Method for operating an HV vehicle electrical system arrangement of an electrically driven vehicle and HV vehicle electrical system arrangement which can be operated by means of the method

Abstract

The invention relates to a method for operating an HV vehicle electrical system arrangement (1) of an electrically driven vehicle (10), the HV vehicle electrical system arrangement (1) having an on-board charger (2) for charging an HV battery (3) at an AC energy source (4) external to the vehicle. According to the invention, in at least one vehicle state in which an inverter (5) of the HV vehicle electrical system arrangement (1) is active and the on-board charger (2) is not being used to charge the HV battery (3) at an AC energy source (4) external to the vehicle, the on-board charger (2) is used as an EMC filter to reduce an interference signal (SS) generated by the inverter (5), by sensing of the interference signal (SS) on a DC connection side of the on-board charger (2) and by control of a power flow of an isolating DC-to-DC converter (6) within the on-board charger (2) such that the interference signal (SS) is compensated (K). The invention further relates to an HV vehicle electrical system arrangement (1) of an electrically driven vehicle (10), which HV vehicle electrical system arrangement can be operated by means of the method.

Description

[0001] Method for operating an HV on-board power supply system of an electrically driven vehicle and HV on-board power supply system operable by means of the method

[0002] The invention relates to a method for operating an HV on-board power supply system of an electrically driven vehicle according to the features of the preamble of claim 1 and an HV on-board power supply system operable by means of the method.

[0003] From the prior art, as described in DE 102019 008 832 A1, a vehicle with a high-voltage electrical system is known. Three installation spaces are provided for components of the high-voltage electrical system. The three installation spaces are arranged one behind the other in the longitudinal axis direction of the vehicle between a front axle and a rear axle of the vehicle. The first installation space is arranged in a central region of the vehicle. The second installation space is arranged in a rear region of the vehicle behind the first installation space. The third installation space is arranged in a front region of the vehicle in front of the first installation space. An AC charging socket is arranged outside the three installation spaces in the region of the second installation space on the vehicle. An isolating DC-DC converter of an electrical on-board charger unit is arranged in the third installation space. An AC EMC filter unit of the electrical on-board charger unit is arranged in the second installation space.Busbars for AC charging by means of the electrical on-board charger unit, for electrical high-voltage DC auxiliary units of the vehicle and for electrical high-voltage drive units of the vehicle run parallel through the first installation space.

[0004] The invention is based on the object of providing a method for operating an HV electrical system of an electrically powered vehicle that is improved over the prior art, and an HV electrical system operable by means of the method. This object is achieved according to the invention by a method for operating an HV electrical system of an electrically powered vehicle with the features of claim 1 and an HV electrical system operable by means of the method with the features of claim 5.

[0005] Advantageous embodiments of the invention are the subject of the subclaims.

[0006] In a method for operating an HV on-board power supply system (HV=high voltage) of an electrically powered vehicle, wherein the HV on-board power supply system has an on-board charger for charging an HV battery from an external vehicle power source (AC=alternating current), according to the invention, in at least one vehicle state in which an inverter of the HV on-board power supply system is active and the on-board charger is not used to charge the HV battery from an external vehicle AC power source, the on-board charger is used as an EMC filter (EMC=electromagnetic compatibility) to reduce an interference signal generated by the inverter, in particular an electromagnetic one, by detecting the interference signal on a DC connection side (DC=direct current) of the on-board charger, in particular by a current measurement and / or voltage measurement and / or by a, in particular fast, communication to the inverter, in particular communication with the inverter,and the power flow of an isolating DC-DC converter within the on-board charger is regulated in such a way that the interference signal is fully or at least partially compensated. The isolating DC-DC converter is also referred to as a galvanically isolated DC-DC converter or an isolating or galvanically isolated DC / DC converter.

[0007] In particular, it is provided that a compensation current is generated for the complete or at least partial compensation of the interference signal and is superimposed on the interference signal generated by the inverter, wherein a bulk capacitor of the on-board charger is used as an energy storage device for generating the compensation current and is charged to a predetermined DC voltage level for this purpose.

[0008] The at least one vehicle state is, for example, a power waste function of the inverter, in particular during charging of the HV battery from a DC energy source external to the vehicle, or a driving operation of the vehicle. The power waste function is, in particular, heat generation by the inverter for heating the vehicle, in particular a passenger compartment of the vehicle, and / or for heating one or more components of the vehicle, i.e., the inverter is operated in the power waste function in such a way that it heats up, and the heat from the inverter can be used for the described heating.

