变速恒频双馈风力发电机有功、无功解耦控制研究与实现

双馈发电机有功功率、无功功率解耦控制是变速恒频风力发电系统的关键技术,在分析双馈发电机有功功率、无功功率解耦控制规律的基础上,给出了基于定子磁场定向控制策略的实现方案,然后利用Matlab工具对该控制方案进行了仿真研究,最后设计和构造了基于TI公司MS320F2407DSP的变速恒频双馈风力发电机有功功率、无功功率解耦控制实验系统,仿真和实验结果表明该控制策略能够有效地实现双馈发电机功率的解耦控制,为兆瓦级变速恒频双馈风力发电机组励磁变换器的研制奠定了基础。     

无刷双馈风力发电机组的自抗扰功率解耦控制

对无刷双馈风力发电机组稳态运行时的功率分配关系进行了详细分析,在此基础上确定了最大风能捕获的控制策略.将自抗扰控制应用到无刷双馈电机有功功率与无功功率的解耦控制,将功率控制系统分解为有功功率子系统和无功功率子系统,从而建立了风力发电机组完整的功率控制模型.基于Matlab/Simulink的仿真结果表明无刷双馈风力发电机组自抗扰控制成功实现了有功功率与无功功率的解耦控制,不仅能够实现最大风能捕获,而且可以根据电网的实际需求调节机组无功功率的输出,验证了控制算法的有效性.     

基于模糊控制的无刷双馈发电机直接功率控制策略

为了对无刷双馈发电机的有功功率和无功功率进行实时有效控制,采用了直接功率控制策略。与矢量控制方法相比,直接功率控制不需要复杂的坐标变换,可简化控制系统,提高系统的响应速度。为克服传统的直接功率控制方法中无法根据功率、磁链的大小来快速准确地选择合适的电压矢量这一缺点,提出了基于模糊控制的无刷双馈发电机直接功率控制策略,采用了新型模糊控制器代替传统的有功功率和无功功率两点式Bang-Bang控制,根据功率误差的大小,实现了大误差大调节、小误差精调节的策略。文中采用转子速模型实现了有功功率和无功功率的解耦,因此可以对有功功率和无功功率进行独立控制,进而实现了对功率因数的控制。在Matlab/Simulink软件中建立仿真模型,仿真结果表明,基于模糊控制的直接功率控制策略不仅可以提高控制精度,还可以提高电机对功率指令的响应速度,保证运行的稳定性,证明了本文控制策略的有效性和正确性。     

滞环矢量控制在双馈风力发电机中的应用

滞环电流控制方法以其动态响应速度快,电路跟踪性能好的优点而获得了广泛的应用和发展。基于双馈发电机数学模型,采用定子磁场定向的矢量控制．转子侧选用改进型滞环电流控制,建立了有功功率、无功功率解耦的控制策略。利用PSCAD软件．建立了仿真控制模型并进行了仿真计算。仿真结果表明,该控制系统能有效地实现双馈发电机有功、无功功率的解耦,验证该控制方案的正确性和有效性。     

交流励磁发电机定子磁场定向的矢量控制研究

论述了交流励磁发电机基于定子磁场定向的控制原理,推导了发电机有功功率、无功功率与转子励磁电流的关系,搭建了交流励磁发电机双闭环控制模型,讨论了定子磁链幅值和位置的确定,进行了采用PID调节器双闭环控制的仿真研究,结果表明定子磁场定向的矢量控制原理能够实现对交流励磁发电机有功和无功功率的快速、解耦控制。     

基于逆系统内模算法的交流励磁发电机

在建立交流励磁发电机空间状态方程的基础上,运用逆系统方法将交流励磁发电机精确线性化成有功功率和无功功率两个一阶线性子系统,并运用内模控制算法对其进行优化以提高系统的稳定性。提出了交流励磁发电机的基于逆系统内模控制策略,并进行了仿真实验。仿真结果表明,该方法能够实现对发电输出功率的解耦控制,并具有更高的控制精确度和稳定性。     

超导储能系统提高风电场暂态稳定性研究

应用超导储能系统(SMES)对提高风电场的暂态稳定性进行了研究。在深入研究超导储能系统运行原理的基础上,建立了基于电压型换流器(VSC)的超导储能系统模型,实现了有功功率和无功功率的解耦控制,并提出了有功、无功功率综合控制策略。利用PSCAD/EMTDC软件进行了仿真计算,结果说明超导储能系统不但能够在风速波动时平滑风电场的功率输出,而且能够提高风电系统的暂态稳定性。     

