Method and device for estimating a magnetic stator flux of an electrical machine, electrical drive device

Abstract

The invention relates to a method for estimating a magnetic stator flux (Ψ) of an electrical machine (2), wherein the machine (2) has a stator with a multi-phase motor winding (6) and a rotatably mounted rotor (3), and wherein an actual electrical voltage value (U Ist ) of the motor winding (6) and an actual electrical current value (I Ist ) of the motor winding (6). It is intended that an actual rotor angle (φ Ist ) of the rotor (3) is determined, and that a magnetic stator flux (Ψ) of the stator is determined as a function of the determined actual voltage value (U Ist ), actual current value (I Ist ) and actual rotor angle (φ Ist ) is estimated.

Description

[0001] The invention relates to a method for estimating a magnetic stator flux of an electrical machine, wherein the machine has a stator with a multi-phase motor winding and a rotatably mounted rotor, and wherein an actual electrical voltage value of the motor winding and an actual electrical current value of the motor winding are determined.

[0002] Furthermore, the invention relates to a device specially designed to carry out such a method, as well as to an electric drive device with such a device. State of the art

[0003] Numerous methods are known from the state of the art for estimating electrical parameters of electrical machines designed as induction machines. Parameters to be estimated include, for example, the resistance of a stator coil, an inductance, or equivalently, a stator flux, and possibly a permanent magnet flux. The estimation of these parameters is typically based on the measured voltages and currents in the machine. Both active and passive methods are used to estimate the parameters.

[0004] In active methods, special signals are introduced into the machine to enable particularly accurate estimation of (individual) parameters. One such method is known, for example, from Simon Delamere Wilson, Paul Stewart, Benjamin P. Taylor: Methods of resistance estimation in permanent magnet synchronous motors for real-time thermal management, IEEE Transactions on Energy Conversion, 25(3):698-707, 2010. Another such method is known, for example, from Sang-Bin Lee, TG Habetler: An online stator winding resistance estimation technique for temperature monitoring of lineconnected induction machines, IEEE Transactions on Industry Applications, 39(3):685-694, 2003.

[0005] Passive methods do not require this signal imposition; instead, the parameters are estimated based on the measured variables that arise during operation. The methods known from the prior art are characterized by the fact that they typically only determine a subset of the parameters. For example, there are flux estimation methods in which the stator resistance is assumed to be known. One such method is known, for example, from the applicant's published application DE 10 2021 206 317 A1 and the prior art cited therein. Methods in which the resistance is estimated by assuming a nominal inductance are also known, for example, from Arie Levant, Miki Livne, Xinghuo Yu: Sliding-mode-based differentiation and its application, IFAC-PapersOnLine, 50(1):1699-1704, 2017.

[0006] A further method is known from a yet unpublished patent application by the applicant, in which both the resistance and magnetic parameters of the machine are estimated using an estimation cascade. For simplicity, the assumption was made that the machine to be characterized can be described by angle-independent quantities in a coordinate system rotating with the rotor. Disclosure of the invention

[0007] The method according to the invention with the features of claim 1 is characterized in that an actual rotor angle of the rotor is determined, and that a magnetic stator flux of the stator is estimated as a function of the determined actual voltage value, actual current value, and actual rotor angle. In contrast to the known methods mentioned above, the invention also determines the actual rotor angle and takes this into account when estimating the magnetic stator flux. As a result, the stator flux, which is dependent on voltage and current, is advantageously linked to the corresponding angle of rotation of the rotor. Compared to the prior art mentioned above, the invention thus enables a more precise representation of the machine behavior because the description of the magnetic flux linkage is not only current-dependent as Ψ(I), but also includes the dependence on the rotor position angle as Ψ(I, φ).This more precise representation creates an advantageous opportunity to improve control quality, which also allows machine harmonics to be taken into account. This, in turn, can be advantageously used to reduce torque ripple. In particular, a characteristic map of the magnetic stator flux with angle-dependent inductances can be identified. According to the invention, this identification is carried out by determining current, voltage, and rotor angle. In particular, current, voltage, and / or rotor angle are measured using suitable sensors. Preferably, a stator resistance of the stator is also estimated depending on the current value, voltage value, and / or rotor angle. Another advantageous property of the method is its passivity, i.e., no special identification signals need to be introduced into the machine.The method according to the invention and the corresponding identification are therefore advantageously carried out during ongoing machine operation, without the need for additional signal injection, as in the aforementioned prior art, which can have a detrimental effect on the machine's efficiency. The method can be used in a wide range of electrical machines, in particular braking systems, for example, electromechanical brake force generators, drive systems, for example, traction drives, steering systems, and industrial drives.

