Research On Control System Of Potentiostat For Pipelines Anticorrosion

Corrosion protection of oil or gas pipeline is essential for extension of service life and energy transport.Cathodic protection method is being recognized as the most effective way to prevent the electrochemical corrosion of metal.Potentiostat,as the impressed current cathodic protection power,has been widely used in underground metallic pipeline anticorrosion.The control system of potentiostat, which is the key technique of the cathodic protection system, has developed rapidly in recent years. However, there are still some shortcomings, such as difficulty of networking and centralized managing, tedious operating procedures and simple man-machine interface.A new type of potentiostat control system has been propsed in this thesis, which can effectively eliminate the above defects and can be used for a variety of controlling purposes.The main research achievements are summarized as follows:Firstly, the author has analyzed the role of potentiostat in the pipeline corrosion protection. According to the requirements of cathodic protection, a control system scheme of modular circuit design has been proposed. Based on electrical isolation, the hardware circuit design and programming has been accomplished, which can realize the function of data acquisition, data storage, data show, data transmission.Secondly, a complex filtering algorithm based on weighted recursive filtering method has been presented in order to eliminate the electromagnetic interference from high-frequency switching power supply and other interference from the field, which has improved data acquisition accuracy.Thirdly, a dynamic tracking control algorithm has been proposed to achieve precise and stable control for reference voltage.Finally, based on RS-232 bus, RS-485 bus or wireless data transmission, the thesis has adopted multi-mode communication methods and developed a set of communication protocols. Not only can this meet various needs of data transmission and remote control. But also can improve the efficiency and flexibility of datacommunication.The system has been tested in laboratory.The experimental results have shown that: (1) the given potential can be adjusted continuously from -2.0V to 0V, and the control precision of reference voltage is±2mV; (2) the stable time of reference voltage is less than 7 seconds; and (3) data communication is accurate. The control system can meet the demand of cathodic protection engineering.