Method and charging system for charging an electrical accumulator of an electrically driven vehicle

Abstract

The invention relates to a method for charging an electrical accumulator (4) of an electrically driven vehicle (3), wherein the charging process of the accumulator (4) is carried out using a charging device (6) of the vehicle (3), in a first phase of the charging process the accumulator (4) is charged with a first direct voltage (U1) of a charging source (2) depending on a charging current (I L ) of the charging source (2), the battery voltage (U Batt ) of the accumulator (4) is determined during the charging process (6), the battery voltage (U Batt ) of the accumulator (4) is compared with a charging voltage of the charging source (2), a transformer (7) is operated depending on the comparison of the battery voltage (U Batt ) with the charging voltage, wherein in a second phase of the charging process following the first phase the accumulator (4) is charged with a second direct voltage (U2) of the transformer (7) depending on a choke current (I D ) of the transformer (7). The invention also relates to a charging system (1).

Description

Technical Field

[0001] One aspect of the present invention relates to a method for charging an electrical storage device for an electrically driven vehicle.

[0002] The present invention also relates to a charging system for charging an electric storage device for an electrically driven vehicle. Background Technology

[0003] Electric vehicles, such as electric cars, have voltage levels as high as 800 volts. In contrast, today's DC charging stations only provide a maximum output voltage of 750 volts.

[0004] Many DC charging stations only have a maximum output voltage of 500 volts. Therefore, buck compatibility can be used with DC charging stations that have a maximum voltage level of 500 volts to charge electric vehicles. Here, the lower voltage can be converted to a higher voltage level using a boost transformer.

[0005] When charging an 800V vehicle at a 700V charging station, the vehicle must be designed to have a voltage level of 750V or less, or the electric vehicle must have a corresponding boost transformer to enable charging from the outset. However, in this case, the boost transformer's power rating may be specified for the electric vehicle's lifespan. Due to cost and / or size (power density) considerations, equipping the vehicle with a high-power boost transformer (e.g., greater than 150kW) is disadvantageous. Typical power values ​​are, for example, 50kW or a maximum of 150kW. To maintain short charging times while keeping the boost transformer's conversion power low, it is recommended to begin charging via a direct connection between the charging station and the vehicle battery. Once the charging station's maximum charging voltage is reached, the direct connection is disconnected, and charging via the boost transformer is initiated. However, this presents two challenges. Charging interruptions may occur when switching between direct charging and charging via the boost transformer. Similarly, when transitioning from direct connection charging to charging via the booster transformer, the bypass contactor can be opened / disconnected and the booster transformer continues the charging process. Therefore, due to the energy stored in the output choke coil of the DC charging pile (W = 0.5 × L × i), 2 There may be the following dangers: when the unenergized inductor in the booster transformer is connected, a high overvoltage may be generated, which may also cause charging interruption.

[0006] For example, in the case of a step-up transformer with capacitor storage devices (such as charge pumps or voltage multipliers), a smooth transition from charging via direct connection to charging via the step-up transformer cannot be achieved.

[0007] DE 10 2015 101 187 A1, DE 10 2017 009 355 A1, DE 10 2017 009352A1, and DE 10 2017 010 390 A1 propose transformer types based on induction storage. However, these have the disadvantage that, depending on the transition from direct connection to charging via a booster transformer, the charging process using a charging station may be unexpectedly interrupted. Summary of the Invention

[0008] Therefore, the objective of this invention is to design a safer DC charging process for electric vehicles in terms of charging interruption.

[0009] This task is accomplished using the methods and charging system described below. Meaningful improvements can be derived from other alternative embodiments.

[0010] One aspect of the present invention relates to a method for charging an electrical storage device in an electrically driven vehicle, wherein,

[0011] - The electric vehicle is connected to an external charging source.

[0012] - The battery charging process utilizes the connected external charging power source and the charging device of the electric drive vehicle, and

[0013] - In the first stage of the battery charging process, the battery is charged using a first DC voltage, which serves as the charging voltage of the external charging source, based on the charging current of the external charging source.

[0014] - Determine the battery voltage of the storage device during the charging process.

[0015] - The charging device compares the battery voltage with the charging voltage of the external charging source.

[0016] - A transformer in the charging system of an electric vehicle operates based on a comparison between battery voltage and charging voltage.

[0017] - In the second stage after the first stage of the charging process, the battery is charged with a second DC voltage higher than the charging voltage based on the transformer choke current, which is lower than the charging current.

