Vehicle onboard power grid

Abstract

The vehicle onboard power supply (BN) is equipped with a battery (AK), an AC voltage terminal (WA) and a DC voltage terminal (GA). The DC voltage terminal (GA) is directly connected to the battery (AK) via a connection point (VP). The AC voltage terminal (WA) is connected to the battery (AK) via a rectifier (GR) and a first switch (S1) via the connection point (VP). The rectifier (GR) is connected to the battery (AK) via a DC isolating DC transformer (W1) and a second switch (S2). The second switch (S2) is connected to the battery via the connection point (VP). There is at least one electrical consumer onboard power supply branch (BZ), which includes a Cy capacitor and is connected to the battery (AK) via the second switch (S2).

Description

Background Art

[0001] Vehicles have a vehicle electrical system for many electrical components. In vehicles with high-power components, such as vehicles with electric drives, there is a high-voltage onboard electrical system, via which a high-voltage battery can be charged and which has high-power loads, such as electric high-voltage drives.

[0002] During charging, care must be taken not to cause dangerous contact voltages, and in particular, energy accumulators in the onboard power grid must not cause dangerous contact voltages when the energy accumulators are still charged. On the other hand, when operating loads, it must be prevented that interferences that occur when operating loads by switching loads in a clocked manner do not cause malfunctions of other components. For this purpose, EMC filters are used, which have energy accumulators (i.e. Cy filter capacitors) for damping these interferences. As mentioned, these energy accumulators exist as dedicated or discrete components, or can be implemented by parasitic Cy capacitors. Cy capacitors are parasitic capacitors or are implemented by filter components. Cy capacitors capacitively connect the supply voltage potential to the ground potential. Summary of the invention

[0003] The object of the present invention is to enable in a simple manner a safe and non-interfering operation of the vehicle electrical system both during charging and during driving.

[0004] This object is achieved by the vehicle electrical system according to the invention. Further features, embodiments, characteristics and advantages are apparent from the description and the drawings.

[0005] It is proposed to connect the AC voltage terminal of the vehicle's onboard power supply system for charging by AC voltage to a downstream rectifier, which is connected to the battery of the vehicle's onboard power supply system via a first switch, and the rectifier is also connected to the battery via a DC-isolated DC transformer and a second switch. With the help of the switch, it can be selected whether the rectifier is connected to the battery directly (i.e. without a converter) or via a DC transformer. In the first case, the second (disconnected) switch is used to separate the load with Cy capacitance from the battery and thus from the AC voltage terminal, which load can be supplied by the DC transformer. Since the DC transformer is DC-isolated (galvanisch isolierend), no dangerous contact voltage is transmitted via the converter. In the second case, the (disconnected) first switch is used to achieve the mentioned separation; here, the DC-isolated DC transformer also allows the Cy capacitor to be separated from the AC voltage terminal. In the second case, the load can be supplied with a voltage, which is used to charge the battery.

[0006] Finally, DC voltage charging is possible with the aid of a DC voltage terminal, which is (directly) connected to the battery. Here, the (disconnected) second switch (and, if necessary, a DC-isolated DC transformer) is used to separate the Cy capacitor from the DC voltage terminal. The load can be supplied with power via the (then closed) first switch via the DC-isolated DC transformer, without the Cy capacitor being able to transmit an excessively high contact voltage to the DC voltage terminal. By connecting the first and second switches via a connection point connected to the battery (and to the DC voltage terminal), a circuit topology is obtained, which can also realize a voltage supply to the load during charging and in driving operation and can realize contact voltage protection with respect to the Cy capacitor.

[0007] A load is an exemplary example for an electrical consumer electrical system branch or for a component in the electrical system branch. The electrical consumer electrical system branch can be supplied with power by means of the vehicle electrical system, wherein the electrical consumer electrical system branch is isolated from the AC voltage and / or the DC voltage connection with respect to the DC voltage of the energy storage device in the electrical consumer electrical system branch.

[0008] A vehicle electrical system is proposed, which has a battery, an AC voltage terminal and a DC voltage terminal. The two terminals are used to charge the battery and, if necessary, also for feedback in the case of a bidirectional design. The AC voltage terminal and the DC voltage terminal are preferably designed according to standards for charging plug-in vehicles. The two terminals can be provided in a common connection device.

[0009] The DC voltage terminal is connected directly to the battery via the connection point. The term "direct" means that the connection is converter-free and in particular has no switches (ie is switchless). The direct connection may have filters or fuses, but is designed without a converter, i.e. without a DC transformer and without a rectifier or inverter.

[0010] The AC voltage terminal is connected to the battery via the rectifier and the first switch via the connection point. In particular, the AC voltage terminal is connected to the rectifier directly or via the first isolating switch. The connection between the AC voltage terminal and the rectifier is preferably converter-free. The rectifier is preferably directly connected to the first switch. The first switch is preferably directly connected to the connection point. The connection point itself is preferably directly connected to the battery. Thus, there is a converter-free connection between the rectifier and the connection point or the battery via the first switch. Another connection between the AC voltage terminal and the connection point or the battery, which is conducted via a DC transformer, is described below.

