CN115021629A - Permanent magnet motor current one-step compensation reconstruction method based on fixed sampling interval - Google Patents

Abstract

The invention discloses a permanent magnet motor current one-step compensation reconstruction method based on a fixed sampling interval, which comprises the following steps of: (1) analyzing a reconstruction dead zone and a reconstruction error existing in the current reconstruction by using the single current sensor; (2) according to the analysis result of the step (1), improving a current sampling method through a fixed sampling time interval and making a current reconstruction error compensation scheme; (3) observing the position of a rotor at a low-speed section of the motor by a high-frequency voltage injection method, and determining a sensorless control scheme of the motor; (4) and (3) combining the current sampling method and the current reconstruction error compensation scheme in the step (2) and the sensorless control scheme of the motor in the step (3) to obtain a one-step compensation scheme aiming at the current reconstruction error and having self-applicability of the motor, so that the error of the reconstructed high-frequency current can be reduced, and the observation precision of the low-speed rotor position can be improved.

Description

A one-step compensation reconstruction method for permanent magnet motor current based on fixed sampling interval

technical field

The invention relates to the technical field of motor drive control, in particular to a one-step compensation and reconstruction method for permanent magnet motor current based on a fixed sampling interval.

Background technique

Traditional permanent magnet synchronous motor (PMSM) control systems require at least two current sensors to sample the current and one position sensor to observe the rotor position. Due to the high cost, bulk, and poor reliability of position sensors, sensorless control has been widely studied.

There are two main control methods without position sensors, which are used in the high-speed range and the low-speed range. The position of the rotor is estimated by observing the back electromotive force (EMF) in the high speed range. At low speeds, the signal-to-noise ratio of the back EMF is low, so the rotor position is estimated by injecting a high frequency (HF) signal.

By using only a single current sensor, the cost and size of the system can be reduced. Furthermore, it can avoid errors caused by different gains among multiple current sensors. Therefore, the phase current reconstruction method using a single current sensor has received extensive attention.

There is a reconfiguration dead zone in the traditional current reconfiguration scheme. Some studies have proposed methods to modify the pulse width modulation (PWM) algorithm to overcome the reconstruction dead zone problem. Sampling the currents of multiple branches with Hall current sensors can eliminate the reconfiguration dead zone. However, such methods require special circuit forms and the multi-branched Hall current sensors take up more space.

The existing sensorless control of high-frequency voltage injection is affected by the reconstruction dead zone and reconstruction error of a single current sensor; the higher the injection frequency, the lower the accuracy of the reconstructed high-frequency current; the lower the injection frequency The dynamic bandwidth of sensorless control is limited; at the same time, the compensation calculation of reconstruction error is also complicated.

SUMMARY OF THE INVENTION

In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a one-step compensation and reconstruction method for permanent magnet motor current based on a fixed sampling interval, which can reduce the error of reconstructing high-frequency current, improve the observation accuracy of rotor position at low speed, and improve Performance of position sensorless control using a single current sensor in the low speed range.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

The present invention provides a one-step compensation and reconstruction method for permanent magnet motor current based on a fixed sampling interval, comprising the following steps:

(1) Analyze the reconstruction dead zone and reconstruction error in the current reconstruction using a single current sensor;

(2) According to the analysis result of step (1), improve the current sampling method through a fixed sampling time interval and formulate a current reconstruction error compensation scheme;

(3) The rotor position is observed by the high-frequency voltage injection method in the low-speed section of the motor, and the sensorless control scheme of the motor is determined;

(4) Combining the current sampling method of step (2), the compensation scheme of current reconstruction error and the sensorless control scheme of the motor of step (3), a one-step compensation scheme for the current reconstruction error of the motor self-applicability is obtained.

Preferably, the improved current sampling method in step (2) is specifically as follows: by shifting the switching state with an intermediate duty cycle, the sampling moment is moved to the falling edge of the trigger pulse, and the time interval between the two sampling moments is fixed as Minimum sampling time T _min .

