AT523199A1 - Converter device, test system and method for controlling a converter device - Google Patents

Abstract

The invention relates to a converter device (10), in particular for a vehicle (4), having a converter unit (11) for connecting an AC voltage unit (3) to a DC voltage unit (2), the converter unit (11) having at least one first converter stage (20) and a second converter stage (30) each having switching elements (22, 32) for converting (104) a current between the DC voltage unit (2) and the AC voltage unit (3). The invention also relates to a test system and a method (100).

Description

Converter device, test system and method for controlling a

Converter device

The present invention relates to a converter device with a converter unit for connecting an AC voltage unit to a DC voltage unit with integrated galvanic isolation, a test system, in particular a battery test system, and a method for controlling a

Converter device.

Power converters are known from the prior art, for example in order to convert an alternating voltage into a direct voltage or vice versa. A converter for a battery charger of an electric vehicle is known, for example, from US 2012/0229088 A1.

It is known to provide the conversion in several stages, which are designed differently in terms of circuitry. As a result, in particular a voltage drop can be limited in stages, as a result of which the service life of installed semiconductor components can be extended. In this case, however, it is disadvantageous that high losses occur in the stages, in particular on semiconductor switches. In particular, if the converter is to be operated over a wide current and voltage range, known converters often cannot prevent high losses. The semiconductor components are mostly operated with what is known as the DC link voltage, in particular at the stage on the DC side. H. a voltage that is applied to an intermediate circuit of the DC-side stage and through the DC source, such as. B. a battery is specified. However, this can reduce the efficiency and the efficiency of the power converter device

be negatively influenced. The object of the present invention is that described above

The problem has to be taken into account at least in part. In particular, it is the object of the present invention to reduce losses in the transmission of energy through a

To reduce power converter device and for the power converter device at the same time

to create the widest possible range of applications.

The above object is achieved by a converter device with the features of claim 1, a test system with the features of claim 14, and a method with the features of claim 15. Further features and details of the invention emerge from the respective subclaims, the description and the drawings. Features and details that are described in connection with the converter device according to the invention naturally also apply in connection with the test system according to the invention and / or the method according to the invention and in each case vice versa, so that with regard to the disclosure of the individual aspects of the invention

is or can be mutually referenced.

According to a first aspect of the invention, a power converter device is provided which has a power converter unit for connecting an AC voltage unit to a DC voltage unit. The converter unit has at least a first converter stage and a second converter stage for converting a current between the DC voltage unit and the AC voltage unit. Furthermore, the first converter stage has an AC voltage connection for the electrically conductive connection to the AC voltage unit. The second converter stage has a DC voltage connection for the electrically conductive connection to the DC voltage unit. The second converter stage has at least four bridge units. The converter device also has a control unit with a first operating module for controlling the bridge units in at least one first operating mode for a high-power range, in particular the second converter stage or the converter device, and a second operating module for controlling the bridge units in a second operating mode for a low-power range, in particular the second Converter stage or the converter device on. In the first operating mode the bridge units can be operated in a first switching state and in the second operating mode at least two of the bridge units are in the first switching state and, in particular at the same time, at least two of the bridge units are in one

second switching state operable.

The AC voltage unit can be an alternating current source, such as a power grid, or a consumer that is operated with alternating current. The DC voltage unit can be a direct current source, such as a battery, or a consumer that is operated with direct current. The DC voltage unit is preferably a vehicle battery, in particular a traction battery of a vehicle, which can be used for charging the vehicle battery as a consumer and / or for discharging the vehicle battery as a direct current source.

The converter unit is designed in particular in two stages. The first converter stage is preferably electrically connected directly to the second converter stage. The first converter stage is designed in particular to convert a direct voltage into an alternating voltage and / or vice versa. The first converter stage can preferably be a rectifier, inverter and / or an AC / DC converter. The second converter stage is designed in particular for converting between two DC voltages. The second converter stage can preferably be a DC voltage converter and / or a DC / DC converter. The AC voltage connection and the DC voltage connection can be electrical contact points to which the AC voltage unit and / or the DC voltage unit can be connected. However, it is also conceivable for the AC voltage unit and / or the DC voltage unit to be permanently connected to the converter unit via the AC voltage connection and / or the DC voltage connection. To convert the current between the DC voltage unit and the AC voltage unit, the first and second converter stages can each have switching elements. The switching elements can advantageously be semiconductor switches. In particular, switching elements of the second converter stage for converting the current are integrated into the bridge units. The respective switching state can also include, for example, an in particular evenly alternating switching sequence of switching elements of the bridge units.

