Charging circuit and method for charging a traction battery, electric vehicle

Abstract

The invention relates to the charging of a traction battery by means of AC voltage, wherein a frequency of the AC voltage used for this purpose is taken into account during the charging. An initial starting value is used in order to determine the frequency of the AC voltage. This initial starting value can be provided by a non-volatile memory.

Description

[0001] Description

[0002] title

[0003] Charging circuit and method for charging a traction battery, electric vehicle

[0004] Technical area

[0005] The present invention relates to a charging circuit and a method for charging a traction battery. The present invention further relates to an electric vehicle with such a charging circuit.

[0006] State of the art

[0007] Vehicles that are fully or at least partially electrically powered have an electrical energy storage device, also known as a traction battery. This traction battery can provide electrical energy to drive the vehicle. Furthermore, such a traction battery can also be charged from an external energy source. Charging can generally be carried out using direct current (DC) or alternating current (AC). If charging is carried out using a single- or multi-phase alternating current, a charging circuit is required that converts the alternating current into direct current and, if necessary, adjusts the voltage level. Particularly when the alternating current is provided by an electrical power grid, predetermined framework conditions for the influence on the power grid during charging of the traction battery must be taken into account.

[0008] For example, the publication DE 10 2009 050 042 A1 describes a charging station for electric vehicles. It proposes grid stabilization. Specifically, grid stabilization is to be achieved by determining a grid frequency and regulating the load depending on the determined grid frequency.

[0009] Disclosure of the Invention The present invention provides a charging circuit and a method for charging a traction battery, as well as an electric vehicle, having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent patent claims.

[0010] Accordingly, it is provided:

[0011] A charging circuit for charging a traction battery, comprising a detector device and a control device. The detector device is configured to determine a frequency of an alternating voltage present at an input terminal of the charging circuit. The control device is configured to adjust at least one of the operating characteristics of the charging circuit using the detected frequency of the alternating voltage at the input terminal. The detector device is further configured to determine the frequency of the alternating voltage at the input terminal using an initial start value. For this purpose, the detector device comprises a non-volatile memory. This non-volatile memory is configured to store a frequency of the alternating voltage at the input terminal detected by the detector device.Furthermore, the memory is designed to provide the stored value of the detected frequency as an initial value for determining the mains frequency.

[0012] Furthermore, it is planned:

[0013] An electric vehicle with a traction battery and a charging circuit according to the invention for charging the traction battery.

[0014] Finally, it is planned:

[0015] A method for charging a traction battery. The method comprises a step for determining a frequency of an alternating voltage applied to an input terminal. The frequency of the alternating voltage at the input terminal is determined using a provided initial start value. The initial start value can be provided by a non-volatile memory. The method further comprises a step for providing at least one operating characteristic of a charging circuit for charging the traction battery. The at least one operating characteristic is set using the detected frequency of the alternating voltage at the input terminal. The method further comprises a step for storing the determined frequency of the alternating voltage applied to the input terminal in the non-volatile memory.The value of the determined frequency stored in the non-volatile memory thus serves as a future initial starting value for a further determination of the frequency of the alternating voltage at the input terminal at a later time.

[0016] Advantages of the invention

[0017] The present invention is based on the finding that the operation of a charging circuit for charging a traction battery using alternating voltage from a power grid may require knowledge of the grid frequency, i.e., the frequency of the alternating voltage provided by the power grid. Based on this grid frequency, the operating behavior of the charging circuit can be controlled or regulated. This makes it possible, for example, to minimize feedback from the charging circuit to the power grid during charging of the traction battery.

[0018] Furthermore, it is a finding of the present invention that not all electrical power supply networks worldwide are operated with the same network frequency.

[0019] It is therefore an idea of ​​the present invention to improve the determination of a grid frequency by the charging circuit of an electric vehicle by not determining a grid frequency from an arbitrary starting value, but rather using a value from a previously determined grid frequency as the initial starting value for determining the grid frequency. In this way, the grid frequency can be determined much more quickly. The determined grid frequency can, for example, be used to control the operating behavior of the charging circuit, which converts an electrical alternating voltage from a power supply network into a direct voltage for charging the traction battery. For example, the determined grid frequency can be used to adjust a phase shift between an electrical current and an electrical voltage. This allows the reactive power component to be adjusted.In particular, based on the determined grid frequency, the operating behavior of the charging circuit can be adjusted in such a way that the reactive power component is minimized, thus minimizing the phase shift between electrical current and electrical voltage. In this way, the charging circuit acts as an at least approximately resistive load relative to the connected power grid.

