Method for adjusting the voltage of a motor vehicle's high-voltage electrical system to the switching and / or operating states of the vehicle.

Abstract

Method (100) for voltage adjustment of a high-voltage intermediate circuit (202) of an electric or hybrid vehicle when a high-voltage battery (204) is disconnected from the high-voltage intermediate circuit (202) by means of a switch (218), comprising: Determining (102) a preset value for the voltage adjustment of the high-voltage intermediate circuit (202) depending on a vehicle state or on a change in the configuration of the electrical system (200) of the vehicle immediately following a voltage drop; Operating (104) a first DC-DC converter (206) which electrically connects a constant-voltage intermediate circuit (208) to the high-voltage intermediate circuit (202); Switching on (106) a high-voltage heating device (210) connected to the constant-voltage intermediate circuit (208) until the voltage in the constant-voltage intermediate circuit (208) and / or the high-voltage intermediate circuit (202) has dropped to the target value, namely check (108) for this purpose.whether the target value is reached, wherein if the target value is not reached, the high-voltage heater (210) remains switched on, and wherein if the target value is reached, the high-voltage heater (210) is switched off and checked (114) whether a new target value is present, then if a new target value is present, operation (116) of a second DC-DC converter (214), which connects a low-voltage vehicle electrical system (212) to the constant-voltage intermediate circuit (208) in order to supply the constant-voltage intermediate circuit (208) with electrical energy, and furthermore, operation (118) of the first DC-DC converter (206), which supplies the high-voltage intermediate circuit (202) from the constant-voltage intermediate circuit (208) with electrical energy until the high-voltage intermediate circuit (202) from the constant-voltage intermediate circuit (208) reaches the target value. The new target value is pre-charged with the corresponding voltage, namely check (120) for this purpose.whether the new setpoint value is reached, whereby if the new setpoint value is not reached, the first and second DC voltage transformers (206, 214) remain switched on, and where if the new setpoint value is reached, the operation of the first and second DC voltage transformers (206, 214) is terminated.

Description

The present invention relates to the power supply of an electric or hybrid vehicle with an electrical high-voltage intermediate circuit and an electrical high-voltage energy storage device comprising one or more battery banks, in particular a method for adjusting the voltage of the electrical high-voltage intermediate circuit to switching and / or operating states of the vehicle. Electric vehicles, i.e., hybrid vehicles (Hybrid Electric Vehicles, HEVs), plug-in hybrid vehicles (PHEVs), and pure electric vehicles (EVs), generally include a high-voltage electrical system. This system comprises a high-voltage battery, a motor controller connected to the battery, and an electric drive motor connected to the motor controller, as well as other high-voltage components that depend on the type and features of the electric vehicle, such as air conditioning compressors, heaters, and the like. If a DC motor is not used, a frequency converter can convert the direct current supplied by the high-voltage battery into, usually, three alternating current phases, which drive an electric motor designed for operation with alternating current. The high-voltage system of most electric cars available today is based on an architecture with a system voltage of approximately 400 volts, although vehicles with a system voltage of around 800 volts are becoming increasingly common. The high-voltage battery is typically connected to the high-voltage electrical components via an electrical high-voltage intermediate circuit, also known as the vehicle intermediate circuit. This intermediate circuit, primarily composed of capacitors in the electronic power circuits designed to limit current and voltage ripple, is connected to the battery via switches, such as contactors. These switches disconnect the high-voltage intermediate circuit from the battery when the vehicle is switched off and also after accidents, thus largely preventing contact with the high voltage. Even after the switches have opened, a high voltage may still be present in the high-voltage intermediate circuit, due to factors such as the capacitance of high-voltage components connected to the circuit. The resulting safety risk is eliminated by a dedicated discharge device that dissipates any residual high voltage remaining in the high-voltage intermediate circuit after the contactors have been disconnected. The vehicle's system voltage can vary between 300 and 1000 volts, depending on the battery's state of charge and the wiring configuration, such as whether