Power supply unit for an electric vehicle and method for operating a power supply unit

Abstract

A power supply unit (8) for providing electrical energy to a drive unit (4) of an electric vehicle. The power supply unit (8) includes a DC-DC converter (2) and a battery having a battery voltage. The DC-DC converter (2) is arranged or can be switched to provide a drive DC link voltage to the drive unit (4) via a DC link (3). The voltage ratio between the battery voltage and the drive DC link voltage can be set by the DC-DC converter (2). The DC-DC converter (2) is designed for operation where the drive DC link voltage is higher than the battery voltage. The DC-DC converter (2) may be a boost converter and / or is designed for bidirectional energy flow.

Description

Technical Field

[0001] This invention relates to the field of drive systems for electric vehicles, and more particularly to a power supply unit for an electric vehicle and a method for operating the power supply unit as described in the preamble of each independent patent claim. Background Technology

[0002] Battery-powered electric vehicles, such as those using lithium-ion batteries, have a battery voltage that depends on the battery design and, generally also, the state of charge (SOC) of individual cells. The maximum power achievable by electric drive in an electric vehicle depends on the battery voltage. This applies to all cases where high-voltage batteries are used for traction drive, that is, also to vehicles using fuel cells, since smaller lithium-ion cells are typically used as buffers in high-voltage circuits. Therefore, the maximum power specified for the drive, that is, the power that the drive can reliably provide, is based on a relatively low SOC, i.e., a relatively low battery voltage, such as 20%. This results in the drive being used only within a limited range and / or with low efficiency, depending on the operating point and SOC. Summary of the Invention

[0003] Therefore, the object of the present invention is to provide a power supply unit for electric vehicles and a method for operating a power supply unit of the above type, which allows for improved utilization of the drive, particularly the drive motor.

[0004] These objectives are achieved through a power supply unit for an electric vehicle having the features of the corresponding independent patent claims, and a method for operating the power supply unit.

[0005] The power supply unit is used to provide electrical energy to the drive unit of an electric vehicle. In this article, the situation is as follows:

[0006] • The power supply unit includes a DC-DC converter and a battery with battery voltage, wherein:

[0007] • The DC-DC converter is arranged or switchable to provide drive DC link voltage to the drive unit via the DC link, and

[0008] • The voltage ratio between the battery voltage and the drive DC link voltage can be set via a DC-DC converter;

[0009] • DC-DC converters are designed to drive DC link voltages higher than battery voltages, specifically, at least as boost converters, and

[0010] • DC-DC converters are designed for bidirectional energy flow, specifically, at least as boost converters or boost-buck converters.

[0011] Therefore, the drive unit can operate at a voltage independent of the battery voltage. Consequently, depending on the situation, the drive unit can thus operate with higher power and / or improved efficiency than without a DC-DC converter.

[0012] As a result, the drive unit can also operate with higher power and / or higher torque than in the case without a DC-DC converter, especially at a higher speed range.

[0013] Therefore, the above advantages can be achieved even under generator operation conditions of the drive unit (where energy is fed into the battery).

[0014] In one embodiment, in addition to the battery, there is a fuel cell that can provide electrical power to the vehicle during driving operation and can be arranged to feed power to a DC link for this purpose.

[0015] In one embodiment, the DC-DC converter is also designed to drive operation where the DC link voltage is lower than the battery voltage.

[0016] Therefore, under low-speed conditions of the drive unit, the DC link voltage can be adjusted to the corresponding reduced induced voltage of the drive unit. In this way, the electrical losses of the drive unit can be reduced.

[0017] In one embodiment, the power supply unit includes a drive closed-loop control device that controls the DC-DC converter to set the drive DC link voltage according to the operating point of the drive unit.

[0018] Therefore, the drive closed-loop control device can be designed, for example, to detect the current operating state of the drive system and generate a setpoint for the drive DC link voltage accordingly, and control the DC-DC converter such that the drive DC link voltage is closed-loop controlled to the setpoint. In this document, the drive closed-loop control device may include feedforward control, for example, based on the current obtained by the drive unit from the DC link, and / or based on the power consumed by at least one motor or the power required by the motor.

[0019] In this embodiment, the DC-DC converter is arranged, or switchable, to be connected between the battery and the charging terminal. Specifically, this can be achieved via a battery disconnect unit.

[0020] Thus, the power supply unit can change from the drive operation state (where the power supply unit switches to be connected to the drive unit) to the charging operation state (where the power supply unit switches to be connected to the charging station via the charging terminal).

[0021] In one embodiment, the DC-DC converter is designed to charge the battery at a charging DC link voltage higher than the battery voltage. To this end, the power supply unit may include a charging closed-loop control device that controls the DC-DC converter to set the charging DC link voltage to a maximum charging voltage, which may be set by the charging station.

