Computer-implemented method for determining a phase shift for actuating a double inverter arrangement for a vehicle, data-processing device, computer program, computer-readable storage medium, double inverter arrangement

Abstract

The invention relates to a computer-implemented method for determining a phase shift for actuating a double inverter arrangement (1) for a vehicle, wherein the double inverter arrangement (1) comprises a first inverter (2), a second inverter (3) and a DC link (4), in particular wherein the DC link (4) comprises at least one DC link capacitor (5), wherein the first inverter (2) is connected to the DC link (4) and wherein the second inverter (3) is connected to the DC link (4), comprising: providing a prediction model for determining the phase shift between PWM pulse patterns of the two inverters for actuating the double inverter arrangement (1), wherein the prediction model determines the phase shift based on at least one input parameter such that voltage fluctuations of the DC link and resonance effects of the DC link are reduced (310), receiving the at least one input parameter (S20), determining the phase shift by means of the prediction model on the basis of the at least one received input parameter (S30), and providing the determined phase shift for actuating the double inverter arrangement (1) (S40). The invention also relates to a data-processing device, to a computer program, to a computer-readable storage medium and to a double inverter arrangement.

Description

[0001] Computer-implemented method for determining a phase shift for controlling a dual-inverter arrangement for a vehicle, data processing device, computer program, computer-readable storage medium, dual-inverter arrangement

[0002] The invention relates to a computer-implemented method for determining a phase shift for controlling a dual inverter arrangement, a data processing device, a computer program, a computer-readable storage medium, and a dual inverter arrangement.

[0003] Dual inverter systems are known in the art. A dual inverter system comprises two inverters, each driving a load or machine. The two inverters are connected to a common DC link. This arrangement is referred to as a "back-to-back inverter system." The machine can be a motor or a generator. When operating the dual inverter system, voltage fluctuations and resonance effects can occur in the common DC link. These voltage fluctuations, also known as "ripple," can negatively impact power losses and the thermal load of the dual inverter system.Resonance effects in the common DC link can have negative impacts on power losses and thermal stress, among other things. One parameter for influencing voltage fluctuations and resonance effects is the phase shift with which the two inverters of the dual-inverter arrangement are driven. In the context of the present invention, "phase shift" refers to the time offset between the switching operations with which the inverters draw energy from the DC link. It is assumed that pulse-width modulation (PWM) with a specific (but not necessarily constant) PWM switching frequency is used.

[0004] German patent DE 102020 124496 A1 discloses a method for operating at least two inverters connected to a DC network. US patent 2021 / 0305919 A1 discloses an inverter arrangement for an electric vehicle.

[0005] In this context, it has become apparent that there is a need to provide a method for determining a phase shift for controlling a dual inverter arrangement, which on the one hand reduces the voltage fluctuations in the common DC link and on the other hand avoids the excitation of resonance effects in the common DC link.

[0006] It is therefore an object of the present invention to eliminate, or at least partially eliminate, the disadvantages described above in the control of a dual inverter arrangement. In particular, it is an object of the present invention to provide a method for determining a phase shift for controlling a dual inverter arrangement that reduces voltage fluctuations in the common DC link and avoids the excitation of resonance effects in the common DC link.

[0007] This problem is solved by a method having the features of independent claim 1.

[0008] Furthermore, the problem is solved by a device with the features of independent claim 7, a computer program with the features of independent claim 8, a computer-readable storage medium with the features of independent claim 9, and by a double inverter arrangement with the features of independent claim 10.

[0009] Features disclosed in connection with the inventive method naturally also apply in connection with the inventive device, the inventive computer program, the computer-readable storage medium, the inventive double inverter arrangement and vice versa, so that with regard to the disclosure of the individual aspects of the invention, mutual reference is always made or can be made.According to a first aspect of the present invention, a computer-implemented method for determining a phase shift for controlling a dual-inverter arrangement is provided, wherein the dual-inverter arrangement comprises a first inverter, a second inverter and a DC link, in particular wherein the DC link comprises at least one DC link capacitor, wherein the first inverter is connected to the DC link and wherein the second inverter is connected to the DC link, comprising the steps:.

