T-type 3-point converter with quasi 2-point clocking for minimising the load on the midpoint switches by means of minimum dwell time at the midpoint potential

Abstract

The invention relates to a voltage converter assembly and to a method for operating a voltage converter assembly on the basis of modified three-level modulation. According to the invention, the average voltage level of the three-level modulation is set in each case only for a very short period of time, in particular a time period which is substantially shorter than the period duration of a switching frequency in the voltage converter assembly.

Description

[0001] Description

[0002] title

[0003] T-TYPE 3-POINT CONVERTER WITH NEAR 2-POINT CLOCKING TO MINIMIZE THE LOAD ON THE MID-POINT SWITCH BY MEANS OF MINIMAL DISTANCE TIME ON THE MID-POINT POTENTIAL

[0004] Technical field

[0005] The present invention relates to a voltage converter arrangement and a method for operating a voltage converter arrangement. The present invention further relates to an inverter and an electrical drive system with such an inverter.

[0006] background

[0007] Electrical power converters are used in numerous applications to convert an input voltage into another electrical voltage and provide it at an output terminal. In particular, inverters are known to convert an input DC voltage into a single-phase or multi-phase AC voltage and provide this at the output terminal. In some cases, reverse operation is also possible, in which a single-phase or multi-phase AC voltage is converted into a DC voltage.

[0008] Various circuit and control concepts are known for the design and operation of such power converters. For example, a distinction can be made between so-called two-point or two-level modulation on the one hand and so-called three-point or three-level modulation on the other. German patent application DE 10 2013 202 649 A1, for instance, describes an inverter arrangement that can be controlled alternatively in two-level or three-level operation.

[0009] Disclosure of the invention

[0010] The present invention provides a voltage converter arrangement, an inverter, an electrical drive system, and a method for operating a voltage converter arrangement with the features of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

[0011] Accordingly, the following is planned:

[0012] A voltage converter arrangement comprising a DC terminal, an AC terminal, a capacitor arrangement, and at least one switching device. The DC terminal includes a positive terminal and a negative terminal. The AC terminal includes at least one AC terminal. The capacitor arrangement comprises two capacitors. A first capacitor is arranged between the positive terminal of the DC terminal and a node. A second capacitor is arranged between the node and the negative terminal of the DC terminal. The voltage converter arrangement includes one switching device for each AC terminal.In particular, each switching device has a first switching element arranged between an AC voltage connection point and the positive connection point of the DC voltage connection. Furthermore, a second switching element is arranged between an AC voltage connection point and the negative connection point of the DC voltage connection. Additionally, a third switching element is arranged between the AC voltage connection point and the node of the capacitor arrangement. The voltage converter arrangement is designed to open the first switching element and close the second switching element in a first switching state in each switching device. In this way, the respective AC voltage connection point can be electrically connected to the negative connection point of the DC voltage connection.Alternatively, in each switching device, the second switching element can be opened and the first switching element closed in a second switching state. In this way, the respective AC voltage connection point can be electrically connected to the positive terminal of the DC voltage connection. The voltage converter arrangement is further designed to close the third switching element of the respective switching device for a predetermined time period during the transition from the first switching state to the second switching state, as well as during the transition from the second switching state to the first switching state. The predetermined time period for closing the third switching element during such a transition is significantly shorter than the period of a switching frequency used to control the first and second switching elements.

[0013] Furthermore, the following is planned:

[0014] An inverter with a voltage converter arrangement according to the invention. The DC voltage connection of the voltage converter arrangement can be designed to be connected to a DC voltage source. The DC voltage source can, in particular, be a battery, such as the traction battery of an electric vehicle. Furthermore, the AC voltage connection of the voltage converter arrangement can be designed to be connected to an AC voltage load, in particular an electric machine. Additionally or alternatively, the AC voltage connection can also be designed to be coupled to an AC voltage source, for example, a single-phase or multi-phase power supply network.

