Abstract：In DC microgrid, the inconsistency of DC-DC converter parameters and line impedance reduces the current sharing accuracy of droop control. Meanwhile, droop control inevitably causes DC bus voltage drop. To improve the current sharing performance among DC-DC converters, a droop control method based on virtual frequency is proposed by simulating the frequency droop control mechanism in AC microgrid. In the controller, a virtual AC variable whose frequency is proportional to the output current is constructed. The virtual frequency of each converter is shared by low bandwidth communication and the average value is calculated. The average frequency and virtual AC variable are further used to generate virtual reactive power to adjust the voltage setting point of the converter and coordinate the output current of each converter. On the premise of not causing bus voltage drop, the accuracy of load current distribution among converters is improved and the communication pressure is reduced. The stability of virtual frequency droop control is analyzed using small signal model. Finally, simulation and experiment based on Starsim and dSPACE verify the validity of the method.
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2021, Vol. 36 
