Converter assembly and method for operating a converter assembly

Abstract

The invention relates to a converter assembly comprising at least two converters (7, 7) and a control unit (1) connected to the converters (7, 7), wherein the control unit (1) is designed, continuously or at discrete time intervals, to transmit to the converters (7, 7) their permissible electrical power range, in particular their minimum power value P.sub.min and/or their maximum power value P.sub.max, to determine the current power balance of the individual converters (7, 7) or to receive it from same, and to adjust the permissible electrical power range of the converters (7, 7) in such a way that the power balance of the entire converter assembly does not leave a predefined range. The invention also relates to a method for operating a converter assembly of this type.

Claims

1. Converter assembly comprising at least two converters and a control unit connected to the at least two converters, wherein the control unit is designed, continuously or at discrete time intervals, to transmit electrical power to the at least two converters, wherein the electrical power is within an electrical power range, of a minimum power value Pmin and a maximum power value Pmax, to determine the current electrical power balance of each of the at least two converters or to receive the electrical power balance from same, and to calculate the electrical power balance of the converter assembly, to adjust the electrical power range of each of the at least two converters, wherein the at least two converters are supplied by an intermediate circuit with voltage, VDC, the electrical power range adjusted if VDC falls below a predetermined value or exceeds a predetermined value, and to adjust the electrical power range of the at least two converters in such a way that the power balance of the converter assembly is within a predetermined range.

2. Converter assembly according to claim 1, wherein, in order to determine the current power balance of the at least two converters, the control unit is connected to at least one voltage sensor to measure the input voltage of each of the at least two converters and to current sensors to measure the input currents of each of the at least two converters.

3. Converter assembly according to claim 1, wherein the control unit is connected to a voltage sensor to measure the VDC.

4. Converter assembly according to claim 1, wherein, to determine the current power balance of the at least two converters, the control unit is connected to voltage sensors to measure the output voltage of the at least two converters and to current sensors to measure the output currents of the at least two converters.

5. Converter assembly according to claim 1, wherein the at least two converters are connected to voltage sensors to measure their output voltage and to current sensors to measure their output currents, and transmit the measured values to the control unit.

6. Converter assembly according to claim 1, wherein a discharge device connected to the control unit is provided to reduce the voltage in the DC voltage intermediate circuit, wherein the control unit activates the discharge device if the VDC exceeds a predetermined value.

7. Converter assembly according to claim 1, wherein the at least two converters are active front-end converters with bidirectional power flow.

8. Converter assembly according to claim 1, wherein the active front-end converters are machine converters in a drive test stand or DC-DC converters in a battery test stand.

9. Converter assembly according to claim 1, having at least four converters, wherein at least two of the converters are designed as line AC-DC converters, each of the line AC-DC converters supply separate sub-networks as separate DC voltage intermediate circuits, from a central network, wherein the control unit adjusts the electrical power range of the line converters in such a way that the power balance of the at least two line converters of the central network is within a predetermined range.

10. Converter assembly according to claim 9, wherein at least two line converters are arranged in at least one of the separate sub-networks, wherein the control unit adjusts the electrical power range of the the at least two line converters in such a way that the power balance of the line converters of each sub-network is within a predetermined range.

11. Method for operating a converter assembly with at least two converters and a control unit connected to each of the at least two converters, comprising the following steps: a. transmitting, via the control unit (1), electrical power to each of the at least two converters, in a range with a minimum power value Pmin and a maximum power value Pmax, b. receiving or calculating, via the control unit, the current power balance of the each of the at least two converters, c. calculating, via the control unit, the power balance of the converter assembly, d. adapting, via the control unit, the electrical power range of the at least two converters if the voltage VDC of a DC voltage intermediate circuit supplying each of the at least two converters falls below a predetermined value or exceeds a predetermined value, and e. adapting, via the control unit, the electrical power range of the at least two converters in such a way that the power balance of the converter assembly is within a predetermined range.

12. Method according to claim 11, wherein, in order to calculate the current power balance of the at least two converters, the control unit receives the input voltage of the at least two converters from at least one voltage sensor and the input currents of the at least two converters from current sensors.

13. Method according to claim 11, wherein the control unit receives the VDC from a voltage sensor.

14. Method according to claim 11, wherein the control unit receives the output voltages of the at least of two converters from voltage sensors and the output currents of the at least two converters from current sensors.

15. Method according to claim 11, wherein the at least two converters are connected to voltage sensors to measure output voltages and to current sensors to measure output currents, and transmits the measured values to the control unit.

16. Method according to claim 11, wherein the control unit activates a discharge device connected to the control unit to reduce the VDC if the VDC exceeds a predetermined value.

