CN110999035A

CN110999035A - Method for controlling a polyphase rotating electrical machine and rotating electrical machine for implementing the method

Info

Publication number: CN110999035A
Application number: CN201880052525.6A
Authority: CN
Inventors: P-S.法拉; R.弗拉蒂拉
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2017-07-11
Filing date: 2018-07-11
Publication date: 2020-04-10
Also published as: WO2019012010A1; EP3652840A1; FR3069113A1

Abstract

The invention relates to a method for controlling a polyphase rotating machine comprising a rotor rotating with respect to a stator comprising a first (B1) and a second (B2) three-phase winding positioned with respect to each other according to a mechanical and electrical angle, wherein the first (B1) and the second (B2) three-phase winding define a plurality of pole pairs and opposite around a predetermined number of slots (100), wherein the electrical angle between the first (B1) and the second (B2) three-phase winding is out of phase with respect to the mechanical angle in order to optimize at least one of the technical features of the motor torque.

Description

Method for controlling a polyphase rotating electrical machine and rotating electrical machine for implementing the method

Technical Field

The present invention relates to a method for controlling a polyphase rotary electric machine of an alternator, a starter or an alternator starter. The invention also relates to a rotating electric machine for implementing the method. The invention has application in the field of rotating electrical machines for motor vehicles, in particular in the field of electrical machines operating in alternator mode, starter mode or alternator-starter mode.

Background

The rotating electric machine comprises in a manner known per se a stator and a rotor integral with a central shaft. The rotor may be integral with the drive shaft and/or the driven shaft and may belong to a rotating electrical machine in the form of an alternator, an electric motor or a reversible electrical machine operating in two modes.

The motor includes a housing supporting a stator. The housing includes front and rear bearings at the ends of the stator, respectively, and is configured to rotate the shaft by means of bearings such as ball bearings and/or needle bearings.

The rotor comprises a body formed by a stack of metal plates, which are held in a set by means of a suitable fixing system, for example rivets passing axially through the rotor from one side to the other. The rotor comprises poles, for example formed by permanent magnets, which are accommodated in cavities provided in the magnetic mass of the rotor. Alternatively, in a so-called "salient" pole structure, the poles are formed by coils wound around the arms of the rotor.

The stator includes a body composed of stacked thin metal plates forming a crown having an inner cylindrical surface and an outer cylindrical surface. The inner cylindrical surface is provided with notches extending axially and opening radially towards the rotor for receiving windings forming a phase winding. The notches are regularly distributed in a predefined step (called P) in the internal face of the stator. The phase windings can be obtained by wires entering and leaving the slots at each step P, or by conductive pins inserted in the slots and interconnected every P slots. The phase windings, also referred to simply as phases, are coupled to each other according to a configuration in the form of a star or a triangle.

In the field of motor vehicles, it is known to use polyphase rotating electrical machines, for example three-phase or dual three-phase machines. A three-phase motor typically includes three pairs of poles distributed on the rotor and three-phase windings angularly distributed on the inner cylindrical surface of the stator. In a three-phase motor, the phases are generally assigned according to an electrical angle of 120 ° and a mechanical angle of 120 ° divided by the number of poles p. For example, if p is 2, the mechanical angle is 120/2 is 60 °, or if p is 8, the mechanical angle is 120/8 is 15 °.

The dual three-phase machine comprises a first three-phase system B1 and a second three-phase system B2, the phases of the second three-phase system B2 being offset with respect to the first three-phase system in order to obtain six phases regularly distributed in the stator. In fact, in a double three-phase machine, the windings are distributed in regular steps between the slots, the number of which is typically a multiple of 6. The total number of slots may be, for example, 48, 54, or 72. Each phase winding may fill one slot or two slots, or three slots, or 1.5 slots, depending on the number of slots of the stator. For example, in a motor with 6 phases, 3 pairs of poles, and 72 slots, each phase winding fills 2 slots. For a motor with 6 phases, 3 pairs of poles and 54 slots, each winding fills 1.5 slots. Two examples of rotating electrical machines with 6 phases, 3 pairs of poles and 54 slots (reference number 100) are partially shown in fig. 1 and 2, where fig. 1 illustrates a stator winding with normal steps, i.e. steps of 9 slots, and fig. 2 shows a stator winding with shortened steps, i.e. steps of 8 slots.

