电流互感器饱和的检测和补偿等相关问题的研究

发布时间：2018-07-20 09:29

【摘要】：电力系统发生故障时，一次侧电流可达负荷电流的几十倍甚至上百倍，且含有一定分量的衰减直流偏移分量。在这种情况下，用于继电保护和测量用的电流互感器铁心会发生饱和，电流互感器不能准确传变一次侧电流，致使二次侧电流发生畸变。进而影响继电保护误动作，同时由于测量误差影响其它二次设备的正常运行。本论文就电流互感器饱和的相关问题进行了较为全面的研究，具体内容如下。 1.简要介绍电流互感器以及其数学模型，从理论和实际仿真两个角度综合研究一次电流波形、衰减直流偏移分量、二次侧负载、铁心剩磁、铁心截面积、电流互感器变比以及电流互感器匝数等因素对电流互感器铁心饱和情况的影响。 2.基于数学形态学理论，首次提出基于形态学梯度小波的电流互感器铁心饱和检测方法。由于电流互感器二次侧畸变电流波形在进、出饱和点处梯度发生明显变化，能够对电流波形各采样点处的梯度进行分析的形态学梯度小波方法结合形态学开-闭和高帽变换能够准确检测出电流互感器的进、出饱和点。仿真结果表明该检测方法能够准确检测出不同故障情况下的饱和区间，并且具有较高的抗噪声和抗谐波能力。此外，该方法具有计算量小、延时短以及较高可靠性和广泛适用性的优点。 3.首次提出基于提升形态学梯度和形态学分解的电流互感器铁心饱和检测方法。由于畸变电流波形在进、出饱和点处，梯度变化明显，因此，基于对采样点梯度分析的提升形态学梯度算法和形态学分解算法均能得出准确的检测结果。最终检测结果由以上两种检测算法的结果综合分析得到。仿真结果表明该方法能够准确检测出不同故障情况下的饱和区间，并且具有运算量小、延时短、检测精度高、适用范围广和可靠性高等优点。 4.提出了基于线性回归的二次侧电流畸变补偿方法。该方法基于上述电流互感器饱和检测方法的检测结果，利用未饱和区各采样点的幅值分别计算饱和区各采样点的基波分量幅值和衰减直流偏移分量幅值，实现对畸变电流的补偿。与其它补偿方法相比，该方法运算量小、补偿精度高、实时性强、适用范围广，并且不引入截断误差。仿真结果表明该补偿方法针对不同故障情况下的畸变电流均能实现准确的补偿。 5.开发以现场可编程门阵列(FPGA)为核心的片上系统，并且在该片上系统实现了基于提升形态学梯度和形态学分解的铁心饱和检测方法。设计开发板硬件平台和软件平台，搭建测试平台，实现片上系统整体设计。实验结果表明，，在该片上系统内，检测方法能够有效发挥作用，且硬件、软件平台具有良好的可靠性和实用性。
[Abstract]:When the power system fails, the primary side current can reach tens or even hundreds times of the load current, and contains a certain component of the attenuated DC offset component. In this case, the core of the current transformer used for relay protection and measurement will be saturated, and the current transformer can not accurately transfer the primary current, resulting in distortion of the secondary side current. Then the relay protection maloperation is affected, and the normal operation of other secondary equipments is affected by the measurement error. In this paper, the saturation of current transformers is studied in detail, and the details are as follows. 1. The current transformer and its mathematical model are briefly introduced. The primary current waveform, attenuated DC offset component, secondary load, core remanence, core cross section area are comprehensively studied from both theoretical and practical simulation points. The influence of the current transformer ratio and the turn number of the current transformer on the saturation of the current transformer core. 2. Based on the mathematical morphology theory, a new method for detecting the core saturation of current transformer based on morphological gradient wavelet is proposed for the first time. The gradient at the saturation point of the secondary side of the current transformer changes obviously because the current waveform is in and out of the secondary side of the transformer. The morphological gradient wavelet method, which can analyze the gradient of each sampling point of the current waveform, can accurately detect the saturation point of the current transformer by combining the morphological opening and closing and the high cap transform. The simulation results show that the proposed method can accurately detect the saturation regions in different fault cases and has high anti-noise and anti-harmonic capability. In addition, the method has the advantages of less computation, shorter delay, higher reliability and wider applicability. A method for detecting iron core saturation of current transformer based on lifting morphological gradient and morphological decomposition is proposed for the first time. Because the distortion current waveform changes obviously at the point of entering and leaving the saturation point, the improved morphological gradient algorithm and morphological decomposition algorithm based on gradient analysis of sampling points can get accurate detection results. The final detection results are obtained by comprehensive analysis of the results of the above two detection algorithms. The simulation results show that this method can accurately detect the saturation interval in different fault cases, and has the advantages of small computation, short delay, high detection precision, wide application range and high reliability. 4. A linear regression based compensation method for secondary side current distortion is proposed. Based on the detection results of the above current transformer saturation detection method, the amplitude of the fundamental wave component and the decaying DC offset component of each sampling point in the unsaturated region are calculated by using the amplitude of the sample points in the unsaturated region. The compensation of distortion current is realized. Compared with other compensation methods, this method has the advantages of low computation, high compensation accuracy, high real-time performance, wide range of application and no truncation error. The simulation results show that the proposed compensation method can accurately compensate the distortion current in different fault cases. An on-chip system with field programmable gate array (FPGA) as the core is developed and the core saturation detection method based on lifting morphological gradient and morphological decomposition is implemented. Design development board hardware platform and software platform, build a test platform to achieve the overall design of the system on a chip. The experimental results show that the detection method can play an effective role in the system, and the hardware and software platform has good reliability and practicability.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM452

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