CN1405973A - Method for directly controlling structure-change torque of inductive motor modulated by space vector - Google Patents

Abstract

The characters of the method are as follows. Based on the amplitude of the stator magnetic linkage and the quantity of each error, the stator voltage vector is calculated through the magnetic linkage of the various structures and the torque controller is order to control the convergence of the errors. Then, with space vector modulation type, the switch control signal of the voltage inverter is generated so as to control the torque of the induction-motor. Comparing with the directional control of the rotor magnetic field, the method provides the features of small calculating quantity, simple implemention and the robustness of the changed parameters. Comparing with the directive torque control, the invented method realizes constant switch cycle of the voltage inverter and overcomes the dithering issue in the directive torque control.

Description

Direct Control Method of Variable Structure Torque of Induction Motor Based on Space Vector Modulation

technical field

The invention relates to a space vector modulation induction motor variable structure torque direct control method, which belongs to the technical field of AC motor transmission.

Background technique

Induction motor is the most widely used motor in AC drive, but due to its complex control characteristics, high-performance control of induction motor is one of the main research problems in AC drive technology.

In the two-term stationary coordinate system (α, β), the dynamic equation of the induction motor can be expressed as follows where  _s ＝[ _sα  _sβ ] ^T  _r ＝[ _rα  _rβ ] ^T represents stator flux linkage and rotor flux linkage respectively, _is ＝[i _sα is _sβ ] ^T represents stator current, R _s , R _r respectively represent the stator resistance and rotor resistance, ω _r is the rotor speed, u _s = [u _sα u _sβ ] ^T is the stator voltage, $J=\left[\begin{array}{cc}0& -1\\ 1& 0\end{array}\right]$ . The stator current, flux linkage and rotor current, flux linkage satisfy the following relationship,

In the formula, L _s is the self-inductance of the stator, L _r is the self-inductance of the rotor, and M is the mutual inductance. Without loss of generality, if the number of pole pairs of the induction motor is n _p = 1, then the torque equation is

The core problem of high performance control of induction motor is torque control.

In the 1970s, German engineer F.Blashke proposed the rotor field-oriented control principle of induction motors, commonly known as the vector control principle, which made a qualitative leap in AC speed regulation technology. It basically solves the problem that induction motor control can be equivalent to DC motor in terms of static and dynamic characteristics in theory. The vector control technology imitates the control of the DC motor, adopts the method of rotor field orientation, and realizes the decoupling of the induction motor speed and the rotor flux control. In the vector control, the stator current and the rotor flux linkage are selected as the state variables, and the torque dynamic equation (3) of the induction motor combined with the equation (2) is rewritten as

其中转子磁链幅值满足如下动态方程

For formula (4), in the synchronous rotating coordinate system (M, T) oriented to the rotor magnetic field, there is  _rM = ‖ _r ‖,  _rT = 0, then the torque dynamic equation is

The amplitude of the rotor flux linkage satisfies the following dynamic equation

When the amplitude of the rotor flux linkage remains constant, the torque of the induction motor is linearly proportional to the torque component i _sT of the stator current. At this time, the induction motor has the same torque control characteristics as the DC motor. However, the rotor flux linkage is not easy to measure directly and it is difficult to observe accurately, and the control characteristics of vector control are greatly affected by the change of motor parameters. The actual control effect is difficult to achieve the results of theoretical analysis.

In 1985, German scholar M.Depenbrock first proposed direct torque control [US-4678248, July7, 1987], which opened up a new direction for the high-performance control of induction motors. In terms of implementation, it largely solves the shortcomings of the vector control algorithm being complex and the control performance easily affected by the parameter changes on the motor rotor side. At present, major international companies such as ABB are also devoting themselves to the development of high-performance AC drive products based on direct torque control. Compared with vector control, the main features of direct torque control are: 1. Control the easily observed stator flux and control the torque through direct feedback; 2. No need for rotating coordinate transformation; The space voltage vector selection table is used to directly generate the switching signal of the inverter to drive the motor. In direct torque control, the torque dynamic equation (3) is expressed as

在忽略定子电阻上的压降的假设下，在控制周期ΔT内对定子磁链动态方程积分 Where σ=1-M ² /L _s L _r , θ _s and θ _r represent the rotation angles of the stator and rotor flux vectors on the stationary coordinate system, respectively. When the magnitudes of the stator flux and rotor flux remain constant, the torque of an induction motor is proportional to sin(θ _s -θ _r ). The direct torque control of the induction motor controls the torque by adjusting the magnitude and rotation angle of the stator flux vector. By equation (1) the dynamics of the stator flux linkage satisfies

Under the assumption that the voltage drop across the stator resistance is neglected, the stator flux dynamic equation is integrated over the control period ΔT

Different from vector control, direct torque control is within the control period ΔT, and the stator voltage is one of the 6 (or 8 voltage vectors including zero vector) generated by the inverter. Then for (8), in The stator voltage remains constant within the control period ΔT. The principle of the space voltage vector generated by the inverter to control the dynamics of the stator flux linkage is shown in Figure 1. It can be seen that under the action of u _s (t _K ), the amplitude and rotation angle of the stator flux vector vary as

Assuming that within the control period ΔT, when the stator flux linkage changes, the amplitude of the rotor flux linkage ‖ _r ‖ and the rotation angle  _r do not change, and the counterclockwise direction is defined as the positive direction of the stator flux angle change, then The amplitude and torque of the stator flux linkage can be changed by correspondingly selecting the space voltage vector according to the position of the stator flux linkage. For example, as shown in Figure 1, assuming that the rotation angle of the stator flux linkage of the induction motor at time k - π/6<θ _s ≤ π/6, in the control period ΔT, V ₃ is selected as the constant voltage vector, then under the action of V ₃ , satisfying ‖ _s (k+1)‖<‖ _s (k)‖ at time k+1, T(k+1)>T(k). That is, under the action of V ₃ , the magnitude of the stator flux linkage decreases and the torque increases. According to Fig. 1 and formula (9), the space voltage vector selection table for controlling the stator flux amplitude and torque can be generated. Table 1 is the selection table of space voltage vectors commonly used at present.