Preferably, the current reconstruction error compensation scheme in step (2) includes:

(21) Calculate the difference between the actual three-phase current and the reconstructed three-phase current at time _t2 :

where T _c and T _ic are the Clarke and inverse Clarke transformation matrices, [Δi _d1 , Δi _q1 ] ^T represents the current change of the dq-axis current from time t ₁ to time t ₂ , T _f is the Park transformation matrix,

(22) Calculate the reconstruction error of the current at time t ₂ and the time t _end at the end of the switching cycle on the αβ axis:

where [Δi _d0 , Δi _q0 ] ^T represents the current change of the dq-axis current from time t ₂ to time t _end ;

(23) Using the formulas of steps (21) and (22) to calculate the current reconstruction error under the motor model:

According to the model of the permanent magnet synchronous motor under the dq axis, the current change rate is obtained:

The above formula is simplified to:

Considering the different switching states of the inverter in the dead time T _d , the output voltage of the inverter on the αβ axis of any sector from time t ₁ to time t ₂ is obtained, and the difference between the current and the reconstructed current at time t ₂ is calculated. The error between is:

Wherein, K _sel =T _min T _c S _sel T _ic ;

At the same time, the current error from time t ₂ to time t _end is:

Among them, T ₀ is the time interval from time t ₂ to time t _end , and

Preferably, the sensorless control scheme for determining the motor in step (3) includes:

(31) Under the excitation of high frequency voltage, the motor is regarded as a pure inductive load model, there are:

(32) According to the load model of step (31), inject high-frequency current in the dq axis, there are:

When the estimated rotor position is close to the actual rotor position, there are:

in:

(33) For the estimated rotor position under high frequency injection, there are:

where Δi _αhc and Δi _βhc are the compensated reconstructed high-frequency current differences;

(34) Calculate the reconstruction error existing between the reconstructed high-frequency current and the actual high-frequency current according to the formula of step (32) and step (33), there are:

in:

The two adjacent switching cycles in the high frequency square wave injection are:

Preferably, in step (4), the one-step compensation scheme for the current reconstruction error for the self-applicability of the motor includes the following steps:

将电机的电感误差简化为

和

其中，

和

为用于实际计算中的值；(41) Simplify the DC bus voltage and switching device voltage drop as

Simplify the inductance error of the motor as

and

in,

and

is the value used in the actual calculation;

(42) According to the above simplified formula, define the compensation gain [K _dcomp K _qcomp ] ^T as:

(43) The reconstruction error [εi _α1 , εi _β1 ] ^T , which is expressed as:

和

是根据u_{α_comp}和u_{β_comp}的计算方法，由

计算得到；离线状态下

和

可以通过dq轴高频电压注入获得，且K_dcomp和K_qcomp近似等于1；in

and

is the calculation method according to u _{α_comp} and u _{β_comp} , given by

Calculated; offline

and

It can be obtained by dq axis high frequency voltage injection, and K _dcomp and K _qcomp are approximately equal to 1;

此时，在αβ轴下的重构电流表示为：(44) During the operation of the motor, the high-frequency voltage is injected into the d-axis, then K _dcomp can be estimated online, and the estimated gain is defined as

At this time, the reconstruction current under the αβ axis is expressed as:

in:

In the formula: T _f is the coordinate transformation matrix obtained by estimating the rotor position, we have

The estimated compensation gain is obtained online as:

是从电流环路输出和

中得到，且有in,

is the output from the current loop and

obtained from, and have

The compensated high frequency current is calculated as:

(45) Analyze the accuracy of the compensation method, and define ε _Kd and ε _Kq as the estimation errors of K _dcomp and K _qcomp , respectively, that is, the compensation errors are:

in:

The beneficial effects of the present invention are:

1. By adjusting the PWM strategy and fixing the sampling time interval proposed by the present invention, the reconstruction error is reduced and the compensation method is simplified.

2. The one-step compensation method proposed by the present invention simplifies the reconstruction error compensation calculation, and the compensation gain has self-applicability.

