Circuit arrangement for an intermediate circuit capacitance, motor vehicle with such a circuit arrangement and method for precharging an intermediate circuit capacitance and method for balancing battery charge states of parallel-connected battery modules

Abstract

Circuit arrangement for an intermediate circuit capacitance, comprising: a) an electrical energy storage system (1) comprising a plurality of energy storage modules (2) with - at least one memory cell (3), - a first (4) and a second (5) pole, - a first (6) and a second (7) main current path, each of which is connected to one of the poles (4, 5) of the respective energy storage module (2) and of which at least the first main current path (6) can be interrupted by means of a switching device (8) arranged therein, and - a pre-charging current path (20) connected in parallel to the switching device (8) in the first main current path (6), which can be interrupted by means of a clocked semiconductor switching device (21) arranged therein and which has a fuse (22a, 22b) arranged in series with the semiconductor switching device (21) and a switch (24) arranged in series with the semiconductor switching device (21), as well as a measuring device (27) arranged for current measurement in the pre-charging current path and / or at least one measuring device (25, 26) arranged in the pre-charging current path for voltage measurement; and b) an intermediate circuit capacitor (9) which is electrically connected directly or indirectly to the plurality of energy storage modules (2) via the first and second main current paths (6, 7); wherein, c) a first control device (23) is assigned to each pre-charging current path (20) and is arranged in the respective pre-charging current path (20), which first control device is designed to detect information from at least one of the following components in the pre-charging current path (20): the measuring devices for current measurement (27), the at least one measuring device for voltage measurement (25, 26), the semiconductor switching device (21), the switch (24) arranged in series with the semiconductor switching device and the at least one fuse (22a, 22b); d) the first control device (23) is designed to output the information detected in the pre-charging current path (20) to an energy storage module control device (30) of the respective energy storage module (2) and to receive control signals from the energy storage module control device (30); and e) a central control device (100) is provided which is designed to receive information from the energy storage module control devices (30) and to output control signals to the energy storage module control devices (30).

Description

[0001] The invention relates to a circuit arrangement for an intermediate circuit capacitor, in particular for an intermediate circuit capacitor connected upstream of an inverter of an at least partially electrically driven motor vehicle. The invention further relates to a method for precharging an intermediate circuit capacitor and a method for charge balancing of battery modules connected in parallel.

[0002] Motor vehicles for road traffic that are at least partially electrically powered, such as hybrid vehicles or electric vehicles, are often equipped with an electrical energy storage system, e.g. a battery pack, which has several energy storage modules, e.g. several battery systems, connected in parallel to enable the required range of the vehicle.

[0003] Often, the energy storage system with its battery systems is connected to the so-called intermediate circuit (DC link) with inverter systems and / or DC-DC converters. This intermediate circuit is equipped with a high-capacitance intermediate circuit capacitor, i.e., one or more capacitive components or intermediate circuit capacitors, to maintain a constant DC voltage and suppress voltage spikes.

[0004] If necessary, the intermediate circuit capacitor is precharged from the energy storage system. The energy storage system is connected in parallel with the intermediate circuit capacitor in the intermediate circuit. The energy storage system can usually be connected or disconnected from the intermediate circuit capacitor in two poles using two poles of a contactor.

[0005] If the electrical energy storage system were connected directly to the intermediate circuit capacitance without precharging, an extremely high switching current would flow briefly until the intermediate circuit capacitance is charged, since an energy storage module such as a battery has a low internal resistance and the intermediate circuit capacitors serving as intermediate circuit capacitance have a high electrical capacitance. This would lead to significant aging of these components and early failure.

[0006] This problem is usually circumvented by initially closing only one of the contactor poles. The second pole is then bypassed using a precharging circuit consisting of a switch and a precharging resistor. Once the DC link capacitance has reached a sufficient charge level, the second pole of the contactor is finally closed, thereby short-circuiting the precharging circuit. This results in a charging current that initially reaches a maximum due to the precharging resistor and then decreases as the DC link voltage rises across the DC link capacitance.

[0007] However, the pre-charging resistors are usually designed based on the DC link capacitance. The DC link capacitance is relatively small compared to the capacity of an energy storage module that is to be connected. If a battery, which can have different states of charge between the vehicle being switched off and the next time it is started up, is connected to the DC link to charge the DC link capacitance, large currents will occur at a high state of charge, which will load the pre-charging resistor. Therefore, a larger value for the resistor is selected. If the battery's state of charge is lower, the time required to charge the DC link capacitance will be too long for the same selected design value for the resistor. This also means that the vehicle takes too long to start up.Therefore, a compromise is chosen in the design of the resistor: on the one hand, to charge the capacitance in an acceptable time even at lower charging currents, or to design the resistor for a correspondingly high thermal load at high currents.

[0008] If multiple battery systems are connected in parallel, unpredictable equalizing currents between the battery modules, which also flow through the precharging branches during charging of the intermediate circuit capacitance, can place additional strain on the individual precharging resistor, thus overloading it. This can lead to premature failure of the component. A sensible design of the precharging resistor is no longer possible.

