多电平逆变器特定谐波消除控制技术研究

为了深入分析多电平逆变器特定谐波消除脉宽调制技术的非线性求解法,建立了多种迭代算法求解模型,研究了模型求解特点,对传统数值算法在特定谐波消除求解时所体现的不足进行了分析和改进。以七电平逆变器为例,给出了各算法在不同调制波段下的求解情况,对各算法中一些参量的设置及消谐效果进行了比较。仿真结果证明了各算法求解结果的正确性。     

一种用于三电平能馈逆变器的改进型特定次谐波消除脉宽调制算法

大功率变换器的最高开关频率受散热系统限制而无法提高,导致低次谐波含量增大.为了更好地抑制谐波含量和提高并网电能质量,在对三电平逆变器和传统特定消谐算法深入分析和研究的基础上,文章提出了一种应用于三电平逆变器的改进型特定次谐波消除脉宽调制(SHEPWM)方法.该方法在保持传统SHEPWM算法优点的基础上,克服了在消除低次...     

五电平逆变器双波段SHEPWM控制方法研究

将能拓宽多电平逆变器调制比的SHEPWM方案与Walsh变换相结合,提出了一种五电平逆变器双波段SHEPWM控制方法;分析了傅里叶级数变换下的多电平多波段SHEPWM电压波形,归纳出了各波段模式下SHEPWM非线性方程组的一般形式;并利用Walsh变换将非线性方程组转换为易解的分段线性方程组,从而达到简化计算过程和拓宽调制比的目的。以五电平H桥级联逆变器为例,给出了A,B波段模式下的Walsh函数分段线性方程组,并通过实验验证了五电平逆变器双波段SHEPWM控制方法的正确性及可行性,为实现SHEPWM控制技术的在线运算及实时控制奠定了基础。     

串联H桥多电平逆变器特定谐波控制组合法

针对串联H桥多电平逆变器输出阶梯电压波形中存在低频谐波的问题,提出了一种特定谐波控制组合法。该方法以梯形波调制为基础,利用等面积法原理和谐波注入组合法,通过简单的三角公式递推计算获得实现特定谐波消除的开关导通角,并对开关导通角进行优化,从而实现谐波抑制。以三相九电平串联H桥逆变器为例,进行了仿真和实验,结果验证了该方法的可行性和有效性。     

DSP在多电平逆变器中的应用

分析研究了多电平逆变器中消谐波PWM的技术原理,在此基础上利用TI公司TMS320LF2407A控制器的事件管理器模块中的比较单元特性,得到了DSP实现消谐波PWM技术的算法。最后在实验样机上得到了实验结果,验证了此算法的可行性。     

萤火虫算法在三电平NP C逆变器中的应用

针对特定谐波消除脉宽调制(SHEPWM)策略工作过程中准确求解开关角度难度较大的问题,利用萤火虫算法(FA)对SHEPWM策略的非线性方程组进行求解.同时,针对传统FA收敛速度慢、易陷入局部最优解的问题,通过加入惯性权重和高斯扰动策略,分别对FA中的个体位置更新和最优个体更新操作进行改进.利用MATLAB进行仿真.仿真...     

一种改进的三电平逆变器空间矢量脉宽调制算法研究

二极管中点箝位型三电平逆变器广泛用于中高压大容量交流调速系统,具有对器件耐压要求低,输出谐波含量低等优点,但同时存在如何保持中点电压平衡和防止电压跳变等问题.空间矢量脉宽调制(SPVWM)算法能很好地跟踪转矩和磁链的设定值,有效地降低转矩和磁链的脉动,但算法复杂,运算量大.本文在分析了影响三电平逆变器中点电压平衡的主要因素的基础上,提出一种改进的SVPWM算法.该算法用中矢量、长矢量和两个短矢量合成参考矢量,并采用矢量调制的方法,利用短矢量的电流特性,消除中矢量对中点电压的影响,简化了算法,有效地控制了逆变器的中点电压,抑制了电压跳变.仿真结果证明了这种方法的可行性.     

用于多电平逆变器的多载波PWM技术的研究

介绍了2H桥级联电路结构,研究和分析了用于多电平逆变器的三种不同的多载波PWM调制策略,并分析了逆变器侧输出电压频谱。在上述调制策略基础上结合多参考波调制方法,采用新型的多参考波和多载波的PWM技术,在Matlab/Simulink环境下构建了PWM调制模型。仿真结果与典型的多载波PWM策略结果的比较显示,新型的多载波控制方法能够小幅减小总谐波的失真率(THD),改善了输出电压频谱。     

一种改进的混合级联多电平逆变器研究

文章以实际功率器件的耐压值为基础,采用增加低压单元的混合级联拓扑,辅以优化的PWM算法,设计出了适用中高压场合的多电平逆变器方案。改进的混合级联多电平逆变器不但输出波形质量好,而且有效地解决了倒灌电流的问题。     

3H桥级联型多电平逆变器的改进SVPWM方法的研究

钳位型多电平逆变器和2H桥级联型多电平逆变器电路结构和控制复杂,3H桥级联型多电平逆变器可克服该缺点;五电平逆变器的SVPWM控制方法已经实现,若将其应用于输出更多电平数的逆变器,则计算量非常大,控制困难,而在该控制方法的基础上,通过在电压空间矢量之间采用合适的相移角度,则可方便地实现3H桥级联型多电平逆变器的SVPWM控制。文章以3H桥级联型九电平逆变器为例,采用Matlab仿真验证了该控制方法的可行性和正确性。     

