Showing papers on "Converters published in 1982"

A Regulated DC-DC Voltage Source Converter Using a High Frequency Link

Abstract: Power converters which employ a high frequency (HF) link possess several attractive features such as reduced size of reactive components, fast response, and ease of commutation. Either series or parallel connection of the load to the link capacitor can be employed by such converters. Converters that have a series link capacitor-load configuration are seen by the load as a current source. A dc-dc converter which uses a parallel link capacitor-load configuration is investigated. The output dc voltage is regulated by varying the link frequency. Such a converter behaves as a voltage source and is suitable for voltage source inverter applications. The converter is analyzed. Based on the analysis, a design procedure is given. A control scheme is outlined. Results from a prototype converter are presented.

Current Injected Equivalent Circuit Approach to Modeling and Analysis of Current Programmed Switching DC-DC Converters (Discontinuous Inductor Conduction Mode)

Abstract: The current injected equivalent circuit approach (CIECA) to modeling switching converter power stages is extended to model the current programmed converter power stages operating in fixed frequency discontinuous inductor conduction mode. To demonstrate the method, the modeling is carried out for the buck, boost, and buckboost converters to obtain small signal linear equivalent circuit models that represent both input and output properties. The results of these analyses are presented in the form of linear equivalent circuit models as well as transfer functions.

The closed-loop stability of power converters with an integrating controller

Abstract: A theory is developed to predict the stability characteristics of static converters as a function of the controlled-firing angle for closed-loop systems using an integrating controller. The controlled quantity can be either the output voltage or current. Revealed in the analysis was how the degree of stability is dependent on the operating point, the waveform and pulse number of the supply, the commutating reactance, and the method of modulating the firing angle. The factors that determine stability are related to the step change in the output voltage waveform at the instant of switching. In practical application of the theory, the closed-loop performance can be improved by suitably shaping the modulating function or `firing wave'. It is found that the optimum shape of the firing wave is not the same shape that produces a linear open-loop voltage gain.

Analysis and Design of a Standardized Control Module for Switching Regulators

Abstract: Three basic switching regulators: buck, boost, and buck/boost, employing a multiloop standardized control module (SCM) were characterized by a common small signal block diagram. Employing the unified model, regulator performances such as stability, audiosusceptibility, output impedance, and step load transient are analyzed and key performance indexes are expressed in simple analytical forms. More importantly, the performance characteristics of all three regulators are shown to enjoy common properties due to the unique SCM control scheme which nullifies the positive zero and provides adaptive compensation to the moving poles of the boost and buck/boost converters. This allows a simple unified design procedure to be devised for selecting the key SCM control parameters for an arbitrarily given power stage configuration and parameter values, such that all regulator performance specifications can be met and optimized concurrently in a single design attempt.

Load control for energy converters

Abstract: A load control for a system comprised of a plurality of energy converters wherein a System Control Signal proportional to system load is developed and utilized to simultaneously adjust the rate of energy conversion of each of the converters in parallel in accordance with changes in system load. The rate of energy conversion for each converter, while operating under stead-state conditions for a predetermined period of time, is readjusted until its actual incremental cost of production is equal to a desired incremental cost.

CIECA: Application to Current Programmed Switching Dc-Dc Converters

Abstract: Sundstrand Advanced Technology Corporation The current injection equivalent circuit approach (CIECA) to modeling switching converter power stages is extended to model the current programmed converter power stages operating in fixed frequency, continuous inductor conduction mode. To demonstrate the method, modeling is carried out for the buck, boost, and buckboost converters to obtain small-signal linear equivalent circuit models which represent both input and output properties. The results of these analyses are presented in the form of linear equivalent circuit models as well as transfer functions. Though current programmed converters exhibit single-pole response, the addition of artificial ramp changes converters to exhibit well damped two-pole response. This has been investigated for the first time using CIECA. The results of these analyses are presented in the form of linear equivalent circuit models as well as transfer functions.

Distribution System Harmonics: Controls for Large Power Converters

Abstract: Because of the anticipated applicaton of large ac/dc power converters on utility distribution systems, the Electric Power Research Institute (EPRI) funded Project RP1024-1 to study distribution system surge and harmonic characteristics. The harmonics produced by large converters depends on converter type (line-or self-commutated), converter pulse number, thyristor firing angle controls, commutation angles, voltage regulation techniques, voltage unbalance, and?very importantly?network impedance frequency response. Of particular significance is the fact that a great deal of effort is still required to determine tolerable levels of harmonic voltages and currents on distribution systems. Harmonic controls for power converters-important because of their effect on converter cost and efficiency-are now specified on the basis of engineering data which need to be enhanced by further testing and analysis. In the face of observable and ever-increasing background levels of distribution system harmonics, more precise anticipation of future concerns is required. Test methods and instrumentation need to be standardized to ensure conformance to yet-to- be-determined permissible harmonic limits. This paper discusses line-and self-commutated power converters and techniques for controlling the harmonics associated with them and presents the principal results of EPRI Project RP1024-1.

