Method for identifying inductance of surface-mounted permanent magnet motor by using observer

Abstract

The invention provides an observer-based surface-mounted permanent magnet motor inductance identification method, which has the following remarkable advantages: firstly, by selecting a flux linkage as an estimation target of an observer, the stability problem caused by the fact that inductance exists in a motor mathematical model in a denominator form in a traditional method is avoided; the stability and the accuracy of the inductance identification process are ensured; secondly, the method can dynamically estimate the inductance value of the motor in real time, fully considers the change of the inductance under different working conditions, and overcomes the limitation that the traditional static measurement method cannot reflect the inductance fluctuation, thereby realizing the real-time tracking and accurate estimation of the inductance value. The inductance identification method not only can effectively support the high-performance control requirement of the surface-mounted permanent magnet motor, but also provides a new thought and technical path for inductance estimation of other types of motors, thereby providing reliable technical guarantee for improving the overall performance and stability of a motor system; wide application prospects and research values are realized.

Description

Technical Field

[0001] The invention belongs to the field of permanent magnet motor inductance identification, and in particular relates to a method for identifying the inductance of a surface-mounted permanent magnet motor by using an observer. Background Art

[0002] Surface-mounted permanent magnet motors have been widely used in electric vehicles, industrial automation, robotics and other fields due to their high power density, excellent electromagnetic properties and high efficiency. Inductance is a key parameter of surface-mounted permanent magnet motors. It directly affects the motor's back electromotive force, torque output and current waveform, and is the basis of high-performance control strategies. Accurately obtaining the real-time value of motor inductance is one of the keys to achieving high-performance control systems. However, accurate acquisition of inductance values ​​is a difficult point. Traditional inductance measurement methods usually rely on external instruments for offline measurement, and the obtained inductance value is usually used as a constant value. Although this method is simple, it cannot reflect the fluctuation of inductance in real time as the motor's working state and environmental changes occur. In order to solve this problem, online inductance identification methods have emerged. One of the common online identification methods is the identification method based on high-frequency signal injection. This method injects a high-frequency signal into the motor control system and then estimates the inductance value of the motor through the response characteristics of the signal. For example, Guo Honghao et al. proposed a technology for identifying motor inductance using high-frequency injection signals and system responses in the patent "Permanent Magnet Synchronous Motor Inductance Parameter Identification Method Based on High-Frequency Rotating Voltage Injection". This method excites the motor system through the disturbance of high-frequency signals, so that the inductance value of the motor can be estimated online and dynamically adjusted according to actual needs.

[0003] At present, observers are important tools for identifying parameters such as motor back EMF, but they are rarely used to directly observe inductance. The reason is that inductance does not directly affect the motor state as an independent variable like back EMF. Inductance usually appears as a denominator in the motor mathematical model (mathematical expression), which makes it difficult to ensure the stability of the observer when designing the observer. Therefore, the traditional observer that directly targets inductance has low accuracy in use.

[0004] The present invention proposes a method for identifying the inductance of a surface-mounted permanent magnet motor using an observer. Different from the traditional observer concept, the present invention does not directly use the inductance as the estimation target of the observer, but selects the variable, flux, which is independent of the denominator of the motor mathematical model and does not change much in practical applications, as the target of the observer. Then, the motor inductance value is calculated through the observation error of the flux and the relationship between the flux and the inductance change. This method breaks through the limitations of traditional observers in inductance identification, not only improves the stability of inductance identification, but also can estimate the inductance change in real time and dynamically, with significant advantages and broad application prospects. Summary of the invention

[0005] In order to obtain the inductance value of a surface-mounted permanent magnet motor online, the present invention proposes a method for identifying the motor inductance using an observer. The method selects flux as the estimation target and combines the relationship between the observation error of flux and the inductance change to dynamically estimate the motor inductance, thereby overcoming the limitations of traditional methods in inductance identification.

