Theory and Method of Distributed Virtual Zero-Sequence Synchronous Generators for Cooperative Fault Arc Suppression in Active Distribution Networks

Single-line ground (SLG) faults in distribution networks may cause hazards such as fire, electric shock, and overvoltage. Active power electronic converters (PECs) can suppress the fault current and fault voltage. However, the application is limited due to the low suppression rate and high cost of additional power electronic equipment. This article proposes to employ distributed power electronics of active distribution networks to cooperatively eliminate fault. In this method, PECs are modeled as virtual zero-sequence synchronous generators (VZSGs), and the line-to-ground impedances (LGIs) are modeled as zero-sequence loads. A theory of distributed VZSGs supplying zero-sequence loads, which can realize fault current and voltage suppression, is proposed. The required supply current can be adaptively allocated between these VZSGs based on their reserve capacity ratio, and their supply current can be dynamically corrected based on the droop coefficients of VZSGs when the LGI changes. The fault current and voltage suppression rate is improved because the adaptive calculation of the VZSGs reference value combines the voltage- and current-based suppression methods. Simulation study and experimental validation results demonstrate that not only is the proposed method cost-effective, but it also efficiently improves the fault current and voltage suppression rate for various fault conditions.