Architecture Development of an SME Microgrid with Intelligent Power Controllers

Presently, the predominant electrical energy production is based upon central power plants and the use of fossil resources. Efforts to change this kind of supply are more and more in the focus of government and society, but the alternatives lead to many technical challenges. The vision of sustainable electrical supply is in general characterized by a decentralized supply with renewable sources such as wind and solar energy. Thus, the goal is clear but open questions still remain:

How do we guarantee safe delivery of energy at reasonable costs and quality?

How do we solve the problems of the existing supply grid related to the new situation?

This questions are legitimate because, firstly, the energy of renewable sources is normally not controllable (in the best case predictable), and secondly, the supply grid is not developed for the resulting energy flow (this leads to several different problems). Especially for SMEs (small and medium enterprises) is the safe energy supply at low costs very important. Short breaks of the supply can lead to high costs (e.g. for restarting of production lines) and comparatively too high costs for the supply leads to competitive disadvantages.

Microgrids can provide options to reduce these problems beside many other benefits.

A microgrid consists of sources, storages and loads of electrical (and other) energy which are mostly connected via power electronic converters. The control of the power flow in such a microgrid is carried out by operation algorithms which are implemented in a central controller. The main controller also utilizes forecasts and information like weather data. The reference values of the central controller are distributed to the local power electronic converters. The control loops and the topologies of the local converters are also adapted to the requirements of the microgrid. Special tasks for this distributed control systems are the stability assurance within the grid and active filtering.

The key features of a SME microgrid:

  • Reducing of the peak power at the point of common coupling (through the use of storage and load management)
  • Increasing of the self-consumption of renewable sources
  • Reducing the need of additional (central) storages in the public supply grid
  • Reducing of transmission losses in the public supply grid
  • Decreasing of the maximum load (load management)
  • Identification of bottlenecks in the local network  

Development and research regarding SME microgrids:

  • SME Microgrid specific load monitoring system (including measurement, load forecasting and load management)
  • Overview of selection possibilities regarding energy sources for a SME microgrid (including advantages and disadvantages, electrical behavior, ...)
  • SME Microgrid specific storage operation algorithms
  • SME Microgrid specific hybrid energy storage systems (selection, coupling and control)
  • SME Microgrid architecture (advantages and disadvantages of different connecting types like shared DC link, mixed AC/DC grids, …)
  • General developments of SME microgrid specific power electronic converters (topology and control technics)
  • Communication system of a SME microgrid
  • Economic Aspects of a SME microgrid  

Figure 1: Exemplary topology of a SME microgrid

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