Active filtering of electric power has now become a mature technology for harmonic and reactive power compensation in two-wire (single phase), three-wire (three phase without neutral), and four-wire (three phase with neutral) AC power networks with nonlinear loads. This paper presents a comprehensive review of active filter (AF) configurations, control strategies, selection of components, other related economic and technical considerations, and their selection for specific applications. It is aimed at providing a broad perspective on the status of AF technology to researchers and application engineers dealing with power quality issues. A list of more than 200 research publications on the subject is also appended for a quick reference.

A review of active filters for power quality improvement

Iron, the most ubiquitous of the transition metals and the fourth most plentiful element in the Earth's crust, is the structural backbone of our modern infrastructure. It is therefore ironic that as a nanoparticle, iron has been somewhat neglected in favor of its own oxides, as well as other metals such as cobalt, nickel, gold, and platinum. This is unfortunate, but understandable. Iron's reactivity is important in macroscopic applications (particularly rusting), but is a dominant concern at the nanoscale. Finely divided iron has long been known to be pyrophoric, which is a major reason that iron nanoparticles have not been more fully studied to date. This extreme reactivity has traditionally made iron nanoparticles difficult to study and inconvenient for practical applications. Iron however has a great deal to offer at the nanoscale, including very potent magnetic and catalytic properties. Recent work has begun to take advantage of iron's potential, and work in this field appears to be blossoming.

Synthesis, Properties, and Applications of Iron Nanoparticles

WITH the ever-widening scope of modern mathematical analysis and its many ramifications, it is quite impossible to include, in a single volume of reasonable size, an adequate and exhaustive discussion of the calculus in its more advanced stages. It therefore becomes necessary, in planning a thoroughly sound course in the subject, to consider several important aspects of the vast field confronting a modern writer. The limitation of space renders the selection of subject-matter fundamentally dependent upon the aim of the course, which may or may not be related to the content of specific examination syllabuses. Logical development, too, may lead to the inclusion of many topics which, at present, may only be of academic interest, while others, of greater practical value, may have to be omitted. The experience and training of the writer may also have, more or less, a bearing on both these considerations.Advanced CalculusBy Dr. C. A. Stewart. Pp. xviii + 523. (London: Methuen and Co., Ltd., 1940.) 25s.

Advanced Calculus I

Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.

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Non-Destructive Techniques Based on Eddy Current Testing

Fast acting static synchronous compensator (STATCOM), a representative of FACTS family, is a promising technology being extensively used as the state-of-the-art dynamic shunt compensator for reactive power control in transmission and distribution system. Over the last couple of decades, researchers and engineers have made path-breaking research on this technology and by virtue of which, many STATCOM controllers based on the self-commutating solid-state voltage-source converter (VSC) have been developed and commercially put in operation to control system dynamics under stressed conditions. Because of its many attributes, STATCOM has emerged as a qualitatively superior controller relative to the line commutating static VAR compensator (SVC). This controller is called with different terminologies as STATic COMpensator advanced static VAR compensator, advanced static VAR generator or static VAR generator, STATic CONdenser, synchronous solid-state VAR compensator, VSC-based SVC or self-commutated SVC or static synchronous compensator (SSC or S2C). The development of STATCOM controller employing various solid-state converter topologies, magnetics configurations, control algorithms, switching techniques and so on, has been well reported in literature with its versatile applications in power system. A review on the state-of-the-art STATCOM technology and further research potential are presented classifying more than 300 research publications.

Static synchronous compensators (STATCOM): a review

A simple and practical method of correcting the hysteresis loss in a thin lamination for the effects of minor loops is described. The necessary correction is applied to the losses that would occur under conditions of sinusoidal flux density and the required empirical factor is derived using a broad range of loss measurement data. It is shown that the correction, to a very good approximation, varies linearly with the unweighted algebraic sum of the flux density reversals in the driving waveforms. Used together with a similar factor that corrects the eddy current component of loss for the effects of flux density harmonics, the total loss can be easily estimated to an accuracy of less than 5%.

A simple method of estimating the minor loop hysteresis loss in thin laminations

The authors consider eddy current diffusion problems in which the electromagnetic field is computed in 2-D but external circuit connections, between the conductors with eddy currents are taken into account. The approach combines conventional circuit analysis techniques with the integro-differential finite element formulation of the transient eddy current problem. Conductors with eddy currents are treated as circuit elements with terminal voltages implicitly defined by the field equations. A numerical example is presented to illustrate the proposed formulation. >

A method for circuit connections in time-dependent eddy current problems

This paper considers the problem of estimating the core losses in a thin magnetic steel lamination when the driving flux contains not only the fundamental, but also odd harmonic components. Two numerical methods of predicting the eddy current losses due to an arbitrary flux waveform are briefly described. The important case of 3rd harmonic distortion is specifically considered. The digital simulations are used to develop a very simple model that describes the eddy current and hysteresis losses under the assumed distortion conditions with good accuracy.

Prediction of core losses for high flux densities and distorted flux waveforms

This paper reviews the use of numerical methods in simulating and solving problems that arise in the electroheat industry. Particular attention is given to the coupled electrothermal and induction stirring problems that are typical of this industry. Following a brief review of the nature of electrothermal problems, the Finite Difference, Volume Integral Equation and Finite Element simulation techniques are critically examined. It is shown that each technique has a definite role and each is illustrated with practical examples. A brief discussion of unsolved problems is presented.

Numerical solution methods for electroheat problems

Three sequential optimization methods, sequential least square method, sequential Kriging method, and sequential linear Bayesian method, are presented for the optimization design of electromagnetic device. Sequential optimization method (SOM) is composed of coarse optimization process and fine optimization process. The main purpose of the former is to reduce the design space; while the target of the latter is to update the optimal design parameters. To illustrate the performance of the proposed methods, an analytic test function and the TEAM Workshop Problem 22 are investigated. Experimental results of test function demonstrate that SOM can obtain satisfactory solutions; and practical application illustrates that the number of finite element sample points is less than 1/10 compared with that by direct optimization method, while the optimal results are even better than that by direct optimization method.

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J.D. Lavers

Papers

A simple method of estimating the minor loop hysteresis loss in thin laminations

A method for circuit connections in time-dependent eddy current problems

Prediction of core losses for high flux densities and distorted flux waveforms

Numerical solution methods for electroheat problems

Sequential Optimization Method for the Design of Electromagnetic Device