Comparative Study of Four Droop Control Strategies in Buck Converter Based DC Microgrid

Direct Current (DC) microgrids have the potential to improve efficiency and reliability of power system operations in many applications. Droop control has been introduced as one of the most popular strategies. However, basic characteristics of different types of droop control have not been fully examined. While there are a lot of work about the voltage-current (VI) and current-voltage (IV) droop characteristics, analysis of voltage-power (VP) and power-voltage (PV) has not been fully considered and compared for low voltage DC networks. This paper provides the comparative analysis, testing, and performance evaluation of VI, VP, PV, IV droops for buck converter-based DC microgrids. The analytical and simulation results provide a picture of similarities and differences among the four droops. Instead of conventional conception of similar VI and VP, as well as IV and PV, their steady state performance and stability assessment results are different. Ranking of stability of the four droops are verified by Middlebrook criterion and passivity-based stability assessment.