基于FPGA改进型串联混合有源电力滤波器的研究

为了解决电力电子等非线性变流装置和大容量动态负载所带来的电网日益严重的谐波问题,本文分析了能有效抑制谐波的带基波电流旁路通道的串联混合有源电力滤波器的结构特点、工作原理及双dq变换控制方法,提出基于FPGA的脉宽调制PWM硬件实现方法,设计了混合有源电力滤波器数字控制电路结构.基于Modelsim的仿真实验验证了FPGA模块的可行性,同时对其补偿特性进行了MATLAB仿真研究,仿真结果表明在负载不平衡情况下该方法能很好地进行谐波补偿并很大程度地降低有源部分的容量.     

基于改进l1范数最小化组合算法的欠定盲源分离

基于稀疏假设,欠定盲源分离问题一般可采用线性规划、最短路径法和组合算法等l1范数最小化方法进行求解,但是这些传统方法对源信号的稀疏性要求较高,从而限制了源信号的估计精度。为此,本文提出了一种改进的l1范数最小化组合算法.该算法根据一定阈值找到与最小l1范数解最接近的若干次优解,将这些次优解和最小l1范数解进行加权叠加,并替代最小l1范数解,作为源信号的估计。采用语音信号的仿真实验表明,对于观测信号个数不太小的高维混合情况,该算法的源信号估计精度能够比传统的l1范数最小化组合算法提高10%左右。     

基于改进对偶分解的智能电网快速实时定价方法

实时电价是需求侧管理策略的重要手段,是解决智能电网供需平衡的理想需求响应机制,能起到削峰填谷的作用。为此,为智能电网设计了一种分布式实时电价算法:基于改进对偶分解的近端中心算法,求解用户总效用与电能供应商成本之差最大的优化问题。在此算法中,对偶问题的拉格朗日乘子即为实时电价,通过迭代更新拉格朗日乘子,形成电能供应商的实时电价与用户的实时能耗水平之间的互动,算法最终为每个用户找到最优的能耗水平(即用户的总效用最大化),同时使得电能供应商的成本最小化。所提算法既保留了问题的可分离性,又加快了收敛速度,克服了基于对偶分解的次梯度法求解该优化问题在用户规模较大时收敛慢甚至不收敛的缺点。仿真结果充分表明了所提算法具有快速收敛的特性。     

HDTV音频解码综合滤波器组算法优化及FPGA实现

在HDTV音频(AC-3,MPEG-2)解码中均采用了综合滤波器组(IMDCT)实现时频变换,它们的共同点是其长度N是4的整数倍,而且其结构具有很好的对称性.本文推导出了用两个N/4点的DCT-II来实现N点的IMDCT的优化算法.该优化算法可以得出MDCT和IMDCT拥有共同的转换核,使得MDCT和IMDCT可以共用一个统一的结构,节省了硬件开销.可以有效的应用于MDCT和IMDCT的并行VLSI结构.本文以AC-3标准为例,在FPGA上实现了其256点IMDCT单元,结果表明该算法减少了运算次数,降低了复杂度,提高了运算速度.     

基于ZUPT的车载MEMS惯性系统的混合滤波

针对车载系统在运动过程中运行时间长、动态性能变化频繁、车载导航系统不同的非线性特点,提出通过零速修正方法确定其动态特性。针对动态检测结果提出了混合滤波算法,根据车载导航系统不同的动态特性,特别是在GPS故障的情况下,采用本文提出的滤波方法有效地降低了载体在不同动态特性下的误差影响。实验表明,该方法能有效提高车载系统动态定位,改善由非线性误差导致车载系统误差积累造成的影响。     

一种抑制非理想反电势的BLDC电机转矩脉动的方法

转矩特性是电机性能的重要指标,而抑制转矩脉动是无刷直流机(BLDC motors)控制领域中的关键技术之一.本文针对非理想反电势的无刷直流机,对转矩脉动谐波构成进行了推导,分析了转矩脉动和反电动势谐波、电流谐波的关系,提出了一种基于离线反电势测量的优化电流算法,结合空间电压PWM,实现了抑制转矩脉动的电流闭环控制.仿真和实验证明,该方法可以显著抑制转矩六次谐波,是一种有效的改善无刷直流机转矩性能的方案.     

