Coordinated fault‐ride‐through strategy for doubly‐fed induction generators with enhanced reactive and active power support

Abstract

With the fault ride through (FRT) requirement of grid codes, wind generators must stay connected and provide the reactive and active power support during and after the grid faults. The doubly fed induction generators (DFIGs) usually employ an active rotor crowbar to ride-through the faults. The solution works well to protect the DFIG itself, but it has shortcomings in the power support. In the paper, a coordinated FRT control strategy is investigated to improve the power support capability of the DFIGs under the fault conditions. In this strategy, a seamless switch is designed to resume the power control mode after the short-term crowbar interruption. Additional compensation terms are inserted into the converter's control loops to relieve the side-effect of rotor transient current. The coordinated control of dcchopper circuit and rotor-side converters is proposed to keep the dc-link voltage within its acceptable range. Moreover, a novel voltage limiter is designed with consideration of the conflicting effect of rotor transient current, converter's rating constraints and desired power goals. Compared with the conventional crowbar-based strategies, the proposed strategy can fully utilise the DFIG's potential to generate reactive and active power effectively. These performances have been demonstrated through the simulation and experimental tests.

Short-Circuit Current Calculation and Harmonic Characteristic Analysis for a Doubly-Fed Induction Generator Wind Turbine under Converter Control

“…After the occurrence of the three-phase short-circuit fault on the terminal of the wind turbine, GSC is mainly responsible for maintaining the stability of DC bus voltage. Meanwhile, GSC is also able to generate a small amount of reactive power independently to support the grid voltage [25]. To realize the goal of fast regulation, the outer loop of reactive power is open and the reference value of the inner current loop is given directly after the fault.…”

“…Equation (25) reveals that the a-phase stator short-circuit current contains a steady-state fundamental component, a fundamental attenuation component, a DC attenuation component, and an oscillating attenuation component with ω ci as the period and time constant. It can be concluded from Table 1 that the transient attenuation component of the stator current mainly contains a DC attenuation component, while fundamental attenuation and ω ci relevant components account for a small proportion and attenuate quickly.…”

Fault Ride Through Technique for DFIG-based Wind Turbines Under Grid Three-phase Faults

“…When a fault is detected, the switching control engages the crowbar by short circuiting the generator rotor through its resistor (Rcrw). With the crowbar protection circuit, the power converter (RSC) is temporarily blocked, and the generator excitation control is usually lost [9,18,19]. In this mode of operation, the DFIG is transformed into the conventional induction machine, i.e., squirrel-cage induction generator (SCIG) with very high slip value (s).…”

“…The SCIG temporary operating characteristics are noticed by its behavior of drawing reactive currents from the grid via the generator stator to support generator magnetization process. The result of such scenario is a further decrease of network voltage at the PCC which in turn may lead to a failure complying with the grid-code requirements [9,19]. Fig.…”

Design of advanced artificial intelligence protection technique based on low voltage ride-through grid code for large-scale wind farm generators: a case study in Egypt

“…Many researchers have focused their attentions on the LVRT capabilities enhancement for DFIG wind turbines [24][25][26][27][28]. The improvement of fault ride through capability for wind turbine driven by DFIG is introduced in [29][30][31][32][33][34]. The design of DFIG active and reactive power control using energy storage system and static synchronous compensator is introduced [35].…”