A Fast Precharge Circuit for Modular Multilevel Converter

Abstract

The invention provides a rapid precharging circuit for a modular multi-level converter. The rapid precharging circuit comprises a main current-limiting charging portion, an accelerated charging portion and a normal running portion. The main current-limiting portion is a current-limiting resistor. According to the accelerated charging portion, a contactor is in series connection with a current-limiting resistor. The normal running portion is a contactor. The main current-limiting charging portion, the accelerated charging portion and the normal running portion are of a parallel-connection structure. After the parallel connection, one common end is connected with a charging power source, the other common end is connected with the modular multi-level converter, and the charging power source can be a direct-current power source or an alternating-current power source. If charging is carried out with the alternating-current power source, the precharging circuit needs a three-phase alternating-current structure. The rapid precharging circuit for the modular multi-level converter can achieve the charging function of a traditional precharging circuit for the modular multi-level converter, and the circuit is simple in structure and control mode, capable of greatly shortening the charging time and effectively reducing charging losses, and particularly suitable for occasions with high voltage and high power or longer precharging time.

Description

technical field [0001] The invention belongs to the technical field of power electronics applications, and in particular relates to a fast precharging circuit for precharging a modular multilevel converter and its working method. Background technique [0002] With the rapid development of the economy and the gradual expansion of the scale of social production, the demand and consumption of energy are also increasing, the demand for various forms of electricity is constantly increasing, and the requirements for energy saving and consumption reduction of power electronic equipment are also increasing. High, power electronics technology has developed rapidly, among which multilevel converters are gradually becoming high-voltage large converters because of their advantages such as high output voltage, low harmonic content, small voltage change rate, small voltage stress of power switching devices, and low switching frequency. Research hotspots in the field of power electric appl...

AI Technical Summary

Problems solved by technology

[0004] In the research and application of existing modular multilevel converter pre-charging methods, no matter what kind of pre-charging circuit is used, a current-limiting resistor must be connected in series in the pre-charging circuit, such as figure 1 As shown, in order to prevent the charging current from being too large, when the capacitor voltage rises to the rated value, the current-limiting resistor is short-circuited, but there is only one charging branch and one current-limiting resistor. During the charging process, as the capacitor voltage gradually rises, the charging current will gradually decrease, and the charging speed will also become slower and slower

If it is applied in high-voltage and high-power occasions, such as in the field of high-voltage direct current transmission, the voltage level is very high, and the number of capacitors required to be charged is also large, and the time required for pre-charging is generally very long, which is not only not conducive to the application in engineering practice , and increases the power loss on the current limiting resistor, which also has a great impact on the safety and reliability of the equipment

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