CN102638216A - Method for starting motor without position sensor - Google Patents

Abstract

The invention discloses a method for starting a motor without a position sensor, which includes: applying a fixed voltage vector to the motor and obtaining Is; subjecting the Is to Clark conversion and obtaining i <alpha> and i <beta>; presetting rotation speed omega r and torque T<e> as 0 by computing to obtain rotor flux-linkage vector angle theta r, subjecting omega r and omega r to PI operation to obtain Te, then subjecting Te and the T3 to PI operation to obtain delta, obtaining theta<s> according to the formula theta <s>=theta <r> +delta, giving Psi* <s> to obtain U<alpha> and U<beta>, subjecting the U<alpha> and the U<beta> to inverse Clark conversion and obtaining U<a>, U<b> and U<c>, acquiring I<a>, I<b> and I<c> through current, subjecting the I<a>, the I<b> and the I<c> to Clark conversion and obtaining I alpha and I beta, obtaining Psi <s> alpha and Psi<s> beta by stator flux linkage operation, obtaining Psi<s> and theta<s> by modular angle operation, obtaining the Te by torque estimate, discretizing the theta<s> to obtain omega<r>, and finishing motor starting process if the omega<r> is equal to the omega*<r>. The method for starting the motor without the position sensor has the following advantages that by combining initial position detection technology with DTC (direct torque control) strategy, loop-locked stable control of the integral control strategy is realized.

Description

Position-sensor-free electric motor starting method

Technical field

The invention belongs to the electronic engineering technical field, particularly a kind of to utilize the initial position detection method to combine the advanced electric motor starting method that does not need position transducer of Strategy of Direct Torque Control be position-sensor-free electric motor starting method.

Background technology

Space vector pulse width modulation Space Vector Pulse Width Modulation abbreviation: SVPWM

Direct torque control Direct Torque Control abbreviation: DTC

Field orientation control Field Oriented Control abbreviation: FOC

Integration scale operation Proportion Integral abbreviation: PI

Though prior motor field orientation control FOC strategy need not position transducer; But after when electric motor starting, needing dragging motor to arrive a certain rotating speed; Could make motor speed adjustable continuously, that is to say in the electric motor starting process speed of employing open loop control strategy, accelerate to the rotating speed of setting when motor after; Switch to the speed closed loop control strategy, prolonged the start-up time of motor; In order to overcome the defective that electric motor starting needs open loop to drag in the field orientation control FOC strategy; Motor direct torque control DTC strategy has appearred; When electric motor starting, do not need dragging motor to arrive a certain rotating speed; But need be used, therefore in use following problem can occur with position transducer or velocity transducer:

1) needs in the design process to increase and the supporting hardware circuit of transducer, cause the raising of design cost;

2) transducer hardware support kit circuit is easy to receive electromagnetic interference, causes signal transmission errors, and then control strategy was lost efficacy;

3) receive the restriction in the useful life of transducer itself, need the periodic replacement transducer, when emat sensor more, need dismantle whole motor encapsulation, it is loaded down with trivial details more to change jobs.

Summary of the invention

Technical problem to be solved by this invention is, provides a kind of initial position detection technique and DTC control strategy to combine, and makes the The whole control strategy reach the position-sensor-free electric motor starting method of the stable control of closed loop.

Space vector pulse width modulation SVPWM algorithm is used for according to voltage vector, adopts the space voltage vector pulse width modulation algorithm to generate the power device pulse width signal;

Voltage source inverter is used for producing the three-phase winding current according to said power device pulse width signal, sends to permagnetic synchronous motor;

The Clark conversion, it is last to two phase coordinate system α, β that static coordinate is fastened the coordinate transform of three-phase winding current.

