# US 12,222,738 B2 · Method and system for controlling electric drive system according to predicted temperature of DC-link capacitor to prevent overheating > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,222,738 B2 - Document ID: US12222738B2 - Status: Granted - Kind: B2 - Application number: 17/590,237 - Filed: 2022-02-01 - Published: 2023-08-03 - Granted: 2025-02-11 - Earliest claimed: 2022-02-01 - Assignees: Ford Global Technologies, LLC - Applicants: Ford Global Technologies, LLC - Inventors: Monty J. Anderson; William Robert Brown; Jogendra Singh Thongam; Joseph Sherman Kimmel; Papiya Bagchi - Web page: https://patentgrep.com/patent/US12222738B2 ## CPC - B60L 3/003: {relating to inverters} - G05D 23/2033: {details of the sensing element} - B60L 3/12: Recording operating variables {; Monitoring of operating variables} - B60L 15/007: {Physical arrangements or structures of drive train converters specially adapted for the propulsion motors of electric vehicles} - B60L 2210/40: DC to AC converters - B60L 2240/525: Temperature of converter or components thereof - Y02T 10/70: Energy storage systems for electromobility, e.g. batteries - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract An electric drive system includes a power electronics module (PEM) having a DC-link capacitor and an inverter. A controller reduces power output of the inverter while a sensed temperature of an inverter power switch, a sensed current of the PEM, such as a sensed ripple current of the DC-link capacitor, and parameter values of the DC-link capacitor are indicative of a predicted temperature of the capacitor being greater than a threshold to maintain capacitor temperature lower than the threshold. The parameter values are obtainable from a thermal model of the DC-link capacitor. The thermal model may be derived from testing a test version of the PEM under different drive cycles in which for each drive cycle a set of information is recorded including a sensed temperature of the inverter power switch test version, a current of the PEM test version, and a sensed temperature of the DC-link capacitor test version. ## Claims ### Claim 1 An electric drive system, comprising: a power electronics module having a DC-link capacitor and an inverter; and a controller configured to reduce power output of the inverter while a temperature of the DC-link capacitor, predicted from a thermal equation given a sensed temperature of a power switch of the inverter, a sensed current of the power electronics module, and values of parameters of the thermal equation obtained from a thermal model of the DC-link capacitor, is greater than a threshold to thereby maintain DC-link capacitor temperature lower than the threshold. ### Claim 2 (depends on 1) The electric drive system of claim 1 wherein: the thermal model of the DC-link capacitor is derived from a test version of the power electronics module being tested under a plurality of drive cycles in which for each drive cycle a set of information is recorded including a sensed temperature of the power switch of the inverter of the test version of the power electronics module, a sensed current of the test version of the power electronics module, and a sensed temperature of the DC-link capacitor of the test version of the power electronics module. ### Claim 3 (depends on 2) The electric drive system of claim 2 wherein: the sensed current of the test version of the power electronics module is a sensed ripple current of the DC-link capacitor of the test version of the power electronics module. ### Claim 4 (depends on 1) The electric drive system of claim 1 wherein: the sensed current of the power electronics module is a sensed ripple current of the DC-link capacitor. ### Claim 5 (depends on 1) The electric drive system of claim 1 wherein: the sensed current of the power electronics module includes either a sensed DC current drawn by the inverter, the sensed DC current drawn by the inverter and a sensed ripple current of the DC-link capacitor, or the sensed DC current drawn by the inverter and a sensed AC current outputted by the inverter. ### Claim 6 (depends on 1) The electric drive system of claim 1 wherein: the controller is further configured to reduce power output of the inverter by de-rating operation of the DC-link capacitor. ### Claim 7 (depends on 1) The electric drive system of claim 1 wherein: the electric drive system is of an electric vehicle and further includes a traction battery and a motor, the DC-link capacitor is disposed between the traction battery and the inverter, and the inverter is configured to convert an input electrical power from the traction battery via the DC-link capacitor into an output electrical power and provide the output electrical power to the motor for propelling the electric vehicle. ### Claim 8 (depends on 1) The electric drive system of claim 1 wherein: the power switch of the inverter is an