Research And Experiment Of Water Cooling System Of Converter Valve

Converter station is conversion site for AC and DC in theUHV and HVDC transmission system,as well as the central link in DC transmission.The maximum voltage level is up to 1100kV.The converter valve is an important part of the converter station,and it is also a high-power power electronic equipment for AC and DC conversion.A large amount of heat is generated during the operation of the valve,which mainly concentrates the high heating element,such as the converter valve,the damping resistance,the reactor and so on.Therefore,it is necessary to cool it through the cooling water system.In order to solve the existing problems of corrosion and deposition,HVDC converter station usually takes the high resistivity deionized water as the medium of water cooling to cool the device.Corrosion and deposition is not only affected by the ionic state materials in waterway,but also affected by other factors,such as the pH value,temperature,electrode materials and so on.Therefore,Corrosion and deposition still exists in the waterway of deionized water as a cooling medium.According to the existing research results,the water corrosion of the valve is mainly concentrated on the surface of the aluminum sink and the high potential pressure electrode,and the deposition of water is mainly on the surface of the high potential average pressure electrode.In addition,corrosion and deposition also exists on low potential average pressure electrode.In this case,it is difficult to suppress corrosion and deposition with the simple change of the electrode structure.Therefore,study on the mechanism of electrochemical corrosion deposition from the microscopic point of view provide a way for this problem.In the paper,the simulation platform from the microscopic point of view for corrosion process of commutation valve is designed and implemented.The main factors and mechanism of corrosion are explored by measuring ion variation under different conditions,such as the voltage,the switchsituation of the nitrogen tank and resin bed.The electrochemical inhibitors of aluminum are determined according to the measurements from the simulation platform.Polarization curve mode is measured by the electrochemistry workstation to further study the inhibition efficiency for corrosion.Modeling and simulation are implemented in the COMSOL according to Tafel slope and other factors from the electrochemical workstation.Then the corrosion current reflecting the corrosion condition is calculated,which pays theoretical foundation for the further study on the corrosion process of water cooling system for converter valve.