Transient Stability Enhancement and Fault Current Limiting Control Strategy for VSG and SVG Hybrid System

ABSTRACT Renewable energy stations are often equipped with virtual synchronous generators (VSG) for frequency and voltage support, but the transient instability of VSGs and the weak overcurrent capacity constrain the safe and stable operation of Renewable energy stations. A large number of existing studies have only considered the parameter design and control strategy improvement of VSG itself, which requires high energy storage capacity and control capability of VSG and does not make full use of the existing resources of the Renewable energy station; therefore, this paper considers the synergistic control of static var generator (SVG) and VSG. Firstly, the feasibility of co‐regulation between SVG and VSG is analysed from the transient characteristics and current characteristics of VSG. It is proposed that SVG can enhance the transient stability of VSG and reduce the VSG fault current under grid voltage dips. Based on the above analysis, considering the hybrid system's low voltage ride through (LVRT) and fault current limiting requirements, the critical clearing time (CCT) is used to portray the operating range of the hybrid system during faults, and the cooperative control strategy of SVG and VSG during faults is proposed. Finally, in order to solve the current mutation problem in the fault recovery phase, the power angle tracking control is introduced in the VSG active‐frequency loop. In summary, the transient stability and current limiting of the hybrid system during the whole process of the fault are realised, and the above theory is verified by simulation and experiment.