With the development of AC/DC power system

much attention is focused on the voltage stability of the receiving system of the high-power and long-distance DC transmission system. In order to analyze the interconnected AC/DC system

the inverter and the compensation capacitor are referred to as the inverter station. By virtue of the trait that the power of DC transmission system can be described as a function of the receiving line voltage

new forms of the characteristics of the reactive power supplied by the receiving system and the reactive power absorbed by the inverter station are proposed

revealing that the mismatch of the reactive power is the root cause of voltage instability. Considering the control strategy of the DC transmission line

a dominance index is proposed on the basis of Thevenin equivalent parameters

which can be used to compare the stability level of various strategies. Test results prove its conciseness and effectiveness.