Method for determining a pilot angle of a synchronous motor and synchronous motor
Patent Information
- Application Number
- DE112022006498
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-06-14
- Publication Date
- 2024-12-19
AI Technical Summary
The high cost and precision requirements of rotor position sensors in synchronous motors make them expensive and limit the affordability of efficient synchronous motor production.
A method to determine the pre-control angle of a synchronous motor without a rotor position sensor, using power electronics to record and analyze winding voltage and current profiles, allowing for the calculation of the pre-control angle through Fourier analysis, enabling efficient operation and reducing production costs.
This method allows for the production of a relatively inexpensive synchronous motor with precise regulation and efficient operation by eliminating the need for expensive rotor position sensors and ensuring smooth running and low noise.
Abstract
Description
[0001] DESCRIPTION
[0002] Method for determining a pre-control angle of a synchronous motor and synchronous motor
[0003] The present invention relates to a method for determining a pre-control angle of a synchronous motor, in particular an electronically commutated synchronous motor. The present invention further relates to a synchronous motor comprising: a permanent-magnet motor rotor, an electromagnetic motor stator with a winding system having at least one winding, and motor electronics configured to control the winding system to drive the motor rotor.
[0004] The pre-control angle, also called pre-commutation angle, specifies the angle between an electromotive force (EMF), also called the pole wheel voltage, induced in the winding system of the motor stator by the rotating permanent magnet motor rotor, which is also called the pole wheel, and a winding current impressed into the winding system. By controlling the winding system with a defined pre-control angle, which is typically between 0° and 45°, particularly efficient operation of the synchronous motor can be achieved. Typically, a (rotatory) rotor position, from which an (electrical) angle of the EMF can be directly derived, is detected via at least one rotor position sensor, typically designed as a magnetic field sensor. However, the rotor position sensors must be mounted relatively precisely and are relatively expensive, resulting in relatively high manufacturing costs for the synchronous motor.Against this background, the task is to enable a relatively cost-effective synchronous motor.
[0005] This object is achieved by a method for determining a pilot control angle of a synchronous motor, having the features of claim 1, and by a synchronous motor having the features of claim 5.
[0006] In the method according to the invention for determining a pre-control angle of a synchronous motor, a winding system of the synchronous motor is controlled in such a way that a defined operating point of the synchronous motor, i.e., a defined speed of a permanent-magnet motor rotor of the synchronous motor, is set. Typically, the winding system is controlled by means of special power electronics comprising several semiconductor switches, via which individual windings of the winding system can be selectively connected to a supply voltage.Typically, an effective control voltage provided to the respective windings is varied by means of so-called pulse width modulation (PWM), whereby the semiconductor switches assigned to the respective winding are alternately switched on and off at a relatively high frequency and the effective control voltage can be adjusted via a ratio between the on-time and off-time during a defined period.
[0007] In the method according to the invention, at least one winding voltage curve and one winding current curve of the winding system, i.e., the voltage curve and the current curve at at least one winding of the winding system, are recorded. Typically, a temporal sequence of winding voltage values and winding current values is recorded using appropriate sensors and stored in a corresponding data memory.
[0008] In the method according to the invention, the control of the winding system is interrupted at a defined point in time, thus stopping the motor rotor of the synchronous motor from being actively driven. Typically, all semiconductor switches of the power electronics are switched to high impedance to electrically disconnect the winding system from the supply voltage. However, due to mass inertia, the motor rotor continues to rotate after the control is interrupted, so that the alternating rotor magnetic field generated by the rotating permanent magnet motor rotor continues to induce the EMF in the winding system.
[0009] In the method according to the invention, an EMF fundamental oscillation is determined by evaluating a section of the winding voltage waveform recorded after the interruption of the control, i.e., by evaluating a section of the winding voltage waveform in which the winding voltage is substantially equal to the EMF. Furthermore, a winding current fundamental oscillation is determined by evaluating a section of the winding current waveform recorded before the interruption of the control.
[0010] The fundamental EMF and the fundamental winding current can each be defined either by an amplitude, a frequency, and a phase angle, or by a complex fundamental oscillation space vector with a magnitude and a phase angle. Methods for determining the fundamental oscillation or a corresponding fundamental oscillation space vector based on a recorded voltage or current waveform are well known in the art and will therefore not be explained in detail here.
[0011] In the method according to the invention, the pre-control angle is determined based on the phase angle of the EMF fundamental and the phase angle of the winding current fundamental. Since the speed of the motor rotor shortly after the interruption of control approximately corresponds to the speed of the motor rotor during control, the pre-control angle for the operating point set before the interruption of control can be determined with a good approximation from the difference between the phase angle of the EMF fundamental and the phase angle of the winding current fundamental.
