Capacitance Estimation Using Frequency-Domain Signal Processing
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Solution Overview
Problem
Capacitors in electrical devices face fluctuations in capacitance due to temperature, voltage, humidity, vibrations, and ripple currents, leading to potential failure and downtime, requiring continuous monitoring and detection of faults, but existing methods like LCR meters are intrusive and offline.
Innovation Solution
A method that passively determines the capacitance value of a capacitor by receiving current and voltage signals, filtering them, performing a Fast Fourier Transform, and calculating impedance and reactance to estimate capacitance without interrupting the capacitor's operation, using sensors and a capacitance estimator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LCR meter is used to measure capacitance, then capacitance value can be estimated, but the measurement is intrusive and requires offline operation
Solution Approach 1:
The capacitor is monitored during its normal operation without requiring external measurement equipment. The system uses the capacitor's own operating signals (voltage and current) to determine its capacitance value, enabling continuous online monitoring while the capacitor remains in service
Solution Approach 2:
The patent replaces the mechanical LCR meter measurement system with an electronic signal processing system that analyzes voltage and current signals in the frequency domain to determine capacitance, eliminating the need for physical connection and offline measurement
2Reliability
If continuous monitoring is implemented to detect degradation, then reliability is improved, but device complexity increases
Solution Approach 1:
The monitoring system uses existing voltage and current signals from the capacitor's normal operation, making the measurement system universal and applicable to capacitors in various applications without requiring additional sensors or complex measurement circuitry
Solution Approach 2:
The patent introduces a signal processing intermediary that transforms voltage and current signals into the frequency domain to extract capacitance information, simplifying the monitoring system while maintaining reliability through mathematical transformation rather than complex hardware
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 real-time, online estimation of capacitance and Equivalent Series Resistance (ESR) at dominant and ripple frequencies, reducing downtime and maintenance costs, applicable to various capacitor types and applications, with lower sampling rates suitable for embedded systems.
Implementation Method 1
The received voltage signal and the received current signal are filtered with a low pass filter
Implementation Method 2
The discretized voltage signal and the discretized current signal are transformed into a frequency domain
Implementation Method 3
Magnitudes of the transformed current signal and the transformed voltage signal are filtered at a pre-defined frequency with a band pass filter
Data Source
AI summary
A method for determining a capacitance value of a capacitor is provided. The method includes receiving a current signal flowing through the capacitor and receiving a voltage signal applied across the capacitor. The received voltage signal and the received current signal are filtered with a low pass filter. The filtered voltage signal and the filtered current signal are then discretized. The discretized voltage signal and the discretized current signal are transformed into a frequency domain. The capacitance value of the capacitor is determined from the transformed voltage signal and the transformed current signal.