[0011] The rectifier is connected to the battery via a DC-isolating DC transformer and a second switch. In this case, the second switch is connected to the battery via the connection point, preferably directly. The converter is also preferably connected directly to the second switch. The DC transformer is preferably connected directly to the rectifier. This results in a further connection path between the connection point and the rectifier, which leads via the DC transformer (and via the second switch).

[0012] The vehicle onboard power supply has at least one electrical consumer onboard power supply branch. The electrical consumer onboard power supply branch has a Cy capacitor. The electrical consumer onboard power supply branch is connected to the battery via a second switch. At least one electrical consumer onboard power supply branch is in particular directly connected to a DC transformer. The DC transformer thus connects the rectifier to the electrical consumer onboard power supply branch in a DC-interrupting manner.

[0013] The battery (or the connection point) is connected to the electrical consumer electrical system branch via a second switch. The DC voltage terminal (via the connection point) is connected to at least one electrical consumer electrical system branch via a second switch. The second switch can thus be used to disconnect the Cy capacitance of the electrical consumer electrical system branch from the connection point, so that the Cy capacitance is disconnected when power flows from the AC voltage terminal via the rectifier (and the first switch) to the battery. When the second switch disconnects the battery from the electrical consumer electrical system branch, the electrical consumer electrical system branch can be supplied with power via the converter.

[0014] The electrical consumer onboard power supply branch preferably has a traction drive onboard power supply branch. The traction drive onboard power supply branch is equipped with an electric motor. In addition, the traction drive onboard power supply branch is equipped with an inverter. In particular, the electric motor is connected to the second switch via the inverter. If the second switch is closed, energy can be transmitted from the battery (via the inverter) to the electric motor. In the case of a structure that can be fed back, energy can also be transmitted from the electric motor to the battery via the second switch. Since the AC voltage terminal and the DC voltage terminal are necessarily separated from the external power grid and the vehicle moves when driving, that is, when the motor is activated, the Cy capacitor is not or only limitedly dangerous in terms of contact voltage. Other electrical consumer onboard power supply branches connected to the same point may include an electric heating device, an electric air conditioning compressor, a low-voltage DC transformer or other loads with a Cy capacitor. Due to the same connection, the separation of the Cy capacitor from the AC voltage terminal and the DC voltage terminal can be achieved by means of the second switch.

[0015] The rectifier can be connected to the AC voltage terminal via a first disconnect switch. The connection point can be connected to the DC voltage terminal via a second disconnect switch. In the event of a fault, the mentioned terminal can thus be disconnected from the remaining onboard electrical system (by opening the corresponding disconnect switch).

[0016] The vehicle onboard power system preferably has a control device, which is connected to the first switch and the second switch in a control manner. The control device is set up to control the first switch to be in an open state and the second switch to be in a closed state at a first state. In this first state, the AC voltage terminal is separated from the Cy capacitor via the first switch. In the first state, the second isolating switch and / or the first isolating switch can also be disconnected. In the first state, the second switch connects the battery to the electrical consumer onboard power system branch so that energy can flow between the battery and the electrical consumer onboard power system branch. The connection is then a DC connection (galvanisch verbindend). Therefore, the first state can be a traction or recovery state. In this state, the first isolating switch is preferably disconnected.

[0017] In addition, the first state can also be a charging state, in which the rectifier is connected to the electrical vehicle power supply branch via a DC-isolating DC transformer. In addition, in the first state (as a charging state), the rectifier is connected to the battery (via a second switch) via a DC transformer. As a result, energy can be transmitted to the battery in a DC-isolated manner, while, for example, the electrical vehicle power supply branch is also powered by the DC transformer. If the second state is a charging state, the first isolating switch is preferably closed. It is possible to charge the battery via the AC voltage terminal through the disconnected first switch, wherein the AC voltage terminal is separated from the Cy capacitor of the electrical vehicle power supply branch via the disconnected first switch (at least in terms of direct voltage transmission) because the DC transformer is DC-isolated. The control device is also set up to control the first switch in the second state to be in a closed state and the second switch to be in an open state. In this case, the electrical vehicle power supply branch and thus also its Cy capacitor can be decoupled from the AC voltage terminal by means of the second switch, because, as mentioned, the DC transformer is DC-isolated or disconnected. In this second state, the AC voltage terminals are connected directly to the battery via the rectifier and can therefore transfer energy to the battery without DC voltage conversion. The second state is therefore a charging state without a DC converter, while the first state, if designed as a charging state, is a charging state based on a DC converter.

