Proposal for optimising the provision of inertial response reserve of variable-speed wind generators

Wind generators provide efficient harvesting of wind energy at the cost of worsening the inertial response during load-frequency events. The inertial response may be improved, however, by emulating the response of synchronous generators by means of additional control loops that sense frequency deviations. Energy reserve is needed in such a case if overloading, stalling or power request for speed recovery are to be avoided. In this study, the authors formulate an optimal problem to achieve the aim of conciliating the opposite objectives of minimum loss of power production and required minimum inertial reserve. The solution to the problem gives the pitch angles and the associated, modified speed against power tracking characteristics needed to support high kinetic energy storage with minimum loss of power production. The analyses confirm that a proper reserve can be maintained, mainly at low wind speeds, with a reduced amount of de-loading.