消弧线圈跟踪调谐及其优化控制方案的研究

发布时间：2018-06-17 02:18

本文选题：谐振接地系统 + 消弧线圈　；参考：《中国矿业大学》2014年硕士论文

【摘要】：目前，我国配电网中性点大多采用中性点不接地或经消弧线圈接地的方式运行，统称之为小电流接地系统。按照消弧线圈调谐方式的不同，消弧线圈可分为预调式与随调式两种；按照对电网电容电流补偿程度的差异，消弧线圈的工作状态可分为全补偿、欠补偿和过补偿三种。现有消弧线圈自动跟踪补偿设备仅能补偿接地电流中的有功分量。因而，对于绝缘老化较为严重、架空线为主或电力线路网络较大的电网有必要测量其线路绝缘阻抗。实际运行中，中性点位移电压普遍存在，特别是消弧线圈全补偿时的谐振过电压，而较大中性点位移电压对系统安全运行显然是有害的，需通过增加电网阻尼率或脱谐度的方式实现中性点位移电压的限制。但是目前抑制零序电压的方法仅给出大致的控制范围，未给出将中性点位移电压限制至某一定值的精确控制条件。电网单相接地故障时往往伴随一定值的过渡电阻，过渡电阻弱化故障特征，降低保护装置的灵敏度，因而有必要根据电网故障前后的特征预估过渡电阻值的大小。本文针对谐振接地系统现有中性点位移电压抑制方法的不足，提出电网正常运行时脱谐度和阻尼率的最优控制条件。分析随调式消弧线圈不同脱谐度和预调式消弧线圈不同阻尼率下的零序电压轨迹。根据电网绝缘参数和当前消弧线圈支路阻抗下的零序电压值，可计算出限制中性点位移电压的精确控制条件。针对消弧线圈并阻尼接地的电网，本文根据阻尼电阻调节前后零序电压的特性实现消弧线圈补偿状态的判断。本文提出基于“失谐量”的消弧线圈调谐方法，可实现电网电容电流的跟踪测量，该方法适用于消弧线圈并阻尼接地电网；提出消弧线圈变阻尼跟踪调谐方法，该方法不仅可实现电网电容电流的测量还可精确测量电网绝缘总电阻；提出消弧线圈变参调谐通用方法，该方法不受消弧线圈调谐变参方式的限制，实现电网电容电流和绝缘电阻的精确测量，在预调式和随调式消弧线圈中均可适用。本文分别针对中性点不接地和谐振接地的电网，根据单相接地故障前后中性点电压的位移度，判断过渡电阻的分布区间。最后针对本文提出的中性点电压精确控制方法、消弧线圈跟踪调谐控制方法和过渡电阻的识别进行了仿真实验研究。仿真实验的结果均证明了所提理论的正确性和有效性。
[Abstract]:At present, the neutral point of distribution network in our country is mostly operated by neutral point ungrounded or grounded by arc-suppression coil, which is called small current grounding system. According to the different tuning modes of the arc-suppression coil, the arc-suppression coil can be divided into two types: presetting type and accompanying mode, and the working state of arc-suppression coil can be divided into three types: full compensation, undercompensation and over-compensation according to the difference of compensation degree of capacitor current in power network. The existing arc suppression coil automatic tracking compensation equipment can only compensate the active power component in the grounding current. As a result, it is necessary to measure the insulation impedance of the power grid with the main overhead line or the larger power line network for the serious insulation aging. In actual operation, the neutral displacement voltage is widespread, especially the resonant overvoltage when the arc suppression coil is fully compensated, but the larger neutral displacement voltage is obviously harmful to the safe operation of the system. It is necessary to limit the neutral displacement voltage by increasing the damping ratio or detuning degree. However, at present, the method of suppressing zero-sequence voltage only gives the approximate control range, and does not give the accurate control condition to limit the neutral displacement voltage to a certain value. Single phase grounding fault of power network is usually accompanied by a certain value of transition resistance, which weakens the fault characteristics and reduces the sensitivity of the protective device, so it is necessary to estimate the magnitude of the transition resistance according to the characteristics of the power network before and after the fault. In this paper, the optimal control conditions of detuning degree and damping rate are proposed to overcome the deficiency of the existing neutral point displacement voltage suppression methods in resonant grounding system. The zero-sequence voltage trajectories with different detuning degrees and different damping ratios of preset arc-suppression coil are analyzed. Based on the insulation parameters of the power network and the zero sequence voltage values under the current impedance of the arc-suppression coil branch, the accurate control conditions limiting the displacement voltage of the neutral point can be calculated. According to the characteristics of zero-sequence voltage before and after damping resistor adjustment, the compensation state of arc-suppression coil is judged in this paper for the power network with arc-suppression coil and damping grounding. In this paper, a tuning method of arc-suppression coil based on detuning is proposed, which can be used to track and measure the capacitance current of power network. This method is suitable for arc-suppression coil and damping grounding power network, and a variable damping tracking and tuning method for arc-suppression coil is proposed. This method can not only measure the capacitance current of power network but also measure the total insulation resistance of power network accurately, and put forward a general method of tuning arc suppression coil, which is not limited by the tuning method of arc-suppression coil. The accurate measurement of capacitance current and insulation resistance can be used in presetting and adjusting arc suppression coils. In this paper, according to the voltage displacement of neutral point before and after single-phase grounding fault, the distribution range of transition resistance is judged for the grid with neutral point ungrounded and resonant grounding respectively. Finally, simulation experiments are carried out on the precise control method of neutral voltage proposed in this paper, the tracking tuning control method of arc suppression coil and the identification of transition resistance. The simulation results show that the proposed theory is correct and effective.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM475

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