Trimmable resistive scaling network suitable for digital to analog converters

Abstract: A trimmable resistive scaling network suitable for use in digital-to-analog converters or the like. At least two trimmable resistors with low order integral relative values provide for either scaling up or scaling down with high accuracy.

Pulse width modulation type converter

Abstract: PURPOSE:To prevent cross current between pulse width modulation type converters connected in parallel with each other by a method wherein output voltages of the converters are controlled in accordance with deviation between respective current commands and AC input and output current signals of the pulse width modulation type converters. CONSTITUTION:The AC sides of the pulse width modulation type converters 1, 1' being controllable outputs thereof voltage variably and frequency variable are connected in parallel with each other, and AC output currents of the converters 1, 1' are detected 14-16, 14'-16'. Deviations between signals of a current command circuit 8 and output signals of the detectors 14-16, 14'-16' are amplified 17-19, 17'-19', and frequencies to make GTO's of the converters 1, 1' to perform ON- OFF action are generated 20.

Controlling method for rectifier

Abstract: PURPOSE:To reduce the harmonic component of a polyphase AC input current and to obtain a constant DC output having small ripple by controlling the conducting time of switching elements by a specific method so that the polyphase AC input current flows in the sinusoidal waveform. CONSTITUTION:A 3-phase AC input is applied through inductors Lu-Lw, capacitors Cu-Cw and rectifiers Rec1-Rec3 to converters G1-G3, and the outputs are applied through smoothing circuits to a load F. Switching transistors Q1, Q'1 in the converters G1-G3 are respectively switched in high conversion frequency by the frequency of 3-phase AC by the output of a control circuit Con. The energy produced at the output side from the 3-phase AC at every period of the conversion frequency is controlled to be proportional to the product of the square of the instantaneously voltage value of the 3-phase AC and the control amount, and proportional in the total energy produced from the respective phases to the control amount.

Computer Simulations of Optimum Boost and Buck-Boost Converters

Abstract: The development of mathematical models suitable for minimum weight boost and buck-boost converter designs are presented. The facility of an augumented Lagrangian (ALAG) multiplier-based nonlinear programming technique is demonstrated for minimum weight design optimizations of boost and buck-boost power converters. ALAG-based computer simulation results for those two minimum weight designs are discussed. Certain important features of ALAG are presented in the framework of a comprehensive design example for boost and buck-boost power converter design optimization. The study provides refreshing design insight of power converters and presents such information as weight and loss profiles of various semiconductor components and magnetics as a function of the switching frequency.

A dynamic test method for high-resolution A/D converters

Abstract: A dynamic test method is described for A/D converters having up to 16 bits of resolution. The technique exercises the test converter with stepped input changes, simulating the output of an S/H amplifier. Dynamic errors as low as 4 ppm can be measured within 4 ss following a step change as large as 20 V.

Method for preventing oscillations between the load and the intermediate circuit in converters whose frequency is followed-up and which have a variable intermediate-circuit voltage

Abstract: In a converter whose frequency is followed-up and which has a variable intermediate circuit voltage which has a controlled mains rectifier (1), an (intermediate circuit) capacitor (3) and a load converter (2), when the asynchronous motor (15) which is supplied from the load converter is braked or accelerated, osciallations occur in a variable which is proportional to the current flowing between the asynchronous motor (15) and the capacitor (3) and which is used as an additional reference variable for the frequency of the load converter (2).

The stability of DC/DC converters in current programmed mode

Abstract: Recent work on current programmed DC/DC converters has indicated.that these systems are unstable for duty cycles greater than 0–5 and this is independent of the precise configuration (boost, buck or buck-boost.) used in the converter. The purpose of this note is to show that the above result is incorrect ; the- boost and bunk-boost are always stable and the buck is stable for all duty cycles less than an amount determined by tin; circuit parameters and the switching frequency. In addition explicit expressions are obtained for the small-signal linearized model describing a converter in current programmed mode and an alternative method for stabilizing the buck converter is proposed.

The Design and Control of DC/DC Converters

Abstract: In this paper the design of fourth order (2 inductor/2 capacitor) pulse width modulated DC/DC converters with mutual coupling between the inductors is considered. Expressions relating the input and disturbances to the output voltage are obtained for the family of fourth order converters i.e. the buck with input filter, the boost with output filter and the buck/boost or Cuk. From these expressions, the effect of the various converter parameters on the open loop poles and zeros are investigated. A design procedure is described which aims at component selection based on both static power considerations and dynamic control criteria. This basically involves selecting inductances to satisfy current ripple requirements and capacitances to position the open loop poles and zeros favourably so that good transient response and disturbance rejection can be obtained with a simple 3 -term controller. As an illustration, a closed loop buck/boost (Cuk) converter is designed.

