CN108322122B - Initial position positioning method for magnetic pole of rotor of salient pole type three-phase permanent magnet synchronous motor - Google Patents

Abstract

The invention relates to a method for positioning an initial position of a magnetic pole of a rotor of a salient pole type three-phase permanent magnet synchronous motor, which solves the problems of long positioning time and low positioning precision of the conventional method for positioning the initial position of the magnetic pole of the rotor of the salient pole type three-phase permanent magnet synchronous motor. Book (I)The method comprises the following steps: 1. determining PWM period T for which saturated phase current can be achieved_PWM(ii) a 2. Controlling the period T using non-saturation₁＝0.2T_PWM～0.25T_PWMCollecting A, B, C unsaturated phase currents of the motor; 3. calculating the initial direction angle theta of the magnetic pole of the rotor by using the acquisition result of the step 2_0raw(ii) a 4. Selecting theta_0rawClose phase loading with T_PWMCollecting saturated phase current of the phase for controlling the phase current of the period; 5. calculating a polar offset angle θ_0offsetAnd calculating theta₀＝θ_0raw+θ_0offset. The initial positioning method for the magnetic pole position of the rotor of the salient pole type three-phase permanent magnet synchronous motor does not need complex high-frequency voltage injection or sequential pulse voltage injection, and is simple to implement, high in positioning speed and high in positioning accuracy.

Description

Initial position positioning method for magnetic pole of rotor of salient pole type three-phase permanent magnet synchronous motor

Technical Field

The invention belongs to the field of motors, relates to a motor control method, and particularly relates to a method for positioning an initial position of a magnetic pole of a rotor of a salient pole type three-phase permanent magnet synchronous motor.

Background

The salient pole type three-phase permanent magnet synchronous motor has the characteristics of high power density, convenience in control, good control performance, large speed regulation range and the like. However, when the motor is started, the initial position of the magnetic pole of the motor rotor needs to be known, otherwise, the motor is failed to start, so that the position detection of the magnetic pole of the motor rotor is generally realized by adopting an encoder, the problem of motor starting can be solved by adopting an absolute encoder or an incremental encoder with UVW, but the cost is increased, and the initial positioning precision of the magnetic pole of the incremental encoder with UVW is only +/-30 degrees of electrical angle.

According to the traditional initial positioning method for the magnetic pole position of the rotor of the salient pole type three-phase permanent magnet synchronous motor, a forced positioning method, a voltage pulse vector sequence positioning method, a high-frequency voltage injection positioning method, an INFORM inductance method and the like are adopted, the forced positioning method forces the motor to be pulled to a fixed position by supplying a fixed voltage vector to the motor, although the initial positioning of the motor is completed, the motor rotates, and the application requirements cannot be met in some occasions; a voltage pulse vector sequence positioning method is characterized in that a voltage vector corresponding to the maximum current response is searched by injecting a series of voltage pulse vectors and comparing the amplitude of the motor synthesized phase current response corresponding to the voltage pulse vectors, wherein the corresponding angle is the position of the initial position of a rotor magnetic pole. The high-frequency voltage injection method needs to introduce high-frequency voltage signals into a motor winding, can determine the magnetic pole direction after complex high-frequency signal processing (band-pass filtering) and phase-locked loop adjustment, and can finally determine the initial position of the rotor magnetic pole only by combining the positive voltage vector injection with the direction voltage vector injection. The inductance method needs to actually calculate the inductance, and has a complex operation process and low precision.

