Charger, especially for a vehicle, and methods for operating a charger

Abstract

1. Charger (200), in particular for a vehicle, with a converter circuit (250) and a DC voltage output (220), for each phase (L1, L2, L3) of the input connection unit (210) the converter circuit (250) includes an AC voltage input (330, 430, 530) on the input side, and on the output side the converter circuit (250) is connected to the DC voltage output (220).The charger (200) comprises a changeover switching element (520) which is connected on one side to a third AC voltage input (530) of the converter circuit (250) and is configured to either connect the third AC voltage input (530) of the converter circuit (250) to the associated third phase (L3) of the input connection unit (210) or to connect the third AC voltage input (530) of the converter circuit (250) to a buffer capacitor (540), wherein the charger (200) includes the buffer capacitor (540) on the input side of the converter circuit (250), which is connected on one side to the switchable contact of the changeover switching element (520) and on the other side to a ground potential (N).

Description

[0001] The invention relates to a charger, in particular for a vehicle, and a method for operating a charger. Furthermore, the invention relates to a drive train with a charger, a vehicle with a drive train, a computer program, and a computer-readable medium. State of the art

[0002] Chargers with a multi-phase input connection, preferably for vehicles, include voltage converters that convert a single- or multi-phase AC input voltage into a DC output voltage for charging a connected traction battery of the vehicle. For example, a converter circuit, such as a multi-phase PFC, a DC link capacitor, and a connected galvanically isolated DC-DC converter, converts a multi-phase AC input voltage into a DC output voltage. Alternatively, identical converters are used for each phase, each of which generates a DC output voltage from a single-phase AC input voltage. The converters are connected in parallel on the output side.

[0003] It is often desired that the energy flow on the DC side does not have any power pulsation. This is achieved by implementing the power electronics topology in two stages and having a large intermediate circuit capacitor between the two stages. A first stage acts as a rectifier / inverter stage (depending on the power direction) and provides a constant voltage at its output. This module is also referred to as a PFC stage (power factor correction). A second stage can then convert this voltage to the desired voltage (e.g. the charging voltage of a battery) and can also provide galvanic isolation. If this power electronics is operated on a three-phase network, no power buffering is necessary, as constant power can be drawn from a three-phase network. However, it may happen that the same power electronics also has to operate on a single-phase or two-phase network.In this case, the intermediate circuit capacitor between the two stages, which is typically an electrolytic capacitor, serves as a power buffer. Due to the variability of the mains voltages and the operating limits of the power electronics, the voltage fluctuation of the intermediate circuit capacitor that can be used for energy storage is limited to approximately + / - 5%, which means that its capacitance must be large. This leads to considerable costs and disadvantages in terms of installation space. Since grids or supply networks are structured differently around the world (for example, in North America, a single-phase grid is usually available in households, while in Europe a three-phase grid is usually available), chargers are often designed with a "phase-modular" design. This means that the charger can be connected to and operated with a single-, two-, or three-phase supply network regardless of the grid configuration.This means that corresponding intermediate circuit capacitors are equipped for power buffering depending on the number and the power to be transmitted per phase, since each individual phase draws pulsating power from the grid. If, for example, only one or two grid phases are available, the individual grid phases can be connected in parallel to an input phase using a switching unit or an interconnection module consisting of a relay, for example. This necessary modularity leads to power electronic topologies with redundancy of functions and discrete components or the design of components, for example the intermediate circuit capacitor, which has an impact on the required installation space, the amount of resources and components required. There is a need to reduce the number of components required while still retaining the required functionality. Disclosure of the invention

[0004] A charger, in particular for a vehicle, is provided with a single- to at least three-phase input connection unit, a converter circuit, and a DC voltage output. Furthermore, the converter circuit comprises an AC voltage input for each phase of the input connection unit on the input side. On the output side, the converter circuit is connected to the DC voltage output. The charger comprises an alternating switching element, which is connected, on the one hand, to a third AC voltage input of the converter circuit and which is configured to either connect the third AC voltage input of the converter circuit to the associated third phase of the input connection unit or to connect the AC voltage input of the converter circuit to a buffer capacitor.The charger includes the buffer capacitor on the input side of the converter circuit, which is connected on the one hand to the switchable contact of the changeover switching element and on the other hand to a ground potential.