[0009] From the published patent application DE 10 2014 011 795 A1, a circuit arrangement is known in which, with the help of a DC / DC converter, energy is transferred from the 24V vehicle electrical system battery to the high-voltage DC intermediate circuit before a connection is established between the high-voltage battery and the high-voltage DC intermediate circuit. This requires a DC-DC converter that is, on the one hand, designed for large currents in order to be able to charge the intermediate circuit capacitance quickly according to specifications, and on the other hand, this component is no longer required after start-up, which represents an expensive solution in practice. This document does not address the problem of multiple battery modules connected in parallel. When multiple battery modules are connected in parallel without pre-charging branches, very large uncontrolled currents arise that are triggered when the battery is connected.In addition to the excessively high equalizing currents between the batteries via the contactors, this can also lead to a drop in the voltage at the intermediate circuit capacitance. The DC converter's precharging of the intermediate circuit capacitance from the 24V onboard battery must be restarted, which prolongs the precharging process or the vehicle's starting process. Furthermore, the DC converter can be subjected to uncontrolled loads due to the equalizing currents from the traction batteries.

[0010] From the published patent application DE 10 2008 013 706 A1, a circuit arrangement is known in which the precharging circuit is designed as a current source and / or as a semiconductor operated in the linear range. The current source variant is complex to implement in terms of circuitry, which is due to Fig. 2. The variant using a semiconductor operated in the linear range has the disadvantage that the semiconductor is operated as an amplifier and thus generates a comparatively high resistance and thus high power dissipation. Furthermore, even with this proposed circuit arrangement, the precharging current can only be controlled as a whole from the voltage source. When controlling the precharging current, it is not possible to take into account the different operating states of individual submodules of the energy storage system, such as operating temperature, state of charge, voltage level of individual battery modules, etc.

[0011] WO 2015 / 124161 A1 describes an electrical storage system with at least one electrical storage unit for a vehicle. The electrical storage unit is connectable to a DC intermediate circuit via a main contactor, wherein the DC intermediate circuit is configured to feed current into or divert current from the electrical storage system. The electrical storage unit is connectable to the DC intermediate circuit via a DC / DC converter connected in parallel with the main contactor.

[0012] DE 10 2015 203 912 A1 proposes an electric drive system for an electric motor vehicle, wherein the electric drive system comprises a DC power source and a contactor with an output coupled to a main bus and an input adapted to be connected to the DC power source. The contactor is selectively switched between an open state and a closed state. A DC link capacitor is coupled to the main bus. A precharging circuit consisting of a controlled current source is coupled between the DC power source and the DC link capacitor. The controlled current source is selectively activated when the contactor is in the open state to charge the DC link capacitor to a predetermined voltage before the contactor is charged to the closed state.

[0013] US 2013 / 0 175 857 A1 discloses systems and methods for precharging bus capacity in vehicles that derive at least a portion of their propulsion power from electricity generated by a battery. One embodiment includes a vehicle control unit (VCU) that receives battery pack data from a battery management unit (BMU) from each of a plurality of battery packs and, based on the battery pack data, determines which battery packs can be used to precharge the bus capacity in parallel. The VCU issues commands to each of the BMUs to connect precharging circuits between the battery packs and the bus capacity and receives status information from each of the BMUs to determine whether or not the bus capacity has been successfully precharged by the battery packs.

[0014] WO 2011 / 095 624 A1 shows a circuit for connecting and disconnecting a switchable electrical system and an electrical network of a vehicle, wherein the circuit has at least one mechanical main isolating switch for disconnecting and connecting the switchable electrical system to the electrical network of the vehicle and at least one pre-charging unit connected in parallel to the main isolating switch with at least one controllable semiconductor switch, wherein the pre-charging unit has at least one mechanical isolating switch for disconnecting and connecting the switchable electrical system and the electrical network of the vehicle, wherein the semiconductor switch is connected in series with the mechanical isolating switch.

[0015] EP 2 562 896 A2 discloses a first control circuit for indirectly limiting a load current flowing through a controllable semiconductor component, configured to control a controllable semiconductor component taking into account a measured and / or calculated load-current-dependent power loss of the semiconductor component. Furthermore, a second control circuit for indirectly limiting a load current flowing through a controllable semiconductor component, configured to control a controllable semiconductor component taking into account a measured and / or calculated load-current-dependent component temperature of the controllable semiconductor component, is disclosed.

[0016] It is therefore an object of the invention to provide an improved circuit arrangement for an intermediate circuit capacitance, in particular for precharging an intermediate circuit capacitance, with which the disadvantages of conventional approaches can be avoided. A further object is to provide an improved method for precharging an intermediate circuit capacitance. A further object is to provide an improved method with which compensating currents of parallel-connected battery modules can be better handled when connected during precharging.

[0017] These objects are achieved by devices and methods having the features of the independent claims. Advantageous embodiments and applications of the invention emerge from the dependent claims and are explained in more detail in the following description, with partial reference to the figures.