Disclosure of Invention

The invention aims to solve the problems of long positioning time and low positioning precision of the prior initial positioning method for the magnetic pole position of the rotor of the salient pole type three-phase permanent magnet synchronous motor, provides a positioning method for the initial position of the magnetic pole of the rotor of the salient pole type three-phase permanent magnet synchronous motor, the method obtains the initial direction angle of the magnetic pole of the motor rotor by constructing a calculation formula by using the structural salient pole effect of the motor when the duration time of the basic voltage vector voltage introduced to the motor winding is short, and then leads the magnetic field of the motor to show the saturated salient pole effect by prolonging the duration time of the voltage vector to correct the positive and negative directions of the magnetic pole, therefore, initial positioning of the magnetic pole position of the rotor of the salient pole type three-phase permanent magnet synchronous motor can be effectively and quickly realized, and an effective starting position signal is provided for the initial positioning of the motor without encoder control or an incremental encoder.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for positioning the initial position of a magnetic pole of a rotor of a salient pole type three-phase permanent magnet synchronous motor is characterized by comprising the following steps: the method comprises the following steps:

step 1: PWM period T_PWMDetermination of (1);

PWM period initialization toThe duration of the motor isPWM control of (2): wherein the content of the first and second substances,a voltage vector with an input electrical angle of 0 DEG,Is in a PWM full-off state,A voltage vector with an input electrical angle of 180 DEG,For a PWM full OFF state, inThe current value of A phase collected at any moment is recorded asIn a time period ofWhen the PWM control is finished, ifWhen the current is less than the rated current peak value of the motor, the PWM period is gradually increased to enablep is 1, 2, 3 … …, k is the PWM cycle increment and the motor is run for a period of timePWM control of (1), acquisitionAnd judgeIn relation to the peak value of the rated current of the motor untilEqual to or more than the rated current value of the motor, and the PWM period is marked as T_PWM；

Step 2: acquiring a phase current signal in an unsaturated state, and sequentially acquiring A, B, C phase currents of two wheels;

control period T for unsaturated acquisition₁＝0.2T_PWM～0.25T_PWMEnsuring that the motor current is always in an unsaturated state in the acquisition process;

the phase current collection of the first round of A phase is carried out for continuously 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with input electric angle of 0 degree, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 180 degrees, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_A11+At 2T₁The current collected at the moment is recorded as i_A12+At 4T₁The current collected at the moment is recorded as i_A11-At 5T₁The current collected at the moment is recorded as i_A12-；

After the phase current acquisition of the phase A of the first round is finished, the phase current acquisition of the phase B of the first round is carried out, and the phase current acquisition of the phase B of the first round carries out continuous 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with 120 degree input electric angle, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 300 degree, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_B11+At 2T₁The current collected at the moment is recorded as i_B12+At 4T₁The current collected at the moment is recorded as i_B11-At 5T₁The current collected at the moment is recorded as i_B12-；

First round of phase current of phase BAfter the acquisition is finished, the phase current acquisition of the C phase of the first round is carried out, and the phase current acquisition of the C phase of the first round carries out continuous 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with input electric angle of 240 degree, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 60 degrees, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_C11+At 2T₁The current collected at the moment is recorded as i_C12+At 4T₁The current collected at the moment is recorded as i_C11-At 5T₁The current collected at the moment is recorded as i_C12-；

And (5) arranging the phase current acquisition results of the first round, and sequentially recording the phase current acquisition results as i_A11+、i_A12+、i_A11-、i_A12-、i_B11+、i_B12+、i_B11-、i_B12-、i_C11+、i_C12+、i_C11-、i_C12-；

The phase current acquisition of the second round is the same as the phase current acquisition method of the first round, and the phase current acquisition results of the second round are sequentially recorded as i_A21+、i_A22+、i_A21-、i_A22-、i_B21+、i_B22+、i_B21-、i_B22-、i_C21+、i_C22+、i_C21-、i_C22-；

And step 3: processing a current signal;

wherein:

and 4, step 4: calculating the initial direction angle of the rotor magnetic pole;

will be provided withMapping to [0,2 π]Then, then

And 5: rotor magnetic pole initial position electric angle theta₀Calculating polarity correction;

to theta_0rawThe positive and negative polarities of the magnetic poles are judged and corrected to determine the final initial position electrical angle theta of the magnetic poles₀；

