Method for determining initial position of high-precision motor rotor

Abstract

The invention provides a method for determining the initial position of a high-precision motor rotor, and relates to the technical field of permanent magnet synchronous motor control, the method ensures that the current attenuation of a three-phase winding of a motor is zero by turning off all power tubes of a motor driving inverter, and two-phase bridge arms are selectively conducted pairwise, so that the initial position of the motor rotor is determined. Forward and reverse voltage pulses are injected for six times every two phases; six sampling currents are obtained; calculating a difference value of positive and negative phase sampling currents of every two phases; calculating an initial position estimated value of the motor rotor through an arc tangent function by using a relationship between the difference value and the rotor position; and judging the polarity of the motor rotor according to the difference to obtain the initial position of the motor rotor. According to the invention, rotor position detection can be realized without enabling the magnetic field to enter a saturation state, and the initial position of the rotor with enough precision can be obtained only by injecting a current with a relatively small amplitude. It can be guaranteed that the motor is completely static in the detection process, and mechanical abrasion and positioning deviation caused by rotor micro-motion in a traditional dynamic detection method are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motor control, and in particular to a method for determining the initial position of a motor rotor with high precision. Background Art

[0002] Existing technologies use the inductor saturation effect to detect the initial angle. This requires injecting a voltage for a long time to obtain a sufficiently large current feedback, thereby reaching a magnetic saturation state. The inductor saturation effect in this magnetic saturation state is then used to derive rotor position detection methods based on the relationship between inductance changes and the rotor magnetic field position. Larger current injections can damage the motor itself and place higher current requirements on the inverter power transistors. Furthermore, larger currents generate greater output torque, causing the motor rotor to rotate. This can lead to significant errors in the initial angle detection results and even cause external mechanical failures. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-precision method for determining the initial position of a motor rotor, which can realize rotor position detection without saturating the magnetic field. It only needs to inject a current of a smaller amplitude to obtain the rotor initial position with sufficient accuracy.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A high-precision method for determining an initial position of a motor rotor, comprising:

[0006] S1. Turn off all power transistors of the motor drive inverter to ensure that the current decay of the motor's three-phase windings is zero. Selectively turn on two-phase bridge arms in pairs, injecting forward and reverse voltage pulses into each two phases, and ensure that the current decays to zero before each injection. A total of six voltage pulses are injected. After each voltage pulse injection, current sampling is performed to obtain forward and reverse current samples for each two phases, for a total of six current samples.

[0007] S2. Calculate the difference between the positive and negative phase sampling currents of each two phases;

[0008] S3. Calculate the estimated initial position of the motor rotor using the inverse tangent function using the relationship between the difference between the positive and negative phase sampling currents and the rotor position;

[0009] S4. Determine the polarity of the motor rotor based on the difference between the positive and negative phase sampling currents to obtain the initial position of the motor rotor.

[0010] As a preferred solution, step S1 specifically includes:

[0011] S11. Turn off all power transistors of the motor drive inverter to ensure that the current of the motor's three-phase winding decays to zero;

[0012] S12. Turn on the upper power tube of phase A and turn off the lower power tube of the motor's three-phase winding, turn off the upper power tube of phase B and turn on the lower power tube, turn off both the upper and lower power tubes of phase C, and inject a positive voltage into phases AB.

[0013] S13. After a period of injection, the forward current of the AB phase is sampled to obtain the forward sampling current of the AB phase;

[0014] S14. Turn off the power tubes of phases A and B that were originally turned on to ensure that the current of phases A and B decays to zero;

[0015] S15. Turn off the upper power tube of phase A and turn on the lower power tube of the motor's three-phase winding, turn on the upper power tube of phase B and turn off the lower power tube, turn off both the upper and lower power tubes of phase C, and inject reverse voltage into phases AB.

[0016] S16. After a period of injection, reverse current sampling is performed on the AB phase to obtain reverse sampling current of the AB phase;

[0017] S17. Obtain the forward and reverse sampling currents of the BC phase and the forward and reverse sampling currents of the CA phase respectively according to the above methods of S11 to S16.

