Method for transmitting energy from a charging device to a vehicle's electrical system and system comprising a charging device and a vehicle's electrical system connected to the charging device

Abstract

Method for transmitting energy from a charging device (2) to an on-board electrical system (3) of a vehicle, wherein the on-board electrical system (3) has a positive potential (HV+), a negative potential (HV-), and a ground potential (E), wherein a first Y-capacitor (CF1) is arranged between the positive potential (HV+) and the ground potential (E), a second Y-capacitor (CF2) is arranged between the negative potential (HV-) and the ground potential (E), wherein a first adjustable resistance device (4) is connected in parallel to the first Y-capacitor (CF1) and a second adjustable resistance device (5) is connected in parallel to the second Y-capacitor (CF2), wherein the first and second adjustable resistance devices (4, 5) each have a field-effect transistor (10) and a circuit breaker (9), comprising the following method steps: - connecting (101) the charging device (2) to the vehicle electrical system (3); - measuring a first voltage across the first Y capacitor (CF1), wherein the isolating switches (9) of the first adjustable resistance device (4) and the second adjustable resistance device (5) are switched on before measuring the first voltage; - Adjusting (107, 108) an ohmic resistance of the first adjustable resistance device (4) or of the second adjustable resistance device (5) as a function of the measured first voltage, wherein before adjusting an ohmic resistance of the first adjustable resistance device (4), the isolating switch (9) of the second adjustable resistance device (5) is switched non-conductive or before adjusting an ohmic resistance of the second adjustable resistance device (5), the isolating switch (9) of the first adjustable resistance device (4) is switched non-conductive; and - Transferring (113, 114) energy from the charging device (2) to the vehicle electrical system (3).

Description

[0001] The invention relates to a method for transmitting energy from a charging device to a vehicle's electrical system. The invention further relates to a system comprising a charging device and a vehicle's electrical system connected to the charging device.

[0002] The invention can be applied to direct current (DC) fast charging devices for electric vehicles and / or plug-in hybrid vehicles.

[0003] Such vehicles typically have an on-board electrical system with a positive potential, a negative potential, and a ground potential. In such on-board electrical systems, Y capacitors are typically placed between the positive potential and ground potential, as well as between the negative potential and ground potential, to suppress common-mode interference. To protect against electric shock, maximum permissible limits are specified for the energy that can be stored in such a Y capacitor.

[0004] DE 10 2004 038 534 A1 describes a low-loss voltage divider for compensating leakage currents in capacitors in intermediate circuits for drive systems. Furthermore, EP 2 945 257 A1 discloses a circuit arrangement for balancing electrical voltages across electrical capacitors in a series circuit.

[0005] DE 10 2017 113 533A1 describes an adjustable resistance device with a circuit breaker and a first measuring device for measuring a first voltage between the positive and ground potential. Also disclosed is a control device configured to adjust an ohmic resistance of the adjustable resistance device depending on the measured first voltage.

[0006] US 2008 / 0 158 756 A1 relates to a system for leakage current detection and leakage current compensation with two adjustable resistance devices designed as FETs.

[0007] When charging an energy storage device in the vehicle electrical system using a charging device, Y capacitors in the charging device are connected in parallel with the Y capacitors in the vehicle electrical system, increasing the total capacity and thus the total stored energy. Furthermore, the insulation resistance between the respective positive or negative potential of the vehicle electrical system and ground potential can change due to aging in the vehicle electrical system and / or the charging device. As a result of these effects, an asymmetrical distribution of the voltages across the Y capacitors in the vehicle electrical system can occur. If the permissible limits for the energy stored in the Y capacitors are exceeded, the charging process must be aborted or cannot be started at all.

[0008] Against this background, the object of the present invention is to increase the charging availability of a system consisting of a charging station and on-board network.

[0009] To solve the problem, a method for transmitting energy from a charging device to an on-board network of a vehicle with the features of patent claim 1 is proposed.

