Domain of stability of AC/DC power systems

The domain of stability (DOS) is the sub-state space within which, if the states vary due to a fault, the post-fault system converges to a stable equilibrium state (SES). There is no generic method to find the DOS of higher order dynamic systems. The cell mapping technique (CMT) can be used to find the DOS of mainly two-dimensional systems. If the system has several DOSs, the CMT is capable of finding each DOS. We modify the present CMT to find the DOSs of higher order dynamic systems. The transient energy function (TEF) can be used to find the DOS of power systems. While the TEF for AC-only systems has been in existence for several years, the authors recently derived a TEF for integrated AC/DC systems with explicit representation of HVDC dynamics. The DOS of power systems has also only been found for AC-only systems. The paper presents the DOS of higher order AC/DC systems with HVDC controls. First, the DOS for a single-machine infinite-bus AC/DC system that is equipped with a DC damping power controller is found using CMT and TEF. Then, the DOS for a 12-bus AC/DC multi-machine system that is equipped with detailed rectifier and inverter controllers is found using CMT and TEF. The resulting DOSs are compared.