[0009] An inventive HV on-board power system arrangement operable by the described method comprises the inverter and the on-board charger for charging the HV battery from an external AC power source. The on-board charger comprises the DC / DC converter and the bulk capacitor. The DC / DC converter is a bidirectional DC / DC converter, and the clock frequency of the DC / DC converter is several times higher than the clock frequency of the inverter. For example, the clock frequency of the DC / DC converter is 15 to 50 times higher than the clock frequency of the inverter.

[0010] In particular, to comply with HV safety regulations when accessing an AC junction box in the vehicle is required, it is provided, for example, that the maximum voltage of the bulk capacitor is limited to less than 60V DC or less than 30Vrms AC, or that a, in particular additional, galvanically isolating switch, for example a contactor, is provided in a first HV connection to the bulk capacitor, and at least one blocking semiconductor, for example a diode, is provided in a second HV connection to the bulk capacitor. The first HV connection can be a positive potential connection and the second HV connection a negative potential connection, or vice versa.

[0011] The described solution particularly solves the challenges that when the inverter is to be operated in power waste mode during DC charging, i.e. when the power waste function is to be carried out by means of the inverter, more stringent EMC requirements must be met, and / or that interference occurs during charging due to the inverter, which previously, i.e. without the described solution, led to an increased voltage ripple on all HV components, so that all HV components had to be designed for this increased voltage ripple.

[0012] The described solution addresses these challenges, i.e., it meets the more stringent EMC requirements for operating the inverter in power-waste mode during DC charging, and reduces the voltage ripple during ferry operation, eliminating the need to design the HV components for this increased voltage ripple. The described solution, in particular, improves or simplifies the vehicle's HV electrical system layout. In vehicle states in which the inverter is active and the on-board charger is unused for its primary function of charging the HV battery from the vehicle's external AC power source, the on-board charger assumes a new role and, particularly in the case of the inverter's power-waste function or during ferry operation, reduces the interference generated by the inverter by acting as an EMC filter.The disturbance on the DC connection side of the on-board charger is detected, particularly through current and / or voltage measurement and / or through communication with the inverter, particularly fast communication, and the power flow of the isolating DC-DC converter within the on-board charger is regulated in such a way that the inverter disturbance signal is compensated. Since the disturbances are AC quantities, the on-board charger must have an energy storage device. The so-called bulk capacitor contained in the on-board charger is used for this purpose.

[0013] The described solution thus provides, in particular, an active differential-mode filter through the use of the on-board charger. The galvanically isolated DC-DC converter and the bulk capacitor in the on-board charger are used to act as an active differential-mode filter. The compensation current is superimposed on the inverter interference. The bulk capacitor of the on-board charger serves as the energy storage device for generating the compensation current; it is charged to the specified DC voltage level for this purpose.

[0014] The described solution eliminates the need for an additional filter in the inverter to meet EMC requirements for power-waste operation during DC charging. Such an additional filter would require approximately 20 liters of space and weigh approximately 20 kg. This space requirement and weight can thus be eliminated. Furthermore, the described solution eliminates the need for an additional HV heater in the vehicle, as the inverter can be used as a heater during power-waste operation.

[0015] The described solution prevents further propagation of the inverter-induced interference in the vehicle through unwanted coupling paths, as this interference is completely or at least partially compensated in the manner described, i.e., at least reduced, in particular, sufficiently reduced. The described solution also enables the reduction of the voltage ripple requirements of all HV components in the vehicle during ferry operation and / or a reduction of the X-capacitor size in the inverter.

[0016] Embodiments of the invention are explained in more detail below with reference to drawings.

[0017] Showing:

[0018] Fig. 1 schematically shows a DC charging of an HV battery of an electrically powered vehicle from a vehicle-external DC energy source, and

[0019] Fig. 2 shows a schematic diagram of an HV electrical system arrangement.

[0020] Corresponding parts are provided with the same reference numerals in all figures.

[0021] With reference to Figures 1 and 2, a method for operating an HV on-board power supply system 1 of an electrically powered vehicle 10 and an HV on-board power supply system 1 of an electrically powered vehicle 10 operable by the method are described below. The HV on-board power supply system 1 has an on-board charger 2 for charging an HV battery 3 from an AC energy source 4 external to the vehicle.

[0022] In the method, in at least one vehicle state in which an inverter 5 of the HV on-board power system 1 is active and the on-board charger 2 is not used to charge the HV battery 3 from an AC energy source 4 external to the vehicle, the on-board charger 2 is used as an EMC filter to reduce an interference signal SS generated by the inverter 5. The interference signal SS is detected on a DC connection side of the on-board charger 2 by a current measurement, voltage measurement, or by fast communication to the inverter 5, and a power flow of an isolating DC-DC converter 6 within the on-board charger 2 is regulated such that compensation K of the interference signal SS takes place. This is shown schematically as an example in Figure 2.

