DE102017216468A1 - Charging an electrical energy storage of a motor vehicle - Google Patents

Abstract

The invention relates to a method for charging an electrical energy store (10) of a motor vehicle with electrical energy from a vehicle-external charging station (14), in which the charging station (14) has a single-phase electrical alternating voltage (18) with respect to a predetermined electrical reference potential (16). wherein the electrical energy store (10) is electrically coupled to the vehicle-external charging station (14) by means of a cycled energy converter (20), wherein the cycled energy converter converts the electrical energy by means of at least two series-connected series circuits (22, 24) each comprising two switching elements (28 , 30) for which purpose respective center connections (32, 34) of the series circuits (22, 24) are electrically coupled to the charging station (14). The invention provides that the switching elements (28, 30) are controlled at least as a function of an electrical reference voltage (38) between one of at least two energy storage potentials of the electrical energy store (10) and the electrical reference potential (16).

Description

The invention relates to a method for charging an electrical energy storage device of a motor vehicle with electrical energy from a vehicle external charging station, wherein the charging station provides a single-phase electrical AC voltage with respect to a predetermined electrical reference potential, wherein the electrical energy storage by means of a clocked energy converter with the vehicle external charging station electrically is coupled, wherein the clocked energy converter converts the electrical energy by means of at least two parallel-connected series circuits of two switching elements, for which purpose respective center terminals of the series circuits are electrically coupled to the charging station. The invention further relates to a charging device for charging an electrical energy store of a motor vehicle with electrical energy from a charging station external to the vehicle, with a charging station connection for supplying a single-phase electrical alternating voltage with respect to a predetermined electrical reference potential, an energy storage connection for electrically coupling the electrical energy store, a clocked energy converter at least two series circuits each comprising two switching elements, wherein the series circuits are connected in parallel and electrically coupled to the energy storage terminal, wherein each of the at least two series circuits has a center terminal and wherein the center terminals are electrically coupled to the charging station terminal. Finally, the invention also relates to a motor vehicle with an electrical system which has a DC voltage intermediate circuit and an electrical energy store connected to the DC intermediate circuit, a charging connection for connection to a vehicle-external charging station providing a single-phase electrical AC voltage and one electrically coupled to the charging connection and the electrical energy store Charging device for charging the electrical energy storage with electrical energy from the charging station.

The charging of an electrical energy storage device of a motor vehicle with electrical energy from a vehicle-external charging station is basically well-known in the prior art, so that a separate documentary evidence for this need not. A motor vehicle usually comprises an electrical system, in order to be able to supply electric devices that are connected to the electrical system and also units of the electrical system in a predeterminable manner with electrical energy. The electrical system thus serves the electrical power distribution.

In general, the electrical system includes a DC voltage intermediate circuit to which the electrical energy storage is connected. The electrical energy storage is used to store excess energy in the electrical system, as well as to provide for a demand for electrical energy for the electrical system. The electrical energy storage is often formed for this purpose by an accumulator or the like, which is able to chemically store electrical energy reversibly. In addition, the electrical energy store may also include an electrical capacitor.

Of particular importance is the electric energy storage in an electrically driven motor vehicle, which comprises an electric drive device by means of which the motor vehicle can be driven in the intended driving operation. As a rule, such a drive device comprises an inverter connected to the vehicle electrical system, in particular to an intermediate circuit of the electrical system, to which in turn a usually rotating electrical machine is connected, which is capable of providing the mechanical drive power. Usually, a three-phase electrical machine is used for this purpose, for example in the manner of a synchronous machine, an asynchronous machine and / or the like.

In an electrically driven motor vehicle, which may be, for example, an electric vehicle or hybrid vehicle, it is usually necessary to charge the electrical energy storage regularly so that it can provide electrical energy for the intended driving operation. For this purpose, the motor vehicle has a charging device which is electrically coupled to the electrical energy store and which is connected, for example, to the DC voltage intermediate circuit of the electrical system in order to be able to establish the electrical connection to the electrical energy store. In addition, the charging device is electrically connected to the charging port of the motor vehicle, via which an energy-related connection to the vehicle-external charging station can be made.

Usually, the vehicle-external charging station is formed by a charging station, for example a charging station or the like. The vehicle-external charging station can be either wired or wireless, for example by means of an alternating magnetic field or the like, be coupled to the charging port of the motor vehicle to be able to promote electrical energy from the charging station to the electrical energy storage.

In order to be able to produce an energy-technical coupling, the charging device generally has a clocked energy converter, for example in the manner of a rectifier, which can occasionally also be coupled to a DC / DC converter and / or the like. In addition, a galvanic isolation is usually provided due to the electromagnetic compatibility and / or electrical safety, which separates the vehicle external charging station galvanically from the electrical system of the motor vehicle. The galvanic isolation is often formed by a transformer.

Frequently, the vehicle external charging station for the purpose of energy supply an electrical AC voltage ready, which is related to a predetermined electrical reference potential, such as the ground potential, another suitable ground potential and / or the like. Since the electrical energy is usually taken from a public power grid or is provided by this, the AC voltage usually has an AC frequency corresponding to that of the public power distribution network. In Europe and much of Asia, this is predominantly a frequency of about 50 Hz. In America, however, the frequency is usually 60 Hz.

Depending on the design of the vehicle external charging station is usually provided a single-phase or a three-phase AC voltage.

In the case of a line-connected energy-related coupling, special requirements with regard to electrical safety and electromagnetic compatibility must be observed. For this reason, a corresponding filter circuit is usually provided, for example, on the charging station side and / or on the motor vehicle side, so that the respective prescribed requirements can be met. A corresponding requirement is, for example, compliance with a maximum permissible leakage current. The leakage current is an electrical current that flows in the normal operation of an electrical system in an undesirable current path. The current path is often formed by a protective conductor, which is usually electrically connected to the electrical reference potential. The electrical reference potential is often the ground potential.

In many electrical applications, the leakage current is essentially determined by the filter circuit, which serves to comply with the electromagnetic compatibility, in particular with regard to conducted radio interference. To suppress such conducted radio interference, Y-capacitors are often used in the filter circuit, which electrically couple a respective potential to be suppressed with the reference potential. This results in that upon application of an alternating voltage, a corresponding alternating current flows through the Y-capacitor, which at least partially determines the leakage current. In addition, the leakage current can also be dependent on further, in particular capacitive, couplings.

Especially with a connection of a charging station, which provides a single-phase AC voltage, the effort in terms of electromagnetic compatibility and electrical safety, in particular with respect to the leakage current, proves to be significant. For physical reasons, the corresponding expense for a three-phase AC voltage is significantly lower. Especially when connected to a charging station, which provides a single-phase AC voltage, special requirements are therefore to be considered, which require a high technical complexity.

The invention has for its object to improve the situation with respect to a leakage current when charging an electrical energy storage of a motor vehicle.

As a solution, the invention proposes a method, a charging device and a motor vehicle according to the independent claims.

