Main motor rotor position estimation method without parameter

Abstract

The invention relates to the technical field of electrically excited synchronous motors, in particular to a parameter-free main motor rotor position estimation method, which comprises the following steps of: acquiring a resultant current derivative function of an exciter; generating a first square wave signal and a second square wave signal; sampling stator current of the exciter to obtain an envelope signal of a rotor position of the exciter; obtaining a main motor rotor position angle increment; a rotor position of the main motor is estimated. The whole process does not need motor parameters, the calculated amount is smaller, the method is suitable for the full-speed section of the starting process, the stability of the exciter-based nonlinear harmonic rotor position estimation method can be improved, and the estimation result is more accurate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrically excited synchronous motor, in particular to a main motor rotor position estimation method without parameters. BACKGROUND

[0002] The start and power generation integrated system is an important part of the more electric aircraft. In the starting process, the main generator works in the electric state to start the load of the aero-engine, which greatly reduces the volume and weight of the start and power generation integrated system, improves the reliability of the system and the space utilization of the aircraft. The aviation brushless excitation synchronous motor is the key research object of this technology, which is widely used in the aviation field due to its mature power generation technology and high reliability. The brushless excitation synchronous motor mainly consists of a main motor, an exciter, a permanent magnet auxiliary exciter and a rotating rectifier, and its structural diagram is shown in Figure 2 .

[0003] In the starting stage, the high-precision main motor rotor position is the key to realize the high-performance starting control of the brushless excitation synchronous motor. This process is generally realized by a mechanical position sensor installed on the motor shaft. However, most of the time, the main motor operates as a generator, at which time the position sensor utilization is low. In addition, the brushless excitation synchronous motor works in a high-temperature, high-voltage and strong-vibration working environment for a long time, which reduces the reliability of the position sensor. Therefore, the position sensorless starting control of the brushless excitation synchronous motor is an attractive topic.

[0004] Due to the special nonlinear rectification process of the rotating rectifier, a large number of high-order harmonics are brought to the rotor of the exciter. When the motor rotates, the frequency and phase of these harmonics change, which depends on the relative speed of the rotor and the rotating magnetic field. Therefore, these harmonics naturally contain the relevant information of the rotor position of the exciter. Since the main motor and the exciter are coaxially installed, the rotor position of the main motor can be calculated by the rotor position of the exciter, and the initial position of the main motor is added to obtain the rotor position of the main motor.

[0005] The back electromotive force and the flux linkage of the exciter are the direct sources of harmonics. Due to the brushless electrical structure, the back electromotive force needs to be observed to obtain, and this process depends on the correct stator parameters of the exciter. When the parameters have errors, the estimation of the rotor position will also be deviated, which will affect the accuracy of the estimation of the rotor position. And the harmonic demodulation method based on the rotating transformation is only suitable for low-speed working conditions. When the speed of the main motor increases, the relative speed of the rotor and the stator magnetic field continues to change, which will amplify the position estimation error, thereby reducing the accuracy of the estimation of the rotor position.

[0006] Therefore, it is necessary to provide a main motor rotor position estimation method without parameters and suitable for higher speed range to solve the above problems. SUMMARY

[0007] The application provides a parameter-free main motor rotor position estimation method to solve the existing problems.

[0008] The parameter-free main motor rotor position estimation method of the application adopts the following technical scheme, comprising: Obtaining three-phase stator currents of the exciter, converting the three-phase stator currents into stator axis currents of the exciter in a stationary coordinate system, and obtaining a synthesized current derivative function of the exciter according to the stator axis currents of the exciter and the stator axis currents; generating a first square wave signal with the same frequency as the synthesized current derivative function of the exciter, and generating a sine signal with the same frequency and orthogonal phase as the first square wave signal as a second square wave signal; sampling the stator currents of the exciter when the first square wave signal and the second square wave signal are at rising edges to obtain an envelope signal of the rotor position of the exciter; obtaining a rotor position angle increment of the exciter according to the envelope signal of the rotor position of the exciter, and obtaining a rotor position angle increment of the main motor according to the rotor position angle increment of the exciter and the relationship between the pole pairs of the exciter and the main motor; estimating the rotor position of the main motor according to the rotor position angle increment of the main motor and an initial rotor position estimation.

[0009] The further technical scheme of the application is that the step of obtaining the three-phase stator currents of the exciter is that three-phase symmetrical voltages are applied to the stator side of the exciter, and the three-phase stator currents of the exciter are collected.

