Determining initial angular position of rotor of salient pole permanent magnet motor

Abstract

The subject matter of the application is to determine the initial angular position of the rotor of a salient pole permanent magnet motor. The invention relates to the field of electrical machines and to a method and device for controlling an electrical machine, more particularly to determining the initial angular position of the rotor of a salient pole permanent magnet electrical machine. A method for determining an initial angular position of a rotor of a salient pole permanent magnet machine connected to a frequency converter comprises: performing a first signal injection step in which an initial angle [theta] d, axis, 1 of the permanent magnet flux axis is determined; performing direct current injection (12) in which direct current is injected into the free permanent magnet motor in a direct current injection direction [theta] DC, dir = [theta] d, axis, 1 + / -[theta] add; carrying out a second signal injection step, in which the angle [theta] d, axis, 2 of the permanent magnet flux axis is determined; and determining (16) an initial angular position of the rotor of the permanent magnet electric machine.

Description

Technical Field

[0001] The present invention relates to the field of electric machines and methods and devices for controlling electric machines, and more particularly to determining an initial angular position of a rotor of a salient-pole permanent magnet electric machine. Background Art

[0002] Permanent magnet motors, such as permanent magnet assisted synchronous motors and salient pole permanent magnet synchronous motors, are used in a variety of applications.

[0003] Rotating electrical machines are usually controlled using frequency converters, and for controlled operation, information about the electrical behavior of the machine is required. This information is fed to the controller of the frequency converter in the form of electrical parameters of the machine. For field oriented control, an accurate initial rotor position is required as an initial state for adjusting the direct quadrature (dq) coordinate system, torque and flux / voltage estimation, etc. Therefore, errors in the initial rotor position have an impact on the start-up of the PMSM drive and may lead to performance degradation.

[0004] Initial rotor position estimation is used to determine the angular position of the magnetic flux of a permanent magnet motor such as a permanent magnet synchronous motor (PMSM). One known method for initial rotor position estimation is the DC injection method, i.e., DC injection, which is used to intentionally align the axis with the desired direction. In the DC injection method, where a DC current is injected, the permanent magnet flux axis (also called the d-axis) is aligned with the current direction of the surface mounted permanent magnet (SPM) motor. As a result, after the DC injection, the initial rotor position will be the same as the DC current direction.

[0005] However, for other permanent magnet machines, such as in the case of highly protruding interior permanent magnet (IPM) motors and permanent magnet assisted synchronous reluctance motors (PMaSynRMs), the magnetic flux may not be aligned with the DC current direction.

[0006] In this type of permanent magnet motor, the magnetic flux usually turns in the DC direction according to the saliency and stabilizes at a position much less than 90 degrees from the DC direction. This is called DC parking of the rotor shaft. Therefore, it is incorrect to use the DC direction as the initial position of the magnetic flux.

[0007] There are also different types of AC injection methods in the literature, such as voltage pulse signal injection method, sinusoidal high frequency (HF) signal injection method, and high frequency (HF) square wave signal injection method. However, these methods may give an error of 180 degrees due to the polarity of the permanent magnetic flux. In addition, these methods usually use the saturation behavior of the motor to find the polarity of the permanent magnetic flux.

[0008] Hereinafter, the prior art will be described with reference to the accompanying drawings, in which:

[0009] Figure 1AAn example of the angular position of the rotor of a permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown.

[0010] Figure 1B An example of the angular position of the rotor of a permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown.

[0011] Figure 2A Another example of the angular position of the rotor of a permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown.

[0012] Figure 2B Another example of the angular position of the rotor of a permanent magnet motor after direct current injection in a rotor angular position estimation method according to the prior art is shown.

[0013] Figure 3A A third example of the angular position of the rotor of a permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown.

[0014] Figure 3B A third example of the angular position of the rotor of a permanent magnet motor after direct current injection in a rotor angular position estimation method according to the prior art is shown.

[0015] Figure 1A An example of the angular position of the rotor of a permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown. Figure 1A An example of DC parking is shown in FIG. 1 , where the angular position of the rotor of the permanent magnet motor before DC injection is 0 degrees θ DC，dir = 0°, i.e., the initial electrical position of the axis is 36 degrees θ PM = 36°. When DC injection is performed, this will shift the flux further to 74°.