融合注意力机制与GhostUNet的路面裂缝检测方法

路面裂缝是道路最为常见的缺陷,随着深度学习技术的发展,利用深度学习的方法对路面图像中的裂缝信息提取的方法愈来愈多。针对现有深度学习路面裂缝检测方法提取裂缝特征不完整导致精度低以及实时性不足的问题,提出一种融合注意力机制与GhostUNet的路面裂缝检测方法。本方法由编码器和解码器组成,将U-Net中的常规卷积改进为Ghost卷积,减少模型参数量;在编码和解码部分,为了提高对裂缝特征的提取能力,引入ECA注意力机制和残差连接,ECA注意力模块可以过滤不相关的特征信息,利用残差连接可以避免网络退化现象。为评估本方法在裂缝检测方面的有效性,使用两个公开裂缝数据集,并进行消融实验和对比实验,实验结果F1＿score、P和R分别比U-Net平均提高了14.48%、14.35%和14.45%;该模型相比U-Net参数量下降了14.2 MB。该模型与同类模型比较,分割的准确率更高,参数量更少。     

多模块矩阵变换器改进型线电压合成闭环控制策略研究

针对常规三相-三相矩阵变换器电压传输率低的缺陷,文章研究了一种多模块矩阵变换器拓扑结构,详细介绍了线电压合成调制策略的实现过程,给出输入侧与输出侧扇区划分方式、占空比表达式,提出以输出调制系数作为控制对象的闭环控制策略。在闭环控制中因输入无阻尼LC滤波器引起输入电流谐振进而影响输入性能的问题,在上述线电压合成闭环控制策略基础上,改进了原有采用高通滤波器提取高频谐波量的谐振抑制方法,提出了通过简单的数学计算将输出负载电流dq轴分量中的高频谐波量反馈到闭环控制中,实现了多模块矩阵变换器输入谐振的有效抑制。最后,建立仿真模型,采用Matlab有效抑制输入谐振,同时具有良好的动态与静态性能。     

基于改进S变换的电压骤降自适应检测方法

由于传统S变换(S-Transform,ST)在检测电压骤降问题时存在时频分辨率不高,计算量大的问题,深入研究传统S变换(Modified S-Transform,MST),给出了一种基于改进S变换的电压骤降自适应检测方法,可以准确、快速地实现电压骤降参数的准确提取。首先给出MST中调节因子的取值依据,并用实验分析法给出调节因子的取值范围;而后依据调节因子的取值分布情况,提出分段的调节因子;最后基于调节因子取值函数,建立自适应检测方法。在MATLAB上对算法进行仿真,能够准确的检测出电压骤降参数,且抑制噪声和谐波影响的效果好。实际构建的硬件测试平台验证了该算法的正确性和可行性。     

基于单片机的FPGA/CPLD测试接口板设计

文中介绍了一种基于单片机的FPGA/CPLD测试接口板,通过该测试接口板将计算机与FPGA/CPLD的数字单元电路连接,可以在计算机上比较和分析数字单元电路的输入和输出,从而测试其电路性能。     

利用改进Prony算法的励磁调节器中PSS的设计

提出了基于Prony分析的电力系统等值线性模型的辨识方法.对传统的Prony方法进一步扩充,首先通过小波变换对信号去噪来提高辨识的准确性,然后建立多信号样本函数矩阵来辨识振荡特征,并考虑了输入信号对输出信号的影响,得到了系统的传递函数,采用留数方法对模拟励磁调节器进行了参数的协调配置.在此基础上设计了一种含PSS的励磁...     

一种链条炉粉煤复合燃烧增容节能改造方案

分析了SHL20-25/400型链条炉燃烧效率低及锅炉出力不够的原因,介绍了链条炉复合燃烧机理。通过对锅炉运行测试及热力计算,提出一种链条炉粉煤复合燃烧增容节能改造方案。通过适当增加汽水系统受热面积,改造制粉系统,能使锅炉出力及锅炉效率大幅度提高,具有明显的节能效果及经济效益。     

An improved tabu search for economic dispatch with multiple minima

This paper develops an improved tabu search algorithm (ITS) for economic dispatch (ED) with noncontinuous and nonsmooth cost functions. ITS employs a flexible memory system to avoid the entrapment in a local minimum and developed the ideal of "distance" to the fitness to accelerate optimization. The new approach extends simple tabu search algorithm (STS) to real valued optimization problem and applies parallelism to weaken the dependence of the convergence rate of modified tabu search algorithm (NITS) on the initial condition. Effectiveness of the method was compared with many conventional methods. Results show that the proposed algorithm can provide accurate solutions with reasonable performance and has a great potential for other applications in the power system     

Highly accelerated PSF-mapping for EPI distortion correction with improved fidelity

Objective

This study presents an improved point-spread-function (PSF) mapping-based distortion correction method and accelerated PSF acquisition for distortion correction in EPI without loss of quality or reliability compared to full encoding.