[0018] Using the proposed method, a transition from DC charging via a direct connection between the charging source and the battery to charging via a transformer can be performed, where no charging interruption is expected due to overvoltage or a drop in charging current to 0 amperes. This is particularly advantageous for 800-volt vehicles undergoing DC charging at a 700-volt charging station. Through this hybrid charging method (both direct connection and transformer-based charging), the vehicle can be charged faster than if charging were performed solely via the transformer from the start of the charging process (assuming the transformer's charging power is less than that of direct connection charging).

[0019] In particular, the proposed method can prevent vehicle charging interruptions at DC charging stations. This is achieved by reducing the charging current to 0 amperes, as the switching between the two charging variants (or the first and second stages) only occurs when there is current in the transformer choke. The closer the current values ​​of the charging source and the transformer are to each other, the lower the voltage peak during the switching between the first and second stages. This is because a current corresponding to the charging source current needs to be applied to the transformer choke before switching between the two stages of the charging process.

[0020] In particular, the proposed method stabilizes the DC charging process. Specifically, the switching from the first stage to the second stage of the charging process is performed such that the charging current equals the choke current. This prevents induced voltage peaks that could potentially interrupt the charging process for safety reasons.

[0021] The energy storage device can be, for example, a traction battery, a battery pack, or a high-voltage battery. In particular, the energy storage device has a voltage level of 500 volts, especially a maximum of 850 volts. Electric vehicles are particularly electric vehicles, hybrid vehicles, plug-in hybrid vehicles, or pure electric vehicles. Specifically, electric vehicles have a drive motor, drive unit, or drive assembly that is powered by the energy storage device, thus enabling the electric vehicle to move.

[0022] External charging sources can be, for example, DC charging stations, DC charging piles, charging infrastructure, charging systems, or DC voltage charging sources. External charging sources, in particular, can provide DC voltage. Specifically, external charging sources have a maximum voltage level of 750 volts.

[0023] In particular, the charging process of the battery is carried out and monitored by a charging device. The charging device is especially a charging unit for electric vehicles, such as an on-board charger. In particular, the charging device can be part of the on-board power supply of the electric vehicle.

[0024] This invention specifies that in the first stage of the charging process, the battery is directly connected to an external charging source via a bypass circuit of the charging device, allowing the charging current from the external charging source to flow directly to the battery. Specifically, the transformer is bridged via the bypass circuit in the first stage of the charging process. In particular, the bypass circuit bridges or bypasses the transformer, thereby establishing a direct current flow between the external charging source and the battery. Therefore, the external charging source can be used directly to charge the battery. Here, the charging process, or direct charging process, continues until the voltage level of the battery is substantially equal to the voltage level of the charging source. For example, the external charging source can provide a maximum voltage of 750 volts, so the battery can be charged via the bypass circuit at a voltage not exceeding 750 volts. In particular, the bypass circuit can include two paths or two voltage paths. On one hand, the bypass circuit can be connected to the positive and negative voltage paths respectively. Therefore, the two voltage potentials used for the battery charging process can be bridged / bypassed with respect to the transformer.

[0025] This invention specifies that, in the second stage of the charging process, the bypass circuit is switched to a voltage-free state by means of at least one disconnecting element, thereby interrupting the current flow from the external charging source to the battery. Therefore, the bypass circuit is disconnected, specifically by means of this at least one disconnecting element, disconnecting switch, or contactor, thereby interrupting the direct current flow between the external charging source and the battery. The second stage is particularly performed when the voltage level of the battery is substantially equal to the voltage level of the external charging source. Thus, the charging process switches from the first stage, where a direct current flow is established between the charging source and the battery, to the second stage, where the battery is charged indirectly through a transformer. Therefore, the charging current from the charging source no longer flows to the battery via the bypass circuit, but instead flows to the transformer, allowing the transformer to operate accordingly.

[0026] In another embodiment of the invention, the transformer is operated according to the battery voltage of the storage device such that a choke current is applied to the transformer choke coil in accordance with the charging current. Specifically, in the second stage after the bypass circuit is disconnected, the charging current flows towards the transformer, particularly the transformer choke coil. Therefore, the choke current can be applied to the choke coil (inductor) by means of the charging current flow from the charging source. Specifically, a choke current is formed in the choke coil. Specifically, the choke current is applied to the choke coil such that it has a current value of 105 amps, 110 amps, or 115 amps, or a current value between 105 and 115 amps. The charging current value can be between 320 and 380 amps. Thus, a smaller choke current is provided by the transformer to charge the storage device. Due to the lower choke current than the charging current, the transformer can step up and convert a voltage higher than the first DC voltage.

