Control device, inverter, assembly with inverter and electric machine, method for operating an inverter and computer program

Abstract

A control device (8) for an inverter (2) for powering an electric machine (3), wherein the control device (8) is configured to provide a pulse width modulated switching signal (15) to drive switching elements (12) of the inverter (2), wherein the control device (8) is configured to determine a modulation type by which the pulse width modulated switching signal (15) is generated depending on operating point information describing an operating point defined by at least one operating parameter, and to use a first modulation type in at least one first operating region (21, 28, 30, 31) and a second modulation type in another operating region (32, 32a, 32b).

Description

Technical Field

[0001] The present invention relates to a control device for an inverter for supplying power to a motor, wherein the control device is configured to provide pulse width modulated switching signals for driving the switching elements of the inverter.

[0002] The present invention also relates to an inverter, an assembly having an inverter and a motor, a method for operating the inverter, and a computer program. Background Technology

[0003] The growing importance of electric vehicles has brought inverters and related control devices for this application to the forefront of industrial development efforts. One type of control device is known that provides pulse-width modulated switching signals of a predefined modulation type for driving the switching elements of the inverter.

[0004] During this switching operation, switching losses are inevitable and have a significant impact on the overall efficiency of the inverter and motor components. Especially when operating under partial load, switching losses can constitute a large portion of the inverter's total losses.

[0005] Meanwhile, the peak-to-peak value of the inverter's DC link voltage represents a strict constraint that must be adhered to, especially in the case of electric vehicles. The lower the maximum permissible peak-to-peak value, the larger the inverter's DC link capacitor must be. Increasing the DC link capacitor here leads to an increased space requirement for intermediate circuit capacitors, which is undesirable. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide a method for reducing switching losses during operation and / or reducing the required DC link capacitance.

[0007] According to the invention, this objective is achieved in a control device of the type described at the beginning, since the control device is configured to determine the modulation type of the switching signal that generates pulse width modulation based on operation point information describing the operation point defined by at least one operation parameter, and to use a first modulation type in at least one first operation region and a second modulation type in another operation region.

[0008] This invention is based on the understanding that different modulation types lead to different levels of switching losses, but also require different peak-to-peak values ​​in the DC link voltage depending on the operating point defined by at least one operating parameter. Therefore, this invention proposes using a first modulation type in at least one first operating region, where a second modulation type, which typically results in lower switching losses, produces excessively high peak-to-peak values ​​in the DC link voltage. Thus, this invention advantageously allows for reduced switching losses while the maximum peak-to-peak value of the DC link voltage remains substantially constant across all operating points.

[0009] Preferably, in the control device according to the invention, the first modulation type is a continuous pulse width modulation type, particularly SVM (space vector modulation). Alternatively or additionally, the second modulation type can be a discontinuous pulse width modulation type, particularly GDPWM (generalized discontinuous pulse width modulation).

[0010] In the control device according to the invention, it is further preferred that the operating parameter is the torque of the motor or the magnitude of the machine current of the motor.

[0011] It can be specified here that the first operating region or multiple first operating regions lie within an operating parameter range defined by a lower operating parameter boundary and an upper operating parameter boundary. Experiments and simulations have determined that, under typical operating conditions, starting from a specific value of the torque or current amplitude of the motor current, a second modulation type can be replaced by a first modulation type to reduce the peak-to-peak value of the DC link voltage. Typically, the value of the lower boundary of the operating parameter is equal to at least 10%, preferably at least 25%, and particularly preferably at least 40% of the maximum value of the operating parameter. The operating parameter boundaries of each first operating region typically have the same arithmetic sign. Multiple first operating regions can be provided for positive and / or negative operating parameters, each first operating region having an operating parameter range.

[0012] In a particularly easy-to-implement embodiment, one or more first operating regions are limited by one or more operating parameter ranges.

[0013] Another operating parameter that can be provided for the control device according to the present invention is the motor speed.

[0014] It can be specified here that at least one first operating region lies within a speed range defined by a lower speed limit and an upper speed limit. Here, again, it has been determined through experiments and simulations that, under typical operating conditions, for a specific speed value, a second modulation type can be replaced by a first modulation type to reduce the peak-to-peak value of the DC link voltage. Typically, the value of the lower speed limit is at least 5% of the maximum speed, preferably at least 10%, and particularly preferably at least 15%.

