Method, computing unit and computer program for operating a power converter arrangement, power converter arrangement and vehicle

Abstract

The invention relates to a method for operating a power converter arrangement (100) comprising an AC voltage side (110) with one or more phase connections (1, 2, 3) and a neutral conductor connection (4), an input power converter circuit (135) with each phase connection of a phase connection half-bridge (S11, S12, S13, S14, S15, S16) each comprising two series-connected semiconductor switches and a center tap between the two series-connected semiconductor switches, wherein the center tap is connected to the phase connection (1, 2, 3), and a neutral conductor half-bridge (137) comprising two series-connected rectifier elements and a center tap between the two series-connected rectifier elements, wherein the center tap is connected to the neutral conductor connection (4), a DC voltage side (120) with a first pole connection (121) and a second pole connection (122), a capacitor arrangement (125),which is connected between the first pole terminal (121) and the second pole terminal (122) on the DC voltage side (120). The method comprises generating a DC voltage (142) at the capacitor arrangement (125) with a first voltage level that is lower than a nominal voltage level of the capacitor arrangement (125). Furthermore, a computing unit and a computer program for implementing the method, a power converter arrangement, and a vehicle are proposed.

Description

[0001] The present invention relates to a method for operating a power converter arrangement as well as a computing unit and a computer program for carrying out the method, a power converter arrangement and a vehicle. Background of the invention

[0002] Electrolytic capacitors can age if stored for extended periods without use under voltage. Aging results in the degradation of an oxide layer on at least one electrode of the capacitor. Subsequent recharging of such an aged capacitor can lead to undesirable side effects. For example, hydrogen can be produced, causing pressure within the capacitor to rise. Leakage current (unwanted self-discharge) in the capacitor can also increase, and in extreme cases, this can even lead to capacitor failure (e.g., due to a short circuit or—as a result of the aforementioned pressure increase—the capacitor bursting or a pressure relief valve opening, allowing the electrolyte to escape, etc.). Disclosure of the invention

[0003] According to the invention, a method for operating a power converter arrangement, as well as a computing unit and a computer program for implementing the method, a power converter arrangement, and a vehicle having the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0004] The invention makes use of the measure of deliberately and slowly increasing a DC voltage applied to a capacitor arrangement of the power converter arrangement in order not to damage the capacitor arrangement. Typically, such capacitor arrangements, in particular in power converter arrangements that are used in at least partially electrically powered vehicles, are not directly accessible from outside the power converter arrangement. Therefore, such a power converter arrangement would have to be at least partially dismantled in order to slowly charge the capacitor arrangement directly, which typically entails a high level of effort and may possibly even result in the destruction of a housing of the power converter arrangement. According to the invention, the power converter arrangement itself is therefore controlled such that the capacitor arrangement is slowly charged, i.e. the voltage (and current) applied to the capacitor arrangement are slowly increased.This allows the oxide layer to build up on an aged capacitor without the negative side effects described above. This buildup of the oxide layer is also referred to as formation.

[0005] A power converter arrangement which can be used within the scope of the invention comprises an AC voltage side with one or more, in particular three, phase connections and a neutral conductor connection, an input power converter circuit with, for each phase connection, a phase connection half-bridge comprising two semiconductor switches connected in series and a center tap between the two semiconductor switches connected in series, the center tap being connected to the phase connection, and a neutral conductor half-bridge comprising two rectifier elements connected in series (e.g. semiconductor switches or diodes) and a center tap between the two rectifier elements connected in series, the center tap being connected to the neutral conductor connection. Furthermore, the power converter circuit comprises a DC voltage side with a first pole connection and a second pole connection, and a capacitor arrangement (e.g.two capacitors in series) connected between the first pole terminal and the second pole terminal on the DC side.

[0006] According to the invention, the method comprises generating a DC voltage across the capacitor arrangement at a first voltage level that is lower than a nominal voltage level of the capacitor arrangement. According to the invention, the first voltage level corresponds to a voltage that is at most 30%, 20%, 10%, 5%, or 2% of the nominal voltage level.

[0007] In at least one embodiment, generating a DC voltage at the capacitor arrangement with a first voltage level comprises applying an external voltage between the one or one of the plurality of phase connections and the neutral conductor connection. The capacitor arrangement can thus be formed directly from the outside, i.e. without changing the internal circuitry or without additional hardware, for example simply by switching switches that are already present, e.g. relays. The semiconductor switches of the phase connection half-bridge, which are connected to the one phase connection or to one of the plurality of phase connections, are in particular not controlled but operated in a non-conductive state. If a DC voltage is applied as an external voltage, it is applied directly to the capacitor arrangement via the body diode of the upper semiconductor switch of the phase connection half-bridge.If an alternating voltage is applied as an external voltage, it is rectified via the body diode of the upper semiconductor switch and applied to the capacitor arrangement.