[0005] A charger with at least three phases is provided. The charger comprises a converter circuit that has an AC voltage input for each phase on the input side and a preferably common DC voltage output on the output side. Furthermore, the charger comprises an alternating switching element with which, on the one hand, a third AC voltage input of the converter circuit can be connected to a third phase of the input connection unit or the third AC voltage input of the converter circuit can be connected to a buffer capacitor. The buffer capacitor is connected between ground, a ground potential, a neutral conductor connection, or the housing potential and the switchable contact of the alternating switching element.

[0006] Advantageously, a charger is provided which, instead of a DC link capacitor designed for all phases or individual AC-side buffer capacitors per phase, comprises a changeover switching element in combination with a buffer capacitor assigned to the input side of the converter circuit. This topology advantageously enables, on the one hand, a uniform power supply at the DC voltage output of the charger and, on the other hand, the capacitance of the buffer capacitor can be reduced compared to the otherwise required capacity or the voltage ripple on the buffer capacitor can be increased. This preferably saves costs and installation space.

[0007] In this description, the term “connected” or “connecting” or “switched” is used synonymously with “electrically conductively connected” or “connecting”.

[0008] In one embodiment of the invention, the alternating switching element connects the third alternating voltage input of the converter circuit to the associated third phase of the input connection unit when the charger is operated when the charger is supplied with a three-phase supply network.

[0009] For operation of the charger on a three- or multi-phase supply network, the changeover switching element connects the third AC voltage input of the converter circuit to the corresponding third phase of the input connection unit. The converter circuit thus converts a three-phase AC input voltage into a DC output voltage. Preferably, a pulsating power is passed from the input to the output for each phase. Since the AC input voltages and AC input currents in a three-phase supply network are each 120° out of phase, a constant, non-pulsating output power results at the DC voltage output. Advantageously, operation of a charger with a changeover switching element with a constant output power is provided.

[0010] In another embodiment of the invention, the alternating switching element connects the third alternating voltage input of the converter circuit to the buffer capacitor when the charger is operated when the charger is supplied with a single-phase or two-phase supply network.

[0011] For operation of the charger on a single- or two-phase supply network, the alternating switching element connects the third AC voltage input of the converter circuit to the buffer capacitor. Preferably, the power electronics of the converter circuit connected to the third AC voltage input are controlled in such a way that any power pulsations that occur are compensated by the connected buffer capacitor. Advantageously, operation of a charger with an alternating switching element is provided, which enables operation of the charger on a single- or two-phase supply network with a uniform output line.

[0012] In one embodiment of the invention, the converter circuit is designed to compensate for power pulsations resulting from operation of the charger when the charger is supplied with a single-phase or two-phase supply network, preferably at the DC voltage output.

[0013] For operation of the charger on a single- or two-phase supply network, the alternating switching element connects the third AC voltage input of the converter circuit to the buffer capacitor. With a single- or two-phase supply network and corresponding operation of the converter circuit, depending on the circuit topology, a pulsating power results either at a DC voltage intermediate circuit or at the DC voltage output. To avoid pulsating power, the power electronics of the converter circuit connected to the third AC voltage input are operated in such a way that they transfer energy towards the buffer capacitor 180° out of phase with the pulsating power of the first and second phases, and vice versa. This in turn provides a uniform, non-pulsating power at a DC voltage intermediate circuit or at the DC voltage output of the charger, or otherwise compensates for resulting power pulsations.For this purpose, at least the power electronics connected to the third AC voltage input are preferably bidirectional. Advantageously, operation of a charger with a changeover switching element with a uniform output power is provided.

[0014] In another embodiment of the invention, the converter circuit comprises a multi-phase PFC stage connected to the AC voltage inputs, a DC-DC converter connected to the PFC stage for converting the single-phase DC voltage into a DC output voltage, wherein the DC-DC converter is connected on the output side to the DC voltage output.