[0020] Although energy supply grids are generally operated at at least approximately the same grid frequency, it is nevertheless possible that, due to regional differences, an electric vehicle may be connected to energy supply grids with different grid frequencies. Therefore, it is possible that the underlying grid frequency for a charging circuit may change at least occasionally. However, if the determination of the respective underlying grid frequency were always started from a same, fixed grid frequency, this would result in the grid frequency always taking significantly longer to determine reliably, particularly in areas with a different grid frequency.

[0021] According to the invention, it is therefore possible to adapt the initial grid frequency, which forms the basis for determining the current grid frequency. In particular, the previously determined grid frequency can always be used as the initial starting value. This allows the respective grid frequency to be determined very quickly until the vehicle is to be charged for the first time in a region with a different grid frequency. According to one embodiment, the detector device for determining the frequency at the input terminal of the charging circuit comprises a proportional-integral controller (PI controller). The PI controller can be designed to determine the frequency of the alternating voltage at the input terminal by comparing the initial value for determining the grid frequency with a controlled variable. In this way, the initial starting value for determining the grid frequency can be regarded as a type of feedforward control value.To further determine the exact grid frequency, it is then only necessary to determine any deviation from this initial value. If the current grid frequency at least approximately corresponds to the current grid frequency, the grid frequency can be determined very quickly.

[0022] According to one embodiment, the charging circuit comprises a position-determining device. The position-determining device is designed to determine a geographical position. For example, a position can be determined using a satellite-based navigation system, such as GPS, Galileo, or similar. The detector device can thus determine the frequency of the alternating voltage at the input terminal using the determined geographical position. In this case, it is also possible to store corresponding variables for different geographical positions for an initial starting value for determining the alternating voltage at the input terminal of the charging circuit and to use them to determine the grid frequency. Thus, even with regular use of charging points with different grid frequencies, the respective applied grid frequency can be determined very quickly.

[0023] According to one embodiment, the detector device is designed to store a current value of the frequency of the alternating voltage at the input terminal as a new initial value in a non-volatile memory if a predefined storage condition is met. Such a predefined storage condition can, for example, include a condition that the determined grid frequency remains within a predefined value range over a predefined period of time. In this way, a new initial value for a starting value for determining the grid frequency can be stored in the non-volatile memory if a stable frequency has been determined during the determination of the currently valid grid frequency.

[0024] According to one embodiment, the control device is designed to adjust a phase shift between current and voltage using the detected frequency of the AC voltage at the input terminal. In particular, a phase shift between current and voltage can be minimized. In this way, a reactive power component can be minimized, so that essentially only active power is drawn by the charging circuit.

[0025] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0026] Short description of the drawings

[0027] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0028] Fig. 1: a schematic diagram illustrating the charging of the traction battery of an electric vehicle with a charging circuit according to an embodiment;

[0029] Fig. 2: a block diagram of a charging circuit according to an embodiment; and

[0030] Fig. 3: A flowchart underlying a method for charging a traction battery according to one embodiment. Description of embodiments

[0031] Figure 1 shows a schematic representation of a diagram illustrating a charging process for charging a traction battery 20 in an electric vehicle 1. To charge the traction battery 20, the electric vehicle 1 can be parked at a charging station 2. The charging station 2 can then be electrically connected to a charging circuit 10 of the electric vehicle 1. Electrical energy can then be provided from a power grid 3 via the charging station 2 to the charging circuit 10 of the vehicle 1. If a single-phase or multi-phase alternating voltage is provided by the charging station 2, this alternating voltage can be converted into a direct voltage by the charging circuit 10. Furthermore, the voltage level of the provided direct voltage can be adjusted by the charging circuit 10 in such a way that it is suitable for charging the traction battery 20.

[0032] For charging the traction battery 20 in the vehicle 1, it is desirable that, if possible, only active power is transmitted from the charging station 2 to the electric vehicle 1. In order to keep the reactive power component as low as possible, the electrical current and electrical voltage should therefore be at least approximately in phase. To achieve such operating behavior, it may be necessary for the electrical fundamental frequency of the alternating voltage provided by the charging station 2 to be known or determined in the charging circuit 10. In this case, it is desirable to determine the fundamental frequency of the provided alternating voltage as quickly as possible. For such a determination of the fundamental frequency of an alternating voltage, it is advantageous to begin determining the fundamental frequency from an initial starting value that is as close as possible to the fundamental frequency of the alternating voltage.However, since various power grids exist worldwide, some of which have different base frequencies, it is not possible to provide a uniform initial starting value for determining the base frequency that represents an optimum for all applications. Therefore, the charging circuit 10 can adjust the value of the initial frequency to determine the grid frequency in order to determine the base frequency of an AC voltage supplied to an input terminal.

