永磁直驱式变桨距风力发电机组的建模与控制

根据机组在高风速区和低风速区的特点,设计了变桨距控制系统,使得机组能够在低风速区实现最大风能跟踪。为了增强机组在复杂条件下运行特性,在高风速区采用了PID控制器。建立了机组的仿真模型,对不同风速下的机组的稳态和动态特性进行了仿真分析。仿真结果验证了采用方案和控制策略的可行性。     

基于模糊控制的风电机组变桨距控制

针对风力发电机组非线性、时变性的问题,提出采用模糊PID控制器作为变桨距控制器,在风速高于额定风速时,依据风速变化情况调整桨距角,从而使风电机组保持恒功率输出,最后在MATLAB平台上搭建仿真模型。结果表明,采用模糊PID控制比传统PID控制具有更好的动态性能和静态误差,能够优化变桨距控制方法。     

Controller design for a wind farm, considering both power and load aspects

In this paper, a wind farm controller is developed that distributes power references among wind turbines while it reduces their structural loads. The proposed controller is based on a spatially discrete model of the farm, which delivers an approximation of wind speed in the vicinity of each wind turbine. The control algorithm determines the reference signals for each individual wind turbine controller in two scenarios based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted, taking the trade-off between power maximization and load minimization into account. In high wind speed, the power and pitch reference signals are determined while structural loads are minimized. To the best of authors’ knowledge, the proposed dynamical model is a suitable framework for control, since it provides a dynamic structure for behavior of the flow in wind farms. Moreover, the controller has been proven exceptionally useful in solving the problem of both power and load optimization on the basis of this model.     

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.     

兆瓦级风力发电机组变桨距控制系统研究

分析和建立了兆瓦级风力发电机组各个部分机理模型以及有效风速的模型,针对变桨距风力发电机组在低风速最大风能捕获和高风速额定功率保持的控制目标,建立数学模型。并应用MATLAB对PID控制器下的系统模型进行仿真,结果表明模型的可行性。     

Robust and fault-tolerant linear parameter-varying control of wind turbines

High performance and reliability are required for wind turbines to be competitive within the energy market. To capture their nonlinear behavior, wind turbines are often modeled using parameter-varying models. In this paper we design and compare multiple linear parameter-varying (LPV) controllers, designed using a proposed method that allows the inclusion of both faults and uncertainties in the LPV controller design. We specifically consider a 4.8 MW, variable-speed, variable-pitch wind turbine model with a fault in the pitch system.We propose the design of a nominal controller (NC), handling the parameter variations along the nominal operating trajectory caused by nonlinear aerodynamics. To accommodate the fault in the pitch system, an active fault-tolerant controller (AFTC) and a passive fault-tolerant controller (PFTC) are designed. In addition to the nominal LPV controller, we also propose a robust controller (RC). This controller is able to take into account model uncertainties in the aerodynamic model.The controllers are based on output feedback and are scheduled on an estimated wind speed to manage the parameter-varying nature of the model. Furthermore, the AFTC relies on information from a fault diagnosis system.The optimization problems involved in designing the PFTC and RC are based on solving bilinear matrix inequalities (BMIs) instead of linear matrix inequalities (LMIs) due to unmeasured parameter variations. Consequently, they are more difficult to solve. The paper presents a procedure, where the BMIs are rewritten into two necessary LMI conditions, which are solved using a two-step procedure.Simulation results show the performance of the LPV controllers to be superior to that of a reference controller designed based on classical principles.     

The use of preview wind measurements for blade pitch control

Light detection and ranging systems are able to measure conditions at a distance in front of wind turbines and are therefore suited to providing preview information of wind disturbances before they impact the turbine blades. In this study, preview-based disturbance feedforward control is investigated for load mitigation. Performance is evaluated assuming highly idealized wind measurements that rotate with the blades and compared to performance using more realistic stationary measurements. The results obtained using idealized, “best case” measurements show that excellent performance gains are possible with reasonable pitch rates. However, the results using more realistic wind measurements show that without further optimization of the controller and/or better processing of measurements, errors in determining the shear local to each blade can remove any advantage obtained by using preview-based feedforward techniques.     

