基于MPPT的变速恒频双馈风力发电系统控制策略

充分利用风能是风力发电控制的主要目的之一,为达此目的,本文基于风力机特性和双馈风力发电机的数学模型,提出了一种不依赖于风速测量来实现双馈风力发电系统最大功率点追踪(MPPT)控制的策略。该策略应用定子磁链定向矢量控制技术,对双馈发电机进行有功功率和无功功率的解耦控制,然后通过对发电机输出有功功率进行控制来间接得到与风速相对应的最佳叶尖速比和最优转速,从而实现最大功率点追踪(MPPT)控制。仿真结果证实了基于该方法,双馈风力发电系统在风速变化过程中能自动寻找并追随最大功率点,且控制相对简单,运行可靠,有较高的实用价值。     

开关磁阻风力发电系统最大风能跟踪控制仿真研究

介绍了开关磁阻发电机工作模式并选用了他励发电模式。在此基础上搭建了以跟踪最大风能为目的开关磁阻风力发电系统模型。针对开关磁阻电机的特点,选择了转速反馈控制方案来实现系统的风能跟踪。在阵风、渐变风、随机风三种典型风速变化下对所搭建系统进行了仿真研究,证明该系统能够完成最大风能跟踪。     

基于最佳功率给定的永磁直驱同步风力发电系统控制策略研究

直驱型风力发电系统由于不需要增速箱,在风电场中得到广泛的发展和应用.该文研究了发电机和风机的特性分析,提出了基于最佳功率给定的最大风能控制策略,该方法通过对发电机进行闭环控制,使输出功率按照最优功率曲线进行输出,实现最大风能跟踪.并研究了永磁直驱风电系统的双PWM变流器控制策略;搭建了直驱型风电机组整体模型,该系统能够实现并风能最大功率跟踪及并网控制,仿真验证了控制系统的正确性.     

Wind Speed Estimation Based Sensorless Output Maximization Control for a Wind Turbine Driving a DFIG

This paper proposes a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs). A specific design of the proposed control algorithm for a wind turbine equipped with a doubly fed induction generator (DFIG) is presented. The aerodynamic characteristics of the wind turbine are approximated by a Gaussian radial basis function network based nonlinear input-output mapping. Based on this nonlinear mapping, the wind speed is estimated from the measured generator electrical output power while taking into account the power losses in the WTG and the dynamics of the WTG shaft system. The estimated wind speed is then used to determine the optimal DFIG rotor speed command for maximum wind power extraction. The DFIG speed controller is suitably designed to effectively damp the low-frequency torsional oscillations. The resulting WTG system delivers maximum electrical power to the grid with high efficiency and high reliability without mechanical anemometers. The validity of the proposed control algorithm is verified by simulation studies on a 3.6MW WTG system. In addition, the effectiveness of the proposed wind speed estimation algorithm is demonstrated by experimental studies on a small emulational WTG system.     

A Fuzzy Logical MPPT Control Strategy for PMSG Wind Generation Systems

Making full use of wind power is one of the main purposes of the wind turbine generator control. Conventional hill climbing search (HCS) method can realize the maximum power point tracking (MPPT). However, the step size of HCS method is constant so that it cannot consider both steady-state response and dynamic response. A fuzzy logical control (FLC) algorithm is proposed to solve this problem in this paper, which can track the maximum power point (MPP) quickly and smoothly. To evaluate MPPT algorithms, four performance indices are also proposed in this paper. They are the energy captured by wind turbine, the maximum power-point tracking time when wind speed changes slowly, the fluctuation magnitude of real power during steady state, and the energy captured by wind turbine when wind speed changes fast. Three cases are designed and simulated in MATLAB/Simulink respectively. The comparison of the three MPPT strategies concludes that the proposed fuzzy logical control algorithm is more superior to the conventional HCS algorithms.     

一种基于变速恒频的双馈风力发电MPPT设计

采用双PWM控制型变流器,变速恒频发电技术,变浆距角进行最佳风能追踪(MPPT)控制。分析了如何由绕线式异步电动机参数设计出双馈风力发电最大风能跟踪控制的风力机参数。通过Matlab仿真,分析了风机的切入风速、切出风速、风速过大情况下的变桨距角控制及浆距角随风速减小而自动恢复的最大风能跟踪特性,验证了控制策略的有效性和可行性。     

An intelligent maximum power extraction algorithm for inverter-based variable speed wind turbine systems

This paper focuses on the development of maximum wind power extraction algorithms for inverter-based variable speed wind power generation systems. A review of existing maximum wind power extraction algorithms is presented in this paper, based on which an intelligent maximum power extraction algorithm is developed by the authors to improve the system performance and to facilitate the control implementation. As an integral part of the max-power extraction algorithm, advanced hill-climb searching method has been developed to take into account the wind turbine inertia. The intelligent memory method with an on-line training process is described in this paper. The developed maximum wind power extraction algorithm has the capability of providing initial power demand based on error driven control, searching for the maximum wind turbine power at variable wind speeds, constructing an intelligent memory, and applying the intelligent memory data to control the inverter for maximum wind power extraction, without the need for either knowledge of wind turbine characteristics or the measurements of mechanical quantities such as wind speed and turbine rotor speed. System simulation results and test results have confirmed the functionality and performance of this method.     

