Wind Turbine Converter Control for Grid Fault Power Curtailment
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Solution Overview
Problem
Existing wind turbines struggle to effectively manage active power output reductions in response to grid abnormalities such as high frequency or voltage sags, often leading to operational issues like overspeed and high loads, which conventional control methods fail to address adequately.
Innovation Solution
Implementing separate power set-points for the line-side and machine-side converters, allowing for independent control of power output, and utilizing resistive elements in the DC-link to dissipate surplus power, thereby managing grid abnormalities and maintaining stable turbine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single power set-point is used for both line-side and machine-side converters, then the control system is simple, but the wind turbine cannot rapidly reduce active power output to comply with grid code requirements during abnormal grid conditions
Solution Approach 1:
The power set-point control is segmented into two independent components: a first power set-point for the line-side converter and a second power set-point for the machine-side converter. This allows independent optimization of each converter's response to grid conditions, enabling rapid active power reduction while maintaining system reliability.
Solution Approach 2:
The control system dynamically adjusts the two power set-points based on grid conditions. During abnormal conditions, the first power set-point can be reduced more rapidly than the second, creating a time-varying control strategy that adapts to changing grid requirements while preventing operational issues.
2Reliability
If the active power output is rapidly reduced to comply with grid requirements, then grid compliance is achieved, but operational problems such as overspeed and excessive loads may occur
Solution Approach 1:
The control system performs preliminary action by setting the first power set-point for the line-side converter to achieve the required active power reduction in advance, while the second power set-point for the machine-side converter is adjusted more gradually. This preliminary adjustment of the line-side converter enables grid compliance before the machine-side converter is modified, preventing harmful overspeed and load conditions.
Solution Approach 2:
The system employs dynamic control where the first power set-point can change more rapidly than the second power set-point. This creates a controlled transition period where the line-side converter handles the rapid power reduction requirement, while the machine-side converter maintains more stable operation, thereby avoiding mechanical stress and overspeed conditions.
3Reliability
If the power set-point for the line-side converter is reduced to meet grid requirements, then active power output is reduced, but surplus power must be managed to avoid energy waste
Solution Approach 1:
The DC-link serves as an intermediary energy storage element between the line-side and machine-side converters. When the first power set-point is reduced to meet grid requirements, the surplus power is temporarily stored in the DC-link. This intermediary allows the system to decouple the rapid power reduction requirement from the mechanical system, avoiding immediate energy waste while maintaining grid compliance.
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
Enables wind turbines to comply with grid code requirements by reducing active power output rapidly and safely, preventing overspeed and high loads, while ensuring reliable grid connection during disturbances.
Implementation Method 1
dissipating a power surplus in one or more resistive elements
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Methods of operating a wind turbine (1) having a generator (10) and a power converter (60). The methods may comprise: determining a reduced first power setpoint (94) in response to an operational condition; reducing active power from a line-side converter (66) to an electrical grid (80) according to the reduced first power setpoint (94); determining a reduced power setpoint (92) for a machine-side converter (62); reducing a torque applied to the generator (10) by the machine-side converter (62) such that active power according to the reduced second power setpoint (92)is produced by the generator (10); and dissipating a power surplus in one or more resistive elements (68) as long as the second power setpoint is superior to the first power setpoint. Wind turbines configured for such methods are also provided.