| EPE 1993 - 55 - Dialogue Session DS4.4: GENERATION AND TRANSMISSION: ACTIVE FILTERS, HARMONICS, APPLICATIONS |
| You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1993 - Conference > EPE 1993 - 55 - Dialogue Session DS4.4: GENERATION AND TRANSMISSION: ACTIVE FILTERS, HARMONICS, APPLICATIONS |
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 | SLIDING MODE CONTROL OF A VOLTAGE-SOURCE ACTIVE FILTER
By C. Tuttas | [View]
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Abstract: A voltage-source active filter needs a robust control concept due to parameter variations of the power system. This condition can be realized by a sliding mode control concept. The compensator is then stable also at capacitive load compensation. Using sliding mode control theory one obtain an insight to the stability of the controlled system.
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| | CYCLOCONVERTER FOR HIGH SPEED PERMANENT MAGNET GENERATOR UNITS
By H. Polinder; N. H. M. Hofmeester; L. J. J. Offringa; W. Deleroi | [View]
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Abstract: A generator-converter unit, consisting of a high speed permanent rnagnet generator and a high frequency cycloconverter, is developed. The generator-converter unit is intended for use in total energy systems connected to the utility grid, or hybrid systems in vehicles, or vessels. It will be driven by a high speed high efficiency gas turbine. The advantages of this variable speed constant frequency (VSCF) system, such as optimal turbine speed and small size and weight, are discussed. The 6-pulse cycloconverter, used to change the 800 Hz generator frequency to 50 Hz, is described in detail. A new combination of control methods results in a substantial improvement of the power factor load of the generator. Individual pulse control of the cycloconverter by means of digital signal processing results in excellent control properties of the generator-converter unit. Measurements are given on a 50 kW experimental system, consisting of a 600 Hz test generator and a single phase cycloconverter.
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| | DC FEEDING SYSTEM SUITABLE FOR ROLLING STOCKS WITH RE-GENERATlVE BRAKING SYSTEM UTILIZING THYRISTOR RECTIFIER
By A. Abe; H. Fujimori; T. Ito | [View]
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Abstract: In DC electric railway of Japan, most of newly produced electric rolling stocks have regenerative braking system. For the re-generative brake which acts reliably and saves energy utilizing re-generative power, we produced a feeding rectifier with feeding voltage control by thyristor, and introduced it on a commercial line. There is about 5% decrease in consumed power at the substation equippd with this rectifier.
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| | PWM CONVERTER FOR EXCITATION OF INDUCTION GENERATORS
By S. R. Silva; R. O. C. Lyra | [View]
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Abstract: Due to its low cost and low maintenance characteristics, the induction generator is an important option for low power generation and non conventional energy sources exploitation, such as, for example, wind engines. Nevertheless, the main drawback of these machines is that its excitation must be provided by external means. In this article, a reactive controllable power source which enables efficient induction generator excitation over a large speed and load ranges is presented. The device consists of a three phase PWM inverter driven by a capacitor in the DC bus. The inverter output currents are controlled to provide the necessary excitation for the generator and the active power required to keep the DC capacitor voltage constant or to supply a DC Ioad. The work is illustrated by dynamic simulation, where the start-up of the DC bus voltage and the self-excitation process and the dynamic behavior of the system are investigated and control policies are presented.
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| | A GENERALIZED MODEL FOR HARMONIC ANALYSIS OF NATURAL COMMUTATION CONVERSION SYSTEMS
By S. Bolognani; M. Fracchia; P. Pozzobon; M. Zigliotto | [View]
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Abstract: In order to take into account the wide spreading of high power non linear loads continuously increasing harmonic pollution in the utility networks and the new directives regarding electromagnetic compatibility, accurate evaluation of harmonic distortion introduced by conversion systems is necessary both for new plants and for upgrading of existing ones. This paper presents a generalized model for harmonic analysis and its implementation on a Personal Computer. The proposed methodology can be defined as a deterministic approach operating in the frequency domain by means of an iterative algorithm and allows to obtain the harmonic content of the required currents and voltages in steady state conditions as well as the time waveforms of any relevant system variable. With respect to the time domain models this one eliminates the computation time necessary for the transient behaviour determination which is not required for harmonic analysis. In comparison with the frequency domain models it presents two main characteristics: an accurate frequency model for any natural commutation static conversion structure (comparable with the time domain static converters models) and no convergence problems for the iteration process. The results of the implementation of the algorithm are reported and discussed in the case of a significant power application: the twelve pulse bridge rectifier for 3 kV dc railway traction supply. A comparison with the results achieved by a time domain method is pointed out in terms of computation time and results accuracy.
