Methods for operating motors
By detecting the operating status of the motor and modulating the rotor movement, the overheating problem caused by uneven load in the electric drive is solved, and more uniform load distribution and component protection are achieved, avoiding the damage of the motor.
Patent Information
- Application Number
- CN201980082387.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2018-12-12
- Filing Date
- 2019-11-06
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2039-11-06
AI Technical Summary
In electric drives, uneven loads of switching branches cause the motor to heat rapidly under high electrical conditions, which may damage power electronics, and the prior art is difficult to effectively reduce the torque provided by the motor to avoid overheating.
By detecting the operating state, we judge whether we have entered a special state, and when necessary, the rotor movement of the motor is modulated to a pre-designed target value, changing periodically to avoid thermal overload, and switching the load of the branch using the oscillation distribution of the target value , select the frequency close to the natural frequency of the system to achieve effective motion of the rotor position.
It effectively reduces the thermal load of each component, avoids damage to the electrical mechanism parts, significantly limits the fulfillment of the target value, achieves a more uniform power loss distribution, protects the electrical mechanism parts, and avoids unnecessary detection and overheating.
Smart Images
Figure CN113169704B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for operating an electric machine and to a regulating device for carrying out such a method. Background Art
[0002] Electric machines, such as permanently excited synchronous machines, are used in many technical fields. Such permanently excited synchronous machines are used, for example, in motor vehicles, in particular electric and hybrid vehicles, but also in small drives in the 12V or 48V range.
[0003] WO 2014 / 001028 A1 discloses a method for operating an electric traction drive and an associated control device.
[0004] The background of the invention is that in electric drives, in the case of uneven loading of the switching branches, at high electrically generated torques and simultaneous stopping of the drive machine, the loaded switching branches quickly reach maximum temperatures. In order to avoid overheating and thus destruction of the power electronics, the electric machine is adjusted so that the torque provided by the electric machine is significantly reduced. Summary of the invention
[0005] It is therefore an object of the present invention to provide a method and a device with which the full torque of an electric machine can be used without causing damage to the power electronics.
[0006] This object is achieved by a method for operating an electric machine according to claim 1. With regard to a device for carrying out such a method, reference is made to claim 11. The respectively cited dependent claims reflect advantageous developments of the invention.
[0007] The method according to the present invention comprises a normal operation and a special operation depending on a predetermined target value, wherein the normal operation comprises the step of detecting an operating state, wherein in the case where the detected operating state is a special state, a special operation is performed, and wherein the special operation comprises the step of modulating a periodic value to a predetermined target value, the step of detecting the operating state, wherein in the case where the operating state is a normal state, the normal operation is performed.
[0008] In the sense of the present invention, operating states are understood to be state variables that describe the system, such as, for example, the frequency of the voltage applied by the converter, the rotational frequency of the motor, the temperature or the torque, so that it can be determined whether the variable is outside a specified range and thus a special state or a normal state can be determined. In this case, any operating state that does not belong to a special state is understood to be a normal state.
[0009] In the context of the present invention, a periodic value is understood to be a periodically varying value, for example in the form of a sinusoidal oscillation, a sawtooth oscillation or the like, which results in an oscillation about a target value.
[0010] This method has the advantage that individual components are not thermally overloaded and thus damaged due to the periodic movement of the rotor. As a result, the thermal load on the individual components can be reduced. As a result, it is possible to avoid adjusting the electric machine in order to protect the components from damage, which would otherwise mean significant restrictions in the implementation of the target values.
[0011] In a preferred embodiment of the invention, the periodic value is modulated in such a way that a periodic movement of the rotor of the electric machine is obtained, the movement having an amplitude which is greater than 1 / 6 of an electrical revolution. In this case, the rotor of the electric machine preferably oscillates with a total oscillation width greater than 1 / 3 of an electrical revolution. In this case, the average value of the oscillation is the currently predetermined target value. Such a periodic value or such an amplitude achieves a better distribution of the power losses to the switching branches of the output stage, so that damage to components can be avoided.
[0012] The frequency of the periodic value is preferably selected such that it is close to or equal to the natural frequency of a dynamic system, which is composed in particular of a machine controller, power electronics, an electric machine and / or a subsequent mechanical drive system, so that the desired amplitude of the periodic movement of the rotor position is achieved with a reduced amplitude of the periodic value. This has the advantage that the system can be easily oscillated due to the natural frequency, so that a high effect can be achieved with a small excitation.
[0013] In another preferred embodiment of the invention, a target torque is used as the target value. As an alternative, a target current of a current regulator of the motor is used as the target value. In another alternative, a target angle of the rotor of the motor is used as the target value. These values can be measured in a simple manner so that the target value can be compared with the actual value and, therefore, the deviation can be determined in a simple manner.
