System for operating an electric machine

Abstract

The invention relates to a system for operating an electric machine with a rotor and a stator, wherein the system comprises a rotor position sensor (2), a characteristic map (14) for operating points (8) and a computing unit (40), wherein the system is configured to determine a current operating point (8) of the electric machine, taking into account the characteristic map (14) it is to be determined whether a primary operating point (8) or a secondary operating point (8) is currently present, wherein in the case that the primary operating point (8) is present, a position of the rotor measured by the rotor position sensor (2) is to be used to operate the electric machine, and wherein in the case that the secondary operating point (8) is present, a position of the rotor estimated by the computing unit (40) with an estimation algorithm (12) is to be used to operate the electric machine.

Description

[0001] The invention relates to a system for operating an electric machine and a method for operating an electric machine.

[0002] The publications CN 115189601 A, CN 117134665 A and CN 105915127 A describe different electric motors.

[0003] Against this background, it was a task to operate an electric machine appropriately.

[0004] This problem is solved by a system and a method with the features of the independent claims. Embodiments of the system and the method are described in the dependent claims and the description.

[0005] The system according to the invention is designed to operate an electric machine comprising a rotor or shaft and a stator, wherein the rotor rotates relative to the stator and assumes different, usually angle-dependent, positions relative to the stator. The electric machine typically has three phases and is usually controlled by electrical voltages applied to or that can be applied to the phases and / or by currents supplied to or that can be supplied to the phases.

[0006] The system according to the invention comprises, as sensors, a rotor position sensor, at least one current sensor, a characteristic map for possible operating points of the electric machine, and a processing unit. The system is configured to determine the current operating point of the electric machine. Furthermore, the processing unit is configured to determine, taking the characteristic map into account, whether a primary or a secondary operating point is currently present. The rotor position sensor is configured to measure the position of the rotor relative to the stator and, in a specific configuration, to generate a corresponding measured position signal that includes the measured position. The measured position can be used, or is usable, for operating the electric machine if the primary operating point is present. The processing unit is configured to determine the position of the rotor relative to the stator using an estimation algorithm.to estimate by and / or during the execution of an estimation algorithm and, in its embodiment, to generate a corresponding estimated position signal that includes the estimated position, wherein the estimated position is to be used or usable for operating the electric machine if the secondary operating point is present.

[0007] The current sensor is designed to measure, detect, and / or determine instantaneous currents, typically phase currents, flowing through the coils of the rotor and / or stator of the electric machine. Taking into account the rotor's position measured by the rotor position sensor and the currents measured by the current sensor, the rotational speed and torque of the electric machine are determined. These values ​​are derived as a function of the measured position and currents. The rotational speed and torque represent the operating point of the electric machine. The characteristic curve describes the relationship between possible operating points—either primary or secondary—and the rotational speed and torque. This characteristic curve allows for the definition of which operating points are considered primary and which are considered secondary.Depending on the currently determined operating point, either the measured position signal (primary operating point) or the estimated position signal (secondary operating point) is used to control the electric machine. Typically, the respective operating point is directly dependent on the rotational speed and torque, and indirectly dependent on the currents and the rotor position initially measured by the rotor position sensor. If a primary operating point is currently being determined for the electric machine, the initially measured rotor position is also adopted and / or used. However, if a secondary operating point is determined, the rotor position estimated by the estimation algorithm is used instead.

[0008] The rotational speed can usually be determined and / or calculated directly from the measured and / or estimated angle-dependent position or a corresponding position signal. The torque at the operating point is typically calculated using at least one additional characteristic map, which describes the dependence of the rotational speed on currents flowing through the stator and, if applicable, on at least one current-dependent magnetic parameter of the electric machine. The currents calculated using a Park transformation during control can usually be used for this purpose.

[0009] The computing unit is designed to estimate, or usually calculate, the position of the rotor during or under the execution of the estimation algorithm, depending on the applied voltages and the currents measured by the current sensor for the phases of the electric machine.

