Patent Description:
The power supply system according to the disclosure can be arranged in any type of vehicle, and even if the system and method according to the disclosure will be described primarily in relation to a car, the system and method is not restricted to this particular vehicle, but may as well be installed or implemented in another type of vehicle, such as a truck, a bus, a rail vehicle, a flying vehicle, a marine vessel, an off-road vehicle, a working vehicle, a motorcycle or the like.

In the field of power supply systems for electric vehicles, there is a trend towards increased voltage level of the power supply system because it enables shorter charging time. For example, a <NUM> V High-voltage power supply system has the ability to be charged at a power level of 300kW, thereby enabling full charging of a 100kWh battery in less than <NUM> minutes.

On the other hand, a drawback with the 800V power supply system is generally the need of a DC/DC converter within the vehicle, because conventional Fast Charging stations present across the globe has a charging voltage of <NUM> V. Hence, a <NUM> V to <NUM> V DC/DC converter is typically required, thereby increasing cost and complexity of the power supply system. Moreover, the DC/DC converter typically has a limited power level, for example in the range of <NUM> - <NUM> kW, thereby resulting in longer charging time period.

It is also known for example from document <CIT> to apply sequential charging of two battery units. Another example of prior art can be found in <CIT>.

However, despite the activities in the field, there is still a demand for a further improved power supply system that is capable of providing high-voltage level combined with fast charging from conventional charging stations at a low cost.

An object of the present disclosure is to provide a power supply system for an electric vehicle, and corresponding method for operating a power supply system where the previously mentioned problems are avoided. This object is at least partly achieved by the features of the independent claims.

According to a first aspect of the present disclosure, there is provided a power supply system for an electric vehicle drivetrain. The power supply system comprising: a first high-voltage battery unit; a second high-voltage battery unit connected in series with the first high-voltage battery unit; a circuit arrangement having a plurality of high-power switching semiconductor devices connected to the first and second high-voltage battery units; and an electronic control system. The electronic control system is configured for controlling operation of the plurality of high-power switching semiconductor devices for: during a charging mode of the first and second high-voltage battery units, routing high-voltage DC received from a vehicle external charging source alternatingly to the first high-voltage battery unit and to the second high-voltage battery unit, with an alternating frequency of at least <NUM>, specifically at least <NUM>, and more specifically in the range of <NUM> - <NUM><NUM>; and during a power supply mode of the power supply system, supplying high-voltage DC from both the first and second high-voltage battery units for driving a vehicle electrical traction machine of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units.

According to a second aspect of the present disclosure, there is provided a method for operating a power supply system for an electric vehicle drivetrain. The power supply system includes a first high-voltage battery unit connected in series with a second high-voltage battery unit. The method comprises, during a charging mode of the first and second high-voltage battery units, routing, by means of a circuit arrangement having a plurality of high-power switching semiconductor devices connected to the first and second high-voltage battery units, high-voltage DC received from a vehicle external charging source alternatingly to the first high-voltage battery unit and to the second high-voltage battery unit, with an alternating frequency of at least <NUM>, specifically at least <NUM>, and more specifically in the range of <NUM> - <NUM><NUM>, and during a power supply mode of the power supply system, supplying, by means of said circuit arrangement, high-voltage DC from both the first and second high-voltage battery units for driving a vehicle electrical traction machine of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units.

In this way, it becomes possible to provide the vehicle with for example a 800V electrical storage system, thereby enabling high power output of the electrical propulsion machine, while still enabling charging of the electrical storage system using conventional 400V charging station but without requiring a costly and power-limiting 800V/400V DC/DC converter. Moreover, the relatively fast alternating frequency of at least <NUM> enables battery pulse charging instead of conventional CC-CV charging.

During conventional DC charging, there are typically two major parts: the initial charging part where the charging is done by maintaining a constant current (CC) and the second part where the charging is done with a constant voltage (CV). This is called CC-CV charging, but CC-CV charging for charging HV Battery may have a negative impact on the lifetime of the HV Battery.

Pulsed charging of for example Li-Ion batteries with pulse frequency of at least <NUM> on the other hand can improve battery lifetime. Pulse charging involves using controlled charge current pulses to charge each battery unit. Compared with CC-CV charging, pulse charging provides increased battery charge, reduced charge time and improved safety, since the relaxation times in between charge current pulses allows time for positive ions to successfully intercalate in the anode and may help to prevent dendrite formation.

In other words, by configuring the battery cells of the high-voltage battery system into two stacks of cells, or two separate battery units, that each has about <NUM>% of the total voltage, it is possible to charge one half of the battery pack at a time with a short current pulse at about <NUM>% of the total voltage level, and after charging having access to the total voltage level for electric vehicle propulsion. This enables charging of for example a 800V battery at a 400V charging station. Moreover, by alternatively charging the battery cell stacks, one part of the HV battery is always being charged by the high current pulses, such that the need for a separate <NUM>/800V DC/DC converter to handle 400V charging stations is eliminated, and the pulse charging results in increased lifetime of the battery.

Further advantages are achieved by implementing one or several of the features of the dependent claims.

In some example embodiments, the electronic control system is configured for controlling operation of the plurality of high-power switching semiconductor devices to operate with an alternating frequency equal to a frequency associated with a battery minimal internal resistance or battery minimal internal impedance of the first and/or second high-voltage battery unit; or a frequency located between a frequency associated with battery minimal internal resistance or battery minimal internal impedance of the first high-voltage battery unit and a frequency associated with battery minimal internal resistance or battery minimal internal impedance of the second high-voltage battery unit. Thereby, the internal resistance losses associated with the first and/or second high-voltage battery units during charging thereof may be minimized. Battery impedance can be examined by electrochemical impedance spectroscopy, so that the frequency with minimal resistive impedance can be identified and used for the pulsed charging current.

In some example embodiments, the power supply system further comprises a battery internal resistance or impedance detection arrangement configured for determining said frequency associated with said minimal internal resistance or minimal internal impedance of the first and/or second high-voltage battery units. Thereby, online detection of the minimal internal resistance or minimal internal impedance of the first and/or second high-voltage battery units may be detected and subsequently used during charging of said battery units.

In some example embodiments, the battery internal resistance or impedance detection arrangement is configured for first, for each of a set of different frequencies, supplying a AC signal having a certain frequency to a selected battery unit out of the first and second high-voltage battery units or to both the first and second high-voltage battery units, registering a resulting alternating voltage or current, and determining an internal impedance of the selected battery unit or both the first and second high-voltage battery units, and secondly, identifying the minimal internal resistance or minimal internal impedance of the selected battery unit or both the first and second high-voltage battery units from the collected set of internal impedances, and determining the frequency associated with said identified minimal internal resistance or minimal internal impedance. Thereby, a cost-effective and easily implemented approach for online detection of the minimal internal resistance or minimal internal impedance of the first and/or second high-voltage battery units is accomplished.

