DC Link Capacitor Voltage Balancing in a Three-Phase Diode Clamped Inverter Controlled by a Direct Space Vector of Line-to-Line Voltages

In this paper, the direct modulation strategy of a three-level inverter with self stabilization of the dc link voltage is extended to a five-level inverter. Therefore, a new modeling and control strategy of a five-level three-phase diode-clamped inverter (DCI) is presented. The obtained modeling shows that modulated multilevel voltages are obtained by combination of eight different three-level functions, which are called modulation functions. Therefore, a space-vector scheme without using a Park transform is explained. Based on this algorithm, the location of the reference voltage vector can be easily determined. Then, the voltage vectors are selected to generate corresponding levels and simultaneously their durations are calculated. More over, the redundancies of different switch configurations for the generation of intermediate voltages are used to limit the deviation of capacitor voltages. Experimental results are given to illustrate the proposed control strategy of the three-phase three-level diode clamped inverter. Then, obtained results for a five-level three-phase DCI with the extended version of the control strategy are presented to show the good performances of the proposed balancing modulation.     

三相电压型PWM整流器空间矢量控制研究及仿真分析

以电压空间矢量控制的基本原理和概念为基础,结合Matlab／Simulink软件包构建了三相PWM整流器空间矢量控制系统的仿真模型,并详细给出各模型的具体参数。仿真结果显示,该方法简单,控制精度高,用于三相PWM整流器中具有良好的动、静态性能。     

Analysis of Output Current Ripple rms in Multiphase Drives Using Space Vector Approach

Multiphase variable-speed drives, supplied from two-level voltage source inverters (VSIs), are nowadays considered for various industrial applications. Although numerous pulsewidth modulation (PWM) schemes for multiphase VSIs, aimed at sinusoidal output voltage generation, have been developed, no detailed analysis of the impact of these modulation schemes on the output current ripple has ever been reported. This paper presents a comprehensive analytical analysis and comparison of the output current ripple caused by the application of three different continuous PWM schemes, using a five-phase VSI as an example. Main properties of sinusoidal PWM, fifth harmonic injection PWM, and space vector PWM are elaborated and analyzed using the harmonic flux concept. Space vector theory is applied in the analysis. As a result, harmonic distortion factors are obtained for each PWM scheme. Theoretical considerations are verified by simulations and experimental investigation using a custom-designed five-phase VSI-fed induction motor drive.      

反转矢量透射反馈求解光电混合全加器

提出了利用反转矢量透射反馈算法研制偏振编码光电混合全加器，该加法器可以实现两输入的光学算术运算，研制成的各单元器件可用于其它各种光计算机系统中。     

四象限矢量型高压变频器在矿井提升机上的应用

矿井提升机的使用工况决定了其高可靠性、大启动转矩及四象限运行的特性,这对高压变频器的应用提出了更高的技术要求。本文结合现场应用情况,阐述了北京动力源科技股份有限公司四象限矢量型高压变频器的基本原理、功麓特点及技术指标,现场应用效果显示该型产品运行平稳可靠,性能良好。     

变频器在全自动粉粒料包装机中的应用

介绍全自动粉粒料包装机的生产工艺，变频器两种应用方案的电路设计及工作过程和调速方法。     

On the Modeling of Commutation Transients in Split-Phase Synchronous Motors Supplied by Multiple Load-Commutated Inverters

Split-phase synchronous motors equipped with multiple-stator three-phase windings, each supplied by a load-commutated inverter, play an important role in today's very high power electrical-drive applications. A criticality of these systems is the possibility that commutations occur in different motor windings simultaneously. The resulting electromagnetic transient depends on the magnetic coupling of motor phases among them and with rotor circuits. In this paper, a model to describe this phenomenon is presented along with some dedicated tests, conducted on various split-phase configurations, to assess the model validity.     

用单端矢量网络分析仪测试手机RF电路的差分散射参数

本文以声表的测试为例,说明了采用单端矢量网络分析仪测试手机射频(RF)电路的差分散射参数的原理及方法,其中包含物理三端口的散射参数和模式三端口网络散射参数。     

基于高维空间典型样本Steiner最小树覆盖模型的一类分类算法

最小生成树数据描述方法在刻画高维空间样本点分布时,将所有图形的边作为新增虚拟样本以提供同类样本分布描述,这种描述存在分支多覆盖模型复杂,且局部覆盖不够合理的问题。针对该问题,依据特征空间中同类样本分布的连续性规律,提出基于高维空间典型样本Steiner最小树覆盖模型的一类分类算法,该算法首先对目标类训练集进行样本修剪,去除冗余信息和噪声信息,选择最具代表性的样本作为训练集,然后对保留的典型样本构建Steiner最小树覆盖模型。算法分析和仿真实验结果表明,相比最小生成树数据描述,文中提出的方法能在较低覆盖模型复杂度的前提下更合理的描述目标类样本空间分布,构建更合理的覆盖模型,在分类正确率和适用样本规模上都表现出一定的优越性。      

