CN101694985A - Method for identifying on-line parameters of linear induction motor - Google Patents

Abstract

The invention relates to a method for identifying on-line parameters of a linear induction motor, which realizes the closed-loop control of exciting current component and thrust current component of a motor and enables the exciting current component to be equal to the thrust current component under the directional control of an indirect magnetic field. The method comprises the following steps: adjusting a secondary time constant value used in a motor controller and changing the specified slip frequency and the synchronous frequency of the motor in the controller by an on-line identification arithmetic to adjust the synchronous angle for the magnetic field to locate; searching the minimum value of the input current of the motor in a steady-state operation condition when the load torque is kept constant, enabling the secondary time constant used in the motor controller to be approximate to the real value of the secondary time constant of the motor, therefore realizing the on-line identification of the secondary time constant of the motor. The invention can realize the correct directional control of the indirect magnetic field of the linear induction motor without depending on other motor parameters hard to be controlled exactly through on-line operation, avoid influence of end effect, parameter change and the like on the control performance, does not need the input voltage component of the motor and improves the practicability of a parameter on-line identification system.

Description

Method for identifying on-line parameters of linear induction motor

Technical field

The present invention relates generally to line inductance electromotor control field, proposes a kind of on-line identification method of motor secondary time constant.This method is also in the on-line identification control algolithm applicable to the rotary inductive motor.

Background technology

Linear induction motor is a kind of linear electric motors of widespread, can directly produce the straight line mechanical movement.But because structure is special, have the limit end effect, the parameter of electric machine is in operation and changes, and causes field orientation inaccurate, and the control deleterious need be grasped the parameter of electric machine in real time by the method for on-line identification.People such as Z.R.Zhang are at document LIM dynamicperformance assessment from parameter identification. (IEEE Industry applicationssociety annual meeting, Vol.1, Aug, 1993:295-300.) in a kind of on-line parameter identification algorithm of line inductance electromotor has been proposed, the motor dynamic property is assessed.This algorithm is measured voltage, the electric current of motor port in real time, adopts hardware circuit to calculate fundametal compoment, obtains the motional impedance of motor, utilizes parameter identification algorithm real-time update magnetizing inductance L then _mWith secondary resistance R ₂But the algorithm of its proposition is based on the motor steady-state model, and needs the fundametal compoment of real-time calculating voltage, electric current, and error is bigger, uses inconvenient.

Field orientation control is a kind of high performance motor control strategy indirectly, can realize the decoupling zero control of magnetic linkage and torque, has good static and dynamic performance.In the indirect field orientation control of electric rotating machine, the accuracy of rotor flux angle calculation is subjected to rotor time constant to influence very big (" rotor " corresponds to " secondary " in the line inductance electromotor), if used rotor time constant and real electrical machinery is different in the controller, to cause magnetic linkage angle calculation mistake, field orientation generation deviation, make and produce coupling between excitation and the torque current component, motor dynamic characteristic variation, loss increases.In fact, in service at motor, motor internal rotor temperature rise meeting causes rotor resistance value to change, and magnetic saturation effect also can change motor inductance and rotor time constant, thereby makes magnetic linkage angle calculation mistake, field orientation generation deviation.Therefore, adopt the on-line parameter identification, overcoming the adverse effect that service conditions causes parameter to change is the important subject in electric rotating machine control field, becomes the research focus gradually.

