基于频率测量值的相量及电气量的DFT修正算法

为解决频率偏移时电力系统相量及电气量的测量误差大的问题,提出了一种改进的离散傅里叶(DFT)修正算法。建立了相量的实部、虚部与幅值、初相角、频率偏移量之间的函数关系式,根据此关系式得到实部、虚部与频率之间所满足的一个恒等式。在频率已知条件下计算出修正后的相量幅值和相角,进一步推导出了修正后的相量实部与虚部,最后得到其他电气量的修正算法。仿真结果表明,当系统频率偏移时,在信号为纯正弦信号,或者含有高次谐波及随机噪声等情况下,算法均可有效地提高相量及电气量的计算精度。同时,该算法对采样频率和频率误差不敏感,计算量小,不增加额外的延迟时间。     

一种基于变步长差分的电压暂降检测方法

电压暂降的实时、准确检测是快速补偿的前提,但频率偏移下基于软件锁相环的检测方法无法准确地检测出相位跳变角。基于αβdq变换,提出利用变步长差分来构造出电压的αβ分量,采用恒定50Hz单位正、余弦信号瞬时采样值来构成αβdq 变换阵,从而计算出电压幅值与相位跳变角,避免了锁相保持给相位跳变角带来的测量误差。并就谐波、噪声及频率偏移等影响因素,对改进方法进行了详细的检测特性分析。理论分析和仿真结果表明,基于变步长差分的改进检测方法,实现方式简单且计算量小,无需同步锁相,可通过调节检测点间隔满足实时性与精确度的不同要求。     

基于自适应神经网络的磁编码器角度误差补偿算法

针对磁编码器中各类误差导致的解码精度低的问题,在神经网络原理的基础上提出单层自适应神经网络对正余弦信号中存在的幅值不相等、相位不正交、直流偏置、谐波与噪声等误差进行补偿。采用锁相环算法对补偿后的正余弦信号进行解码。电路中采用TLE5501磁阻芯片检测角度变化,利用TL082C运放芯片对信号进行调理,最后采用STM32G431单片机验证算法的性能。通过仿真与试验验证,证明了该算法的有效性与可行性。     

Pure-Integration-Based Flux Acquisition With Drift and Residual Error Compensation at a Low Stator Frequency

We have developed a pure-integration-based flux acquisition method for ac adjustable-speed drives. Based on the current-measurement-error analysis, a simple resonant-type observer is utilized to eliminate the drift or dc offset that originated in the current acquisition process. All the processes in correcting the problem do not rely on motor parameters and do not interfere with other higher frequency contents such as inverter nonlinearity and motor cogging effects. The proposed technique further contains a residual error compensator to completely correct the initial value error and to eliminate miscellaneous dc offset errors of the integrator. The acquisition accuracy of the flux is significantly improved through pure integration by restraining the error of the flux magnitude and phase angle at a low stator frequency. Since the proposed scheme is based on a two-phase current measurement system, it is suitable for retrofitting ac drives, where two current sensors are commonly used.     

高精度低频正弦信号相位差测量

文章介绍了几种不同的数字化测正弦信号相位差的方法,分析了各自的优缺点;针对引起误差的主要因素,提出了改进措施,并设计了一个基于ARM7微处理器的相位差测量系统。该系统采用的整形、鉴相电路,提高了测量的抗干扰能力,并利用信道交换技术消除了两个通道不严格匹配产生的测量误差。经过性能分析,该系统可以提高相位差的测量精度。     

发动机进气可调导流叶片转角检测系统设计与实现

介绍并比较了三种自整角传感器角度测量方法的原理、特点,并选用数字测量计算法实现进气可调导流叶片转角检测系统。重点介绍了检测系统硬件部分的正余弦分解器、相敏整流器、滤波、信号测量等模块电路的设计和软件部分的准确计算角度的方法。实际使用结果表明：设计的转角检测系统角度测量最大误差为-0．4度,满足误差绝对值小于1．0度的要求。此外,该系统经简单改进后还可用于发动机喷口直径的测量。     

用加Hanning窗插值高阶正弦拟合法测介损角

电力系统频率偏离50Hz时常规的傅立叶变换用于频谱分析时易产生频谱泄漏和栅栏效应,使介损角计算产生误差。高阶正弦拟合法以信号的基波频率、谐波幅值和相角作为变量对信号进行拟合,该法能有效减轻谐波存在和频率波动的影响,精确测量电气设备的介损角。高阶正弦拟合法的关键是最小二乘的计算,通常使用傅立叶变换结果作为最小二乘法的初始值,当频率偏离50Hz较多时,傅立叶变换结果与谐波分析的真实值相差较大,将其作为初值的最小二乘计算量大,影响了高阶正弦拟合法的实时性。加Hanning窗插值谐波分析法通过加窗和插值能有效减轻频率偏离50Hz时的频谱泄漏和栅栏效应,且有快速算法较之傅立叶变换增加的计算量很少。为提高高阶正弦拟合法计算介损角时的实时性,将加Hanning窗插值谐波分析法的结果作为高阶正弦拟合法的初始值,所得初始值与精确值的差值减少,最小二乘法的迭代次数从2次减到1次,容性设备仿真信号的计算时间从约0.82ms减到约0.45ms,结果表明所提出的方法能有效减少介损角的计算时间,提高介损角测量的实时性。     