[0018] In one embodiment, the control device is further configured to control the first switch in the third state to be in the open or closed state and to control the second switch in the open state. In this third state, the battery can be charged via the DC voltage terminal GA, because in this third state, in particular the second isolating switch, that is, the isolating switch between the DC voltage terminal and the battery is closed. The control device is configured to control the first and / or second isolating switch. If the first switch is open in the third state, a DC voltage can be transmitted to the battery via the DC voltage terminal (in the sense of a direct DC voltage charging state), wherein the DC voltage onboard power supply branch is disconnected from the DC voltage terminal via the first and second switches. In this state, energy can be transmitted to the electrical consumer onboard power supply branch via the AC voltage terminal via the DC transformer, wherein this is performed in a DC-connected manner. By means of the open switch, the Cy capacitor of the electrical consumer onboard power supply branch is thus disconnected from the DC voltage terminal, and the electrical consumer onboard power supply branch can be supplied with power at the same time via the DC-connected DC transformer, without its Cy capacitor being connected to the AC voltage terminal (or the DC voltage terminal) in a DC-connected manner.

[0019] If the first switch is closed and the second switch is disconnected in the third state, the DC voltage can be transmitted to the battery via the DC voltage terminal, while at the same time energy can be transmitted to the battery via the AC voltage terminal and the rectifier. This corresponds to a combined charging operation (AC voltage + DC voltage in a combined manner). Here, the Cy capacitor is also separated from the terminals (DC voltage terminal and AC voltage terminal) via the disconnected second switch, and the DC isolating DC transformer enables the electrical vehicle power supply branch to be powered in a DC isolating manner. In the third state, the second isolating switch is preferably closed so that energy can be transmitted from the DC voltage terminal to the battery, or vice versa. Therefore, the third state corresponds to a DC voltage charging state. The second isolating switch can also be referred to as a DC voltage charging isolating switch. The first isolating switch can also be referred to as an AC voltage charging isolating switch.

[0020] The rectifier can be constructed as a single-phase or three-phase device. In addition, the rectifier can be constructed to selectively operate in a single-phase or three-phase manner. Thus, for example, a charging voltage of 400 volts or 800 volts can be set for the battery. In a DC voltage charging state corresponding to the third charging state, the first switch can be closed so that the electrical consumer onboard power supply branch can be powered from the DC voltage terminal via the first switch and the DC transformer. Since the second switch is opened, a different DC voltage may be obtained at the battery or at the connection point than at the electrical consumer onboard power supply branch, so that two different rated voltages can be set. If the second switch is closed in the third state, the electrical consumer onboard power supply branch obtains the same voltage as the battery, wherein, for example, the rated charging voltage can be set as the rated voltage.

[0021] The control device is preferably further configured to detect the charging state. In particular, the control device is configured to detect the charging state by detecting whether the cable to the external unit is plugged into an AC voltage terminal, a DC voltage terminal or both terminals, or whether a voltage greater than a predefined voltage threshold is present at one of the terminals. In particular, the control device can be configured to detect the charging state by detecting whether a charging valve or a charging terminal of the charging device is disconnected.

[0022] The control device is set up to control the second switch to be in an open state when a charging state exists. As a result, the Cy capacitor of the electrical vehicle power supply branch can be separated from the DC voltage terminal and the AC voltage terminal (DC). The control device can also be set up to control the second switch to be in a closed state when there is no charging state. The control device can be set up to set a closed state for the second switch when there is a power supply state for the electrical vehicle power supply branch, in which the electrical vehicle power supply branch can be supplied with voltage. When there is no state and when the traction drive of the vehicle (preferably in the electrical vehicle power supply branch) is activated, the second switch is preferably controlled to be in a closed state. When the vehicle is moving, when the vehicle is accelerating or when the vehicle is braking, the second switch is preferably controlled to be in a closed state. When no voltage is applied to the DC voltage terminal and the AC voltage terminal, or when the charging valve of the charging device to which the two terminals belong is closed, the second switch is controlled to be in a closed state. This ensures, on the one hand, that the onboard power supply of the load network is supplied, and on the other hand that the Cy capacitor of the onboard power supply network has no DC connection to the DC voltage terminal and the AC voltage terminal, as long as both are occupied.