Step 5.1: selecting the phase to which the loading voltage vector belongs in the polarity judgment process;

let svp be the phase to which the selected voltage vector belongs,

when svp is phA, the loaded voltage vector in the polarity judgment process belongs to the phase A, the electrical angle of the positive voltage vector is 0 degree, and the electrical angle of the negative voltage vector is 180 degrees; when svp is phB, the loaded voltage vector in the polarity judgment process belongs to the B phase, the electric angle of the positive voltage vector is 120 degrees, and the electric angle of the negative voltage vector is 300 degrees; when svp is phC, the loaded voltage vector in the polarity judgment process belongs to the C phase, the electric angle of the positive voltage vector is 240 degrees, and the electric angle of the negative voltage vector is 60 degrees;

step 5.2: collecting polarity judgment phase current i of svp phase_X1+、i_X2+、i_X1-、i_X2-；

By T_PWMJudging a phase current acquisition period for polarity, ensuring that the motor current can reach a saturated state in the acquisition process and showing a saturated salient pole effect; phase current collection of an svp phase for continuously 7T for a motor_PWMPWM control of (1), 0-2T_PWMInput positive voltage vector, 2T_PWM～3T_PWMFor PWM full OFF state, 3T_PWM～5T_PWMInput negative voltage vector, 5T_PWM～7T_PWMFor PWM full OFF state, at 1T_PWMThe current collected at the moment is recorded as i_X1+At 2T_PWMThe current collected at the moment is recorded as i_X2+At 4T_PWMThe current collected at the moment is recorded as i_X1-At 5T_PWMThe current collected at the moment is recorded as i_X2-；

Step 5.3: calculating a polarity offset angle;

let Δ i_X＝|i_X2--i_X1-|-|i_X2+-i_X1+|；

Determining a polarity offset angle θ according to the following formula_0offset：

θ_0offset＝π·[(svp＝＝phA)·(Δi_X＞0)+(svp＝＝phB)·(Δi_X＜0)·(θ_0raw＜0)

+(svp＝＝phC)·(Δi_X＜0)]；

In the formula, (svp ═ phA), (svp ═ phB), (svp ═ phC), (Δ i ═ phA, and_X＞0)、(Δi_X＜0)、(θ_0rawless than 0) are judgment formulas, and the judgment formulas are 1 when the judgment formulas are satisfied and 0 when the judgment formulas are not satisfied;

step 5.4: according to theta_0raw、θ_0offsetCalculating the initial position electrical angle theta of the rotor magnetic pole₀：

θ₀＝θ_0raw+θ_0offset。

In step 2, in the phase current collection process of A, B, C three phases, the last collected phase current of each phase is two T₁And the PWM full-off state of the period ensures that the current response of the negative voltage vector is reduced to 0 after the phase current of the current phase is acquired, and the influence on the acquisition of the current of the next phase is eliminated.

In step 2, the duration of the basic voltage vector voltage introduced to the motor winding is short, the motor magnetic field is in an unsaturated state, a structural salient pole of the salient pole type permanent magnet synchronous motor is utilized, the d-axis inductance Ld is smaller than the q-axis inductance Lq, a variable related to a trigonometric function of the initial position angle of the rotor magnetic pole is constructed, and the initial direction angle theta of the rotor magnetic pole can be realized through the calculation of an inverse trigonometric function_0rawDetection of (3). In step 5, the initial direction angle theta of the rotor magnetic pole is passed_0rawClosest (included angle less than 30 °) toInputting a group of positive and negative voltage vectors corresponding to each phase into full-period PWM control to ensure that a motor magnetic field is in a saturated state, ensuring that the positive direction inductance of a magnetic pole is saturated and is smaller than the negative direction inductance during saturation, and combining the initial direction angle theta of the magnetic pole of a rotor by utilizing the difference of current response of the positive and negative voltage vectors_0rawThe polar offset angle theta of the initial direction of the magnetic pole can be realized_0offsetDetecting and further determining the initial direction angle theta of the rotor magnetic pole_0rawOffset angle theta from polarity_0offsetAnd adding to obtain the initial position electrical angle of the rotor magnetic pole.

