Converter Transformer Noise Equivalent Evaluation Method in Multi-Harmonic Operating Conditions Based on the Electro-Induced Noise Frequency Response Function

When the noise assessment of the converter transformer before leaving the factory, the basic data generally adopts the test value of the equipment manufacturer or the previous engineering data, and there is a certain gap between the test conditions and the actual working conditions of the site and the actual working conditions, which is difficult to accurately reflect the actual noise situation of the equipment. The electrical equipment in the converter station is larger in size and close to the distance, and a series of reflections, diffraction and other phenomena will occur when obstacles are encountered in the process of noise propagation, and it is difficult to accurately measure the sound source and achieve accurate evaluation of the sound power level of a single device. In order to accurately evaluate the noise level of a single power device, it is particularly important to propose a more accurate factory test method for converter transformer noise. The injection of harmonic current and voltage is the main factor in the rise of the noise level of the converter transformer operation. By using the relationship between the radiated sound pressure of the converter transformer and the square of the excitation voltage and the square of the current, the equivalent evaluation method of the noise of the converter transformer is proposed, taking the equivalent actual multi-harmonic operating conditions as the goal. The single-frequency superposition test is to evaluate the noise level of the converter transformer under the loaded complex frequency excitation by using the result of the single frequency excitation loading noise test through the superposition theorem. Capacitance reduction test is an alternative loading scheme in the case that the capacity of multi-frequency harmonic power supply cannot meet the direct loading, and add 40lgm (reduction ratio) to the capacity reduction test result to obtain the noise level at full capacity. The single-frequency superposition and capacitance reduction tests of the converter transformer are carried out to obtain the radiated noise under different harmonic operating conditions of the converter transformer, and the effectiveness and accuracy of the proposed method are analyzed and compared to verify the noise frequency characteristics and sound field distribution measured and evaluated. The results show that the noise error obtained by the single-frequency superposition test is within 1.8 dB, and the noise error obtained by the capacitance reduction loading test is within 1.6 dB, which greatly improves the accuracy of the noise evaluation of the converter transformer compared with the previous power frequency loading method. The proposed equivalent evaluation test method provides an effective method for converter transformer manufacturers to grasp the noise performance of product operation, and at the same time provides a strong support for the noise design and treatment of converter station. © 2023 Chinese Machine Press. All rights reserved.