PMG Stator Winding Fault Interruption Using Delayed Breaker Sequencing

Solution Overview

Problem

Permanent magnet generators (PMGs) face challenges in safely interrupting fault currents due to their inductive and asymmetric nature, which can lead to re-ignition in circuit breakers and increased risk of damage, especially when mutual coupling from healthy stator windings exacerbates fault currents.

Innovation Solution

A method involving a power generating assembly with controllable circuit breakers connected to each set of stator windings, where the current in healthy windings is interrupted before the faulty windings, using a predetermined delay to manage mutual coupling and reduce fault current magnitude, thereby facilitating safer interruption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If the current in healthy stator windings is interrupted before the faulty windings, then the fault current magnitude is reduced, but the device complexity increases due to coordinated control requirements

Engineering Contradiction:

Improvefault current magnitudeVSAvoidcontrol system complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The control system performs preliminary action by detecting the fault and interrupting the current in healthy stator windings before the faulty windings. This sequence is predetermined and executed automatically upon fault detection, reducing the fault current magnitude before the main interruption occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stator windings are segmented into healthy and faulty sets, each controlled independently through separate circuit breakers. This segmentation allows selective interruption of healthy windings first, isolating the fault source and reducing overall fault current.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a controllable circuit breaker is used to interrupt PMG fault current, then the fault can be isolated, but the circuit breaker may experience re-ignition due to high frequency and asymmetric current

Engineering Contradiction:

Improvefault isolation capabilityVSAvoidre-ignition risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system performs preliminary action by detecting the fault and interrupting the current in healthy stator windings before the faulty windings. This sequence is predetermined and executed automatically upon fault detection, reducing the fault current magnitude before the main interruption occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system applies preliminary anti-action by interrupting healthy windings first, which counteracts the mutual coupling effect that would otherwise sustain high fault currents in the faulty windings, making the subsequent interruption safer.

Inventive Principle:

Principle #9Preliminary anti-action

3Loss of time

If the current in faulty stator windings is interrupted immediately, then the fault isolation is faster, but the mutual coupling from healthy windings sustains higher fault current

Engineering Contradiction:

Improvefault isolation timeVSAvoidfault current magnitude

Core Design Contradiction:

Loss of timeVSObject-generated harmful factors

Solution Approach 1:

The control system performs preliminary action by detecting the fault and interrupting the current in healthy stator windings before the faulty windings. This sequence is predetermined and executed automatically upon fault detection, reducing the fault current magnitude before the main interruption occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system implements periodic action through a predetermined time delay between interrupting healthy and faulty windings. This delayed periodic interruption allows the fault current to be reduced in a controlled manner while still achieving rapid fault isolation.

Inventive Principle:

Principle #19Periodic action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively reduces PMG fault currents by up to 320% and allows for safer and more reliable interruption of fault currents, minimizing damage to circuit breakers and extending their lifespan.

Implementation Method 1

the current in a healthy second set of stator windings, i.e. not faulty stator windings, contributes significantly to the PMG fault current in the first set of stator windings due to a mutual coupling between sets of stator windings, including the first and second sets of stator windings, in the PMG

Methodology Applied

Scientific EffectMutual coupling: Electromagnetic Induction

Data Source

PatentUS11855576B2Method for operating a permanent magnet generator in the event of a fault

Publication Date: 2023.12.26 VESTAS WIND SYSTEMS AS

AI summary

The present invention relates to a method for operating a power generating assembly in the event of a fault, wherein the power generating assembly comprises a PMG comprising at least first and second sets of stator windings, wherein each set of stator windings is connected to a power converter via a controllable circuit breaker, the method comprising the steps of detecting a fault associated with the first set of stator windings, and lowering, such as interrupting, the current in the second set of stator windings, and, after a predetermined delay, lowering, such as interrupting, the current in the first set of stator windings. The present invention also relates to a power generating assembly being capable of handling such faults, and a wind turbine generator comprising such a power generating assembly.