A novel control strategy of a variable-speed doubly-fed-induction-generator-based wind energy conversion system

This paper aims to address the issue of control of a variable-speed wind turbine based on doubly-fed induction generators. In this work,an effort is made to extract the maximum efficiency from a doubly-fed induction generator-based variable-speed wind turbine by controlling the rotor current. In the first step, a maximum power point tracking technique is used to extract the maximum power from theturbine. Then a stator-flux-oriented vector control strategy is employed to control the rotor-side current. Subsequently, a grid voltagevector-oriented control strategy is used to control the grid-side system of the grid-connected generator. Considering the nonlinearityand parameter uncertainty of the system, an active disturbance rejection controller with a sliding-mode-based extended-state observeris developed for the above-mentioned control strategies. Furthermore, the stability of the controller is tested and the performance of thecontroller is compared with the classical proportional-integral controller based on disturbance rejection, robustness and tracking capability in a highly non-linear wind speed variation scenario. Modelling, control and comparison are conducted in the MATLAB®/Simulink®environment. Finally, a real-time hardware set-up is presented using the dSPACE ds-1104 R&D processing board to validate the controlscheme. From the result of the experiments, it is seen that the proposed controller takes 10-15 control cycles to settle to its steady-statevalues, depending on the control loop, whereas the conventional proportional-integral controller takes 60-75 control cycles. As a result,the settling time for the proposed control scheme is shorter than that of the proportional-integral controller.

Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions

This paper proposes an analysis and a direct power control (DPC) design of a wind turbine driven doubly-fed induction generator (DFIG) under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions.

A Long-Range Generalized Predictive Control Algorithm for a DFIG Based Wind Energy System

This paper presents a new Long-range generalized predictive controller in the synchronous reference frame for a wind energy system doubly-fed induction generator based. This controller uses the state space equations that consider the rotor current and voltage as state and control variables, to execute the predictive control action. Therefore, the model of the plant must be transformed into two discrete transference functions, by means of an auto-regressive moving average model, in order to attain a discrete and decoupled controller, which makes it possible to treat it as two independent single-input single-output systems instead of a magnetic coupled multiple-input multiple-output system. For achieving that, a direct power control strategy is used, based on the past and future rotor currents and voltages estimation. The algorithm evaluates the rotor current predictors for a defined prediction horizon and computes the new rotor voltages that must be injected to controlling the stator active and reactive powers. To evaluate the controller performance, some simulations were made using Matlab/Simulink. Experimental tests were carried out with a small-scale prototype assuming normal operating conditions with constant and variable wind speed profiles. Finally, some conclusions respect to the dynamic performance of this new controller are summarized.

New energy power generation-wind power generation

This paper introduced the status quo of wind power and wind power generation technology. Focusing on the introduction of wind power generating system ibrational self-consistent field（VSCF）, program implementation included Alternating Current （AC）-Direct Current （DC）-AC conversion system, magnetic field modulation generator system, doubly-fed generator system etc. Among these, doubly-fed generator system is the trend. Where to build the wind farm is very important, so a perfect site is needed. Wind power generation will have a bright future. As long as the wind power can be linked to the grid in large scale.

Simulation of grid tracking control of power system connection and maximum power brushless doubly-fed generator in point wind

In this paper, based on the analysis of the mathematical model in a common synchronous reference frame of the brushless doubly-fed generator （BDFG）, the grid connection strategy and maximum energy extraction control were both analyzed. Besides, the transient simula- tion of no-load model and generation model of the BDFG have been developed on the MATLAB/Simulink platform. The test results during cutting-in grid confirmed the good dynamic performance of grid synchronization and effective power control approach for the BDFG-based variable speed wind turbines.

Fault-tolerant control of an open-winding brushless doublyfed wind power generator system with dual three-level converter

To improve the fault redundancy capability for the high reliability requirement of a brushless doubly-fed generation system applied to large offshore wind farms,the control winding of a brushless doubly-fed reluctance generator is designed as an open-winding structure.Consequently,the two ends of the control winding are connected via dual three-phase converters for the emerging open-winding structure.Therefore,a novel fault-tolerant control strategy based on the direct power control scheme is brought to focus in this paper.Based on the direct power control(DPC)strategy,the post-fault voltage vector selection method is explained in detail according to the fault types of the dual converters.The fault-tolerant control strategy proposed enables the open-winding brushless doubly-fed reluctance generator(BDFRG)system to operate normally in one,two,or three switches fault of the converter,simultaneously achieving power tracking control.The presented results verify the feasibility and validity of the scheme proposed.