永磁同步电机旋转变压器解码算法优化设计

针对旋转变压器解码电路误差对永磁同步电机(PMSM)转子位置检测精度的影响,深入分析了解码电路工作原理,基于角度/速度观测器,设计了一种高精度快响应的旋转变压器信号估算方法。电路采用低电压运放MCA33202对旋变输出正弦和余弦信号进行解码,基于解码后的估算角度构建了单位反馈闭环系统,优化了解码电路关键器件参数,提高了PMSM转子位置检测精度。通过1台2.5 kW高速PMSM验证了该算法的有效性和可行性。     

基于惯量中心动态信号的交直流互联系统稳定控制

针对交直流互联电力系统的稳定控制问题，提出了基于系统惯量中心(center of inertia，COI)动态信号的发电机励磁和直流功率调制综合控制方案。该方案中各发电机功角和频率动态跟踪由广域测量系统提供的系统COI动态功角和频率轨迹。直流输电线路功率调制的目标是阻尼区域COI功角和频率间的相互振荡。考虑到模型误差和外部干扰因素，采用反步法设计了非线性鲁棒控制器。对某4机2区域系统进行仿真实验，结果表明该控制方案和控制器突破了系统只能稳定于工频下的局限，增大了系统的稳定域，显著改善了系统的功角稳定性。     

永磁同步电机角度软锁相环估算方法研究

分析了永磁同步电机无传感器控制的研究现状,设计一种电机角度软锁相环估算方法。在两相静止坐标系下建立永磁同步电机数学模型,获得包含电机角度和转速信息。通过对反电动势信息的积分、高通滤波及归一化处理,获得仅包含电机角度正余弦信息。借角度观测器理论,设计了软锁相环并确定了其关键参数,最终获得永磁同步电机电角度及同步转速。仿真分析及试验结果表明,此永磁同步电机角度软锁相环能够准确获得电机角度和转速信息,基于此方法的矢量控制系统稳定且动态特性好。     

Determination of phase angle and amplitude error of voltage and current transformers up to some 100 Hz for loss measurements on power transformers

Contents  For the load loss measurement of power transformers, current and voltage transformers with usually extremely low errors of phase angle and amplitude are used. However, even small errors of the measuring transformers may result in an error in the measured load loss. Therefore, national and international standards allow the correction of the measured value by the amount caused by phase angle and amplitude error of the measuring equipment [2–4]. The determination of the errors of phase angle and amplitude of measuring transformers is carried out on the basis of calibrated standard measuring transformers which are traceable to national standard equipment at rated frequency, e.g. at 50 and 60 Hz. For some applications – e.g. the load loss measurement of HVDC power transformers according to the draft of IEC standard 61378-2 [1] – a load loss measurement at frequencies other than rated frequency is required. For that, the errors of phase angle and amplitude of the measuring transformers must be known. This paper describes a method how to determine the phase angle and amplitude errors of the measuring transformers at arbitrary frequencies on the basis of the calibrated error values at rated frequency. Received: 9 August 2000     

基于经验模态分解和正弦波参数法的介损角测量算法

将基于经验模态分解(empirical mode decomposition，EMD)的新型时空滤波方法应用于介损角的测量中。利用EMD对强噪声背景下的采样信号进行分解，根据所得到的固有模态分量的频谱特性进行选择性滤波，提取其基波分量，并结合正弦波参数法计算介损角。探讨了系统频率变化和介损角变化对测量真实值的影响。仿真结果表明该方法可明显减小计算误差，对提高数字化测量d 的精确性具有实际意义。     

Removal of dc offset and subsynchronous resonance in current signals for series compensated transmission lines using a novel Fourier filter algorithm

In this paper, a novel Fourier filter algorithm for high-accuracy and high-convergence-speed fundamental frequency component calculation of series compensated transmission line is proposed. The performance of digital relaying is highly reliant on the algorithm of digital filtering, especially involving the dc offset and subsynchronous resonance. Input signals of protective relays must be filtered in advance to reject unwanted quantities and retain signal quantities of interest. Accuracy and convergence speed of filter algorithms are essential for protective relays. However, the voltage and current signals contain large harmonics and dc offset during fault intervals. A widely applied filter algorithm, the Discrete Fourier Transform (DFT), can easily eliminate harmonics via simple calculations. The dc offset heavily influences the precision and convergence speed of fundamental frequency component from DFT. Under high resistive fault conditions, the current signals will have subsynchronous resonance. The subsynchronous resonance current and voltage signals influence the performance of DFT much more than the dc offset. Although capable of erasing high order harmonics, the low pass filter cannot remove the dc offset and subsynchronous resonance. The Alternative Transient Program (ATP) of the Electromagnetic Transients Program (EMPT) is utilized to simulate the transient responses of series compensated transmission lines during the fault period. Adopting the proposed algorithm in distance relays effectively locks the dc offset and subsynchronous resonance signals and quickly estimates the accurate fundamental frequency components.     

