An Adaptive Low-Voltage Ride-Through Method for Virtual Synchronous Generators During Asymmetrical Grid Faults

Existing low-voltage ride-through (LVRT) methods of virtual synchronous generators (VSGs) are facing the problem of inverter damage due to prolonged overcurrent caused by the delay in fault detection. Additionally, the newly updated grid codes (GCs) mandate that inverter-based resources (IBRs) should inject negative-sequence current during asymmetrical faults. To address this issue while complying with the new GCs, this article proposes an adaptive LVRT method. At the onset of the fault, the proposed method compensates for the voltage difference between the reference and feedback values of voltage control loop, while simultaneously adjusting the angle output of the active power loop based on the phase change of the point of connection (POC) voltage and the active power output of the VSG. Thus, it enables a seamless transition between normal and LVRT conditions. Furthermore, it complies with the new GCs and guarantees the maximum utilization of the phase current. The method offers two notable advantages. First, it can achieve fast fault current limitation without the need for fault detection. Second, it eliminates the necessity for parameter design, making it straightforward to implement. The simulation results in PSCAD confirm the effectiveness of the proposed method under different asymmetrical fault conditions.