People such as S.Wade are at document A new method of rotor resistance estimation forvector-controlled induction machines (IEEE Trans on Industry Electronics., Vol.44 (2), 1997:247-257) by applying the excitation current component short pulse, the variation of judging torque current component comes identification, and shortcoming is that convergence time is longer.K.T.Hung and R.D.Lorenz. are at document A rotor flux error-basedadaptive tuning approach for feedforward field oriented induction machine drives (Industry applications society annual meeting, Vol.1, IEEE 1990:589-594) whether be zero to judge whether rotor time constant is correct according to the q axle component of observation magnetic linkage in, this method calculation of complex, and very big to parameter dependence.J.K.Seol and S.K.Sul are at document Induction motor parameter tuning for highperformance drives (IEEE Trans on Industry Application.Vol.37 (1), whether accurately whether utilize when unloaded speed regulator output 2001:35-41) is zero as rotor time constant criterion, can't on-line automatic identification, need human intervention to judge.People such as K.Tungpimolrut and F.Z.Peng is at document Robust vector control ofinduction motor without using stator and rotor circuit time constant. (IEEE Transon Industry Applications Vol.30 (5), calculate energy function by electric moter voltage, electric current 1994:1241-1246), adopt simple pi regulator identification rotor time constant.Calculating fundamental voltage needs low pass filter, also needs other parameters of electric machine during the calculating energy function.People such as A.B.Razzouk are at document Implementation of DSP based realtime estimator of induction motors rotor time constant (IEEE Trans on PowerElectronics, Vol.17 (4), adopt the formula of deriving to calculate rotor time constant 2002:534-542), do not need iteration, do not produce and disperse, but parameter is more in the formula, is not suitable for carrying out on-line identification, and can influences identification result.People such as M.W.Degner are at document Slip gain estimation in field oriented controlled inductionmachines using the system transient response (IEEE Trans on Industry applications, Vol.42 (3), 2006:702-711) in according to given voltage dynamic response trend identification rotor time constant.When given torque changes, whether shorten by the transient process time of judging voltage and to come the on-line identification rotor time constant, this method can be searched for automatically, needs the filtering of employing window function obtain stator voltage amount accurately.M.W.Degner has applied for United States Patent (USP) Methodand system for rotor time constant tuning in indirect field oriented control (patent No. 6566840B1, May20,2003) with Method and system for controlling torque in a powertrain that includes an induction motor (patent No. 6646412B2, Nov.11,2003).The United States Patent (USP) Automatic fine-tuning of rotor time constant and magnetizingcurrent in field-oriented elevator motor drive (patent No. 5909018 of people such as Vecchiotti application, Nov.11,2003) variation of component of voltage is carried out on-line identification to rotor time constant when moving up and down according to elevator.

Method in above-mentioned existing document or the patent has depends on other parameters of electric machine such as motor excitation inductance, leakage inductance, resistance, and the online accurate grasp of these parameters itself is just very difficult.The calculation of complex that has is unfavorable for on-line implement.And great majority are based on the computational methods of component of voltage, because the voltage of frequency converter drive motors is the PWM ripple, obtain accurately comparatively difficulty of voltage fundamental component.

Summary of the invention

The objective of the invention is to overcome prior art calculation of complex, rely on shortcomings such as other parameter of electric machine that is difficult to online accurate grasp and electric moter voltage measure error be bigger, the secondary time constant on-line identification of a kind of line inductance electromotor method is proposed.The present invention can the on-line identification line inductance electromotor secondary time constant, realize field orientation control indirectly accurately.The present invention does not rely on motor, and other is difficult to the parameter of online accurate grasp, does not need the component of voltage of motor, adopt simple relatively and be easy to realize at line method, thereby improved the practicality of on-line identification system.

The present invention is under the indirect field orientation control of line inductance electromotor, in order to descend motor slip-frequency in the directed control of slip-frequency Equation for Calculating secondary magnetic:

${\mathrm{\ω}}_{\mathrm{sl}}=\frac{1}{T_2}\frac{I_{q1}}{I_{d1}}---\left(1\right)$

In the formula, I _D1Be electric motor primary exciting current, I _Q1Be push current component, ω _SlBe motor slip-frequency, T ₂Be secondary time constant.

The motor slip-frequency ω that will calculate by formula (1) then by following formula (2) _SlWith the rotating speed angular frequency that obtains by the motor lines rate conversion ₂Summation obtains synchronous angle θ, i.e. secondary magnetic chain angle behind the integration.

θ＝∫(ω ₂+ω _sl)dt (2)

In the formula: ω _SlBe slip-frequency, ω ₂Be the rotating speed angular frequency.

Through conversion (trigonometric coordinates conversion) synchronously current of electric is decomposed into exciting current and push current component, realizes field orientation control: carry out the motor excitation electric current I _D1With push current component I _Q1Closed-loop control, and make exciting current I _D1With push current component I _Q1Equate.Pass through the PI regulating and controlling again, obtain the inverter output voltage vector, carry out the PWM modulation then, export corresponding alternating voltage drive motors operation by inverter.Simultaneously, by the on-line identification algorithm, adjust used secondary time constant value in the electric machine controller, change given motor slip-frequency and synchro angle frequency in the electric machine controller, make the synchronous angle θ of secondary magnetic orientation obtain adjusting, under loading moment keeps constant steady operation condition, the motor input current changes with the adjustment of synchronous angle θ, in the process of searching motor input current minimum value, the secondary time constant of using in the identifying motor controller, make this time constant approach time constant actual value in the motor, realize on-line parameter identification.