Thus, different operating modes can preferably be provided for different power ranges. This makes it possible for the operating modes to be matched to the respective power range and for circuit losses to be kept low as a result. In particular, the control unit can thus control the bridge units as a function of the power range. The high-power range can preferably include rated powers of 40% to 100% of the maximum rated power of the converter device. The lowest power range can advantageously include nominal powers of less than 40% of the maximum nominal power, in particular less than 20% or even a reduction to zero. Through the two operating modes, a current can be kept below a maximum current limit of the converter device, even if, for. B. a voltage of the DC voltage unit drops. The control unit can preferably have a processor and / or a microcontroller. The control of the converter unit by the control unit can in particular be understood to mean controlling and / or regulating the converter unit. The converter device can preferably have exactly four bridge units. The bridge units can enable efficient operation of the switching elements and / or a broad power range of the converter device can be enabled as a function of activation of the bridge units. However, it is also conceivable that more than four bridge units are provided. In this case, an even number of bridge units can preferably be provided. As a result, the second switching state can be produced in pairs.

Overall, this results in a high and broad power range for the converter device, preferably from zero to the nominal power. For example, the power range can be up to 60kW. Different combinations of current intensities and electrical voltages are preferably conceivable. Furthermore, the converter device can be operated with a high degree of efficiency. In particular, an efficiency of 98% over both converter stages and / or an efficiency of over 99% for the second converter stage can be achieved.

Furthermore, it is conceivable in a converter device according to the invention that the first switching state of the bridge units comprises a power flow in a first direction. In particular, it can be provided that the converter unit can be operated in a charging mode for charging the DC voltage unit and in a discharge mode for discharging the DC voltage unit. In particular, the power flow and / or the first direction can be defined by the charging or discharging process. In particular, the first operating mode can include operating all bridge units in charging mode or operating all bridge units in discharging mode. During the charging process, the power flow can be oriented in the direction of the DC voltage unit and during the discharging process in the direction of the AC voltage unit. As a result, charging and / or discharging of the DC voltage unit can be carried out by the converter device.

In a converter device according to the invention, the second switching state of the bridge units can preferably include a power flow in a second direction which is opposite to the first direction. In particular, it can be provided that the first operating module of the control unit is designed to orient a power flow between the AC voltage unit and the DC voltage unit, in particular completely, in the first direction in the first operating mode, in particular wherein the second operating module of the control unit is designed to be oriented in the second Operating mode to orient a power flow between the AC voltage unit and the DC voltage unit partly in the first direction and partly in the opposite direction in the second direction. The bridge units of the second converter stage can preferably be operable in the second operating mode, in particular alternately, in each case or in pairs in the charging mode and / or in the discharging mode. Thus, in the second operating mode, preferably two of the bridge units, in particular a parallel pair, can be operated in the charging mode and two of the bridge units, in particular a parallel pair, can be operated in the discharging mode. In the first operating mode, all the bridge units of the second converter stage can preferably be operable together either in the charging mode or in the discharging mode. The second converter stage can preferably be controllable in the second operating mode in such a way that the bridge units, in particular in pairs, can be switched offset, in particular

wherein the first operating module is designed to switch the bridge units together in the first operating mode. Preferably, two bridge units connected in series can be switched together in each case in the second operating mode. Furthermore, an intermediate circuit element can thereby be stabilized in the lowest power range. With four bridge units, the converter unit, in particular the second converter stage, can be operated with an advantageous phase shift.

In a converter device according to the invention, it can advantageously be provided that the control unit has a third operating module for controlling the bridge units in a third operating mode for a low-power range with improved effectiveness, with at least two of the bridge units in the first switching state and, in particular simultaneously, at least two of the Bridge units can be operated in a third switching state, in particular wherein the third switching state of the bridge units includes a deactivation of the, in particular respective, bridge units. The low-power range can be understood to mean, in particular, a power range between the low-power range and the high-power range. In the third operating mode, the low-power range preferably comprises nominal powers of more than 20% and less than 50% of the maximum nominal power of the converter device. The lowest power range in the second operating mode can preferably include rated powers from 0 to 20% of the maximum rated power of the converter device. When deactivating, it can be provided that the respective bridge units, i.e. in particular the bridge units in the third switching state, are switched off and / or do not transmit any power. If there are more than four bridge units, the third switching state can preferably be in pairs

be producible.

