Improved VSG Control for Type-IV Wind Turbine Generator Considering Operation Limitations

The gradually reduced inertia in powers system due to proliferation of renewable energy resource may lead to larger frequency deviation and change rate and thus fault protection triggering. Type-IV wind turbine generator (WTG) can provide inertia and damping via releasing the rotational energy by adopting virtual synchronous generator (VSG) control. However, the energy stored for inertia emulation depends on its machine side inertia and wind speed. To investigate its impact on inertia and damping emulation, linearized model of VSG-controlled type-IV WTG is established in the present research. It is revealed that lower machine-side inertia and higher wind speed will result in worse frequency response than the ideal VSG. An inverse control block is introduced to mitigate this effect. Supplementary control blocks are also added to limit the power and rotor speed of WTG and help damp the oscillation between synchronous generator and WTG. Comprehensive case studies demonstrated the effectiveness of the proposed control strategy.