JP2024068123A - Method for regulating the voltage of a high-voltage electrical system of a vehicle as a function of the switching and/or operating conditions of the vehicle - Patents.com - Google Patents

Abstract

A method, an electrical system, a control unit, a program and an electric or hybrid vehicle for regulating the voltage of a high-voltage intermediate circuit of a vehicle, which is an electric or hybrid vehicle with a high-voltage battery separated from the high-voltage intermediate circuit by a switch. The method comprises activating a first DC/DC converter, which electrically connects a constant voltage intermediate circuit to a high-voltage intermediate circuit, and switching on a high-voltage heater, which is connected to the constant voltage intermediate circuit, until the voltage in the constant voltage intermediate circuit and/or the high-voltage intermediate circuit drops to a specified value. If the voltage needs to be regulated to a higher voltage, a second DC/DC converter, which connects a low-voltage electrical system of the vehicle to the constant voltage intermediate circuit, is activated and the first DC/DC converter is activated until the high-voltage intermediate circuit is precharged.

Description

The present invention relates to the supply of voltage to an electric or hybrid vehicle having a high-voltage electrical energy (power) storage system with a high-voltage electrical intermediate circuit and one or more battery banks, and in particular to a method for regulating the voltage of the high-voltage electrical intermediate circuit depending on the switching and/or operating state of the vehicle.

Electric vehicles, i.e. hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and pure electric vehicles (EV), are generally equipped with a high-voltage electrical system. The high-voltage electrical system includes a high-voltage battery, a motor control unit connected to the high-voltage battery, an electric drive motor connected to the motor control unit, and, depending on the type and equipment of the electric vehicle, further high-voltage components such as an air conditioner compressor, a heater, etc. If a DC motor is not used, a frequency converter can convert the DC current provided by the high-voltage battery into AC current, usually three phases, to drive an electric motor designed to operate with AC current.

The high-voltage electrical systems of most currently available electric vehicles are based on architectures with a system voltage of around 400 volts, with vehicles with system voltages of around 800 volts being increasingly common.

The high-voltage battery is connected to the high-voltage components via a high-voltage electrical intermediate circuit, also commonly referred to as the vehicle intermediate circuit. The high-voltage intermediate circuit, which is mainly formed from the capacitance of electronic power circuits intended to limit current or voltage ripple, is separably connected to the battery via a switch, e.g. a contactor, which disconnects the high-voltage intermediate circuit from the high-voltage battery when the vehicle is switched off and also after an accident, so that contact with the high voltage is largely avoided.

High voltages may be present in the high voltage intermediate circuit even after the switch is opened, due to capacitances on the high voltage intermediate circuit, e.g. connected high voltage components, the resulting safety risk is eliminated by a dedicated discharge device, which removes any high voltage remaining in the high voltage intermediate circuit after disconnecting the contactor.

The system voltage of a vehicle can vary in the range of 300 to 1000 volts depending on the state of charge of the batteries and the circuit configuration, for example a series or parallel circuit of several battery banks. In vehicles with a nominal system voltage of 800 volts, there are often two battery banks connected in series with a voltage of 400 volts each. The most common charging stations today have a charging voltage of up to 400 to 500 volts. The series connection of the two battery banks of the vehicle can therefore be disconnected and the battery banks can be charged separately or in parallel by a charging circuit configured for a nominal system voltage of 400 volts via the high-voltage intermediate circuit, for example if a charging device for a system voltage of 800 volts is not available. For this purpose, the high-voltage intermediate circuit must also be discharged after the series circuit has been removed from the dedicated discharge device in order to avoid damaging or destroying the individual battery banks through impermissible overvoltages when they are reconnected to the high-voltage intermediate circuit. This discharge is also carried out by a dedicated discharge device.

