Research on sub/super-synchronous oscillation suppression method for direct-drive wind turbine based on energy compensation

A method to suppress sub/super-synchronous oscillation of direct-drive wind turbines based on energy compensation is proposed. First, the transient energy model of direct-drive wind turbine is built, and the negative damping energy terms that lead the oscillation of direct-drive wind turbine are extracted. On this basis, the expressions of voltage compensation terms corresponding to negative damping energy terms are derived by backward deduction, thus supplementary energy branches are constructed, and their impact on fundamental frequency characteristics of wind turbine is analyzed. And then, with the compensation energy of supplementary branches reaching the maximum and the increment of fundamental-frequency voltage being the minimum as the objective, and with the frequency-domain characteristic and fundamental-frequency voltage characteristic of control links being satisfied as constraints, a scheme to optimize the compensation coefficients of multiple branches is established. Finally, the model of direct-drive wind turbine is built in RT-LAB for hardware-in-the-loop tests. Simulation results verify that, the method can realize fast frequency-dependent suppression of sub/super-synchronous oscillation in different frequency bands concerning different grid strengths.