Comprehensive local control design for eliminating line resistance effect on power sharing degradation in DC microgrids

In droop-controlled DC microgrids, parasitic resistances of long conductive lines introduce additional terms for the power calculation and impact the power sharing accuracy. This paper proposed a comprehensive local control design for enhancing power sharing accuracy and restoring DC bus voltage while increasing stability performance in DC microgrids. A passive controller is used in the primary control to ensure the sufficient bandwidth of controller in case of frequent operation modes alteration and voltage deviation in the DC microgrid. A concept of Virtual Negative Line Resistance (VNLR) is used in the secondary control layer to compensate the real line resistance such that line resistance no longer degrades power sharing accuracy. The common DC bus voltage needs to be monitored in the proposed secondary controller. Simultaneously, the common DC bus voltage can be restored as the designed value. The monitored DC bus voltage signal is filtered by a designed low-pass filter such that mid-high frequency dynamics can be decoupled between secondary controls and primary controls. Then the entire local control scheme relaxes three Degrees of Freedom (DoF) which can be used for upper layer controls. Finally, the proposed control method has been experimentally validated in a 50 V DC microgrid laboratory testing system.

Automated summary

This paper proposes a comprehensive local control design for enhancing power sharing accuracy and restoring DC bus voltage while increasing stability performance in DC microgrids. By using a passive controller in the primary control and introducing the concept of Virtual Negative Line Resistance in the secondary control layer, the impact of parasitic resistances of long conductive lines on power sharing accuracy is mitigated. Monitoring and restoring the common DC bus voltage is essential in the proposed secondary controller.