Research on Double-Fed Induction Generator Low Voltage Ride Through Based on Double Braking Resistors Using Fuzzy Control

Abstract

The stator side of a double-fed induction generator (DFIG) is directly connected to the grid, so the DFIG is sensitive to a voltage drop caused by power system faults. A double resistors braking method based on fuzzy control is proposed to improve the performance of low-voltage ride through (LVRT) in this paper. Based on the mathematical model of DFIG, it analyzes the function of a series dynamical braking resistor (SDBR) theoretically. The series impedance value of the SDBR is determined by the variation of the rotor's open circuit voltage, the voltage and current of the stator and the rotor, and also the heat capacity of the SDBR. In order to improve the LVRT capability of a DFIG under different fault grads, a double series resistors braking mode is presented. Through adopting a fuzzy control strategy, double series resistor switching is implemented. With the example system, the correctness and validity of the proposed method is verified.Energies 2018, 11, 1155 2 of 16 sequence current compensation strategy can smooth the electromagnetic torque and reactive power during steady-state faults [9,10]. And the optimization of the control strategy is complex in the period of unsymmetrical faults [11][12][13]. On the other hand, hardware solutions have also been proposed. A DFIG with a crowbar circuit is a very common solution for LVRT [14,15], but this solution is confined to the rotor side, such as limiting DC capacitor voltage and rotor current. A STATCOM can improve the LVRT performance of a wind farm [16], and it is often used in collaboration with crowbar circuits. The SDBR in [17] could improve the LVRT capacity of a DFIG, and the bypass switching control mode uses the method introduced in [18]. They realized the switching function of the SDBR when the fault occurred or removed, but it could not change the switching state according to the degree of failure. The switching strategy of different SDBRs and the effect under different power factors are current research topics [19]. The effective position of the SDBR in the DFIG structure was investigated using different types of switching signals in [20,21], but they have no specific research on the SBDR controller.In this paper, a double resistors braking method based on fuzzy control is proposed, which is based on the system characteristics of a DFIG at different voltage drop depths. The double resistance switching mode of an SDBR is also designed. The series resistance values are selected by the open circuit voltage and the resistor's heat capacity. In order to improve the LVRT performance of the DFIG, the fuzzy control mode is used to realize double resistance switching.Compared with existing LVRT devices, the contributions of the proposed method can be described as:(1) There are few studies on the value of series resistance. In addition to the stator and rotor voltage and current, the open circuit voltage and the heat capacity of the brake resistance are considered in this paper, and the range of the braking resistance is designed.(2) The proposed double resista...

Low voltage and high voltage ride‐through technologies for doubly fed induction generator system: Comprehensive review and future trends

“…In the literature [24–46], different auxiliary protection devices have been used to supplement the LVRT requirements for the DFIG system, which will be explained in the following paragraph of the paper.…”

“…Different controllers have been proposed for SDBR to optimise the series resistance of the SDBR. Recently, [37] proposed the double braking resistors using fuzzy control to improve the DFIG performance under LVRT. An alternative hardware‐based solution called stator‐series passive resistive hardware (SSPRH) is recently proposed in [38].…”

A Dynamic Multi-Cell FCL to Improve the Fault Ride through Capability of DFIG-Based Wind Farms

“…These latter may lead to high transient over-currents in the rotor circuit and over-voltage in the DC link capacitor [3]. This problem can either be mitigated using software [4][5][6] or hardware [7][8][9][10][11][12][13][14][15][16][17][18][19][20] approaches. The software-type solutions are based on modifications of the DFIG converters, especially the rotor side converter (RSC).…”

“…The above-mentioned problems can be overcome using hardware approaches [3]. These latter encompass (1) shunt flexible ac transmission systems (FACTS) controllers which include STATCOM devices [7]; (2) series hardware schemes, which include dynamic voltage restorers (DVR) [8], unified inter-phase power controllers (UIPC) [9], and series braking resistors (SBR) [10]; (3) energy storage systems (ESS) [11]; and (4) fault current limiters (FCLs) [12][13][14][15][16][17][18][19][20].…”

Effects of Voltage Sags on the Doubly Fed induction Generator using PI Controllers

“…In recent years, using of the wind energy for generating electricity is growing fast because it is an important source of renewable energy [1]. With increasing penetration level of wind energy into the network, wind turbine should remain connected to the grid to maintain the reliability during various grid fault scenarios based on grid codes' requirement [2].…”