提高火电厂辅机变频改造后控制可靠性的探讨

为了节能减排,许多电站已经或者正在实施大型辅机的变频改造,如何提高辅机变频改造后的可靠性是一个很重要的课题。结合工程实践,比较了不同类型辅机的变频改造方案,重点阐述了辅机变频改造的关键控制技术,包括变频运行时的控制原则、故障工况下的变频工频切换方式、RB工况下的控制策略等方面,并对正确安排辅机变频改造后的相关试验提出了建议。针对不同辅机的特点,采用合理可靠的控制方案,将会有效提高辅机变频改造后机组运行的可靠性。     

变频技术在蒸汽锅炉节能改造中的应用

应用变频技术对3台6t／h锅炉进行节能改造，将锅炉辅机、鼓风机、引风机、给水泵由工频控制改为变频控制。实践证明，年节约23．21万元，节能效果显著，是锅炉节能的有效途径。     

风机变频控制焦炉集气管压力

本文介绍了柳钢焦化厂两座43—80型焦炉风机高压变频改造后，焦炉集气管压力控制效果，并与改造前全由蝶阀控制的焦炉集气管压力进行比较，分析各自优缺点。同时对风机高压变频PID控制方案进行分析和介绍调试过程中的几点经验。     

变频调速器在供水系统中的应用

结合石家庄白楼宾馆供水管网改造的实例，对“变频调速器”在供水系统中的应用从“节能原理、控制方式、控制方式、系统设计及变频调速后的节能效果”等几个方面进行论述。     

变频控制在热电厂凝泵中的应用

介绍热电厂抽凝机组凝结水系统的概况及采用调节阀控制热井水位存在的问题，分析凝泵实施变频调节的可行性，比较各种控制模式的优缺点，指出凝泵变频改造项目安装调试的注意事项。运行实践表明“一用一备”控制模式是水泵节能改造的最佳方案之一，在该热电厂得到了推广应用，获得了较大的经济效益和良好的控制效果。     

企业自备热电站锅炉辅机变频调速改造的建议

将变频调速控制相对传统调节方式的节能原理进行了比较分析。通过成功的变频调速控制改造实例说明改造的技术经济效益,建议有条件的自备热电站进行这种改造。     

变频控制在机泵节能改造中的应用

介绍了变频控制器在机泵节能改造中的工作原理、变频器的配置方案及应用方法 ,阐述了其工作特点。对变频控制在机泵节能改造中的应用提供了经验     

300MW机组凝结水泵变频改造方案及应用分析

通过比较四种变频改造的技术方案,分析某电厂4号机组凝结水泵变频改造后的节能效果与运行情况。采用高压变频技术对凝结水泵进行调速改造后,降低了母管压力,实现了"软启停",延长了系统寿命,经济分析表明凝结水泵采用变频控制具有较好的经济效益。     

新型FBJ自动扶梯变频节能控制装置的研究与应用

本文针对在用老旧自动扶梯节能改造中存在的一些。缺点，研究了一种不改变原有自动扶梯控制电路．实现自动扶梯节能运行的变频控制装置。分析了其工作原理和技术关键，重点介绍了方向检测电路、负载检测电路和变频控制回路，指出了变频节能控制装置的特点，并结合应用实际进行了节能效果分析，该装置已经获得国家发明专利。     

分布式变频调节系统的工程应用

传统集中供热系统能耗大、控制手段落后、水力失调严重等诸多问题,直接影响到居民生活质量和我国供热行业的整体发展.本文以实际工程为例,对原有系统进行改造,将其改造为节能效益高的分布式变频调节系统.通过改造可使整个系统达到按需供热.     

Design and performance analysis of the three-level isolated DC-DC converter with the nanocyrstalline core transformer

In this study, an isolated three-level DC-DC converter is proposed for high power and high conversion ratio applications such as fuel cells. The proposed system consists of a single phase three-level inverter, a medium frequency transformer and a diode rectifier unit. In the proposed system, a DC supply voltage is converted to a medium frequency AC voltage via a three-level inverter instead of the conventional two-level inverter. Since the three-level inverter generates an AC waveform with multiple steps, lower voltage harmonics and lower EMI levels than conventional two-level inverter are achieved. Thus, the three-level inverter provides higher efficiency value. The medium frequency transformer enables high voltage conversion ratio and provides galvanic isolation as well. The output voltage of the medium frequency transformer is converted to the DC voltage and thus the DC-DC conversion is achieved. According to simulation and experimental results, it is seen that the proposed DC-DC converter structure provides higher power density and higher efficiency values than conventional system.     