Furthermore, in a converter device according to the invention, it can advantageously be provided that the control unit has a circulation module in order to switch the bridge units in a circulating manner in the second and / or third operating mode, in particular in pairs. The bridge units can preferably be offset in pairs and can be switched in a circulating manner. In particular, this can enable interleaved operation of the bridge units. This in turn can be high

Enable frequencies on the intermediate circuit element and / or on the output element,

7735

whereby components can be dimensioned smaller and / or the

Converter unit can have an improved efficiency.

The second converter stage in a converter device according to the invention is preferably electrically coupled to the first converter stage on a circuit inside via an intermediate circuit element for carrying an intermediate circuit voltage, in particular that is generated when converting the current between the DC voltage unit and the AC voltage unit, and has the second converter stage on a circuit outside DC voltage connection for the electrically conductive connection to the DC voltage unit. The inside and outside of the circuit represent, in particular, electrical interfaces of the second converter stage, at which the second converter stage is designed for an electrically conductive connection to further components. When the intermediate circuit voltage is passed through the intermediate circuit element, energy can be temporarily stored. The intermediate circuit element can form an intermediate circuit which is connected between the first and second converter stage. To carry the intermediate circuit voltage, the intermediate circuit element can have at least one intermediate circuit capacitance, for example in the form of an intermediate circuit capacitor. The intermediate circuit element can preferably be provided with several, preferably two, intermediate circuit capacitances. The intermediate circuit capacitances can each be related to a neutral conductor, so that a positive and / or a negative portion of the intermediate circuit voltage can be divided between the intermediate circuit capacitances. The intermediate circuit voltage can in particular be a voltage at an intermediate circuit capacitance of the intermediate circuit element. In particular, the intermediate circuit voltage can also be referred to as a DC link voltage. A further intermediate circuit element can also be connected to the DC voltage connection

be provided.

Furthermore, it can advantageously be provided that the circuit inside and the circuit outside of the second converter stage are designed asymmetrically and / or symmetrically to each other in order to the switching elements of the second converter stage, in particular when the presence or generation of the

Intermediate circuit voltage on the intermediate circuit element, below an operating voltage

operate which, in particular in terms of amount, is lower than the intermediate circuit voltage. A switchover unit can preferably be used to switch between the asymmetrical and the symmetrical design. The fact that the inside and outside of the circuit of the second converter stage are asymmetrical to one another can be understood to mean that the inside and outside of the circuit are different, in particular have different interconnections. With a symmetrical design, the interconnections can be the same on both sides. Thus, in particular through a clever interconnection of the first converter stage, it can be achieved that the operating voltage of the switching elements of the second converter stage is lower than the intermediate circuit voltage. The switching elements of the second converter stage can preferably be operated at an operating voltage of the switching elements of, in particular, less than 80% of the intermediate circuit voltage, particularly preferably of, in particular, 50% of the intermediate circuit voltage, in particular. It can also advantageously be provided that the switching elements of the first converter stage can be operated at an operating voltage which is lower than the intermediate circuit voltage. The converter device can thereby preferably be operable with a nominal power at the DC voltage connection and / or at the AC voltage connection with a voltage range of 5V to 200V and / or with a current range of 0A or essentially 0A to 600A. Preferably, an asymmetrical design is used for a high-current operating mode of the second converter stage and a symmetrical design of the second converter stage is used for a high-voltage operating mode.

Because of the lower operating voltage in the second converter stage, losses in the converter device can be reduced. Thus, the efficiency of the power converter device can be increased. In particular, the operating voltage is adapted to the design of the transformer ratio. In particular over a wide range of achievable currents and / or achievable voltages, the different operating modes can enable efficient operation of the converter device. Furthermore, the reactive components of the switching elements in particular can have smaller dimensions. By dividing the switching elements over several bridge units, the

asymmetrical design of the circuit inside and the circuit outside of the second converter stage are made possible. In particular in combination with semiconductor components, the bridge units can advantageously be controllable in order to enable the current to be converted by switching the switching elements. If exactly four bridge units are provided, it can be achieved that the operating voltage of the switching elements is 50% of the intermediate circuit voltage. In particular, the asymmetrical configuration of the inside and outside of the circuit can enable interleaved operation.

