Means of transport, on-board electrical system arrangement, control unit and arrangement for voltage conversion in a means of transport

Abstract

An on-board electrical system (11), a means of transport (10), a control unit (EMS), and a voltage conversion arrangement between a primary side (1) and a secondary side (2) of an on-board electrical system (11) of a means of transport (10) are proposed. The arrangement comprises a DC / DC converter (3) for converting a primary-side DC voltage into a secondary-side DC voltage and vice versa, a primary-side voltage sensor (31) for measuring the primary-side DC voltage, a secondary-side voltage sensor (32) for measuring the secondary-side DC voltage, a data storage device (33), and an evaluation unit (34). The evaluation unit (34) is configured to initiate an operation for converting primary-side energy into secondary-side energy, depending on the data.provided that the secondary-side voltage (U2) is below a first predefined threshold (U2min) and / or the primary-side voltage (U1) is above a second predefined threshold (U1max), and depending on the data, to initiate an operation to convert secondary-side energy into primary-side energy, provided that the secondary-side voltage (U2) is above a third predefined threshold (U2max) and / or the primary-side voltage (U1) is below a fourth predefined threshold (U1min).

Description

[0001] The present invention relates to an on-board power system, a means of transport, a control unit, and an arrangement for voltage conversion between a primary side and a secondary side of an on-board power system of a means of transport. In particular, the present invention relates to improving efficiency and stability in an on-board power system with two sub-on-board power systems with different voltage levels.

[0002] The electrification of passenger transport is currently progressing rapidly. Increasingly higher voltage levels are being achieved for the traction-side electrical systems. While 400 V DC represented the upper limit for generating traction energy for some time, 800 V and more are now being achieved to improve the efficiency of electric propulsion. However, low-voltage electrical systems are also commonly found in vehicle electrical systems. This is due in particular to the fact that combustion engine-powered derivatives are still being manufactured, which feature 12 V, 24 V, or 48 V electrical systems and corresponding 12 V, 24 V, or 48 V components. On the other hand, the insulation measures for 12 V, 24 V, or 48 V electrical systems are not as costly and volume / mass-intensive.

[0003] Batteries or large capacitors are typically used to buffer the on-board power system components or stabilize their voltage. The ever-increasing size of traction batteries would essentially eliminate the need for low-voltage batteries, provided sufficient real-time conversion from high-voltage DC to low-voltage DC could be ensured. Autonomous stabilization measures for the on-board power system voltage in a motor vehicle are known for this purpose.

[0004] DE 10 2015 219 950 A1 discloses an autonomous shutdown of loads that detects an undervoltage in the vehicle electrical system and reduces their power consumption to stabilize the voltage. Multi-voltage vehicle electrical systems are also known, which transfer energy between different voltage levels using a central DC / DC converter. Furthermore, power supply systems with multiple parallel DC / DC converters are known.

[0005] US 6,866,934 A discloses a power supply system with a master that switches the other converters, which are electrically connected in parallel, on and off via a communication bus and specifies their operating point. Another known variant for controlling distributed DC-DC converters is decentralized control (e.g., droop control). In this variant, all converters are permanently switched on.

[0006] With voltage conversion via a master-slave architecture, individual slaves are switched on by the master as soon as the measured on-board system voltage falls below or exceeds a critical value. The latency of the communication bus between master and slave means that highly dynamic changes in current / power consumption, for example, in the event of a fault, can only be compensated for by the additional power of the slaves after the latency has elapsed. This results in a dynamic voltage drop. In decentralized control, however, all converters are permanently active. At low load conditions, these converters do not operate at a high efficiency level, which reduces the efficiency of the on-board system.

[0007] Based on the aforementioned prior art, it is an object of the present invention to provide autonomous voltage stabilization through a plurality of converters in an on-board power system of a vehicle, thereby reducing voltage fluctuations during highly dynamic current surges. In particular, high efficiency is to be achieved without compromising latency or real-time capability.