[0015] With a single- or two-phase supply network and corresponding operation of the PFC stage on one or two phases of the supply network, a pulsating power results on the output side of the PFC stage. To avoid this pulsating power, preferably also at the DC output, the third phase of the PFC stage is operated in such a way that it transfers energy from the output side of the PFC stage towards the buffer capacitor and vice versa, 180° out of phase with the pulsating power of the first and second phases of the PFC stage. This in turn provides a uniform, non-pulsating power on the output side of the PFC stage and thus also at the DC output of the charger, or otherwise resulting power pulsations at the DC output are compensated. Accordingly, at least the third phase of the PFC stage is operated bidirectionally.Advantageously, an operation for a topology of the converter circuit of a charger with an alternating switching element with a uniform output power is provided.

[0016] Advantageously, a topology is provided for the construction of the converter circuit for the charger.

[0017] In another embodiment of the invention, the converter circuit comprises at least one converter for each phase of the input connection unit for converting a single-phase alternating voltage into a direct voltage, wherein the converters are connected in parallel on the output side at the direct voltage output, wherein each of the converters is connected on the input side to an alternating voltage input of the converter circuit.

[0018] With a single- or two-phase supply network and corresponding operation of one or two converters in the converter circuit, a pulsating output power results at the DC voltage output of the parallel-connected first and second converters. To avoid the pulsating output power at the DC voltage output, the third converter is operated in such a way that it transfers energy from the DC voltage output to the buffer capacitor and vice versa, 180° out of phase with the pulsating output power of the first and second converters, so that a uniform, non-pulsating output power is provided at the DC voltage output of the charger or otherwise resulting power pulsations at the DC voltage output are compensated. For this purpose, at least the third converter is preferably designed as a bidirectional third converter.Advantageously, an operation for a topology of the converter circuit of a charger with an alternating switching element with a uniform output power is provided.

[0019] Advantageously, a topology is provided for the construction of the converter circuit for the charger.

[0020] When the charger is operated on a single- or two-phase supply network, the first and / or second phase of the multi-phase PFC stage preferably transfers pulsating power from the input to the DC-DC converter, or the first and / or second converter per phase transfers pulsating power from the input to the DC-DC output of the charger, which overlap but do not cancel each other out. Therefore, the power pulsation on the input side of the DC-DC converter is preferably actively compensated by the third phase of the multi-phase PFC stage, or the power pulsation at the DC-DC output is actively compensated by the third converter. In the event of a power surplus, this is transferred to the buffer capacitor and stored, so that the third phase of the PFC stage or the third converter works in reverse, and in the event of a power shortage, the difference is taken from the buffer capacitor and made available.This advantageously reduces the total DC link capacitance required for a phase-modular charger, as only two-thirds of the maximum power is buffered. Furthermore, in typical three-phase operation, no DC link capacitance is loaded, thus reducing the operating load on the DC link capacitance. This increases the expected service life of the DC link capacitance, or it could be constructed more simply and inexpensively with the same specified service life. Furthermore, the voltage ripple on the capacitor can be significantly increased, since a PFC module is designed to operate on a strongly fluctuating voltage or AC voltage. This higher voltage ripple allows the capacitance of the DC link capacitance to be reduced, resulting in further advantages in terms of cost and space.

[0021] Furthermore, the invention relates to a drive train of a vehicle with an inverter, an electric machine and / or a traction battery, wherein the drive train comprises at least one described charger.

[0022] A vehicle's powertrain converts fossil or electrical energy from an energy source into mechanical energy, which is used to propel the vehicle. In an electric powertrain, for example, the electrical energy from an energy source is converted by an inverter into an alternating current, which powers an electric motor. Using the charger described above, it is advantageous to recharge the energy source with energy from a power grid.

[0023] The invention further relates to a vehicle with a drive train as described above. A vehicle is advantageously provided with a charging device as described.

