Review on FRT solutions for improving transient stability in DFIG‐WTs

Abstract

Fault-ride-through (FRT) is an imperative capability in wind turbines (WTs) to ensure grid security and transient stability. However, doubly fed induction generator-based WTs (DFIG-WTs) are susceptible to disturbances in grid voltage, and therefore require supplementary protection to ensure nominal operation. The recent amendments in grid code requirements to ensure FRT capability has compelled this study of various FRT solutions. Therefore, for improving FRT capability in pre-installed WTs, re-configuration using external retrofit-based solutions is more suitable and generally adapted. The most relevant external solutions based on retrofitting available are classified as (a) protection circuit and storage-based methods and (b) flexible alternating current transmission system-based reactive power injection methods. However, for new DFIG-WT installations, internal control modification of rotor-side converter (RSC) and grid-side converter (GSC) controls are generally preferred. The solutions based on modifications in RSC and GSC control of DFIG-WT are classified as (a) traditional control techniques and (b) advanced control techniques. This study ensures to curate and compare the FRT solutions available based on external retrofitting-based solutions and internal control modifications. Also, the future trends in FRT augmentation of DFIG-WTs are discussed in this study.

Low-Voltage Ride-Through Techniques in DFIG-Based Wind Turbines: A Review

“…In recent years, renewable energy generation made great progress worldwide to meet the challenge of drastic climate changes and increasing energy demands [1]. Among various renewable energy sources, wind energy is the most rapidly growing one around the world [2,3].…”

“…RSC is used to control the active power and reactive power delivered and to achieve the maximum power capture. GSC is used to control the active power and reactive power delivered, as well as maintain the direct current (DC)-link voltage [1,7]. In the past, the penetration level of wind energy was extremely small compared with conventional generation systems [9].…”

“…With emphasis on the LVRT capability of DFIG-WTs, many countries updated their grid code requirements (GCRs). The German LVRT grid criteria are mostly preferred over other GCRs in practical applications [1]; they require that (1) wind turbines shall remain connected to grid for at least 0.65 s after fault inception, (2) the permitted fault voltage is 15% of its rated voltage, and (3) the voltage should recover to 90% of its rated voltage within 3 s after the clearance of faults. According to the GCR for LVRT, wind turbines should have the ability to ensure continuous operation during voltage dips, and the voltage should be kept above the curve shown in Figure 2.…”

Analysis of Doubly Fed Induction Generators Participating in Continuous Frequency Regulation with Different Wind Speeds Considering Regulation Power Constraints

“…At present, DFIG is the trunk stream model of a large-scale wind farm [4]. In the traditional control mode, the DFIG operates at the maximum power point tracking (MPPT) mode, with only downward regulation capability (regulating the positive frequency difference), and cannot regulate in two directions.…”

Study of Inertia and Damping Characteristics of Doubly Fed Induction Generators and Improved Additional Frequency Control Strategy

“…Because of the high power generation efficiency, small capacity of the converter and decoupling control of active power and reactive power, doubly-fed induction generator (DFIG) has become the main model of large-scale wind farms. DFIGs have become a dominant wind turbine (WT) technology, therefore, this paper takes DFIGs as the research object [5,6]. However, the rotor speed is decoupled from the system frequency when DFIGs adopt the converter control mode [7][8][9], which reduces the equivalent inertia of the system.…”