[0008] The aforementioned object is achieved according to the invention by an arrangement for voltage conversion between a primary side and a secondary side of an on-board electrical system of a means of transport. The means of transport can be an electrically driven means of transport. It can be designed as a car, van, motorcycle, truck, aircraft and / or watercraft. The primary side can, for example, be a high-voltage side, which can have a nominal voltage of 48 V (or higher). The secondary side of the on-board electrical system can, for example, be a low-voltage on-board electrical system side, which has a voltage of 6 V, 12 V or 24 V DC. The arrangement has a DC-DC converter for converting a primary-side DC voltage (energy) into a secondary-side DC voltage (energy).The DC-DC converter can be designed as a component with an energy conversion unit, electrical and information technology connections, an evaluation unit, and other elements. The DC-DC converter is configured at least to convert a primary-side DC voltage into a secondary-side DC voltage, which of course does not preclude the DC-DC converter from also converting the secondary-side voltage (energy) into a primary-side voltage (energy). The DC-DC converter can also have a first part, which is provided for the energy conversion from the primary side to the secondary side, and a second part, which is provided for the energy conversion from the secondary side to the primary side.The energy conversion can be carried out by two fundamentally separate DC-DC converters, which for the sake of simplicity are referred to as (a) "DC-DC converter" in the context of the present disclosure. The arrangement further comprises a primary-side voltage sensor for measuring the primary-side DC voltage and a secondary-side voltage sensor for measuring the secondary-side DC voltage. The respective voltage sensor can be configured as a component of the DC-DC converter or as a component of the arrangement according to the invention (e.g., an electronic control unit, which can have a housing). Last but not least, an evaluation unit is also provided, which is configured to determine and transmit an operating point and / or an efficiency of the operation of the DC-DC converter (e.g., via a data line or a bus of the means of transport).The efficiency can be determined automatically by the arrangement by calculating the output power in relation to the input power. This does not preclude the possibility of merely measuring individual electrical parameters (e.g. current and / or voltage) on the input and / or output side based on a predefined reference representing the efficiency characteristics of the DC-DC converter and using these parameters to identify the current efficiency based on the predefined reference. Since this assignment could also take place in the higher-level control unit, the transmission of a value characterizing the operating point of the arrangement (e.g. a message) to the higher-level control unit is also considered to be within the scope of the present invention, from which value the control unit determines the current operating point or the current efficiency of the arrangement based on a predefined reference known to it.By also receiving the operating point information or efficiencies of the remaining arrays / DC converters, the higher-level control unit can orchestrate the operating modes so that, on the one hand, the electrical target values ​​for the primary and secondary sides are all met, while, on the other hand, the overall efficiency of the array / DC converter ensemble is maximized. For example, for a DC converter with a comparatively high rated power, an individual maximum efficiency may be more important than the individual efficiency of an array with a comparatively lower rated power. In this way, high overall efficiencies can be achieved without having to forego the advantages of a decentralized architecture.The arrangement according to the invention enables a particularly stable and fault-resistant, but also very efficient, operation for the ensemble of arrangements according to the invention, in conjunction with a higher-level control unit that simultaneously manages several arrangements or DC-DC converters. The arrangement can autonomously initiate operation for converting primary-side energy into secondary-side energy, provided the secondary-side voltage is below a first predefined threshold and / or the primary-side voltage is above a second predefined threshold. In other words, the arrangement itself can use the voltage sensors to determine whether an undervoltage on the secondary side or an overvoltage on the primary side requires energy to be converted from the primary side to the secondary side. In this way, the respective voltage level can be brought into a standard range (IO range).Accordingly, the arrangement can be designed to operate in such a way that, in the event of a secondary overvoltage or primary undervoltage, secondary energy is converted into primary energy, thus bringing the respective voltage level into a standard range (IO range). The presence and any existing influence and / or the operating point and / or the current efficiency of additional DC-DC converters connected in parallel can be taken into account by the higher-level control unit in order to influence the efficiency of the overall system through latency-prone bus communication. Furthermore, it is possible to dispense with all existing voltage converters constantly participating in the voltage conversion, which would result in low energy conversion efficiency in the state of the art in an operating state of reduced energy demand.