Table 1 Space voltage vector selection table for direct torque control

Direct torque control selects one of the 6 (or 8) stator voltage vectors to control the increase or decrease of flux linkage and torque according to the positive or negative of flux linkage and torque error in a control cycle. small trend. In this sense, direct torque control is a "qualitative" control of flux linkage and torque, which causes the shortcomings of the inverter's switching cycle is not constant, torque and flux linkage control jitter. The main reason is the lack of strict theoretical analysis on the control of stator flux amplitude and torque. Although following the introduction of direct torque control, several improved methods of space voltage vector selection table have been developed to address its shortcomings, but limited by the lack of theoretical analysis of direct torque control itself, these methods cannot fundamentally overcome the shortcomings of direct torque control .

Vector control and direct torque control have greatly promoted the development of high-performance control of induction motors in theory and practice, but because of their respective advantages and disadvantages, the two cannot be replaced by one of them. Developing a control method with simple structure, strong robustness, and good dynamic and static performance is a difficult problem in the theory and practice of high-performance control of induction motors, and this problem has not been well resolved so far.

Contents of the invention

The invention proposes a direct control method of variable structure torque of an induction motor with space voltage vector modulation. This method controls the stator flux linkage which is easy to observe, and does not require field orientation to realize the decoupling of flux linkage and torque control. By directly feeding back the amplitude and torque of the stator flux linkage, the variable structure flux linkage and torque controller is used to control the stator flux linkage. Chain amplitude and torque converge to reference values. The principle block diagram of the control system of the method of the present invention is shown in FIG. 2 . The flux linkage and torque observer calculates the observed value of the stator flux amplitude and torque, and the errors e _ψ and e _Te between the observed value and the reference value are generated by the variable structure flux controller and the variable structure torque controller respectively The stator voltage components u _sd and u _sq are transformed and synthesized into space voltage vector by u _sd and u _sq and a space vector modulation (Space Vector Modulation, SVM) generator is used to generate the switching signal of the voltage inverter to drive the induction motor.

The present invention is characterized in that: it adopts variable structure flux linkage and torque controller to calculate the stator voltage vector to control the convergence of these errors according to the magnitude of the stator flux linkage amplitude and the respective errors of the torque, and then modulates with space vector ( SVM) generator to send the switching signal of the voltage inverter to control the torque of the induction motor. Specifically, it contains the following steps in turn:

(1). Set the stator flux linkage amplitude reference value ψ _sREF and torque reference value T _eREF , and input them into the computer;

(2). Then send the following parameters obtained from the control system adjustment and controller parameter setting program into the computer: variable structure flux controller parameters: ε _ψ > ε _Δψ , ${\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}}=R_{\mathrm{the\; <figure-callout\; id="2"\; label="s\; m"\; filenames="A0214865000231.png,A0214865000232.png"\; state="\{\{state\}\}">s</figure-callout>}}{m}^{}{}^2{\mathrm{\&psi;}}_{\mathrm{sREF}}/\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}^2{L}_r,$ K _ψ >0; among them, σ=1-(M ² /L _s L _r ), L _s : stator self-inductance; L _r : rotor self-inductance, M: mutual inductance; R _s : stator resistance; Convergence time: $t_{\mathrm{\&psi;}}\&le;\left|e_{\mathrm{\&psi;}}\left({\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">t</figure-callout>}}_0^{\mathrm{\&psi;}}\right)\right|/({\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}-{\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}})$ Among them, e _ψ ＝ψ _sREF -ψ _s , ψ _s : stator flux amplitude, t ₀ ^ψ is the initial moment of stator flux ψ _s control; variable structure torque controller parameters: ${\mathrm{\&epsiv;}}_{\mathrm{Te}}>\left|{\mathrm{\&psi;}}_{\mathrm{sREF}}{\stackrel{..}{\mathrm{\&theta;}}}_{\mathrm{the\; s}}\right|,$ _KTe >0;

(3). Flux linkage and torque observer to calculate the stator flux linkage amplitude and torque observations

(3.1). The computer measures the phase current i _A , i _B , i _C and the bus voltage V _dc from the inverter circuit powered by AC through the voltage and current measurement circuit, and the switching state SA(t) of the inverter in the observation period , SB(t), SC(t);

(3.2). Calculate the components of stator current and stator voltage on the stationary coordinate system by the following formula: $i_{\mathrm{s\&alpha;}}=i_A-\frac{1}{2}(i_B+i_C),i_{\mathrm{s\&beta;}}=\frac{\sqrt{3}}{2}(i_B-i_C),$ ${\tilde{u}}_{\mathrm{s\&alpha;}}=\frac{V_{\mathrm{dc}}}{3}(2\mathrm{SA}-\mathrm{SB}-\mathrm{SC}),$ ${\tilde{u}}_{\mathrm{s\&beta;}}=\frac{V_{\mathrm{dc}}}{\sqrt{3}}(\mathrm{SB}-\mathrm{SC});$

(3.3). Calculated by the following formula

(3.4). Calculated by the following formula

(3.5). Calculated by the following formula

(4). The variable structure flux linkage and torque controllers respectively calculate the components _u sd and u _sq of the stator voltage u _s on the dynamic coordinate system of the stator flux linkage according to e _ψ and e _Te :

