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EPE 1991 - 40 - Session 4.7: CONVERTERS SIMULATION
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	A NOVEL HIGH PERFORMANCE FREQUENCY CHANGER WlTH SlNE WAVES BASED ON "VOLTAGE COMPARlNG-TRACKING-AMPLIFYlNG (CTA)" SCHEME - A probable future competitor for PWM   By Qianzhi Zhou; Zhiguo Chen; Peng Jiang; Shaoming Li	[View]   [Download]
Abstract: A novel high-performance frequency-changer based on "Voltage Comparing-Tracking-Amplifying (CTA)" scheme is introduced in this paper. lts commutating method is neither the same as in phase-shift controlling scheme, nor as in duty factor controlling scheme. It keeps the advantages of high efficiency, high power factor like PWM frequency changer, by ingeniously combining a switch circuit with an amplifying circuit, and it gives out sine-wave voltages and sine-wave currents that the loads need without adding complex filter circuit or adopting the controlling means to eliminate harmonic contents for thoroughly solving torque pulsation problems. An interesting linear sine-wave generator as a reference suitable for a CTA frequency-changers it also introduced in this paper a CTA inverter with combination of this signal generator can form a CTA frequency changer. Then this novel frequency changer acquires high efficiency, high power factor and good waveforms synthetically prior to PWM frequency changer.
	INTRODUCING SWITCH FUNCTION IN POWER ELECTRONIC SIMULATOR AS A SPEED LIMITER   By B. Dhalluin; D. Lafore; J. N. Fiorina	[View]   [Download]
Abstract: Some power electronic simulators use a very simplified switching model: binary representation (Ron, Roff). They give waveforms in the converter and short computer time. The model excludes switching phenomena. In the other simulators, an electrical model of the semiconductor is used; their relative complexity leads to long computer times and difficulties in finding parameters. In this paper we propose a different approach for modelising switching function which satisfies the requirements of simulator users: -macroscopic - microscopic information -limited computer times -parameters that are easy to find in semiconductor hand book or to work out from circuit designer know-how. We examine dynamic interactions between switch and networks, show the speed limitation effect (dl/dt, dV/dt) proper to the device and its drive. The principles of modeling the switch function as speed limiter are proposed. A model for bicontrolled switch and diode is presented. The simulation of a static converter is given and demonstrates the utility of this new approach of modeling.
	MODELING OF GENERATOR POWER ELECTRONIC BASED AUTOMATIC VOLTAGE REGULATOR (AVR) FROM SMALL VOLTAGE DISTURBANCES   By A. Keyhani; H. Tsai; L. Xu	[View]   [Download]
Abstract: In this paper, a new approach to establish a synchronous machine power electronic based automatic voltage regulator (AVR) model is presented. The field measurement used for AVR parameter identification was obtained from excitation system reference voltage small step responses. The mathematical technique used in the parameter estimation process was based on the advanced maximum likelihood (ML) estimation method. By using the available measurement and the power electronic circuit structure, the AVR under investigation was modeled by two separate sections. By carrying out the actual modeling process, this paper presents a coherent procedure to determine the AVR small disturbance model parameters and a real-time performance evaluation of the ML under the presence of data noise.
	AN APPLICATION OF THE DESCRIBING FUNCTION METHOD TO THE CALCULATION OF THE AC LINE CURRENT IN CAPACITOR-FlLTERED RECTIFIERS   By Shoji Nishikata; Jun Kawakami	[View]   [Download]
Abstract: A novel, but simple method of calculating the AC side currents in capacitor-filtered rectifiers is introduced. The describing function method, which is useful in analyzing nonlinear systems, is used in the calculation. The similarity between the waveform in the AC line current in a capacitor-filtered rectifier and that in a thyristor-controlled circuit, to which the describing function method can be applied easily, is first shown, and the relationship between various parameters in the capacitor-filtered rectifier and those in the thyristor-controlled circuit is clarified in a per-unit form for a wide range of the parameters in the rectifier. The way of calculating the AC line current in the equivalent thyristor-controlled circuit on the basis of the describing function method is then discussed. As an application of this new approach, the AC side currents in two rectifiers connected in parallel as well as in the parallel circuit consisting of a rectifier and a R-L series circuit are calculated, and the validity of this method is investigated by comparing the results calculated through the proposed method with the rigorous solution obtained from the state-space model of the circuits. Finally, the AC-line current in three rectifiers connected in parallel is predicted based on this approach, and the usefulness of the method is also shown.