[0024] Furthermore, the invention relates to a method for operating a described charger with the step: controlling the changeover switching element as a function of the operation of the charger when the charger is supplied with a three-phase supply network or a single- or two-phase supply network, wherein in particular the changeover switching element connects the third AC voltage input of the converter circuit to the associated third phase of the input connection unit when the charger is operated when the charger is supplied with a three-phase supply network, wherein in particular the changeover switching element connects the AC voltage input of the converter circuit to the buffer capacitor when the charger is operated when the charger is supplied with a single- or two-phase supply network.

[0025] A method for operating the charger is provided. The changeover switching element is controlled depending on the grid configuration. In a grid configuration of the supply grid that enables a three-phase supply to the charger, the changeover switching element is controlled such that the third AC voltage input of the converter circuit is connected to the corresponding third phase of the input connection unit. In a grid configuration of the supply grid that only allows a single- or two-phase supply to the charger, the changeover switching element is controlled such that the third AC voltage input of the converter circuit is connected to the buffer capacitor. Advantageously, a control strategy for operating the charger is provided that enables a uniform, non-pulsating output power at the DC voltage output of the charger.

[0026] In one embodiment of the invention, the method comprises the further step of operating the converter circuit when the charger is supplied with a single-phase or two-phase supply network in such a way that a resulting power pulsation, preferably at the DC voltage output, is compensated.

[0027] In a supply network configuration that only allows a single- or two-phase supply to the charger, the alternating switching element is controlled such that the third AC voltage input of the converter circuit is connected to the buffer capacitor. Furthermore, to avoid pulsating power, the converter circuit is operated such that it transfers energy toward the buffer capacitor 180° out of phase with the pulsating power transmitted via the first and second phases, and vice versa, so that a uniform, non-pulsating power is provided at the DC voltage output of the charger or otherwise resulting power pulsations are compensated. Advantageously, a method for operating a charger with an alternating switching element with a uniform output power is provided.

[0028] Furthermore, the invention relates to a computer program comprising instructions that cause the charger to carry out the method steps.

[0029] Furthermore, the invention relates to a computer-readable storage medium on which the described computer program is stored.

[0030] It is understood that the features, characteristics and advantages of the charger apply accordingly to the process or the powertrain and the vehicle and vice versa.

[0031] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Short description of the drawing

[0032] In the following, the invention will be explained in more detail with reference to some figures, which show: Fig. 1 a schematic representation of a prior art charger Fig. 2 a schematic representation of a charger with a changeover switching element Fig. 3 another schematic representation of a charger with a changeover switching element Fig. 4 a schematically illustrated vehicle with a drive train with a charger, Fig. 5 a schematically illustrated method for operating the charger. Embodiments of the invention

[0033] The Fig. 1 shows a charger 200, preferably for a vehicle, from the prior art. The charger 200 comprises a single- to at least three-phase input connection unit 210. This means that the input connection unit 210 can be connected to different AC voltage supply networks 230 or supply networks 230 with different network configurations, for example, to supply networks 230 that provide a single-phase, two-phase, or three-phase AC voltage as an energy source for charging, for example, a traction battery 240 of a vehicle with the charger 200. Preferably, the input connection unit 210 comprises a further neutral conductor connection N for connecting a neutral conductor of a supply network 230 to be connected. The charger 200 further comprises a converter circuit 250 and a DC voltage output 220, to which, for example, a traction battery 240 of a vehicle to be charged can be connected.For each phase L1, L2, L3 of the input connection unit 210, the converter circuit 250 comprises at least one AC voltage input 330, 430, 530, which are preferably connected to one of the phases L1, L2, L3 each, preferably switchably connected to one of the phases L1, L2, L3 each via a switching unit 211.