It is known in the field of motor vehicles that dual three-phase machines generally provide lower harmonic levels than three-phase machines, as illustrated by the curves in fig. 3A and 3B, wherein fig. 3A shows the electromotive force obtained in a three-phase machine and fig. 3B shows the electromotive force obtained in a dual three-phase machine, wherein the electrical phase displacement between the first and second three-phase systems is zero. Due to this difference in harmonic levels, the dual three-phase motor reduces torque ripple (or ripple) between the rotor and the stator compared to a three-phase motor. However, fluctuations in torque are the cause of many mechanical problems, such as magnetic noise, lack of accuracy in motion control, and the like. Therefore, motor vehicle manufacturers often try to reduce torque fluctuations as much as possible. For this purpose, it is known to offset the second three-phase system by an electrical angle of 30 ° with respect to the first three-phase system, and to determine a mechanical angle between the phases equal to the electrical angle.

Other techniques for potentially reducing torque ripple have been described in the prior art. These techniques are generally based on modifications of the electromagnetic structure of the polyphase electric machine, or on the current supply mode of the electric machine. For example, one of these techniques, described in application WO 2008/043926 a1, proposes adapting the step size of the slots of the stator to the length of the claws of the rotor.

However, although these techniques according to the prior art make it possible to reduce the torque fluctuations, they do not take into account the average torque of the machine. However, it is well known that the torque value of the motor is an important characteristic of the rotating electric machine.

Disclosure of Invention

In order to solve the above-mentioned problem of not taking into account the average torque of the electric machine, the applicant has proposed a method for controlling a polyphase rotary electric machine which makes it possible to optimize at least one characteristic of the torque of the electric machine according to the level of performance to be obtained.

According to a first aspect, the invention relates to a method for controlling a polyphase rotating machine comprising a rotor rotating with respect to a stator comprising a first and a second three-phase winding positioned with respect to each other according to a mechanical and electrical angle, wherein the first and the second three-phase winding define a plurality of pole pairs and opposite around a predetermined number of slots.

The method is characterized in that the electrical angle between the first and second three-phase windings is out of phase with respect to the mechanical angle in order to optimize at least one of the technical features of the motor torque.

The "electrical angle between the first three-phase winding and the second three-phase winding" refers to an angle formed between phase currents of two three-phase systems. The mechanical angle also represents the angle between the EMFs of two three-phase systems.

The advantage of this method is that the average torque or torque ripple, or both, of the machine can be optimized according to the performance level required by the machine. This optimization is achieved without additional cost by the phase shift of the electrical angle relative to the mechanical angle.

Advantageously, the value of the electrical angle is determined from a curve representing the average torque according to the electrical angle and/or from a curve representing the torque fluctuations according to said electrical angle.

These curves allow to determine precisely the most advantageous values of the electrical angle.

Advantageously, the phase shift of the electrical angle relative to the mechanical angle is controlled by an inverter of the rotating electrical machine.

According to some embodiments, the phase shift in electrical angle is obtained by a time offset of the power supply of the second three-phase winding relative to the first three-phase winding.

According to a second aspect, the invention relates to a multiphase rotating electrical machine comprising a rotor rotating with respect to a stator comprising a first and a second three-phase winding defining a plurality of pole pairs and opposite around a predetermined number of slots. The electric machine is characterized in that the first and second three-phase windings are positioned relative to each other according to a predetermined mechanical angle and according to an electrical angle that is out of phase with the mechanical angle.

According to some embodiments, the first and second three-phase windings define 6 phases and 6 poles wound around the 54 slots.

According to certain embodiments, the first and second three-phase windings define 6 phases and 12 poles wound around 72 slots.

According to some embodiments, the first and second three-phase windings define 6 phases and 8 poles wound around the 48 slots.

