input and output parameters. Maximum power point tracking for relative small systems is achieved by maximization of the output current to the battery, using an optimized hill-climbing, inexpensive microprocessor based algorithm. Extensive practical results are included with a full description of the new converter topology under real operating conditions. A comparative field evaluation on a MPPT and a standard series regulator is included in the paper.
	THE SLIP POWER RECOVERY GENERATOR APPLIED TO THE SEA WAVE ENERGY EXTRACTION   By G. D. Marques	[View]   [Download]
Abstract: The Slip Power Recovery Generator (SPRG) can be employed as a "Variable Speed, Constant Frequency" Generator in the exploitation of some renewable energies, like the Wind Energy the Sea Wave Energy among others. The use of a thyristor bridge in the Slip Power Converter just allows the control of the active power. The replacement of this thyristor bridge by a GTO converter with phase shift and PWM switching, allows the control of both the active and the reactive power within certain limits. This paper discusses the application of the SPRG on the exploitation of ocean Wave-Energy by water column devices. To obtain good performances, the system must be used in closed loop. The system has two degrees of freedom and therefore active and reactive power control are possible at the same time. For the active power regulation, three different controllers are described and compared. The reactive power regulation is of second priority. Some experimental results are presented.
	DITHER RECTIFIER HAVING IMPROVED POWER FACTOR AND ITS APPLICATIONS   By I. Takahashi; R. Y. Igarashi	[View]   [Download]
Abstract: Input current of conventional capacitor input diode rectifiers widely used in high frequency switching power sources present a low power factor and contain many harmonics, which cause many troubles to the power system. This paper proposes a new approach to improve the current waveform of capacitor input rectifiers, which is based on the dither effect used in the linearization of non- linear function in control systems. Two applications of the dither rectifiers are presented in this paper: a switching regulator and a high-frequency current-type inverter. They can be realized by simple modifications in conventional circuits, and more importantly, no control is needed. The experimental circuits achieved over 99% input power factor and current distortion below 11 %.
	DEVELOPMENT OF A SIMPLE FLYWHEEL UPS HAVING ACTIVE FILTER ABILITY   By I. Takahashi; M. Mishima; G. Su	[View]   [Download]
Abstract: A simple uninterruptible power supply / active filter (UPS / AF) system is proposed. The system normally operates as an active filter. A 100V/3kW single phase UPS/AF is developed, which uses a flywheel energy storage unit. The distinguished features of the flywheel UPS/AF system can be summarized as follows: (1) The normal operation of the UPS system as an active filter not only eliminates the harmful harmonics created by nonlinear loads but also realizes a high efficiency UPS system. (2) The use of a high speed flywheel with an induction motor/generator for the energy storage realizes high efficiency, maintenance free and long life as three times of battery UPS's. (3) A half-bridge inverter is utilized to deliver clean power to the loads during power outages, or to suppress the harmonics trom the line current in normal operation. A V-connected three phase inverter is employed to drive the induction motor/generator. The use of the simple inverter circuits enables to assemble the power conversion circuit with a module containing 6 switching devices, and thus contributes to the reduction in the cost and weight. Both the UPS and active filter functions are demonstrated, and excellent performances are achieved of 99.7% input power factor and 93.1 % efficiency in active filter operation, and 2.8% output voltage distortion in UPS operation.
	STATIC WATT VAR COMPENSATORS FOR STABILIZATION OF VERY LONG DISTANCE AC TRANSMISSION SYSTEMS   By R. Giglioli; R. Salutari, G. Zini; M. Ceraolo	[View]   [Download]
Abstract: The applications of Power electronics involve today the whole electric power system. The demand side users of electric energy are undoubtedly the preferential subjects of power electronic applications because of their request of flexibility and the small power generally involved; however, the technological power units of electronic devices are no more a barrier for application also in generation and transmission systems. Two important applications which involve the electric power system regard the reactive power compensation by means of Static Var Compensators and the peak shaving by means of Battery Storage Plants. An electronic apparatus called Static Watt Var Compensator which covers both the application fields of the above mentioned devices has already been conceived and proposed. In this paper, a brief description of this apparatus is reported and attention is focused on an important application in the field of very long distance a.c. transmission systems, pointing out the relevant features of this compensation component and its capability of stabilizing transmission systems which otherwise would be basically unstable.
