Novel Double-Damped Tuned AC Filters in HVDC Systems

This paper presents a performance analysis of novel doubledampedtuned alternating current (AC) filters in high voltage direct current(HVDC) systems. The proposed double-damped tuned AC filters offer theadvantages of improved performance of HVDC systems in terms of betterpower quality, high power factor, and lower total harmonic distortion (THD).The system under analysis consists of an 878 km long HVDC transmissionline connecting converter stations at Matiari and Lahore, two major cities inPakistan. The main focus of this research is to design a novel AC filter usingthe equivalent impedance method of two single-tuned and double-dampedtuned AC filters. Additionally, the impact of the damping resistor on the ACchannel is examined. TheTHDof theHVDCsystem with and without currentAC filters was also compared in this research and a double-damped tuned ACfilter was proposed. The results of the simulation represent that the proposeddouble-damped tuned AC filter is far smaller in size, offers better powerquality, and has a much lower THD compared to the AC filters currently inplace in the converter station. The simulation analysis was carried out utilizingpower systems computer-aided design (PSCAD) software.

ACF的结构及其滤材特性的研究

根据活性炭纤维(Activated Carbon Fiber,简称ACF)与颗粒状活性炭(Granular Activated Carbon,简称GAC)的平行实验,对比了ACF与GAC的物化特性和基本结构,以说明ACF作为新型环境功能材料的特点。在实验室建立的流动法测定材料吸附特性的系统中,对ACF在不同流量下对不同上游浓度污染气体(NH_3)的吸附性能进行了测定,获得了ACF的穿透曲线,对其吸附性能与吸附床流量和上游浓度进行了相关分析。并对以ACF为滤料的空气过滤器的除污性能进行了测试。

TiO_2/ACF滤网在闭式循环系统中降解气相二甲苯的研究

以AlPO_4为粘结剂采用胶粘法制备ACF负载TiO_2滤网(简写为TiO_2/ACF滤网),利用XRD和BET等手段对TiO_2/ACF滤网进行了表征。自行搭建闭式循环实验系统,以气相二甲苯为模型污染物,在系统中进行二甲苯气体的吸附-光催化降解实验,考察了初始质量浓度、迎面风速和相对湿度对降解效果的影响。研究结果表明,纳米TiO_2通过AlPO_4的粘结作用较好地负载到了ACF表面,TiO_2/ACF滤网的BET比表面积为672.8m^2/g.当ρ0=28～42mg/m^3时,初始质量浓度的变化对降解过程影响不显著。随着迎面风速的增大,TiO_2/ACF滤网对二甲苯气体的吸附率和光催化降解率均先升高而后降低,在迎面风速v=0.30m/s时达到最大。随着相对湿度的增加,TiO_2/ACF滤网对二甲苯气体的吸附率逐渐降低,而光催化降解率则是先上升后下降。相对温度(RH)为50%时,TiO_2/ACF滤网对二甲苯气体的吸附-光催化降解率达到最大。

结合ACF和TFBSS的心冲击伪迹抑制方法

同步脑电-功能磁共振成像(EEG-f MRI)可同时对大脑活动进行高时间和高空间分辨率观测,但磁共振扫描导致采集得到的脑电信号中包含心冲击伪迹,严重制约了同步EEG-f MRI应用的发展。为此,提出一种结合自适应梳状滤波器(ACF)与时频盲源分离(TFBSS)的心冲击伪迹抑制方法,首先估计脑电信号中心冲击伪迹的J峰位置,并根据该位置自适应调整梳状滤波器参数,对脑电(EEG)信号进行自适应梳状滤波,初步抑制其中的心冲击伪迹。然后利用TFBSS对心冲击伪迹作进一步抑制,最终获得较为清晰的EEG信号。采用临床EEG信号进行心冲击伪迹抑制实验,选择视觉效果、归一化功率谱比值和峰峰值比值评价性能。实验结果表明,所提出的方法能成功抑制心冲击伪迹;且相对于传统的心冲击伪迹抑制方法更有优势。

