Wind Farm Reactive Power Margin Control at Low Wind Speeds
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Solution Overview
Problem
Conventional wind turbine systems face challenges in efficiently operating at low wind speeds due to high reactive power requirements, which limit the minimum rotor speed and result in poor power coefficients, while existing technologies do not effectively manage reactive power margins during low wind conditions.
Innovation Solution
A method and system for a wind farm that monitors wind speed and determines a reactive power margin to set the lowest possible cut-in rotor speed for each turbine, ensuring sufficient reactive power production to meet grid code requirements, allowing turbines to operate efficiently at lower rotor speeds and adjust dynamically based on active power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the minimum rotor speed is increased to meet reactive power requirements, then reactive power capability is improved, but power coefficient deteriorates
Solution Approach 1:
The patent applies dynamics by making the cut-in rotor speed variable rather than fixed. The controller dynamically adjusts the minimum rotor speed based on real-time assessment of reactive power margin, allowing the system to operate at lower speeds when reactive power demand is low and increase speeds when demand is high, thus resolving the contradiction between reactive power capability and power coefficient
Solution Approach 2:
The patent changes the parameter of rotor speed from a fixed minimum value to a variable parameter that adjusts based on reactive power conditions. By calculating the reactive power margin and adjusting the cut-in speed accordingly, the system optimizes the balance between meeting reactive power requirements and maintaining high power coefficients at low wind speeds
2Reliability
If the rotor voltage is increased to maintain grid synchronization at low speeds, then grid compliance is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the reactive power margin and using this information to adjust the cut-in rotor speed. The controller assesses the difference between available and required reactive power, then feeds this information back to determine the appropriate minimum speed, simplifying control compared to continuously adjusting rotor voltage
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 enables wind turbines to cut in at lower rotor speeds, improving power coefficients at low wind speeds and ensuring sufficient reactive power margin, thereby enhancing efficiency and compliance with grid reactive power demands.
Implementation Method 1
wind impacts the rotor blades and the blades transform wind energy into a mechanical rotational torque
Implementation Method 2
The low-speed shaft drives a gearbox that subsequently steps up the low rotational speed of the low-speed shaft to drive a high-speed shaft at an increased rotational speed
Implementation Method 3
the high-speed shaft rotatably drives a generator rotor
Data Source
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AI summary
A method for operating a wind farm connected to a power grid that demands a reactive power requirement that varies with active power includes monitoring a wind speed at each of the plurality of wind turbines in the wind farm. When the wind speed is within a cut-in wind speed range, the method includes determining a reactive power margin of the wind farm based on the reactive power requirement at an active power output corresponding to the wind speed and a reactive power availability of each of the plurality of wind turbines at the wind speed. The method also includes determining a lowest possible cut-in rotor speed for each of the plurality of wind turbines that satisfies the reactive power margin. Further, the method includes commanding each of the plurality of wind turbines to cut-in and begin to produce power at the lowest possible cut-in rotor speed that satisfies the reactive power margin.