AC charging device and method for single-phase or multi-phase AC charging of a vehicle

Abstract

AC charging device for a vehicle with: - a rectifier (GR); - an accumulator connection (AA1, AA2); and - at least one first intermediate circuit capacitor (C1) provided between the rectifier (GR) and the accumulator connection (AA1, AA2), wherein the charging device comprises a switching device (SV) which connects at least one second intermediate circuit capacitor (C2) to the at least one first intermediate circuit capacitor (C1), wherein the switching device (SW) connects the intermediate circuit capacitors (C1, C2) in parallel to one another in a first switching state (1) and connects the intermediate circuit capacitors (C1, C2) in series to one another in a second switching state (2), and wherein the rectifier (GR) is designed for single-phase and multi-phase charging and the switching device (SV) is set up to assume the first switching state (1) during a single-phase charging process and to assume the second switching state (2) during a multi-phase charging process.

Description

[0001] Electric vehicles have a battery to power the drive. Many vehicles have a charging socket for transferring external energy to the battery, either for charging or for feeding the energy back into a power grid.

[0002] For this purpose, charging stations exist, which can be simplified as an AC voltage source. The number of phases of this AC voltage source varies depending on the connection to the power grid or the characteristics of the power grid. The document US 2013 / 0 314 038 A1 describes that in a three-phase charging mode, several converter modules are connected in parallel. This also applies analogously to the document US 2015 / 0 115 888 A1, in which individual rectifier modules and associated converter modules are connected together in the three-phase case to add current.

[0003] It is an object of the invention to show a possibility by means of which different charging points with different numbers of phases can be used with little effort on the vehicle side.

[0004] This object is achieved by the subject matter of the independent claims. Further embodiments, features, properties, and advantages are revealed by the dependent claims, the description, and the figures.

[0005] The procedure described here is based on the following considerations: Different numbers of phases result in different linkage factors and thus also different peak voltages on the DC side of the rectifier. As the number of phases increases, the linkage factor also increases and thus the requirements for the voltage carrying capacity of the intermediate circuit capacitor. However, with a lower number of phases, higher AC voltage components that need to be smoothed result on the DC side of the rectifier than with a higher number of phases, in each case relative to the DC voltage component. With only one phase, the voltage ripple of the pulsating DC voltage resulting from rectification extends over the entire amplitude, whereas in a three-phase system the phase overlap results in a significantly lower voltage ripple.

[0006] It was recognized that an AC charging system for single-phase and multi-phase charging has an intermediate circuit capacitor that is oversized in one respect in every setting: During single-phase charging, only a comparatively low voltage is generated that needs to be smoothed (compared to multi-phase charging) (corresponding to the lower interlinkage factor), although the capacitor must have a nominal voltage that is appropriate for multi-phase charging, since the same capacitor is usually used in the intermediate circuit. During multi-phase charging, only a comparatively low voltage ripple is generated, although the capacitor must have a capacitance that is appropriate for single-phase charging with increased voltage ripple if the same intermediate circuit capacitor is used as usual.

[0007] It is therefore proposed that an AC charging device designed for single- and multi-phase charging should use multiple DC link capacitors. These are connected in parallel for single-phase charging to achieve high capacitance (while the low voltage load is less critical and can be accepted for single-phase charging). The DC link capacitors are connected in series for multi-phase charging to achieve high voltage carrying capacity, as the voltage to be smoothed is distributed among the DC link capacitors in the series connection (while the low capacitance of the series connection is less critical and can be accepted for multi-phase charging). The DC link capacitors are thus optimally utilized for each of the charging types mentioned; there is no oversizing in terms of capacitance or dielectric strength.

[0008] An AC charging device for a vehicle (in particular a vehicle that can be charged from the outside, i.e. a plug-in vehicle) is therefore described. The AC charging device is preferably an on-board AC charging device. The charging device comprises: a rectifier, an accumulator connection and at least two intermediate circuit capacitors. A rectifier is described as a component that is configured to perform the function of a rectifier. This can be the only function of the component, but can also be one of several functions. If, for example, the rectifier is bidirectional, it is configured for the functions of rectification and inversion. The accumulator connection serves to connect an accumulator, preferably a high-voltage accumulator.A vehicle electrical system with a charging device as described here can be provided, which further comprises a rechargeable battery connected to the rechargeable battery terminal. The rechargeable battery terminal typically comprises (at least) two contacts, in particular a positive contact and a negative contact. The intermediate circuit capacitors can each be formed by a capacitor component, but are preferably configured as a plurality of parallel-connected capacitor components, which are mounted, for example, on a carrier and interconnected. In other words, each of the intermediate circuit capacitors can be implemented as a capacitor bank.

