Effect of excitation capacitors on transient performance ofreluctance generators

The transient responses of a reluctance generator connected to an infinite power system excited by a bank of terminal capacitances are compared to those when load excitation is used. A mathematical model is developed to simulate the machine with its terminal capacitor. With the aid of a least-square-error method, this model is used to optimize the machine parameters. The capacitance excitation requirements for different load conditions are then computed using a steady-state model. The comparison of the transient responses shows that the terminal-capacitor excitation method has several advantages over the load excitation method. It reduces the first rotor swing and gives more damping to the subsequent rotor oscillations. It also increases the critical fault-clearing time and hence the transient stability limits. In addition, it suppresses all power frequency torque oscillations, which are quite pronounced when load excitation is used     

The Role of Governor Control in Transient Stability of Super-Conducting Turbo-Generators

The effect of mechanical power control on transient stability of superconducting alternator for symmetrical and unsymmetrical fault conditions, is studied. A detailed governor-turbine model, with electrohydraulic governors and fast valving is considered.     

Assessment of steady state stability of a multi-machine powersystem with and without a superconducting machine

The steady-state performance of a multi-machine system which includes a superconducting generator is examined. the PQR method for constructing the system matrix, which was developed for a single conventional machine, has been modified and extended to include several generating units, some of which are superconducting. This technique has been applied to obtain the system matrix of a multimachine network which includes hydro, nuclear, steam, and superconducting units. The eigenvalues and dynamic interactions in both the controlled and uncontrolled systems are analyzed. To examine the effects of the superconducting alternators, the results are compared with those obtained by replacing the superconducting generator with conventional machine. The results show that the introduction of a superconducting machine to a multi-machine system increases its steady-state stability limits. However, due to the low inherent damping of this machine, the damping of the rotor oscillatory mode is degraded. It is concluded that the results obtained form a useful guide for introducing the new machine into larger power systems     

Hippocampectomized rats are capable of homing by path integration.

Navigation in rodents is mediated by at least 3 mechanisms: guidance, path integration, and landmark learning. The hippocampus is necessary for spatial learning based on distal landmarks, and it has been suggested that the hippocampal formation performs a form of path integration in updating place cell firing; however, the necessity of the hippocampus for path integration has not been clearly established. Rats with extensive neurotoxin lesions of the hippocampus and control rats were trained on 2 tasks in which they were required to move in total darkness from one location to another and then return to the start point. Hippocampal and control rats both used path integration in solving these tasks and did not differ in terms of the distributions of their arrival points on the return paths. We conclude that neuronal circuits sufficient for computing a homing vector using path integration are located outside the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability of a multi-machine system incorporating a superconductingalternator

A preliminary study on the transient behavior of a superconducting turbo-alternator in a typical multimachine system is described. The study covers the effect of conventional controllers, power-system stabilizers and phase advance networks. The open-loop response of the system is compared to the response when the superconducting alternator is replaced by its conventional counterpart     

A discrete state-space controller for superconductingturbogenerators

The design of a linear multivariable controller for superconducting turbo-alternators is described. The controller design is based on a discrete state-space reduced-order model, which uses measurable state-variables. In the transient mode the alternator is described by its phase quantities to examine the performance under different types of faults. The controller is examined on a nonlinear mathematical mode, and shown to give improved performance for all types of faults