Dynamic Brake DC Bus Voltage Threshold Control for Wind Turbine Grid Faults
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Solution Overview
Problem
Conventional dynamic brake systems in wind turbines are not adequately protected from excess energy during grid faults, leading to potential damage to power converters, and may be gated off prematurely due to temperature issues before sufficient energy is absorbed.
Innovation Solution
A controller-based method that dynamically adjusts the threshold DC bus voltage for the dynamic brake, monitors and adjusts in real-time, and includes a dynamic brake system with a resistor in series with a switch to absorb excess energy, while also blocking the power converter during grid faults to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional dynamic brake systems are used to absorb excess energy during grid faults, then energy absorption capability is improved, but the power converter remains vulnerable to damage from excess line side energy
Solution Approach 1:
The patent introduces a controller as an intermediary that dynamically adjusts the DC bus voltage threshold based on grid fault detection. This mediator coordinates the dynamic brake activation and power converter blocking, ensuring that the brake absorbs excess energy while the converter is protected from damage during grid faults
2Loss of energy
If the dynamic brake is gated on during grid faults to absorb excess energy, then energy dissipation is improved, but the brake may be gated off prematurely due to temperature conditions before sufficient energy is absorbed
Solution Approach 1:
The patent dynamically changes the DC bus voltage threshold parameter based on grid fault detection. By raising the threshold during grid faults, the system allows the dynamic brake to remain gated on longer, overriding normal temperature-based shutdown conditions to ensure complete energy absorption during critical fault periods
Solution Approach 2:
The controller preemptively blocks the power converter when grid faults are detected, preventing excess energy from reaching the converter before the dynamic brake can fully absorb the energy. This preliminary protective action occurs before the brake might otherwise be gated off due to temperature concerns
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 reduces the risk of power converter damage by efficiently managing energy absorption during grid faults and optimizing converter operation, enhancing efficiency and component utilization.
Implementation Method 1
Conventional dynamic brake systems include a resistor in series with a switch, such as an insulated-gate bipolar transistor (IGBT), and absorb excess energy in the converter when gated on during when a grid fault occurs.
Data Source
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AI summary
Methods for operating a wind turbine system are provided. In one embodiment, a method includes adjusting a threshold direct current (DC) bus voltage for a dynamic brake in a wind turbine power converter above a reference DC bus voltage based on at least one system condition. The method further includes gating the dynamic brake on when an experienced DC bus voltage is equal to or greater than the threshold DC bus voltage, and inputting a dynamic brake condition into a controller when the dynamic brake is gated on. The method further includes determining if a grid fault has occurred, reducing power generation of the wind turbine if no grid fault has occurred, and blocking the power converter if a grid fault has occurred. The method further includes gating the dynamic brake off when the experienced DC bus voltage is less than the threshold DC bus voltage.