This paper develops voltage stability analysis of ac/dc systems using static and modal indexes. New indexes treatment is proposed to provide more information on requirements for specific network strengths in terms of voltage stability constituting a means to prevent potential issues of high voltage dc transmission system (HVdc), connected to weak ac nodes. The indexes are per unitized and compared for different short circuit ratios (SCR), in a modified IEEE 14 buses network, with a HVdc system connected to its weakest bus. The approach can assist as much for planning as for on-line monitoring of voltage stability in power systems including ac/dc nodes.