Advanced concept for dispersed power supply system using AC modules

A method of for estimating the reliability of new conceptual stand-alone dispersed power supply systems using AC modules with self-contained logic was proposed and system reliability estimated using a yearly scale simulation. The AC module is able to supply AC power on each module and has the flexibility to enable construction of a grid-connected system. Power storage devices were required when applying AC modules to the stand-alone power supply system. For these power storage devices, we used a battery with a built-in DC/AC micro bi-directional inverter known as AC battery. To maintain the flexibility of the system extension, the AC modules and AC batteries were controlled by self-contained logic. This logic performs parallel operations for the voltage control inverter and keeps supply and demand in balance.     

燃料电池功率调节系统的研究

燃料电池电压输出范围比较宽，电压比较低。针对该特点本文设计了DC/DC和DC/AC两级变换的功率调节系统(PCS)。其中DC/DC将燃料电池输出的低压直流电高频变换成高压直流电，变换器为电压单环控制。DC／AC逆变器采用基于电压电流瞬时值反馈的双闭环控制，将高压直流电逆变为正弦交流电。分析了整个功率调节系统的工作原理及逆变器电路参数对稳定性的影响。0．5KVA佯饥实验结果表明整个系统具有电压输入范围宽、变换效率高、输出波形THD小等优点。为开发高效、高功率密度的燃料电池电源系统提供技术基础。     

循环流化床锅炉二次风机节能改造

300 MW循环流化床（CFB）锅炉二次风机设计余量偏大且为恒速运行风机。机组在低负荷运行时,送风量需求减少,风机入口挡板开度很小,风机效率低,电耗大。通过对300 MWCFB锅炉二次风机电机进行加装变频器的节能技术改造,二次风机运行时入口调节挡板全开,通过变频器调节二次风机电机转速来调节送风量,尤其是在机组低负荷运行期间,能提高风机运行效率,实现了厂用电率的大幅降低,达到了节电降耗的目的。且风机运行调节平滑及精度高,有利于锅炉安全、经济运行。风机经变频调速运行后,运行转速下降较多,故又能降低噪音,延长风机使用寿命。     

An utility interactive power electronics interface foralternate/renewable energy systems

The foreseeable shortages in conventional sources of electric power has increased the emphasis on the research and development of alternate sources of energy. In order to make a noteworthy impact, the alternate sources of energy need to be utility interactive by means of a power electronic interface (a DC to AC converter). The inherent assumption in the control of DC to AC converters is, that the DC voltage available at the input of the converter is constant. However, when the input is an unregulated DC source such as a battery, fuel cell, photovoltaic cells or any other form of alternate source, maintenance of the constant DC voltage at the input of the converter is often impossible. A modified inverter switching technique is proposed for the interface with the utility grid such that the AC output of the inverter becomes immune to fluctuations in the unregulated input DC obtained from alternate energy sources     

通用型水泵电机的光伏驱动系统研究

目前光伏水泵的推广面临两个方面的障碍,一方面是应用较多的专用型光伏机泵成本较高;另一方面利用通用变频器驱动通用机泵时光伏利用率低。为了克服这些不足,设计了一种针对通用型水泵电机的光伏驱动系统。系统基于数字信号控制器dsPIC30F2010和IPM智能功率模块,实现了安全稳定运行、真正的最大功率跟踪（TMPPT）及模块化结构。分析了系统的硬件结构,探讨了系统的控制思想及实现,并用实验结果证明了设计的正确性。     

Analysis and Prediction of the Thermal Performance of Piezoelectrically Actuated Fans

An experimentally validated numerical model is developed to analyze the operation of a piezoelectrically actuated cantilever vibrating close to a heated surface. The vibrating cantilever acts as a fan and provides localized cooling. The numerical results for the flow field and heat transfer show satisfactory agreement with experiments. The numerical model is used to develop fan curves for the piezoelectric fans, using a methodology similar to that used in constructing pump or fan curves for conventional fans. A simplified model based on stagnation region heat transfer in impingement flows is also proposed to estimate the heat transfer from a piezoelectric fan. The velocities obtained from the piezoelectric fan curves generated are used in this impingement heat transfer model, and the predictions are found to agree with measured stagnation zone Nusselt numbers with an average deviation of 17%.     

变频技术在泵与风机系统中应用的节能分析

根据泵与风机在不同工况下运行的性能与特点，分析了变流量运行时，泵与风机流量、扬程(压头)、功率与转速间的关系。介绍了变频器在泵与风机调速上的应用现状，及使用变频器变频调速与挡板节流对比，阐述了变频调速节能原理及经济效益。提出了变流量运行时，泵与风机应采用变频技术，合理配备，并举例分析比较了电厂鼓风机采用变频调节时的特性、耗能情况及其经济性。     

汽车发动机冷却系仿真优选方法的研究

介绍了汽车发动机冷却系散热器、风扇和水泵的仿真优选方法。建立了散热器性能计算模型,提出了散热器优选的方法。通过收集不同结构形式的风扇和水泵的试验数据,建立风扇性能数据库,应用相似理论,对风扇和水泵进行优选,给出了应用实例。