Grid Connected and Islanded Operation of Microgrids Including SMES, SC, and Li/Ion Based PV Systems

This paper investigates the grid-connected and islanded operation of a microgrid including photovoltaic (PV) units, lithium (Li)/Ion batteries, superconducting magnetic energy storage (SMES), and a super-capacitor (SC). Grid connection of the microgrid is achieved using (NPC) neutral point clamped inverter. To the DC bus, by using bidirectional converters and MPPT based on SEPIC converter, each unit of the microgrid is tied. SEPIC MPPT ensures maximum power transfer from the PV array. Also, bidirectional converters provide the discharge and charge of the SC, Li/Ion, and SMES storage units. Furthermore, the operation of the microgrid is carried out using a supervisory controller that operates by sensing the irradiation level, grid condition, SOC of Li/Ion and SC, and SMES current. Computer simulation studies indicate that a seamless operation of the microgrid in both the grid-connected and disconnected modes is carried out with a low level of THD. Moreover, a very smooth operation of the microgrid is managed during the transient from the grid connected to the islanded conditions, or vice versa.