UPFC非线性解耦控制

采用开关函数建模法建立了UPFC的数学模型,通过非线性变换提出一种UPFC的非线性解耦控制策略。为了验证UPFC及控制策略的有效性,用数字仿真软件包MATLAB建立仿真平台对UPFC的特性进行了仿真分析。仿真结果表明,提出的控制策略可以快速、准确地响应电力系统的需求,有效实现有功功率和无功功率的解耦控制。     

基于双环控制的双馈风力发电机组控制策略

在分析了双馈风力发电机组运行特性的基础上,提出一种基于双环控制的变换器控制策略。在转子侧,变换器采用定子磁链定向矢量控制技术,推导出了用转子有功电流和无功电流独立解耦控制有功功率和无功功率的策略,并实现了风能的最大跟踪;在电网侧,变换器采用电网电压定向矢量控制技术,构建了电流内环、电压外环的双闭环PI控制系统。利用PSCAD/EMTDC软件,构建了双馈风力发电机组仿真模型。仿真结果验证了所提控制策略的有效性和合理性     

基于MPPT运行模式的光伏发电系统低电压穿越无功控制策略

针对光伏发电系统通常以单位功率因数运行,造成故障时光伏并网逆变器一定视在功率浪费的现状,提出一种低电压穿越无功控制策略。分析光伏并网逆变器的有功、无功功率解耦控制和其无功功率输出极限,建立光伏逆变器无功功率输出与并网点电压跌落的关系,通过比较故障前光伏阵列发出有功功率与光伏逆变器允许输出最大有功功率,确定光伏发电系统在低电压穿越过程以最大功率模式运行或者以非最大功率模式运行。利用RTDS软件搭建仿真算例,验证该低电压穿越无功控制策略的可行性。     

无刷双馈风力发电机的自抗扰解耦控制

针对无刷双馈电机(BDFM)结构的复杂性、随环境的可改变性及传统的PID控制在BDFM中应用不理想等,提出了一种新型基于扩张观测器的非线性PID控制——自抗扰控制方法来实现对风力发电系统有功功率和无功功率的解耦控制。仿真结果证明了该方法的正确性和有效性,具有更强的鲁棒性和可实现性。     

An input‐output linearization–based control strategy for wind energy conversion system to enhance stability

This paper proposes a novel control strategy for doubly fed induction generator (DFIG)‐based wind energy conversion system to investigate the potential of enhancing the stability of wind energy transmission system, a synchronous generator weakly integrated to a power system with a DFIG‐based wind farm. The proposed approach uses state feedback to exactly linearize the nonlinear wind energy transmission system from control actions (active power and reactive power control order of DFIG) to selected outputs (power angle and voltage behind transient resistance of synchronous generator) at first. Then, on account of the linearized subsystem, the stability enhancement controller is designed based on linear quadratic regulator algorithm to contribute adequate damping characteristics to oscillations of the synchronous generator system under various operation points. The proposed control strategy successfully deals with the nonlinear behaviors exist from the inputs to outputs and improve the robustness with respect to the variation of system operation points. Furthermore, not only the rotor angle stability but also the voltage stability is enhanced by using the proposed control strategy. The simulation results carried on the studied system verify the effectiveness of the proposed control strategy of wind energy conversion system for system stability enhancement and the robustness against various system operation points.     

基于PSCAD的双馈感应发电机矢量控制研究

在各种风力发电系统方案中,双馈感应电机（DFIG）变速恒频风力发电系统以其独特的优点逐渐成为当今风力发电的主流。在分析双馈电机的数学模型及原理的基础上,建立了基于定子磁链定向矢量控制的双馈感应电机风力发电系统模型。运用目前国外广泛应用的电力系统计算机辅助设计软件PSCAD/EMTDC对该系统进行仿真研究,并分析风力发电机运行时的动态性能。仿真结果表明,该控制方式实现了定子端口有功功率和无功功率的解耦控制,具有良好的控制效果。     

Voltage and Frequency Controller for a Three-Phase Four-Wire Autonomous Wind Energy Conversion System

This paper deals with control of voltage and frequency of an autonomous wind energy conversion system (AWECS) based on capacitor-excited asynchronous generator and feeding three-phase four-wire loads. The proposed controller consists of three single-phase insulated gate bipolar junction transistor (IGBT)-based voltage source converters (VSCs) and a battery at dc link. These three single-phase VSCs are connected to each phase of the generator through three single-phase transformers. The proposed controller is having bidirectional flow capability of active and reactive powers by which it controls the system voltage and frequency with variation of consumer loads and the speed of the wind. VSCs along with transformer function as a voltage regulator, a harmonic eliminator, a load balancer, and a neutral current compensator while the battery is used to control the active power flow which, in turn, maintains the constant system frequency. The complete electromechanical system is modeled and simulated in the MATLAB using the Simulink and the power system blockset (PSB) toolboxes. The simulated results are presented to demonstrate the capability of the proposed controller as a voltage and frequency regulator, harmonic eliminator, load balancer, and neutral current compensator for different electrical (varying consumer loads) and mechanical (varying wind speed) dynamic conditions in an autonomous wind energy conversion system.     

