Dynamic performance evaluation of hybrid multi-terminal HVAC/HVDC grid

The multi-terminal DC grid can be integrated to the existing meshed AC grid system to provide back-up in case of transmission line failure and enhance power transmission capacity and flexibility in existing ac grids. In addition to that, Power oscillations can also be damped effectively through modulation of both active and reactive power of a voltage source converter (VSC) based multi-terminal DC grid. In this paper, the ability of the multi-terminal DC grid to effectively damp the power oscillation in an interconnected AC grid has been investigated. Also, VSC based MTDC transmission systems are vulnerable to DC side fault. This paper demonstrates a control method of a dc fault resilient voltage source converter that has ultra-fast electronic isolation capability following dc fault which can be protected against dc fault. To verify the control structure, the dynamic performance of the integrated multi-terminal DC grid in a reduced order three-bus AC equivalent power system is investigated through hardware-in-the-loop testing. Controller hardware-in-the-loop simulation of the embedded multi-terminal DC grid in a meshed AC power system is performed by Real Time Digital Simulator (RTDS), and RTDS results are presented to verify the control structure.