A Rotating Reference Signal Based on Nonlinear Control for Multi-bus Single Phase Micro-grids

In islanding Micro-Grids (MGs), distributed generation units are in charge of controlling voltage, frequency, and current of the grid on their own without any assistance from the main grid. Therefore, it is of utmost importance to select and design a controller that is robust against disturbances and load variations. In this study, a new sliding mode controller with a rotating reference voltage algorithm is proposed which improves the load sharing between distributed generators (DGs) in an islanded mode MG. In the proposed algorithm, the amplitude of the reference voltage signal of the controller is adaptively modified to improve the performance and convergence rate of the controller. As a case study, the proposed strategy is studied based on the assumption that there are three DGs in the grid. One of the DGs is in charge of regulating voltage and frequency based on a reference signals, and the two other DGs are responsible for load sharing and loads current control mode. The MG under study consists of three low voltage distributed generation units operating in parallel mode. In order to have a realistic case study, it is assumed that the MG consists of different types of loads such as resistive, inductive and nonlinear loads. Extensive simulations carried out in MATLAB environment indicate that the proposed framework is able to provide more desirable total harmonic distortion (THD), lower steady state error, and faster response compared with classic sliding mode controllers.