[0008] In at least one embodiment, the power converter arrangement further comprises an inverter circuit for inverting the DC voltage applied to the capacitor arrangement and a transformer for transferring the inverted DC voltage to an intermediate rectifier circuit. Generating a DC voltage at the capacitor arrangement with a first voltage level comprises applying a DC voltage to the intermediate rectifier circuit and operating the intermediate rectifier circuit as an inverter and the inverter circuit as a rectifier. This makes it possible, e.g. in battery-electric vehicles, to apply a voltage to the capacitor arrangement even when no external voltage is available, or to apply a higher voltage to the capacitor arrangement than can be made available from a typical AC network.Thus, the capacitor arrangement can be formed for use at a higher nominal voltage than would be the case with pure mains operation from a standard household power network.

[0009] In particular, the power converter arrangement can further comprise a further inverter circuit for inverting the DC voltage applied to the intermediate rectifier circuit and a further transformer for transmitting the inverted DC voltage to a final rectifier circuit. For example, an electric vehicle can have a low-voltage network or low-voltage network with a low-voltage battery (e.g., less than 100 V, less than 50 V, or less than 30 V nominal voltage of the low-voltage battery) and a high-voltage network or high-voltage network with a high-voltage battery (e.g., a nominal voltage of the high-voltage battery can be over 100 V, over 300 V, or over 500 V).According to this embodiment, the low-voltage grid and the high-voltage grid are electrically connected to one another by means of the further inverter circuit, the further transformer, and the final rectifier circuit, so that electrical energy can be exchanged between the high-voltage grid and the low-voltage grid. According to this embodiment, applying a DC voltage to the intermediate rectifier circuit involves applying a DC voltage to the final rectifier circuit and operating the final rectifier circuit as an inverter and the further inverter circuit as a rectifier. This allows the capacitor arrangement to be precharged to a high first voltage level from the low-voltage grid and thus formed for use at high nominal voltages.

[0010] In at least one embodiment, the method further comprises increasing the voltage applied to the capacitor arrangement to a second voltage level over an increase period such that a predetermined voltage gradient is not exceeded. In particular, the increase period can be selected from an interval between 5 s and 20 s, in particular between 8 s and 16 s, and / or the voltage gradient from an interval between 5% / s and 10% / s, in each case based on the nominal voltage level of the capacitor arrangement. This reliably prevents damage to the capacitor arrangement during forming. The second voltage level can be maintained over a holding period, for example, of 30 s to 60 s, in order to carry out the forming sufficiently extensively.

[0011] If the method is carried out at least partially using the AC voltage side, increasing the voltage applied to the capacitor arrangement can, according to at least one embodiment, comprise driving one of the semiconductor switches of the phase-connection half-bridge, which is connected to one of the phase connections, in a boost mode. This allows the maximum DC voltage achievable at the capacitor arrangement from the external voltage applied between the phase connection and the neutral conductor connection to be increased, so that the capacitor arrangement can be (further) formed using the external voltage.

[0012] Alternatively or additionally, when using the DC side to apply the DC voltage at the first voltage level, increasing the voltage applied to the capacitor arrangement can involve controlling the intermediate rectifier circuit as an inverter and the inverter circuit as a rectifier such that the voltage is increased (in particular gradually or as desired). Energy from the high-voltage grid can thus be used for (further) forming the capacitor arrangement.

[0013] Controlling the intermediate rectifier circuit can involve controlling the final rectifier circuit as an inverter and the further inverter circuit as a rectifier, so that the voltage applied to the intermediate rectifier circuit is increased. This also enables the use of the low-voltage grid for increasing the DC voltage.

[0014] In at least one embodiment, the method further comprises limiting a current flowing into the capacitor arrangement. This limits the reaction rate during oxide buildup, which further contributes to avoiding the harmful side effects mentioned above, in particular the pressure increase within the capacitor arrangement.

[0015] A computing unit according to the invention, e.g. a control unit of a motor vehicle, is configured, in particular in terms of programming, to carry out a method according to the invention.