Preferably, the method is characterized in that: in step 1k＝2μs。

The initial positioning method for the magnetic pole position of the rotor of the salient pole type three-phase permanent magnet synchronous motor does not need complex high-frequency voltage injection or sequential pulse voltage injection, and is simple to implement, high in positioning speed and high in positioning accuracy.

Drawings

The invention is further described below with reference to the accompanying drawings.

FIG. 1 is a schematic view of unsaturated phase current collection points for phase A in step 2 of the present invention.

Fig. 2 is a schematic diagram of the polarity determination phase current collection point of the svp phase in step 5.2 of the present invention.

Detailed Description

The invention is further illustrated by the following specific examples in conjunction with the accompanying drawings.

Example (b): a method for positioning the initial position of the magnetic pole of a rotor of a salient pole type three-phase permanent magnet synchronous motor. The method comprises the following steps:

step 1: PWM period T_PWMDetermination of (1);

PWM period initialization toThe duration of the motor isPWM control of (2): wherein the content of the first and second substances,a voltage vector with an input electrical angle of 0 DEG,Is in a PWM full-off state,A voltage vector with an input electrical angle of 180 DEG,For a PWM full OFF state, inThe current value of A phase collected at any moment is recorded asIn a time period ofWhen the PWM control is finished, ifWhen the current is less than the rated current peak value of the motor, the PWM period is gradually increased to enablep is 1, 2, 3 … …, k is the PWM cycle increment and the motor is run for a period of timePWM control of (1), acquisitionAnd judgeIn relation to the peak value of the rated current of the motor untilEqual to or more than the rated current value of the motor, and the PWM period is marked as T_PWM；

Step 2: acquiring a phase current signal in an unsaturated state, and sequentially acquiring A, B, C phase currents of two wheels;

let the non-saturation control period T₁＝0.2T_PWM～0.25T_PWMEnsuring that the motor current is always in an unsaturated state in the acquisition process; phase current collection of the phase A is shown in figure 1, and the cycle control and collection time points of phase current collection of the phase B and the phase C are consistent with the phase A;

the phase current collection of the first round of A phase is carried out for continuously 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with input electric angle of 0 degree, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 180 degrees, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_A11+At 2T₁The current collected at the moment is recorded as i_A12+At 4T₁The current collected at the moment is recorded as i_A11-At 5T₁The current collected at the moment is recorded as i_A12-；

After the phase current acquisition of the phase A of the first round is finished, the phase current acquisition of the phase B of the first round is carried out, and the phase current acquisition of the phase B of the first round carries out continuous 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with 120 degree input electric angle, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 300 degree, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_B11+At 2T₁The current collected at the moment is recorded as i_B12+At 4T₁The current collected at the moment is recorded as i_B11-At 5T₁The current collected at the moment is recorded as i_B12-；

After the phase current collection of the first round of B phase is finished, the phase current collection of the first round of C phase is carried out, and the phase current of the first round of C phase is collectedCollecting continuous 7T for motor₁PWM control of (1), 0-2T₁Voltage vector with input electric angle of 240 degree, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 60 degrees, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_C11+At 2T₁The current collected at the moment is recorded as i_C12+At 4T₁The current collected at the moment is recorded as i_C11-At 5T₁The current collected at the moment is recorded as i_C12-；

And (5) arranging the phase current acquisition results of the first round, and sequentially recording the phase current acquisition results as i_A11+、i_A12+、i_A11-、i_A12-、i_B11+、i_B12+、i_B11-、i_B12-、i_C11+、i_C12+、i_C11-、i_C12-；

The phase current acquisition of the second round is the same as the phase current acquisition method of the first round, and the phase current acquisition results of the second round are sequentially recorded as i_A21+、i_A22+、i_A21-、i_A22-、i_B21+、i_B22+、i_B21-、i_B22-、i_C21+、i_C22+、i_C21-、i_C22-；