Further advantageous embodiments will become apparent from the features of the dependent claims.

With regard to a generic method, it is in particular proposed that the switching elements are controlled at least as a function of an electrical reference voltage between one of at least two energy storage potentials of the electrical energy store and the electrical reference potential.

With regard to a generic charging device is in particular proposed that it has a control unit which is designed to control the switching elements at least depending on an electrical reference voltage between one of at least two energy storage potentials at the energy storage port and the electrical reference potential.

With regard to a generic motor vehicle, it is in particular proposed that the charging device is designed according to the invention.

The invention is based on the finding that by appropriately controlling the clocked Energy converter, in particular its arranged in a given circuit structure switching elements is made possible that even the bottom of the generation of a leakage current can be reduced. The invention uses the idea that the AC voltage of the charging station is usually related to a reference potential, usually the ground potential. The charging station usually provides the AC voltage to two electrical terminals, one of the electrical terminals being a neutral terminal and the second of the electrical terminals being a phase terminal. In most cases, the zero terminal is electrically connected to the ground potential in the charging station itself or by a subsequent electrical infrastructure to which the charging station is connected to the ground potential as the reference potential.

Since the charging station is electrically connected to the charging port of the motor vehicle during charging, these electrical potentials are correspondingly present in the motor vehicle. In general, therefore, the reference potential of the charging station with an electrical reference potential of the motor vehicle, for example, a mass, electrically connected. In general, the electrical reference potential of the motor vehicle is formed by a motor vehicle mass, which is connected via a separately guided connection cable to the reference potential of the charging station. As a result, dangerous electrical states can be reduced or avoided during the charging of the electrical energy store.

The invention makes use of the fact that the electrical energy store is usually connected with its energy storage connection to the DC voltage intermediate circuit and thus provides the intermediate circuit DC voltage with its at least two electrical energy storage potentials. The energy storage connection therefore generally also includes the DC voltage intermediate circuit at the same time.

The DC voltage intermediate circuit has line capacitors for interference suppression connected to the energy storage potentials of the electrical energy storage Y capacitors that electrically couple each of the at least two energy storage potentials that also correspond to the DC link potentials with the vehicle-side reference potential or the vehicle mass. As a result, a conducted radio interference suppression can be achieved or improved.

Since the motor vehicle in the intended driving operation with the charging station and thus with the reference potential of the charging station, in particular the ground potential, is not electrically coupled, and special requirements regarding the leakage current in island operation of the electrical system of the motor vehicle are more generous than stationary electrical facilities, have the Y capacitors usually have a comparatively large capacitance value. However, since the DC link voltage is subject to relatively small voltage fluctuations during normal operation as DC voltage, the leakage current is correspondingly low despite the large capacitance value. A common capacity of such Y-capacitors is for example about 1uF.

The situation changes when the charging station provides a single-phase AC voltage for charging the electrical energy storage device and the motor vehicle is connected thereto for the purpose of charging the energy storage device. On the basis of the bridge rectification principle during charging, namely, if no electrical isolation is provided, the energy storage potentials with respect to the reference potential fluctuate in the rhythm of the AC voltage frequency. As a result, of course, the motor vehicle side Y capacitors are acted upon by this AC voltage accordingly. This results in charging a significant leakage current, which exceeds the allowable limit for stationary systems to which the motor vehicle is connected when charging the electrical energy storage. In the prior art elaborate filters and compensation measures are provided here.

The invention is based on the further idea of reducing the fluctuation of the energy storage potentials with respect to the reference potential during charging of the electrical energy store by controlling the semiconductor switches. As a result, it can be achieved that the leakage current can be reduced correspondingly on the motor vehicle side, in particular on the intermediate circuit side. The effects of the invention can thus be achieved in particular when the electrical energy store is charged by a charging station which merely provides a single-phase AC voltage. In the case of a three-phase AC voltage, the leakage current on the motor vehicle side is fundamentally already considerably lower due to the underlying principle of rectification, so that the aforementioned problem with respect to the leakage current does not occur here or can already be reduced in a suitable manner by other simple cost-effective measures. Basically, however, the inventive principle can also be used here to reduce the leakage current. Nevertheless, the effect according to the invention is particularly suitable for charging stations which provide a single-phase AC voltage.

The clocked energy converter, which is preferably designed in the manner of an inverter, has at least two parallel-connected series circuits each consisting of two switching elements. The two series circuits are also connected to the electrical energy storage, for example, to the DC voltage intermediate circuit when the electrical energy storage is also connected to the DC voltage intermediate circuit. However, it can also be provided that the electrical energy storage is separated for the purpose of charging from the DC voltage intermediate circuit and electrically coupled to the charging device.

Each of the series circuits has a corresponding center terminal provided at a junction of the respective two switching elements of the respective series circuit. Each of the two center terminals is electrically connected to one of the potentials provided by the charging station, between which is the AC voltage provided by the charging station for the purpose of charging.

The clocked power converter further includes an energy converter control connected to the switching elements and operating the switching elements in a clocked mode to provide the energy conversion in a desired manner. For this purpose, switching patterns or clock patterns for the switching elements are provided, by means of which the desired energy conversion can be realized.

The switching elements of the energy converter are preferably semiconductor switching elements which may be formed, for example, by transistors such as bipolar transistors, field-effect transistors, in particular metal oxide semiconductor field effect transistor (MOSFET), isolated gate bipolar transistor (IGBT) or the like. The transistors are operated in a switching mode.

The switching operation of the semiconductor switching element means that in the on state during the switch-on between terminals of the semiconductor switching element between which the switching path is formed, a very low electrical resistance is provided so that a high current flow at very low residual voltage is possible. In the off state during the off time, the switching path of the semiconductor switching element, however, has high impedance, that is, it provides a high electrical resistance, so that there is substantially no or only a very low, in particular negligible, current flow even at high voltage applied to the switching path , This differs from a linear operation, which is usually not used in clocked energy converters. The switching operation preferably provides only the on state and the off state.

Thus, not only the switching elements for reducing the leakage current can be controlled by means of the energy converter control, but it is also possible to be able to set the converted power in a predeterminable manner. This makes it possible to operate the electrical energy storage in the most favorable operating condition for the purpose of charging. As a result, an aging of the electrical energy store can be kept as low as possible and at the same time, if appropriate, a high efficiency with respect to the electrical charging can be achieved.

According to the invention, the switching elements are controlled at least as a function of the electrical reference voltage between one of at least two energy storage potentials of the electrical energy store and the electrical reference potential. Since the at least two energy storage potentials are coupled together in a predetermined manner by the electrical energy store, the reference voltage need only be taken into account with respect to one of the two energy storage potentials.