Generator speed regulation in the presence of structural modes through adaptive control using residual mode filters

Wind turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, potentially causing component fatigue and failure. Two key technology drivers for turbine manufacturers are increasing turbine up time and reducing maintenance costs. Since the trend in wind turbine design is towards larger, more flexible turbines with lower frequency structural modes, manufacturers will want to develop control paradigms that properly account for the presence of these modes. Accurate models of the dynamic characteristics of new wind turbines are often not available due to the complexity and expense of the modeling task, making wind turbines ideally suited to adaptive control approaches. In this paper, we develop theory for adaptive control with rejection of disturbances in the presence of modes that inhibit the controller. A residual mode filter is introduced to accommodate these modes and restore important properties to the adaptively controlled plant. This theory is then applied to design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed wind turbine. The adaptive pitch controller is compared in simulations with a baseline classical proportional integrator (PI) collective pitch controller.     

Pitch controller for wind turbine load mitigation through consideration of yaw misalignment

Recent developments in sensor and actuator technologies have promoted the design and implementation of individual pitch controllers (IPCs) to mitigate fatigue loads on turbine blades caused by vertical wind shear. So far, IPCs have been designed assuming perpendicularity of the oncoming wind with respect to the turbine rotor plane as an independent yaw controller is dedicated to eliminate any misalignments. In this paper, a multi-input-multi-output (MIMO) IPC is designed based on the knowledge of mitigated blade load at a yawed inflow condition (i.e., yaw misalignment at certain angular position). Nonetheless, the proposed IPC is still to operate in the typical turbine configuration, in which the turbine is aligned with the wind direction. Performance of the proposed IPC is compared with that of the baseline collective pitch controller (CPC) and baseline IPC on simulations of the NREL 5 MW reference turbine at various turbulent wind conditions. Compared with the baseline CPC, the proposed controller is shown to contribute at least a 31.54% reduction in the blade out-of-plane fatigue load, a 35.32% reduction in the tower fore-aft fatigue load, and a 29.80% reduction in the tower side-to-side fatigue load.     

Performance analysis of individual blade pitch control of offshore wind turbines on two floating platforms

Individual blade pitch state space (IBP SS) control and disturbance accommodating control (DAC) that reject wind speed perturbations are applied on a 5 MW wind turbine mounted on the barge and tension leg floating platforms for performance comparison in above rated wind speed region. The DAC used in this study is simply an IBP SS controller with a wind speed disturbance rejection component. For each controller implemented onshore and on the floating platforms, 60 10-min simulations with a variety of wind and wave conditions, where applicable, are carried out in accordance with the IEC-61400-3 standard design load case 1.2 for fatigue load testing. Results show that even with large tower load reductions by the IBP SS controller on the barge platform, these loads are still at least two and up to five times more than that for an onshore wind turbine. DAC on the barge platform has little impact on further improving the performance of the IBP SS controller. DAC on the tension leg platform manages to achieve loads comparable to that of the onshore system. Power and rotor speed regulation are improved and tower side-side load is reduced. Only the tower fore-aft load is 24% higher than the onshore wind turbine.     

基于半物理仿真平台的风力机PID控制研究

针对变速变桨风力机组的特点,基于风力机半物理仿真平台,根据建立的组合风速模型及风力机不同的运行区域,研究了考虑机械传递、阻尼等因素的风力机PID控制方法,并进行了实验验证。结果表明,真实物理平台实验更能体现风力机的机械特性,建立的PID控制方法也较为贴近真实风机的控制特性。     

Adding feedforward blade pitch control to standard feedback controllers for load mitigation in wind turbines

Combined feedback/feedforward blade pitch control is compared to industry standard feedback control when simulated in realistic turbulent winds. The feedforward controllers are designed to reduce fatigue loads, increasing turbine lifetime and therefore reducing the cost of energy. Two feedforward designs are studied: collective-pitch model-inverse feedforward using a non-causal series expansion and individual-pitch gain-scheduled shaped compensator. The input to the feedforward controller is a measurement of incoming wind speed, which could potentially be provided by LIDAR. Three of the designs reduce structural loading compared to standard feedback control, without reducing power production.     