基于ACF BP滤波的国际油价长周期测定(1861-2016年)

为判断新一轮油价长周期拐点是否已经出现,应用ACF BP滤波方法对1861-2016年国际原油价格进行周期成分测定。结果显示,国际原油价格存在三个明显的长周期:第一个从1861年开始到1885年结束;第二个从1967年开始到1996年结束;第三个从1997年开始,2010年后已经进入下行通道。1886-1966年国际原油价格波动较小,因此认为是不确定周期波动时期。油价长周期除受经济周期的影响外,还受到固定资产投资周期的影响。在已经结束的两个长周期中,下行周期最短为15年。如果油价周期波动特性不发生明显偏离,那么本轮油价的下行周期将持续至2025年左右。当前全球经济增长乏力,可替代能源迅猛发展,非常规油气开采技术不断进步,都是阻碍油价进入新一轮上行周期不利因素。在油价可能持续低迷的情景下,石油企业除加强对油价的监测预测和采取金融工具对冲外,还应针对油价的不同周期阶段采取不同的经营策略。

污秽潮湿条件下ACF瓷柱式断路器直流泄漏电流和直流电压分布规律研究

为了模拟交流滤波器瓷柱式断路器开断容性负载后直流电压分布,在人工气候室开展污秽潮湿环境下断路器双断口直流电压分布规律及电压—电流特性研究,在不同断口污秽比值与环境湿度条件下,通过直流高压发生器使断路器双断口同时承受直流高压,测量断口泄漏电流及断口间直流电压。试验结果表明:环境相对湿度达到90%及以上时,断路器2个断口由于污秽分布不均引起瓷套表面电导率不一致,导致开断容性负载后负载侧的直流电压大部分集中在同一个断口上,且随着相对湿度提高,断口泄漏电流会出现急剧增加的拐点。此外,还提出解决直流电压分布不均匀的研究方向。

REALIZATION OF FUZZY-FILTER CONTROL ON A BRUSHLESS AC GENERATOR

The transistor voltage regulators have been widely adopted in the brushless AC generators in aircraft. This paper researches the digital voltage regulator. The paper presents the hardware platform of the digital voltage regulator, which is based on a DSP chip — TMS320C32. A novel fuzzy filter control structure is developed from normal fuzzy control strategy. And the fuzzy filter control algorithm is adopted in the hardware platform successfully. The computer simulation has been conducted. Some control parameters have been obtained through the simulation. The same parameters have been applied in the digital regulation experiments on a brushless AC generator. In the experiment, the digital voltage regulator results in good responses. From the experiment results, it can be seen that the new control algorithm is efficient for the digital voltage regulator.

Harmonic detection an AC excited generation system based on in-phase correlation filtering

The paper reports results of investigation on the harmonic detection technique of a complicated power supply system such as an AC excited generation system, which has a variable fundamental frequency and low order harmonics with rich sub-harmonics whose frequencies are lower than the fundamental one. The in-phase correlation filtering technique, based on the frequency shifting principle, is proposed in this paper.Theoretical analysis and experimental results validate the effectiveness of this technique for the harmonic detections of AC excited generation systems.

AC Line Filter Electrochemical Capacitors:Materials,Morphology,and Configuration

Recently,more and more supercapacitors(SCs)have been developed as AC line filter capacitors,which are generally named AC line filter electrochemical capacitors(FECs).Compared to traditional bulky aluminum electrolytic capacitors(AECs),FECs have higher capacity and lower space occupancy,which makes them a strong competitor.However,different from the common SCs for energy storage,it is necessary to consider the frequency response of the SCs for AC line filtering,where the contradiction between frequency response and specific capacitance is a challenge.The researchers have proposed different solutions from the perspective of materials,morphology,and configuration for this challenge.Based on the above background,in this review,we briefly introduce the principle and parameters of AC line filter electrochemical capacitors.We systematically summarize the state-of-the-art progresses of FECs and discuss their possible application and development in the future.The development of FECs can greatly promote the planarization,integration,and miniaturization of filter capacitors,and provide a new solution for the utilization of green and unstable energy.