[0015] Furthermore, the following is planned:

[0016] An electric drive system comprising an inverter according to the invention and an electric machine which is electrically coupled to the AC voltage connection of the voltage converter arrangement in the inverter.

[0017] Finally, the following is planned:

[0018] A method for operating a voltage converter arrangement. The voltage converter arrangement comprises a DC voltage terminal, an AC voltage terminal, and a capacitor arrangement. The DC voltage terminal comprises a positive terminal and a negative terminal. The AC voltage terminal comprises at least one AC terminal. The capacitor arrangement comprises two capacitors, a first capacitor being arranged between the positive terminal of the DC voltage terminal and a node, and a second capacitor being arranged between the node and the negative terminal of the DC voltage terminal. The voltage converter arrangement further comprises a switching device for each AC terminal.In each switching device, a first switching element is arranged between an AC voltage connection point of the AC voltage terminal and the positive connection point of the DC voltage terminal. Furthermore, a second switching element is arranged in each switching device between the AC voltage connection point of the AC voltage terminal and the negative connection point of the DC voltage terminal. Finally, a third switching element is arranged in each switching device between the AC voltage connection point of the AC voltage terminal and the node of the capacitor arrangement. The method can comprise the following two steps.In a first step, the first switching element in a switching device is opened, then the third switching element of the respective switching device is closed for a predetermined period of time, and subsequently the second switching element in the respective switching device is opened. In this way, a transition from a first switching state, in which the first switching element of a switching device is closed and the second switching element of this switching device is open, to a complementary second switching state, in which the first switching element of the switching device is open and the second switching element of the respective switching device is closed, can be achieved.The method further comprises a step in which the second switching element of a switching device is first opened, followed by the third switching element of the respective switching device being closed for a predetermined period, and then the first switching element of the respective switching device being closed. In this way, a transition from the second switching state to the first switching state can be achieved. The predetermined period during which the third switching element is closed is significantly shorter than the period of a switching frequency used to actuate the first and second switching elements. It is understood that after the predetermined period for closing the third switching element has elapsed, the third switching element is opened again before the second or first switching element of the respective switching device is closed.

[0019] Advantages of the Invention: The present invention is based on the understanding that different circuit and control concepts are available for electrical power converters, especially electrical inverters. In particular, a distinction can be made between so-called two-level modulation and so-called three-level modulation. Three-level modulation makes it possible to switch an additional intermediate potential via a switch in a cross branch. This can, for example, reduce interference and potentially increase efficiency. However, with such three-level modulation, the load on the additional switching element in the cross branch can vary depending on the current operating point. To design this switching element for the entire operating range, it must therefore be dimensioned accordingly, which increases installation space and costs.If, on the other hand, such three-level modulation were to be at least partially dispensed with depending on the operating point, the corresponding disadvantages would then have to be accepted for operation with two-level modulation.

[0020] It is therefore an idea of ​​the present invention to take this knowledge into account and to create a voltage converter arrangement and a method for operating such a voltage converter arrangement which, on the one hand, takes into account the operating point-dependent high load of the switching elements in the cross branch in the case of three-level modulation and, on the other hand, can minimize the disturbance excitations for the entire operating range.

[0021] The present invention provides for closing the switching element in the cross branch for a relatively short period of time during a change of switching state in a half-bridge, i.e., between the opening of a previously closed upper switching element and the closing of a previously opened lower switching element, as well as between the opening of a previously closed lower switching element and the subsequent closing of a previously opened upper switching element of a half-bridge. Since the switching element in the cross branch is only closed for a short period of time, the load on this switching element in the cross branch can be reduced or limited. In this way, smaller switching elements with lower load-bearing capacity can be used for the switching elements in the cross branches. This reduces the requirements for the necessary installation space and the costs for the switching elements in the cross branches.

[0022] However, by briefly closing the switching elements in the cross branches when the switching state in the respective half-bridge changes, significant improvements can be achieved compared to conventional two-level modulation, especially improvements in the area of ​​interference frequencies and thus electromagnetic compatibility.

