Fault analysis of converter interfaced generator embedded power system considering control mode switching

Converter interfaced generation (CIG) may switch into different control modes under different fault scenarios, which poses a significant challenge to the fault calculation of modern power systems. This paper first establishes a reduced fault analysis model of CIG considering control mode switching. By neglecting the fast dynamic processes of the converter controller, CIG with each control mode can be expressed by equality and inequality constraints. Then, an alternative iteration algorithm is proposed to determine the control mode of each grid‐tied converter after fault, which mainly contains the estimation and discrimination steps. In the estimation step, the voltage of the point of common coupling (PCC) and output current of CIG are obtained by simultaneously solving the equality constraints of CIG and the reduced network equation. In the discrimination step, the inequality constraints of CIG are utilized to judge and revise the control mode of each converter. With alternative execution of the estimation and discrimination steps, the fault network can be solved. Simulation studies based on PSCAD/EMTP validate that the proposed method has high accuracy in fault calculation of the CIG embedded system under various fault locations and fault resistances. This paper proposes a quasi‐static fault calculation method for the CIG embedded system considering control mode switching. CIGs with current limiting and LVRT control are expressed by a series of steady‐state equations corresponding to each mode and a switching rule that connects the switching between these modes. A mode‐discriminative algorithm is then proposed to solve the faulted system containing CIGs with unfixed control modes, which alternatively estimates the PCC voltage and output current of CIGs and modifies the control mode of CIGs based on the switching rule.