	REDUCTION OF HARMONIC CURRENTS GENERATED BY PARALLEL CONNECTED ELECTRIC TRACTION RECTIFIERS   By E. Destobbeleer; J. P. Hautier	[View]   [Download]
Abstract: Harmonic current perturbations generated by electric locomotive rectifiers must be kept within strict limits particularly defined by the "equivalent disturbing current" led. The series or parallel connection of these rectifiers allow phase shifts between their controls. Three different controls of two to four, parallel connected, P.W.M. four quadrant choppers are theoretically studied. The P.W.M. consists in a triangular carrier intersecting a sinusoidal modulating wave the harmonic content of the drawn current is spread among "families". The three control methods are: • Global phase shift of the input voltage of the rectifiers, • Phase shift of the triangular carrier of each rectifiers, • Combination of the two preceeding methods. The actions of the three control methods on the total harmonic current families and on the led are studied.
	THYRISTOR CONTROLLED CAPACITORS FOR INDUCTION GENERATOR - INDUCTION MOTOR SYSTEMS   By Faeka M. Khater; Farouk I. Ahmed; Khaled S. Sakkoury	[View]   [Download]
Abstract: This work presents a new thyristor control scheme to switch the excitation capacitors of a wind driven induction generator supplying an induction motor. The excitation capacitors are composed of three groups, the first one is a fixed capacitor bank giving the minimum required excitation and permanently connected to the lines. The second group is a starting capacitor bank used only at the moment of starting of the system. The third group consists of switched capacitors to supply the additional excitation required under any changes in the wind speed or motor load. The switching strategy depends only on the terminal voltage signal. The voltage amplitude to frequency ratio is employed to control the firing signals of thyristors which result in switching on or off the excitation capacitors.
	USING SEPIC TOPOLOGY FOR IMPROVING POWER FACTOR IN DISTRIBUTED POWER SUPPLY SYSTEMS   By J. Sebastián; J. Uceda; J. A. Cobos; J . Arau; R. Lorenzo	[View]   [Download]
Abstract: The Single Ended Primary lnductance Converter (SEPIC) presents several advantages over boost and flyback topologies which makes this converter very convenient to be used as a Power Factor Preregulator (PFP). Due to this fact, the PWM SEPIC used as PFP is studied in this paper. Stress in compo,nents and operation in continuous and discontinuous conduction mode are considered in thios paper. The study reveals that both types of PFP control (multiplier approach and voltage-follower approach) can be used in PWM SEPIC, the first one when it operates in continuous mode and the second one when it operates in discontinuous conduction mode. Finally, the theoretical analysis is validated in two prototypes (continuous and discontinuous conduction mode).
	POWER CONVERTERS USING INTERPHASE ENERGY EXCHANGE CONTROL FOR DISTORTION REDUCTION   By V. Sarv; J. Soojärv; A. Tuisk	[View]   [Download]
Abstract: The performance characteristics of power converters depend on the energy conversion processes in corresponding circuits. Therefore, efficient principles to improve energy exchange and transfer processes create possibilities to synthesize new conversion circuits with improved characteristics. In case of three-phase converters an interphase time-variable transformer enables efficient distortion reduction via energy exchange control between the supply phases. The design principles of the corresponding switched-mode AC controllers and AC-DC converters are analyzed. Performance characteristics of three 12-pulse AC-DC converters are described. Trends for further improvement in the converter characteristics using interphase energy exchange control technique are discussed.
	Fast Controllers for High-Power Factor AC-DC Converters   By Aleksandar M. Stankovic; George C. Verghese; Xiaojun Liu; V. Joseph Thottuvelil	[View]   [Download]
Abstract: This paper shows that the large signal behavior of a popular family of high-power-factor ac-dc converters can be effectively controlled by a fast linear controller with periodic gains and feedforward of load power. The modeling process based on a dynamic power balance is described, together with the controller design procedure. An estimation scheme which deals with circuit parameter uncertainty is given, improving the robustness of the proposed controller. Simulations corroborating theoretical results are presented.