Drawings

Other advantages and features of the invention will become apparent upon reading the description presented in the drawings, in which:

fig. 1, which has been described, schematically shows a first example of a partial winding of a stator.

Fig. 2, which has been described, schematically shows a second example of a partial winding of a stator.

Fig. 3A to 3B, which have been described, show graphs of electromotive forces obtained in a three-phase motor and a double three-phase motor, respectively.

Fig. 4A-4C show examples of average torque and torque ripple in a dual three-phase machine with 3 pairs of poles and 54 slots.

Fig. 5A-5B illustrate examples of average torque and torque ripple for a dual three-phase motor including 6 pairs of poles and 72 slots.

Fig. 6A-6C show examples of average torque and torque ripple for a dual three-phase motor including 4 pairs of poles and 48 slots.

Fig. 7A-7B show the dieting of the first and second out-of-phase windings according to the method of the invention, and curves representing the electromotive force and current of these windings.

Fig. 8A and 8B show a schematic cross-sectional view and an electrical diagram, respectively, of an example of an electrical machine (rotor and stator) in which the method of the invention can be implemented.

Detailed Description

Hereinafter, an example of a method for controlling a multiphase rotary electric machine, taking into account the performance level that the machine has to obtain, is described with reference to the accompanying drawings. This example illustrates the features and advantages of the present invention. It should be borne in mind, however, that the present invention is not limited to this example.

In the drawings, like elements are denoted by like reference numerals. For reasons of clarity of the drawing, no dimensional ratios between the elements represented are observed.

The rotating electric machine implementing the method according to the invention is a polyphase electric machine as described previously in the paragraph entitled "prior art". The motor is of the double three-phase type, an example of which is schematically shown in fig. 8A. It comprises a stator 200 equipped with a predetermined number of slots around which six phase windings 150 are wound. The motor further comprises a rotor 300 provided with a predetermined number of pole pairs. In the examples described below, the number of pole pairs of the rotor is 3, 4 or 6 and the number of slots of the stator is 48, 54 or 72, it being understood that the method according to the invention can be applied to any type of rotor and stator of a double three-phase machine, regardless of their number of pole pairs and number of slots.

The method according to the invention proposes one of the technical features of controlling a dual three-phase motor in order to optimize the motor torque. The motor is specifically controlled by an inverter 400 such as that shown in fig. 8B. The torque of a multiphase motor is characterized by its average torque and ripple. In some applications, priority is given to the average torque of the motor, whereas in other applications, priority is given to reducing torque ripple. To this end, the method according to the invention proposes to phase-shift the electrical angle between the first and second windings with respect to the mechanical angle. In other words, it is proposed to de-synchronize the electrical and mechanical angles of the motor windings in order to obtain different torque characteristics.

Fig. 4A-4C show examples of average torque and torque ripple in a dual three-phase machine with 3 pairs of poles and 54 slots. Fig. 4A schematically shows the distribution of phases in 54 slots 100 of the motor. In this example, each phase winding is wound around 1.5 slots of the stator. Fig. 4C shows a histogram showing the radial forces exerted on the stator for each harmonic order and for a plurality of electrical angle values, in particular 0 °, 10 °, 20 °, 30 °, 40 ° and 50 °. Since the harmonic order number depends on the slot number and pole pair number, it is 18 in the example of fig. 4C (18 harmonic orders for 54 slots divided by 3 pole pairs). Thus, FIG. 4C compares the harmonic orders for different offset angles. This fig. 4C shows the effect of the electrical angle on the acoustic performance of the motor. Fig. 4C also shows the content of force harmonics in the air gap. These forces affect the acoustic level of the motor. Therefore, reducing these harmonics makes it possible to reduce the noise of the motor. Fig. 4B shows a curve Ccm of the average torque in Nm according to the electrical angle between the first and second three-phase windings of the electric machine in fig. 4A, and a curve Coc of the torque ripple measured in peak-to-peak values in percent according to this same electrical angle. These curves are provided for a given offset angle, independent of the harmonic order. The curve in fig. 4B, shown for the same harmonic order, indicates that the torque ripple is not optimized for the same electrical angle as the average torque. In fact, in this example, the average torque is optimized for an electrical angle of 20 °, i.e. the average torque is at a maximum, while the torque ripple is optimized for an electrical angle of 30 to 40 °, i.e. it is at its minimum.