基于互相关算法的旋转变压器角度解算方法

提出基于快速互相关算法的旋转变压器角度解算方法。采集略多于一周期的旋转变压器激励信号、定子正弦信号和定子余弦信号。利用四参数最小二乘法计算激励信号频率的精确值,用此频率构造一个任意幅值的正弦信号,将其与激励信号,定子正弦信号、定子余弦信号分别进行互相关运算滤除噪声。通过搜索除噪激励信号、定子正弦信号、定子余弦信号的最大值点和索引值得到信号的幅值和相位,再查表并计算出360°范围内的角度值。算法应用的通用性强。仿真和工程应用表明该方法有很高应用价值。     

存在脉冲噪声情况下的介损角算法

脉冲干扰是影响介损角测量精确度的重要因素之一,对含有脉冲噪声的电压和泄漏电流信号必须使用滤波方法进行抑制。采用53H算法抑制采样所得电压和电流信号中的脉冲噪声。对滤波前后的信号分别使用了相关函数法、高阶正弦拟合法、加汉宁窗插值算法、谱泄漏对消算法、改进基波相位分离法和改进修正理想采样频率法计算介损角,发现各种算法对滤波后信号的计算结果均要比滤波前信号使用对应算法具有更高的精确度;无论是对滤波前信号还是滤波后信号改进基波相位分离法和改进修正理想采样频率法均具有更高的精确度。同时分析了53H算法的相关参数对算法精确度的影响。对信号使用53H算法滤波后,使用改进基波相位分离法和改进修正理想采样频率法能有效提高在脉冲情况下介损角测量的精确度。     

基于傅里叶算法的衰减直流分量消除的研究

针对消除衰减直流分量算法中,存在用时长和误差大的缺陷,提出一种在假定输入信号只含有基频分量、衰减直流分量和各整次谐波分量的情况下,对全波傅里叶算法进行改进.其基本原理是对衰减直流分量的正弦、余弦分量的系数进行补偿,消除衰减直流分量对全波傅里叶算法的影响.并用Matlab对算法进行仿真,从仿真结果可以看出,在不考虑非整次...     

三相不对称系统任意次谐波电流检测新方法

提出了在三相不对称系统下,一种新的检测任意次谐波电流的方法。该方法通过构造任意初相角、具备与需要检测的任意次谐波相同频率的正弦信号和余弦信号,使其与三相电流进行相关运算,可分别检测出任意次谐波电流正序分量、负序分量和零序分量,将三种分量相加即可得到三相四线制系统任意次谐波电流的检测结果。该方法不存在锁相环电路,简化了电路结构。理论分析和仿真结果都证明了所提方法的正确性。     

Fourier Transform-Based Modified Phasor Estimation Method Immune to the Effect of the DC Offsets

This paper proposes a Fourier transform-based modified phasor estimation method to eliminate the adverse influence of the exponentially decaying dc offsets when discrete Fourier transform (DFT) is used to calculate the phasor of the fundamental frequency component in a relaying signal. By subtracting the result of odd-sample-set DFT from the result of even-sample-set DFT, the information of dc offsets can be obtained. Two dc offsets in a secondary relaying signal are treated as one dc offset which is piecewise approximated in one cycle data window. The effect of the dc offsets can be eliminated by the approximated dc offset. The performance of the proposed algorithm is evaluated by using computer-simulated signals and Electromagnetic Transients Program-generated signals. The algorithm is also tested on a hardware board with TMS320C32 microprocessor. The evaluation results indicate that the proposed algorithm can estimate the accurate phasor of the fundamental frequency component regardless of not only the primary decaying dc offset but also the secondary decaying dc offset caused by CT circuit itself including its burden.      

Quasi‐active power factor correction on flyback‐based dc/dc converter

This paper presents a novel input current shaper based on a quasi‐active power factor correction (PFC) scheme. In this method, high power factor and low harmonic content are achieved by providing an auxiliary PFC circuit with a driving voltage which is derived from a third winding of the transformer of a cascaded dc/dc flyback converter. It eliminates the use of active switch and control circuit for PFC. The auxiliary winding provides a controlled voltage‐boost function for bulk capacitor without inducing a dead angle in the line current. Since the dc/dc converter operates at high switching frequency, the driving voltage is also of high switching frequency, which results in reducing the size of the magnetic components. Operating principles, analysis and experimental results of the proposed method are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

多模式磁偏码器设计

为了提供电动机伺服控制所需要的不同模式的位置信号而设计的磁编码器采用了一种全新的双磁钢复合磁路结构。利用2S-10芯片的三轴霍尔效应,感应平行芯片表面的磁场,把磁信号转换成正余弦电信号;在对原始信号误差进行理论分析的基础上,通过DSP对原始正余弦信号进行误差补偿并对角度进行反正切运算,实现增量模式、PWM模式和同步串口模式信号;三步锁定型开关霍尔元件输出无刷直流电机换相信号,最终实现了3种模式信号同时输出。信号右达8位精度、10位分辨率。