Furthermore, it is conceivable in a converter device according to the invention that each of the bridge units has two active full bridge elements that are galvanically separated from one another. In particular, a transformer element, preferably in the form of a high-frequency transformer, can be arranged between the full bridge elements. The bridge units can in particular be designed as dual-active bridges. The full bridge elements can each have four switching elements, preferably in the form of semiconductor switches. As a result, the conversion of the current between the alternating current source and the direct current source, in particular bidirectionally, can be improved. Furthermore, the bridge units can be operated for a high frequency range, so that in particular there is an advantageous combination option with the asymmetrical configuration of the inside and outside of the circuit and a transformer in the intermediate circuit element can be dimensioned smaller. As a result, a leakage inductance of the transformer element can advantageously be used with the choke to avoid high operating frequencies.

The series-parallel connection can include that the bridge units on the inside of the circuit are partially or completely connected in parallel to one another and two or more bridge units connected in parallel to one another are connected in series with one another. It can preferably be provided that two bridge units are each connected in parallel to form a parallel pair and the two parallel pairs are connected in series. The bridge units can thus be arranged in a cascade, in particular in a two-two pattern.

Furthermore, in a converter device according to the invention, it can advantageously be provided that the first converter stage has at least one three-stage converter unit, preferably three three-stage converter units. In particular, the at least one converter unit can have a 3L-NPC topology, i. H. the at least one three-stage converter unit can be a converter of the type of a three-stage neutral-point-clamped converter. As a result, the converter unit can be designed in particular for high power ranges and / or with reduced EMC filter measures for the converter device. At the same time, losses due to the three-stage converter unit can also be kept low in high power ranges

become.

It is also conceivable in a converter device according to the invention that the AC voltage connection of the first converter stage has at least three phase connections, which are in particular connected to the converter units in the middle of the steps. As a result, the converter device can be designed in particular for polyphase AC voltage units. In particular, such AC voltage units have high power ranges in which circuit losses can lead to correspondingly high energy losses. Consequently, due to the combination with the asymmetrical configuration of the circuit inside and the circuit outside and the low operating voltage of the switching elements made possible by this, a high energy loss can occur even in the case of a polyphase AC voltage unit with a high power range

be prevented.

In a converter device according to the invention, the control unit can preferably have a direction module for bidirectional operation of the converter unit. By means of the direction module, the converter unit can preferably be switchable between the charging mode and the discharging mode. This can influence the direction of a power flow. In particular, the converter unit can be operated bidirectionally. This enables both discharging and charging of the DC voltage unit. These include, in particular, an energy withdrawal from and a

Understand energy return to the AC voltage network.

Furthermore, it is conceivable in a converter device according to the invention that a measuring device for determining the power range is connected to the DC voltage connection. The measuring device can preferably have a data communication connection with the control unit in order to forward measurement results to the control unit. The measuring device can thus regularly or continuously check a current input and / or output power of the converter device in order to be able to implement advantageous control, in particular in the high, low and / or low power range. The measuring device can have a voltmeter and / or an ammeter to determine the current parameters

To be able to measure the performance range.

It is also conceivable in a converter device according to the invention that the second converter stage, in particular on the outside of the circuit, has a switching unit for switching between a high-voltage operating mode and a high-current operating mode, in particular the bridge units in the high-current operating mode, in particular on the outside of the circuit, in a parallel connection and in the High voltage mode are connected in a series parallel connection. As a result, a voltage range and / or a current range of the converter device can be increased even further. In particular, it can be provided that the converter device can be operated in the high-voltage operating mode with a higher output voltage than in the high-current operating mode and in the high-current operating mode with a higher current than in the high-voltage operating mode. In the high-voltage operating mode, the converter device can be or can be operated in particular at a direct voltage of up to 400V and a current strength of up to 150A. In the high-current operating mode, the converter device can be or can be operated in particular at a direct voltage of up to 200V and a current strength of up to 300A.

According to a further aspect of the invention, a test system for testing a DC voltage unit in the form of an energy store, in particular for a vehicle, is provided. The test system has an alternating voltage unit, in particular in the form of an electrical machine or an alternating current network, and the direct voltage unit. It is also provided that the

AC voltage unit and the DC voltage unit are connected by a converter device according to the invention, in particular in

bidirectional and galvanically isolated way.

A test system according to the invention thus brings the same advantages as have already been described in detail with reference to a converter device according to the invention. The test system allows the energy store to be operated, in particular, in a discharging and / or charging mode. Ripple currents can be induced or impressed and / or the battery behavior can be tested and / or monitored in different operating situations. In particular, with the converter device according to the invention, this is possible with low losses in a wide power range. The energy store is preferably a battery module, a battery cell or a battery. The battery module can comprise several interconnected battery cells. It is conceivable that the DC voltage unit has a plurality of battery modules which are connected to the converter device. In particular, the entire battery of the vehicle can be connected to the converter device. The vehicle can preferably be at least partially electrically operated

Act as a motor vehicle or a rail vehicle.