[0023] The control device can also be connected to the DC transformer in a controlled manner. In this case, the control device can be set up to control the DC transformer according to the charging rated voltage in the first state. In this case, a possible charging rated voltage can be used, the value of which comes from the battery monitoring unit. For this purpose, the control device can have an input, which is connected to the corresponding output of the device and sends a signal, which reproduces the charging rated voltage. It can be provided that when the second switch is closed, the control device controls the DC transformer to send a voltage as close to the charging rated voltage as possible. In this case, the DC transformer can have an input, at which a value corresponding to the rated voltage can be received. The control device can be connected to the input in a controlled manner and accordingly send a signal to the input, which reproduces the charging rated voltage. Alternatively or in combination with this, the control device can be set up to control the DC transformer according to the supply rated voltage in the second state, usually when the second switch is disconnected. Due to the disconnected second switch, the supply of the onboard power supply branch can be controlled separately from the battery via the DC transformer. As a result, the component supplying the onboard power supply branch can predetermine the rated voltage in the form of a supply rated voltage as a value (or as a signal) in order to thereby actuate the DC converter in accordance with this rated voltage. This is particularly the case when the AC voltage terminals are occupied and a voltage is generated via a rectifier on the side of the converter facing the rectifier. The first and second states mentioned here are in particular AC voltage charging states, in which the AC voltage terminals are used for charging, while the DC voltage terminals can be separated.

[0024] In the third state, in particular when the DC voltage terminal is used for charging, it can be provided that the control device actuates the DC converter in accordance with the supply setpoint voltage. The control device is designed to control this accordingly.

[0025] In addition, it can be provided that the rectifier is controllable. The control device can be connected to the rectifier in a controlled manner. The control device can be set up to control the rectifier according to the charging rated voltage and to control the DC transformer according to the supply rated voltage. The voltages may be different. Thus, for example, in the case of a closed first switch and an open second switch, a supply rated voltage can be set for supplying the onboard power supply branch, the supply rated voltage is determined by the control device and converted by the DC transformer, and the rated charging voltage is predetermined by the control device and converted by the rectifier, which supplies this voltage to the battery via the closed first switch. This is particularly related to an AC voltage charging state, during which the AC voltage terminals are active, while the DC voltage terminals are inactive and in particular separated.

[0026] As mentioned, the rectifier can be a controlled rectifier, in particular a controlled rectifier designed in a multiphase manner. The rectifier can be a bridge rectifier or can be implemented as a power factor correction filter, for example as a Vienna filter. When implemented as a power factor correction filter, the rectifier is set up to also perform a step-up function and can generate a voltage higher than the rectified peak voltage. For this purpose, the rectifier configured as a power factor correction filter has, in particular, a temporary storage element for each phase, such as an inductor (if necessary for each phase). The rectifier therefore includes a switching element, which can be controlled by means of an external signal, that is, the switching element is at least guided by a current, which is signal-guided, in particular voltage-guided. The rectifier includes a switching element, which can be configured in particular as a semiconductor switch, such as an IGBT, a MOSFET or a thyristor.

[0027] The DC transformer also includes such semiconductor switches, at least some of them. The DC transformer also includes a temporary energy storage device, such as a coil. The DC transformer can be designed as a unidirectional or bidirectional DC transformer. The DC transformer can be designed as a step-up converter, a synchronous converter or a step-down converter.

[0028] The DC transformer is connected to the battery via a second switch. The DC transformer is connected to the connection point, in particular, via the second switch. The rectifier is connected to the battery via the first switch. Therefore, the second switch is arranged between the connection point and the DC transformer, via which the electrical consumer onboard power supply branch can be separated from the connection point, in particular from the battery or the AC voltage terminal and the DC voltage terminal. The electrical consumer onboard power supply branch is DC-isolated toward both sides, i.e., on the one hand, in a switchable manner via the second switch, and on the other hand, at the other end via a DC-isolating DC transformer. The DC transformer is located between the connection point and the rectifier. As a result, the connection between the DC voltage terminal and the connection point is neither separated by the first switch nor by the second switch. In particular, neither the first nor the second switch is located between the DC voltage terminal and the connection point or the battery. A (second) isolating switch can be arranged between the DC voltage terminal and the connection point, wherein the isolating switch can be opened and closed separately from the first switch. The (first) isolating switch between the AC voltage terminal and the rectifier enables the rectifier to be separated toward the AC voltage terminal.

[0029] The electrical consumer onboard power supply branch may have an electric traction drive. The electric traction drive is preferably equipped with an electric motor. In particular, the traction drive further comprises an inverter. The inverter connects the second switch to the electric motor. As a result, the electric motor can be operated via the second switch by means of a battery. The traction drive drives a vehicle in which a vehicle onboard power supply is arranged. Therefore, a vehicle can be arranged, which has a vehicle onboard power supply and has wheels, which are connected to the traction drive, in particular to its electric motor, in a torque-transmitting manner. Both the inverter and the electric motor have a Cy capacitor, which can exist as a parasitic capacitor and / or can be arranged as a dedicated capacitor of a filter. The electrical consumer onboard power supply branch may also have other components or electrical consumers, which have a running capacitor, which is constructed as a parasitic capacitor or a dedicated discrete filter capacitor. A second electrical consumer onboard power supply branch may be arranged, which is connected to the connection point VP via another switch. The other switch has the same function as the second switch, but can be operated separately from the second switch in order to thereby connect a specific electrical consumer to the connection point or disconnect it from the connection point. When setting the charging state, the further switch is preferably opened.