The minimum value that identification algorithm adopts one dimension global optimizing searching algorithm to search current of electric is carried out secondary time constant identification.Judge that at first motor speed is whether stable, behind velocity-stabilization, under the constant condition of loading condition, the motor output torque is constant, begins to adopt the identification searching algorithm this moment, seeks the minimum value of current component, adjusts given secondary time constant.According to slip-frequency equation (1) in the field orientation control as can be known, when the given component of exciting current and push current equates, regulate secondary time constant and just regulate the motor slip-frequency, thereby adjusted the synchronous angle of motor secondary field orientation.At this moment, for obtaining certain output torque, the motor input current will change, under loading moment keeps constant steady operation condition, search the minimum value of motor input current, make secondary time constant used in the electric machine controller approach the time constant actual value of motor, realize the on-line identification of motor secondary time constant.

Description of drawings

Phasor diagram under Fig. 1 field orientation mode;

The phasor diagram that the secondary magnetic linkage directional angle of Fig. 2 lags behind;

Fig. 3 controls block diagram;

Fig. 4 identification algorithm flow chart;

Fig. 5 searching algorithm flow chart.

Embodiment

Further specify the present invention below in conjunction with the drawings and specific embodiments.

The present invention is based on following principle:

Stable state phasor diagram under the line inductance electromotor secondary magnetic oriented approach as shown in Figure 1.Definition primary current angle γ, and arctan γ=I _Q1/ I _D1, I wherein _Q1Be elementary push current component, I _D1Be elementary excitation current component.Definition motor secondary impedance loop angle φ ₂, and

ω _SlSlip-frequency, L ₂Secondary inductance, R ₂Secondary resistance.

Because primary current phasor I _DqsInduced potential in the secondary loop is-j ω _SlL _mI _Dq1, space lagging current phasor 90 degree, j is a complex operator, L _mBe motor excitation inductance, I _Dq1Be elementary steady-state current phasor.When satisfying

Relation, promptly keep slip-frequency

The field orientation condition time, primary current angle γ equals secondary loop impedance angle φ ₂, i.e. γ=φ ₂, this moment secondary current phasor I _Dq2Be positioned on the negative semiaxis of q axle I _Dq2=I _Q2, I _D2=0, I _D2Be secondary current d axle component, I _QrBe secondary current q axle component.According to similar triangle theory, can get L _mI _Q1=-L _rI _Q2, promptly secondary magnetic linkage ψ _Q2=L _mI _Q1+ L _rI _Q2=0, on the q axle, there is not component.As seen secondary accurately time constant is to satisfy the accurately directed condition in magnetic field.

The parameter of electric machine is inaccurate will to cause the secondary loop impedance angle

Change, the field orientation condition is destroyed.As shown in Figure 2, if the field orientation angle is constant in primary current and the electric machine controller, secondary current phasor I then _Dq2No longer be positioned on the negative semiaxis of q axle, secondary magnetic linkage will not have only d axle component, and the primary current component is fastened at the secondary magnetic chain rivet of two reality all projection, no longer has the characteristic of decoupling zero control.If given secondary time constant is greater than the secondary time constant of reality, the angle of given secondary magnetic linkage will lag behind actual secondary magnetic chain angle.The deviation that defines between given secondary magnetic chain angle and the actual secondary magnetic chain angle is δ, then according to motor phase magnitude relation.Actual magnetic linkage d axle is d in the definition motor ^/, the q axle is q ^/, given and actual excitation axle d-d ^/Between angle of deviation δ for just.If given secondary time constant is greater than actual value, then given secondary magnetic linkage d axle lags behind actual excitation d ^/Axle, angle of deviation δ is for negative, and analytical method is similar.

In given dq coordinate system, d axle excitation current component I _D1=I _mCos γ=I _mCos (φ _r+ δ), q axle thrust current component I _Q1=I _mSin γ=I _mSin (φ _r+ δ), I _mBe the electric current phasor amplitude.In the secondary magnetic linkage coordinate system of reality, excitation current component Letter has apostrophe in the formula ^/Variable represent actual value, the variable of no apostrophe is represented the set-point in the electric machine controller.