[0008] According to a preferred development of the invention, the actual voltage value, actual current value, and actual rotor angle are determined repeatedly, in particular continuously, and the actual voltage value and actual current value are stored as memory contents in one of at least two electronic memories, each as a function of the respectively determined actual rotor angle, and the corresponding memory contents are evaluated to estimate the magnetic stator flux. The continuous determination and the use of multiple memories advantageously ensure that the method delivers reliable estimated values, and corresponding angle dependencies are also reliably identified. Preferably, a plurality of memories is provided to further optimize the management of the memory contents.For example, the memory contents in the respective memory are evaluated when a memory location is completely filled with memory contents, and / or the memory contents are deleted from the memory after evaluation so that it can be filled again with new memory contents.

[0009] It is particularly preferred that at least a first and a second memory are provided, and that for a predetermined angular range only memory contents are stored in the first memory, and the memory contents of the second memory are evaluated. Thus, only one of the memories is used for reading and another of the memories for writing. The read accesses and write accesses are thus distributed between the memories, so that the efficiency of the method is advantageously further improved. Accordingly, the efficiency can optionally be further improved if a plurality of memories is provided. For example, several of the memories are used for writing, in particular in parallel, in order to be able to increase a sampling frequency, and / or several of the memories are used for reading, in particular in parallel, in order to speed up the evaluation and thus the estimation.Preferably, at least two of the memories are of equal size in terms of their storage space, i.e., they have an identical storage space; alternatively, at least one of the memories has a larger storage space.

[0010] According to a preferred embodiment of the invention, the predetermined angular range corresponds to a fraction or multiple of a full rotation of the rotor. This provides a particularly advantageous option for distributing the storage contents among the storage units. For example, the predetermined angular range corresponds exactly to half or a full rotation of the rotor or rotor shaft.

[0011] Particularly preferably, the function of the memories is swapped after each predetermined angular range, so that alternately only memory contents are stored in the first memory, and the memory contents of the second memory are evaluated, and subsequently only memory contents are stored in the second memory, and the memory contents of the first memory are evaluated. Each of the memories is thus used alternately for reading and writing. This further improves the efficiency of the method according to the invention because the filling of one of the memories with memory contents takes place in parallel with the evaluation of the memory contents of another of the memories.

[0012] According to a preferred embodiment of the invention, the respective memory content is preprocessed before evaluation using a time series-based extraction method, in particular standard deviation and / or Fourier analysis. Appropriate preprocessing advantageously ensures that the estimated values ​​are determined particularly robustly.

[0013] Particularly preferably, a characteristic map for the estimated magnetic stator flux is determined depending on the respective, in particular preprocessed, memory content, in particular by means of a recursive estimation method. Determining the characteristic map offers the advantage that the dependencies represented therein can be used particularly easily for tasks such as control or diagnostics.

[0014] According to a preferred development of the invention, a sampling frequency for determining the actual voltage value, actual current value, and / or actual rotor angle is selected depending on an angular velocity and / or an electrical frequency of a control of the electric machine. By selecting the sampling frequency accordingly, it is advantageously ensured that the estimated values ​​are always generated with sufficient resolution.

[0015] The device for estimating a magnetic stator flux of an electrical machine with the features of claim 9 is characterized by an evaluation unit that is specifically designed to carry out the method according to the invention. This results in the advantages already mentioned. In particular, the device has a control unit that is designed to control the electrical machine, for example, depending on the estimated stator flux. Preferably, the evaluation unit and control unit are part of a common control device. In particular, the device each has at least one current sensor, voltage sensor, and / or rotor position sensor for determining actual voltage values, actual current values, and / or actual rotor angles.

[0016] The electric drive device with the features of claim 10 comprises an electric machine, the machine having a stator with a multi-phase motor winding and a rotatably mounted rotor. It is characterized by the device according to the invention. This also results in the aforementioned advantages. In particular, the electric drive device is designed as a drive device of a motor vehicle.

[0017] Further preferred features and combinations of features emerge from the above description and from the claims. The invention is explained in more detail below with reference to the drawings. Fig. 1 a drive device with an electric machine, Fig. 2 a detailed view of the drive device, and Fig. 3 a method for estimating a magnetic stator flux of the electric machine.

[0018] Fig. 1 shows a schematic representation of an electric drive device 1. In the present case, the drive device 1 is, merely by way of example, the drive device 1 of a motor vehicle not shown in detail. The drive device 1 comprises an electric machine 2. The electric machine 2 has a rotatably mounted rotor 3. The rotor 3 has a permanent magnet arrangement 4 with a plurality of permanent magnets 5.