[0030] The battery can be designed as a high-voltage battery. In particular, the battery is a lithium-based battery. The battery thus has a voltage of at least 350, 400, 600 or 800 volts. In addition, the battery can be designed in multiple parts and equipped with a configuration circuit, which (depending on the selection) connects multiple parts of the battery in series (in Reihe) or in series. It is thus possible to refer to the voltage present at the connection point. In particular, the configuration circuit of the battery can configure the battery according to the rated charging voltage, the voltage at the connection point or the number of activated phases of the rectifier.

[0031] As mentioned, the battery can be constructed in multiple parts. For this purpose, the battery can have a configuration circuit. The cells of the battery are preferably divided into different battery groups. With the help of the configuration circuit, different battery groups can be selectively connected in parallel or in series with one another. The battery groups correspond to the parts of the above-mentioned multi-part battery.

[0032] An additional onboard power supply system may be present, which has a capacitance Cy. The additional onboard power supply system may be connected to the connection point via an additional switch of the onboard power supply system BN.

[0033] The control device can be configured for a charging sequence with different charging phases. First, it can be provided that, while the DC converter is active, the first switch is opened and the second switch is closed. In this case, charging is performed from the AC voltage terminal. As a next step, the first switch can be closed so that the rectifier connects the battery to the AC voltage terminal via the closed first switch. In this case, the DC converter can be active and the second switch can be opened. The DC converter can be operated in this case according to the rated voltage of the consumer onboard power supply branch of the consumer, while the rectifier is operated according to the rated charging voltage, which is used to charge the battery (and can be predefined by the battery monitoring device). In this case, the rectifier can be operated in a single-phase or multi-phase manner. In the first step, the consumer onboard power supply branch is supplied via the DC converter and / or the DC converter charges the battery via the closed second switch, corresponding to DC-isolated charging. In the second step, the first switch connects the rectifier to the connection point, and the AC voltage terminal is connected to the battery via the rectifier. This corresponds to a non-DC-isolated charging process. Depending on the specifications of the connected charging station, charging can thus be performed in a DC-disconnected or DC-connected manner, wherein in addition to this, charging can also be performed in a single-phase and / or three-phase manner (alternatingly).

[0034] Only when the battery voltage is greater than the grid peak voltage, i.e. greater than the effective voltage multiplied by the square root of 2, is charging preferably performed in a DC-coupled manner via the first switch (the first switch is then closed). In the case of the European grid, this corresponds to 230 V multiplied by the square root of 2. If the voltage of the battery is smaller, the first switch is opened and the second switch is closed, so that the rectifier is connected to the battery via the transformer. In this case, the connection is made in a DC-isolated manner via the transformer. Even in the case of three-phase charging, preferably only when the battery voltage is greater than the effective voltage multiplied by the square root of 2 multiplied by the coupling factor (in the case of three phases: the square root of 3), is charging performed in a DC-connected manner via the first switch. In the case of the European grid system, this corresponds to a voltage of 230 V multiplied by the square root of 2 multiplied by the square root of 3, wherein a three-phase system is also assumed. If the voltage of the battery is lower than this voltage, the first switch is opened and the second switch is closed, so that the battery is connected to the rectifier via the DC transformer. These charging methods involve charging with an AC voltage via an AC voltage terminal.

[0035] Another DC transformer can be provided between the first switch on the one hand and the DC transformer and the rectifier on the other hand, and the DC transformer can be provided, for example, a DC coupling DC transformer. In addition, another DC transformer can be provided between the battery and the first switch, and the other DC transformer can be provided, in particular, a DC conducting DC transformer.

[0036] It can be provided that the rectifier is regenerative, in particular in the form of a power factor correction filter or a controllable rectifier different from the rectifier. In addition, it can be provided that the DC transformer (between the second switch and the rectifier) ​​is regenerative. In particular, the rectifier or the power factor correction filter and / or the DC transformer is designed to be bidirectional.

[0037] During DC-coupled AC charging, i.e. with the first switch closed and the second switch open, the DC transformer can be used to supply the onboard power supply branch of the electrical consumer. Since the second switch is open, the battery can have a different voltage than the onboard power supply branch of the electrical consumer. Thus, different rated voltages can be set for the converter and for the rectifier, i.e. the rated voltage of the electrical consumer and the rated voltage of the battery. At the same time, the open second switch and the DC-isolating DC transformer ensure that the Cy capacitor of the onboard power supply branch of the electrical consumer does not affect the AC voltage terminal.

[0038] As mentioned, the battery can be multi-part and have a configuration circuit which connects the battery cells in parallel or in series with one another. In the same way, the DC transformer can also be multi-part and consist of two or more DC transformer elements which can be connected in series or in parallel via a configuration circuit (of the converter). In particular, the configuration circuit is provided between these converter elements and the rectifier. The configuration circuit thus relates to the side of the DC transformer facing the rectifier and also configures the side of the DC transformer facing the rectifier.

