Stability Improvement of a Multi-Machine Power System Using a DC Microgrid with a Vanadium Redox Flow Battery-based Energy Storage System

This paper presents the stability-improvement results of a multimachine power system (MMPS) connected with a DC microgrid (MG) consisting of a high-capacity hybrid wind/PV farm, a DC load, and a vanadium redox flow battery (VRFB)-based energy storage system (ESS) with a bidirectional DC/DC converter. The common DC link of the DC MG is integrated into the AC bus of the MMPS through a DC/three-phase AC voltage-source inverter (VSI), a step-up transformer, and a power transmission line. The supplementary damping controllers (SDCs) located at the control loop of the bidirectional DC/DC converter of the VRFB-ESS and the DC/three-phase AC VSI are respectively designed using a pole-placement method based on modal control theory. The simulation results show that the designed SDC at the control loop of the DC/three-phase AC VSI can contribute better damping characteristics to the electromechanical modes of the studied MMPS.