彩色图像超复数空间的自适应水印算法

 针对彩色载体图像,本文提出了一种超复数频域的自适应水印算法,它首先对彩色载体图像进行快速超复数傅氏变换,在超复数频谱实部选择合适频段的基础上,再利用人类视觉系统对彩色载体图像的纹理、边缘和亮度的掩蔽特性,对选择的频段赋予不同的掩蔽强度而嵌入水印,从而在超复数频域内实现了一种彩色载体图像自适应的水印算法.实验结果表明,通过彩色图像的自适应掩蔽,大大提高了超复数频域水印算法的不易感知性和鲁棒性,且抗攻击性能也优于无自适应掩蔽的超复数频域水印算法;和现有文献的比较结果验证了本算法的这些优越性.     

空间矢量脉宽调制在有源滤波器中的应用

文章针对典型的三相整流电路中产生的谐波对电网产生的影响,研究易于数字化的SVPWM,将其应用于并联有源电力滤波器内层跟踪控制中,给出一种补偿功能较为完善的并联有源电力滤波器及其控制方法。仿真结果表明：SVPWM调制用于并联有源滤波控制可以明显改进补偿的动态性能,提高滤波效果。     

Stable Parametric Macromodeling Using a Recursive Implementation of the Vector Fitting Algorithm

A novel least-squares fitting technique is presented for the macromodeling of parameterized frequency responses. Such parametric macromodel can be used for the design, study, and optimization of microwave structures. A key benefit of the proposed method, is that the poles of the macromodel are guaranteed stable by construction. This can easily be enforced when using the presented macromodel representation.      

虚拟电阻在逆变电源输出滤波器中的应用

简述了输出滤波器在逆变电源中减小输出电流波动的作用,对传统LC滤波器存在的瞬时振荡使波形发生畸变的情况进行了分析,提出应用虚拟电阻改变系统振荡阻尼的方法,虚拟电阻是通过一种附加的控制算法来模拟LC输出滤波器的电阻,分析了他的工作原理,并与原有的方法进行了比较。理论分析和仿真证明提出的输出滤波器改进方法简单而有效。     

支持向量机在尿沉渣有形成分分类中的应用

计算机显微图像尿沉渣分析仪,是运用图像处理技术和统计学习理论中支持向量机（SVM）技术,对尿沉渣的有形成分进行自动分类和识别,并从形态学方面对其进行了特征描述。在应用SVM分类方法的过程中,首先建立已知分类的图像,进而提取图像的特征,再对这些特征进行训练,同时交叉验证确定最优的SVM核函数和参数。最后根据训练过程建立的模型来对测试图像分类．结果表明,选用了支持向量机来实现沉渣识别,与传统的方法相比,取得了更高的识别率。     

空间映射算法优化共形天线阵方向图特性

将空间映射算法推广到共形天线阵的优化设计之中,并首次使用该方法对天线的方向图特性进行优化。粗糙模型采用腔模理论结合圆形天线阵理论进行分析,精细模型采用全波电磁仿真软件HFSS整体建模仿真进行分析。计算结果表明,该方法对天线阵方向图特性的优化设计是可行的,并且只需对精细模型计算很少的次数就可以实现优化目标,具有很高的设计效率。     

人工蜂群优化支持向量机算法在网络安全中的应用

针对支持向量机(SVM)性能的影响,探讨了人工蜂群算法(ABC)对SVM参数优化方法,建立了SVM参数优化模型,并将其用于网络安全中的网络入侵模型中.采用KDD 1999数据集进行仿真实验,验证了方法的有效性,结果表明,与遗传算法等传统优化算法相比,ABC优化的SVM有效地降低运行时间,可以获得更高的网络入侵检测率.     

DBSCAN算法在雷达全脉冲信号分选中的应用

对雷达辐射源信号进行准确分选是电子对抗情报分析的基础性问题,聚类是进行全脉冲分选的一种有效的方法。基于密度聚类的DBSCAN算法具有抗噪声性能好,能处理任意形状和大小的数据的优点,适合全脉冲信号的数据特征。文章应用DBSCAN算法对雷达全脉冲信号分选进行了研究,仿真结果证明该方法简单有效。     

基于TDMA的分布式全双工链路调度算法研究

为了解决无线Ad hoc网络在负载较重时网络性能差等问题,提出了一种将TDMA（Time Division Media Access）与CCFD（Co-time Co-frequency Full Duplex）相结合的分布式全双工MAC（Media Access Control）协议.数据传输前节点首先在链路共存准则的基础上进行抑制检查,随后主链路按一定的优先级筛选二级链路并发起调度请求,调度所需的四次握手过程在业务时隙头部完成.本协议在不影响传统TDMA半双工通信的条件下,增加同一时隙中可以共存的链路数,改善网络的吞吐量和时延性能.