Power Plant Frequency Control to Avoid Resonant Unit Oscillation

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Solution Overview

Problem

Existing power plant control methods do not adequately protect power production units from uncontrolled oscillations and vibrations caused by grid frequency oscillations that coincide with natural frequency modes, potentially leading to damage.

Innovation Solution

A method and controller that determine grid frequency variations and provide active power set-points to power producing units, ensuring that the active power response includes frequency components different from undesired modes by a defined margin, thereby decoupling grid frequency oscillation modes from power production unit responses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If grid frequency dependent response is provided to counteract grid frequency variations, then grid frequency stability is improved, but power production units may experience uncontrolled oscillations and vibrations when grid frequency modes coincide with natural frequency modes

Engineering Contradiction:

Improvegrid frequency stabilityVSAvoiduncontrolled oscillations and vibrations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system acts as an intermediary between grid frequency variations and power production unit responses. It processes grid frequency signals and generates modified control signals that prevent resonance by filtering out frequency components that would excite natural modes, thus protecting the power production units while maintaining grid frequency stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system continuously monitors grid frequency variations and uses this feedback to adjust the active power set-point in real-time. By detecting when grid frequency modes approach natural frequency modes, the control system can modify the response to prevent harmful oscillations, creating a closed-loop control that adapts to changing grid conditions.

Inventive Principle:

Principle #23Feedback

2Productivity

If deadband is reduced to improve frequency response sensitivity, then grid frequency response capability is improved, but risk of excitation near natural frequency modes increases

Engineering Contradiction:

Improvefrequency response capabilityVSAvoidoperational safety

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The control system dynamically adjusts the frequency response characteristics based on real-time grid frequency conditions. Rather than using a fixed deadband, the system continuously adapts its response threshold and gain, allowing it to operate with high sensitivity when safe and reduce sensitivity when approaching hazardous frequency regions, thus resolving the contradiction between response capability and safety.

Inventive Principle:

Principle #15Dynamics

3Reliability

If active power regulation is performed continuously to maintain grid frequency, then grid frequency control is improved, but power production units may be damaged by resonance with natural frequency modes

Engineering Contradiction:

Improvegrid frequency controlVSAvoidpower production unit integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The system converts potentially harmful frequency components into beneficial ones by actively filtering out frequencies that would cause resonance. The control algorithm identifies harmful frequency components in the grid frequency variations and deliberately modifies the active power response to eliminate these components, transforming what would be damaging resonance into safe, controlled frequency regulation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11799290B2Method for controlling a power plant

Publication Date: 2023.10.24 VESTAS WIND SYSTEMS AS

AI summary

The present invention relates to a method for operating a power plant comprising a plurality of power producing units, the power plant being operatively connected to an associated power grid having a nominal grid frequency, the method comprising the steps of determining grid frequency variations of the associated power grid, and providing, in response to the determined grid frequency variations, an active power set-point to each of the plurality of power producing units, said active power set-point causing each of the plurality of power producing units to produce active power in response to said active power set-point, said produced active power comprising, in a frequency domain, one or more active power frequency components being different from one or more undesired frequency modes. The present invention also relates to a power plant controller for performing the method.