CN113541547B - Method for extracting current harmonic characteristic quantity of built-in permanent magnet synchronous motor - Google Patents

Abstract

The invention discloses a method for extracting current harmonic characteristic quantities of a built-in permanent magnet synchronous motor. Sampling to obtain the real-time three-phase current of the built-in permanent magnet synchronous motor; real-time sampling of the rotor position of the built-in permanent magnet synchronous motor to obtain the real-time rotor position angle, and reconstruct the fundamental wave component of the three-phase current; the real-time three-phase current The total harmonic component is obtained by subtracting the fundamental component of the three-phase current, and then the total harmonic component is subjected to 5 synchronous coordinate transformations and 7 synchronous coordinate transformations, and then the first-order low-pass filter is used to obtain the total harmonic component of the three-phase current 5. The characteristic quantity of the 7th-order current harmonic; reprocessing to obtain the 6th-order current harmonic amplitude and the 6th-order current harmonic characteristic quantity in the d and q currents. The invention does not need a complex filter structure, is simple to implement, and can accurately extract the current harmonic characteristic quantity and amplitude in the phase current of the built-in permanent magnet synchronous motor.

Description

A method for extracting current harmonic characteristic quantity of built-in permanent magnet synchronous motor

technical field

The invention relates to a method for processing data of a permanent magnet synchronous motor in the field of motor control, and more specifically relates to a method for extracting current harmonic characteristic quantities of a built-in permanent magnet synchronous motor.

Background technique

The built-in permanent magnet synchronous motor (IPMSM) has the advantages of compact structure and high power density, and is widely used in the drive system of electric vehicles. Ideally, the motor's phase currents should have a standard sinusoidal waveform. However, in the actual operation process, non-ideal factors will cause a certain amount of harmonics in the phase current of the motor, which will cause additional motor loss. Therefore, effective suppression of current harmonics is very important to ensure the steady-state operation quality of IPMSM.

In recent years, some scholars have proposed a current harmonic suppression strategy based on the multi-frequency synchronous rotating coordinate transform (MSRFT), which aims to extract the current harmonic characteristic quantity of a certain frequency in the phase current. The strategy consists of two parts: the extraction of current harmonic features and the injection of harmonic voltage.

The extraction of current harmonic feature is the basis of the current harmonic suppression method. The current method generally has the form of first converting the three-phase current into a DC quantity (corresponding to a current harmonic of a certain frequency in the phase current) and a combination of several AC components through an MSRFT, and then combining the first-order low-pass The filter is used to realize the open-loop extraction of the harmonic characteristic quantity (DC quantity) in the phase current. However, since the fundamental component in the phase current is much larger than the harmonic component, it is difficult for the first-order low-pass filter to completely eliminate the AC value corresponding to the fundamental current in the phase current, so it is difficult to ensure the extraction accuracy of the current harmonic feature. In order to improve the accuracy, a first-order low-pass filter plus a closed-loop feedback method or a higher-performance filter, such as a second-order Butterworth filter and a Type II Chebyshev filter, can be used. However, the implementation method is slightly complicated. Secondly, the current method is only aimed at extracting the characteristic quantities of the 5th and 7th order current harmonics in the phase current.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a method that can simply and accurately extract the 5th and 7th order current harmonic characteristic quantities in the phase current of the built-in permanent magnet synchronous motor and the 6th order in the d and q axis currents The method of current harmonic amplitude and characteristic quantity.

On the basis of simple and accurate extraction of the 5th and 7th order current harmonic characteristic quantities in the phase current, the present invention further accurately realizes the 6th order current harmonic characteristic quantity and the 6th order current harmonic characteristic quantity in the d and q axes Extraction of current amplitude.

As shown in Figure 2, the purpose of the present invention is achieved through the following technical solutions:

The present invention processes the three-phase current obtained by sampling to obtain accurate characteristic quantities of the 5th and 7th order current harmonics in the three-phase current and the amplitude and 6th order current harmonics in the d and q currents. Order current harmonic characteristic quantity.

The method includes the following steps:

1) Sampling and obtaining the real-time three-phase current of the built-in permanent magnet synchronous motor;

2) By sampling the rotor position of the built-in permanent magnet synchronous motor in real time, the real-time rotor position angle is obtained, and the basic value of the three-phase current is reconstructed using the reference values of the d and q-axis currents and the rotor position angle of the built-in permanent magnet synchronous motor. wave component;

3) The real-time three-phase current and the fundamental component of the three-phase current are subtracted to obtain the total harmonic component, and then the total harmonic component is subjected to 5 synchronous coordinate transformations and 7 synchronous coordinate transformations respectively to obtain the transformed quantity, Pass the converted quantity through a first-order low-pass filter to obtain the 5th and 7th-order current harmonic characteristic quantities in the three-phase current;

4) Obtain the 6th order current harmonic amplitude and 6th order current harmonic characteristic quantity in the d and q currents by obtaining the 5th and 7th order current harmonic characteristic quantities in the obtained three-phase current.

