In order to solve the problem of Shenzhen power grid voltage stability during the construction of Guangdong target grid and improve Shenzhen power grid stability under serious AC fault, the mechanism of Shenzhen power grid voltage stability is analyzed with the operation of Guangzhou and Dongguan back-to-back HVDC projects, the proposed adaptive switching voltage dependent current order limiter (VDCOL) strategy is applied to Xindong UHVDC and Xing'an DC, and finally its effectiveness is verified by RTDS simulation. Shenzhen power grid voltage stability is caused by both the lack of dynamic reactive power support and the rapid increase of reactive power consumption demand of HVDC systems after AC fault. The adaptive switching VDCOL strategy can correctly change the optimized parameters in case of serious AC faults at inverter side, and has a great impact on the power recovery characteristics of Xindong DC, but the delay of power recovery characteristics will not cause Yunnan power grid frequency out of limit. Implementation of adaptive switching VDCOL strategy to both Xindong DC and Xing'an DC can well eliminate Shenzhen voltage stability problem of serious AC faults, and the effectiveness of the proposed adaptive switching VDCOL strategy is fully verified.