Fixed Frequency Model Predictive Control of Three-level Bi-directional Flying Capacitor DC-DC converter in DC microgrid

This paper presents a fixed frequency model predictive control (FFMPC) of a three-level bi-directional flying capacitor DC-DC converter for energy management application in a DC microgrid. The presence of three voltage levels give the converter advantage of having reduced voltage stress on the power switches and low ripple in its inductor current. Additionally, the capability of having bi-directional power flow enables the converter to integrate energy storage devices such as the battery to a DC microgrid effectively. An FFMPC algorithm is formulated using the developed mathematical model in order to yield the dual objective of bi-directional power flow and flying capacitor voltage balancing. In this paper the performance of the FFMPC algorithm is compared with the conventional finite control set model predictive control (FCS-MPC) algorithm in terms of dynamic response and inductor current ripple. A significant reduction in current ripple was observed using the proposed algorithm. Furthermore, a DC microgrid comprising photo-voltaic (PV) system, load, and battery are considered to assess the effectiveness of the designed FFMPC algorithm under varying load and PV power injections.