基于扩展DFT的谐波检测算法的研究

传统离散傅里叶变换(DFT)算法因其具有计算效率高,便于在嵌入式系统中应用的优点而广泛应用于谐波检测中,但其在非同步采样下,频谱泄露和栅栏效应的存在将会影响到测量结果的精确性。将扩展傅里叶变换(EDFT)应用于谐波检测中,EDFT以傅里叶积分变换为目标,在扩展的频率范围内优化变换基即利用变换基函数取代传统DFT变换中的指数基来构造信号的目标函数,并将原始数据通过迭代近似拟合从而使测量精度得以提高。经验证,在非同步采样和噪声存在的条件下,该方法依然有较高的频率分辨率和较强的抗干扰特性,适用于高精度测量或检测。     

基于周期扫描的太阳能控制器MPPT方法实现

经典的最大功率点跟踪（MPPT）算法会由于外部环境的变化或系统本身采样的误差而无法·陕速地达到最优点。本文提出了一种基于周期扫描的MPPT算法,当系统启动、检测到外部环境发生变化或间隔一定周期时,重新对特定的占空比进行扫描,以快速、准确的确定新的最大功率点。控制器采用同步降压斩波的拓扑结构．降低了系统的功耗。并采用软启...     

一种用于信号采样速率转换的滤波器

离散信号采样率的精确同步是数字通信和基于傅里叶变换电力谐波分析等技术的关键问题。文中设计了一个只有两阶的滤波器,将周期为2π的余弦函数的单个周期作为滤波器的单位冲激响应,并通过仿真实验证明利用该滤波器对离散信号的采样速率进行转换,可以达到信号的采样完全同步,对离散信号做连续信号的恢复能接近无频谱泄漏,实时性较好,易于实现在线测量,且该采样速率转换方法简单,计算量小,可应用于数字通信技术或各种电力配电系统装置的前端处理中信号的同步采样。     

基于NUFFT 算法的综合孔径辐射计图像反演方法

圆形阵列和旋转阵列排布方式的提出是为进一步降低综合孔径辐射计成像系统的复杂度和成本,然 而其缺陷在于过于复杂的亮温图像反演过程,因为该阵列排布方式下的采样样本不是均匀分布于整个采样平面,常 规的标准傅里叶变换不能直接运用于此反演过程。提出了一种非标准快速傅里叶变换(NUFFT)算法,用于非均匀 采样样本的综合孔径辐射计图像反演计算,该算法结合了高斯栅格算法和对过采样样本的快速傅里叶变换算法,仿 真结果表明该算法能够准确地得到反演图像。     

一种快速高精度的交流采样同步优化算法

分析了软件常规同步采样算法的误差原因并提出了一种交流采样同步优化算法。该算法在每个采样周期内，动态调整采样间隔，它能有效减小同步误差、提高测量精度。通过算法中采样间隔的补差规律，可以减少运算量，增强系统采样的实时性。     

基于压缩传感的相移同轴傅里叶变换数字全息

对于同轴傅里叶数字全息,传统重构算法应用快速傅里叶逆变换算法进行重构,但采样过程需要满足香农采样定理,导致海量采样数据,大大增加了存储和传输的代价。提出了一种基于压缩传感的相移同轴傅里叶数字全息重构方法,利用马赫-曾德尔干涉光路采集同轴全息图,对采集数据进行部分采样、测量;然后利用最小全变分法对采集的数据进行数值再现。数值仿真结果表明,基于压缩传感的傅里叶全息重构算法优于基于快速傅里叶逆变换的传统算法,它将全息数据的采集和压缩合为一步进行,不仅采样数据明显少于传统采样数据,而且利用约8%的数据仍然能精确地重构出原图像。     

一种用于取样示波器的高速数字信号传输速率的测量方法

取样示波器利用顺序等效采样技术可以实现对宽带、高速信号进行采样和波形恢复,从而对信号质量进行分析。因此取样示波器在5G高速通信、雷达等信号测量领域得到广泛应用。但是取样示波器采用的顺序等效采样方法是对被测信号进行多周期间隔、不连续采样,采样间隔周期不确定,导致不能直接从恢复的波形中分析出被测信号的传输速率。为确定传输速率,提出一种基于快速傅里叶变换算法的速率计算方法。通过实验验证,此方法能够准确计算出高速数字信号的传输速率,相对误差均在1%以内,并且在采样点数及眼图叠加次数较少的情况下仍然适用。     