[0006] A method for identifying the inductance of a surface-mounted permanent magnet motor using an observer, characterized by the following steps:

[0007] Step 1: Collect voltage, speed, current and position: Use voltage sensor to measure the three-phase voltage of surface-mount permanent magnet motor, recorded as u a ,u b ,u c , use the position sensor to simultaneously measure the motor speed and rotor position information, denoted as ω m and θ, the three-phase current of the motor is measured by the current sensor, denoted as i a ,i b ,i c ;

[0008] Step 2: Coordinate transformation: transform the collected three-phase voltage u a ,u b ,u c and three-phase current i a ,i b ,i c Use the following calculation formula to transform the voltage and current information into the d and q axis coordinate system:

[0009]

[0010] Among them, u d ,u q is the voltage in the d,q axis coordinate system, i d ,i q is the current in the d,q axis coordinate system;

[0011] Step 3: Build a surface-mount permanent magnet motor flux observer: Use the motor resistance R s And the inductance parameter L s , and the speed ω m 、Voltage u q and current (i d and i q ) and other state quantities to establish the surface-mounted permanent magnet motor flux observer as follows:

[0012]

[0013] In the formula, i q *is the estimated current of the observer, p is the number of pole pairs of the surface-mounted permanent magnet motor, λ is the proportionality coefficient, satisfying the condition of λ≥1, ψ f * To estimate the flux linkage, F(i q * -i q ) is a switching function that satisfies the following characteristics:

[0014]

[0015] Step 4: Set the initial inductance value: Set the observer inductance value L established in step 3 to s Randomly set to an initial value less than 0.5, using L s0 It is indicated that it is used as an initial estimate of the inductance;

[0016] Step 5: Estimate the flux linkage value: L s0 Substitute into the surface mounted permanent magnet motor flux observer in step 3 to estimate the motor flux, denoted as ψ f0 * :

[0017] Step 6: Calculate the motor inductance: Substitute the observer’s estimated current i q * , the number of pole pairs p of the surface-mounted permanent magnet motor, the motor speed ω m , L s0 and ψ f0 * Substitute the following formula to calculate the motor inductance:

[0018]

[0019] Among them, ψ fr It is the flux linkage value of the surface mounted permanent magnet motor. It is an inherent parameter of the motor and is provided by the motor manufacturer.

[0020] The beneficial effects of the present invention are as follows: the present invention proposes an observer-based surface-mounted permanent magnet motor inductance identification method, which has the following significant advantages: first, by selecting flux linkage as the estimation target of the observer, the stability problem caused by the presence of inductance in the denominator in the motor mathematical model in the traditional method is avoided, ensuring the stability and accuracy of the inductance identification process; secondly, the method can estimate the motor inductance value in real time and dynamically, fully considering the changes in inductance under different working conditions, overcoming the limitation of traditional static measurement methods that cannot reflect inductance fluctuations, thereby realizing real-time tracking and accurate estimation of inductance values. The inductance identification method of the present invention can not only effectively support the high-performance control requirements of surface-mounted permanent magnet motors, but also provide a new idea and technical path for inductance estimation of other types of motors, which provides a reliable technical guarantee for improving the overall performance and stability of the motor system, and has broad application prospects and research value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of an observer-based surface-mounted permanent magnet motor inductance identification method. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0023] Inductance is an important parameter that affects the performance of surface-mounted permanent magnet motors. Accurately obtaining the inductance value is of great significance for optimizing the control strategy of the motor and improving the efficiency and reliability of the motor. Traditional inductance measurement methods mostly rely on offline instrument measurement. This method has the limitation of not being able to reflect the change of inductance in real time and cannot adapt to the change of inductance of the motor under dynamic working conditions. In addition, online inductance identification methods also face certain challenges, especially the lack of methods for stably estimating the inductance value of the motor using an observer. Therefore, how to use an observer to achieve high-precision, real-time online estimation of the inductance of the motor has become a key issue in the field of motor control. The present invention proposes an observer-based surface-mounted permanent magnet motor inductance identification method: first, the flux linkage is selected as the estimation target of the observer, avoiding the stability problem caused by the inductance as the denominator in the mathematical model of the motor; secondly, the motor inductance value is calculated by measuring the current and voltage signals of the motor in real time and combining the relationship between the flux linkage and the inductance change. This method can estimate the motor inductance dynamically and in real time, overcome the limitations of traditional static measurement methods, and effectively solve the problem of difficulty in identifying the inductance of the permanent magnet motor using an observer. The present invention proposes an observer-based surface-mounted permanent magnet motor inductance identification method process as follows: Figure 1 In this embodiment, some parameters of the surface-mounted permanent magnet motor are as follows: s is 0.5Ω, the flux linkage ψ provided by the manufacturer fr is 0.083Wb, the permanent magnet logarithm p is 3, and the observer-based surface-mounted permanent magnet motor inductance identification method is implemented as follows:

[0024] Step 1: Collect voltage, speed, current and position

[0025] Use the voltage sensor to measure the three-phase voltage of the surface-mounted permanent magnet motor, denoted as u a ,u b ,u c , use the position sensor to simultaneously measure the motor speed and rotor position information, denoted as ω m and θ, the three-phase current of the motor is measured by the current sensor, denoted as i a ,i b ,i c .

