Study On Vibration And Noise Characteristics And Noise Redction Technology Of Power Capacitor

As a result of generating a large number of high-order harmonics in HVDC transmission,a lot of noise is produced when passing through the converter station,which has a bad effect on the surrounding residents.The main noise sources in converter station are AC / DC filter power capacitor,converter transformer and wave reactor.The filter capacitor equipment is difficult to deal with the noise because of the large harmonic number,the number of stations,the density,and the long-term exposure to the higher capacitor tower.Since the noise of capacitor device is radiated by several capacitor units,the fundamental measure to solve the noise problem of power capacitor is how to reduce the noise of a single capacitor.At present,there are two main ways to reduce the noise of a single power capacitor.One is to take measures from the inside of the capacitor to reduce the vibration of the capacitor core,so as to reduce the noise of the capacitor.The second is to take measures from the capacitor housing structure to reduce the noise of the capacitor.At present,the noise reduction method of shell structure is the lowest cost,the easiest to realize in engineering and the higher safety and reliability.In this paper,the noise reduction problem of power capacitor shell structure is studied as follows:1.The generating mechanism of vibration and noise of power capacitor is discussed.Firstly,the transmission process of vibration and noise of power capacitor is analyzed,and the mathematical model of power capacitor excitation is obtained by solving the vibration excitation of power capacitor.Then the vibration and noise acquisition system of the power capacitor is established in the semi-anechoic chamber,and the frequency domain characteristics of the vibration and noise response of the power capacitor are analyzed.2.The simulation and analysis method of power capacitor shell noise is studied.The finite element simulation model of power capacitor is established in LMS Virtual.Lab,and the vibration and noise response of power capacitor is solved based on FEM method and BEM method,and the vibration and noise of power capacitor is solved by taking a certain type of power capacitor product as an example.The comparison with the experimental results shows that the simulation results of the power capacitor model established in this paper is reliable.3.The optimization model of the dimension parameters of the bottom sound insulation cavity of the power capacitor is established.In order to realize the fast design and optimization of the bottom sound insulation cavity of the power capacitor;This paper presents a design method for the dimension parameters of the bottom sound insulation cavity at a specific noise frequency,and optimizes the air layer and plate thickness of the cavity structure.The experimental results show that the sound insulation of the noise reduction cavity is up to 12 dB.On the basis of this,the sound insulation characteristics of the double-layer sound insulation cavity are studied and compared with that of the single-layer sound insulation chamber.4.The multi-objective morphology optimization model of power capacitor shell is established.In order to effectively reduce the radiation noise of the capacitor shell,the multi-order natural frequency of the capacitor shell is optimized.The vibration and noise simulation of the finite element model before and after optimization is carried out in the LMS Virtual.Lab acoustic simulation platform.The simulation results show that the optimized capacitor shell can reduce the noise before optimization by 4.21 dB.