Power conversion device

The power conversion device addresses DC magnetization in three-winding transformers by using current detectors and an excitation current detection unit to correct DC excitation currents, achieving stable and cost-effective operation.

WO2026154585A1PCT designated stage Publication Date: 2026-07-23KK TOSHIBA
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Patent Information

Authority / Receiving Office
WO · WO
Patent Type
Applications
Current Assignee / Owner
KK TOSHIBA
Filing Date
2025-01-16
Publication Date
2026-07-23

AI Technical Summary

Technical Problem

Conventional power conversion devices with three-winding transformers face challenges in suppressing DC magnetization, leading to potential magnetic saturation and increased size and cost due to the need for larger iron cores to manage DC excitation currents.

Method used

A power conversion device with a three-winding transformer design that includes first and second current detectors and an excitation current value detection unit, utilizing a lead neutral wire and phase-specific current detection to accurately measure and correct DC excitation currents, thereby suppressing DC magnetization without enlarging the transformer core.

Benefits of technology

The solution effectively suppresses DC magnetization at a reduced cost and size, ensuring stable operation by accurately detecting and correcting DC excitation currents, thus maintaining reliable power conversion.

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Abstract

A power conversion device according to an embodiment of the present invention comprises: a plurality of arm units; a transformer; lead-out neutral lines; a first current detector; a second current detector; and an excitation current value detection unit. Each arm unit includes a plurality of unit converters connected in series, each unit converter having an energy storage element and a plurality of switching elements. The transformer includes, for each phase, at least three windings including a first winding electrically insulated from the arm unit, and a second winding and a third winding connected to the arm unit. The lead-out neutral lines for the respective phases are led out from phase neutral points, each of which is a connection point between the second winding and the third winding, and connect the phase neutral points for the respective phases to each other at a common neutral point. The first current detector detects, for each phase, a current flowing in the first winding. The second current detector detects, for each phase, a current flowing in the lead-out neutral line. The excitation current value detection unit detects the excitation current value of the transformer on the basis of the current for each phase detected by the first current detector and the current for each phase detected by the second current detector.
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