[0012] The method according to the invention enables the determination of the pilot angle without the need for a rotor position sensor and thus enables the realization of a relatively cost-effective synchronous motor.
[0013] Preferably, the fundamental EMF and the fundamental winding current are each determined using a Fourier analysis of the corresponding section of the winding voltage waveform or the winding current waveform. Particularly preferred is a so-called discrete Fourier transformation (DFT) or a so-called fast Fourier transformation (FFT). Using Fourier analysis, a fundamental waveform can be determined easily and efficiently from a recorded signal waveform. Fourier analysis therefore enables the determination of the fundamental EMF and the fundamental winding current using a relatively simple and therefore relatively inexpensive computing unit.Typically, the winding system of a synchronous motor comprises a plurality of separate windings, which may have slightly different electrical and electromagnetic properties due to manufacturing tolerances and / or slightly different material properties.Advantageously, for each winding of the winding system, the following are recorded: a winding-specific winding voltage waveform; a winding-specific winding current waveform; a winding-specific fundamental EMF waveform is determined by evaluating the corresponding section of the recorded winding-specific winding voltage waveform; a winding-specific fundamental winding current waveform is determined by evaluating the corresponding section of the recorded winding-specific winding current waveform; and a winding-specific pre-control angle is determined based on a phase angle of the winding-specific fundamental EMF waveform and a phase angle of the winding-specific fundamental winding current waveform. This enables particularly precise control and thus particularly efficient operation of the synchronous motor.
[0014] In order to avoid significant braking of the motor rotor during the suspension and thus "unsmooth" running of the synchronous motor, the control of the winding system is preferably suspended for a maximum of two periods of a control signal.
[0015] The synchronous motor according to the invention comprises a permanent-magnet motor rotor, an electromagnetic motor stator with a winding system having at least one winding, and motor electronics configured to control the winding system to drive the motor rotor. In the synchronous motor according to the invention, the motor electronics are further configured to carry out the previously described inventive method to determine a pilot control angle and to control the winding system based on the determined pilot control angle. For this purpose, the motor electronics in particular have means for detecting the winding voltage and the winding current, as well as for storing and evaluating the winding voltage curve and the winding current curve. The motor electronics typically comprise a microcontroller for evaluating the winding voltage curve and the winding current curve.
[0016] The motor electronics of the synchronous motor according to the invention are thus configured to determine the pilot angle by executing the method according to the invention - as described above - without the need for a rotor position sensor, so that the synchronous motor according to the invention can be manufactured relatively inexpensively.
[0017] Preferably, the motor electronics are configured to carry out the above-described method according to the invention in order to determine a winding-specific pilot control angle for each winding of the winding system, and further configured to control the winding system in a controlled manner based on the determined winding-specific pilot control angles such that all windings have the same winding-specific pilot control angle. The motor electronics are thus configured, by means of a correspondingly configured control system, to individually, i.e., winding-specifically, control the control voltage provided to the individual windings by means of the semiconductor switches of the power electronics based on the corresponding determined winding-specific pilot control angle, specifically such that all windings have the same winding-specific pilot control angle.Typically, the determined winding-specific pre-control angles are each compared with a defined target pre-control angle, and the control voltage supplied to the corresponding winding is adjusted based on the deviation of the respective determined winding-specific pre-control angle from the target pre-control angle. This enables particularly efficient operation of the synchronous motor.
[0018] Since the individual windings of the winding system often have slightly different electrical properties due to manufacturing tolerances, slightly different material properties, and / or structural differences, the motor electronics are preferably configured to control the winding system in a controlled manner such that the winding-specific fundamental current oscillations of all windings have the same amplitude. The motor electronics are therefore configured to individually, i.e., winding-specifically, control the control voltage supplied to each winding by means of an appropriately designed control system such that the winding-specific fundamental current oscillations of all windings have the same amplitude.Typically, the amplitudes of the specific winding-specific fundamental current oscillations are each adjusted to a defined target winding current amplitude, and the control voltage supplied to the corresponding winding is adjusted based on the deviation of the amplitude of the specific winding-specific fundamental current oscillations from the target winding current amplitude. This enables particularly smooth running of the motor rotor and thus particularly quiet operation of the synchronous motor.
[0019] An embodiment of the present invention is described below with reference to the accompanying figures. Figure 1 shows a schematic representation of a synchronous motor according to the invention,
[0020] Figure 2 shows an exemplary image recorded during the execution of a method according to the invention
[0021] Winding voltage curve and an exemplary winding current curve of a winding system of the synchronous motor from Figure 1 recorded during the execution of a method according to the invention, as well as an EMF fundamental oscillation determined from the winding voltage curve and a winding current fundamental oscillation determined from the winding current curve, and
[0022] Figure 3 is a space vector representation of the fundamental EMF and the fundamental winding current from Figure 2.