[0026] Step 2: Coordinate Transformation

[0027] The collected three-phase voltage u a ,u b ,u c and three-phase current i a ,i b ,i c Use the following calculation formula to transform the voltage and current information u in the d and q axis coordinate system d ,u q and i d ,i q :

[0028]

[0029] Step 3: Build a Surface-mounted Permanent Magnet Motor Flux Observer

[0030] Using the motor's resistance R s And the inductance parameter L s , and the speed ω m 、Voltage u q and current (i d and i q ) and other state quantities to establish the surface-mounted permanent magnet motor flux observer as follows:

[0031]

[0032] In the formula, i q * is the estimated current of the observer, p is the number of pole pairs of the surface-mounted permanent magnet motor, λ is the proportionality coefficient, satisfying the condition of λ≥1, ψ f * To estimate the flux linkage, F(i q * -i q ) is a switching function that satisfies the following characteristics:

[0033]

[0034] Set p=3, R s =0.5 and substitute it into the observer, we can get:

[0035]

[0036] Step 4: Set the initial inductance value

[0037] The observer inductance value L established in the third step s Randomly set to 0.1, that is, L s0 =0.1 and use it as the initial estimate of the inductance;

[0038] Step 5: Estimate the magnetic linkage value

[0039] L s0 =0.1Substitute into the surface-mounted permanent magnet motor flux observer in the third step to estimate the motor flux, denoted as ψ f0 * :

[0040] Step 6: Calculate Motor Inductance

[0041] The estimated current i of the observer is q * , the number of pole pairs of the surface-mounted permanent magnet motor p = 3, the motor speed ω m , L s0 =0.1,ψ fr = 0.083 and ψ f0 * Substitute the following formula to calculate the motor inductance:

[0042]

Claims

1. A method for identifying the inductance of a surface-mounted permanent magnet motor using an observer, characterized in that Here are the steps: Step 1: Collect voltage, speed, current and position: Use voltage sensor to measure the three-phase voltage of surface-mount permanent magnet motor, denoted as u a ,u b ,u c , use the position sensor to simultaneously measure the motor speed and rotor position information, denoted as ω m and θ, the three-phase current of the motor is measured by the current sensor, denoted as i a ,i b ,i c ; Step 2: Coordinate transformation: transform the collected three-phase voltage u a ,u b ,u c and three-phase current i a ,i b ,i c Use the following calculation formula to transform the voltage and current information into the d and q axis coordinate system: Among them, u d ,u q is the voltage in the d,q axis coordinate system, i d ,i q is the current in the d,q axis coordinate system; Step 3: Build a surface-mount permanent magnet motor flux observer: Use the motor resistance R s And the inductance parameter L s , and the speed ω m 、Voltage u q and current (i d and i q ) and other state quantities to establish the surface-mounted permanent magnet motor flux observer as follows: In the formula, i q * is the estimated current of the observer, p is the number of pole pairs of the surface-mounted permanent magnet motor, λ is the proportionality coefficient, satisfying the condition of λ≥1, ψ f * To estimate the flux linkage, F(i q * -i q ) is a switching function that satisfies the following characteristics: Step 4: Set the initial inductance value: Set the observer inductance value L established in step 3 to s Randomly set to an initial value less than 0.5, using L s0 It is indicated that it is used as an initial estimate of the inductance; Step 5: Estimate the flux linkage value: L s0 Substitute into the surface mounted permanent magnet motor flux observer in step 3 to estimate the motor flux, denoted as ψ f0 * : Step 6: Calculate the motor inductance: Substitute the observer’s estimated current i q * , the number of pole pairs p of the surface-mounted permanent magnet motor, the motor speed ω m , L s0 and ψ f0 * Substitute the following formula to calculate the motor inductance: Among them, ψ fr It is the flux linkage value of the surface mounted permanent magnet motor. It is an inherent parameter of the motor and is provided by the motor manufacturer.

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