[0010] The system also includes a selector switch and a transformation module, typically for performing the Park transformation. The at least one current sensor is configured to provide the transformation module with the measured currents or phase currents flowing through the rotor and / or stator coils. The selector switch is configured to provide the transformation module with the measured position signal and the measured rotor position if the primary operating point is present, or with the estimated position signal and the estimated rotor position if the secondary operating point is present.The transformation module is designed to transform the phase currents supplied to it, depending on the operating point at hand (i.e., the primary or secondary operating point), either with the measured position signal (i.e., the rotor's position) or with the estimated position signal (i.e., the rotor's position), into at least one vector current in a complex coordinate system, i.e., into only one vector current or into several vector currents, for operating, e.g., controlling, the electric machine, whereby current vector control is carried out with this at least one vector current.

[0011] Depending on the current operating point, the method uses either the measured position signal with the measured rotor position or the estimated position signal with the estimated rotor position to control the electric machine. The transformation module uses the measured position (if a primary operating point is present) or the estimated position (if a secondary operating point is present) for a transformation, usually mathematical, that represents the three-phase currents or phase currents as at least one current vector in the orthogonal complex coordinate system. This enables conventional vector control of the at least one current, i.e., a single current or multiple currents.

[0012] The characteristic map is stored in the computing unit, which is designed to perform the estimation algorithm and to control and / or adjust the selection switch depending on the respective primary or secondary operating point recorded.

[0013] The system is designed for an electric machine that is designed to move and / or propel a vehicle, e.g. a motor vehicle.

[0014] The method according to the invention is provided for operating an electric machine with a rotor and a stator, which is controlled by voltages applied to or already applied to it. An operating point of the electric machine is determined, taking into account a characteristic curve, to ascertain whether a primary or secondary operating point is present, i.e., whether the currently determined operating point is a primary or a secondary operating point. Furthermore, if the primary operating point is present, a rotor position sensor measures the position of the rotor relative to the stator, which is typically angle-dependent, and this measured position is used to operate the electric machine.If, on the other hand, the secondary operating point is present, the position of the rotor relative to the stator is usually estimated, calculated, by an estimation algorithm, and this estimated position is used to operate the electric machine.

[0015] Taking into account the rotor's position as measured by the rotor position sensor and currents, such as phase currents, measured by a current sensor, the rotational speed and torque of the electric machine are derived. Using the characteristic map, and considering these rotational speed and torque values, the operating point—whether it is a primary or secondary operating point—is determined. If a primary operating point is identified, the previously measured rotor position is used for further operation of the electric machine, typically for control purposes. Otherwise, if a secondary operating point is identified, the rotor position estimated by the estimation algorithm is used instead of the measured position for further operation, typically for control purposes.

[0016] It is possible that one embodiment of the presented method is carried out with one embodiment of the presented system.

[0017] The system and method enable a reduction in sensor-based losses that occur when using a measured rotor position or a corresponding measured position signal, since the otherwise used measured position is replaced by the estimated position or an estimated position signal for the rotor, depending on the operating point.

[0018] The measured position or position signal typically contains harmonics, which are reduced or even eliminated in the estimated position. The estimated position, determined by the estimation algorithm, is equivalent to the measured position. When running the estimation algorithm, only existing operating signals for parameters are used in the software to calculate the rotor's position. These parameters include the applied voltages and the measured currents flowing through the phases. The voltages can be measured or pre-calculated as target voltages by the electric machine's control system. This provides the estimated position, which can then be used, for example, for subsequent transformation and / or current control. The estimated position signal...The estimated position is free of any additional harmonic components that would otherwise occur in the measured position of the mechanical rotor position sensor and does not include them. The rotor position sensor itself is not omitted for reasons of functional safety. However, depending on the operating point, the estimated position is used instead of the measured position, whereby losses are actively avoided by using the harmonic-reduced estimated position. Harmonics result, for example, from manufacturing tolerances and mechanical imperfections. Their effects are avoided by this method.

[0019] In this method, the transformation and control of the at least one current, usually vectorial, is provided with either the measured position signal with the measured position or the estimated position signal with the estimated position, depending on the current operating point. This avoids the unwanted harmonic components physically present in the mechanically measured position of the rotor position sensor. The measured position signal from the rotor position sensor is replaced by the estimated position signal depending on the current operating point. This is possible at secondary operating points where losses due to harmonics can be reduced. If the electric machine is used to drive or propel a vehicle, its range can be increased.