3. The compensation error proposed by the present invention is obtained by injecting a high-frequency signal, which improves the precision of the position sensorless control in the low-speed section.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic flowchart of a one-step compensation and reconstruction method for permanent magnet motor current based on a fixed sampling interval according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a permanent magnet motor compensation feedback based on a fixed sampling interval according to an embodiment of the present invention.

FIG. 3 is a sampling time chart of t ₁ and t ₂ of the improved current sampling strategy according to the embodiment of the present invention.

FIG. 4 is a schematic diagram of a reconstructed dead zone after switching states are phase-shifted according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of the relationship between the output voltage and the phase current during the dead time of the inverter according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of a rotor position observer based on a phase-locked loop according to an embodiment of the present invention.

FIG. 7 is a schematic diagram of a high-frequency current difference after compensation using the improved current reconstruction scheme and the proposed current compensation scheme according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in FIG. 1 to FIG. 7 , this embodiment provides a one-step compensation and reconstruction method for permanent magnet motor current based on a fixed sampling interval, including the following steps:

(1) Analyze the reconstruction dead zone and reconstruction error in the current reconstruction using a single current sensor;

(2) According to the analysis result of step (1), improve the current sampling method through a fixed sampling time interval and formulate a current reconstruction error compensation scheme;

(3) The rotor position is observed by the high-frequency voltage injection method in the low-speed section of the motor, and the sensorless control scheme of the motor is determined;

(4) Combining the current sampling method of step (2), the compensation scheme of current reconstruction error and the sensorless control scheme of the motor of step (3), a one-step compensation scheme for the current reconstruction error of the motor self-applicability is obtained.

As shown in the t ₁ and t ₂ sampling timing diagrams of the improved current sampling method in step (2) of Fig. 3, by shifting the switching state with an intermediate duty cycle, the sampling timing is shifted to the falling edge of the trigger pulse, and the The time interval between the two sampling moments is fixed as the minimum sampling time T _min , as shown in the reconstruction dead zone diagram after phase shifting of the switching state in Figure 4, the reconstruction dead zone is moved to the low modulation zone, and the reconstruction error is reduced at the same time, as shown in Fig. The gray polygonal area in the center of 4 is the reconstruction dead zone.

The current reconstruction error compensation scheme in step (2) includes the following steps:

First, calculate the difference between the actual three-phase current and the reconstructed three-phase current at time t ₂ as:

Among them, where T _c and T _ic are the Clarke and inverse Clarke transformation matrices; [Δi _d1 , Δi _q1 ] ^T represents the current change of the dq-axis current from time t ₁ to time t ₂ ; T _f is the Park transformation matrix;

Secondly, calculate the reconstruction error of the current at time t ₂ and the time t _end at the end of the switching cycle on the αβ axis as:

where [Δi _d0 , Δi _q0 ] ^T represents the current change of the dq-axis current from time t ₂ to time t _end .

Then, calculate the current reconstruction error under the motor model:

According to the model of the permanent magnet synchronous motor under the dq axis, the current change rate is obtained:

When the motor is running at low speed, the size of u _{dq_comp} is much larger than the resistance drop and back EMF; and the time between t ₁ and t ₂ is very short, so the current rate of change can be considered constant; the above formula can be simplified as :

Then, as shown in Figure 5, the relationship between the output voltage of the inverter and the phase current in the dead time period of the inverter, considering the different switching states of the inverter in the dead time period T _d , can be obtained for any sector from time t ₁ to time t ₂ . The output voltage of the inverter on the αβ axis, so the error between the current and the reconstructed current at time t ₂ is calculated as:

Wherein, K _sel =T _min T _c S _sel T _ic ;

At the same time, the current error from time t ₂ to time t _end is:

Among them, T ₀ is the time interval from time t ₂ to time t _end , and

The low-speed section observes the rotor position through the high-frequency voltage injection method to realize the sensorless control scheme as follows:

First, under high frequency voltage excitation, the motor can be regarded as a purely inductive load model, with:

Injecting high frequency current in the dq axis, there are:

When the estimated rotor position is close to the actual rotor position, there are:

in:

At the same time, as shown in Figure 6, based on the phase-locked loop to observe the rotor speed and position, for the estimated rotor position under high frequency injection, there are:

where Δi _αhc and Δi _βhc are the compensated reconstructed high-frequency current differences.