	SWITCHING CHARACTERISTICS OF SERIES CONNECTED POWER SEMICONDUCTORS FOR HIGH VOLTAGE CONVERTERS   By Beom-Seok Seo; Dong-Seok Hyun	[View]   [Download]
Abstract: Series connection of power switching semiconductor elements is essential when a high voltage static power converter is made, so researches are being conducted to further develop this technology. In the series connection of power switching semiconductor elements, the main problem is that simultaneous conduction at turn-on and simultaneous blocking at turn-off together with voltage balancing are unattainable because of the difference of their switching chatacteristics. In this paper, a novel series connection algorithm is proposed, which can implement not only the synchronization of the points of turn-on and turn-off time, but the dynamic voltage balancing in spite of the difference of switching characteristics. The presented method is that the compensated control signal is attained from the voltage feedback signal and applied to the series connected power semiconductors independently, and computer simulation and experimental results verify its validity.
	A Design Procedure for a Self-oscillating Hybrid Inverter   By J. L. Duarte; J. Rozenboom	[View]   [Download]
Abstract: A concept of hybrid inverter topology for fixed-frequency low-power (< 1kW) applications is given. An approximate design procedure for the resonant network and the self-tuning circuitry is described. Validation is provided by an example of a circuit aimed at driving a 2.8MHz/50W output load. The proposals are quite appropriate to specific applications such as lighting, induction-heating cooking, etc.
	A NEW EQUIVALENT CIRCUIT APPROACH TO SIMULATION OF CONVERTER - INDUCTION MACHINE ASSOCIATIONS   By R. Szczesny, M. Ronkowski	[View]   [Download]
Abstract: A new method for simulating converter-induction machine associations has been applied as an alternative to the conventional 2-axis machine approach. This method uses an equivalent circuit approach, and yet models the machine characteristics directly in terms of stator (voltages and currents) and mechanical system (torque and velocity) variables. The main advantages are the ease of describing the system by a general set of equations using the efficient nodal method, the flexibility of implementation to other converters and investigation of the system in normal and fault operation. The structure of the machine model allows for its application in general purpose simulation software. The approach is demonstrated using a 3-phase induction machine supplied by a PWM inverter, represented by a varying PWM voltage source as well as a current inverter given by its actual topology. Several examples illustrate the main features of the approach.
	INTERACTIVE DYNAMIC SIMULATION FOR MODELING SWITCHING NETWORKS AND CONTROL CIRCUITRY OF COMPLEX POWER CONVERTERS   By P. J. van Duijsen; J. B. Klaassens; M. P. N. van Wesenbeeck	[View]   [Download]
Abstract: Information from published design data enables an engineer to satisfactorily design and develop a complex power conversion system. To achieve the best possible design, including the effect of non-linear elements and parasitics, a fast computer simulation program is of great practical value in studying the phenomena under regular and irregular conditions of operation. The presented method is implemented in the form of a general-purpose software package for the simulation of power electronics switching networks combined with analog and/or digital control systems. Interaction between the simulation package and programmable electronic systems (DSPs) is implemented for the purpose of debugging. The network is described by piecewise nonlinear state equations, where the time intervals are controlled by state events. An optimization routine for specific network function is available. The main objective is to obtain the dynamic response of the complete conversion system.