[0015] According to a particularly easy-to-implement embodiment, the or corresponding operating range is limited by a speed range and / or a range of operating parameters related to torque or current magnitude.

[0016] It is also advantageous to provide that the operating parameter is the inverter's DC link voltage. Therefore, the modulation type can be set more precisely, and further depends on the measured DC link voltage.

[0017] Using the control device according to the invention, preferably, the operating range is determined such that the peak-to-peak value of the inverter's DC link voltage does not exceed a predetermined value.

[0018] According to a particularly preferred embodiment, the operating region during continuous load operation is determined such that the peak-to-peak value of the DC link voltage does not exceed a predetermined second value less than a first value. Therefore, different permissible peak-to-peak values ​​of the DC link voltage can be achieved for continuous load operation and high-load or full-load operation of the motor. Preferably, the first value is at least 1.5 times, more preferably at least 1.8 times, and / or at most 3 times, particularly at most 2.5 times, the second value. It is also possible that the first and / or second values ​​are functions of operating parameters, such as torque or machine current.

[0019] In addition, for each additional operating region, it is possible to predetermine another value that the peak-to-peak value of the DC link voltage should not be exceeded.

[0020] According to a variant embodiment, the control device according to the invention is configured to provide a switching signal at the same carrier frequency when both modulation types are in use.

[0021] However, according to a preferred variant, the control device according to the invention is configured to provide a switching signal at a different, particularly lower, carrier frequency when using the first modulation type compared to when using the second modulation type. By using a higher carrier frequency for the second modulation type, the peak-to-peak value of the DC link voltage can be significantly reduced at all operating points during continuous load operation and high load operation. This also allows for a reduction in the capacitance of the DC link capacitor compared to operation with the first modulation type using a lower carrier frequency at all operating points. Simultaneously, the maximum value of switching losses is reduced at all operating points, especially when using a discontinuous modulation type throughout high load operation. The carrier frequency of the second modulation type is preferably at least 10% higher than the carrier frequency when using the first modulation type.

[0022] Alternatively or additionally, it may be specified that the carrier frequencies of the first modulation type and / or the second modulation type can be specified based on the operating point.

[0023] To enable the control device according to the invention to be implemented with particularly little effort, it is preferably configured to determine the modulation type to be used by means of a feature map, which assigns a corresponding modulation type to at least one operating parameter. For example, the feature map can be implemented using a lookup table. The control device typically includes a storage unit in which the feature map is stored.

[0024] As an alternative to using feature maps, the control device according to the invention can be configured to determine the modulation type to be used based on a function that evaluates at least one operating parameter.

[0025] For example, characteristic maps or calculation specifications can be determined by measuring or simulating a specific configuration of the inverter and motor.

[0026] The control device according to the invention can also be configured to determine the modulation type to be used in each case upon receiving updated operating point information and / or after a specified or specifyable time period and / or after the end of the electrical cycle of the motor. Therefore, in each case, the modulation type can be adapted to the instantaneous operating point at an appropriate time.

[0027] Alternatively, the control device according to the invention may be configured to determine operating point information based on torque information received at the input and / or speed information received at the input and / or current information describing the current intensity of the motor current and / or voltage information describing the DC link voltage, and / or to estimate the operating point information in the context of a regulation process for determining switching signals. Torque can also be determined from the current information.

[0028] The objective of this invention is also achieved by an inverter comprising a DC link capacitor, switching elements, and a control device according to the invention, wherein the switching elements are interconnected to convert the DC link voltage present at the DC link capacitor into a single-phase or multi-phase AC voltage according to a switching signal driving the switching elements.

[0029] DC link capacitors can be formed by a single capacitor element or by multiple capacitor elements interconnected in parallel and / or series.

[0030] The inverter may also include an analog-to-digital converter designed to convert analog measurement signals into current and / or voltage and / or speed and / or torque information.

[0031] Furthermore, the objective of this invention is achieved through a component having an inverter according to the invention and a motor capable of operating on AC voltage.

[0032] The objective of this invention is also achieved by a method for operating an inverter that supplies power to a motor, the method comprising the following steps performed by a control device: determining a modulation type based on operation point information describing an operation point defined by at least one operation parameter; generating a pulse-width modulated switching signal for driving the switching elements of the inverter by the modulation type, wherein a first modulation type is used for at least one first operation region and a second modulation type is used for another operation region; and providing the switching signal.