Coupling model of AC filter branch in SF6 circuit breaker during the break process

In this paper, a coupling model of the AC filter branch circuit with the arc plasma in the circuit breaker was built to investigate the arcing process considering the harmonic current. The comparisons among the current at power frequency(50 Hz), power frequency combining the 11 th harmonic and power frequency combining the 24 th harmonic show that the high-order harmonic current would lead to higher decreasing rate of current before current-zero period. In addition, the influence of arc on the amplitude of high-order harmonic current is not negligible. Thus, the coupling of arc with AC filter branch circuit is quite necessary in the numerical modeling of the circuit breaker in the AC filter branch at the high voltage direct current converter station.

A Review of Nonlinear Kalman Filter Appling to Sensorless Control for AC Motor Drives

Sensorless control of AC motor drives,which takes the advantages of cost saving,higher reliability,and less hardware,has been developed for several decades.Among the existing speed sensorless control methods,nonlinear Kalman filter-based one has attached widespread attention due to its superb estimation accuracy and inherent resistibility to noise.However,the determination of noise covariance matrix and robustness of model uncertainties are still open issues in practice.A great number of studies try to solve these problems in resent years.This paper reviews the application of extended Kalman filter(EKF),unscented Kalman filter(UKF),and cubature Kalman filter(CKF)in speed sensorless control for AC motor drives.As an iterative algorithm,EKF has advantages in processor implementation.However,EKF suffers from the linearization error and model uncertainties when applying to sensorless control system.This paper presents the predominant improvements of EKF which is also applicative in UKF and CKF mostly.

High-frequency supercapacitors with phosphorus-doped Ketjen black

Compact supercapacitors(SCs)have attracted attention for their great potential to replace bulky aluminum electrolytic capacitors(AECs)in alternating current(AC)line filtering applications.Herein,the fabrication of a high-frequency SC is reported using Ketjen black(KB)nanoparticles doped with phosphorus(P)to achieve a high areal capacitance of up to 2.26 mF cm^(-2)along with a high-rate capability,with a phase angle of-80.2°at 120 Hz.The high performance of the phosphorus-doped KB(designated PKB)SC with a 6 M KOH aqueous electrolyte is associated with its increased surface wettability and additional capacitive sites provided by the P-doping.Density functional theory(DFT)calculations further indicate that the P-doping enhances the interactions between the electrolyte ions and the carbon surface,thus leading to an improved electrochemical performance.These results suggest that the P-doped carbonbased SC could be highly favored in replacing conventional AECs in various high-frequency electronic devices.

Power Factor Improvement of AC-DC Converter Based on Separately Excited DC Motor Using Passive Filter

In industries DC motor drives are very essential due to their high performance applications such as its reliability, ease of control, low cost and simplicity. And speed control of these motors is very easy due to power electronic AC-DC converters. These power electronic converters are with prominent low power factor and higher Total Harmonic Distortion (THD). These converters operate only for short time resulting non-sinusoidal waveform. This problem of harmonic distortion can be mitigated by reshaping the non-sinusoidal waveform to pure sine wave. Different wave shaping techniques have been developed by using different filters among which one is tuned passive filter. This paper proposed power factor improvement and harmonic mitigation of AC-DC converters based on separately excited DC motor using tuned passive filter. In this context experimental model is designed and results are analyzed by power quality analyzer.

