阅读说明：本技术 一种基于无位置传感器的永磁同步电机if开环起动切入闭环的方法 (Position-sensor-free permanent magnet synchronous motor IF open-loop starting switch-in closed-loop method ) 是由 李光明 李胜 关彦彬 于 2021-09-01 设计创作，主要内容包括：本发明提供了一种基于无位置传感器的永磁同步电机IF开环起动切入闭环的方法,在预定位阶段,控制定子电流矢量的角速度不变,幅值以第一设定函数增至设定幅值；然后控制定子电流矢量的幅值不变且指令位置角以第二设定函数增加,直至定子电流矢量与转子位置同步；在I/F加速阶段,使定子电流矢量与转子磁链位置通过“转矩-自平衡”特性保持同步跟随,直至达到速度闭环运行的最低转速；在闭环切入阶段,电机转速保持速度闭环运行的最低转速不变,逐渐降低定子电流矢量幅值,根据本发明的推导公式,通过判断E0xd,是否小于某一个设定阀值DltLmt,作为切入闭环的标识。通过本方法切换过程,速度以及电流基本无波动,提高了起动可靠性和平顺性。(The invention provides a position sensor-free permanent magnet synchronous motor IF open loop starting cut-in closed loop method, wherein in a pre-positioning stage, the angular speed of a stator current vector is controlled to be unchanged, and the amplitude is increased to a set amplitude by a first set function; then controlling the amplitude of the stator current vector to be unchanged and the command position angle to be increased by a second set function until the stator current vector is synchronous with the rotor position; in the I/F acceleration stage, the stator current vector and the rotor flux linkage position are kept to synchronously follow through the torque-self-balancing characteristic until the lowest rotating speed of the speed closed-loop operation is reached; in the closed loop cut-in stage, the rotating speed of the motor keeps the lowest rotating speed of the speed closed loop operation unchanged, the amplitude of the stator current vector is gradually reduced, and according to the derivation formula of the invention, whether the rotating speed is smaller than a certain set threshold DltLmt or not is judged by E0xd to be used as the mark for cut-in of the closed loop. By the method, the switching process has basically no fluctuation of speed and current, and the starting reliability and smoothness are improved.)

1. A permanent magnet synchronous motor IF open loop starting switch-in closed loop method based on no position sensor is characterized by comprising the following steps:

s1, pre-positioning stage: applying a rotating current vector in an armature winding of a stator of the motor to enable the motor to operate in a current closed-loop and speed open-loop mode, defining a synchronous coordinate system where the open-loop current vector is located as a coordinate system, setting the synchronous coordinate system taking the position of a rotor of the motor as a reference as a dq coordinate system, and setting the phase difference of the two coordinate systems as theta L;

s11: controlling the angular speed of the stator current vector to keep low-frequency rotation, and increasing the amplitude of the stator current vector to a set amplitude by a first set function so that the current of a rotor winding is gradually increased under the regulation of a current loop PI controller;

s12: controlling the amplitude of the stator current vector to be unchanged and the command position angle to be increased by a second set function, so that the rotor rotates at a low frequency and a constant speed until the stator current vector is synchronous with the rotor position;

s2, I/F acceleration stage: controlling a motor stator current vector to rotate at a set angular acceleration, enabling the stator current vector and a rotor flux linkage position to keep synchronous following through a torque-self-balancing characteristic, enabling a motor rotor to keep synchronous rotation under the traction of the stator current vector until the lowest rotation speed of speed closed-loop operation is reached, and enabling a presumed coordinate system position estimator to accurately estimate an included angle theta L between a coordinate system and a dq coordinate system;

s3, closed-loop cut-in stage: the rotating speed of the motor keeps the lowest rotating speed of the speed closed-loop operation unchanged, the amplitude of the stator current vector is gradually reduced, and the motor is subjected to the mathematical model in the static coordinate system according to the IPMSM

