Novel Nonlinear Droop Control Techniques to Overcome the Load Sharing and Voltage Regulation Issues in DC Microgrid

Abstract

In a dc microgrid, good load sharing and voltage regulation are desirable. These are affected by practical factors like sensor calibration errors and cable resistances. To enhance the load-sharing accuracy among the parallel-connected voltage-controlled sources and to improve the dc-bus voltage regulation, three novel nonlinear droop control techniques are proposed for the smart grid scenario. The proposed methods are completely decentralized methods and require only local information (output voltage and output current of the individual converter) for achieving aforementioned merits. Since no communication channel is required, it is easy to implement them. Furthermore, the absence of communication channel improves system reliability and offers plug-and-play features, as only local information is utilized. Also, failure of one converter does not affect the operation of other converters connected to the grid as no information is exchanged between the converters. Effect of sensor calibration errors and cable resistances is minimized by these techniques. Theoretical analysis and experimental results are presented to demonstrate the efficacy of the proposed control methods. Finally, a performance analysis of the three droop control techniques is presented along with their advantages over the conventional methods under different operating conditions.