基于功率解耦的微电网改进下垂控制策略

在中、低压微网中,线路存在较高阻感比,无法满足传统下垂控制的控制条件。对此,提出一种修正相角的改进下垂控制策略,通过将引入的转换矩阵用于功率变换中,构造出具有统一旋转角的下垂控制器,保证了系统在拥有高R/X值的线路下微源逆变器输出有功功率和无功功率的解耦。利用Matlab/Simulink仿真平台搭建了两台逆变器并联的微电网仿真模型,将线路参数与逆变器接入情况不同的多种仿真结果分别与基于虚拟阻抗改进下垂控制的仿真结果进行对比,结果表明,提出的改进下垂控制策略解决了系统输出功率耦合的问题,且实现了功率合理分配。     

电网故障条件下风储联合系统无功自适应控制

针对电网三相对称故障条件下风电场电压不稳定的问题,文章提出了一种基于神经元的风储联合系统无功功率自适应控制策略,该策略以风储联合系统公共耦合点(Point of Common Coupling,PCC)的电压和电流为控制器的输入,采用Hebb学习算法作为自适应律,以获得准确的无功补偿。通过动态调整控制器的参数,使储能系统协调风电达到自适应输出无功功率的效果,提高系统在电网故障下的电压稳定性和风电故障穿越能力。最后,利用Matlab/Simulink仿真验证了该控制策略的有效性和正确性,与常规PI控制策略相比,文章所提出的控制策略可使风储系统迅速提供无功功率,PCC点的电压得到明显上升。     

Modelling–based approach for digital control design for nonlinear WECS in the power system

The case has been established that the wind power plant must be treated as an integral part of the electric system, thereby constituting the wind energy conversion system. Recent advancement in size and technology of wind turbines requires sophisticated control systems to effectively optimize energy conversion and enhance grid integration. As a first step toward controller design, modelling has become a prerequisite. This paper explores controller design based on modelling the wind speed as a stochastic process, and the wind turbine as a multi‐mass system with a soft shaft linking the turbine with the doubly fed induction generator. A control strategy incorporating a linear quadratic Gaussian (LQG) that relies on state estimation for full‐state feedback is proposed to augment a linear controller for generator torque control. The control objectives are to reduce stresses on the drivetrain and to ensure operation geared toward optimal power conversion. This study focuses on above‐rated wind speeds, and the LQG's main purpose is to add damping to the drivetrain, thereby minimizing cyclic fatigue, while a pitch control mechanism prevents rotor overspeed, thereby maintaining rated power. Simulations show the efficacy of the proposed paradigm in meeting the control objectives. Copyright © 2009 John Wiley & Sons, Ltd.     

Multivariable control algorithm for laboratory experiments in wind energy conversion

Advanced experimentation with wind energy conversion systems is described. The real time multivariable control of a wind turbine is designed for investigation of theoretical concepts and their physical implementation. The control system includes a speed controller and a disturbance estimator for enhanced robustness of the control system. In order to provide students with deeper understanding of wind energy and energy extraction, a maximum power point tracking algorithm is developed and integrated into the control system. The multivariable control system is implemented in a small wind turbine laboratory system. A power electronic interface is based on two DC–DC converters: a buck converter for control of the speed and a boost converter controlling the load voltage. Experimental results demonstrate effectiveness of the multivariable control system for a wind turbine providing maximum power extraction. The experiment can be reconfigured for teaching various control concepts to both undergraduate and graduate students.     

Reactive power compensation and active filtering capability of WECS with DFIG without any over‐rating

This paper presents a novel approach for reactive power compensation and active filtering capability of a variable speed wind energy conversion system (WECS) with doubly fed induction generator (DFIG), without any over‐rating. First, the WECS is capable of capturing maximum wind power under fluctuating wind speed. Second, depending on the available wind power value versus nominal WECS power, power quality can be improved by compensating the reactive power and the grid harmonic currents, without any system over‐rating. The proposed rotor side converter (RSC) control manages the WECS function's priorities, between main active power generation and power quality management. To ensure high filtering performances, we used an improved harmonic isolator in the time domain, based on a selective pass band filter (SPBF) developed in our laboratory. Moreover, we took advantage of the high amplification effect of the rotor side‐controlled DFIG to compensate harmonic currents. Consequently, no over‐rating is necessary for the proposed additional active filtering capability. Simulation results for a 2 MW WECS with DFIG confirm the effectiveness and the performances of the proposed approach. Copyright © 2009 John Wiley & Sons, Ltd.