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| | ACTIVE POWER FILTER USING SOLID STATE PHASE SHIFTER
By Satoshi Uemura; Minoru Arimitsu; Hirotaka Chikaraishi; Ryuichi Shimada | [View]
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Abstract: The load leveling for an induction motor with pump load using the power angle regulator is described. The power flow is controlled by changing the power angle of voltage vector. The power angle is controlled using phase shifter so as to reduce the power pulsations which are produced by pump load. The novel power angle regulator which is called Solid State Phase Shifter (SSPS) employs AC switch with PWM schemes for continuous and rapid control. The power pulsation has been reduced from 63% to 10% of average level.
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| | EXAMINATIONS OF ZnO-VARISTORS IN THE LEAKAGE REGION WITH REGARD TO HIGH FREQUENCY STRESSES
By J. Bak-Jensen; B. Bak-Jensen; S. Damsgaard Mikkelsen; J. Tolstrup Sorensen | [View]
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Abstract: ZnO-varistors and ZnO-arresters are widely used for protection of HVDC-systems and switch-mode power supplies. Because of high frequency components in the leakage current, a model of the leakage region of a ZnO-arrester is of interest. In this paper an equivalent circuit model for the leakage region of a ZnO-arrester is set up. The model is able to describe the frequency, current and temperature dependency of the arrester in the leakage region. The lumped parameters of the model is achieved from tests with frequency sweep analysis, FFT-analysis and DC-resistance measurements at different temperatures. The method for determination of the lumped parameters of the equivalent circuit model is verified by tests on a ZnO-varistor, and the validity of the parameters is tested by parametric simulations. The set up method gives stable parameters and it is possible to simulate a measured voltage with high frequency components from a measured current signal with reasonable accuracy.
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| | THE THEORETICAL AND EXPERIMENTAL STUDY OF A.C. HARMONICS OF TWELVE-PULSE RAILWAY RECTIFIERS
By R. N. Tuncay; A. Kaypmaz; Ç. M. Yilmaz; P. J. Brown | [View]
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Abstract: This study deals with the A.C. harmonics of twelve-pulse uncontrolled rectifiers of Istanbul Light-Railway System. The experimental results are obtained by a data-acquisition system. The theoretical values are computed by 'Piecewise Estimation' technique and SPICE technique. The latter technique is used for taking the phase and amplitude unbalances, interphase transformer insymmetry and time varying behavior of the load into account. The correlation between experimental and theoretical values are found to be satisfactory.
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| | FREQUENCY DOMAIN ANALYSIS FOR MULTIPLE CONTROLLED RECTIFIERS
By A. David Graham | [View]
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Abstract: Harmonic studies or power rectifiers usually make simplifying assumptions about overlap angle and dc ripple current to enable the waveforms to be analysed more easily. This paper uses these simplifications to compute an initial estimate or the ac line current harmonics and then uses that estimate to calculate all the dc side harmonics with the aid of both a Voltage Switching function and a corresponding Current Switching function. The method can be extended to two or more rectifiers on a common ac bus where the commutation notches on one bridge errect the dc current in the other one, and to more complex switching systems such as twelve pulse rectitiers.
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| | EXPERIENCES WITH A DIGITAL REAL TIME SIMULATOR FOR TESTING A COMBINED STARTUP AND EXCITATION CONTROL UNIT
By F. Krutemeier; K. Schulz; S. Lichtenberger | [View]
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Abstract: The functional and dynamic performance test of the control equipment is an important part of the work schedule for an installation. The integration and testing of the control cubicles in a system test field improves the quality and eliminates errors which occurred during design and implementation. A Hardware-in-the-loop test summarizes the original control cubicles and a simulation which serves the measurement interface. lt also tests the developed hardware and software in a full dynamic mode. The high power devices which are not available during testing are simulated in real time. This report deals with the test results of a combined startup and excitation control unit for the gas and steam power station BUGGENUM (Netherlands). The results are compared to the experiences which have been made during the commissioning of the tested control equipment. One of the results was that the tested control equipment was easy to bring into operation and that the commissioning could be done quicker in general.