[0016] Figure 1B An example of the angular position of the rotor of a permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown. Figure 1B In the DC parking example, the angular position of the rotor of the permanent magnet motor after DC injection, that is, the electrical position of the shaft is 74 degrees θ PM =74°.

[0017] Figure 2A Another example of the angular position of the rotor of a permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown. Figure 2A Another example of DC parking is shown in FIG. 1 , where the angular position of the rotor of the permanent magnet motor before DC injection, i.e., the initial electrical position of the axis, is 158 degrees θ PM= 158°. When DC injection is performed, this will move the flux further to 289 degrees.

[0018] Figure 2B Another example of the angular position of the rotor of a permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown. Figure 2B In another DC parking example, the angular position of the rotor of the permanent magnet motor after DC injection, i.e., the electrical position of the shaft, is 289 degrees θ PM =289°.

[0019] Figure 3A A third example of the angular position of the rotor of a permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown. Figure 3A , a third example of DC parking is shown, in which the angular position of the rotor of the permanent magnet motor before DC injection, that is, the initial electrical position of the axis is 180 degrees θ PM = 180°. When DC injection is performed, this will not move the angular position of the rotor, i.e. the flux remains at 180 degrees.

[0020] Figure 3B A third example of the angular position of the rotor of a permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown. Figure 3B In the third DC parking example, the angular position of the rotor of the permanent magnet motor after DC injection, that is, the electrical position of the shaft remains at 180 degrees θ PM =180°.

[0021] In the prior art solutions for determining the initial angular position of the rotor of the salient pole permanent magnet motor, the main problem is the 180 degree misalignment of the initial angular position of the rotor of the permanent magnet motor and the DC parking behavior of the rotor shaft. Moreover, in the prior art solutions for determining the initial angular position of the rotor of the salient pole permanent magnet motor, a two-phase current measurement sensor or a three-phase current measurement sensor is required to measure the current in the pulse direction.

[0022] In today's demanding environments, a more efficient and elegant solution for determining the initial angular position of the rotor of a salient pole permanent magnet motor is needed that will be more efficient and will not require a two-phase current measurement sensor or a three-phase current measurement sensor.

[0023] In the art, there is a particular need for a method for determining the initial angular position of a rotor of a salient-pole permanent magnet electric machine which is more efficient than prior art solutions. Summary of the invention

[0024] The object of the invention is to introduce a method for determining the initial angular position of a rotor of a salient-pole permanent-magnet motor which is more efficient than prior art solutions. Advantageous embodiments are also presented.

[0025] A new method for determining the initial angular position of a rotor of a salient-pole permanent magnet motor connected to a frequency converter is proposed, in which a first signal injection step is performed in which the initial angle θ of the permanent magnet flux axis is determined. d，axis，1 ; Perform DC injection, in which the DC injection direction θ DC，dir =θ d，axis，1 ±θ add The DC is injected into the idle salient pole permanent magnet motor, where the DC injection direction θ DC，dir is the angle of injected DC, the increased angle θ add is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 performing a second signal injection step, in which the angle θ of the permanent magnet flux axis is determined d，axis，2 ; The initial angular position of the rotor of the salient pole permanent magnet motor Determined as:

[0026]

[0027] In a preferred embodiment of the method, in the first signal injection step, a first pulse test is performed, wherein a first pulse test number of external pulses are injected into an idle salient pole permanent magnet motor at a selected angle, for each injected pulse, the current to flux ratio is measured, and the initial angle θ of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio. d，axis，1 ; and in the second signal injection step, a second pulse test is performed, wherein a second pulse test number of external pulses are injected into the idle salient pole permanent magnet motor at a selected angle, for each injected pulse, the current to flux ratio is measured, and the angle of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio.

[0028] In a preferred embodiment of the method, in the first signal injection step, the initial angle θ of the permanent magnet flux axis is determined by using AC injection. d，axis，1 , and / or wherein in the second signal injection step, the angle θ of the permanent magnet flux axis is determined by using AC injection d，axis，2 .

[0029] In a preferred embodiment of the method, in the first signal injection step, the initial angle θ of the permanent magnet flux axis is determined by injecting a voltage pulse signal. d，axis，1 , and / or wherein in the second signal injection step, the angle θ of the permanent magnet flux axis is determined by injecting a voltage pulse signal d，axis，2 .

