'Institute of Electrical and Electronics Engineers (IEEE)'
Doi
Abstract
The virtual synchronous control is regarded as an effective solution for grid-tied converters to operate under weak grid conditions and provide inertia support. However, for those grid-tied converters which control the DC voltage, e.g., the receiving end converter (REC) in modular multilevel converter based high-voltage direct-current (MMC-HVDC) transmission systems with wind farm integration, the application of virtual synchronous control is difficult due to the cascade control loops. The dynamic performance of DC voltage control may also be degraded. To address these issues, a novel grid-forming control strategy with real-time inertia support and fast DC voltage control is proposed for the REC. The cascade control loops of the virtual synchronous control are simplified by utilizing the internal energy stored in sub-module capacitors to emulate synchronous generator rotors. Moreover, the DC voltage is decoupled with the submodule capacitors voltage, thus being robust to sudden power change. Simulation results in PSCAD/EMTDC show that the proposed control realizes fast inertia support and desired dynamic control of the DC voltage, especially in weak grid operation
