VSC-HVDC decoupling control strategy for enhancing system inertia and damping

Aming at the frequency stability problem caused by the low inertia characteristics of electronic power system, this paper proposes a self-synchronization decoupling control strategy for active support of system inertia in flexible DC power transmission system from the perspective of exploiting the regulation potential of power transmission link. By analyzing the available energy of the inertia support of the flexible DC system, the feasibility of using its energy margin to improve the level of the receiving-end grid's inertia is quantitatively analyzed. By analogy with the rotor motion equation of the synchronous generator, a self-synchronization control strategy of the converter station taking into account the energy margin of each energy storage element in the flexible DC system is proposed, which can actively support the receiving-end grid inertia while realizing self-synchronization without phase-locked loop. On this basis, considering the influence of DC voltage safety constraint on capacitor energy margin utilization, the decoupling control strategy and parameter design method of DC voltage and submodule capacitor voltage of flexible DC system are proposed, through the adaptive adjustment module input quantity and capacitance voltage reference, implement flexible DC system make full use of the energy storage element energy margin, The recovery strategy and start-up criterion are designed to effectively improve the level of inertia and frequency stability of the receiving power grid.