[0009] The charging device thus comprises a first intermediate circuit capacitor. This capacitor is designed to smooth the pulsating DC voltage generated at the rectifier. This first intermediate circuit capacitor is provided between the rectifier and the battery terminal, in particular connected in parallel, for example, to a busbar between the rectifier and the battery terminal.

[0010] A switching device is provided to select whether the intermediate circuit capacitors are connected in parallel or in series. The charging device comprises such a switching device. The switching device connects the at least one second intermediate circuit capacitor to the at least one first intermediate circuit capacitor, in particular selectable in parallel or in series. The switching device is configured to connect the intermediate circuit capacitors (i.e. the at least one first and the at least one second intermediate circuit capacitor) in parallel in a first switching state. The switching device is configured to connect the intermediate circuit capacitors in series in a second switching state. The switching device can be implemented by means of electromechanical switches or by means of semiconductor switches such as transistors, for example MOSFETs or IGBTs.

[0011] A series switch may be connected in series between the capacitors, which, when closed (i.e., in the second switching state), connects the capacitors in series. The capacitors each have a first and a second electrode. The first electrode of the first capacitor may be fixedly connected to a first potential of the DC side of the rectifier, such as the positive potential. The first electrode of the second capacitor may be fixedly connected to a second potential of the DC side of the rectifier, such as the negative potential. The series switch connects the second electrodes (i.e., inner electrodes) to one another (in a switchable manner).

[0012] A first parallel switch switchably connects - and preferably in the first switching state - the second electrode of the first capacitor to the second potential, in particular the negative potential. A second parallel switch switchably connects - and preferably in the first switching state - the second electrode of the second capacitor to the first potential, for example a supply potential. The series switch on the one hand and the parallel switches on the other hand are alternately closed (and in particular also alternately open). A controller can be provided which is connected to the switches in a controlling manner and which is configured to alternately open and close the switches in the manner shown. Only when the series switch is controlled to be open (i.e. in the first switching state) are the parallel switches in the closed state, corresponding to the first switching state. Only when the parallel switches are controlled to be open (i.e.In the second switching state, the series switch is in the closed state, corresponding to the second switching state. The control system is configured to control the switches accordingly.

[0013] The second potential can be a reference potential, such as ground, or can correspond to the negative potential of the device. The first potential can be a supply potential, such as the positive potential of the device.

[0014] The charging device, and in particular the rectifier, is designed for single-phase (“single-phase mode,” corresponding to the first switching state) and multi-phase charging (“multi-phase mode,” corresponding to the second switching state). Preferably, the modes are only active alternately and not simultaneously. The switching device is configured to assume the first switching state (corresponding to a parallel connection of the capacitors) during a single-phase charging process and to assume the second switching state (corresponding to a series connection of the capacitors) during a multi-phase charging process.

[0015] The rectifier preferably has an AC voltage side. This is connected to several phase terminals. The phase terminals are configured, for example, for single-phase charging and multi-phase charging. Alternatively, the AC voltage side is connected to a multi-phase terminal and a single-phase terminal. The terminals are then arranged electrically parallel to one another.

[0016] The rectifier can be a passive rectifier. The rectifier can also be an active rectifier. In addition, the rectifier can be a bidirectional rectifier. Finally, the rectifier can be an inverter, which is designed to adjustably rectify single- or multi-phase voltage in a rectifier mode, and to convert direct voltage into single- or multi-phase alternating voltage in an inverter mode in the opposite direction. Components designed to perform the function of rectification are therefore referred to as rectifiers. However, this can be one of several functions. As an active rectifier, it comprises externally controllable switches, for example semiconductor switches such as transistors, for example MOSFETs or IGBTs. This also applies to the design as an inverter. As a passive rectifier, it comprises diodes as switches.

[0017] In one embodiment, the rectifier is designed as an inverter. The inverter is connected to an electrical machine (as part of the device) or has machine phase connections for connecting an electrical machine. The electrical machine may connect the inverter to the charging connection. In this case, the charging current path also passes through the windings of the electrical machine (or at least one of them) to enable a filtering effect or voltage conversion (in addition to rectification).