When the vehicle is switched on, before the switch connects the high-voltage intermediate circuit to the high-voltage battery, the high-voltage intermediate circuit must be precharged to a voltage that corresponds at least approximately to the voltage of the high-voltage battery. This serves, among other things, to avoid current peaks through the switch in order to comply with its component-dependent current limitations and the associated electromagnetic interference emissions of the switch, in which the safety function is guaranteed. A separate low-power precharge circuit is used to precharge the capacitances present in the high-voltage intermediate circuit to the voltage of the high-voltage battery. In the simplest case, this can be done via a resistor switchably connected to the high-voltage battery.

The dedicated discharge and precharge devices that have always been required are undesirable because they are costly and can also be a source of error.

The problem addressed by this invention is therefore to implement the functionality of a dedicated charging device in an electric or hybrid vehicle by other means.

Description of the invention The aforementioned problem is solved by a method according to claim 1, an electrical system according to claim 4 and a control unit according to claim 6. Advantageous further developments and configurations are specified in the dependent claims.

The first aspect of the invention takes advantage of the finding that heater elements in hybrid or electric vehicles that serve to heat the passenger compartment or control the temperature of a high voltage battery can dissipate power quickly and easily.

According to this first aspect of the invention, a method for regulating the voltage of a high-voltage intermediate circuit of a vehicle, which is an electric or hybrid vehicle having a high-voltage battery separated from the high-voltage intermediate circuit by a switch, comprises the steps of: activating a first DC/DC converter operatively electrically connecting the constant voltage intermediate circuit to the high-voltage intermediate circuit; and switching on a high-voltage heater connected to the constant voltage intermediate circuit until the voltage in the constant voltage intermediate circuit and/or the high-voltage intermediate circuit drops to a specified value. The voltage of the high-voltage intermediate circuit is monitored accordingly by a voltage measuring device. The first DC/DC converter is at least configured to power the constant voltage intermediate circuit from the high-voltage intermediate circuit. The first DC/DC converter may also be configured to power the high-voltage intermediate circuit, and thus the high-voltage battery from the constant voltage intermediate circuit, for example when the constant voltage intermediate circuit is powered from an external voltage source, such as when the electric or hybrid vehicle is electrically connected to a charging station. For example, the first DC/DC converter may be a so-called buck-boost converter, which is capable of stepping down and stepping up an input voltage. The first DC/DC converter is also preferably bidirectionally operable.

As mentioned above, in some cases it may be desirable or necessary to pre-charge the high-voltage intermediate circuit to a voltage corresponding to the voltage of the high-voltage battery. This may also be necessary when switching two battery banks of a high-voltage battery from a series circuit to a parallel circuit or vice versa, as mentioned above, 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 may be performed according to the first aspect described above.

In one embodiment, the voltage reduction can be terminated when a specified value is reached that is significantly greater than the limit value of the voltage range I according to IEC 60449. If the high-voltage heater is switched off (powered off) early enough, or if the off-time is selected such that the voltage remaining in the high-voltage intermediate circuit after switching off corresponds to the specified 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 to a parallel connection of two battery banks of high-voltage batteries, or before the connection of only one battery bank to the high-voltage intermediate circuit.

In a further embodiment, the voltage of the high-voltage intermediate circuit can be lower than the limit of voltage range I according to IEC 60449, for example close to 0 volts. In this configuration, for example, when switching two battery banks of a high-voltage battery from a series to a parallel connection with the aforementioned switch, or before connecting only one battery bank to the high-voltage intermediate circuit, the voltage in the high-voltage intermediate circuit may subsequently need to be increased to a higher value.

Since the voltage of the high-voltage battery varies with its state of charge (SOC), if the high-voltage intermediate circuit is directly connected to the high-voltage battery or to at least one battery bank of the high-voltage battery after a voltage drop, the default value can be derived from the SOC of the high-voltage battery. If the voltage needs to drop below the limit for voltage range I according to IEC 60449, for example when the vehicle is turned off (powered off) or after an accident, a fixed default value can be used.