基于MATLAB GUI的交流电路频率特性仿真教学平台设计

为了使学生更加直观地理解交流电路中的频率特性,构建了一种基于MATLAB GUI的交流电路频率特性仿真教学平台。该仿真平台包括RC滤波电路和RLC谐振电路两个模块,其中RC滤波电路能够实现低通滤波、高通滤波和带通滤波电路频率特性的仿真研究,RLC谐振电路能够实现串联谐振和并联谐振电路频率特性的仿真研究。借助该仿真平台,只需手动输入电路元件参数,就能获得各交流电路的幅频和相频特性曲线,最后将源程序封装成.exe文件。该仿真平台操作简单,便于任课教师和学生使用,能够显著地提高课堂教学质量。

计及AC-UHVDC系统无功补偿和谐波特性的UHVDC交流滤波器可靠性建模

特高压直流输电(ultra high voltage direct current,UHVDC)故障对电网影响严重,建立精确的可靠性模型十分必要。交流滤波器(ACfilter,ACF)子系统与交流母线并联,可补偿无功,减少谐波。谐波过大或无功不足均可能导致UHVDC降额。提出一种计及无功补偿和谐波特性的ACF可靠性模型,用矩阵组合将单一型号滤波器状态空间(state space,SS)合并成ACF所有配置方案的SS模型。由ACUHVDC基波潮流确定ACF需提供无功容量等级,进而将配置方案分组。由谐波潮流计算各配置方案的谐波指标,若谐波电流超标,将配置方案移至容量等级较低分组。根据分组情况,合并配置方案为五状态容量模型。算例表明,配置方案按无功补偿分组后,可能会因不满足滤波指标而被移至0%CL分组,故0%CL状态概率可能比75%CL、50%CL或25%CL状态高。

直流换流站高通HP3型交流滤波器电抗器匝间故障监测及保护

直流换流站高通HP3型交流滤波器组中电抗器匝间短路故障事故多发,由于缺乏对此故障的快速监测及保护,导致其匝间短路持续存在3~9 min之久并起火燃烧。匝间短路后电抗器的等值电感会不断减小,由此引起了滤波器电路参数变化并进而引发了滤波器配置的热过负荷保护启动告警,长久故障也引发了次生的电抗器底部支撑绝缘子闪络接地致使滤波器差动保护动作出口跳闸。文中分析了3起典型故障案例,结合C型高通HP3型滤波器电路设计理念及运行特点,解释了有关保护启动及动作的原因。基于匝间短路会导致HP3电路中电阻器上的工频电压、电流会随着匝间短路的不断发展而剧烈增大的特性,提出了一种基于工频电压差动原理的故障监测及保护方法。

基于引导滤波分层的宽动态范围红外图像细节增强算法

针对宽动态范围红外图像在视觉效果方面出现的对比度低、细节信息不凸显及整体清晰度较差问题,本文提出了一种基于引导滤波分层的宽动态范围红外图像细节增强算法。该算法采用方差决策加权引导滤波对原图作分层,得到了更接近原图的基础层和更精细的细节层。为提高基础层的对比度,首先改进CLAHE的全局剪切点提升增强效果,然后基于AC视觉显著模型指导全局和改进局部直方图的融合,合理兼顾了图像背景和目标;为有效加强细节信息,基于多尺度加权引导滤波得到了信息更全面的新细节层,接着采用梯度域导向滤波对其消噪,再由Sigmoid函数压缩强边缘并突显细微目标,最后将两层信息融合并输出。实验结果表明,该算法在主观视觉和定量指标上均强于对比算法,且自适应强,鲁棒性好。

基于双向DC/AC变换器的混合储能系统动态控制策略

针对风电和光伏并网发电系统的功率波动问题,研究了一种基于双向DC/AC变换器的混合储能系统的动态控制策略。对含有超级电容器与蓄电池组的混合储能系统,通过双闭环控制器对变换器内部的电压电流进行控制,把波动变化较快的电流分量分配给超级电容器,由蓄电池来响应波动变化较慢的电流分量。同时,控制系统将超级电容器的电压稳定在预设范围内。基于扩展卡尔曼滤波(Extended Kalman Filter,EKF)对蓄电池的荷电状态(State of Charge,SOC)进行控制,使其SOC值稳定在安全范围内并延长了蓄电池的使用寿命。通过仿真实验,验证了控制方法的有效性。