Coordinated Control of an Ultracapacitor Bank and a Variable-Speed Wind Turbine Generator for Inertial Response Provision During Low and Above Rated Wind Speeds

There is a risk of wind turbine stalling when virtual inertial response is provided during low wind speeds due to the turbine speed reduction. Therefore, it is wise to consider minimum rotor speed limitation during inertial response provision so it can be suspended in time to avoid stalling. However, since low wind speed conditions can happen fairly often, the capability for inertial response is lost which may be crucial for scenarios with high wind penetration. On the other hand, during above rated wind speeds, generator and converter maximum current limit the amount of extra power that can be injected. In this paper, we present a coordinated control of a wind turbine and an ultracapacitor bank to provide inertial response during both low and above rated wind speed conditions. The developed algorithm is implemented in DIgSILENT PowerFactory and tested in a standard IEEE 9-bus test system. Results show superiority of the proposed method compared to the approach when only wind turbine generators are participating in virtual inertial response.