[0022] Therefore, the maximum power corresponding to the charging station's maximum charging voltage and maximum charging current can be obtained, as the power is not limited by the power supply unit itself. In this paper, the charging power is not limited by the battery voltage, which differs from the case without a DC-DC converter.

[0023] The power of a fast charging station used for charging electric vehicles is limited by the maximum voltage U of the charging station. ChargeMax and maximum current I ChargeMax The charging power achievable by an electric vehicle is limited by the maximum current of the charging station when the battery is directly connected to it. The charging power is U. Batt *I ChargeMax And therefore depends on the current battery voltage U. Batt Since batteries can typically be charged at high power even under low state of charge conditions, existing technologies may not be able to achieve the fastest possible charging speed. Performance enhancers can eliminate the dependence of the maximum achievable charging power on battery voltage. Furthermore, it is possible to achieve charging speeds greater than U... Batt *I ChargeMax The maximum power. The charging power is limited by the maximum power of the charging station, and is therefore U. ChargeMax *I ChargeMax The charging voltage and charging current can be set via communication between the vehicle or power supply unit and the charging station.

[0024] In one embodiment, the DC-DC converter is also designed to charge the battery at a charging DC link voltage lower than the battery voltage. Similarly, in this case, the power supply unit may include a charging closed-loop control device that controls the DC-DC converter to set the charging DC link voltage to a maximum charging voltage, which may be set by the charging station.

[0025] Therefore, the power supply unit can be charged even at charging stations where the maximum charging voltage is lower than the maximum battery voltage. This eliminates the need to convert the battery topology to half voltage as in existing technologies, or to double the charging voltage using existing charging boosters. The corresponding maximum possible charging power can be transmitted via the charging DC link voltage, which can be adjusted according to the maximum possible charging voltage of the charging station.

[0026] For example, an 800V battery system can also be charged at a charging station with a 400V battery system. This feature is advantageous if vehicles with 800V battery systems are to be sold globally, as charging stations designed for such high charging voltages are not available in all parts of the world. According to existing technology, this is achieved by using a contactor to halve the battery voltage (here, the two half-cells are switched to a parallel connection and charged in parallel, a so-called voltage halving function); or by using a dedicated charging booster to double the voltage (a so-called voltage multiplier). Here, the maximum possible power cannot be obtained from the charging station using existing technology. Using a performance booster, the maximum possible charging power of the charging station can be obtained, independent of the maximum available charging voltage, and thus the battery can be charged at the fastest speed for the corresponding charging station.

[0027] In this embodiment, the DC-DC converter performs one or more of the following functions:

[0028] • Connect the battery directly to the DC link;

[0029] • In the event of a drive unit failure, particularly a drive inverter failure, the power supply to the DC link is automatically disconnected.

[0030] • Adjust the drive DC link voltage to follow the induced voltage in the drive unit.

[0031] In this embodiment, the function of switching the battery to direct connection to the drive DC link is implemented by a battery disconnection unit. In this document, in the event of a drive unit failure, the DC-DC converter closes the voltage of the DC link so that the drive motor does not build up significant torque when the drive inverter is disconnected. This means that the drive DC link voltage can be higher than the voltage induced in the motor.

[0032] In the embodiments, one of the following situations applies:

[0033] • The DC-DC converter is a stand-alone device with a separate housing, power electronic terminals to the battery and to the DC link and / or to the charging terminal, and electrical signal and / or communication interfaces for controlling the DC-DC converter and for communicating with other control devices;

[0034] • The DC-DC converter is integrated into the extended battery;

[0035] • The DC-DC converter is integrated into the drive inverter.

[0036] In this paper, the extended battery or drive inverter is a standalone device with a separate housing, power electronic terminals for connecting to other devices, and electrical signal and / or communication interfaces for exchanging signals with other devices.

[0037] In one embodiment, the DC-DC converter is integrated into a so-called drive unit, which consists of a drive inverter, a drive motor, and, optionally, a transmission.

[0038] The method is used to operate a power supply unit, wherein in drive operation, a DC-DC converter feeds electrical energy from a battery to a DC link, wherein the DC link includes a drive DC link voltage, and the battery has a battery voltage, and the drive DC link voltage is higher than the battery voltage. In this paper, the drive DC link voltage can be closed-loop controlled by the energy fed from the DC-DC converter to the DC link.

[0039] This can be achieved by setting the current fed into the DC link.

[0040] In one embodiment, the drive DC link voltage can be between 10% and 250% higher than the battery voltage. In another embodiment, it is at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, or at least 250% higher than the battery voltage. In yet another embodiment, it is based on an intermediate value between 10% and 250% higher than the battery voltage.

[0041] In one embodiment, the driving DC link voltage is lower than the battery voltage during driving operation.

[0042] In one embodiment, the drive DC link voltage is between 10% and 90% lower than the battery voltage relative to the battery voltage. In another embodiment, it is at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90% lower than the battery voltage. In yet another embodiment, it is based on an intermediate value between 10% and 90% lower than the battery voltage.