multiple battery banks are connected in series or parallel. Vehicles with a nominal system voltage of 800 volts often have two 400-volt battery banks connected in series. Most charging stations currently available have charging voltages up to a maximum of 400-500 volts. Therefore, the series connection of the vehicle's two battery banks can usually be disconnected, and the battery banks can then be charged separately or in parallel via the high-voltage intermediate circuit by a charging circuit designed for a nominal system voltage of 400 volts, for example, if no charging device for an 800-volt system is available.For this purpose, the high-voltage intermediate circuit must also be discharged after the series connection is disconnected from the dedicated discharge device, among other things to prevent impermissible overvoltages from damaging or even destroying the individual battery banks when they are reconnected to the high-voltage intermediate circuit. This discharge is also carried out by the dedicated discharge device. When the vehicle is switched on, the high-voltage intermediate circuit must be pre-charged to a voltage that is at least approximately equal to the voltage of the high-voltage battery before the switches can connect the high-voltage intermediate circuit to the high-voltage battery. This serves, among other things, to prevent current spikes through the switches, to ensure compliance with the component-dependent current limits of the switches, and also to minimize associated electromagnetic interference. Separate, low-power pre-charging circuits are used for this purpose, which pre-charge the capacitors present in the high-voltage intermediate circuit to the voltage of the high-voltage battery. In the simplest case, this can be achieved via a resistor connected to the high-voltage battery via a switch. WO 2015 / 181 660 A1 discloses an electrical system of a fuel cell vehicle comprising a first DC-DC converter connected to an electrical energy storage device via a contactor, and a second DC-DC converter connected to a fuel cell unit via a contactor. The two DC-DC converters are electrically connected in series. DE 10 2020 202 468 A1 discloses a method for operating an on-board network of an electric vehicle with a pre-charging phase for pre-charging an intermediate circuit by means of a DC voltage converter from a low-voltage network. DE 10 2014 201 440 A1 discloses further state of the art. The dedicated unloading and preloading devices, hereinafter referred to as transfer devices, which have always been required until now, are undesirable not only because of the costs they incur, but also because of the additional potential source of error they create. It is therefore an object of the present invention to implement the function of a dedicated charging device in an electric or hybrid vehicle by other means. The aforementioned problem is solved by the method specified in claim 1, the electrical system specified in claim 2, and the control unit specified in claim 4. Advantageous further developments and embodiments are specified in the dependent claims. A first aspect of the invention utilizes the knowledge that heating elements present in hybrid or electric vehicles, which serve to heat the passenger compartment or to regulate the temperature of the high-voltage battery, can consume electrical energy quickly and easily. According to this first aspect of the invention, a method for adjusting the voltage of a high-voltage intermediate circuit of an electric or hybrid vehicle, when the high-voltage battery is disconnected from the intermediate circuit by means of a switch, comprises operating a first DC-DC converter, which electrically connects a constant-voltage intermediate circuit to the high-voltage intermediate circuit, and switching on a high-voltage heating device connected to the constant-voltage intermediate circuit until the voltage in the constant-voltage intermediate circuit and / or in the high-voltage intermediate circuit has dropped to a predetermined value. The voltage of the high-voltage intermediate circuit is monitored accordingly by means of a voltmeter. The first DC-DC converter is at least configured to supply the constant-voltage intermediate circuit with electrical energy from the high-voltage intermediate circuit.The first DC-DC converter can also be configured to supply the high-voltage intermediate circuit, and thus the high-voltage battery, with electrical energy from the constant-voltage intermediate circuit, for example, when the constant-voltage intermediate circuit is supplied with electrical energy from an external voltage source, such as when the electric or hybrid vehicle is electrically connected to a charging station. The first DC-DC converter can, for example, be a so-called buck-boost converter, which can both step down and step up an input voltage. The first DC-DC converter is also preferably bidirectional. As described at the outset, in certain cases it may be