Fig. 5A-5B show examples of average torque and torque ripple obtained in another multi-phase electric machine. In this example, the motor is a dual three-phase motor, including 6 pole pairs and 72 slots. Fig. 5A shows that in this example, the motor includes one notch per pole and per phase. In other words, the windings of a phase fill one slot per pole. Fig. 5B shows a curve Ccm of the average torque in Nm according to the electrical angle between the first three-phase winding and the second three-phase winding of the electric machine in fig. 5A, and a curve Coc of the torque ripple measured in percent peak-to-peak value according to this same electrical angle. The curve in fig. 5B shows that the torque ripple is not optimized for the same electrical angle as the average torque. In fact, in this example, the average torque is optimized for an electrical angle of about 35 °, while the torque ripple is optimized for an electrical angle of about 10 °.

Fig. 6A-6C show examples of average torque and torque ripple obtained in yet another multi-phase electric machine. In this example, the motor is a dual three-phase motor, including 4 pole pairs and 48 slots. Fig. 6A schematically shows the phase distribution in the 48 slots of the motor. In this example, each phase winding fills one slot per pole and per phase. Fig. 6C shows the radial forces exerted on the stator for each of the 12 harmonic orders and for a plurality of values of the electrical angle, in particular 0 °, 10 °, 20 °, 30 °, 40 ° and 50 °. This fig. 6C shows the effect of electrical angle on the motor performance. Fig. 6B shows a curve Ccm of the average torque in Nm according to the electrical angle between the first three-phase winding and the second three-phase winding of the electric machine in fig. 6A, and a curve Coc of the torque ripple measured in percent peak-to-peak value according to this same electrical angle. The plot of fig. 6B for the same harmonic order representation indicates that the torque ripple is not optimized for the same electrical angle as the average torque. In fact, in this example, the mean torque is optimized for an electrical angle of 20 to 25 °, i.e. the mean torque is at its maximum, while the torque ripple is optimized for an electrical angle of about 35 °, i.e. the torque ripple is at its minimum.

The different examples in fig. 4A to 6C show the advantage of shifting the electrical angle relative to the mechanical angle of the machine. The performance of the motor varies depending on the electrical angle selected, which may improve the average torque or torque ripple of the motor. Those skilled in the art will appreciate that the electrical angle may also be selected to optimize both characteristics of torque (average torque and torque ripple) simultaneously. In this case, the value of the electrical angle will be chosen so as to obtain a balance between the mean torque and the torque ripple, without maximizing the mean torque or minimizing the torque ripple. Then, the value of the average torque and the value of the torque ripple are weighted with each other. In the example of fig. 6A-6C, the value of the electrical angle may be, for example, included in the range of 8 ° to 10 ° in order to weight the average torque and the torque ripple.

As can be understood from the foregoing information, the most advantageous value of the electrical angle can be determined by reading a curve such as the curves in fig. 4B, 5B, and 6B. The selected value is controlled by an inverter of the multi-phase motor. In fact, any polyphase rotating machine is controlled by an electronic power module called inverter. An example of this type of inverter has reference numeral 400 in fig. 8B. The electronic power module 400 comprises a plurality of electronic power components 410, such as power transistors, which are connected to form control switches of the stator. In a conventional double three-phase motor, the electronic power components are controlled so that the signals emitted by the sensors of the motor are synchronized with the electromotive forces to which the phases are subjected. The control switch of the stator is therefore switched to emit the sensor signal. In a double three-phase machine implementing the method according to the invention, for example in fig. 8B, the control switches of the stator 200 are switched with a time delay with respect to the emission of the sensor signals, whereby this delay is obtained by means of a counter installed in the electronic power module. The control switch is thus switched in a time-shifted manner, which produces a phase shift in electrical angle. Thus, the electrical angle between the two windings is out of phase with respect to the mechanical angle of the phase windings. It is this phase shift between electrical and mechanical angles that makes it possible to vary the technical characteristics of the torque of the electric machine.

