直流偏磁對變壓器電流影響及其抑制研究
高歌，徐建源，曹辰
（沈陽工業大學 電氣工程學院，遼寧 沈陽 110870）
摘 要：以SZ11-100000/220 變壓器為研究對象，應用PSCAD/EMTDC搭建變壓器模型進行時域仿真，分析不同直流偏置量下變壓器勵磁電流及諧波特性的影響規律。基于阻容隔直法抑制措施進行優化分析，提出一種具有故障保護作用的阻容隔直法抑制措施。通過設計電路主要參數，搭建變壓器模型，仿真分析直流偏磁抑制措施使用前后的變壓器直流偏磁情況。仿真結果表明，變壓器勵磁電流畸變程度與流入中性點的直流量呈正相關。當直流分量為5 A時，勵磁電流正半周為6.23 A，負半周為-0.30 A，并出現偶次諧波。當采取所提出的抑制措施后，中性點的直流量控制在了可允許范圍內，極大地減弱了直流偏磁程度，若系統故障，裝置中旁路立即接地，保護了電容器安全運行。
關鍵詞：變壓器；直流偏磁；阻容隔直法；勵磁電流；諧波特性；抑制措施
中圖分類號：TM401+.1 文獻標識碼：A 文章編號：1007-3175(2020)04-0011-05
Research on the Influence of Transformer Current and Its Suppression Under DC Bias
GAO Ge, XU Jian-yuan, CAO Chen
（School of Electrical Engineering, Shenyang University of Technology, Shenyang 11 0870, China）
Abstract: Taking SZ11 -100000/220 transformers as the research object, PSCAD/EMTDC was used to build the transformer model for time domain simulation. The influences of transformer excitation current and harmonic characteristics under different DC offsets are analyzed. Based on the optimization analysis of resistive-capacitor DC-blocking method, a resistive-capacitor DC-blocking method with fault protection is proposed. By devising the main parameters of the circuit, a transformer model is built, and the DC bias of the transformer before and after the DC bias suppression measures are simulated and analyzed. The simulation results show that the degree of distortion of the transformer's excitation current is positively related to the direct current flowing into the neutral point.When the DC component is 5 A, the positive half cycle of the excitation current is 6.23 A, the negative half cycle is -0.30 A, and even harmonics appear.When the proposed suppression measures are taken, the DC value of the neutral point is controlled within the allowable range, which greatly reduces the degree of DC bias.If the system fails, the bypass in the device is immediately grounded to protect the capacitor's safe operation.
Key words: transformer; DC bias; resistive-capacitor DC-blocking method; excitation current; harmonic characteristics; suppression measures
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