[0016] A power converter arrangement according to the invention has an AC voltage side with one or more phase connections and a neutral conductor connection, an input power converter circuit with each phase connection of a phase connection half-bridge having two semiconductor switches connected in series and a center tap between the two semiconductor switches connected in series, the center tap being connected to the phase connection, and a neutral conductor half-bridge having two rectifier elements connected in series and a center tap between the two rectifier elements connected in series, the center tap being connected to the neutral conductor connection, a DC voltage side with a first pole connection and a second pole connection, a capacitor arrangement which is connected between the first pole connection and the second pole connection on the DC voltage side, and a computing unit according to the invention.

[0017] An on-board charger of a vehicle according to the invention has a power converter arrangement according to the invention.

[0018] A vehicle according to the invention, which in particular is at least partially electrically drivable, comprises such a power converter arrangement, a charging socket which is connected to the one or more phase connections and the neutral conductor connection of the power converter arrangement, and a battery.

[0019] The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this entails particularly low costs, in particular if an executing control unit is also used for other tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored thereon, as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or cable-based or wireless (e.g. via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.).

[0020] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0021] The invention is illustrated schematically in the drawing using exemplary embodiments and is described below with reference to the drawing. Short description of the drawings Fig. 1 schematically shows a power converter arrangement as can be used in embodiments of the invention, in the form of a section of a simplified circuit diagram in a first operating mode. Fig. 2 shows the converter arrangement from Fig. 1 in the form of a larger section of the circuit diagram in one of Fig. 1 different second operating mode. Embodiment(s) of the invention

[0022] In Fig. 1 is a power converter arrangement as can be used in embodiments of the invention, shown schematically using a section of a simplified circuit diagram and designated overall by 100. In this case, Fig. 1 a first operating mode of the power converter arrangement is illustrated by arrows showing a current flow.

[0023] The power converter arrangement can in particular be part of an on-board charger for charging a battery (cf. Fig. 2) of a vehicle and, in the example shown, comprises three phase connections 1, 2, 3, a neutral conductor connection 4, and a protective conductor connection 5 on an AC voltage side 110. The connections can be arranged, in particular, in a vehicle socket, which can be connected to an AC voltage source by means of a charging cable. In the present case, it is a three-phase power converter with a neutral conductor connection, which can be connected, for example, to a three-phase current source (e.g., 230 / 400 V); however, it can also be a single-phase power converter with a neutral conductor connection, which can be connected, for example, to an AC current source (e.g., 230 V).

[0024] The phase terminals 1, 2, 3 and the neutral conductor terminal 4 are connected to an input converter circuit 135. The input converter circuit 135 comprises three phase connection half-bridges, each having two series-connected semiconductor switches S11 and S12, S13 and S14, as well as S15 and S16, and a center tap between the two series-connected semiconductor switches, wherein each center tap is connected to one of the phase terminals 1, 2, 3. Furthermore, the input converter circuit 135 comprises a neutral conductor half-bridge 137 having two series-connected rectifier elements (shown here as diodes) and a center tap between the two series-connected rectifier elements, wherein the center tap is connected to the neutral conductor terminal 4.

[0025] On a DC voltage side 120 of the input converter circuit 135, a capacitor arrangement 125 is provided which is connected between a first pole terminal 121 and a second pole terminal 122 and, in the example shown here, has a first electrolytic capacitor 126 and a second electrolytic capacitor 127 which are connected in series with one another.

[0026] In the first operating mode, in the example shown, a DC voltage is applied as an external voltage between one of the phase terminals 1, 2, 3 (here, a first phase terminal 1) and the neutral conductor terminal 4 of the AC voltage side 110. For example, a voltage level 140 of the DC voltage applied to the AC voltage side can be 4-40% of a nominal voltage of the capacitors 126, 127, which can correspond in particular to a nominal voltage of the first phase terminal 1 (in AC voltage operation). As a result, a first DC voltage 142 is applied to each of the two capacitors 126, 127, which in the example chosen here can be 2-20% of the nominal voltage of the capacitors 126, 127 (half of the voltage 140 applied to the AC voltage side). For this purpose, switch S5 is open so that the voltage can drop across both capacitors 126, 127.This corresponds to a passive formation of the capacitors 126, 127, wherein the applied voltage is passed on to the DC voltage side 120 without active control of the semiconductor switches S11, S12, which are connected to the first phase terminal 1, in particular (depending on the polarity of the applied voltage) via the body drain diode of the semiconductor switch (e.g. MOSFET) S11.

