Subsea Capacitor Bank Segmentation and Current Limiting
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Solution Overview
Problem
Subsea capacitor banks face reliability and lifetime issues due to the failure of individual capacitors, which can cause short circuits and affect the entire system, especially since traditional capacitors cannot withstand high pressures and require multiple, less reliable film or ceramic capacitors to achieve sufficient capacitance.
Innovation Solution
Incorporating a series connection of capacitors with resistors and parallel diodes to limit current and prevent system-wide failures, allowing for the use of more critical capacitors like film or ceramic types, and configuring capacitors in parallel or series circuits to enhance redundancy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If electrolytic capacitors are used in subsea applications, then they can withstand atmospheric pressure, but they require atmospheric pressure canisters which generate heat that is difficult to dissipate
Solution Approach 1:
The capacitor bank is divided into multiple independent sections, each with its own failure isolation capability. This segmentation allows heat and failures to be contained within individual sections rather than affecting the entire bank, addressing both pressure resistance requirements and heat dissipation challenges.
Solution Approach 2:
Resistors are introduced as intermediary components connected in series with each capacitor or capacitor group. These resistors limit current flow during capacitor failures and help distribute heat generation more evenly across the bank, preventing localized overheating while maintaining pressure resistance.
2Stress or pressure
If film capacitors or ceramic capacitors are used instead of electrolytic capacitors, then atmospheric pressure canisters are not needed, but the capacitors have lower capacitance and are more subject to failures
Solution Approach 1:
Multiple film or ceramic capacitors are combined in parallel configurations to achieve the required total capacitance. By merging multiple lower-capacitance components, the system achieves both the necessary capacitance value and improved reliability through redundancy, eliminating the need for atmospheric pressure canisters.
Solution Approach 2:
Resistors are pre-connected in series with each capacitor to provide beforehand protection against failure propagation. This prior cushioning measure ensures that if one capacitor fails, the resistor limits the current and prevents the failure from affecting other capacitors, thereby maintaining system reliability.
3Quantity of substance
If capacitors are connected in parallel to achieve sufficient capacitance, then the overall capacitance increases, but a single capacitor failure can short the entire storage capacity
Solution Approach 1:
The capacitor bank is segmented into independent sections with failure isolation capabilities. Each section contains capacitors connected in parallel to achieve the required capacitance, but the segmentation ensures that a failure in one section does not propagate to other sections, maintaining both high capacitance and system reliability.
Solution Approach 2:
Resistors are introduced as intermediary components in series with each capacitor or capacitor group. These resistors act as current limiters during failure conditions, preventing a single capacitor short circuit from affecting the entire bank while maintaining the parallel configuration needed for sufficient capacitance.
4Object-affected harmful factors
If huge capacitor banks are sectioned by fuses to avoid electric arc formation, then the entire capacitor bank is excluded when one fails, but this protection is not present in smaller banks
Solution Approach 1:
The capacitor bank is divided into multiple independent sections, each with its own failure isolation capability. This segmentation allows smaller banks to have the same level of protection as huge banks, preventing electric arc formation and ensuring that failures in one section do not affect the entire bank, thereby maintaining system availability.
Solution Approach 2:
Resistors are introduced as intermediary components that provide inherent protection against electric arc formation by limiting current flow during failure conditions. This approach provides the same protection as fuse-based systems in huge banks but without the need to exclude the entire bank upon failure, maintaining higher system availability.
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 ensures that a single capacitor failure does not affect the entire bank, improving reliability and allowing for higher current delivery during discharge, thus enhancing the overall performance and longevity of subsea electrical components.
Implementation Method 1
a plurality of resistors, each of the capacitors being in series with at least one of the resistors
Implementation Method 2
a plurality of diodes, each of the diodes being in parallel with one of the resistors
Implementation Method 3
capacitor bank for direct current (DC) storage
Data Source
AI summary
A capacitor bank includes a plurality of capacitors; a plurality of resistors, each of the capacitors being in series with at least one of the resistors; and a plurality of diodes, each of the diodes being in parallel with one of the resistors. A subsea power cell for converting an electrical three phase input into an electrical one phase output, includes the capacitor bank; a diode rectifier connected to the three phase input; and a plurality of Insulated Gate Bipolar Transistors connected to the electrical one phase output.