Hold-Up Capacitor Voltage Control for Lifetime and Weight Trade-Off
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Solution Overview
Problem
Existing electrical systems, particularly in aircraft, face challenges with the cost, size, and weight of hold-up capacitors due to the need for oversized capacitors to maintain capacitance over their operational lifetime, which is affected by environmental factors and increased internal resistance, leading to accelerated degradation.
Innovation Solution
A method and system that dynamically adjust the operating voltage of energy storage units based on monitored time constants to optimize energy storage and extend the operational lifetime of capacitors, allowing for the use of smaller capacitors while maintaining desired hold-up times, involving charging, discharging, and voltage monitoring processes controlled by a controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitance of hold-up capacitors is increased to maintain suitable capacitance throughout operational lifetime, then the reliability is improved, but the cost, size and weight of electrical systems increase
Solution Approach 1:
The patent implements dynamic voltage adjustment of the hold-up capacitor based on real-time monitoring of its degradation state. Instead of using a fixed oversized capacitor design, the system dynamically adapts the operating voltage to compensate for capacitance reduction over time, allowing the use of smaller capacitors while maintaining reliable hold-up performance throughout their operational lifetime.
Solution Approach 2:
The patent changes the operating voltage parameter of the hold-up capacitor dynamically. By adjusting the voltage based on the capacitor's degradation level (monitored through time constant measurements), the system compensates for capacitance reduction and maintains adequate hold-up capability without requiring oversized capacitors from the outset.
2Duration of action of moving object
If the operating voltage of hold-up capacitors is increased to maximize storable energy, then the hold-up time is improved, but the operational lifetime of the capacitor deteriorates
Solution Approach 1:
The patent implements dynamic voltage adjustment rather than using a fixed high voltage. The system starts with a lower operating voltage to extend capacitor lifetime, then progressively increases the voltage as the capacitor degrades, maintaining adequate hold-up time throughout the capacitor's extended operational lifetime rather than sacrificing lifetime for initial hold-up performance.
Solution Approach 2:
The patent applies preliminary derating by operating the capacitor at a reduced voltage initially, which slows degradation and extends lifetime. This preliminary action allows the capacitor to remain operational longer, after which voltage can be increased to compensate for the gradual capacitance loss, optimizing the trade-off between hold-up time and lifetime.
3Reliability
If oversized capacitors are used to compensate for capacitance reduction over time, then the reliability is improved, but the cost and size of electrical systems increase
Solution Approach 1:
The patent implements a self-adjusting system that monitors the capacitor's own degradation state (through time constant measurement) and automatically adjusts the operating voltage to compensate. This self-service approach allows the system to maintain reliable hold-up capability using a smaller capacitor, as the voltage adjustment compensates for the capacitor's natural aging and capacitance reduction over time.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the capacitor's time constant and using this information to adjust the operating voltage. This feedback mechanism ensures that the hold-up capability remains adequate throughout the capacitor's lifetime without requiring an oversized initial capacitor design, as the system adapts to the capacitor's actual state in real-time.
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 enables the use of smaller, less expensive capacitors while ensuring reliable power delivery during interruptions and extending the operational lifetime of capacitors, reducing the overall size and weight of electrical systems.
Implementation Method 1
Energy storage capacitors can be used to provide smooth and reliable deliverance of electrical power to components powered by the electrical systems for supplying power during such interruptions. The capacitors charge during periods of uninterrupted power supply, and discharge during power interruptions.
Implementation Method 2
As the internal resistance of the capacitor increases, it experiences increased localised heating which further accelerates degradation of the capacitor.
Data Source
Figure 1~2
AI summary
A method of controlling an operating voltage of an electrical system for supplying electrical power to a load and an electrical system for supplying electrical power to a load are described herein. The method comprises charging an energy storage unit (4) using electrical power at a predetermined voltage, wherein the energy storage unit (4) comprises a capacitor; removing the operating voltage; and discharging the energy storage unit (4) across a fixed load (6). The method further comprises monitoring a discharge voltage across the fixed load (6) over a period of time; determining a time constant of the energy storage unit (4) based on the monitored discharge voltage; and comparing the time constant to a threshold value. If the time constant is higher than the threshold value, the method comprises decreasing the operating voltage. If the time constant is lower than the threshold value, the method comprises increasing the operating voltage. In this way, the hold-up time of the capacitor may be dynamically adjusted according to a determined capacitance of the capacitor.