Offshore Wind Turbine Auxiliary Control for Grid Restart
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Solution Overview
Problem
Restarting offshore wind turbines after a power fault or HVDC link failure poses challenges due to the need for reliable backup power systems and efficient grid reconnection methods, especially when the HVDC link is unavailable or faulty.
Innovation Solution
Implementing an auxiliary control system in wind turbines that allows them to operate independently and supply power to the grid, combined with a backup generator in the substation, to form a weak grid and gradually increase power levels, enabling the turbines to reconnect to the HVDC link or AC grid during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a backup generator is used to supply power to the local power network when the HVDC link is unavailable, then the local power network can be restarted, but the backup generator must be large and complex to provide sufficient power
Solution Approach 1:
The patent combines the backup generator with the wind turbine park's existing power generation resources. When the HVDC link is unavailable, the local power network is restarted using a combination of the backup generator and power from available wind turbines, merging multiple power sources to reduce the burden on the backup generator alone.
Solution Approach 2:
The wind turbines serve multiple functions: they generate power for the HVDC link during normal operation and can also supply power to the local power network during restart operations when the HVDC link is unavailable. This multi-functionality reduces the requirement for a large dedicated backup generator.
2Productivity
If the backup generator operates alone to form a weak grid, then the grid can be restarted, but the power level is insufficient and the restart process is slow
Solution Approach 1:
The patent implements preliminary action by having wind turbines start generating power as soon as possible after the HVDC link becomes unavailable, before the full grid restart is complete. This preliminary power generation from wind turbines supplements the backup generator and accelerates the grid restart process.
Solution Approach 2:
The patent merges the power output from the backup generator with the power output from available wind turbines to create a combined power supply that is greater than either source alone, thereby increasing the power level and accelerating the grid restart process.
3Adaptability or versatility
If wind turbines are operated using an auxiliary control system when the HVDC link is unavailable, then they can supply power to the local grid, but the control system complexity increases
Solution Approach 1:
The patent implements a dynamic control approach where the control system adapts its behavior based on the availability of the HVDC link. When the HVDC link is available, the primary control system operates; when unavailable, the auxiliary control system takes over. This dynamic switching allows the system to maintain adaptability while managing control complexity through clear operational boundaries.
Solution Approach 2:
The auxiliary control system replicates the essential functions of the primary control system but is simplified for the specific purpose of operating when the HVDC link is unavailable. This copying approach allows the wind turbines to function independently while keeping the auxiliary control system less complex than a fully independent control system would be.
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 size and complexity of backup generators, enhances grid stability, and allows for efficient brown or black starts, minimizing downtime and operational costs by leveraging wind turbine power to supplement backup systems during faults.
Implementation Method 1
A wind turbine rotor 106 may be connected with the nacelle 104 through a low speed shaft extending out of the nacelle 104. The wind turbine rotor 106 comprises three rotor blades 108 mounted on a common hub 110
Implementation Method 2
The low speed shaft 202 may be connected to a gearbox 204 disposed in the nacelle 104
Implementation Method 3
The gearbox 204 may be of the planetary type, although other types of gearboxes may be used
Implementation Method 4
The high speed shaft 208 may be connected to a generator 206. The generator 206 may be directly coupled to the high speed shaft 208
Data Source
AI summary
Embodiments herein describe operating wind turbines in an offshore park to provide auxiliary power to a local AC grid or to an onshore grid during a grid malfunction. In one embodiment, the offshore park is coupled via a HVDC link to an onshore grid. When the HVDC link is down, a substation in the park includes a backup generator for creating a weak grid for powering auxiliary systems in a pilot turbine. The wind turbines in the park can switch to an auxiliary control system help power the auxiliary systems in the substation and in other turbines. In another embodiment, the offshore park is AC coupled to an onshore grid using a transformer in the substation. The wind turbines can participate in a brown or black start following a grid fault by switching to operating using the auxiliary control system.