Wind Turbine DC-Link Voltage Decay via Energy Dissipating Unit
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Solution Overview
Problem
Wind turbines take an excessively long time for the DC-link voltage to decay naturally during shutdown, posing safety risks for technicians and potentially causing damage due to residual voltages and inrush currents when reconnecting parallel DC-links.
Innovation Solution
Incorporating an energy dissipating unit, such as a DC chopper circuit, coupled to the DC-link, which is activated by a controller to rapidly dissipate energy and reduce the DC-link voltage to near zero upon shutdown request, thereby reducing waiting time for safe maintenance and preventing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DC-link voltage is allowed to decay naturally with default high resistance, then the system maintains safety and stability, but the time required for voltage decay increases significantly
Solution Approach 1:
The patent applies dynamics by making the DC-link resistance variable rather than fixed. The system automatically adjusts the resistance value based on operational requirements: using high resistance during normal operation for stability, and switching to low resistance during shutdown for rapid voltage decay. This dynamic adjustment resolves the contradiction between safety (requiring complete voltage decay) and time (requiring quick shutdown).
Solution Approach 2:
The patent changes the resistance parameter of the DC-link from a constant high value to a variable value that can switch between high and low states. This parameter change enables the system to achieve both objectives: maintaining stability during operation with high resistance and achieving rapid voltage decay during shutdown with low resistance, thus resolving the time-safety contradiction.
2Loss of time
If the resistance across the DC-link is reduced to accelerate voltage decay, then the shutdown time is reduced, but inrush currents may cause damage during reconnection
Solution Approach 1:
The patent applies preliminary action by reducing the DC-link resistance before shutdown occurs and maintaining this low resistance state throughout the shutdown process. This preliminary adjustment ensures that when shutdown is initiated, the voltage can decay rapidly without risking inrush currents during reconnection, as the low resistance state has been established in advance.
Solution Approach 2:
The patent provides beforehand cushioning by pre-adjusting the DC-link resistance to a low value before shutdown. This preparatory measure cushions against the potential harmful effect of inrush currents during reconnection, ensuring that the system is already in a safe state for rapid voltage decay without risking damage upon reconnection.
3Loss of time
If an active voltage reduction system is implemented, then the shutdown time is significantly reduced, but the device complexity increases
Solution Approach 1:
The patent applies self-service by implementing a control system that automatically adjusts the DC-link resistance based on shutdown signals without requiring complex external intervention. The system serves itself by detecting the shutdown condition and autonomously switching the resistance state, thereby achieving rapid voltage decay while minimizing the complexity of the control architecture.
Solution Approach 2:
The patent applies universality by designing the control system to handle multiple functions: normal operation monitoring, shutdown detection, resistance adjustment, and reconnection management. This multi-functional approach consolidates control tasks into a single integrated system, reducing overall complexity while achieving rapid shutdown capability.
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 significantly reduces the time required for the DC-link voltage to reach a safe level for technicians to work on the wind turbine, ensuring faster and safer maintenance while preventing damage from residual voltages and inrush currents.
Implementation Method 1
an energy dissipating unit, such as a DC chopper circuit, coupled to the DC-link, which is activated by a controller to rapidly dissipate energy
Data Source
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AI summary
A wind turbine is provided. The wind turbine comprises a generator, a power converter for converting at least a portion of electrical power generated by the generator, an energy dissipating unit and a controller. The power converter comprises a generator-side converter, a grid-side converter and a DC (direct current) link there between. The energy dissipating unit is operatively coupled to the DC-link. The controller is adapted to activate the energy dissipating unit to dissipate energy from the DC-link in response to a shutdown request.