CN103872951B - Permanent magnet synchronous motor torque control method based on sliding mode flux linkage observer - Google Patents

Abstract

The invention discloses a permanent synchronization motor torque control method based on a sliding mode flux linkage observer. Direct torque control is performed on a permanent synchronization motor through a 3/2 coordinate conversion module, the sliding mode flux linkage observer, an electromagnetic torque calculation module, a rotating speed PI adjustor, a torque PI adjustor, a flux linkage self-adaptation module, an expected voltage calculation module, an SVPWM module and an inverter. The sliding mode flux linkage observer is adopted for estimating the size, phase and rotator speed of stator flux linkage, and set torque is processed through the flux linkage self-adaptation module to obtain a set value of the stator flux linkage. Expected voltage calculation is performed on size and phase estimation values and the set value of the stator flux linkage and the output quantity of the torque PI adjustor, so that two-phase alternating-current voltage reference values on a two-phase static coordinate system are obtained, and then through SVPWM conversion, a switching signal is obtained to drive the voltage source inverter to achieve direct torque control over the permanent synchronization motor.

Description

Permanent magnet synchronous motor torque control method based on sliding mode flux linkage observer

Technical Field

The invention belongs to the field of permanent magnet motor control, and particularly relates to a permanent magnet synchronous motor torque control system based on a sliding mode flux observer.

Background

The permanent magnet synchronous motor has the advantages of small volume, high efficiency, convenience in maintenance, strong environmental adaptability and the like, and is widely applied to the field of high-performance driving. The direct torque control has the advantages of fast torque response, simple system structure, strong robustness to parameter change and the like, and is attracted by people. The stator flux linkage needs to be acquired in the direct torque control of the permanent magnet synchronous motor, and flux linkage signals are accurate and negative to determine the control performance of the system. Therefore, for a high-performance permanent magnet synchronous motor direct torque control speed regulating system, how to accurately observe stator flux linkage is particularly important. In conventional direct torque control, a voltage model or a current model is generally employed to calculate the stator flux linkage. However, in the voltage model, because of the integral of the back electromotive force of the stator winding, when the motor runs at low speed, the estimation accuracy of the stator flux linkage is seriously reduced, and even the system can not work; in the current model, the position of the rotor needs to be known, and an additional position sensor is added, so that the cost of a control system is increased, the reliability of the system is reduced, and the application occasions of the permanent magnet synchronous motor are limited. In addition, in the direct control of the traditional hysteresis loop comparison, the defects of large torque and flux linkage pulsation, unfixed switching frequency and the like exist, and reactive current is introduced when the motor runs in no-load, so that the power factor of the motor is reduced. Therefore, in order to solve the above problems, it is necessary to provide a new flux linkage observation method on the premise of increasing the switching frequency and reducing the direct axis current during no-load, so as to improve the dynamic and static performance, reliability, robustness and anti-interference capability of the direct torque control system of the permanent magnet synchronous motor.

Disclosure of Invention

The technical problem is as follows: aiming at the defects in the prior art, the method for controlling the torque of the permanent magnet synchronous motor based on the sliding mode flux linkage observer is provided, and the robustness and the anti-interference capability of the direct torque control of the permanent magnet synchronous motor are improved on the premise of improving the switching frequency and reducing the direct axis current in no-load.

The technical scheme is as follows: the permanent magnet synchronous motor torque control method based on the sliding mode flux linkage observer is used for directly controlling the torque of a permanent magnet synchronous motor through an 3/2 coordinate transformation module, the sliding mode flux linkage observer, an electromagnetic torque calculation module, a rotating speed PI regulator, a torque PI regulator, a flux linkage self-adaption module, an expected voltage calculation module, an SVPWM module and an inverter, and comprises the following specific steps:

step 1), detecting three-phase current i of the permanent magnet synchronous motor_a、i_b、i_cAnd three phase voltage u_a、u_b、u_cObtaining a current component i under a two-phase static alternating current coordinate after 3/2 coordinate transformation_α、i_βAnd a voltage component u_α、u_βThen the current component i_α、i_βAnd a voltage component u_α、u_βSending to a sliding mode flux linkage observer, and adding a current component i_α、i_βSending the data to an electromagnetic torque calculation module;

step 2), according to the current component i_α、i_βAnd a voltage component u_α、u_βThe sliding mode flux linkage observer module estimates the estimated value of the stator flux linkage sizeAnd stator flux linkage phase estimationAnd rotor speed estimate

