Method for centrally discharging a high-voltage intermediate circuit of an electrical system of an electrically powered vehicle

Abstract

The invention relates to a method for the centralized discharge of a high-voltage intermediate circuit of an electrical system of an electrically powered vehicle, wherein an energy flow between a high-voltage circuit (3) and a low-voltage circuit (8) of the electrical system (1) is ensured by an HV-LV DC / DC converter (19). In a method with which a voltage below 300 V can be undercut during discharge, the HV-LV DC / DC converter (19) is used to decouple a low-voltage battery (7) supplying the vehicle's electrical system from the electrical system (1) and subsequently to discharge the high-voltage circuit (3) to a predetermined voltage value, wherein the low-voltage battery (7) is only reconnected to the electrical system (1) once the predetermined voltage value has been undercut.

Description

[0001] The invention relates to a method for centrally discharging a high-voltage intermediate circuit of an electrical system of an electrically driven vehicle, wherein an energy flow between a high-voltage circuit and a low-voltage circuit of the electrical system is ensured by an HV-LV DC / DC converter.

[0002] EP 4 186 733 A1 discloses an active discharge of an electric drive system for electric vehicles. In this system, a high-voltage intermediate circuit comprising a capacitor is discharged by means of an inverter whenever the vehicle is to be switched off. To support the active discharge process, an optional DC / DC converter is provided. This converter is connected between the high-voltage circuit comprising a high-voltage battery and a low-voltage circuit generating an on-board voltage. The HV-LV DC / DC converter is not capable of discharging the capacitor below a predetermined voltage, normally around 300 V.

[0003] The object of the invention is to provide a method for centrally discharging a high-voltage intermediate circuit of an electrical system of an electrically driven vehicle, with which a voltage of less than 300 V can be undercut during discharging.

[0004] The invention is based on the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims. Further features, possible applications, and advantages of the invention will become apparent from the following description and the explanation of exemplary embodiments of the invention, which are illustrated in the figure.

[0005] The problem is solved by the subject matter of patent claim 1.

[0006] In the method explained at the beginning for the central discharging of a high-voltage intermediate circuit of an electrical system of an electrically powered vehicle, wherein an energy flow between a high-voltage circuit and a low-voltage circuit of the electrical system is ensured by an HV-LV DC / DC converter, the HV-LV DC / DC converter is used to decouple a low-voltage battery feeding the vehicle's on-board electrical system from the electrical system and then to discharge the high-voltage range down to a predetermined voltage value, with the low-voltage battery only being reintegrated into the electrical system when the voltage falls below the predetermined voltage value. By switching off the low-voltage voltage of the on-board electrical system, it is possible to reduce the high-voltage voltage during discharging from around 800 V to as little as 60 V. This discharging process takes place exclusively with the help of the HV-LV DC / DC converter inherent in the vehicle's electrical system.Additional components for discharge circuits are eliminated. This makes the high-voltage components more cost-effective while simultaneously extending their service life.

[0007] Advantageously, the high-voltage intermediate circuit includes a capacitor to stabilize the HV DC voltage and limit its fluctuations. For safety reasons, the capacitor must be discharged when the vehicle is shut down, which in this case is done exclusively by the HV-LV DC / DC converter.

[0008] In one embodiment, a control unit monitors the vehicle for a reason for the active discharge process and automatically starts the discharge process upon detection of such a reason. This ensures that the discharge process is reliably initiated even in the event of a malfunction in the vehicle's electrical system. This reliably prevents dangerous situations.

[0009] In one variant, the reason for activating the discharge process is considered to be a shutdown request from the driver, a voltage drop, an open vehicle lock, or an insulation fault. The discharge process is also triggered by the control unit monitoring the vehicle, regardless of driver intervention.

[0010] In one embodiment, the specified voltage value is selected to be higher than the minimum voltage required for safe operation of the high-voltage battery. This ensures that the high-voltage battery can resume operation as quickly as possible after the vehicle's ignition is switched on.

[0011] Further advantages, features, and details will become apparent from the following description, in which at least one exemplary embodiment is described in detail—possibly with reference to the drawings. Described and / or illustrated features may form the subject matter of the invention alone or in any meaningful combination, possibly independently of the claims, and may, in particular, also be the subject of one or more separate applications. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.