[0023] Fig. 1 shows a synchronous motor 10 comprising an electromagnetic motor stator 12 with a winding system 14 and a permanent magnet motor rotor 16. In the present embodiment, the winding system 14 comprises three windings 18, wherein one winding end of each winding 18 can be electrically contacted via a contact element 20 and the other winding end is electrically connected to a so-called star point.
[0024] The synchronous motor 10 comprises motor electronics 22 with: a control unit 24, a detection unit 26, a data memory 28, an evaluation unit 30, and a control unit 32.
[0025] The control unit 24 is electrically connected to the contact elements 20 of the three windings 18. The control unit 24 is configured to read control parameters from the data memory 28 and to control the windings 18 based on the control parameters in order to drive the motor rotor 16 at a defined speed. The control unit 24 is configured to interrupt, i.e., temporarily suspend, the control of the windings 18 at predefined times in order to enable the evaluation unit 30 to determine a current pre-control angle W.
[0026] The detection unit 26 is electrically connected to the three contact elements 20. The detection unit 26 is configured to detect a winding voltage applied to the respective contact element 20 as well as a winding current impressed into the respective contact element 20 and to record a respective winding-specific winding voltage curve Uw and a respective winding current curve Iw, i.e., to store a chronological sequence of the detected values of the winding voltage and the winding current in the data memory 28.
[0027] The evaluation unit 30 is configured to read out and evaluate the winding-specific winding voltage curves Uw and the winding-specific winding current curves Iw from the data memory 28 at predefined times after the interruption of the control of the windings 18. In particular, the evaluation unit 30 is configured to determine a winding-specific fundamental EMF oscillation EMKO with a phase angle cpemkO and an amplitude AemkO for each winding 18 by means of Fourier analysis of a section A2 of the corresponding winding-specific winding voltage curve Uw recorded after the interruption of the control, and to determine a winding-specific winding current fundamental oscillation I0 with a phase angle cpiO and an amplitude AiO for each winding 18 by means of Fourier analysis of a section A1 of the corresponding winding-specific winding current curve Iw recorded before the interruption of the control.
[0028] The evaluation unit 30 is further configured to determine a winding-specific pre-control angle W for each winding 18 based on the phase angle cpemkO of the winding-specific EMF fundamental oscillation EMKO and the phase angle cpiO of the winding-specific winding current fundamental oscillation 10.
[0029] The evaluation unit 30 is further configured to store the phase angles cpemkO and amplitudes AemkO of the winding-specific EMF fundamental oscillations EMKO, the phase angles cpiO and amplitudes AiO of the winding-specific winding current fundamental oscillations 10, as well as the winding-specific pre-control angles W in the data memory 28.
[0030] The control unit 32 is configured to read the amplitudes AiO of the winding-specific fundamental winding current oscillations 10, the winding-specific pilot control angles W, as well as a desired pilot control angle and a desired winding current amplitude from the data memory 28. The control unit 32 is further configured to determine winding-specific control parameters in a control-based manner by comparing the amplitudes AiO of the winding-specific fundamental winding current oscillations 10 with the desired winding current amplitude and by comparing the winding-specific pilot control angle W with the desired pilot control angle, and to store them in the data memory 28.The control parameters are specifically determined such that when the control parameters are used to control the windings 18 by the control unit 24 after a transient phase, the amplitudes AiO of all winding current fundamental oscillations 10 essentially correspond to the desired winding current amplitude and all winding-specific pre-control angles W essentially correspond to the desired pre-control angle.
[0031] Fig. 2 shows an exemplary winding voltage curve Uw recorded by the detection unit 26 and an exemplary winding current curve Iw recorded by the detection unit 26. Fig. 2 also shows the corresponding fundamental EMF oscillation EMKO determined by the evaluation unit 30 and the corresponding fundamental winding current oscillation I0 determined by the evaluation unit 30.
[0032] Between a time toff and a time ton, the control of the winding system 14 by the control unit 24 was interrupted. The duration of the interruption is approximately 1.75 periods of the fundamental winding current oscillation 10, with the period of the fundamental winding current oscillation 10 corresponding to the period of a control signal. Thus, the control of the winding system 14 is interrupted for less than two periods of the control signal.
[0033] The section A1 of the winding current waveform Iw recorded before time toff, i.e., during activation, is evaluated by the evaluation unit 30 using Fourier analysis to determine the corresponding winding current fundamental oscillation I0. The section A2 of the winding voltage waveform Uw recorded between time toff and time tein, i.e., during the interruption of activation, is evaluated by the evaluation unit 30 using Fourier analysis to determine the corresponding EMF fundamental oscillation EMKO.