In some example embodiments, the electronic control system comprises a data memory having, for each of the first and second high-voltage battery units or jointly for both the first and second high-voltage battery units, a plurality of stored data records, each associated with: a unique combination of a battery state of charge value and a battery temperature value; a data field for storing a calculated frequency value reflecting a minimal internal resistance or minimal internal impedance of the battery at said unique combination of battery state of charge and battery temperature; and a data field for storing an age indicator indicating the age of the calculated frequency value, wherein the electronic control system is configured to, upon receiving an instruction to enter charging mode of the first and second high-voltage battery units, detecting current temperature level and current state of charge level associated with the first and/or second high-voltage battery units, and subsequently using an associated calculated frequency value from the data record as the alternating frequency if the associated age indicator indicates that the calculated frequency value is up-to-date.

The data memory having a plurality of stored data records may be deemed corresponding to a lookup data table having stored frequency values and associated age indicators for enabling swift identification of suitable alternating frequency for charging.

In some example embodiments, the electronic control system is configured to, upon detecting that the associated age indicator indicates an outdated calculated frequency value, applying the battery internal resistance or impedance detection arrangement for determining a new calculated frequency value reflecting the minimal internal resistance or minimal internal impedance of each of the first and second high-voltage battery units, updating the stored calculated frequency value and the age indicator in the data record, and using said updated calculated frequency value as the alternating frequency. Thereby, it is ensured that a reasonable valid and suitable alternating frequency value always is used during charging without requiring a new online calculation of minimal impedance of the battery units at the beginning of each charging event.

In some example embodiments, the first high-voltage battery unit in a fully charged state has a first voltage level, wherein the second high-voltage battery unit in a fully charged state has a second voltage level that does not differ more than <NUM>% from the first voltage level, wherein the circuit arrangement is configured for routing a high-voltage DC from the vehicle external charging source to each of the first and second high-voltage battery units having a third voltage level that does not differ more than <NUM>% from any of the first and second voltage levels, and wherein the circuit arrangement is configured for supplying a high-voltage DC for driving the vehicle electrical traction machine at a power supply output having a fourth voltage level that amounts to substantially the sum of the first and second voltage levels. Consequently, charging of for example 800V battery system, composed of two series connected 400V battery units, may be performed using a conventional 400V charger without requiring a <NUM>/<NUM> DC/DC converter for converting a 400V charging voltage to 800V battery voltage.

In some example embodiments, the power supply system comprises a charging inlet configured for, during a charging mode of the first and second high-voltage battery units, receiving high-voltage DC from a vehicle external charging source for charging of the first and second high-voltage battery units, and wherein the power supply system is free from a DC/DC converter in the charging current path between the charging inlet and the first and second high-voltage battery units. Thereby, the overall cost of the power supply system may be reduced and the charging power may be increased.

In some example embodiments, the power supply system comprises a first bypass line connected in parallel with the first high-voltage battery unit, wherein the first bypass line includes a first high-power switching semiconductor device for controlling a bypass current flowing through the first bypass line, and a second bypass line connected in parallel with the second high-voltage battery unit, wherein the second bypass line includes a second high-power switching semiconductor device for controlling a bypass current flowing through the second bypass line. Thereby, a cost-efficient and reliable switching of the charging current is accomplished for implementing the desired alternating frequency.

In some example embodiments, the power supply system additionally comprises a third high-power switching semiconductor device connected in series with the first high-voltage battery unit and configured for selectively isolating the first high-voltage battery unit from the power supply system, and a fourth high-power switching semiconductor device connected in series with the second high-voltage battery unit and configured for selectively isolating the second high-voltage battery unit from the power supply system. Thereby, a cost-efficient and reliable switching of the charging current is accomplished for implementing the desired alternating frequency.

In some example embodiments, the power supply system comprises a first DC/DC converter connected in parallel with the first high-voltage battery unit and configured for providing a first low-voltage DC output, and a second DC/DC converter connected in parallel with the second high-voltage battery unit and configured for providing a second low-voltage DC output. Thereby, a redundant low-voltage power supply is accomplished for vehicle safety critical loads.

The disclosure also relates to a vehicle comprising the power supply system as described above.

In some example embodiments, the power supply system includes, for each of the first and second high-voltage battery units or jointly for both the first and second high-voltage battery units, a lookup data table having a plurality calculated frequency values, each reflecting a minimal internal resistance or minimal internal impedance of the battery for a unique combination of battery state of charge and battery temperature and each being associated with an age indicator indicating the age of the calculated frequency value, and wherein the method described above further comprises the steps of: receiving an instruction to enter charging mode of the first and second high-voltage battery units; detecting current temperature level and current state of charge level associated with the first and/or second high-voltage battery units; obtaining from the lookup data table the associated age indicator of the corresponding calculated frequency value; and when the associated age indicator indicates that the calculated frequency value is up-to-date, using the calculated frequency value from the lookup data table as the alternating frequency. Thereby, a reasonably valid and correct frequency value for the alternating frequency may be obtained without requiring online calculating of the frequency associated with the minimal impedance of the battery units.

In some example embodiments, the method further comprises: when the associated age indicator indicates that the calculated frequency value is outdated, applying a battery internal resistance or impedance detection arrangement for determining a new frequency value reflecting the minimal internal resistance or minimal internal impedance of each of the first and second high-voltage battery units; updating the stored calculated frequency value and the age indicator in the lookup data table; and using said new, updated, calculated frequency value as the alternating frequency. Thereby, the frequency value of the lookup data table to be used as alternating frequency may be updated and ready for use for near future charging events.

In some example embodiments, the step of applying the battery internal resistance or impedance detection arrangement for determining a new calculated frequency value reflecting the minimal internal resistance or minimal internal impedance of each of the first and second high-voltage battery units involves: for each of a set of different frequencies, supplying an AC signal having a certain frequency to a selected battery unit out of the first and second high-voltage battery units or to both the first and second high-voltage battery units, registering a set of resulting alternating voltages, and determining a set of internal impedances of the selected battery unit or both the first and second high-voltage battery units; and subsequently identifying the minimal internal resistance or minimal internal impedance of the selected battery unit or both the first and second high-voltage battery units from the collected set of internal impedances, and determining the frequency associated with said identified minimal internal resistance or minimal internal impedance. Thereby, a cost-effective and easily implemented approach for online detection of the minimal internal resistance or minimal internal impedance of the first and/or second high-voltage battery units is accomplished.

Further features and advantages of the invention will become apparent when studying the appended claims and the following description. The skilled person in the art realizes that different features of the present disclosure may be combined to create embodiments other than those explicitly described hereinabove and below, without departing from the scope of the present disclosure.

The disclosure will be described in detail in the following, with reference to the attached drawings, in which.

Those skilled in the art will appreciate that the steps, services and functions explained herein may be implemented using individual hardware circuitry, using software functioning in conjunction with a programmed microprocessor or general purpose computer, using one or more Application Specific Integrated Circuits (ASICs) and/or using one or more Digital Signal Processors (DSPs). It will also be appreciated that when the present disclosure is described in terms of a method, it may also be embodied in one or more processors and one or more memories coupled to the one or more processors, wherein the one or more memories store one or more programs that perform the steps, services and functions disclosed herein when executed by the one or more processors.

