Method for estimating rotor position of multi-stage motor at low speed based on exciter harmonic

Abstract

The application relates to a multi-stage motor low-speed rotor position estimation method based on an excitation machine harmonic. Two-phase symmetric voltage is applied to a two-phase excitation machine stator winding, and two-phase excitation machine stator currents are collected; the two-phase excitation machine stator currents are sequentially subjected to coordinate transformation and low-pass filtering to obtain cos signals and sin signals related to the excitation machine rotor position, and the excitation machine rotor position is obtained through phase-locked loop processing; the excitation machine rotor position increment is obtained according to the obtained excitation machine rotor position and the excitation machine rotor initial position; and finally, the main motor rotor position estimation value is obtained in combination with the main motor rotor initial position. The method provided by the application does not need high-frequency signal injection, is not affected by the change of the main motor salient pole, has higher estimation accuracy, and the signal extraction and position estimation method is simple, and the processor performance requirement is low.

Description

Technical Field

[0001] This invention belongs to the field of synchronous motor rotor position estimation technology, and relates to a method for estimating the rotor position of a multi-stage motor in the low-speed section based on exciter harmonics. Specifically, it relates to a method for estimating the rotor position of a multi-stage brushless synchronous motor in the low-speed section without high-frequency signal injection and without relying on the salient polarity of the motor. Background Technology

[0002] Three-stage brushless synchronous motors offer advantages such as high power quality and reliability, and are widely used as generators in aircraft power systems. By operating the three-stage brushless synchronous motor in electric mode to start the aircraft engine, and then having the engine drive it in generator mode to supply power to onboard electrical equipment after starting, the three-stage brushless synchronous motor achieves integrated starting and generating. This eliminates the need for a dedicated engine starter, reduces system size and weight, and increases integration, which is of great significance to aircraft power systems.

[0003] When a three-stage brushless synchronous motor operates in electric mode to start an aero engine, accurate rotor position information is required. Traditional mechanical position sensors for obtaining rotor position suffer from low reliability and increased system size and weight. Online rotor position estimation for a three-stage brushless synchronous motor can eliminate the need for mechanical position sensors, enabling sensorless start-up control, improving system reliability, and reducing size and weight.

[0004] A three-stage brushless synchronous motor consists of a coaxially mounted permanent magnet auxiliary exciter, an exciter, and a main motor. Its structural diagram is shown below. Figure 1 As shown. In some applications, the permanent magnet auxiliary exciter can be omitted, forming a two-stage brushless synchronous motor. Since the core components and operating principles are basically the same, three-stage and two-stage brushless synchronous motors are collectively referred to as multi-stage brushless synchronous motors.

[0005] Traditional rotor position estimation methods for low-speed multi-stage brushless synchronous motors largely rely on the salient polarity of the main motor. However, when the multi-stage brushless synchronous motor operates in electric mode to start an aero-engine, the salient polarity of the main motor changes, causing traditional methods to fail. Rotor position estimation methods based on "main motor injection - exciter detection" do not depend on the salient polarity of the main motor, but require the injection of high-frequency signals into the stator side of the main motor. The injection of high-frequency signals can lead to problems such as vibration and increased losses. Rotor position estimation methods without high-frequency signal injection include the exciter current harmonic method and the exciter rotor current trajectory method, but these methods are complex, computationally intensive, and require high processing power from the controller. Summary of the Invention

[0006] Technical problems to be solved

[0007] To avoid the shortcomings of existing technologies, this invention proposes a rotor position estimation method for a multi-stage motor in the low-speed section based on exciter harmonics. This method overcomes the problems of existing technologies, such as dependence on motor salient polarity, vibration and loss caused by high-frequency injection, and complex estimation methods with large computational load. It does not depend on motor salient polarity, does not require high-frequency signal injection, and has a small computational load.