Wherein:

derived from equation (1):

in equation (1): rs is a motor phase resistor resistance value Ld, and Lq is a quadrature-direct axis inductor respectively;

electrical angular velocity of the Wr motor; p is a differential operator;

i alpha and i beta are currents of an alpha-beta static coordinate system;

ualpha and Ubeta are the voltage of an alpha-beta static coordinate system;

in equation (2): psi f is the flux linkage of the permanent magnet;

s31: the stationary coordinate system EOx_α、EOx_βProjected under the virtual instruction coordinate system dq:

in equation (4): theta is the vector angle of the applied rotating current in the armature winding;

s32: substituting EOxd and EOxq into the formula (5), calculating is (n) as a reference instruction of a current loop in the switching process,

in equation (5): kc is an adjusting amplitude coefficient and ranges from 0 to 1;

s33: and judging whether the EOxd is smaller than a certain set threshold DltLmt or not, wherein the EOxd is used as an identifier for switching into a closed loop.

2. The position-sensorless permanent magnet synchronous motor IF open-loop starting cut-in closed-loop method according to claim 1, wherein: in step S11, the first setting function is a ramp function by which the magnitude of the stator current vector is increased to a set value.

3. The position-sensorless permanent magnet synchronous motor IF open-loop starting cut-in closed-loop method according to claim 1, wherein: in step S12, the second setting function is a linear function, and the command position angle increases as a linear function of a low frequency.

Technical Field

The invention relates to the technical field of permanent magnet synchronous motor control, in particular to a permanent magnet synchronous motor IF open-loop starting switch-in closed-loop method based on a position-sensorless.

Background

A driving system based on a vector control technology of a permanent magnet synchronous motor without a position sensor is widely applied to the field of household appliances, particularly to air-conditioning compressor products.

The current algorithms without position sensors mainly have two categories: one extracts rotor position signals by high frequency signal injection using motor saliency, and one observes rotor speed and position information by using motor back emf.

The high-frequency injection algorithm has high requirements on hardware and software and has a limited application range. On the basis of the algorithm of the counter electromotive force, the control requirement can be met by simply calculating through a motor model, but in the starting and low-speed running processes of the motor, the phase voltage or the counter electromotive force is small, and the algorithm based on the counter electromotive force observation is invalid.

Considering that the air conditioner compressor normally runs at a medium-high speed section and cannot run at a low speed section for a long time, a control strategy for starting the air conditioner compressor based on the permanent magnet synchronous motor without the position sensor needs to be designed, the air conditioner compressor is accelerated to the lowest rotating speed of a closed loop through an I/F (constant current frequency) open loop, and then the system is smoothly transited to the closed loop running stage based on the observation of the back emf without the position sensor according to the switching method provided by the text.

Disclosure of Invention

In order to achieve the purpose, the invention adopts the following technical scheme that the method comprises the following steps:

s1, pre-positioning stage: applying a rotating current vector in an armature winding of a stator of the motor to enable the motor to operate in a current closed-loop and speed open-loop mode, defining a synchronous coordinate system where the open-loop current vector is located as a coordinate system, setting the synchronous coordinate system taking the position of a rotor of the motor as a reference as a dq coordinate system, and setting the phase difference of the two coordinate systems as theta L;

s11: controlling the angular speed of the stator current vector to keep low-frequency rotation, and increasing the amplitude of the stator current vector to a set amplitude by a first set function so that the current of a rotor winding is gradually increased under the regulation of a current loop PI controller;

s12: controlling the amplitude of the stator current vector to be unchanged and the command position angle to be increased by a second set function, so that the rotor rotates at a low frequency and a constant speed until the stator current vector is synchronous with the rotor position;

s2, I/F acceleration stage: controlling a motor stator current vector to rotate at a set angular acceleration, enabling the stator current vector and a rotor flux linkage position to keep synchronous following through a torque-self-balancing characteristic, enabling a motor rotor to keep synchronous rotation under the traction of the stator current vector until the lowest rotation speed of speed closed-loop operation is reached, and enabling a presumed coordinate system position estimator to accurately estimate an included angle theta L between a coordinate system and a dq coordinate system;

s3, closed-loop cut-in stage: the rotating speed of the motor keeps the lowest rotating speed of the speed closed-loop operation unchanged, the amplitude of the stator current vector is gradually reduced, and the motor is subjected to the mathematical model in the static coordinate system according to the IPMSM