According to a further aspect of the invention, a method for controlling a converter device, in particular a converter device according to the invention, is provided. The converter device is connected to an AC voltage unit and a DC voltage unit, so that a current between the AC voltage unit and the DC voltage unit can be converted via a first and a second converter stage of the converter device. To convert the current between the AC voltage unit and the DC voltage unit, the bridge units for a high-power range are controlled in a first operating mode, in which the bridge units are operated in a first switching state, and the bridge units for a low-power range are controlled in a second operating mode, in which at least two of the bridge units in the first switching state and at least two of the bridge units

can be operated in a second switching state.

A current can be converted between the AC voltage unit and the DC voltage unit, for example, by switching elements of the first and second converter stages, in particular when the intermediate circuit voltage is present. In this case, at least the switching elements of the second converter stage can be operated at an operating voltage which, in particular in terms of amount, is lower than an intermediate circuit voltage that is generated between the first converter stage and the second converter stage

becomes.

In particular, the method can further comprise the following step:

- Generating the intermediate circuit voltage between the first converter stage and the second converter stage, in particular when converting a current between the AC voltage unit and the DC voltage unit.

The converter device can advantageously be part of a test system according to the invention. The intermediate circuit voltage can be generated before the current is converted or at the same time as the current is converted. In particular, it is also conceivable that the intermediate circuit voltage is generated by partially converting the current by the first or second converter stage. The method steps can preferably be carried out or initiated by a control unit of the converter device.

It is also conceivable in a method according to the invention that the method comprises the following steps:

- Determination of a power range of the converter device,

Control of a second converter stage as a function of the power range, the second converter stage being controlled with a first operating mode when the converter device is in a high-power range, and with a second operating mode when the converter device is in a very low-power range.

The power range can be determined by a measuring device and / or a control unit of the converter device. For this purpose, a voltage and a current can be measured at the DC voltage connection and / or at the AC voltage connection. The two, in particular three, operating modes can provide an advantageous switching option for the second converter stage as a function of the power range. As a result, efficient operation of the converter device can be made possible over a wide power range.

Furthermore, in a method according to the invention it can advantageously be provided that when the second converter stage is activated in the first operating mode, a power flow between the AC voltage unit and the DC voltage unit is oriented, in particular completely, in a first direction, in particular with a power flow between the AC voltage unit and the DC voltage unit in the second operating mode is oriented partially in the first direction and partially in a second direction, which is opposite to the first direction. Provision can preferably be made for the second converter stage to be operated in the second operating mode in a circulation mode in which an orientation of the power flow, in particular in an oscillating manner, is changed. In particular, bridge units or pairs of bridge units of the second converter stage can be operated alternately in the predetermined direction and the direction opposite to the predetermined direction. Furthermore, it can be provided that the second converter stage is operated in a third operating mode for a low-power range. In the third operating mode, at least two of the bridge units can advantageously be operated in the first switching state and at least two of the bridge units can be operated in a third switching state. The third switching state of the bridge units can

preferably include a deactivation of the respective bridge units.

Further measures improving the invention emerge from the following description of various exemplary embodiments of the invention, which are shown schematically in the figures.

They each show schematically:

Figure 1 shows a converter device according to the invention with a first and

a second converter stage in a schematic representation,

Figures 2-4 the second converter stage in a first, a second and a

third operating mode in a high current operating mode,

FIG. 5 shows the second converter stage in a high-voltage operating mode,

FIG. 6 shows a method according to the invention for operating the converter device according to the invention,

FIG. 7 power ranges of the converter device according to the invention in a diagram.

Elements with the same function and mode of operation are shown in FIGS. 1 to 7

each provided with the same reference numerals.

FIG. 1 shows a test system according to the invention for testing a DC voltage unit 2. A converter device 10 according to the invention is connected between the DC voltage unit 2 and an AC voltage unit 3. The converter device 10 is connected to the direct voltage unit 2 via a direct voltage connection 34 and to the alternating voltage unit 3 via an alternating voltage connection 24. In order to convert a current between the AC voltage unit 3 and the DC voltage unit 2, the converter device 10 has a converter unit 11 with a first converter stage 20 and a second converter stage 30. The first converter stage 20 is preferably designed as an AC / DC converter and the second converter stage 30 as a DC / DC converter. The converter unit 11 is bidirectional, so that a power flow 202 both from the AC voltage unit 3 to the DC voltage unit 2 and from the

DC voltage unit 2 can be directed to AC voltage unit 3. The converter unit 11 is designed to be galvanically insulated by the converter stage 30.

