Optimization Scheme of Fault Ride through Strategy for Improving Transient Stability and DC Voltage Security of Power Grid

The impact on the grid transient stability under the action of coordinated control strategy is unclear for the multi-terminal voltage source converter-based high voltage direct current transmission (VSC-HVDC) system receiving converter stations connected to different locations of the same AC grid. The existing optimization scheme of single converter station fault ride-through strategy to improve the transient stability of the grid increases the change of DC voltage of the VCS-HVDC system and reduces the stability of DC voltage. How to take advantage of multi-terminal VSC-HVDC to improve the grid transient stability and DC voltage security needs to be studied. Based on the Zhangbei VSC-HVDC project, the external power and key definite values of the receiving converter station under the AC-DC fault ride-through strategy are studied. The external power output is related to the voltage dependent current order limiter (VDCOL) inflection point current value and the DC voltage margin droop control proportionality factor. The effects of VDCOL inflection point current value and DC voltage margin droop control proportionality factor on transient stability and DC voltage stability are investigated, and the optimization scheme of fault ride-through strategy to improve transient stability and DC voltage stability is proposed. The effectiveness of the scheme is verified in the Zhangbei VSC-HVDC grid-connected system, which provides a reference for the optimization of the fault ride-through strategy of the actual project.