17. Method according to claim 11, wherein the control unit, adjusts the electrical power range of the at least two converters of a central network in such a way that the power balance of the at least two converters of the central network is within a predetermined range, and adjusts the electrical power range of the at least two converters of at least one sub-network in such a way that the power balance of the at least two converters of each sub-network is within a predetermined range.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Further features according to the invention arise from the claims, the figures and the following description of the figures. The invention is explained below on the basis of non-exclusive exemplary embodiments.

(2) FIG. 1 shows a schematic block diagram of the topology of a converter assembly according to the invention in a test stand for drives;

(3) FIG. 2 shows a schematic block diagram of the topology of a converter assembly according to the invention in a test stand for batteries (so-called battery cycler);

(4) FIGS. 3a-3b show schematic block diagrams of the topologies of converter assemblies according to the invention in a hierarchical network structure with two sub-networks.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(5) FIG. 1 shows a schematic block diagram of the topology of an exemplary embodiment of a converter assembly according to the invention in a test stand for drives. The test stand includes a line converter that converts a central network 14 (multiphase AC line voltage) available at the test stand into a DC voltage of around 820 V. This DC voltage is referred to as intermediate circuit voltage (DC link) and is available at the test stand to supply the device under test. The line converter is a DC voltage converter (AC-DC converter) in the form of a switched active front-end bridge rectifier.

(6) In this exemplary embodiment, the test stand is designed for testing the electrical and mechanical components of a drive device under test 13 with a drive unit 11, for example an electric motor, and a transmission 12. The drive which is to be tested may be the drive of a motor vehicle, in particular an electric vehicle or a hybrid vehicle. In this exemplary embodiment, two electrical machines 16, 16 (load machines, so-called dynamometers) are provided which are coupled to the shaft of the drive device under test 13. These electrical machines 16, 16 are supplied by two converters 7, 7 (machine converters) which convert the intermediate circuit DC voltage V.sub.DC into an AC voltage. The converters 7, 7 are designed as AC voltage converters (DC-AC converters), for example as switched active front-end bridge inverters.

(7) In addition to the mechanical drive train of the drive 13, the electric drive unit 11 of the drive device under test 13 is also tested in this exemplary embodiment.

(8) For this purpose, the test stand includes a further bidirectional converter 7 which is connected to the intermediate circuit 9 and provides the drive unit 11 with a variable AC voltage. Depending on the operating state, the drive unit 11 consumes power or supplies power to the intermediate circuit.

(9) Current sensors 6, 6, 6 are arranged in the DC voltage input lines of the converter 7, 7, 7, and a voltage sensor 5 is arranged in the DC voltage intermediate circuit 9. These sensors continuously supply measured values of the voltage in the intermediate circuit 9 and the input currents of the converters 7, 7, 7 to a control unit 1 via a data bus 10. In this exemplary embodiment, the converter assembly includes the three converters 7, 7, 7, but not the line converter.

(10) The control unit 1 is connected to the converters 7, 7, 7 and to a discharging device 8, likewise via the data bus 10. These connections are used to specify for the converters a permissible power range and, optionally, a power setpoint P.sub.soil, or to activate the discharge device 8 to reduce the voltage in the intermediate circuit 9.

(11) In this exemplary embodiment, the control unit 1 is designed 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 to a storage unit 3 and an interface unit 4 via a data bus. The storage unit 3 can be any machine-readable data memory, for example a non-volatile semiconductor memory or volatile semiconductor memory, ROM, EPROM, EEPROM, RAM, SRAM, flash memory and the like.

(12) The interface unit 4 can be based on industry standards such as USB, FireWire, Ethernet, USART, I2S and the like. Wireless network protocols can also be provided, such as Wi-Fi, Bluetooth and the like. Embodiments of suitable control units are part of the general expertise of the skilled person, so that not every component of the control unit 1 needs to be explained in detail.

(13) During operation, the control unit 1 continuously measures the voltage in the intermediate circuit 9 and the currents of the converters 7, 7, 7, and provides the converters 7, 7, 7 in each case with power setpoints and their permissible power ranges. If the DC voltage measured by the DC voltage sensor 5 falls below a predetermined threshold value, or if this DC voltage exceeds a predetermined threshold value, then the control unit 1 adapts the permissible power range in such a way that the voltage drop or voltage rise is counteracted.

(14) This ensures that the voltage in the intermediate circuit 9 always remains within a certain bandwidth, so that the line converter is only moderately loaded.

(15) Ideally, the control unit 1 adapts the power flows of the converters 7, 7, 7 in such a way that the line converter is only required to the cover the power loss. This can be achieved if at least one of the converters 7, 7, 7 supplies power to the intermediate circuit 9, and at least one of the converters 7, 7, 7 draws power from the intermediate circuit 9. The control unit 1 may be designed to actively induce such back-to-back operating states, even if this involves modifying predefined test models. This makes it possible to achieve a particularly compact dimensioning of the line converter.