<FIG> schematically shows a side view of an electric vehicle <NUM> having front wheels 2a, rear wheels 2b, a passenger compartment <NUM> and an electric vehicle drivetrain, which includes a high-voltage battery <NUM> connected to an electrical machine <NUM>, for example via a power converter such as an inverter or the like. An output shaft of the electric machine <NUM> is drivingly connected the front and/or rear wheels 2a, 2b, of the vehicle. The drivetrain further comprises a charging inlet <NUM> configured for receiving a charging connector of a charging station during charging of the high-voltage battery <NUM>.

During charging of the high-voltage battery <NUM>, electrical charge is supplied to the high-voltage battery <NUM> from the charging station via the charging inlet <NUM>, and during vehicle driving, electrical charge is supplied from the high-voltage battery <NUM> to the electrical machine <NUM> for propulsion of the vehicle.

The high-voltage battery <NUM> may comprises two parts, namely a first high-voltage battery unit and a second high-voltage battery unit.

The drivetrain includes a power supply system for controlling and operating the drivetrain. <FIG> shows a first example embodiment of the power supply system for the electric vehicle drivetrain. The power supply system comprises a first high-voltage battery unit <NUM>, a second high-voltage battery unit <NUM> connected in series with the first high-voltage battery unit <NUM>, a circuit arrangement <NUM> having a plurality of high-power switching semiconductor devices <NUM>-<NUM> connected to the first and second high-voltage battery units <NUM>, <NUM>, and an electronic control system <NUM> configured for controlling operation of the plurality of high-power switching semiconductor devices <NUM>-<NUM>.

Specifically, the electronic control system <NUM> is configured for controlling operation of the plurality of high-power switching semiconductor devices <NUM>-<NUM> for, during a charging mode of the first and second high-voltage battery units <NUM>, <NUM>, routing high-voltage DC received from a vehicle external charging source <NUM> alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, with an alternating frequency of at least <NUM>, specifically at least <NUM>, and more specifically in the range of <NUM> - <NUM><NUM>.

Furthermore, the electronic control system <NUM> is also configured for controlling operation of the plurality of high-power switching semiconductor devices <NUM>-<NUM> for, during a power supply mode of the power supply system, supplying high-voltage DC from both the first and second high-voltage battery units <NUM>, <NUM> for driving a vehicle electrical traction machine <NUM> of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units <NUM>, <NUM>.

The step of routing high-voltage DC alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, with an alternating frequency of at least <NUM>, means that the high-voltage DC is routed in an alternating manner to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, i.e. sequentially to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, one after the other.

By routing high-voltage DC alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM> with a certain alternating frequency, the desired pulse charging of each of the first and second high-voltage battery units <NUM>, <NUM> is automatically accomplished, because when routing charging DC to the first high-voltage battery unit <NUM>, the second high-voltage battery unit <NUM> is bypassed and thus isolated from the charging DC, and when routing charging DC to the second high-voltage battery unit <NUM>, the first high-voltage battery unit <NUM> is bypassed and thus isolated from the charging DC. Thereby, each of the first and second high-voltage battery units <NUM>, <NUM> is intermittently charge, i.e. pulse charged.

The circuit arrangement <NUM> with the plurality of high-power switching semiconductor devices <NUM>-<NUM> for routing a high-voltage DC from the vehicle external charging source <NUM> to each of the first and second high-voltage battery units <NUM>, <NUM>, and for supplying a high-voltage DC from the first and second high-voltage battery units <NUM>, <NUM> to the vehicle electrical traction machine <NUM>, may be designed and implemented by various alternative circuit layouts for accomplishing the desired tasks. Two example designs of the circuit arrangement <NUM> are described below with reference to <FIG>, but the circuit arrangement <NUM> is not restricted to any of these two designs, and other circuit arrangements <NUM> for accomplishing the desired routing are possible.

The circuit layout of the example embodiment of the power supply system of <FIG> is described more in detail hereinafter. Specifically, the first and second high-voltage battery units <NUM>, <NUM> are connected in series, i.e. a positive pole of the second high-voltage battery unit <NUM> is connected to a negative pole of the first high-voltage battery unit <NUM> via a battery intermediate conductor <NUM>. Moreover, a positive pole of the first high-voltage battery unit <NUM> is connected to a positive DC bus <NUM>, and a negative pole of the second high-voltage battery unit <NUM> is connected to a negative DC bus <NUM>.

The circuit arrangement <NUM> has a first high-power switching semiconductor device <NUM> is configured for operating as bypass of the first high-voltage battery unit <NUM>, and a second high-power switching semiconductor device <NUM> is configured for operating as bypass of the second high-voltage battery unit <NUM>. For enabling this functionality, the first high-power switching semiconductor device <NUM> is arranged in a first conductor <NUM> that has a first end connected to the positive DC bus <NUM> at a first connection point <NUM> and a second end connected to the battery intermediate conductor <NUM> at a second connection point <NUM>. Similarly, the second high-power switching semiconductor device <NUM> is arranged in a second conductor <NUM> that has a first end connected to the negative DC bus <NUM> at a third connection point <NUM> and a second end connected to the battery intermediate conductor <NUM>, for example at the second connection point <NUM>.

The circuit arrangement <NUM> further has a third high-power switching semiconductor device <NUM> arranged in series with the first high-voltage battery unit <NUM>, for example somewhere between the first connection point <NUM> and the second connection point <NUM>. In addition, the circuit arrangement <NUM> further has a fourth high-power switching semiconductor device <NUM> arranged in series with the second high-voltage battery unit <NUM>, for example somewhere between the second connection point <NUM> and the third connection point <NUM>. Consequently, the first high-power switching semiconductor device <NUM> is configured for operating as bypass also of the third high-power switching semiconductor device <NUM>, and the second high-power switching semiconductor device <NUM> is configured for operating as bypass also of the fourth high-power switching semiconductor device <NUM>.

<FIG> schematically illustrates a further example embodiment of the circuit layout, which conceptually corresponds to the circuit layout as shown in <FIG>, and thus has essentially the same functionality and operating behaviour. Reference is therefore made to the description of <FIG> for layout and operation of the first to fourth high-power switching semiconductor devices <NUM>-<NUM>.

The circuit layout of <FIG> merely differs slightly in terms of circuit layout, for example, the first conductor <NUM> is connected to the positive DC bus <NUM> at a first connection point <NUM> and to the battery intermediate conductor <NUM> at a second connection point <NUM>, whereas the second conductor <NUM> is connected to the negative DC bus <NUM> at a third connection point <NUM> and to the battery intermediate conductor <NUM> at a fourth connection point <NUM>.

For each of the circuit layouts of <FIG>, during charging of the first and second high-voltage batteries <NUM>, <NUM>, the first to fourth high-power switching semiconductor devices <NUM>-<NUM> operate with a synchronised switching frequency of at least <NUM> for continuously switching between a first charging state and a second charging state, thereby supplying charging power from the charging source <NUM> alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>.

The first and second charging states are schematically illustrated in <FIG>, respectively, wherein the dash-dotted line <NUM> illustrates the current path.

