Research On Protection Theory And Realization For High Voltage Three-level Converter

With high efficiency saving energy, excellent speed regulation and other extensive scope of application merits, the high voltage variable frequency speed regulation is generally acknowledged that it has a great future in the high power speed regulation drives. Recently, with the development of power electronic technology, the development and applications of high voltage converters have drawn more and more attentions. And many products go into running. Relay protection is the basic guarantee to the safe run of converters. The converters'structure is complicated and faults are easily caused,so the relay protection system should be highly abled to meet all these demands. At the same time, since the converters contain many parts, such as rectifier, inverter, and variable frequency AC output, of which protection becomes very difficulty. So far, existing protections are mostly over current, over voltage and low voltage protections. The protection theory is too simple, so the practical protection demands of converters are difficult to fulfill. Therefore, aiming at the structure trait and possible faults, research on the protection theory and its realization is on edge.In this paper the present status and development direction of high voltage converters and the correlative relay protection are summarized, and then existing problems are analyzed. And also the background and important application of protection system for high voltage converters are narrated.On the introduction of topology of a high voltage three-level converter, aiming at the trait, possible faults are analyzed in detail, simulation models are established. The characters of internal faults are analyzed by simulation and calculation.According to simulation analysis, design principle of relay protection system is brought forward. The protection system can offer efficient and comprehensive protection to the input transformer, rectifier, DC bus, inverter, output circuit and the motor. The basic protection theory, protection algorithm, protection action are narrated in detail.The modularization based on protection logic diagram is adopted in the software of the protection system. Therefore, the program is clear-cut, and easily modified. Some protection logic diagrams and the flow chart of the program are depicted in detail.Finally, parts static simulation experiments for the protection system of high voltage converter is described. The results of the experiments and some specific problems are analyzed. The done experiments show that the performance of the protection system has achieved the goals of the design.