[0043] In one embodiment, during a charging operation to charge a battery, a DC-DC converter feeds electrical energy to the battery from a charging terminal, wherein a DC link is connected to the charging terminal and has a charging DC link voltage, and the battery has a battery voltage, and the charging DC link voltage is higher than the battery voltage.

[0044] In an embodiment, the charging DC link voltage is between 10% and 250% higher than the battery voltage relative to the battery voltage, but is at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 250%, or an intermediate value between 10% and 250% higher than the battery voltage.

[0045] In one embodiment, during a charging operation to charge a battery, a DC-DC converter feeds electrical energy from a charging terminal to the battery, wherein a DC link is connected to the charging terminal and has a charging DC link voltage, and the battery has a battery voltage, and the charging DC link voltage is lower than the battery voltage.

[0046] In the embodiment, the charging DC link voltage is between 10% and 90% lower than the battery voltage relative to the battery voltage, but is at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or an intermediate value between 10% and 90% lower than the battery voltage.

[0047] In both of the above cases, the charging voltage fed to the charging terminal can be set to an increased charging voltage of the charging station, specifically, the maximum charging voltage of the charging station. The charging voltage can also be determined as the maximum of two maximum charging voltages of the charging station and the power supply unit. For this purpose, the charging station and the power supply unit can exchange information to automatically determine the charging voltage to be applied. The charging DC link voltage is similarly set to this charging voltage and can be closed-loop controlled by a closed-loop control device.

[0048] In this embodiment, one or more of the following steps are performed:

[0049] • A DC-DC converter or battery disconnect unit connects the battery directly to the DC link;

[0050] • In the event of a drive unit failure, particularly in the event of a drive inverter failure, the DC-DC converter automatically shuts off the power supply to the DC link.

[0051] • The DC-DC converter adjusts the drive DC link voltage to follow the induced voltage in the drive unit.

[0052] The above steps can be performed by a closed-loop control device. For this purpose, the closed-loop control device may include a communication or signal interface to the drive unit, and specifically to one or more drive inverters. In this paper, in the event of a drive unit failure, the DC-DC converter closes the voltage of the drive DC link so that the drive motor does not build up significant torque when the drive inverter is disconnected. This means that the drive DC link voltage can be higher than the voltage induced in the motor.

[0053] Typically, in this specification, when referring to the connection of two components or elements to each other, it means a typical bipolar connection, that is, a connection via two terminals. Typically, there is a voltage between the two ends of the connection or between the two terminals, and current flows through the two terminals.

[0054] In the literature, the terms "boost converter," "buck converter," and "boost / buck converter" are not always used consistently. In some contexts, the term should be understood as limited to electrically isolated converters and synonymous with "flyback converter," while non-electrically isolated converters operating on the same basic principle are referred to as "inverter converters." Conversely, in other contexts, "boost-buck converter" should be understood as distinct from "flyback converter." In English nomenclature, the term "flyback converter" can be used for electrically isolated converters, and "boost-buck converter" for non-electrically isolated converters. In the context of this document, "boost converter," "buck converter," and "boost / buck converter" should be understood as both electrically isolated and non-electrically isolated embodiments. Furthermore, a boost converter should be understood as a DC-DC converter that allows energy to flow from an input voltage to a higher output voltage. A buck converter should be understood as a DC-DC converter that allows energy to flow from an input voltage to a lower output voltage. "Boost / buck converter" or "boost and buck converter" should be understood as a DC-DC converter in which energy flows from the input voltage to a higher and / or lower output voltage. If the boost converter is operable for bidirectional energy flow, it can operate as a boost converter in a first operating mode and as a buck converter with energy flow in the opposite direction in a second operating mode.

[0055] Other preferred embodiments can be obtained from the dependent patent claims. In this document, features of the method claims in the context of the invention may be combined with those of the apparatus claims, and vice versa. Attached Figure Description

[0056] The subject matter of the invention is explained in more detail below with reference to preferred embodiments illustrated in the accompanying drawings. In each case, the following is schematically shown:

[0057] Figure 1 It is the drive unit for electric vehicles;

[0058] Figure 2 It is an extended battery with a DC-DC converter;

[0059] Figure 3 It is a bidirectional boost converter;

[0060] Figure 4 It is a bidirectional boost / buck converter;

[0061] Figure 5 It is the characteristic curve of the torque and power of the electric drive as a function of rotational speed;

[0062] Figure 6 It is the speed-torque characteristic line;

[0063] Figure 7 It is the speed-power characteristic curve.

[0064] The reference numerals used in the accompanying drawings and their meanings are listed in the reference numeral list. Basically, in the accompanying drawings, identical or functionally equivalent parts are given the same reference numerals. Detailed Implementation

[0065] Figure 1 The diagram illustrates a drive system for an electric vehicle. This drive system includes a power supply unit 8 and a drive unit 4. The power supply unit 8 includes a battery 1 (typically a lithium-ion battery) and a DC-DC converter 2. The DC-DC converter 2 is coupled to a DC link 3, meaning it supplies power to or draws power from the DC link 3.

