A PV Based Multilevel Inverter with Ultra-Capacitor Bank for Microgrid Applications

Nowadays, hybrid utilization of power energy sources in microgrids or small distribution networks has received much attention for economic and technical reasons to support the utility. Providing systems with the ability to simultaneously take power from PhotoVoltaic (PV) units and inject this power to the utility in the presence of storage devices is also essential for the development of modern power systems. In this paper, a Hybrid Renewable Energy System (HRES) consisting of a PV unit and Ultra-Capacitor (UC) bank is proposed to create power balance and inject power with low variations into the microgrid. This HRES is connected to the microgrid with a proposed single-phase flying-capacitor five-level inverter with the ability to increase the voltage gain. In order to receive the maximum power from the PV unit, a suitable DC/DC converter with high efficiency has been introduced. Power exchange of UC bank with DC-link is also accomplished with a bi-directional DC/DC converter to power control. With the aim to improve the reliability of the proposed system, interlude topologies have been utilized in the interface converters of the PV unit and the UC bank with a common DC-link. The proposed HRES has a robust and simple control system to stabilize the DC-link voltage and provide power balance between different units. In order to demonstrate the productivity of the proposed HRES, the theories expressed along with the control system have been approved via MATLAB-Simulink software.