共查询到19条相似文献,搜索用时 93 毫秒
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一种电流互感器饱和误差补偿算法研究 总被引:1,自引:0,他引:1
在故障情况下,电流互感器(cT)的一次电流非常大,且含有衰减的直流分量,容易使cT饱和,导致二次电流严重失真,使继电保护装置或控制设备不能正常动作.本文提出了一种饱和二次电流的误差补偿算法.该算法根据测得的二次电流估计铁芯中的磁通量及激磁电流,并将估计的激磁电流加入到实测二次电流中,起到补偿作用,矫正失真的二次电流.EMPT仿真及算例分析证明了本文算法的有效性. . 相似文献
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电流互感器铁心饱和引起二次电流畸变的补偿研究 总被引:8,自引:3,他引:8
电流互感器(TA)铁心饱和将引起二次电流发生畸变,对此,该文提出一种新的补偿方法。新方法采用TA二次绕组感应电压和二次电流波形的奇异性特征检测饱和的开始和结束,并通过适当延时检测结果来确定铁心不饱和时段。在铁心不饱和时段,通过定义新的目标函数并引入实时最小二乘算法来估计一次电流参数;在铁心饱和时段和铁心饱和状态发生变化的过渡时段,则以参数估计结果求取二次电流的补偿值。该方法具有补偿精度高、便于实时实现等特点。仿真分析表明,该方法适用范围广,能够在含有噪声的环境下正常工作。实验结果进一步验证了该方法的实用性。 相似文献
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为了提高测量用电流互感器(CT)的精度,通常采用高磁导率的材料和大横截面积的核心使励磁电流最小化,这种做法会增加CT的制造成本。提出了一种提高测量用CT精度的数字补偿算法,根据副边电流测量值和铁心磁化特性,通过算法计算并补偿励磁电流来提高测量用CT的精度,仿真和实验验证了该算法的有效性。 相似文献
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本文基于极大似然估计理论及虚拟噪声补偿技术,提出了关于电压、电流噪声参数的一种在线优化估计方法,据此可构成自适应卡尔曼滤波器,以对保护所需的基频电压、电流分量进行“最优”估计,该算法无需象常规卡尔曼滤波器那样,需事先对电压、电流噪声进行复杂的统计分析以求取滤波算法所需的噪声参数。因此,该算法使用起来将更为灵活、方便,此外,算法的收敛速度较快,噪声参数的估计计算简便,易于在微机保护中加以采用。 相似文献
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为解决并网逆变器存在的死区效应,介绍了一种并网逆变器的死区补偿方法。分析了并网逆变器死区效应产生的原因,提出用带通滤波器滤除电流信号的纹波和干扰,根据滤波后的电流信号极性来确定PWM驱动信号的补偿量。给出了一种基于带通滤波器的死区补偿算法。试验结果表明,该算法能有效地补偿并网逆变器的死区效应,消除输出电流的交越失真。 相似文献
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电能计量系统误差估计是针对由电能表、电流互感器(Current Transformer, CT)、电压互感器(Voltage Transformer, VT)和二次回路组成的电能计量装置潜在危害的有效手段。电能表和二次回路的计量误差可以在线监测,但CT和VT的计量误差不能直接测量,且随温度、泄漏电流等因素的变化而变化。文中提出了一种利用隶属云(Membership Cloud, MC)和动态时间规整(Dynamic Time Warping, DTW)连续估计CT和VT变比和相位误差的方法。该方法构造了一个新的混合半梯形MC生成器(MC Generator, MCG),以解决在不同影响因素下误差偏差的随机性和模糊性问题。利用改进的DTW算法(Modified DTW,MDTW),可以根据误差时间序列与量化影响因素之间的相似性,估计CT和VT误差。将电能表和二次回路的测量误差与估计的电流互感器和电压互感器误差相结合,便可得到电能计量系统的综合误差。通过110 kV变电站电能计量装置的现场测试数据,验证了所提方法的有效性。 相似文献
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Yong Cheol Kang Ui Jai Lim Sang Hee Kang Crossley P.A. 《Power Delivery, IEEE Transactions on》2004,19(4):1642-1649
Current-transformer (CT) saturation may cause the maloperation of a protection relay. This is particularly onerous when the remanent flux in the core of the CT adds to the flux change caused by the fault. The CT is forced into deep saturation and the waveshape of the secondary current is severely distorted. An algorithm for compensating the distortion in the secondary current caused by saturation and remanence in a CT is described in this paper. A second-difference function detects when the CT first starts to saturate. At this instant, the negative value of the second-difference function corresponds to the magnetizing current which, in conjunction with the magnetization curve, is used to estimate the core flux. This is then used as an initial value to calculate how the flux changes during the fault. The magnetizing current is estimated by inserting the estimated core flux into the magnetization curve and added to the secondary current; the result, the compensated secondary current, is equal to the secondary referred primary current. Various test results indicate that the proposed algorithm can accurately compensate a severely distorted secondary current and is not affected by remanence. The paper concludes by describing the hardware implementation of the algorithm on a prototype compensation unit based on a digital signal processor. 相似文献
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应用模糊贴近度原理识别励磁涌流的新方法 总被引:1,自引:1,他引:0
为提高我国220kV及以上变压器保护正确动作率,提出了一种基于模糊贴近度原理的识别变压器励磁涌流的新方法。该方法通过比较归一化后前后半周期波形的贴近程度来区分励磁涌流和故障电流:励磁涌流的波形畸变严重,在波形上以间断角和波形不对称的形式出现,因此归一化后前后半波贴近程度低,接近于0;而内部故障电流波形含有较少的2次谐波和高次谐波分量,在波形上以对称的形式出现,前后半波贴近程度高,接近于1。同时,应用模糊数学工具将该原理的3种类型相结合以使其优势互补。理论分析和动模实验结果表明:该方法原理简单、易于实现,可准确识别故障电流和励磁涌流,即使空载合闸于内部短路故障时保护也能迅速可靠动作。 相似文献