[0018] According to a first aspect of the invention, a circuit arrangement for an intermediate circuit capacitor is provided. The intermediate circuit capacitor can, in particular, be connected upstream of a converter of an at least partially electrically driven motor vehicle, e.g., an electric vehicle or hybrid vehicle. The motor vehicle can be a commercial vehicle. The invention can also be used in watercraft and aircraft.

[0019] The circuit arrangement comprises an electrical energy storage system having a plurality of energy storage modules. The energy storage module can be a battery system or battery pack. The plurality of energy storage modules can, in particular, be electrically connected in parallel, e.g., via a high-voltage distributor. The individual energy storage modules can be structurally identical and / or each have an energy storage housing in which an energy storage module control device and a plurality of individual cells connected in parallel and / or series to one another and combined to form a cell network are arranged.

[0020] The energy storage modules each have: at least one storage cell, a first and a second pole, and a first and a second main current path, each of which is connected to one of the poles of the respective energy storage module and of which at least the first main current path can be interrupted by means of a switching device arranged therein. The energy storage modules each further have a precharging current path (also referred to as a precharging branch) connected in parallel to the switching device in the first main current path, which can be interrupted by means of a clocked semiconductor switching device arranged therein. The clocked semiconductor switching device can be a pulse-width-modulated semiconductor switching device.

[0021] The circuit arrangement further comprises an intermediate circuit capacitance, e.g., in the form of at least one intermediate circuit capacitor, which is electrically connected directly or indirectly to the plurality of energy storage modules via the first and second main current paths. The intermediate circuit capacitance referred to here can also be understood as the sum of all input and output capacitances of all connected devices, e.g., additional inverters or DC converters. The intermediate circuit capacitance can be connected to the energy storage modules, for example, via a high-voltage distributor, via which the energy storage modules are electrically connected in parallel.

[0022] A particular advantage of the invention is that each energy storage module has its own pre-charging current path, and a clocked semiconductor switching device is arranged in this pre-charging current path, which operates particularly efficiently, in particular more efficiently than a linear transistor circuit. In this way, the pre-charging current can be controlled separately for each energy storage module of the energy storage system. The currents for charging the intermediate circuit capacitance can be drawn simultaneously from all energy storage modules via their pre-charging branches. This ensures that the intermediate circuit capacitance is charged in a time-optimized manner according to its current limits. Furthermore, the fact that each energy storage module has its own pre-charging current path increases flexibility during pre-charging, since, for example, individual pre-charging paths can be deactivated if necessary.Furthermore, these pre-charging current paths can be used not only for pre-charging the intermediate circuit capacitance, but also for temperature management and / or voltage equalization between the individual energy storage modules, which will be explained below.

[0023] According to a particularly preferred embodiment, the semiconductor switching device, which is arranged in each of the individual precharging current paths, is controlled and regulated via pulse width modulation. This reduces heat losses during precharging, for example, compared to a semiconductor operated in the linear range. Thus, a semiconductor operated in the linear range essentially represents an amplifier element or a voltage-controlled resistor whose resistance is increased or decreased depending on the operating state. With pulse width modulation-based control according to this embodiment, the semiconductor element, e.g., the transistor, switches on with minimal resistance when the semiconductor element is conductive. Thus, according to this embodiment, the transistors or semiconductor switches in the semiconductor switching device are not operated in the linear range, but in a clocked manner in the saturated range.This mode of operation of semiconductors is typical in the known circuits of switched-mode power supplies and DC-DC converters. Therefore, the semiconductor switching device can also be viewed as a low-power DC-DC converter in the precharge path, e.g., in the form of a secondary-switched switching regulator. During operation, the properties of an ideal switch, combined with the smallest resulting resistance R_On, are then effective. For better understanding, the semiconductor switching devices are therefore shown in the figures in an equivalent circuit diagram with these two components (ideal switch, R_On). For cost reasons, the circuit design with a minimum of components is preferred. Ideally, only one semiconductor with its control circuit is required. The semiconductor switching device can also be designed as a semiconductor relay.The possible designs of clocked semiconductor switches with and without potential separation of the input and output sides are described in the specialist literature.

[0024] A further advantage is that the clocked semiconductor switching device can be controlled by pulse width modulation in such a way that the current in the pre-charging current path can be controlled.

[0025] A further advantageous possibility of implementing the invention provides for a fuse arranged in series with the semiconductor switching device in the precharging current path. The fuse serves to disconnect the energy storage module in the event of a fault and protects the semiconductor switching device from destruction during the precharging phase from the associated battery. The fuse is preferably arranged upstream of the semiconductor switching device in the precharging current path, i.e., on the side of the semiconductor switching device facing the energy storage module or on which the current from the energy storage module arrives.

[0026] Likewise, a second fuse can be located at the end of the pre-charging path, since a parallel-connected battery system would cause further consequential damage via the intermediate circuit in the semiconductor switching device in the event of a fault and therefore disconnects the pre-charging path on the second side.

