Abstract

This paper presents a fast coordinated control scheme of the rotor side converter (RSC), the Direct Current (DC) chopper and the grid side converter (GSC) of doubly fed induction generator (DFIG) wind turbine generators (WTGs) to improve the low voltage ride through (LVRT) and high voltage ride through (HVRT) capability of the DFIG WTGs. The characteristics of DFIG WTGs under voltage sags and swells were studied focusing on the DFIG WTG stator flux and rotor voltages during the transient periods of grid voltage changes. The protection schemes of the rotor crowbar circuit and the DC chopper circuit were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were verified by time domain simulations using Matlab-Simulink.

Highlights

  • The doubly fed induction generator (DFIG) is one of the most popular types of generators used in large scale wind turbines with several advantages compared to other wind turbine generators (WTGs) [1].because the stator windings are directly connected to the grid, DFIG WTGs are quite sensitive to grid disturbances

  • It is shown that the Direct Current (DC) link voltage can be kept below the threshold by the combination of the crowbar scheme, and the enhanced rotor side converter (RSC) and grid side converter (GSC) control and the DFIG WTG can successfully ride through the low voltage conditions and the high voltage conditions

  • This paper analyses the transient response of the DFIG WTG with consideration of the phase-angel jump under both grid voltage sag and swell conditions

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Summary

Introduction

The doubly fed induction generator (DFIG) is one of the most popular types of generators used in large scale wind turbines with several advantages compared to other wind turbine generators (WTGs) [1]. The transient behaviour of DFIG WTGs under grid fault conditions has been comprehensively investigated by analysing the transient electromagnetic force characteristic of stator flux [8,9,10,11,12], and the oscillating response of the DC link voltage was studied in [13,14]. In addition to the hardware solutions, many control strategies have been developed for improving the transient response performance of DFIG WTGs under grid voltage sags [20,21,22]. This paper aims to further analyse the transient response of DFIG WTGs with consideration of phase-angel jumps under both grid voltage sags and swells.

Analysis of Grid Fault Conditions
Symmetrical Voltage Sag Fault
Voltage Swell Condition
DFIG Model and GSC Model
Behavior of the DFIG WTG under Voltage Sag Condition
Behavior of the DFIG WTG under Voltage Swell Conditions
Protection Schemes of the DFIG WTG for Fault Ride Through
Active Crowbar Protection Scheme
DC Chopper Control Scheme
Enhanced Control of RSC and GSC for LVRT and HVRT
Enhanced RSC Control
Enhanced GSC Control
Case Studies
Conclusions

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