Cooperative Virtual Inertia and Reactive Power Control of PMSG Wind Generator and Battery for Improving Transient Stability of Power System

Renewable energy sources are a promising future power source. However, many of the renewable energy power sources such as solar and wind power are connected to the power grid through inverters. Such power sources controlled with an inverter have almost no inertia and synchronization power. Therefore, as the amount of the renewable energy power sources increases, conventional synchronous generators need to be disconnected, and thus, the inertial and synchronization powers of the system decrease. Such systems are vulnerable to network fault and can have large frequency fluctuations. In this paper, virtual inertia control and reactive power control are applied to a variable speed wind turbines with permanent magnet synchronous generator (VSWT-PMSG) based wind farm and storage battery connected to the grid. The reactive power control is activated after a ground fault accident to prevent fixed speed wind turbines with squirrel cage induction generator (FSWT-SCIG) based wind farm from becoming unstable and disconnected. Then the virtual inertia control (active power control) is activated when the system frequency fluctuations become large due to the FSWT-SCIG based wind farm disconnection. Effectiveness of the proposed method on the transient stability improvement during a grid fault is evaluated by simulation analyses on PSCAD/EMTDC.