[0018] As a preferred solution, in step S1 , the sampled currents obtained for every two phases are current amplitudes.

[0019] As a preferred solution, the injection time each time remains consistent and is determined by the time it takes for the first injection time to reach the set current amplitude.

[0020] As a preferred solution, in step S1, the time of each injection is the time corresponding to the maximum current that the motor can withstand.

[0021] As a preferred solution, S3. uses the sinusoidal relationship between the difference between the positive and negative phase sampling currents and the rotor position to calculate the estimated initial position of the motor rotor through the inverse tangent function. The specific calculation formula is as follows:

[0022]

[0023] in is the estimated value of the initial position of the motor rotor, Δi BC The difference between the forward and reverse sampling currents of the BC phase, Δi AB The difference between the forward and reverse sampling currents of the AB phase, Δi CA It is the difference between the forward and reverse sampling currents of phase CA.

[0024] As a preferred solution, step S13 specifically includes: after a period of injection, the AB phase current amplitude reaches a given value, recording the current AB phase current amplitude and injection time, and the obtained AB phase current amplitude is the forward sampling current of the AB phase; the subsequent five injection times are consistent with the injection time.

[0025] As a preferred solution, in steps S11 and S14, the method steps for ensuring that the current decays to zero are: after turning off the power tube, delay for a period of time, and detect whether the current of the AB phase, BC phase, and CA phase is zero. If it is not zero, continue to delay until it is zero, and then complete.

[0026] As a preferred solution, in step S3, the relationship between the difference between the positive and negative phase sampling currents and the rotor position is a sinusoidal relationship, and the phase difference between the two is 120°.

[0027] As a preferred solution, in step S4, the rotor pole is judged specifically by the positive or negative difference between the positive and negative sampling currents of the BC phase. When the difference is greater than 0, the initial position of the motor rotor is the estimated value of the initial position of the motor rotor; when the difference is less than 0, the initial position of the motor rotor is the estimated value of the initial position of the motor rotor plus 180°.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The present invention detects the rotor position based on the difference between the positive and negative three-phase injection currents. It only needs to inject a current of a smaller amplitude, and does not need to make the magnetic field enter a saturated state to achieve rotor position detection. Usually, within the rated current range of the motor, the rotor position with sufficient accuracy can be obtained, which can ensure that the motor is completely stationary during the detection process, avoid the mechanical wear and positioning deviation caused by the rotor micro-motion in traditional dynamic detection methods, and accurately detect the initial position of the motor rotor. Moreover, it does not require the current level of the inverter power tube with higher requirements. The present invention can also identify the rotor polarity by the positive and negative current difference, without the need for additional polarity identification operations, thereby improving the efficiency of the detection process. Therefore, the present invention is applicable to application scenarios such as industrial automation, new energy vehicles, and servo systems that require high initial position accuracy of permanent magnet synchronous motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0031] Figure 1A step diagram of a method for determining the initial position of a high-precision motor rotor provided by a specific embodiment of the present invention;

[0032] Figure 2 A specific step diagram of step S1 in a method for determining the initial position of a high-precision motor rotor provided by a specific embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the PMSM drive inverter;

[0034] Figure 4 The magnetic potential distribution diagram of the AB phase injected current;

[0035] Figure 5 is the relationship diagram between the three-phase current difference and the rotor position;

[0036] Figure 6 This is the forward conduction magnetic potential distribution diagram of BC phase;

[0037] Figure 7 A single voltage injection flow chart in a method for determining the initial position of a high-precision motor rotor provided by a specific embodiment of the present invention;

[0038] Figure 8 A flow chart of determining the initial position of a motor rotor in a method for determining the initial position of a motor rotor with high precision provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] Please refer to Figure 1 In one embodiment, a method for determining the initial position of a motor rotor with high precision is provided, which is mainly implemented by the following steps:

[0041] S1. Turn off all power tubes of the motor drive inverter to ensure that the current decay of the motor's three-phase winding is zero. Selectively turn on two-phase bridge arms in pairs, inject forward and reverse voltage pulses into every two phases, and ensure that the current decays to zero before each injection. A total of six voltage pulses are injected; after each voltage pulse is injected, current sampling is performed to obtain forward and reverse sampling currents of every two phases, for a total of six sampling currents.

