A grid interface current control strategy for DC microgrids

In this paper, a grid interface current control strategy is presented for a DC microgrid, which aims to reduce the disturbance from PV generation and the load variation to the main grid without a grid interface converter. The grid interface current is directly controlled by a battery DC-DC converter within the DC microgrid. Based on a comprehensive analysis of the battery DC-DC converter and interface current control, the control system has been mathematically modelled. This enabled two transfer functions to be derived that reflect the dynamic response of the inductor current to the duty cycle variation (inner loop), and the dynamic response of the grid interface current to the inductor current variation (outer loop). Experimental study has been done to assess the effectiveness of the proposed control strategy. The experimental results indicate that the proposed control strategy has a good performance to control the grid interface current without an interface converter, regardless the variations of both PV and the load conditions.