[0066] DC link 3 includes a DC link capacitor. This DC link capacitor can be implemented by a capacitor that is part of the DC-DC converter 2 and / or the drive inverter 41, or it can be implemented by a separate structural unit.

[0067] Drive unit 4 is also coupled to DC link 3. Drive unit 4 may contain one or more parallel drive systems, including drive inverters 41, 41', motors 42, 42' (typically three-phase drives), and mechanical drive systems 43, 43'. In this example, there are two parallel drive systems, and in other embodiments, there is a single drive system with drive inverter 41, motor 42, and mechanical drive system 43. In other embodiments, there are more than two drive systems. Mechanical drive systems 43, 43' can drive one or more wheels and include differential transmissions herein. Mechanical drive systems 43, 43' may also include shiftable transmissions or a transmission with a fixed gear ratio. One or more drive inverters 41, 41' are coupled to DC link 3, meaning they draw power from DC link 3 or, if the drive system is capable of energy recovery, feed power back to DC link 3.

[0068] In the driver according to the prior art, there is no DC-DC converter 2, and the drive unit 4 is directly powered by the battery 1.

[0069] according to Figure 1 The interconnection of the units corresponds to the drive operation. In the drive operation, the drive unit 4 is powered by the power supply unit 8. In the case of providing energy recovery mode, energy can be fed back from the drive unit 4 to the power supply unit 8 through the operation of the generator of the motor 42 or the motors 42 and 42'.

[0070] During charging, the power supply unit 8 can be switched to connect to the charging station via DC link 3 and charging terminal 7. During charging, the power supply unit 8 obtains power from the charging station via DC link 3, and the battery 1 is charged.

[0071] In the charging operation of hybrid drive, DC link 3 can be fed by a separate generator. In embodiments, under hybrid drive conditions, the DC link can be fed by a generator during drive operation and / or charging operation. The drive operation described herein may include feeding power from power supply unit 8 to drive unit 4, and energy feedback in the opposite direction.

[0072] Closed-loop control unit 31 is designed to control DC-DC converter 2 based on measured values. Typically, the measured values ​​(i.e., the acquired variables) include battery voltage U. Batt DC link voltage U of DC link 3 z This includes variables necessary to describe the operating state of the driver. In drive operation, the DC link voltage can also be referred to as the drive DC link voltage, and the closed-loop control device 31 functions as a drive closed-loop control device. In charging operation, the DC link voltage can also be referred to as the charging DC link voltage, and the closed-loop control device 31 functions as a charging closed-loop control device.

[0073] Figure 2 An extended battery 1a with a DC-DC converter 2 is shown. The extended battery 1a includes a battery cell 13, a battery disconnection unit 12, and a battery management system 11. When the vehicle is parked, the battery disconnection unit 12 electrically disconnects the battery from the DC link 3. During driving and charging operations, the battery disconnection unit 12 switches the battery to the DC link 3, and similarly ensures the switching between driving and charging operations. For this purpose, both sides of the DC-DC converter are connected to the battery disconnection unit 12. Two or more of the following operating states can be achieved through the battery disconnection unit 12:

[0074] • The DC-DC converter 2 is switched to be connected between the battery 1 or battery cell 13 and the drive unit 4;

[0075] • The DC-DC converter 2 is switched to be connected between the battery 1 or battery cell 13 and the charging terminal 7;

[0076] • When battery 1 or a single battery cell is switched to be directly connected to drive unit 4, DC-DC converter 2 will not work;

[0077] • When battery 1 or battery cell 13 is switched to direct connection to charging terminal 7, DC-DC converter 2 does not work.

[0078] The battery management system 11 monitors the state of charge of the individual battery cells 13, controls the battery disconnection unit 12, and communicates with the DC-DC converter 2 (the communication connection is indicated by a dashed line).

[0079] In other embodiments, the battery disconnection unit 12 is not part of the extended battery 1a, but is implemented as a separate structural unit or as part of the drive unit 4. The interconnection possibilities in different operating states are independent of the structural implementation of the unit.

[0080] The DC-DC converter 2 or DC voltage converter can be implemented in a manner known per se. The following embodiments illustrate boost converters and boost / buck converters that are not electrically isolated. In other embodiments not shown, the input and output sides are electrically isolated.