[0027] Alternatively or additionally, in the first operating mode, passive forming can be carried out using, for example, a 230V mains voltage (i.e., an alternating voltage between the first phase connection 1 and the neutral conductor connection 4) on the alternating voltage side 110. In this case, the voltage is also passed on to the direct voltage side 120 without actively controlling the semiconductor switches S11, S12. By using an alternating voltage, however, a higher first direct voltage 142 can be achieved, approximately 160 V in the example explained here. A current flowing in this case can be limited - regardless of the selected current supply on the alternating voltage side 110 - by means of a current limiting device 112, for example in the form of temperature-dependent resistors (e.g., "positive temperature coefficient," PTC elements).

[0028] By means of a boost converter operation of the semiconductor switches S11, S12 (in combination with the inductance shown), the voltage 142 applied to the capacitor arrangement 125 can be further increased, for example following the passive forming.

[0029] Both in Fig. 1, as well as in Fig. 2 advantageous measuring points for voltages are marked with “V” and those for currents with “A”.

[0030] In Fig. 2, the converter arrangement 100 is made of Fig. 1 in the form of a larger section of the circuit diagram in one of Fig. 1 different second operating mode is shown.

[0031] The DC side 120 is connected to an inverter circuit 136 for inverting the DC voltage applied to the capacitor arrangement 125, and a transformer 150 for transmitting the inverted DC voltage to an intermediate rectifier circuit 155. The intermediate rectifier circuit 155 is connected to pole terminals of a high-voltage or high-voltage network 170, which includes a high-voltage battery 172, which may, for example, have a nominal voltage of over 100 V, in particular over 300 V or over 500 V.

[0032] The high-voltage network 170 is further connected to a low-voltage network 180 with a low-voltage battery 182 via a further inverter circuit 165 and a further transformer 160, as well as a final rectifier circuit 166. The low-voltage network 180 or the low-voltage battery provided therein can, for example, have a nominal voltage of less than 100 V, in particular less than 50 V or less than 30 V. In vehicles, nominal voltages of 12 V, 24 V, or even 48 V are common for low-voltage networks. These nominal voltages can also be used within the scope of embodiments of this invention.

[0033] In the second operating mode, the voltage required to form the capacitors 126, 127 is taken at least partially from the DC voltage networks 170 and / or 180.

[0034] In a first embodiment of the second operating mode, the electrical energy for forming the capacitor arrangement 125 is provided from the high-voltage network 170. The low-voltage network 180 can be used to supply a computing unit that controls the power converter arrangement 100. However, the voltage applied to the capacitor arrangement 125 is taken from the high-voltage battery 172 and converted into an alternating voltage by the intermediate rectifier circuit 155, which in the embodiment shown here comprises two half-bridges S41, S42 and S43, S44, respectively, and is operated as an inverter in the second operating mode. The alternating voltage thus generated is transmitted by the transformer 150 to the inverter circuit 136, which is operated as a rectifier in the second operating mode, and converted by the inverter circuit 136 into a direct voltage.This DC voltage, which is then applied to the capacitor arrangement 125, can be slowly increased. For example, a first voltage level of, for example, 200 V can be applied to the capacitor arrangement 125 at the beginning, and this DC voltage can then be slowly and / or gradually increased to a second voltage level, for example, 300 V or up to 800 V (or up to the rated voltage of the capacitor arrangement).

[0035] Alternatively or additionally, the electrical energy for forming the capacitor arrangement 125 can also be taken from the low-voltage network 180 and initially converted to a voltage level of the high-voltage network 170, wherein the final rectifier circuit 166 is operated as an inverter in order to convert the DC voltage from the low-voltage network 170 into an AC voltage, which is then transferred by means of the further transformer 160 to the further inverter circuit 165, which is operated as a rectifier in this embodiment of the second operating mode. The further inverter circuit 165 then converts the AC voltage received from the further transformer 160 into a DC voltage at the voltage level of the high-voltage network 170. This DC voltage is then converted into the first or second voltage level analogously to the procedure already described in the context of the explanation of the first embodiment of the second operating mode.second DC voltage is converted to form the capacitor arrangement and applied to the capacitor arrangement 125.

[0036] This means that depending on the charge state and availability of the various networks 170, 180 or the AC voltage side 110, a suitable operating mode can be used to form the capacitor arrangement.

