Torsional torque suppression of decentralized generators using H∞ observer

The output power fluctuations of renewable energy plants such as wind turbine generators and photovoltaic systems cause frequency deviations and terminal voltage fluctuations. Furthermore, these power fluctuations also affect the turbine shaft of diesel generator and gas-turbine generators which are usually the main electric power systems in isolated islands. This paper presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of the torsional torque is technically difficult and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using a H_∞ observer. The simulation results validate the effectiveness of the proposed control system.     

电网短路故障下双馈风电机组传动链扭振疲劳可靠性分析

双馈风电机组电气故障扰动引起的电磁转矩波动易造成轴系传动链扭振疲劳,有必要研究电网短路故障对机组传动链扭振疲劳可靠性的影响.首先建立考虑关键部件柔性的传动链有限元模型,通过模态分析获取传动扭振模态.其次基于集中质量法,建立机电耦合模型,以电网短路故障为扰动因素,仿真分析电网短路故障下电磁转矩动态响应.最后将电网短路故障...     

Comparison of the response of doubly fed and fixed-speed induction generator wind turbines to changes in network frequency

Synchronous and fixed-speed induction generators release the kinetic energy of their rotating mass when the power system frequency is reduced. In the case of doubly fed induction generator (DFIG)-based wind turbines, their control system operates to apply a restraining torque to the rotor according to a predetermined curve with respect to the rotor speed. This control system is not based on the power system frequency and there is negligible contribution to the inertia of the power system. A DFIG control system was modified to introduce inertia response to the DFIG wind turbine. Simulations were used to show that with the proposed control system, the DFIG wind turbine can supply considerably greater kinetic energy than a fixed-speed wind turbine.     

Qualitative performance assessment of semiconductor switching device,converter and generator candidates for 10 MW offshore wind turbine generators

This paper investigates the possibilities of viable power electronics converters, semiconductor switching devices and electric machines for 10 MW variable‐speed wind turbine generators. The maximum rated power of existing wind turbine configurations is in the range of 6 MW. The proposed alternatives are compared against several technical and economical factors, and their advantages over the present wind turbines are highlighted. A comprehensive performance comparison of modern power semiconductor devices, their electrical characteristics and the key differentiators among them are presented. The power electronics converters considered include all commercially available multilevel voltage source and current source converters as well as the opportunities offered by power electronics building block‐based design. The factors used for the comparison include the converter power range, capacitor voltage balancing, common mode voltage and current, electromagnetic interference emissions, fault ride‐through capability, reliability, footprint, harmonic performance, efficiency and losses, component count, risk of torsional vibration by the harmonics and inter‐harmonics, complexity, ease of back‐to‐back operation and filtering requirements. For the electric machines, this study concentrates on high‐temperature superconducting machines, multi‐phase induction machines and permanent magnet synchronous machines. These machines are compared against existing wind generator technologies in terms of their power range, torque density, efficiency, fault ride‐through capability, reliability, footprint, harmonic performance, ease of fault detection, excitation control, noise and vibration signature, oscillation damping, gearbox requirement, cost and the size of the associated converter. Copyright © 2010 John Wiley & Sons, Ltd.     

小型风力发电机组优化控制策略与实验研究

提出一种小型风力发电机组功率的优化控制策略.根据选定的300 W/24 V永磁发电机,使用Wilson叶片设计计算模型,应用MATLAB语言设计了300 W风机叶片;并针对现有风机控制系统中将控制器的设计与叶片、电机的匹配特性彼此孤立、分离的现象,设计出与风力发电机的电机、叶片相互匹配的控制器.在风洞试验中测试了样机在8、10 、12 、15 m/s等风速一定条件下,功率随系统电压的变化规律,当降低系统电压时,风机输出功率会一直下降,在此过程中并没有出现功率增加的现象,也就充分证明了工作在峰前区域的风力发电机,当风速大于额定风速时,控制系统可以通过减小接入系统的负载电阻值来控制其功率.这对研究小型风力发电系统的可控性、可靠性和耐久性有一定的指导意义和实用价值.     

