一种改进的模块化SVG并联交错调制方式

针对模块化SVG系统交错并联调制时存在较大的电流总谐波畸变率(THD)的问题,提出了一种改进的模块化SVG并联交错调制方式。首先,根据该交错并联电路结构,分析交错并联系统的电流纹波,推导出交错并联系统最大电流纹波输出的计算公式。其次,将改进的交错并联调制方式与传统的交错并联方式进行对比,得出改进方式在抑制纹波等方面优于传统方式。最后,通过Matlab/Simulink进行仿真,实验验证所提的改进的模块化SVG并联交错调制方式的可行性和有效性。结果表明,这种交错并联方式在较低的开关频率下,效果十分明显,为低频、小电流的交错并联系统提供了应用基础。     

基于平行图像的糖尿病视网膜病变智能诊断

针对深度学习诊断糖尿病视网膜病变（diabetic retinopathy, DR）面临数据集小、类别不均衡及诊断效果不佳等问题,本文提出基于平行图像和Swin Transformer的DR分级模型。首先基于StyleGAN2-ada构建平行图像生成模型,解决训练图像过少和类别失衡问题。经FID、KID和目视评估,构建的平行图像符合后续工作要求。然后,基于注意力与窗口滑动机制构建DR诊断模型改善诊断效果。最后,使用平行图像训练诊断模型。经验证,本文提出的诊断模型准确率为93.5%、特异性最高为99%、F1分数最高为0.96。与原始图像相比,使用平行图像训练模型后其准确率提升20%、精确率最高提升70%。与其他三种深度学习模型对比,本文所提方法各项指标均达到最优。以上结果表明,本文构建的模型可在小样本数据集下实现较好的诊断效果。     

基于可行空间并行的安全约束最优潮流

为了提高电网控制决策的实时性,文中将计及预想故障安全约束的经济性优化问题分解为以发电成本最小为目标的基态最优潮流主问题和预想故障安全校核子问题,并提出一种基于可调空间切片并行的分解协调算法进行求解,以避免交替迭代。首先,按不同比例对可调空间进行切片形成多个切片方案,并基于并行计算平台采用原始-对偶内点法对各切片方案进行基态最优潮流主问题求解;然后,对各优化后方式进行预想故障并行安全校核;接着从通过安全校核的切片方案中挑选出发电成本最小的方案;最后,以贵州省某市电网为算例分析验证了所提方法的有效性。     

基于并行遗传算法的企业互操作资源选择

为了解决企业互操作环境下的共享资源择优选择的问题,提出了一种基于粗粒度并行遗传算法(CGGA)的企业互操作资源选择策略.首先给出企业互操作环境下的资源选择问题的数学描述;然后结合并行遗传算法的特性,提出基于此算法的解决企业互操作资源选择问题的策略以及相应算法,给出算法设计、实现以及详细的算法过程;最后针对一个企业互操作中的典型实例,对该策略及算法进行了有效验证,并且与传统遗传算法相比较.本算法完成任务的时间平均减少约26%,适应度随遗传代数的增加提高约8%.     

用多种群并行自适应遗传算法解混合FloWshop调度问题

混合流水车间（Flowshop）调度问题是一个NP完全问题，很难用一般的方法解决。构造并采用多种群并行自适应遗传算法求解该问题。仿真结果表明，此算法不仅具有较强的全局收敛性，而且有更快的寻优速度，是求解复杂调度问题的有效算法。     

配置HSS的并联多端高压直流输电线路保护选择性研究

文中综述了并联多端直流线路保护的研究现状,基于并联多端直流主回路拓扑,提出了配置直流高速隔离开关(HSS)的并联多端直流的线路保护配置方案。为解决配置HSS的并联多端直流线路主保护选择性问题,对现有的多端线路主保护存在选择性盲区的原因进行分析,并提出一种新的线路保护策略:将线路主保护分为2段,通过定值配合和新增保护辅助判据策略,解决了通信正常和通信故障下线路主保护选择性问题。通过RTDS仿真系统试验,验证了提出的线路保护策略能有效区分线路区内故障和区外故障,解决选择性问题,实现了某一线路全长范围内发生永久故障时无需多端直流全停,只需隔离故障线路而剩余线路可继续运行,可应用于配置HSS的并联多端直流输电系统中。     

Computation efficiency of parallel systems related to granularity and application form in power system calculations

Many techniques for enhancing the calculation speed of power system analysis by utilizing parallel systems have been proposed. However, the speedups gained in these systems have been small compared to other applications such as circuit simulation, mainly due to the smallness of the problem size of power calculations. The abovementioned studies concentrated on “space parallel computing,” and the parallel implementation granularity is therefore fine due to the inherent size of power system calculations. In this paper, we first study the effect that the ratio of data transmission time to calculation time per grain has on the speedup of total calculation. We show that the smaller ratio raises the efficiency of parallel implementation. Coarser granularity of the problem generally yields smaller ratios. Thus, it is shown that attaining a coarser granularity is important. In power system calculations, the method of time-domain parallel computing produces larger granularity. Another application form which results in much coarser granularity is multiple case analysis. We studied the application of these parallel approaches to transient stability analysis using an MIMD (multiple instruction stream, multiple data stream) distributed memory parallel processor system. On a 16 PE system, we attained a speedup of 6.3 in time-domain parallel computing and a speedup of up to 15.8 in multiple case parallel analysis. These values are much larger than the speedup in space parallel computing, which was less than 2.0. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 14–26, 1997     

