Wind Turbine Torque Limiter for Grid Frequency Support
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Solution Overview
Problem
Existing methods for controlling wind energy installations during virtual inertia operations face challenges in reliable and efficient management of increased electrical power feed-in, particularly in maintaining stable speed and torque conditions, which can lead to unintended operating points and potential system instability.
Innovation Solution
A method that uses speed-dependent torque control with a limiter to manage generator torque, allowing for increased electrical power feed-in during boost modes while maintaining normal operation conditions, by setting upper and lower limits for the torque and adjusting these limits based on speed and frequency changes, enabling seamless transition between boost and recovery modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excessive power is fed into the electrical supply network during boost mode to support grid frequency, then grid stability is improved, but the wind turbine operates at unintended speed and torque points that are not suitable for continuous operation
Solution Approach 1:
The patent implements dynamic control by switching between two distinct operating modes: boost mode for temporary grid support and recovery mode for returning to optimal operating conditions. The control system dynamically adjusts generator torque and power feed-in based on real-time grid frequency conditions, allowing the wind turbine to adapt its operating characteristics rather than maintaining a fixed operating point
Solution Approach 2:
The control method employs periodic operation cycles consisting of boost phases followed by recovery phases. During boost mode, excessive power is fed into the grid for a limited time, then the system transitions to recovery mode to restore optimal speed and torque conditions. This periodic alternation allows the wind turbine to provide grid support while periodically returning to stable operating points suitable for continuous operation
2Power
If a two-point controller is used to generate increased power during virtual inertia operation, then power feed-in is improved, but control complexity increases
Solution Approach 1:
The patent merges the virtual inertia control function with the existing regular speed/torque control system. By integrating the boost mode control into the existing control architecture and using the same converter and converter controller, the system achieves enhanced power feed-in capability without requiring completely separate control systems or additional hardware components
Solution Approach 2:
The control system is designed with multi-functionality, where the same converter and converter controller handle both regular power generation and boost mode operation. The limiter component serves dual purposes by providing both normal operational limits and boost mode torque specifications, reducing the need for separate dedicated control elements
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 approach ensures reliable control of wind energy installations during virtual inertia operations, allowing for efficient power feed-in without disrupting normal operation, and facilitates faster response to frequency changes, thereby enhancing grid stability and reducing the risk of system instability.
Implementation Method 1
the rotational energy stored in the rotating mass of the wind turbine is briefly and briefly converted into electrical power via the generator
Implementation Method 2
the setpoint value determined for the generator torque is applied to a converter and its associated converter controller via a limiter with a definable upper and lower limit
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
Method for controlling a wind turbine having a converter-controlled generator, wherein in boost mode the electrical power fed into an electrical supply network is increased by means of a generator delay, comprising the following method steps: - Determining a setpoint for a generator torque (N*) depending on an actual value of a rotational speed (nmeas), - Applying the determined setpoint for the generator torque (N*) to the converter via a limiter with predefinable upper and lower limits (Nup, Nlow), - Responding to a boost signal (flagboost), determining the setpoint for the generator torque (N*boost) in boost mode, which leads to an increased electrical power input (Pfreeze + Pinc) compared to an actual value of the power fed in (Pfreeze).where the calculated setpoint for the generator torque (N*boost) in boost mode is applied to the limiter as both an upper and a lower limit.