阅读说明：本技术 一种永磁电机转子初始位置检测方法 (Method for detecting initial position of permanent magnet motor rotor ) 是由 张海峰 李海涛 毛琨 陈宝栋 金浩 郑世强 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种永磁电机转子初始位置检测方法,属于永磁电机控制的技术领域,由转子位置初次估计、转子磁极方向判别和转子位置初次估计的补偿三部分组成。首先,向估计的d轴注入高频载波电压,通过采集估计的q轴载波电流并进行闭环控制实现对转子位置的初次估计。在完成转子位置的初次估计后,利用离散傅里叶变换对该载波电流的幅值进行检测以对转子磁极方向进行判别。最后,根据转子磁极方向的判别结果对转子位置的初次估计值进行补偿,实现转子初始位置检测。本发明实现转子位置的初次估计与转子磁极方向判别算法的集成,检测算法简单,具有检测速度快、可靠性高的优点。(The invention discloses a method for detecting the initial position of a permanent magnet motor rotor, which belongs to the technical field of permanent magnet motor control and consists of three parts of compensation of initial estimation of the rotor position, judgment of the rotor magnetic pole direction and initial estimation of the rotor position. Firstly, injecting high-frequency carrier voltage into an estimated d axis, and realizing the primary estimation of the rotor position by collecting estimated q axis carrier current and carrying out closed-loop control. After the primary estimation of the rotor position is completed, the amplitude of the carrier current is detected by using discrete Fourier transform to judge the rotor magnetic pole direction. And finally, compensating the primary estimation value of the rotor position according to the judgment result of the magnetic pole direction of the rotor, and realizing the detection of the initial position of the rotor. The invention realizes the integration of the primary estimation of the rotor position and the discrimination algorithm of the rotor magnetic pole direction, has simple detection algorithm, and has the advantages of high detection speed and high reliability.)

1. A method for detecting the initial position of a permanent magnet motor rotor is characterized by comprising the following steps:

step 1: the d-axis of the direction estimate isShaft, injecting high-frequency carrier voltage, by collectingCarrying out closed-loop control on the carrier current of the shaft to realize primary estimation on the position of the rotor;

(1-1) establishing a two-phase static coordinate system as an alpha-beta coordinate system, an actual rotor synchronous rotation coordinate system as a d-q coordinate system and an estimated rotor synchronous rotation coordinate system as an alpha-beta coordinate systemCoordinate system, where the angle between d-axis and alpha-axis is the actual rotor position θ_e，The angle between the axis and the alpha axis being the estimated rotor positionAnd is

(1-2) in the direction ofAxial injection high frequency carrier voltage V_mcos(ω_ht) when coupled toThe carrier current of the shaft is:

in the formula, V_mFor injecting the amplitude, omega, of the high-frequency voltage_h＝2πf_hFor injecting angular velocity of high-frequency voltage, f_hFor injecting the frequency of the high-frequency voltage (250Hz ≦ f)_hLess than or equal to 1000Hz), R is the inductance of the motor winding, L_d、L_qD-axis and q-axis inductances, DeltaL, of the motor winding_h＝(L_q-L_d) The/2 is half-difference inductance, j is an imaginary unit, and t is time;

(1-3) rewriting the formula as a magnitude phase angle form:

in the formula (I), the compound is shown in the specification,is the impedance strength of the d-axis,The impedance strength of the q-axis,Is the impedance angle of the d-axis,For the q-axis impedance angle, the equation is multiplied by sin (ω)_ht) is demodulated and low-pass filtered and sin (2 Δ θ)_e) Is approximately 2 Delta theta_eObtaining an expression containing the position error of the rotor:

(1-4) Using PI controller to f (Delta theta)_e) Performing closed-loop control to estimate the position error delta theta_eAdjusting to 0, finishing the primary estimation process of the rotor position, and obtaining a primary estimation value of the rotor position;

step 2: after the initial estimation of the rotor position is completed, the amplitude of the carrier current is detected by using discrete fourier transform to judge the rotor magnetic pole direction, which is specifically as follows:

(2-1) collecting when step 1 is performedCarrier current i of the shaft_d0And extracting i_d0Amplitude of (I)_d0；

(2-2) inSuperimposing a forward DC bias voltage V on the shaft high-frequency carrier voltage_dAt this time of collectionCarrier current i of the shaft_d1And extracting i_d1Amplitude of (I)_d1；

