Complex Impedance Phase Measurement Using Hysteresis Thresholding
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Solution Overview
Problem
Existing methods for measuring the phase of complex impedance are complex, require specific power sensors, and are sensitive to noise, especially when using zero-crossing comparators.
Innovation Solution
A method and device using Schmitt flip-flops to generate square wave signals from input signals, combined with time-to-digital conversion and phase correction based on amplitude and threshold measurements, to estimate the phase of complex impedance with reduced complexity and noise sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If zero-crossing comparators are used to measure phase shift, then the measurement method is simple, but the sensitivity to noise increases causing multiple switching near threshold crossing
Solution Approach 1:
The patent introduces an intermediary mechanism (the specific thresholding and time-shift measurement approach) between the voltage and current signals to measure phase difference. Instead of directly comparing zero-crossings which are noise-sensitive, the invention uses threshold-based detection with hysteresis and measures the time shift between threshold crossings, acting as a mediator that reduces noise impact while preserving phase information.
Solution Approach 2:
The invention changes the parameter used for phase measurement from zero-crossing detection to threshold-based time-shift measurement. By measuring the time difference between corresponding points on the signals (threshold crossings) and converting this time shift to phase angle, the method achieves noise immunity while maintaining measurement simplicity.
2Measurement precision
If complex calculations and specific power sensors are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex computational methods and specialized power sensors with a simpler time-domain measurement approach. Instead of performing complex calculations on amplitude and phase parameters or using dedicated power sensors, the invention measures the time shift between threshold crossings of voltage and current signals and directly converts this to phase angle, eliminating the need for complex computation hardware or specialized sensors.
Solution Approach 2:
The invention uses standard, readily available components (comparators, timers, or digital logic elements) rather than expensive specialized power sensors. The threshold-based detection method can be implemented with simple circuits or even software on microcontrollers, providing an economical alternative to complex measurement systems.
3Power
If amplitude differences between voltage and current signals are present, then signal strength varies, but phase estimation accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-establishing corresponding points on the voltage and current waveforms using threshold detection before measuring the time shift. By defining specific reference points (threshold crossings) on each waveform and measuring the time difference between these predetermined points, the method eliminates the influence of amplitude variations on phase measurement accuracy.
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 accurate and simple measurement of complex impedance phase using a low-complexity device, such as a microcontroller or FPGA, by compensating for amplitude-induced errors in phase estimation.
Implementation Method 1
perform a thresholding with hysteresis of said first and said second analog signals
Implementation Method 2
determine a third numerical value representing a time shift between a time when said first analog signal crosses a threshold and a time when said or another threshold is crossed by said second analog signal
Implementation Method 3
determine an estimate of said phase of the complex impedance of the electrical element as a function of said first, second and third numerical values, as well as a fourth numerical value representative of the frequency
Data Source
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AI summary
Method for measuring the phase of the complex impedance of an electrical element (EL) comprising: - applying to said electrical element (EL) an excitation signal (sex) at a known frequency f; - acquiring a first (uV) and a second (uI) analog signal representative of a voltage and a current, respectively; - converting the first and second analog signals into digital format; - performing thresholding with hysteresis of the first and second analog signals; - measuring a time shift between an instant of crossing of a threshold by said first analog signal and said second analog signal; and - determining an estimate (φ̂') of said phase of the complex impedance of the electrical element as a function of the amplitudes of the first and second analog signals converted into digital format, said time shift and the frequency f of the excitation signal. Apparatus for implementing this method.