INVESTIGATION OF DIFFERENT METHODS FOR LOAD SHARING AND POWER MANAGEMENT IN A HYBRID MICRO-GRID

Abstract

A grid consists of a set of distributed generation units, energy storage resources, communication links and local loads, and can operate in two modes connected to the grid and separate from the grid. Power management and load sharing between grid units in a separate mode can be in both centralized or decentralized. In a decentralized way, with decentralized method is preferable due to local measurements, and the lack of a fast communication link and reliability. In this thesis, a micro grid consisting of distributed generation units of a solar type and a storage source of a kind of battery is considered that can be connected independently (by separate inverters) or in combination of PV / battery (by a common inverter) to the grid. The purpose of this thesis is to provide a power management method and a decentralized load distribution for offshore grids, consisting of a variety of independent solar panels, independent batteries, and solar / battery combinations. In the proposed method, the operation of each grid unit is divided into six states and, depending on the different conditions, each unit operates in one of these situations. The control of the solar cells, the battery and the inverter unit vary according to the performance status. In this method, only the local measurements of the conditions of change are examined. The automatic balancing of battery charge rates and the optimal use of solar array capacity to supply power and charge the batteries is one of the most important features of this method. This method is firstly investigated for a single-phase grid, and then generalized to a single-phase / three-phase mixed-grid grid in which single-phase units are connected to different phases of a three-phase grid. Power transmission from phase to another phase and supplying the charge or charge power of a phase from another fuzzy is a feature of this method in single-phase / three-phase combination mode