离散傅里叶变换在被采样信号频率波动时的计算结果误差原因及解决方案

在被采样信号和周期信号测量处理中,离散傅里叶变换得到广泛的应用。依据傅里叶变换相关内容可知,若采样信号持续处于有限长状态,此时频谱为无限宽。反之,若信号频谱处于有限宽状态,采用信号持续时间为无限长。文章根据离散傅里叶变换相关理论进行分析,确定产生误差的原因,从而采取恰当的处理方法,降低误差发生率。     

基于MSP430系列微控制器的FFT算法实现

傅里叶变换算法在供电质量监测系统中被用来进行谐波分析,如何加快分析速度和降低系统成本是当前这种监测系统设计关注的主要问题。TI公司的MSP430系统微控制器具有功耗低、供电范围宽及外围模块齐全等特点,适合实现各种监测设备。该系列芯片内部充足的数据存储器满足快速傅里叶变换算法过程中的数据存储,芯片内部大量的代码存储器存储相位因子的计算结果和所需要的三角函数数值,采用查表的方法以提高分析速度;采用芯片内部硬件乘法器模块可以进一步提高分析速度。实测结果显示对一个信号周期256个采样点的快速傅里叶变换分析,完成全部计算仅需要0.3 s的时间,前10次谐波的计算相对误差低于千分之一。所研制的在供电质量监测系统完全满足用户要求。     

基于Nuttall窗插值FFT算法的谐波分析

采用快速傅里叶变换(Fast Fourier Transformation,FFT)算法进行谐波分析时不易实现同步采样和整数周期截断,由此造成的频谱泄漏和栅栏效应将影响到谐波分析的精度。加窗和插值修正算法能提高基于FFT的谐波参数计算的准确度,由此提出一种用于谐波分析的加4项5阶Nuttall窗的双谱线插值FFT算法,给出了实用的插值修正公式。实验结果表明,与Blackman-harris窗、4项3阶Nuttall窗插值FFT算法相比,该算法具有更小的计算量和更高的分析精度。     

Software-synchronized all-optical sampling for fiber communication systems

This paper describes a software-synchronized all-optical sampling system that presents synchronous eye diagrams and data patterns as well as calculates accurate Q values without requiring clock recovery. A synchronization algorithm is presented that calculates the offset frequency between the data bit rate and the sampling rate, and as a result, synchronous eye diagrams can be presented. The algorithm is shown to be robust toward poor signal quality and adds less than 100-fs timing drift to the eye diagrams. An extension of the software synchronization algorithm makes it possible to automatically find the pattern length of a periodic data pattern in a data signal. As a result, individual pulses can be investigated and detrimental effects present on the data signal can be identified. Noise averaging can also be applied. To measure accurate Q values without clock recovery, a high sampling rate is required in order to establish the noise statistics of the measured signal before any timing drift occurs. This paper presents a system with a 100-MHz sampling rate that measures accurate Q values at bit rates as high as 160 Gb/s. The high bandwidth of the optical sampling system also contributes to sampling more noise, which in turn results in lower Q values compared with conventional electrical sampling with a lower bandwidth. A theory that estimates the optically sampled Q values as a function of the sampling gate width is proposed and experimentally verified.     

Real-Time Estimation of Fundamental Frequency and Harmonics for Active Shunt Power Filters in Aircraft Electrical Systems

A novel algorithm for fundamental frequency and harmonic components detection is presented in this paper. The technique is based on a real-time implementation of discrete Fourier transform, and it allows fast and accurate estimation of fundamental frequency and harmonics of a distorted signal with variable fundamental frequency. It is suitable for active shunt filter applications, when fast and accurate tracking of the reference signal is required to achieve a good control performance. The main application for the algorithm is aircraft ac power systems, where the fundamental frequency can be either fixed on 400 Hz and its actual value fluctuates around the nominal value, or variable in the range 360–900 Hz. Hence, a real-time estimation of fundamental frequency is essential for active filter control. The proposed algorithm has been at first implemented in Matlab/Simulink for computer simulation, and it has been compared with a Phase Locked Loop (PLL) algorithm for frequency detection and the synchronous $dq$ reference method for harmonic detection. Experimental tests have been carried out in order to validate the simulation results. The distorted current absorbed by a nonlinear load is analyzed and processed by means of a digital implementation of the algorithm running on the active shunt power filter control DSP, in order to calculate the active filter compensating current.      