[0018] In another embodiment, the rectifier is an inverter. This is connected via a selector switch either to the charging port or to an electrical machine or to machine phase connections for connecting an electrical machine. In this case, the charging current path does not pass through the electrical machine.

[0019] It can be provided that the at least one first and / or the at least one second intermediate circuit capacitor are designed as a plurality of capacitor components connected in parallel. This allows for more flexible installation space. At least one additional smoothing capacitor can be provided, which is connected in parallel (and in particular is not switchable or configurable) to the DC side of the rectifier.

[0020] The DC-DC converter or its DC side can be connected directly (i.e., without any voltage-converting elements) to the battery terminal. Alternatively, a DC-DC converter can be provided between the intermediate circuit capacitors and the battery terminal.

[0021] Instead of a rectifier, a DC-DC converter or another component with a DC voltage side can also be provided, which is connected to the intermediate circuit capacitors as described here, for example a DC-DC converter which has one side on which a pulsating (such as a chopped and / or pulse-width modulated) DC voltage occurs during operation, which is smoothed by means of the intermediate circuit capacitors. The device can be provided for a general purpose and is not limited to a charging device; in particular, the device can be a converter or a power converter. The device described here is preferably vehicle-mounted or used in a vehicle's on-board electrical system, but can also be provided in a stationary device, such as in a charging station or in a vehicle-external (mobile) charging unit.Finally, a vehicle electrical system (or charging station) may be provided which is equipped with a device as described here.

[0022] In addition, a method for single-phase or multi-phase AC charging of a vehicle is described. The method provides for rectifying an AC charging voltage. The rectified charging voltage is smoothed or supported by means of a first and a second intermediate circuit capacitor. If a multi-phase AC charging voltage is rectified, the rectified charging voltage is smoothed by means of a series connection of the intermediate circuit capacitors. If a single-phase AC charging voltage is rectified, the rectified charging voltage is smoothed by means of a parallel connection of the intermediate circuit capacitors (i.e., the same intermediate circuit capacitors). In both cases, the identical intermediate circuit capacitors are used, but in different configurations (i.e., connected in parallel or in series).

[0023] Preferably, before smoothing, it is determined whether a single-phase alternating charging voltage or a multi-phase alternating charging voltage is present at a charging connection. If a multi-phase alternating charging voltage is present, the intermediate circuit capacitors are connected in series (corresponding to the second switch position). If a single-phase alternating charging voltage is present, the intermediate circuit capacitors are connected in parallel (corresponding to the first switch position). Preferably, after the intermediate circuit capacitors have been connected, smoothing is carried out using the intermediate circuit capacitors. The connecting can also be referred to as configuring. The connecting is preferably carried out using the switching device.

[0024] The determination can be provided by a controller, which is in particular connected to the switches of the device in a controlling manner. Furthermore, a higher-level control unit can carry out the determination and transmit a corresponding configuration signal to the controller, which is connected to the switching device in a controlling manner. An occupancy sensor, a voltage sensor, a frequency determination unit, or a signal input interface (preferably wireless) can be provided, which are connected to an input of the controller or the higher-level control unit. If the occupancy sensor or the voltage sensor detects only one or two occupied, potential-carrying contacts on the AC voltage side of the rectifier, on the phase connections (including a neutral conductor), or (one occupancy) on the single-phase connection, then single-phase charging can be assumed, corresponding to the first switching state.If the occupancy sensor or the voltage sensor detects several occupied, potential-carrying contacts on the AC side of the rectifier (corresponding to phases of a three-phase network), at the phase connections or (an occupancy) at the multi-phase connection, then multi-phase charging can be assumed, corresponding to the second switching state. If the frequency determination unit detects a frequency of 60 Hz, corresponding to the frequency in a US supply network, then single-phase charging can be assumed. If the frequency determination unit detects a frequency of 50 Hz and a multi-phase occupancy, then multi-phase charging can be assumed. Similarly, the signal input interface can be configured to receive a signal that explicitly or inherently indicates the charging type (i.e., single-phase or multi-phase), so that the switch position is selected depending on this charging type.

[0025] The charging device is configured to carry out the method.