[0027] Furthermore, a switch, in particular a contactor, can be arranged in series with the semiconductor switching device in the precharging current path. The switch is preferably connected upstream of the fuse. A cost-effective contactor, designed for the same maximum currents, can thus be connected upstream of the semiconductor switching device to easily enable all-pole disconnection of the battery. However, manual switches can also be used here, which ensure the required disconnection only during electrical work on the HV distributor. Alternatively, the fuse can be removed while live by trained personnel to ensure the disconnection.

[0028] To ensure a high level of protection in HV networks, insulation monitors are now used in isolated networks to detect the first fault in the network before a contactor is switched on. In this context, the use of fuses is optional. Since this is state of the art, it will not be discussed further below.

[0029] To monitor the precharge current path, a measuring device for measuring the current in the precharge current path can also be arranged in the precharge current path. Furthermore, at least one measuring device for measuring the voltage can be arranged in the precharge current path. It is particularly advantageous if two such measuring devices for measuring the voltage are provided, which are arranged in the precharge current path on opposite sides of the semiconductor switching device.

[0030] Furthermore, the semiconductor switching device can be operated bidirectionally. This means that, depending on the switching state, the semiconductor switching device can conduct current in both directions and block voltage in both directions. Conceptually, this means that two unidirectional semiconductor switching devices must be connected in antiparallel, since current flow in a semiconductor is generally only possible in one direction. Bidirectionally operated clocked components would simplify the circuitry and eliminate the need for antiparallel circuits.

[0031] The semiconductor switching device can, in a known manner, comprise at least one semiconductor (bipolar and field-effect transistors) that can be switched on and off. Another possible implementation provides for the semiconductor switching device to also contain switchable thyristors and, in addition, to be combined with other semiconductors (transistors). Diode circuits for operation as switches are also known and can be used in the semiconductor switching device. Depending on the design, mixed forms with the aforementioned components and other circuit elements such as resistors, capacitors, coils, and other diodes can be used in the semiconductor switching device in a known manner. The semiconductor switching device can also have its own connection to the ground potential of the energy storage module.

[0032] Furthermore, the circuit arrangement can comprise a high-voltage distribution device (high-voltage distributor), to which the first and second main current paths are connected on the one hand, and to which the intermediate circuit capacitor is connected on the other. The energy storage modules of the energy storage device can be electrically connected in parallel via the high-voltage distribution device.

[0033] According to a further embodiment, each pre-charging current path can be assigned a control device which is designed to receive information from at least one of the following components in the pre-charging current path: the measuring devices for current measurement, the at least one measuring device for voltage measurement, the semiconductor switching device, the switch arranged in series with the semiconductor switching device, and the at least one fuse. This control device is referred to below as the first control device to distinguish it from a control device of the energy storage module and from a central control device which monitors and controls the operation of all energy storage modules of the energy storage system. It is particularly advantageous if all components of the pre-charging current path have an interface to the first control device.

[0034] The first control device can be configured to output the measured values ​​determined in the pre-charging current path to an energy storage module control device of the respective energy storage module and to receive control signals from the energy storage module control device. The energy storage module control device is responsible for the overall control of the energy storage module, e.g., state of charge management, and is also referred to as a battery management system (BMS).

[0035] Furthermore, a central control device is preferably provided, which is designed to receive information, in particular measured values, from the energy storage module control devices (BMS) and to output control signals to the energy storage module control devices, in particular control signals for the semiconductor switching device. In other words, all individual battery management systems (BMS) are connected to a higher-level central controller unit, which collects all information from the subsystems and returns corresponding control signals to the subsystems. The central control device (central controller unit) can be a standalone control unit or simply represent a logical software module within a larger management software system. The state of the art allows for all variants and mixed forms.

[0036] Furthermore, within the scope of the invention, it is possible for the energy storage module control devices (BMS) to be each configured to monitor a temperature of the respective energy storage module while the motor vehicle is in operation and, if the monitored temperature exceeds a first temperature threshold and preferably a partial load situation exists, to close the semiconductor switching device in the precharging current path and interrupt the first main current path by means of the switching device arranged therein. If the monitored temperature falls below a second temperature threshold again, the energy storage module control device can interrupt the precharging current path again and close the first main current path again.

[0037] In other words, the pre-charging current path can also be used for temperature management of the energy storage modules. An energy storage module with a higher internal resistance will be noticeable by a higher temperature compared to the other energy storage modules. During driving, the main contactors that bridge the pre-charging current path can then be closed to relieve the load on the energy storage module with the increased temperature. In a low load situation, for example, the main contactor is opened at a low current. The current direction of the pre-charging current path again indicates the equalizing current, which is controlled by the semiconductor switching device. This function can occur automatically, and the duration of this gentle equalization with battery cooling is monitored by the energy storage module control unit of this subsystem.Once the energy storage module has cooled down, it can be reconnected, allowing the affected energy storage module to contribute to traction again. This can extend the service life of battery systems.

[0038] According to a further embodiment of the invention, the circuit arrangement is used for voltage equalization or state of charge equalization among the individual energy storage modules. In this case, the central control device and / or the first energy storage module control devices are configured to monitor a differential voltage between a voltage at the respective energy storage module and a voltage present on the output side of the precharging current path during a precharging process of the intermediate circuit capacitance, and to terminate a precharging process via the respective precharging current path only when the differential voltage has fallen below a predetermined threshold value.

