The application relates to a
hybrid cascade HVDC
power transmission project power
transfer capacity optimization control method and
system, which comprises the following steps: calculating a steady-state modulation ratio, judging whether the
operation mode of a flexible
DC converter is single-pole half-
voltage operation according to the steady-state modulation ratio, and selecting the maximum modulation ratio according to the judgment result; judging whether the steady-state modulation ratio is greater than the maximum modulation ratio, raising the converter gear position if yes, and maintaining the original gear position if no; calculating the modulation ratio of a
DC control system, judging whether to inject the
third harmonic according to the modulation ratio of the
DC control system; when a fault occurs, the maximum power under the
voltage reduction capability limitation of the flexible
DC converter is obtained, and the power of the
DC control system after the fault is calculated according to the maximum power; the power instruction value is updated according to the power of the DC
control system after the fault, the flexible
DC converter adjusts the
DC voltage according to the power instruction value, and the adjustment result is fed back to an
automatic control device to execute generator
tripping. The application can improve the power
transfer capacity of the
hybrid cascade HVDC
power transmission project, and improve the reliability of system operation.