Wherein:

derived from equation (1):

in equation (1): rs is the resistance value of the motor phase resistor; ld and Lq are respectively a quadrature-direct axis inductor;

electrical angular velocity of the Wr motor; p is a differential operator;

i alpha and i beta are currents of an alpha-beta static coordinate system;

ualpha and Ubeta are the voltage of an alpha-beta static coordinate system;

in equation (2): psi f is the flux linkage of the permanent magnet;

s31: stationary coordinate system E0x_α、E0x_βProjected under the virtual instruction coordinate system dq:

in equation (4): theta is the vector angle of the applied rotating current in the armature winding;

s32: substituting E0xd and E0xq into formula (5), calculating is (n) as a reference command of a switching process current loop,

in equation (5): kc is an adjusting amplitude coefficient and ranges from 0 to 1;

s33: and judging whether the E0xd is smaller than a certain set threshold DltLmt or not as an identifier for cutting into the closed loop.

Preferably, in step S11, the first setting function is a ramp function, and the magnitude of the stator current vector is increased to a setting value by the ramp function.

Preferably, in step S12, the second setting function is a linear function, and the command position angle increases as a linear function of a low frequency.

The invention has the beneficial effects that: compared with the prior art, the air conditioner compressor is started and accelerated to the minimum rotating speed of a closed loop through an I/F (constant current frequency) open loop, then the system is stably transited to a closed loop operation stage based on back electromotive force non-position sensor observation according to the switching method provided by the text, the switching process, the speed and the current are basically free of fluctuation, the problem of triggering system hardware overcurrent is avoided, and the starting reliability and the smoothness are improved.

Drawings

FIG. 1 is a block diagram of a position sensorless PMSM starting system according to the present invention;

FIG. 2 is a schematic diagram of a pre-positioning end phase;

FIG. 3 is a schematic diagram of a coordinate system of an I/F startup acceleration phase;

FIG. 4 is a graph of measured phase current waveforms for an IF start switch-in closed loop according to the present invention;

fig. 5 Is a graph of measured | Is |, Tan Δ θ, and ω waveforms.

Detailed Description

The invention is further illustrated by the following specific examples.

The structural block diagram of the position sensorless permanent magnet synchronous motor starting system shown in fig. 1 comprises a current sampling unit, a position estimator of a hypothetical coordinate system, Clarke and PARK transformation units, a speed loop, a dq-axis current loop, Clarke inverse transformation and PARK inverse transformation units, a three-phase PWM inverter, an SVPWM computing unit, an I/FStartUp unit and the like. The I/FStartUp unit comprises an I/FStartUp generator, a RAMP function unit RAMP and the like.

The permanent magnet synchronous motor starting method comprises a pre-positioning stage, an I/F acceleration stage, a closed-loop cut-in stage and a closed-loop stage.

At zero low-speed starting, a speed estimation algorithm based on back emf observation cannot obtain accurate and stable position and speed signals, so that only current closed-loop and speed open-loop control can be performed on a system at starting. The motor speed is in the interval from rest to the lowest speed of the closed loop, the system adopts I/F (constant current frequency) control, as shown in figure 1, the switches Swt1 and Swt2 are both in the 1 position. The I/FStartUp generator in the wire frame is used for giving current vector command values, command position angles and other operation parameters in the pre-positioning stage and the I/F open loop acceleration stage.

After the positioning is finished, the motor rotor is dragged to a specified position, as shown in fig. 2. Keeping the amplitude of the current vector unchanged, rotating according to the specified angular acceleration, and synchronously rotating along the coordinate axis of the command dq under a mechanism of 'power self-balancing', namely I/F (constant current frequency) control.