desirable or necessary to pre-charge the high-voltage intermediate circuit to a voltage closely corresponding to that of the high-voltage battery. This may also be desirable or necessary, as also described at the outset, when switching two battery banks of a high-voltage battery from a series connection to a parallel connection and vice versa, before the high-voltage battery is electrically connected to the high-voltage intermediate circuit. In particular, when switching two battery banks from a series connection to a parallel connection, a voltage reduction of the high-voltage intermediate circuit and the constant-voltage intermediate circuit is first required, which can be carried out according to the first aspect described above. If voltage adjustment requires an increase in the voltage in the high-voltage intermediate circuit, for example, after the vehicle is switched on, after the voltage of the high-voltage intermediate circuit has dropped below the limit value for voltage range I according to IEC 60449, or when switching two battery banks from a parallel connection to a series connection, the high-voltage intermediate circuit must be pre-charged. In an electrical system of a vehicle described below according to a second aspect of the invention, the pre-charging is carried out from the battery of a 12-volt circuit already present in the vehicle. For this purpose, the 12-volt battery is connected to the constant-voltage intermediate circuit via a bidirectional second DC-DC converter, and the pre-charging of the high-voltage intermediate circuit is carried out from the constant-voltage intermediate circuit by means of the first DC-DC converter.Since pre-charging does not require a large amount of energy, the 12-volt battery, which usually has a low capacity, is not unduly stressed. Accordingly, the method according to the invention also includes operating a second DC-DC converter, which connects a low-voltage vehicle electrical system, e.g. a 12-volt circuit, to the constant-voltage intermediate circuit and, in order to supply the constant-voltage intermediate circuit with electrical energy, operating the first DC-DC converter until the high-voltage intermediate circuit from the constant-voltage intermediate circuit is pre-charged to a voltage corresponding to the predetermined value. In one configuration, the voltage reduction can be terminated upon reaching a predetermined value, which is significantly higher than the limit for voltage range I according to IEC 60449. If the high-voltage heater is switched off sufficiently quickly, or if the switch-off time is chosen such that the voltage remaining in the high-voltage intermediate circuit after switch-off corresponds to the predetermined value, a subsequent adjustment to a higher voltage level is not necessarily required. This configuration can be used, for example, when switching from a series connection of two high-voltage battery banks to a parallel connection, or before connecting only one battery bank to the high-voltage intermediate circuit. In another configuration, the voltage in the high-voltage intermediate circuit can be reduced below the limit value for voltage range I according to IEC 60449, e.g., to close to 0 volts. With this configuration, it may be necessary to subsequently raise the voltage in the high-voltage intermediate circuit back to a higher value, for example, during the aforementioned switch from a series connection of two high-voltage battery banks to a parallel connection, or before connecting only one battery bank to the high-voltage intermediate circuit. Since the voltage of the high-voltage battery fluctuates with its state of charge (SOC), if the high-voltage intermediate circuit is to be connected directly to the high-voltage battery, or at least to one of its battery banks, following a voltage reduction, the setpoint value can be derived from the high-voltage battery's SOC. If the voltage needs to be reduced below the limit for voltage range I according to IEC 60449, for example, when the vehicle is switched off or after an accident, a fixed setpoint value can be used. Accordingly, the method according to the invention also includes determining a target value for the voltage of the high-voltage intermediate circuit as a function of a vehicle state or a change in the configuration of the vehicle's electrical system immediately following a voltage drop. The term "vehicle state" can, for example, refer to a vehicle that is switched off, and the change in the configuration of the vehicle's electrical system can refer to a switch from a series connection of two high-voltage battery banks to a parallel connection, or to the connection of only one battery bank to the high-voltage intermediate circuit. At least during voltage adjustment, a control unit monitors the voltage in the high-voltage battery and the high-voltage intermediate circuit. As soon as the voltage difference is less than a predefined threshold, and the high-voltage