Methods for operating an electric motor and electric motor
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2025-01-27
- Publication Date
- 2026-07-30
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
The invention relates to a method for operating an electric motor according to claim 1. Furthermore, the invention relates to an electric motor. German patent DE 10 2018 127 709 A1 describes a method for limiting the control values in the field-oriented current control of permanent magnet synchronous machines to ensure stable operation near the voltage limit. In this method, the control values of the voltage components are set based on their current effect, depending on the operating point. The object of the present invention is to improve the control of the electric motor and to operate the electric motor more cost-effectively and efficiently. At least one of these problems is solved by a method for operating an electric motor with the features according to claim 1. This allows the electric motor's control system to reliably and accurately set the target current. The stability of the electric motor's control system can be increased. The electric motor can be operated more reliably and efficiently. The current controller can operate with more precise and accurate inputs. The motor parameters can be calculated based on more accurate and correct operating points of the electric motor. The electric motor can be located in a vehicle. The electric motor can provide drive power to propel the vehicle. The electric motor can be a permanent magnet synchronous motor or a separately excited synchronous motor. The electric motor can have a stator and a rotor that rotates relative to the stator. The electric motor can have three motor phases, each with a phase voltage applied for operation. The rotating electrical coordinate system can specify the electrical quantities in the rotor-fixed dq coordinate system. The electrical quantities in the rotating coordinate system can be calculated from the quantities of the stator-fixed coordinate system by Park transformation. The phase currents can flow into the motor windings of the electric motor to operate it. The current regulator can output the voltage to the inverter. By limiting the target current gradient, exceeding the target current gradient beyond the maximum rate of change can be prevented. This prevents excessive demands on the current dynamics, which cannot be met due to the maximum output voltage. The maximum output voltage can depend on the input voltage applied to the inverter. The input voltage can be a DC voltage. The maximum output voltage can be calculated from the known input voltage. The described limitation of the target current gradient to the maximum rate of change can be implemented specifically for a coordinate direction of the rotating coordinate system. In this case, for example, the target current, the target current gradient, the output voltage, the maximum output voltage, and the maximum rate of change are specific to the respective coordinate direction, such as the d-direction or the q-direction. The described limitation of the target current gradient to the maximum rate of change can be implemented for all coordinate directions of the rotating coordinate system. The described limitation of the set current gradient to the maximum rate of change can be implemented specifically for a given sign direction. In this case, for example, the set current gradient, the output voltage, the maximum output voltage, and the maximum rate of change are specific to the respective sign direction, such as positive or negative. The described limitation of the set current gradient to the maximum rate of change can be implemented for all sign directions. In a preferred embodiment of the invention, it is advantageous if the target current is calculated by a feedforward control system as a function of a preset current. The preset current can be predetermined based on a requested motor power and motor parameters of the electric motor, for example, inductances, ohmic resistances, and other parameters. In a preferred embodiment of the invention, the maximum rate of change is calculated as a function of the current difference between the setpoint current and the target current. In the static case and / or, if the limiter does not intervene, even in the dynamic case, the setpoint current can correspond to the target current supplied to the current controller. In an advantageous embodiment of the invention, the voltage reserve value is calculated as the voltage difference between the maximum output voltage and the steady-state output voltage. The voltage reserve value can be calculated as the voltage difference between the maximum output voltage and the steady-state output voltage component. The steady-state output voltage component can be formed depending on decoupling components that compensate for the inductive coupling between the coordinate directions and the resistance components that compensate for the ohmic resistances in the motor windings. The steady-state output voltage component can be the portion of the output voltage required to maintain the set current. In a preferred embodiment of the invention, the voltage reserve value includes a positive voltage reserve value, which is calculated as the voltage difference between the positive maximum output voltage and the output voltage. In a particular embodiment of the invention, it is advantageous if the voltage reserve value includes a negative voltage reserve value, which is calculated as the voltage difference between the negative maximum output voltage and the output voltage. In a preferred embodiment of the invention, it is advantageous if the maximum rate of change comprises a maximum positive rate of change component and a maximum negative rate of change