Independent five-level output diode clamping bridge type frequency converter

Abstract

The invention discloses an independent five-level output diode clamping bridge type frequency converter which is composed of eight controllable switches having a same structure and four diodes. The eight controllable switches are in bridge type connection. In the eight controllable switches, four controllable switches are serially connected to form a series circuit, two ends of the two series circuits after parallel connection are used as two ends of an output power source, the center nodes of the two series circuits are used as two ends of an input power source, and every two diodes are serially connected and then serially connected between two nodes on two sides of the center node of a series circuit. According to the invention, through the control of the eight controllable switches, the output of five different levels can be realized, so that the frequency conversion process of an alternating-current power source can be completed, and advantages of less required devices and easy modularization can be realized, so the frequency converter of the invention is suitable for being used as the frequency converter of a grid interface; and at the same time, the balance of the selection of the redundant state is kept through the four diodes separately to form the clamping control of the output voltage.

Description

technical field [0001] The invention relates to a frequency converter, in particular to an independent five-level output diode-clamped 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...

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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