First judge whether t>t _ψ If: the amplitude of the stator flux linkage has entered a steady state at time t, t≥t _ψ , then: $e_{\mathrm{\&psi;}}={\mathrm{\&psi;}}_{\mathrm{sREF}}-{\widehat{\mathrm{\&psi;}}}_{\mathrm{the\; s}},e_{\mathrm{Te}}=T_{\mathrm{eREF}}-{\hat{T}}_e,$ then: $u_{\mathrm{sd}}=\frac{R_{\mathrm{the\; s}}}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}}{\mathrm{\&psi;}}_{\mathrm{the\; s}}+K_{\mathrm{\&psi;}}{e}_{\mathrm{\&psi;}}+{\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}\mathrm{sgn}{e}_{\mathrm{\&psi;}},$ $u_{\mathrm{sq}}=\frac{R_{\mathrm{the\; s}}}{{\mathrm{\&psi;}}_{\mathrm{sREF}}}{T}_{\mathrm{eREF}}+{\&Integral;}_{t_T^0}^t(K_{\mathrm{Te}}{e}_{\mathrm{Te}}+{\mathrm{\&epsiv;}}_{\mathrm{Te}}\mathrm{sgn}{e}_{\mathrm{Te}})\mathrm{d\&tau;};$ Where t ₀ ^T is the initial moment of induction motor torque control; if: the stator flux amplitude does not enter the steady state at time t, t<t _ψ , then: $e_{\mathrm{\&psi;}}={\mathrm{\&psi;}}_{\mathrm{sREF}}-{\widehat{\mathrm{\&psi;}}}_{\mathrm{the\; s}},e_{\mathrm{Te}}=0-{\hat{T}}_e,$ then: $u_{\mathrm{sd}}=\frac{R_{\mathrm{the\; s}}}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}}{\mathrm{\&psi;}}_{\mathrm{the\; s}}+K_{\mathrm{\&psi;}}{e}_{\mathrm{\&psi;}}+{\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}\mathrm{sgn}{e}_{\mathrm{\&psi;}},$ $u_{\mathrm{sq}}=\frac{R_{\mathrm{the\; s}}}{{\mathrm{\&psi;}}_{\mathrm{sREF}}}{T}_{\mathrm{eREF}}+{\&Integral;}_{t_T^0}^t(K_{\mathrm{Te}}{e}_{\mathrm{Te}}+{\mathrm{\&epsiv;}}_{\mathrm{Te}}\mathrm{sgn}{e}_{\mathrm{Te}})\mathrm{d\&tau;};$

计算逆变器所需要的三相开关控制信号SA，SB，SC：(5). Voltage vector synthesis and space vector modulation (SVM) generator according to u _sd , u _sq ,

Calculate the three-phase switch control signals SA, SB, SC required by the inverter:

(5.1). Calculate u _sα and u _sβ by the following formula: $u_{\mathrm{the\; s}}=\left[\begin{array}{c}{u}_{\mathrm{s\&alpha;}}\\ u_{\mathrm{s\&beta;}}\end{array}\right]=\left[\begin{array}{cc}\cos {\mathrm{\&theta;}}_{\mathrm{the\; s}}& -\sin {\mathrm{\&theta;}}_{\mathrm{the\; s}}\\ \sin {\mathrm{\&theta;}}_{\mathrm{the\; s}}& \cos {\mathrm{\&theta;}}_{\mathrm{the\; s}}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{sd}}\\ u_{\mathrm{sq}}\end{array}\right]$

(5.2). Calculate the magnitude U _s and rotation angle θ _us of the stator voltage vector by the following formula $u_{\mathrm{the\; s}}=\sqrt{u_{\mathrm{s\&alpha;}}^2+u_{\mathrm{s\&beta;}}^2},$

θ _us = cos ^-1 (u _sα /U _s );

(5.3). Determine the two adjacent basic voltage vectors of the synthesized stator voltage by θ _us : $0\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{\mathrm{\&pi;}}{3},$ The stator voltage vector is between V1 and V2, N=1, using V1 and V2 $\frac{\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{2\mathrm{\&pi;}}{3},$ The stator voltage vector is between V2 and V3, N=2, using V2 and V3 $\frac{2\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\mathrm{\&pi;},$ The stator voltage vector is between V3 and V4, N=3, using V3 and V4 $\mathrm{\&pi;}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{4\mathrm{\&pi;}}{3},$ The stator voltage vector is between V4 and V5, N=4, using V4 and V5 $\frac{4\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{5\mathrm{\&pi;}}{3},$ The stator voltage vector is between V5 and V6, N=5, using V5 and V6 $\frac{5\mathrm{\&pi;}}{3}{\&le;\mathrm{\&theta;}}_{\mathrm{us}}<2\mathrm{\&pi;},$ The stator voltage vector is between V6 and V1, N=6, V6 and V1 are used;

(5.4). At the current moment, the stator voltage vector is in the interval N, and the basic voltage vectors V _N and V _N+1 of the inverter adjacent to the stator voltage vector are calculated by the following formula (if N=6, take V _N+1 = V1) and the action time of zero vector V0, V7: within the set SVM cycle T _p , $\mathrm{\&gamma;}={\mathrm{\&theta;}}_{\mathrm{us}}-\frac{(N-1)\mathrm{\&pi;}}{3}$ $0\&le;\mathrm{\&gamma;}<\frac{\mathrm{\&pi;}}{3}$ The action time T _N of V _N : $T_N=T_P\frac{{2u}_{\mathrm{the\; s}}}{\sqrt{3}{V}_{\mathrm{dc}}}\sin (\frac{\mathrm{\&pi;}}{3}-\mathrm{\&gamma;}),$ The action time T _N+ 1 of V _N+1 : $T_{N+1}=T_P\frac{{2u}_{\mathrm{the\; s}}}{\sqrt{3}{V}_{\mathrm{dc}}}\sin \left(\mathrm{\&gamma;}\right),$ The action time T ₀ and T ₇ of V0 and V7: ${\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">T</figure-callout>}}_0=T_7=\frac{T_P-T_1{-\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A0214865000231.png,A0214865000232.png"\; state="\{\{state\}\}">T</figure-callout>}}_2}{2};$

(5.5). Determine the three-phase switch control signals SA, SB, and SC of the inverter according to the basic voltage vector and zero vector and their respective action times:

The three-phase switching signals corresponding to the basic voltage vector and zero vector generated by the inverter are V ₁ (SA SB SC): V0(000), V1(100), V2(110), V3(010), V4( 011), V5(001), V6(101)V7(111); in one SVM cycle T _p , the basic voltage vectors V _N , V _N+1 and zero vectors V0 and V7 adjacent to the stator voltage vector act in the following order :

V0 acts on T ₀ /2→V _N acts on T _N /2→V _N+1 acts on T _N+1 /2→V7 acts on T ₇ →V _N+1 acts on T _N+1 /2→V _N acts on T _N / 2→V0 acts on T ₀ /2;

