Wind Turbine Control System for HVDC Link Activation

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Solution Overview

Problem

The high cost and inefficiency of coupling offshore wind turbines to a high-voltage direct current (HVDC) link due to expensive circuitry requirements, particularly in activating diode rectifiers for power transmission.

Innovation Solution

Implementing a control system with a reactive power control leg and an active power control leg, coupled with a proportional-integral (PI) controller, that operates in two modes: island mode for local AC grid power generation and high-power mode for HVDC link transmission, using an uncontrolled diode rectifier to switch between modes and activate the diode rectifier by increasing output power until the diode cut-in voltage is exceeded.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If self-commutated converters are used to couple wind turbines to HVDC link, then power transmission efficiency is improved, but system cost and complexity increase significantly

Engineering Contradiction:

Improvepower transmission efficiencyVSAvoidcircuitry complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent replaces expensive self-commutated converters with inexpensive diode rectifiers that perform the same power transmission function. The diode rectifier is a simple, passive component that converts AC to DC without requiring complex control circuitry or expensive active switches, thereby dramatically reducing system cost while maintaining adequate transmission efficiency.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent extracts and removes the complex control system (reactive power control leg and active power control leg) from the power transmission path. By using a simple diode rectifier instead, the complex control circuitry is eliminated, leaving only the essential power conversion function performed by the passive diode components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Device complexity

If diode rectifier is used to couple wind turbine to HVDC link, then system cost is reduced, but activation reliability is improved only when output power exceeds diode cut-in voltage

Engineering Contradiction:

Improvecircuitry costVSAvoidactivation reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The control system performs preliminary action by actively managing the wind turbine's output power to ensure it exceeds the diode rectifier's cut-in voltage threshold. The reactive power control leg and active power control leg work together to preemptively adjust operating parameters, ensuring reliable activation of the diode rectifier before power transmission begins.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system implements feedback mechanisms through the reactive power control leg and active power control leg that monitor system conditions and adjust turbine output accordingly. This feedback ensures the output power remains sufficient to activate and maintain operation of the diode rectifier, thereby ensuring reliable power transmission activation.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If controller with integral action is activated to switch between modes, then adaptability is improved, but control system complexity increases

Engineering Contradiction:

Improvemode switching capabilityVSAvoidcontrol system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The controller with integral action serves multiple functions: it manages both reactive power control and active power control, and handles mode switching between different operating conditions. This multi-functional controller consolidates what could be separate control systems into a single integrated unit, achieving adaptability while limiting the increase in overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces the need for expensive circuitry and enhances the reliability of wind turbine operations by allowing efficient power transmission to the HVDC link while maintaining local AC grid functionality, without requiring high-speed data communication between turbines or phase locked loops.

Implementation Method 1

the wind turbine is coupled to the HVDC link using a diode rectifier

Methodology Applied

Scientific EffectDiode rectification: Diode

Implementation Method 2

activating a controller with an integral action coupled between the reactive power control leg and the active power control leg

Methodology Applied

Scientific EffectIntegral control action:

Data Source

PatentUS11028831B2Controlling power exchange from self-commutated converters

Publication Date: 2021.06.08 VESTAS WIND SYSTEMS AS

AI summary

Embodiments herein describe operating a control system for a wind turbine in a first mode and second mode of operation. When in the first mode, the wind turbine provides power to a local AC grid. However, when in the second mode, the wind turbine provides power to a high-voltage direct current (HVDC) link. The control system includes a reactive power control leg and an active power control leg. To switch from the first mode to the second mode, the control system activates a PI controller coupled between the reactive and active power control legs which increases the output voltage of the wind turbine until the magnitude of the voltage activates a diode rectifier and permits the power outputted by the wind turbine to be transmitted along the HVDC link.