[0014] Advantageously, the reaching of a special state is detected when the rotational frequency of the voltage indicator applied by the power electronics is less than a limit frequency and the temperature, the phase current and / or the torque generated exceeds a threshold value. In the sense of the invention, the frequency of the voltage applied by the converter is understood to be a limit frequency, from which the destruction of the component can occur due to a unilateral load on the component, wherein the mere reaching of the limit frequency does not yet lead to the destruction of the component. Therefore, in order to enter a special state, this condition must exist together with the exceeding of the temperature, the temperature difference, the current and / or the torque. The advantage of detecting a special state is that damage to the component is avoided.
[0015] In an advantageous development, the special state is detected only after a predetermined duration of exceeding the threshold value. This means that the special state is not detected when one or more threshold values are exceeded for a short time. Therefore, the special state is detected only when at least one threshold value is exceeded for a predetermined duration. In this case, it can be determined during this duration that this leads to heating of the switching branch. This avoids unnecessary detection of special states that are not critical for the switching branch. Therefore, only the critical exceeding for the switching branch is detected as a special state.
[0016] Preferably, the limit frequency is determined according to the thermal characteristics of the power electronic device, so that the limit frequency can be better adapted to the power electronic device.
[0017] In a preferred development of the invention, the disappearance of the special state is detected when the rotational frequency of the voltage indicator applied by the power electronics is greater than a limit frequency. When the special state disappears, the rotor of the electric machine starts to rotate again, so that unilateral loads and thus damage to components can be eliminated. This is detected by means of the frequency of the voltage applied by the power electronics, which is greater than the limit frequency.
[0018] In addition, the present invention includes a regulating device for operating an electric motor, wherein the regulating device is configured to implement the method according to the present invention. The regulating device includes a target value presetting unit for presetting a target value, a signal processor for regulating the electric motor, a power electronic device as an actuator for the electric motor, an operating state detection and judgment unit for detecting an operating state and for judging whether a special operation or a normal operation is to be performed based on the operating state, and a modulation unit for modulating a periodic value to a target value during a special operation. Such a regulating device can provide the advantages described for the method.
[0019] In a preferred embodiment, the electric machine is a synchronous machine. The advantages of a synchronous machine are that it has a high efficiency, a low moment of inertia and is relatively maintenance-free due to the excitation without slip rings.
[0020] In order to implement the method according to the invention, the invention comprises a computer program product with program code means for carrying out the method when the computer program product is stored on a control unit of a regulating device or on a computer-readable data carrier. The invention also comprises a machine-readable storage medium on which the computer program product is stored. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Embodiments of the present invention are shown in the drawings and explained in more detail in the following description.
[0022] Figure 1 Exemplary embodiments of a method for operating an electric machine and a regulating device for carrying out the method are shown, and
[0023] Figure 2 FIG. 1 is a diagram for illustrating an exemplary embodiment of the method according to the invention. DETAILED DESCRIPTION
[0024] Figure 1 An exemplary embodiment of a method for operating an electric machine 6 and a regulating device 10 for carrying out the method is shown. In this case, the regulating device 10 comprises a target value presetting unit 14, which in normal operation Ψ 正常 During this time, the target value presetting unit will be, for example, the target torque M 目标 The target value M is transmitted to a signal processor 15, which consists of a machine controller, a transformation into a rotating coordinate system and a space vector pulse width modulation. The control device adjusts the torque of the electric machine 6 to the target value M using a power electronic device 17 as an actuator. 目标 In another embodiment, the target value can also be a target current of a current regulator.
[0025] Additionally, the regulating device 10 comprises an operating state detection and determination unit 18, which detects the operating state M of the motor 6 and the power electronic device 17. 实际 The operating state detection and judgment unit 18 determines the actual operating state of the driver, wherein the state parameter M of the driver 实际 or M 目标 are the position and rotational frequency of the rotor, the temperature of the switches in the power electronics 17 and, if necessary, other state variables. If the rotational frequency of the voltage indicator applied by the power electronics 17 is below the limit frequency and if, in addition, the temperature T of the switches of the power electronics 17 极限 , the current and / or torque exceeds the threshold, that is, above the threshold, then the judgment unit in the operating state detection and judgment unit 18 switches to the special operation Ψ 特殊 .
[0026] In special operation 特殊 During this period, the modulation unit 26 changes the periodic value M 周期 Modulate to the target value M 目标Due to the generally sufficiently significant elasticity in the drive, the modulated oscillation of the torque leads to a periodic movement of the rotor of the electric motor 6, which results in the switching cycles in the power electronics 17 being distributed more evenly to the individual components. This reduces the unilateral thermal load of the components. When the judgment unit in the operating state detection and judgment unit 18 receives a signal that the electrical rotation frequency of the rotor is above the limit frequency, the special operating state Ψ 特殊 It disappeared and resumed normal operation. 正常 .