The current harmonic feature extracted by the method of the present invention can be more helpful to the suppression of the current harmonic.

In a specific implementation, the obtained 5th and 7th order current harmonic characteristic quantities, the 6th order current harmonic amplitude and the 6th order current harmonic characteristic quantity can further generate harmonic voltages to suppress current harmonics.

In the step 1), the three phases of the built-in permanent magnet synchronous motor are all arranged with current sensors, and each current sensor is connected to the DSP, and the three phases of the built-in permanent magnet synchronous motor are sampled by the current sensors to carry out AD sampling current as the built-in permanent magnet synchronous motor. The real-time three-phase current of the magnetic synchronous motor is sent to DSP for control processing.

In the described step 2), carry out the reconstruction of the three-phase current according to the following formula to obtain the fundamental wave component of the three-phase current:

In the formula, i _{a_ref} , i _{b_ref} and i _{c_ref} are the fundamental wave components of the reconstructed three-phase current; I _{s_ref} is the amplitude of the fundamental wave component of the three-phase current; θ _e is the rotor position angle; α is the d-axis current The angle between the reference value of and the reference value of the q-axis current;

The included angle α and magnitude I _{s_ref} are calculated as:

In the formula, i _{d_ref} and i _{q_ref} are the reference values of d and q axis currents respectively.

Described step 3) specifically is:

3.1) The acquisition of the total harmonic component of the three-phase current is shown in the following formula:

In the formula, _ia , _ib and _ic are the three-phase current obtained by real-time sampling in step 1); _{ia_h} , _{ib_h} and _{ic_h} are the total harmonic components of the three-phase current;

3.2) The total harmonic component of the three-phase current obtained in step 3.1) is subjected to 5 synchronous coordinate transformations and 7 synchronous coordinate transformations respectively, and the specific formula is as follows:

和

表示三相电流中的总谐波分量经过5次同步坐标变换后在5次dq坐标系下的d轴分量和q轴分量；

和

表示三相电流中的总谐波分量经过7次同步坐标变换后在7次dq坐标系下的d轴分量和q轴分量；ω_e表示内置式永磁同步电机中转子的电角速度，t表示时间；In the formula, I _sn and η _n are the amplitude and initial phase angle of the nth order harmonic in the three-phase current respectively; n=5, 7, 11, 13...∞;

and

Indicates the d-axis component and q-axis component in the 5th dq coordinate system of the total harmonic component in the three-phase current after 5 synchronous coordinate transformations;

and

Indicates the d-axis component and q-axis component in the seven-order dq coordinate system of _the total harmonic component in the three-phase current after seven times of synchronous coordinate transformation; time;

和

分别通过一阶低通滤波器后得到5、7阶次电流谐波特征量：I_s5cosη₅、I_s5sinη₅、I_s7cosη₇、I_s7sinη₇，其中I_s5cosη₅、I_s5sinη₅分别表示三相电流中的5阶次电流谐波特征量的余弦分量和正弦分量，I_s7cosη₇、I_s7sinη₇分别表示三相电流中的7阶次电流谐波特征量的余弦分量和正弦分量。3.3) Get d, q axis components in step 3.2)

and

After passing through the first-order low-pass filter respectively, the 5th and 7th order current harmonic characteristic quantities are obtained: I _s5 cosη ₅ , I _s5 sinη ₅ , I _s7 cosη ₇ , I _s7 sinη ₇ , where I _s5 cosη ₅ , I _s5 sinη ₅ respectively represent the cosine component and sine component of the 5th order current harmonic characteristic quantity in the three-phase current, I _s7 cosη ₇ , I _s7 sinη ₇ respectively represent the cosine component of the 7th order current harmonic characteristic quantity in the three-phase current and sine components.

