基于电力电子扰动技术的谐波阻抗测量在对地电容检测中的应用研究

发布时间：2018-02-02 22:47

本文关键词： “预调式”消弧线圈阻尼电阻晶闸管系统对地电容　出处：《山东大学》2016年硕士论文　论文类型：学位论文

【摘要】：在我国,中压配网广泛采取中性点非有效接地运行方式。近期,随着配网范围的不断扩大,电网馈线量逐渐增加,线路对地电容电流日益增大,单相接地故障电弧难以自熄,且产生较高的过电压,可能危害健全相造成两相短路。因此,具有自动调谐功能的消弧线圈装置被广泛用来补偿故障电流以保证配电网运行可靠性。在谐振接地系统中,消弧线圈的存在使得流经接地点的电容电流得到了补偿,大大提高了供电系统自身运行的可靠性与安全性。而对地电容的准确测量是保证消弧线圈对故障电流进行有效补偿的前提。本文在对各类系统对地电容计算方法进行了归纳总结的基础上,针对“预调式”消弧线圈提出了一种检测系统对地电容的新方法,利用投切消弧线圈阻尼电阻的电力电子开关,通过短时控制其导通状态以产生含有丰富频率成分的扰动电压、电流。利用该扰动电压、电流信号并结合基于电力电子扰动技术的谐波阻抗测量方法测量系统对地电容以用于“预调式”消弧线圈的自调谐。电网正常工作情况下,通过短时改变投切阻尼电阻的晶闸管的导通状态,等效于将阻尼电阻短时退出工作,进而在晶闸管两端产生含有丰富频率成分的扰动电压、电流信号。基于配电网的近似线性,各频次下扰动电压与扰动电流呈现线性关系。利用扰动电压、电流信号并结合基于电力电子扰动技术的谐波阻抗测量方法计算系统对地电容。本文首先对方案的工作原理进行了阐述,利用故障分析原理和电路理论对电网模型进行等效简化,利用简化模型并结合基于电力电子扰动技术的谐波阻抗测量方法给出了两种阻尼电阻接线方式下系统对地电容与扰动信号持续时间的理论表达式,针对个别频次下检测结果存在误差的现象,利用最小二乘法对检测结果进行优化,提高检测精度。其次,利用仿真手段对方案的可行性进行验证。通过设置仿真参数,在不同谐波频次、晶闸管触发角、脱谐度、不平衡度下的谐振接地系统进行仿真分析,测量对地电容,同时研究阻尼电阻短时间退出工作对中性点位移电压的影响。最后,通过模拟实验验证了仿真结果的正确性,基于模拟实验的结果,对晶闸管触发角及中性点最小位移电压的确定给出了指导性建议。本文为系统对地电容的计算提供了一种新的可行方案,对消弧线圈的自动补偿具有积极意义。同时,通过本文进一步拓展了电力电子扰动技术在电力系统中的应用。
[Abstract]:In our country, neutral point is widely used in medium voltage distribution network. Recently, with the expansion of distribution network, the number of feeders is increasing gradually, and the capacitance current of line to ground is increasing day by day. Single-phase grounding fault arc is difficult to self-extinguish and produce higher overvoltage, which may harm the sound phase and cause two-phase short circuit. The arc-suppression coil with automatic tuning function is widely used to compensate the fault current to ensure the reliability of the distribution network. The existence of the arc-suppression coil compensates the capacitive current flowing through the junction. The reliability and safety of the power supply system is greatly improved, and the accurate measurement of the earth capacitance is the premise to ensure the effective compensation of the fault current by the arc suppression coil. In this paper, the calculation method of the earth capacitance for all kinds of systems is presented. On the basis of summing up. In this paper, a new method of detecting system to ground capacitance is proposed for "preset" arc-suppression coil. The power electronic switch is used to damp the resistance of arc-suppression coil. A disturbance voltage, current, which contains rich frequency components, is generated by controlling its conduction state for a short period of time.; the disturbance voltage is utilized. The current signal and harmonic impedance measurement method based on power electronic disturbance technique are used to measure the system capacitance to the ground for self-tuning of the "preset" arc suppression coil. By changing the on-on state of the thyristor with damped resistance in a short time, it is equivalent to withdraw the damping resistor from work for a short time, and then generate the disturbance voltage with rich frequency components at the two ends of the thyristor. Current signal. Based on the approximate linearity of the distribution network, the disturbance voltage is linearly related to the disturbance current at each frequency. The current signal and the harmonic impedance measurement method based on power electronic disturbance technology are used to calculate the capacitance of the system. Firstly, the working principle of the scheme is described in this paper. The fault analysis principle and circuit theory are used to simplify the power network model. Based on the simplified model and the harmonic impedance measurement method based on the power electronic disturbance technique, the theoretical expressions of the system ground capacitance and disturbance signal duration under two damping resistance wiring modes are presented. In order to improve the accuracy of detection, the least square method is used to optimize the detection results. Through setting the simulation parameters, the resonant grounding system with different harmonic frequency, thyristor trigger angle, detuning degree and unbalance is simulated and analyzed. Measure the capacitance to the ground and study the influence of the short time withdrawal of damping resistance on the neutral displacement voltage. Finally, the correctness of the simulation results is verified by the simulation experiment, based on the results of the simulation experiment. Some guiding suggestions are given for the determination of the trigger angle and the minimum displacement voltage of the neutral point of the thyristor, and a new feasible scheme for calculating the ground capacitance of the system is provided in this paper. It has positive significance for automatic compensation of arc-suppression coil. At the same time, the application of power electronic disturbance technology in power system is further expanded in this paper.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM934

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