[0009] The subclaims show preferred developments of the invention.

[0010] Preferably, the evaluation unit can be configured to discontinue conversion operation when the secondary-side voltage lies between the first and third predefined thresholds and the primary-side voltage lies between the second and fourth predefined thresholds. In other words, if there is no need, the DC-DC converter of the inventive arrangement is omitted from participating in the voltage stabilization in order to eliminate switching losses and ohmic losses therein. This can improve the efficiency of a DC-DC converter operating electrically in parallel with the inventive arrangement, and the overall efficiency increases.

[0011] The primary-side voltage sensor and / or the secondary-side voltage sensor can have an A / D converter and / or include a comparator. In other words, an analog sampled vehicle electrical system voltage can be converted to the digital domain using the A / D converter and further processed digitally. This enables fast and error-robust processing by mass-produced computing units (chips).

[0012] The magnitude of the deviation from standard operation for the primary / secondary voltage can determine how the evaluation unit initiates the operation of the arrangement according to the invention. For example, if the voltage falls slightly below a minimum value, slight or minimal operation of the DC-DC converter can be initiated to return the voltage to the standard range, while a significant deviation of the actual voltage from the standard range triggers a higher converter output. For example, the duty cycle can be adjusted depending on a difference (distance) between the standard range and the actual value of the DC voltage. For example, a linear relationship between the difference and the converter output can be defined.

[0013] Thanks to the particularly stable and efficient real-time control of the voltage levels according to the invention, buffering by means of a battery for either the primary or secondary side is no longer necessary. In other words, one battery is sufficient for the entire vehicle electrical system, since the energy stored in the battery can be transferred sufficiently quickly to the other vehicle electrical system side via the arrangement according to the invention, thus eliminating the need for buffering by a battery there.

[0014] Communication between the arrangement according to the invention and the higher-level control unit can be established, for example, via bus systems known in the automotive industry (e.g., twisted-pair power or optical cables), such as LIN, CAN, and / or MOST. In particular, a bidirectional line can be provided between the respective evaluation units or data input / output.

[0015] The control unit can send the (new) operating point that is more suitable for the system to the system in the form of a control message. For example, a duty cycle and / or a target value for the power on the secondary and / or primary side can be encoded into the control message. In this way, the control unit can achieve improved overall performance and / or improved overall efficiency for the vehicle bus or the vehicle, particularly based on a priori knowledge.

[0016] According to a second aspect of the present invention, a control unit for an on-board electrical system of a means of transport is proposed, which can be configured, for example, as a battery management system (EMS), as an electronic control unit, or similar. The control unit has a data input, a data output, and an evaluation unit. The data input and the data output can be configured as bus participants. In particular, the data input and the data output can be spatially combined and have a data connection to the evaluation unit of the control unit. The data input is configured to receive a message from an arrangement as described in detail above and to forward it to the evaluation unit. Based on the received message, the evaluation unit is able to determine a new operating point for the arrangement.This can be done using predefined references, which are stored, for example, in a data memory of the control unit. The control unit considers all operating points of the connected devices or DC-DC converters and determines a new operating point for each parallel-connected voltage converter involved in the voltage conversion (or the need to shut down one, several, or all of the voltage converters). To do this, the control unit sends a control message to the device from which the message was received, thus orchestrating the operation of the units involved in the voltage conversion. This communication is sometimes subject to latency.However, since the DC-DC converters can find their respective (possibly non-efficiency-optimized) operating points even without the control unit and thus contribute to stabilizing the primary and / or secondary side, one of the two sides can operate without a supporting energy storage device (battery, accumulator, capacitor, or similar). The real-time capability of the arrangements is therefore in no way affected by the "orchestration" proposed by the invention (which may not be real-time capable) by the control unit. It is assumed, of course, that the control unit can also comprise a DC-DC converter, which means it can be understood as an arrangement with a master function or similar.In other words, the control unit can comprise a DC-DC converter, several voltage sensors, several current sensors, the data input, the data output and the evaluation unit in a single housing and can also be electrically connected in parallel with the other arrangements.

