变频器的转矩控制功能及其应用

转速控制与转矩控制 　　1.转速控制 　　变频调速在绝大多数情况下,都是通过调节频率来调节电动机转速的,称为转速控制,其特点如图1a和图1b所示.当调节变频器的给定信号UG时,变频器的输出频率fx和电动机的转速nM将随UG的改变而改变. 　　……     

变频调速在中央空调系统节能中的应用

在我国能源紧缺,提高能源的利用率,为现代化建设提供能源保证迫在眉睫.实践证明,在中央空调的循环系统(冷却泵和冷冻泵)中接入PLC和变频器组成的PID闭环控制系统,利用变频技术改变电机转速来调节流量和压力的变化,取代用阀门控制流量,能取得明显的节能效果.     

中央空调变频节能的着眼点

1　前言在许多楼堂馆所,中央空调系统是必不可少的基本设施,也是耗电量极大的设备,往往配备2台以上的制冷机组,多台泵机配套同时运行。单台泵机容量少则数千瓦,多则几十千瓦。因此,从节能的角度来看,这是一个开源节流潜力很大的场所。变频器(ＶＶＶＦ)自80年代推广使用以来,价格逐步下降,近两年销量显著上升。泵类设备在变频技术改造和应用方面获得广泛的好评和经济效益。实践证明,在中央空调现有循环泵上接入变频器,不论进行开环或闭环控制,采用变频调速技术改变轴功率的方式来代替阀门控制流量,均获得显著的节能效果。2　空调系统节能的依…     

高岭土回转窑下料口物料降温的自动控制

采用PLC+触摸屏控制单元对温度高低和喷水量大小进行PID闭环控制,温度采集通过热电阻和温度变送器把采集到的信号送入PLC模拟量扩展单元,在PLC内部通过和设定的温度相比较运算,最后把需要控制的模拟量通过PLC输出来控制变频器输出电压的频率大小以其控制水泵的转速来改变喷水量,从而使物料温度达到可控。     

变频器在电梯控制中的应用

介绍了电梯专用变频器在电梯拖动系统中的应用，通过变频器驱动曳引机电动机，采用速度反馈控制，跟踪设定的速度曲线，通过改变变频器的PI参数，S曲线形状、加速度时间等参数来调整电梯运行的舒适感，满足电梯的起制动要求。再通过改变变频器的速度指令使电梯运行在不同的速度上，最大限度的减少乘客的候梯时间，使电梯高效、安全、节能的运行。以富士5000G11UD电梯专用变频器为例，介绍其应用、调试方法。     

工业锅炉汽包水位给水自动调节系统优化改进

把变频器应用到串级三冲量汽包给水自动调节系统中,通过调节给水泵频率进而调节其转速以改变给水流量,从而达到改变汽包水位的目的.此系统解决了传统串级三冲量汽包水位给水自动调节系统在锅炉启动、停炉、低负荷时产生较大的节流损失、调节阀承受压力大,容易磨损和损坏等缺点,并且降低了厂用电,也使汽包水位自动调节系统得到了简化,锅炉运行加安全可靠.     

基于PLC控制的变频调速技术在中央空调系统中的应用

针对传统中央空调调节方式的局限性、能源浪费严重等特点，设计开发了一种以PLC、变频器为核心构成的中央空调控制系统。介绍了该系统的节能原理、系统构成及工作原理、硬件、软件设计及系统优点，证明了该系统优越的技术性能和极其显著的经济效益。     

空调水系统变频节能控制的若干问题

通过实例分析，指出水系统在水泵变工况运行时，其工作点，转速，功率等应通过水泵相似律确定。在不同场合，变频器的节能效果是不同的。正确选择变频器是发挥变频节能控制效果的重要保证。     

海洋工程船舶吊机矢量控制变频器参数整定简介

变频器是变频驱动系统的关键设备,是实现电机转矩和转速调节的核心.通过对变频器的控制,最终实现对电机的控制,达到操作人员的预期目的.因此,变频器控制系统的稳定性就显得尤为重要,为达到相应的控制效果,要求变频器能够快速稳定地实现外部设定.为此需要对变频器控制电路的PID参数进行整定,以实现对吊机马达的稳定控制.     