And according to the corresponding relationship between the basic voltage vector and the three-phase switching signals SA, SB, SC of the inverter, the switching control signals SA, SB, SC of the inverter are obtained, so as to drive the induction motor to control the rotation of the induction motor moment. The described control system performance adjustment and controller parameter tuning procedures contain the following steps in sequence:

(1). Determine K _ψ , ε _ψ , K _Te , ε _Te according to the following formula and system performance requirements: ${\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}}=\frac{R_{\mathrm{the\; s}}{m}^2}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}^2{L}_r}{\mathrm{\&psi;}}_{\mathrm{sREF}},$

ε _ψ ≈2ε _Δψ , the initial value of K _ψ is set to K _ψ = 1,

ε _Te ≈10ψ _sREF T _eREF , the initial value of K _Te is set as K _Te ＝1;

(2). Set ψ _sREF and T _eREF according to the characteristics of the induction motor itself and system performance requirements;

(3). The variable structure flux linkage controller uses the method of increasing K _ψ according to the control main program to make the flux linkage convergence speed meet the performance requirements;

(4). After the flux linkage amplitude is stabilized, the variable structure torque controller uses the method of increasing K _Te according to the control main program to make the torque convergence speed meet the performance requirements;

(5). Determine the K _ψ and K _Te that meet the system performance requirements;

(6). End.

Experiments prove that it achieves the intended purpose.

Description of drawings

Fig. 1. Schematic diagram of direct torque control stator flux dynamics.

Figure 2. Schematic block diagram of induction motor variable structure torque direct control system with space vector modulation.

Fig. 3. Vector diagram of stator voltage components u _sd and u _sq synthesized space voltage vector u _s .

Figure 4. Three-phase voltage source inverter.

Fig. 5. Vector diagram for generation of stator space voltage vector u _s .

Figure 6. System hardware circuit structure block diagram.

Figure 7. Control main program flow chart.

Fig. 8. Flow chart of stator flux magnitude and torque observer program.

Figure 9. Program flow chart of variable structure flux linkage and torque controller.

Fig. 10. Flow chart of stator voltage vector synthesis and SVM generator program.

Figure 11. Flowchart of control system performance adjustment and controller parameter tuning procedure.

Figure 12. Torque and stator flux amplitude response curves:

a. Torque response curve; b. Stator flux amplitude response curve.

Figure 13. Induction motor stator current response curve:

ai _sα response curve; bi _sβ response curve.

Figure 14. Induction motor speed response curve.

Figure 15. The inverter switching frequency is 5KHz, and the induction motor torque and stator flux amplitude response curve when the load torque of 4Nm is suddenly added for 0.5s:

a. Torque response curve; b. Stator flux amplitude response curve.

Figure 16. The induction motor stator current response curve when the switching frequency of the inverter is 5KHz and the load torque of 4Nm is suddenly added for 0.5s:

ai _sα response curve; bi _sβ response curve.

Figure 17. The speed response curve of the induction motor when the switching frequency of the inverter is 5KHz and the load torque of 4Nm is suddenly added for 0.5s.

Detailed ways:

Flux linkage and torque control principle

表示定子磁链矢量和转子磁链矢量之间夹角，U_s，θ_us分别表示定子电压矢量的幅值和转角。则有_sα＝ψ_scosθ_s，_sβ＝ψ_ssinθ_s；_rα＝ψ_rcosθ_r，_rβ＝ψ_rsinθ_r；u_sα＝U_scosθ_us，u_sβ＝U_ssinθ_us。通过如上的变换，可以得到定子磁链幅值与转角的动态方程为

式中u_sd＝U_scos(θ_us-θ_s)，u_sq＝U_ssin(θ_us-θ_s)。转矩的动态方程为

进而得出定子磁链幅值和转矩与定子电压之间的动态方程为 Firstly, aiming at the nonlinear coupling equation of the induction motor, the present invention deduces the dynamic equation between the amplitude and torque of the stator flux linkage and the stator voltage, and designs a variable structure flux linkage and torque controller on this basis. In the two stationary coordinate system, the dynamic equations of the stator flux and rotor flux of the induction motor are Define ψ _s ＝‖ _s ‖, ψ _r ＝‖ _r ‖ to denote the amplitude of stator and rotor flux linkage respectively,

Indicates the angle between the stator flux vector and the rotor flux vector, U _s , θ _us represent the magnitude and rotation angle of the stator voltage vector, respectively. Then  _sα = ψ _s cosθ _s ,  _sβ = ψ _s sinθ _s ;  _rα = ψ _r cosθ _r ,  _rβ = ψ _r sinθ _r ; u _sα = U _s cosθ _us , u _sβ = U _s sinθ _us . Through the above transformation, the dynamic equation of the stator flux amplitude and rotation angle can be obtained as

In the formula, u _sd = U _s cos(θ _us -θ _s ), u _sq = U _s sin(θ _us -θ _s ). The dynamic equation of torque is

Then the dynamic equation between the stator flux amplitude and torque and the stator voltage is obtained as

By equation (13), the stator flux amplitude and torque can be controlled by the stator voltage u _sd and u _sq components. The control principle of the variable structure flux linkage and torque controller in the system is as follows.

Variable Structure Flux Linkage and Torque Controller

The method of the present invention is based on the dynamic and torque dynamic equation (13) of the stator flux linkage, designs the variable structure flux linkage and the torque controller, and controls the stator flux linkage amplitude of the induction motor by adjusting the u _sd and u _sq components of the stator voltage respectively The values and torques converge to the reference values ψ _sREF and T _eREF .