[0017] According to a third aspect of the present invention, an on-board power supply arrangement for a means of transport is proposed, which arrangement has a control unit (central or higher-level control unit) and two electrically parallel voltage conversion arrangements. At least one of the arrangements is designed according to the invention so that it can ensure the real-time buffering capability of both on-board power supply units without the need for buffer batteries on both sides. The control unit can be connected to the parallel voltage conversion arrangements for information technology purposes, in particular by means of a communication bus. This provides a redundant option for (centrally) influencing the operation of the arrangements and thus for improving the overall efficiency of the on-board power supply arrangement. However, due to the communication bus, this option entails certain disadvantages of the prior art, if used.

[0018] According to a fourth aspect of the present invention, a means of transportation is proposed, which is configured as a car, van, motorcycle, truck, aircraft, and / or watercraft. The arrangement according to the invention is provided between two sub-vehicle electrical systems of the means of transportation and can thus ensure real-time buffering of both on-board electrical system components from a single battery, while an overall efficiency monitors the operating points and adjusts them as needed by means of a control unit provided for coordinating several DC-DC converters. Furthermore, the arrangement according to the invention increases the electrical efficiency of the means of transportation, as described above.

[0019] Further details, features, and advantages of the invention will become apparent from the following description and the figures. They show: Fig. 1 a schematic representation of the efficiency of a DC-DC converter versus the converter power; Fig. 2 a schematic representation of an arrangement according to the invention together with its electrical components; Fig. 3 a means of transport designed according to the invention comprising an embodiment of an arrangement according to the invention; Fig. 4 is a flowchart illustrating an operating strategy of an embodiment of an arrangement according to the invention; Fig. 5 a power-voltage diagram illustrating the operating behavior of an arrangement according to the invention as a function of a primary voltage; and Fig. 6 a power-voltage diagram illustrating the operating behavior of an arrangement according to the invention as a function of a secondary voltage.

[0020] Fig. Figure 1 illustrates the efficiency versus power of a DC-DC converter according to the invention in an arrangement according to the invention. A maximum efficiency η_ max The converter reaches this value at an average power P. This shows that efficiency decreases particularly when a large number of converters are operated in parallel without there being an acute need for this. Due to the different electrical specifications of the parallel-connected converters, and also due to the oscillation potential of uncoordinated arrangements, it is not necessarily beneficial to the overall efficiency of an on-board electrical system if the arrangements according to the invention always attempt to achieve their individual efficiency maxima.

[0021] Fig. Figure 2 shows a basic circuit diagram of an on-board electrical system of a means of transport comprising a high-voltage side / primary side 1 and a low-voltage side / secondary side 2. An energy management system EMS and a buffer battery 5 are provided only on the primary side. Electronic control units 7 are connected to both the primary side 1 and the secondary side 2. Between the primary side 1 and the secondary side 2, a required power flow is generated by arrangements 3, 4 according to the invention, depending on the current voltage levels determined by a primary-side voltage sensor 31 and a secondary-side voltage sensor 32. In order to maintain the operating mode and data references, the arrangements 3, 4 have data memories 33, which provide digital information for an evaluation unit 34.Using this data storage 33, the arrangements 3, 4 can determine an operating point and / or a current efficiency from the electrical variables determined by the voltage sensors 31, 32. They can also store information here about the circumstances under which a message should be sent to an energy management system (EMS) as the control unit via a bus 6 and which information should be included. The arrangements 3, 4 are connected to the energy management system EMS via a communication bus 6. Independent of the energy management system EMS, decentralized control can take place in real time. If the current voltage on the primary side 1 is too high or the current voltage on the secondary side 2 is too low, energy is transferred to the secondary side 2 via the arrangement 3, 4.If the current voltage on primary side 1 is too low or the current voltage on secondary side 2 is too high, energy is transferred to primary side 1 by means of arrangements 3, 4. Not all arrangements 3, 4 have to operate identically. In the event of a fault 8, a component of primary side 1 cut off by fault 8 can be continuously supplied with electrical energy by arrangements 4 first transferring energy from primary side 1 to secondary side 2 and arrangement 3 alone transferring energy from secondary side 2 to the cut-off area of ​​primary side 1. Due to fault 8 and the consumer located in the cut-off area of ​​primary side 1 (electronic control unit 7), primary-side DC voltage sensor 31 of arrangement 3 independently determines the need to support primary side 1, even if the energy management system EMS has not yet detected this fault.Therefore, the present invention can enable faster backup of (disconnected) vehicle electrical system components and, in particular, eliminates the need for a secondary-side buffer battery. Also shown are the switching thresholds U1min and U1max for the operating behavior of arrangements 3, 4 as a function of the primary-side voltage, as well as the switching thresholds U2min and U2max for the switching behavior as a function of the secondary-side voltage.