component. The maximum positive rate of change component can be calculated depending on the positive voltage reserve value and / or the maximum negative rate of change component can be calculated depending on the negative voltage reserve value. The limiting of the target current gradient can comprise limiting a positive target current gradient and / or a negative target current gradient. The positive target current gradient can be limited depending on the maximum positive rate of change component. The negative target current gradient can be limited depending on the maximum negative rate of change component. In a preferred embodiment of the invention, it is advantageous if the maximum rate of change is calculated as a function of the electric motor parameters. The motor parameters can include inductances and / or ohmic resistances of the electric motor. In an advantageous embodiment of the invention, the motor parameters are calculated based on the target current, which is limited, in particular, by the limiting factor. The motor parameter values can be calculated from the target current using a lookup table. Furthermore, within the scope of the invention, an electric motor with the features according to claim 10 is proposed to solve at least one of the previously specified problems. Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustration. Character description The invention is described in detail below with reference to the illustration. The figure shows a method for operating an electric motor in a specific embodiment of the invention. The method for operating 10 of an electric motor 12 comprises providing the electric motor 12 with motor windings. Furthermore, a current controller 14 is provided, which, with respect to at least one coordinate direction 18 of a rotating electrical dq coordinate system 16 of the electric motor 12, outputs a voltage Ua, which is limited to a maximum output voltage Ua,m with respect to the coordinate direction 18, depending on a setpoint current I. For example, the current controller 14 can output a voltage Ua, which is limited to a maximum output voltage Ua,m, with respect to the q-direction, depending on a setpoint current I. The current controller 14 can additionally or alternatively output a voltage Ua, which is limited to a maximum output voltage Ua,m, with respect to the d-direction, depending on a setpoint current I. If the electric motor 12 is a separately excited synchronous motor, an excitation direction is present as a further coordinate direction 18. The current controller 14 can additionally or alternatively output a voltage Ua with respect to the excitation direction, depending on a set current I, which is limited to a maximum output voltage Ua,min with respect to the excitation direction. The target current Isin in the respective coordinate direction 18 is calculated by a feedforward control 20, depending on a setpoint current Iv. The setpoint current Iv can be specified depending on a requested motor power and motor parameters P of the electric motor 12, for example, inductances, ohmic resistances, and other parameters. Furthermore, an inverter 22 is provided to output phase voltages Upan to the motor windings to adjust a phase current Ipin to the motor windings, at least depending on the output voltage Ua. The electric motor 12 can comprise three motor phases 23, each of which receives a phase voltage Upan for the operation of the electric motor 12. The maximum output voltage Ua,m depends on the input voltage Ue applied to the inverter 22, which is a DC voltage. The maximum output voltage Ua,m can be calculated from the known input voltage Ue. Furthermore, a calculation is performed of at least one voltage reserve value Urzu of the output voltage Ua, depending on the maximum output voltage Ua, and the output voltage Ua, in particular a steady-state output voltage component Ua,s of the output voltage Ua. The steady-state output voltage component is formed depending on decoupling components that compensate for the inductive couplings between the coordinate directions 18 and resistance components that compensate for the ohmic resistances in the motor windings. The steady-state output voltage component Ua,s can be the portion of the output voltage Uase that is required to maintain the target current Is. The voltage reserve value Urr is calculated as the voltage difference between the maximum output voltage Ua, and the output voltage Ua, here the steady-state output voltage component Ua,s. The voltage reserve value Urr comprises a positive voltage reserve value Urr,p and a negative voltage reserve value Urr,n. The positive voltage reserve value Urr,p is calculated as the voltage difference between the positive maximum output voltage Ua, and the steady-state output voltage component Ua,s, and the negative voltage reserve value Urr,n as the voltage difference between the negative maximum output voltage Ua, and the steady-state output voltage component Ua,s. From the positive voltage reserve value Ur,p and the negative voltage reserve value Ur,n, as well as from motor parameters P of the electric motor 12 and a current difference ΔI between the set current Iv and the target current Isin with respect to the respective coordinate direction 18, a maximum rate of change R is calculated coordinate-related by a calculation 25. The maximum rate of change R comprises a maximum positive rate of change component Rp and a maximum negative rate of change component Rn, whereby the maximum positive rate of change component Rpin with respect to the voltage reserve value Ur is dependent on the positive voltage reserve value Ur,p, and the maximum negative rate of change component Rnin with respect to the voltage reserve value Ur is dependent on the negative voltage reserve value Ur,n. The calculation 25 can calculate a respective