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This paper suggests the possibility of improving digital power transformer protection. The establishment of inrush in power transformers is becoming unreliable in existing numerical protection. An artificial neural network (ANN) was applied to inrush detection. The saturation of protective current transformers (CT) cannot be totally eliminated despite proper dimensioning. ANN was used for the reconstruction of distorted secondary CT currents due to saturation. In both cases, an ANN was included in the protection algorithm as an extension of the existing methods, which improved the reliability of the protection operation. The paper presents the digital protection algorithm completed in this way and the laboratory equipment by means of which experimental results were obtained. The results confirm faster and more reliable recognition of transformer inrush, as well as satisfactory reconstruction of the distorted secondary CT currents 相似文献
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Jiuping Pan Khoi Vu Yi Hu 《Power Delivery, IEEE Transactions on》2004,19(4):1623-1628
Current transformer (CT) saturation leads to inaccurate current measurement and, therefore, may cause malfunction of protective relays and control devices that use currents as input signals. This paper introduces an efficient compensation algorithm capable of converting from a sampled current waveform that is distorted by CT saturation to a compensated current waveform. Attractive features include quick response time, no cumulative estimation errors, desired sample-by-sample output, independent of CT parameters/characteristics and secondary burdens, and simplicity for online implementation. The accuracy and robustness of the introduced compensation algorithm are demonstrated through extensive test cases reflecting a wide range of variations in fault conditions and CT parameters. 相似文献
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《Electric Power Systems Research》2007,77(5-6):527-533
Current transformers (CTs) are used in electric power systems for protection and measurement purposes. The current signals in the secondary side of a CT should be exact reproductions of the corresponding current signals on its primary side. CTs are susceptible to the saturation phenomenon which leads to inaccurate current measurement and therefore, may cause malfunction of the protective relays. This paper presents an approach to the correct the distorted waveforms caused by CT saturation. A dynamic filter based on weighted least absolute value minimization is used to produce compensated secondary current samples from the distorted ones. The proposed technique is independent of CT parameters/characteristics or secondary burdens. Various test results indicate that the proposed technique can successfully detect CT saturation and accurately compensate the distorted secondary currents. 相似文献
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基于PREISACH理论的电流互感器建模研究 总被引:6,自引:2,他引:6
提出了一种新型电流互感器(CT)数字化模型。该模型由CT电磁感应方程和基于Preisach理论的新型铁心磁化模型组成:基于Priesach理论的WIPING—OUT特性,提出了确定铁心运行所在磁化曲线的方法,并在新坐标系下分离Preisach函数的变量,得到了不同情况下铁心磁通密度的计算方法,由此建立了铁心磁化模型;提出了一种新的寻解算法,通过该算法将铁心磁化模型同CT电磁感应方程相耦合,建立了CT数字化模型。该模型只需极限磁滞回环下降支、一次电流和二次负荷等少量易被直接测得的参数,即可较准确地仿真铁心内部磁化过程,具有实现简便,仿真精度高等特点。采用文中CT模型对保护CT的饱和特性进行了仿真研究,仿真结果和实测数据的比较验证了模型的有效性。 相似文献
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Kang Y.C. Park J.K. Kang S.H. Johns A.T. Aggarwal R.K. 《Power Delivery, IEEE Transactions on》1997,12(1):116-124
Current transformer (CT) saturation may cause power system relays to malfunction. The conventional method used to deal with the problem is overdimensioning of the transformer core so that CTs can carry up to 20 times the rated current without exceeding 10% ratio correction. However, this not only reduces the sensitivity of power system relays, but also increases the CT core size. This paper presents a technique of estimating the secondary current corresponding to the CT ratio under CT saturation. The proposed algorithm can improve the sensitivity of relays to low level internal faults, minimize the instability of relays for external faults, and might ultimately assist in reducing the dimension of the required CT core cross-section 相似文献