As the most environmentally friendly source of power generation, wind power turbines is expanding in the grid. It will also have a broad and deep impact on power system stability. In this paper, a comparison of characteristics is made among three mainly used wind turbines currently which are constant speed wind turbine (CSWT), doubly fed induction generator (DFIG), direct drive synchronous generator (DDSG). Then a MATLAB-based Power System Analysis Toolbox PSAT is used for investigating the dynamic behavior of three generators in a strongly coupled two regional systems. Finally, a complicated two regional test system was introduced to analyze the small signal stability of different wind turbines when wind penetration power is increasing.