HVDC Backfeed Control for Offshore Wind Farm Auxiliary Power
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Solution Overview
Problem
Offshore wind farms face high costs due to the need for expensive bi-directional power converters and additional AC transmission links to provide auxiliary power during downtime, especially in remote locations where laying an additional AC subsea cable is economically and technically challenging.
Innovation Solution
A power supply arrangement that utilizes a backfeed control system to apply a backfeed voltage on the HVDC link during downtime, allowing an onshore converter to supply auxiliary power via the HVDC link, using a bidirectional power converter to convert DC power to AC for the wind farm, and an auxiliary power supply connected to the wind farm by a high-voltage busbar with a transformer and bi-directional converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bi-directional power converter is used to provide auxiliary power during downtime, then auxiliary power can be supplied back to the wind farm, but the cost of the power converter increases considerably
Solution Approach 1:
The patent inverts the traditional power flow direction by enabling the onshore converter to feed power back to the offshore wind farm through the HVDC link during downtime, rather than only transmitting power from offshore to onshore. This reverse power flow allows auxiliary power supply without requiring expensive bi-directional converters at the offshore location.
Solution Approach 2:
The HVDC transmission link serves as an intermediary medium that enables bidirectional power flow. By utilizing the existing HVDC link as a mediator, the system can transfer auxiliary power from the onshore converter to the offshore wind farm without requiring additional dedicated power conversion equipment at the offshore site.
2Reliability
If an additional AC transmission link is laid parallel to the HVDC link, then auxiliary power can be provided to the wind farm, but the overall cost of the wind farm increases considerably
Solution Approach 1:
The existing HVDC transmission link is made multi-functional by enabling it to serve both its primary function of transmitting generated power from the wind farm to the grid, and a secondary function of delivering auxiliary power back to the wind farm during downtime. This eliminates the need for a separate dedicated AC transmission link.
Solution Approach 2:
The patent merges the auxiliary power supply function with the existing HVDC transmission infrastructure. Instead of creating a separate AC transmission path, the system combines multiple functions (power transmission and auxiliary power supply) into the single existing HVDC link, reducing overall system complexity and cost.
3Reliability
If an additional AC subsea cable is laid for remote offshore wind farms, then auxiliary power can be supplied, but the economic and technical challenges increase severely
Solution Approach 1:
The system uses its own existing infrastructure (the HVDC transmission link) to provide auxiliary power, rather than relying on external additional cabling. The wind farm's existing connection to the grid is turned into a self-sufficient solution for auxiliary power supply, eliminating the need for separate cable laying operations.
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 solution provides a cost-effective and efficient method to ensure backup power for wind turbines during downtime, allowing for quick restart and return to rated power output, independent of battery charge levels, and can be integrated with existing onshore facilities.
Implementation Method 1
a power converter for converting the backfeed voltage to auxiliary power for the wind farm
Data Source
AI summary
A power supply arrangement adapted to provide auxiliary power to a wind farm that feeds into a HVDC transmission link is provided. The power supply arrangement has an auxiliary power supply to deliver auxiliary power (Paux) to the wind farm; a backfeed control for initiating provision of a backfeed voltage on the HVDC link during a wind farm downtime; a backfeed switch to close a DC current path between the HVDC link and the auxiliary power supply; and a power converter for converting the backfeed voltage into auxiliary power (Paux). A wind farm arranged to feed into a HVDC transmission link is also provided, having such a power supply arrangement for providing auxiliary power (Paux) to the wind farm during a wind farm downtime. A method of providing auxiliary power (Pbackfeed) to a wind farm during a wind farm downtime is also provided.