Specifically, with reference to <FIG>, in the first charging state, the electronic control system <NUM> controls the first and fourth high-power switching semiconductor devices <NUM>, <NUM> to be in an open state, i.e. non-conducting state, and the second and third high-power switching semiconductor devices <NUM>, <NUM> to be in a closed state, i.e. a conducting state. As a result, charging power from the charging source <NUM> is supplied to the first high-voltage battery unit <NUM> via the second and third high-power switching semiconductor devices <NUM>, <NUM>, but not to the second high-voltage battery unit <NUM>, because the second high-voltage battery unit <NUM> isolated by means of the fourth high-power switching semiconductor device <NUM> being in open state, and because the second high-voltage battery unit <NUM> is bypassed by means of the second high-power switching semiconductor device <NUM> being in closed state.

Furthermore, with reference to <FIG>, in the second charging state, the electronic control system <NUM> controls the second and third high-power switching semiconductor devices <NUM>, <NUM> to be in an open state, i.e. non-conducting state, and the first and fourth high-power switching semiconductor devices <NUM>, <NUM> to be in a closed state, i.e. a conducting state. As a result, charging power from the charging source <NUM> is supplied to the second high-voltage battery unit <NUM> via the first and fourth high-power switching semiconductor devices <NUM>, <NUM>, but not to the first high-voltage battery unit <NUM>, because the first high-voltage battery unit <NUM> is isolated by means of the third high-power switching semiconductor device <NUM> being in open state, and because the first high-voltage battery unit <NUM> is bypassed by means of the first high-power switching semiconductor device <NUM> being in closed state.

Consequently, each of the first and second high-voltage batteries <NUM>, <NUM> may be charged alternatingly with the charging voltage supplied by the charging source <NUM>, which for example may be about 400V.

Moreover, with reference to <FIG>, when the electronic control system <NUM> controls the first and second high-power switching semiconductor devices <NUM>, <NUM> to be in an open state, i.e. non-conducting state, and the third and fourth high-power switching semiconductor devices <NUM>, <NUM> to be in a closed state, i.e. a conducting state, the accumulated voltage level of both the first and second high-voltage batteries <NUM>, <NUM> is available between the positive and negative DC buses <NUM>, <NUM>, e.g. about 800V when each of the first and second high-voltage batteries <NUM>, <NUM> delivers a voltage level of about 400V. This operating state typically corresponds to a driving state of the electric vehicle, wherein the full voltage level of the combined first and second high-voltage batteries <NUM>, <NUM> is supplied to a vehicle electrical traction machine <NUM> via an electric power converter <NUM>, such as for example an inverter. This scenario is schematically illustrated in <FIG>, wherein the dash-dotted line <NUM> illustrates the current path.

In other words, the power supply system may according to some example embodiments comprise a first bypass line <NUM> connected in parallel with the first high-voltage battery unit <NUM>, wherein the first bypass line <NUM> includes a first high-power switching semiconductor device <NUM> for controlling a bypass current flowing through the first bypass line <NUM>. Moreover, the power supply system comprises a second bypass line <NUM> connected in parallel with the second high-voltage battery unit <NUM>, wherein the second bypass line <NUM> includes a second high-power switching semiconductor device <NUM> for controlling a bypass current flowing through the second bypass line <NUM>.

Furthermore, the power supply system may according to some example embodiments comprise a third high-power switching semiconductor device <NUM> connected in series with the first high-voltage battery unit <NUM> and configured for selectively isolating the first high-voltage battery unit <NUM> from the power supply system, and a fourth high-power switching semiconductor device <NUM> connected in series with the second high-voltage battery unit <NUM> and configured for selectively isolating the second high-voltage battery unit <NUM> from the power supply system.

The high-power switching semiconductor devices <NUM>-<NUM> may have various designs, such as for example Bipolar Junction Transistors (BJTs), MOSFETs, Insulated-Gate Bipolar Transistor (IGBTs), or Thyristors, such as a Gate-turn-Off thyristors (GTOs), Static Induction Thyristors (SITs), Mos-controlled Thyristors (MCTs), Reverse conducting Thyristors (RCTs), etc..

<FIG> shows schematically the alternating charging of the first and second high-voltage battery units <NUM>, <NUM>, wherein the upper plot shows the charging pattern of the first high-voltage battery unit <NUM> over time and the lower plot shows the charging pattern of the second high-voltage battery unit <NUM> over time, wherein for each of the upper and lower plots, the y-axis represent charging power in watts and the x-axis represents time in seconds.

In the illustrated example embodiment of <FIG>, each of the first to fourth high-power switching semiconductor devices <NUM>-<NUM> are switched at a frequency f. A time period T of the switching is equal to: T=T1=T2 =<NUM>/f. Consequently, T1 and T2 are the duration of the pulses for charging the first and second high-voltage battery units <NUM>, <NUM>, respectively.

The parameter t_on is the amount of time the first and second high-voltage battery units <NUM>, <NUM> are charged during the a time period T, and t_off is the amount of time the first and second high-voltage battery units <NUM>, <NUM> are not charged during the time period T. The duty cycle D of operation, i.e. charging of each of the first and second high-voltage battery units <NUM>, <NUM>, is <MAT>. The duty cycle may be selected to be about <NUM> - <NUM>%, specifically about <NUM> - <NUM>%, and more specifically <NUM>%. The duty cycle may be selected depending on the specific operating conditions, such as battery temperature, state of charge, etc..

<FIG> shows schematically a corresponding state of charge (SOC) of each of the first and second high-voltage battery units <NUM>, <NUM> over time. During time period t1, when the first high-voltage battery unit <NUM> is supplied with a charging current and the second high-voltage battery unit <NUM> is isolated, the state of charge of the first high-voltage battery unit <NUM> increases correspondingly, while the state of charge of the second high-voltage battery unit <NUM> remains constant. Similarly, during time period t2, when the second high-voltage battery unit <NUM> is supplied with a charging current and the first high-voltage battery unit <NUM> is isolated, the state of charge of the second high-voltage battery unit <NUM> increases correspondingly, while the state of charge of the first high-voltage battery unit <NUM> remains constant.

<FIG> show schematically the alternating charging of the first and second high-voltage battery units <NUM>, <NUM> over time, as well as the corresponding state of charge (SOC), corresponding to <FIG>, but with a lower duty rate, in particular about <NUM>% duty rate.

The charging duty-rate of the first and second high-voltage battery units <NUM>, <NUM> is equal in the example embodiment described with reference to <FIG>, but charging duty-rate of the first high-voltage battery unit <NUM> may alternatively differ from the charging duty-rate of the second high-voltage battery unit <NUM>, for example for equalizing a difference in state of charge and/or voltage level of the first and second high-voltage battery units <NUM>, <NUM>.

As described above, the electronic control system <NUM> is configured for routing high-voltage DC received from a vehicle external charging source <NUM> to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM> during a charging mode, and supplying high-voltage DC from both the first and second high-voltage battery units <NUM>, <NUM> to the electrical traction machine <NUM> during a power supply mode. The circuit layout may have various designs for accomplishing these tasks. One example design is described below with reference to <FIG>, but the circuit layout is not restricted to this particular design, and other circuit designs for accomplishing the desired routing are possible.