[0081] Figure 3 A bidirectional boost converter is shown, including an input side 21, an output side 22, an inductor 23, and a half-bridge circuit with a switch 24 and a diode 25. The switch can be a semiconductor valve capable of being turned on and off. The circuit can transfer energy from the input side 21 to the output side 22, where the voltage at the output side 22 is equal to or greater than the voltage at the input side 21. For this purpose, for example, diode 25 operates in the upper half of the half-bridge circuit, and switch 24 operates in the lower half of the half-bridge circuit. For example, to achieve energy flow from the output side 22 to the input side 21 (thus achieving bidirectional energy flow), diode 25 operates in the lower half of the half-bridge circuit, and switch 24 operates in the upper half of the half-bridge circuit. From the output side 22, in this operating mode, the circuit can also be considered a buck converter.

[0082] Figure 4 A bidirectional boost / buck converter with the same components but featuring a dual half-bridge circuit is shown. Therefore, alternatively, the input side 21 can have a higher voltage than the output side 22, where bidirectional energy flow remains feasible.

[0083] In the embodiments, DC-DC converter 2 is implemented using other types of DC-DC converters with or without electrical isolation, such as split π-type converters (boost-buck converters), cascaded buck-boost converters, push-pull converters, resonant converters, etc.

[0084] Figure 3 and Figure 4 Individual converter units are shown separately. For the power typically required, such as in the range of 100kW and above, such converters can also be constructed as so-called multiphase converters by connecting several converter units in parallel and / or in series.

[0085] Several advantages can be achieved by applying a DC-DC converter 2 (hereinafter also referred to as a "performance booster"): if the performance booster 2 boosts the operating voltage of the driver to a level exceeding the maximum battery voltage present in a fully charged state (SOC=100%), the electric driver can operate at a higher maximum power. This is because electric vehicle drivers are typically designed so that the so-called reference speed range (where the applied three-phase motor can operate without magnetic field weakening or voltage reduction because the voltage induced in the three-phase motor is lower than the voltage that can be delivered from the drive inverter to the machine stator terminals) can be extended to higher speeds.

[0086] For example, the situation is as follows:

[0087] • Without performance booster 2, the battery voltage is 650V, and a 50V closed-loop control margin is provided for the inverter. Therefore, a reference speed range with an inductance voltage of up to 600V is maintained.

[0088] • With performance booster 2, the driver's operating voltage is closed-loop controlled to 950V. Due to the 50V inverter's closed-loop control margin, the reference speed range maintains an induced voltage of up to 900V. This results in a 50% increase in the reference speed range.

[0089] In this configuration, the drive can operate with 50% more power. At higher speeds within the field weakening range, the available torque is increased by approximately 1.5 times. This assumes the maximum speed is approximately three times the base speed, and that performance booster 2 can increase the base speed range by 50%. This means that, through performance booster 2, the drive's configuration changes from 1:3 to 1:2 in terms of the ratio of base speed to maximum speed.

[0090] Therefore, no changes to the mechanical structure are necessary: ​​the maximum torque remains unchanged, as does the motor speed and, consequently, the design of the transmission. The commonly used semiconductor switches with a 1200V blocking voltage also require no alteration. Depending on the specific circumstances, minor adjustments may be necessary, such as improving the insulation of the motor stator windings to accommodate higher operating voltages.

[0091] If two shafts in an electric vehicle are electrically driven, the power of the two drive shafts can be improved by applying the performance enhancer 2.

[0092] Figure 5 The diagram schematically illustrates the characteristic curves of torque M and power P as a function of speed n at a given battery voltage (solid line) and the voltage increased by the performance booster (PB) (dashed line). The speed-torque characteristic curves show how the reference speed range changes from n... G Starts to increase and approaches maximum speed n max(Horizontal arrow). It can also be seen how torque increases at higher speeds for a given speed. The speed-power characteristic curve shows how maximum power increases from P... max Increase to P max,PB .

[0093] Figure 6 The actual speed-torque characteristic curves are shown under different voltages V1, V2, and V3, and... Figure 7 The speed-power characteristic curves are shown for different voltages V1, V2, and V3. Dashed lines represent continuous operation, and solid lines represent brief peak operation.

[0094] The drive power of electric vehicles can be implemented as follows:

[0095] Phase 1: One shaft is driven by one motor.

[0096] Phase 2: Each of the two axes is driven by a separate motor.

[0097] Phase 3: Each of the two shafts is driven by a motor, and one shaft has a shift gearbox.

[0098] Phase 4: Two shafts are driven, one shaft is driven by one drive motor, and the other shaft is driven by two motors, which are mechanically coupled via a gearbox.

[0099] Phase 5: Four motors or four hub motors located near the wheels.

[0100] Different motors with varying power can be used in different architectures to achieve the required drive power. The performance booster 2 enables power increases without altering the mechanical structure or drive architecture, providing a new possibility for power enhancement. In this paper, the performance booster 2 can be applied to vehicles with only one axle driven, as well as vehicles with more than one axle driven. All motors benefit from the voltage boost in this paper.