[0012] It shows: Fig. 1 a schematic diagram of an electrical system of an electrically powered vehicle for carrying out the method according to the invention.

[0013] In Fig.Figure 1 shows a schematic diagram of an electrical system of an electrically powered vehicle for carrying out the method according to the invention. The electrical system 1 comprises a high-voltage circuit 3 with a high-voltage battery 5 for supplying the vehicle's electric drive with energy, and a low-voltage battery 7 of a low-voltage circuit 8, which, in addition to the drive, supplies all other components of the vehicle with energy. The low-voltage battery 7 can be designed, for example, as a 12V lithium-ion battery. The high-voltage battery 5 is coupled via two high-voltage switches 9, 11 to a high-voltage intermediate circuit 13 comprising a capacitor 12, which is connected to two high-voltage terminals 15, 17 of a DC-DC converter 19. A voltmeter 21 for measuring the applied high-voltage voltage HV is connected between these two high-voltage terminals 15, 17.In addition, the DC / DC converter 19 has two low-voltage terminals 23, 25, each connected to one of the two poles of the low-voltage battery 7. A low-voltage switch 27 is arranged in the connection between the low-voltage terminal 23 and the negative pole of the low-voltage battery 7.

[0014] A high-voltage control unit 29 is connected via a bus system 31 of the vehicle to both the high-voltage battery 5 and the DC / DC converter 19, as well as the low-voltage battery 7. The high-voltage control unit 29 controls the inventive discharging process of the high-voltage intermediate circuit 13 by monitoring the vehicle to determine whether a prerequisite for the discharging process is met. Such a reason occurs, for example, when the vehicle driver turns off the ignition, thereby generating a shutdown request to the electrical system. As a result of this shutdown request, the low-voltage switch 27 in the connection between the low-voltage connection 23 and the negative pole of the low-voltage battery 7 is opened, thereby decoupling the low-voltage battery 7 from the DC / DC converter 19. The DC / DC converter 19 begins discharging the capacitor 12 of the high-voltage intermediate circuit 13.At the same time, the applied high-voltage voltage HV is continuously measured using the voltmeter 21. If the measured high-voltage voltage HV is below a specified value, e.g., 60 V, the DC / DC converter 19 interrupts the discharge process and the low-voltage switch 27 on the low-voltage battery 7 is closed. This reconnects the vehicle's electrical system to the DC / DC converter 19. List of reference symbols 1 electrical system 3 High-voltage circuit 5 high-voltage battery 7 Low-voltage battery 8 Low-voltage circuit 9 high-voltage switches 11 high-voltage switches 12 Capacitor 13 High-voltage intermediate circuit 15 High-voltage connection 17 High-voltage connection 19 DC / DC converters 21 Voltmeter 23 Low-voltage connection 25 Low-voltage connection 27 low-voltage switches 29 High-voltage control unit 31 Bus system QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 4 186 733 A1

[0002]

Claims

[1] Method for centrally discharging a high-voltage intermediate circuit of an electrical system of an electrically driven vehicle, wherein an energy flow between a high-voltage circuit (3) and a low-voltage circuit (8) of the electrical system (1) is ensured by an HV-LV DC / DC converter (19), characterized by that the HV-LV-DC / DC converter (19) is used to decouple a low-voltage battery (7) feeding the vehicle's electrical system from the electrical system (1) and then to discharge the high-voltage circuit (3) to a predetermined voltage value, wherein the low-voltage battery (7) is only reintegrated into the electrical system (1) when the predetermined voltage value is undershot. [2] Method according to claim 1, characterized by that the high-voltage intermediate circuit (13) comprises a capacitor (12) for stabilizing the HV direct voltage and for limiting its fluctuations. [3] Method according to claim 1 or 2, characterized by that a control unit (29) monitors the vehicle for the existence of a reason for the active discharging process and automatically starts the discharging process upon detection of such a reason. [4] Method according to claim 3, characterized by that the reason for activating the discharge process is considered to be a shutdown request by the driver or a voltage drop or an open vehicle lock or an insulation fault. [5] Method according to at least one of the preceding claims, characterized by that the specified voltage value is selected to be greater than the minimum voltage provided for the safe operation of the high-voltage battery (3).

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