Small-signal Angular Stability of Power System as Affected by Grid-connected Variable Speed Wind Generators-A Survey of Recent Representative Works

This paper reviews the status and progress of the investigation on power system small-signal angular stability as affected by grid-connected variable speed wind generators (VSWGs). The review is carried out on the basis of a survey of recently published representative papers. Strategies of the investigation made in those selected papers are classified into two groups: 1) VSWGs displacing synchronous generators (SGs); 2) VSWGs simply being added in a power system. The diversification of the results of the investigation is highlighted in the survey. Careful analysis on two strategies of the investigation is conducted in this paper. It is revealed that in the strategy of VSWGs displacing SGs, there are two factors which could affect power system small-signal angular stability differently: 1) Withdrawing the SGs' dynamics; 2) adding the VSWGs' dynamics. In the strategy of adding VSWGs in the power system, there are also two affecting factors: 1) Change of load flow brought about by the VSWGs; 2) dynamic interactions with the SGs introduced by the VSWGs. Hence diversified results of the investigation obtained so far are not only due to the dependence of the investigation on sample power systems used, but also caused by the mixture of different affecting factors. This paper is concluded with a summary of key issues of the investigation for future work.