[0023] In particular, it is provided that a compensation current is generated to compensate K for the interference signal SS and is superimposed on the interference signal SS generated by the inverter 5, as schematically illustrated in Figure 2 by means of current flow diagrams represented by arrows. A bulk capacitor 7 of the on-board charger 2 is used as an energy storage device to generate the compensation current and is charged to a predetermined DC voltage level for this purpose.

[0024] A possible vehicle state for this procedure is a power waste function of the inverter 5 while charging the HV battery 3 from a vehicle-external DC energy source 8, as shown by way of example in Figure 1. Another possible vehicle state for this procedure is ferry operation of the vehicle 10.

[0025] The HV on-board power system arrangement 1, which can be operated by means of the described method, has the inverter 5 and the on-board charger 2 for charging the HV battery 3 from an AC energy source 4 external to the vehicle, wherein the on-board charger 2 has the DC-DC converter 6 and the bulk capacitor 7, wherein the DC-DC converter 6 is a bidirectional DC-DC converter 6, and wherein a clock frequency of the DC-DC converter 6 is many times higher than a clock frequency of the inverter 5. For example, the clock frequency of the DC-DC converter 6 is higher than the clock frequency of the inverter 5 by a factor of 15 to 50.

[0026] In particular, in order to comply with HV safety regulations when accessing an AC connection box of the vehicle 10, it is provided, for example, that a maximum voltage of the bulk capacitor 7 is set to less than 60V DC or less than 30V rms alternating voltage is limited, or that a, in particular additional, galvanically isolating switch 9, for example a contactor, is provided in a first HV connection to the bulk capacitor 7 and at least one blocking semiconductor 11, for example a diode, is provided in a second HV connection to the bulk capacitor 7. The first HV connection can be a positive potential connection and the second HV connection a negative potential connection, or vice versa.

[0027] The solution described is based on the following general challenges:

[0028] To reduce interference in the HV system of a vehicle 10, intermediate circuit capacitors (X-capacitors) and EMC filters are used. They are dimensioned such that the AC component of the pulsing power electronics at the connection terminals is reduced to a required maximum, for example, + / - 8V or compliance with legal and internal EMC emission limits. The so-called intermediate circuit capacitor (or X-capacitor) partially absorbs the low-frequency differential mode components of the pulsating interference generated by the power electronics. The greater the pulsating power or the lower the permissible interference in the HV electrical system, the larger the intermediate circuit capacitor must be dimensioned. For example, in a drive inverter, the X-capacitor occupies the largest installation space within the component and is therefore the crucial component for determining the installation space for the inverter 5 in the vehicle 10.The size of the capacitor must be selected so that the specified AC ripple limits at the terminals of the inverter 5 are not exceeded during operation. These limits are, for example, + / - 8V (as long as the vehicle 10 is not connected to a DC energy source 8, such as a DC charging station!).

[0029] Harmonics of this pulsating fundamental wave are primarily reduced by the EMC filter. The EMC filter typically consists of magnetic components, such as a common-mode choke, which also require a lot of space. For example, several ferrites arranged one behind the other over DC busbars represent the common-mode choke. Furthermore, the EMC filter contains small X-capacitors to reduce higher-frequency and low-power differential-mode interference, and Y-capacitors to reduce common-mode interference. The components that reduce common-mode interference require less space, but are subject to other limiting values, such as a C1 characteristic curve to prevent dangerous discharges when a person comes into physical contact with one of the HV potentials.

[0030] The described solution is also based on the following challenges, especially with regard to the power waste function during DC charging, as shown in Figure 1:

[0031] During this DC charging, i.e., when charging the HV battery 3 from a vehicle-external DC energy source 8, a DC charging port 12 of the vehicle 10 is connected via a charging cable 13 to an operating terminal 14 of the DC energy source 8, which is connected via a connecting cable 15 to power electronics 16 of the DC charging station, i.e., the DC energy source 8. A connection length L of this connection, i.e., from the power electronics 16 to the DC charging port 12 of the vehicle 10, may, for example, be a maximum of 30 meters.

[0032] It is possible to eliminate the need for an electric heater for controlling the temperature of the HV battery 3 or heating the interior of the vehicle 10 by controlling the inverter 5 in such a way that higher currents than necessary flow in an electric drive motor 17 of the vehicle 10. This is referred to as a power waste function. Although driving efficiency is reduced, the losses can be utilized via drive cooling in the form of cooling water heating, for example, for the battery heating or the interior heating. Thus, an HV heater can be eliminated as a component in the vehicle 10.