The push current component

Secondary magnetic linkage during stable state

As seen when there was misalignment angle δ in magnetic linkage, the actual excitation level of motor also can change.Variable quantity is relevant with magnetic linkage misalignment angle δ.

The electromagnetic push F of motor reality ^/(this moment, there was misalignment angle in magnetic linkage) is

$F^{/}=\frac{3\mathrm{\&pi;}}{2\mathrm{\&tau;}}\frac{L_m}{L_r}{\mathrm{\&psi;}}_{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="H2009100931604E0000011.png"\; state="\{\{state\}\}">d</figure-callout>}2}^{/}{i}_{q1}^{/}=\frac{3\mathrm{\&pi;}}{2\mathrm{\&tau;}}\frac{L_m^2}{L_r}{I}_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="H2009100931604E0000011.png"\; state="\{\{state\}\}">m</figure-callout>}}^2\cos {\mathrm{\&phi;}}_2\sin {\mathrm{\&phi;}}_2---\left(3\right)$

In the formula, τ is the linear electric motors polar moment.

Motor thrust when secondary magnetic linkage is correctly directed

$F=\frac{3\mathrm{\&pi;}}{2\mathrm{\&tau;}}\frac{L_m}{L_r}{\mathrm{\&psi;}}_{d2}{i}_{q1}=\frac{3\mathrm{\&pi;}}{2\mathrm{\&tau;}}\frac{L_m^2}{L_r}{I}_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="H2009100931604E0000011.png"\; state="\{\{state\}\}">m</figure-callout>}}^2\cos \mathrm{\&gamma;}\sin \mathrm{\&gamma;}---\left(4\right)$

The electromagnetic push that calculates according to given current component with the ratio of actual electromagnetic thrust is

$\frac{F^{/}}{F}=\frac{\sin 2{\mathrm{\&phi;}}_2}{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="H2009100931604E0000011.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&gamma;}}---\left(5\right)$

Thereby the variation that can take place by the trigonometric function relationship analysis electromagnetic push of judging different misalignment angle, the variation that actual thrust takes place during the magnetic linkage angular deviation is as shown in table 1.

The actual thrust rule that the changes during angular deviation of table 1 magnetic linkage

By table 1 as seen, if two current component I _D1, I _Q1Unequal, during, hysteresis actual magnetic chain angle leading in secondary magnetic chain angle, electromagnetic push increases sometimes, reduces sometimes.Have only the motor excitation current component of working as to equate, i.e. I with the push current component _D1=I _Q1The time, secondary magnetic chain angle is just producing or negative deviation all can cause dynamic thrust to descend.Therefore, keep excitation current component to equate with the push current component, if field orientation is accurate, then this moment, motor produced the thrust maximum.

Based on this principle, the present invention proposes secondary time constant on-line identification method:

When applied load moment keeps constant, when promptly motor is in stable state, adjust secondary time constant, calculate the synchronous angle of slip-frequency and secondary magnetic linkage, when magnetic field is accurately directed, the electric current minimum of motor input this moment, thus obtain secondary accurately time constant.The characteristics of the inventive method are to keep excitation current component to equate with the push current component, i.e. I _D1=I _Q1, change secondary time constant and synchronous angle by the on-line identification algorithm, search for the exact value of secondary time constant, realize parameter identification.

The indirect field orientation basic control system block diagram that comprises the inventive method as shown in Figure 3, this control system is made up of with the parameter identification system field orientation control.Linear electric motors velocity setting value is v ^*, export through pi regulator with measuring linear velocity v difference, obtain push current component set-point I _Q1 ^*In the control of tradition field orientation, also need independent control excitation current component I _D1 ^*, the rotating speed angular frequency _rBe converted to by the slotted line speed v.In the inventive method, the given I of excitation current component _D1 ^*Keep and push current component I _Q1 ^*Equate, under motor is fully loaded, carry out, can determine, therefore can not exceed current limit according to the motor rated current because discrimination method is unnecessary.Obtain carrying out the PI closed-loop control behind excitation, the push current component, obtain voltage vector, through PWM modulation output control inverter drive motors, this part is identical with traditional field orientation control system.In the calculating of the synchro angle θ of rotational coordinates, according to slip-frequency with measure the rotating speed angular frequency sum integration that motor speed obtains, try to achieve synchronous angle θ according to formula (2), finish the synchronous rotation transformation of voltage, current phasor.Key in this process is to calculate slip-frequency, and the present invention is to secondary time constant T wherein ₂Carry out on-line identification.

