1.China Electric Power Research Institute, Beijing 100192, China;2.State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (North China Electric Power University), Beijing 102206, China

The fluctuation of wind power may lead to the change of operation point in power system. In order to effectively improve the adaptability of subsynchronous oscillation damping control, a subsynchronous oscillation robust damping controller is designed by using the additional control method of direct-drive wind turbines. Firstly, based on the linearized state space model, the mixed H ₂/H _∞ control with regional pole placement is used to suppress the power system subsynchronous oscillation caused by random disturbance. The convex polytope model is constructed by using different operation points as the vertices of the convex polytope to adapt to the wide variation of system operation points caused by wind power output fluctuations and improve the robustness of the controller. Secondly, a linear matrix inequality is applied to solve the state feedback matrix and design a subsynchronous oscillation robust damping controller. Finally, a four-machine two-area system with two direct-drive wind turbines is used as the test system for time domain simulation. The simulation results show that the robust damping controller based on convex polytope can provide sufficient damping for the subsynchronous oscillation modes, and the controller also has good control effect when the outputs of wind power change over a wide range.