Thus, in one or more embodiments, the method also includes determining a default value for the voltage of the high-voltage intermediate circuit in response to a vehicle state immediately after the voltage drop or a change in the configuration of the vehicle's electrical system. The term "vehicle state" may, for example, mean a vehicle that is turned off, and a change in the configuration of the vehicle's electrical system may represent a switch from a series connection of two battery banks of the high-voltage battery to a parallel connection, or a connection of only one battery bank to the high-voltage intermediate circuit.

If the voltage regulation requires an increase in the voltage of the high-voltage intermediate circuit, for example when the vehicle is switched on (powered on), when the voltage in the high-voltage intermediate circuit is reduced to a value below the threshold of the voltage range I according to IEC 60449, or when switching two battery banks from a parallel connection to a series connection, a pre-charging of the high-voltage intermediate circuit must be performed. In the vehicle electrical system according to the second aspect of the invention, which is further described below, the pre-charging is performed from the battery of the 12-volt circuit also 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 charging of the high-voltage intermediate circuit is performed from the constant voltage intermediate circuit by the first DC/DC converter. Since a large amount of power is not required for pre-charging, the 12-volt battery, which generally has a low capacitance, is not overloaded.

Thus, one or more embodiments of the method include the steps of operating a second DC/DC converter connecting the vehicle's low voltage electrical system, e.g. a 12 volt current circuit, to the constant voltage intermediate circuit to power the constant voltage intermediate circuit, and operating the first DC/DC converter until the high voltage intermediate circuit is precharged from the constant voltage intermediate circuit to a voltage corresponding to a specified value.

At least during voltage regulation, the control unit monitors the voltages of the high-voltage battery and the high-voltage intermediate circuit. When the voltage difference is less than a predetermined threshold and the high-voltage battery is connected to the high-voltage intermediate circuit, the control unit controls the switch to establish an electrical connection.

In one or more embodiments, the precharging of the high-voltage intermediate circuit is performed by continuously increasing the voltage of the high-voltage intermediate circuit, for example according to a ramp function. As soon as the target value of the voltage of the high-voltage intermediate circuit is reached, the precharging can be terminated, if necessary, after an electrical connection between the high-voltage intermediate circuit and the high-voltage battery has been established.

According to a second aspect of the invention, an electrical system of a vehicle, which is an electric or hybrid vehicle, includes 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 comprises a high-voltage heater powered from the constant voltage intermediate circuit. A control unit is associated with the electrical system for controlling the first and second DC/DC converters and the high-voltage heater. The control unit is configured to control components controlled by the control unit according to the method according to the first aspect of the invention.

In one or more embodiments of the electrical system, at least the first and second DC/DC converters and the high voltage heater are integrated into a power supply unit provided to the vehicle.

The method according to the invention can be implemented in an electronic control unit comprising one or more microprocessors, volatile and non-volatile memories associated with the microprocessors, signal inputs for at least signals representative of the voltage values of the high voltage intermediate circuit and the voltage intermediate circuit, and control outputs for controlling at least one high voltage heater connected to the constant voltage intermediate circuit, a second bidirectional DC/DC converter connected to the constant voltage intermediate circuit and the low voltage battery, and one or more switches for connecting the high voltage intermediate circuit to the high voltage battery. The aforementioned elements are communicatively connected to each other via one or more data lines and/or buses. The non-volatile memory contains computer program commands which, when executed in the volatile memory by the microprocessor, cause the control unit to execute one or more embodiments or further developments of the above-mentioned method.

A computer program product implementing the method according to the invention includes commands which, when executed by a processor of the control circuit, control components of the electrical system of an electric or hybrid vehicle connected to the control outputs and signal inputs of the control unit, to perform one or more configurations or further developments of the method described above.

The computer program product may be stored on a computer-readable medium or data carrier. The medium or data carrier may be physically embodied, for example, as a hard drive, CD, DVD, flash drive, or the like, but may also include a modulated electrical, electromagnetic, or optical signal that may be received by a computer by a corresponding receiver and stored in the computer's memory.

