Multiple Stages Coordinated Control of Wind Turbine Generators and Energy Storage Systems for Frequency Support Considering Multiple Constraints

The current method of primary frequency support for the system using wind farms didn't consider the rotor speed and torque constraints at the same time. To improve the support effect while ensure the rotor speed and torque safety, this paper proposes a multiple stages coordinated control (MSCC) using wind turbine generators (WTGs) and energy storage systems (ESSs). In the beginning of the frequency event, the wind farm is under consensus coordinated control to fully utilize the WTGs' kinetic energy. ESSs act under adaptive droop control. When the torques of some WTGs reach the limit, these WTGs are switched to torque limit control (TLC). At the same time, the power reference values of ESSs are updated to make up for power shortage of TLC. In the recovery stages, the WTGs use gradual recovery control, while the ESSs use adaptive ramp recovery control. Both of the recovery controls alleviate the second frequency drop (SFD). Based on MATLAB/Simulink platforms, the two-area power system with wind farm and ESSs is analyzed. Simulation results show that the proposed TLDC method has a better effect compared with other frequency support methods, and also ensure the rotor speed and torque safety.