And step 3: processing a current signal;

wherein:

and 4, step 4: calculating the initial direction angle of the rotor magnetic pole;

will be provided withMapping to [0,2 π]Then, then

And 5: rotor magnetic pole initial position electric angle theta₀Calculating polarity correction;

to theta_0rawThe positive and negative polarities of the magnetic poles are judged and corrected to determine the final initial position electrical angle theta of the magnetic poles₀；

Step 5.1: selecting the phase to which the loading voltage vector belongs in the polarity judgment process;

let svp be the phase to which the selected voltage vector belongs,

when svp is phA, the loaded voltage vector in the polarity judgment process belongs to the phase A, the electrical angle of the positive voltage vector is 0 degree, and the electrical angle of the negative voltage vector is 180 degrees; when svp is phB, the loaded voltage vector in the polarity judgment process belongs to the B phase, the electric angle of the positive voltage vector is 120 degrees, and the electric angle of the negative voltage vector is 300 degrees; when svp is phC, the loaded voltage vector in the polarity judgment process belongs to the C phase, the electric angle of the positive voltage vector is 240 degrees, and the electric angle of the negative voltage vector is 60 degrees;

step 5.2: collecting polarity judgment phase current i of svp phase_X1+、i_X2+、i_X1-、i_X2-(ii) a The polarity judgment phase current collection of the svp phase is shown in fig. 2;

by T_PWMJudging a phase current acquisition period for polarity, ensuring that the motor current can reach a saturated state in the acquisition process and showing a saturated salient pole effect; phase current collection of an svp phase for continuously 7T for a motor_PWMPWM control of (1), 0-2T_PWMInput positive voltage vector, 2T_PWM～3T_PWMFor PWM full OFF state, 3T_PWM～5T_PWMInput negative voltage vector, 5T_PWM～7T_PWMFor PWM full OFF state, at 1T_PWMThe current collected at the moment is recorded as i_X1+At 2T_PWMThe current collected at the moment is recorded as i_X2+At 4T_PWMThe current collected at the moment is recorded as i_X1-At 5T_PWMThe current collected at the moment is recorded as i_X2-；

Step 5.3: calculating a polarity offset angle;

let Δ i_X＝|i_X2--i_X1-|-|i_X2+-i_X1+|；

Determining a polarity offset angle θ according to the following formula_0offset：

θ_0offset＝π·[(svp＝＝phA)·(Δi_X＞0)+(svp＝＝phB)·(Δi_X＜0)·(θ_0raw＜0)

+(svp＝＝phC)·(Δi_X＜0)]；

In the formula, (svp ═ phA), (svp ═ phB), (svp ═ phC), (Δ i ═ phA, and_X＞0)、(Δi_X＜0)、(θ_0rawless than 0) are judgment formulas, and the judgment formulas are 1 when the judgment formulas are satisfied and 0 when the judgment formulas are not satisfied;

step 5.4: according to theta_0raw、θ_0offsetCalculating the initial position electrical angle theta of the rotor magnetic pole₀：

θ₀＝θ_0raw+θ_0offset。

Taking a 16-antipodal three-phase salient pole type permanent magnet synchronous motor as an example, the rated current of the motor is 23.7A, the peak value of the rated current of the motor is 33.5A, the phase resistance of the motor is 0.7 omega, the d-axis inductance of the motor is 10mH, and the q-axis inductance is equal and is 16 mH. The electric angle of the initial position of the magnetic pole of the motor rotor is 210 degrees.