[0010] Providing a predictive model for determining the phase shift for driving the dual inverter arrangement, wherein the predictive model determines the phase shift as a function of at least one input parameter in such a way that voltage fluctuations of the DC link and resonance effects of the DC link are minimized.

[0011] Receiving at least one input parameter,

[0012] Determining the phase shift using the prediction model based on at least one received input parameter,

[0013] Providing the specified phase shift to control the dual inverter arrangement.

[0014] In this context, the term inverter refers to a device that converts direct current (DC) voltage into alternating current (AC) voltage. The inverter could, for example, be a B6 bridge inverter. The inverter can be connected to a machine, such as a motor or a generator. Depending on the application, the machine can operate as either a motor or a generator. The DC link can have a single, shared capacitor or multiple capacitors, for example, one for each side. These are typically connected via low-impedance capacitors.

[0015] The dual inverter configuration can, for example, drive an electric axle with two wheels of a vehicle. Both machines can operate either as motors or as generators. The dual inverter configuration can, for example, drive a series hybrid drive, where one machine operates as a motor and the other as a generator. The dual inverter configuration can be used for a rear axle and / or a front axle.

[0016] The term phase shift refers here to the time offset of the PWM switching operations with which the first inverter and the second inverter draw energy from the DC link or feed it into the DC link. The phase shift is expressed in degrees and can be between 0° and 360°.

[0017] The predictive model can include an analytical model. The predictive model can include a table of values. The table of values ​​may, for example, have been created using simulation calculations. The predictive model can include voltage fluctuations and resonance effects as target variables. The predictive model can include a power loss as a common target variable, which indirectly describes the voltage fluctuations and resonance effects. The predictive model can be created for dual inverter configurations with different characteristics or designs. The predictive model can be created for different operating points of the machine.

[0018] Machines, such as generators or motors, comprise multidimensional value pairs or a multidimensional value table for the dual-inverter configuration. The operating point can be described, for example, by the following parameters: AC-side current IAC, DC-link voltage UDC, power factor cos(ω), modulation index m, modulation method, switching frequency f, and / or phase shift Phi. The predictive model can, for example, determine the resulting power loss for different operating points by varying the phase shift. The predictive model can, for example, determine the resulting power loss for different operating points by varying both the phase shift and the switching frequency. The corresponding value pairs can, for example, be stored in tables.The prediction model can include one or more of the following parameters as at least one input parameter: AC current IAC, DC link voltage UDC, power factor cos( ), modulation index m, modulation method. Preferably, the at least one input parameter can be a switching frequency.

[0019] The invention is based on the understanding that voltage fluctuations and resonance effects can occur when driving dual inverter arrangements in the DC link. Furthermore, the phase shift and the switching frequency influence these voltage fluctuations and resonance effects in the DC link. To solve this problem, the invention proposes determining a phase shift that minimizes the voltage fluctuations and resonance effects in the DC link. For this purpose, a predictive model is provided that receives at least one input and outputs a phase shift. In this way, the resonance effects and voltage fluctuations in the DC link can be advantageously minimized. Furthermore, power losses can be reduced. Additionally, the thermal load on the dual inverter arrangement can be reduced.

[0020] In other words, with back-to-back inverter configurations, it can be advantageous to design the machine control in such a way that current and voltage ripple, and thus the load on the DC link, remains as low as possible. One way to achieve this is by phase-shifting the PWM pulse patterns of both inverters. However, this can also lead to resonance phenomena. These resonance phenomena generate additional currents, which can result in a suboptimal power factor and additional losses. In some cases, extreme resonance phenomena can even cause thermal damage to components.

[0021] Another problem is that reducing voltage ripple in the DC link and avoiding resonance phenomena can be conflicting goals; that is, operating conditions that are advantageous for one goal can negatively affect the other. The invention solves these problems by determining a phase shift for driving the dual inverter arrangement, minimizing DC link voltage fluctuations and resonance effects.

