Fault Modeling and Analysis of Grid-connected Inverters with Decoupled Sequence Control

With an increasing number of inverter-interfaced generators (IIGs), the power system is undergoing massive shifts toward the power electronic dominated power system. Such paradigm change poses significant challenges to existing fault analysis theory and the protection system, as a result of the disparate short-circuit response. Given this, the fault analysis theory needs to be further investigated and expanded to address issues arising from the new grid paradigm. Under this context, this article proposes an analytic model for short-circuit analysis of IIGs with decoupled sequence control (DSC) based on the Laplace transform. With the proposed model, the analytic fault current expression can be obtained and the fault characteristic can be analyzed. Compared with existing studies, the proposed model distinguishes itself by three key merits. First, the proposed model takes into account the delay feature of the controller, which enables transient analysis. Second, the model covers the impact of controller parameters and low voltage ride through strategy in detail which is missing in the most existing literature. Third, the proposed model provides a theoretical foundation of IIGs with DSC in the fault analysis, which makes it more applicable for the protection setup issues in reality. In the end, the correctness and feasibility of the proposed model is validated by the simulation and experimental result.