Sensorless variable-speed controller for existing fixed-speed wind power generator with unity-power-factor operation

A variable-speed controller, for an existing 225 kW fixed-speed wind power generator, is presented in this paper. A sensorless direct torque control algorithm-based controller is proposed for the squirrel-cage induction generator. Generator torque reference is derived based on sensorless maximum power tracking mode algorithm, up to the base speed of the generator. A three-phase front-end converter is used here to deliver the generated power to the grid with unity-power-factor operation at all wind speeds. This algorithm is based on direct active and reactive power control. The experimental waveforms from the actual installation site are presented in this paper with a comparison of the existing fixed-speed system. An interpretation of the results is also presented here.     

小型风光互补控制策略研究

文中通过对比风光互补系统各种常用最大功率点跟踪（MPPT）控制策略,提出了改进的MPPT控制策略。光伏电池阵列输出功率通过电压反馈扰动MPPT控制策略进行控制,风力发电机输出的功率采用变步长扰动MPPT控制策略;在蓄电池支路上串联一个MOSFET管,起到截止充电功能,并提出了改进的三段式充电方法。     

Current Source Inverter Based Grid Connected Hybrid PV-Wind Power Generation Unit

ABSTRACT

This paper presents a current source inverter (CSI)-based hybrid power generation system, which uses wind turbine and photovoltaic cells (PVs). A permanent magnet synchronous generator (PMSG) is connected to the CSI using a diode rectifier and a buck converter that is used to control the speed of the rotor. Another buck converter is used to control the maximum power point tracking of PVs. The operation of proposed system is studied under normal and grid voltage dip conditions. According to new grid codes, most power generating units are supposed to remain connected to the grid during voltage sag conditions and inject reactive current to grid as defined by grid codes. The CSI has fault current limiting capability that makes it appropriate to use in grid-connected applications and during voltage sag conditions in particular. The proposed system tracks the maximum power point of wind turbine and PVs under normal mode and injects required reactive current to the grid during voltage drop. However, incorporation of CSI with the inherent behaviour of wind turbine and PVs causes fault current to be within the tolerable range for power electronic devices. Simulations are carried out by using PSCAD/EMTDC software to verify the proposed system.     

A Seamless Mode Transfer Maximum Power Point Tracking Controller For Thermoelectric Generator Applications

A boost-cascaded-with-buck converter-based power conditioning system employing a seamless mode transfer maximum power point tracking controller is proposed to maximize energy production of a thermoelectric generator while balancing a vehicle battery, alternator output power, and vehicle load. When a vehicle battery is fully charged, the proposed controller switches to a power matching mode seamlessly by a dual loop control system, which detects the input and output voltages and currents of the boost-cascaded-with-buck converter, and adjusts the commands accordingly. Both voltage and current loops are designed in a frequency domain using small signal models to ensure stable operation. A mode selection and voltage and current commands are determined by a digital signal processor-based controller. The experimental results with a dynamic source and load steps are presented to show the effectiveness of the proposed approach.      

High-Order Sliding-Mode Control of Variable-Speed Wind Turbines

This paper deals with the power generation control in variable-speed wind turbines. These systems have two operation regions which depend on wind turbine tip speed ratio. A high-order sliding-mode control strategy is then proposed to ensure stability in both operation regions and to impose the ideal feedback control solution in spite of model uncertainties. This control strategy presents attractive features such as robustness to parametric uncertainties of the turbine. The proposed sliding-mode control approach has been validated on a 1.5-MW three-blade wind turbine using the National Renewable Energy Laboratory wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code. Validation results show that the proposed control strategy is effective in terms of power regulation. Moreover, the sliding-mode approach is arranged so as to produce no chattering in the generated torque that could lead to increased mechanical stress because of strong torque variations.      

实验室模拟风力机的研究

为了解决实验室风力机的模拟问题,提出了直流电机模拟风力机的方案。同时分析了风力机的运行特性及最佳风能利用原理,采用简单有效的转速、转矩控制,搭建风力机的Matlab仿真模型。该风力机模拟系统应用于变速恒频风力发电系统中,满足了双馈电机在不同状态下运行以及追踪最大风能的变速恒频发电运行等方面研究的需要。     

双馈风力发电系统功率控制的相关问题研究

针对目前在风电系统最大风能捕获控制策略中应用较为广泛的功率控制方法,本文首先分析了当前此法中有关反馈量的选取所存在的误区,并通过仿真验证了理论分析结果。在此基础上,结合双馈风电系统的慢动态模型,通过对其功率控制的稳定性分析,给出了系统的闭环稳定性条件,结果表明,闭环系统的稳定性取决于控制器的参数以及系统的工作点。     

Flexible control of small wind turbines with grid failure detection operating in stand-alone and grid-connected mode