[0022] According to a preferred embodiment, at least one input parameter can include a predetermined synchronized switching frequency.

[0023] The predetermined synchronized switching frequency refers to the PWM switching frequency used to control both inverters. The switching frequency can be an externally specified, but not necessarily constant, value. It may be determined by the application's requirements. For example, electromagnetic compatibility, AC switching losses, or noise effects may necessitate the use of a specific switching frequency.

[0024] Certain combinations of switching frequency and phase shift can lead to resonance phenomena in the DC link. These are undesirable because they can cause additional losses and potentially damage. These resonance phenomena can occur at specific combinations of switching frequency and phase shift that are characteristic of the respective DC link.

[0025] In this case, the prediction model can comprise a one-dimensional table. When creating the model, for example, the switching frequency could have been varied as an input variable for a representative operating point, and the phase shift could have been determined in such a way as to minimize voltage fluctuations and resonance effects in the DC link.

[0026] In this way, a phase shift can advantageously be determined with only one input parameter, minimizing voltage fluctuations and resonance effects in the DC link. According to a preferred embodiment, the prediction model can determine a synchronized switching frequency as a function of the at least one input parameter such that voltage fluctuations and resonance effects of the DC link are minimized, further comprising determining the synchronized switching frequency using the prediction model based on the at least one received input parameter.

[0027] Providing the specified synchronized switching frequency to control the dual inverter arrangement,

[0028] wherein the prediction model may include a cost function, in particular wherein the at least one input parameter includes one or more of the following parameters: AC current IAC, DC link voltage UDC, power factor cos ( ), modulation index m, modulation method, rotational speed n, torque M.

[0029] By determining a synchronized switching frequency, voltage fluctuations and resonance effects in the DC link can be further minimized. Depending on at least one input parameter, such as the operating point, the predictive model can determine and output the synchronized switching frequency in addition to the phase shift. Voltage fluctuations and resonance effects in the DC link are primarily influenced by these two quantities. Preferably, the predictive model can receive at least the following parameters as input parameters: AC-side current IAC, DC link voltage UDC, power factor cos(ω), modulation index m, and modulation method. These parameters enable a precise description of the inverter's operating point. These parameters refer to the dual-inverter configuration.Alternatively, the predictive model can use the machine's rotational speed and torque as input parameters. From these, and given knowledge of the system behavior, the corresponding operating point for the inverter can be derived. This can be predefined in the predictive model or calculated. Using the cost function (a performance criterion), the phase shift and synchronized switching frequency can be advantageously determined in such a way as to minimize voltage fluctuations and resonance effects in the DC link. The cost function can advantageously weight the voltage fluctuations and resonance effects as a combined target variable, depending on the requirements. For example, voltage fluctuations can be weighted more heavily than resonance effects.For example, power loss represents such a combined cost function, as it includes losses from voltage fluctuations in the DC link as well as losses from resonance effects. Alternatively, other cost functions can be used.

[0030] According to a preferred embodiment, the prediction model can include a table of values.

[0031] In this way, a predictive model can be efficiently provided. This can be a one-dimensional or multi-dimensional table of values. The table of values ​​can include single values ​​for phase shifts. In other words, the table of values ​​can be one-dimensional. The table of values ​​can include pairs of values ​​for phase shifts and switching frequencies. In other words, the table of values ​​can be multi-dimensional. The table of values ​​can be created for specific operating points. The table of values ​​can be created for a general operating point.

[0032] According to a preferred embodiment, the prediction model can include an analytical equation.

[0033] For example, instead of a one-dimensional table of values, this can be represented as an analytical equation. For instance, the equation can take the predetermined synchronized switching frequency as its input and calculate the phase shift. This advantageously minimizes the memory required for the predictive model.

[0034] According to a preferred embodiment, the at least one input parameter can include an operating mode for the first machine and the second machine, wherein the operating mode comprises motor operation and generator operation. Depending on whether the first and second machines are operated identically as generators or as motors, or differently, a different phase shift or a different phase shift and switching frequency are required, since the optimal values ​​or value pairs vary. The prediction model can, for example, include two different tables of values ​​to take the operating mode into account accordingly.