	A PARAMETER OPTIMIZING SOFTWARE TOOL FOR NETWORK- AND ANALOGUE SIMULATING SYSTEMS   By Michael Peppel	[View]   [Download]
Abstract: This paper describes a software tool for optimizing parameters of control- and power electronic systems. This optimizing tool uses a commercially available network- and analogue simulating system for modeling the real-world electronic equipment. The tool is particularly designed to achieve maximum flexibility concerning the mathematical structures of the optimizing problem, the good/bad evaluating procedure, and the input and control data. Due to its purely statistic optimizing strategy and the flexible good/bad evaluating procedure the tool is able to perform successful parameter optimizing in any power electronic or drives application of practical importance.
	PROGRAMMABLE MODULES IN SIMULATION PROGRAMS FOR POWER ELECTRONIC CIRCUITS   By Robert Nilssen	[View]   [Download]
Abstract: This paper presents basic ideas for programmable Modules (components) used in simulation of power electronic circuits. Such a function is frequently questioned by experienced designers who are not satislied by the standard components available, and should be an inevitable part of any general purpose program (like SPICE and EMTP). Programmable Modules can be used to simulate nonlinear dynamic problems described by algebraic, differential or logical equations. Examples of applications are detailed models of switches, electrical machines (advanced two axis modelling), controllers for resonant converters (including sampled systems) and average models tor high frequency switching. After the Modules are programmed they are appliable as ordinary circuit components connected arbitrarily in the circuit. Many Modules can be used simultaneously with individual parameters. The paper focus on the need for such Modules, mathematical description of Modules in connection with the global circuit, and the solution of the differential and algebraic equations.
	CONTROL OF A RESONANT DC·LINK CONVERTER WITH A HIGH MAINS POWER FACTOR - THE NEED FOR A POWERFUL SIMULATION TOOL   By Astrid Petterteig; Tore Undeland	[View]   [Download]
Abstract: In this paper the low loss resonant DC-link power converter is analyzed. The resonant link is common for both the rectifier and the output converters. Thus, both the input rectifier and the output converters are switched nearly lossless. The resonant DC-link is supplied by a switched rectifier to achieve a sinusoidal mains current. Two different output converters are analyzed, one DC-DC converter and one three phase inverter for AC-motor load. The circuit simulation program KREAN has got the possibility to define user programmable modules. These features are used to be able to analyze this converter. The control of the zero voltage interval and the current controllers with different modulation methods, are performed inside the programmable modules. To maintain the resonant voltage it is necessary to have a controlled zero voltage interval. The length of each interval is calculated, based on the last and the next state of all the converters connected to the DC link. Different modulation methods are analyzed to see their influence on the ripple currents and on the power flow in the circuit. A method for current control of the three phase inverter for AC-motor load is discussed and verified.
	Performance of a single-phase pwm boost rectifier using a hysteresis current controller   By John C. Salmon	[View]   [Download]
Abstract: The performance of the step-up pwm boost rectifier is obtained when the rectifier is controlled using a hysteresis current controller. Operating regions are identified, determined by the magnitude of the inductance and by the magnitude of the output dc voltage, where the ac-line current has a low current distortion and near unity power factor. Control restrictions are defined, for the output dc voltage and the input current, to restrict the distortion experienced in the ac-line current. An asymmetrical half-bridge boost rectifier circuit is described that improves the quality of the ac-line current. Extensive analyses of the circuits used are undertaken with reference to theoretical predictions, computer simulations and experimental results.
	MODELLING, ANALYSIS AND PERFORMANCE OF AN EXCITATION CONTROL SYSTEM   By L. L. Lai; A. D. Wang; Y. Z. Ge	[View]   [Download]
Abstract: A practical excitation control system (ECS) is looked at. A model for its analysis is developed by using both a three-phase representation and transfer function approach. Test results have been used to establish the degree of correlation of the predictions to a practical example. The model is then used to conduct a sensitivity study which not only explores the degrees of model complexity necessary for adequate representation but also provides guidelines to system designers on the effects of certain practical conditions. The thyristor exciter offers possibilities for improving dynamic / transient performance and future aspects on ECS have also been discussed.
