Research On Intelligent Thyristor Converter Based On CAN Bus

With the increasing of generator capacity , request is more and more high to the excitation system. The application of self excited static excitation system is becoming more and more widespread. Self excited static excitation system request thyristor converter has the high performance. In present stage the thyristor converter produced in China cannot achieve the excitation system to its request, even has the serious accident in the movement. There are many problems in traditional thyristor converter, but the most severe trouble is the communications between thyristor converter and excitation regulators,the selection of overvoltage protective electric circuit parameters, state of thyristor monitoring.The data communication of CAN bus has the prominent reliability, timeliness and the flexibility. The CAN bus is the best communication way which corresponds between the excitation installment.In this paper, microcontroller 80C196KD and CAN controller SJA1000 are embedded in thyristor converter, the communication points are connected with the twisted pair line for the medium, thus causes between the thyristor converter and the regulator can mutually communicate. The experiment confirmed when the maximum signal distance doesnot surpass 150 meters, the communication speed may reach 250Kbps, can satisfy the thyristor converter and the regulator data transmission timely request. The unobservability problem of the thyristor converter in excitation system has been solved, thus strengthened the robustness of excitation system.Through analysis thyristor's internal structure, discovers the relations which the voltage drop between gate and negative pole and the state of thyristor, and regards as this relations is the criterion of monitoring. Using hall sensor LV28-P to extract the voltage signal, and completes the monitoring together with the peripheral electric circuit . This method has applied in the actual product. Excitation system movement condition is good process scene test.The mechanism of the generation and the restrictive measure of overvoltage in the thyristor converter has been analyzed in this paper. Through the establishment mathematical model and the determination equation optimal solution method, discovers the relations between the switching current overvoltage and the protective part parameter,and through example explanation computation process. The parameter value according to this method and the recommendatory value in authoritative reference extremely approached, the question of the inappropriate selection of the protective part parameter has been solved.