[0042] S2. Calculate the difference between the positive and negative phase sampling currents of each two phases.

[0043] S3. Using the relationship between the difference between the positive and negative phase sampling currents and the rotor position, an estimated value of the initial position of the motor rotor is calculated using an inverse tangent function.

[0044] S4. Determine the polarity of the motor rotor based on the difference between the positive and negative phase sampling currents to obtain the initial position of the motor rotor.

[0045] Please refer to Figure 2 In a preferred embodiment, step S1 is specifically implemented by the following steps:

[0046] S11. Turn off all power transistors of the motor drive inverter to ensure that the current of the motor's three-phase winding decays to zero;

[0047] S12. Turn on the upper power tube of phase A and turn off the lower power tube of the motor's three-phase winding, turn off the upper power tube of phase B and turn on the lower power tube, turn off both the upper and lower power tubes of phase C, and inject a positive voltage into phases AB.

[0048] S13. After a period of injection, the forward current of the AB phase is sampled to obtain the forward sampling current of the AB phase;

[0049] S14. Turn off the power tubes of phases A and B that were originally turned on to ensure that the current of phases A and B decays to zero;

[0050] S15. Turn off the upper power tube of phase A and turn on the lower power tube of the motor's three-phase winding, turn on the upper power tube of phase B and turn off the lower power tube, turn off both the upper and lower power tubes of phase C, and inject reverse voltage into phases AB.

[0051] S16. After a period of injection, reverse current sampling is performed on the AB phase to obtain reverse sampling current of the AB phase;

[0052] S17. Obtain the forward and reverse sampling currents of the BC phase and the forward and reverse sampling currents of the CA phase respectively according to the above methods of S11 to S16.

[0053] The following will explain in more detail the implementation process of steps S1 to S4 of a method for determining the initial position of a high-precision motor rotor in this embodiment in principle:

[0054] The rotor position detection is achieved by selectively conducting the two-phase bridge arm to realize the "two-phase injection, one-phase floating" excitation mode. Assuming that the current initial position of the motor rotor is θ, the structure diagram of the motor (PMSM) drive inverter is as follows Figure 3 As shown in the figure, the three-phase windings of the motor ABC are all equipped with two upper and lower power tubes (switching tubes). The upper power tubes of the three-phase ABC are VT1, VT3 and VT5 respectively, and the lower power tubes of the three-phase ABC are VT4, VT6 and VT2 respectively.

[0055] When the power tubes VT1 and VT6 are turned on and all other power tubes are turned off, a voltage U is injected into the AB phase series winding in the positive direction. d , the C-phase winding is suspended. At this time, the rotor magnetic potential and the winding magnetic potential distribution are as follows Figure 4 As shown. Figure 4 It can be seen that the voltage U is injected into the AB phase d When phase C is suspended, the current flows into phase A and out of phase B, and phase C is suspended, and the current is 0. Therefore, the current in phase A generates a magnetic potential F a Along the A axis, the B phase current generates magnetic potential F b Reverse along the B axis. A =i B =i AB And the number of turns of the three-phase winding of PMSM is the same, so the combined magnetic potential F of phase AB is ab It is -30° with the A axis. At this time:

[0056]

[0057] Among them, F0 is the permanent magnet magnetic potential, N is the number of turns of the PMSM three-phase winding, R m is the magnetic resistance, L AB and i AB are the inductance and line current of line AB respectively.

[0058] Similarly, when the power tubes VT3 and VT4 are turned on and the other switch tubes are all turned off, a positive voltage -U is injected into the AB phase series winding. d , the C phase winding is suspended, the current flows in from direction B and flows out from direction A, the current magnitude is i BA , the magnetic circuit saturation state is mirror-symmetrical to the forward injection state, at this time:

[0059]

[0060] The current i obtained by the forward injection voltage AB The current i obtained by the reverse injection voltage BA Different sizes, forward line inductance L AB and reverse line inductance L BA The sizes are also different, so the difference between formula (1) and formula (2) is:

[0061]

[0062] For the convenience of the following description, we define it here:

[0063]

[0064] Then formula (3) can be written as:

[0065]

[0066] In formula (3) and formula (5), i AB with i BA Both are current magnitudes, namely the forward current of phase AB and the reverse current of phase AB.