Fast power flow for radial power systems using parallel processing

Power flow calculation is a basic tool for power system planning and control which includes power flow analysis, voltage control, service restoration, network reconfiguration, and other operation functions for control centers. In these applications, it is very important to solve the power flow problem as efficiently as possible. This paper presents a fast power flow using parallel processing for radial power systems. This method can be applied to secondary systems and distribution systems. Since it uses as state variables only active and reactive power injection to main lines and laterals, reduction of the number of state variables can be realized. Radical networks are mapped to the tree structure of parallel processor systems in the proposed method. The forward/backward sweep approach is realized by communication from a root processor to leaf processors and vice versa. Using the mapping scheme of the proposed method, each processor has to communicate with only neighboring processors. The proposed method is evaluated on various radial systems with promising results.     

基于混合遗传算法的并行测试任务调度研究

并行测试任务调度核心是将资源合理地分配给测试任务,合理排列任务的执行顺序,最终使整个系统任务执行时间最短。本文提出了一种基于改进的混合遗传算法的并行任务调度算法,并以该算法为基础运用WPF和SQL Server技术实现了一个任务调度工具软件。算法采用一种结合贪婪算法思想的基因编码方式和交叉变异方法;设计了尺度变换的适应度函数,采用确定式采样选择方法,提高了种群质量。试验结果表明该方法及该工具软件可以有效地解决并行测试任务调度问题。     

基于FFT和小波变换的交直流并联输电系统间谐波研究

运用谐波调制理论,结合开关函数的傅里叶分析,研究了在交直流并联输电系统下,交流系统供电电源含有畸变谐波时,直流线路和交流侧都产生间谐波的机理。给出了整流侧直流电压、直流电流以及交流电流产生的间谐波的一般形式。经过小波变换除去信号中的非稳态分量以后,再使用加窗快速傅里叶变换可以很好地得出其中的稳态分量。通过一个典型交直流并联输电系统数字仿真,同时在供电电源含有畸变谐波的情况下,对交直流系统的电压和电流量进行了间谐波计算。利用傅里叶小波分析综合分析法得到的仿真结果和计算结果相比较,验证了间谐波产生机理的正确性和有效性。     

多路LLC谐振变换器交错并联均流控制

LLC谐振变换器多路交错并联具有良好的应用前景,然而谐振元件的参数偏差会导致各路LLC谐振变换器电流不均衡的问题。为了解决这一问题,通过将二次侧的同步整流替换为可控整流方式,利用各路输出电流作为控制信号对二次侧进行脉宽调制控制,提供附加的电压增益,形成均流控制环路,保证各路的电压增益相同,从而实现多路LLC谐振变换器在相同开关频率下运行的均流调节。介绍了该控制的原理及实现方法。基于电磁暂态过程进行仿真,得出不同负载率下的电流不平衡度;同时搭建100 W的实验样机,在电流不平衡度最大的工况下,验证了该均流控制方法的可行性和有效性。     

A parallel genetic algorithm approach to solving the unitcommitment problem: implementation on the transputer networks

Through a constraint handling technique, this paper proposes a parallel genetic algorithm (GA) approach to solving the thermal unit commitment (UC) problem. The developed algorithm is implemented on an eight-processor transputer network, processors of which are arranged in master-slave and dual-direction ring structures, respectively. The proposed approach has been tested on a 38-unit thermal power system over a 24-hour period. Speed-up and efficiency for each topology with different number of processor are compared to those of the sequential GA approach. The proposed topology of dual-direction ring is shown to be well amenable to parallel implementation of the GA for the UC problem     

基于动态虚拟阻抗的多并联逆变器间环流抑制控制策略

孤岛微电网中基于下垂控制的各分布式电源逆变器并联运行,其参数差异会引发系统环流.为此提出一种基于动态虚拟阻抗的环流抑制策略.首先分析了采用下垂控制的逆变器并联时所产生环流的组成成分,得出无功环流占主导以及线路阻抗不匹配造成无功环流的结论.其次在虚拟阻抗中引入无功反馈项,实现无功精确分配,从而抑制无功环流.通过在电压控制方程中加入电压补偿项以消除线路压降,对传统的下垂控制策略进行改进,进一步抑制无功环流.最后在MATLAB/Simulink中搭建了3台逆变器并联的微电网模型,仿真实验结果表明,动态虚拟阻抗控制策略可以消除线路阻抗的影响,实现逆变器间无功功率的精确分配,解决多并联逆变器间的环流问题.     