The alternating voltage unit 3 is a polyphase, in particular three-phase alternating voltage unit 3. Therefore, the alternating voltage connection 24 has three phase connections 24.1. The first converter stage 20 also has three three-stage converter units 21, in particular with a 3L-NPC topology. Each of the converter units 21 has four switching elements 22, by means of which a conversion of the current between the AC voltage unit 3 and the second converter stage 30 is made possible.

The first converter stage 20 is also connected to the second converter stage 30 on a circuit inside 23 of the second converter stage 30 via an intermediate circuit element 25. The intermediate circuit element 25 has two intermediate circuit capacitors 25.1, in particular in the form of intermediate circuit capacitors. When the converter device 10 is in operation, the intermediate circuit element 25 carries an intermediate circuit voltage 200. To convert 104 a DC voltage between the first converter stage 30 and / or the intermediate circuit element 25 and the DC voltage unit 2, the second converter stage 30 also has four bridge units 31, which are connected to the circuit inside 23 in In the form of a series-parallel circuit and on a circuit outside 33 on which the second converter stage 30 is connected to the DC voltage unit 2, they are connected in a parallel circuit in a high-current operating mode 230. The two pairs of bridge elements 31 connected in parallel are also connected in series with one another, so that a cascading arrangement of two bridge elements 31 is obtained. To convert the current, the bridge units 31 each have two full bridge elements 31.1, each with four switching elements 32, in particular in the form of semiconductor switches. Transformer elements 31.2, in particular in the form of high-frequency transformers, for galvanic separation of the full bridge elements are located between the full bridge elements 31.1

31.1 provided from each other. To convert 104 the current in the second

Converter stage 30, a further intermediate circuit element 35 can be provided on the outside of the circuit 33.

In particular, the combination of the parallel connection of the bridge units 31 on the outside of the circuit 33 and the series-parallel connection of the bridge units 31 on the inside of the circuit 23 results in an asymmetrical formation of the inside of the circuit 23 and of the outside of the circuit 33 with respect to one another in the high-current operating mode 230. Preferably, the control unit 12 makes it possible to operate the switching elements 32 of the second converter stage 30 when the intermediate circuit voltage 200 is present at the intermediate circuit element 25 at an operating voltage 201 that is lower than the intermediate circuit voltage 200. The operating voltage 201 can preferably be 50% of the intermediate circuit voltage 200 . In particular, the bridge units 31 can also be connected to a neutral conductor of the converter units 21 for this purpose. Because the operating voltage 201 is lower than the intermediate circuit voltage 200, the converter unit 11 and thus the converter device 10 can be operated with high efficiency and with low losses at the switching elements 32 over a wide power range 210. In particular, the second converter stage 30 can be operated in an interleaved mode.

A method 100 according to the invention for controlling the converter device 10 is shown in FIG. 6 in a schematic illustration of the method steps. In this case, the intermediate circuit voltage 200 is generated 101 at the intermediate circuit element 25 to convert 104 the current between the AC voltage unit 3 and the DC voltage unit 2. The converter device 10 can preferably have a connection voltage 203 at the DC voltage connection 34 and / or over a range of from 5V to 200V 0A or essentially 0A to 600A of a connection current 203.1 can be operated at the direct voltage connection 34. The power range 210 can be determined 102 in particular by a measuring device 13 which is arranged at the DC voltage connection 34.

Depending on the power range 210, a control 103 of the converter unit 11 by a control unit 12 can be made possible. For this purpose, the control unit 12 has a first operating module 12.1 for operating the converter unit 11 in a first operating mode I, a second operating module 12.2 for operating the converter unit 11 in a second operating mode II, and a third operating module 12.3 for operating the converter unit 11 in a third operating mode III on. The first operating mode | is provided for a high-power range 211, the second operating mode II for a low-power range 213 and the third operating mode III for a low-power range 212. Figure 7 shows the high-power range 211, the low-power range 213 and the low-power range 212 schematically in a diagram with the connection voltage 203 in volts compared to the connection current 203.1 in amperes. In particular, the low power range 213 includes rated powers at the DC voltage connection 34 from 0 to 40% of a maximum rated power of the converter unit 11 and the high power range 211 rated powers 40% to 100% of the maximum rated power. The low-power range 212 includes, in particular, nominal powers of 20% to 40% of the maximum nominal power.

