Protection control system for power converter of alternating-current and direct-current hybrid power grid and control method of system

The invention discloses a protection control system for a power converter of an alternating-current and direct-current hybrid power grid, and aims to solve the problem in control on an output behavior of an access converter when faults occur on the alternating-current power grid side. The protection control system is suitable for unbalanced alternating-current power grids. The influence of the negative sequence component of the power grid on the system has to be reasonably controlled as the safety of the converter is endangered and the service life of the converter is shortened due to the problems of unbalanced or non-sinusoidal three-phase current, relatively large voltage ripple on the direct-current side, power fluctuation and the like of the system caused by the negative sequence component of the power grid during fault occurrence of the alternating-current power grid. The positive and negative sequence content of an alternating-current grid-side current reference is reasonably adjusted by adjusting parametric variables according to flexible positive and negative sequence control strategies in a d-q synchronous coordinate system, so that the waveform quality of the grid-side current and the instantaneous active power and instantaneous reactive power of the system can be reasonably controlled and the protection control of the converter can be realized.