The variable structure flux linkage controller controls the amplitude of the stator flux linkage by changing the u _sd component of the stator voltage, and the control law is $u_{\mathrm{sd}}=\frac{R_{\mathrm{the\; s}}}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}}{\mathrm{\&psi;}}_{\mathrm{the\; s}}+K_{\mathrm{\&psi;}}{e}_{\mathrm{\&psi;}}+{\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}\mathrm{sgn}{e}_{\mathrm{\&psi;}}---\left(14\right)$ where e _ψ = ψ _sREF -ψ _s , the parameters K _ψ and ε _ψ in the control law respectively satisfy the following constraints

K _ψ ＞0 ${\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}}=\frac{R_{\mathrm{the\; s}}{m}^2}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}^2{L}_r}{\mathrm{\&psi;}}_{\mathrm{sREF}}---\left(15\right)$

ε _ψ > ε _Δψ

The stator flux amplitude of the induction motor can converge to the reference value ψ _sREF within a limited time under the action of the above variable structure flux controller, that is, the stator flux amplitude satisfies

ψ _s (t) = ψ _{s REF} , $\&ForAll;t\&Greater\; Equal;t_{\mathrm{\&psi;}}+{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">t</figure-callout>}}_0^{\mathrm{\&psi;}}$ $t_{\mathrm{\&psi;}}\&le;\frac{|{\mathrm{\&psi;}}_{\mathrm{sREF}}\left({\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">t</figure-callout>}}_0^{\mathrm{\&psi;}}\right)-{\mathrm{\&psi;}}_{\mathrm{the\; s}}\left({\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">t</figure-callout>}}_0^{\mathrm{\&psi;}}\right)|}{{\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}-{\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}}}---\left(16\right)$

Where t ₀ ^ψ is the initial moment of flux linkage control. The stability proof and parameter selection method of the variable structure flux controller are given in Appendix A.

The Initial Moment of Torque Control of Induction Motor $t_0^T>t_{\mathrm{\&psi;}}+{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">t</figure-callout>}}_0^{\mathrm{\&psi;}},$ That is, the amplitude of the stator flux linkage has entered a steady state at this time. When t≤t ₀ ^T, the reference value T _eREF =0 for torque control. The torque variable structure controller is: $u_{\mathrm{sq}}=\frac{R_{\mathrm{the\; s}}}{{\mathrm{\&psi;}}_{\mathrm{sREF}}}{T}_{\mathrm{eREF}}+{\&Integral;}_{t_T^0}^t(K_{\mathrm{Te}}{e}_{\mathrm{Te}}+{\mathrm{\&epsiv;}}_{\mathrm{Te}}\mathrm{sgn}{e}_{\mathrm{Te}})\mathrm{d\&tau;}---\left(17\right)$ where e _Te ＝T _eREF -T _e , the parameters K _Te and ε _Te in the control law respectively satisfy the following constraints K _Te ＞0 ${\mathrm{\&epsiv;}}_{\mathrm{Te}}>\left|{\mathrm{\&psi;}}_{\mathrm{sREF}}{\stackrel{..}{\mathrm{\&theta;}}}_{\mathrm{the\; s}}\right|---\left(18\right)$

The torque of the induction motor converges to the reference value T _eREF under the action of the above variable structure torque controller. Appendix B gives the stability proof and parameter selection method of the variable structure torque controller.

Voltage Vector Transform Synthesis and SVM Generator

The variable structure flux linkage and torque controllers respectively output the u _sd and u _sq components of the stator voltage, which are converted into space voltage vectors, so that the SVM generator can be used to generate the switching signals of the inverter.

The stator voltage vector is: $u_{\mathrm{the\; s}}=\left[\begin{array}{c}{u}_{\mathrm{s\&alpha;}}\\ u_{\mathrm{s\&beta;}}\end{array}\right]=\left[\begin{array}{cc}\cos {\mathrm{\&theta;}}_{\mathrm{the\; s}}& -\sin {\mathrm{\&theta;}}_{\mathrm{the\; s}}\\ \sin {\mathrm{\&theta;}}_{\mathrm{the\; s}}& \cos {\mathrm{\&theta;}}_{\mathrm{the\; s}}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{sd}}\\ u_{\mathrm{sq}}\end{array}\right]---\left(19\right)$ $u_{\mathrm{the\; s}}=\sqrt{u_{\mathrm{s\&alpha;}}^2+u_{\mathrm{s\&beta;}}^2},{\mathrm{\&theta;}}_{\mathrm{us}}={\cos }^{-1}(u_{\mathrm{s\&alpha;}}/u_{\mathrm{the\; s}})---\left(20\right)$

The principle of synthesizing the space voltage vector by the stator voltage components u _sd and u _sq is shown in Fig. 3 .

Figure 4 is a schematic diagram of a three-phase voltage-type inverter, where V _dc is the DC bus voltage, and power electronic power devices are regarded as ideal switches. Use "1" to indicate that the upper arm is on and the lower arm is off; use "0" to indicate that the lower arm is on and the upper arm is off. The switch control signals of the three phases are SA, SB, and SC respectively, and the corresponding values are 1 or 0 respectively. Use V _i (SA SB SC) to represent the space voltage vector generated by the inverter, then the 8 basic voltage vectors V0~V7 output by the inverter can be obtained by combining the values of SA, SB, and SC: V0 (000), V1 (100), V2 (110), V3 (010), V4 (011), V5 (001), V6 (101), V7 (111). Among them V0, the magnitude of V7 is zero, called zero vector. The principle of using SVM to generate the space voltage vector is shown in Figure 5. At any given moment, the stator voltage vector will fall in one of the six intervals divided by the basic voltage vectors V1-V6. Table 2 shows the selection of adjacent basis vectors according to _θus . In this way, within the set SVM period T _P , the stator voltage vector can be expressed by combining two adjacent basic voltage vectors and zero vectors. The stator voltage vector is in the interval N, and the basic voltage vectors V _N and V _N+1 of the two inverters adjacent to the stator voltage vector are calculated by the following formula (if N=6, take V _N+1 = V1) and the zero vector The action time of V0 and V7: $\mathrm{\&gamma;}={\mathrm{\&theta;}}_{\mathrm{us}}-\frac{(N-1)\mathrm{\&pi;}}{3}$ $0\&le;\mathrm{\&gamma;}<\frac{\mathrm{\&pi;}}{3}$ $T_N=T_P\frac{2u_{\mathrm{the\; s}}}{\sqrt{3}{V}_{\mathrm{dc}}}\sin (\frac{\mathrm{\&pi;}}{3}-\mathrm{\&gamma;})---\left(\mathrm{twenty\; one}\right)$ $T_{N+1}=T_P\frac{{2u}_{\mathrm{the\; s}}}{\sqrt{3}{V}_{\mathrm{dc}}}\sin \left(\mathrm{\&gamma;}\right)$ ${\mathrm{<figure-callout\; id="0"\; label="T"\; filenames="A0214865000231.png,A0214865000242.png"\; state="\{\{state\}\}">T</figure-callout>}}_0=T_7=\frac{T_P-T_1-{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A0214865000231.png,A0214865000232.png"\; state="\{\{state\}\}">T</figure-callout>}}_2}{2}$