并网型风电机组自稳速传动系统设计

针对变频器对风电系统的影响,设计了一种自稳速传动系统,可用于风力发电机的恒频输出。从机构学角度对该系统中的电动机与差动轮系进行特殊设计,维持电动机转速恒定,即可实现系统变转速输入、恒转速输出。搭建了采用该系统的并网型风电机组模型,通过FAST和SIMULINK软件的仿真试验,验证了该系统的有效性。     

Developing the dual system of wind chiller integrated with wind generator

The successfully developed wind chiller in our CCT Lab. directly uses wind force to drive refrigeration system and hence reduces two times energy conversions between mechanical and electrical energies. The wind chiller needs high wind speed for its effective work due to the large working torque is required by the compressor. For the purpose of enlarging the applied wind field by the wind machine, this work aims to develop a dual system of wind chiller integrated with wind generator. The integrated wind generator can use the wind energy which cannot effectively drive the compressor. Therefore, the new developed dual system can apply larger range of the wind field and further increase the total working efficiency of the wind machine. A programmable logic controller (PLC) is applied in this wind forced dual system to select the wind chiller or the wind generator separately in terms of the rotational speed of the wind machine. In this work, the wind chiller is switched on while the accelerated rotational speed reaches 80 rpm and off while the decelerated rotational speed reaches 60 rpm. The integrated wind generator is switched on while the decelerated rotational speed reaches 60 rpm and off while the decelerated rotational speed reaches 40 rpm. The two apparatuses in the dual system always work separately. The results show that there is ca. 18.5% increment of effective working efficiency which is captured by the wind generator.     

An experimental study of the two-staged wind turbines

In order to improve the torque performance of the propeller type wind turbine, and to increase the relative rotational speed of the generator, two-staged wind turbines were proposed. The experimental results of a wind tunnel test showed that self-starting characteristics of two-staged co-axial type were improved by attached front wind turbines for two bladed main wind turbine, and the relative rotational speed of counter-rotating type was increased.Then, a counter-rotating type trial machine was constructed and a wind tunnel test was also conducted. The test result demonstrated the technical possibility of conterrotating type wind powered generator.     

Performance of a 3 kW wind turbine generator with variable pitch control system

A prototype 3 kW horizontal upwind type wind turbine generator of 4 m in diameter has been designed and examined under real wind conditions. The machine was designed based on the concept that even small wind turbines should have a variable pitch control system just as large wind turbines, especially in Japan where typhoons occur at least once a year. A characteristic of the machine is the use of a worm and gear system with a stepping motor installed in the center of the hub, and the rotational main shaft. The machine is constructed with no mechanical breaking system so as to avoid damage from strong winds. In a storm, the wind turbine is slowed down by adjusting the pitch angle and the maximum electrical load. Usually the machine is controlled at several stages depending on the rotational speed of the blades. Two control methods have been applied: the variable pitch angle, and regulation of the generator field current. The characteristics of the generator under each rotational speed and field current are first investigated in the laboratory. This paper describes the performances of the wind turbine in terms of the functions of wind turbine rotational speed, generated outputs, and its stability for wind speed changes. The expected performances of the machine have been confirmed under real wind conditions and compared with numerical simulation results. The wind turbine showed a power coefficient of 0.257 under the average wind speed of 7.3 m/s.     

A torque matched aerodynamic performance analysis method for the horizontal axis wind turbines

An analysis method is developed to test the operational performance of a horizontal axis wind turbines. The rotor is constrained to the torque–speed characteristic of the coupled generator. Therefore, the operational conditions are realized by matching the torque generated by the turbine over a selected range of incoming wind velocity to that needed to rotate the generator. The backbone of the analysis method is a combination of Schmitz' and blade element momentum (BEM) theories. The torque matching is achieved by gradient‐based optimization method, which finds correct wind speed at a given rotational speed of the rotor. The combination of Schmitz and BEM serves to exclude the BEM iterations for the calculation of interference factors. Instead, the relative angle is found iteratively along the span. The profile and tip losses, which are empirical, are included in the analysis. Hence, the torque at a given wind speed and rotational speed can be calculated by integrating semi‐analytical equations along the blade span. The torque calculation method is computationally cheap and therefore allows many iterations needed during torque matching. The developed analysis method is verified experimentally by testing the output power and rotational speed of an existing wind turbine model in the wind tunnel. The generator's torque rotational speed characteristic is found by a separate experimental set‐up. Comparison of experiments with the results of the analysis method shows a good agreement. Copyright © 2013 John Wiley & Sons, Ltd.     

