共查询到20条相似文献,搜索用时 187 毫秒
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随着电力用半导体应用设备的增加,高次谐波的产生和故障成了日本电网的问题.所谓高次谐波是50HZ、60HZ工频繁数倍频率(100、150、200HZ等)的电压或电流.最近,从产业到家庭广泛采用了可控硅和晶体管等电力用半导体应用设备.如:整流器、变换器、循环换流器、交流电力调整器等.因为这些设备通过工频电源正弦波对可控硅.晶体管输入和截出,配合连接物向负荷供直流或可变频的电压或电流.系统的负荷电流只在可控硅导电期间流过形成畸变波形.这种电流除基波外含有多阶高次揩波.图1为其概要,由于高次谐波电压下降影响,电源电压也畸变. 相似文献
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一、高次谐波源在我国电力系统中,发电机所产生的电能是标准的正旋波形,其频率为50HZ,额定电压(低压用户侧)规定为380V(三相)和220V(单相)。然而,由于电力用户的用电设备有一部分是非线性负载,它们从电网中吸收的电流为非正旋波,导致电力系统的电源波形发生畸变,从而成为对电网的污染源。变频调速装置的主电路由晶闸管整流器和逆变器组成,输出电流、电压均为非正旋波,都不可避免地产生高次谐波,使电源波形畸变,对电网产生污染。图1为典型的三相全波桥式晶闸管整流电路,其电源电压波形虽为正旋波形,但其吸取的电流波形… 相似文献
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变频设备中的变频器产生大量6k±1次谐波,此特征谐波使电网电流波形严重畸变,THD超过国标(GB/T14549-93)限值。对此本文提出有效的谐波抑制方案,并给出了单调谐滤波器的详细设计过程,同时通过仿真分析验证了谐波抑制效果的明显性。 相似文献
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大容量海上风电机组的接入改变了传统电力系统结构,给电网带来了谐波等问题,影响了电能质量。为抑制海上风电机组产生的低次谐波,文章首先建立了海上风电机组并网电流的低次谐波理论模型;然后,在仿真软件ETAP上搭建海上风电机组仿真模型,验证不同出力情况下风电场的输出谐波特性;最后,基于风电场输出谐波特性,提出变异系数(Variation Coefficient,VC)综合赋权法对风电场有源滤波器(APF)进行优化配置,提升了风电场谐波的治理效果。基于实际算例验证了所提方法的有效性。 相似文献
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M701F燃气轮机在启动时,通过SFC装置在发电机定子通入变频电流,使发电机作为电动机带动机组旋转直至自持转速。本文结合SFC装置,阐述了其变频工作原理,并对可控硅触发脉冲的控制原理、相关运行参数的设定、机组升速过程进行了分析。 相似文献
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模块化多电平换流器(Modular Multilevel Converters,MMC)具有维护方便,易扩容等优点,在柔性直流输电(High Voltage Direct Current,HVDC)、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容,在实际使用中会产生谐波环流,影响了模块电容电压波动,降低换流器的安全裕度和经济性。文章首先介绍了MMC组成结构;然后通过建立桥臂瞬时功率方程,分析环流产生机理,并得出桥臂环流中存在二次谐波分量的结论,通过控制直流侧电压与桥臂等效输出电压之间的差值,调节环流中的谐波分量,进而将现阶段国内、外环流抑制方法分为间接环流抑制方法与直接环流抑制方法,并对环流的利用也做了相关阐述。最后对环流抑制存在的问题进行总结与展望。 相似文献
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结合西门子燃机和三菱燃机的典型配置,介绍了燃气轮发电机静态变频启动(SFC)装置的结构、工作原理和保护配置。基于燃气轮发电机SFC的步骤,分析了SFC的特点以及对发电机保护的影响。通过理解和分析低频过流保护、SFC装置直流接地保护的设计思想,提出了减少燃气轮发电机SFC过程中,防止发电机差动保护、频率保护和逆功率保护误动的措施,实际运行表明这些技术措施是可行的。 相似文献
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《International Journal of Hydrogen Energy》2019,44(14):7059-7072
This paper deals with hydrogen production via water electrolysis, which is considered the most attractive and promising solution. Specifically, the use of renewable energy sources, such as wind electric power generators, is hypothesized for supplying the electrolyzer, aiming to strongly reduce the environmental impact. In particular, micro-wind energy conversion systems (μWECSs) are attractive for their low cost and easy installation. In order to interface the μWECS and the electrolyzer, suitable power conditioning systems such as step-down DC-DC converters are mandatory. However, due to the requested high conversion ratio between the DC bus grid, i.e. the output of a three-phase diode rectifier connected to the output of the electric generator, and the rated supply voltage of the electrolyzer, the classic buck converter alone is not suitable. Therefore, a converter is proposed and designed, consisting of a buck converter, a full-bridge IGBT converter, a single-phase transformer, and a