移动电站直流并联功率分配研究

在分析了交流电源直接并联存在的不足的基础上,提出了采用三相PWM整流—并联—PWM逆变的供电模式。三相PWM整流器输出的直流电压含有谐波导致直流电压不断脉动,交流电源通过三相PWM整流器进行直流并联时,必须考虑电压脉动的影响。针对此问题,通过在整流器输出侧添加电阻的方式,抑制了电压脉动对并联稳定的影响;分析了并联模块接入时机对并联过程的影响;提出了一种实现并联条件下,单个模块输出功率自由分配的控制方式。最后,通过仿真验证了该控制方式的可行性。     

带同杆双回线的T型支接线的故障测距的研究

针对T型线路中出现同杆双回线的线路结构,提出了首先做故障分支判定,然后进行精确测距的新方法。当某支路发生故障时,求取各支路保护安装处的突变量,通过正序网络图,计算两个必要参数用于判别故障支路,区分出非同杆双回线故障、同杆双回线的跨线故障,以及同杆双回线的单回线故障。在此基础上,将非故障支路化简合并,并对同杆双回线故障以及非同杆双回线故障进行分别测距。该方法不仅能够对单回线准确测距,而且针对双回线,也保证了故障测距的精确性,一定程度上克服了T型线路中出现双回线给测距带来的困难。大量的ATP仿真结果表明故障测距的精度基本上不受故障支路,故障类型、系统运行方式、故障点过渡电阻等因素的影响。     

孤岛微网并联逆变器环流抑制与母线电压控制

针对孤岛微网中采用传统下垂控制的并联微源逆变器之间存在较大环流及母线电压和频率偏移问题,文中从环流的一般性定义出发,分析了环流与负荷功率分配之间的定量关系,在此基础上将环流抑制问题转化为功率精确分配问题,并提出了一种母线电压和频率自恢复的改进鲁棒下垂控制方法.将PI控制器引入无功电压控制环中,实现无功功率的精确分配并加...     

Tabu search algorithm for network synthesis

Large scale combinatorial problems such as the network expansion problem present an amazingly high number of alternative configurations with practically the same investment, but with substantially different structures (configurations obtained with different sets of circuit/transformer additions). The proposed parallel tabu search algorithm has shown to be effective in exploring this type of optimization landscape. The algorithm is a third generation tabu search procedure with several advanced features. This is the most comprehensive combinatorial optimization technique available for treating difficult problems such as the transmission expansion planning. The method includes features of a variety of other approaches such as heuristic search, simulated annealing and genetic algorithms. In all test cases studied there are new generation, load sites which can be connected to an existing main network: such connections may require more than one line, transformer addition, which makes the problem harder in the sense that more combinations have to be considered     

基于Spark的并行模拟退火算法求解TSP

模拟退火算法是求解无约束优化问题的有效方法,但求解旅行商问题时存在精度较差、容易陷入局部最优且收敛速度慢等缺点。为了改进上述问题,本文提出了一种基于Spark平台的并行模拟退火算法。修改模拟退火算法的降温函数,构造旅行商问题的解空间,采用大邻域搜索技术和2-opt算子增强局部搜索能力,引入OX交叉思想增强全局搜索能力,提出交叉协同试验并行策略与Spark平台并行实现。选取若干TSPLIB数据集进行仿真实验,对求解质量和运行时间两个方面进行测试,与其它Spark框架的并行算法进行对比实验。仿真结果表明,该算法求解精度有较大的提高,求解速度上对比其他算法提升3-10倍,能够有效求解旅行商问题。     

Transformed HCT for parallel Huffman decoding

This paper proposes a novel and generic Huffman code table (HCT) transform and a simple parallel Huffman decoding method. Codes of the original HCT are left‐aligned, reordered in value, and partitioned into sub‐bands. Two kinds of modification to the codes are introduced in order to reduce the number of sub‐bands. The Huffman decoder can be implemented with a minimized size of single LUT, and the parallel decoding can be completed easily, at a constant rate of up to one code per cycle. An example of MP3 decoder and AAC decoder has been designed to demonstrate the efficiency of the proposed method. Copyright © 2014 John Wiley & Sons, Ltd.     

LLC谐振变换器交错并联技术研究

LLC串联谐振变换器(LLC-Series Resonant Converter)因具有高效率、低EMI、便于磁集成等特有的优点而被广泛应用在现代电力电子设备中,但其本身固有的副边电流纹波系数大的缺点使得LLC-SRC难以被应用于低压大功率的场合。然而,两相或多相LLC-SRC交错并联技术能有效减小输出电流的纹波,提高电源的功率等级,但是并联又带来了负载不均流的问题。采用一种简单的并联结构,解决了两相LLC交错并联中负载不均流问题,300 W实验样机验证了理论分析的正确性和方案的可行性。