(2-3) if I_d1≥I_d0Then, thenThe direction of the shaft is the same as that of the d shaft, namely the estimated rotor magnetic pole direction is the same as the actual rotor magnetic pole direction; if I_d1＜I_d0Then, thenThe direction of the axis is opposite to that of the d axis, namely the estimated rotor magnetic pole direction is opposite to the actual rotor magnetic pole direction;

and step 3: according to the primary estimation of the rotor position in the step 1 and the judgment result of the magnetic pole direction of the rotor in the step 2, if the estimated magnetic pole direction of the rotor is the same as the actual magnetic pole direction of the rotor, the primary estimation value of the rotor position is the initial position of the rotor; and if the estimated rotor magnetic pole direction is opposite to the actual rotor magnetic pole direction, the initial position of the rotor is the initial estimation value of the rotor position plus 180 degrees, and the compensation of the initial estimation of the rotor position is realized.

2. The method for detecting the initial position of the rotor of the permanent magnet motor according to claim 1, wherein the angular velocity ω of the high-frequency voltage injected in step 1_hNeed to satisfy omega_h＞R/L_dTo ensure the stability of the initial estimation of the rotor position.

3. The method for detecting the initial position of the rotor of the permanent magnet motor according to claim 1, wherein the carrier current amplitude in the steps (2-1) and (2-2) is extracted as follows:

(3-1) pairs of i_d0、i_d1With f_sThe sampling frequency of (a) acquires M data points to obtain two current sequences, i_d0(0),i_d0(1)…i_d0(M-1)、i_d1(0),i_d1(1)…i_d1(M-1)；

(3-2) performing discrete Fourier transform on the two current sequences to obtain i_d0、i_d1The amplitudes of (a) are:

Technical Field

The invention relates to the field of motor control, in particular to a method for detecting an initial position of a permanent magnet motor rotor.

Background

The permanent magnet motor has the advantages of compact structure, high power density, good dynamic performance, high efficiency and the like, and is more and more widely applied. Real-time rotor position feedback is essential to achieve high-precision control of permanent magnet motors. Typically, a photoelectric encoder, a rotary transformer and a linear hall sensor are used to obtain continuous rotor position information, and a switching hall sensor is used to obtain discrete rotor position information. However, these mechanical sensors may have problems of difficult installation, difficult wire outlet and poor reliability, so that the position-sensor-free control is an effective way to solve these problems. When the motor operates at a medium or high speed, position information of the rotor may be extracted using a counter electromotive force generated by the rotation of the motor. When the motor is at rest or at low speed, the back electromotive force of the motor is zero or small, and the position information of the rotor is difficult to detect from the back electromotive force, which becomes an important factor for restricting the wide application of the sensorless control.

In order to solve the starting problem of a permanent magnet motor position sensorless device, a three-section open-loop starting method is widely adopted in engineering to start the motor, the method does not need position information of a rotor, but has the problems of long starting time, large starting current and volatile steps. In order to further optimize the starting problem of the permanent magnet motor, a closed-loop starting method based on rotor position detection is widely concerned by utilizing a salient pole structure or a saturated salient pole effect of the motor. The inductance measurement method, the carrier frequency component analysis method and the high-frequency signal injection method are three important rotor position detection methods at zero speed and low speed.

The inductance measurement method, the carrier frequency component analysis method and the high-frequency signal injection method solve the problem of rotor position detection of the motor at zero speed and low speed to a certain extent. Although the inductance measurement method is simple in principle and algorithm implementation, the inductance values of the windings at different positions of the rotor need to be acquired off-line or on-line, excessive hardware resources are occupied, and the detection effect of the position of the rotor depends excessively on the accuracy of a detection circuit and parameters. The rotor position detection method based on the carrier component analysis method occupies less system resources, but the detection precision is influenced by the sine pulse width modulation precision, and the method cannot be applied to the motor control of space vector pulse width modulation. Both an inductance measurement method and a rotor position detection method based on a carrier component analysis method depend on a salient pole structure of a rotor, the position detection effect on a permanent magnet motor with low salient pole rate is poor, and the rotor position detection on the permanent magnet motor without the salient pole structure cannot be performed. Compared with the two methods, the high-frequency signal injection method has the advantages of flexible injection signal, high signal-to-noise ratio and good detection effect, and becomes the most important method for solving the problem of rotor position detection of the motor at zero speed and low speed.