The method can be implemented in all double three-phase machines without additional costs, since the phase shift of the electrical angle relative to the mechanical angle is obtained only by controlling the time shift of the control of the switches without adding electronic components.

Fig. 7A shows an example of a first winding B1 and a second winding B2 of a dual three-phase motor according to the present invention. The first winding B1 comprises 3 phases with

reference numbers

11, 12, 13, which are angularly distributed according to an electrical angle of 120 °. Similarly, the second winding B2 comprises 3

phases

21, 22, 23 angularly distributed according to an electrical angle of 120 °. In this example, the two windings B1, B2, shown in solid lines, are out of phase at an electrical angle of 30 °. The dashed line represents the positioning of the second winding B2 relative to the first winding B1 when the electrical angle is different from 30 ° (e.g., when it is contained in the range of 0 to 50 °).

Figure 7B shows the electromotive force EMF (in volts) and current (in amps) as a function of electrical angle. Electromotive force of each of the first winding B1 and the second winding B2 is shown. The current for each of the first winding B1 and the second winding B2 is shown when the second winding B2 is out of phase at 30 ° electrical angle with respect to the first winding (curve B2) and when it is out of phase 0 to 50 ° with respect to the first winding B1 (curves B2' and B2 "). With these curves, fig. 7B shows the electrical effect of the phase shift between the first winding B1 and the second winding B2, which results in a change in the average torque and/or torque ripple of the bi-tertiary winding.

Although described with a certain number of examples, modifications and embodiments, the method for controlling a polyphase rotating machine according to the invention comprises different variants, modifications and improvements, which will be apparent to the skilled person and which form part of the scope of the invention.

Claims

1. A method for controlling a multiphase rotating electrical machine comprising a rotor rotating with respect to a stator comprising a first (B1) and a second (B2) three-phase winding positioned with respect to each other according to a mechanical and electrical angle, wherein the first (B1) and the second (B2) three-phase winding define a plurality of pole pairs and opposite around a predetermined number of slots (100),

the method is characterized in that the electrical angle between the first three-phase winding (B1) and the second three-phase winding (B2) is out of phase with respect to the mechanical angle in order to optimize at least one of the technical features of the motor torque.

2. A method according to claim 1, characterized in that the value of the electrical angle is determined from a curve (Ccm) representing the average torque according to the electrical angle and/or from a curve (Coc) representing the torque fluctuation according to the electrical angle.

3. Method according to claim 1 or 2, characterized in that the phase shift of the electrical angle relative to the mechanical angle is controlled by an inverter of a rotating electrical machine.

4. The method according to claim 3, characterized in that the phase shift in electrical angle is obtained by a time offset of the power supply of the second three-phase winding (B2) with respect to the first three-phase winding (B1).

5. A multiphase rotary electric machine comprising a rotor rotating with respect to a stator, the stator comprising a first three-phase winding (B1) and a second three-phase winding (B2), the first three-phase winding (B1) and the second three-phase winding (B2) defining a plurality of pole pairs and opposing around a predetermined number of slots (100),

characterized in that the first three-phase winding (B1) and the second three-phase winding (B2) are positioned with respect to each other according to a predetermined mechanical angle and according to an electrical angle that is out of phase with the mechanical angle.

6. The electric machine of claim 5, wherein the first three-phase winding (B1) and the second three-phase winding (B2) define 6 phases and 6 poles wound around 54 slots.

7. The electric machine of claim 5, wherein the first three-phase winding (B1) and the second three-phase winding (B2) define 6 phases and 12 poles wound around 72 slots.

8. The electric machine of claim 5, wherein the first three-phase winding (B1) and the second three-phase winding (B2) define 6 phases and 8 poles wound around 48 slots.