范文无忧网1 倍世界当前能源的需求。
1.1 变速风力发电机系统的基本组成
典型的变速风力发电系统如图1-1-1所示。
图1-1-1 典型变速风力发电机组
许多商业用途的
通过对图1-1-1的分析可知，图中虚线方框处为功率电子变换器。在本文中功率电 子变换器也被称为逆变器。
1.2风力机性能
如一台风力机风轮的摩擦力被忽视的话,那么风力机的动力表达式就为等式(1.2.1)至等式(1.2.4)。在等式（1.2.1）中，Tm是风力机风轮的机械转矩，
d dt
TmTLoadJ
。而TSR
图1-2-1
1.3风力发电机组及逆变器
研究目的和方法 目标 本文的研究目的是通过对变速风力发电系统的软硬件的调查、策划和实施来获取最
的建模和仿真结果，且论证了逆变器布局创新的优势。在文中提及了我们研究小组建立的风机仿真系统用于论证最大能量获取算法的方法。
2 最大风能获取智能算法
2.1看法
2.1.1无风速测量的独立算法
风力机理论说明当尖速比保持在最佳值时风力机的转换效能才会最大。回顾第一章可知，尖速比控制方式的原理是直接监测和控制尖速比值。然而对于尖速比值的测量难度很大。特别是基于尖速比控制策略的执行相当复杂。而功率信号回馈是一种无须测量尖速比就能获取最大风能的控制方式。这主要是由于功率信号回馈控制方式依赖于风力机的特性。这就意味着在该控制初期和控制计划期间都要实时的获取风力机的特性
图2-1-1 最大功率算法信号流程图
Maximum Wind Energy Extraction Strategies Using Power Electronic Converters
Chapter 1 Introduction
The atmosphere of the Earth works like a huge heat engine. The air in tropical area arises and the air from the polar area fills its place. This huge heat engine is an abundant wind energy supplier. According to the U.S. Department of Energy, the world's winds could theoretically supply more than 15 times current world energy demand.
Compared to fossil fuel and nuclear electrical power generation, wind energy conversion has several notable advantages, including abundant supplies, renewable sources, environmental friendliness, and economical competitiveness, in addition to its widespread availability and relatively small land usage. As such an attractive means of alternative energy conversion, wind energy generation has a world-wide average growth rate of 31 % in the last 10 years. The cost of electricity from utility-scale wind systems has dropped by more than 80% over the last 20 years. In the early 1980's, wind-generated electricity cost was as much as 30 cents (US) per kilowatt-hour (kWh). Now, large wind power plants are generating electricity at costs as low as 4 cents (US) per kWh. As a result, Wind Power Generation Systems (WPGS) have been developing rapidly in recent years all over the world. Research work on WPGS is also receiving more and more attentions.
.
1.1 Basic VSWT System Configuration
Figure1-1-1 shows a typical VSWT energy generation system. Various wind turbines from a hundred watts power level to mega watts power level have been used in WPGSs, such as horizontal axis wind turbines with different numbers of blades, vertical axis wind turbines which are also named as Darrieus Turbines, and other innovative turbines like Savonius wind turbine [1]. Horizontal Axis Wind Turbine is the most popular type.
Many commercial WPGSs adopt high speed induction or synchronous generators coupled to the wind turbines through gearboxes. In recent years, low speed synchronous generators, which are directly coupled to wind turbines without gear boxes, are gaining popularity. This structure benefits the WPGS in eliminating the gear box maintenance, reducing the noise and lowering the cost.
Inside the inverter, the variable-frequency variable-voltage electricity from the generator is first converted from AC to DC through a rectifier. Both controlled or uncontrolled rectifiers may be adopted. An uncontrolled rectifier has the benefit of simplicity, while a controlled rectifier is able to contain the dc-link voltage within the inverter's operational voltage range during high wind speed situations.
1.2 Wind Turbine Characteristic
If the rotor friction of a wind turbine is ignored, the dynamics of the turbine can be simply expressed using Equations (1.2.1) to (1.2.4)[1]. In Equation (1.2.1),Tmis the turbine rotor's mechanical torque,TLoadis the load torque,Jis the turbine rotor's moment of inertia, andwis the turbine rotor's angular speed. Equation (1.2.2) is derived from Equation (1.2.1) multiplied byw, wherePmandPLoad are the turbine's mechanical power and the load power respectively.
TmTLoadJ
dw （1.2.1） dt
Chapter 2 Intelligent Maximum Wind Power Extraction Algorithm
2.1 Overview
2.1.1 An Independent Algorithm without Wind Speed Measurements
Wind turbine theory reveals that a maximum turbine energy conversion efficiency occurs when the Tip-Speed Ratio (TSR) is kept at its optimal value. As reviewed in Chapter 1，the principle of TSR Control method is to directly detect and control the TSR value. However, due to the difficulties of TSR measurement, a control strategy based on the tip-speed ratio is practically difficult to implement. Power Signal Feedback (PSF) control method was then proposed to extract maximum wind power without measuring the TSR. Basically PSF Control method is dependent of the characteristics of a wind turbine, which means the turbine characteristics have to be obtained either before or during the execution of the control scheme.
2.1.2 The Algorithm Existence Analysis