[0039] The invention further relates to a motor vehicle, in particular a commercial vehicle, with a circuit arrangement as described in this document.

[0040] According to a second aspect of the invention, a method for precharging an intermediate circuit capacitance is further provided, wherein the intermediate circuit capacitance can be connected upstream of an inverter of an at least partially electrically driven motor vehicle. According to the method, the intermediate circuit capacitance is precharged by means of a circuit arrangement according to the invention, as described in this document.

[0041] According to a preferred embodiment of the method, an embodiment of the circuit arrangement according to the invention is used, which comprises a measuring device arranged in the pre-charging current path for measuring the current in the pre-charging current path, at least one measuring device arranged in the pre-charging current path for measuring the voltage, a switch, in particular a contactor, arranged in series with the semiconductor switching device in the pre-charging current path, and at least one fuse arranged in series with the semiconductor switching device in the pre-charging current path. According to the preferred embodiment of the method, the pre-charging current in each pre-charging current path can be individually started, adjusted, and regulated according to the following steps: a) Check whether the switch arranged in series with the semiconductor switching device is closed in the respective pre-charging current path, for example by measuring the voltage for each of the pre-charging current paths; b) If this is the case, starting a pulsed operation of the corresponding semiconductor switching device and regulating a permissible value of the current in the respective pre-charging current path via the pulse width modulation at the control input of the semiconductor switching device in order to increase or decrease the current through the respective pre-charging current path according to a predetermined curve function, wherein an emerging branch current is monitored at the current measuring point, in particular with the sign of the branch current; and c) Abort the pre-charging if one of the fuses in the pre-charging current path has blown.

[0042] According to a third aspect of the invention, a method is further provided for balancing battery charge states of parallel-connected battery modules, which are connected upstream of an inverter of an at least partially electrically driven motor vehicle, in particular via a high-voltage distribution (HV distribution). The method is characterized in that balancing battery charge states between the batteries is carried out by means of a switching arrangement according to the invention, as described in this document.

[0043] The above-described preferred embodiments and features of the invention can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. They show: Fig. 1 a schematic representation of a circuit arrangement according to an embodiment of the invention; Fig. 2 a schematic representation of a circuit arrangement according to a further embodiment of the invention; and Fig. 3 a schematic representation of a circuit arrangement according to a further embodiment of the invention.

[0044] Identical or functionally equivalent elements are designated by the same reference numerals in all figures and are partly not described separately.

[0045] Fig. 1 shows a schematic representation of a circuit arrangement according to one embodiment of the invention. The circuit arrangement comprises an electrical energy storage system 1, which is formed from a plurality of energy storage modules 2, here in the form of battery systems, which are electrically connected in parallel. In the present case, only three energy storage modules are shown. However, the number of energy storage modules connected in parallel can be any natural number n. Each of the energy storage modules 2, in turn, has a plurality of individual cells 3 connected in parallel and / or serially to one another and combined to form a cell network. The energy storage modules 2 further each have a first 4 and a second 5 pole and a first 6 and a second 7 main current path, each of which is connected to one of the poles 4, 5 of the respective energy storage module 2.

[0046] In order to satisfy the isolation of HV-carrying energy systems, i.e. in order to be able to isolate the energy storage system 1 in a corresponding vehicle from the vehicle electrical system on all poles, two switching devices 8 designed as circuit breakers, e.g. contactors, are typically provided, which are arranged in one of the main current paths 6, 7 of each of the energy storage modules 2.

[0047] The energy storage modules 2 are electrically connected in parallel via a high-voltage distributor 16, to which the main current paths 6, 7 of the individual energy storage modules 2 are connected on the input side. On the output side, the high-voltage distributor is connected to an intermediate circuit capacitor 9 via two connecting lines 14, 15. The intermediate circuit capacitor represents the sum of all capacitors directly connected to the high-voltage distributor 16 and can include multiple intermediate circuit capacitors.

[0048] A load 13 is shown as an example parallel to the intermediate circuit capacitor 9. This can be, for example, a discharge circuit and / or an inverter, in particular an inverter of an at least partially electrically driven motor vehicle. DC-DC converters can also be connected. Generally, multiple loads can be arranged in parallel.

[0049] However, when the two contactors 8 are switched on, a significant current would flow into the intermediate circuit capacitance 9. Therefore, a precharging current path 20 is provided in parallel with the contactor 8 in the first main current path 6, in which a first fuse 22a, a second fuse 22b, and a semiconductor switching device 21 are provided and connected in series.

[0050] The semiconductor switching device (with at least one switching semiconductor) 21 is controlled by pulse width modulation. The semiconductor switching device 21 is represented as a combination of an ideal switch 21a with the resistor R_On 21b, which represents the resistance remaining when semiconductors are switched on. In the switched state, the semiconductor switching device 21 allows an amount of energy to pass through, so that the pulse-width modulated control creates so-called ripple currents, which the precharging path 20 can transmit according to its design. The fuse 22a serves to disconnect the energy storage module in the event of a fault and protects the semiconductor switching device 21 from destruction during the precharging phase. The second fuse 22b is arranged towards the intermediate circuit and prevents continued damage in the event of a fault in the semiconductor switching device itself.