[0010] In the method according to the invention, a first voltage is measured across the Y capacitor so that a deviation from a symmetrical voltage distribution across the first and second Y capacitors can be determined. Depending on the measured voltage, the ohmic resistance of an adjustable resistance device connected in parallel to the first Y capacitor and / or an adjustable resistance device connected in parallel to the second Y capacitor is then adjusted in order to limit the voltage drop across the first Y capacitor. It is therefore possible to convert the on-board electrical system to a symmetrical voltage distribution in which the permissible limits for the energy in the Y capacitors are observed. This can increase the availability of the system comprising the charging device and the on-board electrical system of the vehicle.

[0011] If a target voltage is specified across the first Y capacitor for the symmetrical state of the vehicle electrical system, the ohmic resistance of the first and / or second adjustable resistance device can be adjusted solely based on the measured first voltage. In this case, it is not necessary to measure a second voltage across the second Y capacitor.

[0012] However, it has proven advantageous if a second voltage is additionally measured across the second Y capacitor, and the ohmic resistance of the first adjustable resistance device is additionally adjusted as a function of the measured second voltage. With such a configuration, a voltage difference between the first voltage and the second voltage can be determined, and the ohmic resistance of the first adjustable resistance device can be adjusted as a function of the voltage difference. Preferably, the ohmic resistance of the first adjustable resistance device is adjusted when the voltage difference is greater than zero or greater than a predetermined minimum voltage difference value.

[0013] The invention provides that the first and second adjustable resistance devices comprise a field-effect transistor. The field-effect transistor can be operated as an adjustable resistor. Preferably, the field-effect transistor is operated in an operating range in which a gate-source voltage of the field-effect transistor is greater than a threshold voltage of the field-effect transistor.

[0014] In this context, it is particularly advantageous if the field-effect transistor is operated in a clocked manner to adjust the ohmic resistance of the first and / or second adjustable resistance device. By clocked control of the field-effect transistor, the average drain current of the field-effect transistor, and thus its average ohmic resistance, can be adjusted.

[0015] According to the invention, it is provided that the first and the second adjustable resistance device each have a disconnector, in particular a relay or a contactor. With such an embodiment, both the first and the second Y capacitor can be monitored and, depending on the determined voltage difference, the ohmic resistance of one of the two adjustable resistance devices can be adjusted optionally in order to obtain a symmetrical voltage distribution in the vehicle electrical system, or both the ohmic resistance of the first adjustable resistance device and the ohmic resistance of the second adjustable resistance device can be adjusted. Preferably, the first and the second adjustable resistance device have a field-effect transistor, which can in particular be operated in a clocked manner.Particularly preferably, the first adjustable resistance device and the second adjustable resistance device are of identical design.

[0016] According to the invention, the isolating switches of the first adjustable resistance device and the second adjustable resistance device are switched to conducting before measuring the first voltage, and the isolating switch of the second adjustable resistance device is switched to non-conducting before setting an ohmic resistance of the first adjustable resistance device. Starting from a switching position in which both isolating switches are conducting, the isolating switch of the second adjustable resistance device, which is not required to set a symmetrical state, can be switched to non-conducting depending on the measurement taken.Particularly preferably, the field effect transistors of the first and second adjustable resistance devices are switched to non-conductive during the measurement of the first and second voltages, so that the result of the measurement is not influenced by the first and / or second adjustable resistance devices.

[0017] According to an advantageous embodiment, one or more charging switches, in particular charging relays or charging contactors, of the vehicle are switched on to transfer energy from the charging device to the vehicle electrical system. The charging switches can initially be switched off, so that a symmetrical voltage distribution can be established before the energy is transferred from the charging device to the vehicle electrical system, for example, to charge an energy storage device of the vehicle electrical system.

[0018] In this context, it is preferred if a voltage difference is formed between the first voltage and the second voltage, and the transfer of energy from the charging device to the vehicle electrical system only occurs if the voltage difference is smaller than a predetermined maximum voltage difference value. This approach ensures that the voltages across the Y capacitors are within a permissible range before the actual charging process begins.

[0019] To solve the problem mentioned above, a system with the features of patent claim 7 is also proposed.