[0023] The specified time interval for closing the third switching element can be fixed. Alternatively, the time interval can also be set randomly within defined limits or depending on an operating parameter of the voltage converter arrangement. In any case, the specified time interval in which the third switching element closes is significantly shorter than one period of the switching frequency for the first and second switching elements.

[0024] According to one embodiment, the specified time interval for closing the third switching element is less than one fifth of the period of the switching frequency for controlling the first and second switching elements.

[0025] Preferably, the specified time interval is less than one tenth or, if necessary, even less than one twentieth of the period of the switching frequency for controlling the first and second switching elements.

[0026] According to one embodiment, the predetermined time interval for closing the third switching elements is less than 5 microseconds. In particular, the predetermined time interval for closing the third switching elements can be less than 3.3 microseconds, less than 3 microseconds, or optionally even less than 2 microseconds. By setting an absolute value for the maximum predetermined time interval, very precise control can be exercised over the interfering frequencies and the associated electromagnetic interference.

[0027] According to one embodiment, the predetermined time interval for closing the third switching elements can be set randomly or pseudo-randomly. In particular, the predetermined time interval can be set (pseudo-)randomly within a predefined range of values. For example, an individually determined (pseudo-)random time interval can be specified for each switching operation. In this way, depending on the predefined range of values, it is possible to influence the occurring interference frequencies within a frequency range corresponding to that range.

[0028] According to one embodiment, the predetermined time interval for closing the third switching element can be selected from a group of predetermined time intervals. In this way, a predetermined value can be selected alternately, for example cyclically or randomly, from a group of fixed, predetermined time intervals for each switching operation.

[0029] According to one embodiment, the predetermined time interval for closing the third switching element is determined using an electrical angle of an alternating voltage applied to the AC voltage terminal. In particular, the time interval for closing the third switching element can be determined by specifying the electrical angle of an alternating voltage applied to the AC voltage terminal. According to one embodiment, the first switching element and the second switching element each comprise a single semiconductor switching element. Alternatively, a parallel connection of several semiconductor switching elements can be provided for the first switching element and the second switching element, respectively. The third switching element can be formed from a series connection of two complementary semiconductor switching elements.Such a series connection allows for bipolar isolation when the semiconductor switching elements are open, provided that a single semiconductor switching element does not already possess bipolar blocking capability. In principle, to close the third switching element, it is sufficient if, in the series connection, the corresponding polarity-blocking semiconductor switching element is activated in each of the two semiconductor switching elements, while the electrical current can also flow through the (internal) body diode in the other semiconductor switching element. Alternatively, however, both series-connected semiconductor switching elements of the third switching element can always be activated.

[0030] The above embodiments and further developments can be combined with one another as appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0031] Brief description of the drawings

[0032] Further features and advantages of the invention are explained below with reference to the figures. Figure 1 shows a schematic representation of a basic circuit diagram of an inverter with a voltage converter arrangement according to one embodiment;

[0033] Fig. 2: a schematic representation of a basic circuit diagram of an inverter with a voltage converter arrangement for an electric drive system according to one embodiment;

[0034] Fig. 3: a voltage-time diagram to illustrate two-level modulation;

[0035] Fig. 4: a voltage-time diagram to illustrate three-level modulation;

[0036] Fig. 5: a voltage-time diagram to illustrate the control method according to the invention;

[0037] Fig. 6: a flowchart as it underlies a method for operating a voltage converter arrangement according to one embodiment; and

[0038] Fig. 7: an exemplary representation to illustrate the comparison of interference excitations in different modulation methods, a

[0039] Description of embodiments

[0040] Figure 1 shows a schematic representation of a basic circuit diagram of a voltage converter arrangement 1 according to an embodiment, such as that which can be used for an inverter. The embodiment shown here for a three-phase AC voltage serves only as an example and does not represent a limitation of the present invention. In principle, the principle according to the invention can also be applied to a single-phase AC voltage or an AC voltage with any number of phases.