When the synchronous speed of the system is accelerated to the minimum rotating speed of the closed loop, the rotor position information can be effectively extracted based on the back emf observer, and the angle difference theta L between a virtual instruction dq coordinate shaft system and a real dq rotor coordinate system under the open loop can be estimated through the assumed coordinate system position estimator and used as the basis for adjusting the current vector amplitude in the switching process.

When the IF open loop operates to a certain rotating speed and the system is stabilized at a certain stable state, the motor torque is adjusted in a self-balancing mode, and theta L is stabilized at a certain value. If the direct switching is carried out, the change of the output torque before and after the system switching is too large due to overlarge theta L, so that mechanical impact, system rotating speed fluctuation are caused, and even system hardware overcurrent is triggered. In order to avoid or reduce the irregularity of the switching process, before switching into the closed loop, the closed loop operation state of the position estimator of the assumed coordinate system needs to be switched to when the error of the two coordinate systems is gradually attenuated to a smaller value. The switching algorithm is to deduce the optimal adjustment rate of the current vector amplitude corresponding to the smooth and fast attenuation track of the theta L by analyzing the relation between the angle difference theta L and the current vector amplitude.

During the cut-in closed-loop process, switch Swt1 is in the 2 position and Swt2 remains in the 1 position. When the cut-in closed-loop condition is met, switch Swt1 is in the 3 position and Swt2 is in the 2 position.

The working principle of each stage is described below by combining a block diagram and computational analysis:

s1, pre-positioning stage: applying a rotating current vector in an armature winding of a stator of the motor to enable the motor to operate in a current closed-loop and speed open-loop mode, defining a synchronous coordinate system where the open-loop current vector is located as a coordinate system, setting the synchronous coordinate system taking the position of a rotor of the motor as a reference as a dq coordinate system, and setting the phase difference of the two coordinate systems as theta L;

s11: controlling the angular speed of the stator current vector to keep low-frequency rotation, and increasing the amplitude of the stator current vector to a set amplitude by a first set function so that the current of a rotor winding is gradually increased under the regulation of a current loop PI controller;

s12: controlling the amplitude of the stator current vector to be unchanged and the command position angle to be increased by a second set function, so that the rotor rotates at a low frequency and a constant speed until the stator current vector is synchronous with the rotor position;

s2, I/F acceleration stage: controlling a motor stator current vector to rotate at a set angular acceleration, enabling the stator current vector and a rotor flux linkage position to keep synchronous following through a torque-self-balancing characteristic, enabling a motor rotor to keep synchronous rotation under the traction of the stator current vector until the lowest rotation speed of speed closed-loop operation is reached, and enabling a presumed coordinate system position estimator to accurately estimate an included angle theta L between a coordinate system and a dq coordinate system;

s3, closed-loop cut-in stage: the rotating speed of the motor keeps the lowest rotating speed of the speed closed-loop operation unchanged, the amplitude of the stator current vector is gradually reduced, and the motor is subjected to the mathematical model in the static coordinate system according to the IPMSM

Wherein:

derived from equation (1):

in equation (1): rs is the resistance value of the motor phase resistor; ld and Lq are respectively a quadrature-direct axis inductor;

electrical angular velocity of the Wr motor; p is a differential operator;

i alpha and i beta are currents of an alpha-beta static coordinate system;

ualpha and Ubeta are the voltage of an alpha-beta static coordinate system;

in equation (2): psi f is the flux linkage of the permanent magnet;

s31: stationary coordinate system E0x_α、E0x_βProjected under the virtual instruction coordinate system dq:

in equation (4): theta is the vector angle of the applied rotating current in the armature winding;

s32: substituting E0xd and E0xq into formula (5), calculating is (n) as a reference command of a switching process current loop,

in equation (5): kc is an adjusting amplitude coefficient and ranges from 0 to 1;

s33: and judging whether the E0xd is smaller than a certain set threshold DltLmt or not as an identifier for cutting into the closed loop.

In step S11, the first setting function is a ramp function to which the magnitude of the stator current vector is increased to a setting value; in step S12, the second setting function is a linear function, and the command position angle increases as a linear function of a low frequency.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Although the present invention has been described with reference to the specific embodiments, it should be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.