Coordination control method for multi-wind farm systems to prevent sub/super-synchronous oscillations

Abstract

In recent years, the sub/super-synchronous oscillations occur frequently in the large-scale wind power bases of 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 the complex operation conditions and continuous development of wind power, the off-line improvement measure on wind turbines cannot eliminate the potential oscillations risks. This paper is to propose an oscillation risk screening and stability assessment method, and develop a coordination control method for the large-scale wind farm systems to prevent the 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. Detailed simulation model of a multiple wind farms system originated from the actual wind power base in China is presented to verify the effectiveness of the proposed method.