[0027] In another embodiment of the invention, the charging current of the external charging source is adjusted according to the choke current during the second stage of the charging process, specifically to match the charging current value with the choke current value. Since the transformer and, in particular, the transformer choke coil only require a current of, for example, 110 amps, the charging current, which would normally be three times the rated current, is reduced. Here, the charging current value is reduced or adjusted to the choke current value, particularly by means of a step-down transformer (BUCK type transformer) of the charging source. Thus, matching is achieved between the charging source current value and the transformer current value. This prevents voltage peaks and / or voltage arcing and / or induced interference switching effects between the two stages of the charging process.

[0028] In particular, when the current value of the charging source and the current value of the transformer are basically close, the voltage peak when the blocking element of the bypass circuit is opened can be reduced and / or decreased, or even avoided.

[0029] The voltage and current values ​​mentioned above are not absolute values. The given voltage and current values ​​may include deviations. These deviations can occur due to tolerances, especially measurement tolerances. For example, each value may have a deviation of 5%, or more specifically, 10%.

[0030] Another aspect of the present invention relates to a charging system for charging an electric storage device in an electric vehicle, comprising:

[0031] - An external charging source used to provide charging voltage for the vehicle.

[0032] - A charging interface for electric vehicles used to connect them to an external charging source.

[0033] - A charging device for an electric vehicle to perform a charging process for an electric battery, wherein, in the first stage of the charging process, the electric battery can be charged with a first DC voltage, which is the charging voltage of the external charging source, based on the charging current of the external charging source.

[0034] Its characteristics are,

[0035] - A determining device for determining the battery voltage of an electrical storage device during the charging process.

[0036] - An evaluation unit designed to compare the battery voltage with the charging voltage of an external charging source.

[0037] - The transformer in this charging device is used to provide a choke current lower than the charging current based on a comparison between the battery voltage and the charging voltage, wherein,

[0038] - The charging device is designed to charge the battery in the second stage of the charging process, after the first stage, using a second DC voltage that is higher than the charging voltage, based on the transformer choke current.

[0039] In particular, the charging system just proposed can be used to implement the method or its embodiments according to one of the foregoing aspects.

[0040] In particular, the proposed charging system enables a more efficient and less prone-to-failure DC charging process for electric vehicles. Specifically, the proposed charging system allows for a two-stage charging process: first, the battery is charged directly from a charging source in the first stage, and then in the subsequent second stage, the battery is charged via a transformer. Therefore, charging of the battery (with a voltage level of 850 volts) via a DC charging station (up to 750 volts) is particularly efficient. Furthermore, the proposed charging system allows for highly efficient methods for fast charging.

[0041] This invention specifies that a charging device has a bypass circuit for charging an electrical storage device according to a charging current, wherein the bypass circuit is connected between the positive potential of an external charging source and the positive potential of the electrical storage device. With the aid of the bypass circuit, the electrical storage device can be directly charged by the charging source. In particular, the bypass circuit allows direct current flow between the electrical storage device and the charging source. In particular, the bypass circuit can be a bridging branch or path. In particular, the bypass circuit can be connected between the positive potential (HV positive potential) of the external charging source and the positive potential (HV positive potential) of the electrical storage device. In particular, the bypass circuit is connected to the HV positive potential of the charging system. In other words, the bypass circuit is connected in the positive voltage path between the charging source and the electrical storage device. In particular, the bypass circuit allows for the bridging of a transformer.

[0042] In particular, bypass circuits can be connected to both positive and negative voltage paths. For example, one part of the bypass circuit can be connected between the positive potential of the charging source and the positive potential of the battery, while the second part of the bypass circuit can be connected between the negative potential of the charging source and the negative potential of the battery.

[0043] In another embodiment of the invention, the first connection side of the bypass circuit is connected to the primary side of the transformer, and the second connection side of the bypass circuit is connected to the secondary side of the transformer. In other words, the transformer can be electrically bridged, so that the charging current from the charging source does not flow through the transformer, but instead flows to the storage device via the bypass circuit. This allows for a more efficient charging process for the storage device, while avoiding unnecessary load on the transformer during the first stage of the charging process.

[0044] In another embodiment of the invention, an isolation element is connected between the first and second terminals of the bypass circuit, wherein the isolation element can be used to bridge the transformer. In particular, the isolation element can be a disconnecting switch, a protective element, or a contactor. Specifically, the isolation element can be used to switch the bypass circuit to current flow or to disconnect the bypass circuit. Therefore, the isolation element can be used to apply charging current to the transformer or to the bypass circuit.

