CONVERTER ORDER AND PROCEDURES FOR OPERATION OF A CONVERTER ORDER

Description

[0001] The invention relates to a converter arrangement and a method for operating a converter arrangement.

[0002] Inverter arrangements with multiple inverters are known for a wide variety of applications in the field of electrical engineering. In particular, the drives of electric and hybrid vehicles utilize inverter arrangements with multiple inverters to provide drive power and to control the electric machines, converting the DC voltage supplied by a battery into suitable AC or DC voltages for the driven electric machine and other consumers in the vehicle.

[0003] Electrically operated test benches also regularly include inverter configurations with multiple inverters, whether for testing the powertrains of electric vehicles, hybrid vehicles, conventional vehicles with combustion engines, mechanical components such as the transmission, or the battery storage systems themselves. Battery storage system testing, in particular, is often performed in parallel, with several battery cells, battery modules, or battery packs being tested simultaneously using inverters arranged in parallel.

[0004] Electronic control units for such inverter arrangements are known from the prior art. These are generally designed to activate the individual inverters in a specific sequence based on a required target variable, which can also include the simultaneous activation of all inverters. Such a control system is known, for example, from document EP 1 931 586 A1. For instance, in an electric vehicle, maximum acceleration (kickdown) or full braking may be required, resulting in the simultaneous activation of several of the vehicle's inverters. Similarly, in a test bench for a powertrain with multiple electric machines or for a multi-cell battery module, the specified test methodology (the so-called test run) may require the simultaneous activation of several inverters in the inverter arrangement.

[0005] This presents the problem that the power supply for such converter arrangements is generally limited, either by the battery installed in an electric vehicle or by the central grid typically provided at a test bench, which can be an AC grid or a DC link. DC links, in particular, should be manufactured on-site using the most compact components possible (so-called line rectifiers), which in turn limits the maximum energy flow during test runs. The simultaneous activation of multiple converters can also lead to an overload of the central grid, both in the form of excessive power consumption from the power supply (for example, during kickdown) and in the case of excessive power output to the power supply (for example, during emergency braking).

[0006] The object of the invention is, among other things, to create a converter arrangement and a method for controlling a converter arrangement which avoids overloading the power supply and enables the most homogeneous load distribution of the converters possible in order to place as little or no strain on the power supply from the central grid as possible.

[0007] These and other problems are solved according to the invention with a converter arrangement and a method for controlling a converter arrangement according to one of the independent patent claims.

[0008] An inverter arrangement according to the invention comprises at least two inverters and a control unit connected to the inverters. The control unit can be implemented as an electronic data processing unit, in particular as a computer, microcontroller, microprocessor or the like, and can comprise an electronic data processing unit and an electronic storage unit.

[0009] According to the invention, the control unit is designed to continuously or at discrete time intervals receive measurement data from the inverters, in particular current and voltage measurements or power data, and to transmit control data to the inverters. For this purpose, the control unit can be connected via an interface unit to a data bus designed for bidirectional communication with the inverters, for example a USB interface or the like.

[0010] The control unit is further configured to transmit the permissible electrical power range to the inverters of the inverter arrangement. This power range can be defined, in particular, by a minimum power value Pmin and / or a maximum power value Pmax. During operation, the control unit receives measurement data from the inverters or other electrical components and provides each inverter of the inverter arrangement with its permissible power range. The invention is not limited to positive power (power input, motor operation) but also includes negative power (power output, generator operation).

[0011] Furthermore, the control unit can also be configured to transmit current power setpoints to the inverters. These could be, for example, the desired states of a test bench during a test run, or the requirements of a vehicle driver during operation. The control unit ensures that the power setpoints remain within the permissible power range for the respective inverter.

[0012] According to the invention, the control unit is designed to determine the current power balance of the inverters or to receive it from the inverters via the data bus. The term "current power balance" refers to the current power input or output of the inverters. It should be noted that inverters according to the invention can enable bidirectional operation, meaning they can both input and output power. In particular, the inverters can be so-called active front-end inverters. In this context, an active front-end inverter is a bidirectional inverter that can transfer electrical energy in both directions, for example, an actively switched bridge rectifier or bridge inverter.

