Control strategies of microgrid with Hybrid DC and AC Buses

This paper focuses on control strategies of Microgrid which consists of wind turbines, photovoltaic panels, batteries and super-capacitors with Hybrid DC and AC Buses. In grid-connected operation, voltage of DC bus is kept steady by inverter and voltage and frequency of AC bus are the same with utility grid. Energy Management System controls hybrid storage system to release or absorb power with the strategies according to grid condition, state of charge of batteries and super-capacitor, electricity price and so on. In islanded operation, voltage of DC bus is controlled by storage system and amplitude and frequency of AC-Bus voltage are regulated by parallel inverters with voltage-frequency or droop control strategy. In this paper, different control strategies in grid-connected and islanded operation are described which can keep power balanced and AC/DC bus stable. Simulation and experimental results are shown to verify the proposed control method.