Excitation control of synchronous machine is done in order to keep the terminal voltage constant. This paper describes the advantage of using a nonlinear technique called Dynamic Inversion (DI) in order maintain the voltage at the terminals constant. An excitation model which includes the excitation system stabilizer (ESS) and the transient gain reduction (TGR) blocks is considered. The referen...

This paper proposes decentralized improved synergetic excitation controllers (ISEC) for synchronous generators to enhance transient stability and obtain satisfactory voltage regulation performance of power systems. Each generator is considered as a subsystem, for which an ISEC is designed. According to the control objectives, a manifold, which is a linear combination of the deviation of generat...

The majority of industrial controlled induction machine drives are connected to the mains via a diode bridge. However, if reduction of harmonic currents and / or regenerative operation is desired, replacing the diode bridge by an active front-end (AFE) is required. This paper describes two models of an AFE: a power balance model disregarding switching effects, and an ideal switching model of a ...

Abstract-Voltage sag or unbalance conditions at the input rectifier stage of the ac-dc-ac rectifier-inverter induction motor drive can cause the significant amounts of harmonic voltage at twice the line frequency 2f1. This voltage ripple can have a degrading effect on the induction-machine performance characteristics. This paper presents an analytical closed-form mathematical model and analysis...

A shipboard power system is a stiff, isolated power system. Power is generated locally, and distributed over short distances making the system vulnerable to transients. Power quality problems such as voltage sags, which arise due to a fault or a pulsed load, can cause interruptions of critical loads. This can be of a serious concern for the survivability of a combat ship. A series voltage injec...

This paper presents a new nonlinear backstepping controller for a direct-driven permanent magnet synchronous generator-based wind turbine, which is connected to the power system via back-to-back converters. The proposed controller deals with maximum power point tracking (MPPT) in normal condition and enhances the low-voltage ride-through (LVRT) capability in fault conditions. In this method, to...

Hydrogen is an unusual substance in that its molecule exists in two forms, known as ortho and para, with markedly different properties. Energy level of the ortho molecule is higher than para, therefore, the latter is employed for industrial purposes. Consequently, for a high  conversion of  ortho to para hydrogen a catalyst reactor must be employed.  Therefore, one of  the main obj...

The use of methanesulfonic acid as a Brønsted acid for direct ortho-acylation of phenols and naphthols proves to be a convenient, more general and direct route to various hydroxyaryl ketones. The route is regioselective, leading to ortho C-acylated products in satisfactory to high yields in most cases. The solvent free reactions described below exhibited environmentally benign in terms of faste...

The first regioselective oxidative coupling of 2-hydroxycarbazoles is described. With a vanadium catalyst and oxygen as the terminal oxidant, dimers with an ortho-ortho' coupling pattern were obtained with high selectivity. Further oxidation led to ortho'-ortho' coupling to generate a tetramer, which provided insight that the atropisomerization barriers of the unsymmetrical biaryl bonds are muc...

The ortho to para conversion of water ion, H2O(+), due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin-nuclear spin interaction term, Tab(SaΔIb + SbΔIa) mixes ortho (I = 1) and para (I = 0) levels to cause the "forbidden" ortho ...