[0051] The semiconductor switching device 21 can also have its own connection 7a to the ground potential of the energy storage module 2.

[0052] The pulse width modulation for controlling the semiconductor switching device 21 is designed to generate an effective current that generally always remains below the tripping current of the fuses 22a and 22b. By changing the pulse width modulated control of the semiconductor switching device 21, the effective current through the precharging current path 20 can be changed and controlled.

[0053] Fig. Figure 2 shows a schematic representation of a circuit arrangement according to a further embodiment of the invention. Components with the same reference numerals correspond to the components of Fig. 1 and are not described separately. For reasons of clarity, Fig. 2 only one energy storage module 2 with the corresponding main current paths 6, 7 is shown. The other modules are analogous to Fig. 1 parallel-connected n energy storage modules 2 are not shown. The special feature of this embodiment lies in the pre-charging current path 40, which is connected in parallel to the contactor 8 in the first main current paths 6. The pre-charging current path comprises a first branch, comprising the series connection of the fuses 22a and 22b and the semiconductor switching device 21, which is controlled by means of pulse width modulation, as described above for Fig. 1. A conventional pre-charging current path (pre-charging resistance path) is connected in parallel, with a so-called pre-charging contactor 11 and a protective resistor 12 in series therewith.

[0054] This allows the precharging path with the expensive components of the semiconductor switching device to be dimensioned even smaller in terms of power, since the total current is additionally distributed across the conventional precharging resistor. The precharging path with the semiconductors is operated first, and the precharging resistor path is connected to it according to a connection criterion and at a suitable voltage difference. The process is completed when the main contactor 8 in the first main current path 6 is connected.

[0055] Fig. Figure 3 shows a schematic representation of a circuit arrangement according to a further embodiment of the invention. Components with the same reference numerals correspond to the components of Fig. 1 and are not described separately.

[0056] In the embodiment shown, the pre-charging current path 20 is only shown with one fuse 22a. However, the pre-charging current path 20 can in turn have a second fuse 22b, which is arranged towards the intermediate circuit. The special feature of the Fig. The advantage of the embodiment shown in Figure 3 is that the pre-charging current path 20 now, in addition to the fuse 22a or fuses 22a and 22b and the semiconductor switching device 21, which is controlled by pulse width modulation, also has a cost-effective contactor 24 connected upstream of the fuse 22a. The contactor 24 is designed for the same maximum currents as those of the semiconductor switching device 21 in order to easily enable all-pole isolation of the energy storage module 2. However, manual switches could also be used here, which only ensure the prescribed isolation in the event of electrical work on the HV distributor. Alternatively, the fuse 22a can also be removed by trained personnel while live to ensure the isolation.

[0057] A current measuring point 27 and two voltage measuring points 25, 26 are also provided to monitor the precharging current path. If a second fuse 22b (not shown) is arranged toward the intermediate circuit, the current measuring point 27 and the voltage measuring point 26 can be arranged, for example, between the semiconductor switching device 21 and the second fuse 22b.

[0058] Furthermore, a current measuring point 31 and a voltage measuring point 29 are provided in the first main current path 6. All components of the pre-charging current path 20, i.e., the contactor 24, the current and voltage measuring points 25, 26, 27, the fuse 22a and possibly the fuse 22b (if present), and the semiconductor switch 21, have an interface to a control device 23, which is connected to the control device (battery management system, BMS) 30 of the energy storage module 2 via a communication connection 28, e.g., in the form of a data bus. The control device 23 generates the pulse width modulation control signals for controlling the semiconductor switching device 21. The control device 30 (BMS) continuously checks with the current and voltage measuring points 31, 29 whether the operating conditions of the energy storage module 2 are being maintained.

[0059] For the sake of clarity, only the Fig.1 upper energy storage module 2 with the main current paths 6, 7 and the pre-charging current path 20 is provided with reference numerals. The n additional energy storage modules 2 connected in parallel with the corresponding main current paths and pre-charging current paths are constructed identically.

[0060] All control devices 30 of the individual energy storage modules 2 are connected via a communication link 32, e.g., via a data bus, to a higher-level central controller unit 100, which collects all information from the subsystems and returns corresponding control signals to the subsystems. The central controller unit 100 can be a standalone control unit or simply a logical software module within a larger management software system. [c1] The individual steps in the pre-loading phase are described below as examples:

[0061] In a first step, during a typical charging process of the intermediate circuit capacitor 9, this capacitor is initially connected to the respective energy storage modules 2 in a single-pole manner by closing the main contactors 8 in the second main current paths 7. The contactors 8 in the first main current paths 6 are open. The single-pole connection does not yet result in any current flow, i.e., the second main current path 7 is switched without load and thus wear-free. Subsequently, all pre-charging current paths 20 are closed by closing the switches 24, thereby bypassing the contactor 8 in the first main current path 6. However, no current flows yet.