[0035] In other words, the prediction model takes into account whether the machines are operated symmetrically or asymmetrically and provides special prediction models for this purpose.

[0036] Another aspect of the present invention relates to a device for data processing, comprising means for carrying out a method described in more detail above.

[0037] The device according to one or more embodiments can be implemented using hardware, software, and / or a combination thereof. The device can be a single component or multi-component. For example, the device can be implemented by processing circuits such as a processor, central processing unit (CPU), controller, arithmetic logic unit (ALU), digital signal processor, microcomputer, field-programmable gate array (FPGA), system-on-chip (SoC), programmable logic unit, microprocessor, or any other device capable of responding to instructions and executing them in a defined manner.

[0038] The device may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the internet, a wide area network (WAN), or combinations thereof.

[0039] The device may also include one or more storage devices. The one or more storage devices may be physical or non-transient computer-readable storage media, such as random-access memory (RAM), read-only memory (ROM), a permanent mass storage device (e.g., a hard disk drive), a solid-state device (e.g., NAND flash), and / or any other data storage mechanism capable of storing and recording data. The one or more storage devices may be used to store computer programs, program code, instructions, or a combination thereof.

[0040] The explanations and advantages of individual embodiments described here also apply analogously to the other embodiments. Various exemplary features of the embodiments can be combined according to the invention wherever this is technically sensible and feasible.

[0041] Another aspect concerns a computer program, comprising commands that, when the program is executed by a computer, cause it to perform the procedure described above.

[0042] Another aspect concerns a computer-readable storage medium, comprising instructions which, when executed by a computer, cause it to perform the procedure described above.

[0043] Another aspect concerns a double inverter arrangement with a device described in more detail above.

[0044] The dual-inverter arrangement preferably comprises a first inverter, a second inverter, and a DC link. The DC link may include at least one DC link capacitor. The first inverter and the second inverter may be connected to the DC link.

[0045] The invention is explained below with the aid of a drawing. The drawing shows:

[0046] Figure 1 shows a dual inverter arrangement, Figure 2 shows a flowchart for a method for determining a phase shift for controlling a dual inverter arrangement.

[0047] Figure 3 shows a representation of power losses in an intermediate circuit of a dual inverter arrangement as a function of the switching frequency and the phase shift.

[0048] Figure 4 illustrates the process,

[0049] Figure 5 provides a further illustration of the process, and

[0050] Figure 6 provides a further illustration of the process.

[0051] Identical elements are provided with the same reference numerals. Features of the individual embodiments can be interchanged, complement each other, or replace each other.

[0052] Figure 1 shows a dual-inverter arrangement 1. The dual-inverter arrangement 1 comprises a common DC link 4. The DC link 4 includes at least one DC link capacitor 5. Alternatively, the DC link 4 can include several DC link capacitors. The dual-inverter arrangement 1 comprises a first inverter 2, which is connected to the DC link 4. The dual-inverter arrangement 1 comprises a second inverter 3, which is also connected to the DC link 4. The first inverter 3 is connected to a load 7. The load 7 can, for example, be an electric machine that can be operated as a motor or generator. The second inverter 4 is connected to a machine 8. The machine 8 can, for example, be an electric machine that can be operated as a motor or generator.The dual inverter arrangement 1 comprises a controller 9 for controlling the dual inverter arrangement 1. The dual inverter arrangement 1 includes, in this case, a device 6 for carrying out the inventive method for determining a phase shift or for determining a phase shift and a switching frequency. Figure 2 shows a flowchart for a method for determining a phase shift for controlling a dual inverter arrangement 1. The method can, for example, be carried out by a device 6.

[0053] Step S10 includes providing a prediction model to determine the phase shift for controlling the double inverter arrangement 1, wherein the prediction model determines the phase shift as a function of at least one input parameter in such a way that voltage fluctuations of the DC link and resonance effects of the DC link are minimized.