Table 2 Determine the basic voltage vector according to the stator voltage vector angle

The three-phase switching signals corresponding to the basic voltage vector and zero vector generated by the inverter are V _i (SA SB SC): V0(000), V1(100), V2(110), V3(010), V4( 011), V5(001), V6(101)V7(111): In one SVM cycle T _P , the basic voltage vectors V _N , V _N+1 and zero vectors V0 and V7 adjacent to the stator voltage vector act in the following order : V0→V _N →V _N+1 →V7→V _N+1 →V _N →V0, the action time is respectively V0 acting on T ₀ /2, V _N acting on T _N /2, V _N+1 acting on T _{N+ 1} /2, V7 acts on T ₇ , V _N+1 acts on T _N+1 /2, V _N acts on T _N /2, and V0 acts on T ₀ /2. According to the corresponding relationship between the basic voltage vector and the three-phase switching signals SA, SB, SC of the inverter, the switch control signals SA, SB, SC of the inverter are obtained to drive the induction motor to control the torque of the induction motor .

Flux and Torque Observer

通过测量相电流i_A，i_B，i_C，母线电压以及逆变器的开关信号SA，SB，SC可以得到i_sα，i_sβ’

计算公式如下 $i_{\mathrm{s\&alpha;}}=i_A-\frac{1}{2}(i_B+i_C)$ $i_{\mathrm{s\&beta;}}=\frac{\sqrt{3}}{2}(i_B-i_C)$ ${\tilde{u}}_{\mathrm{s\&alpha;}}=\frac{V_{\mathrm{dc}}}{3}(2\mathrm{SA}-\mathrm{SB}-\mathrm{SC})---\left(23\right)$ ${\tilde{u}}_{\mathrm{s\&beta;}}=\frac{V_{\mathrm{dc}}}{\sqrt{3}}(\mathrm{SB}-\mathrm{SC})$ 则定子磁链的幅值观测值为：

定子磁链转角的观测值为：

转矩的观测值为： The stator flux and torque of the induction motor are not easy to measure directly. Through the stator voltage and stator current of the motor that can be directly measured, the flux and torque observer can be used to obtain the observed values of the flux and torque. At present, there are many observer design methods for stator flux and torque. For example, the stator flux dynamic equation in equation (1) can be integrated. The observed value of stator flux is:

By measuring phase current i _A , i _B , i _C , bus voltage and switching signals SA, SB, SC of the inverter, i _sα , i _sβ ' can be obtained

Calculated as follows $i_{\mathrm{s\&alpha;}}=i_A-\frac{1}{2}(i_B+i_C)$ $i_{\mathrm{s\&beta;}}=\frac{\sqrt{3}}{2}(i_B-i_C)$ ${\tilde{u}}_{\mathrm{s\&alpha;}}=\frac{V_{\mathrm{dc}}}{3}(2\mathrm{SA}-\mathrm{SB}-\mathrm{SC})---\left(\mathrm{twenty\; three}\right)$ ${\tilde{u}}_{\mathrm{s\&beta;}}=\frac{V_{\mathrm{dc}}}{\sqrt{3}}(\mathrm{SB}-\mathrm{SC})$ Then the observed value of the stator flux linkage is:

The observed value of the stator flux linkage angle is:

The observed value of torque is:

The hardware structure of the system is shown in Figure 6. The system includes: rectification circuit, filter circuit, inverter circuit, isolation circuit, voltage and current detection circuit, microprocessor (CPU) and corresponding interface circuit. For this system, the speed measurement device and the corresponding speed control algorithm can also be added to form an induction motor speed control system.

The main control flow chart of the control system is shown in Figure 7. It consists of three main parts: the observer unit, the variable structure controller unit, the space voltage vector synthesis and the SVM generator unit, and the program flow charts are shown in Figures 8-10 respectively. Show. Fig. 11 is a flow chart of system performance adjustment and controller parameter setting procedure. First, according to the system performance requirements and the controller parameter selection method, the reference values ψ _sREF and T _eREF of the stator flux amplitude and torque are determined, and the variable structure controller parameters K _ψ , ε _ψ , K _Te , ε _Te and t _ψ are determined. The parameters are sent to the control main program. Adjust K _ψ , K _Te according to the system performance, and finally determine the controller parameters that meet the system requirements.

In order to verify the method of the present invention, MATLAB5.3-SIMULINK3 is used for simulation verification. The parameters of the induction motor in the simulation are selected as follows: stator and rotor self-inductance L _s = L _r = 0.47H; mutual inductance M = 0.44H; stator resistance R _s = 8.0Ω; rotor resistance R _r = 3.6Ω; induction motor moment of inertia J _M =0.06Kgm ² ; number of pole pairs n _p =1. After the controller parameters are adjusted, the parameters of the torque and flux linkage variable structure controllers are K _ψ ＝10Ω/H; K _Te ＝10Ω/H; e _ψ ＝160V; e _Te ＝40V. The simulation is divided into two parts, the theoretical verification of the performance of the invented method, and the simulation verification of the actual system. In the theoretical verification part, ignoring the influence of the SVM generator on the system performance, ψ _sREF = 0.9Wb, set t _ψ = 0.1s, T _L = 0Nm, and the torque reference value is:

Figure 12 is the torque and stator flux amplitude response curve, Figure 13 is the stator current response curve, and Figure 14 is the speed response curve. In the simulation of the actual system, the switching frequency of the inverter is 5KHz, the DC bus voltage V _dc = 380V, ψ _sREF = 0.9Wb, t _ψ = 0.05s, T _eREF = 4Nm and a sudden load torque of 4Nm is added at 0.5s . Figures 15-17 are the response curves of torque, stator flux amplitude, stator current and rotational speed respectively.

