Seamless cut-off controlling method for chained multi-level inverter error unit

Abstract

The invention discloses a seamless cut-off controlling method for a chained multi-level inverter error unit. The method comprises the following steps of: monitoring each physical parameter of a system in real time; judging a current operation state of the system by a control part according to monitored information; cutting actions of error cut-off power unit / bypass mechanisms by a power unit controller when an abnormal situation is found out and cannot be eliminated; and updating a triangular carrier period as well as a modulation ratio and / or direct current side voltage in real time. According to the scheme, the problems of unbalanced three-phase voltage, poor electric energy quality and the like caused by a bypass error power unit are solved, so that the seamless cut-off of errors can be realized. The method is simple and feasible, and complicated calculation and judgment are avoided; and because the characteristic of a redundancy design is fully utilized, the reliability of a system is greatly improved, and the working service life of the system is prolonged so as to propel that a chained multi-level inverter is reliably applied to high-pressure high-volume power electronic devices.

Description

Technical field: [0001] The invention belongs to the research field of power grid power quality control, and in particular relates to correct operation steps and a specific method for seamless removal of CMI faulty units of chained multilevel inverters. Background technique: [0002] With the rapid progress of power electronics technology and the popularity of green and low-carbon concepts, the requirements for power quality in industrial production and even residential electricity use are also increasing. Power quality controllers represented by APF, STATCOM, etc., as well as New energy generation grid-connected devices represented by wind power generation and photovoltaic power generation are rapidly developing in the direction of high voltage and high power. The core circuit of the above-mentioned device is the most widely used multi-level inverter in chain structure. [0003] The high-voltage and large-capacity power electronic device composed of a chain structure is a ...

AI Technical Summary

Problems solved by technology

But this method still has many shortcomings and problems: 1. It can only keep the output line voltage amplitude equal, while the output harmonic will increase significantly

2. The fundamental voltage amplitudes are not exactly equal, the greater the harmonic content, the lower the fundamental voltage amplitude

3. The amount of calculation is huge, the logic is complex, and it is very troublesome to implement

4. Although the amplitude of the output line voltage is equal, and the maximum voltage amplitude is output as much as possible, the amplitude is still reduced compared to the output voltage during normal operation. 5. More importantly, this method is only applicable to The structure of the star connection is not suitable for the widely used delta connection structure

Many of these shortcomings belong to the inherent defects of the neutral point shift method, which cannot be completely resolved through optimization and improvement measures

Images