Unlike in the conventional art, according to the invention not only exclusively a conversion power of the clocked energy converter is set, but the operation of its switching elements is adjusted taking into account the reference voltage so that the leakage current can be influenced. For this purpose, the electrical reference voltage is detected, for example by using a voltage sensor or the like. The reference voltage also represents a measure of the electrical voltage with which the Y capacitors, which comprise the vehicle electrical system of the motor vehicle and are electrically coupled to the electrical energy store, are acted upon. This reference voltage thus also represents a measure of which the leakage current is dependent. It should be noted that due to the physical properties of the Y capacitors, the leakage current may also be frequency-dependent. Incidentally, this also explains why at a reference voltage, which is essentially only a DC voltage, the leakage current is correspondingly low.

With the invention, it is thus possible, by means of a suitable control concept, which uses predetermined switching pattern for the switching elements to reduce the leakage current accordingly. In addition, with the invention, a control in the manner of a control can be achieved, in which detects the electrical reference voltage by means of a suitable voltage sensor and a Control unit of the control unit of the charging device is supplied, by means of which the switching pattern for the switching elements are suitably adapted or provided so that the reference voltage has the smallest possible ripple, preferably is substantially constant. The suitable switching patterns can be determined by means of simulation methods. With decreasing ripple of the reference voltage, the leakage current caused by the Y capacitors is reduced at the same time. With the invention, for example, depending on the reference voltage, a suitable switching pattern for respective switching elements can be selected.

In particular, a Y capacitor is a capacitor specially designed for the function of radio interference suppression, which must meet special technical requirements, in particular with respect to its dielectric strength, its current carrying capacity and / or the like. These capacitors are electronic components which have to meet special requirements, in particular with regard to the radio interference suppression, as is the case for example with standards relating to electromagnetic compatibility, such as EN 61000, or also with regard to electrical safety. Y capacitors are usually covered by standardization, for example according to IEC 60364 , These are capacitors, which are usually connected between the phase or the zero terminal and the reference potential, for example a touchable, in particular protective earthed, part, whereby they can bridge a usually required due to electrical safety basic insulation. You must therefore meet very high, especially standardized, requirements. Y capacitors are commonly used to suppress common mode noise. Incidentally, this is a special constellation in which the reference potential, as may be provided, for example, by the protective conductor, may be used for purposes other than protective earthing and thus protection against electric shock. This differs from the X-capacitors also used for the purpose of radio interference suppression of conducted radio interference, which are commonly used to suppress push-pull interference. In order not to jeopardize the protective function of the reference potential or of the protective conductor, increased protection requirements are imposed both on X capacitors and on Y capacitors.

In order to be able to realize the method according to the invention, the charging device is also proposed with the invention. The charging device is preferably designed for arrangement on or in the motor vehicle. It is in particular designed to be connected to the DC voltage intermediate circuit of the electrical system of the motor vehicle, and in particular when the electrical energy storage is connected to this intermediate circuit and thus can be acted upon directly by the charging device with electrical charge. In addition, it is of course also possible to connect the charging device with its energy storage connection directly to the electrical energy storage. It can be provided to electrically disconnect the DC intermediate circuit during charging of the electrical energy storage device from the electrical energy storage, for example by means of electromechanical switching elements, which are provided by a contactor and / or the like.

However, the leakage current need not only be caused by the Y capacitors, but it can equally or additionally also by parasitic capacitive couplings, the reference potential with one or both of the energy storage potentials of the electrical energy storage or the DC link potentials of the DC voltage intermediate circuit can be effected. Parasitic capacities are often present due to design and can be avoided even with the most careful construction hardly or only insufficiently. In general, however, the leakage current is essentially determined by the Y capacitors, because in reality their electrical capacitance is usually significantly greater than the electrical capacitance of parasitic capacitances.

The charging device has the control unit, by means of which the switching elements can be controlled in a suitable manner. Preferably, the control unit comprises the energy converter control. However, it can also be provided that the control unit represents a separate structural unit, which is connected to the energy converter control and supplies the energy converter control with corresponding control signals for the switching elements. The control unit is preferably an electronic circuit, which may be connected to a voltage sensor, in particular for detecting the reference voltage, or may even include this. In addition, the control unit may also include a program-controlled computer unit, which may also be combined with the electronic circuit. By means of the computer program, the computer unit can provide the desired functionality.

It proves particularly advantageous if the AC voltage is provided at a predetermined AC voltage frequency and only a spectral portion of the electrical reference voltage in a predetermined range of the AC voltage frequency is taken into account for controlling the switching elements. The area of AC voltage frequency includes, for example, a range that can be provided by a maximum deviation from the AC frequency by about 10%, preferably 5%. Preferably, the predetermined range corresponds exactly to the AC voltage frequency. This has the advantage that it is precisely the frequencies that are particularly unfavorably to be filtered that can be compensated for in the range of the AC voltage frequency. The AC voltage frequency is, for example, 50 Hz or 60 Hz, depending on in which region and in which energy supply network the charging station is connected. In isolated networks, moreover, a frequency of 400 Hz may be provided, such as on-board networks on ships, in aircraft and / or the like. Especially due to the low frequency only with great effort to reduce leakage currents in the range of 50 Hz or 60 Hz can thus be reduced, whereby a related effort in terms of filtering can be reduced accordingly. In addition, this procedure is of course particularly suitable for control purposes, in which the switching pattern for the switching elements are changed depending on the detected reference voltage.

In addition, it is proposed that the switching elements are controlled such that the electrical reference voltage is substantially constant. This embodiment takes into account that only very small or negligible leakage currents are caused at a substantially constant reference voltage, in particular by the Y capacitors. This results from the functionality of capacitors.

According to one embodiment, it is proposed that the switching elements are controlled in such a way that the electrical reference voltage corresponds to 40% to 60%, preferably 50%, of an electrical energy storage voltage between the at least two energy storage potentials of the electrical energy store. If the electrical energy store is connected directly to the DC voltage intermediate circuit, this voltage corresponds to the DC link voltage. This embodiment has the advantage that a voltage load of the components can be made uniform with respect to the electrical reference potential. In addition, effects that result in, for example, differential mode noise can be reduced.

It is further proposed that one of the electrical AC potentials of the AC electrical voltage is electrically coupled to the electrical reference potential, wherein the center terminals of the two series circuits are coupled to the two provided by the charging station terminals or electrical potentials. A power-frequency component of the voltages, for example at a frequency of approximately 50 Hz, which are set at the two center connections of the two series connections with respect to the reference potential, essentially follows the power-frequency component of the two connected electrical potentials with respect to the reference potential. Furthermore, the voltage drops across the line filter chokes can be taken into account when setting the voltages at the two center terminals of the two series circuits, which can lead to a nearly complete elimination of the mains frequency components of the leakage currents.

In a conventional power supply in Germany, for example, a public power grid, in which the zero terminal is fixed to the reference potential, while the phase connection performs the full working voltage compared to the reference potential, an advantageous control of the circuit breaker would be characterized in that the series circuit, the center port electrically coupled to the reference potential, about 40% to 60%, preferably about 50%, the energy storage voltage or optionally the DC link voltage, and the other series circuit performs the full stroke of the charging voltage, ie sinusoidally, for example, between 10% and 90% of the energy storage voltage with the Mains frequency oscillates. In a further advantageous embodiment, the voltage drops across the line filter chokes can be superimposed on these two voltages.