Figure 2 shows the second converter stage 30 in the first operating mode | and FIG. 3 shows the second converter stage 30 in the second operating mode II in a simplified, schematic illustration. In the first operating mode | the power flow 202 of all bridge elements 31 of the second converter stage 30 is jointly oriented in one direction. The direction can run from the AC voltage unit 3 to the DC voltage unit 2 (shown in dashed lines in FIG. 2) or vice versa (shown as a solid line in FIG. 2). In particular, the control unit 12 can have a direction module 12.5 for determining a direction of the power flow 202. A charging mode of the converter unit 11 for charging the DC voltage unit 2 and / or a discharge mode of the converter unit 11 for discharging the DC voltage unit 2 can be enabled by the direction module 12.5. Depending on whether the converter unit 11 is operated in the charging mode or in the discharging mode, the power flow 202 can be oriented. In the second operating mode II it is provided that the bridge units 31, in particular driven by the second operating module 12.2 of the control unit 12, are switched in pairs so that the

Power flow 202 of two of the bridge units 31 is oriented in a first direction and the power flow 202 of the two other bridge units 31 is oriented in a second direction opposite to the first direction. The bridge units 31 can preferably be operated by a circulation module 12.4 of the control unit 12 in a circulation mode 103.1, so that the switching states 220, 221 and thus the direction of the power flow 202 change, in particular in opposite directions (shown in dashed lines in FIG. 3). The converter device 10 can thus advantageously be operated over a broad power range 210.

FIG. 4 shows the second converter stage 30 in a third operating mode III for controlling the bridge units 31 in a low-power range 212 of the second converter stage 30. In the third operating mode III, at least two of the bridge units 31 are in the first switching state 220 and at least two of the bridge units 31 are in a third switching state 222 can be operated, in which a deactivation of the respective bridge units 31 is provided. Thus, no power is transmitted from two of the bridge units 31 in the third operating mode III. By means of the circulation module 12.4, the bridge units 31 can be deactivated and deactivated in the third operating mode III, in particular alternating in pairs

be activated.

The second converter stage 30 can preferably be switched from the high-current operating mode 230 to a high-voltage operating mode 231. For this purpose, the converter device 10 has a switchover unit 14. FIG. 5 shows the second converter stage 30 in the high-voltage operating mode 231. The circuit inside 23 and the circuit outside 33 of the second converter stage 30 are symmetrical. In particular, in the high-voltage operating mode 231, the bridge units 31 are connected on both sides in a series-parallel connection. In the high-voltage operating mode 231, the second converter stage 30 can preferably also be in the first, second and / or

third operating mode I, II, III are operated.

In addition to the illustrated embodiments, the invention allows further design principles. I. E. the invention should not be viewed as restricted to the exemplary embodiments explained with reference to the figures.

List of reference symbols

10 11 12 12.1 12.2 12.3 12.4 12.5 13 14

20 21 22 23 24 24.1 25

30 31 31.1 31.2 32 33 34 35

DC voltage unit AC voltage unit

Converter device converter unit control unit

first operating module second operating module third operating module circulation module direction module measuring device switching unit

first converter stage converter unit switching element circuit inside AC voltage connection phase connection

DC link element

second converter stage bridge unit full bridge element transformer element switching element circuit outside DC voltage connection

DC link element

20th

21735

100 101 102 103 103.1 104

200 201 202 203 203.1

210 211 212 213

220 221 222

230

231

Procedure Generating 200 Determining 210 Activation of 20 circulation operations

Convert

Intermediate circuit voltage Operating voltage Power flow Connection voltage Connection current

Performance range High performance range Low performance range Low performance range

first switching state second switching state third switching state

High current mode High voltage mode

first operating mode, second operating mode, third operating mode

21

Claims (14)

