Simulation of Hybrid inverter with fuzzy logic controller for distributed generators applied to unbalanced loads

Abstract

Micro grids are small-scale electricity supply networks that have local power generation. Micro grid became one of the key spot in research on distributed energy systems.Micro grids are capable of both generating their own electric power with small-scale distributed generation (micro sources) and receiving/exporting power to the main utility grid. In this paper a control strategy for inverter based MG which can ensure stability and proper power sharing among the inverters, in islanded mode, is proposed. A MG can be operated in two modes, grid connected and islanded mode. Each mode has its own control strategy. Microgrid (MG), mainly inverter based, are gaining more and moreimportance as they can accommodate various types of DGs effectively and for their superior power quality. A MG can be operated in two modes, grid connected and islanded mode. Each mode has its own control strategy. The general control philosophy within a micro grid is that sources must rely only on local information, yet must cooperate with other sources. To accomplish that goal, the proposed controller uses droop characteristics for active-power/frequency and reactive-power/voltage. The proposed control strategy is based on the use of a phase locked loop to measure the micro grid frequency at the inverter terminals, and to facilitate regulation of the inverter phase relative to the micro grid. This control strategy allows micro grids to seamlessly transition between grid-connected and autonomous operation, and vice versa. The controller has been implemented in an actual micro grid that incorporated multiple sources.The main objective of the proposed controller is to inject a clean sinusoidal current to the grid, even in the presence of nonlinear/unbalanced loads and/or grid-voltage distortions. The repetitive control technique is adopted because it can deal with a very large number of harmonics simultaneously with fuzzy logic controller  by using Matlab/Simulink.