Effect of Differences in Control Characteristics on Microgrid Power Balancing

Abstract

A clear criterion for evaluating the degree of contribution to a power system by microgrids is needed to facilitate the spread of microgrids. This requires clarifying the composition and scale of distributed generators (DGs) in the microgrid. Once the criterion has been identified, the control system characteristics needed to meet the criterion must be determined.
To evaluate how differences in the control characteristics of the DGs in a microgrid affect the power flow at the grid-connection point, we conducted tests for the four cases. The goal was to control the energy so as to keep the difference between supply and demand within ±3% over 30 min. In our experiments, the goal was met for each case. However, there was a distinctive trend in the variation in power flow at the grid-connection point and in the imbalance between supply and demand over 30 min. There was superiority or inferiority from the viewpoint of control accuracy. Moreover, there were significant differences among the four cases in terms of the amount of the change and the cycle of power flow fluctuation at the grid-connection point that can be controlled. It is thus important to clarify how the composition and scale of the DGs in a microgrid and the characteristics of the control system affect the contribution of the microgrid to the power system.