NONLINEAR DYNAMIC ANALYSIS OF THE PLATFORM STRUCTURES SUBJECTED TO ICE EXCITATION(PART Ⅱ): PRIMARY RESONANCE

In this paper the method of multiple scales is used to study the nonlinear dynamics of the ice soil platform system. Results show that the system exhibits multiple kinds of combination resonances and that its natural frequencies accord with the testing results of the model platform. Under the condition of primary resonance,we discussed the nonlinear dynamic characteristics of self excited, locking,forced vibrations. They conform to the on site observation. This paper explains the ice induced vibration mechanism and thus establishes an appropriate mechanical model for the nonlinear analysis of the offshore platform systems.

Averaging Analysis of Self-Excited Motion of a Quasi-Axisymmetrical Gyrostat

The averaging analysis was carried out to study the motion of a quasi axisymmetrical gyrostat under a small magnitude self excited control torque. The common approach to investigating the problem of rigid body rotation under the action of a small torque known in the body frame was described. Using this approach, the problem (Grammel's problem for the case of small torque) that is maintaining the angular velocity of a quasi axisymmetrical gyrostat using a control torque quadratic in the angular velocity was solved.

The Nature, Origin and Propagation of the Electric Field: A New Insight to Fundamental Physics

The nature, origin and propagation of the electric field are discussed for the first time on the basis of the presence of vibrating strings in the space and their self-excitation process. It is considered that the electron is formed from strings and it has specific vibrational frequency. This excites the strings which are close by with the self-excitation process. This procedure which is continuous in the space according to the symmetry and vibrational energy in the form of waves spreads near the electron (or the charge particle), which behaves and carries energy known as electric field. In fact, the electron does not continuously emit energy in any form but induces (or excites) and organizes energy in a self-sustain vibrational form and extends in three dimensional space. Only on the basis of the presence of strings (vibrational energy), several electromagnetic phenomena have been explained in a consistent way. The vibrational nature of the electric field is also examined with the help of Stark effect and X-ray diffraction approach to support the present view.

Enhancing the Stability of SEIG Connected Distribution System Using Reactive Power Control Capabilities of DFIG under Varying Wind Speeds

The increased level of penetration of wind generators into modern power system has significant effect on network operation. The time varying nature of wind speed has significant effect on performance of wind generator, therefore efficient mechanism for stabilizing the output of the wind generator is very much needed. Self-excited induction generators （SEIG） already existing in the network are sensitive to wind speeds. In this paper, a new method for voltage control of SEIG utilizing reactive power enhancing capabilities of doubly-fed induction generator （DFIG） is simulated and its effect on the network is analyzed for varying wind speeds. The choice of placing DFIG adjacent to SEIG or at another bus is also addressed in this paper with simulation results. The results show that this method of utilizing the reactive power capabilities of DFIG enhances voltage stability of SEIG as well as system stability.

Transient Performance of an Isolated Induction Generator under Unbalanced Loading Conditions

This paper presents a new transient model ofa standalone （isolated） self excited induction generator （SEIG）. This model is based on direct phase quantities and is suitable to study the performance of the generator under any balanced or unbalanced conditions. It includes a general load as well as general excitation capacitor model. The model has the advantage of connecting or disconnecting the neutral points of the generator electrical system with both excitation capacitors and load. Furthermore, a more accurate magnetization curve is used. Moreover, the simulation results have been verified experimentally.

Full function Numerical Method for Flow over a Self excited Vibrating Body

This paper presentsthe concept ofafull function numerical methodforflow overa self excited vibrating body.It contains three dimensional (3 D) numerical analysis of unsteady aerodynamic force for a self excited vibrating body, calculation ofthe work done by unsteady aerodynamic force and damping, determination of the equilibrium amplitude and dynamic stress as wellas correspondinglife evaluation.