battery is to be connected to the high-voltage intermediate circuit, the control unit activates the contactor(s) accordingly to establish the electrical connection. In one or more configurations, the high-voltage intermediate circuit is pre-charged by continuously increasing the voltage in the high-voltage intermediate circuit, for example, following a ramp function. Once the target voltage value of the high-voltage intermediate circuit is reached, and possibly after the electrical connection between the high-voltage intermediate circuit and the high-voltage battery has been established, the pre-charging process can be stopped. According to a second aspect of the invention, an electrical system of an electric or hybrid vehicle comprises a high-voltage battery switchably connected to a high-voltage intermediate circuit and a constant-voltage intermediate circuit connected to the high-voltage intermediate circuit via a bidirectional first DC-DC converter. The electrical system also includes a high-voltage heater supplied with electrical energy by the constant-voltage intermediate circuit. A control unit is associated with the electrical system for controlling the first and second DC-DC converters as well as the high-voltage heater. The control unit is configured to control the components controlled by the control unit in accordance with a method according to the first aspect of the invention. In one or more configurations of the electrical system, at least the first and second DC voltage converters and the high-voltage heating unit are integrated into a power unit provided by the vehicle. The method according to the invention can be implemented in an electronic control unit comprising one or more microprocessors, associated volatile and non-volatile memory, signal inputs representing at least voltage values ​​of a high-voltage intermediate circuit and a constant-voltage intermediate circuit, as well as control outputs for controlling at least one high-voltage heating device connected to the constant-voltage intermediate circuit, one bidirectional DC-DC converter connected to the constant-voltage intermediate circuit and a low-voltage battery, and one or more contactors for connecting the high-voltage intermediate circuit to a high-voltage battery. The aforementioned elements are communicatively interconnected via one or more data lines and / or buses.The non-volatile memory contains computer program instructions which, when executed by the microprocessor in the volatile memory, configure the control unit to perform one or more iterations or further developments of the procedure described above. A computer program product implementing the method according to the invention contains instructions which, when executed by a processor of a control circuit, cause the latter to control components of a power supply of an electric or hybrid vehicle connected to control outputs and signal inputs of the control circuit in order to carry out one or more embodiments or further developments of the method described above. The computer program product can be stored on a computer-readable medium or data carrier. The medium or data carrier can be physically embodied, e.g., as a hard drive, CD, DVD, flash memory, or the like; however, the medium or data carrier can also comprise a modulated electrical, electromagnetic, or optical signal that can be received by a computer using a suitable receiver and stored in the computer's memory. The invention is described below with reference to the drawing. In the drawing, Fig. 1 shows an exemplary flowchart of a method according to the invention, Fig. 2 shows an exemplary schematic representation of an electrical system according to the invention suitable for carrying out the method according to the invention, and Fig. 3 shows a schematic block diagram of an exemplary control circuit for carrying out the method according to the invention. Fig. 1 shows an exemplary flowchart of a method 100 according to the invention for voltage adjustment of a high-voltage intermediate circuit 202 of an electric or hybrid vehicle when a high-voltage battery 204 is disconnected from the high-voltage intermediate circuit 202 by means of a switch 218. First, in step 102, a setpoint value is determined, e.g., depending on a vehicle state. Subsequently, in step 104, a first DC-DC converter 206 is operated, which electrically connects a constant-voltage intermediate circuit 208 to the high-voltage intermediate circuit 202 and transfers electrical energy from the high-voltage intermediate circuit 202 to the constant-voltage intermediate circuit 208. In step 106, a high-voltage heating device 210 connected to the constant-voltage intermediate circuit 208 is switched on. Alternatively, the high-voltage intermediate circuit 202 can be separated from the constant-voltage intermediate circuit 208, and only the latter can be discharged by the high-voltage heating device 210.In step 108, it is checked whether the target