Claims

[1] Method for operating a power converter arrangement (100) comprising an AC side (110) with one or more phase connections (1, 2, 3) and a neutral conductor connection (4), an input converter circuit (135) with each phase connection of a phase connection half-bridge (S11, S12, S13, S14, S15, S16) comprising two series-connected semiconductor switches and a center tap between the two series-connected semiconductor switches, wherein the center tap is connected to the phase connection (1, 2, 3), and a neutral conductor half-bridge (137) comprising two series-connected rectifier elements and a center tap between the two series-connected rectifier elements, wherein the center tap is connected to the neutral conductor connection (4), a DC voltage side (120) with a first pole connection (121) and a second pole connection (122), a capacitor arrangement (125) connected between the first pole terminal (121) and the second pole terminal (122) on the DC voltage side (120) the procedure includes: Generating a DC voltage (142) across the capacitor arrangement (125) having a first voltage level that is lower than a nominal voltage level of the capacitor arrangement (125), in particular wherein the first voltage level is between 2% and 30% of the nominal voltage level of the capacitor arrangement. [2] The method of claim 1, wherein generating a DC voltage (142) across the capacitor array (125) having a first voltage level comprises: Applying an external voltage (140) between the one or one of the plurality of phase terminals (1, 2, 3) and the neutral conductor terminal (4). [3] Method according to claim 1 or 2, wherein the power converter arrangement (100) further comprises: an inverter circuit (136) for inverting the DC voltage (142) applied to the capacitor arrangement (125), and a transformer (150) for transmitting the alternating direct voltage to an intermediate rectifier circuit (155), wherein generating a DC voltage across the capacitor arrangement (125) having a first voltage level comprises: Applying a DC voltage to the intermediate rectifier circuit (155) and operating the intermediate rectifier circuit (155) as an inverter and the inverter circuit (136) as a rectifier. [4] The method of claim 3, wherein the power converter arrangement (100) further comprises: a further inverter circuit (165) for inverting the DC voltage applied to the intermediate rectifier circuit (155) a further transformer (160) for transmitting the alternating direct voltage to a final rectifier circuit (166) wherein applying a DC voltage to the intermediate rectifier circuit (155) comprises: Applying a DC voltage to the final rectifier circuit (166) and operating the final rectifier circuit (166) as an inverter and the further inverter circuit (165) as a rectifier. [5] Method according to one of the preceding claims, further comprising increasing the voltage applied to the capacitor arrangement (125) to a second voltage level over an increase period such that a predetermined voltage gradient is not exceeded, in particular wherein the increase period consists of the interval between 5 s and 20 s and / or the voltage gradient consists of the interval between 5 % / s and 10% / s, each based on the nominal voltage level of the capacitor arrangement. [6] Method according to claim 5 in combination with claim 2, wherein increasing the voltage applied to the capacitor arrangement (125) comprises driving one of the semiconductor switches (S11) of the half-bridge connected to the one phase terminal or to the one of the plurality of phase terminals (1) in a boost setting mode. [7] The method of claim 5 in combination with claim 3, wherein increasing the voltage across the capacitor array (125) comprises driving the intermediate rectifier circuit (155) as an inverter and the inverter circuit (136) as a rectifier such that the voltage is increased. [8] The method according to claim 7, wherein driving the intermediate rectifier circuit (155) comprises driving the final rectifier circuit (166) as an inverter and the further inverter circuit (165) as a rectifier such that the voltage applied to the intermediate rectifier circuit (155) is increased. [9] Method according to one of the preceding claims, comprising limiting (112) a current flowing into the capacitor arrangement (125). [10] Computing unit which is designed to carry out all method steps of a method according to one of the preceding claims. [11] Power converter arrangement (100), in particular an on-board charger, comprising an AC side (110) with one or more phase connections (1, 2, 3) and a neutral conductor connection (4), an input converter circuit (135) with each phase connection of a phase connection half-bridge (S11, S12, S13, S14, S15, S16) comprising two series-connected semiconductor switches and a center tap between the two series-connected semiconductor switches, wherein the center tap is connected to the phase connection (1, 2, 3), and a neutral conductor half-bridge (137) comprising two series-connected rectifier elements and a center tap between the two series-connected rectifier elements, wherein the center tap is connected to the neutral conductor connection (4), a DC voltage side (120) with a first pole connection (121) and a second pole connection (122), a capacitor arrangement (125) connected between the first pole terminal (121) and the second pole terminal (122) on the DC voltage side (120), a computing unit according to claim 10. [12] A vehicle which is at least partially electrically drivable, comprising the power converter arrangement (100) according to claim 11, a charging socket connected to the one or more phase terminals (1, 2, 3) and the neutral conductor terminal (4) of the power converter arrangement, and a battery (172, 182). [13] Computer program which causes a computing unit to carry out all the method steps of a method according to one of claims 1 to 9 when executed on the computing unit. [14] A machine-readable storage medium having stored thereon a computer program according to claim 13.

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