In the described step 4), according to the 5th and 7th order current harmonic characteristic quantities I _s5 cosη ₅ , I _s5 sinη ₅ , I _s7 cosη ₇ and I _s7 sinη ₇ in the three-phase current by the following formula, obtain d , 6th-order current harmonic amplitude and 6th-order current harmonic characteristic quantity in the q-axis current:

In the formula, I _d6 and I _q6 are the amplitudes of the 6th-order current harmonics of the d-axis and q-axis respectively; μ _d6 and μ _q6 represent the initial phase angles of the 6th-order current harmonics of the d-axis and q-axis respectively; I _d6 cosμ _d6 and I _d6 sinμ _d6 are the cosine component and sine component of the 6th-order current harmonic characteristic quantity in the d-axis and q-axis respectively, and I _q6 cosμ _q6 and I _q6 sinμ _q6 are the cosine components in the d-axis and q-axis respectively The cosine component and sine component of the 6th order current harmonic characteristic quantity.

The beneficial effects of the present invention are:

(1) the present invention does not need complex filter structure, simple to implement;

(2) The present invention can accurately extract the 5th and 7th order current harmonic characteristic quantities in the phase current of the built-in permanent magnet synchronous motor;

(3) The present invention further accurately extracts the 6th-order current harmonic amplitude and 6th-order current harmonic characteristic value in the d and q currents.

(4) The present invention can simplify the step of extracting the current harmonic feature quantity in the process of suppressing the current harmonic of the built-in permanent magnet synchronous motor, and the accurate extraction provides a good basis for subsequent effective harmonic suppression.

The invention can be applied to the fields of drive control of built-in permanent magnet synchronous motors and the like.

Description of drawings

Figure 1 is a block diagram of a built-in permanent magnet synchronous motor vector control current harmonic extraction system.

Fig. 2 is a block diagram of current harmonic extraction proposed by the present invention.

Fig. 3 is the real-time three-phase current diagram of the reconstructed three-phase current fundamental component and the sampled internal permanent magnet synchronous motor.

Figure 4 is a graph of the extracted 5th and 7th order current harmonic characteristic quantities in the phase current.

Fig. 5 is a diagram of the extracted 6th-order current harmonic characteristic quantity in the d and q-axis currents.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the present invention comprises the following steps:

As shown in Figure 1, the specific implementation equipment includes a built-in permanent magnet synchronous motor, a two-level inverter and a controller, the built-in permanent magnet synchronous motor is connected to the two-level inverter, and the controller is connected to the built-in permanent magnet synchronous motor.

1) Sampling and obtaining the real-time three-phase current of the built-in permanent magnet synchronous motor;

The three phases of the built-in permanent magnet synchronous motor are equipped with current sensors, each current sensor is connected to the DSP, and the current sensor is used to sample the three phases of the built-in permanent magnet synchronous motor for AD sampling. The phase current is sent to DSP for control processing.

2) By sampling the rotor position of the built-in permanent magnet synchronous motor in real time, the real-time rotor position angle is obtained, and the basic value of the three-phase current is reconstructed using the reference values of the d and q-axis currents and the rotor position angle of the built-in permanent magnet synchronous motor. wave component.

Reconstruct the three-phase current according to the following formula to obtain the fundamental component of the three-phase current:

In the formula, i _{a_ref} , i _{b_ref} and i _{c_ref} are the fundamental wave components of the reconstructed three-phase current, a, b, and c represent the three phases respectively; I _{s_ref} is the amplitude of the fundamental wave component of the three-phase current; θ _e Indicates the rotor position angle; α is the angle between the reference value of the d-axis current and the reference value of the q-axis current;

The included angle α and magnitude I _{s_ref} are calculated as:

In the formula, i _{d_ref} and i _{q_ref} are the reference values of d and q axis currents respectively.

3) The real-time three-phase current and the fundamental component of the three-phase current are subtracted to obtain the total harmonic component, and then the total harmonic component is subjected to 5 synchronous coordinate transformations and 7 synchronous coordinate transformations respectively to obtain the transformed quantity, Pass the converted quantity through a first-order low-pass filter to obtain the 5th and 7th-order current harmonic characteristic quantities in the three-phase current;

3.1) The acquisition of the total harmonic component of the three-phase current is shown in the following formula:

In the formula, _ia , _ib and _ic are the three-phase current obtained by real-time sampling in step 1); _{ia_h} , _{ib_h} and _{ic_h} are the total harmonic components of the three-phase current;

3.2) The total harmonic component of the three-phase current obtained in step 3.1) is subjected to 5 synchronous coordinate transformations and 7 synchronous coordinate transformations respectively, and the specific formula is as follows:

和

表示三相电流中的总谐波分量经过5次同步坐标变换后在dq坐标系下的d轴分量和q轴分量；

和

表示三相电流中的总谐波分量经过7次同步坐标变换后在dq坐标系下的d轴分量和q轴分量；ω_e表示内置式永磁同步电机中转子的电角速度，t表示时间；In the formula, I _sn and η _n are the amplitude and initial phase angle of the nth order harmonic in the three-phase current respectively; n=5, 7, 11, 13...∞;

and

Indicates the d-axis component and q-axis component in the dq coordinate system of the total harmonic component in the three-phase current after 5 synchronous coordinate transformations;

and

Indicates the d-axis component and q-axis component in the dq coordinate system of the total harmonic component in the three-phase current after seven times of synchronous coordinate transformation; _ωe indicates the electrical angular velocity of the rotor in the built-in permanent magnet synchronous motor, and t indicates the time;

和

分别通过一阶低通滤波器后得到5、7阶次电流谐波特征量：I_s5cosη₅、I_s5sinη₅、I_s7cosη₇、I_s7sinη₇，其中I_s5cosη₅、I_s5sinη₅分别表示三相电流中的5阶次电流谐波特征量的余弦分量和正弦分量，I_s7cosη₇、I_s7sinη₇分别表示三相电流中的7阶次电流谐波特征量的余弦分量和正弦分量。3.3) Get d, q axis components in step 3.2)

and

After passing through the first-order low-pass filter respectively, the 5th and 7th order current harmonic characteristic quantities are obtained: I _s5 cosη ₅ , I _s5 sinη ₅ , I _s7 cosη ₇ , I _s7 sinη ₇ , where I _s5 cosη ₅ , I _s5 sinη ₅ respectively represent the cosine component and sine component of the 5th order current harmonic characteristic quantity in the three-phase current, I _s7 cosη ₇ , I _s7 sinη ₇ respectively represent the cosine component of the 7th order current harmonic characteristic quantity in the three-phase current and sine components.

4) Obtain the 6th order current harmonic amplitude and 6th order current harmonic characteristic quantity in the d and q currents by obtaining the 5th and 7th order current harmonic characteristic quantities in the obtained three-phase current.

In step 4), according to the 5th and 7th order current harmonic characteristic quantities I _s5 cosη ₅ , I _s5 sinη ₅ , I _s7 cosη ₇ and I _s7 sinη ₇ in the three-phase current, the following formulas are used to obtain d, q 6th-order current harmonic amplitude and 6th-order current harmonic characteristic quantity in shaft current:

In the formula, I _d6 and I _q6 are the amplitudes of the 6th-order current harmonics of the d-axis and q-axis respectively; μ _d6 and μ _q6 represent the initial phase angles of the 6th-order current harmonics of the d-axis and q-axis respectively; I _d6 cosμ _d6 and I _d6 sinμ _d6 are the cosine component and sine component of the 6th-order current harmonic characteristic quantity of the d-axis and q-axis respectively, and I _q6 cosμ _q6 and I _q6 sinμ _q6 are the 6th-order of the d-axis and q-axis respectively The cosine component and sine component of the sub-current harmonic characteristic quantity.

In order to verify the feasibility of the proposed current harmonic feature extraction method, the simulation verification is carried out on the Matlab/Simulik platform, and the experimental verification is carried out on the experimental platform of the built-in permanent magnet synchronous motor. The reconstructed fundamental component of the three-phase current and the real-time three-phase current of the built-in permanent magnet synchronous motor obtained by sampling are shown in Fig. 3 . It can be seen that the reconstructed fundamental component of the three-phase current can accurately reflect the fundamental component in the real-time three-phase current. Figure 4 is a graph of the extracted 5th and 7th order current harmonic characteristic quantities in the phase current. Fig. 5 is a diagram of the extracted 6th-order current harmonic characteristic quantity in the d and q-axis currents. It can be seen from the figure that the extracted 5th and 7th order current harmonic feature quantities and the 6th order current harmonic feature quantities in the d and q axis currents do not contain AC components.

Claims (5)

1. A method for extracting current harmonic characteristic quantity of a built-in permanent magnet synchronous motor is characterized by comprising the following steps:

1) Sampling to obtain real-time three-phase current of the built-in permanent magnet synchronous motor;

2) The method comprises the steps that the position of a rotor of the built-in permanent magnet synchronous motor is sampled in real time, so that a real-time rotor position angle is obtained, and fundamental wave components of three-phase currents are reconstructed by using reference values of d-axis currents and q-axis currents of the built-in permanent magnet synchronous motor and the rotor position angle;

3) Subtracting the real-time fundamental wave components of the three-phase current and the three-phase current to obtain a total harmonic component, respectively carrying out 5-time synchronous coordinate transformation and 7-time synchronous coordinate transformation on the total harmonic component to obtain transformed quantities, and carrying out a first-order low-pass filter on the transformed quantities to obtain 5-order and 7-order current harmonic characteristic quantities in the three-phase current;

4) And processing the obtained 5 and 7 order current harmonic characteristic quantities in the three-phase current to obtain 6 order current harmonic amplitude and 6 order current harmonic characteristic quantities in the d and q currents.

