Wind Plant Inertial Response Control Without Secondary Frequency Dip
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Solution Overview
Problem
Wind power plants with variable-speed turbines face limitations in inertial response, leading to a secondary grid frequency dip during recovery from under-frequency events, as the rotational speed decreases and kinetic energy is depleted, resulting in a prolonged return to nominal frequency.
Innovation Solution
A control arrangement that includes monitoring and computation modules to determine power stored in rotating masses and storage devices, predicting power curve progression, and a response management module to optimize the release of stored power, ensuring the combined output power remains above a pre-defined threshold during and after inertial response, thereby avoiding a secondary frequency dip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the wind turbine releases kinetic energy stored in its rotating mass to provide inertial response, then additional power can be injected into the grid to assist frequency recovery, but the rotational speed of the aerodynamic rotor decreases to its minimum allowable speed and takes time to recover towards the operating point
Solution Approach 1:
The control arrangement predicts the power curve progression during the injection phase and subsequent recovery phase before the actual event occurs. By anticipating the recovery time requirement and planning the power injection duration accordingly, the system prepares in advance to ensure sufficient time for rotor speed recovery while maximizing power injection to the grid during the under-frequency event.
Solution Approach 2:
The system dynamically adjusts the power injection strategy based on real-time rotor speed measurements and predicted power curve progression. The control arrangement continuously monitors the aerodynamic rotor speed and modifies the power injection profile to maintain optimal balance between power delivery and rotor speed recovery, enabling adaptive response to changing wind conditions and grid frequency requirements.
2Adaptability or versatility
If the wind turbine operates at variable speed to maximize wind energy conversion, then it can respond to grid under-frequency events, but the inertial response is limited and grid frequency may exhibit a further subsequent dip during the recovery period
Solution Approach 1:
The control arrangement implements a feedback mechanism that continuously monitors grid frequency, rotor speed, and power output. Based on this feedback, the system adjusts the power injection profile during under-frequency events and modifies the recovery strategy to prevent secondary frequency dips. The feedback loop ensures that the wind turbine responds adaptively to grid conditions while maintaining reliable frequency support throughout the entire event duration.
Solution Approach 2:
The control arrangement acts as an intermediary between the aerodynamic rotor and the grid, mediating the power transfer during under-frequency events. It manages the conversion of mechanical energy from the rotating mass into electrical power injection while coordinating the recovery process to maintain grid frequency stability. The control system serves as a buffer that smooths the transition during power injection and recovery, preventing direct negative impacts on grid frequency.
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
The control method maintains positive active power provision throughout the grid frequency event, ensuring the grid frequency returns to nominal levels without a secondary dip, by carefully timing the release of stored power from storage devices, thus minimizing the recovery period's negative impact on grid stability.
Implementation Method 1
a wind power plant must be controlled in such a way as to comply with various grid requirements, one of which is the ability to respond to grid under-frequency events in order to contribute to grid frequency stability. In case of a drop in grid frequency, a variable-speed wind turbine can release kinetic energy stored in its rotating mass.
Data Source
AI summary
A control arrangement of a wind power plant includes a number of wind turbines and a number of storage arrangements, which control arrangement includes a first monitoring module configured to determine a first power quantity stored in the rotating mass of a wind turbine; a computation module configured to predict a power curve progression during injection of the first power quantity into the grid and during a subsequent theoretical recovery phase; a second monitoring module configured to determine a second power quantity available in a storage arrangement; and a response management module configured to identify a time instant at which to commence release of the second power quantity in order to maintain the combined output power of the wind power plant at a pre-defined threshold during inertial response following a grid under-frequency event.