[0020] With this system, the same advantages can be achieved as have been described in connection with the method according to the invention.

[0021] According to an advantageous embodiment of the system, the vehicle electrical system has a second measuring device for measuring a second voltage across the second Y capacitor and the control device is configured to additionally adjust the ohmic resistance of the first adjustable resistance device and / or the second adjustable resistance device as a function of the measured second voltage.

[0022] Alternatively or in addition to the advantageous embodiment of the system described above, the advantageous embodiments and features explained in connection with the method can also be used in the system alone or in combination.

[0023] Further details and advantages of the invention will be explained below with reference to the embodiment shown in the drawings. Fig. 1 shows an embodiment of a system with a charging device and an on-board network of a vehicle connected to the charging device in a circuit diagram; Fig. 2 an embodiment of an adjustable resistance device; and Fig. 3 an exemplary sequence of a method according to an embodiment of the invention in a flowchart.

[0024] In the Fig. Figure 1 shows an embodiment of a system 1 according to the invention comprising a charging device 2 and a vehicle electrical system 3 connected to the charging device 2. The vehicle electrical system 3 is designed as a DC voltage electrical system with a positive potential HV+, a negative potential HV-, and a ground potential E. The charging device 2 is a charging device suitable for high-voltage DC charging.

[0025] The charging device 2 has a first charging device insulation resistor RS1 and a first charging device Y capacitor CS1 between the positive potential HV+ and the ground potential. A second charging device insulation resistor RS2 and a second charging device Y capacitor CS2 are connected between the negative potential HV- and the ground potential in the charging device 2.

[0026] The vehicle electrical system 2 has corresponding insulation resistors RF1, RF2 and Y-capacitors CF1, CF2. A first Y-capacitor CF1 is provided between the positive potential HV+ and the ground potential E, and a second Y-capacitor CF2 is provided between the negative potential HV- and the ground potential E. The vehicle electrical system 3 further comprises a first adjustable resistance device 4, which is connected in parallel to the first Y-capacitor CF1, and a second adjustable resistance device 5, which is connected in parallel to the second Y-capacitor CF2. In addition, the vehicle electrical system 3 has a first measuring device 6 for measuring a first voltage across the first Y-capacitor CF1 and a second measuring device 7 for measuring a second voltage across the second Y-capacitor CF2.A control device 8 of the vehicle electrical system is connected to the measuring devices 6, 7 and is configured to adjust an ohmic resistance of the first adjustable resistance device 4 and / or the second adjustable resistance device 5 depending on the measured first voltage and / or second voltage. The vehicle electrical system 3 can be converted to a symmetrical voltage distribution, in which the permissible limits for the energy in the Y capacitors 4, 5 are maintained. This can increase the availability of the system comprising the charging device 2 and the vehicle electrical system 3.

[0027] The Fig. 2 shows the structure of an adjustable resistance device which is used as the first or second adjustable resistance device 4, 5 in the vehicle electrical system 3 according to Fig. 1 can be used. The adjustable resistance device 4, 5 has a isolating switch 9, which is designed, for example, as a relay or contactor. The adjustable resistance device 4, 5 can be isolated from the vehicle electrical system 3 via the isolating switch 9, i.e. it provides an infinitely high ohmic resistance. A further component of the adjustable resistance device 4, 5 is an adjustable resistor 10, which according to the exemplary embodiment is designed as a field-effect transistor. The field-effect transistor can be operated in a clocked manner in order to set the ohmic resistance of the adjustable resistance device 4, 5. Furthermore, the adjustable resistance device 4, 5 comprises a constant resistor 11. The isolating switch 9, the adjustable resistor 10 and the constant resistor 11 are connected in series.

[0028] In the Fig. In the vehicle electrical system 3 shown in Figure 1, the first and second adjustable resistance devices 4, 5 are preferably of identical design.

[0029] In the Fig. 3 shows a flowchart which is intended to explain an exemplary sequence of a method according to the invention. This is based on a Fig. 1 shown system 1 with adjustable resistance devices 4, 5 according to Fig. 2 was assumed.