[0020] Furthermore, the harmonic content of the electric machine's rotational speed, calculated from the estimated rotor position, is also reduced. Additionally, the downstream filtering effort for the transformed vector currents required for further operation, typically for control, of the electric machine can be reduced.

[0021] The position estimated during the procedure is a supplement to the measured position at each predetermined, previously applied, or typically secondary operating point of the rotating electric machine, which, while stationary, has its rotor rotating relative to the stator. Depending on the operating point, the measured position signal is overwritten by the estimated position signal.

[0022] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0023] The invention is schematically illustrated with reference to embodiments in the drawing and is described schematically and in detail with reference to the drawing.

[0024] Fig. Figure 1 shows a schematic representation of an embodiment of the system according to the invention for carrying out an embodiment of the method according to the invention.

[0025] The in Fig. Figure 1, a schematically illustrated embodiment of the system according to the invention, is designed for an electric machine (not shown in detail here) that has a stator and a rotor rotating relative to it. The system includes a rotor position sensor 2 and a current sensor 4 as components of the electric machine. The system also comprises a computing unit 40, which has a selection switch 10 and / or is configured to implement the selection switch 10 or a selection circuit. Furthermore, the computing unit 40 is configured to implement an estimation algorithm 12.

[0026] Furthermore, the computing unit 40 has a characteristic map 14, e.g., an application characteristic map. The system also has a transformation module 16 for performing a transformation, here a Park transformation, of currents, which in a further embodiment is also designed as a component of the computing unit 40 and / or can be implemented by it.

[0027] In the embodiment of the method according to the invention and during the operation of the electric machine, in or at each time interval, e.g. sample time step, here a k-th time interval of a plurality of successive time intervals of the same length, the rotor position sensor 2 directly detects and / or measures an angle-dependent position θ_m or position of the rotor relative to the stator, wherein the rotor position sensor 2 generates, provides and transmits a measured position signal 20, which includes the measured position θ_m, to the selection switch 10.

[0028] Currents I_abc of the phases or phase currents of the electric machine are measured by the current sensor 4, whereby a measured current signal 22, which includes the measured currents I_abc, is generated and provided by the current sensor 4, which is transmitted both to the estimation algorithm 12 and to the transformation module 16.

[0029] Furthermore, voltages 6 U_abc, here the terminal voltages applied to the terminals of the phases of the electric machine, are taken into account. Based on these voltages 6 U_abc, a measured voltage signal 24, comprising the voltages 6 U_abc intended for this purpose, is generated, provided, and transmitted to the estimation algorithm 12. The voltages 6 U_abc of the electric machine, as input for the estimation algorithm 12, can be measured as terminal voltages or pre-calculated as target voltages by a control system of the electric machine and made available to the estimation algorithm 12.

[0030] In each k-th time interval, a current operating point 8 of the electric machine is determined, which corresponds to a respective rotational speed n and a respective torque M of the electric machine, or results depending on the respective rotational speed n and the respective torque M. The rotational speed n and the torque M can be measured by sensors provided for this purpose, here by the rotor position sensor 2 and the current sensor 4, or taken from the control system of the electric machine and / or a predefined setpoint.

[0031] Using the estimation algorithm 12, an angle-dependent position θ_s of the rotor relative to the stator is estimated from the measured current signal 22 and the provided measured voltage signal 24, whereby an estimated position signal 30, which includes the estimated position θ_s, is generated and provided, which is transmitted to the selection switch 10.

[0032] The characteristic map 14 describes the dependence of the operating points 8 on the rotational speed n and the torque M, whereby an operating point 8 or a coordinate for this operating point 8 in the characteristic map 14 is assigned to a specific rotational speed n and a specific torque M, or to a corresponding tuple of the specific rotational speed n and the specific torque M. Using the characteristic map 14, the processing unit 40, taking into account the operating point signal 26, which includes the current operating point 8, determines the coordinate of the current operating point 8 in the characteristic map 14 for the k-th time interval, which depends on the current rotational speed n and the current torque M for the k-th time interval.