[0039] In addition to the motor and the inverter, an auxiliary unit is considered in the onboard power supply network of the electrical consumer as an electrical consumer or a component located there. Therefore, an electric heating device (Heizrichtung) can be set in the onboard power supply network of the electrical consumer, and the electric heating device can especially have an actuator. Such an actuator is, for example, a pulse width modulation actuator, which controls the average power by switching and changing the on-time (An-Zeiten) in a clock-controlled manner. Since this clock pulse may cause interference, this actuator also includes an interference filter, which in turn has a Cy capacitor. The heating element and the actuator itself can also have a parasitic Cy capacitor. The heating device can be set to heat the catalytic converter, the interior space or the cooling circuit. In addition, an electric compressor can be set as an electrical consumer. This electric compressor also has an actuator, which works in a pulse width modulation mode or in a clock-controlled mode, such as an inverter. The actuator and the compressor itself or its motor can also have a dedicated discrete Cy capacitor and / or a parasitic Cy capacitor. The DC transformer itself can also have a filter which has a dedicated Cy capacitor in the area of ​​the filter, in particular on the side facing the onboard power supply branch of the electrical load.

[0040] Furthermore, a further DC converter can be provided as a component or a consumer in another onboard power supply branch connected to the connection point or the battery. In this case, it can be a low-voltage DC converter, for example a step-down converter, which is provided, for example, to generate a voltage of 12 or 24 V. Here, parasitic capacitances can also be provided in this further converter and / or a filter can be provided, which has a Cy capacitor (for example as a filter). BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A vehicle electrical system BN is shown, which is connected to voltage sources WQ and GQ via terminals of the vehicle electrical system BN with reference numerals GA and WA. One of the sources is an AC voltage source WQ, and the other is a DC current source GQ. Both sources are located outside the vehicle electrical system and are in particular stationary. DETAILED DESCRIPTION

[0042] The vehicle onboard power supply system BN thus comprises an AC voltage terminal WA and a DC voltage terminal GA. The AC voltage terminal WA is connected to the rectifier GR via a first disconnect switch. The DC voltage terminal GA is connected to the connection point VP via a second disconnect switch T2, to which the battery AK is connected. The rectifier is connected to the connection point VP via a first switch S1. The rectifier thus connects the disconnect switch T1 to the first switch S1, which in turn connects the rectifier GR to the connection point and thus to the battery. The first disconnect switch T1 is thus connected to the first switch S1 via the rectifier GR. The DC voltage terminal GA is connected to the connection point and to the first switch S1 via the second disconnect switch T2. The rectifier is connected to the second disconnect switch T2 via the first switch S1.

[0043] The first DC transformer W1 is likewise connected to the first switch S1, which is a DC isolating DC transformer. The first DC transformer W1 is connected to the connection point VP via the first switch S1. The first DC transformer W1 also connects the rectifier to the electrical consumer onboard power supply branch BZ. The first DC transformer W1 is connected to the connection point VP via the second switch S2 (which is connected to the battery or also to the first switch). The electrical consumer onboard power supply branch BZ is connected to the connection between the second switch S2 and the first DC transformer W1. In other words, the electrical consumer onboard power supply branch is connected to one side of the first DC transformer W1, wherein the second side of the first DC transformer is connected to the rectifier.

[0044] A switchable connection V connects the rectifier GR to the connection point, wherein the connection V comprises a first switch S1. If the second switch S2 is open, a DC voltage cannot reach the rectifier or the terminals WA or GA in the form of a DC connection. On the one hand, the first DC transformer W1 isolates the DC voltage in the consumer onboard power supply branch BZ from the rectifier GR or from the terminals WA, GA, while on the other hand, the second switch S2 isolates any voltage in the consumer onboard power supply branch BZ from the connection point and therefore also from the terminals WA, GA and from the rectifier.

[0045] If the electrical consumer onboard power supply branch BZ thus comprises components with Cy capacitors, the first DC transformer W1 and the second switch S2 serve to isolate the voltage that can be stored therein, so that in particular the terminals or rectifiers are free of contact voltages resulting therefrom, which may be hazardous. The first switch S1 or the connection V enables charging from the AC voltage terminal WA via the rectifier GR and the first switch to the battery. In the same way, a connection that also allows feedback is obtained. If voltage adaptation is required, the first switch S1 can be opened and the second switch S2 can be closed, so that the voltage can reach the connection point from the AC voltage terminal via the rectifier GR and the first DC transformer W1 (via the second switch S2). In this case, the switch S1 serves to DC-isolate the Cy capacitors in the electrical consumer onboard power supply branch BZ with respect to the AC voltage terminals. Since the first DC transformer W1 is DC-isolated, no path for hazardous contact voltages is obtained either from the Cy capacitors of the electrical consumer onboard power supply branch BZ via the first DC transformer W1 to the rectifier GR or the AC voltage terminal WA connected thereto. Furthermore, when the second switch S2 is open, on the one hand, as mentioned, energy can be transferred from the AC voltage terminal to the battery, while the voltage is simultaneously transferred to the consumer onboard power supply branch via the first DC transformer W1. Due to the open second switch, the first DC transformer W1 can set a voltage for the consumer onboard power supply branch BZ that is different from the voltage at the battery AK (the voltage at the battery AK being essentially defined by the rectifier GR).

