Cost-based droop scheme with lower generation costs for microgrids

In an autonomous microgrid where centralised management and communication links are not viable, droop control has been the preferred scheme for distributed generators (DGs). At present, although many droop variations have surfaced, they mainly focus on achieving proportional power sharing based on the DG kilovolts ampere (kVA) ratings. Other factors like generation costs, efficiencies and emission penalties at different load demands have not been considered. This omission might not be appropriate if different types of DGs are present in the microgrids. As an alternative, this study proposes a cost-based droop scheme, whose objective is to reduce a generation cost function realised with various DG operating characteristics taken into consideration. Where desired, proportional power sharing based on the DG kVA ratings can also be included, whose disadvantage is a slightly higher generation cost, which is still lower than that produced by the traditional droop schemes. The proposed droop scheme therefore retains all advantages of the traditional droop schemes, whereas at the same time, keeps its generation cost low. These findings have been validated in experiments.