[0013] The control unit is further designed to calculate the power balance of the entire converter assembly from the power balances received from the individual converters. This is generally the sum of the power balances of the individual converters. Alternatively, the control unit can also be connected to higher-level voltage and current sensors, which enable the calculation of the power balance of the entire converter assembly.

[0014] The control unit is further configured to modify the permissible electrical power range of the inverters in such a way that the power balance of the entire inverter assembly does not exceed a predetermined range. The control unit is also configured to modify the permissible electrical power range of the inverters if the voltage of a DC link supplying the inverters falls below or exceeds a predetermined threshold. The control unit thus ensures that the DC voltage of the DC link remains within a predetermined range. If the DC voltage exceeds the range, the permissible power range of individual or all inverters is reduced; if the DC voltage falls below the range, the permissible power consumption of individual or all inverters is reduced.This prevents excessive stress on the DC link. If this necessitates changing power values ​​defined in test runs, modifying the test runs is still preferable to an unforeseen test run termination due to DC link overload.

[0015] In this process, the power ranges of motor-driven and generator-driven inverters can cancel each other out, so that the entire inverter arrangement is operated in a small power range, even though the individual inverters each consume or deliver a high power.

[0016] To determine the current power balance of the inverters, the control unit can be connected to at least one voltage sensor to measure the input voltage of the inverters and to current sensors to measure the input currents of the inverters.

[0017] In particular, it can be provided that the inverters are powered by a DC link and the control unit is connected to a voltage sensor to measure the voltage at the DC link. This allows the control unit to easily calculate the current power consumption or output of each inverter.

[0018] However, the control unit can also be connected to voltage sensors to measure the output voltage of the inverters and to current sensors to measure the output currents of the inverters in order to determine the current power balance of the inverters. This allows the power balances of the inverters to be determined on the output side. These can be AC ​​voltage or AC current sensors.

[0019] However, the inverters can also be connected to internal or external voltage sensors to measure their output voltage and to internal or external current sensors to measure their output currents, and be configured to transmit the measured values ​​to the control unit. In these cases, the inverters themselves provide their current power balance or their current current and voltage values ​​to the control unit.

[0020] Furthermore, the system may include a discharge device connected to the control unit for reducing the voltage across a DC link, and the control unit may be configured to activate the discharge device when the voltage across the DC link exceeds a predetermined threshold. The discharge device may, for example, be a heating resistor designed to reduce the voltage across the DC link. This allows for a particularly rapid reduction of the voltage across the DC link, for example, in the event of emergency braking of a vehicle or when all batteries in a battery test bench are discharged simultaneously.

[0021] The device according to the invention thus ensures that the DC link is subjected to the lowest possible load. In particular, a "back-to-back" arrangement of the converters can be provided, whereby the power output of a first converter is used directly to supply a second converter, so that energy only needs to be supplied to overcome losses. Specifically, the control unit can be configured to modify a predetermined test run in such a way that the power balance of the converter arrangement does not deviate from a predetermined range at any point during the test run.

[0022] The inverters can be configured as active front-end inverters with bidirectional power flow. They can be used, in particular, as machine inverters in a drive test bench or as DC-DC converters in a battery test bench.

[0023] Further converter arrangements according to the invention can be used in hierarchical network structures for network balancing. According to the invention, at least two of the converters can be configured as network converters, in particular AC-DC converters, which supply separate subnetworks, preferably in the form of separate DC link circuits, from a central network. The control unit can be configured to modify the permissible electrical power range of the converters such that the power balance of the central network does not exceed a predetermined range. In this case, the control unit thus regulates the power distribution from the central network to the individual subnetworks in such a way that the power balance of the central network remains as close as possible to a specific power range.

[0024] According to the invention, such network structures can be provided with at least two further converters arranged in at least one of the subnetworks, the control unit being designed to also modify the permissible electrical power range of these converters in such a way that the power balance of each subnetwork does not exceed a predetermined range. This enables hierarchical network balancing; on the one hand at the level of the subnetworks, and on the other hand at the level of the central network.

[0025] The invention further relates to a test bench for preferably several test specimens, for example for the components of a drive or for electrical energy storage devices such as batteries, comprising a converter arrangement according to the invention. In particular, it can be provided that a DC link for power supply is included and that all converters are connected to the control unit via a bidirectional data bus.

