Wind Turbine Pitch Control Backup Battery DC Link

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Solution Overview

Problem

Existing wind turbine pitch control systems, particularly those using DC link capacitors and H bridge power converter circuits, are unable to maintain blade pitch control once the energy stored in DC link capacitors is depleted during AC input power loss or dip, leading to turbine shutdown and overspeed issues.

Innovation Solution

A backup battery system is integrated to supply energy to the DC link capacitor, allowing the pitch control system to operate during AC power loss or dip, and maintaining charge on the capacitor using the battery as the voltage drops, ensuring continuous blade pitch control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If DC link capacitors are used to store energy for pitch control during AC power loss, then the pitch control system can operate for a limited time during power disturbances, but the energy storage capacity is insufficient to maintain operation through extended outages

Engineering Contradiction:

Improveoperation duration during power lossVSAvoidenergy storage capacity

Core Design Contradiction:

Duration of action of moving objectVSQuantity of substance

Solution Approach 1:

The patent combines DC link capacitors with backup batteries to create a hybrid energy storage system. The capacitors provide immediate power during brief disturbances while the batteries provide sustained power during extended outages, merging two different energy storage technologies to overcome the limitations of each individual system.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The backup battery system serves multiple functions: it charges from the DC link during normal operation, provides power during AC power loss, and can be recharged during power dips. This multi-functional approach allows the same battery system to handle various power disturbance scenarios without requiring separate systems for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If backup batteries are integrated into the DC link to extend operation during power loss, then the wind turbine can maintain pitch control through extended outages, but the system complexity increases

Engineering Contradiction:

Improveavailability during grid disturbancesVSAvoidsystem structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The backup batteries automatically charge from the DC link during normal operation without requiring external intervention. During AC power loss, the batteries automatically discharge to maintain pitch control, and the system self-manages the transition between power sources without complex control systems.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The DC link serves as an intermediary energy transfer medium between the AC power source, the backup batteries, and the pitch control system. It facilitates bidirectional energy flow, allowing the batteries to charge during normal operation and discharge during power loss, simplifying the overall system architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Duration of action of stationary object

If the backup battery supplies energy to the DC link during power loss, then continuous pitch control is maintained, but the battery charge depletes over time requiring recharge capability

Engineering Contradiction:

Improvecontinuous operation timeVSAvoidbattery charge consumption

Core Design Contradiction:

Duration of action of stationary objectVSUse of energy by moving object

Solution Approach 1:

The system maintains continuous useful action by enabling the backup batteries to recharge from the DC link during AC power dips and normal operation. This ensures that the batteries remain charged and ready to provide power during extended outages, eliminating the need for manual intervention and ensuring continuous pitch control capability.

Inventive Principle:

Principle #20Continuity of useful 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 solution enhances wind turbine availability by enabling operation through grid disturbances and power outages, preventing turbine overspeed and maintaining control of blade pitch.

Implementation Method 1

The AC voltage drop is sensed by the pitch control system and the emergency pitch system is activated... known wind turbine systems use DC link capacitors and an H bridge power converter circuit

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

maintaining charge on the DC link capacitor using the charged backup battery as voltage across the DC link capacitor drops during the operation of the pitch control system

Methodology Applied

Scientific EffectBattery (electricity): Battery (electricity)

Data Source

PatentUS7740448B2Pitch control battery backup methods and system

Publication Date: 2010.06.22 GE INFRASTRUCTURE TECH LLC

AI summary

A method for controlling a pitch control system of a wind turbine includes providing a charged backup battery configured to supply no energy to a DC link when full AC input power is available, wherein the DC link includes a DC link capacitor. The method further includes using energy stored in the DC link capacitor to operate a pitch control system during a loss or dip of AC input power, and maintaining charge on the DC link capacitor using the charged backup battery as voltage across the DC link capacitor drops during the operation of the pitch control system.