	APPLICATION OF PROGRAMMABLE MODULES IN SIMULATION OF POWER ELECTRONICS   By Olve Mo; Astrid Petterteig; Nils Arild Ringheim; Robert Nilssen	[View]   [Download]
Abstract: The need of programmable components in power electronic simulation programs is stated. The paper points out how useful it is to have an opportunity to define new components when problems involving nonlinear and dynamic devices are to be simulated. One way to implement programmable components is to allow the user to specify a component through a Fortran subroutine. This is done in the simulation program Krean. The paper describes the powerful tool given to the user through this implementation. The user is allowed to apply his own general multiterminal components with dynamic and/or nonlinear behaviour. Finally, the paper presents results from two different simulations where programmable modules are used. The first example is from an active filter simulation. In this case a user programmed component simplifies the circuit by averaging methods and thus speeds up the simulation. The second is a simulation of a digital controlled resonant converter where the digital controller is a user programmed component.
	ACCURATE COMPUTER SIMULATION OF A TRIAC IN A MOTOR APPLICATION   By L. J. Giacoletto; Andrew Reck	[View]   [Download]
Abstract: A computer model is developed which accurately simulates the following TRIAC operating properties: (1) ON-OFF four-mode control of main terminal current via gate pulsing. (2) Different gate triggering sensitivity for +/-main terminal current and +/-gate current. (3) lnhibit gate triggering for -main terminal current and +gate current. (4) TRIAC OFF resistance. (5) Transfer from ON to OFF state as related to main terminal hold current of either polarity. (6) Transfer from OFF to ON state due to main terminal exceeding rated blocking voltage of either polarity (self-triggering). (7) Main terminal diode-like ON characteristics tor either polarity as a function of temperature to provide exact power dissipation determination. (8) Gate terminal diode-like ON characteristics for either polarity as a function of temperature to provide power dissipation. (9) Minimum gate pulse width required for ON triggering. (10) Turn-on time and turn-off time. (11) Critical rate of rise of commutating voltage. Methods for determining the various model parameters are presented and applied specifically to a BTA10-700CW (2N6349A) TRIAC. Two of these TRIACS are used to simulate the simplified forward-reverse operation of an induction motor using a phase-shifting capacitor switched between the motor coils.
	Electronic Design Automation (EDA) approach to Power Electronic Control & Signal Processing   By D. Morley; E. B. Patterson	[View]   [Download]
Abstract: This paper illustrates the advantages arising from the use of Electronic Design Automation tools in the development of complex signal processing circuits for power electronic systems. Time critical circuits close to the waveform generation in power electronic applications may be closely simulated, giving an accurate representation of the performance of the expected hardware without recourse to physical prototyping. However, more sophisticated and flexible software solutions for the control strategy may also be developed using similar models thus allowing an extremely high confidence in the final product before commiting to experimental hardware. The 'right first time' ethos which is predominant in the integrated circuit environment may now be expanded to encompass power engineering digital control systems design. The process is illustrated by practical design examples implemented by the authors.
	THREE-PHASE AC-AC CONVERTER CONTROLLED BY P.W.M.   By M. Boulier; A. Castelain; C. Rombaut	[View]   [Download]
Abstract: Thyristor regulators are normally used to regulate the power supplied to an alternative load. Their use may pose certain problems to the power network and the use of turn-off switches may be envisaged. An easily applied P.W.M. strategy enables the current wave to be realigned and the first harmonics to be directed towards higher frequencies, thus making any filtering much easier. In three-phase mode, only three arrangements are possible. This paper aims to compare these and, in particular, to show that the delta-connected regulator arrangement, combined with a suitable chopping frequency, brings about a considerable reduction in line current harmonics and a consequent improvement in the converter power factor.
