Robust Hierarchical Non-linear Droop Control Design for the PV based Islanded Microgrid

Abstract

This paper presents the design and analysis of a non-linear droop controller of two different secondary controllers that are used in hybrid islanded microgrid systems. Distribution generators are used to provide power to the load in alternating current (AC) microgrid, and photo-voltaic (PV) arrays, connected with a boost converter for obtaining an optimum and stable voltage, are employed in direct current (DC) microgrids where the incremental conductance (InC) Maximum Power Point Tracking (MPPT) algorithm is applied for the extraction of maximum power. An Interlinking Converter (IC) between AC and DC microgrids is controlled by hierarchical architecture primary and secondary controllers during power fluctuations to mitigate non-linearity. The conventional proportional integral (PI) controller and the Sliding Mode Controller (SMC) are employed as secondary controllers. We present a comparison of the performance characteristics of two secondary controllers designed in a MATLAB/Simulink environment. The results demonstrate that a hierarchically controlled AC/DC hybrid microgrid can be effectively, robustly, and reliably operated with the proposed secondary control scheme.