[0026] The invention also relates to a method for operating a converter arrangement with at least two converters and a control unit connected to the converters, comprising the following steps: In a first step, the control unit transmits a permissible electrical power range to the converters, in particular a minimum power value Pmin and / or a maximum power value Pmax. In a further step, the control unit receives or calculates the current power balance of the individual converters. In a further step, the control unit calculates the power balance of the entire converter arrangement.In a further step, the control unit adapts the permissible electrical power range of the converters in such a way that the power balance of the entire converter arrangement does not leave a predetermined range if the voltage of a DC link supplying the converters falls below a predetermined threshold or exceeds a predetermined threshold.

[0027] The control unit continuously supplies the inverters with target values ​​for their electrical power. This can be a planned supply, for example during a test run, or an unplanned supply, for example in response to a driver request from a vehicle.

[0028] The control unit can use the input voltage of the inverters from at least one voltage sensor and the input currents of the inverters from current sensors to calculate the current power balance of the inverters. The control unit can also receive the voltage of a DC link from a voltage sensor.

[0029] The control unit can receive output voltages from voltage sensors and output currents from current sensors. The control unit adjusts the permissible electrical power range of the inverters if the voltage of the DC link supplying the inverters falls below or exceeds a predefined threshold.

[0030] The control unit can activate a discharge device connected to the control unit to reduce the voltage at a DC link if the voltage at the DC link exceeds a predetermined threshold.

[0031] The control unit can also modify the permissible electrical power range of the converters of a central network in such a way that the power balance of the converters of the central network does not leave a predetermined range, and modify the permissible electrical power range of the converters of at least one subnetwork in such a way that the power balance of the converters of each subnetwork does not leave a predetermined range.

[0032] The invention further extends to a computer-readable storage medium comprising computer-readable instructions that cause an electronic control unit, for example a computer, a microcontroller or a microprocessor, to execute a method according to the invention.

[0033] Further features of the invention will become apparent from the claims, the figures, and the following description of the figures. The invention is explained below with reference to non-exclusive embodiments. Fig. 1 shows a schematic block diagram of the topology of a converter arrangement according to the invention in a test bench for drives; Fig. 2 shows a schematic block diagram of the topology of an inverter arrangement according to the invention in a test bench for batteries (so-called battery cycler); Fig. 3a-3b show schematic block diagrams of the topologies of converter arrangements according to the invention in a hierarchical network structure with two subnetworks.

[0034] Fig. 1 Figure 1 shows a schematic block diagram of the topology of an embodiment of a converter arrangement according to the invention in a test rig for drives. The test rig comprises a Netzumrichter, which converts a central power supply 14 (multiphase AC mains voltage) available at the test bench into a DC voltage of approximately 820 V. This DC voltage is referred to as the intermediate circuit voltage (DC link) and is available at the test bench to supply the device under test. The power converter is a DC-DC converter in the form of a switched active front-end bridge rectifier.

[0035] In this embodiment, the test bench is designed for testing the electrical and mechanical components of a drive unit 13, comprising a drive assembly 11, for example, an electric motor, and a gearbox 12. The drive unit under test can be the drive unit of a motor vehicle, in particular an electric vehicle or a hybrid vehicle. In this embodiment, two electric machines 16, 16' (load machines, so-called dynamometers) are provided, which are coupled to the shaft of the drive unit 13. These electric machines 16, 16' are supplied by two inverters 7, 7' (machine inverters), which convert the DC link voltage VDC into an AC voltage. The inverters 7, 7' are designed as DC-AC converters, for example, as switched active front-end bridge inverters.

[0036] In addition to the mechanical drive train of the drive 13, the electrical drive unit 11 of the drive test specimen 13 is also tested in this embodiment.

[0037] For this purpose, the test bench includes a further bidirectional converter 7", which is connected to the DC link 9 and provides the drive unit 11 with a variable AC voltage. Depending on the operating state, the drive unit 11 either consumes power or supplies power to the DC link.

[0038] Current sensors 6, 6', 6" are arranged in the DC input lines of the inverters 7, 7', 7" and a voltage sensor 5 is arranged in the DC link 9. These sensors continuously supply measured values ​​of the voltage at the DC link 9 and the input currents of the inverters 7, 7', 7" to a control unit 1 via a data bus 10. In this embodiment, the inverter arrangement comprises the three inverters 7, 7', 7", but not the mains inverter.

