Subsea AC Power Transmission Frequency Adjustment
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Solution Overview
Problem
Conventional AC power transmission is limited to distances of 100-200 km, requiring complex and unreliable DC to AC conversion systems for subsea power transmission, which increases equipment size and cost, and poses reliability challenges in subsea power grids.
Innovation Solution
A method that adjusts the frequency of AC power transmitted through a cable based on its length to avoid resonance peaks, using an AC-DC-AC converter with power transistors and pulse width modulation, stabilizing voltage and reducing equipment size and complexity by maintaining voltage ratios within acceptable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If DC transmission is used to extend transmission distance beyond 200 km, then transmission distance is improved, but equipment complexity and size increase due to required DC to AC conversion systems
Solution Approach 1:
The patent changes the frequency parameter of AC power transmission to extend transmission distance. By operating at higher frequencies (e.g., 100-300 Hz instead of 50/60 Hz), the cable's capacitive reactance decreases, allowing power to be transmitted over distances exceeding 200 km without requiring DC conversion equipment.
Solution Approach 2:
Instead of converting DC to AC at the subsea end (conventional approach), the patent inverts the approach by transmitting AC power directly from the shore end and adjusting its frequency to match the cable's resonant characteristics, thereby avoiding the need for subsea DC to AC conversion equipment entirely.
2Adaptability or versatility
If DC to AC conversion systems are installed at subsea exploration sites, then AC power can be provided to consumers, but reliability decreases due to complex systems with extreme high amount of components
Solution Approach 1:
The patent extracts and removes the DC to AC conversion equipment from the subsea exploration site. By transmitting AC power directly from shore and adjusting its frequency, the system eliminates the unreliable conversion equipment that would otherwise be required at the subsea end to power AC consumers.
Solution Approach 2:
The AC-DC-AC converter at the shore end performs multiple functions: it converts grid AC to a variable frequency AC suitable for long-distance cable transmission, and also provides frequency regulation to match the cable's resonant frequency, thereby serving both conversion and optimization purposes in one device.
3Device complexity
If conventional AC power transmission is used, then equipment size is reduced, but transmission distance is limited to 100-200 km due to cable properties
Solution Approach 1:
The patent changes the frequency parameter of AC power transmission to extend transmission distance. By operating at higher frequencies (e.g., 100-300 Hz instead of 50/60 Hz), the cable's capacitive reactance decreases, allowing power to be transmitted over distances exceeding 200 km without requiring DC conversion equipment.
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
Enables reliable and efficient transmission of AC power over longer distances, reducing equipment size and complexity, and maintaining stable voltage ratios despite changes in power consumption, thus enhancing the reliability of subsea power grids.
Implementation Method 1
guiding, in particular at least partially under water, the AC power through a cable from a first end of the cable to a second end of the cable
Implementation Method 2
adjusting a frequency of the AC power guided through the cable in dependence of a length of the cable between the first end and the second end of the cable
Data Source
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AI summary
It is described a method for transferring electrical power (103), the method comprising: generating AC power (103); guiding, in particular at least partially underwater, the AC power (103) through a cable (111) from a first end (113) of the cable to a second end (117) of the cable; and adjusting a frequency of the AC power (103) guided through the cable in dependence of a length (1) of the cable (111) between the first end (113) and the second end (117) of the cable (111).