Operation strategies of axial flow fans in a direct dry cooling system under various meteorological conditions

For a direct dry cooling system, the turbine back pressure fluctuates with the meteorological conditions. Moreover, the operation of axial flow fans plays an important role in the cooling performance of air-cooled condensers (ACC). It is of significant use to study the operation strategies of axial flow fans under various ambient conditions. Based on typical 2 × 660 MW direct dry cooling power generating units, the ACC model coupled with the turbine thermodynamic characteristics is developed, by which the thermo-flow performances of the ACC are predicted in the dominant wind direction, and then the standard coal consumption is calculated. The results show that the increased ambient temperature and wind speed, or the reduced fan rotational speed leads to the high turbine back pressure. At the low ambient temperature and wind speed, the standard coal consumption rate of the unit can be reduced by reducing the speed of axial flow fans appropriately, with the maximum drop in coal consumption rate reached 0.734 g/(kWh) when the ambient temperature is 10°C without wind. If the wind speed exceeds 12 m/s or the ambient temperature reaches 25°C, 110% of the rated fan rotational speed is recommended.     

加装后缘小翼的垂直轴风力机输出特性研究

为了研究H型垂直轴风力机后缘加装小翼的输出特性变化规律,文章以NACA0012翼型叶片为例,采用风洞试验与数值模拟的方法,对加装后缘小翼的风力机进行了研究。模拟结果表明,加装后缘小翼的风力机的单叶片扭矩系数及功率性能要优于未加装小翼的风力机,整体功率较未加装小翼的风力机略有提升。风洞实验结果表明:加装后缘小翼可以提高风力机的最大输出功率,其中径长比对于加装小翼的垂直轴风力机功率提升的影响较大;当转速小于300 r/min时,安装径长比为0.6的后缘小翼的风力机输出功率最高;当转速超过300 r/min时,径长比为0.4的后缘小翼的风力机输出功率最高。     

参与电网调频的风电机组线性变参数变桨控制策略

风电机组参与调频时其输出功率的调整将改变风电机组变桨动作的风速范围,同时由于桨距角调节气动功率的灵敏度随风况变化,使得传统PI变桨控制难以适用于风电机组参与调频时的复杂工况,出现风电机组转速振荡问题。提出一种基于线性变参数(Linear Parameter Varying, LPV)系统的风电机组变桨控制方法,对风电机组模型进行线性化,根据风速和桨距角的变化范围进行凸分解,得到其具有四面体结构的LPV模型,通过求解不同平衡点处的线性矩阵不等式(Linear Matrix Inequality, LMI)设计出相应的变桨控制器。仿真结果表明:与传统PI变桨控制相比,LPV变桨控制能有效减小转速的波动,降低低速轴载荷以及减小桨距角的波动程度,验证了该控制策略的有效性和先进性。     

Assessment of low-frequency aeroacoustic emissions of a wind turbine under rapidly changing wind conditions based on an aero-servo-elastic CFD simulation

A meteorologically challenging situation that represents a demanding control task (rotational speed, pitch and yaw) for a wind turbine is presented and its implementation in a simulation is described. A high-fidelity numerical process chain, consisting of the computational fluid dynamics (CFD) solver FLOWer, the multi-body system (MBS) software SIMPACK and the Ffowcs Williams-Hawkings code ACCO, is used. With it, the aerodynamic, servoelastic and aeroacoustic (<20 Hz) behaviour of a generic wind turbine during a meteorological event with strong and rapid changes in wind speed and direction is investigated. A precursor simulation with the meteorological model system PALM is deployed to generate realistic inflow data. The simulated strong controller response of the wind turbine and the resulting aeroelastic behaviour are analysed. Finally, the low-frequency sound emissions are evaluated and the influence of the different operating and flow parameters during the variable inflow is assessed. It is observed that the wind speed and, linked to it, the rotational speed as well as the turbulence intensity are the main influencing factors for the emitted low-frequency sound power of the wind turbine. Yawed inflow, on the other hand, has little effect unless it changes the operational mode to load reduction, resulting in a swap of the main emitter from the blades to the tower.     

永磁同步风力发电系统最大功率跟踪控制策略及仿真分析

以永磁同步风力发电系统为研究对象,分析了永磁同步风力发电系统的风速、风力机、Boost电路和逆变器模型,研究了风力发电系统的最大功率跟踪控制和并网逆变器控制,在Boost升压电路中利用转速、整流直流电压和导通比三者之间的传递关系制定了最大功率跟踪控制策略,通过简易的PQ解耦幅相控制实现系统并网,提高了系统输出功率因数,恒定了直流母线电压,并基于Matlab/Simulink搭建仿真模型验证了该系统控制策略的有效性。     

Power coefficient measurement on a 12 kW straight bladed vertical axis wind turbine

A 12 kW vertical axis H-rotor type wind turbine has been designed and constructed at Uppsala University. A measurement campaign has been performed to collect data to calculate the power coefficient using the method of bins. The measurement was performed at different constant rotational speeds on the turbine during varying wind speeds to observe the power coefficients dependence on tip speed ratio. The power coefficient peaked at 0.29 for a tip speed ratio equal to 3.3.