Hierarchical control of isolated power system with DFIG-based wind turbine and parallel-connected battery energy storage system

In this paper a two-level hierarchical control scheme is proposed for the coordinated control of DFIG-based wind turbine(DFIG) and battery energy storage system(BESS) within an isolated power system. The primary level consists of the local controllers associated with DFIG and BESS. With the indirect air gap flux linkage orientation technology adopted and the pitch control strategy improved, DFIG can maintain the voltage and frequency of isolated power system and operate along the transfer trajectory set by the second level control. With the P/Q control technology adopted, BESS can output special level of active and reactive power. The second level, consisting of a coordinate controller, is designed to coordinately regulate the active power output of DFIG and BESS, which can optimize the transfer trajectory of DFIG operation point and prolong the service life of BESS. Finally, Matlab/Simulink software is applied to verify the effectiveness of the proposed control strategy for the isolated power system.