[0062] The precharging current can now be started, set, and regulated individually in each precharging current path. A voltage measurement is performed for each of the precharging current paths 20 to check whether the contactor 24 in the respective precharging current path 20 is closed. If this is the case, the pulsed operation of the corresponding semiconductor switch 21 begins to increase or decrease the current through the respective precharging current path 20 according to a predetermined characteristic function. The current measurement at measuring point 27 tracks the resulting branch current with a sign. The permissible current value in a precharging current path 20 is regulated via pulse width modulation at the control input of the semiconductor switch 21. If fuses 22a and 22b have blown, an error message is generated because the current is zero. In this case, precharging is aborted.

[0063] The voltage measurement at the voltage measuring points 26 tracks the charging process of the intermediate circuit capacitance 9, and the current measurement 27 monitors the permissible currents.

[0064] If, during charging, the intermediate circuit capacitance 9's potential exceeds the voltage level of one of the energy storage modules 2, the sign in the affected pre-charging current path 20 is reversed. The corresponding battery module 2 now behaves like a consumer. The charging of the intermediate circuit capacitance 9 continues with increasing potential through the remaining energy storage modules 2, and a compensating current would now flow into the corresponding energy module 2 with the lower voltage. The pulsed operation of the semiconductor switching device is set to the permissible compensating currents of the affected battery module 2. A gentle and controlled charging of the affected battery module 2 takes place. The compensating process lasts until a permissible remaining differential voltage has been established between the battery voltage 29 and the HV distributor at the voltage measuring point 26.Then the semiconductor switching device 21 can be stopped, the switch 24 opened and the main contactor 8 in the current path 6 closed.

[0065] The precharging phase is completed with the switching on of the main contactors 8 in the first main current paths 6 to bridge the precharging branches 20.

[0066] The added energy storage module 2 now also contributes to the overall operation of the vehicle.

[0067] The BMS 30 control unit now monitors the operation of this energy storage module 2 and continuously checks, using its own temperature and current measurements 31, whether operation of this energy storage module 2 can be continued. If the temperature exceeds a preselected value, the BMS 30 control unit triggers the control unit 23 to operate the semiconductor switching device 21 for the controlled equalization of the affected battery module 2. Before the pre-charging path 40 can be used again, however, care must be taken to ensure that a load case with a low current has occurred to switch off contactor 8 in current path 6. This current must not cause the main contactor 8 to age in order to avoid premature replacement. If a fault is detected by the BMS 30, pulse operation is stopped during a pre-charging or equalization phase, and contactor 24 can also be opened again for isolation.

[0068] It should be noted that the battery systems may complete the pre-charging phase at different times. The higher-level central control device 100 decides whether a sufficient number of batteries are connected to the intermediate circuit, i.e., to the high-voltage distributor 16, and starts driving if this is the case.

[0069] At the same time, energy storage modules 2 may still be in the pre-charging phase. If an energy storage module is not connected, this subsystem can be shut down and the vehicle will continue to operate, provided the remaining number of energy storage modules allows for satisfactory and permissible driving.

[0070] Although the invention has been described with reference to specific embodiments, it will be apparent to one skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. Accordingly, the invention is not intended to be limited to the disclosed embodiments, but is intended to include all embodiments falling within the scope of the appended claims. In particular, the invention also claims protection for the subject matter and features of the dependent claims, independent of the referenced claims. List of reference symbols 1 energy storage system 2 Energy storage module 3 memory cells 4, 5 poles 6 First main current path 7 Second main current path 7a Circuit connection between semiconductor switching device 21 and the ground potential of the energy storage module 8 Main contactor 9 DC link capacitance, e.g. DC link capacitor 13 Load, e.g. inverter 14, 15 connecting cables 16 high-voltage distributors 20, 40 Precharge current path 21 semiconductor switching device, semiconductor switch 21a Switch (equivalent circuit for ideal switching properties of semiconductors) 21b Resistor R_On (equivalent circuit for ideally switched semiconductors) 22a fuse on the battery side 22b Fuse on the DC link side 23 Precharge path control device 24 switches, e.g. contactor 25, 26, 29 Voltage measuring device 30 Control unit energy storage module, BMS 27, 31 Current measuring device 28, 32 Communication connection 100 Superior central controller unit, e.g. logical SW module in management software