[0039] The control unit 1 is also connected to the inverters 7, 7', 7" and to a discharge device 8 via the data bus 10. These connections serve to specify a permissible power range and, if necessary, a power setpoint P for the inverters, or to activate the discharge device 8 to reduce the voltage at the intermediate circuit 9.

[0040] In this embodiment, the control unit 1 is implemented as an electronic microcontroller with a central data processing unit (CPU) 2, for example, an ARM microprocessor or an ASIC. The data processing unit 2 is connected via a data bus to a memory unit 3 and an interface unit 4. The memory unit 3 can be any machine-readable data storage medium, for example, non-volatile semiconductor memory or volatile semiconductor memory, ROM, EPROM, EEPROM, RAM, SRAM, flash memory, and the like.

[0041] The interface unit 4 can be based on industry standards such as USB, FireWire, Ethernet, USART, I2S, and the like. Wireless network protocols such as Wi-Fi, Bluetooth, and the like can also be provided. Design elements of suitable control units are part of the well-known knowledge of those skilled in the art, so it is not necessary to explain every component of the control unit 1 in detail.

[0042] During operation, the control unit 1 continuously measures the voltage at the intermediate circuit 9 and the currents of the inverters 7, 7', 7", and provides the inverters 7, 7', 7" with target power values ​​and their permissible power ranges. If the DC voltage measured by the DC voltage sensor 5 falls below a predefined threshold, or if this DC voltage exceeds a predefined threshold, the control unit 1 adapts the permissible power range in such a way as to counteract the voltage drop or increase.

[0043] This ensures that the voltage at the intermediate circuit 9 always remains within a certain bandwidth, so that the power converter is only lightly loaded.

[0044] Ideally, the control unit 1 adapts the power flows of the converters 7, 7', 7" such that the grid converter only needs to cover the power losses. This can be achieved if at least one of the converters 7, 7', 7" supplies power to the DC link 9, and at least one of the converters 7, 7', 7" draws power from the DC link 9. The control unit 1 can be configured to actively generate such "back-to-back" operating states, even by modifying predefined test patterns. This allows for a particularly compact grid converter design.

[0045] Fig. 2 Figure 1 shows a schematic block diagram of the topology of another embodiment of a battery test bench according to the invention (so-called battery cycler). In this embodiment, four active front-end inverters 7, 7', 7", 7‴, controlled by the control unit 1, are provided. Each inverter is designed as a switched DC / DC converter and charges or discharges a battery 15, 15', 15", 15‴. In this embodiment, the inverter arrangement comprises the four inverters 7, 7', 7", 7‴, but not the mains inverter that generates the intermediate circuit voltage.

[0046] The operating principle of control unit 1 is similar to that in the embodiment shown below. Fig. 1 The control unit 1 adapts the permissible power ranges of the inverters 7, 7', 7", 7‴ such that the sum of the inverter powers is below a specified threshold.

[0047] If the voltage at the DC link 9 exceeds a predefined threshold, the control unit 1 activates a discharge unit 8, for example a heating resistor, to relieve the DC link. If the voltage at the DC link 9 falls below another threshold, the control unit 1 reduces the power output of individual or all inverters so that the voltage at the DC link 9 recovers.

[0048] Instead of individual batteries 15, 15', 15", 15‴, separate battery cells or battery modules (combinations of battery cells) can also be tested in embodiments not shown.

[0049] Fig. 3a-3b The schematic block diagrams of the topologies of the converter arrangements according to the invention are shown in a hierarchical network structure with two subnetworks. Fig. 3a Two subnetworks 17, 17' are provided, which are supplied by a central network 14 (3-phase AC network) via converters 7, 7'. In this embodiment, the converters 7, 7' are grid converters, i.e., rectifiers, each of which supplies a DC link 9, 9'. Voltage sensors 5, 5' are arranged in the DC links 9, 9', which transmit their measured values ​​to a control unit 1 via the data bus 10. Furthermore, current sensors 6, 6' are arranged in the DC lines of the converters 7, 7', which also transmit their measured values ​​to the control unit 1 via the data bus 10. The DC intermediate circuits 9, 9' supply two inverters for testing batteries 15 in the first subnetwork 17, and one inverter for operating an electric machine 16 for testing a drive test piece 13 in the second subnetwork 17'. However, these inverters are not connected to the control unit 1.

