Driven by the high penetration of renewable energy and the increasing deployment of power electronic equipment

converters with grid-forming capability have attracted considerable attention because of their ability to support AC grids. The controlled current source converter (CCSC) has prominent advantages in high-voltage direct-current (HVDC) transmission

such as high power density

low conduction losses

and controllable power factor. However

its grid-forming operation capability has not been sufficiently investigated. This paper proposes a grid-forming control strategy for CCSC in HVDC transmission systems. The proposed strategy enables the CCSC to rapidly and autonomously establish its internal electromotive force and maintain stable operation under the dual constraints of a low short-circuit ratio (SCR) and a low switching frequency. The controller parameters are designed based on a small-signal model. Finally

simulations are conducted to investigate the operating characteristics of the GFM-CCSC when supplying power to an islanded system and when connected to AC grids with different SCRs. The results show that the GFM-CCSC can achieve fast dynamic response at a switching frequency of 150 Hz

maintain the AC voltage and frequency at their rated values

and realize stable power output. It can also adapt to power fluctuations in islanded operation and variations in the SCR of the AC grid.