This paper presents the development and test of a flexible control strategy for an 11-kW wind turbine with a back-to-back power converter capable of working in both stand-alone and grid-connection mode. The stand-alone control is featured with a complex output voltage controller capable of handling nonlinear load and excess or deficit of generated power. Grid-connection mode with current control is also enabled for the case of isolated local grid involving other dispersed power generators such as other wind turbines or diesel generators. A novel automatic mode switch method based on a phase-locked loop controller is developed in order to detect the grid failure or recovery and switch the operation mode accordingly. A flexible digital signal processor (DSP) system that allows user-friendly code development and online tuning is used to implement and test the different control strategies. The back-to-back power conversion configuration is chosen where the generator converter uses a built-in standard flux vector control to control the speed of the turbine shaft while the grid-side converter uses a standard pulse-width modulation active rectifier control strategy implemented in a DSP controller. The design of the longitudinal conversion loss filter and of the involved PI-controllers are described in detail. Test results show the proposed methods works properly.     

Fuzzy logic based intelligent control of a variable speed cagemachine wind generation system

The paper describes a variable speed wind generation system where fuzzy logic principles are used for efficiency optimization and performance enhancement control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which pumps power to a utility grid or can supply to an autonomous system. The generation system has fuzzy logic control with vector control in the inner loops. A fuzzy controller tracks the generator speed with the wind velocity to extract the maximum power. A second fuzzy controller programs the machine flux for light load efficiency improvement, and a third fuzzy controller gives robust speed control against wind gust and turbine oscillatory torque. The complete control system has been developed, analyzed, and validated by simulation study. Performances have then been evaluated in detail     

风光互补系统的最大功率研究

为了获得风光互补系统最大功率的目的,在此采用了极值搜索的基本方法。依据风机和光伏阵列具有相同的功率曲线,采用双乘法,根据导数的结果判断是否达到最大值。该算法基于扰动的基础上运用到最大功率跟踪系统。基于极值搜索法的最大功率跟踪控制的稳定性分析是为风光互补系统提供一个直流控制的转换器。运用Matlab进行仿真结果分析,获得了功率曲线图,证明采用极值搜索法,根据电压电流曲线图可以达到功率最大值。风光互补系统的最大功率跟踪控制的特点是稳态行为在最大功率点附近稳定地振荡。     

Wind turbine speed control of a contactless piezoelectric wind energy harvester

ABSTRACT

Wind turbine control is an important task to make the electricity generation secure in terms of energy demand and machine safety. It also yields to control the desired power level and optimized energy because of the assignment of turbine speed. The contactless piezoelectric wind energy harvester (CPWEH) used in this study has three piezoelectric layers located around the shaft with 120 degrees apart and they are buckled by the magnetic force without any physical contact. The superiority of this device is to generate energy for low wind speeds such as 1.5 m/s. However, for high speeds, high total harmonic distortions (THDs) govern the waveforms, thus controlling the turbine speed becomes necessary for optimizing the output power. Encouraged by this, a small low inertia dc generator is coupled with the wind turbine, and the generator terminals are connected to a resistor through a power switch to generate a braking torque that opposes to wind speed direction. By controlling the switch properly, turbine speed is ensured to remain within a certain band, which accordingly prevents the turbine from rotating very fast at damaging wind speeds. Several experiments are performed on the developed CPWEH with/without the presented control scheme which prove the existence of promising performance of our proposal.     

基于滑模控制的三相四线制有源滤波器的研究

为了实现三相四线制系统中有源滤波器电流跟踪控制的快速性和鲁棒性．提出了一种基于滑模控制的有源滤波器。在d-q-0坐标系中建立三相四线有源滤波器的数学模型,通过逆系统的方法实现解耦和线性化,并对滑模控制的趋近律进行改进以削弱抖振、加快跟踪速率。仿真结果表明,采用滑模控制实现指令电流跟踪的有源滤波系统鲁棒性强、快速性好、跟踪误差低,总体性能得到明显提升。     

Sliding mode control combined with extended state observer for an ankle exoskeleton driven by electrical motor

A novel sliding mode control combined with extended state observer (ESO) is proposed for an ankle exoskeleton driven by electrical motor. During the process of assisting, it is necessary to design an effective controller for assisting torque of ankle exoskeleton. However, the parameter uncertainty of complex dynamics model and the irregular motion of human ankle may affect the torque control accuracy. For a high control precision of assisting torque when facing the modeling uncertainty, the sliding mode control is employed, but a large switching gain is usually needed in order to suppress the disturbance, which cause the control signal vibrate greatly. ESO can observe and suppress the disturbance and modeling uncertainty, but its tracking performance needs to be improved. Therefore, the proposed complex controller takes the advantages of sliding mode control and extended state observer, which can not only improve torque tracking performance but also overcome the disturbance force caused by the change of human joint angle without increasing chattering of control signal. Experimental studies are carried out to validate the effectiveness of the proposed control. The results show the presented controller have better torque tracking performance and robustness stability, and the proposed controller can reduce the chattering compared with the tradition sliding mode control.