High-voltage traction drive

Abstract

The invention relates to a high-voltage traction drive (100) comprising a high-voltage traction battery (110) with a positive and a negative high-voltage terminal (HV+, HV-), a high-voltage traction motor (120), high-voltage power electronics (30) which electrically supplies the high-voltage traction motor (120), wherein the high-voltage power electronics (30) is connected to the two high-voltage terminals (HV+, HV-) of the high-voltage traction battery (110) via a positive and a negative electrical high-voltage line (112, 114), a vehicle ground line (12) which is electrically at the potential of the vehicle ground (GND), an intermediate circuit capacitor arrangement (20) which is electrically arranged between the high-voltage power electronics (30) and the high-voltage traction battery (110), and a pyrotechnic disconnect switch (10) which, upon activation, disconnects the positive electrical High-voltage line (114) disconnects,simultaneously connects its electronic section (114'), which is electrically isolated from the high-voltage traction battery (110), to the negative high-voltage line (112) via an electrical short-circuit connection (16), and simultaneously connects the electronic section (114') of the high-voltage line (114), which is disconnected from the high-voltage traction battery (110), to the vehicle ground line (12) via a ground connection (17).

Description

The invention relates to a high-voltage traction drive for a battery-electric motor vehicle, comprising a high-voltage electric traction motor and a high-voltage traction battery. In the event of a crash, the high-voltage traction battery must be reliably electrically disconnected from the high-voltage traction motor and the high-voltage power electronics that supply the high-voltage traction motor with electrical energy. The high-voltage power electronics are electrically connected to an intermediate circuit capacitor arrangement for interference suppression. For electrical isolation in a crash, a pyrotechnic disconnect switch is provided, which disconnects a positive high-voltage line between a high-voltage terminal of the high-voltage traction battery and the high-voltage power electronics, including the intermediate circuit capacitor arrangement. From DE 10 2023 132 221 A1, a high-voltage traction drive with a high-voltage traction battery and a high-voltage traction motor is known. Furthermore, the arrangement includes a high-voltage auxiliary unit which, in the event of a crash, is short-circuited by a pyrotechnic switch to establish a de-energized state. From DE 10 2016 222 339 A1, an arrangement is known in which the pyrotechnic disconnect switch, in addition to disconnecting the positive high-voltage line, simultaneously establishes an electrical short-circuit connection to a negative high-voltage line connected to a negative high-voltage terminal of the high-voltage traction battery. Due to the short-circuit connection thus created in the event of a crash, the electrical energy or voltage stored in the DC link capacitor arrangement is dissipated in a controlled manner, so that after a maximum of a few seconds, no significant electrical voltage of more than 60 V is present at the DC link capacitor arrangement. However, a potential difference to the vehicle's electrical ground may still exist, which means that a risk of injury remains. From DE 10 2018 201 995 A1, an arrangement with a pyrotechnic disconnect switch is known, which, in the event of activation, disconnects an electrical high-voltage line and connects the disconnected part to the vehicle's electrical ground. To minimize the risk of injury, two pyrotechnic disconnect switches would therefore have to be provided, which is complex and inherently less reliable. In contrast, the object of the invention is to create a high-voltage traction drive with high safety with regard to the risk of electrical injury after a crash event. This problem is solved according to the invention with a high-voltage traction drive having the features of claim 1. The high-voltage traction drive according to the invention comprises a high-voltage traction battery, a high-voltage traction motor, high-voltage power electronics, an intermediate circuit capacitor arrangement, a separate vehicle ground line and a pyrotechnic disconnect switch. The high-voltage traction battery has a system voltage or terminal voltage at its two high-voltage terminals of over 100 V, typically 400 V or 800 V. The positive high-voltage terminal is connected to a positive high-voltage line, and the negative high-voltage terminal of the traction battery is connected to a negative high-voltage line. These two high-voltage lines electrically connect the high-voltage traction battery to the DC link capacitor assembly and the high-voltage power electronics. The high-voltage power electronics are electrically powered by the high-voltage traction battery and generate a corresponding voltage pattern for the electrical supply of the high-voltage traction motor, for example in the form of a three-phase rotating field. Electrically, an intermediate circuit capacitor assembly is provided between the high-voltage power electronics and the high-voltage traction battery. This assembly is connected to the two high-voltage electrical lines and serves primarily for interference suppression. The system voltage of the high-voltage traction battery is typically applied to the intermediate circuit capacitor assembly. Furthermore, a vehicle ground wire is provided, which is electrically at the potential of the vehicle ground. The two high-voltage electrical wires are therefore electrically isolated from the vehicle ground wire, with the vehicle ground preferably representing the negative electrical potential for a low-voltage power supply of the vehicle in question, which, for example, has a nominal voltage of 12 V, 24 V, or 48 V. A pyrotechnic disconnect switch is provided along the positive high-voltage electrical line. In the event of a crash-induced activation, for example, this switch divides the positive high-voltage line into two sections. The pyrotechnic disconnect switch is located between the high-voltage traction battery and the DC link capacitor assembly. When the pyrotechnic disconnect switch is activated and open, the positive high-voltage electrical line is electrically divided into an electronics section isolated from the high-voltage traction battery and a battery-side section that is electrically isolated from the electronics section containing the DC link capacitor assembly and the high-voltage power electronics. When the pyrotechnic disconnect switch is triggered and open, an electrical short circuit simultaneously establishes a connection between the electrically isolated electronic section of the positive high-voltage line and the negative high-voltage line. This short circuit, which only occurs when the pyrotechnic disconnect switch is triggered, rapidly dissipates the electrical energy stored in the DC link capacitor assembly, so that after at most a few seconds, no high voltage exceeding 60 V is present between the disconnected electronic section of the high-voltage line and the negative high-voltage line. When the pyrotechnic disconnect switch is triggered and open, the disconnected electronic section of the positive high-voltage line is electrically connected to the vehicle ground via a ground connection. This equalizes any potential difference that may exist between the vehicle ground on the one hand and the two high-voltage lines or the electronic section of the positive high-voltage line and the negative electrical high-voltage line on the other. This is particularly important if the DC link capacitor arrangement also includes two so-called Y-capacitors, which are electrically connected between the vehicle ground