[0026] The Fig. 1 shows an example of a possible embodiment of the charging device described here and serves to explain the method mentioned here.

[0027] The Fig. The charging device shown in Figure 1 comprises a rectifier GR, the DC voltage side of which is connected to a battery terminal AA1, AA2 of the charging device. AA1 forms the positive potential rail and AA2 the negative potential rail. In other words, AA1 and AA2 form the positive and negative pole connections for the battery AK. A first capacitor C1 and a second capacitor C2 (for example, representing respective capacitor banks) are shown between the rectifier GR on the one hand and the battery terminal AA1, AA2 on the other. The first capacitor C1 and the second capacitor C2 are coupled to one another via a switching device SV.

[0028] A series switch SS (of the switching device SV) connects the capacitors C1 and C2. The capacitors C1, C2 are also connected to the DC side of the rectifier GR. The first capacitor C1 comprises a first electrode C1E1, which is connected to the positive supply potential (i.e., to terminal AA1). The first capacitor comprises a second electrode C1E2. The latter electrode is connected to the series switch SS. In a mirror image, the capacitor C2 comprises a first electrode C2E1, which is connected to the negative supply potential, and a second electrode C2E2, which is also connected to the switch SS. The second electrodes of the capacitors C1 and C2 are connected to one another via the series switch SS. If the series switch SS is closed, corresponding to a switch position 2, then the capacitors C1 and C2 are connected in series.This results in a higher dielectric strength (compared to parallel connection), but a lower capacity (which plays a less important role in multi-phase charging).

[0029] There is also a first parallel switch SP1 and a second parallel switch SP2. The first parallel switch SP1 connects the second electrode C1E2 of the first capacitor C1 to the negative supply potential. In other words, the switch SP1 switchably connects that electrode of the first capacitor which faces the second capacitor C2 to the negative supply potential. In a mirror image, there is a second parallel switch SP2 which switchably connects the second electrode C2E2 of the second capacitor C2 to the positive supply potential. Here, too, the second parallel switch SP2 connects that electrode of the second capacitor which faces the first capacitor C1 to the positive supply potential. The points at which the parallel switches SP1, SP2 are connected to the capacitors C1, C2 are switchably connected to one another via the series switch SS.In switch position 1 ("first switch position"), the parallel switches SP1 are connected (and the series switch SS is open), which connects the capacitors C1 and C2 in parallel. This results in higher capacitance, at the expense of dielectric strength, which, however, is less important for single-phase charging. These properties are complementary to those resulting from switch position 2 ("second switch position").

[0030] An optional DC-DC converter (DC) is located between capacitors C1 and C2, which can also be referred to as intermediate circuit capacitors, and the battery terminals AAl, AA2. In one version, this is not provided, and the supply potentials of the rectifier GR are connected directly to the battery terminals Al. A battery AK is connected to the battery terminals Al.

[0031] The rectifier GR also has a charging terminal LA, which includes several phases L1 to L3 and, if applicable, a neutral conductor N. If only L1 (and N) is occupied, charging occurs in single-phase mode, and the capacitors are connected in parallel via the switching device SV. If, in addition to phase L1, another phase L2 or L3, or all phases L1 to L3, are used, or if they are occupied, the capacitors C1 and C2 are connected in series, with the switching device SV establishing the series connection via the series switch SS.

[0032] A selection switch S can be provided on the AC side, via which an electric machine M can be connected. In the embodiment shown, the inner phase connections are connected to an optional charging connection LA'. This allows charging current to be passed through the electric machine during charging. However, the inner phase connections (or their lead-out) and the charging connection LA' are merely optional and can be omitted. In this case, the selection switch S only connects the AC side of the rectifier GR to the electric machine when power is exchanged between the electric machine and the rest of the vehicle electrical system, for example in traction. The traction case is represented by the power flow arrow TR (and the arrow leading to the selection switch S).

[0033] However, if the optional charging connection LA' is provided, a charging path LR may result in which power is delivered via the optional charging connection LA' through the motor (particularly via its inner phase connections) to the AC side of the rectifier GR and is then passed from the rectifier GR to the capacitors C1, C2. Here, too, the optional charging connection LA' can be single-phase or multi-phase. This results in the corresponding switch positions for the switching device SV.