[0046] If the DC voltage terminal GA is occupied, for example, for charging the battery AK, energy is transferred to the battery via the isolating switch T2 (closed in this case). In the same way, energy can also be transferred in the opposite direction. Either an AC voltage can be simultaneously transferred to the load onboard power supply branch via the AC voltage terminal WA (preferably with the first and second switches S1, S2 open), or the first switch S1 is closed and the first DC transformer W1 supplies the load onboard power supply branch BZ with the voltage at the connection point or the voltage applied to the DC voltage terminal in a manner fed by the DC voltage terminal GA. Alternatively, the second switch S2 can be closed (while the first switch S1 is preferably open), so that with the closed second isolating switch T2, a DC voltage can be applied to the DC voltage terminal GA, which DC voltage is also supplied to the load onboard power supply branch BZ via the second switch S2. Here, the first switch S1 and the first DC transformer W1 also serve to DC-isolate the Cy capacitor in the load onboard power supply branch BZ with respect to the AC voltage terminal.

[0047] Finally, it is possible to close both disconnect switches T1 and T2 so that combined charging can take place. In this case, for example, the first switch S1 can be closed and the second switch S2 can be opened in order to charge the battery via the AC voltage terminals and the DC voltage terminals WA, GA (while at the same time the electrical consumer onboard power supply branch BZ can be supplied via the first DC transformer W1). Alternatively, the first switch S1 can be opened and the second switch S2 closed, wherein the first DC transformer W1 can be designed to generate an output voltage that substantially corresponds to the voltage at the DC voltage terminal GA in order to thereby achieve a substantially uniform distribution of the loads at the terminals WA and GA.

[0048] The AC voltage terminal WA is connected to the rectifier GR via a first disconnect switch T1. The DC voltage terminal GA is connected to the connection point VP via a second disconnect switch T2. The two disconnect switches are located on different sides of the first switch S1. This also applies to the second switch S2. The DC voltage terminal and the AC voltage terminals GA, WA are part of the vehicle's onboard power supply BN and can be configured as plug connector elements, for example. These plug connector elements can be configured according to the criteria for charging electric vehicles. The plug connector elements can be part of a common charging socket device.

[0049] An electrical vehicle power supply branch BZ having an electric motor M is shown, which is connected to a second switch S2 or a first DC transformer W1 via an inverter I. Other components, namely electrical consumers or loads or energy sources, are also shown. For example, the electrical vehicle power supply branch may further include a component K, which is particularly configured as a heating element, a controllable heating element, an air conditioning compressor, etc. In addition, a low-voltage vehicle power supply network NV may be provided as a component or electrical consumer, which is connected to a first DC transformer W1 or a second switch S2 via a second DC transformer W2. It is schematically shown that these components are loaded with Cy capacitors. In this case, as mentioned, these components may be configured as filter components, and therefore may also be configured as dedicated capacitors, or capacitors may exist as parasitic Cy capacitors. In this case, the side of the first DC transformer W1 of the DC transformer that turns to the second switch S2 may also have a Cy capacitor in the form of a filter capacitor. The same applies to the inverter I, the motor M, the component K (especially its actuator) or also to the second DC transformer W2. The second DC transformer W2 may also have a side facing the second switch S2 or the first DC transformer W1 and have a parasitic capacitance and / or a filter capacitance that functions as a Cy capacitance.

[0050] For the sake of completeness, the Cy capacitance at the battery AK is also shown symbolically, but said Cy capacitance is located on the other side of the second switch S2. If the first switch is closed, a non-isolated DC connection to the AC voltage terminal via the rectifier GR and a direct connection to the DC voltage terminal GA are obtained. However, it can be seen that at least the Cy capacitance of the electrical consumer onboard power supply branch BZ can be disconnected by means of the DC-isolating separation by means of the opened second switch S2 and by the DC-isolating first DC transformer W1. As a result, the Cy capacitance acting on the terminal GA or WA in total is small (but not less than the inseparable Cy capacitance of the battery AK).

[0051] Furthermore, an additional onboard power supply branch is shown, which includes a component X, wherein the component is connected to the connection point VP via an additional switch S2'. The additional switch S2' is opened and closed like the second switch S2. As a result, the Cy capacitance of the additional onboard power supply branch can be separated from the terminals such as WA and GA. However, since the first DC transformer W1 is not connected to the component X, the component X cannot be supplied with power using the first DC transformer W1. Therefore, the component X can be a component that does not require a voltage supply even during charging (for example, a component that is only active in the driving state).