(16) FIG. 2 shows a schematic block diagram of the topology of another exemplary embodiment of a test stand for batteries according to the invention (so-called battery cycler). In this exemplary embodiment, four active front-end converters 7, 7, 7, 7 controlled by the control unit 1 are provided which are each designed as switched DC/DC converters and which charge or discharge a battery 15, 15, 15, 15. In this exemplary embodiment, the converter assembly includes the four converters 7, 7, 7, 7, but not the line converter which generates the intermediate circuit voltage.

(17) The functionality of the control unit 1 is similar to the exemplary embodiment according to FIG. 1. The control unit 1 adapts the permissible power ranges of the converters 7, 7, 7, 7 in such a way that the sum of the powers of the converters lies below a predetermined threshold value.

(18) In the event that the voltage in the intermediate circuit 9 exceeds a predetermined threshold value, the control unit 1 activates a discharge unit 8, for example a heating resistor, in order to relieve the intermediate circuit. In the event that the voltage in the intermediate circuit 9 falls below a different threshold value, the control unit 1 reduces the power ranges of individual or all converters, so that the voltage in the intermediate circuit 9 recovers again.

(19) Instead of the individual batteries 15, 15, 15, 15, in exemplary embodiments which are not shown, separate battery cells or battery modules (combinations of battery cells) can also be tested.

(20) FIGS. 3a-3b show schematic block diagrams of the topologies of converter assemblies according to the invention in a hierarchical network structure with two sub-networks. In FIG. 3a, two sub-networks 17, 17 are provided which are supplied by a central network 14 (3-phase AC network) via converters 7, 7. In this exemplary embodiment, the converters 7,7 are line converters, i.e. rectifiers which each supply a DC voltage intermediate circuit 9, 9. Voltage sensors 5, 5 are arranged in the DC voltage intermediate circuits 9, 9 which supply 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 supply their measured values to a control unit 1 via the data bus 10. The DC voltage intermediate circuits 9, 9 supply two converters for testing batteries 15 in the first sub-network 17, and in the second sub-network 17 supply a converter for operating an electrical machine 16 for testing a drive device under test 13. However, these converters are not connected to the control unit 1.

(21) The control unit 1 ensures a measured balance between the two sub-networks 17, 17 by continuously transmitting permissible power ranges to the converters 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 in the intermediate circuits 9, 9. However, an active influencing of the powers of the converters in the sub-networks does not take place in this exemplary embodiment.

(22) FIG. 3b shows a direct further development of the exemplary embodiment according to FIG. 3a. In this exemplary embodiment, the two converter 7, 7 of the sub-network 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 the sub-networks 17, 17 with respect to the central network 14 but also, within the sub-network 17, supply the two converters 7, 7 with permissible power ranges in such a way that the power balance in the sub-network 17 remains within a predetermined range. Such a design is particularly advantageous in practice, since it allows the operation of various test systems on a common central network 14.

(23) In other exemplary embodiments, not shown, not the control unit, but each converter itself is connected to internal or external voltage sensors to measure their output voltage and to internal or external current sensors to measure their output currents. The converter transmits these measured values for current and voltage to the control unit, or calculates its current power balance itself and transmits this to the control unit. Naturally, exemplary embodiments are also envisaged in which some of the controlled converters determine their power balance themselves, and others do not determine their power balance themselves; instead, the control unit is responsible for determining the power balance of these converters. In this respect, the invention is not limited to the exemplary embodiments described above.

(24) However, the invention is not limited to the present exemplary embodiments, but includes all converter assemblies and methods for operating converter assemblies within the framework of the following claims.

(25) Terms used herein such as converter, line converter or machine converter should not be interpreted too narrowly. A converter according to the invention, be it a machine converter or a line converter, can be understood as any controlled electrical and/or electronic circuit that converts one DC voltage into another DC voltage or AC voltage, or converts an AC voltage into another AC voltage or DC voltage. Such a circuit may for example, but not exclusively, be a direct converter, a matrix converter, an AC voltage converter, a DC voltage converter, a switched bridge inverter, a switched bridge rectifier or the like. The concrete realisation of the converter in terms of circuitry is not critical. Converters provided according to the invention can also feature internal galvanic isolation and can be intended for high electrical powers, for example powers in the region of 100 kW at a DC voltage of 850 V or 300 kVA alternating current power.

LIST OF REFERENCE SIGNS

(26) 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, 77 converter 8, 8 discharge device 9, 9 DC voltage intermediate circuit 10 data bus 11 drive unit 12 transmission 13 drive device under test 14 central network 15, 15, 15, 15 battery 16, 16 electrical machine 17, 17 sub-network