A seven-level converter and its flying capacitor voltage control method and system

Abstract

The invention discloses a seven-level converter, and a flying capacitor voltage control method and system thereof. Three-phase bridge arms which are connected in parallel are included. Each phase bridge arm comprises four IGBT switch tubes which are connected in series. One side of a midpoint of each phase bridge arm is connected with two branches. Each branch is formed by connecting two IGBT switch tubes with different directions in series. The other end of each branch is connected to a joint of each two of the three series connection flying capacitors. Two ends of branches of the three series connection flying capacitors are connected between two adjacent IGBT switch tubes of each phase bridge arm. The other side of each phase bridge arm is connected with a load or a power grid through afilter. A direct-current voltage source is connected to an input end of each bridge arm connected in parallel. And each IGBT switch tube is driven by a control circuit. Compared with a traditional seven-level topology and other improved seven-level topologies, the topology of the invention has advantages that the number of switch devices is greatly reduced; and a system structure is simplified, and system cost is reduced.

Description

technical field [0001] The invention relates to the technical field of multi-level converters, in particular to a seven-level converter embedded with a midpoint clamp and a method and system for controlling the voltage of a flying capacitor. Background technique [0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art. [0003] Compared with two-level and three-level converters, the comprehensive performance of multi-level converters has been improved, and it has been used more and more in industrial applications such as renewable energy conversion, motor drive, reactive power compensation, and transportation. s concern. The multilevel converter can significantly reduce the total harmonic distortion (Total Harmonic Distortion, THD) of the AC output, reduce the switching loss, reduce the voltage stress (dv / dt) of the switch tube, increase the input voltage range of the converter...

AI Technical Summary

Problems solved by technology

[0004] Traditional seven-level topology converters include: Flying capacitor (FC) converters, neutral point clamped (NPC) converters, cascaded H-bridge (CHB) converters, etc.; The number of flying capacitors in the flying capacitor converter is large, which makes it difficult to control the capacitor voltage; the number of switching tubes in the midpoint clamp converter is large, the structure is complex, and the production cost is high; the cascaded converter requires multiple independent DC power supplies, and the structure and algorithm complex, high production cost

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