Coordinated Control of DC Grid and Offshore Wind Farms to Improve Rotor-Angle Stability

This paper proposes a coordinated control strategy for voltage source converter (VSC) based dc grids and offshore wind farms connected by the dc grids. The strategy could enhance the stability of the onshore synchronous power system subjected to disturbances. Based on the mathematical model of dc grid connected power system and control Lyapunov function, the active and reactive control law for onshore VSC stations is presented. And to maintain the power balance of dc grid and reduce the rotor swing of wind turbines, the windfarms' power modulation and distribution method is given. A layered control structure to implement the proposed strategy which combines the dc grids and windfarms control is also put forward. Simulations are run in a modified New England 39-bus system by DIgSILENT/Power Factory to validate the effectiveness of the proposed scheme.