[0033] Figure 2 shows a block diagram of a charging circuit 10 according to one embodiment. An alternating electrical voltage can be provided at an input terminal E. This can be, for example, a single-phase or multi-phase alternating electrical voltage, such as that provided by a charging station 2. This alternating electrical voltage provided at the input terminal E can be converted by means of a voltage converter 19 into a direct voltage, which is suitable for charging a traction battery 20 of the vehicle. The voltage converter 19 can be controlled accordingly by a control device 15. As already mentioned, the voltage converter 19 should be controlled, among other things, in such a way that the phase difference between the electrical voltage and the electrical current of the electrical power flowing into the voltage converter 19 is as small as possible.In this way, the reactive power component can be minimized. Such control may require knowledge of the respective fundamental frequency of the alternating voltage provided at the input terminal E. For this purpose, a detector device 12 can be provided in the charging circuit 10, which determines the fundamental frequency of the alternating voltage provided at the input terminal E. An initial starting value can be used to determine the electrical frequency of the alternating voltage provided at the input terminal E.

[0034] Preferably, the initial starting value can be a value that is as close as possible to the frequency of the alternating voltage to be analyzed. Since conventional approaches for determining the fundamental frequency of an alternating voltage using an initial starting value already exist, these will not be explained in detail here. However, to account for the fact that various energy supply grids with different fundamental frequencies exist worldwide, the initial starting value for determining the grid frequency can be adjusted. For this purpose, for example, a previously determined value for the fundamental frequency of the alternating voltage provided at the input terminal E can be stored as the initial starting value in a non-volatile memory 13.This stored value can be read from the non-volatile memory 13 for a new determination of the frequency of the alternating voltage at the input terminal E and used as a new initial starting value. In this way, a suitable initial starting value is used as long as the vehicle 1 with the described charging circuit 10 is located in an area with a corresponding mains frequency. If such a vehicle is connected to an electrical alternating voltage with a different electrical frequency for the first time, a new initial value can be stored in the non-volatile memory 13 after the different frequency has been detected. The new initial value for determining the frequency of the alternating voltage is then available as a new starting value in the non-volatile memory 13.Accordingly, a suitable initial starting value can be used for determining the electrical frequency of the alternating voltage during further charging processes.

[0035] Furthermore, it is also possible to determine a respective geographical position of the vehicle 1 with the described charging circuit 10 using a corresponding position-determining device 16. Accordingly, the determined geographical position can also be taken into account in order to determine a suitable initial starting value for determining the frequency of an alternating voltage provided at the input terminal E. Such a position-determining device 16 can, for example, be a satellite navigation system such as GPS, Galileo, or the like. Furthermore, any other position-determining devices are also possible. Accordingly, it is possible to store several initial starting values ​​with corresponding geographical positions in the non-volatile memory 13.Depending on the current geographical position, a suitable initial starting value for determining the frequency of the alternating electrical voltage at the input terminal E can then be read out from the non-volatile memory 13 and used.

[0036] In principle, it is possible, after each determination of the current

[0037] Frequency of the alternating voltage at the input terminal E, the determined value is stored as a new initial value in the non-volatile memory 13. Furthermore, it is also possible to link the storage of a suitable initial value for determining the frequency to further conditions. For example, an initial value for determining the frequency can only be stored in the non-volatile memory 13 if a predetermined period of time has passed since the last storage and / or the last determination of a value for the frequency of the alternating voltage at the input terminal E.

[0038] Furthermore, a new initial value may only be stored in the non-volatile memory 13 if further predefined conditions for determining the current frequency are met. Such a condition may, for example, include the condition that the determined frequency remains within a predefined value range, for example, within ± a maximum of 1%, over a predefined period of time.

[0039] Furthermore, the conditions for storing a new initial value in the non-volatile memory 13 can also take into account an amplitude or an effective value of the mains voltage. For example, a new initial value can only be stored in the non-volatile memory 13 if the value of the electrical voltage at the input terminal E is within a predetermined value range. Analogously, only those initial values ​​for the frequency of an electrical voltage that meet predetermined conditions can be stored in the non-volatile memory 13. For this purpose, for example, several frequency ranges can be defined that specify valid frequency ranges for mains frequencies of energy supply networks. Such frequency ranges can include, for example, 50 Hz and 60 Hz, whereby tolerance ranges, for example ±1 Hz or similar, are also possible for such specific frequencies.