on the one hand and the negative electrical high-voltage line and the positive electrical high-voltage line or its electronic section on the other.Y-capacitors can also store a potentially hazardous electrical voltage, which is dissipated via the ground connection within a maximum of a few seconds. The pyrotechnic disconnect switch according to the invention, after the triggering of a single pyrotechnic charge, ensures the separation or opening of the positive electrical high-voltage line, the closing of the electrical short-circuit connection between the electrically positive electronic section and the negative electrical high-voltage line, and the closing of the ground connection of the electronic section of the high-voltage line with the vehicle ground line. Preferably, the pyrotechnic disconnect switch has a switch arm that is moved by a ignited pyrotechnic charge into a tripping position of the switch arm that is separated from a battery section of the high-voltage line. Particularly preferably, the switch arm is electrically connected to the electronic section of the positive high-voltage line via a pivot joint, both in its rest position and in its tripping position. Particularly preferably, the pivot joint is formed by a material bridge, so that the switch arm remains integrally electrically connected to the electronic section of the positive high-voltage line even in its tripping position. In its activated position, the switch arm is electrically connected to the electronic section of the positive high-voltage line, to a short-circuit contact of the short-circuit connection, and to a ground contact of the ground connection. Thus, via the switch arm in its activated position, the electronic section of the positive high-voltage line is electrically connected to the negative high-voltage line and to the vehicle ground, all of which are ultimately at the same electrical potential. In its unactivated rest position, however, the switch arm is not electrically connected to either the short-circuit connection or the ground connection. These two electrical connections are only established by the switch arm in its activated position. The switch arm is preferably electrically connected in its rest position to the positive high-voltage electrical line via a predetermined disconnect point, for example, a material reduction. When the pyrotechnic charge is triggered, the predetermined disconnect point opens reliably and completely. Preferably, a short-circuit discharge resistor is arranged in the course of the electrical short-circuit connection, which ensures a current limit of the discharge current in order to prevent uncontrolled discharge or overheating of the short-circuit line. Additionally or alternatively, a ground discharge resistor is provided along the ground connection to limit the discharge current through the ground connection. The short-circuit discharge resistor and / or the ground discharge resistor are dimensioned to ensure that the capacitors in the intermediate circuit capacitor arrangement are largely discharged within a few seconds at most. An embodiment of the invention is explained in more detail below with reference to the figure. The figure schematically shows a high-voltage traction drive with a high-voltage traction battery, a high-voltage traction motor, high-voltage power electronics, an intermediate circuit capacitor arrangement, a vehicle ground line, and a pyrotechnic disconnect switch. The figure shows a schematic representation of a high-voltage traction drive 100 for a battery-electric vehicle. The high-voltage traction drive comprises a high-voltage traction battery 110, a three-phase high-voltage traction motor 120, high-voltage power electronics 30, an intermediate circuit capacitor assembly 20, a vehicle ground line 12, and a pyrotechnic disconnect switch 10. The high-voltage traction battery 110 has a nominal voltage of, for example, 400 V or 800 V and is equipped with a positive high-voltage terminal HV+ and a negative high-voltage terminal HV-. The positive high-voltage terminal HV+ is connected to the high-voltage power electronics 30 via a positive electrical high-voltage line 114, while the negative high-voltage terminal HV- is also connected to the high-voltage power electronics 30 via a negative electrical high-voltage line 112. The high-voltage power electronics 30 converts the high-voltage DC voltage of the traction battery 110 into a three-phase rotating field for the electric traction motor 120. The vehicle ground line 12 is electrically at the potential of the vehicle ground GND and is electrically isolated from the high-voltage lines 112 and 114.The vehicle ground (GND) represents the reference potential for a separate low-voltage power supply for the vehicle in question, with a nominal voltage of, for example, 12 V, 24 V or 48 V. The pyrotechnic disconnect switch 10 is arranged along the positive high-voltage electrical line 114 and, upon activation, separates it into two electrically isolated sections. The disconnect switch 10 comprises a pyrotechnic charge 13' of a pyrotechnic trigger 13 and a switch arm 14, which is moved into an activation position 14' by the ignited pyrotechnic charge 13'. Only in this activation position 14' does the switch arm 14' reliably contact both a short-circuit connection contact 16' and a ground connection contact 17'. When the disconnect switch 10 is triggered, the positive high-voltage line 114 is electrically divided into a battery section 114'' and an electronics section 114'. Simultaneously, the electronics section 114' is connected to the negative high-voltage line 112 via the short-circuit contact 16'. A short-circuit discharge resistor 16'' is arranged along the short-circuit connection 16 to ensure controlled discharge. Additionally, when the disconnect switch 10 is triggered, the electronic section 114' of the positive high-voltage line 114 is simultaneously electrically connected to the vehicle ground line 12 via the ground connection contact 17'. A ground discharge resistor 17'' is arranged along the ground connection 17 to ensure safe discharge. The intermediate circuit capacitor arrangement 20 is electrically located between the high-voltage power electronics 30 and the high-voltage traction battery 110. It comprises several capacitors 201, 202, and 203, which serve for interference suppression and electrical energy storage. The intermediate circuit capacitor arrangement 20 essentially consists of a so-called X-capacitor 201, which connects the positive electrical high-voltage line 114, or rather its electronic section 114', to the negative high-voltage line 112; a first Y-capacitor 202, which connects the electronic section 114 of the positive high-voltage line 114 to the vehicle ground line 12; and a second Y-capacitor 203, which connects the negative high-voltage line 112 to the vehicle ground line 12. The high-voltage power electronics 30 supplies the high-voltage traction motor 120 with electrical energy provided by the high-voltage traction battery 110. In normal operation, the switch arm 14 is in its rest position and electrically connects the battery section 114'' of the positive high-voltage line 114 to the battery section 114'' via a closed predetermined disconnect point 142 and an arm joint 140 designed as a film joint. When the pyrotechnic disconnect switch 10 is triggered, the predetermined disconnect point 142 opens completely, and the switch arm 14', rotating about its arm joint 140, establishes the electrical connections to the short-circuit connection 16 and to the ground connection 17 via the contacts 16', 17' it contacts. The figure shows the integration and interaction of the various components of the high-voltage traction drive 100, including the safety mechanisms for electrical isolation and discharge in the event of a crash.