[0030] In a preferred embodiment of the method, in the first signal injection step, the initial angle θ of the permanent magnet flux axis is determined by using a sinusoidal high frequency (HF) signal injection or a high frequency (HF) square wave signal injection. d，axis，1 , and / or wherein in the second signal injection step, the angle θ of the permanent magnet flux axis is determined by using a sinusoidal high frequency (HF) signal injection or a high frequency (HF) square wave signal injection. d，axis，2 .

[0031] In a preferred embodiment of the method, the increased angle θ add It's 90 degrees.

[0032] In a preferred embodiment of the method, the increased angle θ add Between 50 degrees and 130 degrees.

[0033] In a preferred embodiment of the method, the increased angle θ add Between 30-150 degrees.

[0034] In a preferred embodiment of the method, the first pulse test and / or the second pulse test is performed as a six-pulse test, in which the current to flux ratio is measured with pulses at angles of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees.

[0035] In a preferred embodiment of the method, six voltage pulses are generated in a sequence that minimizes the likelihood of a rotor of the salient-pole permanent magnet machine rotating.

[0036] Furthermore, a new frequency converter suitable for connection to a salient-pole permanent-magnet motor is proposed, the frequency converter comprising means configured to determine an initial angular position of a rotor of the salient-pole permanent-magnet motor by performing a first signal injection step in which an initial angle θ of the permanent-magnet flux axis is determined. d，axis，1 ; Perform DC injection, where DC injection is in the DC injection direction θ DC，dir =θ d，axis，1 ±θ add The DC is injected into the idle salient pole permanent magnet motor, where the DC injection direction θ DC，dir is the angle of injected DC, and the increased angle θadd is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 The angle of the offset; performing a second signal injection step, in which the second signal injection step determines the angle θ of the permanent magnet flux axis d，axis，2 ; and the initial angular position of the permanent magnet motor rotor Determined as:

[0037]

[0038] In a preferred embodiment of the frequency converter, when performing the first signal injection step, the frequency converter includes a device configured to perform a first pulse test, in which a plurality of external pulses are injected into an idle salient-pole permanent magnet motor at a selected angle, for each injected pulse, a current-to-flux ratio is measured, and an initial angle θ of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio. d，axis，1 ; and in performing the second signal injection step, the frequency converter includes a device configured to perform a second pulse test in which a plurality of external pulses are injected into an idle salient-pole permanent magnet motor at a selected angle, for each injected pulse, a current-to-flux ratio is measured, and an angle θ of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio d，axis，2 .

[0039] In a preferred embodiment of the frequency converter, when performing the first signal injection step, the frequency converter includes a signal generator configured to determine the initial angle θ of the permanent magnet flux axis using AC injection, voltage pulse signal injection, sinusoidal high frequency (HF) signal injection, or high frequency (HF) square wave signal injection. d，axis，1 and / or wherein when performing the second signal injection step, the frequency converter includes a device configured to determine the angle θ of the permanent magnet flux axis using AC injection, voltage pulse signal injection, sinusoidal high frequency (HF) signal injection or high frequency (HF) square wave signal injection. d，axis，2 device.

[0040] In a preferred embodiment of the first pulse test and / or the second pulse test, the first pulse test and / or the second pulse test is performed as a six-pulse test, in which the current to flux ratio is measured using pulses with angles of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees.

[0041] Furthermore, a new computer program product is proposed comprising a computer program code, wherein execution of the program code in a computer causes a computer of the new frequency converter to cause the computer to perform the steps of the new method. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In the following, the invention will be described in more detail by way of example and with reference to the accompanying drawings, in which:

[0043] Figure 1A An example of the angular position of the rotor of a salient-pole permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown.

[0044] Figure 1B An example of the angular position of a rotor of a salient-pole permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown.

[0045] Figure 2A Another example of the angular position of the rotor of a salient-pole permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown.

[0046] Figure 2B Another example of the angular position of the rotor of a salient-pole permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown.

[0047] Figure 3A A third example of the angular position of the rotor of a salient-pole permanent magnet motor before DC injection in a rotor angular position estimation method according to the prior art is shown.

[0048] Figure 3B A third example of the angular position of the rotor of a salient-pole permanent magnet motor after DC injection in a rotor angular position estimation method according to the prior art is shown.

[0049] Figure 4 A flow chart of an embodiment of a method for determining an initial angular position of a rotor of a salient-pole permanent magnet motor according to the present invention is shown.

[0050] Figure 5 A simplified structure of an embodiment of an inverter of a frequency converter according to the invention is shown.