Compared with the vector control, the method of the present invention has a small amount of calculation, is simple to implement, and is robust to the parameter change of the induction motor; compared with the direct torque control, the method of the present invention calculates the control according to the magnitude of the flux linkage and torque error The stator voltage vector of these errors converges, and the switching signal of the inverter is sent out in the form of SVM, which not only realizes the constant switching cycle of the inverter, but also overcomes the jitter of flux linkage and torque control in direct torque control question.

Claims (2)

1. The variable structure torque direct control method of the induction motor with space voltage vector modulation, which contains the steps of controlling the easier-to-observe stator flux linkage and controlling the torque by direct feedback. It is characterized in that it is a method based on the stator flux linkage amplitude The size of the respective errors of torque and torque is calculated by the variable structure flux linkage and torque controller to control the stator voltage vector of these errors, and then the switching signal of the voltage inverter is sent out by means of a space vector modulation (SVM) generator to A method of controlling the torque of an induction motor, specifically, it comprises the following steps in sequence: (1). Set the stator flux linkage amplitude reference value ψ _sREF and torque reference value T _eREF , and input them into the computer; (2). Then send the following parameters obtained from the control system adjustment and controller parameter setting program into the computer: Variable structure flux linkage controller parameters: ε _ψ > εΔ _ψ , ${\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}}=R_{\mathrm{the\; s}}{m}^2{\mathrm{\&psi;}}_{\mathrm{sREF}}/\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}^2{L}_r,$ K _ψ >0: among them, σ=1-(M ² /L _s L _r ), L _s : stator self-inductance; L _r : rotor self-inductance, M: mutual inductance; R _s : stator resistance; Convergence time: $t_{\mathrm{\&psi;}}\&le;\left|e_{\mathrm{\&psi;}}\left(t_0^{\mathrm{\&psi;}}\right)\right|/({\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}-{\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}})$ Among them, e _ψ ＝V _sREF -ψ _s , ψ _s : stator flux amplitude, t ₀ ^ψ is the initial moment of stator flux ψ _s control; variable structure torque controller parameters: ${\mathrm{\&epsiv;}}_{\mathrm{Te}}>\left|{\mathrm{\&psi;}}_{\mathrm{sREF}}{\stackrel{..}{\mathrm{\&theta;}}}_{\mathrm{the\; s}}\right|,$ _KTe > 0: (3). Flux linkage and torque observer to calculate the stator flux linkage amplitude and torque observations (3.1). The computer measures the phase current i _A , i _B , i _C and the bus voltage V _dc from the inverter circuit powered by AC through the voltage and current measurement circuit, and the switching state SA(t) of the inverter in the observation period , SB(t), SC(t); (3.2). Calculate the components of stator current and stator voltage on the stationary coordinate system by the following formula: $i_{\mathrm{s\&alpha;}}=i_A-\frac{1}{2}(i_B+i_C),i_{\mathrm{s\&beta;}}=\frac{\sqrt{3}}{2}(i_B-i_C),$ ${\tilde{u}}_{\mathrm{s\&alpha;}}=\frac{V_{\mathrm{dc}}}{3}(2\mathrm{SA}-\mathrm{SB}-\mathrm{SC}),$ ${\tilde{u}}_{\mathrm{s\&beta;}}=\frac{V_{\mathrm{dc}}}{\sqrt{3}}(\mathrm{SB}-\mathrm{SC});$ (3.3). Calculated by the following formula

(3.4). Calculated by the following formula (3.5). Calculated by the following formula (4). The variable structure flux linkage and torque controllers respectively calculate the components _u sd and u _sq of the stator voltage u _s on the dynamic coordinate system of the stator flux linkage according to e _ψ and e _Te : First judge whether t>t _ψ If: the amplitude of the stator flux linkage has entered a steady state at time t, t≥t _ψ , then: $e_{\mathrm{\&psi;}}={\mathrm{\&psi;}}_{\mathrm{sREF}}-{\widehat{\mathrm{\&psi;}}}_{\mathrm{the\; s}},e_{\mathrm{Te}}=T_{\mathrm{eREF}}-{\hat{T}}_e,$ then: $u_{\mathrm{sd}}=\frac{R_{\mathrm{the\; s}}}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}}{\mathrm{\&psi;}}_{\mathrm{the\; s}}+K_{\mathrm{\&psi;}}{e}_{\mathrm{\&psi;}}+{\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}\mathrm{sgn}{e}_{\mathrm{\&psi;}},$ $u_{\mathrm{sq}}=\frac{R_{\mathrm{the\; s}}}{{\mathrm{\&psi;}}_{\mathrm{sREF}}}{T}_{\mathrm{eREF}}+{\&Integral;}_{t_T^0}^t(K_{\mathrm{Te}}{e}_{\mathrm{Te}}+{\mathrm{\&epsiv;}}_{\mathrm{Te}}\mathrm{sgn}{e}_{\mathrm{Te}})\mathrm{d\&tau;};$ Where t ₀ ^T is the initial moment of induction motor torque control; if: the stator flux amplitude does not enter the steady state at time t, t<t _ψ , then: $e_{\mathrm{\&psi;}}={\mathrm{\&psi;}}_{\mathrm{sREF}}-{\widehat{\mathrm{\&psi;}}}_{\mathrm{the\; s}},e_{\mathrm{Te}}=0-{\hat{T}}_e,$ then: $u_{\mathrm{sd}}=\frac{R_{\mathrm{the\; s}}}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}}{\mathrm{\&psi;}}_{\mathrm{the\; s}}+K_{\mathrm{\&psi;}}{e}_{\mathrm{\&psi;}}+{\mathrm{\&epsiv;}}_{\mathrm{\&psi;}}\mathrm{sgn}{e}_{\mathrm{\&psi;}},$ $u_{\mathrm{sq}}=\frac{R_{\mathrm{the\; s}}}{{\mathrm{\&psi;}}_{\mathrm{sREF}}}{T}_{\mathrm{eREF}}+{\&Integral;}_{t_T^0}^t(K_{\mathrm{Te}}{e}_{\mathrm{Te}}+{\mathrm{\&epsiv;}}_{\mathrm{Te}}\mathrm{sgn}{e}_{\mathrm{Te}})\mathrm{d\&tau;};$ (5). Voltage vector synthesis and space vector modulation (SVM) generator according to u _sd , u _sq ,

