The technique of vector space decomposition control of voltage source inverter fed dual three-phase induction machines is presented in this paper. By vector space decomposition, the analytical modeling and control of the machine are accomplished in three two-dimensional orthogonal subspaces and the dynamics of the electromechanical energy conversion related and the nonelectromechanical energy conversion related machine variables are thereby totally decoupled. A space vector PWM technique is also developed based on the vector space decomposition to limit the 5th, 7th, 17th, 19th,... harmonic currents which in such a system would be otherwise difficult to control. The techniques developed in this paper can be generalized for the control of an induction machine with an arbitrary number of phases. >

Space vector PWM control of dual three phase induction machine using vector space decomposition

This paper presents a new multiresonant frequency-adaptive synchronization method for grid-connected power converters that allows estimating not only the positive- and negative-sequence components of the power signal at the fundamental frequency but also other sequence components at other harmonic frequencies. The proposed system is called MSOGI-FLL since it is based on both a harmonic decoupling network consisting of multiple second-order generalized integrators (MSOGIs) and a frequency-locked loop (FLL), which makes the system frequency adaptive. In this paper, the MSOGI-FLL is analyzed for single- and three-phase applications, deducing some key expressions regarding its stability and tuning. Moreover, the performance of the MSOGI-FLL is evaluated by both simulations and experiments to show its capability for detecting different harmonic components in a highly polluted grid scenario.

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Multiresonant Frequency-Locked Loop for Grid Synchronization of Power Converters Under Distorted Grid Conditions

??????????? ????? Stanley Horowitz H Power System Relaying May 13th, 2020 With emphasis on power system protection from the network operator perspective this classic textbook explains the fundamentals of relaying and power system phenomena including stability protection and reliability The fourth edition brings coverage up to date with important advancements in protective relaying due to significant changes in the conventional electric power system that will

Power System Relaying

This paper presents a new control strategy for the rotor-side converter (RSC) of wind turbines (WTs) based on doubly fed induction generators (DFIG) that intends to improve its low-voltage ride through capability. The main objective of this work is to design an algorithm that would enable the system to control the initial overcurrents that appear in the generator during voltage sags, which can damage the RSC, without tripping it. As a difference with classical solutions, based on the installation of crowbar circuits, this operation mode permits to keep the inverter connected to the generator, something that would permit the injection of power to the grid during the fault, as the new grid codes demand. A theoretical study of the dynamical behavior of the rotor voltage is also developed, in order to show that the voltage at the rotor terminals required for the control strategy implementation remains under controllable limits. In order to validate the proposed control system simulation, results have been collected using PSCAD/EMTDC and experimental tests have been carried out in a scaled prototype.

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Rotor Voltage Dynamics in the Doubly Fed Induction Generator During Grid Faults

Although the symmetrical component transformation has existed for 80 years, its application in the time-dependent form is practically restricted to the electric-machine theory. In the power systems field one uses the transformation applied to steady-state sinusoidal phasors in a nonunitary form for fault calculations. For time-domain calculations the real equivalent, 0, /spl alpha/, /spl beta/, is preferred, usually extended to 0, d, q-components. In network calculations, however, the application of time-dependent symmetrical components makes sense, since many net-component parameters are already available in this form. In this paper a short historical overview of the symmetrical-component transformation and the application of unitary and orthogonal transformations are presented. From these general transformations logic choices for base quantities necessary in per unit calculations are derived. The relations between real and complex transformations, steady-state phasors and well-known sequence networks are given and illustrated through the use of some examples with asymmetrical faults.

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Symmetrical components in the time domain and their application to power network calculations

In the introduction a general discussion of unsymmetrical systems of co-planar vectors leads to the conclusion that they may be represented by symmetrical systems of the same number of vectors, the number of symmetrical systems required to define the given system being equal to its degrees of freedom. A few trigonometrical theorems which are to be used in the paper are called to mind. The paper is subdivided into three parts, an abstract of which follows. It is recommended that only that part of Part I up to formula (33) and the portion dealing with star-delta transformations be read before proceeding with Part II. Part I deals with the resolution of unsymmetrical groups of numbers into symmetrical groups. These numbers may represent rotating vectors of systems of operators. A new operator termed the sequence operator is introduced which simplifies the manipulation. Formulas are derived for three-phase circuits. Star-delta transformations for symmetrical co-ordinates are given and expressions for power deduced. A short discussion of harmonics in three-phase systems is given. Part II deals with the practical application of this method to symmetrical rotating machines operating on unsymmetrical circuits. General formulas are derived and such special cases, as the single-phase induction motor, synchronous motor-generator, phase converters of various types, are discussed.

Method of Symmetrical Co-Ordinates Applied to the Solution of Polyphase Networks

This paper describes the mechanics of the development of a lightning stroke in a cloud and the formation of a surge on a line. It shows that the energy of a stroke can vary between wide limits so that the actual surge on the line may be of practically any magnitude. Fundamental types of high-tension line construction are analyzed to show the performance that would be obtained with them. Experience obtained on the 220-kv. lines of the Public Service Electric and Gas Company is offered to substantiate the belief that induced surges are of relatively small importance and that the direct stroke is the criterion for good design. The effects of line construction on the character of surges impressed on the terminal substation apparatus is discussed to indicate the degree of protection that would be required.

Lightning Discharges and Line Protective Measures

THIS paper is a more complete presentation of the subject of power representation by means of symmetrical coordinates, which was briefly outlined in the author's paper on Symmetrical Co-ordinates presented at the 30th Annual Convention, 1918.

Polyphase Power Representation by Means of Symmetrical Coordinates

This paper gives a review of some recent developments in the methods of studying lightning phenomena. The Norinder form of cathode ray oscillograph and its application in Tennessee are discussed, together with the information secured. The second part gives the theory of traveling waves along transmission lines. Reflections at open and grounded ends are considered. A mirror scheme of an infinite series of waves on a double infinite line equivalent to actual waves along a finite line is developed. The third part discusses the manner in which surges are actually produced on lines by lightning and the effect of ground resistance on the protection afforded by ground wires, both with respect to induced and direct strokes.

Theoretical and Field Investigations of Lightning

The subject of stability has been much discussed lately, because it has an important bearing on future large power developments. In the early stages of a large program, such as the proposed superpower program, good engineering and commonsense dictate that each step should be very carefully considered from all points of view, since a blunder or failure to give proper weight to some important factor, such as stability, might set back the development program for many years. A brief historical review of the subject of stability follows; for those who are not familiar with ``static'' stability there is a review of the subject in the Appendix. A criterion of stability is suggested based on present operating conditions, namely, that for reliability each unit of the superpower shall be at least equal to the best that has heretofore been obtained with similar power systems. The necessity of a careful study of the characteristics of all machinery connected to the transmission line is pointed out. The necessity of proper inherent characteristics in generators and synchronous condensers is emphasized, and particular stress is laid on the necessity of proper volt ampere characteristics both inherent and with the exciter.

Charles Le G Fortescue

Papers

Method of Symmetrical Co-Ordinates Applied to the Solution of Polyphase Networks

Lightning Discharges and Line Protective Measures

Polyphase Power Representation by Means of Symmetrical Coordinates

Theoretical and Field Investigations of Lightning

Transmission Stability Analytical Discussion of Some Factors Entering into the Problem