A multi-stage motor low-speed rotor position estimation method

Abstract

The application relates to a multi-stage motor low-speed section rotor position estimation method, which is a multi-stage motor low-speed section rotor position real-time estimation method based on low-frequency rotating signal injection. A forward rotating low-frequency voltage signal is injected into a main motor stator winding, two-phase excitation motor stator winding currents are collected in real time, the main motor excitation current is estimated in real time, the estimated excitation current is filtered through a band-pass filter, and the forward rotating low-frequency voltage signal and the excitation current are respectively subjected to single-phase phase-locked loops; the difference increment of the two phase-locked loop outputs is the main motor rotor position increment. The method is not affected by the saliency of the main motor and the rotor position of the excitation motor, has high estimation accuracy, and is simple in signal extraction and position estimation, and has low requirements on the processor performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric machines, and relates to a rotor position estimation method for a multi-stage electric machine in a low-speed section, in particular to a rotor position real-time estimation method for a multi-stage brushless electrically excited synchronous electric machine in a low-speed section based on low-frequency rotating signal injection and independent of the saliency of the electric machine and the rotor position of an exciter. BACKGROUND

[0002] A three-stage brushless synchronous electric machine has the advantages of good power generation quality and high reliability, and has been widely used in aircraft power supply systems as a generator. The three-stage brushless synchronous electric machine is operated in a motor state to drive the aircraft engine to start, and after the start is completed, the engine is used to drive the three-stage brushless synchronous electric machine to operate in a generator state to supply power to the on-board electrical equipment, that is, the start and generation integration of the three-stage brushless synchronous electric machine is realized, the special starter for the engine can be omitted, the system size and weight are reduced, and the integration level is improved, which is of great significance to the aircraft power supply system.

[0003] When the three-stage brushless synchronous electric machine is operated in a motor state to drive the aircraft engine to start, accurate rotor position information is required. The traditional mechanical position sensor for obtaining the rotor position has the problems of low reliability and increased system size and weight. Online estimation of the rotor position of the three-stage brushless synchronous electric machine can omit the mechanical position sensor, realize start control without a position sensor, improve system reliability, and reduce the size and weight.

[0004] The three-stage brushless synchronous electric machine is composed of a permanent magnet auxiliary exciter, an exciter and a main electric machine which are coaxially installed, and a structural diagram thereof is shown in FIG. 1. In some applications, the permanent magnet auxiliary exciter can be omitted to form a two-stage brushless synchronous electric machine. Since the core components and operating principles are basically the same, the three-stage brushless synchronous electric machine and the two-stage brushless synchronous electric machine are collectively referred to as a multi-stage brushless synchronous electric machine. Figure 1

[0005] The traditional rotor position estimation method for the low-speed section of the multi-stage brushless synchronous electric machine is mostly based on the saliency of the main electric machine. However, when the multi-stage brushless synchronous electric machine is operated in a motor state to drive the aircraft engine to start, the saliency of the main electric machine changes, resulting in failure of the traditional method. The rotor position estimation method based on "main electric machine injection-excitation machine detection" is independent of the saliency of the main electric machine. When the main electric machine injects, the excitation machine detects and processes the signal, complex square and filtering operations are required to extract the signal. The rotor position estimation method based on no high-frequency signal injection includes the excitation machine current harmonic method and the excitation machine rotor current trajectory method, but the estimation method is relatively complex and the calculation amount is large, which requires high controller operation capability.

[0006] ​In summary, the current multi-stage brushless synchronous motor rotor position estimation method in low speed section mainly faces two problems: 1) the change of saliency in low speed process will cause the failure of traditional low speed section rotor position estimation method based on saliency; 2) the rotor position estimation method independent of saliency is complex, large in calculation amount, and high in requirement for controller performance. SUMMARY

[0007] Technical problems to be solved

[0008] In order to avoid the shortcomings of the prior art, the present application proposes a multi-stage motor low speed section rotor position estimation method, which overcomes the shortcomings of the prior art in dependence on saliency and large data processing amount in the low speed section rotor position estimation technology.

