【作者】 张艳；

【导师】 李红斌；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2008， 博士

【摘要】 近年来,我国高压直流输电技术蓬勃发展,高压电流测量设备国产化的需求越来越迫切。传统的直流电流测量方法大都基于电磁感应原理,用零磁通或磁调制的方法,对绝缘要求高,结构复杂,设备体积大而笨重;而铁芯式电流互感器由于线路上存在较大的直流分量,铁芯严重饱和,难以测量谐波电流,研究新的高压电流测量方法及技术已迫在眉睫。本文在全面比较分析直流电流和谐波电流测量方法的基础上,研究了将常规的传感元件与光纤通信技术相结合的有源式电流测量系统和代表未来测量技术发展趋势的非接触型无源式电流测量系统两种不同的技术方案。利用光纤传输系统连接测量系统的高低压侧,解决了高压测试系统绝缘及抗干扰两大难题,具有独特的优越性。在有源式电流测量系统中,采用分流器和Rogowski线圈分别作为直流大电流和谐波电流的传感元件,介绍了分流器的误差分析与补偿措施,设计了基于PCB的新型Rogowski线圈,深入研究比较了在高压直流输电系统这个特殊环境下高压侧电子线路的能量供给技术。经武汉高压研究所测试,在300A～3000A电流范围内,基于频率调制方案的直流电流测量相对误差小于0.15%,高压侧电子电路功耗为17mW,响应速度为47mS。针对频率调制方案直流测量响应速度较慢的缺点,高压侧改用数字调制式处理方案,试验数据表明,基于数字调制方案进行直流电流测量,电路及信号处理部分所引入的相对测量误差在0.2%之内,响应速度为0.46mS,超调小于10%,8k采样率时高压侧功耗为46mW;基于数字调制方案进行谐波电流测量,100Hz～2500Hz频率范围内,电压从0.107V变化到1.06V,电路及信号处理部分所引入的相对测量误差在2.3%之内,12.8k采样率时高压侧电子电路功耗为63mW。本文还推导了无源式光学直流电流传感器的传感机理和补偿机理,分析了原有基于比较法测量交流电流时磁路设计存在的不足,以永磁组件在参考光学传感臂轴线上的磁场强度达到8000A/m为设计目标,深入研究了影响永磁体稳定性的主要因素,设计了永磁组件及其屏蔽盒,并通过磁场仿真给出了参考臂与测量臂相对位置的合适距离,最后在基于LabVIEW的试验平台上对样机性能测试。试验结果表明,在300A ~ 3000A范围内,测量准确度优于0.5%,在光功率波动达25.2%、双光路光功率不对称度为34.2%的情况下,双光源双输出传感器相对误差变化范围为-0.4% ~ +0.42%,远高于相同测试条件下单光源双输出传感器的性能。此外,永磁组件的抗外磁场干扰能力提高了约2个数量级。最后,本文研究了上述两种传感器的可靠性,通过建立相应的可靠性结构模型和数学模型,采用元器件计数法和元器件应力法对有源式电流测量系统和无源式电流测量系统的失效率进行统计,给出了定量的可靠性指标,指出影响和制约光纤电流测量系统稳定、有效运行的各种因素,采取各种可靠性保障措施来提高设备的固有可靠性。更多还原

【Abstract】 In recent years, growing demand has arisen for high-voltage current measurement equipment localization with the vigorous development of high pressure direct current transmission technology in china. Conventional techniques for measuring dc current are mostly based on inductive principle adopting zero-flux or Magnetic modulation method, which has intrinsic high electric insulation requirement, complicated configuration, heavy and bulky. For large DC current superimposed on the harmonic currents, iron core current transformers hardly measure harmonic currents accurately because of CT saturation. Thus, A great demand has arisen for studying novel high-voltage current measurement technique.Based on general comparison and analysis of the measurement methods for direct and harmonic current, active current measuring system and noncontact passive current measuring system are studied as two distinct technique solutions, the former combines prevalent sensing head with optical fiber communication technology and the latter is the developing trend of direct current measurement in high voltage environment. These measuring methods are very promising because optical fibers are good isolators and immune to electromagnetic interference while used to link the high voltage module with low voltage module.DC shunt and Rogowski coil are utilized as sensing heads respectively for direct and harmonic current measurement in active current measuring system. Errors analysis and compensated solutions are presented, a novel Rogowski coil is designed based on PCB, electric energy supply techniques to high voltage side circuit in this special HVDC system are compared and analyzed in detail. Tested by Wuhan High Voltage Institute, the relative error for direct current measurement based on frequency modulation method is less than 0.15% from 300A to 3000A, high voltage side circuit power consumption is 17mW and the rise time of step response is 47mS. Aiming at the shortcoming of slow response speed, high voltage side circuit based on digital modulation method is proposed. Test results show that the relative error of circuit and signal process segment for direct current measurement system is less than 0.2%, the rise time of step response is 0.46mS, overshoot is less than 10% and high voltage side circuit power consumption is 46mW with sampling frequency of 8kHz. Test results show that the relative error of circuit and signal process segment for harmonic current measurement system is less than 2.3% from 100Hz to 2500Hz while input voltage varying from 0.107V to 1.06V, high voltage side circuit power consumption is 63mW with sampling frequency of 12.8kHz.The sensing principle and compensating principle of passive current measuring system are also derived in this paper, and the deficiency of the magnetic path design for AC measurement based on comparative method is analyzed. By taking the magnetic field strength on the axis line of reference arm reaching 8000A/m as design goal, factors affecting permanent magnet stability are deeply studied. Permanent magnet component and its shielding box are designed, and the suitable relative position between reference arm and measurement arm is determined by magnetic field simulation. The performance of passive current measuring system is tested on LabVIEW experimental platform. Test results show that the accuracy for DC measurement is less than 0.5% from 300A to 3000A. Even on the condition of 25.2% light power fluctuation and 34.2% asymmetric degree of the dual channel, the relative error varies from -0.4% to +0.42%. All data on the same test condition validates that passive strip-glass type current sensor with two incident light sources and dual output paths has better performance than traditional bulk-glass type current sensor. In addition, anti-electromagnetic interference ability of permanent magnet component is two order of magnitude larger than that of the original magnetic path design.Finally, the reliability of the two sensors mentioned above are studied. The system block diagram together with mathematical model is established, the parts count method and the parts stress method are adopted to estimate system failure rate so that quantificational reliability index is obtained. Various factors degrading and influencing the system reliability are pointed out. All kinds of safeguards are taken to enhance system inherent reliability.更多还原