[0051] Figure 6 Shows the use of Figure 5 The voltage vector obtained by the inverter.

[0052] Fig. 7A An embodiment of the angular position of the rotor of a salient-pole permanent magnet motor after a first signal injection according to the present invention is shown.

[0053] Figure 7BAn embodiment of the angular position of the rotor of the salient-pole permanent magnet motor before and after DC injection is shown according to the present invention.

[0054] Figure 7C An embodiment of the angular position of the rotor of a salient-pole permanent magnet motor after the second signal injection according to the present invention is shown.

[0055] Fig. 8A Another embodiment of the angular position of the rotor of the salient-pole permanent magnet motor after the first signal injection according to the present invention is shown.

[0056] Figure 8B Another embodiment of the angular position of the rotor of the salient-pole permanent magnet motor before and after DC injection according to the present invention is shown.

[0057] Figure 8C Another embodiment of the angular position of the rotor of the salient-pole permanent magnet motor after the second signal injection according to the present invention is shown.

[0058] The foregoing aspects, features and advantages of the present invention will be apparent from the accompanying drawings and detailed description associated therewith.

[0059] Figures 1A to 3B The accompanying drawings of the prior art have been given above. Figures 4 to 8C The preferred embodiments are described in more detail. DETAILED DESCRIPTION

[0060] In the method for determining the initial angular position of the rotor of a salient-pole permanent magnet motor connected to a frequency converter according to the present invention: a first signal injection step is performed in which the initial angle θ of the permanent magnet flux axis is determined. d，axis，1 ; Perform DC injection, in which the DC injection direction θ DC，dir =θ d，axis，1 ±θ add The DC is injected into the idle salient pole permanent magnet motor, where the DC injection direction θ DC，dir is the angle of injected DC, and the increased angle θ add is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 performing a second signal injection step, in which the angle θ of the permanent magnet flux axis after the DC injection is determined d，axis，2 ; The initial angular position of the rotor of the salient pole permanent magnet motor Determined as:

[0061]

[0062] Figure 4A flow chart of an embodiment of a method according to the invention for determining an initial angular position of a rotor of a salient-pole permanent-magnet motor is shown. In this embodiment, the salient-pole permanent-magnet motor is connected to a frequency converter. The frequency converter may have current measurement using one or more current sensors in the intermediate voltage circuit and / or in the three-phase output. In the method according to this embodiment, a first signal injection 11 is first performed as a first pulse test 11.

[0063] In the first pulse test 11, an external pulse (ie, external flux) is injected into an idle salient pole permanent magnet motor. When harmonics, saturation and core losses are neglected, the ratio of current to flux in the pulse direction can be expressed as

[0064]

[0065] where θ is the angle of the external pulse and θ d，axis is the angle of the permanent magnet flux axis. The angle of the permanent magnet flux axis θ d，axis is the angle of the d-axis, i.e. the electrical angular position of the rotor in the stator reference frame.

[0066] With the help of the first pulse test 11, the initial angle θ of the permanent magnet flux axis is found d，axis，1 The initial angle θ of the permanent magnet flux axis d，axis，1 is the initial angle θ of the d-axis d，axis，1 , that is, the initial electrical angular position of the rotor in the stator reference coordinate system.

[0067] In the first pulse test 11, voltage pulses are generated at selected angles, and the current is measured with each pulse, and the permanent magnet flux is estimated. Thereafter, the ratio of current to flux is calculated with pulses of the selected angle. Thereafter, the inductance value L is determined by performing a discrete Fourier transform (DFT) on the measured ratio. d , L q The initial angle θ between the axis and the d axis d，axis，1 .

[0068] In one embodiment, the first pulse test 11 is performed as a six-pulse test. In the six-pulse test, the ratio of current to flux is measured with pulses at angles of 0, 60, 120, 180, 240 and 300 degrees, and the inductance value L is determined by performing a discrete Fourier transform (DFT) on the measured ratio. d , L q The initial angle θ between the axis and the d axis d，axis，1An example of performing a six-pulse test is further explained in European patent specification EP3220535B1. The initial angle θ of the d-axis d，axis，1 is determined to wrap around 0° and 360°, i.e., 0°≤θ d，axis，1 ≤360°.