[0052] The control device C is connected to the first switch S1, the second switch S2, the additional switch S2', the first DC transformer W1 and the rectifier GR in a controlled manner, as symbolically shown by a double arrow. As a result, the control device allows coordinated operation, for example two charging modes, in which the first switch S1 and the second switch S2 are alternately opened and closed and the first switch or the second switch S1, S2 can be closed. If the second switch S2 is opened, the voltage in the onboard power supply branch BZ of the electrical consumer can be set according to the rated voltage of the electrical consumer by controlling the first DC transformer W1. In addition, by controlling the rectifier GR, the voltage at the connection point and thus at the battery can be predetermined, which voltage can deviate from the output voltage of the first DC transformer W1 when the second switch S2 is opened. The rectifier can therefore be controlled according to the rated charging voltage. It is also conceivable that the control device C controls the disconnecting switches T1 and T2, wherein if there is a charging state, at least one of the two switches T1 and T2 is closed and in the driving state, the two disconnecting switches are preferably opened. In the traction mode, the control device C controls the second switch S2 to be in the closed state, while the first switch S1 or the additional switch S2' is preferably controlled to be open. The converter is also preferably inactive in the traction state, which can also be controlled by the control device C. The control device can be a central control device or can exist in multiple parts and in particular in a hierarchical distribution.

Claims

1. A vehicle onboard power system (BN) having a battery (AK), an AC voltage terminal (WA) and a DC voltage terminal (GA), wherein - the DC voltage terminal (GA) is connected to the battery (AK) via a connection point (VP); The AC voltage terminal (WA) is connected to the battery (AK) via a rectifier (GR) and a first switch (S1) and via the connection point (VP); - the rectifier (GR) is connected to the battery (AK) via a DC-isolating DC transformer (W1) and a second switch (S2), wherein the second switch (S2) is connected to the battery via the connection point (VP); and at least one electrical consumer onboard power supply branch (BZ), which comprises a Cy capacitor and is connected to the battery (AK) via the second switch (S2), wherein the connection point (VP) is directly connected to the battery (AK), The vehicle onboard power supply system (BN) further comprises a control device (C), which is connected to the first switch (S1) and the second switch (S2) in a controllable manner and is configured to: - in a first state, the first switch (S1) is operated to be in an open state and the second switch (S2) is operated to be in a closed state, - in a second state, the first switch (S1) is operated to be in a closed state and the second switch (S2) is operated to be in an open state, and - In the third state, the first switch (S1) is controlled to be in an open or closed state and the second switch (S2) is controlled to be in an open state.

2. The vehicle onboard power supply system (BN) according to claim 1, wherein the at least one electrical consumer onboard power supply branch (BZ) comprises a traction drive onboard power supply branch having an electric machine (M).

3. The vehicle electrical system (BN) according to claim 1, wherein the control device is configured to detect the charging state, and - when the charging state is present, the second switch (S2) is actuated to the open state in order to thereby disconnect the Cy capacitor of the electrical consumer onboard power supply branch (BZ) from the DC voltage terminal and from the AC voltage terminal (WA), and - When there is no charging state, the second switch (S2) is controlled to be in a closed state.

4. A vehicle onboard power system (BN) according to claim 1 or 3, wherein the control device (C) is connected to the DC converter (W1) in a control manner and is configured to control the DC converter (W1) according to a charging rated voltage in a first state, control the DC converter (W1) according to a supply rated voltage in a second state, and control the DC converter (W1) according to a supply rated voltage in a third state. 5 . The vehicle onboard power system (BN) according to claim 1 , wherein the rectifier (GR) is a controllable rectifier or a power factor correction filter.

6. The vehicle onboard power system (BN) according to any one of claims 1 to 3, wherein the DC transformer (W1) is connected to the battery (AK) via the second switch (S2), and the rectifier (GR) is connected to the battery (AK) via the first switch.

7. The vehicle onboard power supply system (BN) according to claim 1, wherein the electrical consumer onboard power supply branch (BZ) has an electric traction drive with an electric machine (M). 8 . The vehicle onboard power supply system (BN) according to claim 1 , wherein the battery (AK) is designed as a high-voltage battery.

9. The vehicle onboard power supply (BN) according to claim 1, wherein the battery (AK) is constructed in multiple parts and has a configuration circuit, by means of which different cell groups of the battery can be selectively connected in parallel or in series with one another.

10. The vehicle electrical system (BN) according to claim 1, further comprising an additional onboard electrical system (X) with a Cy capacitor and an additional switch (S2'), the additional onboard electrical system (X) being connected to the connection point (VP) via the additional switch (S2').

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