Control of Multiple PV Integrated Parallel Inverters for Microgrid Applications

Abstract

To enhance the accessibility and reliability for a distributed generation system (DGS), a grid-tied photovoltaic (PV) generation system based on multiple parallel connected PV-inverters is developed for microgrid application in this work. This microgrid is designed to operate in the grid tied mode (GTM) as well as a standalone mode (SAM) and vice-versa. Here, a grid-forming inverter (GFI) technology is utilized for system with high penetration of renewables. The single stage PV-battery interfaced GFI inverter in parallel with a PV array supported inverters is considered to operate in the GTM as well as in (SAM) of operation. In SAM, the grid forming inverter maintains constant voltage and frequency across the load The control strategies of each unit are independent and using multi-loop controllers with switching logic. In the GTM, each PV panel in DGS is interfaced with an inverter with independent maximum power point tracking (MPPT) to harvest maximum power. The battery supports the PV units during peak load periods and maintains the power balance in the microgrid. Controlled charging and discharging profile of the battery is achieved by a DC-DC bidirectional converter (DBC). The control strategy of microgrid is verified with simulated results in detail.