[0010] The further technical scheme of the application is that the three-phase stator currents of the exciter are subjected to clark transformation to obtain the stator axis currents, and the stator axis currents.

[0011] The further technical scheme of the application is that the stator axis currents of the exciter are obtained.

[0012] In the formula, Iq represents the synthesized current derivative function of the exciter; represents the synthesized current derivative function of the exciter; represents the derivative function of the stator axis currents of the exciter; represents the derivative function of the stator axis currents of the exciter.

[0013] The further technical solution of the present application is that the expression of the envelope signal of the rotor position of the exciter is:

[0014] In the formula, represents the envelope sine signal related to the rotor position of the exciter obtained by sampling the stator current of the exciter when the first square wave signal is at the rising edge; represents the envelope cosine signal related to the rotor position of the exciter obtained by sampling the stator current of the exciter when the second square wave signal is at the rising edge; is the number of pole pairs of the exciter, is the mechanical rotating speed of the exciter when the exciter is running; is the sampling time.

[0015] The further technical solution of the present application is that the exciter angle increment is obtained by inputting the envelope signal of the rotor position of the exciter into a quadrature phase-locked loop, and the exciter rotor position angle increment of the exciter running is obtained according to the exciter angle increment and the rotating speed ratio of the exciter field running rotating speed and the mechanical rotating speed of the exciter when the exciter is running.

[0016] The further technical solution of the present application is that the exciter rotor position angle increment is obtained by dividing the exciter angle increment by the rotating speed ratio of the exciter field running rotating speed and the mechanical rotating speed of the exciter when the exciter is running.

[0017] The further technical solution of the present application is that the step of obtaining the main motor rotor position angle increment according to the exciter rotor position angle increment and the pole pair number relationship of the exciter and the main motor is: obtaining the pole pair number ratio of the main motor and the exciter; dividing the exciter rotor position angle increment by the pole pair number ratio to obtain the main motor rotor position angle increment.

[0018] The further technical solution of the present application is that the main motor rotor position angle increment and the initial rotor position sum are taken as the rotor position of the main motor.

[0019] The present application has the following beneficial effects: Compared with the existing rotor position estimation method based on the rotor flux linkage or back electromotive force of the exciter, the application analyzes the waveform characteristics of the back electromotive force of the exciter in the exciter stator current, i.e. the waveform characteristics of the synthesized current derivative function of the exciter, generates two square wave signals with two phase quadratures and the same frequency as the frequency of the synthesized current derivative function of the exciter based on the waveform characteristics, extracts the envelope signal of the rotor position of the exciter based on the two square wave signals and the exciter stator current signal, and thus realizes the estimation of the rotor position angle increment of the exciter based on the envelope signal of the rotor position of the exciter. Based on the rotor position angle increment of the exciter, the rotor position angle increment of the main motor is obtained based on the pole pair number relationship between the exciter and the main motor, and the rotor position of the main motor is estimated based on the rotor position angle increment and the initial rotor position. The whole process does not require the rotor parameters of the exciter, has smaller calculation amount, is suitable for the full speed range, can improve the stability of the excitation machine nonlinear harmonic rotor position estimation method, and is more accurate in rotor position estimation. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0021] Figure 1 A flowchart of a parameter-free main motor rotor position estimation method of the present application; Figure 2 A structure diagram of a brushless electrically excited synchronous motor in the embodiment; Figure 3 A rotor three-phase current waveform diagram of the exciter; Figure 4 A diagram of the synthesized current derivative function of the exciter; Figure 5 A first square wave signal diagram; Figure 6 A detailed flowchart of the main motor rotor position estimation method proposed by the present application; Figure 7 A rotor actual position result diagram of the main motor in the embodiment of the present application; Figure 8 A main motor rotation angle and exciter rotation angle estimation result diagram in the embodiment of the present application; Figure 9 A rotor estimation position result diagram of the main motor proposed by the present application; Figure 10The error diagram of the actual position of the rotor of the main motor and the estimated position of the rotor according to the application is shown in the figure; Figure 11 The estimated rotating speed of the main motor according to the application is shown in the figure; DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the application.

[0023] An embodiment of the parameter-free rotor position estimation method of the main motor according to the application is shown in the figure, Figure 1 and Figure 6 , which comprises: S1, obtaining the synthesized current derivative function of the exciter; Specifically, the three-phase stator currents of the exciter are obtained, and the three-phase stator currents are converted into the stator axis current and the stator axis current of the exciter in the stationary coordinate system. The stator axis current of the exciter is obtained, and the synthesized current derivative function of the exciter is obtained according to the stator axis current and the stator

[0024] axis current of the exciter. , that is, the three-phase stator currents of the exciter, i.e., the A-phase stator current , the B-phase stator current , and the C-phase stator current , can be collected.