For solving the problems of the technologies described above, position-sensor-free electric motor starting method provided by the invention may further comprise the steps:

(1) apply the fixed voltage vector V to motor and promptly a is switched on mutually, b, c phase no power and another fixed voltage vector V ' promptly are to a no power mutually, and b, c switch on mutually, obtain I respectively through voltage source inverter then _s, I ' _sIf, I _s-I ' _s＞0 so-π/6＜θ _r＜π/6 promptly

If I _s-I ' _s＜0,5 π/6＜θ so _r＜7 π/6 promptly ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}[\frac{i_{\mathrm{\&beta;}}}{(i_{\mathrm{\&alpha;}}-I_s)}+2\mathrm{\&pi;}];$

(2) to I _sCarry out the Clark conversion, obtain the current i in two phase coordinate systems _α, i _β, through calculating $\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right]=\sqrt{\frac{2}{3}}\frac{V_{\mathrm{DC}}}{R}*\left[\begin{array}{c}1-\frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}+e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})+\frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}-e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})\mathrm{Cos}2{\mathrm{\&theta;}}_r\\ \frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}+e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})\mathrm{Sin}2{\mathrm{\&theta;}}_r\end{array}\right]=\left[\begin{array}{c}{I}_s+{\mathrm{\&Delta;\; I}}_s\mathrm{Cos}2{\mathrm{\&theta;}}_r\\ {\mathrm{\&Delta;\; I}}_s\mathrm{Sin}2{\mathrm{\&theta;}}_r\end{array}\right]$

To rotor flux azimuth θ _r

Wherein: i _α, i _βBe known quantity; V _DCBe DC bus-bar voltage; R is an armature winding resistance; Ld is a d axle inductance; Lq is a q axle inductance; Ts applies the time that the voltage vector time promptly applies V and V '; E is mathematical constant; Δ I _sFor the bus current variable quantity (is I _s, I ' _sDifference).

(3) given rotating speed of target Right

And ω _rCarry out the PI computing and obtain target torque Again to T with

Carry out obtaining angle of torsion δ after the PI computing, at this moment ω _r=0, T _e=0;

Wherein: the PI computing is used for said difference

And ω _rCarry out ratio, integral operation obtains target torque

To said difference T _eWith

Carry out ratio, integral operation obtains angle of torsion δ.

(4) through rotor flux azimuth θ _rWith stator magnetic linkage azimuth θ _sConversion formula θ _s=θ _r+ δ obtains stator magnetic linkage azimuth θ _s

(5) give the magnetic linkage that sets the goal again

Carry out the voltage vector computing $\begin{array}{c}{u}_{\mathrm{\&alpha;}}=i_{\mathrm{\&alpha;}}{r}_s+\frac{\left|{\mathrm{\&psi;}}_s^{*}\right|\mathrm{Cos}({\mathrm{\&theta;}}_s+\mathrm{\&delta;})-\left|{\mathrm{\&psi;}}_s\right|\mathrm{Cos}{\mathrm{\&theta;}}_s}{\mathrm{\&Delta;\; T}}\\ u_{\mathrm{\&beta;}}=i_{\mathrm{\&beta;}}{r}_s+\frac{\left|{\mathrm{\&psi;}}_s^{*}\right|\mathrm{Sin}({\mathrm{\&theta;}}_s+\mathrm{\&delta;})-\left|{\mathrm{\&psi;}}_s\right|\mathrm{Sin}{\mathrm{\&theta;}}_s}{\mathrm{\&Delta;\; T}}\end{array}$

Obtain the voltage U in two phase coordinate systems _α, U _β

Wherein: i _α, i _β, δ, θ _sFor known; r _sBe stator resistance; Δ T is sampling time (equating with Ts).(6) to U _α, U _βCarry out contrary Clark conversion, obtain voltage U a, Ub, Uc in three phase coordinate systems, adopt through electric current

Collection obtains three-phase current I _a, I _b, I _c

Contrary Clark conversion transforms to three phase coordinate system a, b, the last winding voltage of c with two phase coordinate system α, the last winding voltage of β.

(7) to I _a, I _b, I _cCarry out the Clark conversion, obtain current I _α, I _β, calculate through stator magnetic linkage $\begin{array}{c}{\mathrm{\&psi;}}_{\mathrm{S\&alpha;}}=\&Integral;(u_{\mathrm{\&alpha;}}-i_{\mathrm{\&alpha;}}{r}_s)\mathrm{Dt}\\ {\mathrm{\&psi;}}_{\mathrm{S\&beta;}}=\&Integral;(u_{\mathrm{\&beta;}}-i_{\mathrm{\&beta;}}{r}_s)\mathrm{Dt}\end{array}$ Obtain the component Ψ of current stator magnetic linkage _{S α}, ψ _{S β}

Wherein: r _sBe stator resistance.

