Ramp control of active power electronics loads in microgrid

Droop control is an effective power sharing control scheme of distributed generation (DG) inverters in islanding AC microgrid, which can stabilize the grid as long as the distributed generation systems have sufficient residual power. On the contrary, many loads have equipped with power conversion circuits in front to improve the operational efficiency, e.g. air conditioners and LED lighting, which in fact can also provide the regulation function for stabilizing grid during transient process. This paper therefore proposes a ramp control theory for insensitive active power electronics loads in microgrid to control grid frequency together with DGs. The load ramp control method can effectively reduce the frequency variation especially when microgrid enters islanding mode from grid-tied mode, meanwhile the ramp control can release the burden of fast energy storage systems in microgrid and then reduce the construction cost of microgrid. Control wise, load ramp control is also a communication-less control theory, which only assumes the local information. Matlab simulations and experimental results are presented to show the effectiveness of the proposed theory in islanding microgrid.