Step 3), setting the rotating speed omega^*And said rotor speed estimateAfter difference is made, a given torque Te is obtained through a rotating speed PI regulator^*；

Step 4), estimating the size of the stator flux linkage according to the estimated valueAnd the current component i_α、i_βThe electromagnetic torque calculation module obtains the actual torque Te of the motor;

step 5), the given torque Te^*Obtaining stator flux set value psi through flux linkage self-adaptive module_sref；

Step 6) of applying the predetermined torque Te^*Obtaining an output quantity delta through a torque PI regulator after making a difference with the actual torque Te of the motor;

step 7), the output quantity delta and the stator flux linkage given value psi_s.refStator flux linkage size estimationAnd stator flux linkage phase estimationObtaining a two-phase alternating current voltage reference value on a two-phase static coordinate system through an expected voltage calculation module

Step 8) according to the stator flux linkage vector position and the two-phase alternating voltage reference valueAnd after a corresponding space voltage vector is selected from the switch state table, a modulation signal is output to the inverter through the SVPWM module, and the direct torque control of the permanent magnet synchronous motor is realized through the inverter.

As a preferred embodiment of the present invention, the step 2) comprises the following specific steps:

step 2.1) of the method,according to the current component i_α、i_βAnd a voltage component u_α、u_βConstructing a sliding-mode observer to obtain the back electromotive force e of the motor_α、e_β；

Step 2.2), based on the back electromotive force e_α、e_βObtaining the estimated position of the rotor by a rotor position calculation module

Step 2.3), estimating the position according to the rotorObtaining a current stator flux linkage vector psi through a stator flux linkage estimation module_α、ψ_β；

Step 2.4), according to the current stator flux linkage vector psi_α、ψ_βObtaining the estimated value of the stator flux linkage size through a flux linkage observerAnd rotor speed estimate

Step 2.5), estimating the size of the stator flux linkage according to the estimated value of the size of the stator flux linkageObtaining stator flux linkage phase estimation value through flux linkage position calculation module

As an improvement of the present invention, the variable structure function of the sliding mode observer in step 2.1) is a sigmoid function.

Has the advantages that: the invention estimates the stator flux linkage and the rotor position by using the sliding mode control algorithm, can accurately control the stator flux linkage in real time, realizes the direct torque control of the permanent magnet synchronous motor based on the control without the position sensor, and has the following beneficial effects:

(1) the method combines the SVPWM technology and the flux linkage self-adaptive method, so that the torque and flux linkage pulsation in direct torque control can be reduced, the switching frequency is greatly improved, the current waveform is improved, and the direct-axis current component of the motor in no-load or sudden load is reduced, so that the motor loss can be reduced, and the motor efficiency is improved;

(2) the sliding mode flux linkage observer is constructed to estimate the speed of the stator flux linkage and the rotor, the estimation precision of the stator flux linkage at low speed is improved, the low-speed performance of the system is improved, and a position sensor is omitted, so that the cost of the control system is reduced, the reliability of the system is improved, and the structure of the system is simplified;

(3) the method combines and applies the flux linkage self-adaptive method, the sliding-mode flux linkage observer and the SVPWM to the direct torque control system of the permanent magnet synchronous motor for the first time, so that the control system not only keeps good dynamic and static performance, anti-interference capability and robustness in sliding-mode control, but also widens the operating range of the system;

(4) the method has small calculation amount and easy realization, and is beneficial to the engineering and the practicability of a new theory.

Drawings

FIG. 1 is a structural block diagram of a permanent magnet synchronous motor torque control system based on a sliding mode flux linkage observer according to the invention;

fig. 2 is a schematic structural block diagram of a sliding mode flux linkage observer.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to fig. 1 and 2.

As shown in fig. 1, the system for controlling the torque of the permanent magnet synchronous motor based on the sliding mode flux linkage observer of the invention comprises the permanent magnet synchronous motor, 3/2 coordinate transformation, the sliding mode flux linkage observer, electromagnetic torque calculation, a rotating speed PI regulator, a torque PI regulator, flux linkage adaptation, expected voltage calculation, an SVPWM module and an inverter.