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。     

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     

基于直驱型PMSG风力发电系统的变桨自抗扰控制

为了实现大功率风力发电系统的恒功率控制,首先建立了基于直驱型PMSG风力发电系统的数学模型;其次,以功率偏差为控制器的输入信号,设计了一种基于自抗扰算法的风力发电系统变桨距控制器。最后,在阵风叠加随机风的作用下进行仿真研究。仿真结果表明,该控制器能够有效地控制桨距角,可以实现额定风速以上时系统输出功率的恒定。     

A novel pitch control system for a wind turbine driven by a variable-speed pump-controlled hydraulic servo system

The paper aims to develop a novel pitch control system for a large wind turbine driven by a variable-speed pump-controlled hydraulic servo system. To perform practical pitch control experiments, a full-scale test rig of the hydraulic pitch control system for a 2 MW wind turbine’s blade, including a novel pitch control mechanism, a variable-speed pump-controlled hydraulic servo system, a disturbance system and a PC-based control system, is designed and set up. The variable-speed pump-controlled hydraulic servo system, containing an AC servo motor, a constant displacement hydraulic piston pump two differential hydraulic cylinders and hydraulic circuits, achieved high response and high energy efficiency, so it is suitable for wind turbine applications. Besides, to implement the pitch control in the proposed novel pitch control system, an adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC-STFSMC) is developed to design the pitch controller. Finally, the developed variable-speed pump-controlled hydraulic servo system was built and verified for the path tracking control and path-positioning control of the pitch control of the wind turbines by practical experiments in a full-scale test rig under different path profiles, load torques, and random wind speeds.     

基于超级电容的兆瓦级风机变桨系统

变桨系统及其后备电源是大型变速变桨距风电机组的关键组成部分.对风电机组的安全运行具有十分重要的作用。本文探讨了大型风电机组变桨系统备用电源的几种方案.对各种备用电源进行简单对比分析。本文还以中国南车的WT2000D110型风电机组变桨系统为例,介绍了超级电容在变桨系统的一种应用     

VACON变频器在直驱型风力发电系统独立变桨中的应用可行性分析

直驱型风力发电系统是一种应用前景看好的变速恒频风力发电方案,为提高风能的利用率和风力发电经济效益,提高系统稳定性降低维修成本,迫切要求对风力机进行独立变桨控制。本文介绍了直驱型风力发电系统的拓扑原理和风力机的特性曲线,并以基于同步电动机的变桨执行机构为平台,介绍了Vacon NX型变频器的控制功能,并对其在独立变桨场合的应用可行性进行了分析,由Vacon NX系列变频器的各项参数和性能指标可知,其应用于变桨控制中是可行的,是实现高效、可靠独立变桨控制的良好途径之一。     

风力发电机组变桨系统设计初探

在大型风力发电机中,为了追求高的风能利用系数和不断优化的输出功率曲线,变桨距型风力机已经显现出越来越大的优势。本文以国电电力太仆寺旗蜗牛山风电厂3MW风电系统为研究背景,对电动变桨技术进行研究,分析了电动变桨系统的构成、运行状态,并提出了一种控制策略。通过仿真,建立了电动变桨系统的模型,并验证了控制策略的可靠性。     

An optimal fuzzy PID controller

This paper introduces an optimal fuzzy proportional-integral-derivative (PID) controller. The fuzzy PID controller is a discrete-time version of the conventional PID controller, which preserves the same linear structure of the proportional, integral, and derivative parts but has constant coefficient yet self-tuned control gains. Fuzzy logic is employed only for the design; the resulting controller does not need to execute any fuzzy rule base, and is actually a conventional PID controller with analytical formulae. The main improvement is in endowing the classical controller with a certain adaptive control capability. The constant PID control gains are optimized by using the multiobjective genetic algorithm (MOGA), thereby yielding an optimal fuzzy PID controller. Computer simulations are shown to demonstrate its improvement over the fuzzy PID controller without MOGA optimization