maximum positive rate of change component Rp and maximum negative rate of change component Rn for each coordinate direction 18, i.e. the d-direction, the q-direction and the excitation direction, thus calculating a total of six maximum rate of change component parts of the rate of change R. The motor parameters P can be calculated using a lookup table 26 depending on the target current Is. Furthermore, the target current gradient Isin is limited 28 with respect to the respective coordinate direction 18 to the associated maximum rate of change R. For the positive target current gradient, particularly in the q-direction, the limit 28 applies, and correspondingly for the negative The target current gradients of the d-direction and the excitation direction are also limited with a corresponding maximum rate of change R, whereby the respective positive target current gradient is limited by the smaller of the two maximum positive rate of change components Rp of the d-direction and the excitation direction, and the respective negative target current gradient is limited by the larger of the two maximum negative rate of change components Rr of the d-direction and the excitation direction, in order to take into account coupling effects between these two coordinate directions 18. Depending on the limited target current Is and the motor parameters P from the lookup table 26, the current controller 14 calculates the output voltage Uain with reference to the coordinate direction 18 for the inverter 22. Reference symbol list 10 Operating Procedure 12 Electric Motor 14 Current Controller 16 dq Coordinate System 18 Coordinate Direction 20 Feedforward Control 22 Inverter 23 Motor Phase 24 Calculation 25 Calculation 26 Lookup Table 28 Limit Ip Phase Current Is Set Current Iv Target Current P Motor Parameter R Maximum Rate of Change Rn Maximum Negative Rate of Change Component Rp Maximum Positive Rate of Change Component Ua Output Voltage Ue Input Voltage Up Phase Voltage Ur Voltage Reserve Value Ua,m Maximum Output Voltage Ua,sin Steady-State Output Voltage Component Ur,n Negative Voltage Reserve Value Ur,p Positive Voltage Reserve Value ΔI Current Difference Target current gradient QUOTES INCLUDED IN THE DESCRIPTION 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 DE 10 2018 127 709 A1
[0002]
Claims
Method (10) for operating an electric motor (12), comprising providing the electric motor (12) comprising motor windings, providing a current controller (14) which, with respect to at least one coordinate direction (18) of a rotating electrical coordinate system (16) of the electric motor (12), outputs a voltage (Ua) limited to a maximum output voltage (Ua,m) depending on a set current (Is), providing an inverter (22) for outputting phase voltages (Up) at the motor windings for setting a phase current (Ip) in the motor windings at least depending on the output voltage (Ua), calculating (24) at least one voltage reserve value (Ur) for the output voltage (Ua) depending on the maximum output voltage (Ua,m) and the output voltage (Ua).Calculation (25) of a maximum rate of change (R) of the target current (Is) depending on the at least one voltage reserve value (Ur) and limitation (28) of a target current gradient ( d I dt ), of the set current supplied to the current controller (14) (I s ) on the maximum rate of change (R). Method for operation (10) according to claim 1, characterized in that the target current (Is) is calculated as a function of a preset current (Iv) by a feedforward control (20). Method for operation (10) according to claim 1 or 2, characterized in that the maximum rate of change (R) is calculated as a function of a current difference (ΔI) between the set current (Iv) and the target current (Is). Method for operation (10) according to one of the preceding claims, characterized in that the voltage reserve value (Ur) is calculated as the voltage difference between the maximum output voltage (Ua,m) and the output voltage (Ua). Method for operation (10) according to claim 4, characterized in that the voltage reserve value (Ur) comprises a positive voltage reserve value (Ur,p) which is calculated as the voltage difference between the positive maximum output voltage (Ua,m) and the output voltage (Ua). Method for operation (10) according to claim 4 or 5, characterized in that the voltage reserve value (Ur) comprises a negative voltage reserve value (Ur,n) which is calculated as the voltage difference between the negative maximum output voltage (Ua,m) and the output voltage (Ua). Method for operation (10) according to claims 5 and 6, characterized in that the maximum rate of change (R) comprises a maximum positive rate of change component (Rp) and a maximum negative rate of change component (Rn), wherein the maximum positive rate of change component (Rp) is calculated depending on the positive voltage reserve value (Ur,p) and the maximum negative rate of change component (Rn) is calculated depending on the negative voltage reserve value (Ur,n). Method for operation (10) according to claim 7, characterized in that the target current gradient (d I dt ) a positive target current gradient ( d I dt ) p and a negative target current gradient (d I dt ) n includes and the limitation (28) of the positive target current gradient ( d I dt ) p on the maximum positive rate of change component (R p ) and the limitation (28) of the negative target current gradient ( d I dt ) n on the maximum negative rate of change component (R n ). Method for operation (10) according to one of the preceding claims, characterized in that the maximum rate of change (R) is calculated depending on motor parameters (P) of the electric motor (12). electric motor (12) with a stator and a rotor rotatable relative to the stator and operable by a method for operation (10) according to one of the preceding claims.