Noise reduction system

Abstract: A noise reduction system is provided which can operate as either a Dolby B-type or C-type system In either case, an input signal is applied to the variable impedance of a high-level side chain through an identical shared filter circuit network The high-level side chain has two voltage-current converters for controlling the variable impedance By substantially inhibiting the operation of one of the two converters, the system operates as a C-type Dolby system On the other hand, when the system operates as a B-type Dolby system, a bias current is applied to each of the two converters during periods of no input signal This bias current is about half of a minute bias control current which is applied during no signal periods to the single converter used when the system operates as the C-type Dolby system

Detecting indicating device for vehicle position

Abstract: PURPOSE:To enable the safe and reliable detection and indication of a vehicle position on a load plate, by a method wherein outputs of load converters located at the vehicle entry side and the exit side of the load plate are compared by means of a comparator CONSTITUTION:Load converters are individually mounted at a vehicle entry side and withdraw wide at each load plate which is situated so that an axis weight of every axis of a vehicle can be measured After the output is amplified, it is compared by means of a comparator, and an indicator step-indicates a vehicle position For example, load converters 3a-3f and 4a-4f are mounted at the entry side and the exit side of the vehicle, respectively, and the two outputs are compared with each other via amplifiers 10 and 11 by means of a comparator 12 In case the vehicle enters, the output of the converter 3 is high, the two are balanced with each other at a central part, and when the vehicle exits, the output of the load converter 4 is high Thus, the utilization of the output permits the step indication of each vehicle position by means of an indicator 13 An indicator 15 is for use with load indication

Two-pulse bridge converter with transformer-coupled forced commutation circuit

Abstract: Forced commutation schemes have been used in two-pulse converters in order to improve the power factor. Such a scheme also increases the regenerative power. A bridge converter with transformer-coupled forced-commutation circuit is proposed in this paper. The commutation process is analysed and normalized turn-off time curves are presented. The effect of load current on the commutation process is discussed. The proposed converter configuration is useful for both motoring and regenerative operations of series as well as separately excited DC motors. The results are experimentally verified.

Digital Techniques in High-Voltage Measurements

Abstract: A review of digital techniques and instruments developed and applied to high-voltage measurements is presented. Advantages of digital instruments over their analog homologues are exposed together with some examples of processing of digitized signals recorded in HV laboratories.

Firing scheme for pulse-width controlled AC-DC converters

Abstract: A novel firing scheme is proposed for the control of pulse-width modulation type AC-DC converters. The firing circuit is capable of providing control both for rectifying and regenerative operations of the converters, for continuous as well as discontinuous conduction.

Zero current detector for thyristor drive control - uses current converters with additional windings connected in series with phase shifters across supply line pairs

Abstract: The zero current detector uses current converters (4,5,6) inserted in the phase lines (L1,L2,L3) for the input 3-phase supply. Each current converter (4,5,6) has an additional winding (43,53,63) coupled via a phase shifter (44,54,64) across two of the phase lines (L1,L2,L3). The secondary windings (42,52,62) of the current converters are coupled via a rectifier bridge (7) to a threshold device (8) providing a signal indicating the zero current when a defined voltage is present. Pref. the input of the threshold device (8) is supplied with an additional correction voltage corresp. to the difference between the regulated and non-regulated network voltage to maintain a constant response threshold during variations in the network voltage.

Design graphs for optimizing the energy-storage inductor for DC-to-DC power converters

Abstract: Three sets of design graphs and equations are developed to facilitate design of the energystorage inductors for DC-to-DC converters. Using the design graphs, a quick estimate of the inductor minimum weight, the transistor peak current, and the inductor power loss can be obtained. Trade-off study can be conveniently conducted using these graphs. Effects of duty cycle controllers, constant frequency and constant tON, on the optimal selection of the energy-storage inductors are assessed.

Converters with high internal frequency

Abstract: Continuing work on the development of the technology of electric-power converters in­dicates the desirability of relatively high internal operating frequencies in order to sa­tisfy a number of advantageous system characteristics. It appears desirable to equip these power converters with a number of properties which are summarized in the fol­lowing paragraph.

Mismatch between Batteries and Two Module Types P.V. Arrays Interest of D.C.-D.C. Converters

Abstract: This paper concerns the study of mismatch effects between P.V. arrays and batteries. Pue to the modifications of the experimental conditions (depending on the batteries state of charge, the external temperature and light flux), it is not possible to extract at each time the maximum available power from a P.V. array. Similar problems result from the parallel use in the same array of different modules, mismatch effects being enhenced by the fact that different encapsulation lead to different equilibrium for the junctions. The relative power losses in both cases have been analyzed on a small system made of two kinds of modules. Extrapolation to high power P.V. arrays has been done and a P.C.-P.C. converter for 5 kW P.V. arrays is presented. The interest of converters in the case of large generators coupled to batteries is discussed and some applications are proposed.