IGBT Junction Temperature Estimation With Reduced-Order Foster Models
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Solution Overview
Problem
Current methods for estimating the temperature of semiconductor components, such as IGBT modules, require significant computational resources, making real-time implementation challenging, especially in high-speed motor control applications where thermal losses vary rapidly with frequency.
Innovation Solution
A reduced-order version of the Foster temperature model is used, optimized through methods like balanced truncation, to simplify the calculation of barrier junction temperatures, reducing computational complexity while maintaining sufficient precision for effective component protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-order Foster temperature model is used to estimate barrier junction temperature, then measurement precision is improved, but device complexity and computational load increase significantly
Solution Approach 1:
The high-order Foster model (3rd or 4th order) is segmented into multiple first-order subsystems, each representing a specific thermal pathway. By processing these simplified subsystems separately and combining their results, the patent achieves accurate temperature estimation while reducing computational complexity. This segmentation allows the control unit to handle thermal calculations in manageable steps rather than as a single complex computation.
Solution Approach 2:
The patent transforms the high-order differential equations of the Foster model into equivalent first-order equations by changing the mathematical parameters and representation. This parameter transformation maintains the physical accuracy of thermal impedance calculations while enabling real-time computation with limited processing power in automotive control units.
2Reliability
If real-time temperature estimation is implemented in high-speed motor control applications, then component protection is improved, but computational resources are excessively consumed
Solution Approach 1:
The thermal model is divided into first-order subsystems that can be computed independently and efficiently. This segmentation enables real-time temperature monitoring without consuming excessive computational resources, as each subsystem requires minimal processing power compared to solving a single high-order system.
Solution Approach 2:
Instead of implementing the complex high-order Foster model directly, the patent uses simplified first-order model copies that approximate the thermal behavior. These copied simplified models consume far less energy while providing sufficient accuracy for component protection in real-time automotive applications.
3Measurement precision
If computational accuracy is maximized for temperature estimation, then measurement precision is improved, but processing time increases making real-time implementation difficult
Solution Approach 1:
By segmenting the thermal calculation into first-order subsystems, the patent enables parallel or sequential processing that reduces total computation time. Each subsystem can be solved quickly using simple exponential functions, and the results are combined to achieve accurate temperature estimation within real-time constraints.
Solution Approach 2:
The patent applies partial action by using only the essential first-order dynamics of each thermal pathway rather than computing the complete high-order system. This partial computation approach provides sufficient accuracy for safety-critical temperature monitoring while dramatically reducing processing time to meet real-time requirements.
Data Source
AI summary
Semiconductor modules are used for controlling drive motors such as the electric motors of electric vehicles. IGBT modules are one type of such semiconductor modules. During operation, heat losses arise in the power transistors and the diodes of the semiconductor modules, which causes an increase in their temperature. Therefore, the manufacturers of the IGBT modules recommend that the software of a control unit that controls an IGBT module be provided with a protective function which continuously monitors the temperature of the IGBT module and intervenes as necessary if an unacceptable temperature of a component of the IGBT module is reached. A temperature model is used for the calculation. The manufacturers provide a more accurate higher-order temperature model that however causes an increased amount of computation. According to the proposal, a reduced temperature model is used that is calculated using the balanced truncation method and is optimized for certain working ranges.