[0033] The characteristic curve 14 distinguishes between so-called primary operating points 8 and so-called secondary operating points 8, which depend on the respective measured rotational speed n and torque M. Based on the characteristic curve 14, a decision is made as to whether, for the execution of the procedure presented here, the measured position θ_m of the rotor and thus the measured position signal 20, or the estimated position θ_s of the rotor and thus the estimated position signal 30, should be used for further operation, specifically for controlling the electric machine. Information about the decision to be made or already made is provided to the selector switch 10 in a selection signal 28, based on the characteristic curve 14. In this configuration, the currently applicable operating point 8 is determined for each time interval.

[0034] When a so-called primary operating point 8 is present, the measured position θ_m of the rotor is used, and when a so-called secondary operating point 8 is present, the estimated position θ_s of the rotor is used. In its configuration, the characteristic map 14 assigns either a primary operating point 8 or a secondary operating point 8 to each coordinate for the k-th time interval, a coordinate that depends on the current rotational speed n and the current torque M.

[0035] How Fig.As shown in Figure 1, two switching positions are provided for the selector switch 10. If, for the transformation of the measured currents I_abc of the phases depending on the operating point 8 currently detected in the k-th time interval, the measured position θ_m according to the measured position signal 20 is to be used, a primary switching position or measurement switching position is set by and / or for the selector switch 10 taking into account the selection signal 28, and the measured position signal 20 with the measured position θ_m is provided to the transformation module 16. If, on the other hand, the estimated position θ_s according to the estimated position signal 30 is to be used for the transformation of the measured currents I_abc of the phases depending on the operating point 8 currently detected in the k-th time interval, a secondary switching position or measurement switching position is set by and / or for the selector switch 10 taking into account the selection signal 28.Estimation switch position set and the estimated position signal 30 with the estimated position θ_s provided to the transformation module 16.

[0036] Furthermore, the transformation module 16, taking into account whether, depending on the respective operating point 8 in the k-th time interval, the measured position signal 20 with the measured position θ_m or the estimated position signal 30 with the estimated position θ_s is to be used, transforms the currents I_abc of the phases provided with the measured current signal 22 into a current vector I_dq of a complex orthogonal coordinate system by performing the transformation designed here as a Park transformation, which is provided in a transformed current signal 32 for further use or further operation.

[0037] In this configuration, it is possible for the current vector I_dq, transformed in the k-th time interval, to be transmitted by the transformation module 16 in the transformed current signal 32 for further control of the electric machine. From this, newly controlled and / or operationally updated or new currents I_abc and / or voltages 6 U_abc can be determined and / or derived for the phases for an immediately subsequent k+1-th time interval, whereby an inverted Park transformation and other measurable operating parameters of the electric machine, e.g., its speed n and / or torque M, can also be taken into account. In the next k+1-th time interval, the new voltages 6 U_abc for the phases can be applied to the terminals and also used to estimate a new, updated estimated position θ_s for a corresponding new estimated position signal 30.In a closed control loop, the currents I_abc and / or voltages U_abc can be updated for the next k+1 time interval, taking into account the current vector I_dq determined in the previous k time interval.

[0038] Accordingly, the estimation algorithm 12 is used, which estimates the position θ_s from the already existing measured parameters of the electric machine, i.e., from the measured currents I_abc and the measured voltages U_abc. This operating-point-dependent and potentially applicable position signal 30 is then made available to downstream functions for the control of the electric machine. The estimation algorithm 12 is a purely software-based measure implemented by the processing unit 40, therefore no additional hardware is required.

[0039] To identify and / or estimate the rotor position θ_s, a rotor flux estimator can be used, for example, which calculates a rotor flux space vector from the measured currents I_abc of the stator phases and the specific voltages 6 U_abc provided by the control system (e.g., target voltages). The geometric position of the rotor flux space vector represents the instantaneously estimated position θ_s of the rotor. The target voltages from the control system are used as the voltages 6 U_abc to calculate the estimated rotor position θ_s. Therefore, it is not necessary to measure the voltages 6 U_abc at the terminals of the electric machine. For the estimation algorithm 12, only the current values ​​I_abc need to be measured by the current sensor.