[0041] The voltage converter arrangement 1 comprises a DC voltage terminal 10 with a positive terminal 11 and a negative terminal 12. The DC voltage terminal 10 can be electrically coupled to a DC voltage source, for example. A battery or any other DC voltage source, such as a photovoltaic system or similar, is possible as a DC voltage source. The voltage converter arrangement 1 further comprises an AC voltage terminal 20 with one or more AC voltage connection points 21, 22, 23. In particular, one AC voltage connection point 21, 22, 23 is provided for each phase L1, L2, L3. The AC voltage terminal can optionally include an additional connection point 24 for a neutral conductor N. The AC voltage terminal 20 can be electrically coupled to an electrical load, in particular an AC load or an AC power grid.

[0042] A capacitor arrangement 30 is arranged between the positive terminal 11 or the negative terminal 12 of the DC voltage terminal 10. The capacitor arrangement 30 comprises a series connection of a first capacitor C1 and a second capacitor C2. The first capacitor C1 is arranged between the positive terminal 11 of the DC voltage terminal 10 and a junction K. The second capacitor C2 is arranged between junction K and the negative terminal 12 of the DC voltage terminal 10. Optionally, junction K can be connected to terminal 24 of the AC voltage terminal 20 for the neutral conductor N.For each electrical phase, that is, for each AC voltage connection point 21, 22, 23 of the AC voltage connection 20, a switching device with a half-bridge consisting of an upper switching element M1 a, M1 b, M1c and a lower switching element M2a, M2b, M2c as well as a further, third switching element M3a, M3b, M3c is provided.The upper switching elements M1a, M1b, M1c of the half-bridges are each arranged between one of the AC voltage connection points 21, 22, 23 of the AC voltage connection 20 and the positive connection point 11 of the DC voltage connection 10. Similarly, the lower switching elements M2a, M2b, M2c are each arranged between one of the AC voltage connection points 21, 22, 23 of the AC voltage connection 20 and the negative connection point 12 of the DC voltage connection 10. Furthermore, the third switching elements M3a, M3b, M3c are each arranged between the AC voltage connection points 21, 22, 23 of the AC voltage connection 20 and the node K of the capacitor arrangement 30.

[0043] The switching elements M1a, M1b, M1c and M2a, M2b, M2c of the half-bridges can each be individual semiconductor switching elements or parallel circuits of several semiconductor switching elements. The switching elements M3a, M3b, M3c of the cross-branches, which are connected to node K of the capacitor arrangement 30, can, for example, be series circuits of two complementary semiconductor switching elements each. In this way, a bipolar interruption can be realized in each of the cross-branches, regardless of polarity.

[0044] By appropriately controlling the switching elements in the

[0045] Voltage converter arrangement 1 can thus generate an alternating voltage from a direct voltage supplied at the DC voltage terminal 10, which can then be supplied at the AC voltage terminal 20. Optionally, reverse operation is also possible, in which an alternating voltage supplied at the AC voltage terminal 20 can be converted into a direct voltage, which can then be supplied at the DC voltage terminal 10. For both operating modes, the switching elements M1a, M1b, M1c, M2a, M2b, M2c, M3a, M3b, M3c can be controlled in a suitable manner, for example by a control device (not shown).

[0046] Figure 2 shows a schematic representation of a basic circuit diagram for a voltage converter arrangement 1 according to an embodiment, such as that which can be used in an electric drive system. Accordingly, an electric machine 2 is connected to the AC voltage terminal 20 of the voltage converter arrangement 1. If necessary, the connection of a neutral conductor N can be omitted for such operation in an electric drive system. Furthermore, all previously described aspects relating to Figure 1 also apply to the electric drive system according to Figure 2.

[0047] The control of the switching elements in the voltage converter arrangement 1 can, in principle, be based on two-level modulation or three-level modulation. Furthermore, another modified control method according to the invention is described below.