[0045] In another embodiment of the invention, the transformer is designed as a current-regulated step-up transformer. Therefore, the transformer can be regulated, in particular, by means of the charging current of the charging source. Specifically, the transformer is regulated such that the storage device can be charged to the maximum extent. In particular, the charging source voltage is converted to a higher voltage by means of the transformer to charge the storage device.

[0046] Advantageous embodiments of this method should be considered as advantageous embodiments of a charging system. Similarly, advantageous embodiments of this method can be considered as advantageous embodiments of a charging system. The charging system, for this purpose, possesses the subject matter characteristics that allow the execution of the method or its advantageous embodiments. Attached Figure Description

[0047] Other advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and in conjunction with the figures. The features and combinations of features mentioned above in the specification, as well as those mentioned below in the description of the drawings and / or shown individually in the figures, may be used not only in their respective specified combinations, but also in other combinations or individually, without departing from the scope of the invention.

[0048] In the figure, components with the same function are labeled with the same reference numerals. Detailed Implementation

[0049] Figure 1 A schematic side view of an embodiment of the charging system 1 of the present invention is shown. Specifically, the charging system 1 includes an external charging source 2 and an electric vehicle 3. The electric vehicle 3 can be charged, in particular, by means of the external charging source 2. In other words, the charging system 1 includes all components and / or units used in the charging process of the electric vehicle 3 at the charging source 2.

[0050] The electric vehicle 3 is particularly an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, or a pure electric vehicle. In particular, the electric vehicle 3 is a vehicle with a voltage level of up to 850 volts. In particular, the electric vehicle 3 has an energy storage device 4. The energy storage device 4 is a vehicle battery, an HV battery, a high-voltage battery, or a battery pack of the vehicle 3. In particular, the energy storage device 4 has a voltage level of 500 volts, and more particularly, a maximum of 850 volts. With the aid of the energy storage device 4, the electric drive unit, electric drive assembly, or drive motor of the electric vehicle 3 can be charged, thus enabling the electric vehicle 3 to move and travel.

[0051] To enable DC voltage charging of the battery 4, the electric vehicle 3 can be connected to or engaged with the charging source 2 via the charging interface 5 or DC charging interface of the vehicle 3. The charging source 2 can be, for example, a DC charging station, a DC charging pile, charging infrastructure, or a charging system. In particular, the DC charging pile (charging source 2) has a maximum voltage level of 750 volts.

[0052] In particular, the electric vehicle 3 has a charging device 6. The charging device 6 can be, for example, an on-board charger or an on-board charging unit. With the help of the charging device 6, the charging process at the charging source 3 can be specifically executed, controlled, and monitored.

[0053] For example, the battery 4 may have, for example, 500 volts, especially 600 volts at its terminals in a discharged state.

[0054] For example, charging device 6 includes transformer 7. Transformer 7 can be, for example, a step-up transformer, a boost transformer, a DC transformer, or a DC-DC transformer. Transformer 7 is specifically designed such that it can transform or boost the lower voltage of charging source 2 to a voltage suitable for charging battery 4. If charging source 2 can provide a voltage suitable for the vehicle battery (battery 4), transformer 5 can be bridged or switched to no voltage, for example, via bypass circuit 8. This can be done, for example, by the blocking element 9 (bypass contactor) of bypass circuit 8. Bypass circuit 8, in particular, bridges branches or isolates branches. Blocking element 9 can be, for example, a contactor or a disconnect switch. Figure 1 As can be seen in the diagram, the positive and negative voltage branches between the battery 4 and the charging source 2 can be connected or not connected via the bypass circuit 8. It is particularly advantageous that the transformer 7 is connected when its power is lower than the maximum charging power of the electric vehicle 3 or the charging device 6.

[0055] Furthermore, the charging device 6 may include, for example, a switching element 11. With the aid of the switching element 11, the vehicle-side charging port 5 can be switched to a voltage-free state, particularly during vehicle 3 operation or during non-charging processes of the battery 4. Specifically, the switching element 11 is a contactor or switching unit.

[0056] For example, a first voltage U1, which serves as the charging voltage, can be provided by a charging source 2 to charge the battery 4. Alternatively, a second DC voltage U2, which is higher than the charging voltage, can be provided by a transformer 7 to charge the battery 4. Specifically, the battery 4 is charged with the first voltage U1 in the first stage of the charging process, and with the second voltage U2 in the second stage following the first stage. These two stages of the charging process are switched or executed according to the current charging state of the battery 4.