[0019] The machine 2 also has a motor winding 6 with, in this case, three phases: U, V, and W. The motor winding 6 is part of a stator of the machine 2 and is therefore fixed to the body of the motor vehicle. The motor winding 6 is distributed around the rotor 3 such that the rotor 3 can be rotated by appropriately energizing the phases U, V, and W. Due to the above-described configuration of the machine 2, the machine 2 is designed as a permanent magnet synchronous machine 2.

[0020] The drive device 1 also has an electrical energy storage device 7. The motor winding 6 is electrically connected to the energy storage device 7 via power electronics 8 of the drive device 1.

[0021] The power electronics 8 has a number of half-bridges 10 corresponding to the number of phases U, V, and W. Each of the half-bridges 10 is assigned to a different one of the phases U, V, and W. To enable the desired current supply to the phases U, V, and W, each of the half-bridges 10 has at least one high-side switch 11 and at least one low-side switch 12. In this case, the power electronics 8 also has an intermediate circuit capacitor 9.

[0022] The drive device 1 also has a device 13. The device 13 has a Fig. 1 schematically shown voltage sensor device 14. The voltage sensor device 14 is designed to detect electrical terminal potentials of the motor winding 6. For this purpose, the voltage sensor device 14 has at least one Fig. 1 voltage sensor not shown, preferably several voltage sensors.

[0023] The device 13 also has a Fig. 1 schematically shown current sensor device 15. The current sensor device 15 is designed to detect electrical currents flowing through the phases U, V and W. For this purpose, the current sensor device 15 has at least one Fig. 1 current sensor not shown, preferably several current sensors.

[0024] The device 13 further comprises a Fig. 1 also has a rotor position sensor device 16, which is also only shown schematically. The rotor position sensor device 16 is designed to detect a rotor angle of the rotor 3. For this purpose, the rotor position sensor device 16 has at least one Fig. 1 not shown rotor position sensor, preferably several rotor position sensors.

[0025] The device 13 also has an evaluation unit 17. The evaluation unit 17 is communicatively connected to the voltage sensor device 14, the current sensor device 15, and the rotor position sensor device 16.

[0026] The evaluation unit 17 is designed to estimate a magnetic stator flux Ψ, i.e. a magnetic flux generated by the motor winding 6, as a function of the electrical terminal potentials detected by the voltage sensor device 14, the electrical currents detected by the current sensor device 15, and the rotor angles detected by the sensor device 16.

[0027] Finally, the device 13 also has a control unit 18. The control unit 18 is communicatively connected to the evaluation unit 17, and the evaluation unit 17 provides the estimated stator flux ψ̂ to the control unit 18. In this case, the evaluation unit 17 and the control unit 18 are part of the same control device 19.

[0028] The control unit 18 is particularly designed to control the switches 11 and 12 of the half-bridges 10 of the power electronics 8. Preferably, the control unit 18 outputs a target stator flux ψ as a function of a torque specification. Soll for machine 2 and controls switches 11 and 12 in such a way that the estimated stator flux ψ̂ corresponds to the desired stator flux ψ Soll The torque specification is provided, for example, depending on the actuation of a motor vehicle's accelerator pedal or the like.

[0029] In the following, with reference to Fig. 3 describes an advantageous method for estimating the magnetic stator flux of the electric machine 2. For this purpose, the Fig. 3 illustrates the method using a flowchart. In particular, the method ensures that the machine's behavior is accurately reproduced. In this case, the method is implemented using evaluation unit 17.

[0030] In the Fig. Figure 2 shows a detailed view of the drive device 1, also schematically, in which the evaluation unit 17, which is essential for the method according to the invention, is shown in more detail. The resulting communication processes, which will be described below, are shown in the Fig. 2 indicated by corresponding arrows between the components.

[0031] In a step S1, the method begins by determining an actual electrical voltage value U Ist the motor winding 6, an actual electrical current value I Istthe motor winding 6 and an actual rotor angle φ Ist of the rotor 3 are determined repeatedly, in particular continuously. For this purpose, corresponding value pairs are preferably formed at the same time.

[0032] Particularly preferred is a sampling frequency for determining the actual voltage value U Ist , Actual current value I Ist and / or actual rotor angle φ Ist selected as a function of an angular velocity and / or an electrical frequency of the electrical machine 2.