Step 1: determining the PWM period T_PWM＝432μs。

Step 2: order toThe corresponding current values collected were:

variables of	iA11+	iA12+	iA11-	iA12-	iA21+	iA22+	iA21-	iA22-	ΔiA
										value/A	3.7180	7.4099	-0.0771	-3.8632	3.7446	7.4361	-0.0509	-3.8370	14.9556
Variables of	iB11+	iB12+	iB11-	iB12-	iB21+	iB22+	iB21-	iB22-	ΔiB
										value/A	2.4172	4.8314	-0.0087	-2.4335	2.4247	4.8390	-0.0012	-2.4260	9.6781
Variables of	iC11+	iC12+	iC11-	iC12-	iC21+	iC22+	iC21-	iC22-	ΔiC
										value/A	3.7788	7.5711	-0.0550	-3.8066	3.7909	7.5833	-0.0433	-3.7951	15.0880

And step 3: processing a current signal;

since sin _ val > 0 and cos _ val < 0, the angle for the arctangent determination should be in the second quadrant.

And 4, step 4: initial direction angle theta of rotor magnetic pole_0rawCalculating;

and 5: rotor magnetic pole initial position electric angle theta₀Calculating polarity correction;

in the polarity judgment process, the loaded voltage vector belongs to the C phase, the electrical angle of the positive voltage vector is 240 degrees, and the electrical angle of the negative voltage vector is 60 degrees; collecting C-phase polarity to judge phase current:

variables of	iX1+	iX2+	iX1-	iX2-	ΔiX
						value/A	15.4901	33.6491	-14.6672	-28.4854	-4.3407

So that the rotor magnetic pole initial position angle theta₀：

θ₀＝θ_0raw+θ_0offset＝0.5426rad+π＝31.0888°+180°＝211.0888°。

The estimation error of the initial position angle of the rotor magnetic pole is 210-theta₀210-211.0888-1.0888, the estimation accuracy is much higher than +/-30.

Claims (2)

1. A method for positioning the initial position of a magnetic pole of a rotor of a salient pole type three-phase permanent magnet synchronous motor is characterized by comprising the following steps: the method comprises the following steps:

step 1: PWM period T_PWMDetermination of (1);

PWM period initialization toThe duration of the motor isPWM control of (2): wherein the content of the first and second substances,a voltage vector with an input electrical angle of 0 DEG,Is in a PWM full-off state,A voltage vector with an input electrical angle of 180 DEG,For a PWM full OFF state, inThe current value of A phase collected at any moment is recorded asIn a time period ofWhen the PWM control is finished, ifWhen the current is less than the rated current peak value of the motor, the PWM period is gradually increased to enablek is the PWM cycle increment and the motor is performed for a time duration ofPWM control of (1), acquisitionAnd judgeIn relation to the peak value of the rated current of the motor untilEqual to or more than the rated current peak value of the motor, and the PWM period at the moment is recorded as T_PWM；

Step 2: acquiring a phase current signal in an unsaturated state, and sequentially acquiring A, B, C phase currents of two wheels;

control period T for unsaturated acquisition₁＝0.2T_PWM～0.25T_PWMEnsuring that the motor current is always in an unsaturated state in the acquisition process;

the phase current collection of the first round of A phase is carried out for continuously 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with input electric angle of 0 degree, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 180 degrees, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_A11+At 2T₁The current collected at the moment is recorded as i_A12+At 4T₁The current collected at the moment is recorded as i_A11-At 5T₁The current collected at the moment is recorded as i_A12-；

After the phase current acquisition of the phase A of the first round is finished, the phase current acquisition of the phase B of the first round is carried out, and the phase current acquisition of the phase B of the first round carries out continuous 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with 120 degree input electric angle, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 300 degree, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_B11+At 2T₁The current collected at the moment is recorded as i_B12+At 4T₁The current collected at the moment is recorded as i_B11-At 5T₁The current collected at the moment is recorded as i_B12-；

After the phase current collection of the first round of B phase is finished, the phase current collection of the first round of C phase is carried out, and the phase current collection of the first round of C phase continuously carries out 7T on the motor₁PWM control of (1), 0-2T₁Voltage vector with input electric angle of 240 degree, 2T₁～3T₁For PWM full OFF state, 3T₁～5T₁Voltage vector with input electric angle of 60 degrees, 5T₁～7T₁For PWM full OFF state, at 1T₁The current collected at the moment is recorded as i_C11+At 2T₁The current collected at the moment is recorded as i_C12+At 4T₁The current collected at the moment is recorded as i_C11-At 5T₁The current collected at the moment is recorded as i_C12-；