[0034] The phase shift between the specific EMF fundamental oscillation EMKO and the specific winding current fundamental oscillation 10, which is shown in Fig. 2 as an example using the shift of the zero crossings of the EMF fundamental oscillation EMKO and the winding current fundamental oscillation IO, defines the corresponding pre-control angle W.
[0035] Fig. 3 shows a so-called space vector representation of the EMF fundamental oscillation EMKO and the winding current fundamental oscillation IO from
[0036] Fig. 2. Here, the pre-control angle W can be read directly from the difference between the phase angle cpemkO of the EMF fundamental oscillation EMKO and the phase angle cpiO of the winding current fundamental oscillation IO.
[0037] List of reference symbols
[0038] 10 Synchronous motor
[0039] 12 Motor stator
[0040] 14 Winding system
[0041] 16 Motor rotor
[0042] 18 windings
[0043] 20 contact element
[0044] 22 Engine electronics
[0045] 24 control unit
[0046] 26 Recording unit
[0047] 28 data storage
[0048] 30 evaluation unit
[0049] 32 control unit
[0050] A1,A2 sections
[0051] AemkO Amplitude of the fundamental EMF oscillation
[0052] AiO amplitude of the winding current fundamental oscillation
[0053] EMKO EMF fundamental oscillation
[0054] 10 Winding current fundamental
[0055] Iw winding current curve toff,tein times
[0056] Uw winding voltage curve
[0057] W Pre-control angle cpemkO Phase angle of the EMF fundamental cpiO Phase angle of the winding current fundamental
Claims
PATENT CLAIMS Method for determining a pilot angle (W) of a synchronous motor (10), comprising the following method steps: - Controlling a winding system (14) of the synchronous motor (10) to set a defined operating point of the synchronous motor (10), - Recording a winding voltage curve (Uw) of the winding system (14), - Recording a winding current waveform (Iw) of the winding system (14), - Discontinuation of the control of the winding system (14), - Determining an electromotive force fundamental oscillation (EMKO) by evaluating a section (A2) of the winding voltage waveform (Uw) recorded after the cessation of the drive, - Determining a winding current fundamental oscillation (10) by evaluating a section (Al) of the winding current waveform (Iw) recorded before the cessation of the drive, and - Determining the pre-control angle (W) based on a phase angle (cpemkO) of the fundamental electromotive force (EMKO) and a phase angle (cpiO) of the fundamental winding current (10). Method according to claim 1, wherein the fundamental electromotive force (EMKO) is determined by means of a Fourier analysis of the corresponding section (A2) of the winding voltage waveform (Uw) and the fundamental winding current (10) is determined by means of a Fourier analysis of the corresponding section (Al) of the winding current waveform (Iw). Method according to one of the preceding claims, wherein for each winding (18) of the winding system (14) the following is determined: - a winding-specific winding voltage curve (Uw) is recorded, - a winding-specific winding current profile (Iw) is recorded, - a winding-specific electromotive force fundamental oscillation (EMKO) is determined by evaluating the corresponding section (A2) of the recorded winding-specific winding voltage curve (Uw), - a winding-specific winding current fundamental oscillation (10) is determined by evaluating the corresponding section (Al) of the recorded winding-specific winding current waveform (Iw), and - a winding-specific pre-control angle (W) is determined based on a phase angle (cpemkO) of the winding-specific fundamental electromotive force (EMKO) and a phase angle (cpiO) of the winding-specific fundamental winding current (10). Method according to one of the preceding claims, wherein the control of the winding system (14) is suspended for a maximum duration of two periods of a control signal. Synchronous motor (10) comprising: - a permanent magnet motor rotor (16), - an electromagnetic motor stator (12) with a winding system (14) having at least one winding (18), and - a motor electronics unit (22) configured to control the winding system (14) for driving the motor rotor (16), characterized in that the motor electronics unit (22) is further configured as follows: - to carry out a method according to any one of claims 1 to 4 to determine a pilot angle (W), and - the winding system based on the specific To control the pilot angle (W). Synchronous motor (10) according to claim 5, wherein the motor electronics (22) are configured: - to carry out the method according to claim 3 in order to determine a winding-specific pre-control angle (W) for each winding (18) of the winding system (14), and - to control the winding system (14) based on the specific winding-specific pre-control angles (W) in such a way that all windings (18) have the same winding-specific pre-control angle (W). Synchronous motor (10) according to claim 6, wherein the motor electronics (22) are configured to control the winding system (14) in such a way that the winding-specific winding current fundamental oscillations (10) of all windings (18) have the same amplitude (AiO).