value has been reached. If not, the "no" branch of step 108 means the high-voltage heater 210 remains switched on. If the target value has been reached, the "yes" branch of step 108 means the high-voltage heater 210 is switched off in step 110, and in step 112 it is checked whether a new target value exists. If not, the "no" branch of step 112 means the first DC-DC converter 206 can also be switched off, provided it does not need to be operated for other purposes, and the procedure is terminated. If a new target value exists, the "yes" branch of step 114 means a second DC-DC converter 214 is operated in step 116, which supplies the constant voltage intermediate circuit 208 with electrical energy from a low-voltage electrical system 212.Furthermore, in step 118, the first DC-DC converter 206 is operated, which now supplies the high-voltage intermediate circuit 202 with electrical energy from the constant-voltage intermediate circuit 208. In step 120, it is checked whether the new setpoint value has been reached. If not, the "no" branch of step 120, the first and second DC-DC converters 206 and 214 remain switched on. If the new setpoint value has been reached, the "yes" branch of step 120, in step 122, the operation of the second DC-DC converter 214 for supplying the high-voltage intermediate circuit 202 with electrical energy is stopped, and the operation of the first DC-DC converter 206 for supplying the high-voltage intermediate circuit 202 with electrical energy from the constant-voltage intermediate circuit 208 is also stopped, and the procedure is completed. It should be noted that the operation of the first DC-DC converter and the high-voltage heater 210 or of the first 206 and the second 206 DC-DC converter can be carried out in parallel, even though the representation in the figure seems to suggest sequential operation. Fig. 2 shows an exemplary schematic representation of an electrical system 200 according to the invention, suitable for carrying out the method according to the invention. A high-voltage battery 204 is disconnectably connected to a high-voltage intermediate circuit via switches 218. High-voltage electrical loads, not shown in the figure, are connected to the high-voltage intermediate circuit 202, e.g., a drive motor and the like. Capacitors may be present in the high-voltage intermediate circuit 202 which can maintain the high voltage in the high-voltage intermediate circuit 202 for at least a longer period of time, even after the switches 218 are opened. The high-voltage intermediate circuit is bidirectionally connected to a constant-voltage intermediate circuit 208 via a first DC-DC converter 206. A high-voltage heating device 210 and a second bidirectional DC-DC converter 214 are connected to the constant-voltage intermediate circuit 208.The second DC-DC converter 214 connects a low-voltage electrical system 212 to the constant-voltage intermediate circuit 208. The constant-voltage intermediate circuit 208 can be supplied with electrical energy externally by an AC / DC converter 220, e.g., by a charging station (not shown in the figure). The first and second DC-DC converters 206, 214, the constant-voltage intermediate circuit 208, the high-voltage heating device 210, and the AC / DC converter 220 can be combined in an integrated power unit 222. Fig. 3 shows a schematic block diagram of an exemplary control unit 300 for carrying out the method 100 according to the invention. A microprocessor 302, volatile memory 304, non-volatile memory 306, and control outputs 310 or signal inputs 308 are communicatively connected to one or more data lines or buses 312. The non-volatile memory 306 contains computer program instructions which, when executed by the microprocessor 302 in the volatile memory 304, configure the control unit 300 to control components of an electrical system 200 of an electric or hybrid vehicle connected to control outputs 310 and signal inputs 308 of the control unit 300 for carrying out one or more embodiments of the method 100 according to the invention. REFERENCE MARK LIST 100 Procedure 102 Determine setpoint 104 Operate first DC-DC converter 106 Switch on high-voltage heater 108 Setpoint reached? 110 Switch off high-voltage heater 114 New setpoint? 116 Operate second DC-DC converter 118 Operate first DC-DC converter 120 New setpoint reached? 122 End operation of the first and second DC-DC converters 200 Electrical system 202 High-voltage intermediate circuit 204 High-voltage battery 206 First DC-DC converter 208 Constant voltage intermediate circuit 210 High-voltage heater 212 Low-voltage electrical system 214 Second DC-DC converter 218 Switch / contactor 220 AC / DC converter 222 Integrated power unit 300 Control unit 302 Microprocessor 304 Volatile memory 306 Non-volatile memory 308 Signal inputs 310 Control outputs 312 Data lines / buses

Claims