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| | PERFORMANCE OF AN ACTIVE FILTER USING PWM CURRENT SOURCE INVERTER
By M.-X. Wang; H. Pouliquen; M. Grandpierre | [View]
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Abstract: This paper presents an active filter comprising a three-phase current source inverter (30 kVA) operating in PWM. Optimal management of switching pattern makes it possible to isolate the three phases and then to achieve accurate model of the PWM inverter. The regulation takes into account the resonant and very slightly damped output filter. So it allows fast and accurate control of the active filter AC currents to correctly compensate for the non-linear load harmonic currents. The operation of a protection unit against overvoltages on the DC side of inverter is also described. Experimental results show a satisfactory compensating performance.
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| | POWER CONTROL OF A DOUBLE FED INDUCTION GENERATOR WITHOUT SPEED OR POSITION SENSOR
By E. Bogalecka | [View]
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Abstract: Two control systems of the double fed induction generator and simulation results are presented in the paper. Control system controls the active and the reactive powers by means of the rotor currents. The control system produces directly the rotor currents frequency without rotor position measurement and coordinate transformations. An angle controller is introduced instead. This controls the angle between two vectors. Possibilities of the angle real value calculations are presented.
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| | CONVERTER HARMONlCS IN THE FREQUENCY RANGE 3:10 kHz
By Albert Kloss | [View]
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Abstract: Capacitances in power systems can cause converters to produce voltage harmonics of frequencies higher than 3000 Hz. This paper deals on calculation models and filtering possibilities of this kind of harmonic distortions.
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| | COMPENSATION OF AC-DC CONVERTER INPUT CURRENT HARMONICS USING A VOLT AGE-SOURCE ACTIVE POWER FILTER
By J. H. Xu; C. Lott; S. Saadate; B. Davat | [View]
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Abstract: An active power filter should be dimensioned in consideration of the type of nonlinear load it has to filter. When the load is a thyristor rectifier, the performance of the active filter can be evaluated in the semiconductor switching processes. That is, the currents that the active filter applies are often unable to follow the reference currents during the switching. This becomes all the more critical as the triggering delay angle increases, because the switched currents vary even faster. This article presents a theoretical discussion of the relations between the parameters of the active filter and those of the non-linear load (thyristor rectifier), to obtain the optimum dynamic. The conclusions are then applied to a numerical simulation of an active filter with 150 KVA voltage structure used for compensating the harmonics generated by a 400 KVA rectifier. Finally, we present the experimental results obtained from a low-power single-phase model.
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| | SLEW-RATE AND MAXIMUM POWER BANDWITH IN TRANSCONDUCTANCE ACTIVE POWER FILTERS
By J. Femando Silva | [View]
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Abstract: Power inverters operating as active power filters must offer a wide bandwidth, as they supply currents with steep variations, necessary for harmonic and reactive power compensation. Four quadrant inverters, driven by current mode PWM modulators, can perform as transconductance switch mode power amplifiers being, consequently, best suited for this application. An extra feedback loop is needed to obtain a switching mode power operational amplifier, which further allows AC voltage regulation. The abruptness of voltages and currents depend on maximum bandwidths. Therefore, it is important to quantify the relationship of power and small signal bandwidth with the PWM switching frequency. This paper shows and discusses the relationships of the output current and voltage slew-rate, of the small signal and maximum power modulation bandwidths and of the maximum instantaneous output error voltage, with the output filter cut-off frequency, the duty-cycle and the switching frequency of the DC-AC converter used as the active power filter. The major conclusion points to small signal bandwidths roughly one fifth of the switching frequency, and to maximum power bandwidth approximately one seventh of the switching frequency.
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| | APPLICATION OF SOLID STATE SWITCHING DEVICES TO ELECTRONIC LOAD GOVERNING OF MICRO HYDRO GENERATORS
By D. S. Henderson; D. E. Macpherson | [View]
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Abstract: A three phase, Electronic Load Governor has recently been developed. Based on the binary load technique, it uses a balast load to compensate for any torque imbalance on the shaft system. The ballast load which is applied to the generator is connected via solid state type relays incorporating a zero voltage swltching circuit producing virtually no RF interference. They are controlled by a microprocessor and the input is optically isolated from the output circuit. This paper gives an introduction to the design requirements for micro hydroelectric generating schemes and to the load governing principles involved. The paper presents a brief background of the development of the ELG and goes on to describe the ballast load switching circuits. The solid state switches are described and their operational performance discussed. The paper closes with a description of a computer model which simulates the transient frequency performance of the system under the control of the ELG.