According to one example embodiment that is schematically illustrated in <FIG>, the circuit arrangement <NUM> may include a first pair of circuit breakers <NUM> configured for connecting the positive and negative DC buses <NUM>, <NUM> to a charging inlet <NUM>, which is configured for being connected with a charging connector of a charging source <NUM> during charging of the first and second high-voltage battery units <NUM>, <NUM>. Moreover, the circuit arrangement <NUM> may further include a second pair of circuit breakers <NUM> configured for connecting the positive and negative DC buses <NUM>, <NUM> with a power converter <NUM>, such as for example an inverter, associated with the electrical traction machine <NUM>.

The first pair of circuit breakers <NUM> may be set in closed state, and the second pair of circuit breakers <NUM> may be set in open state, during charging of the first and second high-voltage battery units <NUM>, <NUM>, as schematically indicated be the dashed right-arrow 45a. Similarly, the first pair of circuit breakers <NUM> may be set in open state, and the second pair of circuit breakers <NUM> may be set in closed state, during powering of the electrical traction machine <NUM> associated with for example driving of the electrical vehicle, as schematically indicated be the dashed left-arrow 45b.

As schematically illustrated in the example circuit layout described with reference to <FIG>, the charging inlet <NUM> is connected directly to the positive and negative DC buses <NUM>, <NUM> via the first pair of circuit breakers <NUM>, and thus not via a DC/DC converter. In other words, the power supply system comprises a charging inlet <NUM> configured for, during a charging mode of the first and second high-voltage battery units <NUM>, <NUM>, receiving high-voltage DC from a vehicle external charging source <NUM> for charging of the first and second high-voltage battery units <NUM>, <NUM>, wherein the power supply system is free from a DC/DC converter in a charging current path between the charging inlet <NUM> and the first and second high-voltage battery units <NUM>, <NUM>.

Common for all example embodiments described above is that the first high-voltage battery unit <NUM> in a fully charged state may have a first voltage level, that the second high-voltage battery unit <NUM> in a fully charged state may have a second voltage level that does not differ more than <NUM>% from the first voltage level, that the circuit arrangement <NUM> is configured for routing a high-voltage DC from the vehicle external charging source <NUM> to each of the first and second high-voltage battery units <NUM>, <NUM> having a third voltage level that does not differ more than <NUM>% from any of the first and second voltage levels, and that the circuit arrangement <NUM> is configured for supplying a high-voltage DC for driving the vehicle electrical traction machine <NUM> at a power supply output, such as at the second pair of circuit breakers <NUM>, having a fourth voltage level that amounts to substantially the sum of the first and second voltage levels.

In particular, the fourth voltage level may be in the range of +/- <NUM>%, specifically +/-<NUM>%, of the sum of the first and second voltage levels.

As schematically illustrated in <FIG>, <FIG> and <FIG>, the electronic control system <NUM>, which may include a single electronic control unit (ECU), or a system composed of a plurality of cooperating electronic control units operating a more distributed manner, is configured for controlling operation of the plurality of high-power switching semiconductor devices <NUM>-<NUM>, for example via wired conductors <NUM>.

An electrical battery unit, such as for example a Li-lon battery unit, has a frequency dependent battery internal impedance. This is schematically illustrate in <FIG>, which shows the AC impedance magnitude [|Z|] in ohm as a function of pulse charging frequency. According to this example plot, the minimum AC impedance is available at about <NUM> pulse charging frequency, as marked with a ring <NUM> in <FIG>.

The impedance plot of <FIG> is dependent on state of charge and temperature of the battery unit.

The battery internal impedance is composed of a real part [Re(Z)] and an imaginary part [lm(Z)], which parts jointly define a phase angle. This may for example be illustrated by a Nyquist plot, as schematically illustrated in <FIG>, which has the real part [Re(Z)] of the battery internal impedance along the x-axis and the imaginary part [lm(Z)] along the y-axis. The real part [Re(Z)] of the battery internal impedance is also known as the resistive impedance of the battery.

Consequently, a minimum resistive impedance of the battery unit represented by the Nyquist plot of <FIG> may be identified at about <NUM>, as marked with a ring <NUM> in <FIG>.

Pulse charging of the first and second high-voltage battery units <NUM>, <NUM> may in some example embodiments preferably be performed at a pulse charging frequency corresponding to the minimum resistive impedance of the first and/or second high-voltage battery unit <NUM>, <NUM>, because this results in minimal resistive losses, e.g. minimal thermal losses.

In scenarios when the minimum resistive impedance is difficult to obtain or is unknown, but the minimal impedance magnitude [|Z|] is known or may be determined, pulse charging of the first and second high-voltage battery units <NUM>, <NUM> may alternatively be performed at a pulse charging frequency corresponding to the minimal impedance magnitude of the first and/or second high-voltage battery units <NUM>, <NUM>.

The selected alternating frequency associated with a battery minimal impedance magnitude or a battery minimum resistive impedance used for routing high-voltage DC received from a vehicle external charging source to the first and second high-voltage battery units <NUM>, <NUM> may not necessarily correspond to an alternating frequency associated with an absolute minimal impedance or minimal resistive part of the impedance, but must be read in the context of a selected sampling interval, as depicted by the crosses in <FIG>. In other words, the selected alternating frequency may correspond to the sample, e.g. "cross" in <FIG>, that is associated with the smallest battery impedance magnitude or battery resistive impedance out of the tested sample set, but depending on the number of samples, i.e. the resolution of the sample set, the selected alternating frequency may deviate more or less from an alternating frequency associated with an absolute minimal impedance or minimal resistive part of the impedance of the first and/or second high-voltage battery units <NUM>, <NUM>.

Consequently, in some example embodiments, the terms "frequency associated with a battery minimal impedance magnitude" and "frequency associated with a battery minimum resistive impedance" may be deemed corresponding to a frequency +/-<NUM>%, specifically +/- <NUM>%, and more specifically +/- <NUM>%, from an absolute minimal impedance or minimal resistive part of the impedance, for a given battery state of charge and battery temperature level, and possibly also battery state of health.

Moreover, the selected alternating frequency may also deviate from an alternating frequency corresponding to the sample, e.g. "cross" in <FIG>, associated with battery minimal internal resistance or battery minimal internal impedance of the first and/or second high-voltage battery units <NUM>, <NUM>, to an extent that said battery minimal internal resistance or battery minimal internal impedance does not deviate more than +/- <NUM>%, specifically +/- <NUM>%, from said sample, e.g. "cross" in <FIG>, associated with battery minimal internal resistance or battery minimal internal impedance of the first and/or second high-voltage battery units <NUM>, <NUM>.