The invention will now be described with reference to the drawings, in which:
2 is an exemplary flow chart of a method according to the present invention; FIG. 2 is an exemplary schematic diagram of an electrical system suitable for implementing the method according to the present invention; FIG. 2 is a schematic block diagram of an exemplary control circuit for implementing the method according to the present invention;

1 shows an exemplary flow chart of a method 100 according to the invention for regulating the voltage of a high-voltage intermediate circuit 202 of a vehicle that is an electric or hybrid vehicle with a high-voltage battery 204 separated from the high-voltage intermediate circuit 202 by a contactor 218. First, in step 102, a default value is determined, for example depending on the vehicle state. Then, in step 104, the first DC/DC converter 206 is enabled and operatively electrically connects the constant voltage intermediate circuit 208 to the high-voltage intermediate circuit 202 and supplies power from the high-voltage intermediate circuit 202 to the constant voltage intermediate circuit 208. In step 106, a high-voltage heater 210 connected to the constant voltage intermediate circuit 208 is switched on. Alternatively, the high-voltage intermediate circuit 202 may be separated from the constant voltage intermediate circuit 208 and only the latter may be discharged by the high-voltage heater 210. In step 108, it is checked whether the default value has been reached. If not, in the "no" branch of step 108, the high voltage heater 210 remains on. If the default value has been reached, in the "yes" branch of step 108, the high voltage heater 210 is turned off in step 110 and in step 112 it is checked whether a new default value exists. If not, in the "no" branch of step 112, the first DC/DC converter 206 is turned off, unless it needs to be further activated for other purposes, and the process is completed. If a new default value exists in the "yes" branch of step 114, the second DC/DC converter 214 is activated in step 116 and supplies power from the low voltage electrical system 212 to the constant voltage intermediate circuit 208. Furthermore, in step 118, the first DC/DC converter 206 is activated and now supplies power from the constant voltage intermediate circuit 208 to the high voltage intermediate circuit 202. In step 120 it is checked whether a new default value has been reached. If not, in the "no" branch of step 120, the first and second DC/DC converters 206, 214 remain on. If the new default value is reached, in the "yes" branch of step 120, in step 122, operation of the second DC/DC converter 214 to supply power to the high voltage intermediate circuit is terminated, operation of the first DC/DC converter 206 to supply power from the constant voltage intermediate circuit 208 to the high voltage intermediate circuit 202 is also terminated, and the process is completed.

Note that although FIG. 1 appears to show sequential operation, operation of the first DC/DC converter and the high voltage heater 210 or the first DC/DC converter 206 and the second DC/DC converter 206 can occur in parallel.

2 shows an exemplary schematic diagram of an electrical system 200 suitable for implementing the method according to the invention. A high-voltage battery 204 is separably connected to the high-voltage intermediate circuit via a switch 218. High-voltage power consumers (not shown in the drawing), such as a drive motor, are connected to the high-voltage intermediate circuit. A capacitance may be present in the high-voltage intermediate circuit, which may maintain a high voltage in the high-voltage intermediate circuit, at least for an extended period of time, even after the switch 218 is opened. The high-voltage intermediate circuit is operably connected bidirectionally to a constant-voltage intermediate circuit 208 via a first DC/DC converter 206. A high-voltage heater 210 and a bidirectional second DC/DC converter 214 are connected to the constant-voltage intermediate circuit 208. The second DC/DC converter 214 operably connects the low-voltage electrical system 212 to the constant-voltage intermediate circuit 208. The constant-voltage intermediate circuit 208 may be externally powered by an AC/DC converter 220. It may also be powered by a charging station, not shown in the drawing. The first and second DC/DC converters 206, 214, the constant voltage intermediate circuit 208, the high voltage heater 210, and the AC/DC converter 220 can be combined into an integrated power supply unit 222.

