Control Strategy of Improved VSGs with Power Angle Compensation and Reactive Power Support Capability for Hybrid Multi-terminal HVDC Systems

Given shortcomings of traditional virtual synchronous generator (VSG) strategies, such as poor power angle stability and the inability to coordinate reactive power control with fault ride-through requirements, this paper proposes an improved VSG (IVSG) scheme and applies it to a hybrid three-terminal LCC/VSC-HVDC network to improve the system's fault blocking capability. First, this paper presents power angle compensation factor β in active power control loop, which is physically equivalent to increasing electromagnetic power when the system fails, thereby suppressing power angle δ rise. Second, a reactive power self-adjusting controller is intended to compensate for voltage sag. Meanwhile, maximum reference reactive power is derived by evaluating the relationship between suppression of fault current and reactive power, which is coupled with self-adjusting reactive power to obtain the reference value of reactive power loop. Finally, a large number of simulation experiments based on Matlab/Simulink are conducted to compare the proposed method with traditional VSG strategy to highlight its advantages.