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In recent years a multitude of events have created a new environment for the electric power infrastructure. The presence of smallscale generation near load spots is becoming common especially with the advent of renewable energy sources such as wind power energy. This type of generation is known as distributed generation (DG). The expansion of the distributed generators-(DGs-) based wind energy raises constraints on the distribution networks operation and power quality issues: voltage sag, voltage swell, voltage interruption, harmonic contents, flickering, frequency deviation, unbalance, and so forth. Consequently, the public distribution network conception and connection studies evolve in order to keep the distribution system operating in optimal conditions. In this paper, a comprehensive power quality investigation of a distribution system with embedded wind turbines has been carried out. This investigation is carried out in a comparison aspect between the conventional synchronous generators, as DGs are widely in use at present, and the different wind turbines technologies, which represent the foresightedness of the DGs. The obtained results are discussed with the IEC 61400-21 standard for testing and assessing power quality characteristics of grid-connected wind energy and the IEEE 1547-2003 standard for interconnecting distributed resources with electric power systems.

The work aims at developing a new stability approach used to cany out transient stability studies of a rnultimachine power system when the generator int~rnsl voltage components E' and E' d are changing with the time. Considering the generator mechanical damping and the generator control systems (that is, the vol~dge regulator and speed governor), each generator is represented by a 6th-order dynamic model, then the mathenlatical model of the whole system is derived. Applying the decomposition-aggresdion method, the system is decomposed by using the triple-wise decomposition. Then avector Lyapunov function is constructed and used for aggregating the system. An aggregation matrix is obtained. the stability of which implies asymptotic stability of the system equilibrium state. As an iiiustsative example, the developed stability approach is used to ca-1ry out transient stability studies of a i'machine, 14-bus power system assuming a %phase short c~rcnit (with successfill reclosure) near a generator,or a load, bus. The faulted line is tripped out for clearing the fault. An estimate for the system asymptotic stability dom& is determined and used to determine directly the critical time for reconnectin? the isolated Ime. It is found that the proposed