[0022] Fig. 3 shows an embodiment of a means of transport designed according to the invention, which has a buffer battery 5 and an on-board network 11 according to Fig. 2. The means of transport 10 is thus capable of supplying the two sub-vehicle networks with energy and stabilizing their voltage in a more fault-tolerant and efficient manner, using only one buffer battery 5.

[0023] Fig. 4 shows a voltage stabilization mode in decentralized operation of an embodiment of an arrangement according to the invention in the form of a flowchart. Based on the terminal voltage on the primary side 1 and the secondary side 2, the voltage deviation 42, 48 from the respective lower voltage threshold U1min, U2min or upper voltage threshold U1max, U2max is determined using an algorithm 41, 47. If the terminal voltages U1, U2 are within the range defined by the thresholds, the output 42, 15 of these algorithms 41, 47 is zero. In a next step, the voltage deviation is converted into a current specification 44, 50 using a known algorithm 43, 49. This can be done, for example, similar to the known droop control via the virtual resistance or the virtual conductance.If there is a conflict between the two current specifications 44, 50, an algorithm 45 decides which of the two specifications should be met or forms a compromise between the two specifications. This can be done, for example, using a priority table. The output of the algorithm 45 is the stabilizing current 58 of the converter. The operating strategy 52 of the converter decides on the operating state of the converter in normal, i.e., non-stabilizing operation. The operating strategy 52 can be used to set a target current specification 59 in order to operate the converter in a current-controlled manner. This is advantageous, for example, if this converter is to cover base loads. The specification of the operating strategy 59 and the stabilizing current 58 are added in a summer 51 and form the target current specification 53 for the converter. Based on the target current specification 53, an algorithm 55 decides whether the power output stage of the converter is switched on or off.If the setpoint current 53 is "zero" for a configurable period of time, the converter's power output stage is switched off. As soon as the setpoint current 53 is not equal to zero, the power output stage is immediately switched on with signal 56. The setpoint current 53 serves as the input for the current control 54. The current control algorithm calculates the control signals 57 of the power output stage based on the setpoint current 53 and the current operating parameters of the converter. This algorithm can be implemented, for example, as a well-known PI control.

[0024] Fig. Figure 5 shows the functionality of the algorithm for increasing or decreasing the power flow through the stabilization mode in the event of a voltage deviation on the primary side. If the terminal voltage of the respective converter (of the respective arrangement) leaves the voltage range between U1min and U1max, the power flow of the respective converter is adjusted autonomously to stabilize the voltage. A linear dependence of the converter power P on the terminal voltage U1 is defined as an example.

[0025] Fig.Figure 6 shows the functionality of the algorithm for increasing or decreasing the power flow through the stabilization mode in the event of a voltage deviation on secondary side 2. If the terminal voltage U2 of the respective converter (of the respective arrangement) leaves the voltage range between U1min and U2max (standard range), the power flow of the respective converter is adjusted autonomously to stabilize the voltage. In other words, the power P of the respective arrangement is increased or decreased linearly, as shown, depending on a deviation (difference) from the standard range shown.

