Short-Circuit Model for Type-IV Wind Turbine Generators With Decoupled Sequence Control

Abstract

The power system planning and protection studies are becoming more challenging due to the rapid increase in penetration levels of converter-interfaced renewables. Type-IV wind turbine generators (WTGs) and photovoltaic panels (PVs) are interfaced to the grid through a full-scale converter (FSC), and their short-circuit current contributions are mainly designated by the converter control and associated current limits. This paper proposes a new phasor domain modeling approach for the wind parks (WPs) with Type-IV WTGs using the concept of controlbased equivalent circuits. The proposed model precisely represents the detailed electromagnetic transient type (EMT-type) model in steady state and is able to account for the fault-ridethrough (FRT) function of the WTG control as well as its specific decoupled sequence control scheme in addition to the traditional coupled control scheme. Although the collector grid and WTGs inside the WP are represented with their aggregated models, the overall reactive power control structure of the WP is preserved by taking the central wind park controller (WPC) into account. The accuracy of the proposed model is validated through detailed EMT simulations.

Impact of Inverter-Based Resources on Negative Sequence Quantities-Based Protection Elements

“…As the focus of this paper is the impact of IBRs on performances of negative sequence quantities-based protection elements, only the negative-sequence fault current characteristics of IBRs are analyzed and compared with SGs. Reader should refer to [12], [13], [26] and [28] for the detailed analysis of fault current contributions of IBRs and associated phasor domain models that can be used in short-circuit packages.…”

A simplified model of Type‐4 wind turbine for short‐circuit currents simulation analysis

“…The timedomain model is suitable for analyzing the EMT characteristics of short-circuit currents under different voltage sags of single WTG terminal, but not suitable for the EMT analysis of power system connecting with large-scale WPPs [9][10][11]. The phasordomain model can accurately calculate the steady-state shortcircuit currents of the power system connecting with large-scale WPPs, supporting the protection setting calculation [12][13][14], but the transient characteristics of short-circuit currents cannot be well reflected by the phasor-domain model which is mainly based on electrical quantities in steady-state power frequency. Therefore, EMT simulation analysis is the main approach to study characteristics of power system connected to large-scale WPPs under fault.…”

Impact of Inverter Based Resources on System Protection

“…This power electronic interface is a fundamental physical difference between IBRs and traditional synchronous generators (SGs) which results in different fault current characteristics [1,2] and requires fundamental changes in the conventional computation methodology of short circuit currents [3][4][5]. The fault current of a SG is of high amplitude, uncontrolled, and predominantly defined by the electrical parameters of the source and the impedance of short-circuit path; by contrast, the fault current of an inverter-based resource (IBR) typically has a low amplitude and is tightly controlled through fast switching of power electronics devices dependent upon manufacturer specific and often proprietary IBR control scheme.…”

“…Further, I2 is typically partially or entirely suppressed depending on the inverter control [1]. Figure 1a shows that the I2 of a Type IV IBR is close to zero due to the nature of the traditional inverter coupled control scheme [3]. This lack of I2 may lead to protection misoperation problems, and hence grid codes have recently added requirements for IBR I2 injection during unbalanced faults.…”