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| | DIGITAL CONTROL OF LOAD COMMUTATED INVERTERS FOR STARTING EQUIPMENT OF GAS TURBINE POWER STATIONS
By E. Gatti; R. Moruzzi; G. Torri; V. Vaccaro | [View]
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Abstract: Gas Turbines need starting equipment to accelerate from standstill and follow a preset speed-time profile as required by the ignition and start-up procedure. The paper describes a new-design power electronic equipment based on a digitally controlled LCI thyristor converter that supplies the Synchronous Generator with variable-amplitude / variable-frequency a.c. voltage so that it can be utilized as a variable speed electric motor to start the Gas Turbine. The digital control, besides performing all regulator functions, such as feedback control of d.c. current and rotor speed, thyristor firing and converter protection, includes extensive monitoring and diagnostic functions. An Operator Interface is also available that shows on a CRT-display all tuning and configuration parameters as well as the actual values of the main quantities acquired or calculated by the digital regulators. When any pre-selected event, e.g. a fault, occurs, the data stored in a dedicated register buffer can be used to trace the behaviour of the main converter variables, before and after such event.
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| | ASSESSMENT OF A.C. SIDE HARMONICS OF D.C. SUPPLIED RAILWAYS
By R. Kadhim; J. Allan; B. Mellitt | [View]
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Abstract: Harmonics and distortion of current and voltage waveforms in power systems is a subject of great concern to the power industry. This paper presents a numerical method to calculate the harmonics level in the ac supply caused by the operation of dc electrified railways. This technique can be used at the design stage of new railways.
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| | THE INSTANTANEOUS HARMONIC COMPENSATION FOR MAGNETOHYDRODYNAMIC POWER GENERATION SYSTEM
By Yao-De Wang; Yan-Tai Peng; Wei Wei | [View]
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Abstract: To the problem of harmonics in the inverter output of Magneto Hydro Dynamic (MHD) power generation system, the paper discussed some essential methods which use active filters to compensate the harmonic current in the power network. Having analysed the characteristic of the passive and active filters in the form of voltage source and current source, the paper thoroughly discussed a lot of constructions of the instantaneous harmonic current compensating system. At last, the paper introduced an experimental direct compensating active filter with voltage source as well as the experiment result.
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| | LINE FILTER FOR HIGH POWER INVERTER LOCOMOTIVE USING ACTIVE CIRCUIT FOR HARMONIC REDUCTION
By G. Bocchetti; M. Carpita; G. Giannini; S. Tenconi | [View]
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Abstract: One of the most heavy electrical parts in a high power and high performance 3KV locomotive is the passive input filter that has to reduce the armonic contents of overhead line current according to the EMC with the signalling system. In this paper the authors explain how it is possible to reduce input filter weight and dimension using a combination of passive and active parts for a 3 KV, 6 MW inverter locomotive for Italian Railway. Special active filter topologie is designed to combine high voltage operation of 3 KV passive filter and low voltage of the high frequency IGBT PWM inverter included in the active one. Control techniques are explained and simulation results are shown.
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| | GENERATING FIXED VOLTAGE AND FREQUENCY FROM A GENERATOR DRIVEN WITH A VARIABLE SPEED, OPTIMIZES THE POWER-EXTRACTION
By Steen Carlsen | [View]
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Abstract: To maximize the power extraction from a source, the load-impedance must match the internal impedance of the source. For wind and hydroelectric turbines the efficiency is maximized, when the mechanical impedance of the turbine matches the converting-impedance between the flow and turbine. As the efficiency of turbines is dependened on RPM, controlling the RPM operating point, e.g. by placing two three-phase inverters back to back between the generator and the grid, can increase the efficiency of the system. By flow-fluctuations, maximum efficiency for turbine systems with large inertias, the mechanical impedance of the turbine requires the operating point to deviate from its steady state value. Some of the associated control issues are discussed below. This paper presents a concept to maximize the power extraction from a flow, using a standard induction motor. The concept can be used for wind, hydraulic and ship turbine generator systems.
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| | OPTIMAL PERFORMANCE OF DOUBLE OUTPUT INDUCTION GENERATOR USED IN WECS
By M. N.Eskander; M. T. El Hagry | [View]
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Abstract: In this paper a new technique for optimizing the power generated by a DOIG is established. The proposed control strategy ensures stable operation of the DOIG within a wide speed range without overheating the machine. The proposed scheme employed a controllable rectifier, a d.c. link, an inverter, and an isolating transformer in the rotor circuit. Variation of firing angles, overlap angle, voltages, and powers with speed are deduced. Experimental results are given. Results showed that twice the rated machine power is generated at S = -1.
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