Link Capacitor Temperature Monitoring via ESR Modeling
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Solution Overview
Problem
Existing methods for determining the remaining service life of link capacitors in link converters are inaccurate due to the reliance on total power calculations that do not reflect the actual power consumed by the capacitors, requiring additional sensors and being costly and space-intensive.
Innovation Solution
A method that models the link capacitor as a series interconnection of equivalent capacitance and resistance, calculates the capacitor power loss, and uses a temperature model to determine the capacitor temperature, allowing for accurate temperature monitoring and service life prediction without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors are used to measure capacitor temperature directly, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses an intermediary approach by measuring voltage across the capacitor and calculating temperature through a thermal model rather than direct temperature sensing. The voltage measurement serves as an indirect indicator that, when processed through the equivalent circuit model and thermal model, provides temperature information without requiring physical contact with the capacitor interior.
Solution Approach 2:
The patent replaces the mechanical/physical sensor-based temperature measurement system with an electrical measurement and computational system. Instead of using physical temperature sensors inside the capacitor, the system uses voltage measurements combined with mathematical models (equivalent circuit model and thermal model) to calculate temperature, thereby eliminating the need for complex sensor integration.
2Measurement precision
If special link capacitors with integrated temperature sensors are used, then temperature measurement accuracy is improved, but cost increases
Solution Approach 1:
The patent employs an intermediary measurement approach where standard capacitors without integrated sensors are used. Instead of paying for expensive specialized capacitors with built-in temperature sensors, the system uses readily available voltage measurements across the capacitor terminals and processes them through computational models to obtain temperature data, thereby significantly reducing component costs.
Solution Approach 2:
The patent creates a virtual copy or model of the capacitor's thermal behavior through mathematical modeling. Rather than physically modifying the capacitor with sensors, the system creates an equivalent thermal model that replicates the temperature characteristics based on electrical measurements, providing the same information at lower cost.
3Device complexity
If total power calculations are used to estimate ripple current, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the measured voltage across the capacitor is continuously used to calculate the instantaneous capacitor current through the equivalent circuit model. This actual capacitor current measurement feedback provides accurate information about the real power consumed by the capacitor, enabling precise temperature calculation without relying on inaccurate total power estimates from the converter.
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 provides accurate temperature monitoring and service life prediction for link capacitors, reducing costs and space requirements while avoiding the need for additional sensors, enabling effective capacitor management in link converters.
Implementation Method 1
A modeled capacitor power loss is calculated from the modeled capacitor current and the value of the equivalent series resistance by means of a first relationship of the form PC=f(iCm, ESR)
Data Source
AI summary
To determine the temperature of a link capacitor (C) of a link converter (1) more accurately with less expenditure, a device and a method are described, in which the link capacitor (C) is modeled as a series interconnection of an equivalent capacitance (CS) and an equivalent series resistance (ESR), wherein a modeled capacitor current (iCm) flows across the equivalent series resistance (ESR). A modeled capacitor power loss (PC), from which the capacitor temperature (TC) is determined by means of a specified temperature model, is calculated from the modeled capacitor current (iCm) and the value of the equivalent series resistance (ESR) by means of a first relationship of the form PC=f(iCm, ESR). Direct measurement of the capacitor temperature (TC), of the capacitor current (iC), or of the capacitor power loss (PC) is not required. For example, a measurement of the capacitor voltage (uC) and a further calculation of the modeled capacitor current iCm and finally of the capacitor power loss (PC) are sufficient. The method can be used for the monitoring and processing of the capacitor temperature (TC), particularly the switching-off of an element, preferably at least part of the link converter (1), when a maximum temperature, such as a preset maximum temperature, is exceeded. The method can also be used to determine the temporal progression of the capacitor temperature (TC(t)) and also to determine the remaining service life (RL) of the link capacitor (C) of a specified relationship, preferably by means of the Arrhenius formula.