A Control Method Using Two Electromotive Forces and a Disturbance Observer to Improve the Dynamics of a Virtual Synchronous Machine
Geon Heo, Yongsoon Park, Kyungkyu Lee, Ho-Seon Ryu
Abstract
The modern power grid is facing a significant challenge due to decreasing grid inertia, which is caused by the high penetration of renewable energy sources (RESs). Virtual synchronous machines (VSMs) have been considered as effective solutions to support the grid by providing inertial responses similar to that of traditional synchronous machines. However, fast and flexible dynamic responses to reference inputs, which can be achieved by conventional RES interfacing inverters, are degraded when inverters emulate the behavior of a synchronous machine. In this paper, a current-referencing electrified synchronous machine (CURESYM) is proposed as a control method to adjust the dynamics to the reference input regardless of the parameter settings for ec response to follow the current reference. In addition, the accuracy of the current regulation can be enhanced by virtue of a disturbance observer. The fundamental characteristics of CURESYM are described with laboratory-scale experimental results. Finally, the effectiveness of CURESYM is discussed with practical data from on-site tests that applied the proposed method to a battery energy storage system in an actual island microgrid.