[0030] In a connection step 101, the charging device 2 is electrically connected to the vehicle electrical system 3, for example, by connecting a charging cable of the charging device 2 to an interface of the vehicle electrical system 3. In a subsequent activation step 102, the isolating switches 9 of the adjustable resistance devices 4, 5 are switched to conduction. The adjustable resistors 10 are switched to high resistance, in particular non-conductive. In the case of adjustable resistors 10 designed as field-effect transistors, this can be achieved by operating the field-effect transistors with a gate-source voltage that is lower than the threshold voltage of the field-effect transistor. Furthermore, a first voltage is measured across the first Y-capacitor CF1 by means of the measuring device 6, and a second voltage is measured across the second Y-capacitor CF2 by means of the measuring device 7. The measured values ​​of the measuring devices 6.7 are transmitted to the control device 8 and evaluated there. In a test step 103, a voltage difference between the first and the second voltage is formed, and a check is made to determine whether the voltage difference is greater than a predetermined minimum voltage difference value, ie, whether an asymmetrical voltage distribution exists across the Y capacitors CF1, CF2.

[0031] If the voltage difference exceeds the predetermined minimum voltage difference value, a further test step 104 determines whether the ground potential E is shifted towards the positive potential HV+, i.e. whether the first voltage across the first Y capacitor CF1 is lower than the second voltage across the second Y capacitor CF2. If this is not the case, the isolating switch 9 of the second adjustable resistance device 5 is switched non-conductive in a disconnection step 105, since this adjustable resistance device is no longer required in the further course of the method. In a subsequent setting step 107, the ohmic resistance of the first adjustable resistance device 4 is set by appropriately clocking the adjustable resistor 10, which is designed as a field-effect transistor, of the first adjustable resistance device 4.The adjustment is made with the aim of setting the voltage difference to a value smaller than a predetermined maximum voltage difference value, for example by reducing the ohmic resistance 10 of the first adjustable resistance device 4. In a subsequent test step 109, it is checked whether the voltage difference is smaller than the predetermined maximum voltage difference value. If this is not the case, the system returns to the setting step 107. If, on the other hand, the voltage difference is smaller than the predetermined maximum voltage difference value, the system proceeds to a charging start step 111, in which one or more charging switches, in particular charging relays or charging contactors, of the vehicle are switched on. In a subsequent charging step 113, energy is transferred from the charging device 2 to the on-board electrical system 3 to charge an energy storage device of the on-board electrical system 3.The ohmic resistance of the first adjustable resistance device 4 is further adjusted in accordance with steps 107 and 109 in order to ensure the most symmetrical voltage distribution possible even during charging.

[0032] If it is determined in test step 104 that the ground potential E is shifted towards the positive potential HV+, i.e., that the first voltage across the first Y capacitor CF1 is lower than the second voltage across the second Y capacitor CF2, then in a disconnection step 106, the disconnect switch 9 of the first adjustable resistance device 4 is switched to non-conductive, since this adjustable resistance device 4 is no longer required in the further course of the method. In a subsequent setting step 108, the ohmic resistance of the second adjustable resistance device 5 is set by appropriately clocking the adjustable resistor 10, designed as a field-effect transistor, of the second adjustable resistance device 5.The adjustment is made with the aim of setting the voltage difference to a value smaller than a predetermined maximum voltage difference value, for example by increasing the ohmic resistance 10 of the second adjustable resistance device 4. In a subsequent test step 110, it is checked whether the voltage difference is smaller than the predetermined maximum voltage difference value. If this is not the case, the system returns to the setting step 108. If, on the other hand, the voltage difference is smaller than the predetermined maximum voltage difference value, the system proceeds to a charging start step 112, in which one or more charging switches, in particular charging relays or charging contactors, of the vehicle are switched on. In a subsequent charging step 114, energy is transferred from the charging device 2 to the on-board electrical system 3 to charge an energy storage device of the on-board electrical system 3.In this case, the ohmic resistance of the second adjustable resistance device 5 is further adjusted in accordance with steps 108 and 110 in order to ensure the most symmetrical voltage distribution possible even during charging.