[0025] Specifically, in one embodiment, the step of converting the three-phase stator currents into the axis current and the stator axis current in the stationary coordinate system is that the three-phase stator currents of the exciter are subjected to clark transformation to obtain the stator axis current and the stator axis current of the exciter in the stationary coordinate system, wherein the expression is:

[0026] In the formula, ​The stator of the exciter shaft current; The stator of the exciter Axis current.

[0027] For example, according to the stator of the exciter Shaft current, stator The steps to obtain the derivative of the resultant current of the exciter from the shaft current are as follows: Define the stator of the exciter. The derivative of the shaft current is The stator of the exciter The derivative of the shaft current is The stator of the exciter Shaft current, stator The magnitude of the derivative function corresponding to the shaft current is used as the derivative function of the resultant current of the exciter. That is, the derivative of the resultant current of the exciter. The expression is:

[0028] In the formula, The derivative of the resultant current of the exciter; The stator of the exciter The derivative of the shaft current; The stator of the exciter The derivative of the shaft current.

[0029] In one specific embodiment, the waveform of the derivative function of the exciter's synthesized current is shown below. Figure 4 As shown, from Figure 4 As can be seen from this, the frequency is , in, , This represents the number of pole pairs of the exciter. For mechanical rotation speed, The rotational angular frequency of the three-phase AC voltage applied to the stator side of the exciter; ω is the rotational angular frequency of the exciter rotor.

[0030] S2. Generate the first square wave signal and the second square wave signal; Specifically, a first square wave signal with the same frequency as the derivative function of the exciter's synthesized current is generated; a second square wave signal with the same frequency and orthogonal phase as the first square wave signal is generated.

[0031] For example, in one specific embodiment, the step of generating a first square wave signal with the same frequency as the derivative function of the exciter's synthesized current is: [The text abruptly ends here, likely due to an incomplete sentence or a formatting error.] Sampling is performed, and results are obtained through comparison. Maximum value. When the derivative of the exciter's synthesized current... When the maximum value is reached, the generated signal is momentarily set to 1, and then immediately set to 0. This results in a signal with an indefinite duty cycle, an amplitude varying between 0 and 1, and a frequency of... The square wave signal is denoted as the first square wave signal. .

[0032] For example, in one specific embodiment, the step of generating a sinusoidal signal with the same frequency and orthogonal phase as the first square wave signal as the second square wave signal is: that is, generating a sinusoidal signal with a frequency of Phase and the first square wave signal Orthogonal (i.e., second square wave signal) With the first square wave signal A sinusoidal signal with a phase difference of 90° and an amplitude of 1 is denoted as the second square wave signal. .

[0033] S3. Sample the stator current of the exciter to obtain the envelope signal of the rotor position of the exciter; For example, in one specific embodiment, when the first square wave signal and the second square wave signal are at their rising edges, the stator current of the exciter is sampled to obtain the envelope signal of the exciter rotor position. It should be noted that sampling is not performed when the first square wave signal and the second square wave signal are at their falling edges or 0. The expression for the envelope signal of the exciter rotor position is as follows:

[0034] In the formula, This represents the envelope sinusoidal signal related to the rotor position of the exciter, obtained by sampling the stator current of the exciter when the first square wave signal is at its rising edge. This represents the envelope cosine signal related to the rotor position of the exciter, obtained by sampling the stator current of the exciter when the second square wave signal is at its rising edge. This represents the number of pole pairs of the exciter. The mechanical speed of the exciter during operation; Sampling time.

[0035] S4. Obtain the rotor position angle increment of the main motor; Specifically, the exciter rotor position angle increment is obtained based on the envelope signal of the exciter rotor position, and the main motor rotor position angle increment is obtained based on the exciter rotor position angle increment and the pole pair relationship between the exciter and the main motor.

[0036] For example, in one specific embodiment, the step of obtaining the exciter rotor position angle increment based on the envelope signal of the exciter rotor position is as follows: inputting the envelope signal of the exciter rotor position into the quadrature phase-locked loop to obtain the exciter angle increment; and obtaining the exciter rotor position angle increment based on the ratio of the exciter magnetic field operating speed to the exciter mechanical speed during operation. In this embodiment, the ratio of the exciter magnetic field operating speed to the exciter mechanical speed during operation is 6, that is, the exciter rotor position angle increment can be obtained by dividing the exciter angle increment by 6.