[0101] For electric vehicle drives without Performance Booster 2, very high additional losses occur in the inverter and motor at lower speeds within the reference speed range. This is because, in this operating state, the induced voltage of the three-phase detector is significantly lower than the battery voltage, which is equal to the voltage in the inverter's DC link. This situation is improved by applying Performance Booster 2, which sets the voltage in the DC link of the drive according to the operating point.

[0102] For example, a simple setpoint setting can be represented as setting the DC link voltage to the voltage currently sensed in the three-camera system plus the closed-loop control margin (e.g., 50V or 100V) provided to drive the inverter. In this embodiment, the driver's torque demand (corresponding to the accelerator pedal position) is also considered and affects the closed-loop control margin. In this document, a higher torque demand corresponds to a higher closed-loop control margin. In this embodiment, a complete machine and inverter model is implemented, thereby determining the trajectory of the DC link voltage caused by the target setting. For example, starting from the current operating point, the driver changes the position of the accelerator pedal. The resulting acceleration can then be converted in the control loop model into the voltage trajectory required at the motor terminals, and subsequently into the setpoint trajectory of the DC link voltage.

[0103] In summary, during drive operation, closed-loop control can set or control the DC link voltage of DC-DC converter 2 (which is equal to the input voltage of drive inverter 41) to the desired setpoint. In this way, closed-loop control can achieve the following functions. In this document, in the embodiments, the setpoint can be less than or greater than the current battery voltage. In practice, the current setpoint is limited to an upper limit of 1000V because high-voltage systems with rated voltages higher than 1000V have not yet been approved for use in vehicles.

[0104] • In each case, when a greater power is required than that achievable at the current battery voltage without a performance booster, the closed-loop control corresponds to a power level greater than the battery voltage U. Batt A higher voltage setpoint.

[0105] • In each case, when the induced voltage of the motor is higher than the current battery voltage, the closed-loop control is configured to correspond to a voltage U higher than the battery voltage. Batt A higher voltage setpoint is used to avoid so-called voltage drop operation of the motor, as this would cause unnecessary additional losses.

[0106] • In each case, when the induced voltage of the motor is significantly lower than the battery voltage, the closed-loop control is configured to correspond to a voltage U lower than the battery voltage. Batt A lower voltage setpoint is used to avoid unnecessary additional losses in driving the inverter 41 and motor 42, and to increase the service life of the motor 42. In particular, this involves the insulation of the stator windings, as the switching edges in the inverter and the resulting insulation displacement currents can stress the stator windings.

[0107] • If needed, the performance enhancer 2 can also directly connect the drive inverter 41 to the battery 1. In this operating mode, the positive terminal of the battery can be short-circuited to the positive terminal of the DC link.

[0108] Closed-loop control of the DC link voltage is implemented for both motor operation and generator operation (with braking procedures or downhill driving). Therefore, bidirectional energy conversion is required in drive inverter 4 and performance booster 2.

[0109] If the inverter fails, according to existing technology (at least in the voltage drop operation of synchronous motors), so-called ASC (Active Short Circuit) is used because the induced voltage in the motor is higher than the battery voltage, and thus a very high charging current will flow into the battery. ASC prevents this, however, it causes the motor to generate very high braking torque for a short period of time. If performance booster 2 is applied and drive inverter 41 fails, the following strategy can be implemented: turn off all semiconductor switches of inverter 41 and set the voltage in DC link 3 such that it is higher than the induced voltage of the three-phase motor. In this way, the motors then operate at idle, i.e., they generate almost no torque on the drive shaft. When the induced voltage is higher than the maximum output voltage of performance booster 2, energy flows into the battery to maintain the DC link voltage at an allowable value. In this way, a braking torque is generated on the drive shaft, however, the braking torque is smaller and therefore easier to control than using ASC.

[0110] To enable not only the application of the performance enhancer 2 to increase drive power but also its integration with charging applications, the performance enhancer 2 can be integrated into the functionality of the vehicle's drive battery. The drive battery, comprising battery cells 13, may also include, in addition to these battery cells 13, a battery management system 11 (BMS), a thermal management system, and a so-called battery disconnect unit 12 (BDU). The battery disconnect unit 12 can switch the battery cells 13 to be connected to or disconnected from the drive unit 4 at both terminals, and connect the battery cells 13 to a charging socket or charging station under DC fast charging conditions. Alternatively, under AC charging conditions, power can be supplied via a charging device (on-board charger, OBC). To allow the required functionality to also be integrated with the application of the performance enhancer 2, the performance enhancer 2 needs to be correspondingly incorporated into the architecture of the described drive battery system, specifically, integrated into the components of the battery disconnect unit 12 and the battery management system 11.

[0111] For DC fast charging programs at charging stations that can directly charge the battery (because the charging station can directly provide the required charging voltage), the increase in power is achieved by setting the charging station's voltage to a value higher than the current battery voltage, and thus obtaining increased power, for U. Batt *I ChargeMax U ChargeMax *I ChargeMaxThe maximum power of the charging station can be used as a limiting value. Then, the performance booster 2 converts the charging station's voltage to a lower battery voltage.