[0054] The prediction model in this case comprises a table of values. Alternatively, the prediction model can comprise one or more analytical equations.

[0055] Step S20 involves receiving at least one input parameter.

[0056] The at least one input parameter comprises a predetermined synchronized switching frequency. Alternatively or additionally, the at least one input parameter can comprise an operating point. The at least one input parameter can, for example, include the following parameters: AC current IAC, DC link voltage UDC, power factor cos(ω), modulation index m, modulation method. Alternatively or additionally, the at least one input parameter can comprise a rotational speed n and a torque M.

[0057] Step S30 involves determining the phase shift using the prediction model based on at least one received input parameter.

[0058] Step S40 comprises providing the specified phase shift for controlling the dual-inverter arrangement 1. The specified phase shift can be provided or transmitted to a controller 9. The controller 9 can, for example, use the specified phase shift to control the first inverter 5 and the second inverter 6. Alternatively or additionally, a predictive model can determine a synchronized switching frequency based on at least one input parameter such that voltage fluctuations and resonance effects of the DC link are minimized. Alternatively or additionally, step S20 comprises determining the synchronized switching frequency using the predictive model based on at least one received input parameter.Alternatively or additionally, step S40 can include providing the specified synchronized switching frequency for controlling the dual inverter arrangement 1.

[0059] Figure 3 shows an exemplary representation of power losses 12 in a DC link of a dual-inverter arrangement as a function of the switching frequency 11 and the phase shift 10 for a given operating point. It can be seen that peaks in the power losses occur at a switching frequency of approximately 15 kHz and a phase shift of approximately 45°, 135°, 225°, and 315°. A similar pattern can be observed at a switching frequency of 10 kHz, where six peaks occur. The specific location of the peaks is shown here only as an example; in reality, it depends on the design of the inverter system or the DC link and can vary. However, for a given system, the location of the peaks can be determined, so that it is generally known at the time of operation. The invention utilizes this knowledge by determining pairs of values ​​for phase shift and switching frequency for an operating point at which the peaks are avoided.Such a representation or analysis can be used as the basis for creating the prediction model to generate a table of values. The position of the peaks can be described using equations, as recurring patterns emerge. For example, the position of other peaks can be determined as a function of the switching frequency using the following equation: fn = ^fi,n = 2,4,6.

[0060]

[0061] Here is the main resonant frequency at which a single peak forms. At n=2, 4, 6,... secondary resonances occur, each with n peaks.

[0062] The position of the peaks along the axis of the phase shift can be described by the following formula:

[0063] < 360° f 1 t s \ , z \

[0064] T pi ~ — * ? — k . k = 0 t (n 1 ).

[0065] ' n \2 J

[0066]

[0067] For example, for n=4, four peaks result at phase shifts of 45°, 90°, 135°, 225°.

[0068] Figure 4 illustrates the process. A higher-level controller 13 transmits control data to the dual inverter array 14 via an interface. The control data includes, for example, the operating point for machines 7 and 8. The dual inverter array includes a phase-shift controller configured to drive the first and second inverters with a phase shift. The dual inverter array 14 is connected to machines 7 and 8. The phase-shift controller transmits the operating point, described by the parameters AC-side current IAC, DC-link voltage UDC, power factor cos ( ), modulation index m, and modulation method, as input parameters to the device 6, which executes the method for determining a phase shift and a synchronized switching frequency.Alternatively, the operating point can also be transmitted directly from the higher-level controller 13 to the device 6. The device 6 transmits the specified phase shift and the specified switching frequency to the phase shift controller of the double inverter arrangement 14.

[0069] Figure 5 shows a further illustration of the method. Similar to Figure 3, a map of the power losses is plotted against the phase shift 10 and the switching frequency 11. It can be seen that peaks 15 for the power losses again appear as a function of the switching frequency and the phase shift. Furthermore, an exemplary path 16 is shown, which can be used as an input variable at a predetermined switching frequency to determine a phase shift. The exemplary path generally follows a phase shift that minimizes the voltage ripple of the DC link (90° in this example), but deviates from this in some cases to avoid the peaks at a phase shift of 90°. Such a path can be stored in an equation or a one-dimensional table of values ​​for the prediction model.