[0057] For example, bypass circuit 8 may be able to manage two HV potentials (positive HV and negative HV). This is especially applicable when transformer 7 is capable of controlling both HV potentials and its components are not designed for the current directly connected between charging source 2 and storage device 4. However, if transformer 7 only affects one of the two potentials, the connected potential may be designed for a higher current intensity, thus requiring a bypass contactor (isolating element 9).

[0058] Figure 2 Show Figure 1 A schematic analog structure or analog circuit arrangement of the charging system 1 is shown here. In particular, the charging source 2, consisting of a voltage source (750 volts) and a step-down transformer (BUCK type transformer), is shown. The transformer 7 is shown here as a current-regulating boost transformer (BOOST type transformer).

[0059] The following problems may occur or exist during the separate charging process of the battery 4. The purpose of the charging process is, in particular, to perform a continuous charging process without causing charging interruption. When the isolation element 9 of the bypass circuit 8 is disconnected, a zero-ampere charging current may occur, which will cause charging interruption. Another drawback is that disconnecting the isolation element 9 when transitioning from direct-coupled charging to charging via the transformer 7 creates an overvoltage hazard due to the electrical energy stored in the output choke coil of the charging source 2. This may be caused by the unenergized choke coil of the transformer 7. Therefore, there is a risk of charging interruption.

[0060] The adverse effects should be shown, especially with the accompanying simulation structure. In particular, the simulation should be performed such that the charging current I is applied during the first stage of the charging process (not exceeding the voltage of battery 4, i.e., a maximum of 720 volts). L (350 amps, especially between 320 and 380 amps) fed into the storage device 4. When the voltage level of the storage device 4 is between 720 and 750 volts, the charging current I... L It was adjusted to 110 amps. In particular, the charging current I... LThe voltage can be between 110 and 120 amps. When the voltage level exceeds 750 volts of the storage device 4, the step-down transformer of the charging power source 2 is continuously connected. The disconnecting element 9 (DC bypass contactor) opens at 730 volts and the transformer 7 starts to operate or function at 735 volts.

[0061] The following figures ( Figure 3 and Figure 4 This illustrates an exemplary simulation process or Figure 2 The simulation process of the simulated structure. Here, Figure 3 and 4 The time curve is shown in particular. Figure 4 It also shows Figure 3 The time curve is the time interval during the opening or opening process of the partition element 9. Figure 4 The opening time of the isolation element 9 (bypass contactor) is shown in particular.

[0062] For example, voltage curve a shows the time curve of the voltage of charging source 2. Here, in Figure 3 and 4 Voltage peak 12 can be seen in curve a. In the exemplary simulation performed, the value of voltage peak 12 is 864 volts. Here, the initial clamping voltage of charging source 2 is 740 volts.

[0063] Therefore, an overvoltage of approximately 124 volts occurs here, causing an interruption in the charging process. The overvoltage occurs because current is still flowing in the output choke coil of the DC charging station (charging source 2). As the contactor opens, the output capacitor of charging source 2 and the input capacitor of transformer 7 (boost transformer) are charged, and then current can begin to flow in the choke coil L of transformer 7. The charging of the capacitor can be measured as an overvoltage. In curve b, in the two graphs ( Figure 3 and 4 The current curve in charging source 2 is shown in section (). The state at the control gate of switching element SG is shown in curve c.

[0064] The current curve in bypass circuit 8 is shown in particular in curve d. Here, time 13 is the moment when the blocking element 9 (bypass contactor) is opened / closed.

[0065] Curve e shows the current curve of the choke coil of transformer 7. Here, time 14 indicates the moment when the current consumption of the choke coil L of transformer 7 begins or starts.

[0066] Curve f shows the state of the control gate of the switching element SG1. Here, at time 15, we can see that the timing / clocking of transformer 7 begins, especially at a current of 110 amps.

[0067] The voltage curve of the energy storage device 4 is shown in curve g, and the current curve of the energy storage device 4 is shown in curve h.

[0068] Figure 5 Show Figure 1 and Figure 2 Another schematic circuit block diagram of the charging system 1, especially a portion thereof.

[0069] In particular, this paper details how a "smooth" switch from direct-coupled DC charging to DC charging via transformer 7 can be achieved using the charging device and corresponding method of this invention. It is crucial to ensure that the DC charging process is never interrupted. To achieve this, the charging current I... L It should never stop, that is, it should never drop to 0 amperes. On the one hand, when there is no current in the choke coil L of transformer 7 at that moment, the blocking element 9 should not be opened / disconnected. Therefore, it is recommended that the charging current I... L and choke current I D The current values ​​are designed to be essentially the same or identical. This prevents voltage spikes when the blocking element 9 is opened.

