Grid-Forming Power Converter Fault Switching for Higher Short-Circuit Current

Solution Overview

Problem

Electric power converters operating in grid-forming mode face limitations in providing sufficient short-circuit current due to the dimensioning of power semiconductor switches, leading to potential overdimensioning and increased costs.

Innovation Solution

The method involves controlling controllable power semiconductor switches to operate at a lower switching frequency during short-circuit faults, reducing losses and enabling higher short-circuit current supply without altering the converter's dimensioning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the electric power converter is overdimensioned to provide sufficient short-circuit current, then the short-circuit current supply capability is improved, but the size and cost of the converter increase

Engineering Contradiction:

Improveshort-circuit current supply capabilityVSAvoidconverter size

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control system dynamically changes the switching frequency from a first frequency during normal operation to a second frequency during short-circuit conditions, allowing the converter to adapt its performance characteristics to match the operational requirements without permanent overdimensioning

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameters of the power semiconductor switches by adjusting the switching frequency. During short-circuit faults, the switching frequency is reduced from the first frequency to the second frequency, which changes the current waveform characteristics and allows higher peak currents to be supplied without exceeding the thermal and electrical ratings of the switches

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the electric power converter is overdimensioned to provide sufficient short-circuit current, then the short-circuit current supply capability is improved, but the cost of the converter increases

Engineering Contradiction:

Improveshort-circuit current supply capabilityVSAvoidconverter cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control system dynamically changes the switching frequency from a first frequency during normal operation to a second frequency during short-circuit conditions, allowing the converter to adapt its performance characteristics to match the operational requirements without permanent overdimensioning

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameters of the power semiconductor switches by adjusting the switching frequency. During short-circuit faults, the switching frequency is reduced from the first frequency to the second frequency, which changes the current waveform characteristics and allows higher peak currents to be supplied without exceeding the thermal and electrical ratings of the switches

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If the switching frequency is reduced during short-circuit faults, then the losses in power semiconductor switches are reduced, but the normal operation performance may be affected

Engineering Contradiction:

Improveswitching lossesVSAvoidnormal operation performance

Core Design Contradiction:

Loss of energyVSProductivity

Solution Approach 1:

The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control system dynamically changes the switching frequency from a first frequency during normal operation to a second frequency during short-circuit conditions, allowing the converter to adapt its performance characteristics to match the operational requirements without permanent overdimensioning

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies partial action by reducing the switching frequency only during the specific condition of short-circuit faults rather than during all operations. This targeted approach reduces switching losses when needed while preserving the higher switching frequency and associated performance benefits during normal operation

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP4383536A1Method for operating electric power converter and electric power converter

Publication Date: 2024.06.12 ABB (SCHWEIZ) AG

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AI summary

A method for operating an electric power converter, and an electric power converter (10) comprising a plurality of controllable power semiconductor switches and configured to operate in a grid-forming mode of operation such that the controllable power semiconductor switches are operated at a first switching frequency, and in response to detecting a short-circuit fault in an AC network (30) connected to the electric power converter (10) provide an AC current of at least a predetermined magnitude to the AC network (30) such that the controllable power semiconductor switches are operated at a second switching frequency, wherein the second switching frequency is lower than the first switching frequency.