DMA transfer method for wide-range speed and frequency measurement

A frequency measurement method based on both pulse counting and time measurement during a constant sampling time is presented. The content of a free-running timer is transferred by a direct memory access (DMA) to a memory location after each rising edge of an input pulse, so the DMA transfer counter serves as a pulse counter. Several sources of measurement errors are discussed in detail. The DMA method is suitable for real-time speed control system with an integrated DMA controller     

Double buffered wide-range frequency measurement method for digitaltachometers

A new frequency measurement system suitable for a wide range of microprocessor-based applications is presented. The procedure used to calculate the frequency is based on the original double-buffered method. This new method utilizes both pulse counting, and measurement of the fractional pulse period during the fixed sampling time. The sampling time can be chosen to provide high accuracy and high resolution over a wide range of frequencies. Therefore, it is specially applicable in digital tachometers     

结构不对称条件下测速发电机的卡尔曼测速算法

针对基于测速发电机、光电编码器等测速传感器的传统测速系统存在低速测量性能,实时性,对结构不对称、电磁扰动等的抗干扰性等都较差的问题,提出了一种高精度宽范围实时滤波测速方法。以爪极永磁式交流测速电机为例,详细分析了其机械结构特性和工作原理,并在结构不对称条件下建立了爪极永磁式交流测速电机测速模型,提出了一种面向工程应用、计算量小的交互双模自适应降阶无迹卡尔曼滤波算法来实时估计永磁转子转速。该算法同时运行降阶和全阶交互双模自适应算法,当采用降阶估计值保障系统实时性时,在计算耗时较长的全阶算法运行完成一次后修正一次降阶估计值,提高测速精度。仿真结果表明,提出的测速算法对于结构不对称扰动具有良好的鲁棒性,能够适用于宽范围条件下的转速高精度实时跟踪,具有一定的工程指导意义。     

A digital method of frequency measurement for harmonic signals

Conclusions A new method and an algorithm are described for determining the frequency or period of a harmonic signal no matter what the period of the signal. The principle can be used in digital measuring systems, particularly at low and infralow frequencies.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 71–73, November, 1973.     

An extended complex Kalman filter for frequency measurement ofdistorted signals

The design of an extended complex Kalman filter for the measurement of power system frequency has been presented in this paper. The design principles and the validity of the model have been outlined. A complex model has been developed to track a distorted signal that belongs to a power system. The model inherently takes care of the frequency measurement along with the amplitude and phase of the signals. The theory has been applied to standard test signals representing the worst-case measurement and network conditions in a typical power system. The proposed algorithm is suitable for real-time applications where the measurement noise and other disturbances are high. The complex quantities can be conveniently handled using a floating point processor. Comparison of the results of the proposed method with those obtained from a real extended Kalman filter reveals the superior performance of the former method     

Accurate measurement of power system frequency using a digitalsignal processing technique

This paper describes the design, computational aspects, and implementation of a digital signal processing technique for measuring the operating frequency of a power system. The technique provides correct and noise-free estimates for near-nominal, nominal, and off-nominal frequencies in about 25 ms, and it requires modest computations. The proposed technique is implemented using a DSP-based board and has been extensively tested using voltage signals obtained from a dynamic frequency source and from a power system. Some test results are presented in the paper     

Global behaviour of power system frequency in korean power system for the application of frequency monitoring network

Since the concept of building an Internet-based real-time Global Positioning System synchronised wide-area frequency monitoring network (FNET) was proposed in 2001, FNET has been implemented in the Power IT Laboratory at Virginia Polytechnic Institute and State University (Virginia Tech.), and now it is used in monitoring the power system frequency in continuous time at more than 40 locations in the United States. A global view of the power system frequency based on FNET measurements helps understand the frequency behaviour more correctly, and its various applications such as event location estimation have been also studied. The global behaviour of power system frequency in the Korean power system, which has very unique characteristics, is analysed and thereby the possibility of applying FNET is studied. Although the scale of the Korean power system is much smaller than the US power systems, its global behaviour of frequency has its own characteristics, and those findings will help us understand any correlation between system characteristics and the global frequency behaviour. What is found here could serve as the first step to the application of FNET to the Korean power system.     

