Wind Turbine Wake Control With Phase-Shifted Rotor and Pitch

Solution Overview

Problem

Existing wind turbine wake recovery strategies increase turbine loading and actuator duty cycle, failing to effectively reduce near-wake length without significant negative consequences.

Innovation Solution

Implementing harmonic rotor speed control and collective pitch control with a 90-135 degree phase shift to excite fluid dynamic instabilities and accelerate wake breakdown and recovery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If dynamic wake control strategies are implemented to reduce near-wake length, then wake recovery is improved, but turbine loading and actuator duty cycle increase significantly

Engineering Contradiction:

Improvewake recoveryVSAvoidturbine component life

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies periodic action by implementing oscillatory control of rotor speed and collective pitch at specific frequencies (0.05-0.5 Hz) to excite fluid dynamic instabilities in the wake. This periodic modulation creates constructive interference that accelerates wake breakdown and recovery, achieving the desired wake recovery improvement while maintaining acceptable turbine loading through controlled oscillatory behavior rather than continuous high-amplitude actuation

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent employs parameter changes by dynamically adjusting rotor speed and collective pitch parameters within optimized ranges ( rotor speed: 0.95-1.05 nominal speed, collective pitch: 0-5 degrees). These parameter variations are modulated at specific frequencies and phases to trigger wake instabilities, enabling wake recovery enhancement while constraining the changes within safe operational limits to protect turbine components

Inventive Principle:

Principle #35Parameter changes

2Productivity

If dynamic wake control strategies are implemented to reduce near-wake length, then wake recovery is improved, but actuator duty cycle increases significantly

Engineering Contradiction:

Improvewake recoveryVSAvoidactuator duty cycle

Core Design Contradiction:

ProductivityVSDuration of action of moving object

Solution Approach 1:

The patent applies periodic action by implementing oscillatory control of rotor speed and collective pitch at specific frequencies (0.05-0.5 Hz) to excite fluid dynamic instabilities in the wake. This periodic modulation creates constructive interference that accelerates wake breakdown and recovery, achieving the desired wake recovery improvement while maintaining acceptable turbine loading through controlled oscillatory behavior rather than continuous high-amplitude actuation

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements continuity of useful action by maintaining sustained low-amplitude oscillatory control over extended periods. This continuous but gentle modulation keeps actuators engaged at low duty cycles, providing cumulative wake recovery benefits without the intermittent high-stress cycles that would accelerate actuator wear and increase maintenance requirements

Inventive Principle:

Principle #20Continuity of useful action

3Length of stationary object

If rotor speed and collective pitch are controlled to excite fluid dynamic instabilities, then near-wake length is reduced, but turbine loading increases

Engineering Contradiction:

Improvenear-wake lengthVSAvoidturbine loading

Core Design Contradiction:

Length of stationary objectVSForce

Solution Approach 1:

The patent employs parameter changes by dynamically adjusting rotor speed and collective pitch parameters within optimized ranges ( rotor speed: 0.95-1.05 nominal speed, collective pitch: 0-5 degrees). These parameter variations are modulated at specific frequencies and phases to trigger wake instabilities, enabling wake recovery enhancement while constraining the changes within safe operational limits to protect turbine components

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies partial action by implementing sub-maximal control amplitudes that are sufficient to trigger wake instabilities but insufficient to cause excessive turbine loading. The control oscillations are deliberately kept within moderate ranges ( rotor speed ±2%, collective pitch 0-5 degrees) to achieve the critical threshold for wake breakdown without over-actuating the system, thus reducing near-wake length while avoiding harmful increases in turbine mechanical stresses

Inventive Principle:

Principle #16Partial or excessive 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

Reduces near-wake length by up to 30-31% while minimizing adverse effects on turbine components and actuator duty cycle.

Implementation Method 1

oscillating rotor speed and collective pitch control at a frequency defined by a time period between two set points and an amplitude to excite inherent fluid dynamic instabilities in the wake and decrease wake length

Methodology Applied

Scientific EffectFluid dynamic instability: Turbulence

Data Source

PatentUS12535055B1Systems and methods for optimal phase shift between dynamic control actions for wind turbines

Publication Date: 2026.01.27 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

Dynamic wake control (or dynamic induction control) is used to promote wake breakdown and recovery behind a wind turbine that improve wind farm performance/efficiency. Constructive interference is created by simultaneously performing harmonic rotor speed control and harmonic collective pitch control so that the phase of the rotor speed perturbations leads the phase of the collective pitch perturbations by 90-135 degrees.