[0048] Figure 3 shows a schematic representation of a voltage-time diagram for control based on two-level modulation. For such two-level modulation, the third switching elements M3a, M3b, M3c can generally be omitted. Alternatively, these switching elements M3a, M3b, M3c can be permanently open. Thus, at an AC voltage connection point 21, 22, 33, either the positive input voltage is present if the upper switching element M1a, M1b, M1c of the corresponding half-bridge is closed and the lower switching element M2a, M2b, or M2c is open. Alternatively, the negative voltage is present at the corresponding AC voltage connection point 21, 22, 23 of the AC voltage connection 20 if the lower switching element M2a, M2b, M2c is closed and the corresponding upper switching element M1a, M1b, or M1c is open.

[0049] Figure 4 shows a schematic representation of a voltage-time diagram for control according to three-level modulation. As can be seen, in addition to the maximum positive or negative DC voltage, a further zero voltage can be applied. For this purpose, in the corresponding half-bridge, both the upper switching element M1a, M1b, M1c and the lower switching element M2a, M2b, M2c are open, while the respective third switching element M3a, M3b, or M3c is closed. In this way, the average potential at node K of the capacitor arrangement 30 is applied to the corresponding AC voltage connection point 21, 22, 23 of the AC voltage connection 20. If the time period in which this zero potential is to be applied extends over relatively long periods, this can lead to a considerable load on the third switching elements M3a, M3b, M3c.

[0050] Figure 5 shows a schematic representation of a voltage-time diagram according to a further modulation method according to the invention. This modulation method differs from the previously described three-level modulation method, in particular in that the time intervals during which the zero voltage is applied across the third switching elements M3a, M3b, M3c are very short. Consequently, the maximum load on the third switching elements M3a, M3b, M3c is also reduced.

[0051] The time intervals during which the third switching elements M3a, M3b, M3c are closed are significantly shorter than one period T of the switching frequency for the switching elements in the half-bridges. These very short time intervals are highlighted by the circular markings in Fig. 5.

[0052] For example, the time span in which the third switching elements M3a, M3b, M3c are closed can be at most one fifth, preferably at most one tenth or optionally at most one twentieth of the period T of the switching frequency for controlling the upper and lower switching elements M1 a, M1 b, M1 c, M2a, M2b, M2c in the half-bridges.

[0053] In order to minimize interference frequencies and electromagnetic disturbances, particularly in frequency ranges that are highly relevant in connection with electric drive systems, the specified time period in which the third switching elements M3a, M3b, M3c are closed can be a maximum of 5 microseconds, preferably a maximum of 3.3 microseconds or, if necessary, even less, for example a maximum of 2 microseconds.

[0054] The predefined time intervals during which the third switching elements M3a, M3b, and M3c are closed can, for example, be fixed. Thus, when the switching states of the half-bridges change, the same time intervals are always provided for the brief closing of the third switching element M3a, M3b, and M3c. Alternatively, several different time intervals within a value range, particularly the value range according to the criteria described above, can be fixed. This allows the multiple predefined values ​​to be varied cyclically or randomly. Furthermore, it is also possible, for example, to randomly or pseudo-randomly select the maximum time interval within a predefined value range and to define it for each switching operation based on this (pseudo-)random selection.In another alternative embodiment, it is also possible to adjust the predetermined time interval for closing the third switching element M3a, M3b, M3c as a function of an electrical angle of the alternating voltage at the AC voltage terminal 20. The adjustment of the time interval can also be made within a predetermined range of values.

[0055] Figure 6 shows a flowchart that can form the basis of a method for operating a voltage transformer arrangement 1, in particular one of the voltage transformer arrangements 1 described above. Thus, all statements made previously in connection with the voltage transformer arrangements 1 also apply to the method described below. Conversely, the voltage transformer arrangements 1 described above can also be configured in any way to implement the method described below.