Claims

[1] Circuit arrangement for an intermediate circuit capacitance, comprising: a) an electrical energy storage system (1) comprising a plurality of energy storage modules (2) with - at least one memory cell (3), - a first (4) and a second (5) pole, - a first (6) and a second (7) main current path, each of which is connected to one of the poles (4, 5) of the respective energy storage module (2) and of which at least the first main current path (6) can be interrupted by means of a switching device (8) arranged therein, and - a pre-charging current path (20) connected in parallel to the switching device (8) in the first main current path (6), which can be interrupted by means of a clocked semiconductor switching device (21) arranged therein and which has a fuse (22a, 22b) arranged in series with the semiconductor switching device (21) and a switch (24) arranged in series with the semiconductor switching device (21), as well as a measuring device (27) arranged for current measurement in the pre-charging current path and / or at least one measuring device (25, 26) arranged in the pre-charging current path for voltage measurement; and b) an intermediate circuit capacitor (9) which is electrically connected directly or indirectly to the plurality of energy storage modules (2) via the first and second main current paths (6, 7); wherein, c) a first control device (23) is assigned to each pre-charging current path (20) and is arranged in the respective pre-charging current path (20), which first control device is designed to detect information from at least one of the following components in the pre-charging current path (20): the measuring devices for current measurement (27), the at least one measuring device for voltage measurement (25, 26), the semiconductor switching device (21), the switch (24) arranged in series with the semiconductor switching device and the at least one fuse (22a, 22b); d) the first control device (23) is designed to output the information detected in the pre-charging current path (20) to an energy storage module control device (30) of the respective energy storage module (2) and to receive control signals from the energy storage module control device (30); and e) a central control device (100) is provided which is designed to receive information from the energy storage module control devices (30) and to output control signals to the energy storage module control devices (30). [2] Switching arrangement according to claim 1, characterized by that the semiconductor switching device (21) is controlled and regulated via pulse width modulation. [3] Switching arrangement according to one of the preceding claims, characterized by that the switch (24) arranged in series with the semiconductor switching device (21) in the pre-charging current path (20) is a contactor. [4] Switching arrangement according to one of the preceding claims, characterized by that the semiconductor switching device (21) a) comprises at least one semiconductor switching element, or b) is a solid-state relay; or c) is designed as a DC-DC converter with or without potential separation, and / or d) can be operated bidirectionally. [5] Switching arrangement according to one of the preceding claims, characterized by a high-voltage distribution device (16) to which the first and second main current paths (6, 7) are connected on the one hand and to which the intermediate circuit capacitance (9) is connected on the other hand. [6] Switching arrangement according to one of the preceding claims, characterized by that the information received by the energy storage module control devices (30) are measured values ​​and the control signals output to the energy storage module control devices (30) are control signals for the semiconductor switching device (21). [7] Switching arrangement according to one of the preceding claims, characterized by that the energy storage module control devices (30) are designed a) to monitor the temperature of the respective energy storage module; b) if the monitored temperature exceeds a first temperature threshold, to activate the semiconductor switching device (21) in the pre-charging current path (20, 40) and to interrupt the first main current path (6) by means of the switching device arranged therein; and c) if the monitored temperature falls below a second temperature threshold again, to deactivate the pre-charging current path (20, 40) and to close the first main current path (6). [8] Switching arrangement according to one of the preceding claims, characterized bythat the central control device (100) and / or the first energy storage module control devices (30) are designed to monitor a differential voltage between a voltage at the respective energy storage module and a voltage present on the output side of the precharging current path during a precharging process of the intermediate circuit capacitance and to terminate a precharging process via the respective precharging current path (20, 40) only when the differential voltage has fallen below a predetermined threshold value. [9] Switching arrangement according to one of the preceding claims, characterized bythat the central control device (100) and / or the first energy storage module control devices (30) and / or first control device (23) are designed to monitor a compensating current for an energy storage module (2) via the precharging path (20, 40) within set current limits and to regulate the semiconductor switching device (21) with appropriate pulse width modulation taking into account the current sign. [10] Motor vehicle, with a switching arrangement according to one of the preceding claims. [11] Motor vehicle according to claim 10, wherein the motor vehicle is a commercial vehicle. [12] Method for precharging an intermediate circuit capacitance, characterized by that the intermediate circuit capacitance is precharged by means of a switching arrangement according to one of claims 1 to 9. [13] Method according to claim 12, wherein the circuit arrangement comprises a measuring device arranged in the pre-charging current path for measuring the current in the pre-charging current path, at least one measuring device arranged in the pre-charging current path for measuring the voltage, a switch arranged in the pre-charging current path in series with the semiconductor switching device, and at least one fuse arranged in the pre-charging current path in series with the semiconductor switching device, comprising the following steps: a) Check whether the switch arranged in series with the semiconductor switching device is closed in the respective pre-charging current path, for example by measuring the voltage for each of the pre-charging current paths; b) If this is the case, starting a pulsed operation of the corresponding semiconductor switching device and regulating a permissible value of the current in the respective pre-charging current path via the pulse width modulation at the control input of the semiconductor switching device in order to increase or decrease the current through the respective pre-charging current path according to a predetermined curve function, wherein a branch current that arises is monitored at the current measuring point; and c) Abort the pre-charging if one of the fuses in the pre-charging current path has blown. [14] Method for balancing battery charge levels of parallel-connected battery modules, characterized by that a compensation of battery charge states between the batteries is carried out by means of a circuit arrangement according to one of claims 1 to 9. [15] Method according to claim 14, wherein the battery modules are connected upstream of an inverter of an at least partially electrically driven motor vehicle via an HV distribution. [16] Switching arrangement according to one of claims 1 to 9 or method according to one of claims 12 to 13, wherein the intermediate circuit capacitance is connected upstream of an inverter of an at least partially electrically driven motor vehicle.

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