[0034] The charger 200 after Fig. 2 differs from the state of the art according to Fig. 1 in that the charger 200 comprises an alternating switching element 520, which is connected on the one hand to a third alternating voltage input 530 of the converter circuit 250 and is configured to either connect the third alternating voltage input 530 of the converter circuit 250 to the associated third phase L3 of the input connection unit 210 (switching position 1) or to connect the third alternating voltage input 530 of the converter circuit to a buffer capacitor 540 (switching position 2), wherein the charger 200 comprises the buffer capacitor 540 on the input side of the converter circuit 250, which is connected on the one hand to the switchable contact of the alternating switching element 520 and on the other hand to a ground potential N. Depending on the design and if necessary.According to the corresponding specifications, the ground potential N can be connected, for example, to the housing of the charger 200 or to the ground potential of the charger or the vehicle or to a neutral conductor connection of the input connection unit 210. Furthermore, the converter circuit 250 according to . Fig. 2 an at least three-phase PFC stage 252, whose inputs are connected to the AC voltage inputs 330, 430, 530 of the converter circuit 250. The PFC stage 252 is configured to act as a rectifier / inverter stage (depending on the power direction) to convert the input-side multi-phase AC voltage and to provide a preferably constant DC voltage at its output. The converter circuit 250 further comprises a DC-DC converter 254, which converts the DC voltage provided by the PFC stage 252 into an output DC voltage. On the output side, the DC-DC converter 254 is connected to the DC voltage terminal 220 of the charger 220. The reference numerals of the Fig. 2 correspond in content to those of Fig. 1 explained reference symbols.

[0035] The charger 200 after Fig. 3 differs from those after the Fig. 1 and Fig. 2 in that the converter circuit 250 comprises at least one converter 300, 400, 500 for each phase L1, L2, L3 of the input connection unit 210, which converters are preferably connected to one of the phases L1, L2, L3, preferably switchably connected to one of the phases L1, L2, L3 via a switching unit 211. Preferably, a converter 300, 400, 500 comprises, on the input side, a PFC stage 315, 415, 515, which is preferably connected to a DC-DC converter 310, 410, 510, preferably via an intermediate circuit. The DC-DC converters 310, 410, 510 preferably comprise galvanic isolation. Preferably, converters 300, 400, and 500 convert a single-phase AC voltage applied to the converter input into a DC voltage at the converter output. The converter outputs of converters 300, 400, and 500 are connected in parallel to the charger's DC voltage output 220. The reference numerals of the converters (not explained in detail) Fig. 3 correspond in content to those of Fig. 1 and Fig. 2 explained reference symbols.

[0036] Fig. 4 shows a schematically illustrated vehicle 700 with four wheels and a drive train 600 with a charger 200. The vehicle 700 is illustrated here only as an example with four wheels, although the invention can be used equally in any vehicle with any number of wheels on land, on water, and in the air. The drive train 600 illustrated as an example comprises at least the charger 200 with the changeover switching element 520. Furthermore, the drive train 600 comprises, in particular, a traction battery 240 or an electrical energy source, in particular a high-voltage battery, which supplies the electric drive with electrical energy. The energy of the direct voltage source 240 is converted by means of an inverter 610 into, for example, a three-phase alternating voltage for operating an electrical machine 620 as a drive unit for a vehicle 200.

[0037] Fig.5 shows a schematically illustrated flow diagram for a method 100 for operating a charger 200. The method 100 starts with step 105. In step 110, the changeover switching element 520 is controlled depending on the operation of the charger 200 when the charger 200 is supplied with a three-phase supply network 230 or a single- or two-phase supply network 230. Consequently, the alternating switching element 520 preferably connects the third AC voltage input 530 of the converter circuit 250 to the associated third phase L3 of the input connection unit 210 during operation of the charger 200 when the charger 200 is supplied with a three-phase supply network 230. The alternating switching element 520 preferably connects the third AC voltage input 530 of the converter circuit to the buffer capacitor 540 during operation of the charger 200 when the charger 200 is supplied with a single- or two-phase supply network 230.In step 120, when the charger 200 is supplied with a single- or two-phase supply network 230, the converter circuit is operated in such a way that a resulting power pulsation, preferably at the DC voltage output 220, is preferably at least partially compensated. Method 100 ends with step 125.

