Digital input filters for measurement,control and protection in electric power systems

Power system control and protection equipment is subject to especially stringent sensitivity and operational reliability requirements. Projected digital signal processing systems suitable for electric power systems fulfill these requirements by means of fast sampling and digital filtering by a 32-bit floating point DSP (Digital Signal Processor). The sampling rate of 3 kHz is carefully selected in order to separate the power spectra of the A-D conversion output errors from the signal bandwidth. The new 12-bit A-D conversion unit equipped with a recursive-type digital filter achieved a high resolution equivalent to 14-bit conversion. This paper describes the design concept and the operating characteristics and illustrates applications to current differential relays, distance relays and power system controllers.     

IEC 61850数字化保护动模测试系统设计与实现

IEC 61850标准的应用给变电站自动化系统带来了重大变革。在此类变电站中,保护装置可以直接从电子式互感器处获取所需的电流、电压数字量信息,并向智能开关控制器发送数字化跳闸命令。这种数字化保护与传统的微机型保护在硬件结构和信号处理方面都存在差异,传统的保护测试方法将不再适用。文章分析了基于IEC 61850的数字化保护装置的测试要求,提出通过对传统的物理模拟系统进行升级改造,建立符合要求的测试系统。根据这一思路,该新型测试系统在山东大学电力系统动态模拟实验室的基础上开发而成。初步试验结果表明,测试平台能够提供所需要的二次接口特征和测试环境,可以对不同种类的IEC 61850保护装置进行动模测试。     

High-precision voltage-measuring method using fast sampled data for electric power systems

Control and protection equipment in power systems requires higher sensitivity and operational reliability to meet today's changing power system requirements. The voltage-measuring deviation requirement for advanced voltage and var control equipment is less than 0.1 percent under conditions of harmonic distortion in the voltage waveform and power-system frequency variation. Studies on digital signal processing suitable for electric power systems showed that these requirements are satisfied using fast sampling and very fast 32-bit floating point operations by a Digital Signal Processor (DSP). This paper describes the design philosophy of a high-precision power system voltage-measuring method using fast sampled data. In addition, total voltage-measuring deviation characteristics under a combination of the techniques are described along with digital filter characteristics, frequency-measuring deviation characteristics, frequency variation versus gain-compensation characteristics of a digital filter, and peak value operating principles.     

多采样率信号处理在数字化变电站差动保护中的应用

数字化变电站中,差动保护各分支电子式电流互感器(ECT)的采样频率不完全相同时,需要将原各分支ECT的输出数据转换为同一采样频率.文中研究了多采样率信号处理算法和采样数据频率转换对差动保护差电流的影响,通过将信号的抽取和插值环节级联,可以实现任意分数倍采样频率转换.采用基于切比雪夫逼近原理的等波纹设计方法进行低通滤波器设计,与多采样率信号处理算法配合使用,减小了频率混叠造成的误差,从而在ECT应用环境下,将任意不同采样频率的分支电流统一到相同的采样基准下,实现了测量环节与智能电子设备的无缝连接.仿真试验验证了所提出方法的可行性和有效性.     

基于IEC61850标准的数字化电能表丢帧误差分析

数字化电能表做为数字化电能计量系统中关键设备,其误差大小直接决定了数字化电能计量系统的准确度,数字化电能表在信号输入形式上与传统电能表存在很大的差异,传统电能表的输入信号为三相模拟电压/电流,而数字化电能表的输入信号为遵循IEC 61850协议的数据帧,因此数字化电能表相对传统电能表而言存在一个重要的误差来源—丢帧误差。针对数字化电能表的丢帧误差从理论上进行分析,同时对确定等级的数字化电能表允许最大丢帧率进行了推导,并通过实验仿真验证,发现数字化电能表的丢帧误差在丢帧率一定的情况下随着丢帧序号的变化呈现出正弦变化的规律,且最大丢帧误差与采样频率无关。分析得出要忽略丢帧对数字化电能计量系统造成的误差时,数字化电能表允许的最大丢帧率应该在数字化电能表的准确度等级5%以下,且建立相关的丢帧测试项目对数字化电能表入网运行前进行检测具有重要意义。     

Reduced-sample-rate sigma–delta modulation using recursive deconvolution

A reduced-sample-rate sigma–delta modulation method using a recursive deconvolution technique for application in digital-to-analogue conversion is proposed and analysed. The method allows the sigma–delta modulators to operate at a sampling rate which is lower than the output bitstream rate by an integer factor. With the proposed in-loop mapping algorithm to map an m-bit sample to qb-bit samples, the total system inherits the advantages of a multilevel quantization conventional ΣΔ modulator in the digital part with regard to suppression of tones, improved stability and low power, while its output remains single-bit. The effectiveness of the technique is illustrated using simulations for second-and third-order modulators. © by John Wiley & Sons, Ltd.     