[0008] Technical solution

[0009] A method for estimating the rotor position in the low-speed section of a multi-stage brushless synchronous motor based on exciter harmonics, characterized in that the multi-stage brushless synchronous motor includes a coaxially mounted main motor and a two-phase exciter, and the rotor position in the low-speed section of the multi-stage brushless synchronous motor refers to the rotor position in the low-speed section of the main motor in the multi-stage brushless synchronous motor. The method includes the following steps:

[0010] Step 1: Apply two-phase symmetrical voltages to the stator windings of the two-phase exciter, and simultaneously collect the two-phase stator currents of the two-phase exciter;

[0011] Step 2: Perform coordinate transformation on the stator currents of the two-phase exciter. Specifically, the transformation method is to left-hand coordinate transformation matrix on the stator currents of the two-phase exciter. Where θ is the coordinate transformation angle, then low-pass filtering is performed to obtain the cosine and sinine signals related to the exciter rotor position, denoted as f, respectively. cos and f sin ;

[0012] Step 3: Based on the f related to the exciter rotor position cos and f sin The signal indicates the position of the exciter rotor;

[0013] Step 4: Based on the low-speed exciter rotor position θ e and the initial position θ of the exciter rotor e0 The rotor position increment Δθ of the exciter is obtained. e =θ e -θ e0 The low-speed exciter rotor position θ e The exciter rotor position obtained from steps 1 to 3 above is used when the system is at low speed. The initial position θ of the exciter rotor is... e0 The exciter rotor position is obtained from steps 1 to 3 above when the system is at rest.

[0014] Step 5: Determine the position of the main motor rotor based on the exciter rotor position increment and the initial position of the main motor rotor, which is the rotor position of the multi-stage brushless synchronous motor.

[0015] The coordinate transformation of the two-phase current of the exciter stator in step 2 is as follows:

[0016]

[0017] Among them, i α and i β The two-phase exciter stator α-phase and β-phase currents collected in step one; i α1 and i β1 The exciter's two-phase currents after coordinate transformation; Let be the coordinate transformation matrix, where θ is the coordinate transformation angle, and:

[0018] When the excitation magnetic field of the exciter rotates in the same direction as the motor, it is called co-directional excitation, θ=5ω s t;

[0019] When the excitation magnetic field of the exciter rotates in the opposite direction to the rotation of the motor, it is called reverse excitation, θ=-5ω s t;

[0020] Where, ω s It is the excitation angular frequency of the exciter stator, and t represents time.

[0021] Step 2 involves low-pass filtering the two-phase currents of the exciter after coordinate transformation to obtain the cosine signal f related to the rotor position of the exciter. cos and sin signal f sin Specifically:

[0022]

[0023] Here, LPF represents low-pass filtering.

[0024] Step 3 obtains f cos and f sin After processing with a phase-locked loop, the electrical angle θ of the exciter rotor position is obtained as 6 times the angle θ. 6e , that is, θ 6e =6θ e , where θ e The electrical angle of the exciter rotor position is given; thus, the electrical angle θ of the exciter rotor position is obtained. e .

[0025] In step 5, the obtained electric angle increment value of the exciter rotor position is divided by the number of pole pairs of the exciter to obtain the mechanical angle increment value of the exciter rotor position. Then, it is multiplied by the number of pole pairs of the main motor to obtain the electric angle increment value of the main motor rotor position. Finally, the initial value of the electric angle of the main motor rotor position is added to obtain the rotor position of the main motor, which is the rotor position of the multi-stage brushless synchronous motor.

[0026] Beneficial effects

[0027] This invention proposes a method for estimating the rotor position of a multi-stage motor in the low-speed range based on exciter harmonics. Two-phase symmetrical voltages are applied to the stator windings of the two-phase exciter, and the two-phase stator currents of the exciter are collected. The two-phase exciter stator currents are sequentially subjected to coordinate transformation and low-pass filtering to obtain the cosine and sinine signals related to the exciter rotor position. These signals are then processed by a phase-locked loop to obtain the exciter rotor position. Based on the obtained exciter rotor position and its initial position, the exciter rotor position increment is obtained. Finally, combined with the initial position of the main motor rotor, the estimated value of the main motor rotor position is obtained. The method proposed in this invention does not require high-frequency signal injection, is unaffected by changes in the salient polarity of the main motor, has high estimation accuracy, and features simple signal extraction and position estimation methods with low processor performance requirements.

[0028] The beneficial effects of this invention include:

[0029] 1) Since the inherent harmonic signal generated by the exciter itself is used as the effective signal for rotor position estimation, the present invention reduces torque ripple compared with the traditional rotor position estimation method based on additional high-frequency signal injection, which will bring torque ripple. At the same time, it reduces the high-frequency harmonic loss caused by high-frequency signal injection.

