Transformer Bypass Converter Using Thyristor-Tapped Winding

Solution Overview

Problem

Existing Power-Electronics-Enhanced-Transformers (PEETs) using IGBTs are costly and inefficient due to high losses.

Innovation Solution

Replace part of the AC-AC PE converters with thyristor-based AC-AC converters, utilizing thyristors which are cheaper and more efficient, and incorporate a coupled impedance to protect against short-circuit faults.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If IGBT-based AC-AC PE converters are used in transformers, then voltage regulation and power flow control functionalities are achieved, but cost and losses increase significantly

Engineering Contradiction:

Improvevoltage regulation and power flow control functionalityVSAvoidconverter losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent segments the AC-AC PE converter into two independent parts: a thyristor-based converter connected to the transformer winding and an IGBT-based converter connected to the auxiliary winding. The thyristor-based part handles the majority of power conversion with low losses, while the IGBT-based part provides only the necessary voltage regulation functionality. This segmentation allows the system to achieve the required adaptability while minimizing overall energy losses by using the more efficient thyristors for the bulk of the power handling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces expensive IGBTs with cheaper thyristors for the main power conversion function. Thyristors are significantly less costly and have lower conduction losses compared to IGBTs, making them economically advantageous for handling the majority of power conversion requirements, even though they lack full bidirectional control capability.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Adaptability or versatility

If IGBT-based AC-AC PE converters are used in transformers, then voltage regulation and power flow control functionalities are achieved, but device cost increases

Engineering Contradiction:

Improvevoltage regulation and power flow control functionalityVSAvoidconverter cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent segments the AC-AC PE converter into two independent parts: a thyristor-based converter connected to the transformer winding and an IGBT-based converter connected to the auxiliary winding. The thyristor-based part handles the majority of power conversion with low losses, while the IGBT-based part provides only the necessary voltage regulation functionality. This segmentation allows the system to achieve the required adaptability while minimizing overall energy losses by using the more efficient thyristors for the bulk of the power handling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces expensive IGBTs with cheaper thyristors for the main power conversion function. Thyristors are significantly less costly and have lower conduction losses compared to IGBTs, making them economically advantageous for handling the majority of power conversion requirements, even though they lack full bidirectional control capability.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Loss of energy

If thyristor-based AC-AC converters are used to replace IGBT-based converters, then cost and losses are reduced, but fault protection requirements increase

Engineering Contradiction:

Improveconverter lossesVSAvoidfault protection requirements

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent introduces an intermediary impedance element connected between the thyristor-based converter and the transformer winding. This impedance serves as a protective mediator that limits fault currents and protects the thyristors from short-circuit damage. The impedance acts as a buffer that allows the use of less expensive and more efficient thyristors while maintaining system reliability through passive protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP4068608B1Transformer arrangement

Publication Date: 2025.06.25 HITACHI ENERGY LTD

Figure 1
Figure 2a
Figure 2b

AI summary

A transformer arrangement (18) comprising a transformer (10) having a primary side (11) for receiving input voltage and current from a source and a secondary side (12) for providing output voltage and current to a load. The transformer arrangement (18) further comprises an AC-AC PE converter (14) connected to a thyristor (23) used for bypassing the AC-AC PE converter (14) in case of a short-circuit fault in a terminal of the primary side (11) and/or the secondary side (12). The transformer arrangement (18) further comprises a thyristor-based AC-AC PE converter (16) connected to a thyristor-tapped winding (13a). The AC-AC PE converter (14) is connected with the thyristor-tapped winding (13a) via the thyristor-based AC-AC PE converter (16). The thyristor-based AC-AC PE converter (16) is connected to an impedance (21) to protect the thyristor-tapped winding (13a) from short-circuit faults of the thyristor-based AC-AC PE converter (16).