Resonant Controllers Mitigate Harmonic Resonance in Subsea Cable Drives
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Solution Overview
Problem
Variable-speed drives (VSDs) used in subsea power systems generate harmonics that interfere with other equipment, leading to resonance amplification and reduced component lifetime due to harmonic interaction with long cable transmission systems, particularly in subsea applications.
Innovation Solution
The implementation of two resonant controllers in parallel with existing controllers to apply a transfer function tuned for specific harmonic orders (e.g., 6th and 12th harmonic) to adjust magnetizing and torque currents, mitigating harmonic interaction by compensating for dominant harmonics in the power system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If VSDs are used in subsea power systems, then power control and operational flexibility are improved, but harmonic interaction and resonance amplification occur that reduce component lifetime
Solution Approach 1:
The patent applies resonant controllers that are tuned to specific resonance frequencies of the power system. These controllers convert the harmful harmonic interactions into beneficial compensatory actions by injecting counter-phase currents that cancel out the resonant amplification, thereby protecting components while maintaining VSD operational flexibility
Solution Approach 2:
The patent implements a feedback mechanism where the resonant controllers continuously monitor the power system's response and adjust their output to compensate for harmonic interactions. The controllers use the system's resonance characteristics to generate compensating signals that are fed back into the power system, creating a closed-loop control that mitigates harmful effects
2Length of stationary object
If long cable transmission is used in subsea applications, then power delivery to remote loads is enabled, but harmonic resonance and interaction with VSDs increase
Solution Approach 1:
The patent introduces resonant controllers as intermediary devices between the VSD and the long cable transmission system. These controllers act as mediators that detect harmonic interactions and insert compensating signals to neutralize resonance effects, enabling long cable transmission without the harmful harmonic amplification that would otherwise occur
3Object-generated harmful factors
If resonant controllers are added to compensate for harmonics, then harmonic interaction is reduced, but system complexity increases
Solution Approach 1:
The patent divides the control function into separate resonant controllers, each tuned to specific resonance frequencies of the power system. This segmentation allows each controller to handle a particular frequency range independently, making the overall system more manageable and easier to implement despite the added complexity
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 effectively reduces harmonic interaction and resonance excitation, extending the lifetime of power system components and maintaining operational efficiency by applying resonant controllers to compensate for dominant harmonics in the VSD and long cable transmission systems.
Implementation Method 1
two resonant controllers may be in parallel with two respective controllers of the power system that control a magnetizing current and a torque current of the VSD, respectively. The two resonant controllers may apply a transfer function that may be tuned for one or more specified harmonic orders
Data Source
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AI summary
A system includes a variable-speed drive configured to drive a motor, wherein the variable-speed drive is communicatively coupled to first and second resonant controllers. The system also includes a first transformer coupled to the variable-speed drive and an umbilical cable, wherein the first transformer increases a first voltage output by the variable-speed drive. The system further includes a second transformer coupled to the umbilical cable and the motor, wherein the second transformer decreases a second voltage output by the first transformer. The first resonant controller compensates for a harmonic order of the system by adjusting a magnetizing current used to control an operation of the variable-speed drive based on a modeled resonance frequency of the system. The second resonant controller compensates for the harmonic order of the system by adjusting a torque current used to control the operation of the variable-speed drive based on the modeled resonance frequency.