2. The method for extracting the current harmonic characteristic quantity of the interior permanent magnet synchronous motor according to claim 1, is characterized in that: in the step 1), current sensors are arranged at three phases of the built-in permanent magnet synchronous motor, each current sensor is connected to the DSP, and the current sensors are used for sampling the three phases of the built-in permanent magnet synchronous motor to carry out AD sampling current as real-time three-phase current of the built-in permanent magnet synchronous motor and sending the current to the DSP for control processing.

3. The method for extracting the current harmonic characteristic quantity of the interior permanent magnet synchronous motor according to claim 1, is characterized in that: in the step 2), the three-phase current is reconstructed according to the following formula to obtain the fundamental component of the three-phase current:

in the formula i _{a_ref} 、i _{b_ref} And i _{c_ref} Obtaining fundamental wave components of the three-phase current through reconstruction; I.C. A _{s_ref} The amplitude of the fundamental component of the three-phase current; theta _e Representing a rotor position angle; alpha is an included angle between the reference value of the d-axis current and the reference value of the q-axis current;

angle alpha and amplitude I _{s_ref} The calculation is as follows:

in the formula i _{d_ref} And i _{q_ref} Reference values for d and q-axis currents, respectively.

4. The method for extracting the current harmonic characteristic quantity of the interior permanent magnet synchronous motor according to claim 1, is characterized in that: the step 3) is specifically as follows:

3.1 The total harmonic component of the three-phase current is obtained as shown in the following equation:

in the formula i _a 、i _b And i _c Sampling three-phase current obtained by step 1) in real time; i.e. i _{a_h} 、i _{b_h} And i _{c_h} Is the total harmonic component of the three-phase current;

3.2 Respectively carrying out 5 times of synchronous coordinate transformation and 7 times of synchronous coordinate transformation on the three-phase current total harmonic component obtained in the step 3.1), wherein the specific formula is as follows:

in the formula I _sn 、η _n The amplitude and the initial phase angle of the nth order harmonic in the three-phase current are respectively; n =5, 7, 11, 13 … ∞;

and

representing d-axis components and q-axis components of total harmonic components in three-phase current in a 5-time dq coordinate system after 5-time synchronous coordinate transformation;

and

representing a d-axis component and a q-axis component of a total harmonic component in the three-phase current in a 7-time dq coordinate system after 7-time synchronous coordinate transformation; omega _e The method comprises the steps of representing the electrical angular speed of a rotor in the built-in permanent magnet synchronous motor, wherein t represents time;

3.3 The d and q axis components obtained in step 3.2)

And

respectively passing through a first-order low-pass filter to obtain 5-order and 7-order current harmonic characteristic quantities: i is _s5 cosη ₅ 、I _s5 sinη ₅ 、I _s7 cosη ₇ 、I _s7 sinη ₇ In which I _s5 cosη ₅ 、I _s5 sinη ₅ Cosine component and sine component respectively representing 5-order current harmonic characteristic quantity in three-phase current, I _s7 cosη ₇ 、I _s7 sinη ₇ And cosine components and sine components of 7-order current harmonic characteristic quantities in the three-phase current are respectively represented.

5. The method for extracting the current harmonic characteristic quantity of the interior permanent magnet synchronous motor according to claim 1, is characterized in that: in the step 4), according to the 5 and 7 order current harmonic characteristic quantity I in the three-phase current _s5 cosη ₅ 、I _s5 sinη ₅ 、I _s7 cosη ₇ And I _s7 sinη ₇ Obtaining 6-order current harmonic amplitude and 6-order current harmonic characteristic quantity in d-axis and q-axis currents by the following formulas:

in the formula I _d6 、I _q6 6-order current harmonic amplitudes of the d axis and the q axis respectively; mu.s _d6 And mu _q6 Initial phase angles of 6-order current harmonics representing the d-axis and q-axis, respectively; i is _d6 cosμ _d6 And I _d6 sinμ _d6 Cosine and sine components of the 6 th order current harmonic characteristic in the d and q axes, respectively, I _q6 cosμ _q6 And I _q6 sinμ _q6 Cosine component and sine component of the 6 th order current harmonic characteristic quantity in d axis and q axis respectively.

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