For example, with reference to the example of <FIG>, a first alternating frequency corresponding to the "cross" in <FIG> that is marked with a circle <NUM> may be associated with a first battery minimal internal resistive impedance Re(Ze) <NUM> of the tested battery unit, which first battery minimal internal resistive impedance Re(Ze) <NUM> corresponds to the smallest battery internal resistive impedance Re(Ze) out of the set of samples. Moreover, a second alternating frequency corresponding to the "cross" in <FIG> that is marked with a triangle <NUM> may be associated with a second battery internal resistive impedance Re(Ze) <NUM> that does not deviate more than +/- <NUM>%, specifically +/- <NUM>%, from the first battery minimal internal resistive impedance Re(Ze) <NUM>. When selecting a suitable alternating frequency for routing the high-voltage DC to the first and second high-voltage battery units <NUM>, <NUM>, the system may select the second alternating frequency although not strictly associated with the absolute smallest battery internal resistive impedance Re(Ze) out of the set of samples, but since the second battery internal resistive impedance Re(Ze) <NUM> that does not deviate <NUM> more than <NUM>% from the first battery minimal internal resistive impedance Re(Ze) <NUM>, the loss in battery internal thermal efficiency may in some circumstance be outweighed by benefits resulting from the significant reduced switching frequency of the second alternating frequency compared with the first alternating frequency, such as reduced power consumption and/or cost of the plurality of high-power switching semiconductor devices <NUM>-<NUM>, etc..

The internal impedance of a battery unit at a certain AC frequency, at a certain battery unit state of charge and a certain battery unit temperature, may for example be determined by supplying an AC signal having a known current level and frequency to the positive and negative terminals of a battery unit, measuring the resulting voltage level and phase difference, and calculating the internal impedance. Alternatively, the internal impedance may be determined by supplying an AC signal having a known voltage level and frequency to the positive and negative terminals of a battery unit, measuring the resulting current level and phase difference, and calculating the internal impedance.

When having determined the internal impedance or the real part of the impedance of a battery unit at a plurality of different frequencies, as for example illustrated by the individual crosses in the plot of <FIG>, the minimal resistive impedance or minimal impedance magnitude [|Z|] may be identified for a specific battery unit state of charge and temperature level.

Specifically, according to some example embodiments, when a controlled alternating current I(t) = Imax sin(2πft) is supplied to the two terminals of the battery unit, the voltage response is V(t) = Vmax sin(2πft + Ø). Battery unit impedance may then be determined by the equation <MAT>, where the phase angle is Ø, the absolute value of the impedance is <MAT>, and the resistive (Real) part of impedance <MAT>.

In other words, the electronic control system <NUM> may be configured for controlling operation of the plurality of high-power switching semiconductor devices <NUM>-<NUM> to operate with an alternating frequency equal to a frequency associated with a battery minimal internal resistance or battery minimal internal impedance of the first and/or second high-voltage battery unit.

Hence, the frequency may be determined by either handling the first and second high-voltage battery units <NUM>, <NUM> as a single battery, i.e. by supplying the AC signal to both the first and second high-voltage battery units <NUM>, <NUM> connected in series, or based on one of the first and second high-voltage battery units <NUM>, <NUM>, i.e. by supplying the AC signal to only one of the first and second high-voltage battery units <NUM>, <NUM>.

Still more alternatively, the frequency may be selected from a range defined by the minimal internal resistance or battery minimal internal impedance of the first high-voltage battery unit <NUM> and the minimal internal resistance or battery minimal internal impedance of the second high-voltage battery unit <NUM>. In other words, the electronic control system <NUM> may be configured for controlling operation of the plurality of high-power switching semiconductor devices <NUM>-<NUM> to operate with an alternating frequency equal to a frequency located between a frequency associated with battery minimal internal resistance or battery minimal internal impedance of the first high-voltage battery unit <NUM> and a frequency associated with battery minimal internal resistance or battery minimal internal impedance of the second high-voltage battery unit <NUM>.

The process of identifying the internal impedance of a battery unit by supplying, consecutively, a series of AC signals having different frequencies, and measuring for each frequency the resulting voltage or current level and phase difference, may for example involve supplying a set of AC signals having a frequency ranging from <NUM> - <NUM> with about <NUM> - <NUM> steps. An iterative search process with increasingly narrow frequency range and finer steps may be applied.

With reference to <FIG>, the power supply system may according to some example embodiments comprise a battery internal resistance or impedance detection arrangement <NUM> configured for determining said frequency associated with said minimal internal resistance or minimal internal impedance of the first and/or second high-voltage battery units <NUM>, <NUM>.

The battery internal resistance or impedance detection arrangement <NUM> may for example be connected to a positive pole of the first high-voltage battery unit <NUM> and the negative pole of the second high-voltage battery unit <NUM>.

The battery internal resistance or impedance detection arrangement <NUM> may be configured for determining said frequency associated with said minimal internal resistance or minimal internal impedance of each of the first and/or second high-voltage battery units <NUM>, <NUM> by supplying an AC signal having a known current or voltage level to the positive and negative terminals of the first and/or second high-voltage battery units <NUM>, <NUM>, wherein the plurality of high-power switching semiconductor devices <NUM>-<NUM> may be used for routing the test signal to either the first and second high-voltage battery units <NUM>, <NUM> individually or jointly. Moreover, significant power consumers, such as the vehicle electrical traction machine <NUM> and electric power converter <NUM>, may be temporarily disconnected during the testing sequence for determining said frequency associated with said minimal internal resistance or minimal internal impedance.

According to some example embodiments, the battery internal resistance or impedance detection arrangement <NUM> may be configured for performing a first step of, for each of a set of different frequencies, supplying an AC signal having a certain frequency (f) to a selected battery unit out of the first and second high-voltage battery units, or to both the first and second high-voltage battery units, registering a resulting alternating voltage or current, and determining an internal impedance of the selected battery unit, and thereafter performing a second step of identifying the minimal internal resistance or minimal internal impedance of the selected battery unit or both the first and second high-voltage battery units from the collected set of internal impedances, and determining the frequency associated with said identified minimal internal resistance or minimal internal impedance.

The supplied AC signal may be a small amplitude AC signal according to I(t) = Imax sin(2πft). Moreover, the registered resulting alternating voltage signal may have the form V(t) = Vmax sin(2πft + Ø), wherein <NUM> is the phase angle of the selected battery unit. The frequency dependent impedance of the battery unit(s) may subsequently be determined based on the equation <MAT>.

In particular, an absolute value of the impedance is <MAT>, and a resistive (Real) part of impedance <MAT>.

The battery internal resistance or impedance detection arrangement <NUM> may for example include, an electrical storage system, such as a battery, an AC signal generator circuit connected to the electrical storage system, and an electronic controller configured controlling the AC signal generator circuit for supplying an AC signal with a certain frequency and a certain current or voltage to the first and/or second high-voltage battery units <NUM>, <NUM>. Furthermore, the electronic controller may additionally be configured for detecting a resulting alternating voltage or current signal, and for calculating the impedance of the first and/or second high-voltage battery units <NUM>, <NUM>, as well as the phase difference <NUM> between the supplied AC signal and the detected alternating voltage or current signal. Alternatively, the electronic control system <NUM> of the power supply system may be used for controlling said AC signal generator circuit and for calculating said impedance and phase difference Ø.

With reference to <FIG>, according to some example embodiments, the power supply system may additionally comprise a first DC/DC converter <NUM> connected in parallel with the first high-voltage battery unit <NUM> and configured for providing a first low-voltage DC output <NUM>, and a second DC/DC converter <NUM> connected in parallel with the second high-voltage battery unit <NUM> and configured for providing a second low-voltage DC output <NUM>. Thereby, redundant low-voltage power supply is provided for example vehicle safety critical functions, such as power steering, braking, etc..