[0040] The estimation algorithm 12 can be used in parallel with the operation of the control system, whereby the estimated position θ_s of the rotor, e.g., instantaneously, is provided to the selection switch 10 at each time interval. The current operating point 8 is determined via the applicable characteristic map 14, depending on the torque M and speed n. Based on this, a decision is made as to whether, at the given operating point 8 or operating range, and thus in the k-th time interval, the estimated position θ_s or the estimated position signal 30 should be used instead of the measured position θ_m or the measured position signal 20.

[0041] During execution of the procedure, the measured position θ_m of the rotor is replaced by the alternatively used estimated position θ_s of the rotor at the respective secondary operating points 8. This eliminates harmonics that arise at the secondary operating points 8 of the electric machine for the measured position θ_m of the rotor and that could otherwise influence further control.

[0042] Harmonics can be superimposed on the measured position signal 20 of the rotor, for example, due to mechanical or manufacturing reasons of the installed rotor position sensor 2. These harmonics can be of different types and, depending on the rotational speed of the electric machine's rotor, can influence the amplitude and phase of the measured position signal 20. These unwanted harmonics can be present at every operating point 8 of the electric machine, except when the rotational speed n is zero. Using the operating-point-dependent characteristic map 14, the range in which the measured position signal 20 containing harmonics from the rotor position sensor signal is replaced by the less harmonic-laden estimated position signal 30 of the rotor can be set, depending on the application (e.g., the sensors used) and the estimation accuracy of the estimation algorithm 12. REFERENCE MARK: 2 Rotor position sensor 4 Current sensor 6 Voltage 8 working point 10 selection switches 12 Estimation algorithm 14 Characteristic map 16 Transformation module 20 measured position signal 22 measured current signal 24 measured voltage signal 26 Operating point signal 28 Selection signal 30 estimated position signal 32 transformed current signal 40 computing units QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] CN 115189601 A

[0002] CN 117134665 A

[0002] CN 105915127 A

[0002]

Claims

[1] System for operating an electric machine with a rotor and a stator, wherein the system comprises a rotor position sensor (2), a characteristic map (14) for operating points (8) and a computing unit (40), wherein the system is configured to determine a current operating point (8) of the electric machine, taking into account the characteristic map (14) it is to be determined whether a primary operating point (8) or a secondary operating point (8) is currently present, wherein in the case that the primary operating point (8) is present, a position of the rotor measured by the rotor position sensor (2) is to be used to operate the electric machine, and wherein in the case that the secondary operating point (8) is present, a position of the rotor estimated by the computing unit (40) with an estimation algorithm (12) is to be used to operate the electric machine. [2] System according to claim 1, which is configured to detect a rotational speed and a torque of the electric machine, wherein the characteristic map (14) describes a dependence of operating points (8) on the rotational speed and the torque. [3] System according to claim 1 or 2, comprising a current sensor (4) configured to measure currents of the electric machine. [4] System according to claim 3, wherein the computing unit (40) is configured to calculate the position of the rotor to be estimated when performing the estimation algorithm (12) depending on applied voltages (6) and the measured currents. [5] System according to claim 3 or 4, comprising a selection switch (10) and a transformation module (16), wherein the current sensor (4) is configured to provide the measured currents to the transformation module (16), wherein the selection switch (10) is configured to provide the transformation module (16) with the measured position of the rotor if the primary operating point (8) is present, or with the estimated position of the rotor if the secondary operating point (8) is present, wherein the transformation module (16) is configured to transform the phase currents provided to it into at least one vector current for controlling the electric machine, depending on the measured or estimated position of the rotor provided. [6] System according to one of the preceding claims for an electric machine designed to propel a vehicle. [7] Method for operating an electric machine with a rotor and a stator, in which an actual operating point (8) of the electric machine is determined, taking into account a characteristic map (14) it is determined whether a primary operating point (8) or a secondary operating point (8) is currently present, wherein in the case that the primary operating point (8) is present, a measured position of the rotor is used to operate the electric machine, and wherein in the case that the secondary operating point (8) is present, an estimated position of the rotor is used to operate the electric machine.

Images