The two series circuits of the clocked energy converter are preferably operated according to the invention so that it provides an AC voltage with a full amplitude at the AC frequency at one of the two center connections with respect to the DC link voltage available at the clocked power converter, whereas the other series circuit its central terminal provides an anti-phase partial voltage of the AC voltage at the AC frequency. It can thereby be achieved that the corresponding AC voltage component of the reference voltage is reduced, as a result of which the leakage current is correspondingly reduced.

As a rule, each of the at least two energy storage potentials of the electrical energy store is electrically coupled via a respective Y capacitor to the electrical reference potential. So that the charging device can determine which of the center connections is electrically coupled to the reference potential, it is further proposed that the switching elements each have an inverse diode wherein the switching elements are turned off and respective electrical switching element voltages are detected and evaluated to determine which of the center terminals is electrically coupled to the reference potential. This embodiment makes use of the fact that drive circuits provided for the switching elements generally comprise a switching state detection. The switching state detection is based on detecting a switching element voltage applied to the switching element. If the detected switching element voltage is smaller than a predetermined comparison value, this is output as a switched-on state. If, however, the detected switching element voltage is greater than the comparison value, this is output as a switched-off state. This makes it possible to detect the respective switching state of the switching elements. Since a respective diode is connected in parallel to each switching element, so that the switching state of the respective diode can be determined, because the switching elements themselves are in the designed switching state. In this embodiment, the clocked energy converter works like a single-phase bridge rectifier. The comparison value is preferably chosen at an electrical voltage of about 4V. However, it may also be chosen in a range from about 2.5 V to about 8 V, in deviation. Here, this embodiment is based on that a switching state of the switching element in which the center terminal of the series circuit is electrically coupled to the phase terminal oscillates back and forth in accordance with the AC frequency, whereas the switching state of a switching element in the series circuit whose center terminal is connected to the neutral terminal constantly outputs the switched-off state. The thus determined connection situation of the charging station to the clocked energy converter can be used to be able to control the switching elements of the two series circuits in a suitable manner, as has already been explained in detail above.

According to one embodiment, it is proposed that the charging station connection is galvanically coupled to the clocked energy converter. Namely, the invention makes it possible to dispense with galvanic isolation, as is conventional in the prior art. In the prior art, the galvanic separation also serves, among other things, to prevent leakage currents. For this purpose, a suitable transformer is usually provided, by means of which the electrical isolation can be achieved. However, such a transformer is costly and also requires a large amount of space. With the invention, it is possible to avoid the galvanic separation and at the same time to meet the requirements, which may be at least partially justified by the standardization.

It is further proposed that the motor vehicle has an electric drive device which has a three-phase electrical machine for driving the motor vehicle and an inverter connected to the electrical machine and the electrical system, which is designed to provide a three-phase alternating voltage network for the electric machine, wherein the Inverter is designed to provide the clocked energy converter of the charger.

This development uses an existing already in an electrically driven motor vehicle anyway existing inverter to provide the clocked energy converter for the purpose of charging the electrical energy storage. Thus, it is not necessary to provide a separate clocked energy converter in this development. As a result of the fact that the inverter is already designed for three-phase operation, this inverter generally also includes a switching element structure, as is required for the cycled energy converter, which is used to carry out the method according to the invention. As a result, effort, space and weight can be saved. This is particularly advantageous in motor vehicles.

It is further proposed that the clocked energy converter is electrically coupled to the charging port via phase windings of the electrical machine. In this case, the electric machine is at least partially included in the conversion process. This makes it possible to operate the clocked energy converter as a boost converter or buck converter. It proves to be particularly advantageous if stator windings of the electric machine are connected to a star point in a proper driving operation, with the neutral point being resolved for the purpose of charging, so that respective winding connections released thereby can take over the function of the center connections of the cycled energy converter. As a result, additional effects due to the inductances provided by the windings can be used advantageously for the method according to the invention.

The invention also includes developments of the method according to the invention, which have features as they have already been described in connection with the developments of the charging device according to the invention or the motor vehicle according to the invention and vice versa. For this reason, the corresponding developments are not described here again.

• 1 eine schematische Schaltbildansicht eines elektrischen Bordnetzes eines Elektrofahrzeugs als Kraftfahrzeug mit einer elektrischen Antriebseinrichtung in einem bestimmungsgemäßen Fahrbetrieb;
• 2 eine schematische Schaltbildansicht wie 1, bei der jedoch das Elektrofahrzeug zum Aufladen eines Akkumulators des Bordnetzes an eine Ladestation angeschlossen ist, die ein dreiphasiges Wechselspannungsnetz bereitstellt;
• 3 eine schematische Diagrammdarstellung von elektrischen Spannungen, die an Wechselspannungsanschlüssen eines Wechselrichters der Antriebseinrichtung beim Aufladen gemäß 2 anliegen;
• 4 in einer schematischen Diagrammdarstellung ein PWM-Muster für eine der in 3 gezeigten Wechselspannungen;
• 5 eine schematische Diagrammdarstellung von elektrischen Spannungen wie 3, die an Eingangsanschlüssen des Wechselrichters beim Anschluss an eine Ladestation anliegen, die eine einphasige Wechselspannung bereitstellt;
• 6 eine schematische Diagrammdarstellung wie 4 von PWM-Mustern zum Einstellen der Spannungen gemäß 5;
• 7 eine schematische Schaltbilddarstellung wie 2, bei der das Bordnetz zum Aufladen des Energiespeichers an eine Ladestation angeschlossen ist, die eine einphasige Wechselspannung bereitstellt;
• 8 eine schematische Darstellung wie 5 für die Schaltung gemäß 7;
• 9 eine schematische Darstellung wie 6 für die Bereitstellung einer Spannung gemäß 8;
• 10 eine schematische Schaltbilddarstellung wie 7, wobei die Schaltelemente des Wechselrichters gemäß einem Schaltmuster der Erfindung gesteuert werden, wie es anhand von 9 dargestellt ist;
• 11 eine schematische Ersatzschaltbilddarstellung für eine Simulation des Betriebs der Schaltung gemäß 7;
• 12 eine schematische Diagrammdarstellung der Verhältnisse beim Betrieb der Schaltung gemäß 7;
• 13 eine schematische Ersatzschaltbilddarstellung der Schaltung gemäß 10 für Simulationszwecke;
• 14 eine Darstellung wie 12 für die Ersatzschaltbilddarstellung gemäß 13;
• 15 eine schematische Ersatzschaltbilddarstellung für eine weiter verbesserte Gleichtaktunterdrückung;
• 16 eine Darstellung wie 14 für die Ersatzschaltbilddarstellung gemäß 15;
• 17 eine schematische Ersatzschaltbilddarstellung zur Ermittlung, welcher der Wechselrichteranschlüsse mit einem Nullanschluss der Ladestation elektrisch verbunden ist;
• 18 eine schematische Diagrammdarstellung einer Simulation der Schaltung gemäß 17, um zu ermitteln, welcher der Wechselrichteranschlüsse mit dem Nullanschluss der Ladestation elektrisch gekoppelt ist; und
• 19 eine Darstellung wie 18, bei der das Erkennen weiter verdeutlich ist.