A positive input of the first DC/DC converter <NUM> may for example be connected to the a positive pole of the first high-voltage battery unit <NUM> and a negative input of the first DC/DC converter <NUM> may for example be connected to a negative pole of the first high-voltage battery unit <NUM> or to the battery intermediate conductor <NUM>, for example at the second connection point <NUM>. Similarly, a positive input of the second DC/DC converter <NUM> may for example be connected to the a positive pole of the second high-voltage battery unit <NUM> or to the battery intermediate conductor <NUM>, for example at the second connection point <NUM>, and a negative input of the second DC/DC converter <NUM> may for example be connected to a negative pole of the second high-voltage battery unit <NUM>.

Moreover, a first fuse <NUM> may be provided connected in series with the first high-voltage battery unit <NUM> for isolation thereof in case of short-current or other type of similar malfunction.

In the same manner, a second fuse <NUM> may be provided connected in series with the second high-voltage battery unit <NUM> for isolation thereof in case of short-current or other type of similar malfunction.

Moreover, a third fuse <NUM> may be provided connected in series with the first DC/DC converter <NUM> for isolation thereof in case of short-current or other type of similar malfunction. Similarly, a fourth fuse <NUM> may be provided connected in series with the second DC/DC converter <NUM> for isolation thereof in case of short-current or other type of similar malfunction.

Since online execution of test process for identification of a suitable alternating frequency, for example the test process described above, at each single charging occasion may be undesirable due to for example time constraints associated with execution of the test process, or the like, a lookup data table with predetermined alternating frequencies may be provided.

A single lookup data table for the combined, series connected, first and second high-voltage battery units <NUM>, <NUM> may be provided, wherein the first and second high-voltage battery units <NUM>, <NUM> are handled as a single vehicle battery. Alternatively, an individual lookup data table with alternating frequencies may be provided for each of the first and second high-voltage battery units <NUM>, <NUM>.

<FIG> shows schematically a lookup data table having battery state of charge (SOC) along the y-axis and battery temperature (Temp) in Celsius along the x-axis, wherein the lookup data table provides a certain alternating frequency for each unique combination of battery state of charge and battery temperature. Consequently, when a charging event of a vehicle high-voltage battery is initiated, the power supply system may first check current battery state of charge and current battery temperature, and subsequently obtains a suitable alternating frequency from the lookup data table to be used for the charging event.

The lookup data table may additionally include battery state of health as input parameter, such that the power supply system in event of charging first checks current battery state of charge, current battery temperature, and current battery state of health and subsequently obtains a suitable alternating frequency from the lookup data table to be used for the charging event. Even further battery parameters may be used for the lookup data table.

The various alternating frequencies stored in the lookup data table may be provided based on factory settings, i.e. determined during development of the vehicle type and common for all vehicles of the same type, e.g. with the same type of power supply system. This enables offline calculation of the appropriate alternating frequencies.

However, each vehicle battery has a certain individual character in terms of battery cell composition, and each vehicle battery ages differently over time due to individual usage pattern, operating conditions, charging conditions, etc. Hence, predetermined alternating frequencies of a lookup data table based on factory settings or the like may become increasingly incorrect over time. Hence, it may be beneficial to implement an update process for reoccurring updating of appropriate alternating frequencies of the lookup data table over time based on the specific characteristic and aging of each individual vehicle battery.

This may for example be performed by supplementing each individual data entry of the lookup data table, i.e. each individual alternating frequency, with an indicator indicating an estimated correctness of the alternating frequency, wherein the indicator for example takes one or more or the following parameters into account: time since determining or storing the stored alternating frequency (age of data), usage pattern of the battery since said storing of the alternating frequency, operating conditions of the battery since said storing of the alternating frequency, charging conditions of the battery since said storing of the alternating frequency, etc..

According to some example embodiments, each individual data entry (alternating frequency) of the lookup data table may thus be supplemented with an individual age indicator, such as a time stamp, for indicating the age of the stored data. Alternatively, the age indicator may for example be an integer value reflecting for example the age of the stored data in terms of days, weeks, months or years, or the like.

For example, the age indicator may integer value reflecting the age of the stored data in terms of days, and a threshold value may be set to <NUM> days, such that the frequency value stored in the lookup data table is deemed valid and appropriate if the age indicator is smaller than <NUM>, and the frequency value stored in the lookup data table is deemed invalid and inappropriate if the age indicator is equal to or larger than <NUM>. Moreover, the age indicator of each stored frequency value within the lookup data table is increased with one every day.

Consequently, when a charging event of a vehicle high-voltage battery is initiated, the power supply system may first check current battery state of charge and current battery temperature, and subsequently check the age indicator of the associated alternating frequency provided by the lookup data table. If the age indicator indicates that the associated alternating frequency provided by the lookup data table is still reasonably valid, i.e. reasonably correct, the power supply system may use the stored value of the lookup data table. Otherwise, the power supply system may initiate an online execution of a test process for identification of an updated suitable alternating frequency, for example by means of the test process described above, and subsequently storing the updated value on the lookup data table and updating the age indicator. Thereby, a reasonable appropriateness of the used alternating frequency may be ensured, while avoiding an undesirable online recalculation of appropriate alternating frequency at the beginning of each battery charging event.

In other words, the electronic control system <NUM> of the power supply system may comprise a data memory having, for each of the first and second high-voltage battery units or jointly for both the first and second high-voltage battery units, a plurality of stored data records. Each of the stored data records is associated with a unique combination of a battery state of charge value and a battery temperature value and includes: a data field for storing a calculated frequency value reflecting a minimal internal resistance or minimal internal impedance of the battery at said unique combination of battery state of charge and battery temperature, and a data field for storing an age indicator indicating the age of the calculated frequency value. The electronic control system is then configured to, upon receiving an instruction to enter charging mode of the first and second high-voltage battery units <NUM>, <NUM> detecting current temperature level and current state of charge level associated with the first and/or second high-voltage battery units <NUM>, <NUM>, and subsequently using the associated calculated frequency value from the data record as the alternating frequency if the associated age indicator indicates that the calculated frequency value is up-to-date.

The term "associated calculated frequency value" may here represent the calculated minimal resistance frequency value from the data record having a unique combination of a battery state of charge value and a battery temperature value that corresponds to, or most closely resembles, the detected current temperature level and current state of charge level.

In addition, the electronic control system <NUM> of the power supply system may be configured to, upon detecting that the associated age indicator indicates an outdated calculated frequency value, applying the battery internal resistance or impedance detection arrangement <NUM> for determining a new frequency value reflecting the minimal internal resistance or minimal internal impedance of each of the first and second high-voltage battery units <NUM>, <NUM>, updating the stored calculated frequency value with the new frequency value and updating the age indicator in the data record, and using said updated, new, frequency value as the alternating frequency.

In the example embodiment of <FIG>, the circles at each crossing in the lookup data table may represent a data field having a stored frequency value reflecting a minimal internal resistance or minimal internal impedance of the battery at said unique combination of battery state of charge and battery temperature, and the fill status of the circles may represent the age indicator of that specific frequency value. Hence, the data fields associated with filled circles <NUM> have an updated frequency value, and the data fields associated with non-filled circles <NUM> have an outdated, old, frequency value.

