Analysis of voltage instability problems in two- and multiterminal HVDC systems connected to weak AC systems

Abstract In this paper, the conditions of voltage collapse, feasibility of operation, and reactive power compensator requirement to provide voltage support are established analytically for a two-terminal back-to-back HVDC system. For a multiterminal HVDC system, the voltage stability factor for each converter as well as the sensitivity of the AC bus voltage with respect to changes in DC power are also presented in this paper. Simple formulas for each converter operation under different control modes are derived.