Interaction Analysis of two PMSG-based Wind Turbines Connected in Parallel to a Weak AC System

For the dynamic coupling problem of parallel PMSG-based wind turbines under weak AC system, a linearized model of the two-turbine parallel system has been established in this paper, and the low-frequency oscillation modes of the two-turbine system was calculated based on the eigenvalue method. By taking wind turbine 1 as the research object, the paper has put forward the damped torque model of the two-turbine system, constructed an analytical expression for the interaction between the turbines through the damping transfer function, and has carried out quantitative analysis on the trend of the interaction with grid strength, working conditions and control parameters in the form of mutual damping coefficients. The results have shown that:1) when the short-circuit ratio increases from 0.8 to 1.4, the mutual damping coefficient increases continuously and changes significantly; 2) as the working condition increases (0.75 MW to 0.95 MW), the mutual damping coefficient decreases continuously and the negative damping effect increases continuously; 3) control parameters such as DC voltage loop and phase-locked loop all influence the mutual damping coefficient.