Consequently, of a battery charging event is initiated at <NUM>% SOC and <NUM> degrees Celsius, the associated frequency value stored in the lookup data table is deemed outdated and a new frequency value is identified, for example using the battery internal resistance or impedance detection arrangement <NUM>, and subsequently stored in the lookup data table, together with an updated age indicator. Thereafter, the new frequency value is used as alternating frequency during charging of the first and second high-voltage battery units <NUM>, <NUM>. In other words, the filled circles <NUM> in <FIG> reflect a vehicle that is mostly charged at a temperature range of <NUM> - <NUM> degrees C and having at least <NUM>% SOC.

Moreover, during charging of the first and second high-voltage battery units <NUM>, <NUM>, the battery SOC value slowly increases and the battery temperature may vary depending on charging rate, ambient temperature level, etc. Consequently, the electronic control system <NUM> of the power supply system may be configured to, during a charging event, upon passing a non-filled circle, i.e. upon reaching a battery SOC and battery temperature reflecting an outdated frequency value of the lookup data table, trigger the battery internal resistance or impedance detection arrangement <NUM> for determining a new frequency value reflecting the minimal internal resistance or minimal internal impedance said outdated frequency value and updating the stored calculated frequency value with the new frequency value and updating the associated age indicator.

The charging process of the first and second high-voltage battery units <NUM>, <NUM> may be temporarily halted during operation of the battery internal resistance or impedance detection arrangement <NUM>. Alternatively, charging process of the first and second high-voltage battery units <NUM>, <NUM> may operate simultaneously with operation of the battery internal resistance or impedance detection arrangement <NUM>.

In some example embodiments, as described above, the lookup data table may from manufacturing of the vehicle be filled with alternating frequencies based on factory settings. However, according to an alternative example embodiment, the lookup data table may instead be empty at the beginning, and instead being slowly filled with alternating frequencies during use of the vehicle, by means of the update process described above.

The basic steps of a method of one example embodiment for operating a power supply system for an electric vehicle drivetrain is described below with reference to <FIG>, wherein the power supply system includes a first high-voltage battery unit <NUM> connected in series with a second high-voltage battery unit <NUM>. The method comprises a first step S10 of, during a charging mode of the first and second high-voltage battery units <NUM>, <NUM>, routing, by means of a circuit arrangement <NUM> having a plurality of high-power switching semiconductor devices <NUM>-<NUM> connected to the first and second high-voltage battery units <NUM>, <NUM>, high-voltage DC received from a vehicle external charging source <NUM> alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, with an alternating frequency of at least <NUM>, specifically at least <NUM>, and more specifically in the range of <NUM> - <NUM><NUM>. The method further comprises a second step S20 of, during a power supply mode of the power supply system, supplying, by means of said circuit arrangement <NUM>, high-voltage DC from both the first and second high-voltage battery units <NUM>, <NUM> for driving a vehicle electrical traction machine <NUM> of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units <NUM>, <NUM>.

With reference to <FIG>, according to a further example embodiment of the method, the power supply system includes, for each of the first and second high-voltage battery units or jointly for both the first and second high-voltage battery units, a lookup data table having a plurality calculated frequency values, each reflecting a minimal internal resistance or minimal internal impedance of the battery for a unique combination of battery state of charge and battery temperature and each being associated with an age indicator indicating the age of the calculated frequency value. The method further comprises first initialisation step S1 of receiving an instruction to enter charging mode of the first and second high-voltage battery units <NUM>, <NUM>. The method further comprises second initialisation step S2 of detecting current temperature level and current state of charge level associated with the first and/or second high-voltage battery units <NUM>, <NUM>. The method further comprises a third initialisation step S3 of obtaining from the lookup data table the associated age indicator of the corresponding calculated frequency value. Thereafter, when the associated age indicator indicates that the calculated frequency value is up-to-date, for example when the age indicator is smaller than a threshold value, the method involves a first step S10 of routing high-voltage DC alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, while using the calculated frequency value from the lookup data table as the alternating frequency, as described with reference to <FIG>.

With reference to <FIG>, according to a further example embodiment of the method, the method involves, in addition to the method steps described with reference to <FIG>, when the associated age indicator indicates that the calculated frequency value is outdated, a fourth initialisation step S4 of applying a battery internal resistance or impedance detection arrangement for determining a new frequency value reflecting the minimal internal resistance or minimal internal impedance of each of the first and second high-voltage battery units <NUM>, <NUM>. The method further comprises a fifth initialisation step S5 of updating the stored calculated frequency value and the age indicator in the lookup data table, and a first step S10* of routing high-voltage DC alternatingly to the first high-voltage battery unit <NUM> and to the second high-voltage battery unit <NUM>, while using said new, updated, calculated frequency value as the alternating frequency.

With reference to <FIG>, according to a further example embodiment of the method, the fourth initialisation step S4 of applying the battery internal resistance or impedance detection arrangement for determining a new calculated frequency value reflecting the minimal internal resistance or minimal internal impedance of each of the first and second high-voltage battery units involves a first substep S4a of, for each of a set of different frequencies, supplying an AC signal having a certain frequency (f) to a selected battery unit out of the first and second high-voltage battery units or to both the first and second high-voltage battery units, registering a set of resulting alternating voltages, and determining a set of internal impedances of the selected battery unit or both the first and second high-voltage battery units based on the set of resulting alternating voltages, and subsequently a second substep S4b of identifying the minimal internal resistance or minimal internal impedance of the selected battery unit or both the first and second high-voltage battery units from the collected set of internal impedances, and determining the frequency associated with said identified minimal internal resistance or minimal internal impedance.

Claim 1:
A power supply system for an electric vehicle drivetrain, the power supply system comprising:
a first high-voltage battery unit (<NUM>),
a second high-voltage battery unit (<NUM>) connected in series with the first high-voltage battery unit (<NUM>),
a circuit arrangement (<NUM>) having a plurality of high-power switching semiconductor devices (<NUM>-<NUM>) connected to the first and second high-voltage battery units (<NUM>, <NUM>),
an electronic control system (<NUM>) configured for controlling operation of the plurality of high-power switching semiconductor devices (<NUM>-<NUM>) for:
- during a charging mode of the first and second high-voltage battery units (<NUM>, <NUM>), routing high-voltage DC received from a vehicle external charging source (<NUM>) alternatingly to the first high-voltage battery unit (<NUM>) and to the second high-voltage battery unit (<NUM>), with an alternating frequency of at least <NUM>, specifically at least <NUM>, and more specifically in the range of <NUM> - <NUM><NUM>, and
- during a power supply mode of the power supply system, supplying high-voltage DC from both the first and second high-voltage battery units (<NUM>, <NUM>) for driving a vehicle electrical traction machine (<NUM>) of the electric vehicle drivetrain, wherein the supplied high-voltage DC has a voltage level corresponding to the accumulated voltage level of the series connected first and second high-voltage battery units (<NUM>, <NUM>).