A combination of PI and fuzzy logic controllers for seamless transition in dual-mode microgrids

This paper proposes a combination of proportional-integral (PI) and fuzzy logic controllers (FLC) for a microgrid operating in two modes of operation, i.e. grid-connected or islanded, with proper control schemes to enhance power supply reliability in edge-of-grid locations. A seamless transition from grid connected to islanded mode is achieved with a combination of PI and FLC. The aim is to minimize transients when the microgrid unintentionally switches from grid-connected to islanded mode. These transients happen due to the mismatches in phase and frequency of voltages and currents of the two modes. The microgrid in this paper consists of two inverter based distributed generators (photovoltaic systems) connected in parallel for supplying power demand of a local load. The validation of design is carried out by emulating two different (balanced and unbalanced) utility networks connected to the microgrid. A comparative analysis of the PI controller versus the proposed FLC with both utility networks in different operating modes is made using MatLab/Simulink.