Scalable distributed control for hybrid AC-DC microgrids with adaptive load management

Hybrid AC-DC microgrids provide a critical architecture to integrate distributed energy resources, energy storage, and DC loads by minimizing power conversion stages, thereby enhancing overall system efficiency and reliability. This paper proposes a scalable hybrid AC-DC microgrid utilizing the untapped potential of isolated distributed solar lighting systems having their own solar PV panels and battery storage. The proposed hybrid microgrid consists of a 50 kW solar PV plant and 50 units of solar lighting systems. Each solar lighting system has a 200 W photovoltaic panel, a 48 V and 2 kWh battery capacity, and a bidirectional converter. This forms an aggregated 10 kW distributed energy resource having grid-forming capability supporting islanded-mode operation. A virtual impedance-based droop control mechanism is implemented for solar lighting distributed converters to enhance their current sharing accuracy and system stability. The proposed hierarchical control architecture encompasses primary and secondary control, with a 60 kW bidirectional interlinking converter facilitating power flow between the 220 V DC and 220 V AC sides of the hybrid microgrid. In islanded mode, the excess power is managed with the help of an electronic load controller for dump loads. This proposed control strategy enables intensity control of solar LED lights, reducing the lighting load by up to 20 percent during high demand periods to support the grid. The simulation is carried out in MATLAB and results show stable microgrid voltage and proportional current sharing among distributed converters. The microgrid achieves a seamless transition from grid-connected to islanded operation even after unintentional islanding, where the results demonstrate that system restores itself to normal operation within 2 cycles with the current overshoot in acceptable limits.