JPH08205599A - Speed estimation and drive device for induction motor - Google Patents

Abstract

PURPOSE: To compute estimated speed with high accuracy even at no lead or low speed by inputting voltage into which the primary voltage is converted with a value into which the primary current is converted by a fixed coordinate system taken as an observation amount, and multiplying a value derived by raising the sum of respective squares of estimated current and the estimated secondary interlinkage flux converted by a stator coordinate system to the 1/2th power, by the inverse number of mutual inductance. CONSTITUTION: Taking the current into which the primary current of an induction motor is converted by a fixed coordinate system, namely, a formula I as an observation amount, estimated current, namely, a formula III and estimated secondary interlinkage flux converted by the stator coordinate system, namely, a formula VI are estimated, utilizing voltage into which the primary voltage is converted by the stator coordinate system. The sum of respective squares of the estimated secondary interlinkage flux, namely, a formula V is raised to the 1/2th power. Utilizing absolute field current derived by multiplying the above total by 1/Lm, namely, a formula VI, estimated speed, namely, a formula VII is corrected. It is thus possible to compute estimated speed, namely, the formula VII with high accuracy even at no load or low speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed sensorless speed estimation method for an induction motor.

[0002]

2. Description of the Related Art Conventionally, a velocity estimation method using a magnetic flux estimation observer has an all-dimensional observer constructed by equation (1).
Estimated speed as shown in equation (2)

[0003]

[Outside 34] Is the flux estimate vector

[0004]

[Outside 35] And current estimate error vector

[0005]

[Outside 36] The velocity was estimated using the outer product value of (Electronics theory B, vol. 105, P763 (1985), Electronics theory D, vol. 111, No. 11, P954 to 960).
(1991)).

[0006]

[Equation 1]

[0007]

[Equation 2] This will be described in detail with reference to the flowchart of FIG.

At least two phases of voltage and current output from the inverter to the induction machine at the time of K · T _S (T _S : sampling time) seconds (for example, u phase voltage v _u and v phase voltage v _{v as} voltage) , U-phase current i _u and v-phase current i _v ) are detected as currents (step 20), and these are converted into three-phase / two-phase, and α-phase voltage at K · T _S seconds

[0009]

[Outside 37] , Β-phase voltage

[0010]

[Outside 38] , Α phase current

[0011]

[Outside 39] , Β-phase current

[0012]

[Outside 40] Is calculated (step 21), and the α-phase current estimated value at the time of K · T _S seconds calculated in the previous loop is calculated.

[0013]

[Outside 41] β-phase current estimated value

[0014]

[Outside 42] , Α-phase rotor magnetic flux

[0015]

[Outside 43] , Β-phase rotor magnetic flux

[0016]

[Outside 44] Using Eq. (3), the estimated speed of K · T _S seconds

[0017]

[Outside 45] Is calculated (step 22),

[0018]

(Equation 3) this

[0019]

[Outside 46] When,

[0020]

[Outside 47] By using Eq. (1) according to the recurrence difference of the all-dimensional observer of Eq. (4), the estimated value of (K + 1) T _S seconds

[0021]

[Outside 48] Is calculated (step 23).

[0022]

[Equation 4]

[0023]

However, in the prior art, in practice,

[0024]

[Outside 49] The component of the equation (5), which is the outer product of the estimated magnetic flux value and the true magnetic flux value required for the calculation of, is ignored because it is close to zero.

[0025]

(Equation 5) As shown in FIG. 7, the equation (5) is a term having a value when the magnetic flux axis is deviated, and can be rewritten as the equation (6).