Then, the reconstruction error between the calculated reconstructed high-frequency current and the actual high-frequency current is:

in:

in addition:

The two adjacent switching cycles in the high frequency square wave injection are:

thereby:

Therefore, it can be obtained that the reconstruction error of the high-frequency current mainly comes from [εi _α1 , εi _β1 ] ^T .

The one-step compensation scheme for the current reconstruction error with self-applicability is:

电机的电感误差可简化为

和

其中，

和

为用于实际计算中的值，定义补偿增益[K_dcomp K_qcomp]^T为：First, the DC bus voltage and switching device voltage drop can be simplified as

The inductance error of the motor can be simplified to

and

in,

and

For the value used in the actual calculation, define the compensation gain [K _dcomp K _qcomp ] ^T as:

Therefore, the reconstruction error [εi _α1 , εi _β1 ] ^T can be expressed as:

和

是根据u_{α_comp}和u_{β_comp}的计算方法，由

计算得到；离线状态下

和

可以通过dq轴高频电压注入获得，且K_dcomp和K_qcomp近似等于1；在电机运行过程中，高频电压注入d轴，则K_dcomp可以在线估计，估计增益定义为

in

and

is the calculation method according to u _{α_comp} and u _{β_comp} , given by

Calculated; offline

and

It can be obtained by high-frequency voltage injection on the dq-axis, and K _dcomp and K _qcomp are approximately equal to 1; during the operation of the motor, when the high-frequency voltage is injected into the d-axis, K _dcomp can be estimated online, and the estimated gain is defined as

At this time, the reconstruction current under the αβ axis can be expressed as:

in:

where T _f is the coordinate transformation matrix obtained by estimating the rotor position, as follows:

And the estimated compensation gain can be obtained online as:

是从电流环路输出和

中得到，且有：in,

is the output from the current loop and

obtained in , and have:

Meanwhile, the compensated high frequency current can be calculated as:

Finally, the accuracy of the compensation method is analyzed, and ε _Kd and ε _Kq are defined as the estimation errors of K _dcomp and K _qcomp , respectively, that is, the compensation errors are:

in:

Before compensation, ε _Kd =K _dcomp and ε _Kq =K _qcomp , however after compensation ε _Kd and ε _Kq are approximately equal to zero.

In this embodiment, the high-frequency current difference (f _inj = 1/2f _s ) after compensation using the improved current reconstruction scheme and the proposed current compensation scheme is shown in Fig. 7, and the estimated rotor is improved by using the proposed method accuracy of position; the rotor position can still be accurately estimated when the injection frequency is increased to half the switching frequency; the proposed method improves the accuracy of high-frequency currents compared to the traditional method using a single current sensor.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Thus, provided that these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (5)

1. a permanent magnet motor current one-step compensation reconstruction method based on fixed sampling interval, is characterized in that, comprises the following steps: (1) Analyze the reconstruction dead zone and reconstruction error in the current reconstruction using a single current sensor; (2) According to the analysis result of step (1), improve the current sampling method through a fixed sampling time interval and formulate a current reconstruction error compensation scheme; (3) The rotor position is observed by the high-frequency voltage injection method in the low-speed section of the motor, and the sensorless control scheme of the motor is determined; (4) Combining the current sampling method of step (2), the compensation scheme of current reconstruction error and the sensorless control scheme of the motor of step (3), a one-step compensation scheme for the current reconstruction error of the motor self-applicability is obtained. 2. a kind of permanent magnet motor current one-step compensation reconstruction method based on fixed sampling interval as claimed in claim 1, is characterized in that, in step (2), the improved current sampling method is specifically: by having intermediate duty cycle The switching state of , is phase-shifted, the sampling moment is shifted to the falling edge of the trigger pulse, and the time interval between the two sampling moments is fixed as the minimum sampling time T _min . 3. a kind of permanent magnet motor current one-step compensation reconstruction method based on fixed sampling interval as claimed in claim 1 is characterized in that, in step (2), the current reconstruction error compensation scheme comprises: (21) Calculate the difference between the actual three-phase current and the reconstructed three-phase current at time _t2 :