And (5) arranging the phase current acquisition results of the first round, and sequentially recording the phase current acquisition results as i_A11+、i_A12+、i_A11-、i_A12-、i_B11+、i_B12+、i_B11-、i_B12-、i_C11+、i_C12+、i_C11-、i_C12-；

The phase current acquisition of the second round is the same as the phase current acquisition method of the first round, and the phase current acquisition results of the second round are sequentially recorded as i_A21+、i_A22+、i_A21-、i_A22-、i_B21+、i_B22+、i_B21-、i_B22-、i_C21+、i_C22+、i_C21-、i_C22-；

And step 3: processing a current signal;

wherein:

and 4, step 4: calculating the initial direction angle of the rotor magnetic pole;

will be provided withMapping to [0,2 π]Then, then

And 5: rotor magnetic pole initial position electric angle theta₀Calculating polarity correction;

to theta_0rawThe positive and negative polarities of the magnetic poles are judged and corrected to determine the final initial position electrical angle theta of the magnetic poles₀；

Step 5.1: selecting the phase to which the loading voltage vector belongs in the polarity judgment process;

let svp be the phase to which the selected voltage vector belongs,

when svp is phA, the loaded voltage vector in the polarity judgment process belongs to the phase A, the electrical angle of the positive voltage vector is 0 degree, and the electrical angle of the negative voltage vector is 180 degrees; when svp is phB, the loaded voltage vector in the polarity judgment process belongs to the B phase, the electric angle of the positive voltage vector is 120 degrees, and the electric angle of the negative voltage vector is 300 degrees; when svp is phC, the loaded voltage vector in the polarity judgment process belongs to the C phase, the electric angle of the positive voltage vector is 240 degrees, and the electric angle of the negative voltage vector is 60 degrees;

step 5.2: collecting polarity judgment phase current i of svp phase_X1+、i_X2+、i_X1-、i_X2-；

By T_PWMJudging a phase current acquisition period for polarity, ensuring that the motor current can reach a saturated state in the acquisition process and showing a saturated salient pole effect; phase current collection of an svp phase for continuously 7T for a motor_PWMPWM control of (1), 0-2T_PWMInput positive voltage vector, 2T_PWM～3T_PWMFor PWM full OFF state, 3T_PWM～5T_PWMInput negative voltage vector, 5T_PWM～7T_PWMFor PWM full OFF state, at 1T_PWMThe current collected at the moment is recorded as i_X1+At 2T_PWMThe current collected at the moment is recorded as i_X2+At 4T_PWMThe current collected at the moment is recorded as i_X1-At 5T_PWMThe current collected at the moment is recorded as i_X2-；

Step 5.3: calculating a polarity offset angle;

let Δ i_X＝|i_X2--i_X1-|-|i_X2+-i_X1+|；

Determining a polarity offset angle θ according to the following formula_0offset：

θ_0offset＝π·[(svp＝＝phA)·(Δi_X＞0)+(svp＝＝phB)·(Δi_X＜0)·(θ_0raw＜0)+(svp＝＝phC)·(Δi_X＜0)]；

In the formula, (svp ═ phA), (svp ═ phB), (svp ═ phC), (Δ i ═ phA, and_X＞0)、(Δi_X＜0)、(θ_0rawless than 0) are judgment formulas, and the judgment formulas are 1 when the judgment formulas are satisfied and 0 when the judgment formulas are not satisfied;

step 5.4: according to theta_0raw、θ_0offsetCalculating the initial position electrical angle theta of the rotor magnetic pole₀：

θ₀＝θ_0raw+θ_0offset。

2. The method for positioning the initial position of the magnetic pole of the rotor of the salient pole type three-phase permanent magnet synchronous motor according to claim 1, wherein the method comprises the following steps: in the first stepk＝2μs。