Claims

High-voltage traction drive (100) comprising a high-voltage traction battery (110) with a positive and a negative high-voltage terminal (HV+, HV-), a high-voltage traction motor (120), a high-voltage power electronics unit (30) which electrically supplies the high-voltage traction motor (120), wherein the high-voltage power electronics unit (30) is connected to the two high-voltage terminals (HV+, HV-) of the high-voltage traction battery (110) via a positive and a negative electrical high-voltage line (112, 114), a vehicle ground line (12) which is electrically at the potential of the vehicle ground (GND), an intermediate circuit capacitor assembly (20) which is electrically arranged between the high-voltage power electronics unit (30) and the high-voltage traction battery (110), and a pyrotechnic disconnect switch (10) which, upon activation, disconnects the positive electrical high-voltage line (114) separates,simultaneously connects its electronic section (114'), which is electrically isolated from the high-voltage traction battery (110), to the negative high-voltage line (112) via an electrical short-circuit connection (16), and simultaneously connects the electronic section (114') of the high-voltage line (114), which is disconnected from the high-voltage traction battery (110), to the vehicle ground line (12) via a ground connection (17). High-voltage traction drive (100) according to claim 1, wherein the pyrotechnic disconnect switch (10) has a switch arm (14) which is moved by an ignited pyrotechnic charge (13') into a release position of the switch arm (14') separated from a battery section (114'') of the high-voltage line (114). High-voltage traction drive (100) according to claim 2, wherein the switch arm (14') in its release position is electrically contacted both with the electronic section (114') of the positive high-voltage line (114), with a short-circuit contact (16') of the short-circuit connection (16) and with a ground contact (17') of the ground connection (17). High-voltage traction drive (100) according to one of claims 2 or 3, wherein the switch arm (14, 14') is electrically connected to the electronic section (114') of the positive high-voltage line (114) via an arm joint (140) both in its rest position and in its trigger position. High-voltage traction drive (100) according to claim 4, wherein the switch arm (14) is electrically connected to the battery section (14'') via a predetermined disconnect point (142) in its rest position. High-voltage traction drive (100) according to one of the preceding claims, wherein a short-circuit discharge resistor (16'') is arranged in the course of the short-circuit connection (16). High-voltage traction drive (100) according to one of the preceding claims, wherein a mass discharge resistor (17'') is arranged in the course of the ground connection (17).

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