[0033] Finally, the objective of this invention is achieved by a computer program comprising commands that, when executed by a computer, cause the computer to perform the steps of the method according to the invention, which are executed by a control device.

[0034] All explanations relating to the control device according to the invention, the inverter according to the invention, and the components according to the invention can be applied in a similar manner to the method according to the invention and the computer program according to the invention, thereby utilizing these to achieve the aforementioned advantages as well. Attached Figure Description

[0035] Further advantages and details of the present invention will become apparent from the exemplary embodiments described below and based on the accompanying drawings. These are schematic diagrams, in which:

[0036] Figure 1 A block diagram illustrating an exemplary embodiment of a component according to the present invention is shown, including an exemplary embodiment of an inverter according to the present invention and a first exemplary embodiment of a control device according to the present invention;

[0037] Figure 2 A torque-speed diagram is shown, which plots the operating area when the first embodiment of the control device is used to operate the components;

[0038] Figure 3 A torque-speed graph is shown, in which the peak-to-peak contour lines of the DC link voltage are plotted when the components are operated using the first exemplary embodiment of the control device.

[0039] Figure 4 A torque-speed graph is shown, in which contour lines of total losses are plotted when the components are operated using a first exemplary embodiment of the control device;

[0040] Figure 5 A torque-speed graph is shown, in which contour lines are plotted showing the percentage change in total losses when the component with the first exemplary embodiment of the control device is operated, compared with the component according to the prior art.

[0041] Figure 6 and Figure 7Torque-speed graphs are shown separately, plotting the torque-speed ratio when operating according to... Figure 1 The operating area when the component has other exemplary embodiments of the control device;

[0042] Figure 8 A graph shows the possible percentage reduction of the DC link capacitance relative to the carrier frequency of the second modulation type, with the carrier frequency of the first modulation type remaining constant.

[0043] Figure 9 A graph showing the maximum percentage reduction in total loss relative to the carrier frequency of the second modulation type, with the carrier frequency of the first modulation type remaining constant; and

[0044] Figure 10 and 11 Torque-speed curves are shown separately, and the operating conditions are plotted on these curves according to... Figure 1 The operating area when the components of other embodiments have control devices. Detailed Implementation

[0045] Figure 1 This is a block diagram of an exemplary embodiment of component 1, which includes an inverter 2 and an exemplary embodiment of a motor 3 configured to drive a vehicle that can be partially or fully electrically driven. Component 1 also includes a DC voltage source 4, which is designed as a high-voltage battery in this case.

[0046] Inverter 2 includes a filter device 5, which is designed as an EMC filter in the present case, a DC link capacitor 6, a power unit 7, an exemplary embodiment of a control device 8, a first measuring device 9, a second measuring device 10, and an analog-to-digital converter 11.

[0047] Power unit 7 includes multiple switching elements 12, which are designed as semiconductor switching elements, such as IGBTs or power MOSFETs. The switching elements 12 are interconnected in pairs to form a half-bridge. A driver 14 is connected upstream of the control input 13 of the respective switching element 12. For clarity, only one switching element 12 and one driver 14 are referred to here. The driver 14 receives a pulse-width modulated switching signal 15 from the control device 8, which is provided in such a way that an output voltage for feeding motor 3 can be obtained at the corresponding tap of the half-bridge. Therefore, according to the switching signal 15, power unit 7 converts the DC link voltage stabilized by DC link capacitor 6 into an AC voltage that is, in the present case, three-phase. Therefore, the voltage appearing on DC link capacitor 6 is considered the DC link voltage.

[0048] The first measuring device 9 is configured to acquire the machine current and provide a measurement signal to the analog-to-digital converter (ADC) device 11, which converts the analog measurement signal from the first measuring device 9 into digital current information 16. Correspondingly, the second measuring device 10 is configured to acquire the rotational speed of the motor 3 and provide a measurement signal to the ADC device 11, which converts the analog measurement signal from the second measuring device 10 into digital rotational speed information 17. Optionally, the rotational speed information 17 may have already been provided digitally by the second measuring device 10. The control device 8 receives the current information 16 and the rotational speed information 17 at its input. From this, it determines torque information describing the torque of the motor 3. Optionally, the torque information may also be estimated within the context of the rules used by the control device 8 to determine the switching signal 15.

[0049] Optionally, a third measuring device 18 is also provided at the inverter 2, which acquires the DC link voltage present across the DC link capacitor 6. The analog measurement signal of the third measuring device 18 is converted into voltage information 19 by the analog-to-digital converter 11, and the control device 8 also receives the voltage information at its input.