[0033] If it is determined in test step 103 that the voltage difference does not exceed the specified minimum voltage difference value, charging can begin. The system proceeds to a charging start step 115, in which one or more charging switches, in particular charging relays or charging contactors, of the vehicle are switched on. After the charging switches are closed, the control of control device 8 is set to a longer time constant so that rapid and possibly cyclical changes in ground potential are not counteracted. However, voltage-dependent effects, such as those that can arise when charging an energy storage device of the vehicle electrical system 3, e.g., a battery, are compensated for.

[0034] In a subsequent test step 116, it is checked whether the voltage difference exceeds another predetermined minimum voltage difference value. If this is not the case, the isolating switches 9 of both the first and second adjustable resistance devices 4, 5 are switched off in a disconnection step 124, particularly after a predetermined period of time has elapsed. In a subsequent charging step 125, energy is transferred from the charging device 2 to the vehicle electrical system 3 via the Y capacitors CF1, CF2 without regulating the voltages.

[0035] If the test in test step 116 shows that the voltage difference exceeds the further predetermined minimum voltage difference value, a further test step 117 determines whether the ground potential E is shifted towards the positive potential HV+, i.e. whether the first voltage across the first Y capacitor CF1 is smaller than the second voltage across the second Y capacitor CF2. If this is not the case, the isolating switch 9 of the second adjustable resistance device 5 is switched non-conductive in a disconnection step 118, since this adjustable resistance device is no longer required in the further course of the method. In a subsequent setting step 120, the ohmic resistance of the first adjustable resistance device 4 is set by appropriately clocking the adjustable resistor 10, which is designed as a field-effect transistor, of the first adjustable resistance device 4.The adjustment is made with the aim of setting the voltage difference to a value smaller than a predetermined maximum voltage difference value, for example, by reducing the ohmic resistance 10 of the first adjustable resistance device 4. Charging takes place in a charging step 122, wherein energy is transferred from the charging device 2 to the vehicle electrical system 3. The ohmic resistance of the first adjustable resistance device 4 is further adjusted in accordance with step 120 to ensure the most symmetrical voltage distribution possible, even during charging.

[0036] If it is determined in test step 117 that the ground potential E is shifted towards the positive potential HV+, i.e., that the first voltage across the first Y capacitor CF1 is lower than the second voltage across the second Y capacitor CF2, then in a disconnection step 119, the disconnect switch 9 of the first adjustable resistance device 4 is switched to non-conductive, since this adjustable resistance device 4 is no longer required in the further course of the method. In a subsequent setting step 121, the ohmic resistance of the second adjustable resistance device 5 is set by appropriately clocking the adjustable resistor 10, designed as a field-effect transistor, of the second adjustable resistance device 5.The adjustment is made with the aim of setting the voltage difference to a value smaller than a predetermined maximum voltage difference value, for example, by increasing the ohmic resistance 10 of the second adjustable resistance device 4. To charge an energy storage device of the vehicle electrical system 3, energy is transferred from the charging device 2 to the vehicle electrical system 3 in a charging step 123. The ohmic resistance of the second adjustable resistance device 5 is further adjusted in accordance with step 121 to ensure the most symmetrical voltage distribution possible, even during charging.

[0037] In the method described above for transmitting energy from the charging device 2 to the on-board electrical system 3 of a vehicle, the on-board electrical system 3 has a positive potential HV+, a negative potential HV-, and a ground potential E. A first Y capacitor CF1 is arranged between the positive potential HV+ and the ground potential E, and a second Y capacitor is arranged between the negative potential HV- and the ground potential E. Furthermore, a first adjustable resistance device 4 is connected in parallel to the first Y capacitor CF1, and a second adjustable resistance device 5 is connected in parallel to the second Y capacitor CF2.