	Static and Dynamic Characteristics of Non-ideal Step Up Nine Switch Matrix Converter   By Woo H. Kwon; Gyu H. Cho	[View]   [Download]
Abstract: Static and dynamic characteristics of non-ideal step up nine switch matrix converter (NSMC) under the control strategy proposed by Venturini (1981) are evaluated by the circuit DQ transformation technique (Rim, 1988). Power circuit of step up NSMC is considered using non-ideal voltage and current sources by including practical inductance and capacitance filters. SeveraI static and dynamic features of the converter such as steady state input/output voltage gain, input power factor and transient response are predicted and verified by the circuit DQ transformation technique and compared with the computer simulation results.
	THE COMMUTATING AXES METHOD FOR THE ANALYSIS OF THREE-PHASE BRIDGE CONVERTERS   By A. P. Morando; G. Superti-Furga	[View]   [Download]
Abstract: The goal of this paper is to provide a mathematical model of a three-phase bridge-type DC/AC and AC/DC convertes for steady-state and transient conditions. Only analytical expressions of power circuits are to be taken into account, no interest is revealed either at numerical solution methods or control strategies. Simulation models of three-phase power converters can be build as an extension of single phase switching models. More efficient methods take advantage of three-phase symmetry. At this regard the Park transformation is a powerful tool, that furthermore allows the direct connection with the Park models of the rotating machines. In the present paper an approach that further exploits symmetry of bridge converters is proposed. It is based on a suitable discrete-time rotation of Park frame reference as so to follow synchronously the cyclically converter commutation. This way, the different topological connections appear on Park variables as a single repetitive one, obtaining a meaningful model suitable both for numerical simulation of dynamics and closed-form solution of steady-state. This method has been used for analysing a voltage inverter drive and for establishing the basis for first-harmonic simplified models.
	On a general approach for the analysis of switching converters characterized by a periodically time-varying operation   By N. Femia; P. Marino; V. Tucci	[View]   [Download]
Abstract: A method to analyze the operation of dc/dc converters is presented in this paper; it allows to describe such nonlinear systems, characterized by a periodic switch-mode operation, through a discrete, linear, time-invariant (DLTI) model. The proposed technique provides significant tools to evaluate the dynamics of a large class of switching circuits, under not restrictive conditions. Compared to the currently used analytical and numerical methods, the proposed modelling technique exhibite the following distinct advantages: an error-free steady-state analysis with respect to the linear time-varying model of the circuit; the possibility of estimating quantitatively the ripple in the output variable; a good accuracy in the frequency response at high as at low frequencies. Results are presented concerning the analysis of several types of dc/dc converters such as buck, boost and buck-boost. For such circuits the frequency response and the poles location are obtained as a function of either the duty-ratio d or the value of some significant circuit parameters.
	A MULTI-STRATEGY CONTROL SYSTEM FOR THE FIRING OF THYRISTORS BRIDGES   By C. Zanne; J. F. Aubry; H. Godfroid; J. F. Pouliquen	[View]   [Download]
Abstract: This paper first presents the three main numerical strategies for the digital control of thyristors firing: the vertical control issued from analog technology, the time delayed control and the incremental control. The main advantages and drawbacks of each of them are presented. Then the authors propose a hybrid solution in order to profit by the advantages of each classical algorithm: a stable time distribution for the firing pulse in steady state operating mode, a good accuracy for the firing angle and a simple implementation for the securities.This solution is modelised using an interpreted Petri Net and implemented on a RTX 2000 micro controller.
	DIGITAL SIMULATION AND APPLICATIONS OF THE PWM VOLTAGE CONVERTER CONNECTED TO THE AC MAINS   By P. Verdelho; G. D. Marques	[View]   [Download]
Abstract: This paper presents the PWM voltage converter connected to the AC mains. Detailed and global models for the simulation of the system are presented. A personal computer program is introduced, allowing detailed and global simulation with system or with Park's coordinates. The numerical integration method used is an explicit Euler-Backward method. The trapezoidal integration method is also provided. Several applications for the system are possible namely in electrical drives, operating as an AC/DC converter. The DC side has characteristics of constant DC voltage source. Bidirectional power transfer capability is possible by reversing the DC current. Reactive power regulation can be done. The system can also be used as a reactive power compensator. With the evolution on the power semiconductor switches with gate turn off capability, applications on HVDC energy transmission may be feasible. Theoretical results obtained with the detailed and global models and experimental results are presented and compared.