[0009] Technical scheme

[0010] A multi-stage motor low speed section rotor position estimation method, characterized in that the rotor position of the multi-stage brushless electrically excited synchronous motor refers to the rotor position of the main motor in the multi-stage brushless electrically excited synchronous motor, and the estimation steps are as follows:

[0011] Step 1: apply two-phase symmetric voltage on the two-phase excitation machine stator winding, collect the stator current of the two-phase excitation machine, and estimate the real-time excitation current of the main motor to obtain the real-time estimated excitation current

[0012] Step 2: when the main motor excitation current is stable, apply a forward rotating low frequency voltage on the main motor stator winding, send the forward rotating low frequency voltage signal into a first single-phase phase-locked loop 1, and send the estimated excitation current after band-pass filtering into a second single-phase phase-locked loop 2;

[0013] Step 3: when the output frequencies of the first single-phase phase-locked loop 1 and the second single-phase phase-locked loop 2 are stable, the outputs of the first single-phase phase-locked loop 1 and the second single-phase phase-locked loop 2 are and , the phase difference of the two phase-locked loops is and is a fixed value;

[0014] Step 4: the initial position of the main motor is recorded as , and , and the difference between ;

[0015] Step 5: when starting the motor, the outputs of the first single-phase phase-locked loop 1 and the second single-phase phase-locked loop 2 are and , and the dynamic difference is ; then the real-time position of the main motor rotor before compensation in the low speed section is:

[0016] ​ ;

[0017] Step 6: the real-time speed of the motor during starting process is , then the real-time position of the rotor of the main motor after compensation in low-speed section is:

[0018]

[0019] wherein: is the compensation coefficient.

[0020] The multi-stage brushless electrically excited synchronous motor comprises a main motor and a two-phase excitation motor coaxially installed.

[0021] The step 1 applies two-phase symmetrical voltage on the stator winding of the two-phase excitation motor: wherein, and are the two-phase excitation motor stator winding voltage, is the voltage amplitude, is the voltage fundamental angular velocity, is the time.

[0022] The excitation current of the step 1 is: wherein, , and are the estimated three-phase current of the rotor of the two-phase excitation motor, and have:

[0023]

[0024] wherein, and can be any fixed value, is the excitation motor stator-rotor mutual inductance, is the stator winding resistance, is the time differential, and are the two-phase excitation motor stator current collected in real time in step one, is the excitation motor stator inductance.

[0025] The step 2 applies a forward rotating low-frequency voltage on the stator winding of the main motor, and the expression of the low-frequency voltage in the axis is: wherein, is the voltage amplitude, is the time, is the voltage angular velocity, and the period of the low-frequency voltage is .

[0026] The compensation coefficient wherein: is the maximum speed in low-speed section, Maximum estimated error caused by the filter.

[0027] The center frequency of the band-pass filter Bandwidth Satisfies the condition Wherein The number of main motor pole pairs.

[0028] The multi-stage brushless electrically excited synchronous motor further comprises a coaxially installed main motor and a three-phase excitation motor, and the three-phase voltage or the collected three-phase current is subjected to Clark transformation, i.e. And , And .

[0029] Advantages

[0030] The multi-stage motor low-speed section rotor position estimation method provided by the application is a multi-stage motor low-speed section rotor position real-time estimation method based on low-frequency rotating signal injection. A forward rotating low-frequency voltage signal is injected into the main motor stator winding, and two-phase excitation motor stator winding currents are collected in real time, the main motor excitation current is estimated in real time, and the estimated excitation current is filtered through a band-pass filter, and the forward rotating low-frequency voltage signal is subjected to single-phase phase-locked loop, respectively. The increment of the difference between the outputs of the two phase-locked loops is the increment of the main motor rotor position. The method provided by the application is not affected by the saliency of the main motor and the rotor position of the excitation motor, has high estimation accuracy, and the signal extraction and position estimation method is simple, and the processor performance requirement is low.

[0031] The advantages of the application include:

[0032] 1) Based on the mutual inductance between the main motor stator and rotor, the low-speed section rotor position estimation method of the traditional method is avoided, so that the starting failure problem caused by the disappearance of the saliency of the main motor and the reverse rotation during the starting process of the multi-stage motor is avoided;

[0033] 2) Based on the estimated main motor excitation current and the two single-phase phase-locked loops, the low-speed section main motor rotor position is estimated in real time, and the increment of the difference between the outputs of the two single-phase phase-locked loops is the increment of the main motor rotor position, avoiding the complex square sum operation and filter link processing in the traditional "main motor injection-excitation motor detection" method, and the method is simpler;

[0034] 3) The existing low rotor position estimation methods based on exciter current trajectory method and main motor estimated excitation current variance method need to collect, store and process the excitation current of the exciter in one cycle, which requires high processor performance. The application avoids excessive data storage and mathematical operation, thus requiring lower processor performance and being easier to popularize.

[0035] 4) The simulation results are shown in Figure 7 The estimation error is within 0.1 radian, i.e. 5.7°, which can meet the demand of the field that the error is within 10°. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Fig. 1 is a structural schematic diagram of a three-stage brushless synchronous motor.

[0037] Figure 2 Fig. 3 is a flow chart of the low-speed rotor position estimation method of the multi-stage brushless synchronous motor according to the application.