[0034] In principle, it is also possible to feed back power, so that the rectifier (as an active rectifier) transfers power to the charging terminals LA or LA' in order to feed power back from the accumulator AK into a connected supply network or a connected stationary storage device.

[0035] If the rectifier GR is designed as an inverter and can therefore perform the function of the inverter or the corresponding inversion in addition to rectifying, then the AC side of the inverter or rectifier GR is connected to the electrical machine M. In this case, the inverter can be designed to provide that during a traction mode, current is supplied from the inverter to the electrical machine M, which current is set up to induce a rotating field in the electrical machine. In this case, the capacitors C1 and C2 can be connected in series or in parallel (this depends on the battery voltage AK) in order to support the DC voltage supply for the inverter (designed as a rectifier GR) in the traction case. Alternatively, the switches of the switching device SV can be open in the traction case.

[0036] If the rectifier GR is designed as an inverter, it can be configured as a BnC bridge, where n corresponds to twice the number of phases, for example, a B6C bridge. A controller, such as the one mentioned above, can be provided to control the inverter switches, to generate three-phase current for the electric machine in traction mode, and to operate as a (controlled) rectifier in charging mode.

Claims

[1] AC charging device for a vehicle with: - a rectifier (GR); - an accumulator connection (AA1, AA2); and - at least one first intermediate circuit capacitor (C1) provided between the rectifier (GR) and the accumulator connection (AA1, AA2), wherein the charging device comprises a switching device (SV) which connects at least one second intermediate circuit capacitor (C2) to the at least one first intermediate circuit capacitor (C1), wherein the switching device (SW) connects the intermediate circuit capacitors (C1, C2) in parallel to one another in a first switching state (1) and connects the intermediate circuit capacitors (C1, C2) in series to one another in a second switching state (2), and wherein the rectifier (GR) is designed for single-phase and multi-phase charging and the switching device (SV) is set up to assume the first switching state (1) during a single-phase charging process and to assume the second switching state (2) during a multi-phase charging process. [2] The AC charging device according to claim 1, wherein the rectifier (GR) has an AC side connected to a plurality of phase terminals (L1-L3) configured for single-phase and multi-phase charging, or connected to a multi-phase terminal and a single-phase terminal. [3] AC charging device according to claim 1 or 2, wherein the rectifier (GR) is a passive rectifier, an active rectifier, a bidirectional rectifier, or an inverter configured to adjustably rectify single-phase or multi-phase in a rectifier mode and to rectify DC voltage into single-phase or multi-phase AC voltage in an inverter mode in the opposite direction. [4] AC charging device according to claim 3, wherein the rectifier (GR) is designed as an inverter which is connected to an electrical machine (M) and the electrical machine (M) connects the inverter to the charging terminal (LA'). [5] AC charging device according to claim 3, wherein the rectifier (GR) is designed as an inverter which is connected via a selection switch (S) selectively to an electrical machine (M) or to the charging connection (LA). [6] AC charging device according to one of the preceding claims, wherein the at least one first and / or the at least one second intermediate circuit capacitor are formed as a plurality of capacitor components connected in parallel. [7] AC charging device according to one of the preceding claims, wherein a DC-DC converter is provided between the intermediate circuit capacitors (C1, C2) and the accumulator connection (AA1, AA2). [8] Method for single-phase or multi-phase AC charging of a vehicle, comprising: - Rectifying an alternating charging voltage; - smoothing the rectified charging voltage by means of a first and a second intermediate circuit capacitor (C1, C2); wherein (i) if a multi-phase alternating charging voltage is rectified, to smooth the rectified charging voltage by means of a series connection of the intermediate circuit capacitors (C1, C2) and, (ii) if a single-phase alternating charging voltage is rectified, to smooth the rectified charging voltage by means of a parallel connection of the intermediate circuit capacitors (C1, C2). [9] Method according to claim 8, wherein before the smoothing it is determined whether a multi-phase alternating charging voltage is present at a charging terminal (LA) or whether a multi-phase alternating charging voltage is present, wherein (i) if a multi-phase alternating charging voltage is present, the intermediate circuit capacitors (C1, C2) are connected in series, (ii) if a single-phase alternating charging voltage is present, the intermediate circuit capacitors (C1, C2) are connected in parallel, and after the intermediate circuit capacitors (C1, C2) have been connected, the smoothing is carried out by means of the intermediate circuit capacitors (C1, C2).

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