Power Converter Inductance Estimation With Low-Frequency Test Voltage
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Solution Overview
Problem
Conventional power conversion devices face reduced accuracy in inductance estimation due to improper setting of test voltage frequency, leading to current flow through resonant capacitors and increased switching losses.
Innovation Solution
Set the frequency of the fundamental wave component of the test voltage lower than the frequency of the voltage during power transfer to minimize current flow through resonant capacitors, thereby maintaining accurate inductance estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency of the test voltage is set high during inductance estimation, then the estimation speed is improved, but current flows through resonant capacitors causing increased switching losses and reduced measurement accuracy
Solution Approach 1:
The patent changes the frequency parameter of the test voltage to be lower than the resonant frequency of the LC circuit. This parameter change ensures that the resonant capacitor does not conduct significant current during inductance estimation, thereby reducing switching losses while maintaining accurate inductance measurement. The frequency is specifically set below the resonant frequency point where the capacitive reactance becomes excessively low.
2Measurement precision
If the frequency of the test voltage is set high during inductance estimation, then the measurement response time is reduced, but the estimation accuracy deteriorates due to current flow through resonant capacitors
Solution Approach 1:
The patent optimizes the test voltage frequency parameter by setting it below the resonant frequency. This frequency selection achieves a balance between measurement speed and accuracy: it is low enough to prevent resonant capacitor conduction and maintain accuracy, but high enough to provide adequate measurement response time. The frequency is positioned in the optimal range where capacitive current is minimized while measurement efficiency is maintained.
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 enhances the estimation accuracy of transformer inductance by reducing current flow through resonant capacitors, minimizing switching losses, and ensuring precise inductance measurement.
Implementation Method 1
an estimation process to estimate an inductance of the inductance element by outputting a test voltage to the inductance element
Implementation Method 2
an inductance element connecting a first AC terminal of the first circuit and a second AC terminal of the second circuit, and a resonant capacitor connected to the inductance element
Data Source
AI summary
A power conversion device includes a first circuit connected to a first external terminal, a second circuit connected to a second external terminal, an inductance element connecting a first AC terminal of the first circuit and a second AC terminal of the second circuit, a resonant capacitor connected to the inductance element, and a control unit. The control unit performs a power transfer process to transfer power between the first external terminal and the second external terminal via the inductance element by switching control of at least one of the first circuit and the second circuit, and an estimation process to estimate the inductance by outputting a test voltage to the inductance element. A frequency of the fundamental wave component of the test voltage is set to a frequency lower than a frequency of the fundamental wave component of a voltage output to the inductance element in the power transfer process.