HVDC grids stability enhancement through the integration of battery energy storage systems

In high voltage direct current (HVDC) grids, the reference values of power controllers are normally adjusted based on the DC-link voltage as the DC voltage is regulated by the droop controllers. As a matter of fact, except for the DC slack bus, there is a trade-off between power-sharing and voltage regulation of all the remaining HVDC buses. The main issue with this control strategy is that in case of contingencies, significant voltage and power oscillations throughout HVDC grids can be expected. To address such issues, the integration of a battery energy storage system into HVDC grids through a multi-port DC/DC power converter is investigated in this paper. The DC/DC converter used in this paper consists of three ports: (1) two ports are connected in cascade with the intended DC transmission line, formerly named cascaded power flow controller, and (2) the third port is for the integration of the battery energy storage system to form a multi-functional device. Therefore, the proposed framework can potentially achieve small-signal stability enhancement and regulate/adjust the power throughout the HVDC grids.