The invention relates to a permanent magnet synchronous motor torque control method based on a sliding mode flux linkage observer, which comprises the following specific implementation steps:

step 1), detecting three-phase current i of the permanent magnet synchronous motor_a、i_b、i_cAnd three phase voltage u_a、u_b、u_cObtaining a current component i under a two-phase static alternating current coordinate after 3/2 coordinate transformation_α、i_βAnd a voltage component u_α、u_βThen the current component i_α、i_βAnd a voltage component u_α、u_βSending to a sliding mode flux linkage observer, and adding a current component i_α、i_βSending the data to an electromagnetic torque calculation module;

step 2), according to the current component i_α、i_βAnd a voltage component u_α、u_βEstimating the estimated value of the stator flux linkage by using a sliding mode flux linkage observer moduleAnd stator flux linkage phase estimationAnd rotor speed estimateThe functional block diagram is shown in fig. 2, and the specific algorithm is as follows:

step 2.1), based on the current component i_α、i_βAnd a voltage component u_α、u_βConstructing a sliding-mode observer to obtain the back electromotive force e of the motor_α、e_β(ii) a Wherein, a sliding mode current observer is constructed,the method comprises the following specific steps:

the mathematical model of the permanent magnet synchronous motor is expressed as follows under an alpha beta coordinate system:

wherein L is_sIs a synchronous inductance of the motor; psi_fIs a permanent magnetic linkage; omega is the electrical angular speed of the motor rotor; r_sIs a stator resistor; e.g. of the type_αAnd e_βα, β axis components of the motor back emf;

according to the sliding mode variable structure control theory, when the system slides on the sliding mode surface, the following steps are provided:

wherein,is an estimated value of current; i.e. i_s=[i_αi_β]^TIs the actual value of the current;

in order to reduce the buffeting of the system, a sigmoid function is adopted to replace a switch function of a traditional sliding mode variable structure and is used as a sliding mode variable structure function, and then:

wherein k is a sliding mode coefficient; h is a sigmoid function;andto estimate α, β axis components of the stator current;

the variogram function is defined as follows:

wherein S is the difference between the estimated current and the actual current; a is a real number greater than zero and can be adjusted according to actual conditions;

subtracting the formula (1) from the formula (3) to obtain a dynamic equation of the sliding-mode observer:

wherein S is_α(X) and S_β(X) α, β axis components of the difference between the estimated current and the actual current;

according to the existence and stability conditions of sliding mode movement, the premise that the rotor position of the motor can be smoothly estimated is that:

then:

k＞max(|e_α|，|e_β|) (6)

therefore, k is taken to be large enough to ensure the asymptotic stability of the sliding mode movement, and when the system reaches the sliding mode surface, the following steps are provided:

the counter electromotive force e of the motor can be obtained by substituting the above formula into the formula (5)_α、e_β：

Step 2.2), based on the back electromotive force e_α、e_βObtaining the estimated position of the rotor of the motor through a rotor position calculation moduleComprises the following steps:

step 2.3), estimating the position according to the rotorAnd combining the current component i under the two-phase static coordinate system_αAnd i_βObtaining the current stator flux linkage vector psi through the preliminary calculation of the stator flux linkage estimation module_α、ψ_β：

Because the sliding mode current observer constructed in the step 2.1) contains high-frequency components, the estimated stator flux linkage also contains high-frequency components, a low-pass filter is required for filtering, but the use of the low-pass filter can bring phase delay, influence the flux linkage estimation precision, and in order to improve the flux linkage estimation precision, the invention constructs a novel flux linkage observer;

step 2.4), according to the current stator flux linkage vector psi_α、ψ_βObtaining the estimated value of the stator flux linkage size through a flux linkage observerAnd rotor speed estimateThe method comprises the following specific steps:

constructing a flux linkage observer to improve estimation accuracy of flux linkage, and analyzing stability of the flux linkage observer by using Lyapunov theorem, wherein the method specifically comprises the following steps:

by deriving equation (10), we can obtain:

wherein, omega is the electrical angular velocity of the motor rotor;

from the above equation, a flux linkage observer can be constructed:

wherein l is the gain of the flux linkage observer, and the value of l is greater than zero;to estimate the component of the flux linkage in the αβ coordinate system;estimating an electrical angular velocity for the rotor;

by substituting formula (7) for formula (12), it is possible to obtain:

and (3) subtracting the formula (13) from the formula (11) to obtain an error equation of the flux linkage observer:

wherein, omega is the motor rotationSub-electrical angular velocity; l is the gain of the flux linkage observer, and the value of the gain is greater than zero;to estimate the component of the flux linkage in the αβ coordinate system;estimating an electrical angular velocity for the rotor;

the stability of the flux linkage observer is proved by utilizing Lyapunov theorem, and the following are provided:

the derivation for equation (15) is:

by substituting formula (14) for formula (16):

as can be seen from equation (17), the flux linkage observer is asymptotically stable, and therefore, the stator flux linkage estimation value can be calculated according to equation (14)And an estimated value of the rotational speed

Step 2.5), estimating the size of the stator flux linkageObtaining stator flux linkage phase estimation value through flux linkage position calculation module

Step 3), setting the rotating speed omega^*With estimated rotor speedAfter difference is made, a given torque Te is obtained through a rotating speed PI regulator^*；

Step 4), estimating the size of the stator flux linkageAnd a current component i in two-phase stationary coordinates_α、i_βAnd obtaining the actual torque Te of the motor through an electromagnetic torque calculation module, which comprises the following specific steps:

wherein p is₀The number of pole pairs of the motor is shown;

step 5), setting torque Te^*Obtaining stator flux set value psi through flux linkage self-adaptive module_s.refThe method comprises the following steps:

stator flux linkage quadrature-direct axis component psi of permanent magnet synchronous motor_sq、ψ_sdComprises the following steps:

wherein L is_dAnd L_qIs the dq-axis component, i, of the stator inductance_dAnd i_qIs the dq axis component of the stator current;

the relationship between motor torque and stator flux linkage components is as follows:

wherein psi_sIs a stator flux linkage, is a load angle;

in the formula (20), let i_d=0, and the reference value ψ given by the stator flux linkage can be obtained by combining the formula (21)_srefComprises the following steps:

step 6), setting the torque Te^*Obtaining an output quantity delta through a torque PI regulator after making a difference with the actual torque Te of the motor;

step 7), output quantity delta and stator flux linkage given value psi_s.refStator flux linkage size estimationAnd stator flux linkage phase estimationObtaining a two-phase alternating current voltage reference value on a two-phase static coordinate system through an expected voltage calculation module

Step 8) according to the stator flux linkage vector position and the two-phase alternating voltage referenceValue ofAfter a corresponding space voltage vector is selected from the switch state table, a modulation signal is output to the inverter through the SVPWM module, and the direct torque control of the permanent magnet synchronous motor is realized through the inverter.

In the invention, the estimation of the stator flux linkage vector and the rotor speed adopt the sliding mode flux linkage observer, so that the sliding mode flux linkage observer has the advantages of simple sliding mode algorithm, strong robustness and the like, and compared with the traditional voltage model, the estimation precision of the stator flux linkage at low speed is greatly improved, and the low-speed running performance of the motor is improved; compared with the traditional current model, the method does not need an additional position sensor, reduces the cost of the control system and improves the reliability of the system; the stator flux linkage given value is obtained by a flux linkage self-adaptive method, and the value of the stator flux linkage given value changes according to the size of the load, so that the direct-axis current of the motor when the motor runs in no-load or sudden-load is reduced, and the efficiency of the motor is improved. The invention can observe and control the stator flux linkage in real time and combine the flux linkage self-adaptive method and the SVPWM technology, can effectively reduce the torque and the flux linkage pulsation, improve the switching frequency and the motor efficiency, widen the running range of the system, and simultaneously has good dynamic and static performances, reliability, robustness and anti-interference capability.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (2)