$\left|{\mathrm{\&psi;}}_s\right|=\sqrt{{\mathrm{\&psi;}}_{\mathrm{s\&alpha;}}^2+{\mathrm{\&psi;}}_{\mathrm{s\&beta;}}^2}$

(8) through modular angle computing θ _s=arctan (ψ _{S β}/ Ψ _{S α}) draw the mould Ψ of current stator magnetic linkage _sAnd current stator magnetic linkage azimuth θ _s

(9) pass through torque estimating

Draw current torque T _e, and to θ _sCarry out discretization and obtain current rotational speed omega _r

Wherein: p is the magnetic pole logarithm.

(10) if

Then the electric motor starting process finishes; If Repeating step (3)～step (9) then, this moment step (3) medium speed ω _rWith torque T _eBe the rotational speed omega of calculating in the step (9) _rWith torque T _e, the rotational speed omega of in step (9), calculating _rWith rotating speed of target

Equate.

Further; The described current acquisition of step (6) is meant according to voltage vector and adopts space vector pulse width modulation SVPWM algorithm to generate the power device pulse width signal; Through voltage source inverter described power device pulse width signal is produced the three-phase winding current again, send to permagnetic synchronous motor PMSM.

After adopting above structure, position-sensor-free electric motor starting method of the present invention compared with prior art has the following advantages:

1, need not position transducer, calculate the initial position of rotor, need not consider signal transmission errors fully and the loss that causes, and then avoid the control strategy loss that causes out of control, improved stability and reliability with the initial position detection algorithm;

2, electric motor starting and accelerator all are under the closed-loop control state, have shortened the electric motor starting time, improved operating efficiency;

3, reduce design cost greatly, reduce energy resource consumption.

Description of drawings

Fig. 1 is the block diagram of position-sensor-free electric motor starting method of the present invention.

Embodiment

Combine accompanying drawing that the present invention is done further description through embodiment below.

As shown in Figure 1, at first, the initial position that utilizes initial position detection method to calculate rotor is θ _r, concrete grammar is: given voltage vector V obtains three-phase total current I through voltage source inverter _s, again to I _sCarry out the Clark conversion, obtain i _α, i _β,

Pass through formula $\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right]=\sqrt{\frac{2}{3}}\frac{V_{\mathrm{DC}}}{R}*\left[\begin{array}{c}1-\frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}+e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})+\frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}-e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})\mathrm{Cos}2{\mathrm{\&theta;}}_r\\ \frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}+e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})\mathrm{Sin}2{\mathrm{\&theta;}}_r\end{array}\right]$

Obtain after the arrangement $\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right]=\left[\begin{array}{c}{I}_s+{\mathrm{\&Delta;\; I}}_s\mathrm{Cos}2{\mathrm{\&theta;}}_r\\ {\mathrm{\&Delta;\; I}}_s\mathrm{Sin}2{\mathrm{\&theta;}}_r\end{array}\right]$

Calculate ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}\frac{i_{\mathrm{\&beta;}}}{\left(i_{\mathrm{\&alpha;}}{-I}_s\right)}$ Perhaps ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}[\frac{i_{\mathrm{\&beta;}}}{(i_{\mathrm{\&alpha;}}-I_s)}+2\mathrm{\&pi;}],$

A given again voltage vector V ' obtains I ' through voltage source inverter _s, compare I _s, I ' _sSize,

If I _s-I ' _s＞0, so-π/6＜θ _r＜π/6 promptly ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}\frac{i_{\mathrm{\&beta;}}}{\left(i_{\mathrm{\&alpha;}}{-I}_s\right)};$

If I _s-I ' _s＜0,5 π/6＜θ so _r＜7 π/6 promptly ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}[\frac{i_{\mathrm{\&beta;}}}{(i_{\mathrm{\&alpha;}}-I_s)}+2\mathrm{\&pi;}],$

Then, obtain current rotational speed omega through Strategy of Direct Torque Control _r, concrete grammar is following:

1) rotational speed omega of current motor _rWith torque T _eBe 0, given rotating speed of target

Right

And ω _rCarry out obtaining target torque after the PI computing

Again to T _eWith

Carry out obtaining angle of torsion δ after the PI computing;

2) through rotor flux azimuth θ _rWith stator magnetic linkage azimuth θ _sConversion formula θ _s=θ _r+ δ obtains stator magnetic linkage azimuth θ _s

3) giving the magnetic linkage that sets the goal

Carry out the voltage vector formula $\begin{array}{c}{u}_{\mathrm{\&alpha;}}=i_{\mathrm{\&alpha;}}{r}_s+\frac{\left|{\mathrm{\&psi;}}_s^{*}\right|\mathrm{Cos}({\mathrm{\&theta;}}_s+\mathrm{\&delta;})-\left|{\mathrm{\&psi;}}_s\right|\mathrm{Cos}{\mathrm{\&theta;}}_s}{\mathrm{\&Delta;\; T}}\\ u_{\mathrm{\&beta;}}=i_{\mathrm{\&beta;}}{r}_s+\frac{\left|{\mathrm{\&psi;}}_s^{*}\right|\mathrm{Sin}({\mathrm{\&theta;}}_s+\mathrm{\&delta;})-\left|{\mathrm{\&psi;}}_s\right|\mathrm{Sin}{\mathrm{\&theta;}}_s}{\mathrm{\&Delta;\; T}}\end{array}$ Calculate the voltage U in two phase coordinate systems _α, U _β

4) to U _α, U _βCarry out contrary Clark conversion, obtain voltage U a, Ub, Uc in three phase coordinate systems, obtain three-phase current I through SVPWM algorithm and voltage source inverter _a, I _b, I _c

5) to I _a, I _b, I _cCarry out the Clark conversion, obtain two current phase coordinate system α, the last I of β _α, I _β, through the stator magnetic linkage formula $\begin{array}{c}{\mathrm{\&psi;}}_{\mathrm{S\&alpha;}}=\&Integral;(u_{\mathrm{\&alpha;}}-i_{\mathrm{\&alpha;}}{r}_s)\mathrm{Dt}\\ {\mathrm{\&psi;}}_{\mathrm{S\&beta;}}=\&Integral;(u_{\mathrm{\&beta;}}-i_{\mathrm{\&beta;}}{r}_s)\mathrm{Dt}\end{array}$

Calculate the component Ψ of current stator magnetic linkage _{S α}, ψ _{S β}

$\left|{\mathrm{\&psi;}}_s\right|=\sqrt{{\mathrm{\&psi;}}_{\mathrm{s\&alpha;}}^2+{\mathrm{\&psi;}}_{\mathrm{s\&beta;}}^2}$

6) through modular angle operational formula θ _s=arctan (ψ _{S β}/ Ψ _{S α}) draw the mould Ψ of current stator magnetic linkage _sAnd current stator magnetic linkage azimuth θ _s

7) again through the torque estimating formula $T_e=\frac{3}{2}p({\mathrm{\&psi;}}_{\mathrm{S\&alpha;}}{i}_{\mathrm{\&beta;}}-{\mathrm{\&psi;}}_{\mathrm{S\&beta;}}{i}_{\mathrm{\&alpha;}})$ Draw current torque T _eWith to θ _sCarry out discretization and obtain current rotational speed omega _r

8) if

then electric motor starting process end;

If

Repeating step (1)～step (7) then, this moment, motor was worked, so step (1) medium speed ω _rWith torque T _eBe the rotational speed omega of calculating in the step (7) _rWith torque T _e, the rotational speed omega of in step (7), calculating _rWith rotating speed of target

Equate.

So far this position-sensor-free electric motor starting process finishes, and the motor operation after making reaches stable, closed-loop control fast.

