# US 2026/0061850 A1 · Computer system and method to discharge a dc-link capacitor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2026/0061850 A1 - Document ID: US20260061850A1 - Status: Published application - Kind: A1 - Application number: 19/307,691 - Filed: 2025-08-22 - Published: 2026-03-05 - Earliest claimed: 2024-08-29 - Assignees: Volvo Truck Corporation - Applicants: Volvo Truck Corporation - Inventors: Sebastian Hall; Charlie Jägerhag - Web page: https://patentgrep.com/patent/US20260061850A1 ## CPC - B60L 3/0046: {relating to electric energy storage systems, e.g. batteries or capacitors} - B60L 3/04: Cutting off the power supply under fault conditions (protective devices and circuit arrangements in general H01H; H02H) - B60L 3/003: {relating to inverters} - B60L 3/0061: {relating to electrical machines} - B60L 15/025: {using field orientation; Vector control; Direct Torque Control [DTC]} - B60L 50/51: characterised by AC-motors - H02J 7/345: {using capacitors as storage or buffering devices} - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 7/48: using discharge tubes with control electrode or semiconductor devices with control electrode - H02P 21/22: Current control, e.g. using a current control loop - H02P 27/08: with pulse width modulation - H02P 29/0241: {the fault being an overvoltage} - B60L 2210/30: AC to DC converters - B60L 2210/42: Voltage source inverters - B60L 2240/421: Speed - B60L 2240/429: Current - B60L 2240/70: Interactions with external data bases, e.g. traffic centres - H02J 2105/37: exchanging power with electric vehicles [EV] or with hybrid electric vehicles [HEV] - 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 - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract A computer system has processing circuitry to obtain a discharge request of a DC-link capacitor of an electric drive system; disconnect an electrical machine of the electric drive system; determine a q current for the electrical machine being sufficient to start rotation of the electrical machine; and actively discharge the DC-link capacitor by applying the determined q current to the electrical machine. ## Claims ### Claim 1 A computer system comprising processing circuitry configured to: obtain a discharge request of a DC-link capacitor of an electric drive system; disconnect an electrical machine of the electric drive system; determine a q current for the electrical machine being sufficient to start rotation of the electrical machine; and actively discharge the DC-link capacitor by applying the determined q current to the electrical machine. ### Claim 2 (depends on 1) The computer system of claim 1, wherein the processing circuitry is further configured to: determine the q current for the electrical machine based on a reference rotational speed of the electrical machine. ### Claim 3 (depends on 2) The computer system of claim 2, wherein the processing circuitry is further configured to: set the reference rotational speed to a value being higher than the maximum rotational speed being achievable by the electrical energy stored by the DC-link capacitor. ### Claim 4 (depends on 2) The computer system of claim 2, wherein the processing circuitry is further configured to: set the reference rotational speed to a value being less than the maximum rotational speed being achievable by the electrical energy stored by the DC-link capacitor. ### Claim 5 (depends on 4) The computer system of claim 4, wherein the processing circuitry is further configured to: adjust the q current for the electrical machine such that the rotational speed of the electrical machine corresponds to the reference rotational speed. ### Claim 6 (depends on 1) The computer system of claim 1, wherein the processing circuitry is further configured to: determine a d current for the electrical machine being sufficient to discharge the DC-link capacitor to a safe level threshold; and discharge the DC-link capacitor by applying the determined d current to the electrical machine. ### Claim 7 (depends on 6) The computer system of claim 6, wherein the processing circuitry is further configured to: short circuit the electrical machine when the voltage of the DC-link capacitor has reached the safe level threshold. ### Claim 8 (depends on 1) The computer system of claim 1, wherein the processing circuitry is further configured to: disconnect an energy storage system of the electric drive system from the electrical machine; determine the q current for the electrical machine based on a reference rotational speed of the electrical machine; set the reference rotational speed to a value being higher than the maximum rotational speed being achievable by the electrical energy stored by the DC-link capacitor, or set the reference rotational speed to a value being less than the maximum rotational speed being achievable by the electrical energy stored by the DC-link capacitor, and adjust the q current for the electrical machine such that the rotational speed of the electrical machine corresponds to the reference rotational speed; wherein the processing circuitry is further configured to: determine a d current for the electrical machine being sufficient to discharge the DC-link capacitor to a safe level threshold; and discharge the DC-link capacitor by applying the determined d current to the electrical machine; wherein the processing circuitry is further configured to: short circuit the electrical machine when the voltage of the DC-link capacitor has reached the safe level threshold. ### Claim 9 (depends on 1) A vehicle comprising the computer system of claim 1. ### Claim 10 (depends on 9) The vehicle of claim 9, further comprising: an electric drive system, and a DC-link discharge system configured to passively discharge the DC-link capacitor. ### Claim 11 A computer-implemented method, comprising: obtaining, by processing circuitry of a computer system, a discharge request of a DC-link capacitor of an electric drive system; disconnecting, by the processing circuitry, an electrical machine of the electric drive system; determining, by the processing circuitry, a q current for the electrical machine being sufficient to start rotation of the electrical machine; and actively discharging, by the processing circuitry, the DC-link capacitor by applying the determined q current to the electrical machine. ### Claim 12 (depends on 11) The method of claim 11, further comprising: determining, by the processing circuitry, the q current for the electrical machine based on a reference rotational speed of the electrical machine. ### Claim 13 (depends on 11) The method of claim 11, further comprising: short circuiting, by the processing circuitry, the electrical machine when the voltage of the DC-link capacitor has reached a safe level threshold. ### Claim 14 (depends on 11) A computer program product comprising program code for performing, when executed by the processing circuitry, the method of claim 11. ### Claim 15 (depends on 11) A non-transitory computer-readable storage medium comprising instructions, which when executed by the processing circuitry, cause the processing circuitry to perform the method of claim 11.