[0070] In particular, during the first stage of the charging process of the storage device 4, the charging current I of the charging source 2 can be used as a reference. L The storage device 4 is charged with a first voltage U1, which serves as the charging voltage. For example, the storage device 4 is charged with a maximum voltage of 750 volts. Here, the current battery voltage U of the storage device 4 can be continuously determined, identified, or measured using the determining device 16. batt In particular, the current battery voltage U of the storage device 4 during the charging process (DC charging process) is monitored. batt The continuous determination.

[0071] The determining device 16 can be, for example, a voltage measuring device, a measuring circuit, a monitoring unit, an oscilloscope, or a voltage-current measuring device or measuring unit. In particular, the determining device 16 can have multiple individual units, so that current and / or voltage can be measured at multiple different locations in the circuit arrangement of the charging system 1.

[0072] Especially during the charging process, continuously monitor the current battery voltage U. batt The determination or ascertainment. For example, the determining device 16 may be part of the charging device 6. The determined or ascertained battery voltage U batt The battery voltage can be compared with the charging voltage (first voltage U1) using the evaluation unit 17 of the charging device 6. If the battery voltage U battThe voltage value basically corresponds to the charging voltage (first voltage U1) with an error of + / -5%, and the direct charging process (especially the start-up and end-of-life process) via the bypass circuit 8 through the charging source 2 directly connected to the storage device 4 can be terminated. Here, the transformer 7 can be started or switched to operation at the same time.

[0073] Therefore, in the second stage of the charging process, following the first stage (especially in time), the storage device 4 can charge according to the specific charging current I of the transformer 7. L Low choke current I D The transformer 7 is charged with a second DC voltage U2, which is higher than the charging voltage. For example, the charging current I... L It can have a current value of 350 amps, and a choke current I D It has a current value of 110 amps. The second DC voltage U2 can be, for example, a voltage value of 850 volts, compared to which the first voltage can be a voltage value of 750 volts.

[0074] Two variations can be used to switch between these two charging stages or charging process phases. These will be described below.

[0075] In the first variation, the blocking element 9 is closed at the beginning, causing the charging current I to... L The current can flow via a direct connection between the charging source 2 and the storage device 4. In other words, this is approximately done via a bypass circuit 8. Here, a charging current of, for example, 350 amps I can be used. L This is used for the first stage of the charging process. Here, for example, the current value can be in the range of 320 to 380 amperes. The direction of the current flow is shown here by the current flow direction 18.

[0076] In the subsequent steps, transformer 7 begins its operation. This is especially true at a battery voltage of approximately 710 volts U. batt The following is completed. Here, the switching element SG1 is specifically closed. Therefore, the choke current I of the choke coil L is... D The formation of the choke current L is achieved. Here, a choke current in the range of 105–115 amperes is applied. During this phase, the charging current I of the charging source 2 is... L Keep it constant (e.g., at 350 amps). This is represented by the current flow direction 19. At battery voltage U... batt Under a voltage value of 720 volts, the charging current I of charging source 2 is completed. L The charging pile current was adjusted accordingly. Therefore, the charging pile current decreased to a new value, within the range of 100-120 amperes. The choke current I... D The formation is particularly illustrated by the current flow direction 20. For example, this can then be shown at the battery voltage U. battDisconnect isolation element 9 (bypass contactor) at a voltage of 740 volts. Due to the charging current I L and choke current I D With two essentially identical current values, the second stage of the charging process can proceed without any adverse effects (charging interruption).

[0077] In the following two paintings Figure 6 and 7 In the middle, now it is being carried out again. Figure 2 The simulation process of the simulation structure. The first variant used here is for a smooth transition from the first stage to the second stage of the charging process. Figure 6 and 7 These curves or diagrams correspond to the same as... Figure 3 and 4 The same number in, and Figure 7 This is shown in more detail here. Figure 6 This refers to a local portion of a time interval, particularly during the opening or opening process of the partition element 9. Here, Figure 7 The opening time of the isolation element 9 (bypass contactor) is shown in particular.

[0078] Here, we will only introduce how... Figure 3 and 4 The key point. Especially here. Figure 6 and 7 Curve a shows that voltage peak 12 is only 754 volts. Therefore, the overvoltage is only 14 volts when the blocking element 9 is open. Because this overvoltage is small, current is already applied to the choke coil of transformer 7 when the contactor (blocking element 9) is opened, and it is the same magnitude as the current of charging source 2 (more precisely, the current of the output choke coil of charging source 2). Therefore, no charging interruption occurs here. In addition, curves e and f also show that the choke coil L begins to accept current on the one hand, and the transformer 7 begins to work on the other. In particular, at moment 14 in curve e, the current of the choke coil L of transformer 7 is at a similar level before and after the bypass contactor is opened. Therefore, no charging interruption occurs.

