System frequency regulation in doubly fed induction generators

The conventional decoupling controls of variable-speed doubly fed wind turbines provide minimal support to the regulation of system frequency. The characteristics of doubly fed induction generator (DFIG) wind turbines and conventional power plans are compared, and the contributions of DFIG to system inertial response and frequency regulation are investigated. The influence of auxiliary loop parameters on the inertial response is illustrated. We also introduce a novel algorithm to enhance the participation of DFIG in existing frequency regulation mechanisms. The proposed approach takes advantage of the fast responses associated with DFIGs. The control system consists of four functional modules, namely, frequency control, rotational speed delay recovery, speed protection, and coordination control with conventional generators. The simulation results show that the control strategy has a fast response speed to the transient frequency error, thereby proving that wind farms can participate in system frequency regulation to a certain extent. (C) 2012 Elsevier Ltd. All rights reserved.