[0050] The control unit 1 ensures a balanced distribution between the two subnetworks 17, 17' by continuously transmitting permissible power ranges to the inverters 7, 7' via the data bus 10. If necessary, the control unit 1 can also activate one of the two discharge devices 8, 8' to reduce the voltage at the intermediate circuits 9, 9'. However, in this embodiment, the power output of the inverters in the subnetworks is not actively controlled.

[0051] Fig. 3b shows a direct further development of the embodiment according to Fig. 3aIn this embodiment, the two inverters 7", 7' of subnetwork 17, which test the batteries 15, are also connected to the control unit 1 via the data bus 10. Thus, the control unit 1 can not only balance the power of subnetworks 17, 17' with respect to the central network 14, but also supply the two inverters 7", 7' within subnetwork 17 with permissible power ranges such that the power balance in subnetwork 17 remains within a predefined range. Such an embodiment is particularly advantageous in practice, as it allows the operation of a wide variety of test systems on a common central network 14.

[0052] In further embodiments not shown, each inverter itself, rather than the control unit, is connected to internal or external voltage sensors for measuring its output voltage and to internal or external current sensors for measuring its output current. The inverter transmits these current and voltage measurements to the control unit, or calculates its current power balance itself and transmits this to the control unit. Naturally, embodiments are also provided in which some of the controlled inverters determine their own power balance, while others do not, and the control unit performs the calculation of the power balance for these inverters. The invention is not limited to the embodiments described above in this respect.

[0053] However, the invention is not limited to the present embodiments, but includes all converter arrangements and methods for operating converter arrangements within the scope of the following patent claims.

[0054] The terms used herein, such as converter, grid converter, or machine converter, should not be interpreted too narrowly. A converter according to the invention, whether a machine converter or a grid converter, can be understood to be any controlled electrical and / or electronic circuit that converts one DC voltage into another DC voltage or AC voltage, or one AC voltage into another AC voltage or DC voltage. Such a circuit may be, for example, but not exclusively, a direct converter, a matrix converter, an AC-to-DC converter, a DC-to-DC converter, a switched-mode bridge inverter, a switched-mode bridge rectifier, or the like. The specific circuit design of the converter is not essential.Converters provided according to the invention can also provide internal galvanic isolation and can be designed for high electrical power, for example powers in the range of 100 kW at a DC voltage of 850 V or 300 kVA AC power. Reference symbol list

[0055] 1 Control unit 2 Data processing unit 3 Storage unit 4 Interface unit 5, 5' Voltage sensor 6, 6', 6", 6‴ Current sensor 7, 7', 7", 7‴ Inverter 8, 8' Discharge device 9, 9' DC link 10 Data bus 11 Drive unit 12 Gearbox 13 Drive test specimen 14 Central network 15, 15', 15", 15‴ Battery 16, 16' Electric machine 17, 17' Subnetwork

Claims

1. Converter arrangement comprising at least two converters (7, 7') and a control unit (1) connected to the converters (7, 7'), the control unit (1) being configured to continuously or at discrete time intervals - transmit to the converters (7, 7') their permissible electrical power range, in particular their minimum power value Pmin and / or their maximum power value Pmax, - determine the current power balance of the individual converters (7, 7') or to receive it from them, and - calculate the power balance of the entire converter arrangement, - modify the permissible electrical power range of the converters (7, 7') such that the power balance of the entire converter arrangement does not leave a predetermined range, wherein the converter arrangement is characterized in that the control unit is configured to modify the permissible electrical power range of the converters (7, 7') when the voltage VDC of a DC link (9) supplying the converters (7, 7') falls below or exceeds a predetermined threshold value.

2. Converter arrangement according to claim 1, characterized in that the control unit (1) is connected to at least one voltage sensor for measuring the input voltage of the converters (7, 7') and to current sensors (6, 6') for measuring the input currents of the converters (7, 7') in order to determine the current power balance of the converters (7, 7').

3. Converter arrangement according to claim 1 or 2, characterized in that the converters (7, 7') are supplied by a DC link (9) and the control unit is connected to a voltage sensor (5) for measuring the voltage VDC of the DC link (9).