insulated gate bipolar transistor (IGBT). ### Claim 9 An electric vehicle comprising: an electric drive system including a traction battery, a power electronics module having a DC-link capacitor and an inverter, and a motor, the inverter configured to convert an input electrical power from the traction battery via the DC-link capacitor into an output electrical power and provide the output electrical power to the motor for propelling the electric vehicle; a controller configured to predict a temperature of the DC-link capacitor using a sensed temperature of a power switch of the inverter, a sensed current of the power electronics module, and parameter values obtained from a thermal model of the DC-link capacitor, wherein the thermal model of the DC-link capacitor is derived from a test version of the power electronics module being tested under a plurality of drive cycles in which for each drive cycle a set of information is recorded including a sensed temperature of the power switch of the inverter of the test version of the power electronics module, a sensed current of the test version of the power electronics module, and a sensed temperature of the DC-link capacitor of the test version of the power electronics module; and the controller is further configured to de-rate the electric drive system while the predicted temperature of the DC-link capacitor is greater than a temperature threshold to prevent overheating. ### Claim 10 (depends on 9) The electric vehicle of claim 9 wherein: the sensed current of the test version of the power electronics module is a sensed ripple current of the DC-link capacitor of the test version of the power electronics module; and the parameter values are obtained from the thermal model of the DC-link capacitor by finding which values of a DC-link capacitor temperature thermal equation having variables of power switch temperature, DC-link capacitor ripple current, and the parameters fit the set of information recorded for at least one of the drive cycles. ### Claim 11 (depends on 9) The electric vehicle of claim 9 wherein: the sensed current of the power electronics module is a sensed ripple current of the DC-link capacitor. ### Claim 12 (depends on 9) The electric vehicle of claim 9 wherein: the sensed current of the power electronics module includes either a sensed DC current drawn by the inverter, the sensed DC current drawn by the inverter and a sensed ripple current of the DC-link capacitor, or the sensed DC current drawn by the inverter and a sensed AC current outputted by the inverter. ### Claim 13 A method for an electric drive system including a power electronics module having an inverter and a DC-link capacitor, the method comprising: sensing a temperature of a power switch of the inverter; sensing a current of the power electronics module; obtaining parameter values of the DC-link capacitor from a thermal model of the DC-link capacitor, wherein the thermal model of the DC-link capacitor is derived from a test version of the power electronics module being tested under a plurality of drive cycles in which for each drive cycle a set of information is recorded including a sensed temperature of the power switch of the inverter of the test version of the power electronics module, a sensed current of the test version of the power electronics module, and a sensed temperature of the DC-link capacitor of the test version of the power electronics module; and reducing power output of the inverter while the sensed temperature of the power switch, the sensed current of the power electronics module, and the parameter values of the DC-link capacitor are indicative of a predicted temperature of the DC-link capacitor being greater than a threshold to maintain DC-link capacitor temperature lower than the threshold. ### Claim 14 (depends on 13) The method of claim 13 wherein: the sensed current of the test version of the power electronics module is a sensed ripple current of the DC-link capacitor of the test version of the power electronics module; and obtaining the parameter values of the DC-link capacitor from the thermal model of the DC-link capacitor includes finding which values of a DC-link capacitor temperature thermal equation having variables of power switch temperature, DC-link capacitor ripple current, and the parameters fit the set of information recorded for at least one of the drive cycles. ### Claim 15 (depends on 13) The method of claim 13 wherein: the sensed current of the power electronics module is a sensed ripple current of the DC-link capacitor. ### Claim 16 (depends on 13) The method of claim 13 wherein: the sensed current of the power electronics module includes either a sensed DC current drawn by the inverter, the sensed DC current drawn by the inverter and a sensed ripple current of the DC-link capacitor, or the sensed DC current drawn by the inverter and a sensed AC current outputted by the inverter.