[0037] For example, in one specific embodiment, the step of obtaining the main motor rotor position angle increment based on the exciter rotor position angle increment and the pole pair ratio of the exciter and the main motor is as follows: obtain the pole pair ratio of the main motor and the exciter; divide the exciter rotor position angle increment by the pole pair ratio to obtain the main motor rotor position angle increment.

[0038] S5. Estimate the rotor position of the main motor; For example, in one specific embodiment, the sum of the main motor rotor position angle increment and the initial rotor position is used as the estimated rotor position of the main motor.

[0039] The following is in conjunction with the appendix Figures 3 to 11 The invention is further illustrated by specific simulation data: This example uses MATLAB / Simulink to... Figure 2 The brushless electrically excited synchronous motor shown was simulated and verified. The initial rotor position of the main motor was set as follows: When the time is 0-8s, the excitation frequency of the exciter stator is 200Hz, the speed is 0-500r / min, the number of pole pairs of the exciter is 3, and the number of pole pairs of the main motor is 2.

[0040] Step 1: Obtain the derivative function of the synthesized current of the exciter; First, analyze the waveform characteristics of the exciter's back-electrode during motor operation. The specific steps are as follows: like Figure 3 As shown, the expression for the three-phase rotor current of the exciter in discontinuous commutation mode is analyzed. Within a single commutation cycle, the rotor three-phase current can be expressed as:

[0041] in, The excitation current of the main motor ω is the rotational angular frequency of the exciter rotor; For rotor inductance; The amplitude of the induced electromotive force of the exciter rotor; the three-phase rotor currents are as follows: Phase rotor current , b Phase rotor current , c Phase rotor current .

[0042] Rotor three-phase current abc Coordinates, dq After coordinate transformation and derivation, the derivative of the rotor d axis current of the exciter, q The derivative of the rotor

[0043] In the formula, derivative of the rotor d axis current of the exciter; derivative of the rotor q axis current of the exciter; denotes the differential operator; denotes the derivative of the rotor phase current of the exciter; denotes the derivative of the rotor b phase current of the exciter; denotes the derivative of the rotor c phase current of the exciter; where the rotation matrix C is expressed as:

[0044] In the formula, denotes the rotor position of the exciter.

[0045] derivative of the rotor d axis current of the exciter, q The specific expression of the derivative of the rotor

[0046]

[0047] It can be seen that the derivative of the rotor dq axis current of the exciter can be divided into three parts, Part I, Part II, and Part III; since the rotor inductance is relatively small and the amplitude of the induced electromotive force of the exciter rotor is relatively large, therefore, the derivative of the rotor d axis current of the exciter, q The main part of the derivative of the rotor axis current is the part corresponding to Part I respectively. Part II is small enough compared with Part I and can be ignored. For Part III, since Therefore, Part III can also be neglected compared with Part I, so the rotor of exciter d derivative of shaft current, q The derivative of shaft current can be rewritten as:

[0048] The expression of stator voltage equation of exciter is as follows:

[0049] where, represents mutual inductance between stator and rotor of exciter; represents stator inductance of exciter; represents rotor resistance of exciter; in the voltage expression, , , and are main parts, so the stator derivative of shaft current, stator derivative of shaft current is:

[0050] Then in a single commutation period, the length of the modulus of the derivative of stator current of exciter, i.e. the resultant current derivative of exciter, can be expressed as:

[0051] where, as shown in Figure 4 , the waveform of the resultant current derivative of exciter is a monotone increasing sawtooth wave in a commutation period, and the time length of a single sawtooth wave corresponds to the time length of the commutation process of three-phase rotor current in Figure Four . Since a commutation period is 1 / 6 of the period of rotor current of exciter, the frequency of the resultant current derivative of exciter is , and the frequency of this signal changes with the speed of the motor.

[0052] Step two, generate a first square wave signal and a second square wave signal; The frequency of the first square wave signal and the resultant current derivative of exciter is consistent, i.e. the frequency is , as shown in Figure 5 , the phase of the second square wave signal is orthogonal to the first square wave signal (i.e. the phase of the second square wave signal differs by 90° from the first square wave signal ), and the second square wave signal is orthogonal to the first square wave signal The amplitudes of the two signals are both 1.

