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

Abstract

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.