Over-temperature management of DC link capacitor in electric vehicle propulsion drive converter

1 . A method comprising:

after starting an electric drive system, reducing power output of an inverter while sensed temperature of a power switch of the inverter, sensed current of a power electronics module that includes the inverter, sensed DC-link voltage, and thermal impedance parameters of a DC-link capacitor are indicative of a temperature of the DC-link capacitor being greater than a threshold to maintain the temperature lower than the threshold;

obtaining the thermal impedance parameters of the DC-link capacitor from a thermal model of the DC-link capacitor; and

initially deriving the thermal model from testing a test version of the power electronics module under a plurality of conditions in which for each of the conditions a set of information is recorded including sensed temperature of a power switch of an inverter of the test version of the power electronics module, sensed current of the test version of the power electronics module, and sensed DC-link voltage of the test version of the power electronics module.

2 . The method of claim 1 further comprising implementing a Kalman filter observer to estimate the temperature using state and output equations derived from the thermal model.

3 . The method of claim 2 , wherein the state and output equations include the temperature from a previous iteration.

4 . The method of claim 1 further comprising, upon the starting of the electric drive system, estimating the temperature based on a last estimated temperature of the DC-link capacitor and a current temperature of a power switch of the inverter.

5 . The method of claim 1 further comprising, upon the starting of the electric drive system, estimating the temperature based on a maximum allowable temperature that is less than the threshold.

6 . An electric drive control system comprising:

a controller programmed to

after start of the electric drive control system, reduce power output of an inverter responsive to an estimated temperature of a DC-link capacitor being greater than a threshold to maintain DC-link capacitor temperature lower than the threshold, and

upon start of the electric drive control system, generate an initial value for the estimated temperature based on a maximum allowable temperature that is less than the threshold under certain conditions and based on a last estimated temperature of the DC-link capacitor under other conditions.

7 . The electric drive control system of claim 6 , wherein the controller is further programmed to implement a Kalman filter observer to generate subsequent values for the estimated temperature using state and output equations derived from a thermal model of the DC-link capacitor.

8 . The electric drive control system of claim 7 , wherein the state and output equations include a value of the estimated temperature from a previous iteration.