[0070] Figure 6 shows a further illustration of the method. In contrast to Figure 3, the higher-level motor control 13 transmits a predetermined switching frequency to the device 6, which executes the method. The prediction model further distinguishes whether both machines 7 and 8 are operated identically, i.e., as motors or generators, or whether they are operated differently, i.e., one as a motor and one as a generator. The prediction model uses two different value tables as a basis for this. A selection unit 15 is also shown, which, depending on the operating points, respectively,

[0071] The operating modes of the first machine 7 and the second machine 8 determine which value table should be used. For this purpose, the selection unit 15 receives the operating points, for example, from the phase shift control of the double inverter arrangement 14. The selection unit 15 can, for example, also be implemented in the device 6 or, as shown here, separately. If only symmetrical operating modes are present, the selection unit 15 can be omitted. In this case, the path 16.reference sign table applies.

[0072] Dual inverter configuration

[0073] first inverter

[0074] second inverter

[0075] DC link, DC link capacitor

[0076] device

[0077] Engine, generator

[0078] Engine, generator

[0079] steering

[0080] Vertical axis phase shift

[0081] Switching frequency

[0082] Performance loss

[0083] steering

[0084] Dual inverter arrangement with phase shift control selection unit

[0085] path

Claims

Claims 1. Computer-implemented method for determining a phase shift for driving a dual-inverter arrangement (1), wherein the dual-inverter arrangement (1) comprises a first inverter (2), a second inverter (3) and a DC link (4), in particular wherein the DC link (4) comprises at least one DC link capacitor (5), wherein the first inverter (2) is connected to the DC link (4) and wherein the second inverter (3) is connected to the DC link (4), comprising: Providing a prediction model for determining the phase shift between PWM pulse patterns of the two inverters for driving the dual-inverter arrangement (1), wherein the prediction model determines the phase shift as a function of at least one input parameter such that voltage fluctuations of the DC link and resonance effects of the DC link are minimized (S10), receiving the at least one input parameter (S20), Determining the phase shift using the prediction model based on at least one received input parameter (S30), Providing the specified phase shift for driving the double inverter arrangement (1) (S40).

2. Method according to claim 1 , characterized by the fact that which includes at least one input parameter: a predetermined synchronized switching frequency.

3. Method according to claim 1 , characterized by the fact that The prediction model determines a synchronized switching frequency as a function of at least one input parameter in such a way that voltage fluctuations and resonance effects of the DC link are minimized; furthermore, determining the synchronized switching frequency using the prediction model based on the at least one received input parameter. Providing the specified synchronized switching frequency for controlling the dual inverter arrangement (1), wherein the prediction model includes a cost function, in particular wherein the at least one input parameter includes one or more of the following parameters: AC current IAC, DC link voltage UDC, power factor cos ( ), modulation index m, modulation method, rotational speed n, torque M.

4. Method according to any of the preceding claims, the prediction model includes a table of values.

5. Method according to claim 2, characterized by the fact that The prediction model includes an analytical equation.

6. Method according to any of the preceding claims, characterized in that at least one input parameter includes an operating mode of the first machine and the second machine, wherein the operating mode includes motor operation and generator operation.

7. Device (6) for data processing, comprising means for carrying out the method according to any one of claims 1 to 6.

8. Computer program comprising instructions which, when the program is executed by a computer, cause it to execute the method according to any one of claims 1 to 6.

9. Computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to execute the method according to any one of claims 1 to 6. - 19 - 10. Dual inverter arrangement (1) with a device according to claim 6, further comprising a first inverter (2), a second inverter (3) and a DC link (4), in particular wherein the DC link (4) comprises at least one DC link capacitor (5), wherein the first inverter (2) is connected to the DC link (4) and wherein the second inverter (3) is connected to the DC link (4), in particular wherein the dual inverter arrangement comprises a first machine and a second machine.

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