A hybrid power system using alternative energy facilities in isolated island

A hybrid power system uses many wind turbine generators in isolated small islands. The output power of wind turbine generators is mostly fluctuating and has an effect on system frequency. In order to solve this problem, we propose a new power system using renewable energy in small, isolated islands. The system can supply high-quality power using an aqua electrolyzer, fuel cell, renewable energy, and diesel generator. The generated hydrogen by an aqua electrolyzer is used as fuel for a fuel cell. The simulation results are given to demonstrate the availability of the proposed system in this paper.     

Transient and dynamic control of a variable speed wind turbine with synchronous generator

In this article, a controller for dynamic and transient control of a variable speed wind turbine with a full‐scale converter‐connected high‐speed synchronous generator is presented. First, the phenomenon of drive train oscillations in wind turbines with full‐scale converter‐connected generators is discussed. Based on this discussion, a controller is presented that dampens these oscillations without impacting on the power that the wind turbine injects into the grid. Since wind turbines are increasingly demanded to take over power system stabilizing and control tasks, the presented wind turbine design is further enhanced to support the grid in transient grid events. A controller is designed that allows the wind turbine to ride through transient grid faults. Since such faults often cause power system oscillations, another controller is added that enables the turbine to participate in the damping of such oscillations. It is concluded that the controllers presented keep the wind turbine stable under any operating conditions, and that they are capable of adding substantial damping to the power system. Copyright © 2007 John Wiley & Sons, Ltd.     

Strategies to Smooth Wind Power Fluctuations of Wind Turbine Generator

This paper shows that the capability of voltage-source converters (VSCs) to control the real power output of wind turbine generators (WTGs) can be applied to smooth power fluctuations due to wind turbulence. The paper calls attention to instability that can arise from: 1) the wind turbine itself and 2) the doubly fed induction generator (DFIG). The paper presents G_P/V(s) to characterize the dynamic behavior of WTGs.     

Parameterization of a synchronous generator to represent a doubly fed induction generator with chopper protection for fault studies

This paper addresses the representation of the wound rotor asynchronous generators by an equivalent synchronous generator, valid for short circuit current calculations. Modern wind power plants are required and designed to ride through faults in the network, subjected to fault clearing. Accurate knowledge of the wind turbine short circuit current contribution is needed for component sizing and protection relay settings during faults within the wind power plant collector system or in the external networks. When studying fault currents and protection settings for wind power installations, the industry standard is to employ software packages where generators are represented by their equivalent synchronous generator operational impedances. Hence, it is of importance to represent non‐synchronous wind generators by an equivalent synchronous generator. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Parameterization of a synchronous generator to represent a full‐scale converter generator for fault studies

This paper addresses the representation of the full‐scale converter generator technology by equivalent operational impedances valid for short‐circuit current calculations. Modern wind power plants are required and designed to ride through faults in the network, subjected to fault clearing. Accurate knowledge of the wind turbine short‐circuit current contribution is needed for component sizing and protection relay settings during faults within the wind power plant collector system or in the external networks. The industry standard employs software packages where generators are represented by their equivalent synchronous generator operational impedances, calculated according to standards or for electromagnetic simulation models, when studying fault currents and protection settings for wind power plant installations. Hence, it is of importance to represent non‐synchronous wind generators also by an equivalent synchronous generator. The effectiveness of the proposed method has been validated by simulation and site measurements. Copyright © 2013 John Wiley & Sons, Ltd.     

