Abstract

Abstract
We report two effects in permeability measurement: the error introduced by assuming constant injection pressure and the evolution of permeability dispersion with volume fraction. For the first, we proposed a simple modelling approach. For the second, our results showed a reduction in the dispersion with higher fibre volume fractions, which we believe is due to the reduction of the variability of the size of the pores of the reinforcement.

Abstract

Abstract
The condition of voltage stability in a power system can be characterized by the use of voltage stability indices. The voltage stability analyses were conducted on the IEEE 14 and IEEE 57 reliability test system, using several different scenarios of load increase. In this paper, a comparison of the performance of several indices is presented, with satisfactory results. In this paper will also present New Index to Voltage Collapse (NIVCP). NIVCP is a system index and see the all power system.

Abstract

Abstract
A tuning process of the PI (Proportional-Integral) controller gains of a doubly-fed induction generator's (DFIG) rotor side converter is described in this work. The purpose is to tune PI controllers to help the DFIG to survive to network faults, avoiding being tripped-off by under-voltage relays. The ride-through-fault capability of DFIGs improves system reliability and allows them to participate in the control and stabilization of a power system following system disturbances. The robust tuning of the DFIG rotor side converter's PI controllers may avoid undesired disconnections from the grid by, for instance, preventing over-currents in its variable frequency AC/DC/AC converter. This work presents an Evolutionary Particle Swarm Optimization-based (EPSO) approach to this tuning, with the aim of helping to limit the line-to-line voltage dip at the DFIG's terminals after a short-circuit, in order to avoid its tripping-off. The EPSO-based algorithm developed is validated at a typical Portuguese 15 kV Distribution Network with the integration of a DFIG, using the transient electromagnetic software package PSCAD/EMTDC (TM).