	MODELLING, CONTROL, STABILITY STUDY AND MAIN APPLICATIONS OF A HIGH POWER SWITCHING OPERATIONAL AMPLIFIER   By J. Fernando Silva	[View]   [Download]
Abstract: This paper discusses the use of a power inverter, controlled with a dual current mode modulator, as a high efficiency high power operational amplifier. The power converter and PWM modulator are represented by a linear continuous small signal model which is suitable to easily synthesize the feedback loops needed to obtain a four quadrant inverter, which then performs as the operational amplifier. Both maximum power and small signal bandwidths are briefly pointed out. The unsuitability of the continuous model for the stability prediction, led to a discrete model, derived from the continuous one, for the study of the onset of instability. Chaotic behaviour in this region is also illustrated. Theoretical and experimental results concerning the implementation of DC and low frequency AC power supplies, together with their internal reactance for the simulation of AC networks, are presented.
	AUTOMATIC SIMULATION OF STATIC CONVERTERS   By T. M. Oliveira; C. B. Jacobina; E. R. C. da Silva	[View]   [Download]
Abstract: This paper presents an alternative technique of power converter simulation based on the concept of resistive networks. By modeling a semiconductor as a resistor, an inductor as a variable current source in parallel with a resistor and a capacitor as a variable voltage source in series with a resistor, the converter is reduced to a network composed only by voltage sources, current sources and resistors. Therefore, algebraic equations are solved instead of differential equations. The "a priori" knowledg'e of the converter operation is not necessary for simulation. The structured presentation of the method facilitates its modification and/or expansion and the use of non-structured languages . Voltage and/or current behavior in any network branch can be presented graphically.
	A NEW INDUCTION MACHINE MODEL FOR THE SYNTHESIS OF TRACKING-CONTROLLERS - IMPLEMENTATION ASPECTS APPROACH   By A. J. Pires; A. Dente	[View]   [Download]
Abstract: In this paper it is presented a new induction machine dynamic model, based on unusual state variables. This representation is useful for the synthesis of tracking controllers because of its simplicity and system robustness guarantee. The non-linear control techniques "sliding mode control" and "input-output linearization" are used for the controller synthesis. Some implementation aspects related with the system inputs (voltages) are referred. Some simulation results, that illustrate the system performances, are shown .
	COMPUTER MODELLING OF ACTIVE DEVICES USING THE PSPICE MICROCOMPUTER SIMULATION PROGRAM   By K. A. Amarasinghe	[View]   [Download]
Abstract: The paper provides an overview of the methods used to model active semiconductor devices. The computer modelling is done using the PSpice microcomputer simulation program. The modifications that are needed to the built in Power MOSFET models in PSpice, when simulating high frequency circuits are discussed. A two transistor model which replicates the action of a GTO thyristor is also presented. The model enables the designer to estimate the device parameters with ease by adopting a short calculation and graphical design procedure, based on the manufacturer's data sheets.
	A SINGLE-PHASE FREQUENCY CHANGER WITH SINUSOIDAL INPUT AND OUTPUT CURRENTS   By J. Rodriguez; E. Wiechmann; J. Pontt; J. Zamorano	[View]   [Download]
Abstract: This paper presents a high performance frequency changer with only four power switches for single-phase load and single- phase source. The converter uses two power transistors and two antiparalel diodes working as a switch mode rectifier (SMR) to generate a controlled DC voltage. Two power switches are used to generate a sinusoidal load current. The output current has controlled amplitude and frequency. The input current of the frequency changer is also controlled, has a practically sinusoidal waveform and keeps in phase with the source voltage independently of the amplitude and frequency of the output current. The converter works with a high power factor for different load degrees (PF > 0.99). The front-end SMR permits bidirectional power flow and for this reason it provides an excelent control of the DC voltage. The control strategy is very simple. With the addition of two power switches it is possible to supply a three-phase load, like a three-phase machine. The vector control of a three-phase induction motor driven by this converter is also analysed.