[0030] 2) Since the excitation current of the exciter is much smaller than the current of the main motor during startup, and this order of magnitude does not change significantly during the entire startup process, the signal-to-noise ratio is higher and it is not affected by the operating state of the main motor, such as changes in salient polarity, compared with the traditional rotor position estimation method based on high-frequency signal injection from the stator winding of the main motor. This effectively improves the accuracy of rotor position estimation. In actual startup with a load of 50 N·m from 0 rpm to 240 rpm, the estimation error does not exceed 7°. In contrast, in existing literature, when other methods are used for position estimation, the maximum load is 30 N·m and the estimation error is within 10°.

[0031] 3) In the position estimation process of this invention, only simple trigonometric function operations and low-pass filters are used. Compared with the complex mathematical operations used in the signal injection-demodulation-extraction process in existing methods, this invention has lower requirements for processor performance, and most common processors can meet the requirements. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a three-stage brushless synchronous motor.

[0033] Figure 2 This is a flowchart of the rotor position estimation method for the low-speed section of the multi-stage brushless synchronous motor proposed in this invention.

[0034] Figure 3 The waveform of the two-phase excitation current of the exciter stator

[0035] Figure 4 The waveform of the two-phase current of the exciter stator after coordinate transformation.

[0036] Figure 5 The waveform after passing through a low-pass filter (i.e., the cosine and sinine signals related to the exciter rotor position).

[0037] Figure 6 For the estimated exciter rotor position increment

[0038] Figure 7 Estimated value, actual value and estimation error of the main motor rotor position Detailed Implementation

[0039] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0040] In this embodiment, the exciter of the multi-stage brushless synchronous motor is a two-phase exciter. The multi-stage brushless synchronous motor includes a main motor and a two-phase exciter mounted coaxially. The rotor position of the multi-stage brushless synchronous motor refers to the rotor position of the main motor in the multi-stage brushless synchronous motor. In this embodiment, the stator excitation winding of the exciter is a two-phase winding with a 90° electrical angle difference. The exciter has 6 pole pairs, and the main motor has 3 pole pairs. The following detailed explanation uses the motor running at 100 r / min as an example.

[0041] 1. A two-phase symmetrical voltage is applied to the two-phase stator windings of the exciter (denoted as the α-phase winding and the β-phase winding, respectively). The excitation voltage amplitude is 200V, the excitation frequency is 200Hz, and the direction of rotation of the excitation magnetic field is the same as the direction of rotation of the motor. The two-phase stator currents of the two-phase exciter are collected and denoted as i. α and i β ,like Figure 3 As shown.

[0042] 2. For the collected two-phase current i α and i β Perform the following coordinate transformation to obtain i α1 and i β1 .

[0043]

[0044] Where, ω s It is the excitation angular frequency of the exciter stator, ω. s =200*2π, where t represents time.

[0045] i α and i β The two-phase exciter stator α-phase and β-phase currents collected in step one; i α1 and i β1 The exciter's two-phase currents after coordinate transformation; Let be the coordinate transformation matrix, where θ is the coordinate transformation angle, and:

[0046] When the excitation magnetic field of the exciter rotates in the same direction as the motor (referred to as co-directional excitation), θ = -5ω s t;

[0047] When the excitation magnetic field of the exciter rotates in the opposite direction to the rotation of the motor (referred to as reverse excitation), θ = 5ω s t;

[0048] The two-phase current waveform of the exciter stator after coordinate transformation (i.e., i) α1 and i β1 )like Figure 4 As shown.

[0049] 3. The two-phase current i of the exciter after coordinate transformation α1 and i β1 The signal is filtered by a Butterworth low-pass filter with a cutoff frequency of 300Hz. After low-pass filtering, the cosine signal related to the exciter rotor position (denoted as f) is obtained. cos ) and sin signal (denoted as f) sin ),like Figure 5 As shown.

[0050] Specifically:

[0051] Here, LPF represents low-pass filtering.

[0052] 4. Regarding the above f cos and f sin After processing with a phase-locked loop, the electrical angle θ of the exciter rotor position is obtained as 6 times the angle θ. 6e ,like Figure 6 As shown. Figure 6 Dividing the angle shown by 6 yields the electrical angle θ of the exciter rotor position. e .

[0053] That is, θ 6e =6θ e , where θ e Let θ be the electrical angle of the exciter rotor position. Then, the electrical angle θ of the exciter rotor position can be obtained. e .

[0054] 5. Subtract the initial value of the exciter rotor position electrical angle from the obtained exciter rotor position electrical angle to obtain the increment value of the exciter rotor position electrical angle (denoted as Δθ). e ), that is, Δθ e =θ e -θ e0 Where θ e0The initial electrical angle value of the exciter rotor position is the exciter rotor position obtained by the steps described above when the system is stationary.