[0067] Inject forward voltage U into AB phase d When , according to Kirchhoff's voltage law, the voltage equation can be written as:

[0068]

[0069] Among them, R s is the stator resistance.

[0070] Normally, the PMSM stator resistance voltage drop is negligible compared to the DC bus voltage, so Equation (6) can be simplified to:

[0071]

[0072] Integrating both sides of equation (7) yields:

[0073] U d t0=L AB i AB (8)

[0074] Where t0 is the voltage U d Injection time.

[0075] When the AB phase injects a reverse voltage -U d Sometimes:

[0076] U d t0=L BA i BA (9)

[0077] In formula (8) and formula (9), i AB with i BA They are also the magnitude of the current.

[0078] By subtracting formula (8) from formula (9), we can get:

[0079] 0=L AB i AB -L BA i BA (10)

[0080] Substituting formula (10) into formula (5), it is not difficult to obtain:

[0081]

[0082] When the inverter power tube (switch tube) state is switched, BC phase is turned on and A phase is suspended; CA phase is turned on and B phase is suspended, the same analysis can be obtained:

[0083]

[0084] When phase CA is on and phase B is suspended; when phase AC is on and phase B is suspended:

[0085]

[0086] Combining equations (11), (12), and (13), it is not difficult to see that when two phases are injected and one phase is suspended, the difference between the positive and negative injection currents of the three phases (the difference between the positive and negative sampling currents of each two phases is three in total) is sinusoidally related to the rotor position, and the phase difference between each two phases is 120°, that is, the phase difference between the AB phase, the BC phase, and the CA phase is 120°. Figure 5 The relationship between the three-phase current difference and the rotor position is shown.

[0087] Combining equations (11), (12), and (13), it is not difficult to see that:

[0088]

[0089] Therefore, the initial position estimate of the PMSM rotor can be calculated from the three current differences:

[0090]

[0091] After obtaining the estimated initial position of the PMSM rotor, it is necessary to perform polarity analysis. When the inverter switches VT3 and VT2 are turned on and the other switches are all turned off, the BC phase is forward-conducted and the A phase is disconnected. At this time, the motor magnetic potential distribution is as follows: Figure 6 As shown. Figure 6 It can be seen that Figure 6 As shown in (a), if the initial rotor position θ ranges from 0° to 180°, when BC phase is forward-conducted and A phase is suspended, then F d >0 The permanent magnet magnetic potential increases the magnetic potential of the winding. At this time, the BC line inductance decreases and the current i BC Too big Figure 6 As shown in (b), when BC conducts in opposite directions and phase A is left hanging, F d <0 The permanent magnet magnetic potential has a weak magnetic effect on the winding magnetic potential, the BC line inductance increases, and the current i BC Too small, Δi BC >0. Figure 6 As shown in (c), if the initial rotor position θ ranges from 180° to 360°, when BC phase is forward-conducted and A phase is suspended, then F d<0 The permanent magnet magnetic potential has a weak magnetic effect on the winding magnetic potential. At this time, the BC line inductance increases and the current i BC Small Figure 6 As shown in (d), when BC conducts in opposite directions and phase A is left hanging, F d >0 The permanent magnet magnetic potential increases the magnetic potential of the winding, the BC line inductance decreases, and the current i BC Too large, Δi BC <0.