1. The permanent magnet synchronous motor torque control method based on the sliding mode flux linkage observer is characterized by comprising the following steps: the method comprises the following steps of carrying out direct torque control on the permanent magnet synchronous motor through an 3/2 coordinate transformation module, a sliding mode flux linkage observer, an electromagnetic torque calculation module, a rotating speed PI regulator, a torque PI regulator, a flux linkage self-adaption module, an expected voltage calculation module, an SVPWM module and an inverter, and specifically comprises the following steps:

step 1), detecting three-phase current i of the permanent magnet synchronous motor_a、i_b、i_cAnd three phase voltage u_a、u_b、u_cObtaining a current component i under a two-phase static alternating current coordinate after 3/2 coordinate transformation_α、i_βAnd a voltage component u_α、u_βThen the current component i_α、i_βAnd a voltage component u_α、u_βSending to a sliding mode flux linkage observer, and adding a current component i_α、i_βSending the data to an electromagnetic torque calculation module;

step 2), according to the current component i_α、i_βAnd a voltage component u_α、u_βThe sliding mode flux linkage observer module estimates the estimated value of the stator flux linkage sizeAnd stator flux linkage phase estimationAnd rotor speed estimateThe method comprises the following specific steps:

step 2.1), according to the current component i_α、i_βAnd a voltage component u_α、u_βConstructing a sliding-mode observer to obtain the back electromotive force e of the motor_α、e_β；

Step 2.2), based on the back electromotive force e_α、e_βObtaining the estimated position of the rotor by a rotor position calculation moduleStep 2.3), estimating the position according to the rotorObtaining a current stator flux linkage vector psi through a stator flux linkage estimation module_α、ψ_β；

Step 2.4), according to the current stator flux linkage vector psi_α、ψ_βBy magnetic flux linkage observationObtaining stator flux linkage size estimation valueAnd rotor speed estimateThe method comprises the following specific steps:

the flux linkage equation of the permanent magnet synchronous motor is derived to obtain:

$\left\{\begin{array}{c}\frac{{\mathrm{d\ψ}}_{\mathrm{\α}}}{dt}=L_s\frac{{\mathrm{di}}_{\mathrm{\α}}}{dt}-{\mathrm{\ω\ψ}}_{\mathrm{\β}}+{\mathrm{\ωL}}_s{i}_{\mathrm{\β}}\\ \frac{{\mathrm{d\ψ}}_{\mathrm{\β}}}{dt}=L_s\frac{{\mathrm{di}}_{\mathrm{\β}}}{dt}+{\mathrm{\ω\ψ}}_{\mathrm{\α}}-{\mathrm{\ωL}}_s{i}_{\mathrm{\α}}\end{array}\right.---\left(11\right)$

wherein L is_sIs a synchronous inductance of the motor; omega is the electrical angular speed of the motor rotor;

from the above equation, a flux linkage observer can be constructed:

$\left\{\begin{array}{c}\frac{d{\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}}{dt}=L_s\frac{d{\hat{i}}_{\mathrm{\α}}}{dt}-\widehat{\mathrm{\ω}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}+\widehat{\mathrm{\ω}}{L}_s{\hat{i}}_{\mathrm{\α}}-k({\hat{i}}_{\mathrm{\α}}-i_{\mathrm{\α}})-l({\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}-{\mathrm{\ψ}}_{\mathrm{\α}})\\ \frac{d{\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}}{dt}=L_s\frac{d{\hat{i}}_{\mathrm{\β}}}{dt}+\widehat{\mathrm{\ω}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}-\widehat{\mathrm{\ω}}{L}_s{\hat{i}}_{\mathrm{\β}}-k({\hat{i}}_{\mathrm{\β}}-i_{\mathrm{\β}})-l({\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-{\mathrm{\ψ}}_{\mathrm{\β}})\\ \frac{d\widehat{\mathrm{\ω}}}{dt}=({\hat{i}}_{\mathrm{\α}}-i_{\mathrm{\α}}){\hat{i}}_{\mathrm{\β}}-({\hat{i}}_{\mathrm{\β}}-i_{\mathrm{\β}}){\hat{i}}_{\mathrm{\α}}+({\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}-{\mathrm{\ψ}}_{\mathrm{\α}}){\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-({\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-{\mathrm{\ψ}}_{\mathrm{\β}}){\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}\end{array}\right.---\left(12\right)$

wherein l is the gain of the flux linkage observer, and the value of l is greater than zero; k is a sliding mode coefficient;andto estimate α, β axis components of the stator current;

when the system reaches the sliding mode face, we can get:

$\left\{\begin{array}{c}\frac{d{\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}}{dt}=L_s\frac{d{\hat{i}}_{\mathrm{\α}}}{dt}-\widehat{\mathrm{\ω}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}+\widehat{\mathrm{\ω}}{L}_s{\hat{i}}_{\mathrm{\α}}-l({\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}-{\mathrm{\ψ}}_{\mathrm{\α}})\\ \frac{d{\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}}{dt}=L_s\frac{d{\hat{i}}_{\mathrm{\β}}}{dt}+\widehat{\mathrm{\ω}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}-\widehat{\mathrm{\ω}}{L}_s{\hat{i}}_{\mathrm{\β}}-l({\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-{\mathrm{\ψ}}_{\mathrm{\β}})\\ \frac{d\widehat{\mathrm{\ω}}}{dt}=({\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}-{\mathrm{\ψ}}_{\mathrm{\α}}){\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-({\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-{\mathrm{\ψ}}_{\mathrm{\β}}){\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}\end{array}\right.---\left(13\right)$

and (3) subtracting the formula (13) from the formula (11) to obtain an error equation of the flux linkage observer:

$\left\{\begin{array}{c}\frac{d{\widetilde{\mathrm{\ψ}}}_{\mathrm{\α}}}{dt}=-\widetilde{\mathrm{\ω}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}+\widehat{\mathrm{\ω}}{\widetilde{\mathrm{\ψ}}}_{\mathrm{\β}}-l{\widetilde{\mathrm{\ψ}}}_{\mathrm{\α}}\\ \frac{d{\widetilde{\mathrm{\ψ}}}_{\mathrm{\β}}}{dt}=-\widetilde{\mathrm{\ω}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}+\widehat{\mathrm{\ω}}{\widetilde{\mathrm{\ψ}}}_{\mathrm{\α}}-l{\widetilde{\mathrm{\ψ}}}_{\mathrm{\β}}\\ \frac{d\widehat{\mathrm{\ω}}}{dt}={\widetilde{\mathrm{\ψ}}}_{\mathrm{\α}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\β}}-{\widetilde{\mathrm{\ψ}}}_{\mathrm{\β}}{\widehat{\mathrm{\ψ}}}_{\mathrm{\α}}\end{array}\right.---\left(14\right)$

wherein, omega is the electrical angular velocity of the motor rotor; l is the gain of the flux linkage observer, and the value of the gain is greater than zero;

the stator flux linkage size estimation value can be calculated according to the formula (14)And rotor speed estimate

Step 2.5), estimating the size of the stator flux linkage according to the estimated value of the size of the stator flux linkageObtaining stator flux linkage phase estimation value through flux linkage position calculation module

Step 3), setting the rotating speed omega^*And said rotor speed estimateAfter difference is made, a given torque Te is obtained through a rotating speed PI regulator^*；

Step 4), estimating the size of the stator flux linkage according to the estimated valueAnd the current component i_α、i_βThe electromagnetic torque calculation module obtains the actual torque Te of the motor;

step 5), the given torque Te^*Obtaining stator flux set value psi through flux linkage self-adaptive module_sref；

Step 6) of applying the predetermined torque Te^*Obtaining an output △ through a torque PI regulator after making a difference with the actual torque Te of the motor;

step 7), the output quantity △ and the stator flux linkage given value psi_srefStator flux linkage size estimationAnd stator flux linkage phase estimationObtaining a two-phase alternating current voltage reference value on a two-phase static coordinate system through an expected voltage calculation module

Step 8) according to the stator flux linkage vector position and the two-phase alternating voltage reference valueAnd after a corresponding space voltage vector is selected from the switch state table, a modulation signal is output to the inverter through the SVPWM module, and the direct torque control of the permanent magnet synchronous motor is realized through the inverter.

2. The permanent magnet synchronous motor torque control method based on the sliding mode flux linkage observer according to claim 1, characterized in that: the variable structure function of the sliding mode observer in the step 2.1) is a sigmoid function.