[0055] 6. Divide the obtained electrical angle increment of the exciter rotor position by the number of pole pairs (6) to obtain the mechanical angle increment of the exciter rotor position. Since the exciter and the main motor are coaxially mounted, the mechanical angle increment of the exciter rotor position is also the mechanical angle increment of the main motor rotor position. Multiply the obtained mechanical angle increment of the main motor rotor position by the number of pole pairs of the main motor to obtain the electrical angle increment of the main motor rotor position. Finally, add the initial electrical angle value of the main motor rotor position to obtain the main motor rotor position, which is the rotor position of the multi-stage brushless synchronous motor. Figure 7 The figure shows the final estimated position of the main motor rotor, the actual rotor position, and the estimation error.

Claims

1. A method for estimating the rotor position in the low-speed section of a multi-stage motor based on exciter harmonics, characterized in that, A multi-stage brushless synchronous motor includes a coaxially mounted main motor and a two-phase exciter. The low-speed rotor position of the multi-stage brushless synchronous motor refers to the low-speed rotor position of the main motor in the multi-stage brushless synchronous motor. The method includes the following steps: Step 1: Apply two-phase symmetrical voltages to the stator windings of the two-phase exciter, and simultaneously collect the two-phase stator currents of the two-phase exciter; Step 2: Perform coordinate transformation on the stator currents of the two-phase exciter. Specifically, the transformation method is to left-hand coordinate transformation matrix on the stator currents of the two-phase exciter. ,in The coordinate transformation angle is then applied, followed by low-pass filtering to obtain the cosine and sinine signals related to the exciter rotor position, denoted as [reference 1], [reference 2], [reference 3], [reference 4], [reference 5], [reference 6], [reference 7], [reference 8], [reference 9], [reference 10], [reference 11], [reference 12], [reference 13], [reference 14], and ; Step 3: Based on the position of the exciter rotor and The signal indicates the position of the exciter rotor; Step 4: Based on the position of the exciter rotor at low speed and the initial position of the exciter rotor Obtain the rotor position increment of the exciter Low-speed exciter rotor position The exciter rotor position obtained from steps 1 to 3 above is used when the system is at low speed. The initial position of the exciter rotor is... The exciter rotor position is obtained from steps 1 to 3 above when the system is at rest. Step 5: Determine the position of the main motor rotor based on the exciter rotor position increment and the initial position of the main motor rotor, which is the rotor position of the multi-stage brushless synchronous motor. The coordinate transformation of the two-phase current of the exciter stator in step 2 is as follows: in, and The two-phase exciter stator sample collected in step one Harmony Phase current; and The exciter's two-phase currents after coordinate transformation; Let be the coordinate transformation matrix, where For coordinate transformation angle, and: When the excitation magnetic field of the exciter rotates in the same direction as the motor, it is called co-directional excitation. ; When the excitation magnetic field of the exciter rotates in the opposite direction to the rotation direction of the motor, it is called reverse excitation. ; in, It is the excitation angular frequency of the exciter stator. Indicates time.

2. The method for estimating the rotor position of a multi-stage motor in the low-speed range based on exciter harmonics according to claim 1, characterized in that, Step 2 involves low-pass filtering the coordinate-transformed two-phase currents of the exciter to obtain the cosine signal related to the rotor position of the exciter. and sin signal Specifically: Here, LPF represents low-pass filtering.

3. The method for estimating the rotor position of a multi-stage motor in the low-speed range based on exciter harmonics according to claim 1, characterized in that, Step 3 yields the following results: and After processing with a phase-locked loop, the electrical angle of the exciter rotor position is obtained as 6 times the angle. ,Right now ,in The electrical angle of the exciter rotor position is given; thus, the electrical angle of the exciter rotor position is obtained. .

4. The method for estimating the rotor position of a multi-stage motor in the low-speed range based on exciter harmonics according to claim 1, characterized in that, In step 5, the obtained electric angle increment value of the exciter rotor position is divided by the number of pole pairs of the exciter to obtain the mechanical angle increment value of the exciter rotor position. Then, it is multiplied by the number of pole pairs of the main motor to obtain the electric angle increment value of the main motor rotor position. Finally, the initial value of the electric angle of the main motor rotor position is added to obtain the rotor position of the main motor, which is the rotor position of the multi-stage brushless synchronous motor.

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