	THE MODULATION AND CONTROL OF A MATRIX CONVERTER - SYNCHRONOUS MACHINE DRIVE   By T. Svensson; M. Alaküla	[View]   [Download]
Abstract: In this paper the control of a matrix converter - synchronous machine drive is presented. The control strategy of the machine is based on direct flux control and quadrature current control to obtain optimal dynamics even under saturated conditions. Unity power factor in steady state is obtained by field current control. No position or speed transducers are required since the rotor position is calculated from stator and field currents with harmonic analysis. The output voltage of a nine-switch matrix converter (forced commutated cycloconverter) is pulse modulated in a similar way as the dc-link VSI. With a 2-level PWM strategy a less complicated modulation equipment is required. However, the current on the input side of the converter is not sinusoidally pulsed. A 3-level PWM strategy is presented which gives sinusoidally pulsed input current and furthermore unity input displacement factor. All presented PWM methods have maximum output voltage ability. Simulations and experimental results are presented.
	A MODULAR APPROACH TO CONVERTER DESIGN FOR HIGH POWER AC DRIVES   By T. Ghiara; M. Marchesoni; L. Puglisi; G. Sciutto	[View]   [Download]
Abstract: Power electronics at high power levels often implies too high harmonic contents, which usually result in excessive losses and in motor pulsating torques; moreover very high power cannot be obtained when adopting traditional converter topologies, unless using always problematic series/parallel combinations of semiconductor devices. This paper presents a modular approach to converter design based on a particular connection of single-phase H-bridge inverters, which is particularly suitable when both reduced harmonic contents and very high power are required. A multilevel delta modulator suited to the peculiar structure has been devised, which allows a proper functioning of the connected asynchronous motor. An analytical analysis, simulation and experimental results are reported .
	ANALYTIC CURRENT TIME FUNCTIONS IN VOLTAGE SOURCE INVERTER DRIVEN MACHINES   By A. Veltman; P. P. J. van den Bosch; W. Deleroi	[View]   [Download]
Abstract: Analytic time functions, describing inverter output currents that result from periodic pulse patterns, are presented in this paper. With the use of these functions, the impact of such pulse patterns on current-waveforms and developed torque can be evaluated with good accuracy, without the need of time consuming simulations. A distinction between fundamental frequency related effects and auxiliary effects caused by the non-fundamental frequency components of the applied voltage is made. Traditional machine theory can deal with the fundamental effects, while the presented "fish method" manages the auxiliary effects too. Superposition of both outcomes yield the final inverter/machine performance for any periodic voltage pulse pattern, even under dynamic load conditions. Measurements illustrate the practical usefulness of the "fish method".
	A NEW SYMBOLIC APPROACH TO THE ANALYSIS OF SWITCH POWER CONVERTERS   By A. Liberatore; S. Manetti; M. C. Piccirilli; A. Reatti	[View]   [Download]
Abstract: A new symbolic approach to the computation of the transient and steady-state response of electronic switching power converters is presented. The method is based on the applicalion of artificial intelligence techniques and, in particular, on symbolic manipulation of algebraic expressions. A computer program based on this approach has been developed. This program, named SAPTRAN, is able to calculate automatically the requested transfer functions starting from a Spice-like input file describing the circuit under analysis. After determining the transfer functions, it is possible to perform their numerical inverse Laplace transform and to plot the graphic representation of the transient responses.