[0040] Figure 3 shows a flowchart underlying a method for charging a traction battery in an electric vehicle 1. The method can, in principle, comprise any steps as previously described in connection with an electric vehicle 1 or a charging circuit for charging the traction battery 20. Similarly, the previously described charging circuit 10 for charging the traction battery 20 can also comprise any components as described below in connection with the method.

[0041] In step S1, a frequency of an alternating voltage applied to an input terminal E is determined. The frequency of the alternating voltage at the input terminal E is determined, in particular, using a provided initial starting value. This initial starting value can be stored in a non-volatile memory 13 and provided for determining the frequency.

[0042] In step S2, an operating characteristic for charging the traction battery 20 is set using the detected frequency of the alternating voltage at the input terminal E. In particular, setting such an operating characteristic can include controlling a voltage converter 19. The voltage converter 19 can be controlled such that a phase difference between the electrical current and the electrical voltage at the input terminal E is minimized. In this way, a reactive power component can be minimized. This makes it possible to achieve the highest possible active power component for charging the traction battery 20.

[0043] Furthermore, the method may comprise a step S3 for storing the determined frequency of the alternating voltage applied to the input terminal E in a non-volatile memory 13. The value thus stored may be used as a new initial starting value for further detection of the frequency of the alternating voltage at the input terminal E.

[0044] In summary, the present invention relates to the charging of a traction battery using alternating voltage, wherein a frequency of the alternating voltage used for this purpose is taken into account during charging. An initial starting value can be used to determine the frequency of the alternating voltage. This initial starting value can be provided by a non-volatile memory. In particular, the initial starting value in the non-volatile memory can be adjusted if a different value is obtained when detecting the frequency of the alternating voltage.

Claims

Claims 1. Charging circuit (10) for charging a traction battery (20), comprising: a detector device (12) designed to determine the frequency of an alternating voltage applied to an input terminal (E) of the charging circuit (10); and a control device (15) designed to adjust operating characteristics of the charging circuit (10) using the detected frequency of the alternating voltage at the input terminal (E), wherein the detector device (12) is designed to determine the frequency of the alternating voltage at the input terminal (E) using an initial start value, and wherein the detector device (12) comprises a non-volatile memory (13) designed to store a frequency of the alternating voltage detected by the detector device (12) at the input terminal (E) and to provide it as an initial value for determining the mains frequency.

2. Charging circuit (10) according to claim 1, wherein the detector device (12) comprises a proportional-integral controller designed to determine the frequency of the AC voltage at the input terminal (E) by comparing the initial value for determining the mains frequency with a controlled variable.

3. Charging circuit (10) according to claim 1 or 2, comprising a position determination device (16) designed to determine a geographical position and to perform a determination of the frequency of the alternating voltage at the input terminal (E) using the determined geographical position.

4. Charging circuit (10) according to one of claims 1 to 3, wherein the detector device (12) is designed to detect a current value of the to store the frequency of the alternating voltage at the input terminal (E) as a new initial value in the non-volatile memory (13) if a predetermined storage condition is met. Charging circuit (10) according to claim 4, wherein the predetermined storage condition comprises an at least approximately constant frequency over a predetermined period of time. Charging circuit (10) according to any one of claims 1 to 5, wherein the control device (15) is configured to adjust a phase shift between current and voltage using the detected frequency of the alternating voltage at the input terminal (E). Charging circuit (10) according to claim 6, with a voltage converter (19) configured to convert the electrical voltage provided at the input terminal into a DC voltage suitable for charging the traction battery (20).Electric vehicle (1), comprising: a traction battery (20), a charging circuit (10) for charging a traction battery (20) according to one of claims 1 to 7. Method for charging a traction battery (20), comprising the steps:. Determining (Sl) a frequency of an alternating voltage applied to an input terminal (E), wherein the frequency of the alternating voltage at the input terminal (E) is determined using a provided initial start value, and wherein the initial start value is stored in a non-volatile memory (13); Setting (S2) an operating characteristic for charging the traction battery (20) using the detected frequency of the AC voltage at the input terminal (E); and storing (S3) the determined frequency of the AC voltage at the input terminal (I) applied alternating voltage in the non-volatile memory (13) as a future initial starting value.

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