[0033] The challenge is that in order to fully replace the heater with the power waste function, it is necessary to be able to select the power waste function in all necessary vehicle states. However, DC charging represents the critical state here, since the vehicle 10 is connected to the charging infrastructure via an unshielded DC cable, i.e., charging cable 13. Therefore, more stringent EMC requirements apply here with regard to the interference generated. This results in the specification of a maximum connection length L of 30 meters. However, a vehicle user cannot reliably verify this, because the connection length L is considered to be the distance from the vehicle 10 to the power electronics 16 of the DC charging station. At charging stations, the operating terminal 14 often only represents an information interface for billing and displaying the charging process.The total connection length L then also includes the connecting cable 15, which runs unseen to a more distant external station with the actual power electronics 16 of the DC charging station. The length of this cable cannot be checked by the vehicle user.

[0034] Figure 2 shows a circuit diagram of part of an HV architecture, i.e., at least part of the HV on-board power system 1. Inverter 5 is considered a source of interference, which, through its clocking, generates an AC voltage superimposed on the DC voltage. Typical clocking frequencies are a few kHz, for example, 2 kHz up to typically 10 kHz or 20 kHz.

[0035] Inverter 5 is connected via a supply line to a larger HV power electronics unit, which also houses on-board charger 2. This is also where the supply lines to DC charging port 12 and the connection to the two terminals of HV battery 3 meet. On-board charger 2 is shown here as a single-phase example. In other variants, on-board charger 2 can also be three-phase.

[0036] The on-board charger 2 is only active in the vehicle 10 when power is transferred to the HV electrical system via the AC connection, i.e., during charging of the HV battery 3 from an external AC energy source 4, or when power is transferred from the HV electrical system to the AC connection, also known as bidirectional AC charging. In this case, the vehicle 10 can, for example, supply electrical energy to devices connected to the AC connection or, for example, feed it into an external power grid. In all other vehicle states, the on-board charger 2 is inactive.

[0037] In vehicle states in which inverter 5 is active, on-board charger 2 can thus assume new tasks. In the case of the power waste function, it is possible to reduce the interference generated by inverter 5. The interference, i.e., the interference signal SS, is detected on the DC connection side of on-board charger 2, for example, by current measurement, voltage measurement, or through fast communication with inverter 5, and the power flow of the isolating DC-DC converter 6 within on-board charger 2 is regulated such that compensation K of the interference signal SS of inverter 5 occurs.

[0038] Since the interference is AC, it is necessary for the on-board charger 2 to have an energy storage device. For this purpose, the so-called bulk capacitor 7 contained in the on-board charger 2 is used, which is required to reduce input power ripple of, for example, 50 Hz or 60 Hz during AC charging. It has a size of several hundred pF down to the mF range, for example 700 pF. The isolating DC-DC converter 6 in the on-board charger 2 has a clock frequency that is 15 to 50 times higher than the clock frequency of the inverter 5. This means that the isolating DC-DC converter 6 is able to react with its control to the interference from the inverter 5, i.e. to its interference signal SS, and to set a compensating power flow. The isolating DC-DC converter 6 is designed to be bidirectional for this function.

[0039] The AC power of the interference signal SS of inverter 5 is thus compensated by charging and discharging the bulk capacitor 7. The bulk capacitor 7 is charged to a certain averaged DC voltage level to ensure that the diode of a power factor correction filter 18, in particular a boost power factor correction filter, of the on-board charger 2 is switched off. Furthermore, unipolar electrolytic capacitors are typically used as the bulk capacitor 7.

[0040] The power factor correction filter 18 is also abbreviated as PFC and can also be referred to as power factor correction. Rectification also occurs in the area of ​​the on-board charger 2 designated by reference numeral 18.

[0041] In ferry operation, the isolated DC-DC converter 6 can reduce the voltage ripple in the HV on-board network using the same functionality.

[0042] Because the bulk capacitor 7 is only connected to the secondary side of the isolating DC-DC converter 6, and all other connection options are high-impedance, for example, because the diode of the power factor correction filter 18 is blocking and, if necessary, the switch 9 is open, the pulsating AC voltage cannot be emitted as interference. Therefore, no unwanted propagation of the EMC interference is to be expected.

