Enhanced Frequency Regulation Using Multilevel Energy Storage in Remote Area Power Supply Systems

Frequency support from renewable power generators is critical requirement to ensure the frequency stability of remote area power supply (RAPS) systems with high penetration of renewable power generation. However, traditional control strategies and the stochastic nature of wind resource constrain wind energy conversion system (WECS) such as permanent magnet synchronous generator (PMSG) from participating in frequency regulation. This work proposes to integrate hybrid energy storage including ultracapacitors (UCs) and lead-acid batteries (LABs) into a PMSG to provide frequency support. The UCs deal with fast changing frequency by emulating conventional inertial response, whereas the LABs mimic automatic governor response (i.e., primary frequency response). The mechanical power reserved in wind turbine using suboptimal maximum power point tracking strategy is utilized to restore system frequency (i.e., secondary frequency response). Moreover, supplementary control strategies are proposed to enable the UCs and LABs to assist primary frequency response and secondary frequency response, respectively. Simulation study and experimental test are carried out to validate the effectiveness of frequency response provided by the multilevel energy storage. The multilevel energy storage solution can effectively regulate RAPS system frequency while avoiding abrupt and frequent charging/discharging of the LABs and significant mechanical/electromagnetic stress on the WECS.