[0033] The sampling frequency f s is therefore for a fixed memory size with N samples Sampling points depending on the speed or electrical frequency f el elected to: fs=Nsamples⋅fel

[0034] For this purpose, the electrical terminal potentials of the motor winding 6 are preferably monitored using the voltage sensors of the voltage sensor device 14, and information regarding the detected electrical terminal potentials is provided to the evaluation unit 17. For example, the voltage sensors provide their sensor signal to the evaluation unit 17.

[0035] Subsequently, the evaluation unit 17 determines an actual voltage value U depending on the electrical terminal potentials of the motor winding 6. Ist : determined. The actual voltage value U Ist describes the electrical terminal potentials of the motor winding 6 in particular in the form of a vector in a flux coordinate system.

[0036] Furthermore, the electrical currents flowing through phases U, V, and W are preferably monitored by means of the current sensors of the current sensor device 15, and information regarding the detected currents is provided to the evaluation unit 17. For example, the current sensors provide their sensor signal to the evaluation unit 17.

[0037] Subsequently, the evaluation unit 17 determines an actual current value I Ist The actual current value I Ist describes the electrical currents flowing through the phases U, V and W, particularly in the form of a vector in the flux coordinate system.

[0038] Furthermore, the rotor angle of the rotor 3 is preferably monitored by means of the rotor position sensor of the rotor position sensor device 16, and information regarding the detected rotor angle is provided to the evaluation unit 17. For example, the rotor position sensor provides its sensor signal to the evaluation unit 17. Subsequently, the evaluation unit 17 calculates an actual rotor angle φ depending on the information. Ist determined.

[0039] In a step S2, the thus determined actual voltage values ​​U Ist and actual current values ​​I Ist each depending on the determined actual rotor angle φ Ist stored as memory content in one of at least two electronic memories of the evaluation unit 17.

[0040] As in the Fig.2, separate memories are provided for voltages and currents, namely a first current value memory 20 and a second current value memory 21, as well as a first voltage value memory 22 and a second voltage value memory 23. The respectively determined actual rotor angle φ Ist decides in which of the memory the respective actual current value I Ist or actual voltage value U Ist is stored.

[0041] For this purpose, a first switch 24, 25, implemented in hardware or software, is assigned to each of the memories, which is designed to grant write access to either exactly one of the current value memories 20, 21 and one of the voltage value memories 22, 23.

[0042] In the present case, only memory contents are stored in the respective first memory 20, 22 for a given angular range, and then only memory contents are stored in the respective second memory 21, 23 for the given angular range, by controlling the switch for connecting and filling the respective first memory 20, 22 or the second memory 21, 23 as soon as the angular range is reached.

[0043] The angular range preferably corresponds to a fraction or multiple of a full rotation of the rotor. For example, the angular range corresponds exactly to one rotation of the rotor, meaning that each of the memories stores the contents of exactly one period.

[0044] The first and second reservoirs are filled alternately. Of course, embodiments with more than two reservoirs are also conceivable; the underlying principle remains the same.

[0045] In order to empty the memories now filled in this way, the memory contents of the last filled memories that are currently not connected by the respective switch 24, 25 are evaluated in a step S3.

[0046] For this purpose, a first switch 26, 27, implemented in hardware or software, is assigned to each of the memories, which is designed to grant read access to either one of the current value memories 20, 21 and one of the voltage value memories 22, 23. Each of the memories is preferably used for read-only or write-only purposes, but not for read and write purposes simultaneously.

[0047] The function of the memories is swapped after each predetermined angular range, so that alternately only memory contents are stored in the respective first memory 20, 22, and the memory contents of the respective second memory 21, 23 are evaluated, and then only memory contents are stored in the second memory 21, 23, and the memory contents of the first memory 20, 22 are evaluated.

[0048] If the specified angular range, as described above, corresponds to a full revolution of the rotor 3, the corresponding memory contents are alternately written into a double memory for each electrical revolution of the machine 2.

[0049] To switch between memories, the elapse of the angular range is detected, specifically whether a full rotation has been completed. If this is the case, the corresponding measurement data is written to one of the memories, while the other is used exclusively for reading.

[0050] After each complete rotation, the memory functions are swapped (read, write). This ensures that the last full period is always stored in the memory.

[0051] In a step S4, the corresponding memory contents, each accessible for read access, are evaluated to estimate the magnetic stator flux ψ of the machine 2. In this respect, the magnetic stator flux ψ is now calculated as a function of the determined actual voltage value U Ist , the determined actual current value I Ist and the actual rotor angle φ Ist appreciated.