[0079] exist Figure 8 and Figure 9 It is shown again in the middle Figure 2 The simulation process of the simulated structure. Here, in Figure 8 and Figure 9 In, the same number also corresponds to in Figure 3 and Figure 4 The number in, and Figure 9 This is shown in more detail here. Figure 8 This refers to a specific time period, particularly during the opening or opening process of the partition element 9. Figure 9The moment when the isolation element 9 (bypass contactor) is opened is shown in particular.

[0080] Here, only the following variation is described, in which the current of the charging source 2 is first reduced and then the transformer 7 is operated or started.

[0081] In this variation, the blocking element 9 is closed first, thereby utilizing the charging current I L The battery 4 is charged directly via the power supply 9. Here, the charging current I... L It can, for example, have 350 volts. Here, transformer 7 is not specifically used. Then, the charging current I of charging source 2 is applied. L The current is adjusted to the following value, which is then used to charge the storage device 2 via transformer 7 in the second stage of the charging process. For example, the charging current I... L The current is adjusted or reduced to 110 amps.

[0082] At charging current I L The transformer 7 is activated or started after the current reaches 110 amperes (for example, it could be between 100 and 120 amperes). Here, the choke current I... L This current is now applied to the choke coil L. Specifically, a specified current value (e.g., 110 amperes) is applied to the choke coil L. The charging current I of the charging source 2... L This remains constant. Specifically, the charging current I... L and choke current I D The current value can be 110 amps. Especially at a battery voltage of 730 volts U batt The operation of transformer 7 will then begin. The reduction in charging pile current is achieved at a battery voltage of 720 volts.

[0083] After applying a 110 ampere choke current and with the battery voltage U batt Once 740 volts are reached, the isolation element 9 is opened, thus enabling the charging process of the storage device 4 via the transformer 7.

[0084] In particular, the transition from the first stage of the charging process to the second stage of the charging process is smooth.

[0085] Here, Figure 8 and 9 The two simulation results are illustrated in the figure. Figure 6 and 7 Similar results have already been observed and explained. Here, a voltage peak of 754 volts can also be seen in curve a. Therefore, the overvoltage in this variation is only 14 volts, and thus no charging interruption occurs during the charging process.

[0086] In particular, the proposed charging system 1 and corresponding method can be used to stabilize the charging process. Here, the current flowing through the transformer 7 is adjusted to the same current intensity as when the bypass circuit 8 (bypass line) is open, because otherwise, for safety reasons, the charging process would be interrupted due to the induced voltage peak in the bypass line when the contactor opens. In this case, the current in the bypass line can be adjusted to the maximum current intensity of the transformer first, and then a current flow can be formed in parallel in the transformer, or a current flowing through the transformer can be formed first, and then the current in the bypass line can be reduced accordingly. At the same current intensity, the bypass line can then be disconnected without a significant voltage peak.

[0087] In particular, the current (I) can be switched off when the bypass contactor (isolation element 9) opens. L The adjusted current Δ of the charging source 2 or transformer 7 is reduced (e.g., + / - 10 amps instead of more than 100 amps). This significantly reduces the holding force of the bypass contactor (isolating element 9).

[0088] In particular, the given current and voltage values ​​may include measurement tolerances or measurement errors. Therefore, the given current and voltage values ​​may have a deviation of 5%, especially 10%.

