DFIG Converter Active Filter for Harmonic Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Doubly fed induction generator (DFIG) systems in wind turbines generate harmonics during overmodulation regimes, which are difficult to filter due to their proximity to the fundamental frequency, leading to increased energy loss and wear on components.

Innovation Solution

Incorporating an active filter with controlled components, such as IGBTs or MOSFETs, in parallel with the rotor-side converter to reduce harmonics by providing an opposite phase signal at the same frequency, and activating it only when harmonic contributions exceed industry standards to conserve resources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the rotor-side converter operates in overmodulation regime to increase voltage gain and extend operating range, then the generator's operating range and voltage gain are improved, but harmonics are generated that are difficult to filter and cause increased energy loss

Engineering Contradiction:

Improveoperating rangeVSAvoidenergy loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

An active filter is introduced as an intermediary component coupled to the rotor-side converter. The active filter contains controlled switching elements (IGBTs or MOSFETs) that generate compensating currents to cancel out the harmonics produced by the rotor-side converter during overmodulation operation, thereby reducing energy loss while maintaining the extended operating range

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful harmonic components are extracted and separated from the main power signal. The active filter selectively targets and removes lower-order harmonics that are difficult to filter, allowing the rotor-side converter to operate in overmodulation regime without the full burden of harmonic management

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If the rotor-side converter operates in overmodulation regime, then the voltage gain and operating range are improved, but the wear and thermal loading on components are increased

Engineering Contradiction:

Improveoperating rangeVSAvoidcomponent wear

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The active filter acts as a protective intermediary that reduces thermal loading on the rotor-side converter by eliminating harmonics. This decreases the thermal stress and wear on switching components, thereby improving reliability while allowing operation in the extended overmodulation regime

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The active filter provides beforehand protection by preemptively canceling harmonics before they can cause excessive thermal loading and wear on converter components. This cushioning effect allows the system to operate at the limits of its capability without suffering the full consequences of harmonic-induced stress

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Loss of energy

If an active filter is continuously activated to reduce harmonics, then harmonic reduction and energy loss prevention are improved, but the resource consumption and system complexity increase

Engineering Contradiction:

Improveenergy lossVSAvoidsystem complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

Instead of continuous operation, the active filter is activated periodically or conditionally based on the operational state of the rotor-side converter. The filter is engaged during overmodulation regimes when harmonics are generated and can be deactivated during normal operation, reducing unnecessary resource consumption while maintaining harmonic reduction effectiveness

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The active filter system is designed with dynamic control capabilities, allowing it to adapt its operation based on real-time system conditions. The filter can be selectively activated when harmonic levels exceed thresholds and deactivated when not needed, optimizing the balance between harmonic reduction and resource consumption

Inventive Principle:

Principle #15Dynamics

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 solution increases the voltage gain, reduces energy loss, and extends the operating range of the generator while minimizing wear and thermal loading, effectively filtering lower-order harmonics and maintaining grid voltage stability.

Implementation Method 1

reduce harmonics by providing an opposite phase signal at the same frequency

Methodology Applied

Scientific EffectPhase cancellation:

Data Source

PatentUS10778112B2DFIG converter with active filter

Publication Date: 2020.09.15 GE INFRASTRUCTURE TECH LLC

AI summary

An electrical power system connected to a power grid can include a generator having a stator and a rotor and a power converter. The stator is connected to the power grid via a stator power path. The power converter can include a line-side converter coupled to the power grid via a converter power path and a rotor-side converter coupled to a rotor bus of the rotor and the line-side converter via a DC link. The rotor-side converter is configured to convert a DC power on the DC link to an AC signal for the rotor bus. The power system can also include an active filter having one or more active controlled components. The active filter is coupled in parallel with the rotor-side converter to reduce harmonics of the electrical power system.