[0052] In the present case, a characteristic map for the estimated magnetic stator flux is determined depending on the respective, in particular preprocessed, memory content, in particular by means of a recursive estimation method, and stored in an electrical characteristic map memory 28 provided for this purpose.

[0053] A characteristic of the invention is that for learning the magnetic flux characteristic field, not only an instantaneous current-voltage data pair is available, but the data curve over the electrical angle of a full period, as described above.

[0054] Preferably, the respective memory content is preprocessed before evaluating and creating the characteristic map using a time series-based extraction method, in particular Fourier analysis and / or standard deviation.

[0055] The flux map is then learned in a two-stage process: In a preprocessing step, the memory contents are first decomposed into their spectral components using, for example, a Fourier analysis. In a second learning step, the magnetic flux map is updated. For this purpose, the flux map is particularly advantageously represented as the product of the parameter vector w and the basis functions Φ as Ψ=wT⋅Φ(I, φ) Together with the dynamic relationship between flow and current, voltage and angle Ψ˙=f(I, U, φ) A recursive estimation problem is then preferably formulated, with the help of which the map parameters are updated.

[0056] The corresponding characteristic map can now be read out, for example, by the control device 18 and used to control the electric machine 2, as described above. This completes the method. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 206 317 A1

[0005] Cited non-patent literature

[0000] IEEE Transactions on Energy Conversion, 25(3):698-707, 2010. Another such method is known, for example, from Sang-Bin Lee, TG Habetler: An online stator winding resistance estimation technique for temperature monitoring of lineconnected induction machines, IEEE Transactions on Industry Applications, 39(3):685-694, 2003

[0004] Arie Levant, Miki Livne, Xinghuo Yu: Sliding-mode-based differentiation and its application, IFAC-PapersOnLine, 50(1):1699-1704, 2017

[0005]

Claims

[1] Method for estimating a magnetic stator flux (Ψ) of an electrical machine (2), wherein the machine (2) has a stator with a multi-phase motor winding (6) and a rotatably mounted rotor (3), and wherein an actual electrical voltage value (U Ist ) of the motor winding (6) and an actual electrical current value (I Ist ) of the motor winding (6) are determined, characterized by that an actual rotor angle (φ Ist ) of the rotor (3) is determined, and that a magnetic stator flux (Ψ) of the stator is determined as a function of the determined actual voltage value (U Ist ), actual current value (I Ist ) and actual rotor angle (φ Ist ) is estimated. [2] Method according to claim 1, characterized by that the actual voltage value (U Ist ), actual current value (I Ist ) and actual rotor angle (φ Ist ) repeatedly, especially continuously, and the actual voltage value (U Ist ) and actual current value (I Ist) depending on the actual rotor angle (φ Ist ) are stored as memory contents in one of at least two electronic memories (20-23), and that the corresponding memory contents are evaluated to estimate the magnetic stator flux (Ψ). [3] Method according to claim 2, characterized by that at least a first and a second memory (20-23) are provided, and that for a predetermined angular range only memory contents are stored in the first memory (20,22) and the memory contents of the second memory (21,23) are evaluated. [4] Method according to claim 3, characterized by that the specified angular range corresponds to a fraction or multiple of a full revolution of the rotor (3). [5] Method according to one of claims 3 and 4, characterized bythat the function of the memories (20-23) is swapped after each predetermined angular range, so that alternately only memory contents are stored in the first memory (20,22) and the memory contents of the second memory (21,23) are evaluated, and then only memory contents are stored in the second memory (21,23) and the memory contents of the first memory (20,22) are evaluated. [6] Method according to one of claims 2 to 5, characterized by that the respective memory content is preprocessed before evaluation using a time series-based extraction method, in particular Fourier analysis and / or standard deviation. [7] Method according to one of claims 2 to 6, characterized by that a characteristic map for the estimated magnetic stator flux (Ψ) is determined depending on the respective, in particular preprocessed, memory content, in particular by means of a recursive estimation method. [8] Method according to one of the preceding claims, characterized by that a sampling frequency of the determination of the actual voltage value (U Ist ), actual current value (I Ist ) and / or actual rotor angle (φ Ist ) is selected as a function of an angular velocity and / or an electrical frequency of the electrical machine (2). [9] Device (13) for estimating a magnetic stator flux (Ψ) of an electrical machine (2), characterized by an evaluation unit (17) which is specially designed to carry out the method according to one of the preceding claims. [10] Electric drive device, with an electric machine (2), wherein the machine (2) has a stator with a multi-phase motor winding (6) and a rotatably mounted rotor (3), characterized by a device (13) according to claim 9.

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