电能质量数据采集和谐波分析方法的实现

针对电能质量分析问题,设计了基于DSP和CPLD的电能质量检测装置,完成对电网信号数据的实时采集和处理,介绍了系统的总体结构以及数据处理的方法。为消除泄漏误差,采用锁相环电路实现对电网信号的同步采样。为提高计算的准确性,采用基于加窗插值的FFT算法分析电力系统谐波,并对算法的实现进行了详细的描述。     

单相SVG的基波无功电流跟踪算法

作为改善电能质量的一种重要手段,静止无功发生器SVG要求快速的检测出负载电流中的无功分量.本文针对直接电流控制的用户端单相SVG,提出一种新的单相无功电流的跟踪算法,该方法通过在一个计算周期内基波周期前后一段数据的比较来快速跟踪无功电流.仿真表明该方法正确可行.仿真波形可以看出,在一个周期内可以实现对无功电流的准确提取,而且对电流变化跟踪效果好,防干扰能力强.算法简单快速,只需两个乘法器,且易于实现.     

通信机房高频UPS无功就地补偿方法研究

本文在不改变UPS高频机主电路拓扑结构和配电系统结构的前提下,提出一种利用UPS高频机的PWM整流器进行无功就地补偿控制方案,应用同步旋转坐标变换和瞬时功率理论设计控制算法,在不影响UPS有功功率的前提下,利用PWM整流器进行负载侧无功补偿,提高UPS容量利用率,改善负载侧电能质量,减小高低压配电室无功补偿容量,节省成本和占地。     

The algorithm of expanded current synchronous detection for active power filters considering three-phase unbalanced power system

A new algorithm for three-phase active power filters is proposed, which is expanded current synchronous detection (ECSD) theory. It can detect the active or the fundamental reactive currents in each phase symmetrically and equally, based on the decomposition of the fundamental reactive component and the harmonics under unbalanced power condition. Nonlinear load is composed of a 2-hp three-phase squirrel-cage-type induction motor and motor drives (inverter). To prove the validity of the proposed ECSD algorithm, some experiments were performed in steady states and transient states under 15% unbalanced power system. A stand-alone-type TMS320C31 digital signal processor (60 MHz) board is employed to calculate and to decompose the power and the current components of nonlinear load. The experimental results show that the active and the fundamental reactive components detected by the proposed theory were balanced and equal in each phase despite an unbalanced power source.     

基于多率采样的永磁同步电机控制方法设计

在工业自动化领域,永磁同步电动机在中小功率控制系统中发挥着重要作用。本项目采用多采样率方法构建永磁同步电机控制系统,其主要解决的问题包含多采样率下的速度及参数辨识、永磁同步电机多采样率滑模变结构控制系统设计。     

静止同步补偿器STATCOM的d-q直接电流控制仿真

近年来,电力网中电压不平衡给系统带来很多危害,无功电流的补偿已成为亟待解决的问题,传统无功补偿装置已经远不能满足要求,新型静止同步补偿器STATCOM应运而生。本文研究静止同步补偿器STATCOM的工作原理、数学模型、无功功率理论和直接电流控制方法,实现无功功率补偿方式。在对STATCOM模型的建立进行了深入研究的同时,采用d-q电流直接控制法对STATCOM进行了仿真分析。     

一种电感电流同步控制和采样DC转换器设计

双向DC控制器的控制指标衡量主要包括采样和控制两个方面,本系统从电流采样角度出发,设计一种电感电流同步控制和采样转换器,在控制周期的固定位置采集数据,从而达到稳定采样的目的,且控制方式采用集中式管理分布式控制方案,可以实现多模块的并联,为后期扩展留下基础.尤其适用于DC转换器中需要对电感电流进行采样的装置,该转换器主要用来实现采样和控制同步.     

Analysis and design of direct power control (DPC) for a three phase synchronous rectifier via output regulation subspaces

In this paper, the authors present a controller that directly regulates the active and instantaneous reactive power in a synchronous three-phase boost-type rectifier. The controller ensures a good regulation of the output voltage, and guarantees the power factor close to one. The controller builds upon the ideas of the well known direct torque control (DTC) for induction motors. In their case, the active and reactive powers replace the torque and flux amplitude used as the controlled outputs in DTC, thus motivating the name DPC-control. They show that a simple modification to the original algorithm makes the selection of the control inputs more accurate. To formalize this technique, they utilize the concept of output regulation subspaces. A modification is added to the basic controller to deal with disturbances such as unbalance and distortion in the source voltage. Finally, the proposed controller was tested both in simulations and experimentally, and illustrative results are presented.