[0069] Here, the general equation for angles around about 0° and 360° is defined as:

[0070]

[0071] After performing the first signal injection 11 and determining the initial angle θ of the d-axis d，axis，1 Afterwards, a direct current injection 12 is performed to move and park the shaft in a new position (DC, direct current).

[0072] In DC injection 12, a DC current of low magnitude (e.g., 0.5 times the nominal current value) is injected into the idle salient pole permanent magnet motor in a DC injection direction, which is defined as:

[0073] θ DC,dir =θ d，axis，1 ±θ add (2)

[0074] The DC injection direction θ DC，dir is the angle of the injected DC current, and the increased angle θ add is the angle that defines the offset from the initial angle of the permanent magnet flux. The DC injection direction θ DC，dir is determined to wrap around 0° and 360°, i.e., 0°≤θ DC，dir ≤360°.

[0075] In one embodiment, the increased angle θ add In another embodiment, the increased angle θ add In another embodiment, the increased angle θ add It's 90 degrees.

[0076] It has been observed from simulations and laboratory measurements that DC injection 12 ensures shaft movement and DC parking at 90 degrees (±90°) to the DC direction.

[0077] After performing the direct current injection 12 , a second signal injection 13 is performed. In the method according to this embodiment, the second signal injection 13 is performed as a second pulse test 13 .

[0078] In the second pulse test 13, an external pulse (ie, external flux) is injected into the idle salient pole permanent magnet machine. With the aid of the second pulse test 13, the angle θ of the permanent magnet flux axis is found d，axis，2 The angle θ of the permanent magnet flux axis d，axis，2 is determined to wrap around 0° and 360°, i.e. 0°≤θ d，axis，2 ≤360°, angle θ of permanent magnet flux axis d，axis，2 is the angle θ of the d-axis after DC injection d，axis，2 , that is, the electrical angular position of the rotor in the stator reference coordinate system after DC injection.

[0079] In the second pulse test 13, voltage pulses are generated at selected angles, and the current is measured with each pulse, and the permanent magnet flux is estimated. Thereafter, the ratio of the current to the flux is calculated with pulses of the selected angle. Thereafter, the inductance value L is determined by performing a discrete Fourier transform (DFT) on the measured ratio. d , L q The angle θ between the d axis and the DC injection d，axis，2 .

[0080] In one embodiment, the second pulse test is performed as a six-pulse test. In the six-pulse test, the ratio of current to flux is measured using pulses with angles of 0, 60, 120, 180, 240 and 300 degrees, and the inductance value L is determined by performing a discrete Fourier transform (DFT) on the measured ratio. d , L q and the d-axis angle θ after DC injection d，axis，2 .

[0081] After performing the second signal injection 13, the initial angular position of the rotor of the salient-pole permanent magnet motor is determined 16 as:

[0082]

[0083] in is the initial angular position of the rotor of the salient-pole permanent magnet motor.

[0084] Figure 5 A simplified structure of an embodiment of an inverter of a frequency converter according to the invention is shown. Figure 5A three-phase inverter of a frequency converter and a load connected to the output phases are shown. The proposed frequency converter is equipped with a current measuring sensor 21 in the intermediate voltage circuit. By means of the invention, it is not necessary to use a two-phase current measuring sensor or a three-phase current measuring sensor. In an alternative solution, the presented frequency converter may comprise a two-phase current measuring sensor or a three-phase current measuring sensor in the intermediate voltage circuit output instead of or in addition to said current measuring sensor 21 in the intermediate voltage circuit. Figure 5 In the illustrated embodiment, the frequency converter may have three-phase current measurement sensors 22 - 24 in the three-phase output, as indicated by the dashed lines and reference numerals 22 - 24 .

[0085] In the method of the present invention, a frequency converter is used to generate or produce voltage pulses to a salient pole permanent magnet motor. Figure 5 , a voltage pulse is generated by selecting the appropriate switch combination using the output switches s1-s6 of the frequency converter. A voltage pulse is generated to each output phase of the frequency converter and thus to each phase of the connected machine. For example, by closing switches s1, s5 and s6, a voltage pulse is generated to output phase U, and the amplitude of the voltage pulse is the voltage of the intermediate voltage circuit Udc. With six output switches, six different valid combinations of switch states are obtained.

[0086] Figure 6 Shows the use of Figure 5 The voltage vector is obtained by the inverter. Figure 6 In FIG. 1 , the switch combination is represented as a voltage vector, where the above switch combination (s1, s5 and s6 closed) corresponds to vector U1.

