DC Link Power Dissipating Unit for Wind Turbine Stability
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Solution Overview
Problem
Variable speed wind turbines face power imbalances due to sudden wind gusts and grid faults, leading to undesired tower oscillations and drive train damage, as existing methods like crowbar circuits are not effective in managing excess power during these events.
Innovation Solution
A controller-activated power dissipating unit is coupled to the DC link of the wind turbine's power converter, determining power differences and setting a duty ratio to activate the unit when thresholds are exceeded, ensuring efficient dissipation of excess power through a chopper circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crowbar circuit or dump load circuit is used to dissipate excess power during power imbalance events, then the immediate problem of excessive power is addressed, but the resistor bank is excessively stressed and the method is not effective in extreme conditions when wind gust and grid fault happen simultaneously
Solution Approach 1:
The power dissipating unit is divided into multiple resistor elements that can be independently controlled. The controller selectively activates only the necessary number of resistor elements based on the magnitude of power imbalance, rather than always activating all resistors. This segmentation allows the system to handle power imbalance events effectively while reducing stress on individual resistor elements.
Solution Approach 2:
Instead of always using the full capacity of the resistor bank, the controller applies partial action by activating only the required portion of the power dissipating unit. The controller calculates the exact power dissipation needed and activates corresponding resistor elements, avoiding unnecessary stress on the resistor bank while still effectively managing power imbalance.
2Loss of energy
If the power dissipating unit is activated during power imbalance events, then excess power is dissipated effectively, but the resistor bank experiences excessive stress
Solution Approach 1:
The power dissipating unit consists of multiple independently controllable resistor elements. The controller activates only the specific number of resistors needed to dissipate the calculated excess power, rather than activating the entire resistor bank. This selective activation achieves effective energy dissipation while minimizing stress on individual resistor elements.
Solution Approach 2:
The controller dynamically adjusts the resistance value of the power dissipating unit by selectively activating different combinations of resistor elements. This parameter change allows the system to match the dissipation capacity exactly to the excess power level, optimizing energy dissipation efficiency while preventing excessive stress on the resistor bank.
3Power
If pitch control is used to reduce rotor speed in response to wind gust, then power generation is reduced, but the pitch controller dynamics are not fast enough to respond to sudden wind gust
Solution Approach 1:
The controller continuously monitors power balance conditions and prepares to activate the power dissipating unit immediately when power imbalance is detected. This preliminary preparation allows the system to respond faster than pitch control, as the power dissipating unit can be activated electrically without mechanical delays, directly reducing excess power before it causes tower oscillations.
Solution Approach 2:
The power dissipating unit acts as an intermediary mechanism between the generator and the grid. Instead of relying solely on pitch control to reduce power generation, the power dissipating unit provides an additional pathway to manage excess power by dissipating it as heat, thereby complementing and enhancing the effectiveness of pitch control.
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 solution effectively manages power imbalances by quickly activating the power dissipating unit, reducing tower oscillations and preventing damage by dissipating only the necessary excess power, thus maintaining system stability during wind gusts and grid faults.
Implementation Method 1
a power dissipating unit operatively coupled to the DC link... dissipating only the necessary excess power
Data Source
AI summary
A variable speed wind turbine (1) is provided. The wind turbine comprises a generator (101), a power converter (102)for converting at least a portion of electrical power generated by the generator wherein the power converter (102) comprises a generator side converter (110), a grid side converter (111) and a DC link (112) therebetween, a power dissipating unit (105) operatively coupled to the DC link (112) and a controller (121). The controller is adapted to determine power extracted from the wind, power supplied by the wind turbine and power loss in the power dissipating unit, determine the difference between the power extracted from the wind and the sum of the power supplied by the wind turbine and the power loss in the power dissipating unit and activate the power dissipating unit when the difference between the power exceeds a predefined power difference threshold.