Experimental study of a small wind turbine for low‐ and medium‐wind regimes

The results of an experimental assessment of a small prototype battery charging wind turbine designed for low‐ and medium‐wind regimes are presented. The turbine is based on a newly designed axial flow permanent magnet synchronous generator and a three‐bladed rotor with variable twist and taper blades. Overspeed control is performed by a furling mechanism. The turbine has the unique feature of being capable of operating at either 12, 24 or 48 V system voltage, requiring no load control in any case. In the 48 V configuration, the system is capable of providing 2 kWh day^?1 for an average wind speed as low as 3.5 m s^?1 and an air density of 85% of the standard pressure and temperature value. The experimental assessment has been conducted under field conditions with the turbine mounted on a 20 m guy‐wired tubular tower. The experimental power curves are shown to be in good agreement with a detailed aerodynamical and electromechanical model of the turbine for non‐furling conditions and for wind speeds above the theoretical cut‐in speed. In the case of the rapidly spinning load configurations, a finite power production at wind speeds below the theoretical cut‐in speed can be observed, which can be explained in terms of inertia effects. During the measurement campaigns with high loads, we were able to observe bifurcations of the power curve, which can be explained in terms of instabilities arising in situations of transition from attached to separated flow. A full experimental C_p(λ)‐curve has been constructed by operating the turbine under different load conditions and the findings are in good agreement with a variable Reynolds‐number blade‐element momentum model. The three proposed system configurations have been found to operate with a high aerodynamic efficiency with typical values of the power coefficient in the 0.40–0.45 range. Copyright © 2009 John Wiley & Sons, Ltd.     

Linear models‐based LPV modelling and control for wind turbines

The non‐linear behaviour of wind turbines demands control strategies that guarantee the robustness of the closed‐loop system. Linear parameter‐varying (LPV) controllers adapt their dynamics to the system operating points, and the robustness of the closed loop is guaranteed in the controller design process. An LPV collective pitch controller has been developed within this work to regulate the generator speed in the above rated power production control zone. The performance of this LPV controller has been compared with two baseline control strategies previously designed, on the basis of classical gain scheduling methods and linear time‐invariant robust H_∞ controllers. The synthesis of the LPV controller is based on the solution of a linear matrix inequalities system, proposed in a mixed‐sensitivity control scenario where not only weight functions are used but also an LPV model of the wind turbine is necessary. As a contribution, the LPV model used is derived from a family of linear models extracted from the linearization process of the wind turbine non‐linear model. The offshore wind turbine of 5 MW defined in the Upwind European project is the used reference non‐linear model, and it has been modelled using the GH Bladed 4.0 software package. The designed LPV controller has been validated in GH Bladed, and an exhaustive analysis has been carried out to calculate fatigue load reductions on wind turbine components, as well as to analyse the load mitigation in some extreme cases. Copyright © 2014 John Wiley & Sons, Ltd.     

基于间接转矩控制的风电机组功率测控平台

首先分析了风电系统能量转换原理,得出最大功率控制的理论依据。在最大功率控制理论的基础上,采用脉宽调制技术控制发电机输出平均电压,从而以间接控制发电机转矩的方式实现最大功率追踪。研究工作根据理论分析,搭建了风力发电机组功率测控平台,平台具有测试和根据测试进行控制两大功能,为风电机组的设计和研发提供了试验手段。试验证明,该文所采取的控制原理方法正确,搭建的试验平台能够实现预期目标。     

海上石油平台风燃互补发电孤立小电网稳定性研究及应用

"渤海海上风力发电示范工程"于2007年初批准正式立项,建设国内第一台海上风力发电机组,容量为1.5MW。由于风能具有间歇性和随机性的特点,为了实现绥中36-1CEP平台孤立电网与风电机组互补发电,并且保证该电网的平稳运行,进行了海上平台孤立小电网的稳定性研究。海上石油平台电网允许的正常频率波动范围为±0.25Hz,频率偏差报警为±0.5Hz,电网频率将随着透平发电机组输出有功功率的变化而波动。当风力发电机组在额定输出有功功率跳闸退出电网时,对电网频率的影响最大;当风力发电机组在额定风速启动并网时,对电网频率的影响较大。在特定的风燃互补孤立小电网中,采用电网负荷频率调节方程,可以计算风力发电机组容量与电网总负荷之比和频率波动的关系。海上平台风燃互补发电孤立小电网稳定运行的条件为风力发电机组的容量与平台电网总容量的比值小于10%。在满足风力发电机组引起平台电网最大频率波动范围为±0.25Hz的条件下,额定有功功率为1.5MW的风力发电机组,可并入最低总有功功率为15MW的电网。将稳定性研究结论应用于渤海风力发电示范项目,保证了示范工程的顺利进行,实现了国内第一台海上风力发电机组与生产平台并网发电的稳定运行。     

