DEVELOPMENT ANALYSIS OF SMART DISTRIBUTION GRIDS IN PRESENCE OF DISTRIBUTED GENERATION

The integration of distributed generation (DG) units in power distribution network has become increasingly attractive multi-faceted paradigm as economic and environmental factors drive new technologies to be more efficient and less polluting than their earlier counterparts. The installation of DGs impacts critically on the planning and operating characteristics of the distribution network. Type, location, number and capacity of DG are essential factors for studying the effect of DGs on the system behavior. Some possibilities to handle grid planning and operating issues are addressed in this thesis. Firstly, the effect of DG on the power losses of a distribution network is introduced and the performance of the interconnected DG distribution network in terms of power losses is analyzed and investigated. Then, the impact of DG on the voltage profile is demonstrated and studied with and without network faults. Since the protection system requirements turns up as one of the most critical challenge in DG integration; the main part of this research concerns on the studying the impact of DGs on protection system. The effects of interconnecting DGs on fault current level are investigated and described. Also, the possibility and the potentiality of occurring mis-coordination between protection devices in distribution network is studied; different scenarios for mis-coordination problems caused by DG interconnection are discussed. On the other hand, some approaches to overcome the mis-coordination problems occurred are viewed. Also, threshold value and restrictions of DG capacity is presented while the existing protection scheme for distribution network can be maintained. The penetration level, location, number, and type of interconnected DGs are used as parameters in this study in order to verify the effects of DG on the mentioned aspects; the classifications of DG units are based on their terminal characteristics in terms of real and reactive power delivering capability. A comparison among many cases with different numbers, sizes and locations of interconnected DGs are considered and discussed in this research. Finally this thesis presents a framework to determine the limits of interconnecting DG units in distribution system in order to keep protection scheme unchanged, while the voltage profile remains within acceptable range and on the same time having the minimum power losses in the network; applying this framework in the developing countries could save money and time during the integration of DGs to the network on a large scale based on country regulation. Detailed simulations using MATLAB software are illustrated in order to explain and verify the results