Claims 1. Converter device (10) comprising a converter unit (11) for connecting an AC voltage unit (3) to a DC voltage unit (2), the converter unit (11) having at least a first converter stage (20) and a second converter stage (30) for conversion (104 ) a current between the DC voltage unit (2) and the AC voltage unit (3), the first converter stage (20) having an AC voltage connection (24) for an electrically conductive connection to the AC voltage unit (3), the second converter stage (30) having a DC voltage connection (34) for the electrically conductive connection to the DC voltage unit (2), characterized in that the second converter stage (30) has at least four bridge units (31) and a control unit (12) with a first operating module (12.1) for controlling the bridge units ( 31) in at least a first operating mode (I) for a high-performance area I (211) and a second operating module (12.2) for controlling the bridge units (31) in a second operating mode (II) for a low power range (213) is provided, with the bridge units (31) in a first switching state in the first operating mode (I) (220) can be operated and in the second operating mode (II) at least two of the bridge units (31) can be operated in the first switching state (220) and at least two of the bridge units (31) can be operated in a second switching state (221). 2. Converter device (10) according to claim 1, characterized in that the first switching state (220) of the bridge units (31) comprises a power flow (202) in a first direction, in particular wherein the second switching state (221) of the bridge units (31) Comprises power flow (202) in a second direction that is opposite to the first direction. 3. Converter device (10) according to one of claims 1 or 2, characterized in that the control unit (12) has a third operating module (12.3) for controlling the bridge units (31) in a third operating mode (III) for a low-power range (212) , wherein in the third operating mode (III) at least two of the bridge units (31) can be operated in the first switching state (220) and at least two of the bridge units (31) can be operated in a third switching state (222), in particular wherein the third switching state (222) of the bridge units ( 31) deactivation of the respective bridge units (31) includes. 4. converter device (10) according to one of the preceding claims, characterized in that the control unit (12) has a circulation module (12.4) to the bridge units (31) in the second and / or third operating mode (II, III), in particular to be switched in pairs, in a circulating manner. 5. Converter device (10) according to one of the preceding claims, characterized in that the second converter stage (30) is electrically coupled to the first converter stage (20) on a circuit inside (23) via an intermediate circuit element (25) for carrying an intermediate circuit voltage (200) and on a circuit outside (33) has the DC voltage connection (34) for the electrically conductive connection to the DC voltage unit (2). 6. converter device (10) according to any one of the preceding claims, characterized in that the circuit inside (23) and the circuit outside (33) of the second converter stage (30) can be designed asymmetrically and / or symmetrically to one another to the switching elements (32) of the second To operate the converter stage (30) at an operating voltage (201) which is lower than the intermediate circuit voltage (200). 24/35 7. Converter device (10) according to one of the preceding claims, characterized in that each of the bridge units (31) has two active full bridge elements (31.1) which are galvanically separated from one another, in particular wherein a transformer element (31.2) is arranged between the full bridge elements (31.1) is. 8. converter device (10) according to any one of the preceding claims, characterized in that the first converter stage (20) has at least one three-stage converter unit (21), preferably three three-stage converter units (21), having. 9. converter device (10) according to claim 8, characterized in that the AC voltage connection (24) of the first converter stage (20) has at least three phase connections (24.1) which are connected to the converter units (21), in particular in the middle of the steps. 10. Converter device according to one of the preceding claims, characterized in that the control unit (12) has a direction module (12.5) for bidirectional operation of the converter unit (11). 11. Converter device (10) according to one of the preceding claims, characterized in that a measuring device (13) for determining a power range (210) is connected to the DC voltage connection (34). 12. converter device (10) according to any one of the preceding claims, characterized in that the second converter stage (30) has a switching unit (14) for switching between a high-voltage operating mode (231) and one High-current operating mode (230), in particular wherein the bridge units (31) are connected in a parallel circuit in the high-current operating mode (230) and in a series-parallel circuit in the high-voltage operating mode (231). 13. Test system for testing a DC voltage unit (2) in the form of an energy storage device, in particular for a vehicle, comprising an AC voltage unit (3) and the DC voltage unit (2), characterized in that the AC voltage unit (3) and the DC voltage unit (2) by a Power converter device (10) according to one of the preceding claims are connected. 14. The method (100) for controlling a converter device (10), in particular according to one of claims 1 to 12, wherein the converter device (10) is connected to an AC voltage unit (3) and a DC voltage unit (2), so that a current between the AC voltage unit (3) and the DC voltage unit (2) can be converted via a first and a second converter stage (20, 30) of the converter device (10), the second converter stage (30) having at least four bridge units (31), the bridge units (31 ) for converting (104) the current between the AC voltage unit (3) and the DC voltage unit (2) for a high-power range (211) in a first operating mode (I), in which the bridge units (31) are in a first switching state (220) are operated, and the bridge units (31) for a low power range (213) are controlled in a second operating mode (II) in which to while two of the bridge units (31) are operated in the first switching state (220) and at least two of the bridge units (31) are operated in a second switching state (221).