[0050] Based on current information 16 and speed information 17, control device 8 determines operation point information describing the operation point defined by the operation parameter tuple. In the current case, the operation parameters are the torque of motor 3 and the speed of motor 3. In addition to torque, or as a substitute for torque, the magnitude of the machine current of motor 3 determined based on current information 16 can be used as an operation parameter. The operation point information may also optionally include DC link voltage as an operation parameter.

[0051] The control device 8 is configured to determine the modulation type based on operating point information, and generate a pulse-width modulated switching signal 15 using this modulation type. To this end, the control device 8 includes a storage unit 20 storing a feature map implemented in the form of a lookup table, which assigns the modulation type to pairs of speed and torque values. The control device 8 selects the corresponding modulation type with reference to the operating point information from the feature map.

[0052] For both modulation types, a consistent carrier frequency, such as 10 kHz, was used in the preceding exemplary embodiments.

[0053] Figure 2 It is a torque-speed graph, on which the operating conditions have been plotted. Figure 1 The operating area of ​​component 1 is shown, where torque is typically represented by M and rotational speed by f. rot express.

[0054] This feature map has a first operating region 21, which is located between and defined by a positive lower torque boundary 22 and an equally positive upper torque boundary 23. Furthermore, the first operating region 21 is located between a lower operating parameter boundary 24 and an upper operating parameter boundary 25, which in this case are speed boundaries. The first operating region 21 here extends from the basic speed operation 26 to the power limiting operation 27. Figure 2 Another first operating region 28 can also be seen, which extends from the full-load line 29, where the maximum torque exists, towards the torque with a lower value. Additional first operating regions 30 and 31 are defined for negative torque. Other operating points are located in the second operating region 32.

[0055] The control device is configured to use a continuous pulse width modulation type, in this case space vector modulation (SVM), in the first operating regions 21, 28, 30, and 31, and a discontinuous pulse width modulation type, in this case generalized discontinuous pulse width modulation (GDPMW), in the second operating region 32 to generate the switching signal 15. Operating regions 21, 28, 30 to 32 are determined in such a way that if the motor 3 is in high-load operation 33, 34, the peak-to-peak value of the inverter's DC link voltage does not exceed a predetermined first value, and if the motor 3 is in continuous-load operation 35, it does not exceed a second value, which is, for example, twice the size of the first value. The boundary between high-load operation 33, 34 and continuous-load operation 35 is defined by… Figure 2 Lines 36 and 37 are shown in the diagram, and higher torque boundaries, such as the upper torque boundary 23, are also formed in some sections. The boundary between high-load operation 33 and 34 and continuous-load operation 35 is here referenced to a predetermined amplitude of the motor current. And thus, in this exemplary embodiment, it is assumed that... Used for continuous load operation.

[0056] In this exemplary embodiment, the first value is 23.7V and the second value is 13.65V. From Figure 3 As can be seen from the torque-speed diagram, during the operation of component 1, the peak-to-peak contour lines of the DC link voltage have been plotted, and as a result of the modulation type-dependent operating point specification, these values ​​were not exceeded. Figure 4 This is a torque-speed diagram, on which contour lines of total losses are plotted. Total losses are defined as the sum of switching losses and conduction losses in inverter 2 during the operation of component 1. Regarding this, Figure 5 A rotational speed diagram is shown, on which contour lines are plotted representing the percentage change in total loss compared to the component corresponding to component 1 according to the prior art, where only SVN is used. From Figure 5As can be seen, a significant reduction in total loss was observed in the second operating region 32 compared to using only SVM.

[0057] Table 1 below shows the operating characteristics of this component according to the prior art as a reference in column "SVM 10kHz", the corresponding operating characteristics specifically compared using GDPWM in column "GDPWM 10kHz", and the corresponding operating characteristics when operating component 1 according to this exemplary embodiment in columns "SVM 10kHz and GDPWM 10kHz". This is shown for three DC link voltages, namely 270V, 350V, and 450V, at a constant carrier frequency of 10kHz. It is assumed that the DC link capacitance is 650μF. Generally, u DC,pp Pt represents the peak-to-peak value of the DC link voltage. ot Represents the total loss, max(u) DC,pp ) represents the maximum peak-to-peak value of the DC link voltage within a given operating region, max(P tot ) represents the maximum total loss within a given operating area.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, compared to using SVM alone in component 1, no predetermined first or second value of the peak-to-peak DC link voltage was exceeded, and the total loss in operating region 32 was significantly reduced. Using GDPWN alone does indeed reduce the maximum loss during high-load operation. However, due to the significantly higher peak-to-peak DC link voltage in the continuous-mode operating region, the DC link capacitor would need to be increased by 30.9%; this is undesirable considering the associated cost and increased space requirements.