	NEW APPROACH TO THE CONSTRUCTION OF POWER CONVERTERS WITH INTERMEDIATE DC CIRCUIT   By R. Pasterczyk; A. Jaafari; D. Bergogne	[View]   [Download]
Abstract: A new layout design for the construction of pulsewidth modulated power converters with intermediate DC link is presented in the paper. It is based on a special way of interlacing the different power components of the inverter (rectifier diodes, inverter switches and free-wheeling diodes) and on the parralleling of a number of low power devices. Voltage spikes during fast commutations are reduced to a great extend hence eliminating lhe need of clamping. The proposed converter structure performs important parasitic inductances reduction and minimization of parasitic capacitances. The quality of commutation is improved, turn-on and turn-off processes are better controlled. The use of several low ratings power components assembled in standard low cost packages brings down the cost of the converter. High quality/cost ratio is achieved with the design we propose.
	THE ANALYSIS OF THE PWM RECTIFIER VOLTAGE AND CURRENT HARMONICS IN THE PRESENCE OF DC CURRENT RIPPLE   By V. A. Katic; V. S. Vuckovic; B. T. Kriznar	[View]   [Download]
Abstract: PWM rectifier harmonic analysis is usually performed with an assumption of constant DC current (idealized analysis). But in practical DC drive such assumption is not realistic. In this paper a method of voltage and current harmonic analysis which takes into account influence of DC current ripple is presented. The method, based on linear approximation of DC current wave shape, is classified as quasi-real analysis. lts advantage over more accurate real analysis is that it enables explicit expressions for voltage and current harmonics and saves computer time. The presented method is performed on different types of PWM techniques, different values of modulation index, number of pulses, lead time constant and is verified by comparison with method of real analysis. The results show that the method is specially useful in cases of low number of pulses and small load time constant when DC current ripple is the most expressed. The method is applied for analysis of PWM rectifier voltage and current harmonics and calculation of AC filter component values. Results of simulation show significant negative effects of DC current ripple: increase of harmonics values and necessary AC filter size.
	BUCK CONVERTER MODELLING FOR HARMONIC INTERACTION STUDY   By R. Feuillet; J. P. Keradec; J. Perard; Th. Rafesthian	[View]   [Download]
Abstract: Network pollution by harmonic frequencies is caused by power electronics equipments (1), (3), (5), (6). For global study of the isolated network operation, a computer modelling method is presented for the analysis of the harmonics generated and received by a converter. This allows the whole network to be easily simulated and the interaction between the different kinds of converters (chopper, invertor,...) to be predetermined.
	MEDIUM POWER AC/AC CONVERTER WITH FORCED COMMUTATION OF THE DC VOLTAGE SUPPLY   By Antonino Fratta; Roberto Grassi; Franco Villata	[View]   [Download]
Abstract: An innovative power structure suitable for medium power (>10 kVA) AC/AC conversion is presented. Two poliphase inverters are connected in parallel by their DC-side terminals, their DC voltage supply being switched between near zero and the high voltage of a capacitor bank. Only the DC-side switches are designed for the commutation stresses, while the AC-sides switches can be designed for stressless commutations. Timing requirements are taken into account and practical procedures are considered to minimize the null time interval needed for stresless commutations. A dedicated real-time signal processing is needed to allow the exploitation of the theoretical prerogatives. Peculiar techniques are possible and discussed for the overcurrent protection and the inverters modulation. Simple analog integrators, analog to logic conversion and a high-integration Gate Array logic circuit are adopted. The experimental results of a prototype system, designed for industrial purposes (30 kVA, 380 to 440 V) comply with the expected theoretical performance.
	STEADY-STATE ANALYSIS OF POWER CONVERTERS   By Yu. l. Blinov; A. S. Vasiliev; S. G.Gurevich	[View]   [Download]
Abstract: A method of determination of power converters steady-state process without calculation of transient process is described. The direct method of solving boundary value problem for system of ordinary differential equations is presented. Piecewise models of semiconductor devices are used, but also other models can be used in this approach. The instants of valve commutations are unknowns of solution vector, which are defined under decision with others unknown variables. Algorithm of Newton is used for obtaining of solution. This method gives decreasing of calculation time when steady-state process are defined. Also the exact values of all unknowns on steady-state period are calculated. This method was checked on simple half-wave rectifier and thyristor resonant inverter in double frequency connexion with back current diodes. Some examples of calculation are presented.