| Abstract |
DC microgrids based on droop-controlled Distributed Energy Resources (DERs) converters tend to havelarge bus capacitance in order to guarantee stiff bus voltage. Large bus capacitance leads to the increase of weight, size, and cost. Indeed, since the droop control inherently allows the bus voltage to vary in a certain range, there is no need to restrict the dynamic bus voltage fluctuation to such a low level. Thus, as long as the bus voltage is maintained in the acceptable range, smaller bus capacitance can be chosen. This paper firstly gives the design criterion of the output capacitance for DERs converters. Then, the design of droop controllers are presented, so that the output capacitance can be reduced while the bus voltage is still kept in the allowable range during any transient. Since voltage-current (V-I) and current-voltage (I-V) droop control methods show different characteristics, separate design procedures are introduced for them. Finally, the proposed design methods are validated by means of experimental results performed on a dc microgrid prototype composed of two 3kW converters. |