diode bridge rectifier; LC filters are also included between buck and full-bridge converters, and at the output of the diode bridge rectifier with the aim of reducing the ripple on currents and voltages. The components of the described physical system from the output of the three-phase rectifier up to the electrolyzer are then modeled assuming the transformer as ideal, and the model is employed for designing a PI-type controller. Experimental results are provided in order to demonstrate the effectiveness of the developed converter and its control for these applications. 相似文献
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An innovative power conversion system to convert energy from a variable-frequency wind-powered induction generator to a fixed frequency output is presented. A standard six-switch DC link current regulated pulse width modulated (CRPWM) inverter is simultaneously modulated with two current components. A three-phase balanced current component at the induction generator's optimum operating frequency transfers energy from the generator to the converter. A single phase zero sequence current component at a fixed 60 Hz frequency transfers energy from the converter through a zero sequence filter to the load. Unity power factor output is shown both in simulation and experiment, though any arbitrary power factor output may be readily commanded. Maximum power capture for a variable-speed wind turbine is achieved using proven control techniques. This method uses only half of the active power switching devices of conventional conversion methods. Simulation and experimental verification are shown 相似文献
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设计开发了一种配备新型周向变流式排气混合器的筒式后处理系统,以某型3.0L排量的国六柴油机后处理为例,首先设计了排气混合器结构,建立了该催化器的流动及尿素喷射、雾化和扩散模型,进行全尺寸排气流场模拟分析,研究了混合器后的速度均匀性、NH_3浓度分布和压降损失等,并对特征尺寸进行了优化。结果表明,优化的结构尺寸及设计使标定工况下NH_3均匀度可以达到0.996,混合器压降不超过4.17kPa。然后进行了发动机台架试验,验证了新开发设计优化的后处理系统阻力较小,标定工况下实测的NH_3均匀度高达0.98,不同空速和温度情况下,不带扰流板的混合器表现更优。最后进行了发动机排放试验,全球统一瞬态循环和全球统一稳态循环结果达到国六标准要求,确证了新开发的选择性催化还原系统及排气混合器能够用于道路车辆国六重型柴油机。 相似文献
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便携式X射线机为保障特种设备的安全发挥巨大作用。是典型的用低压电产生高管电压的检测设备,管电压可高达400kV。控制精度及稳定性至关重要。文中详细分析便携式X射线机管电压、管电流的测量原理,提出基于以上原理的一种便携式X射线机管电压、管电流的计算机测控方法,同时采用可控硅整流实现管电压控制、IGBT变频实现管电流控制。试验数据证明:其管电压、电流控制精度较高,稳定性好,能满足工程需求。该射线机具有良好市场前景。 相似文献
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It is well known that for a given solar radiation intensity and solar cell temperature there exists a Maximum Power Point at which the power generated from the PV panel is at its maximum. A system designer is interested in optimal matching of the load to the PV generator so that the maximum power can be obtained during operating period. A Maximum Power Point Tracker (MPPT) using a step up converter with a current locked loop is developed. Its performance is compared with the literature (the step down power converter using PWM technique), under different solar irradiance and ambient temperatures. It showed an improvement in the output power by 22.5% (average) over a wide range of solar irradiation in a day. 相似文献