Solid-State Transformer Topology for Common-Mode Pulse Mitigation

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Solution Overview

Problem

Conventional transformers are susceptible to low-frequency common-mode (CM) insults such as high altitude electromagnetic pulses (HEMP) and solar-geomagnetic disturbances (GMD), leading to magnetic core saturation, distorted waveforms, increased losses, and potential transformer damage.

Innovation Solution

A solid-state transformer (SST) with a four-legged converter, dual active bridge, and energy storage system (ESS) to control CM currents and absorb incident energy, maintaining nominal transformer behavior during CM events.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional magnetic transformers are used, then galvanic isolation and voltage transformation are achieved, but the transformers become saturated by low-frequency common-mode currents leading to distorted waveforms and increased losses

Engineering Contradiction:

Improvetransformer operation reliabilityVSAvoidcommon mode current impact

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the conventional magnetic transformer with a solid-state transformer using power electronic converters (ac/dc converter, dc/dc converter, dc/ac converter) to perform voltage transformation and galvanic isolation without magnetic cores, thereby eliminating susceptibility to common-mode current saturation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an energy storage system as an intermediary component connected to the dc side of the solid-state transformer to absorb common-mode energy and prevent it from affecting the transformer operation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If solid-state transformers with power electronic converters are used, then control of common mode currents is achieved, but device complexity increases

Engineering Contradiction:

Improvecommon mode current controlVSAvoidtransformer structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent divides the solid-state transformer into three separate functional modules (ac/dc converter, dc/dc converter, dc/ac converter) that can be independently designed, controlled, and maintained, managing complexity through functional segmentation

Inventive Principle:

Principle #1Segmentation

3Reliability

If energy storage system is added to absorb common mode energy, then mitigation of common mode insults is improved, but device complexity and cost increase

Engineering Contradiction:

Improveprotection against common mode insultsVSAvoidsystem component count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The energy storage system serves multiple functions: absorbing common-mode energy during insults, maintaining dc voltage during transient conditions, and providing backup power capability, thereby justifying its inclusion despite increased complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12500415B1Solid-state transformer for mitigation of common mode insults

Publication Date: 2025.12.16 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

A high altitude electromagnetic pulse (HEMP) or other similar geomagnetic disturbance (GMD) has the potential to severely impact the operation of large-scale electric power grids by introducing low-frequency common-mode (CM) currents which deteriorate the performance of key grid components, such as large power transformers. A solid-state transformer (SST) can replace susceptible equipment and improve grid resiliency by safely redirecting, absorbing, and/or converting these CM insults.