[0087] In the method of the invention, a voltage pulse is generated for each phase of the machine. This means that voltage vectors U1 to U6 are generated. When six voltage pulses are generated, these pulses include a positive pulse and a negative pulse for each phase.

[0088] The pulses are preferably generated in a sequence that minimizes the likelihood of the machine's rotor rotating. Figure 6 In the vectors shown, this order is, for example, U1, U4, U2, U5, U3, U6. Successive voltage vectors are chosen to be in as opposite directions as possible so that the voltages produced cannot generate a rotating magnetic flux in the machine that can rotate the rotor of the machine. Figure 6 In the embodiment shown, the average torque at the end of the generated pulses is zero. This minimizes the movement of the shaft.

[0089] Fig. 7A An embodiment of the angular position of the rotor of a salient-pole permanent magnet motor after the first signal injection according to the present invention is shown. At the beginning of the method of the present invention, the initial angular position of the rotor is unknown. Fig. 7A As shown, after the first signal injection and before the DC injection, the angular position of the rotor of the salient pole permanent magnet motor, that is, the initial electrical position of the shaft is 72 degrees θ PM =72°. At the beginning of the method of the present invention, a first signal injection step is performed to find the initial angle θ of the permanent magnet flux axis. d，axis，1 Accordingly, the first signal injection step gives the initial angle of the permanent magnet flux axis 72 degrees Therefore, at this stage, we only know that the initial electrical position of the axis is 72 degrees θ PM =72° or 72 degrees plus 180 degreesθ PM =72°+180°=252°.

[0090] In the next step of the method, a DC injection is performed to move and park the shaft to a new position in which a DC is injected in the DC injection direction θ DC，dir =θ d，axis，1 ±θ add The increased angle θ add is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 In this embodiment, the increased angle θ add is 90 degrees. Accordingly, the DC injection direction θ DC，dir Theta is 162 degrees DC，dir =162°.

[0091] Figure 7B An embodiment of the angular position of the rotor of the salient pole permanent magnet motor according to the present invention before and after DC injection is shown. Figure 7B In the method of the present invention, when DC injection is performed, this will move the shaft and move the magnetic flux from 72 degrees to 81 degrees. At this stage, we do not know the angular position of the rotor after DC injection. Accordingly, in the method of the present invention, a second signal injection step is performed to find the angle θ of the permanent magnet flux axis d，axis，2 .

[0092] Figure 7C FIG. 1 shows an embodiment of the angular position of the rotor of a salient-pole permanent magnet motor after the second signal injection according to the present invention. Figure 7C In the figure, the angular position of the rotor of the salient pole permanent magnet motor after the second signal injection, that is, the electrical position of the shaft is 81 degrees θ PM =81°. Correspondingly, the angle of the permanent magnet flux axis is In the final step of the method of the present invention, the initial angular position of the rotor of the salient pole permanent magnet motor is determined as:

[0093]

[0094] This gives the initial angular position of the rotor 81 degrees result.

[0095] Fig. 8A Another embodiment of the angular position of the rotor of a salient-pole permanent magnet motor after the first signal injection according to the present invention is shown. At the beginning of the method of the present invention, the initial angular position of the rotor is unknown. Fig. 8A As shown, after the first signal injection and before the DC injection, the angular position of the rotor of the salient pole permanent magnet motor, that is, the initial electrical position of the shaft is 72 degrees θ PM =72°. At the beginning of the method of the present invention, a first signal injection step is performed to find the initial angle θ of the permanent magnet flux axis. d，axis，1 Accordingly, the first signal injection step gives the initial angle of the permanent magnet flux axis 252 degrees Therefore, at this stage, we only know that the initial electrical position of the axis is 252 degrees θ PM = 250° or 252° minus 180°θ PM =252°-180°=72°.

[0096] In the next step of the method, a DC injection is performed to move and park the axis, wherein the DC is injected into the DC injection direction θ DC，dir =θ d，axis，1 ±θ add The increased angle θ add is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 In this embodiment, the increased angle θ ad d is 90 degrees. Accordingly, the DC injection direction θ DC，dir Theta is 342 degrees DC，dir =342°.

