Dynamic equivalent modeling of direct-drive PMSG wind farms based on the transient active power response characteristics

In order to guarantee the consistency of operating characteristics at the point of interconnection, a dynamic equivalent model is proposed for a large-scale wind farm with direct-drive permanent magnet synchronous generator (PMSG) wind turbines, using the transient active power response curves at the point of interconnection. Firstly, the simulation model of a grid-connected PMSG wind turbine is established to simulate and analyze its transient active power response characteristics during grid fault using the PSCAD/EMTDC platform. Two critical issues related to dynamic equivalent modeling of a wind farm are summarized by intensive investigations. The active power curves under different wind speeds are in parallel with each other at steady state and show linear relationship. The transient active power response of wind turbine which are instant to recover power during fault are approximately consistent in the whole, only being short and little consumption of active power when wind speed is quite low. Thus, a wind farm composed of numerous PMSGs that take an instant restoration strategy of active power can be aggregated into one group. Using different groups of wind speed data, the dynamic responses of wind farm under three-phase short circuit fault are compared to check up the validity of the equivalent model. Simulation results show that the output characteristics of the proposed single-machine equivalent model of the wind farm is consistent with the detailed one.