Claims (10)

1. a position-sensor-free electric motor starting method is characterized in that, may further comprise the steps:

(1) applies the fixed voltage vector to motor, obtain three-phase total current I through voltage source inverter then _s

(2) to three-phase total current I _sCarry out the Clark conversion, obtain the current i in two phase coordinate systems _α, i _β, through calculating rotor flux azimuth θ _r

(3) given rotating speed of target

This moment, motor did not start rotational speed omega _rWith torque T _eBe 0, right

And ω _rCarry out obtaining target torque behind the integration scale operation Again to T _eWith

Carry out obtaining angle of torsion δ behind the integration scale operation;

(4) through rotor flux azimuth θ _rWith stator magnetic linkage azimuth θ _sConversion formula θ _s=θ _r+ δ obtains stator magnetic linkage azimuth θ _s

(5) give the magnetic linkage that sets the goal again

Through the i that step (1)～calculate (4) _α, i _β, δ, θ _sCarry out the voltage vector computing and obtain the voltage U in two phase coordinate systems _α, U _β

(6) to the voltage U in two phase coordinate systems _α, U _βCarry out contrary Clark conversion, obtain voltage U a, Ub, Uc in three phase coordinate systems, obtain three-phase current I through current acquisition _a, I _b, I _c

(7) to I _a, I _b, I _cCarry out the Clark conversion, obtain the electric current I in the two current phase coordinate systems _α, I _β, calculate the component Ψ of current stator magnetic linkage through stator magnetic linkage _{S α}, ψ _{S β}

(8) draw the mould Ψ of current stator magnetic linkage through the modular angle computing _sAnd current stator magnetic linkage azimuth θ _s

(9) draw current torque T through torque estimating _eWith to θ _sCarry out discretization and obtain current rotational speed omega _r

(10) if

Then the electric motor starting process finishes; If

Repeating step (3)～step (9) then, this moment step (3) medium speed ω _rWith torque T _eBe the rotational speed omega of calculating in the step (9) _rWith torque T _e, the rotational speed omega of in step (9), calculating _rWith rotating speed of target

Equate.

2. position-sensor-free electric motor starting method according to claim 1 is characterized in that, step (2) and the described Clark conversion of step (7), and it is last to two phase coordinate system α, β that static coordinate is fastened the coordinate transform of three-phase winding current; The described contrary Clark conversion of step (6) transforms to three phase coordinate system a, b, the last winding voltage of c with two phase coordinate system α, the last winding voltage of β.

3. position-sensor-free electric motor starting method according to claim 1 is characterized in that, the described integration scale operation of step (3) is used for said difference

And ω _rCarry out ratio, integral operation obtains target torque

To said difference T _eWith

Carry out ratio, integral operation obtains angle of torsion δ.

4. position-sensor-free electric motor starting method according to claim 1; It is characterized in that; The described current acquisition of step (6) is meant according to voltage vector and adopts space vector pulse width modulation SVPWM algorithm to generate the power device pulse width signal; Through voltage source inverter described power device pulse width signal is produced the three-phase winding current again, send to permagnetic synchronous motor PMSM.

5. position-sensor-free electric motor starting method according to claim 4 is characterized in that described space vector pulse width modulation SVPWM algorithm is used for according to voltage vector, adopts the space voltage vector pulse width modulation algorithm to generate the power device pulse width signal; Voltage source inverter is used for producing the three-phase winding current according to said power device pulse width signal, sends to permagnetic synchronous motor.

6. position-sensor-free electric motor starting method according to claim 1 is characterized in that, obtains rotor flux azimuth θ through the initial position detection in the step (2) _r, concrete formula is:

$\left[\begin{array}{c}{i}_{\mathrm{\&alpha;}}\\ i_{\mathrm{\&beta;}}\end{array}\right]=\sqrt{\frac{2}{3}}\frac{V_{\mathrm{DC}}}{R}*\left[\begin{array}{c}1-\frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}+e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})+\frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}-e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})\cos 2{\mathrm{\&theta;}}_r\\ \frac{1}{2}(e^{-\frac{R}{\mathrm{Lq}}\mathrm{Ts}}+e^{-\frac{R}{\mathrm{Ld}}\mathrm{Ts}})\sin 2{\mathrm{\&theta;}}_r\end{array}\right]=\left[\begin{array}{c}{I}_s+{\mathrm{\&Delta;I}}_s\cos 2{\mathrm{\&theta;}}_r\\ {\mathrm{\&Delta;I}}_s\sin 2{\mathrm{\&theta;}}_r\end{array}\right]$