[0097] Figure 8B Another embodiment of the angular position of the rotor of the salient pole permanent magnet motor according to the present invention before and after DC injection is shown. Figure 8B In the method of the present invention, when DC injection is performed, this will move the shaft and shift the magnetic flux from 72 degrees to 62 degrees. At this stage, we do not know the angular position of the rotor after DC injection. Accordingly, in the method of the present invention, a second signal injection step is performed to find the angle θ of the permanent magnet flux axis d，axis，2 .

[0098] Figure 8C Another embodiment of the angular position of the rotor of the salient-pole permanent magnet motor after the second signal injection according to the present invention is shown. Figure 8C In the figure, the angular position of the rotor of the salient pole permanent magnet motor after the second signal injection, that is, the electrical position of the shaft is 62 degrees θPM =62°. Accordingly, the angle of the permanent magnet flux axis is 242 degrees. In the final step of the method of the present invention, the initial angular position of the rotor of the salient pole permanent magnet motor is determined as:

[0099]

[0100] This gives the initial angular position of the rotor 62 degrees result.

[0101] By means of the solution for determining the initial angular position of the rotor of a salient pole permanent magnet motor according to the present invention, the previously proposed problems of 180 degree misalignment of the initial angular position of the rotor of a salient pole permanent magnet motor and the DC parking behavior of the rotor shaft are solved and / or reduced.

[0102] In the present solution, a two-phase current measuring sensor or a three-phase current measuring sensor for measuring the current in the pulse direction is not required. In the present solution, a single DC link current sensor is sufficient to measure the current in the pulse direction.

[0103] The solution according to the invention provides an efficient and elegant solution for determining the initial angular position of the rotor of a salient pole permanent magnet motor. In the present solution, a single DC link current sensor is sufficient to measure the current in the pulse direction. The proposed solution is more efficient compared to existing solutions and also eliminates the need for phase current measurement, thereby eliminating the need to use two-phase current measurement sensors or three-phase current measurement sensors.

[0104] The present invention can be implemented in an existing frequency converter. The current frequency converter includes a processor and a memory that can be used in the functions according to an embodiment of the present invention. Therefore, all modifications and configurations required to implement an embodiment of the present invention can be performed as a software routine, which can be implemented as an added or updated software routine. If the functions of the present invention are implemented by software, such software can be provided as a computer program product including a computer program code, which, when running on a computer, causes the computer or a corresponding device to perform the functions according to the present invention as described above. Such a computer program code can be stored in or generally included in a computer-readable medium, such as a suitable memory, such as a flash memory or a disk memory, from which it can be loaded to one or more units that execute the program code. In addition, such a computer program code that implements the present invention can be loaded to one or more units that execute the computer program code via, for example, a suitable data network, and it can replace or update a program code that may exist.

[0105] It should be understood that the above description and the accompanying drawings are intended only to teach the best way to make and use the present invention known to the inventor. It will be apparent to those skilled in the art that the concepts of the present invention may be implemented in various ways. Therefore, without departing from the present invention, the above-described embodiments of the present invention may be modified or varied, as those skilled in the art will appreciate from the above teachings. Therefore, it should be understood that the present invention and its embodiments are not limited to the above-described examples, but may vary within the scope of the claims and their equivalents.

Claims

1. A method for determining the initial angular position of a rotor of a salient-pole permanent magnet motor connected to a frequency converter, in which method: - performing a first signal injection step, in which an initial angle θ of the permanent magnet flux axis is determined d，axis，1 ; - performing a direct current injection (12) in which a direct current injection direction θ DC，dir =θ d，axis，1 ±θ add The DC is injected into the idle salient pole permanent magnet motor, where the DC injection direction θ DC，dir is the angle of the injected DC, and the increased angle θ add is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 The angle of the offset; - performing a second signal injection step, in which the angle θ of the permanent magnet flux axis is determined d，axis，2 ;as well as - The initial angular position of the rotor of the salient pole permanent magnet motor Determine (16) as:

2. The method according to claim 1, wherein: - in the first signal injection step, performing a first pulse test (11), in which a plurality of external pulses are injected into an idle salient-pole permanent magnet motor at a selected angle, measuring a current-to-flux ratio for each injected pulse, and determining the initial angle θ of the permanent magnet flux axis by performing a discrete Fourier transform (DFT) on the measured ratio d，axis，1 ;as well as - in the second signal injection step, a second pulse test (13) is performed, in which a plurality of external pulses are injected into the idle salient-pole permanent magnet motor at selected angles, the current-to-flux ratio is measured for each injected pulse, and the angle θ of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio d，axis，2 .