[0061] Other exemplary embodiments of component 1 are described below, which differ from the first exemplary embodiment in that the control device 8 is configured to provide a switching signal at a different carrier frequency when using a continuous modulation type compared to when using a discontinuous modulation type.

[0062] In Table 2 below, the columns “SVM 10kHz” and “SVM 10kHz and GDPWM 10kHz” correspond to the corresponding columns in Table 1. The column “SVM 10kHz and GDPWM 13.5kHz” relates to an exemplary embodiment, wherein a carrier frequency of 10kHz is used when SVM is used in the same manner as in the first exemplary embodiment, and a carrier frequency of 13.5kHz is used when GDPWN is used. The structure of the rest of Table 2 corresponds to that of Table 1.

[0063] Table 2

[0064]

[0065] As can be seen from Table 2, when using GDPWM, by increasing the carrier frequency, the maximum peak-to-peak value of the DC link voltage can be reduced under continuous load and high load operation, and the maximum total loss max(P) can be reduced. tot This can also be reduced. This reduction in maximum peak-to-peak value advantageously provides a range for reducing DC link capacitance by 8.4%, which effectively saves cost and space.

[0066] Figure 6 and Figure 7 The boundaries of the first operating region, represented by lines 38 to 42, are shown in the torque-speed diagram. Compared to the boundary of the first operating region represented by line 44, in a further exemplary embodiment, the carrier frequency is 10 kHz when using SVM, and different when using GDPPWM. In the first exemplary embodiment, the carrier frequency of GDPWM is also 10 kHz. Here, line 38 corresponds to a carrier frequency of 6 kHz, line 39 corresponds to a carrier frequency of 8 kHz, line 40 corresponds to a carrier frequency of 11 kHz, line 41 corresponds to a carrier frequency of 12 kHz, and line 42 corresponds to a carrier frequency of 13 kHz. It can be seen that when using GDPWM, the first operating region becomes smaller as the carrier frequency increases.

[0067] When using GDPWM, the choice of carrier frequency affects the global maximum peak-to-peak value of the DC link voltage, which may reduce DC link capacitance, maximum total loss, and efficiency under partial load. Generally, when using GDPWM, as the carrier frequency increases, the global maximum peak-to-peak value of the DC link voltage decreases, which allows for a reduction in DC link capacitance.

[0068] Regarding this point, Figure 8 Reference line 49 shows a graph illustrating the possible percentage reduction of the DC link capacitance relative to the carrier frequency of the second modulation type, with the case of a constant carrier frequency for the first modulation type. For comparison, line 50 is also plotted, showing the maximum possible reduction of the DC link capacitance when using only GDPWM, compared to using only SVM.

[0069] Figure 9 Finally, a graph showing the maximum percentage reduction in total loss relative to the carrier frequency of the second modulation type is presented, with the carrier frequency of the first modulation type being constant. Here, line 51 shows the maximum relative reduction in total loss at a DC link voltage of 270V, line 52 shows the maximum relative reduction in total loss at a DC link voltage of 350V, and line 53 shows the maximum relative reduction in total loss at a DC link voltage of 450V.

[0070] Figure 10 and 11 Both are torque-speed graphs, and the following parameters are plotted on the graph: Figure 1 The operating area of ​​component 1 in other embodiments having control device 8. Figure 10 and 11 The components of the first operating regions 21, 30 and the second operating regions 32, 32a, 32b are qualitatively illustrated. These exemplary embodiments can be implemented particularly easily and are at least partially capable of achieving similar advantageous effects to the more complex exemplary embodiments described above.

[0071] According to Figure 10 In the first embodiment, the first operating region 21 for positive torque, independent of rotational speed, is defined only by the lower torque boundary 22 and the upper torque boundary 23. Another first operating region 30 for negative torque is also defined independently of rotational speed by the lower torque boundary 22a and the upper torque boundary 23a.

