Search

DE-102025107936-B3 - High-voltage system and a method for its operation

DE102025107936B3DE 102025107936 B3DE102025107936 B3DE 102025107936B3DE-102025107936-B3

Abstract

The invention relates to a method for heating a high-voltage battery (2) of a high-voltage system (1) of an electrically powered vehicle, wherein the high-voltage system (1) comprises an inverter (3) and an intermediate circuit capacitor (Cx) associated with the inverter (3), wherein the inverter (3) has two high-voltage potentials (HV+, HV-) as DC voltage terminals and three phase terminals to which an electric machine (5) is connected, wherein the inverter (3) has a plurality of semiconductor switches (S1 to S6), wherein, using the semiconductor switches (S1 to S6), a resonant resonant circuit, comprising the intermediate circuit capacitor (Cx) and motor inductances (L1, L2, L3) of the electric machine (5) and/or inductances of the inverter (3) and/or a high-voltage cable between the high-voltage battery (2) and the inverter (3), is excited to transfer energy between the high-voltage battery (2) and the to recharge the intermediate circuit capacitor (Cx).

Inventors

  • Urs Boehme
  • Jörg Weigold

Assignees

  • Mercedes-Benz Group AG

Dates

Publication Date
20260513
Application Date
20250303

Claims (7)

  1. Method for heating a high-voltage battery (2) of a high-voltage system (1) of an electrically powered vehicle, wherein the high-voltage system (1) comprises an inverter (3) and an intermediate circuit capacitor (Cx) associated with the inverter (3), wherein the inverter (3) has two high-voltage potentials (HV+, HV-) as DC voltage terminals and three phase terminals to which an electric machine (5) is connected, wherein the inverter (3) has a plurality of semiconductor switches (S1 to S6), and wherein, using the semiconductor switches (S1 to S6), a resonant circuit comprising the intermediate circuit capacitor (Cx) and motor inductances (L1, L2, L3) of the electric machine (5) and/or inductances of the inverter (3) and/or a high-voltage cable between the high-voltage battery (2) and the inverter (3) is excited to transfer energy between the high-voltage battery (2) and the intermediate circuit capacitor. (Cx) to recharge, characterized in that the inverter (3) has three half-bridges, each with an upper semiconductor switch (S1, S3, S5) and a lower semiconductor switch (S2, S4, S6), wherein one or two upper semiconductor switches (S1, S3, S5) are switched on and simultaneously the lower semiconductor switches (S2, S4, S6) of those half-bridges whose associated upper semiconductor switch (S1, S3, S5) is open are switched on, wherein when a predetermined threshold value of a mesh current (I2) in the motor inductors (L1, L2, L3) of the electric machine (5) is reached, the previously closed semiconductor switches (S1 to S6) of the inverter (3) are opened and wherein the mesh current (I2) impressed in the motor inductors (L1, L2, L3) is commutated via body diodes or freewheeling diodes of the other semiconductor switches (S1 to S6).
  2. Procedure according to Claim 1 , characterized in that the resonant circuit is set into oscillation by time-coordinated switching operations of the inverter (3), in which an alternately increasing and decreasing current is generated in the motor inductances (L1 to L3) of the electric machine (5), which leads to a voltage change at the intermediate circuit capacitor (Cx) and a current change in the high-voltage cable.
  3. Procedure according to Claim 1 or 2 , characterized in that a current at at least one of the DC voltage terminals and/or at least one of the phase terminals of the inverter (3) and/or a capacitor voltage (U_Cx) across the intermediate circuit capacitor (Cx) is measured and taken into account for the control of the switching operations of the inverter (3) for oscillation excitation.
  4. Method according to one of the preceding claims, characterized in that when the mesh current (I2) flows through the body diode or freewheeling diode, the respective associated semiconductor switch (S1 to S6) is closed.
  5. High-voltage system (1) for an electrically operated vehicle, wherein the high-voltage system (1) comprises an inverter (3) and an intermediate circuit capacitor (Cx) associated with the inverter (3), wherein the inverter (3) has two high-voltage potentials (HV+, HV-) as DC voltage terminals and three phase terminals to which an electrical a machine (5) is connected, wherein the inverter (3) has a plurality of semiconductor switches (S1 to S6), characterized in that the high-voltage system (1) is configured to carry out the method according to one of the preceding claims.
  6. High-voltage system (1) according to Claim 5 , characterized in that the inverter (3) is designed as a 2-level B6 inverter or as a 3-level inverter.
  7. High-voltage system (1) according to Claim 6 , characterized in that the 3-level inverter has the topology T-Type, NPC, ANPC or Flying-Capacitor.

