Three-Phase Steady-State Models for a Distributed Generator Interfaced via a Current-Controlled Voltage-Source Converter

Abstract

This paper proposes three-phase steady-state models for a distributed generator (DG) interfaced to a main system via a three-wire current-controlled voltage-source converter. In order to represent the DG in a realistic manner, the three major factors that determine the steady-state phase outputs under unbalanced operating conditions are considered: 1) the power control strategy; 2) output filter; and 3) voltage and current sensor positions. Based on these factors, the DGs are classified into various types. According to the position of the voltage sensor, two equivalent circuit models including an equivalent three-phase current source (ETCS) are proposed. For each type of DG, the output current of the ETCS is formulated as a function of the voltage of the ETCS-connected node, the filter impedances, and the active and reactive power references. To verify the accuracy of the proposed models, the results of the power flow incorporating them are compared with those obtained from the PSCAD simulation using detailed dynamic models of the DG.