[0038] Figure 3 Fig. 4 is a waveform diagram of the low-frequency rotating signal injected into the main motor stator winding according to the application.

[0039] Figure 4 Fig. 5 is a waveform diagram of the estimated excitation current of the main motor and the extracted low-frequency signal after passing through a band-pass filter according to the application.

[0040] Figure 5 Fig. 6 is a waveform diagram of the output of two single-phase phase-locked loops during the starting process according to the application.

[0041] Figure 6 Fig. 7 is a comparison diagram of the given speed and the feedback speed according to the application.

[0042] Figure 7 Fig. 8 is a result diagram of the actual position and the estimated position of the main motor and the estimation error according to the application. DETAILED DESCRIPTION

[0043] The application will be further described in combination with embodiments and drawings:

[0044] The new low-speed rotor position estimation method of the multi-stage motor is applied to a multi-stage brushless electrically excited synchronous motor, which comprises a main motor and a two-phase exciter coaxially installed. The rotor position of the multi-stage brushless electrically excited synchronous motor refers to the rotor position of the main motor in the multi-stage brushless electrically excited synchronous motor.

[0045] In the embodiment, the exciter of the multi-stage brushless synchronous motor is a two-phase exciter, i.e. the exciter stator excitation winding is a two-phase winding with a mutual electrical angle of 90°. The exciter has 6 pairs of poles, and the main motor has 3 pairs of poles. The following will be described in detail taking the main motor speed from 0-240 rpm as an example.

[0046] 1. Apply two-phase symmetrical voltage on the two-phase exciter stator winding, and collect the two-phase exciter stator current to estimate the real-time excitation current of the main motor, denoted as ;

[0047] The two-phase exciter stator voltage is:

[0048] (1)

[0049] wherein, and are the two-phase exciter stator winding voltage, is the voltage amplitude, is the voltage fundamental angular velocity, is the time, and the estimated excitation current of the main motor is:

[0050] (2)

[0051] wherein, , and are the estimated two-phase exciter rotor three-phase current, and have:

[0052] (3)

[0053] wherein, and can be any fixed value, is the exciter stator-rotor mutual inductance, is the stator winding resistance, is the time differential, and are the two-phase exciter stator currents collected in step one, is the exciter stator inductance;

[0054] In the embodiment, two-phase symmetrical voltage is applied on the two-phase exciter stator winding (denoted as α-phase winding and β-phase winding, respectively), the excitation voltage amplitude is 50V, the excitation frequency is 200Hz, the two-phase exciter stator two-phase current is collected, denoted as and , and have:

[0055] (4)

[0056] Any is selected, and the excitation current of the main motor can be estimated according to formula (2) and (3). When the error between and the real position of the exciter is , which is referred to as the ideal error of the exciter, only the direct current in the estimated steady-state excitation current of the main motor, which can be represented as When The estimated main motor steady-state field current has a direct current and a periodic alternating current with a frequency of 6 times the frequency of the field motor stator voltage when the error between the actual position of the field motor and the position of the field motor is other values, and the estimated field current can be expressed as ;

[0057] 2. After the main motor field current is stable, a forward rotating low-frequency voltage is applied to the main motor stator winding, the forward rotating low-frequency voltage signal is sent to a single-phase phase-locked loop 1, and the estimated field current is sent to a single-phase phase-locked loop 2 after being filtered by a band-pass filter, and the bandwidth and center frequency of the band-pass filter are determined by the low-frequency voltage frequency and the maximum speed in the low-speed section.

[0058] The forward rotating low-frequency voltage applied to the main motor stator winding is The expression of the shaft is:

[0059] (5)

[0060] Wherein, is the voltage amplitude, is the time, is the voltage angular velocity, and the low-frequency voltage period is ;

[0061] The estimated field current is filtered by a band-pass filter, and the center frequency and bandwidth of the band-pass filter are and , and can be expressed as:

[0062] (6)

[0063] Wherein is the number of pole pairs of the main motor, satisfies the condition:

[0064] (7)

[0065] The low-frequency voltage amplitude injected in the embodiment is , , the injected forward rotating low-frequency signal is as shown in Figure 3 , and can be expressed as:

[0066] (8)

[0067] The center frequency of the band-pass filter is , and the bandwidth is selected as , and the estimated field current expression under the condition of more complex field motor non-ideal error is:

[0068] (9)

[0069] wherein is the low frequency current amplitude induced by the low frequency injection, is the actual rotor position, is the phase delay caused by signal transmission, After the band-pass filter, the expression of the extracted low frequency signal is:

[0070] (10)

[0071] wherein is the low frequency current amplitude after the band-pass filter, is the total phase delay caused by signal transmission;

[0072] 3. After the output frequency of single-phase phase-locked loops 1 and 2 is stabilized, the outputs are recorded as and , and the difference is recorded as , and is a fixed value.