[0072] According to Figure 11 In the first exemplary embodiment, the first operating region 21 with positive torque is defined by a lower torque boundary 22 and an upper torque boundary 23, as well as a lower torque boundary 24 and an upper torque boundary 25. The first operating region 30 with negative torque is defined by a lower torque boundary 22a and an upper torque boundary 23a, as well as a lower torque boundary 24a and an upper torque boundary 25a.

[0073] According to other exemplary embodiments that correspond in other respects to one of the foregoing exemplary embodiments, as an alternative to using feature maps, the control device 8 may alternatively be configured to determine the modulation type to be used based on a function that evaluates at least one operating parameter.

Claims

1. A control device (8) for an inverter (2) for powering an electric machine (3), wherein The control device (8) is configured to provide a pulse width modulated switching signal (15) to drive switching elements (12) of the inverter (2), characterized in that the control device (8) is configured to determine a modulation type from operating point information describing an operating point defined by at least one operating parameter, to generate the pulse width modulated switching signal (15) by the modulation type, and to use a first modulation type in at least one first operating region (21, 28, 30, 31) and a second modulation type in another operating region (32, 32a, 32b), wherein the operating parameter is a DC link voltage of the inverter (2) and the operating regions (21, 28, 30, 31, 32, 32a, 32b) are determined such that a peak-to-peak value of the DC link voltage of the inverter (2) does not exceed a predetermined value.

2. The control device according to claim 1, wherein the first modulation type is a continuous pulse width modulation type and / or the second modulation type is a discontinuous pulse width modulation type.

3. The control device according to claim 1 or 2, wherein the operating parameter is a torque of the electric machine (3) or a current magnitude of a machine current of the electric machine (3).

4. The control device according to claim 3, wherein the first operating region or the plurality of first operating regions (21, 28, 30, 31) is within an operating parameter interval defined by a lower operating parameter boundary (22, 22a) and an upper operating parameter boundary (23, 23a).

5. The control device according to claim 1 or 2, wherein the operating parameter is a rotational speed of the electric machine (3).

6. The control device according to claim 5, wherein the at least one first operating region (21, 28, 30, 31) is within a rotational speed interval defined by a lower rotational speed boundary (24, 24a) and an upper rotational speed boundary (25, 25a).

7. The control device according to claim 1 or 2, wherein the operating region (21, 30, 32) in continuous load operation (35) is determined in such a way that the peak-to-peak value of the DC link voltage does not exceed a predetermined second value which is smaller than a first value.

8. The control device according to claim 1 or 2, configured to provide the switching signal (15) with a different carrier frequency when using the first modulation type than when using the second modulation type.

9. The control device according to claim 1 or 2, configured to determine the modulation type to be used by assigning one of the modulation types to a characteristic map of the at least one operating parameter, or based on a function evaluating the at least one operating parameter.

10. The control device of claim 2, wherein, the first modulation type is a space vector modulation type.

11. The control device of claim 2, wherein, the second modulation type is a generalized discontinuous pulse width modulation type.

12. The control device according to claim 8, configured to provide the switching signal (15) with a lower carrier frequency when using the first modulation type than when using the second modulation type.

13. An inverter (2), comprising: a DC link capacitor (6), a DC link capacitor (6), a plurality of mutually connected switching elements (12) for converting a DC link voltage at a DC link capacitor (6) into a single-phase or multi-phase AC voltage in accordance with a switching signal (15) for driving the switching elements (12), and a control device (8) according to any one of the preceding claims.

14. An assembly (1) having an inverter (2) according to claim 13 and an electric machine (3) which can be operated by an AC voltage.

15. A method for operating an inverter (2) for supplying an electric machine (3) with electrical power, comprising the following steps performed by a control device (8): determining a modulation type from operating point information describing an operating point defined by at least one operating parameter, by which a pulse width modulation switching signal (15) for driving a switching element (12) of the inverter (2) is generated, wherein a first modulation type is used in at least one first operating region (21, 28, 30, 31) and a second modulation type is used in another operating region (32, 32a, 32b), wherein the operating parameter is a DC link voltage of the inverter (2), and the operating regions (21, 28, 30, 31, 32, 32a, 32b) are determined such that a peak-to-peak value of the DC link voltage of the inverter (2) does not exceed a predetermined value; and providing the switching signal (15).

16. A computer program product comprising commands which, when the program is executed by a computer, cause the computer to perform the steps performed by a control device (8) of the method according to claim 15.

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