Energy management system for control of hybrid AC/DC microgrids

Hybrid AC/DC microgrid is getting popularized due to the higher penetration of DC-compatible loads, energy sources and storages. To maintain system power balance in both AC and DC sub-grids, the bidirectional interlinking converter (BIC) is used. Distributed control of hybrid AC/DC microgrid is normally implemented to enhance system reliability. DC bus voltage and AC frequency are used for indication of system active power balance. BIC power flow is determined based on local information to equalize the normalized deviations of DC voltage and AC frequency. However, deviations of AC frequency and DC bus voltage degrade system power quality, which deteriorate the lifetime operation of system units. Multi-level energy management system (EMS) is thus proposed in this paper to enhance control accuracy while retaining system reliability. Distributed control of hybrid AC/DC microgrid is scheduled as the primary control. Restorations of AC frequency and DC bus voltage are implemented in secondary control. In tertiary control, the power references of system units are generated based on the comparison of marginal costs. Power sharing compensation is applied to minimize power tracking errors. MATLAB/Simulink model for hybrid AC/DC microgrid is developed for the verification of the proposed multi-level EMS.