[0027] Figure 2 A diagram is shown for illustrating an exemplary embodiment of the method according to the invention. In this diagram, the target torque M is plotted over time t. 目标 Additionally, the rotor angle θ is plotted over time t R Or the integral of the rotor's speed. It is clear from the two curves that although the target torque M 目标 Increase, the rotor angle θ R After the initial rise it remains relatively constant at one level.
[0028] Additionally, the diagram shows a temperature curve T which reflects the temperature in at least one of the switching branches, which temperature increases above a limit value T 极限 Therefore, a special operation Ψ is implemented 特殊 , where the periodic value M 周期 Modulate to the target value M 目标 This can be Figure 2 In the target value M 目标 The oscillations in the rotor angle θ R The oscillation pattern can be seen in the figure. Due to the rotor angle θ R The oscillations in the switching branches are loaded more evenly so that Figure 2 As shown in , a further temperature increase T can be avoided. The temperature T remains at a more or less constantly high level.
[0029] As the driver expects the torque to increase, the average rotor angle θ Rm continuously increases, which leads to a rotational motion and thus to normal operation Ψ 正常 In the transition. Figure 1 The curve shown in is typical for a driving operation of an electric or hybrid vehicle, which first stops for a while on a slope, wherein the equilibrium state is maintained by the electric drive, and then a starting process is achieved by further pressing the accelerator pedal.
[0030] Another exemplary embodiment is the stopping of the vehicle at an obstacle, for example a curb, wherein by actuating the accelerator pedal the wheel first presses the curb for a time and then by further pressing the accelerator pedal a starting process is effected in which the obstacle is overcome.
Claims
1. A method for operating an electric machine (6), wherein: The method comprises a step of determining a rotor angle (M) as a function of a predetermined rotor target angle (M) 目标 ) for normal operation (Ψ 正常 ) and special operation (Ψ 特殊 ), and wherein the normal operation (Ψ 正常 ) comprises the following steps: Detecting the operating state, wherein, if the detected operating state is a special state, performing a special operation (Ψ 特殊 ), wherein the special operation (Ψ 特殊 ) comprises the following steps: The periodic value (M 周期 ) is modulated to a predetermined rotor target angle (M 目标 )superior, The operating state is detected, wherein, if the operating state is a normal state, normal operation is performed (Ψ 正常 ), When the rotation frequency of the voltage vector applied by the power electronic device (17) is less than the limit frequency and the temperature (T 极限 ) exceeds a threshold value, the arrival of the special state is detected, and the limit frequency is determined according to the thermal characteristics of the power electronic device (17).
2. The method for operating an electric machine (6) according to claim 1, characterized in that The periodic value (M) is modulated in this way. 周期 ) so as to obtain a periodic movement of the rotor of the motor (6), the movement having an amplitude greater than 1 / 6 of the electrical rotation.
3. The method for operating an electric machine (6) according to claim 1 or 2, characterized in that The periodicity value (M 周期 ) so that the frequency is close to or equal to the natural frequency of a dynamic system, the system being composed in particular of a machine controller, power electronics (17), an electric machine (6) and / or a subsequent mechanical drive system, so that at the periodic value (M 周期 ) with a reduced amplitude, the desired amplitude of the periodic movement of the rotor position is achieved.
4. The method for operating an electric machine (6) according to claim 1, characterized in that The special state is detected only after a predetermined duration of time has passed when the threshold value has been exceeded.
5. The method for operating an electric machine (6) according to claim 1, characterized in that The disappearance of the special state is detected when the rotation frequency of the voltage vector applied by the power electronic device (17) is greater than the limit frequency.
6. A regulating device (10) for operating an electric motor (6), wherein: The regulating device (10) is configured to implement the method according to any one of the preceding claims, the regulating device comprising: - a target value presetting unit (14) for presetting a target angle (M 目标 ), - a signal processor (15) for regulating the electric motor (6), - a power electronic device (17) as an actuator for the electric motor (6), - an operation status detection and judgment unit (18) for detecting the operation status and judging whether to execute a special operation (Ψ 特殊 ) or normal operation (Ψ 正常 ),and - modulation unit (26) for special operation (Ψ 特殊 ) will periodically change the value (M 周期 ) is modulated to the target rotor angle (M 目标 )superior.
7. The regulating device (10) according to claim 6, characterized in that The motor (6) is a synchronous motor.
8. A computer program product with program code means for executing a method according to any one of claims 1 to 5 when the computer program product is run on a control unit (14, 15, 18, 26) of a regulating device (10) according to claim 6 or 7 or is stored on a computer-readable data carrier.
9. A machine-readable storage medium on which the computer program product according to claim 8 is stored.