Description

The invention relates to a high-voltage system for an electrically powered vehicle according to the preamble of claim 5 and a method for operating it according to the preamble of claim 1. Electrically operated vehicles with a high-voltage system and a high-voltage battery, a drive inverter and a DC link capacitor associated with the inverter are known in the prior art. A cold high-voltage battery can only accept a very low charging current. Therefore, it is necessary to heat the battery before or during a charging process. It is known to induce an AC current in a battery cell to heat the cell via the power loss generated at its AC resistance. In this process, a certain amount of charge is transferred to a capacitor, and subsequently the capacitor is discharged back into the battery cell. Furthermore, an impedance heating method via an inverter, a star point tap of the electric machine and a battery center tap is known. In impedance heating, a cold battery is charged and then discharged using an AC current. The charging frequency is greater than 1 Hz, for example, 100 Hz, to prevent charging and discharging processes from occurring within the battery cell chemistry. This avoids battery aging. Waste heat from the charging process is generated directly within the battery cell at the battery's internal resistance. The current waveform (sine wave or PWM) can be adjusted via the inverter. The waste heat from the electric motor and the inverter can also be used to heat the battery via the cooling water. CN 118700899 A This describes a battery heating circuit, a control method, a controller, a power supply system, and electrical devices. The battery heating circuit comprises a resonant circuit, an inverter, and an AC drive motor, wherein the resonant circuit is used for electrical connection to a battery, the inverter is electrically connected to the resonant circuit, and the AC drive motor is electrically connected to the inverter; and the inverter is used to control a series current of the AC drive motor such that it changes along a preset PWM waveform to generate a resonant current for heating the battery between the resonant circuit and the battery. From the DE 10 2022 100 433 A1 A vehicle is known comprising an electric machine, a battery, an inverter coupled between the electric machine and the battery, and a controller programmed to switch the inverter at a switching frequency selected to generate an alternating current for heating the battery, to set a d-axis current of the electric machine to increase battery heating power without changing the switching frequency selected to generate the alternating current for heating the battery, and to set a q-axis current of the electric machine according to the set d-axis current. From the DE 10 2021 126 347 A1 A method for preparing a traction battery for a selected battery operation is known, in which the traction battery is used as an electrical energy storage device for an electric drive of a motor vehicle and an inverter circuit is provided for electrically coupling the traction battery to the electric drive, wherein the inverter circuit is operated in an inverter mode to supply at least one phase of the electric drive with an alternating current as a phase current, in which at least one switching element of the inverter circuit is operated according to a predetermined first clock pattern and/or a predetermined first clock frequency in a first frequency range, wherein a DC link capacitor with a predetermined impedance function is connected between the traction battery and the inverter circuit to filter an alternating component of an intermediate circuit current with which the traction battery is supplied in the inverter mode, wherein an impedance of the DC link capacitor according to the impedance function for the first frequency range lies within a predetermined minimum value range comprising a global minimum, wherein, to prepare the traction battery for the selected battery operation, the inverter circuit is operated in a heating mode when a predetermined operating condition is present. is used to heat the drive battery to a predetermined heating temperature value, wherein in the heating operation the at least one switching element is operated according to a predetermined second clock pattern and/or a predetermined second clock frequency in a second frequency range, and an impedance of the intermediate circuit capacitor according to the impedance function for the second frequency range lies in a predetermined heating value range which is disjoint from the minimum value range. From the DE 10 2022 106 506 A1 A method for controlling a vehicle inverter is known, comprising the steps of determining information about the heating requirement of a battery of the vehicle electrically and thermally coupled to the inverter, controlling the inverter in a first mode in which an electric motor of the vehicle, electrically coupled to an AC connection of the inverter, is driv