In the following, embodiments of the invention are described. This shows:

• 1 a schematic diagram view of an electrical system of an electric vehicle as a motor vehicle with an electric drive device in a designated driving operation;
• 2 a schematic diagram view like 1 in which, however, the electric vehicle for charging a battery of the electrical system is connected to a charging station, which provides a three-phase alternating voltage network;
• 3 a schematic diagram of electrical voltages applied to AC terminals of an inverter of the drive device during charging according to 2 issue;
• 4 in a schematic diagram representation of a PWM pattern for one of in 3 shown AC voltages;
• 5 a schematic diagram of electrical voltages such 3 which are applied to input terminals of the inverter when connected to a charging station which provides a single-phase AC voltage;
• 6 a schematic diagram representation as 4 of PWM patterns for adjusting the voltages according to 5 ;
• 7 a schematic diagram representation as 2 in which the vehicle electrical system is connected to a charging station for charging the energy store, which provides a single-phase AC voltage;
• 8th a schematic representation like 5 for the circuit according to 7 ;
• 9 a schematic representation like 6 for providing a voltage according to 8th ;
• 10 a schematic diagram representation as 7 wherein the switching elements of the inverter are controlled in accordance with a switching pattern of the invention, as described with reference to FIG 9 is shown;
• 11 a schematic equivalent circuit diagram representation for a simulation of the operation of the circuit according to 7 ;
• 12 a schematic diagram of the relationships in the operation of the circuit according to 7 ;
• 13 a schematic equivalent circuit diagram of the circuit according to 10 for simulation purposes;
• 14 a representation like 12 for the equivalent circuit diagram according to 13 ;
• 15 a schematic equivalent circuit diagram for a further improved common mode rejection;
• 16 a representation like 14 for the equivalent circuit diagram according to 15 ;
• 17 a schematic equivalent circuit diagram for determining which of the inverter terminals is electrically connected to a zero terminal of the charging station;
• 18 a schematic diagram representation of a simulation of the circuit according to 17 to determine which of the inverter terminals is electrically coupled to the neutral terminal of the charging station; and
• 19 a representation like 18 in which the recognition is further clarified.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the respective embodiment each represent individual, independently to be considered features of the invention, which further develop the invention independently and thus individually or in any other than the combination shown to be considered part of the invention. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

In the figures, functionally identical elements are each provided with the same reference numerals.

1 shows a schematic circuit diagram representation of a DC intermediate circuit 54 an electrical vehicle electrical system of an electric vehicle, not shown, as an electrically driven motor vehicle, to which an electric drive device 56 connected. The electric drive device 56 includes a three-phase electric machine 58 , which is presently designed as a synchronous machine and which serves to drive the electric vehicle.

To the electric machine 58 is an inverter 60 connected, which is formed, a three-phase AC voltage network for the electric machine 58 provide. The inverter 60 includes a control unit 52 , by means of which the inverter 60 is suitably controlled with respect to the alternating voltage network, so that the electric machine 58 to provide the desired drive function during the intended driving operation of the electric vehicle. For this purpose, the Inverter three in the following still further explained inverter connections on which unnamed stator windings of the electric machine 58 are connected. The stator windings of the electric machine 58 are in driving at a common star point 62 connected. The inverter 60 is still connected to the DC voltage intermediate circuit 54 connected.

At the DC voltage intermediate circuit 54 is also a high-voltage battery 10 connected as an electrical energy store, which provides electrical energy for the intended driving of the electric vehicle. Thus, the high-voltage battery provides 10 at the same time the intermediate circuit DC voltage of the DC intermediate circuit 54 ready.

Electrical potentials of the high-voltage battery 10 , which represent energy storage potentials, are via respective Y capacitors 42 . 44 coupled to a reference potential, which in this case by a mass 40 of the electric vehicle is formed. Through the Y capacitors 42 . 44 a radio interference in terms of common mode noise is achieved. The Y capacitors 42 . 44 act in this regard with a current-compensated choke 64 together. In the present embodiment, the electrical capacitance of each of the two Y capacitors 42 . 44 about 1 μF. The electrical capacity of the Y capacitors 42 . 44 If necessary, this can also be chosen differently.

In two in a left area in 1 superimposed diagrams is a respective electrical voltage of the potentials of the high-voltage battery 10 opposite to the mass 40 shown. From the two schematic diagrams it can be seen that a reference voltage 38 between a positive electric potential of the high-voltage battery 10 and the crowd 40 is formed, about half of the DC link voltage corresponds. Accordingly, there is an electrical voltage between the negative electric potential of the high-voltage battery 10 and the crowd 40 ,

In two diagrams, shown in a right-hand area next to the circuit diagram, are electrical potentials of a star point 62 in terms of the negative potential of the high-voltage battery 10 shown. The star point 62 is through respective winding terminals of windings of the electric machine 58 educated. The left of the two diagrams shows an electrical voltage between the two potentials with a resolution in the range of a clock frequency of the inverter 60 , The diagram shown to the right shows the electrical potential relative to an operating frequency of the electric machine 58 ,

During normal driving, the common mode potential on the DC link side is the one on the high-voltage battery 10 over the Y capacitors 42 . 44 to the mass 40 clamped. In contrast, the push-pull potential at the AC voltage side of the electric machine 58 around the crowd 40 jump, in time with the switching frequency of the inverter 60 ,

The inverter 60 in the present case has three series connections 22 . 24 . 26 from two semiconductor switches each 28 . 30 in the present case are formed by isolated gate bipolar transistors (IGBT). The series connections 22 . 24 . 26 are connected in parallel and to the DC voltage intermediate circuit 54 connected. Each of the three series connections 22 . 24 . 26 has a respective middle connection 32 . 34 . 36 on which provide the inverter terminals, where the stator windings of the electric machine 58 are connected. The inverter 60 is thus designed in the manner of a B6 inverter bridge and provides the three-phase AC power supply for driving.

2 shows in a schematic diagram representation based on 1 as the electrical system for charging the high-voltage battery 10 to a vehicle-external charging station 12 is connected, the electrical energy to charge the high-voltage battery 10 provides. The charging station 12 is a stationary charging station, and the electric vehicle is used to connect to the charging station 12 in the area of the charging station 12 switched off. About a not further shown wired connection, in this case a connection cable, the electrical system, as will be explained further below, to the charging station 12 connected. The charging station 12 provides a three-phase AC voltage with a nominal voltage of about 230 V per phase at an AC voltage frequency of about 50 Hz. The three phases are each shifted by 120 ° to each other.

