Modular straight string converter chain, converter and control method

By using a modular direct-series converter chain structure, power semiconductor devices are decomposed into direct-series units and configured with current limiting and bypass units, solving the control synchronization and energy harvesting problems of direct-series converters, and realizing safe and reliable operation and low-cost application of the devices.

CN114629131BActive Publication Date: 2026-06-09STATE GRID HEBEI ELECTRIC POWER CO LTD +2
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
STATE GRID HEBEI ELECTRIC POWER CO LTD
Filing Date
2021-12-17
Publication Date
2026-06-09

AI Technical Summary

Technical Problem

Existing direct-series converters suffer from poor control synchronization when devices are directly connected in series, leading to short-circuit current and overvoltage problems. Furthermore, they lack a stable energy extraction method, resulting in insufficient equipment safety and reliability, which limits their widespread application.

Method used

The modular direct-series converter chain structure divides the power semiconductor devices into direct-series units and configures current limiting units, bypass units, and distributed control units. Through distributed control and dual bypass mechanisms, it avoids damage from overcurrent and overvoltage and provides a stable energy supply.

Benefits of technology

It enables safe and reliable operation of devices, reduces the risk of device damage, and improves the cost-effectiveness and stability of equipment. It is suitable for static var generators and flexible DC transmission converters.

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Abstract

This invention discloses a modular direct-series converter chain, a converter, and a control method. The converter chain includes N direct-series units, each comprising: a valve string, a current-limiting unit, a bypass unit, a distributed control unit, an energy-harvesting current transformer, and a current-harvesting unit. The valve string includes M directly connected power semiconductor devices, where M is an integer greater than or equal to 1, and each power semiconductor device is connected in parallel with a buffer circuit. The current-limiting unit consists of a current-limiting bypass switch and a current-limiting inductor connected in parallel. The bypass unit includes a bypass switch. The converter includes at least three modular direct-series converter chains, which are configured in a star or delta connection, or as a three-phase bridge circuit. The converter provided by this invention can be applied to power electronic equipment such as directly connected static var generators and flexible DC transmission converters, and has the advantages of low cost and high reliability.
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