[0092] According to the above analysis, the rotor polarity can be identified by the positive and negative difference of the BC phase current, so as to obtain the initial position of the PMSM rotor: Δi BC >0, Δi BC <0,

[0093] During specific implementation, follow the above steps S1 to S4, first ensure that the current decays to zero: after turning off the power tube, delay for a period of time, and detect whether the current of the AB phase, BC phase, and CA phase is zero. If it is not zero, continue to delay until it is zero. Then turn on the motor drive inverter VT1 and VT6 tubes, and turn off the other tubes. Apply a positive voltage to the AB phase of the motor winding. The conduction time is t0. In order to ensure the convenience of current sampling and make full use of the magnetic saturation characteristics of the motor winding, t0 is determined to be the time corresponding to the maximum current that the motor can withstand. After the conduction time t0, the AB phase current is sampled and recorded as i AB , then turn off the motor drive inverter VT1 and VT6, and wait for the current to decay to 0 from the diode freewheeling. After ensuring that the current decays to 0, turn on the inverter VT3 and VT4, and turn off the other tubes. Inject reverse voltage into the motor stator winding AB. The conduction time is still t0. Then sample the reverse current of AB at t0 and record it as i BA , turn off the motor drive inverter VT3 and VT4, and then wait for the current to decay to 0 from the diode freewheeling. Follow up with similar operations, and turn on the motor drive inverter VT3 and VT2 to obtain the sampling current i BC , then turn on VT5 and VT6 of the motor drive inverter to obtain the sampling current i CB Finally, VT5 and VT4 of the motor drive inverter are turned on to obtain the sampling current i CA , and turn on VT1 and VT2 to get the sampling current i AC All the above currents are obtained by injecting voltage in the zero state. Six current sampling values are obtained by injecting six voltage pulses. The six current sampling values are subtracted from each other according to formula (4) to obtain the current difference Δi AB , Δi BC , Δi CA, and then put the three current differences into the inverse tangent function (15) to obtain the estimated value of the initial position of the PMSM rotor Finally, according to the current difference Δi BC Determine the rotor polarity:

[0094] a.Δi BC >0,

[0095] b.Δi BC <0,

[0096] The present invention analyzes the interaction between the rotor permanent magnet magnetic potential and the electromagnetic potential generated by the current flowing through the stator winding through the above process, comprehensively analyzes the influence of the permanent magnet flux and the stator current on the winding inductance, and effectively improves the estimation accuracy of the rotor position (angle) self-learning.

[0097] The embodiment of the present invention detects the rotor position based on the difference between the positive and negative three-phase injected currents, which not only ensures that the motor is completely stationary during the detection process, avoiding the mechanical wear and positioning deviation caused by the rotor micro-motion in the traditional dynamic detection method; it can also identify the rotor polarity by the positive and negative current difference, without the need for additional polarity identification operations, thereby improving the efficiency of the detection process.

[0098] Please refer to Figure 7 , Figure 7 This is a single voltage injection process. Before injection, all power tubes are turned off to ensure that the current in the three-phase windings is zero. After a delay, voltage injection begins. Taking the injection of AB voltage as an example, the upper tube of phase A is turned on and the lower tube is turned off, the upper tube of phase B is turned off and the lower tube is turned on, and the upper and lower tubes of phase C are turned off. At the same time, the current amplitudes of phases AB are collected. When the current amplitude reaches a given value, all switching tubes are turned off, and the current amplitude and the first voltage injection time are recorded. The subsequent five injection times need to be consistent with the injection time recorded for the first time. This process is then repeated to achieve the other five injections, obtain the current amplitudes of the six injections, and calculate the difference between the three-phase currents to calculate the initial position of the rotor.

[0099] Please refer to Figure 8 , Figure 8 This figure shows a flowchart for determining (detecting) the initial position of a motor rotor using a high-precision method for determining the initial position of a motor rotor, provided in one embodiment of the present invention. After six pulse voltage injections are completed, the three-phase current difference is calculated based on the current detection results, and then the estimated initial rotor position is calculated. Finally, the polarity is determined to obtain the initial rotor position.