Method (100) for voltage adjustment of a high-voltage intermediate circuit (202) of an electric or hybrid vehicle when a high-voltage battery (204) is disconnected from the high-voltage intermediate circuit (202) by means of a switch (218), comprising: Determining (102) a preset value for the voltage adjustment of the high-voltage intermediate circuit (202) depending on a vehicle state or on a change in the configuration of the electrical system (200) of the vehicle immediately following a voltage drop; Operating (104) a first DC-DC converter (206) which electrically connects a constant-voltage intermediate circuit (208) to the high-voltage intermediate circuit (202); Switching on (106) a high-voltage heating device (210) connected to the constant-voltage intermediate circuit (208) until the voltage in the constant-voltage intermediate circuit (208) and / or the high-voltage intermediate circuit (202) has dropped to the target value, namely check (108) for this purpose.whether the target value is reached, wherein if the target value is not reached, the high-voltage heater (210) remains switched on, and wherein if the target value is reached, the high-voltage heater (210) is switched off and checked (114) whether a new target value is present, then if a new target value is present, operation (116) of a second DC-DC converter (214), which connects a low-voltage vehicle electrical system (212) to the constant-voltage intermediate circuit (208) in order to supply the constant-voltage intermediate circuit (208) with electrical energy, and furthermore, operation (118) of the first DC-DC converter (206), which supplies the high-voltage intermediate circuit (202) from the constant-voltage intermediate circuit (208) with electrical energy until the high-voltage intermediate circuit (202) from the constant-voltage intermediate circuit (208) reaches the target value. The new target value is pre-charged with the corresponding voltage, namely check (120) for this purpose.whether the new setpoint value is reached, whereby if the new setpoint value is not reached, the first and second DC voltage transformers (206, 214) remain switched on, and where if the new setpoint value is reached, the operation of the first and second DC voltage transformers (206, 214) is terminated. Electrical system (200) of an electric or hybrid vehicle comprising a high-voltage battery (204) switchably connected to a high-voltage intermediate circuit (202) and a constant-voltage intermediate circuit (208) connected to the high-voltage intermediate circuit (202) via a bidirectional first DC-DC converter (206), wherein a high-voltage heater (210) is supplied with electrical energy by the constant-voltage intermediate circuit (208), and wherein a low-voltage electrical system (212) is connected to the constant-voltage intermediate circuit (208) via a bidirectional second DC-DC converter (214), wherein a control unit (300) is also provided for controlling the first and second DC-DC converters (206, 214) as well as the high-voltage heater (210), and wherein the control unit (300) is configured to control the components controlled by the control unit (300) in to target conformity with a method according to claim 1. Electrical system (200) according to claim 2, wherein at least the first (206) and the second (214) DC voltage converter and the high-voltage heater (210) are integrated in a vehicle-side power unit (222). Control unit (300) comprising one or more microprocessors (302), associated volatile (304) and non-volatile (306) memory, signal inputs (308) for signals representing at least voltage values ​​of a high-voltage intermediate circuit (202) and a constant-voltage intermediate circuit (208), and control outputs (310) for controlling at least one high-voltage heater (210) connected to the constant-voltage intermediate circuit (208), one second bidirectional DC-DC converter (214) connected to the constant-voltage intermediate circuit (208) and a low-voltage battery (216), and one or more switches (218) for connecting the high-voltage intermediate circuit (202) to a high-voltage battery (204), wherein the aforementioned elements are communicatively interconnected via one or more data lines and / or buses (312), and wherein the non-volatile memory (306) Computer program instructions contain whichwhen executed by the microprocessor (302) in the volatile memory (304), configure the control unit (300) to execute a method (100) according to claim 1. Computer program product comprising instructions which, when the program is executed by a processor of a control unit (300) according to claim 4, cause the latter to control components of an electrical system (200) of an electric or hybrid vehicle connected with control outputs (310) and signal inputs (308) of the control unit (300) for carrying out the method (100) according to one of claims 1 or 2. Computer-readable medium on which the computer program product according to claim 5 is stored. Electric or hybrid vehicle with an electric system (200) according to claim 2 or 3 .

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