Hybrid Fuzzy-Sliding Control Scheme for Bi-directional SEPIC Converter in Renewable Based DC Microgrid

Abstract

This paper describes a hybrid fuzzy-sliding control scheme for bi-directional SEPIC converter in renewable based DC microgrids. The performance of a DC microgrid is directly dependent on the voltage stability of the DC bus. In operation, the voltage level of the system is affected by the power injection of the power sources connected to the microgrid, in particular those dependent on environmental factors (such as sun and wind), and by the power consumption of non-constant loads. This feature of microgrids makes control a complex engineering problem. Considering this problem, we propose a hybrid control scheme for a SEPIC bi-directional converter capable of regulating the power flow and stabilizing the system's DC bus. Proposed control technique is simulated in a 48 V DC microgrid and results are provided.Keyword -Bi-directional converter, Fuzzy-sliding control, Microgrid, SEPIC converter I. INTRODUCTION Colombia has large regions without electricity service (the coverage of electricity service is only 34%), are regions isolated from the traditional power grid (about 52% of the national territory, and inhabited by about 1,800,000 people) which have been called Non-Interconnected Zones (ZNI) [1]. There are many reasons for this type of deprivation of electricity service, but the most common reason is the high cost of installing the network to power an area with low population density. The most promising solution for supplying electricity to these areas is the installation of microgrids. The global market trend indicates that microgrids are becoming consolidated as an energy solution for the end user (and not necessarily for those not connected to the traditional power grid) that can even bring economic benefits [2].A microgrid is a localized group of different kinds of electrical energy sources, which work together to meet the energy needs of a specific area, and which can operate either in conjunction with the traditional power grid or in isolation [3]. This microgrid integrates different energy sources according to the energy availability of the area (solar energy, wind turbines, coal, liquefied petroleum gas, etc., although with a strong propensity for renewable resources, or renewable distributed energy resources -DER), and have a variable architecture according to the advantage of generating energy primarily from one or another energy source. This variable topology makes microgrid control and protection complex and an open-ended engineering research problem [4,5], particularly when considering power flow problems, load sharing, voltage regulation and mitigation of various kinds of power quality issues [6].A great energetic advantage of the microgrids is their greater electrical efficiency when feeding electronic type loads as variable speed drives and LED loads, because they do not need AC/DC and DC/AC converters when feeding them directly in direct current (DC) [7,8]. The DC power supply system has other advantages over the AC (alternating current) system, for example, it has higher reliability and lower cos...