The voltage source converter-high voltage direct current (VSC-HVDC) has become critical for integrating large-scale offshore wind power. To ensure frequency stability in coastal receiving end power grid

the equivalent inertia assessment of offshore wind farms integrated HVDC system (OWF-HVDC) is crucial. However

under grid frequency disturbances

the transient support power of OWFs and VSC-HVDC is complexly coupled

and the inter-port transfer mechanism remains unclear

posing challenges to inertia assessment. This paper reveals the synchronous-like characteristics of the frequency regulation support process and the incremental coupling mechanism of transient support power by analogizing the inertial response and primary frequency regulation of synchronous machines. Based on this

a synchronous-like model of OWF-HVDC is established from the perspective of internal voltage equivalence

enabling accurate assessment of partitioned and total inertia. Additionally

based on the assessment results

the influencing factors and patterns of system equivalent inertia are clarified

and a frequency regulation parameters optimization method using particle swarm optimization is proposed

fully exploring the system's inertia support potential. Finally

the proposed method is validated through MATLAB/Simulink simulations.