The high frequency signal injection method is classified into a rotational high frequency signal injection method and a pulsating high frequency signal injection method. The rotary high-frequency signal injection method realizes the detection of the position of the rotor by utilizing the salient pole structure of the rotor by tracking the salient pole structure; the pulse vibration high-frequency signal injection method realizes the tracking of the position of the rotor through closed-loop control by utilizing the salient pole structure of the rotor or the excited saturated salient pole effect, and can be applied to the permanent magnet motor with the salient pole structure and the permanent magnet motor without the salient pole structure. The carrier signal may be a voltage signal or a current signal regardless of the rotational high-frequency signal injection method or the pulse-oscillation high-frequency signal injection method. The precision of the high-frequency current injection method is not affected by the nonlinearity and the dead zone of the inverter, but the current controller is required to have enough bandwidth and precision to track the high-frequency current signal, and in addition, an additional voltage sensor is required to be added, so that the complexity and the realization difficulty of the system are increased. Therefore, in practical applications, the pulse-oscillation high-frequency voltage signal injection method is more commonly used.

Disclosure of Invention

The invention solves the problems: aiming at the problems of high difficulty and unreliable detection of the rotor position when the motor is static, the method for detecting the initial position of the permanent magnet motor rotor is provided, the integration of the initial estimation of the rotor position and the discrimination algorithm of the rotor magnetic pole direction is realized, the detection algorithm is simple, and the method has the advantages of high detection speed and high reliability.

The method for detecting the initial position of the permanent magnet motor rotor comprises three parts of initial estimation of the rotor position, judgment of the rotor magnetic pole direction and compensation of the initial estimation of the rotor position. Primary estimation of the rotor position: and injecting high-frequency carrier voltage into the estimated d axis, and realizing the primary estimation of the rotor position by collecting the estimated q axis carrier current and carrying out closed-loop control. And (3) judging the magnetic pole direction of the rotor: after the primary estimation of the rotor position is completed, the amplitude of the carrier current is detected by using discrete Fourier transform to judge the rotor magnetic pole direction. Compensation of the initial estimate of rotor position: and compensating the primary estimation value of the rotor position according to the judgment result of the magnetic pole direction of the rotor, thereby realizing the detection of the initial position of the rotor.

The technical scheme adopted by the invention is as follows: the method comprises the following steps:

step 1: injecting high-frequency carrier voltage into an estimated d axis (recorded as d axis) by primary estimation of the position of the rotor, and collectingCarrying out closed-loop control on the carrier current of the shaft to realize primary estimation on the position of the rotor;

(1-1) establishing a two-phase static coordinate system (marked as an alpha-beta coordinate system), an actual rotor synchronous rotating coordinate system (marked as a d-q coordinate system) and an estimated rotor synchronous rotating coordinate system (marked as a d-q coordinate system)Coordinate system) where the angle between the d-axis and the alpha-axis is the actual rotor position theta_e，Shaft andthe angle between the alpha axes being the estimated rotor positionAnd is

(1-2) in the direction ofAxial injection high frequency carrier voltage V_mcos(ω_ht) when coupled toThe carrier current of the shaft is:

in the formula, V_mFor injecting the amplitude, omega, of the high-frequency voltage_h＝2πf_hFor injecting angular velocity of high-frequency voltage, f_hFor injecting the frequency of the high-frequency voltage (250Hz ≦ f)_hLess than or equal to 1000Hz), R is the inductance of the motor winding, L_d、L_qD-axis and q-axis inductances, DeltaL, of the motor winding_h＝(L_q-L_d) The/2 is half-difference inductance, j is an imaginary unit, and t is time;

(1-3) rewrite equation (1) into amplitude phase angle form:

in the formula (I), the compound is shown in the specification,is the impedance strength of the d-axis,The impedance strength of the q-axis,Is the impedance angle of the d-axis,For the q-axis impedance angle, sin (ω) is multiplied by equation (2)_ht) is demodulated and low-pass filtered and sin (2. DELTA.. theta.) is applied_e) Is approximately 2 Delta theta_eObtaining an expression containing the position error of the rotor:

(1-4) Using PI controller to f (. DELTA.. theta.)_e) Performing closed-loop control to estimate the position error delta theta_eAnd adjusting to 0, finishing the primary estimation process of the rotor position and obtaining the primary estimation value of the rotor position.