[0056] In a first step S1, to change the switching state in a half-bridge, an initially closed upper switching element M1a, M1b, M1c can first be opened. Subsequently, the third switching element M3a, M3b, M3c associated with the corresponding half-bridge can be closed for a predetermined time period. After this predetermined time period, the third switching element M3a, M3b, M3c can be closed again, and then the corresponding lower switching element M2a, M2b, M2c of the respective half-bridge can be closed.

[0057] For a reverse change of switching states, in step S2, a lower switching element M2a, M2b, M2c of a half-bridge can first be opened. Then, the corresponding third switching element M3a, M3b, M3c of the corresponding half-bridge can be closed for a predetermined time period. After this time period, the third switching element M3a, M3b, M3c can be opened again, and then the upper switching element M1a, M1b, M1c of the corresponding half-bridge can be closed.

[0058] As previously explained, the specified time interval for closing the third switching element M3a, M3b, M3c is significantly shorter than the period T of the switching frequency for activating the first and second switching elements M1a, M1b, M1c, M2a, M2b, M2c. In particular, the specified time interval can take into account the previously described criteria regarding its relationship to the period of the switching frequency and the maximum time interval.

[0059] Figure 7 shows a comparison of the resulting interference excitations for different modulation methods. Curve 110 describes the interference excitations with two-level modulation, and curve 140 the curve with three-level modulation. Furthermore, curve 120 represents the interference modulation for the case where 1.2 microseconds was chosen for the predetermined closing time of the switching elements. Figure 130 shows the curve where 0.8 microseconds was chosen for the predetermined time. Both curves 120 and 130 show a significant drop in interference, but at different frequencies. Accordingly, this frequency or the frequency range can be influenced by choosing the predetermined closing time of the switching elements.

[0060] In summary, the present invention relates to a voltage converter arrangement and a method for operating a voltage converter arrangement based on a modified three-level modulation. It is provided that the average voltage level of the three-level modulation is set only for a very short period of time, in particular a time interval that is significantly shorter than the period of a switching frequency in the voltage converter arrangement.

Claims

Claims 1. Voltage converter arrangement (1), comprising: a DC voltage terminal (10) with a positive terminal point (11) and a negative terminal point (12); a capacitor arrangement (30), comprising a first capacitor (C1) and a second capacitor (C2), wherein the first capacitor (C1) is arranged between the positive terminal point (11) of the DC voltage terminal (10) and a node (K) and the second capacitor (C2) is arranged between the node (K) and the negative terminal point (12) of the DC voltage terminal (10); an AC voltage terminal (20) with at least one AC voltage terminal point (21, 22, 23);wherein the voltage converter arrangement (1) comprises a switching device for each AC voltage connection point (21 , 22 , 23), wherein in each switching device a first switching element (M1 a, M1 b, M1c) is arranged between an AC voltage connection point (21 , 22 23) and the positive connection point (11) of the DC voltage connection (10), a second switching element (M2a, M2b, M2c) is arranged between the AC voltage connection point (21 , 22 23) and the negative connection point of the DC voltage connection, and a third switching element (M3a, M3b, M3c) is arranged between the AC voltage connection point (21 , 22 23) and the node of the capacitor arrangement; wherein the voltage converter arrangement (1) is designed to either open the first switching element (M1 a, M1 b, M1 c) and close the second switching element (M2a, M2b, M2c) in a first switching state, or to open the second switching element (M2a, M2b, M2c) and close the first switching element (M1 a, M1 b, M1 c) in a second switching state, wherein the voltage converter arrangement (1) is further designed to close the third switching element (M3a, M3b, M3c) for a predetermined time interval during a transition from the first switching state to the second switching state and during a transition from the second switching state to the first switching state, wherein the predetermined time interval for closing the third switching element (M3a, M3b, M3c) is significantly smaller than a period (T) of a switching frequency for controlling the first and second switching elements (M2a, M2b, M2c).

