Inverter Busbar Thermal Prediction for Dynamic Power Derating
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Solution Overview
Problem
Existing electric drive systems face challenges in controlling inverter busbar temperatures effectively, particularly in preventing overheating without the need for direct busbar temperature measurement or overly conservative current limits.
Innovation Solution
A controller uses a thermal model of the busbar, combined with sensed temperatures of power switches and current output of the inverter, to predict busbar temperatures and de-rate the system when necessary to maintain temperatures below a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct temperature measurement of the busbar is implemented, then temperature monitoring accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses the power switch temperature as an intermediary parameter to infer busbar temperature. Instead of directly measuring busbar temperature with dedicated sensors, the system measures power switch temperature (which is easier to access) and uses thermal models to predict busbar temperature based on this intermediary measurement, along with current output data.
Solution Approach 2:
The patent creates a thermal model that copies the thermal behavior of the busbar based on measurements from the power switch. The model replicates the thermal relationships and allows temperature prediction without physical duplication of sensors on the busbar itself.
2Reliability
If conservative current limits are applied to prevent overheating, then reliability is improved, but productivity decreases due to unnecessary de-rating
Solution Approach 1:
The patent implements dynamic current limits that adjust in real-time based on actual thermal conditions. Instead of applying static conservative limits, the system continuously monitors power switch temperature and current output, updates thermal models, and adjusts the allowable current limit dynamically. This allows the inverter to operate at higher power levels when thermal conditions permit while maintaining protection when temperatures approach thresholds.
Solution Approach 2:
The system uses feedback from temperature sensors and current measurements to continuously update the thermal model and adjust operating parameters. The predicted busbar temperature feeds back into the control system to modify current limits, creating a closed-loop control that optimizes both reliability and productivity.
3Manufacturing precision
If thermal modeling and prediction systems are implemented, then temperature control precision is improved, but device complexity increases
Solution Approach 1:
The thermal model serves multiple functions: it predicts busbar temperature, evaluates thermal risk, determines appropriate current limits, and provides feedback for control adjustments. This multi-functionality reduces the need for separate dedicated systems for each thermal management task, thereby limiting the increase in overall system complexity.
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 allows for effective thermal protection of the inverter busbar and other components without the need for direct temperature measurement or overly conservative current limits, thereby optimizing system performance and reducing unnecessary de-rating.
Implementation Method 1
a thermal model of the busbar, combined with sensed temperatures of power switches and current output of the inverter, to predict busbar temperatures
Data Source
AI summary
A controller reduces power output of an inverter of an electric drive system while a sensed temperature associated with the inverter, a sensed current output of the inverter, and parameter values of a busbar of the inverter are indicative of a predicted temperature of the busbar being greater than a threshold to maintain busbar temperature lower than the threshold. The current output of the inverter may be outputted over the busbar. The parameter values are obtainable from a thermal model of the busbar. The thermal model may be derived from testing a test version of the inverter under different drive cycles in which for each a set of information is recorded including a sensed temperature of the test inverter, a sensed current output of the test inverter, and a sensed temperature of the busbar of the test inverter.