[0112] Furthermore, the performance booster 2 allows the vehicle to be charged at DC fast charging stations where the battery cannot be directly charged (because the charging station cannot directly provide the required charging voltage). In this case, the performance booster 2 boosts the output voltage of the charging station to a level that allows battery charging. A further possibility for optimization lies in utilizing the maximum power available at the charging station under these charging conditions by operating the charging station at its maximum voltage (similar to the function described above). This differs from existing charge boosters, which are voltage doublers with a fixed voltage ratio. The performance booster 2 converts a lower charging voltage to a higher battery voltage without being limited by a fixed voltage ratio.

[0113] By using a properly configured closed-loop control device 31, one or more of the following safety functions can be achieved:

[0114] • Under the condition of a fault in drive inverter 41, the electronic (semiconductor) fuse can be activated very quickly and, through programming of the current-time activation curve, achieve better protection for drive unit 4 and / or battery 1 than the combination of currently used fusible fuses (for very high overcurrent) and DC contactors (for less high overcurrent but longer overtime).

[0115] Compared to devices that use dedicated semiconductor switches in the battery disconnect unit to achieve similar functionality, the semiconductor switches are present anyway (for another function), and these switches provide additional safety features without incurring extra cost. Furthermore, in the main current path, inductor 23 prevents the current from rising very rapidly, a situation that would not occur if the battery were directly connected to inverter 41. Therefore, safety features are better implemented, and individual battery cells are better protected from unacceptably high currents.

[0116] • Electronic safety features for drive inverter failure scenarios. According to existing technology, in the event of a severe fault, the motor operates in a so-called "active short circuit" at the stator terminals. This causes the motor to build up high braking torque, which can lead to uncontrollable drive conditions. With the help of performance inverter 2, the DC link voltage is successfully made the same as the voltage currently induced in the three-phase motor, at least over an extended reference speed range. In this way, unwanted braking torque can be prevented, at least under synchronous motor conditions. In this case, drive inverter 41 then does not operate in an active short circuit; instead, all power switches are turned off, and the diodes of drive inverter 41 carry the current path. In this document, each branch has a diode conducting.

[0117] For example, integrating the performance enhancer 2 into the drive system of an electric vehicle could lead to the following possibilities:

[0118] • The performance booster 2 is a standalone device with a separate housing and is integrated into the drive system via a power electronics high-voltage and high-current interface, an electrical signal and communication interface, a mechanical interface, and an interface for thermal management.

[0119] • The performance enhancer 2 is integrated into the drive battery, or integrated with the battery to form a power supply unit 8.

[0120] • The performance enhancer 2 is integrated into the drive inverter, or so-called drive unit.

[0121] Due to the central arrangement of the driver's power electronics architecture, performance booster 2 can integrate additional functions, specifically:

[0122] • Provides, monitors, and controls the flow of electrical energy in electric vehicles, known as a power distribution unit (PDU); and / or

[0123] • Power supply for electrical devices integrated at low voltage levels (below 60V, currently electric vehicles are typically 12V, 24V, or 48V); and / or

[0124] • Power supply integrated into electrical equipment at a high voltage level (between 60V and 1000V), which does not correspond to the voltage driving the inverter; and / or

[0125] • Integration with cable connection to the on-board charger; and / or

[0126] • Integrates the functionality of a vehicle-side cableless inductive charging system (ICS).

[0127] If only the performance of the driver is increased and in U ChargeMax >U BattIf performance at the charging station is improved, performance booster 2 can be designed as a boost converter. This is less expensive, but the operating mode is limited to driving a DC link voltage greater than or equal to the battery voltage. Operating modes with a smaller driving DC link voltage can be eliminated. Electronic (semiconductor) fuses and electronic safety functions can only be implemented to a reduced extent.

[0128] If the goal is simply to improve driver performance, integration with the battery function is unnecessary. A boost / buck converter or a boost converter alone can be used.

[0129] List of reference numerals

[0130] 1 Battery

[0131] 1a Extended Battery

[0132] 11 Battery Management System

[0133] 12 Battery disconnection unit

[0134] 13 battery cells

[0135] 2 DC-DC converters

[0136] 21 Input side

[0137] 22 Output side

[0138] 23 Inductors

[0139] 24 Switches

[0140] 25 Diode

[0141] 3 DC Link

[0142] 31 Closed-loop control device

[0143] 4 drive units

[0144] 41 Drive Inverter

[0145] 42 Electric motor

[0146] 43 Mechanical transmission system (gearbox, differential)

[0147] 7 Charging terminals

[0148] 8 Power Supply Units

Claims

1. A power supply unit (8) for providing electrical energy to a drive unit (4) of an electric vehicle. • wherein, The power supply unit (8) includes a DC-DC converter (2) and a battery (1) with battery voltage, wherein: • The DC-DC converter (2) is arranged or is capable of being switched to provide a drive DC link voltage to the drive unit (4) via the DC link (3), and • The voltage ratio between the battery voltage and the drive DC link voltage can be set through the DC-DC converter (2). The DC-DC converter (2) is designed to drive a DC link voltage higher than the battery voltage, specifically, at least as a boost converter, and • The DC-DC converter (2) is designed for bidirectional energy flow, in particular, at least as a boost converter or a boost and buck converter.