Calculate the three-phase switch control signals SA, SB, SC required by the inverter: (5.1). Calculate u _sα and u _sβ by the following formula: $u_{\mathrm{the\; s}}=\left[\begin{array}{c}{u}_{\mathrm{s\&alpha;}}\\ u_{\mathrm{s\&beta;}}\end{array}\right]=\left[\begin{array}{cc}\cos {\mathrm{\&theta;}}_{\mathrm{the\; s}}& -\sin {\mathrm{\&theta;}}_{\mathrm{the\; s}}\\ \sin {\mathrm{\&theta;}}_{\mathrm{the\; s}}& \cos {\mathrm{\&theta;}}_{\mathrm{the\; s}}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{sd}}\\ u_{\mathrm{sq}}\end{array}\right]$ (5.2). Calculate the magnitude U _s and rotation angle θ _us of the stator voltage vector by the following formula $u_{\mathrm{the\; s}}=\sqrt{u_{\mathrm{s\&alpha;}}^2+u_{\mathrm{s\&beta;}}^2},$ θ _us = cos ^-1 (u _sα /U _s ); (5.3). Determine the two adjacent basic voltage vectors of the synthesized stator voltage by θ _us : $0\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{\mathrm{\&pi;}}{3},$ The stator voltage vector is between V1 and V2, N=1, using V1 and V2 $\frac{\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{2\mathrm{\&pi;}}{3},$ The stator voltage vector is between V2 and V3, N=2, using V2 and V3 $\frac{2\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\mathrm{\&pi;},$ The stator voltage vector is between V3 and V4, N=3, using V3 and V4 $\mathrm{\&pi;}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{4\mathrm{\&pi;}}{3},$ The stator voltage vector is between V4 and V5, N=4, using V4 and V5 $\frac{4\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<\frac{5\mathrm{\&pi;}}{3},$ The stator voltage vector is between V5 and V6, N=5, using V5 and V6 $\frac{5\mathrm{\&pi;}}{3}\&le;{\mathrm{\&theta;}}_{\mathrm{us}}<2\mathrm{\&pi;},$ The stator voltage vector is between V6 and V1, N=6, V6 and V1 are used; (5.4). At the current moment, the stator voltage vector is in the interval N, and the two inverter basic voltage vectors V _N and V _N+1 adjacent to the stator voltage vector are calculated by the following formula (if N=6, V _{N+ 1} = V1) and the action time of zero vector V0, V7: in the set SVM period T _P , $\mathrm{\&gamma;}={\mathrm{\&theta;}}_{\mathrm{us}}-\frac{(N-1)\mathrm{\&pi;}}{3}$ $0\&le;\mathrm{\&gamma;}<\frac{\mathrm{\&pi;}}{3}$ The action time T _N of V _N : $T_N=T_P\frac{2u_{\mathrm{the\; s}}}{\sqrt{3}{V}_{\mathrm{dc}}}\sin (\frac{\mathrm{\&pi;}}{3}-\mathrm{\&gamma;}),$ The action time T _N+ 1 of V _N+1 : $T_{N+1}=T_P\frac{2u_{\mathrm{the\; s}}}{\sqrt{3}{V}_{\mathrm{dc}}}\sin \left(\mathrm{\&gamma;}\right),$ The action time T ₀ and T ₇ of V0 and V7: $T_0=T_7=\frac{T_P-T_1-T_2}{2};$ (5.5). Determine the three-phase switch control signals SA, SB, and SC of the inverter according to the basic voltage vector and zero vector and their respective action times: The three-phase switching signals corresponding to the basic voltage vector and zero vector generated by the inverter are V ₁ (SA SB SC): V0(000), V1(100), V2(110), V3(010), V4( 011), V5(001), V6(101)V7(111); in one SVM cycle T _p , the basic voltage vectors V _N , V _N+1 and zero vectors V0 and V7 adjacent to the stator voltage vector act in the following order : V0 acts on T ₀ /2→V _N acts on T _N /2→V _N+1 acts on T _N+1 /2→V7 acts on T ₇ →V _N+1 acts on T _N+1 /2→V _N acts on T _N / 2→V0 acts on T ₀ /2; And according to the corresponding relationship between the basic voltage vector and the three-phase switching signals SA, SB, SC of the inverter, the switching control signals SA, SB, SC of the inverter are obtained, so as to drive the induction motor to control the rotation of the induction motor moment. 2. the induction motor variable structure torque direct control method of space voltage vector modulation according to claim 1, is characterized in that, described control system performance adjustment and controller parameter tuning program contain following steps successively: (1). Determine K _ψ , ε _ψ , K _Te , ε _Te according to the following formula and system performance requirements: ${\mathrm{\&epsiv;}}_{\mathrm{\&Delta;\&psi;}}=\frac{R_{\mathrm{the\; s}}{m}^2}{\mathrm{\&sigma;}{L}_{\mathrm{the\; s}}^2{L}_r}{\mathrm{\&psi;}}_{\mathrm{sREF}},$ ε _ψ ≈2ε _Δψ , the initial value of K _ψ is set to K _ψ = 1, ε _Te ≈10ψ _sREF T _eREF , the initial value of K _Te is set as K _Te ＝1; (2). Set ψ _sREF and T _eREF according to the characteristics of the induction motor itself and system performance requirements; (3). The variable structure flux linkage controller uses the method of increasing K _ψ according to the control main program to make the flux linkage convergence speed meet the performance requirements; (4). After the flux linkage amplitude is stabilized, the variable structure torque controller uses the method of increasing K _Te according to the control main program to make the torque convergence speed meet the performance requirements; (5). Determine the K _ψ and K _Te that meet the system performance requirements; (6). End.

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