2. Voltage converter arrangement (1), according to claim 1, wherein the predetermined time interval for closing the third switching element (M3a, M3b, M3c) is less than one fifth, in particular less than one tenth, of the period of the switching frequency for controlling the first (M1a, M1b, M1c) and second switching elements (M2a, M2b, M2c).

3. Voltage converter arrangement (1) according to claim 1 or 2, wherein the predetermined time interval for closing the third switching element (M3a, M3b, M3c) is less than 5 microseconds, in particular less than 3.3 microseconds.

4. Voltage converter arrangement (1), according to one of claims 1 to 3, wherein the predetermined time interval for closing the third switching element (M3a, M3b, M3c) is randomly or pseudo-randomly determined within a given range of values.

5. Voltage converter arrangement (1) according to one of claims 1 to 3, wherein the predetermined time interval for closing the third switching element (M3a, M3b, M3c) is selected from a group of predetermined time intervals.

6. Voltage converter arrangement (1) according to any one of claims 1 to 3, wherein the predetermined time interval for closing the third switching element (M3a, M3b, M3c) is determined using an electrical angle of an alternating voltage at the alternating voltage terminal.

7. Voltage converter arrangement (1), according to any one of claims 1 to 6, wherein the first switching element (M1 a, M1 b, M1 c) and the second switching element (M2a, M2b, M2c) each comprise a single semiconductor switching element or a parallel connection of several semiconductor switching elements, and wherein the third switching element (M3a, M3b, M3c) each comprises a series connection of two complementarily arranged semiconductor switching elements.

8. Inverter with a voltage converter arrangement (1) according to one of claims 1 to 7, wherein the DC voltage connection (10) is designed to be connected to a DC voltage source.

9. Electric drive system comprising an inverter according to claim 8; and an electric machine (2) which is electrically coupled to the AC voltage connection (20) of the voltage converter arrangement (1) in the inverter.

10. Method for operating a voltage converter arrangement (1) comprising: a DC voltage terminal (10) with a positive terminal point (11) and a negative terminal point (12), a capacitor arrangement (30) comprising a first capacitor (C1) and a second capacitor (C2), wherein the first capacitor (C1) is arranged between the positive terminal point (11) of the DC voltage terminal (10) and a node (K), and wherein the second capacitor (C2) is arranged between the node (K) and the negative terminal point (12) of the DC voltage terminal (10), an AC voltage terminal (20) comprising at least one AC voltage terminal point (21, 22, 23), wherein the voltage converter arrangement (1) comprises a switching device for each AC voltage terminal point (21, 22, 23), wherein in each switching device a connection is made between an AC voltage terminal point (21, 22, 23)22 23) and the positive terminal point of the DC voltage connection, a first switching element (M1 a, M1 b, M1 c) is arranged, a second switching element (M2a, M2b, M2c) is arranged between the AC voltage connection point (21 , 22 23) and the negative terminal point of the DC voltage connection, and a third switching element (M3a, M3b, M3c) is arranged between the AC voltage connection point (21 , 22 23) and the node (K) of the capacitor arrangement (30), the method comprising the following steps: Opening (S1) of a first switching element (M1 a, M1 b, M1 c) in a switching device, then closing of the third switching element (M3a, M3b, M3c) in the respective switching device for a predetermined time period, and then opening of the third switching element (M3a, M3b, M3c) and closing of the second switching element (M2a, M2b, M2c) in the respective switching device; and Opening (S2) of a second switching element (M2a, M2b, M2c) in a switching device, followed by closing of the third switching element (M3a, M3b, M3c) in the respective switching device for a predetermined time period and then opening the third switching element (M3a, M3b, M3c) and closing the first switching element (M1 a, M1 b, M1 c) in the respective switching device, wherein the predetermined time period for closing the third switching element (M3a, M3b, M3c) is significantly smaller than a period (T) of a switching frequency for controlling the first (M1 a, M1 b, M1 c) and second switching elements (M2a, M2b, M2c).

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