Design of a Flexible and Modular Test Bed for Studies on Islanded Microgrids
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The last two decades in the electric power sector have been increasingly dominated by a rising interest in the integration of distributed energy resources (DERs) into electric power systems, many of them based on renewable energies. A wider-scale deployment of DERs raises questions in the design, planning and operation of electricity grids. In particular, the operational paradigms of distribution grids are about to change significantly. One way proposed for putting small-scale DERs into the heart of an electric power system is through realizing “Microgrids”. The concept of Microgrids proposes methods to allow participation of DERs in main and ancillary services on the level of distribution grids. To foster research and development in the fields of Microgrids and grid-connected power electronic converters, test beds with adequate functionality are required. Around the world, many test beds have been created to allow experimentation and collection of experiences using full-scale, real equipment and fixed network layouts. However, these test beds are expensive, costly and large, and do not offer a high flexibility for reconfiguration. Therefore, this thesis proposes, implements and evaluates a Microgrid test bed using the Hardware-in-the-loop approach to simulate the behavior of different types of generation, energy storage and loads in a Microgrid. Identical power electronic converter modules are used to generate the currents, voltages and powers required to imitate the AC-bus grid connection of such grid participants. Software models govern converter control and plant simulation, allowing for a fast and flexible reconfiguration of the en-tire test bed. This approach heavily cuts down cost, size and weight of test beds and allows a much more flexible and reproducible creation and execution of test scenarios.