The identification algorithm flow chart as shown in Figure 4.This algorithm is the core of the inventive method, and the minimum value that adopts one dimension global optimizing searching algorithm to search the motor input current is carried out secondary time constant identification.At first, judge whether motor speed is stable, behind the velocity-stabilization, when loading condition is constant, the motor output torque is constant, and controller enters the identification searching algorithm, changes given secondary time constant, because exciting current equates that with the given component of push current the slip-frequency calculating formula in the directed governing equation of secondary magnetic is:

${\mathrm{\&omega;}}_{\mathrm{sl}}=\frac{1}{T_2}\frac{I_{q1}}{I_{d1}}---\left(6\right)$

Therefore, regulate secondary time constant and just regulate the motor slip-frequency, the angle of motor-field orientation will be adjusted this moment, and for obtaining certain thrust output, the motor input current changes, when field orientation is accurate, and motor input current minimum.The inventive method is when the initial value of given secondary time constant and slip-frequency, can carry out primary Calculation according to the parameter of line inductance electromotor, because identification algorithm is the exact value of searching parameter automatically, so the accuracy of initial value setting does not influence identification result.

The searching algorithm block diagram as shown in Figure 5, the searching algorithm that the present invention proposes is exactly a minimum value of seeking current component, such as, when increasing the motor secondary time constant, promptly slip-frequency reduces, when current of electric increases, then next step search reduces given secondary time constant value, otherwise then continue to increase, carry out so repeatedly, can guarantee that secondary time constant finally approaches actual value.When current component was searched for error less than threshold epsilon, the global optimizing searching algorithm finished, and finishes the identification of parameter.

In the indirect field orientation control system of line inductance electromotor, secondary time constant has conclusive effect for control performance, the present invention proposes the secondary time constant on-line identification of a kind of line inductance electromotor method.Satisfying under exciting current and the condition that the push current component equates, parameter error will make motor stable state thrust reduce, and adopt global optimizing algorithm search current of electric minimum value under the motor steady operation, can realize changeing secondary time constant on-line identification.This method when the given initial value of parameter is inaccurate, the also accurate secondary time constant of identification line inductance electromotor.Itself does not rely on the parameter of electric machine algorithm, calculates simply, and better astringency, the result is accurate.

Claims (2)

1. a method for identifying on-line parameters of linear induction motor is characterized in that, described method is the exciting current I according to described line inductance electromotor _D1With push current component I _Q1The slip-frequency ω of the directed control of calculating magnetic field cathetus induction machine _Sl, measure motor lines speed, obtain the rotating speed angular frequency through conversion, then with the slip-frequency ω that calculates _SlWith the rotating speed angular frequency ₂The motor synchronous angular frequency is calculated in summation, obtains synchronous angle θ behind the integration, i.e. secondary magnetic chain angle; Adopting synchronous conversion again is exciting current I with the current of electric resolution of vectors _D1With push current component I _Q1, to exciting current I _DsWith push current component I _QsCarry out closed-loop control, and make exciting current I _DsWith push current component I _QsEquate; Through the PI regulating and controlling, obtain the inverter output voltage vector, carry out the PWM modulation then, export corresponding alternating voltage by inverter and drive described line inductance electromotor operation; Adopt the on-line identification algorithm, adjust used secondary time constant value in the electric machine controller, change given motor slip-frequency and synchro angle frequency in the electric machine controller, make the synchronous angle θ of secondary magnetic orientation obtain adjusting, under loading moment keeps constant steady operation condition, the motor input current changes with the adjustment of synchronous angle θ, in the process that adopts search algorithm search motor input current minimum value, the secondary time constant of using in the identifying motor controller, make this time constant approach time constant actual value in the motor, thereby realize parameter of electric machine on-line identification.

2. according to the described method for identifying on-line parameters of linear induction motor of claim 1, it is characterized in that: behind described line inductance electromotor velocity-stabilization, motor load no longer under the change condition, begins to start described search algorithm; , stop search during at the input current variable quantity less than the threshold value that sets in advance, and definite identification result.

Images