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

Moslem Dehghani,Mohammad-Reza Tavana,Taher Niknam,Ghasem Asadi

doi:10.13189/ujca.2016.040302

Moslem Dehghani, Mohammad-Reza Tavana + Show 2 more

Open Access

https://doi.org/10.13189/ujca.2016.040302

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Abstract

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.

Highlights

In any occasions where electricity consumption is far from the main grid, such as remote villages/islands, or isolated communication stations, it is economically inefficient and/or technically difficult to deliver electricity via transmission lines
It is desirable that an MG control (MGC) provides sinusoidal output currents and voltages in all operation modes [4]
To be more precise, MGC is more of a nonlinear, time-variable system due to uncertainties caused by the operation mode transitions and distributed generators (DGs) disturbances

Summary

Introduction

In any occasions where electricity consumption is far from the main grid, such as remote villages/islands, or isolated communication stations, it is economically inefficient and/or technically difficult to deliver electricity via transmission lines. In such circumstances, an economically reasonable approach is to supply power in a form of islanding mode MG that contains renewable energy resources such as wind turbines, fuel cells, photovoltaic generators and etc. The main goal of this paper is to propose a robust nonlinear controller for MGs. It is desirable that an MG control (MGC) provides sinusoidal output currents and voltages (that is with low total harmonic distortion) in all operation modes [4]. Nonlinear controllers look to be more suitable candidates to overcome the uncertainties issues, and to guaranty global stability and better compensation [8]

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