In the present embodiment, a galvanic connection between the charging station 12 and the electrical system of the electric vehicle provided. Accordingly, a protective conductor terminal or a reference potential 16 , here earth potential, the charging station 12 with the crowd 40 electrically coupled to the electric vehicle.

The charging station 12 further comprises a trained for three-phase AC voltage trained net filter, by means of which a filtering of the terminals of the charging station 12 be made in order to fall below the prescribed limits for repercussions.

To the charging station 12 to connect to the electrical system of the electric vehicle is presently provided that the star point 62 the electric machine 58 is opened and the corresponding terminals of the stator windings of the electric machine 58 to the respective phase terminals of the charging station 12 be connected. This will be a charging station connection 48 provided by the electric vehicle.

About the stator windings of the electric machine 58 and the inverter 60 can then supply electrical energy to the high-voltage battery 10 respectively. For this purpose, the IGBT's 28 . 30 of the inverter 60 by means of the control unit 52 of the inverter 60 controlled in a suitable manner. The inverter 60 So provides a clocked energy converter, the use of the inductance of the stator windings of the electric machine 58 an energy conversion realized in a suitable manner. This allows the high-voltage battery 10 electrical energy from the charging station 12 be supplied.

In two superimposed schematic diagrams in a left area in 2 is again the respective reference voltage 38 shown. It can be seen that the reference voltage 38 essentially the same as they are in the in 1 corresponds to the operating situation shown. Only slight fluctuations occur when charging by means of a three-phase alternating voltage. Accordingly, the conditions at the center connections 32 . 34 . 36 as they already are 1 are shown. This is shown by two superimposed diagrams in a central region in the circuit diagram of 2 shown. In the right area of the 2 are the three stages of the charging station 12 provided AC voltage shown.

By means of a charging station provided net filter or filter circuit 120 can be prevented that the reference potential 16 neither with respect to the DC link side nor with respect to the charging station side AC side jumps.

Depending on a respective switching pattern for the respective IGBT's 28 . 30 , which use a respective PWM pattern to realize the respective push-pull voltage with respect to the mains frequency of 50 Hz, different noise components are generated. The filter circuit 120 the charging station 12 is designed adapted for these disorders.

4 shows in a schematic diagram representation of the time course of a PWM pattern of the series circuit 24 of the inverter 60 with a graph 66 and the associated integrated AC voltage with a graph 68 , 3 sets the three corresponding AC voltages at the three input terminals of the inverter 60 with three graphs 70 . 72 and 74 in the diagrams 3 and 4 the abscissa is a time axis in which the time is given in milliseconds. The ordinate is a voltage axis indicating the voltage in volts.

7 shows a schematic diagram representation as 2 Here, however, the electrical system of the electric vehicle to a charging station 14 connected, which is a single-phase AC voltage 18 provides. As a result, are now from the inverter 60 only the series connections 22 and 24 activated with respect to the energy conversion. Together with the stator windings of the electric machine 58 becomes thereby a clocked energy converter 20 educated. The clocked energy converter 20 has an energy storage port 50 on, with which he at the DC voltage intermediate circuit 54 and thus also on the high-voltage battery 10 connected. Thus, the clocked energy converter forms 20 a charging device 46 that is trained at the charging station 14 to be connected.

The central connections 32 and 34 the series connections 22 . 24 are correspondingly with a phase connection L and a zero connection N the charging station 14 electrically connected. Charging station side is at the phase connection L opposite the zero connection N an AC voltage of 230 V at 50 Hz provided. The charging station 14 also has a filter circuit 120 on.

In addition, via a power supply, not shown, to which the charging station 14 connected, the zero connection N with a protective conductor connection as electrical reference potential 16 electrically coupled. The reference potential 16 is in this case the earth potential. The other components as well as their functionalities correspond to those as already described for the embodiment according to the 2 to 4 which is why reference is additionally made to the relevant remarks.

By means of the control unit 52 become the IGBT's 28 30 the series connections 22 . 24 controlled, so that a corresponding energy conversion can be realized. Thus, the charging station 14 taken from electrical energy and the high-voltage battery 10 be supplied.

In the middle area of the 7 are in the schematic diagram two superimposed schematic diagrams - as in 2 - shown. From these diagrams it can be seen that the common mode signal is present at the input terminals of the inverter 60 compensated in the present case. The top of the two Charts show the common mode potential with respect to the negative potential of the high-voltage battery 10 with respect to the PWM pattern, whereas the lower schematic diagram represents the common mode potential with respect to the AC frequency.

In the left area are - as well as in 2 - Also shown two schematic diagrams one above the other. The two diagrams on top of each other represent the reference voltage 38 concerning the positive potential of the high-voltage battery 10 in terms of mass 40 as well as the negative potential in relation to the mass 40 dar. The mass 40 is with the reference potential 16 electrically coupled.

It can be seen that the electrical potentials are in phase with approximately half the mains voltage amplitude with respect to the ground 40 fluctuate with the AC voltage frequency. The resulting reference voltage 38 is therefore superimposed with a comparatively high alternating voltage, so that of the Y capacitors 42 . 44 a correspondingly high leakage current into the ground 40 is dissipated.

Due to the comparatively high capacity for Y capacitors, the leakage current can have an inadmissibly high value. It is therefore through the filter circuit 120 the charging station 14 to provide appropriate measures that prevent a correspondingly high leakage current can occur. With the 5 and 6 the functionality for single-phase charging operation is further clarified in this operating mode.

5 Corresponds to the representation as it already has 3 was explained. With graphs 78 and 80 are the corresponding voltages at the input terminals of the inverter 60 shown at the center connections 32 . 34 , which provide the corresponding input terminals, integrated exist. The representation in 5 essentially shows the AC frequency component without additional spectra, which may be complementary, inter alia, by the PWM operation.

6 shows in a time-expanded representation corresponding PWM signals with graphs 82 . 84 , where the with the graph 78 voltage waveform associated with the PWM signal is associated with the graph 84 is shown and that with the graph 80 shown voltage waveform the PWM signal, that with graphs 82 is shown. As the PWM signal for series connection 24 , whose middle connection 34 to the zero connection N is inverted to the PWM signal which is at the center port 32 the series connection 22 which is connected to the phase connection L is electrically coupled, the corresponding common mode voltages are constant at about half the DC link voltage relative to the negative potential of the high-voltage battery 10 , However, an AC component of the common-mode voltage on the network side is not zero because of the zero connection N with the reference potential 16 is electrically coupled. Since the charging station-side common mode filter of the filter circuit 120 the relatively low AC frequency of about 50 Hz is not able to adequately filter, are the phase connection L and the zero connection N directly connected to the inverter connections. The AC frequency-related common mode component of the inverter outputs follows the AC frequency common mode component on the charging station side. Since there is no common mode component of the inverter terminals with respect to the negative potential of the high-voltage battery 10 is present, follows the common mode voltage on the DC link side of the common mode component on the charging station side.

