Inverter Overvoltage Protection via Temperature-Adaptive Thresholds
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Solution Overview
Problem
Existing inverter protection systems for hybrid and electric vehicles do not effectively manage temperature-dependent withstand voltage fluctuations, leading to inefficient operation and potential damage when dealing with overvoltage conditions.
Innovation Solution
A control apparatus for a load device with an inverter, featuring a temperature detection unit, voltage detection unit, and a control unit that sets a voltage upper limit based on temperature-dependent withstand voltage, ensuring the inverter operates within safe voltage limits by stepping up DC voltage and controlling the inverter's load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant overvoltage detection level is used for inverter protection, then the inverter is protected from overvoltage damage, but the inverter operation is unnecessarily restricted at high temperatures where the withstand voltage is higher
Solution Approach 1:
The overvoltage detection level is made dynamic by adjusting it according to the detected temperature of the inverter. The control unit changes the detection level based on the relationship between temperature and withstand voltage, allowing the inverter to operate at higher voltages when temperature is high while maintaining protection when temperature is low.
Solution Approach 2:
The detection level parameter is changed based on temperature conditions. The control unit stores multiple detection levels corresponding to different temperature ranges and selects the appropriate level based on the currently detected temperature, thereby adapting the protection threshold to the actual withstand voltage capacity of the inverter.
2Reliability
If the inverter is stopped during overvoltage detection, then the inverter is protected from voltage exceeding withstand voltage, but the inverter cannot operate at high temperatures where higher voltages are acceptable
Solution Approach 1:
The overvoltage detection level is dynamically adjusted based on temperature. At high temperatures where the inverter can withstand higher voltages, the detection level is raised accordingly, allowing continuous operation. At low temperatures where withstand voltage is lower, the detection level is reduced to prevent damage, thus expanding the usable temperature range.
Solution Approach 2:
The detection level parameter is changed according to temperature conditions. The control unit stores multiple detection levels corresponding to different temperature ranges and selects the appropriate level based on the currently detected temperature, thereby adapting the protection threshold to the actual withstand voltage capacity.
3Device complexity
If a fixed voltage threshold is used for overvoltage protection, then the protection logic is simple, but the protection is either too conservative at high temperatures or insufficient at low temperatures
Solution Approach 1:
The detection level parameter is changed based on temperature conditions. The control unit stores multiple detection levels corresponding to different temperature ranges and selects the appropriate level based on the currently detected temperature, thereby adapting the protection threshold to the actual withstand voltage capacity of the inverter.
Solution Approach 2:
The control unit continuously monitors the temperature of the inverter and adjusts the overvoltage detection level accordingly. This feedback mechanism ensures that the protection threshold always matches the current withstand voltage capacity of the inverter, providing accurate protection across different operating conditions.
Data Source
AI summary
A control apparatus for a load device mounted on a vehicle is provided with: a temperature sensor detecting a temperature of an inverter; a voltage sensor detecting an applied voltage of the inverter; and a control unit operating the inverter in a case where the applied voltage is a predetermined upper limit value or lower whereas stopping the inverter in a case where the applied voltage is higher than the upper limit value based on a voltage detection result by the voltage sensor. The control unit sets the upper limit value based on temperature dependency of a withstand voltage of an IGBT element included in the inverter and a temperature detection result by the temperature sensor.