Dynamic modelling and robust current control of wind-turbine driven DFIG during external AC voltage dip

Doubly-Fed Induction Generator （DFIG）, with vector control applied, is widely used in Variable-Speed Constant- Frequency （VSCF） wind energy generation system and shows good performance in maximum wind energy capture. But in two traditional vector control schemes, the equivalent stator magnetizing current is considered invariant in order to simplify the rotor current inner-loop controller. The two schemes can perform very well when the grid is in normal condition. However, when grid disturbance such as grid voltage dip or swell fault occurs, the control performance worsens, the rotor over current occurs and the Fault Ride-Through （FRT） capability of the DFIG wind energy generation system gets seriously deteriorated. An accurate DFIG model was used to deeply investigate the deficiency of the traditional vector control. The improved control schemes of two typical traditional vector control schemes used in DFIG were proposed, and simulation study of the proposed and traditional control schemes, with robust rotor current control using Internal Model Control （IMC） method, was carded out. The validity of the proposed modified schemes to control the rotor current and to improve the FRT capability of the DFIG wind energy generation system was proved by the comparison study.

Application of fuzzy logic control algorithm as stator power controller of a grid-connected doubly-fed induction generator

This paper discusses the power outputs control of a grid-connected doubly-fed induction generator （DFIG） for a wind power generation systems. The DFIG structure control has a six diode rectifier and a PWM IGBT converter in order to control the power outputs of the DFIG driven by wind turbine. So, to supply commercially the electrical power to the grid without any problems related to power quality, the active and reactive powers （Ps, Qs） at the stator side of the DFIG are strictly controlled at a required level, which, in this paper, is realized with an optimized fuzzy logic controller based on the grid flux oriented control, which gives an optimal operation of the DFIG in sub-synchronous region, and the control of the stator power flow with the possibility of keeping stator power factor at a unity.

Doubly-fed induction generator drive based WECS using fuzzy logic controller

The purpose of this paper is to improve the control performance of the variable speed, constant frequency doubly-fed induction generator in the wind turbine generation system by using fuzzy logic controllers. The control of the rotor-side converter is realized by stator flux oriented control, whereas the control of the grid-side converter is performed by a control strategy based on grid voltage orientation to maintain the DC-link voltage stability. An intelligent fuzzy inference system is proposed as an alternative of the conventional proportional and integral （PI） controller to overcome any disturbance, such as fast wind speed variation, short grid voltage fault, parameter variations and so on. Five fuzzy logic controllers are used in the rotor side converter （RSC） for maximum power point tracking （MPPT） algorithm, active and reactive power control loops, and another two fuzzy logic controllers for direct and quadratic rotor currents components control loops. The performances have been tested on 1.5 MW doubly-fed induction generator （DFIG） in a Matlab/Simulink software environment.

VSCF双馈型风力发电机并网方法的原理分析

为有效减小发电机并网冲击电流,从而实现风力发电机安全并网,在此详细分析了空载并网方法的原理,并根据该原理设计一套完整的并网系统,最后利用PSIM进行仿真研究的同时借助背靠背试验平台对整个并网过程进行了实验研究。实验结果验证了该并网控制方法原理的正确性和有效性。

VSCF双馈风电机组并网控制的研究

新疆地区地广人稀,风力资源丰富。近几年风力发电技术越来越成熟,在新疆建立大型风力发电厂是一个利国惠民的好项目。单独的风力发电机组的稳定性、可靠性、安全性都比较低。鉴于VSCF双馈风力发电机组具有柔性连接等特点,可考虑在新疆采用VSCF双馈风电机组并网运行。基于双馈感应发电机在国内外的发展状况,研究了VSCF双馈风力发电机组的原理、数学模型等内容,分析了风电机组并网的分段分层控制方法,同时,利用Matlab仿真平台进行了相应的仿真,验证了该分段分层方法的可行性和有效性。

正十二边形矢量集的永磁同步发电机磁链预测控制

针对磁链预测问题,基于广义比例积分观测器原理设计磁链观测器,并基于此实现具有误差校正的磁链预测,提升磁链预测精度;针对备选电压矢量较少的问题,构造一种均匀对称分布的正十二边形矢量集,不仅增加可选矢量数量,而且矢量集的正十二边形分布特征有利于特定次开关谐波的消除。基于以上核心算法,最终为风电系统中PMSG设计FCS-MPFC方案,并通过实验验证所提方案具有较强的参数鲁棒性和较高的转矩控制精度。

适用于缓解双馈感应发电机电磁转矩脉动的新型矢量控制

针对电网电压谐波含量要求,提出一种基于矢量控制的定子电流谐波抑制拓扑结构,重点解决双馈异步发电机DFIG(doubly-fed induction generator)电磁转矩的脉动问题。所提控制器即谐波矢量控制HVC(harmonic vector control),能够抑制电流谐波。电网电压5、7、11、13次谐波分量,由于定子串联阻抗低,导致发电机电流谐波分量为同次,且相对振幅较高,因此,HVC已被测试用于此类电流谐波成分的控制,不需要谐波滤波器来估计定子电流的谐波含量。最后,经过仿真和实验分析,证明了所提控制的适用性和有效性。研究结果表明,该控制器的稳态误差接近于0,此外,HVC可作为DFIG中的谐波滤波器,并可根据应用要求选择谐波。