AD7656及其在电力系统测控中的应用

AD7656是一种16位6通道自同步模数转换器,使用了iCMOS工业制造技术,具有性价比高、精度高、能耗低、转换速度快等优点,尤其适合于电力系统中的模拟量测量。本文主要介绍了AD7656的主要特性、内部结构、电路连接设计及在电力系统测控中的应用。     

新一代微机继电保护测试仪及其基本性能

为微机型继电保护装置和安全自动装置测试的需要，以M2000为例，详细介绍了基于DSP、大功率开关放大器和PC机研制而成的新一代微机型继电保护测试仪，介绍了它的基本性能，描述了该仿真器软、硬件的实现，以及仿真器的功能，如电力系统实时仿真、谐波发生器、故障波形成回放、系统振荡模拟、各种类型的继电器测试。该测试仪体积小、重量轻、操作方便，可广泛适用于继电保护生产厂家、实验室、电厂、变电站等场所测试各类继电保护装置。     

基于并行数据处理结构的电能质量在线监测

提出了基于现场可编程门阵列器件FPGA与数字信号处理器DSP并行结构的在线电能质量监测与分析。由FPGA同步产生系统控制时序,并充分利用FPGA与DSP各自在数字信号处理领域中的特点,在FP GA内设计了16位浮点FFT运算模块用于谐波分析,应用DSP实现电压波动与闪变等电能质量指标数据的计算,采用FPGA与DSP并行数据处理的方式,达到采样与数据处理的同步进行的目的,从而完成对多路信号的无缝采样与分析。     

WAMS中PMU的完整周期抗混迭同步采样方法

基于全球定位系统（GPS）的同步相量测量装置（PMU）是广域测量系统（WAMS）的重要组成部分。提出一种基于GPS同步时钟和数字信号处理器（DSP）以及高速AVR单片机的双CPU同步相量测量装置;利用DSP的一个输入捕获单元捕获GPS秒脉冲并同步到32位高精度定时器,控制每个周期采样的起始时刻,利用另一个输入捕获单元捕获频率并把相应的采样周期传送给16位定时器的周期寄存器控制该完整周期的采样间隔,从而建立了完整周期抗混迭同步采样方法,避免了因频率变化而引起的采样混迭现象;利用DSP的高精度时钟配合同步信号源以提高同步时钟的可靠性。     

Analysis of even harmonics generation in an isolated electric power system

Harmonics bred from loads are mainly odd order because the current waveforms have half‐wave symmetry. Since the even harmonics are negligibly small, they generally are not measured in electric power systems. However, even harmonics were measured at a 500/275/154 kV substation in Hokuriku Electric Power Company after a transmission line fault was corrected. The even harmonics caused malfunctions of protective digital relays because the relays used 4th harmonics at the input filter as the automatic supervisory signal. This paper describes mechanisms of generation of the even harmonics by comparing the measured waveforms with the ATP‐EMTP simulation results. Analysis of these results has clearly shown that there are three different mechanisms of generation of even harmonics. The first mechanism is the appearance of a magnetizing current in transformers due to flux deviation by the DC component of the fault current. The second mechanism is harmonic conversion of a synchronous machine which generates even harmonics when the DC component or the even harmonic current flow into the machine. The third mechanism is an increase of harmonic impedance due to an isolated power system, thus producing the harmonic voltages. The design of the input filter of protective digital relays should take into account even harmonics generation in an isolated power system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 56–63, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20592     

New digital control and protection equipment using multiprocessor architecture of distributed functions for power system

Control and protection of equipment in power systems generally require a high-information processing capability to cope with today's power system requirements. Then, new digital control and protection equipment have been developed using high-speed and high-precision processors. Essential requirements for the new control and protection equipment are a multiprocessor architecture of distributed functions to retain sufficient computing power (fast and high-precision operations), and flexible and expandable hardware with high reliability. In multiprocessor architecture, it is important to determine how the distributed processors share the functions. By analysis and synthesis of relaying and control processings, we divided them into six processing circuits. This paper proposes a multiprocessor architecture of distributed functions, using 32-bit floating-point and 16-bit microprocessors depending on the computational requirements. In addition a digital filter for fast sampled data is described along with performance of a digital relay.     