[0026]

(Equation 6) The generated torque has a relationship such that it is proportional to cos δ (in a steady state). Therefore, since the load and the generated torque are equal when operating at a constant speed, the load is proportional to cos δ. On the other hand, the error is sin (δ′−
Since it is proportional to δ), the proportion of the error with respect to the generated torque becomes larger as δ becomes smaller if (δ′−δ) is the same. That is, as shown in FIG.
Equation (6) has a small effect on the torque and the estimated torque value when the load is sufficiently large, but has a large effect when the load is small and the angle δ between the current axis and the magnetic flux axis is small, as shown in FIG. , Estimated speed as a result

[0027]

[Outside 50] Error occurs. Equation (5) cannot be measured

[0028]

[Outside 51] However, there is a problem that it cannot be used.

An object of the present invention is to provide a speed estimation method for an induction motor and an induction motor drive device which can accurately calculate a speed estimation value even under no load and at low speed.

[0030]

According to the method of estimating the speed of an induction motor of the present invention, a current value obtained by converting a primary current of the induction motor in a fixed coordinate system.

[0031]

[Outside 52] Is the observed amount, and the voltage value obtained by converting the primary voltage in the fixed coordinate system

[0032]

[Outside 53] Enter the estimated current value

[0033]

[Outside 54] And the estimated secondary flux linkage converted in the stator coordinate system

[0034]

[Outside 55] And estimate the secondary flux linkage

[0035]

[Outside 56] Square the sum of the squares of each and add 1 / Lm
Absolute value of field current derived by multiplying (Lm: mutual inductance)

[0036]

[Outside 57] And the speed estimate

[0037]

[Outside 58] To correct.

[0038]

[Function] α phase current

[0039]

[Outside 59] , Β-phase current is

[0040]

[Outside 60] And the α-phase rotor magnetic flux

[0041]

[Outside 61] , Β-phase rotor magnetic flux

[0042]

[Outside 62] Is occurring, a vector diagram as shown in FIG. 5A is applied at the α-β coordinates.

Assuming that the d-axis is in the direction of the magnetic flux vector Φ and the axis spatially advanced by 90 ° from the d-axis is the q-axis, the current vector I _s is projected on the dq coordinate, and the current vector Is is projected as shown in FIG. Similarly, the d-axis current i _sd and the q-axis current i _sq can be defined.

If it is defined that i _mr = (1 / Lm) Φ _r (Lm: mutual inductance), it is obvious from the principle of vector control that i _mr and i _sd match in the steady state.
Further, it is known that at the time of transition, i _mr is represented by the following equation (7).

[0045]

(Equation 7) Therefore, i _mr approaches i _sd with the time constant τ _r .

Here,

[0047]

(Equation 8) , The observer estimated value from the above

[0048]

[Outside 63] If matches the true value, of course,

[0049]

[Outside 64] Also matches i _mr . Also,

[0050]

[Outside 65] Derived from

[0051]

[Outside 66] Also matches the true value i _sd .

From the relational expression between i _mr and i _sd , since i _mr is obtained through a low-pass filter having an i _sd time constant τ _r ,

[0053]

[Outside 67] Is the value obtained through the low-pass filter of τ

[0054]

[Outside 68] Is defined as

[0055]

[Outside 69] Also matches i _mr .

However, when the error in the magnetic flux axis is mainly due to δ'in equation (6),

[0057]

[Equation 9] However,

[0058]

[Equation 10] Becomes

[0059]

[Outside 70] Is

[0060]

[Outside 71] When

[0061]

[Equation 11] Since it is calculated using

[0062]

(Equation 12) Ie

[0063]

(Equation 13) Becomes

On the other hand,

[0065]

[Outside 72] Is

[0066]

[Equation 14] To ask for

[0067]

(Equation 15) Is.

After all, when there is an error in the magnetic flux axis,

[0069]

[Equation 16] , Which affects the velocity estimate,

[0070]

[Equation 17] Becomes For this reason,

[0071]

[Outside 73] When

[0072]

[Outside 74] The deviation of and its integrated value are fed back to the speed estimation value,

[0073]

(Equation 18) If so, the magnetic flux axes match, and as a result,

[0074]

[Outside 75] And ω _r can be matched.

[0075]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of an induction motor controller showing an embodiment of the present invention, and FIG. 2 is a magnetic flux velocity all-dimensional observer 9.
It is a flowchart which shows the process of.

