Electronic control system module junction temperature protection technology
A lot of thermal simulations have been done to get the maximum capacity of the controller. The maximum capability may not protect the motor controller, and the actual working conditions are very complicated.
3.1, IGBT junction temperature estimation of practical significance
The junction temperature is an important condition for determining the safe operation of the IGBT. The operating junction temperature of the IGBT limits the maximum output capability of the controller.
IGBT overheating damage has serious effects. There are many factors, such as design factors, complex working conditions, high vibration, temperature shock, aging of silicone grease, and indirect protection of IGBT junction temperature according to NTC. There are certain limitations, such as blocking. Under extreme conditions, the thermal energy distribution is very uneven, and the temperature difference between IGBT and NTC is not clear. The relationship between NTC and junction temperature is not very clear. It needs preliminary experiment and the NTC response time is slow, and the junction temperature fluctuation state cannot be accurately and timely reflected. It is easy to cause IGBT overheating damage. Traditionally, NTC is used to protect the IGBT junction temperature, which has limitations.
It is dangerous to use NTC for protection only in the case of poor working conditions.
3.2. Estimation of IGBT junction temperature based on NTC
According to the working parameters, such as voltage and current frequency, do accurate thermal simulation, extract the heat flow parameters, calculate the correction, and predict the IGBT junction temperature in advance. After testing, simulation and software model check each other, the final junction temperature estimation error is within ±3 °C.
3.3 Estimation of IGBT junction temperature based on temperature sampling diode
The temperature sampling diode is directly integrated in the middle of the IGBT. Compared with the traditional module, the junction temperature of the wafer can be directly collected (approximate), the module capability can be improved, the junction temperature fluctuation of the wafer can be obtained, the reliability can be improved, and the lifetime can be guaranteed. The disadvantage is that the crystal is directly collected. Yuan junction temperature, high and low voltage safety regulations.
Module 6 junction temperature sampling, module and external circuit cost increase, currently using 1 IGBT junction temperature, single diode temperature, through loss calculation, heat flow parameter calculation, to derive the temperature of other IGBTs.
Using single-channel diode temperature sampling, using advanced loss calculation and heat flow parameter calculation method, test, simulation and software model mutual verification, the junction temperature estimation error can reach within 3 °C, and the transient state is within 10 °C.
3.4. Temperature protection strategy based on junction temperature estimation
Advantage:
The monitoring of junction temperature is more direct, and the acceleration performance of the whole vehicle is better;
Real-time monitoring of junction temperature, under the locked-off limit working conditions, can not only exert the maximum capacity of the controller, but also ensure that the controller will not be over-temperature damaged, and the safety of the whole vehicle is higher;
Under the normal operating conditions of the vehicle, the current capacity of the IGBT is maximized, and the vehicle is more dynamic;
The controller can carry out some more avant-garde algorithm research in combination with the actual operating conditions, such as real-time calculation of IGBT life damage degree, etc., to improve the reliability of the whole vehicle.
Safeguard:
Set the junction temperature limit, when the junction temperature is at risk, carry out the carrier frequency reduction or torque reduction strategy; risk release, frequency reduction or torque data recovery.
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