Improving Grid Frequency Response using Wind Generation Resources
Singarao, Venkatesh Yadav
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New standards/requirements are being proposed by North American Electric Reliability Corporation (NERC) in response to the increasing mix of Wind Generation Resources and growing concerns of system stability and reliability in US interconnections (especially ERCOT region). This concern is due to lack of inertia, primary and secondary frequency response with the current fleet of wind generation resources during under-frequency events. Based on the standards, this dissertation addresses the development of a modified frequency control scheme for variable speed turbine based wind generation resources. Proposed control scheme provides a selective distributed pitch control wherein only few individual generating units use pitch mechanism to create spinning reserves and thus improve the individual generating unit’s reliability. Better voltage and reactive power support is provided with the help of wind generation resource equipped with the proposed controller and auxiliary dynamic reactive power source such as STATCOM (Static compensator). This control methodology selectively combined with inertia and deloading controller is used to obtain optimum frequency response for different generation mix, and varying wind speed conditions. Assuming accurate wind forecasts and adequate wind resource, the ability of wind generation resource in providing secondary frequency control during both over and under frequency events is also investigated. Use of synchronous condensers is suggested to overcome the limitations in performance of wind generation resources in a grid with low short circuit strength. A Proforma financial model to help the wind farm developer in taking the investment decision regarding the operation of turbine at reduced output, or battery storage systems for providing primary control reserves for utility frequency regulation is developed. The sensitivity of different parameters such as battery storage unit’s capital and O & M costs, storage efficiency, installed storage capacity, life cycles/years, replacement costs and depth of discharge with respect to project’s Net Present Value (NPV) and Internal Rate of Return (IRR) was investigated to quantify the economic benefits for deploying them. Finally, this PhD program being multi-disciplinary, prepares review of the regulatory standards and markets for various frequency responsive ancillary services such as Primary Frequency Response (PFR), Synchronous Inertial Response (SIR), Emulated Inertia Response (EIR), and Fast Frequency Response (FFR), and then provides future responsibilities for various stakeholders in the electricity industry to overcome the limitations in the existing standards and policies.