[0100] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above-described embodiments only express several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. For those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A high-precision method for determining the initial position of a motor rotor, characterized in that: include: S1. Turn off all power transistors in the motor drive inverter to ensure that the current in the motor's three-phase windings decays to zero. Selectively turn on two-phase bridge arms, injecting forward and reverse voltage pulses into each two-phase pair, ensuring that the current decays to zero before each injection. A total of six voltage pulses are injected. After each voltage pulse is injected, current sampling is performed to obtain the forward and reverse sampling currents of each two phases, for a total of six sampling currents; S2. Calculate the difference between the positive and negative phase sampling currents of each two phases; S3. Calculate the estimated initial position of the motor rotor using the inverse tangent function using the relationship between the difference between the positive and negative phase sampling currents and the rotor position; S4. Determine the polarity of the motor rotor based on the difference between the positive and negative phase sampling currents to obtain the initial position of the motor rotor.

2. The high-precision motor rotor initial position determination method according to claim 1, characterized in that: Step S1 specifically includes: S11. Turn off all power transistors of the motor drive inverter to ensure that the current of the motor's three-phase winding decays to zero; S12. Turn on the upper power tube of phase A and turn off the lower power tube of the motor's three-phase winding, turn off the upper power tube of phase B and turn on the lower power tube, turn off both the upper and lower power tubes of phase C, and inject a positive voltage into phases AB. S13. After a period of injection, the forward current of the AB phase is sampled to obtain the forward sampling current of the AB phase; S14. Turn off the power tubes of phases A and B that were originally turned on to ensure that the current of phases A and B decays to zero; S15. Turn off the upper power tube of phase A and turn on the lower power tube of the motor's three-phase winding, turn on the upper power tube of phase B and turn off the lower power tube, turn off both the upper and lower power tubes of phase C, and inject reverse voltage into phases AB. S16. After a period of injection, reverse current sampling is performed on the AB phase to obtain reverse sampling current of the AB phase; S17. Obtain the forward and reverse sampling currents of the BC phase and the forward and reverse sampling currents of the CA phase respectively according to the above methods of S11 to S16.

3. The method for determining the initial position of a high-precision motor rotor according to claim 2, wherein: In step S1 , the sampled currents obtained for every two phases are current amplitudes.

4. The method for determining the initial position of a high-precision motor rotor according to claim 3, wherein: In step S1 , the injection time each time remains consistent and is determined by the time it takes for the first injection time to reach the set current amplitude.

5. The method for determining the initial position of a high-precision motor rotor according to claim 4, wherein: In step S1 , the duration of each injection is the time corresponding to the maximum current that the motor can withstand.

6. The high-precision motor rotor initial position determination method according to claim 1, characterized in that: S3. Using the sinusoidal relationship between the difference between the positive and negative phase sampling currents and the rotor position, the initial position estimate of the motor rotor is calculated using the inverse tangent function. The specific calculation formula is as follows: in is the estimated value of the initial position of the motor rotor, Δi BC The difference between the forward and reverse sampling currents of the BC phase, Δi AB The difference between the forward and reverse sampling currents of the AB phase, Δi CA It is the difference between the forward and reverse sampling currents of phase CA.

7. The method for determining the initial position of a high-precision motor rotor according to claim 4, wherein: Step S13 specifically includes: after a period of injection, the AB phase current amplitude reaches a given value, recording the current AB phase current amplitude and injection time, and the obtained AB phase current amplitude is the forward sampling current of the AB phase; the subsequent five injection times are consistent with the injection time.

8. The method for determining the initial position of a high-precision motor rotor according to claim 2, wherein: In steps S11 and S14, the method steps for ensuring that the current decays to zero are as follows: after turning off the power tube, delay for a period of time, and detect whether the current of the AB phase, BC phase, and CA phase is zero. If it is not zero, continue to delay until it is zero, and then complete.

9. The high-precision motor rotor initial position determination method according to claim 1, characterized in that: In step S3, the relationship between the difference between the positive and negative phase sampling currents and the rotor position is a sinusoidal relationship, and the phase difference between the two is 120°.

10. The high-precision motor rotor initial position determination method according to claim 1, characterized in that: In step S4, the rotor pole is determined by the positive or negative difference between the positive and negative sampling currents of the BC phases. When the difference is greater than 0, the initial position of the motor rotor is the estimated initial position of the motor rotor; when the difference is less than 0, the initial position of the motor rotor is the estimated initial position of the motor rotor plus 180°.

Images