Inverter Temperature Estimation Using Oscillating Swings and Observer Feedback
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Solution Overview
Problem
Existing methods for estimating the temperature of power semiconductors in inverters used in hybrid and electric vehicles are not robust, especially at low rotational frequencies, due to their lack of feedback and complexity, which can lead to overloading and potential failure of the electric drive.
Innovation Solution
A method that calculates oscillating temperature swings of inverter components and determines an upper envelope of their amplitude, using a combination of Fourier analysis and thermal transfer functions to estimate the temperature contribution, allowing for improved temperature estimation even at low frequencies through the use of a Luenberger temperature observer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear network method is used to calculate power semiconductor temperatures, then the temperature can be estimated, but the method lacks feedback and becomes complex, reducing robustness against disturbances
Solution Approach 1:
The patent introduces a feedback mechanism by using a temperature observer that continuously monitors the actual temperature and adjusts the estimation accordingly. The observer compares the estimated temperature with measured values and corrects deviations, providing robustness against disturbances while maintaining accuracy.
Solution Approach 2:
The patent employs an intermediary approach by using a simplified thermal model with first-order transfer functions that acts as a mediator between the complex physical system and the control algorithm. This intermediary model reduces calculation complexity while preserving essential thermal behavior for accurate estimation.
2Device complexity
If a temperature observer is used to calculate mean temperatures of IGBTs and diodes, then the calculation is simplified, but it is not suitable for highly transient control processes such as starting or low rotational frequencies
Solution Approach 1:
The patent enhances the temperature observer by making it dynamic and adaptive. The observer parameters are adjusted based on the operating conditions, allowing it to respond effectively to highly transient control processes while maintaining simplicity. The observer gains are modified according to the rotational frequency and load conditions.
Solution Approach 2:
The patent changes the parameters of the temperature observer dynamically based on operating conditions. The observer uses different gain values and time constants depending on whether the system is in steady-state or transient operation, enabling reliable temperature estimation across all operating ranges including starting and low rotational frequencies.
3Force
If high current is applied at low rotational frequencies, then the required torque for starting can be achieved, but the inverter becomes overloaded due to asymmetrical loading of power semiconductors
Solution Approach 1:
The patent uses feedback from the temperature observer to detect asymmetrical loading conditions in real-time. When the observer identifies that certain power semiconductors are overheating due to asymmetrical current distribution, the system responds by adjusting the current distribution to balance the thermal load across all semiconductors.
Solution Approach 2:
The patent applies preliminary anti-action by proactively redistributing the current before thermal damage occurs. The temperature observer predicts which semiconductors will be overloaded based on current trends, and the control system preemptively adjusts the current distribution to prevent overheating, rather than waiting for temperature thresholds to be exceeded.
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 robustness and accuracy of temperature estimation, enabling effective self-protection of power semiconductors by uniformly calculating IGBT and diode temperatures across all frequency ranges, including low frequencies, thereby preventing overloading and ensuring reliable operation.
Implementation Method 1
the thermal dependency between the individual power semiconductors, which are embodied by IGBTs and diodes, is used. This thermal dependency is described by first-order transfer functions
Implementation Method 2
the oscillating temperature swings are calculated based on a specified, in particular sinusoidal, signal shape of an antiderivative of harmonics of the zero-mean oscillating power loss, and are furthermore calculated preferably based on a Fourier analysis
Data Source
AI summary
The invention relates to a method for estimating a temperature contribution of an inverter used to energize an electrical machine, in particular a synchronous machine. The method comprises the steps for calculating oscillating temperature swings of components of the inverter; and determining, as the estimated temperature contribution (ΔT(ω), ΔTi(ω), (ΔTd(ω)) of the inverter, an upper envelope of an amplitude of a sum of the calculated oscillating temperature swings. The method according to the invention or an apparatus designed to carry out the method can be expanded for the purpose of estimating a temperature or a complete temperature contribution of the inverter and is provided, in particular, for use in an electric vehicle or a hybrid vehicle having an electrical drive without a variable speed gear in order to estimate the operating temperature of vehicle drive power electronics accommodated therein.