10 now shows a schematic diagram as 7 , although here in the 10 additionally illustrated schematic diagrams illustrate the resulting due to the different control according to the invention leakage current and common mode potentials. The circuit structure therefore corresponds to that as they already are 7 was explained, which is why reference is additionally made to the relevant remarks.

The idea of the invention is to provide a PWM pattern for single-phase charging of the high-voltage battery 10 to use, because so that the above problems can be solved in single-phase charging. With the 8th and 9 be the 5 and 6 corresponding diagrams are shown, which also voltage curves, such as the 5 and 6 already explained, represent.

With the graphs 86 and 88 are in 8th respective voltages at the inverter terminals as shown in FIG 5 shown. 9 shows a temporally increased resolution, where also the graphs 86 and 88 are shown. In addition, there are supplementary associated PWM signals with graphs 90 . 92 shown. The PWM signal is according to the graph 90 the voltage curve according to the graph 86 and the PWM signal according to the graph 92 the voltage curve according to the graph 88 assigned.

It can be seen in 10 in the schematic diagrams, which are shown one above the other in the left area, that the reference voltage 38 unlike 7 is essentially a DC voltage. The negative potential of the high-voltage battery is also corresponding 10 opposite to the mass 40 a DC voltage. As a result, the Y capacitors 42 . 44 now essentially each acted upon by a constant voltage, so that the leakage current is significantly reduced by these capacitors.

By the control principle of the invention can thus be reduced, if not completely avoided, the aforementioned problem with respect to the leakage current. At the inverter connections, through the center connections 32 . 34 are formed, facing the embodiment according to 7 other voltages. It can be seen that in the upper diagram in the middle of the 10 the common mode potential with respect to the negative potential of the high-voltage battery 10 with the clock frequency of the inverter 60 fluctuates. From the schematic diagram below it can be seen that the common mode potential with respect to the negative potential of the high-voltage battery 10 has a significant spectral component at the AC frequency, in which case an AC voltage of approximately 115 V is present. Overall, a reduction of the leakage current in the range of the AC voltage frequency can thus be achieved with the invention. Although here in contrast to the embodiment according to the 5 to 7 the clock frequency of the inverter 60 In addition to suppress noise, however, this frequency is considerably higher compared to the AC voltage frequency, for example 10 kHz, which is why this high frequency can be filtered in a suitable manner with comparatively little filter effort.

In the following 11 to 20 various simulations and their results are shown, with which the effect of the invention is further clarified.

11 shows a schematic equivalent circuit diagram for a simulation of a balanced full bridge at a common mode current or leakage current to the reference potential 16 with a frequency of about 50 Hz in a symmetrical full bridge operation with a suitable PWM pattern. 12 shows a schematic voltage or current-time diagram, in which with graphs 94 and 96 AC voltages at the inverter terminals of the inverter 60 only the spectral component in the range of 50 Hz with respect to the negative potential of the high-voltage battery 10 is shown. With a graph 98 is the leakage current to the reference potential 16 represented by the Y capacitors 42 . 44 and optionally further Y capacitors of the network filter or the filter circuit 120 is effected. The electrical capacitance of the Y capacitors of a respective phase of the network filter or the filter circuit 120 is usually about 22 nF.

13 shows a schematic equivalent circuit diagram 11 in which now the clocked energy converter 20 operated according to the invention. 14 shows a representation like 12 in which by means of graphs 100 and 102 the corresponding alternating voltages at the center connections 32 . 34 the clocked energy converter 20 are shown for a spectral range around the AC frequency of 50 Hz. With a graph 104 the corresponding leakage current is shown. Compared to the representation according to the 11 and 12 It can be seen that the leakage current can be almost completely reduced by the control principle of the invention.

15 FIG. 12 shows another schematic equivalent circuit diagram based on the equivalent circuit diagrams of FIG 11 and 13 wherein, for further reduction of the leakage current, an expected voltage drop across filter inductances of the network filter or the filter circuit 120 the charging station 14 in the line of the zero connection N caused by the leakage current or the charging current is added to the voltage at the corresponding inverter terminal. 16 shows the corresponding effects in a chart like 12 and 14 ,

In the schematic diagram of 16 are with graphs 106 and 108 again the corresponding AC voltages at the center connections 32 . 34 the clocked energy converter 20 shown. With a graph 110 on the other hand, the leakage current is shown again. It is also apparent here that the leakage current compared to the simulation according to the 11 and 12 is considerably reduced.

In the embodiments is inverter 60 trained, a part of the clocked energy converter 20 the charging device 46 provide. The clocked energy converter 20 Thus, in this case, the series circuits comprise 22 . 24 of the inverter 60 whose central connections 32 . 34 to the corresponding connections of the charging station 14 namely the phase connection L and the zero connection N are connected. For the operation of the clocked energy converter 20 So it's not just the inverter 60 but also its control unit 52 used, which thus also includes an energy converter control, which is designed for the process control according to the invention.

In 17 schematically an equivalent circuit diagram is shown in which only the IGBT 's 28 , 30 parallel inverse diodes D1 . D2 . D3 . D4 are shown. This replacement circuit diagram is intended to explain how the charging device 46 allows to determine which of the connections of the clocked energy converter 20 , namely which of the center connections 32 . 34 , with the phase connection L and which of the center connections 32 . 34 with the zero connection N is electrically coupled. This is for the control of the clocked energy converter in the sense of the process control according to the invention of use.

Basically, of course, there is the possibility of applying the appropriate voltages to each of the center connections 32 . 34 opposite the reference potential 16 to eat. For other applications in which such a voltage can not be measured, a state information of the inverter 60 or by the inverter 60 provided clocked energy converter 20 be used by means of corresponding unillustrated driver units, the corresponding IGBT's 28 . 30 accordingly, can be determined. From the information obtained thereby it can be determined which of the middle connections 32 . 34 with the phase connection L and which with the zero connection N electrically connected.

18 shows a corresponding time diagram like the 12 . 14 . 16 with which the aforementioned measuring method is to be further clarified. Because the DC link side of the inverter 60 or the clocked energy converter 20 over the Y capacitors 42 . 44 with the crowd 40 and consequently with the reference potential 16 is connected, the voltage across the IGBT's 28 . 30 , in the 17 only through their corresponding diodes D1 . D2 . D3 . D4 are shown, very different for connection to the phase connection L and the zero connection N , This is with 18 clarified. For this purpose, this embodiment uses a function of the corresponding driver units that provide a status signal, depending on a switching state of the respective IGBT's 28 . 30 ,

The status signal is dependent on one on a switching path of the respective IGBT 28 . 30 measured electrical voltage. If this voltage is less than approximately 4 V, which corresponds to a predetermined reference voltage, this is signaled as a switched-on state with a suitable signal. Accordingly, a detected voltage greater than about 4 V is reported as being off with an appropriate signal. In this case, this embodiment uses the fact that the on or off state of the respective IGBT 28 . 30 that with the live connection L is electrically coupled, jumping back and forth, whereas a corresponding state of the IGBT's 28 . 30 that with the null connection N are electrically coupled, constantly indicate the off state.

