Structural Damage Detection with Damage InductionVector and Best Achievable Vector

This paper presents a new method using the damage induction vector (DIV) and the best achievable vector (BAV) by which the change of modes due to structural damage can be applied to detcrnlinc the location and scale of damage in structures. By the DIV, undamagc elements can be castly identified and the damage detection can be limited to a few domains of the structure. The structural damage is located by conlputing the Euclidean distance betwcen the DIV and its BAV. The loss of both stiffness and mass properties can be located and quantified.The characteristic of this method is less calculation and there is no limitation of damage scale. Finally, the effectiveness of the method is demonstrated by detecting the damages of the shallow arches.

Geomagnetic vertical transfer function revealed from multi-interval geomagnetic data

The geomagnetic vertical transfer functions(VTFs)are useful to constrain the conductivity structure in the deep Earth.In this study,we propose an approach of estimating the geomagnetic VTFs in the wide:period range from the multi-interval geomagnetic data.Applying the above method to the different interval(such as one-second,one-minute,one-hour)data from some geomagnetic observatories in China,we obtain the corresponding VTFs in the wide period range from 64 s to 9,830,400 s.In order to evaluate the possible ocean effect on different observatories,we make close investigations of the real geomagnetic induction vectors at QZH,SYG and XIC observatories.The results indicate that the ocean effect is clear at the coastal observatory like QZH.However,the ocean effect tends to decrease for the inland observatories(such as SYG and XIC)with the increasing distance from the coast.

Doubly-fed induction generator drive based WECS using fuzzy logic controller

The purpose of this paper is to improve the control performance of the variable speed, constant frequency doubly-fed induction generator in the wind turbine generation system by using fuzzy logic controllers. The control of the rotor-side converter is realized by stator flux oriented control, whereas the control of the grid-side converter is performed by a control strategy based on grid voltage orientation to maintain the DC-link voltage stability. An intelligent fuzzy inference system is proposed as an alternative of the conventional proportional and integral （PI） controller to overcome any disturbance, such as fast wind speed variation, short grid voltage fault, parameter variations and so on. Five fuzzy logic controllers are used in the rotor side converter （RSC） for maximum power point tracking （MPPT） algorithm, active and reactive power control loops, and another two fuzzy logic controllers for direct and quadratic rotor currents components control loops. The performances have been tested on 1.5 MW doubly-fed induction generator （DFIG） in a Matlab/Simulink software environment.