3 shows a schematic block diagram of an exemplary control unit 300 for implementing the method 100 according to the present invention. The microprocessor 302, the volatile memory 304, the non-volatile memory 306, and the control output 310 or the signal input 308 are communicatively connected to each other via one or more data lines or buses 312. The non-volatile memory 306 includes computer program commands that, when executed in the volatile memory 304 by the microprocessor 302, configure the control unit 300 to operate components of the electric or hybrid vehicle electrical system 200 connected to the control output 310 and the signal input 308 of the control unit 300 to implement one or more embodiments of the method 100 according to the present invention.

100 Method 102 Determine default value 104 Activate first DC/DC converter 106 Switch on high voltage heater 108 Default value reached?
110 Switch off high voltage heater 114 New default value?
116 Activate second DC/DC converter 118 Activate first DC/DC converter 120 New default value reached?
122 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 supply unit 300 Control unit 302 Microprocessor 304 Volatile memory 306 Non-volatile memory 308 Signal input 310 Control output 312 Data line/bus

Claims (9)

A method (100) for regulating a voltage in a high voltage intermediate circuit (202) of a vehicle, which is an electric or hybrid vehicle, comprising a high voltage battery (204) separated from the high voltage intermediate circuit (202) by a switch (218), comprising:
activating (104) a first DC/DC converter (206) electrically connecting a constant voltage intermediate circuit (208) to the high voltage intermediate circuit (202);
and turning on (106) a high voltage heater (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) drops to a specified value. The method (100) of claim 1 further comprising determining (102) a default value for the voltage regulation of the high voltage intermediate circuit (202) in response to a change in the vehicle state or configuration of the vehicle's electrical system (200) immediately following a voltage drop. activating (116) a second DC/DC converter (214) connecting a low voltage electrical system (212) of the vehicle to the constant voltage intermediate circuit (208) for powering the constant voltage intermediate circuit (208);
3. The method (100) of claim 1 or 2, further comprising: operating (118) the first DC/DC converter (206) until the high voltage intermediate circuit (202) is precharged from the constant voltage intermediate circuit (208) to a voltage corresponding to the specified value. A vehicle electrical system (200) that is an electric or hybrid vehicle having 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), a high-voltage heater (210) is powered from the constant voltage intermediate circuit (208) and a low-voltage electrical system (212) is connected to the constant voltage intermediate circuit (208) via a bidirectional second DC/DC converter (214), a control unit (300) is additionally provided for controlling the first DC/DC converter (206) and the second DC/DC converter (214) and the high-voltage heater (210), the control unit (300) being configured to operate components controlled by the control unit (300) according to the method of claim 1. The electrical system (200) of claim 4, wherein at least the first DC/DC converter (206) and the second DC/DC converter (214) and the high voltage heater (210) are integrated into a power supply unit (222) provided on the vehicle side. The system includes one or more microprocessors (302), volatile memories (304) and non-volatile memories (306) associated with the microprocessors, signal inputs (308) for at least signals representative of voltage values of a high-voltage intermediate circuit (202) and a constant-voltage intermediate circuit (208), as well as at least one high-voltage heater (210) connected to the constant-voltage intermediate circuit (208), a second bidirectional DC/DC converter (214) connected to the constant-voltage intermediate circuit (208) and a low-voltage battery (216), and a power supply for connecting the high-voltage intermediate circuit (202) to a high-voltage battery (217). 04), and a control output (310) for controlling one or more switches (218) for connecting the elements to one or more of the switches (218) and the non-volatile memory (306), the non-volatile memory (306) includes computer program commands that, when executed in the volatile memory (304) by the microprocessor (302), configure the control unit (300) to perform the method (100) of claim 1. A computer program product comprising commands, which when executed by a microprocessor of a control unit (300) according to claim 6, cause the control unit to operate components of a vehicle electrical system (200) connected to a control output (310) and a signal input (308) of the control unit (300), the vehicle being an electric or hybrid vehicle, and to perform the method (100) according to claim 1. A computer-readable medium on which the computer program product of claim 7 is stored. An electric or hybrid vehicle having an electrical system (200) according to claim 4 or 5.

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