Claims

[1] Charger (200), in particular for a vehicle, with a single- to at least three-phase input connection unit (210), a converter circuit (250) and a DC voltage output (220), for each phase (L1, L2, L3) of the input connection unit (210), the converter circuit (250) comprises an AC voltage input (330, 430, 530) on the input side, on the output side, the converter circuit (250) is connected to the DC voltage output (220), characterized by , that the charger (200) comprises an alternating switching element (520) which is connected on the one hand to a third alternating voltage input (530) of the converter circuit (250) and is designed to either connect the third alternating voltage input (530) of the converter circuit (250) to the associated third phase (L3) of the input connection unit (210) or to connect the third alternating voltage input (530) of the converter circuit (250) to a buffer capacitor (540), wherein the charger (200) comprises the buffer capacitor (540) on the input side of the converter circuit (250), which is connected on the one hand to the switchable contact of the alternating switching element (520) and on the other hand to a ground potential (N). [2] Charger (200) according to claim 1, wherein the alternating switching element (520) connects the third AC voltage input (530) of the converter circuit (250) to the associated third phase of the input connection unit (L3) during operation of the charger (200) when the charger (200) is supplied with a three-phase supply network (230). [3] Charger (200) according to one of the preceding claims, wherein the alternating switching element (520) connects the third alternating voltage input (530) of the converter circuit (250) to the buffer capacitor (540) during operation of the charger (200) when the charger (200) is supplied with a single-phase or two-phase supply network (230). [4] Charger (200) according to claim 3, wherein the converter circuit (250) is configured to compensate for power pulsations (220) resulting from operation of the charger (200) when the charger (200) is supplied with a single-phase or two-phase supply network (230). [5] Charger according to one of claims 1 to 4, wherein the converter circuit (250) comprises a multi-phase PFC stage (252) connected to the AC voltage inputs (330, 430, 530) and a DC-DC converter (254) connected to the PFC stage (252) for converting the single-phase DC voltage at the output of the PFC stage (252) into a DC output voltage, wherein the DC-DC converter (254) is connected on the output side to the DC voltage output (220). [6] Charger according to one of claims 1 to 4, wherein the converter circuit (250) comprises at least one converter (300, 400, 500) for converting a single-phase alternating voltage into a direct voltage for each phase (L1, L2, L3) of the input connection unit (210), wherein the converters (300, 400, 500) are connected in parallel on the output side at the direct voltage output (220), wherein each of the converters (300, 400, 500) is connected on the input side to an AC voltage input (330, 430, 530) of the converter circuit (250). [7] Drive train (600) of a vehicle (700) with an inverter (610), an electric machine (620) and / or a traction battery (240), wherein the drive train comprises at least one charger (200) according to one of claims 1 to 6. [8] Vehicle (700) having a drive train (600) according to claim 7. [9] Method (100) for operating a charger (200) according to one of claims 1 to 6, comprising the step: Controlling (110) the changeover switching element (520) as a function of the operation of the charger (200) when the charger (200) is supplied with a three-phase supply network (230) or a single- or two-phase supply network (230), wherein in particular the changeover switching element (520) connects the third AC voltage input (530) of the converter circuit (250) to the associated third phase (L3) of the input connection unit (210) when the charger (200) is operated when the charger (200) is supplied with a three-phase supply network (230), wherein in particular the changeover switching element (520) connects the AC voltage input (530) of the converter circuit (250) to the buffer capacitor (540) when the charger (200) is operated when the charger (200) is supplied with a single- or two-phase supply network (230). [10] Method (100) for operating the charger (200) according to claim 9, comprising the further step: Operating (120) the converter circuit (250) when supplying the charger (200) with a single-phase or two-phase supply network (230) in such a way that a resulting power pulsation is compensated. [11] A computer program comprising instructions that cause the charger (200) according to any one of claims 1 to 6 to carry out the method steps according to claims 9 to 10. [12] A computer-readable medium comprising instructions which, when executed by a charger (200), cause the charger (200) to perform the steps of the method (100) according to claims 9 to 10.

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