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Control of Multi Inverter Microgrid Considering Hybrid Distributed Generation Systems and Renewable Energy Sources in Island Mode

Ghazanfari, Amin | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42349 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Mokhtari, Hossein
  7. Abstract:
  8. Nowdays, distributed generation (DG) systems based on renewable energy sources have significantly increased around the world as an alternative solution to enhance the power quality and reliability and reduce the need for extensive transmission system as well. An evolved recent concept called microgrid is developed by grouping a cluster of loads and DG units in a common local area which increases the integaration of sustainable energy generation systems. This thesis presents control of a medium voltage (MV) microgrid considering multi-hybrid distributed generation systems (MHGS) and renewable energy resources in island mode. The first part is focused on the development a control strategy for the hybrid distributed generation system consisting of a fuel cell (FC) combined with a supercapacitor (SC) under normal and load change conditions. To respond to a transient power demand, usually an energy storage device is combined with the FC. The dynamic model of the FC is given based on the electrochemical process. Hybrid distributed generation system is connected to the grid via power electronic converters to improve the system integrity, reliability and efficiency. Two full-bridge dc/dc converters are adopted to interface the FC and SC with the dc-link along with load in stand-alone applications. The design methodology for each component of the hybrid power system is illustrated. Then a precise and comprehensive control strategy is designed to keep constant dc-link voltage and supply system power demand under load disturbances. High power application Such as MV microgrids, normally employ large scale DG units. However, due to technical issues and to increase system reliability, it is preferred to use smaller units. On the other hand, power sharing and fast and reliable control of DG units with multiple different energy sources is a challenging issue. In the second part, a modular hybrid distributed generation stracture is proposed to improve the system reliability, redundancy and power quality. A control algorithm to guarantee that the MHGS can be operated within the stable condition is also proposed. The third part concentrates on the study and analysis of the MV microgrid considering the photovoltaic (PV) array as a renewable resource and MHGS. Two case studies are performed and load changes in the feeders and PV output power variations are also considered. Interaction between DG units and the microgrid during load changes is very important and it must be considered when designing a proper control strategy. A multi-loop control strategy is selected while the voltage controller loop, instead of proportional controller, is regulated by a proportional-resonanse (PR) controller. The DG units’ inverter is controlled based on local signals to enhance the system reliability. Simulation results are presented to verify the analysis
  9. Keywords:
  10. Fuel Cell ; Supercapacitor ; Microgrid ; Control Strategy ; Multi-Hybrid Generation System (MHGS)

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