Coordination Control Method for Preventing Sub/Super Synchronous Oscillations of Multi-wind Farm Systems

In recent years, sub/super- synchronous oscillations occur frequently in large-scale wind power bases throughout China. Since the oscillation frequencies are close to the fundamental frequency, the current components can spread over a large area, and may destroy the shafting of rotating devices in the power grid. Improving the control strategy and parameters of wind turbines can prevent this problem to some extent, however, due to complex operational conditions and continuous development of wind power, the off-line improvement measures on wind turbines cannot eliminate the potential oscillation risks. This paper proposes an oscillation risk screening and stability assessment method, and develops a coordination control method for large-scale wind farm systems to prevent sub/super-synchronous oscillations. The Nyquist criterion and the modal analysis method are combined to generate quantitative factors for the stability assessment and the control strategy design. The coordination control method consists of minute-level power coordinated allocation and second-level fast power control to prevent and eliminate the oscillations. A detailed simulation model of a multiple wind farms system originated from an actual wind power base in China is presented to verify the effectiveness of the proposed method.