级联多电平逆变器载波移相调制法的优化研究

针对传统级联高压变频器载波移相调制方法存在开关损耗大、直流电压利用率低等问题,及载波移相与矢量控制相结合的调制方法存在计算量大、计算繁琐、不易实现的问题,提出了级联多电平逆变器的优化控制方法——调制信号叠加零序分量法和两相控制法。该方法采用基于控制自由度组合的思想,通过向调制波中注入零序分量、直流分量等自由度来提高直流电压利用率、减小开关损耗。仿真结果验证了该方法的可行性。     

用于数字图像传感器的脉冲宽度调制读出方法研究

为提高数字像素图像传感器的动态范围,提出了一种具有自适应参考电压的脉冲宽度调制读出方法。该方法将像素阵列分成包含相同数目像素的像素块,通过参考电压产生模块使每个像素块的参考电压和像素块内光照强度相关,理论上这种结构能够将数字像素图像传感器的动态范围从48 dB提升至96 dB,实际仿真结果为88.16 dB。分析了像素分块内主要的噪声来源和参考电压产生模块的采样电容引入的偏差。采用65 nm CMOS工艺实现了4×4的像素块电路,在高光强和弱光强条件下分别将电路输出同理论计算值相比较,并分析了产生误差的原因。     

三相脉宽调制整流器的约束预测控制

本文将基于并行神经网络优化的约束模型预测控制(MPC)应用于脉宽调制(PWM)整流器中,提高了电网的质量.在三相静止坐标系下,建立了三相PWM整流器的解耦数学模型,采用约束模型预测控制策略,突破了有限集和无约束条件下预测控制的局限性.为了提高单步优化的速度,采用神经网络优化算法求解模型预测控制的在线优化.在保证系统单位功率因数的前提下,当系统负载突然变化时,具有快速动态响应稳定输出直流电压的性能.采用FPGA控制器实现并行计算,减少了预测控制算法的计算时间.最后,通过仿真和实验结果得到,采用本文的控制策略,总谐波失真(THD)降低了2.5%,达到稳态的时间大约是PI控制算法的五分之一,为12 ms,验证了该方法的可行性和有效性.     

Comparison of clustering algorithms for analog modulation classification

This study introduces a comparative study of implementation of clustering algorithms on classification of the analog modulated communication signals. A number of key features are used for characterizing the analog modulation types. Four different clustering algorithms are used for classifying the analog signals. These most representative clustering techniques are K-means clustering, fuzzy C-means clustering, mountain clustering and subtractive clustering. Performance comparison of these clustering algorithms and the advantages and disadvantages of the methods are examined. The validity analysis is performed. The study is supported with computer simulations.     

Equivalent load impedance of pulse width modulation excited band pass filters

Many efficiency enhancement concepts for power amplifiers (PAs) rely on pulse width modulation in combination with direct filter connection. Direct connection of bandpass filters results in load modulation for the PA. Therefore, the resulting equivalent impedances, respectively, load trajectories, are important for efficient operation. This article presents analytical equations to calculate these equivalent load impedances. The equations are parameterized with two impedance values making them independent of the filter structure. Based on the presented equations a PA design properly taking the load modulation into account can be done. This is shown based on a design example of a biphase energy recovery transmitter, verifying the general validity of the equations. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:164–172, 2015.     

Comparison of selected algorithms for scheduling workflow applications with dynamically changing service availability

This paper compares the quality and execution times of several algorithms for scheduling service based workflow applications with changeable service availability and parameters. A workflow is defined as an acyclic directed graph with nodes corresponding to tasks and edges to dependencies between tasks. For each task, one out of several available services needs to be chosen and scheduled to minimize the workflow execution time and keep the cost of service within the budget. During the execution ofa workflow, some services may become unavailable, new ones may appear, and costs and execution times may change with a certain probability. Rescheduling is needed to obtain a better schedule. A solution is proposed on how integer linear pro- gramming can be used to solve this problem to obtain optimal solutions for smaller problems or suboptimal solutions for larger ones. It is compared side-by-side with GAIN, divide-and-conquer, and genetic algorithms for various probabilities of service unavailability or change in service parameters. The algorithms are implemented and subsequently tested in a real BeesyCluster environment.     

并联脉宽调制整流器非线性L2增益环流抑制控制

针对由于模型参数分散和外部干扰引起的并联脉宽调制(pulse width modulation,PWM)整流器环流问题,提出了最优L_2增益电流内环控制与非线性L_2增益零序环流外环控制相结合的控制方法.最优L_2增益电流内环控制不仅可以实现干扰对输出的增益最小,还可以灵活实现并联PWM整流器之间的功率平移.非线性L_2增益零序环流外环控制可以有效抑制由于模型参数不确定和外部干扰引起的环流问题.并联PWM整流器双环L_2增益控制仿真结果表明:相对于传统的比例积分控制方法,该方法可以明显降低并联PWM整流器之间的环流,并可提高并联PWM整流器的供电品质,对于增强系统的稳定性具有重要意义.     

Comparison of two construction algorithms for local model networks

The divide-and-conquer approach of local model (LM) networks is a common engineering approach to the identification of a complex nonlinear dynamical system. The global representation is obtained from the weighted sum of locally valid, simpler submodels defined over small regions of the operating space. Constructing such networks requires the determination of appropriate partitioning and the parameters of the LMs. This paper focuses on the structural aspect of LM networks. It compares the computational requirements and performances of the Johansen and Foss (J&F) and LOLIMOT tree-construction algorithms. Several useful and important modifications to each algorithm are proposed. The modelling performances are evaluated using real data from a pilot plant of a pH neutralization process. Results show that while J&F achieves a more accurate nonlinear representation of the pH process, LOLIMOT requires significantly less computational effort.