The Development On Relay Protection System In High Voltage Converter

With the rapid development of power electronic technology and computer control technology,it has become development trend that AC speed regulation system replaces DC motor speed regulation system. The AC variable frequency speed regulation is generally acknowledged by the home and abroad that it has a great future with excellent speed regulation, high efficiency saving energy and other extensive scope of application merits. Relay protection is the basic guarantee to the safe run of converters. But so far, existing protection functions of converters are comparatively weak and mostly aim at the protection of power electronic components so the practical protection demands of converters are difficult to fulfill. Therefore, it is of great necessity and significance to develop more advanced protective relaying for high voltage converters.In this paper the elements and existing application of high voltage converter are introduced, and then the present status and development direction of converters and the correlative relay protection are summarized.On the analysis of topology of a high voltage three-level converter, aiming at the trait and possible faults, a set of design principle of relay protection system is brought forward. The protection system can offer efficient and comprehensive protection to the input transformer, DC circuit and the inverter. The protection system is discussed in detail with the protection design principle, scheme of hardware and software, function configuration and basic protection theory.According to the function demand of the protection system, the hardware is designed and layered hardware configuration is put forward. The type, capability and trait of the DSP used in the ground unit are introduced. The design characteristic and circuit principle of the AC-input board, DC-input board, switch-input board and the switch-output board are especially expatiated.There are 50Hz AC electric components, DC electric components and variable frequency electric components in a converter. The protection configuration is different from traditional electric equipment so the protection principle of converters is entirely researched. The frequency of output electric components is variable so Fourier algorithm with variable data window is brought forward to calculate basic frequency electric components with variable frequency. The calculation methods of 50Hz electric components, DC electric components and sequence components are also introduced.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, the hardware of the system is credible and the software has excellent performance.