[0043] For the differential mode compensation, ie the compensation K of the interference signal SS of the inverter 5, the following features are provided in particular:

[0044] The on-board charger 2 is equipped with a sufficiently large internal bulk capacitor 7. The DC-DC converter 6 of the on-board charger 2 is bidirectional. This only requires minimal additional effort if bidirectional charging is not planned, and if bidirectional charging is to be possible, it is already present. The clock frequency of the DC-DC converter 6 of the on-board charger 2 is several times higher than the clock frequency of the inverter 5. To comply with HV safety regulations while maintaining accessibility to the AC junction box, either

[0045] - the maximum voltage of the bulk capacitor 7 is limited to less than 60V DC or less than 30Vrms AC, or

[0046] - the, in particular additional, galvanically isolating switch 9 is provided in one of the HV connections to the bulk capacitor 7 and at least one blocking semiconductor 11 is provided in the other connection branch.

[0047] Differential mode compensation can be used in the power waste function during DC charging to meet the stricter EMC limits. Differential mode compensation can be used during vehicle operation of the vehicle 10 to attenuate the interference generated by the inverter 5, i.e., the interference signal SS generated by it. This makes it possible to either reduce the DC link capacitor in the inverter 5 or to reduce the ripple requirements of the other HV components in the vehicle 10. These ripple requirements relate specifically to compatibility, especially EMC requirements.

[0048] List of reference symbols

[0049] 1 HV electrical system arrangement

[0050] 2 on-board chargers

[0051] 3 HV battery

[0052] 4 AC power source

[0053] 5 inverters

[0054] 6 DC-DC converters

[0055] 7 Bulk capacitor

[0056] 8 DC power source

[0057] 9 switches

[0058] 10 vehicles

[0059] 11 Semiconductors

[0060] 12 DC charging port

[0061] 13 charging cables

[0062] 14 Operating terminal

[0063] 15 connecting line

[0064] 16 Power electronics

[0065] 17 Drive machine

[0066] 18 power factor correction filters

[0067] K Compensation

[0068] L Connection length

[0069] SS jamming signal

Claims

Patent claims 1. A method for operating an HV on-board power supply arrangement (1) of an electrically powered vehicle (10), wherein the HV on-board power supply arrangement (1) has an on-board charger (2) for charging an HV battery (3) from an AC energy source (4) external to the vehicle, characterized in that in at least one vehicle state in which an inverter (5) of the HV on-board power supply arrangement (1) is active and the on-board charger (2) is not used to charge the HV battery (3) from an AC energy source (4) external to the vehicle, the on-board charger (2) is used as an EMC filter for reducing an interference signal (SS) generated by the inverter (5) by detecting the interference signal (SS) on a DC connection side of the on-board charger (2) and regulating a power flow of an isolating DC-DC converter (6) within the on-board charger (2) such that compensation (K) of the interference signal (SS) takes place.

2. Method according to claim 1, characterized in that a compensation current is generated and is superimposed on the interference signal (SS) generated by the inverter (5), wherein a bulk capacitor (7) of the on-board charger (2) is used as an energy store for generating the compensation current and is charged to a predetermined DC voltage level for this purpose.

3. Method according to one of the preceding claims, characterized in that the interference signal (SS) on the DC connection side of the on-board charger (2) is detected by a current measurement and / or voltage measurement and / or by fast communication to the inverter (5).

4. Method according to one of the preceding claims, characterized in that the at least one vehicle state is a Power waste function of the inverter (5) or ferry operation of the vehicle (10).

5. HV on-board power system arrangement (1) of an electrically powered vehicle (10), operable by means of a method according to one of the preceding claims, comprising the inverter (5) and the on-board charger (2) for charging the HV battery (3) from an AC energy source (4) external to the vehicle, wherein the on-board charger (2) has the DC-DC converter (6) and the bulk capacitor (7), wherein the DC-DC converter (6) is a bidirectional DC-DC converter (6), and wherein a clock frequency of the DC-DC converter (6) is many times higher than a clock frequency of the inverter (5).

6. HV vehicle electrical system arrangement (1) according to claim 5, characterized in that - a maximum voltage of the bulk capacitor (7) of less than 60V DC or less than 30V rm s alternating voltage is limited, or - a galvanically isolating switch (9) is provided in a first HV connection to the bulk capacitor (7) and at least one blocking semiconductor (11) is provided in a second HV connection to the bulk capacitor (7).

7. HV vehicle electrical system arrangement (1) according to claim 6, characterized in that the blocking semiconductor (11) is a diode.

8. HV vehicle electrical system arrangement (1) according to claim 6 or 7, characterized in that the galvanically isolating switch (9) is a contactor.

9. HV vehicle electrical system arrangement (1) according to one of claims 5 to 8, characterized in that the clock frequency of the DC-DC converter (6) is higher by a factor of 15 to 50 than the clock frequency of the inverter (5).

Images