where T _c and T _ic are the Clarke and inverse Clarke transformation matrices, [Δi _d1 , Δi _q1 ] ^T represents the current change of the dq-axis current from time t ₁ to time t ₂ , T _f is the Park transformation matrix,

(22) Calculate the reconstruction error of the current at time t ₂ and the time t _end at the end of the switching cycle on the αβ axis:

where [Δi _d0 , Δi _q0 ] ^T represents the current change of the dq-axis current from time t ₂ to time t _end ; (23) Using the formulas of steps (21) and (22) to calculate the current reconstruction error under the motor model: According to the model of the permanent magnet synchronous motor under the dq axis, the current change rate is obtained:

The above formula is simplified to:

Considering the different switching states of the inverter in the dead time T _d , the output voltage of the inverter on the αβ axis of any sector from time t ₁ to time t ₂ is obtained, and the difference between the current and the reconstructed current at time t ₂ is calculated. The error between is:

Wherein, K _se1 =T _min T _c S _se1 T _ic ; At the same time, the current error from time t ₂ to time t _end is:

Among them, T ₀ is the time interval from time t ₂ to time t _end , and

4. a kind of permanent magnet motor current one-step compensation reconstruction method based on fixed sampling interval as claimed in claim 1, is characterized in that, in step (3), the sensorless control scheme that determines motor comprises: (31) Under the excitation of high frequency voltage, the motor is regarded as a pure inductive load model, there are:

(32) According to the load model of step (31), inject high-frequency current in the dq axis, there are:

When the estimated rotor position is close to the actual rotor position, there are:

in:

(33) For the estimated rotor position under high frequency injection, there are:

where Δi _αhc and Δi _βhc are the compensated reconstructed high-frequency current differences; (34) Calculate the reconstruction error existing between the reconstructed high-frequency current and the actual high-frequency current according to the formula of step (32) and step (33), there are:

in:

The two adjacent switching cycles in the high frequency square wave injection are:

5. The one-step compensation and reconstruction method for permanent magnet motor current based on a fixed sampling interval as claimed in claim 1, wherein the one-step compensation scheme for the current reconstruction error of the motor self-applicability in step (4) comprises the following steps: The following steps: (41) Simplify the DC bus voltage and switching device voltage drop as

Simplify the inductance error of the motor as

and

in,

and

is the value used in the actual calculation; (42) According to the above simplified formula, define the compensation gain [K _dcomp K _qcomp ] ^T as:

(43) The reconstruction error [εi _α1 , εi _β1 ] ^T , which is expressed as:

in

and

is the calculation method according to u _{α_comp} and u _{β_comp} , given by

Calculated; offline

and

It can be obtained by high frequency voltage injection of dq axis, and K _dcomp and k _qcomp are approximately equal to 1; (44) During the operation of the motor, the high-frequency voltage is injected into the d-axis, then K _dcomp can be estimated online, and the estimated gain is defined as

At this time, the reconstruction current under the αβ axis is expressed as:

in:

In the formula: T _f is the coordinate transformation matrix obtained by estimating the rotor position, we have

The estimated compensation gain is obtained online as:

in,

is the output from the current loop and

obtained from, and have

The compensated high frequency current is calculated as:

(45) Analyze the accuracy of the compensation method, and define ε _Kd and ε _Kq as the estimation errors of K _dcomp and K _qcomp , respectively, that is, the compensation errors are:

in:

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