2. The power supply unit (8) according to claim 1, wherein, The DC-DC converter (2) is also designed to drive operation where the DC link voltage is lower than the battery voltage.

3. The power supply unit (8) according to claim 1 or 2 includes a drive closed-loop control device (31) which controls the DC-DC converter (2) to set the drive DC link voltage according to the operating point of the drive unit (4).

4. The power supply unit (8) according to any one of the preceding claims, wherein, The DC-DC converter (2) is arranged or can be switched to be connected between the battery (1) and the charging terminal (7). Specifically, the battery disconnect unit (12) is used.

5. The power supply unit (8) according to claim 4, wherein, The DC-DC converter (2) is designed to charge the battery (1) at a charging DC link voltage higher than the battery voltage. Specifically, it includes a charging closed-loop control device (31) that controls the DC-DC converter (2) to set the charging DC link voltage to the maximum charging voltage, wherein the maximum charging voltage can be set by the charging station.

6. The power supply unit (8) according to claim 4 or 5, wherein, The DC-DC converter (2) is also designed to charge the battery (1) at a charging DC link voltage lower than the battery voltage. Specifically, it includes a charging closed-loop control device (31) that controls the DC-DC converter (2) to set the charging DC link voltage to the maximum charging voltage, wherein the maximum charging voltage can be set by the charging station.

7. The power supply unit (8) according to any one of the preceding claims, wherein, The DC-DC converter (2) performs one or more of the following functions: • Connect the battery (1) directly to the DC link (3); • In the event of a failure in the drive unit (4), particularly a failure in the drive inverter (41), the power supply to the DC link (3) is automatically disconnected; • Adjust the drive DC link voltage to follow the induced voltage in the drive unit (4).

8. The power supply unit (8) according to any one of the preceding claims, wherein one of the following conditions is met: • The DC-DC converter (2) is a stand-alone device with a separate housing, power electronic terminals to the battery (1) and to the DC link (3) and / or to the charging terminal (7), and electrical signal and / or communication interfaces for controlling the DC-DC converter (2) and for communicating with other control devices; • The DC-DC converter (2) is integrated into the extended battery (1a); • The DC-DC converter (2) is integrated into the drive inverter (41).

9. A method for operating a power supply unit (8) according to any one of the preceding claims, wherein, In the driving operation, the DC-DC converter (2) feeds electrical energy from the battery (1) to the DC link (3), wherein the DC link (3) has a driving DC link voltage, and the battery (1) has a battery voltage, and the driving DC link voltage is higher than the battery voltage. Specifically, the driving DC link voltage is controlled in a closed loop by the energy fed from the DC-DC converter (2) into the DC link (3).

10. The method according to claim 9, wherein, During drive operation, the drive DC link voltage is lower than the battery voltage.

11. The method according to claim 9 or 10, wherein, During the charging operation of the battery (1), the DC-DC converter (2) feeds electrical energy to the battery (1) from the charging terminal (7), wherein: The DC link (3) is connected to the charging terminal (7) and has a charging DC link voltage, and the battery (1) has a battery voltage, and the charging DC link voltage is higher than the battery voltage. Specifically, the charging station fed to the charging terminal (7) is set to an increased charging voltage of the charging station, specifically the maximum charging voltage of the charging station, and the charging DC link voltage is similarly set to this charging voltage.

12. The method according to any one of claims 9 to 11, wherein, During the charging operation of the battery, the DC-DC converter (2) feeds electrical energy from the charging terminal (7) to the battery (1), wherein the DC link (3) is connected to the charging terminal (7) and has a charging DC link voltage, and the battery (1) has a battery voltage, and the charging DC link voltage is lower than the battery voltage. In particular, The charging station fed to the charging terminal (7) is set to the increased charging voltage of the charging station, in particular the maximum charging voltage of the charging station, and the charging DC link voltage is also set to this charging voltage.

13. The method according to any one of claims 9 to 12, wherein one or more of the following steps are performed: • The DC-DC converter (2) or battery disconnection unit (12) connects the battery (1) to the DC link (3) in a direct manner; • In the event of a failure in the drive unit (4), particularly in the event of a failure in the drive inverter (41), the DC-DC converter (2) automatically shuts off the power supply to the DC link (3); • The DC-DC converter (2) adjusts the drive DC link voltage to follow the induced voltage in the drive unit (4).

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