	SYMMETRICAL FOLLOW-UP STATIC REACTIVE POWER COMPENSATOR   By Z. Hanzelka; S. Piróg	[View]   [Download]
Abstract: The paper deals with an analysis of a symmetrical reactive power compensator containing a short circuit three-phase thyristor bridge fed by a transformer with a high short circuit voltage and a battery capacitors connected parallel. A special attention is paid to the harmonic analysis of compensator currents. There is presented the principle of selection of power of its components thanks to which the size of the installation could be minimized.
	Operation of the Transformer in the Converter of Stand-alone Photovoltaic Systems   By M. A. Slonim; V. V. Risser; T. S. Key	[View]   [Download]
Abstract: A stand-alone photovoltaic system is described. It consists of a DC source (solar cell array), single phase transistor based inverter, transformer and load. The transistor's control voltage Vg determines the 60 Hz frequency of the AC load. The transformer, with a rated power of 2400W, connects the AC (load) and DC (solar cell array ) sides of the system. lts operation has been analyzed. The analysis and experiments have been carried out for the three main loads of consumer applications: resistive loads, universal and induction motors. Due to the non-sinusoidal waveforms of the voltage and current across the windings, the transformer's operational conditions differ from those arising with the sinusoidal waveforms. A detailed analysis of the transformer's operational conditions is carried out. The influence of magnetization current on the current waveforms and the form of the core flux during the cycle are discussed and explained. A detailed explanation of the waveforms obtained is given.
	GUIDELINES FOR PHOTOVOLTAIC SYSTEM POWER AND SUPERVISORING ELECTRONIC   By Alberto Bonazzelli; Angela Repetto	[View]   [Download]
Abstract: The use of Photovoltaic Power Conversion, in the field of Renawable Energy, is constantly increasing. This paper, in reference with large application (> 50 kW), presents a systematic analysis of the Electrical and Electronic equipment for this type of plant. On analyse the general layout type of Power Conversion, efficiency optimisation and supervisoring System for grid connection and stand alone application. Emphasis was put on the realization of the scheme on a microprocessor-system and the implementation to control the MPPT. Experimental results, showing the Efficiency and Power Factor versus power for a 300 kW power plant are presented.
	SIMULATION STUDY FOR THE SUMMATION 0F CURRENT HARMONICS PRODUCED BY STATIC POWER CONVERTERS WITH RANDOM FIRING ANGLES   By L. Pierrat; Y. J. Wang; R. Feuillet	[View]   [Download]
Abstract: Monte Carlo simulation approach for the summation of random harmonic currents arising from six-pulse converters is presented. Converter models for both characteristic and uncharacteristic harmonics are established respectively. The probability characteristics of the harmonics generated by a single converter, with fluctuating loads and unbalanced supply voltage, are first studied. This is followed by simulating the harmonic generation of several independent converters so that the statistical distribution of the resultant harmonic currents can be found. It will be shown that characteristic harmonics and uncharacteristic harmonics possess different probabilistic features because of their different origin. Diversity factor, one of the useful applications of the simulation results, will be derived from the cumulative density function of harmonic resultant.
	HARMONICS AND POWER FACTOR OF MULTIPLE CONVERTERS   By Muhammad H. Rashid	[View]   [Download]
Abstract: AC-DC converters are extensively used in industrial applications for ac and dc motor drives. The harmonics generated by the converters are high and the power factor is low, especially at the low output voltage range. In practice, a number of converters are operated from the same supply system. As a result, the overall power factor is changed significantly depending the control angles of the various converters. This paper investigates the harmonic behavior and the overall power factor if a number of converters are operated simultaneously supplying their respective load.
	A METHOD FOR REDUCING HARMONICS IN INPUT LINE CURRENTS OF DOUBLE CONNECTED DIODE RECTIFIER   By Yasuyuki Nishida; Shoji Iida; Shigeo Masukawa; Shota Miyairi	[View]   [Download]
Abstract: A new effective method for reducing harmonics involved in input line currents of the three-phase rectifier for fixed-dc-voltage applications is proposed. The method can be easily implemented by adding a simple auxiliary circuit consisting of two diodes and a threetap auto-transformer to a double connected three-phase bridge rectifier. The proposed rectifier apparatus behaves essentially as a conventional 24-pulse rectifier in regard to the harmonics content in the input line currents. In this paper, the principle of harmonics reduction is described, performance of the rectifier is analyzed in detail, and the optimum parameters of the circuit are investigated. The experimental results confirm the validity of the method.