[0026] Compared to the state-of-the-art control of parallel DC-DC converters, the autonomous response to the measured terminal voltage of each individual converter allows for significantly faster response to dynamic load changes and the DC-DC converters can be switched on or off. This allows the connected vehicle electrical systems to be stabilized.

[0027] Dynamic voltage stabilization and the use of redundant parallel DC-DC converters eliminate the need for secondary battery storage. While simultaneously ensuring voltage stability and reliability, this also applies in the event of a fault. List of reference symbols: 1 primary page 2 Secondary side 3 Arrangement 4 Arrangement 5 buffer battery 6 Communication bus 7 Consumers / ECU 8 errors 10 means of transport 11 On-board network 31 voltage sensors 32 voltage sensors 33 data storage 34 Evaluation unit 41 Algorithm 42 Voltage deviation 43 Algorithm 44 Power specifications 45 Algorithm 47 Algorithm 48 Voltage deviation 49 Algorithm 50 power specifications 51 summing devices 52 Operating strategy 53 Target current specification 55 Algorithm 54 Current control 56 Signal 57 Control signal 58 Stabilization current 59 Operating strategy 60 Data input / data output 61 Evaluation unit η efficiency P Performance U1 primary voltage U2 secondary voltage QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2015 219 950 A1

[0004] US 6,866,934 A

[0005]

Claims

[1] Arrangement for voltage conversion between a primary side (1) and a secondary side (2) of an on-board network (11) of a means of transport (10) comprising • a DC-DC converter (3) for converting a primary DC voltage into a secondary DC voltage and vice versa, • a primary-side voltage sensor (31) for measuring the primary-side DC voltage, • a secondary-side voltage sensor (32) for measuring the secondary-side DC voltage, • a data memory (33) and • an evaluation unit (34), wherein • the evaluation unit (34) is set up, ◯ to send a message representing a current operating point and / or an efficiency of the DC-DC converter (3) to a higher-level control unit (EMS) and ◯ to receive a control message from the higher-level control unit (EMS) and to use it for operating point adjustment. [2] Arrangement according to claim 1, wherein the evaluation unit (34) is arranged to send the message representing the operating point to the control unit (EMS) via a bus, in particular a LIN and / or a CAN and / or a MOST. [3] Arrangement according to claim 1 or 2, wherein the evaluation unit (34) is arranged to set an operation for conversion in dependence on the control message. [4] Control unit (EMS) for an on-board network (11) of a means of transport (10) comprising - a data input (60), - a data output (60) and - an evaluation unit (61), wherein the data input (60) is arranged to receive a message from an arrangement (3, 4) according to one of the preceding claims, - the evaluation unit (61) is set up to determine a new operating point for the arrangement (3, 4) based on the message and - to send a control message representing the new operating point to the arrangement (3, 4) by means of the data output (60). [5] Control unit (EMS) according to claim 4, wherein the evaluation unit (61) is configured to determine a new operating point based on information relating to at least one operating point of a further DC-DC converter. [6] Control unit (EMS) according to claim 4 or 5, wherein the evaluation unit (61) is arranged to send the control message representing the new operating point to the arrangement (3, 4) via a bus (6), in particular a LIN and / or a CAN and / or a MOST. [7] On-board power system arrangement for a means of transport (10) comprising - an arrangement (3, 4) according to one of the preceding claims 1 to 3, and - a control unit (EMS) according to one of the preceding claims 4 to 6. [8] On-board power system arrangement according to claim 7, wherein a plurality of arrangements (3, 4) are provided, of which a first arrangement (3) is arranged to regulate a voltage and the remaining arrangements (4) are arranged to carry out a power regulation [9] On-board power system arrangement according to claim 7 or 8, wherein no battery (5) is provided on the secondary side (2). [10] Means of transport including - an arrangement (3, 4) for voltage conversion according to one of the preceding claims 1 to 3 and / or - a control unit (EMS) according to one of the preceding claims 4 to 6 and / or - an on-board power supply arrangement according to claims 7 to 9.

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