Toward Power Quality Management in Hybrid AC-DC Microgrid Using LTC-L Utility Interactive Inverter: Load Voltage-Grid Current Tradeoff

AC-DC hybrid microgrid (HMG) is introduced as the future distribution network to utilize both benefits of alternative and direct currents. Generally, HMG is consisted of ac and dc loads, renewable energy-based distributed generators (DGs), controllable DGs and energy storage systems, and a utility interactive inverter (UII), which provides a bi-directional connection between ac and dc subsystems. In this paper, a inductor, transformer, capacitor, and inductor (LTC-L) topology for the UII has been proposed for managing the power quality of ac subsystem of the HMG. The control strategy of the UII is flexibly changed based on the operating-mode of the HMG. Using the proposed control strategy of the UII in grid-connected mode, not only the voltage quality of the ac-subsystem will be improved, but also the quality of the grid current will be enhanced, considerably. In standalone mode, UII acts as an uninterruptable power supply to minimize the shedding of ac or dc loads. A voltage-current cascaded control structure is used for employing the proposed control strategies. Moreover, two control approaches are investigated on the proposed LTC-L topology of UII, sinusoidal voltage reference (supplying load with pure sinusoidal voltage) and non-sinusoidal voltage reference (supplying load with nonsinusoidal voltage for mitigating grid current harmonics). Effectiveness of the proposed topology and the control strategies are evaluated through a numerical study and discussing the results.