Claims

1. Method for charging an electrical accumulator (4) of an electrically driven vehicle (3), wherein - the electrically driven vehicle (3) is connected to an off-board charging source (2), - a charging process of the electrical accumulator (4) is performed using the connected off-board charging source (2) and a charging device (6) of the electrically driven vehicle (3), - determining the battery voltage (U Batt ) of the electrical accumulator (4) during the charging process, - comparing the battery voltage (U Batt ) of the electrical accumulator (4) with the charging voltage of the off-board charging source (2) by means of the charging device (6), and - operating a transformer (7) of a charging device (6) of the electrically driven vehicle (3) in dependence of a comparison of the battery voltage (U Batt ) with the charging voltage, wherein - in a first phase of a charging process of the electrical accumulator (4), the electrical accumulator (4) is charged with a first direct current voltage (Ul) as a charging voltage of the external charging source (2) for the electrical accumulator (4) in dependence on a charging current (I L ) of the external charging source (2), wherein, in the first phase of the charging process, the electrical accumulator (4) is directly connected to the external charging source (2) by means of a bypass circuit (8) of the charging device (6), such that the charging current (I L ) of the external charging source (2) directly flows to the electrical accumulator (4) through the bypass circuit (8), and - in a second phase of the charging process, following the first phase, the accumulator (4) is charged with a second direct current (I D ) lower than the charging current (I L ) of the transformer (7) and with a second direct voltage (U2) of the transformer (7) higher than the charging voltage, wherein the second phase is performed when the voltage level of the accumulator substantially equals the voltage level of the off-board charging source, wherein, in a second phase of the charging process, the bypass circuit (8) is switched to be currentless by means of at least one interrupting element (9), whereby the current flow of the charging current (I L ) from the off-board charging source (2) to the electrical accumulator (4) via the bypass circuit (8) is interrupted and the charging current (I L ) from the off-board charging source (2) flows through the transformer (7) so that the electrical accumulator (4) is indirectly charged via the transformer (7), characterized in that in the second phase of the charging process the charging current (I L ) of the off-board charging source is adjusted in dependence on the throttling current (I D ).

2. The method of claim 1, wherein, the transformer (7) is bridged by means of the bypass circuit (8) in a first phase of the charging process.

3. The method according to claim 1 or 2, characterized in that, The current value of the charging current (I L ) is adapted to the current value of the throttling current (I D ).

4. The method of claim 1 or 2, wherein, In dependence of the battery voltage (U Batt ) of the electrical accumulator (4), the transformer (7) is operated in such a way that the choke current (I D ) is applied to the choke winding (L) of the transformer (7) in dependence of the charging current (I L ).

5. Charging system (1) for charging an electrical accumulator (4) of an electrically driven vehicle (3), having - an off-board charging source (2) for providing a charging voltage, - a charging interface (5) of the electrically driven vehicle (3) for connecting the electrically driven vehicle (3) to the off-board charging source (2), - a charging device (6) of the electrically driven vehicle (3) for performing a charging process of the electrical accumulator (4), - determining means (16) for determining the battery voltage (U Batt ) of the electrical accumulator (4) during the charging process, - an evaluation unit (17) designed to compare the battery voltage (U Batt ) of the electrical energy storage (4) with the charging voltage of the off-board charging source (2), and - a transformer (7) of the charging device (6) for providing a throttling current (I D ) lower than the charging current (I L ) in dependence of a comparison of the battery voltage (U Batt ) with the charging voltage, wherein - the charging device (6) has a bypass circuit (8) for charging the electrical storage device (4) in dependence on the charging current (I L ), wherein the bypass circuit (8) is connected between the positive potential of the external charging source (2) and the positive potential of the electrical storage device (4) and between the negative potential of the external charging source (2) and the negative potential of the electrical storage device (4), and - the charging device (6) is designed in such a way that, in a first phase of the charging process of the electrical accumulator (4), the electrical accumulator (4) can be charged with a charging current (I L ) from the external charging source (2) via the bypass circuit (8) as a first direct current (Ul) of the charging voltage of the external charging source (2) of the electrical accumulator (4), and - the charging device (6) is designed in such a way that, in a second phase of the charging process following the first phase, the accumulator (4) is charged with a second direct voltage (U2) of the transformer (7) which is higher than the charging voltage, in dependence on the choke current (I D ) of the transformer (7), wherein, in a second phase of the charging process, the bypass circuit (8) is switched to be currentless by means of at least one interrupting element (9), whereby the current flow of the charging current (I L ) from the off-board charging source (2) to the electrical accumulator (4) via the bypass circuit (8) is interrupted and the charging current (I L ) from the off-board charging source (2) flows through the transformer (7), so that the electrical accumulator (4) can be charged indirectly via the transformer (7), The feature is that the charging current (I L ) of the external charging source of the vehicle can be adjusted according to the throttling current (I D ).

6. A charging system (1) according to claim 5, characterized in that The current value of the charging current (I L ) is adapted to the current value of the throttling current (I D ).

7. A charging system (1) according to claim 5 or 6, characterized in that a first connection side of the bypass circuit (8) is connected to a primary side of the transformer (7) and a second connection side of the bypass circuit (8) is connected to a secondary side of the transformer (7).

8. A charging system (1) according to claim 7, characterized in that The interrupting element (9) is arranged between the first connection side of the bypass circuit (8) and the second connection side of the bypass circuit (8), wherein the transformer (7) can be bridged by means of the interrupting element (9).

9. A charging system (1) according to claim 5 or 6, characterized in that The transformer (7) is designed as a current-regulated step-up transformer.

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