In order to reduce the risks concerning system safety and stability brought about by AC/DC interactions, Guangdong Power Grid has taken such measures as adjusting grid structure, deploying dynamic reactive power compensation, and optimizing grid operation mode, etc. In this paper, system stability analysis is carried out before and after refurbishment of conventional HVDCs feeding into the Pearl River Delta region. The results show that VSC-based refurbishment of conventional HVDC can improve the stability of the system to a certain extent, but the improvements are not significant. From the perspective of system stability improvement only, the necessity for VSC-based HVDC refurbishment is not justified. This paper can help to fully appreciate the potential of VSC-based HVDC refurbishment to improve system stability, and provide a good research foundation to further explore the necessity and system scheme of VSC-based refurbishment of conventional HVDCs in Pearl River Delta and Yangtze River Delta power grids. At the same time, this paper provides valuable reference to solve the problems arising from AC/DC system interactions in load center grids with multiple DC infeed.