Autonomous operation of distributed storages in microgrids

Operation of distributed generators in microgrids has been widely discussed, but would not be fully autonomous if distributed energy storages are not considered. Storages are important since they provide energy buffering to load changes, energy levelling to source variations and ride-through enhancement to the microgrids. Recognising their importance, this study presents a scheme for sharing power among multiple distributed storages in coordination with the distributed sources and loads. The scheme prompts the storages to autonomously sense for local operating conditions, requesting for maximum charging energy only when excess generation capacity is available. As generation capacity drops or demand increases, energy drawn by the storages decreases spontaneously to avoid over-stressing the sources. When full generation capacity is near, the storages will automatically release their stored energy to help with meeting the extra load demand. The described process takes place autonomously with energy eventually shared among the storages in proportion to their ratings. To test the concepts discussed, experiments have been performed with favourable results obtained for performance verification.