[0073] 4. The initial position of the main motor is recorded as , and , and the difference is recorded as .

[0074] 5. The starting motor, and the outputs of single-phase phase-locked loops 1 and 2 are recorded as and , and the dynamic difference is , and the real-time position of the rotor of the main motor before compensation in the low-speed section can be expressed as:

[0075] (11)

[0076] 6. When the maximum speed of the low-speed section is reached r / min, the maximum estimation error caused by the filter is , and the compensation coefficient is:

[0077] (12)

[0078] Step seven: the real-time speed of the motor during the starting process is , and the real-time position of the rotor of the main motor after compensation in the low-speed section can be expressed as:

[0079] (13)

[0080] In the embodiment, when the maximum speed of the low-speed section is reached 240 r / min, the maximum estimation error caused by the filter is radians, and the compensation coefficient is:

[0081] (14)

[0082] 7. The real-time speed of the motor during starting is The real-time position of the rotor of the main motor after compensation in the low-speed section can be expressed as:

[0083] (15)

[0084] In the present application, when the excitation current of the main motor is estimated, if in the ideal error state of the excitation mechanism, is always 0, After the band-pass filter, the expression of the extracted low-frequency signal is the same as that in the non-ideal error state of the excitation mechanism.

Claims

1. A method for estimating rotor position in a low speed range of a multi-stage electric machine, characterized by The rotor position of the multi-stage brushless electrically excited synchronous motor refers to the rotor position of a main motor in the multi-stage brushless electrically excited synchronous motor, and the estimation steps are as follows: Step 1: two-phase symmetric voltage is applied on the stator winding of the two-phase exciter, the stator current of the two-phase exciter is collected to estimate the real-time excitation current of the main motor, and the real-time estimated excitation current is obtained ; Step 2: When the main motor excitation current is stable, a positive rotating low-frequency voltage is applied to the main motor stator winding, the positive rotating low-frequency voltage signal is sent into the first single-phase phase-locked loop 1, and the estimated excitation current After band-pass filtering, it is sent into the second single-phase phase-locked loop 2; Step 3: When the first single-phase phase-locked loop 1 and the second single-phase phase-locked loop 2 output frequency stability, the output of the first single-phase phase-locked loop 1 and the second single-phase phase-locked loop 2 is and The phase difference of the two phase-locked loops is and is a fixed value; Step 4: The initial position of the main motor is recorded as , The difference between and is recorded as Step 5: When the motor is started, the outputs of the first single-phase phase-locked loop 1 and the second single-phase phase-locked loop 2 are and , and the dynamic difference is ; then the real-time position of the main motor rotor before low-speed stage compensation is: ； Step 6: Real-time speed of motor during starting process is Then the real-time position of the main motor rotor after compensation in the low-speed section is: wherein: is a compensation factor.

2. The method of claim 1, wherein: The multi-stage brushless electrically excited synchronous motor comprises a main motor and a two-phase excitation motor coaxially installed.

3. The method of claim 1, wherein: The step 1 applies a two-phase symmetric voltage on the two-phase exciter stator winding is: wherein, and is the two-phase exciter stator winding voltage, is the voltage amplitude, is the voltage fundamental angular velocity, is the time.

4. The method of claim 1, wherein: the field current of step 1 is: wherein , and are the estimated two-phase field machine rotor three-phase currents, respectively, and have: wherein, and can be any fixed value, is the mutual inductance of the exciter machine stator and rotor, is the stator winding resistance, is the time derivative, and is the real-time sampled two-phase exciter stator current in step one, is the exciter stator inductance.

5. The method of claim 1, wherein: Said step 2 applies a positive rotating low frequency voltage on the main motor stator winding The expression of the shaft is: where, is the voltage amplitude, is the time, is the voltage angular velocity, the low frequency voltage period is .

6. The method of claim 1, wherein: The compensation coefficient wherein: maximum speed in low speed section, in revolutions per minute, maximum estimation error caused by the filter.

7. The method of claim 1, wherein: The bandpass filter center frequency , bandwidth satisfies the condition wherein is the main motor pole pair number, is the voltage angular velocity, rpm is the maximum speed at the low speed stage.

8. The method of claim 1, wherein: The multi-stage brushless electrically excited synchronous motor further comprises a main motor and a three-phase excitation motor coaxially installed, and the three-phase voltage or three-phase current of the three-phase excitation motor is subjected to Clark transformation, i.e. and , and wherein: and is the two-phase excitation motor stator winding voltage, and is the two-phase excitation motor stator current collected in real time in step 1.

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