Synchronous condensers (SCs) are generally used at the receiving-end stations of ultra-high-voltage direct current (UHVDC) transmission systems due to their strong reactive power support and flexible regulation of reactive power according to the interconnected grids operating conditions. In this paper

different starting control schemes of a SC integrated power grid are investigated providing four main contributions: 1) The principle of reactive power support of the SC on the interconnected power grid is analytically studied

providing the establishment of mathematical models. 2) Four different starting control schemes are developed for the initialization and SC integration

i.e. in Scheme 1

a preset initial falling speed is directly utilized without initialization; in Scheme 2

a black start sequential control approach with a static frequency converter (SFC) is proposed; in Scheme 3

PI/PD/PID controllers are respectively applied for the excitation device at the speed-falling stage; in Scheme 4

a pre-insertion approach of an energy absorption component with R/L/RL is utilized to suppress the surges at the SC integration instant. 3) The dynamic behaviors of four different starting schemes at specific operating stages are evaluated. 4) The success rate of SC integration is analyzed to evaluate starting control performance. Performance of the SC interconnected system with four different starting control schemes is evaluated in the time-domain simulation environment PSCAD/EMTDC™. The results prove the superiority of the proposed starting control approach in Scheme 4.