Mitigating distribution power loss of dc microgrids with DC electric springs

DC microgrids fed with substantial intermittent renewable energy sources face the immediate problem of power imbalance and the subsequent dc bus voltage fluctuation problem (that can easily breach power system standards). It has recently been demonstrated that dc electric springs (DCES), when connected with series non-critical loads, are capable of stabilizing the voltage of local nodes and improving the power quality of dc microgrids without large energy storage. In this paper, two centralized model predictive control (CMPC) schemes with: 1) non-adaptive weighting factors and 2) adaptive weighting factors are proposed to extend the existing functions of the DCES in the microgrid. The control schemes coordinate the DCES to mitigate the distribution power loss in the dc microgrids, while simultaneously providing their original function of dc bus voltage regulation. Using the DCES model that was previously validated with experiments, simulations based on MATLAB/Simulink platform are conducted to validate the control schemes. The results show that with the proposed CMPC schemes, the DCES are capable of eliminating the bus voltage offsets as well as reducing the distribution power loss of the dc microgrid.