Aiming at the problems of reduced inertia level

damping

and frequency support capability caused by large-scale new energy connected to the grid through modular multilevel converter-based high voltage direct current (MMC-HVDC) transmission

a multi-time scale frequency regulation control strategy based on dead zone to realize the coordination of MMC-HVDC systems and synchronous generators is proposed

which realizes the wide-area coordination and complementarity of multi-type frequency regulation resources. In terms of inertia support

the coupling relationship between receiving-end AC grid frequency

DC voltage

and the number of modular multilevel converter (MMC) sub-modules is established. A control method for inertia support of sending-end and receiving-end MMC based on local DC voltage and frequency information is proposed respectively

whichbroadens the operating range of capacitor voltage by extending the control dimensionality. Control parameters and the adaptive recovery strategy are designed based on system safety constraints to achieve the maximum utilization of energy margin in the MMC-HVDC system. In terms of damping regulation and primary frequency regulation

an adaptive control strategy is proposed for frequency support of sending-end MMC considering frequency regulation dead zone to meet the frequency support demand under various disturbance scenarios. The dead zone is designed based on the adjustment margin of synchronous generator in receiving-end system

endowing it with the adaptive switching capability between damping regulation and primary frequency regulation. The proposed strategy realizes wide-area coordinated control of frequency support in MMC-HVDC interconnected grid under different disturbance scenarios

and reduces the range of disturbance impact while ensuring the frequency stability of the system. Finally

based on the real-time digital simulation platform

the simulation model of the MMC-HVDC system is built to verify the effectiveness of the proposed control strategy.