${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}\frac{i_{\mathrm{\&beta;}}}{\left(i_{\mathrm{\&alpha;}}{-I}_s\right)}$ Perhaps ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}[\frac{i_{\mathrm{\&beta;}}}{(i_{\mathrm{\&alpha;}}-I_s)}+2\mathrm{\&pi;}]$

Wherein: V _DCBe DC bus-bar voltage; R is an armature winding resistance; Ld is a d axle inductance; Lq is a q axle inductance; Ts applies the time that the voltage vector time promptly applies V and V '; E is mathematical constant; Δ I _sFor the bus current variable quantity (is I _s, I ' _sDifference).

Initial position detection method: at first feed voltage vector V and promptly a is switched on mutually, b, c phase no power obtain I through current acquisition _s, feeding another voltage vector V ' then promptly to a phase no power, b, c switch on mutually, obtain I ' _sIf, I _s-I ' _s＞0 so-π/6＜θ _r＜π/6 promptly

If I _s-I ' _s＜0,5 π/6＜θ so _r＜7 π/6 promptly ${\mathrm{\&theta;}}_r=\frac{1}{2}\mathrm{Arctan}[\frac{i_{\mathrm{\&beta;}}}{(i_{\mathrm{\&alpha;}}-I_s)}+2\mathrm{\&pi;}].$

7. position-sensor-free electric motor starting method according to claim 1 is characterized in that, the said voltage vector operational formula of step (5) does $\begin{array}{c}{u}_{\mathrm{\&alpha;}}=i_{\mathrm{\&alpha;}}{r}_s+\frac{\left|{\mathrm{\&psi;}}_s^{*}\right|\mathrm{Cos}({\mathrm{\&theta;}}_s+\mathrm{\&delta;})-\left|{\mathrm{\&psi;}}_s\right|\mathrm{Cos}{\mathrm{\&theta;}}_s}{\mathrm{\&Delta;\; T}}\\ u_{\mathrm{\&beta;}}=i_{\mathrm{\&beta;}}{r}_s+\frac{\left|{\mathrm{\&psi;}}_s^{*}\right|\mathrm{Sin}({\mathrm{\&theta;}}_s+\mathrm{\&delta;})-\left|{\mathrm{\&psi;}}_s\right|\mathrm{Sin}{\mathrm{\&theta;}}_s}{\mathrm{\&Delta;\; T}}\end{array},$

Wherein: r _sBe stator resistance; Δ T is sampling time (equating with Ts).

8. position-sensor-free electric motor starting method according to claim 1 is characterized in that, the described stator magnetic linkage computing formula of step (7) does $\begin{array}{c}{\mathrm{\&psi;}}_{\mathrm{S\&alpha;}}=\&Integral;(u_{\mathrm{\&alpha;}}-i_{\mathrm{\&alpha;}}{r}_s)\mathrm{Dt}\\ {\mathrm{\&psi;}}_{\mathrm{S\&beta;}}=\&Integral;(u_{\mathrm{\&beta;}}-i_{\mathrm{\&beta;}}{r}_s)\mathrm{Dt}\end{array},$

Wherein: r _sBe stator resistance.

9. position-sensor-free electric motor starting method according to claim 1 is characterized in that step (8) is described

$\left|{\mathrm{\&psi;}}_s\right|=\sqrt{{\mathrm{\&psi;}}_{\mathrm{s\&alpha;}}^2+{\mathrm{\&psi;}}_{\mathrm{s\&beta;}}^2}$

The modular angle operational formula is θ _s=arctan (ψ _{S β}/ Ψ _{S α}).

10. position-sensor-free electric motor starting method according to claim 1 is characterized in that, the described torque estimating formula of step (9) does $T_e=\frac{3}{2}p({\mathrm{\&psi;}}_{\mathrm{S\&alpha;}}{i}_{\mathrm{\&beta;}}-{\mathrm{\&psi;}}_{\mathrm{S\&beta;}}{i}_{\mathrm{\&alpha;}}),$

Wherein: p is the magnetic pole logarithm.