Materials and methods

To correct geometric distortions accurately, the PSF in the EPI phase-encoding coordinates (EPI-PSF) was measured and used as a kernel for distortion correction. FOV reduction was applied in the PSF mapping dimension for highly accelerated PSF acquisition. A novel approach for fold-over artifact correction in this reduced dimension is introduced. Conventional gradient-echo EPI and corresponding full PSF reference data were acquired in phantoms and in human brain at 7 T. The distortion corrected EPI data with the proposed acceleration were compared to result with full encoding. Previously published interpolation methods based on shift maps, non-uniform Fourier transformation and a b-spline interpolation were compared with the proposed method.

Results

The results demonstrate that the proposed method corrects geometric distortions in EPI with high accuracy and quality despite the high acceleration. In contrast to partial parallel imaging acceleration, no noise enhancement is introduced.

Conclusion

The proposed EPI-PSF-based distortion correction improves correction of EPI and accelerates PSF reference data acquisition and computation.     

Brightness regulators for airfield lighting equipment with improved energetic characteristics

Regulators with improved energetic characteristics are considered for powering airfield lighting equipment. The regulators used now are shown to have low power factors and high levels of current disturbance. Thus, a new regulator structure is proposed based on six-phase rectifiers and a two-inverter cascade with PWM control.     

A new efficient dcvs circuit synthesis technique used for an improved implementation of a serial/parallel multiplier

This paper describes an efficient technique for the design of fault-secure VLSI circuits based on differential cascode voltage switch (DCVS) logic. We propose a new synthesis method for constructing DCVS circuits with a near-optimal transistor count based on binary decision diagrams (BDDs). the time and memory resources required are very low, making the technique practical even for PC-based synthesis tools. This method is the basis for a CAD tool that allows automatic synthesis of fault-secure circuits based on the DCVS technology. We finally present an improved design and implementation of a 2's complement serial/parallel multiplier as an application of the proposed technique and algorithm.     

The minimization of voltage sag effect for specially connected transformers with a sensitive load and distributed generation systems

This paper improves the voltage sag for a distributed generation (DG) system with three-phase to two-phase connected transformers. The proposed connection system is compared with the systems designed by Scott and Le Blanc. A particle swarm optimization method with nonlinear time-varying evolution (PSO-NTVE) is used to determine the design values. This analysis considers sensitive loads and the coordination of over-current relays. The model uses a node admittance matrix for voltage sag calculation, in order to calculate the severity of system sag after single or two-phase faults. The analytical equations are useful in the mathematical optimal planning method. The PSO-NTVE is then used to derive suitable transformer impedances and relay time multiplier parameter values. The search for a global optimal solution for the voltage sag problems involves tests on the Scott and Le Blanc connected transformer power systems, in order to verify the effectiveness of the proposed method. Finally, the results show that the severity of the voltage sag is reduced by tuning the transformer impedances and relay settings.     

基于事例推理的电力系统短期负荷预测

短期负荷预测对于电力系统安全、稳定、经济地运行有重要意义。将粗糙集信息熵理论和统计学主成分分析方法用在负荷事例属性的约简上,分别针对负荷数据的重要性和相关性进行了有效处理。这样,不仅减少了事例重用过程的训练时间,还有效控制了次要负荷因素对重要因素的干扰;在事例修正过程中,针对非正常日提出一些有效的修正方案。最后,用河北省保定供电公司2000~2004年的负荷数据对该方案验证,结果表明,提出的预测方案是有效,可行的。     

抑制载荷的风力机扰动前馈与预测反馈复合控制

针对实际作用在风力机上的有效风速难以测量的问题,设计Kalman滤波器,通过对风轮气动转矩的最优估计及其与风速的关系,对风速进行递推计算。优化抑制扰动的前馈控制律,减小湍流风对风力机性能的不利影响。同时,以风轮转速的平稳性和塔顶位移的最小化为优化控制目标,设计了变桨距预测控制器。在Matlab平台上,使用5MW风力机的数据,进行仿真实验。结果表明,前馈控制与预测反馈控制相结合的复合控制,可有效地抑制扰动,减小风力机机械部件的疲劳载荷,改善整机性能,延长风力机寿命。