A power management system for interconnected AC islanded microgrids using back-to-back converter

Abstract

Islanded AC microgrids are mini-power grids formed by assembling distributed generation sources, energy storage systems and loads. They are reliable and can operate at different voltages and frequencies to meet the requirements of the load. Interconnected Islanded Microgrids consist of multiple islanded microgrids interconnected to improve power system availability and stability, control flexibility, resiliency and reserve capacity. Islanded microgrids can be interconnected using back-to-back power converters to decouple connecting frequencies whose active and reactive power control can be done wirelessly and autonomously under a low communication link. This paper proposes a novel structure and control strategy using back-to-back converters and power transformers to interconnect multiple islanded AC microgrids to a global AC bus. Microgrids and global bus can utilise their resources to improve their operation and benefits. The control strategy uses a frequency signalling mechanism to limit the power demand of individual global converters and adjusts its droop coefficients accordingly and in proportion to deviation in frequency. The global droop controllers of the global connecting converters receive information about the status of the frequencies of individual microgrids using a low bandwidth communication link to enhance network power flow. MATLAB/Simulink results validate the performance of the proposed structure and control strategy.