Step 2: and (4) judging the magnetic pole direction of the rotor, and detecting the amplitude of the carrier current by utilizing discrete Fourier transform to judge the magnetic pole direction of the rotor after the primary estimation of the position of the rotor is finished.

(2-1) collecting while performing the step ACarrier current i of the shaft_d0And extracting i_d0Amplitude of (I)_d0；

(2-2) inSuperimposing a forward DC bias voltage V on the shaft high-frequency carrier voltage_dAt this time of collectionHigh-frequency carrier current i of shaft_d1And extracting i_d1Amplitude of (I)_d1；

(2-3) if I_d1≥I_d0Then, thenAxial and d-axial directionsThe same, i.e. the estimated rotor pole direction is the same as the actual rotor pole direction; if I_d1＜I_d0Then, thenThe direction of the axis is opposite to that of the d axis, namely the estimated rotor magnetic pole direction is opposite to the actual rotor magnetic pole direction;

and step 3: compensating for the initial estimation of the rotor position, wherein if the estimated rotor magnetic pole direction is the same as the actual rotor magnetic pole direction, the initial estimation value of the rotor position is the initial position of the rotor; if the estimated rotor pole direction is opposite to the actual rotor pole direction, the initial position of the rotor is the initial estimate of the rotor position plus 180 °.

Angular velocity omega of injected high frequency voltage_hNeed to satisfy omega_h＝R/L_dTo ensure the stability of the initial estimation of the rotor position;

the calculation process of the high-frequency carrier current amplitude in the steps (2-1) and (2-2) is as follows:

(3-1) pairs of i_d0、i_d1With f_sThe sampling frequency of (a) acquires M data points to obtain two current sequences, i_d0(0),i_d0(1)…i_d0(M-1)、i_d1(0),i_d1(1)…i_d1(M-1)；

(3-2) performing discrete Fourier transform on the two current sequences to obtain i_d0、i_d1The amplitude of (d) is:

the beneficial effects brought by the invention can be embodied in the following aspects:

(1) the stability condition of the rotor position primary estimation system is provided, the parameter range of the system is quantized, the repeated trial and error process in the design of system parameters is avoided, and the efficiency of parameter setting of the rotor position primary estimation system is improved;

(2) according to the invention, the amplitude of the carrier current injected into the carrier voltage frequency is extracted by utilizing the principle of discrete Fourier transform, compared with a conventional amplitude acquisition method by using a traversal method, the operation amount is reduced, and the influence of measurement noise on amplitude detection is avoided;

(3) the rotor magnetic pole direction distinguishing method only needs to superpose direct bias voltage on the basis of the rotor position primary estimation system, so that the primary estimation of the rotor position and the rotor magnetic pole direction distinguishing algorithm can be integrated, the design is simplified, and the detection speed is improved.

Drawings

FIG. 1 shows an ABC coordinate system,A schematic diagram of a coordinate system and a d-q coordinate system;

FIG. 2 is a schematic view of a rotor initial position detection method;

FIG. 3 is a schematic diagram of the initial estimation of rotor position.

Detailed Description

The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, a two-phase stationary coordinate system alpha-beta, an actual rotor synchronous rotation coordinate system d-q and an estimated rotor synchronous rotation coordinate system are establishedWherein the angle between the d-axis and the alpha-axis is the actual rotor position theta_e，The angle between the axis and the alpha axis being the estimated rotor positionAnd is

As shown in fig. 2, the method for detecting the initial position of the rotor of the permanent magnet motor of the present invention includes the following steps:

step A) rotorPrimary estimation of the position: towards the estimationShaft injection of high frequency carrier voltage by collectionCarrying out closed-loop control on the carrier current of the shaft to realize primary estimation on the position of the rotor;

step B) judging the magnetic pole direction of the rotor: after the primary estimation of the rotor position is completed, the amplitude of the carrier current is detected by using discrete Fourier transform to judge the rotor magnetic pole direction.

Step C) compensation of the initial estimation of the rotor position: according to the rotor position primary estimation in the step A and the rotor magnetic pole direction judgment result in the step B, if the estimated rotor magnetic pole direction is the same as the actual rotor magnetic pole direction, the primary estimation value of the rotor position is the initial position of the rotor; if the estimated rotor pole direction is opposite to the actual rotor pole direction, the initial position of the rotor is the initial estimate of the rotor position plus 180 °.

