Coordinate control of distributed generations with power converters in a micro grid

For extensive utilization of distributed generation with the objectives of more efficient use of energy and introduction of renewable energy sources, the construction of a micro grid at demand end is inevitable. The micro grid should operate independently and have a good neighbor relation with the power grid, which supplies base power to it. A coordinate control scheme of distributed generations is studied. It has three layers of structure. The integrated control system is quite similar to that of power system other than its scale. Because of the limited number of generations and customers, the variation of power unbalance between supply and demand is fast and large. To stabilize the system and maintain power supply quality, the micro grid is subdivided into local distribution network groups. The local group control system regulates generations inside it in coordination with other groups and transmits operational information in it to the integrated control system. Each controllable generation has its own control system and regulates its output with the command from the local group control system. The distributed generation on the market, including the battery energy storage, is generally connected to the network through the power converter system. Because it can not autonomously follow the power variation, a novel control scheme should be incorporated into the control system of power converter system and the local level control. Their performances in operation of a micro grid are verified with simulations using EMTDC/PSCAD. The coordination between local group control systems for the load following control is under test in a model grid for experiment. A demonstration system is planned to construct on this control scheme.