4. Converter arrangement according to any of claims 1 to 3, characterized in that the control unit (1) is connected to voltage sensors for measuring the output voltage of the converters (7, 7') and to current sensors for measuring the output currents of the converters (7, 7') in order to determine the current power balance of the converters (7, 7').

5. Converter arrangement according to any of claims 1 to 4, characterized in that the converters (7, 7') are connected to voltage sensors for measuring their output voltage and to current sensors for measuring their output currents, and are configured to transmit the measurement values to the control unit (1).

6. Converter arrangement according to any of claims 1 to 5, characterized in that a discharge device (8) connected to the control unit (1) is provided to reduce the voltage of a DC link (9), and that the control unit (1) is configured to activate the discharge device when the voltage of the DC link (9) exceeds a predetermined threshold value.

7. Converter arrangement according to any of claims 1 to 6, characterized in that the converters (7, 7') are designed as active-front-end converters with bidirectional power flow.

8. Converter arrangement according to claim 7, characterized in that the converters (7, 7') are used as machine converters in a drivetrain test bench or as DC-DC converters in a battery test bench.

9. Converter arrangement according to any of claims 1 to 8, characterized in that at least two of the converters (7, 7') are designed as grid converters, in particular AC-DC converters, which supply separate sub-networks (17, 17'), preferably in the form of separate DC links (9, 9'), from a central grid (14), the control unit (1) being configured to modify the permissible electrical power range of the converters (7, 7') such that the power balance of the converters (7, 7') of the central grid (14) does not leave a predetermined range.

10. Converter arrangement according to claim 9, characterized in that at least two additional converters (7", 7‴) are arranged in at least one of the sub-networks (17, 17'), the control unit (1) being configured to modify the permissible electrical power range of the converters (7", 7‴) such that the power balance of the converters (7", 7‴) of each sub-network (17, 17') does not leave a predetermined range.

11. Method for operating a converter arrangement with at least two converters (7, 7') and a control unit (1) connected to the converters (7, 7'), comprising the following steps: a. transmitting, by the control unit (1), a permissible electrical power range to the converters (7, 7'), in particular a minimum power value Pmin and / or a maximum power value Pmax, b. receiving or calculating, by the control unit (1), the current power balance of the individual converters (7, 7'), c. calculating, by the control unit (1), the power balance of the entire converter arrangement, d. adapting, by the control unit (1), the permissible electrical power range of the converters (7, 7') such that the power balance of the entire converter arrangement does not leave a predetermined range, and when the voltage VDC of a DC link (9) supplying the converters (7, 7') falls below or exceeds a predetermined threshold value.

12. Method according to claim 11, characterized in that the control unit (1) receives the input voltage of the converters (7, 7') from at least one voltage sensor (5) and the input currents of the converters (7, 7') from current sensors (6, 6') to calculate the current power balance of the converters (7, 7').

13. Method according to any of claims 11 or 12, characterized in that the control unit (1) receives the voltage VDC of the DC link (9) from a voltage sensor (5).

14. Method according to any of claims 11 to 13, characterized in that the control unit (1) receives the output voltages of the converters (7, 7') from voltage sensors and the output currents of the converters (7, 7') from current sensors.

15. Method according to any of claims 11 to 14, characterized in that the converters (7, 7') are connected to voltage sensors for measuring their output voltage and to current sensors for measuring their output currents, and transmit the measurement values to the control unit (1).

16. Method according to any of claims 11 to 15, characterized in that the control unit (1) activates a discharge device (8) connected to the control unit (1) to reduce the voltage of a DC link (9) when the voltage of the DC link (9) exceeds a predetermined threshold value.

17. Method according to any of claims 11 to 16, characterized in that the control unit (1) - modifies the permissible electrical power range of the converters (7, 7') of a central grid (14) such that the power balance of the converters (7, 7') of the central grid (14) does not leave a predetermined range, and - modifies the permissible electrical power range of the converters (7", 7‴) of at least one sub-network (17, 17') such that the power balance of the converters (7", 7‴) of each sub-network (17, 17') does not leave a predetermined range.

18. Computer-readable storage medium comprising computer-readable instructions that cause an electronic control unit (1), for example a computer, a micro-controller, or a microprocessor, to carry out a method according to any of claims 11 to 17.