[0053] Step three, obtaining the envelope signal of the exciter rotor position; The stator current of the exciter is sampled to obtain the envelope signal of the exciter rotor position when the first and second square wave signals are at the rising edges.

[0054] Step four, obtaining the main motor rotor position angle increment and estimating the rotor position of the main motor; After the estimation process shown in Figure 6 , the main motor rotor position angle increment is obtained. Then, the estimated position of the main motor is obtained by adding the known initial rotor position of the main motor.

[0055] The estimation process is shown in Figures 7-10 . First, Figure 7 The actual rotor position result of the main motor at the start-up is given first, Figure 8 The rotor position angle increment of the exciter (dashed line) obtained by the envelope signal via a quadrature phase-locked loop (QPLL) shown in Figure 6 , and the rotor position angle increment of the main motor (solid line) obtained according to the pole pair number relationship; Figure 9 The estimated rotor position result of the main motor is obtained by adding the known initial position of the main motor to the rotor position angle increment of the main motor; Figure 10 The error between the actual rotor position and the estimated rotor position of the main motor, Figure 11 The estimated speed of the main motor, from Figure 10 It can be found that the error of the start-up process is controlled within plus or minus 5 electrical degrees, which meets the demand of the three-stage motor start-up control without position sensor, and proves the effectiveness and advantages of the method.

[0056] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A parameter-free method for estimating the rotor position of a main motor, characterized in that, include: Obtain the three-phase stator current of the exciter and convert it into the stator current of the exciter in a stationary coordinate system. Shaft current, stator Shaft current; and according to the stator of the exciter. Shaft current, stator The derivative function of the synthesized current of the exciter is obtained from the shaft current. Generate a first square wave signal with the same frequency as the derivative of the synthesized current of the exciter; generate a sine wave signal with the same frequency and orthogonal phase as the first square wave signal as the second square wave signal; When the first square wave signal and the second square wave signal are at their rising edges, the stator current of the exciter is sampled to obtain the envelope signal of the rotor position of the exciter. The exciter rotor position angle increment is obtained from the envelope signal of the exciter rotor position. The main motor rotor position angle increment is obtained from the pole pair relationship between the exciter and the main motor based on the exciter rotor position angle increment. The rotor position of the main motor is estimated based on the rotor position angle increment and the initial rotor position.

2. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, The steps to obtain the three-phase stator current of the exciter are as follows: apply a three-phase symmetrical voltage to the stator side of the exciter and collect the three-phase stator current of the exciter.

3. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, Perform a Clark transform on the three-phase stator currents of the exciter to obtain the values ​​in the stationary coordinate system. shaft current, Axis current.

4. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, According to the stator of the exciter Shaft current, stator The steps to obtain the derivative function of the exciter's synthesized current from the shaft current are as follows: In the formula, This represents the derivative of the exciter's synthesized current. The stator of the exciter The derivative of the shaft current; The stator of the exciter The derivative of the shaft current.

5. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, The expression for the envelope signal of the exciter rotor position obtained by sampling is: In the formula, This represents the envelope sinusoidal signal related to the rotor position of the exciter, obtained by sampling the stator current of the exciter when the first square wave signal is at its rising edge. This represents the envelope cosine signal related to the rotor position of the exciter, obtained by sampling the stator current of the exciter when the second square wave signal is at its rising edge. For the number of pole pairs of the exciter, The mechanical speed of the exciter during operation; Sampling time.

6. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, The envelope signal of the exciter rotor position is input into the quadrature phase-locked loop to obtain the exciter angle increment. Based on the exciter angle increment, the ratio of the operating speed of the exciter magnetic field to the mechanical speed of the exciter during operation is used to obtain the exciter rotor position angle increment during operation.

7. The parameter-free main motor rotor position estimation method according to claim 6, characterized in that, The exciter rotor position angle increment is obtained by dividing the exciter angle increment by the ratio of the exciter magnetic field operating speed to the exciter mechanical speed during operation.

8. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, The steps to obtain the main motor rotor position angle increment based on the exciter rotor position angle increment and the pole pair relationship between the exciter and the main motor are as follows: Obtain the pole pair ratio of the main motor and the exciter; The increment of the exciter rotor position angle is obtained by dividing the pole pair ratio.

9. The parameter-free main motor rotor position estimation method according to claim 1, characterized in that, The rotor position angle increment of the main motor and the sum of the initial rotor position are used as the rotor position of the main motor.

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