3. The method according to claim 1 or 2, wherein in the first signal injection step, the initial angle θ of the permanent magnet flux axis is determined by using AC injection d，axis，1 , and / or wherein in the second signal injection step, the angle θ of the permanent magnet flux axis is determined by using AC injection d，axis，2 .

4. The method according to claim 1 or 2, wherein in the first signal injection step, the initial angle θ of the permanent magnet flux axis is determined by injecting a voltage pulse signal. d，axis，1 , and / or wherein in the second signal injection step, the angle θ of the permanent magnet flux axis is determined by injecting a voltage pulse signal d，axis，2 .

5. The method according to claim 1 or 2, wherein in the first signal injection step, the initial angle θ of the permanent magnet flux axis is determined by using a sinusoidal high frequency (HF) signal injection or a high frequency (HF) square wave signal injection. d，axis，1 , and / or wherein in the second signal injection step, the angle θ of the permanent magnet flux axis is determined by using a sinusoidal high frequency (HF) signal injection or a high frequency (HF) square wave signal injection. d，axis，2 .

6. The method according to any one of claims 1 to 5, wherein the increased angle θ add It's 90 degrees.

7. The method according to any one of claims 1 to 5, wherein the increased angle θ add Between 50 degrees and 130 degrees.

8. The method according to any one of claims 1 to 5, wherein the increased angle θ add Between 30 degrees and 150 degrees.

9. A method according to any one of claims 2 to 8, wherein the first pulse test (11) and / or the second pulse test (13) is performed as a six-pulse test, in which the current-to-flux ratio is measured using pulses with angles of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees.

10. The method of claim 9, wherein six voltage pulses are generated in a sequence that minimizes the likelihood of rotation of the rotor of the salient pole permanent magnet motor.

11. A frequency converter, the frequency converter being adapted to be connected to a salient pole permanent magnet motor, the frequency converter comprising means configured to determine an initial angular position of a rotor of the salient pole permanent magnet motor by performing the following operations: - performing a first signal injection step, in which an initial angle θ of the permanent magnet flux axis is determined d，axis，1 ; - performing a direct current injection (12) in which a direct current injection direction θ DC，dir =θ d，axis，1 ±θ add The DC is injected into the idle salient pole permanent magnet motor, where the DC injection direction θ DC，dir is the angle of the injected DC, and the increased angle θ add is defined as the initial angle θ from the permanent magnet flux axis d，axis，1 The angle of the offset; - performing a second signal injection step, in which the angle θ of the permanent magnet flux axis is determined d，axis，2 ;as well as - The initial angular position of the rotor of the salient pole permanent magnet motor Determined as:

12. The frequency converter according to claim 11, wherein - in performing the first signal injection step, the frequency converter comprises means configured to perform a first pulse test (11), in which a plurality of external pulses are injected into an idle salient-pole permanent magnet motor at a selected angle, a current-to-flux ratio is measured for each injected pulse, and the initial angle θ of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio d，axis，1 ;as well as - when performing the second signal injection step, the frequency converter comprises means configured to perform a second pulse test (13), in which a plurality of external pulses are injected into an idle salient-pole permanent magnet motor at a selected angle, a current-to-flux ratio is measured for each injected pulse, and the angle θ of the permanent magnet flux axis is determined by performing a discrete Fourier transform (DFT) on the measured ratio d，axis，2 .

13. The frequency converter according to claim 11 or 12, wherein in performing the first signal injection step, the frequency converter comprises a signal source configured to determine the initial angle θ of the permanent magnet flux axis using AC injection, voltage pulse signal injection, sinusoidal high frequency (HF) signal injection, or high frequency (HF) square wave signal injection. d，axis，1 and / or wherein in performing the second signal injection step, the frequency converter includes a device configured to determine the angle θ of the permanent magnet flux axis using AC injection, voltage pulse signal injection, sinusoidal high frequency (HF) signal injection or high frequency (HF) square wave signal injection. d，axis，2 device.

14. A frequency converter according to any one of claims 11-13, wherein the first pulse test (11) and / or the second pulse test (13) is performed as a six-pulse test, in which the current to flux ratio is measured using pulses with angles of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees.

15. A computer program product comprising a computer program code, wherein execution of the program code in a computer causes a computer of a frequency converter according to claim 11 to cause the computer to perform the steps of the method according to any one of claims 1 to 10.

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