Active and Reactive Power Optimization of VSG-IIDG during Fault Ride Through Considering Inrush Fault Current Constraints

As the penetration rate of renewable energy continues to rise, grid connection standards now require renewable energy systems to achieve fault ride-through during grid faults and provide voltage support. However, voltage support occupies converter capacity, reducing its available active power output and threatening system frequency in high renewable ratio systems. The virtual synchronous machine (VSGs) can regulate voltage and frequency similar to conventional generators, although inrush currents pose a threat to inverter safety. This paper proposes an optimization strategy for active and reactive power during grid faults for VSGs. Both voltage and frequency support are considered for VSGs. The rate of change of frequency (RoCoF) and inrush current constraints are constructed and incorporated into the optimal model to guarantee the security of the frequency and prevent the damage of the converter. Case studies validate the effectiveness of the proposed model.