基于转矩极限的改进风电机组虚拟惯量控制策略

为解决大规模风电并网带来的系统频率稳定性降低问题,风电机组通过虚拟惯量控制可为系统提供短期频率支撑,然而惯性响应期间风电机组转速收敛缓慢,导致一部分转子动能被无故浪费;转速恢复阶段的有功突变易造成频率二次跌落。为此,提出基于转矩极限的改进风电机组虚拟惯量控制策略,实现在释放较少动能的前提下提供与传统策略相同的频率响应服务;并在频率步入准稳态时,借助时变功率函数开始转速恢复,实现转速快速恢复的同时缓解二次频率跌落。基于EMTP-RV仿真软件搭建包含风电场的电力系统模型,验证了所提策略的有效性。     

Development of a novel wind turbine simulator for wind energy conversion systems using an inverter-controlled induction motor

A wind turbine simulator for wind energy conversion systems has been developed with a view to design, evaluate, and test of actual wind turbine drive trains including generators, transmissions, power-electronic converters and controllers. The simulator consists of a 10-hp induction motor (IM) which drives a generator and is driven by a 10-kW variable speed drive inverter and real-time control software. In this simulator, a microcontroller, a PC interfaced to LAB Windows I/O board, and an IGBT inverter-controlled induction motor are used instead of a real wind turbine to supply shaft torque. A control program based on C language is developed that obtains wind profiles and, by using turbine characteristics and rotation speed of IM, calculates the theoretical shaft torque of a real wind turbine. Comparing with this torque value, the shaft torque of the IM is regulated accordingly by controlling stator current demand and frequency demand of the inverter. In this way, the inverter driven induction motor acts like a real wind turbine to the energy conversion system. The drive is controlled using the measured shaft torque directly, instead of estimating it as conventional drives do. The experimental results of the proposed simulator show that this scheme is viable and accurate. This paper reports the operating principles, theoretical analyses, and test results of this wind turbine simulator.     

风力发电机大风限速保护方法的研究

小型风力发电机面临的最大难题是其可靠性问题,即大风时的限速保护问题.从能量守恒的角度分析了利用风轮与发电机的功率匹配特性实现风力发电机限速保护的可行性.另外,设计了2台风轮与发电机具有不同匹配特性的300 W/26 V风力发电机,为了使其具有可比性,使用了同样型号的发电机.通过实验测试了风轮的机械输出特性、发电机在输出电压不同时的功率特性和整机的功率输出,实验结果表明,风速12 m/s以下时2台风力机输出功率基本相同,风速12 m/s以上时其中1台随着风速的增加功率不断增加,而另外1台随着风速的增加输出功率不再上升,甚至有点下降,与大风机功率特性相似.     

Optimum siting of wind turbine generators

This paper investigates optimum siting of wind turbine generators from the viewpoint of site and wind turbine generator selection. The methodology of analysis is based on the accurate assessment of wind power potential of various sites. The analytical computations of annual and monthly capacity factors are done using the Weibull statistical model using cubic mean cube root of wind speeds. As many as fifty-four potential wind sites, with and without wind turbine installations, geographically distributed in different states of India are used for the siting analysis. As an outcome of this analysis several definitive conclusions of archival nature have been arrived at and are presented in the paper. If this analysis is done at the planning and development stages of installation of wind power stations, it will enable the wind power developer or the power utilities to make a judicious choice of potential site and wind turbine generator system from the available potential sites and wind turbine generators respectively     

Wind-diesel hybrid power system integration in the south Algeria

In most isolated sites situated in south Algeria, the diesel generators are the major source of electrical energy. Indeed, the power supply of these remote regions still poses order problems (technical, economical and ecological). The electricity produced with the help of diesel generators is very expensive and responsible for CO₂ emission. These isolated sites have significant wind energy potential. Hence, the use of twinning wind-diesel is widely recommended, especially to reduce operating deficits. The objective of this paper is to study the global modeling of a hybrid system which compounds wind turbine generator, diesel generator and storage system. This model is based on the control strategy to optimize the functioning of the hybrid system and to consolidate the gains to provide proper management of energy sources (wind, diesel, battery) depending on the load curve of the proposed site. The management is controlled by a controller which ensures the opening/closing of different power switches according to meteorological conditions (wind speed, air mass, temperature, etc).