An Explanation of Oscillations Due to Wind Power Plants Weak Grid Interconnection

An existing wind power plant at ERCOT experienced poorly damped and undamped voltage oscillations under weak grid conditions. The oscillations became worse during high power outputs. This letter aims to find the root cause of such oscillations. Our research provides a linearized system model by combining the vector control of wind power plants and the weak grid interconnection. Using this model, this letter succeeds in explaining that the weak grid condition introduces a zero in right half plane for the open-loop system, which can lead to poorly damped or undamped oscillations.