A Novel Coordination Control Strategy for Parallel-Connected Boost Converters in DC Microgrid

Since the constant power loads (CPLs) have negative-impedance characteristics, the system damping of DC microgrid is reduced, which will lead to the collapse of bus voltage. In addition, the errors of current sharing within parallel-connected DC-DC converters amplify due to different line impedances. To address these issues, a hybrid coordination control strategy is proposed for parallel-connected boost converters, which realizes the stable control and maintains the accuracy of current distribution. Firstly, a passivity-based control (PBC) with a proportional-integral (PI) regulator is developed for the boost converter with CPL. The virtual damping based PBC enhances the system damping and PI regulator eliminates the steady-state error caused by the variation of load. On this basis, a secondary voltage control (SVC) featuring in simplicity and weak dependence on communication is introduced to remove the errors of current distribution. Finally, a RT-LAB-based hardware in the loop (HIL) experimental platform is established and the experimental results verify the effectiveness of the proposed hybrid coordination control strategy.