[0038] The following procedural steps are carried out: - Connecting the charging device 2 to the vehicle electrical system 3; - Measuring a first voltage across the first Y capacitor CF1; - Adjusting an ohmic resistance of the first adjustable resistance device 4 and / or the second adjustable resistance device 5 as a function of the measured first voltage; and - Transferring energy from the charging device 2 to the vehicle electrical system 3.

Claims

[1] A method for transmitting energy from a charging device (2) to an on-board electrical system (3) of a vehicle, wherein the on-board electrical system (3) has a positive potential (HV+), a negative potential (HV-), and an earth potential (E), wherein a first Y-capacitor (CF1) is arranged between the positive potential (HV+) and the earth potential (E), a second Y-capacitor (CF2) is arranged between the negative potential (HV-) and the earth potential (E), wherein a first adjustable resistance device (4) is connected in parallel to the first Y-capacitor (CF1) and a second adjustable resistance device (5) is connected in parallel to the second Y-capacitor (CF2), wherein the first and second adjustable resistance devices (4, 5) each have a field-effect transistor (10) and a circuit breaker (9), comprising the following method steps: - connecting (101) the charging device (2) to the vehicle electrical system (3); - measuring a first voltage across the first Y capacitor (CF1), wherein the isolating switches (9) of the first adjustable resistance device (4) and the second adjustable resistance device (5) are switched on before measuring the first voltage; - Adjusting (107, 108) an ohmic resistance of the first adjustable resistance device (4) or of the second adjustable resistance device (5) as a function of the measured first voltage, wherein before adjusting an ohmic resistance of the first adjustable resistance device (4), the isolating switch (9) of the second adjustable resistance device (5) is switched non-conductive or before adjusting an ohmic resistance of the second adjustable resistance device (5), the isolating switch (9) of the first adjustable resistance device (4) is switched non-conductive; and - Transferring (113, 114) energy from the charging device (2) to the vehicle electrical system (3). [2] Method according to claim 1, characterized by that in addition a second voltage is measured across the second Y capacitor (CF2) and the ohmic resistance of the first and / or second adjustable resistance device (4, 5) is adjusted additionally as a function of the measured second voltage. [3] Method according to one of the preceding claims, characterized by that the field effect transistor is operated in a clocked manner to adjust the ohmic resistance of the first and / or second adjustable resistance device. [4] Method according to one of the preceding claims, characterized by that the circuit breaker is a relay or a contactor. [5] Method according to one of the preceding claims, characterized bythat in order to transfer energy from the charging device to the vehicle electrical system, one or more charging switches, in particular charging relays or charging contactors, of the vehicle are switched on. [6] Method according to one of claims 2 to 5, characterized by that a voltage difference is formed between the first voltage and the second voltage and the transfer of energy from the charging device to the vehicle electrical system only takes place if the voltage difference is smaller than a predetermined maximum voltage difference value (U1, U2). [7] System (1) with a charging device (2) and an on-board electrical system (3) of a vehicle connected to the charging device (2), wherein the on-board electrical system (3) has a positive potential (HV+), a negative potential (HV-) and an earth potential (E), wherein a first Y-capacitor (CF1) is arranged between the positive potential (HV+) and the earth potential (E) and a second Y-capacitor (CF2) is arranged between the negative potential (HV-) and the earth potential (E), wherein a first adjustable resistance device (4) is connected in parallel to the first Y-capacitor (CF1) and a second adjustable resistance device (5) is connected in parallel to the second Y-capacitor (CF2), wherein the first and the second adjustable resistance device (4, 5) each have a field-effect transistor (10) and a circuit breaker (9), wherein the on-board electrical system (3) has a first measuring device (6) for measuring a first voltage across the first Y-capacitor (CF1) and a control device (8),which is designed to adjust an ohmic resistance of the first adjustable resistance device (4) and / or the second adjustable resistance device (5) as a function of the measured first voltage., [8] System according to claim 7, characterized by that the vehicle electrical system has a second measuring device (7) for measuring a second voltage across the second Y capacitor (CF2) and the control device (8) is designed to additionally adjust the ohmic resistance of the first adjustable resistance device (4) and / or the second adjustable resistance device (5) as a function of the measured second voltage.

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