Robust power system stabiliser design under multi-operating conditions using differential evolution

A power system stabiliser (PSS) design method, which aims at enhancing the damping of multiple electromechanical modes in a multi-machine system over a large and pre-specified set of operating conditions, is introduced. With the assumption of normal distribution, the statistical nature of the eigenvalues corresponding to different operating conditions is described by their expectations and variances. A probabilistic eigenvalue-based optimisation problem used for determining PSS parameters is then formulated. Differential evolution (DE) is applied for solving this highly nonlinear optimisation problem. Different strategies for control parameter settings of DE have been studied to verify the robustness of DE in PSS optimisation problems. The performance of the proposed PSS, with a conventional lead/lag structure, has been demonstrated based on two test systems by probabilistic eigenvalue analysis and nonlinear simulation.     

基于广义谐波小波的工频功率因数测量算法

针对传统功率因数测量方法存在的问题,基于广义谐波小波的优良特性,结合功率因数定义,提出测量工频功率因数的广义谐波小波算法。该算法通过对采样离散化后的电压与电流信号进行工频提取,然后对其进行重构,最终结合功率因数定义来实现。建立算法的数学模型,对其进行仿真分析,最后通过液压系统实验对算法进行验证,提取出完全基于工频的功率因数。分析结果表明:与其他算法特别是与正交小波相比,基于广义谐波小波的工频功率因数测量算法速度快、精度高,测量误差3.5%,具有较好的工程实用价值。     

Strategies for enhancing noise immunity in measurement of the average frequency of secondary doppler signals

We analyze algorithms for measurement of the average frequency of the secondary Doppler signal which possess much higher noise immunity than the traditional maximum likelihood method.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 25–29, June, 1995.     

基于改进形态滤波与TLS-ESPRIT算法的电力系统低频振荡模态辨识

针对广域测量低频振荡辨识过程中的噪声干扰和定阶问题,提出一种高精度低频振荡模态辨识方法。该方法基于粒子群优化算法(PSO-GA)设计广义形态滤波器的加权参数,改进后的滤波器可以较好去除噪声;将低频振荡信号通过该滤波器滤波后再使用改进总体最小二乘法-旋转不变技术(TLS-ESPRIT)算法进行模态辨识,可以准确获得各个模态参数。对于辨识算法的定阶问题,把奇异值差值与最大奇异值比值引入到TLS-ESPRIT算法中,采用该方式进行系统定阶,不仅计算量和受主观因素影响小,而且还可以提高辨识效率以及辨识的准确性。通过系统模型仿真以及电网实际案例证明提出的方法能够较快速准确地辨识低频振荡参数,且在抗噪性及辨识精度方面有较大的优势。     

采用脉搏波信号对折原理的血压测量新算法

针对示波法测量的准确性,提出一种新的血压测量算法.该算法通过将脉搏波信号负半轴的波形基于水平轴对折,充分利用了脉搏波信号的负半轴信息,增加了可利用峰值点的个数,提高了峰值拟合方程的准确性,最终提高了血压测量的准确性.实验表明,该算法的血压测量准确性与传统的只利用脉搏波正半轴峰值点的方法相比,有了明显的提高.     

A modular system for the measurement of parameters and spectral analysis of weak signals

The article considers the operating principle and technical characteristics of a modular system that supports spectral analysis and measurement of the parameters of the harmonic components of low-frequency signals in the range of amplitudes from 0 to ±10·10^–3 V with error at most 0.5% and which may be used for work with bridge circuits.     

Beat frequency measurement system for multiple dual polarization fiber DFB lasers

This paper describes the design and testing of an electronic system intended to record the beat frequency signal from up to eight serially multiplexed dual polarization fiber distributed feedback lasers. The beat frequency from each laser is first mixed down to around 70 MHz and then measured using a PC based counter system. The gate frequency and, hence, the sampling rate, is designed to be around 1 kHz, and the frequency resolution of the system is found to be equal to the gate frequency. The system has been used to measure the beat frequency variation of fiber lasers due to either rapidly varying temperature or flexing motion. Measurements made with multiple fiber laser sensors show that the crosstalk between different sensors is very low.     

星点高压电源测量与控制系统的抗干扰设计

星点高压电源是为中国环流器二号A装置的辅助加热系统提供高压的一套重要高压电源,为保证星点高压电源控制系统稳定运行,在分析干扰源产生、分类及作用机理的基础上,从硬件和软件两方面对测量控制系统进行抗干扰设计.硬件方面主要是通过改善电源、滤波处理、接地等方面采取措施,软件则是采用多种数字滤波相结合的方法减少干扰.实践证明:适当的抗干扰设计确实能增强控制系统的可靠性,提高星点高压电源的控制精度.