Multi‐Dimensional Stability Constrained Bi‐Level Topology Optimisation Method for HVDC Systems Embedded in Dense AC Grids

ABSTRACT The massive integration of renewable energy has imposed new challenges on traditional AC power networks, such as excessive short‐circuit currents, overload risks of N‐1 contingencies, and voltage/frequency instability. With the capabilities of electrical decoupling and flexible power flow control, embedded high‐voltage direct current (HVDC) systems have emerged as a key technology for enhancing the security and stability of dense AC grids. Focusing on the topological optimisation of embedded HVDC systems, this paper first analyses the coupling characteristics between HVDC systems and intensive AC grids from four technical dimensions. Then, integrating multi‐dimensional stability constraints — power flow under steady‐state and N‐1 contingency, short‐circuit current, voltage and transient stability, a multi‐dimensional stability constrained bi‐level topology optimisation model is proposed for HVDC systems embedded in dense AC grids, which incorporates upper‐level economic optimisation and lower‐level stability correction using penalty functions, addressing the limitations of traditional planning in multi‐objective coordination and computational efficiency for large‐scale grids. Finally, simulation calculations are conducted on a typical 500 kV dense AC transmission network in a provincial region. The results demonstrate the feasibility and scientific validity of the optimisation method in suppressing short‐circuit currents, optimising power flow distribution and enhancing the grid stability margin.