When a DC voltage due to passive rectification across the inverse diodes D1 . D2 . D3 . D4 is detected, which is not increased by any other DC voltage source is the rectified DC voltage with the reference potential 16 coupled. Without the Y capacitors 42 . 44 of the DC intermediate circuit 54 For example, the rectified voltage would only rise to the maximum peak voltage of the supplied AC voltage. Because the Y capacitors 42 . 44 act on the DC link side like bootstrap capacitors, if the AC side is not symmetrical with respect to the reference potential 16 is, the DC voltage increases to about twice the peak voltage of the AC voltage when the phase connection L or the zero connection N with the reference potential 16 be coupled. 18 clarifies this.

With a graph 114 is in 18 the corresponding voltage of the IGBT's 28 . 30 shown connected to the phase connection L are coupled. With the graph 112 is the situation for the IGBT's 28 . 30 shown at the zero connection N are connected. A graph 116 represents the reference potential 16 out 18 It can be seen that it can be easily determined that the diodes D1 and D3 with the phase connection L are coupled. Accordingly, their IGBTs are 28 . 30 with the phase connection L electrically coupled. This can be used to control the IGBT's 28 . 30 be used to realize the process control according to the invention can.

19 shows in a schematic representation as 18 detection areas 118 that can be used to assign the by the charging station 14 provided connections to the reference potential 16 to be able to determine.

Overall, the exemplary embodiments show how leakage currents, in particular when charging an electrical energy store of a motor vehicle with a single-phase AC voltage of a charging station, can be reduced with the method according to the invention. The embodiments are merely illustrative of the invention and are not intended to limit this.

LIST OF REFERENCE NUMBERS

10

High-voltage battery

12

charging station

14

charging station

16

reference potential

18

AC

20

energy converters

22

series connection

24

series connection

26

series connection

28

Semiconductor switches

28

IGBT

30

IGBT

32

medium connection

34

medium connection

36

medium connection

38

reference voltage

40

Dimensions

42

Y-capacitor

44

Y-capacitor

46

loader

48

Charging Connector

50

Energy storage connection

52

control unit

54

Dc link

56

driving means

58

electric machine

60

inverter

62

star point

64

throttle

66

graph

70

graph

72

graph

74

graph

76

graph

78

graph

80

graph

82

graph

84

graph

86

graph

88

graph

90

graph

92

graph

94

graph

96

graph

98

graph

100

graph

102

graph

104

graph

106

graph

108

graph

110

graph

112

graph

114

graph

116

graph

118

detection range

120

filter circuit

L

phase connection

N

zero connection

D1 to D4

inverse diodes

Claims (11)

A method of charging an electrical energy store (10) of a motor vehicle with electrical energy from a vehicle external charging station (14), wherein the charging station (14) provides a single phase AC electrical voltage (18) with respect to a predetermined electrical reference potential (16); electrical energy store (10) by means of a clocked energy converter (20) with the vehicle external charging station (14) is electrically coupled, wherein the clocked energy converter by means of at least two parallel series circuits (22, 24) of two switching elements (28, 30) converts for which purpose respective center connections (32, 34) of the series connections (22, 24) are electrically coupled to the charging station (14), characterized in that the switching elements (28, 30) are connected between at least one electrical reference voltage (38) of at least two energy storage potentials of the electrical Energiespe Iers (10) and the electrical reference potential (16) are controlled. Method according to Claim 1 , characterized in that the AC voltage (18) is provided with a predetermined AC voltage frequency and for controlling the switching elements (28, 30) only a spectral portion of the electrical reference voltage (38) is taken into account in a predetermined range of the AC frequency. Method according to Claim 1 or 2 , characterized in that the switching elements (28, 30) are controlled such that the electrical reference voltage (38) is substantially constant. Method according to one of the preceding claims, characterized in that the switching elements (28, 30) are controlled such that the electrical reference voltage (38) 40% to 60%, preferably 50%, of an electrical energy storage voltage between the at least two energy storage potentials of the electrical energy storage (10). Method according to one of the preceding claims, characterized in that one of the electrical potentials (N) of the alternating electrical voltage is electrically coupled to the electrical reference potential (38), wherein the middle terminals (32, 34) of the two series circuits (22, 24) with the both terminals (L, N) provided by the charging station (14) are coupled. Method according to one of the preceding claims, characterized in that the switching elements (28, 30) each have an inverse diode (D1, D2, D3, D4), wherein the switching elements (28, 30) are turned off and respective electrical switching element voltages are detected and evaluated to determine which of the center terminals (32, 34) is electrically coupled to the reference potential (16). Charging device (46) for charging an electrical energy store (10) of a motor vehicle with electrical energy from a vehicle-external charging station (14), with a charging station connection (48) for supplying a single-phase electrical alternating voltage (18) with respect to a predetermined electrical reference potential (16) an energy storage connection (50) for electrically coupling the electrical energy store (10), a clocked energy converter (20) having at least two series circuits (22, 24) each of two switching elements (28, 30), wherein the series circuits (22, 24) connected in parallel and to the energy storage terminal (50) electrically coupled to each of said at least two series circuits (22, 24) has a medium connection (32, 34) and wherein the fluid connections (32, 34) electrically connected to the charging station terminal (48) are coupled, characterized by a control unit (52), which is formed, the switching elements (28, 30) at least dependent ig of an electrical reference voltage (38) between one of at least two energy storage potentials on the energy storage connection (50) and the electrical reference potential (16) to control. Charging after Claim 7 , characterized in that the charging station connection (48) is galvanically coupled to the clocked energy converter. Motor vehicle with an electrical vehicle electrical system which has a DC intermediate circuit (54) and an electrical energy store (10) connected to the DC intermediate circuit (54), a charging station connection (48) for connection to a charging station (14) providing a single-phase electrical AC voltage (18) ) and one to the charging station (48) and the electrical energy storage (10) electrically coupled charging device (46) for charging the electrical energy storage device (10) with electrical energy from the charging station (14), characterized in that the charging device (46) Claim 7 or 8th is trained. Motor vehicle after Claim 9 characterized by an electric drive device (56) which has a three - phase electrical machine (58) for driving the motor vehicle and an inverter (60) connected to the electrical machine (58) and the electrical system, which is designed to provide a three - phase alternating voltage network for the electrical machine (58), wherein the inverter (60) is adapted to provide the clocked energy converter (20) of the charging device (46). Motor vehicle after Claim 10 , characterized in that the clocked energy converter (20) via phase windings of the electric machine (58) to the charging station terminal (48) is electrically coupled.

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