双馈风力发电系统双矢量模型预测电流控制

针对双馈风力发电系统传统模型预测电流控制中电流波动和转矩脉动较大的问题,提出一种双矢量模型预测电流控制策略。在一个采样周期中进行两次电压矢量选择,将第一阶段的最优矢量作为第二阶段的初值,结合候选电压矢量作用时间,计算最小代价函数,使候选电压矢量范围扩大,电压矢量选择更加精确。仿真结果表明:所提出的策略可以实现对双馈风力发电系统的有效控制,与矢量控制和传统模型预测电流控制相比,该策略有效降低了电流波动和电磁转矩脉动。

Performance of PI controller for control of active and reactive power in DFIG operating in a grid-connected variable speed wind energy conversion system

Due to several factors, wind energy becomes an essential type of electricity generation. The share of this type of energy in the network is becoming increasingly important. The objective of this work is to present the modeling and control strategy of a grid connected wind power generation scheme using a doubly fed induction generator （DFIG） driven by the rotor. This paper is to present the complete modeling and simulation of a wind turbine driven DFIG in the second mode of operating （the wind turbine pitch control is deactivated）. It will introduce the vector control, which makes it possible to control independently the active and reactive power exchanged between the stator of the generator and the grid, based on vector control concept （with stator flux or voltage orientation） with classical PI controllers. Various simula- tion tests are conducted to observe the system behavior and evaluate the performance of the control for some optimization criteria （energy efficiency and the robustness of the control）. It is also interesting to play on the quality of electric power by controlling the reactive power exchanged with the grid, which will facilitate making a local correction of power factor.

直驱永磁风力发电系统的建模仿真研究

通过分析直驱永磁同步风力发电系统各组成部分,建立各部分相应的数学模型。针对风机特征,研究了风力发电机组的最大风能追踪控制技术和变桨距控制系统,实现风机功率的平滑输出。通过在Simulink环境下建立系统仿真模型,结合仿真结果验证了该控制策略的有效性。

电网电压骤降故障下双馈风力发电机建模与控制

双馈感应发电机(DFIG)在变速恒频风力发电中得到广泛应用,对DFIG采用矢量控制可使风电系统实现最大风能追踪和有功、无功解耦调节,从而获得优良的发电运行性能。但在传统的矢量控制方式中,通常认为是无穷大理想电网,忽略了定子励磁电流变化的动态过程,从而得到简化的DFIG数学模型,并以此作为电流内环控制器的设计依据。这种控制器在电网正常的情况下可使系统获得优良的动静态特性,但当电网出现故障时,其控制性能将恶化。为了提高电网电压故障情况下DFIG不间断运行能力,文中以DFIG的精确数学模型为依据,针对传统的2种矢量控制方式的不足,提出了改进的控制方案,并对改进前后电网电压骤降情况下DFIG的动态过程进行了仿真对比,结果表明改进方案可以有效控制转子电流,保护转子励磁变频器,提高DFIG变速恒频风电系统在电网故障下的不间断运行能力,是并网DFIG风力发电机的一种有效、实用的控制策略。

交流励磁变速恒频风力发电系统控制策略的仿真研究

介绍了交流励磁变速恒频(VariableSpeedConstantFrequency,VSCF)风力发电系统运行的基本原理及发电机的定子磁链定向矢量控制技术。在此基础上,以Matlab/Simulink为工具,建立了系统仿真模型,进行了发电机空载运行、并网、有功、无功功率独立调节、最大风能捕获运行等工况的仿真研究,仿真结果证明理论分析正确,对系统的实验研究具有一定的理论指导意义。

矩阵式变换器交流励磁的变速恒频风力发电系统研究

结合矩阵式变换器、交流励磁发电技术和矢量控制的优点,建立了矩阵式变换器供电的变速恒频交流励磁风力发电机定子磁场定向的矢量变换控制系统模型,该系统能够在不同风速下最大程度地获得风能,高质量发电,并实现有功、无功功率的独立调节。仿真结果展现了系统的优良特性,验证了该方案的正确性和有效性。

基于最佳功率给定的最大风能追踪控制策略

采用双馈异步发电机(DFIG)的交流励磁发电技术不但能在变速情况下实现恒频发电,更能 通过对DFIG输出有功、无功功率的解耦控制,实现最大风能的追踪。为能在不检测风速的条件下 实现最大风能的捕获,提出了基于参考功率优化计算模型的最大风能追踪控制策略,其本质是通过 控制DFIG的输出有功功率来间接控制风电机组转速以追踪风力机最佳功率曲线。在此基础上, 建立了基于矢量变换控制技术的完整的变速恒频(VSCF)风力发电控制系统。仿真和实验结果验 证了该最大风能追踪控制策略的可行性、有功与无功解耦控制的有效性及工程应用的现实性。