A Novel Voltage-Current Dual-Drop Control Method for Shipboard DC Micro-Grid With Energy Storage Systems

Abstract

The DC micro-grid system, as a new generation of shipboard DC micro-grid system, has the advantages of integrating renewable energy and enhancing the stability and reliability of the power system. For the energy distribution problem of energy storage battery charging and discharging in shipboard DC micro-grid, P-V voltage droop control and SOC-I current droop control methods are proposed. The SOC-I control method incorporated in the battery charging and discharging process can effectively balance the SOC and output power of the energy storage battery. For the on/off-grid process of shipboard power converter and onshore power, the control method of voltage and current control mode switching is proposed, which realizes the fast response of output voltage in off-grid mode and the controllable transfer of power interacting with the grid in grid-connected mode. Secondly, a pre-synchronized control based on amplitude and frequency modulation achieves a flexible on-grid/off-grid connection of the power converter. A method based on the parallel connection of multiple reduced-order generalized integrator (ROGI) is introduced to achieve suppression of output voltage unbalance as well as 5th and 7th harmonics. Finally, the efficiency and correctness of the proposed control method has been successfully evaluated an level 750KVA shipboard micro-grid system.INDEX TERMS Energy storage converter, harmonic suppression, on/off-grid control, shipboard DC microgrid system, voltage-current dual-droop control