Analysis and Suppression in Subsynchronous Oscillation of Doubly-Fed Wind Farm through Series Compensation Grid-Connected System

Wind energy has been vigorously developed as a clean energy and has become an important part of the national energy strategy. However, as the doubly-fed wind farms increases, its problems become more and more prominent. In the event of a grid fault or an asymmetric fault, the power flow between the Rotor Side Converter (RSC) and the Grid Side Converter (GSC) may cause subsynchronous oscillation, resulting in system stability. This paper aims to study the subsynchronous oscillation problem and suppression methods of wind farms. Firstly, a system model of doubly-fed wind turbines connected to the grid through series compensation was established based on mathematical equations. Next, based on the eigenvalue method, the effects of wind speed, series compensation degree and RSC inner current loop proportional on the subsynchronous oscillation mode were analyzed. Finally, a measure based on Static Var Compensator (SVC) is proposed to suppress subsynchronous oscillations, the mechanism of SVC suppressing subsynchronous oscillations is analyzed, also an SVC damping control strategy is designed, and its rationality is verified through time-domain simulation.