用于太阳能集热装置的太阳跟踪传感器

太阳跟踪系统精度偏低对太阳能热发电的效率的提高有一定的影响,如何提高跟踪系统的精度也是研究太阳能利用的一个重要方面。本文介绍了一种新的太阳跟踪传感器的设计方法,把太阳位置的偏差信号通过数模转换转化成数字量作为控制信号来精确控制步进电机调整传感器位置,与以往运用简单的电平信号来判断太阳位置的方法相比,能够实现高精度测量,也有利于把信号的传输。实验表明,测量精度能够满足太阳跟踪系统的需要,该设计具有一定的实用价值。     

WXH-801/802数字式微机线路保护的研究

介绍了基于 32位DSP研制开发高压、超高压线路保护的情况及WXH - 80 1/ 80 2微机线路保护在 5 0 0kV系统动模及试运行情况。该装置采用了数字信号处理器DSP、大容量FLASH、大容量RAM、可编程CPLD和 16位A/D数据采集系统等先进技术作为保护CPU板 ,采用嵌入式 80x86作为人机对话MMI板 ;保护原理采用了自适应频率跟踪及自适应综合判据     

数字滤波技术在精密测量仪表中的应用研究

数字滤波技术是信号处理中一种重要的去噪消除下扰方法。通过分析,在介绍嵌入式计算机和24位A／D数据采集系统在微弱信号测量仪表中应用的基础上,给出了数字滤波的一般方法和步骤,研究了平均值滤波、零点偏移滤波和输入短路本机噪声滤波3种数字滤波方法,实验结果表明数字滤波技术在精密测量仪表中能提高仪表的测量精度,具有良好的实用性。     

基于DSP的电力电压测量信号放大系统

基于CVT电容式电压互感器的电力系统电压测量现状,提出应用于电压互感器的二次测的一种基于DSP的数字化高精度信号放大系统.该放大系统用数字化逆变器实现电力系统正弦电压信号功率的放大,利用DSP数字处理器高速的处理能力和电流预估计的PI控制算法实现逆变系统的高性能和高精度.最后,给出了输入电压信号和输出放大后电压的比较波形.     

基于嵌入式系统的接地网测量装置

探讨了一种基于嵌入式系统新型接地网特性测量装置的开发方案,采用变频测量方法,能在30～70Hz频段间1Hz步进,选择最佳测量频率,避开工频环境中的干扰信号,实现接地网特性参数的准确测量。设计的测量装置由变频电源、测量处理模块、嵌入式控制核心组成,其中处理器采用ARM7TDMI内核的32位高速处理器。系统软件包括准同步采样、数字滤波、电参量计算等,由固化在嵌入式ARM芯片中的程序实现。方案充分利用嵌入式技术特点,通过传感器、A/D转换器等较少硬件,完成接地网参数的测量,应用结果证明设计方案高效、可靠,满足测量要求。     

数字化变电站二次系统仿真测试方案

提出了一种基于数字动态实时仿真技术的数字化变电站二次系统测试方案.测试系统具有静态和动态测试功能.通过建立变电站一次系统的模型,对电网进行高精度的电磁暂态实时仿真计算,并将计算结果按照IEC 61850标准输出至实际的数字保护装置,可以对单个装置进行常规测试,也适合对各种电压等级的全套数字化变电站二次设备进行整体的闭环测试.     

基于DSP的双通道励磁调节器

介绍了以高性能数字信号处理器（DSP）TMS320F2812芯片为控制核心的同步发电机双通道微机励磁调节器,实现了同步交流采样、数字移相触发、数字式电力系统稳定器（PSS）等功能。采用同步交流采样,对同步发电机的机端电压、定子电流进行准确测量;通过PID＋PSS的控制方法,得到精确的晶闸管触发脉冲,并抑制系统的低频率振荡,实现了晶闸管触发脉冲的形成和移相的完全数字化。实验结果表明,该双通道微机励磁调节器具有良好的性能,并具有硬件简单、可靠性高等特点。     

基于DSP的继电保护数字式动态仿真测试装置的研究

介绍一种基于DSP的数字式动态仿具继电保护测试装置的硬件结构和软件仿真。该装置充分发挥了DSP在数字信号处理方面的优势,将电力系统数字仿真的模型和算法软件植入DSP。结合灵活设计的人机接口,使该装置能够快速、灵活而精确地仿真故障时继电保护安装处电流、电压的实际动态过程,从而为继电保护动态试验提供一种便捷而有力的工具。