Electric Energy Measurement Method for Traction Loads
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摘要: 为了研究牵引负荷产生的负序对电能计量的影响，在建立牵引供电系统及电力系统三相模型的基础上，分析了牵引供电系统负序功率潮流，阐述了牵引负载采用传统功率理论定义下的功率因数计量方式存在的问题，基于IEEE Std 1459-2010功率理论所推荐的等效视在功率及功率因数定义，提出不平衡牵引负载功率因数计量方案，并将有效功率因数限值取为0.68. 理论分析及实测数据均表明：牵引负荷负序有功功率与正序有功功率方向相反，牵引负荷作为负序源向系统注入负序功率，被系统阻抗和对称负载吸收. 通过仿真与56组实测数据统计分析并验证本文算法的有效性和结论的正确性，实测数据统计结果表明，等效视在功率及等效功率因数能计及不平衡牵引负载对线路传输效率的影响，计量更合理准确.Abstract: In order to explore the influence of negative sequence from traction loads on electric energy measurement results, the negative-sequence power flow in traction power supply system is analyzed on the basis of the established traction power supply system and three-phase power system models. The shortcomings of the power factor metering method based on the traditional power theory are provided. In this regard, an unbalanced power factor metering scheme for traction load is proposed according to the equivalent apparent power and power factor definitions recommended by the IEEE Std 1459-2010 power theory, in which the limit of the effective power factor is 0.68. Theory analysis and measured data show that the direction of negative-sequence active power is opposite to that of the positive-sequence active power; as a negative-sequence source, traction loads add negative-sequence power to the system, which can eventually be absorbed by the system impedance and balanced load. Finally, algorithm effectiveness and conclusion correctness are analyzed and validated by simulation and statistical analysis on 56 groups of measured data in this paper. The simulation and statistical analysis on 56 groups of measured data are used to validate the algorithm and conclusions. Statistical results of measured data show that the equivalent apparent power and the definition of power factor can account for the effect of nonlinear unbalanced traction load on transmission efficiency, which is more reasonable and accurate.
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Key words:
- negative-sequence flow /
- electric power measurement /
- power factor
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图 2 牵引变压器从次边看进的等效模型
Figure 2. Equivalent model of traction transformer viewed from secondary side
图 5 对称负载和系统阻抗吸收的负序功率
Figure 5. Negative-sequence power absorbed by symmetric load and system impedance
图 6 牵引负荷总有功功率与正序有功功率对比
Figure 6. Total active power vs. positive-sequence active power of traction load
图 13 负序条件下功率因数变化趋势
Figure 13. Power factor variation under negative-sequence condition
图 15 电压偏移百分百与等效功率因数的关系
Figure 15. Relation between 100% voltage offset and equivalent power factor
表 1 仿真数据
Table 1. Simulation data
牵引负荷 数据 牵引负荷 数据 电压有效
值/kVUA = 119.281 电流有效值/A IA = 52.274 UB = 119.858 IB = 49.316 UC = 119.343 IC = 50.118 三相功率/MW P = 15.500 
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表 2 正序、负序、一次侧有功功率统计值
Table 2. Statistics of positives-sequence，negative-sequence andprimary-side active powers
数据 P+/kW P−/kW Pall/kW 1 10 990.738 −7.776 10 982.960 2 25 446.428 −28.387 25 418.040 3 10 993.926 −13.376 10 980.550 4 9 364.372 −8.226 9 356.146 5 9 796.182 −10.992 9 785.190 6 10 238.528 −9.785 10 228.740 7 11 963.221 −14.299 11 948.920 8 16 037.273 −22.767 16 014.510 9 14 341.452 −20.299 14 321.150 10 9 928.211 −14.339 9 913.872 11 18 299.214 −21.378 18 277.840 12 16 257.203 −20.077 16 237.130 13 17 255.028 −16.395 17 238.630 14 11 326.549 −12.397 11 314.150 15 14 889.862 −16.739 14 873.120 16 13 853.902 −13.293 13 840.610 17 11 926.001 −13.431 11 912.570 18 15 182.937 −16.105 15 166.830 19 9 896.732 −10.206 9 886.526
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表 3 传统功率因数、有效功率因数与电压平衡度统计值
Table 3. Statistics of traditional power factor，effective power factor and voltage balance
序号 λ λe εU（95%）/% εU（最大）/% 1 0.995 0.789 1.12 1.42 2 0.986 0.794 1.10 1.51 3 0.998 0.765 1.24 1.56 4 0.983 0.801 1.01 1.82 5 0.982 0.693 1.27 1.85 6 0.982 0.686 1.30 1.79 7 0.979 0.742 1.25 1.52 8 0.948 0.646 1.59 2.47 9 0.981 0.797 1.10 1.62 10 0.991 0.808 0.92 1.96 11 0.949 0.628 1.74 2.66 12 0.977 0.670 1.48 2.33 13 0.998 0.741 1.25 1.63 14 0.987 0.792 1.13 1.82 15 0.992 0.691 1.28 1.63 16 0.988 0.762 1.25 1.83 17 0.946 0.616 1.84 2.59 18 0.980 0.738 1.25 1.72 19 0.995 0.698 1.27 1.95 20 0.962 0.589 1.72 2.52 21 0.990 0.748 1.23 1.68 22 0.991 0.715 1.25 1.59 23 0.995 0.699 1.28 1.94 24 0.998 0.706 1.27 1.61
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