The rotor position primary estimation in the step A comprises the following steps:

(1) to the direction ofAxial injection high frequency carrier voltage V_mcos(ω_ht) when coupled toThe carrier current of the shaft is:

in the formula, V_mFor injecting the amplitude, omega, of the high-frequency voltage_h＝2πf_hFor injecting angular velocity of high-frequency voltage, f_hFor injecting the frequency of the high-frequency voltage (250Hz ≦ f)_hLess than or equal to 1000Hz), R is the inductance of the motor winding, L_d、L_qD-axis and q-axis inductances, DeltaL, of the motor winding_h＝(L_q-L_d) The/2 is half-difference inductance, j is an imaginary unit, and t is time;

(2) rewrite equation (1) to the amplitude phase angle form:

in the formula (I), the compound is shown in the specification,is the impedance strength of the d-axis,The impedance strength of the q-axis,Is the impedance angle of the d-axis,For the q-axis impedance angle, sin (ω) is multiplied by equation (2)_ht) is demodulated and low-pass filtered and sin (2. DELTA.. theta.) is applied_e) Is approximately 2 Delta theta_eObtaining an expression containing the position error of the rotor:

(3) using PI controller pair f (Delta theta)_e) Performing closed-loop control to estimate the position error delta theta_eAnd adjusting to 0, finishing the primary estimation process of the rotor position and obtaining the primary estimation value of the rotor position.

In one embodiment, the amplitude V of the pulsating voltage_mIs 10V, frequency f_hAt 500Hz, the proportional gain of the PI controller is 30 and the integral gain is 120.

After the initial estimation of the rotor position is completed, the initial estimation of the rotor position may be the actual rotor position or may be 180 ° different from the actual rotor position due to the periodicity of the trigonometric function. Fig. 3 shows a schematic diagram of the initial estimated value of the rotor position and the actual rotor position in the α - β coordinate system, where position 1, position 2, position 3 and position 4 are actual rotor positions, and position 1 ', position 2', position 3 'and position 4' are actual rotor positions. It can be seen that when the actual rotor position is at position 1 and position 4, the rotor position first estimate values position 1 'and position 4' converge to the actual rotor position; when the actual rotor position is at position 2 and position 3, the rotor position first estimate values position 2 'and position 3' converge to the opposite direction of the actual rotor position. Further analysis shows that when the actual rotor position is located on the right half plane of the alpha-beta coordinate system, the initial estimation value of the rotor position is the same as the actual rotor position; when the actual rotor position is in the left half plane of the alpha-beta coordinate system, the initial estimate of the rotor position is 180 deg. from the actual rotor position. Therefore, it is necessary to further determine the magnetic pole direction of the rotor to obtain the actual rotor position.

The step B of judging the magnetic pole direction of the rotor comprises the following steps:

(1) during the initial estimation of the rotor position, the value is calculated as f_sSampling frequency of (2) acquiring MHigh-frequency carrier current i of shaft_d0Current sequence is i_d0(0),i_d0(1)…i_d0(M-1)；

(2) Extracting i by transforming_d0The amplitude of (d) is:

(3) in thatSuperimposing a forward DC bias voltage V on the shaft high-frequency carrier voltage_dWith f_sSampling frequency of (2) acquiring MHigh-frequency carrier current i of shaft_d1Current sequence is i_d1(0),i_d1(1)…i_d1(M-1)；

(4) Extracting i by transforming_d1The amplitude of (d) is:

(5) if I_d1≥I_d0Then, thenThe direction of the shaft is the same as that of the d shaft, namely the estimated rotor magnetic pole direction is the same as the actual rotor magnetic pole direction; if I_d1＜I_d0Then, thenThe direction of the axis is opposite to that of the d axis, namely the estimated rotor magnetic pole direction is opposite to the actual rotor magnetic pole direction;

in a particular embodiment, the sampling frequency f of the current_sAt 5kHz, the length M of the sample sequence is 20.

The compensation of the primary estimation of the rotor position in the step C comprises the following steps:

(1) according to the primary estimation value of the position of the rotor, judging results of the magnetic pole directions of the rotor are obtained according to the third step;

(2) if the estimated rotor magnetic pole direction is the same as the actual rotor magnetic pole direction, the initial estimated value of the rotor position is the initial position of the rotor; if the estimated rotor pole direction is opposite to the actual rotor pole direction, the initial position of the rotor is the initial estimate of the rotor position plus 180 °.

The invention has not been described in detail and is within the skill of the art.