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Abstract- Recently, several types of Distributed Generators (DGs) have been connected together to form a small power system called a micro grid (MG). MG usually operates in normal connecting mode and is connected to the main grid. If a fault occurs in the main grid, MG will transfer immediately to the islanding mode. This paper developed a complete model which can simulate, in detail, the dynamic performance of the MG during and subsequent to islanding occurrence. The developed model is used to investigate the effect of using storage batteries for enhancing MG dynamic performance during all modes. Two cases are studied, the first case discusses the effect of the islanding process on the frequency, voltages and active powers of all micro sources when there are no storage batteries installed inside the MG. The second studied case investigates the effect of islanding occurrence on the MG performance when MG is equipped with two storage batteries. In the two studied cases, wind speed and irradiance vary continuously. Results proved that the existence of storage batteries led to dramatic improvement in the dynamic performance of the MG during subsequent islanding occurrence. Also, MG performance, when exposed to a severe disturbance, led to an unacceptable frequency drop is studied and load shedding strategy activation during this situation is also highlighted.
Keywords- MG, dynamic performance, islanding, micro sources, inverter, storage batteries and load shedding
1. INTRODUCTION
Micro-scale Distributed Generators (DGs), or micro sources, are being increasingly applied to provide electricity for the expanding energy demands in the network. The development of micro DGs also help to reduce green house gas emissions and increase energy efficiency [1]. MG usually consists of a cluster of micro DGs, the energy storage system (e.g. flywheel, batteries...) and loads, operating as a single controllable system. The architecture of the MG is formed to be radial with a few feeders. It often provides both electricity and heat to the local area. It can be operated in both grid-connected mode and islanded mode. From the customer point of view, MG provides both thermal and electricity needs, in addition to enhancing local reliability, reducing emissions, and improving power quality by supporting voltage and reducing voltage dip. From the utility point of view, application of distributed energy...