Cascaded five-level output capacitor clamping bridge type frequency converter

Abstract

The invention discloses a cascaded five-level output capacitor clamping bridge type frequency converter. The cascaded five-level output capacitor clamping bridge type frequency converter comprises a plurality of five-level output frequency converter units having a same structure. Each five-level output frequency converter unit is composed of eight controllable switches having a same structure and two capacitors. Every four controllable switches are serially connected into a series circuit. Each capacitor is connected between two nodes on two sides of the center node of a series circuit. Two ends of the two series circuits after parallel connection are used as power output ends of a corresponding five-level output frequency converter unit. The center node of the first series circuit of the previous five-level output frequency converter unit is connected with the center node of the second series circuit of the next five-level output frequency converter unit. The center node of the second series circuit of the first five-level output frequency converter unit and the center node of the first series circuit of the last five-level output frequency converter unit are used as two ends of power input ends respectively. According to the invention, the advantage of easy modularization can be realized, and the frequency converter of the invention is suitable for being used in a grid interface.

Description

technical field [0001] The invention relates to a frequency converter, in particular to a cascaded five-level output capacitor clamp bridge frequency converter which is easy to realize a modular structure. Background technique [0002] With the in-depth development of modern industry, high-power converters are more and more widely used in the national economy, such as large-capacity frequency converters, high-power power active filters, static var compensation devices, and transformers for MW-level wind turbines. In the case of high-power converters, there is often a contradiction between the power handling capability of high-power switching devices and the switching frequency. Usually, the higher the power, the lower the switching frequency. Due to the limitation of switching frequency, it is difficult to apply PWM technology to improve the performance of traditional large-capacity converters. Therefore, in the case of high-power converters, people often hope that high-po...

AI Technical Summary

Problems solved by technology

[0003] Ordinary inverters are usually also called two-level inverters. This topology is relatively simple. In order to obtain high power, the switching devices are generally connected in series to withstand high voltage, and the switching devices are connected in parallel to withstand high current. However, due to the parameters of power devices Discrete, which will bring a series of problems such as static and dynamic voltage equalization and current equalization. The technical uncertainties have a great influence and the reliability is not high; but because the output has only two levels, the voltage fluctuates greatly, causing large harmonic

Therefore, the scope of application of this structure is very limited

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