The induction motor control device of this embodiment has a speed feedback controller 1, a feedforward controller 2, a torque current feedback controller 3, an exciting current feedback controller 4, a vector control unit 5, an inverter 6, and a three-phase / two-phase conversion circuit 7. And magnetic flux / velocity all-dimensional observer 8.

Speed command

[0079]

[Outer 76] And speed estimate

[0080]

[Outside 77] Is input to the speed feedback controller 1 and the torque current command

[0081]

[Outside 78] Is given. On the other hand, the field current command is determined according to the motor operating conditions,

[0082]

[Outside 79] Given as. Respectively

[0083]

[Outside 80] When

[0084]

[Outside 81] And the value is input to the torque current feedback controller 3 and the field current feedback 4, and its output is added to the value output from the feedforward controller 3 to obtain the q-phase voltage command.

[0085]

[Outside 82] , D-phase voltage command

[0086]

[Outside 83] Is input to the vector control unit 5 together with the magnetic flux position. Primary voltages v _u , v _v , and v _w are applied to the induction motor 9 from the vector control unit 5 via the inverter 6, and the current i is applied to each phase.
_u , _iv , and _iw flow.

The 3-phase / 2-phase converter 7 converts the primary current and the primary voltage of the induction motor into 3-phase / 2 phase, respectively.

The magnetic flux / velocity all-dimensional observer 8 performs the processing shown in FIG. The two-phase voltage and two-phase current applied to the induction motor are input (step 10), and these are applied to the stator coordinates (α-
Converted by β coordinate and K · T _S (K = 0, 1, 2, 3,
…, T _S is the sampling time) Current value in seconds

[0089]

[Outside 84] , Voltage value

[0090]

[Outside 85] Is output (step 11). Next, the previously derived estimate

[0091]

[Outside 86] And using equations (9) and (10)

[0092]

[Outside 87] Is calculated (step 12).

[0093]

[Formula 19]

[0094]

(Equation 20) Next, according to the equation (11),

[0095]

[Outside 88] Is calculated (step 13).

[0096]

[Equation 21] Next, at (K + 1) T _S seconds

[0097]

[Outside 89] Is calculated by the equation (4) (step 14). here,

[0098]

[Outside 90] Is calculated by the equation (12).

[0099]

[Equation 22] Finally,

[0100]

[Outside 91] , The magnetic flux position is output (step 15).

FIGS. 3A, 3B, and 3C are diagrams showing the results of simulation of the estimated speed according to this embodiment. ω _r is the true value,

[0102]

[Outside 92] Is the estimated value. ω _r is 200 (rpm), 100 (r
pm) and 10 (rpm), respectively, and it can be seen that the error is smaller in the present embodiment compared to the conventional result of FIG.

[0103]

As described above, the present invention reduces the error in the estimated speed value by correcting the estimated speed value with the absolute value of the secondary interlinkage magnetic flux obtained from the estimated secondary interlinkage magnetic flux. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an induction motor control device according to an embodiment of the present invention.

FIG. 2 is a flowchart of processing of a magnetic flux / velocity full-dimensional observer 8 in FIG.

FIG. 3 is a diagram showing a simulation waveform of an estimated speed value when the embodiment of FIG. 1 is used.

FIG. 4 is a diagram showing a waveform of a speed estimation value simulation according to the related art.

FIG. 5 is a diagram for explaining the principle of the present invention.

FIG. 6 is a flowchart showing a conventional speed estimation method for an induction motor.

FIG. 7 is a diagram showing a relationship between current and magnetic flux vectors and an estimated torque error.

[Explanation of symbols]

 1 Induction motor 2 Speed feedback controller 3 Feed forward controller 4 Torque current feedback controller 5 Field current feedback controller 6 Vector control unit 7 Inverter 8 3 phase / 2 phase converter 9 Magnetic flux / speed all-dimensional observer 10 to 15 steps

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinya Morimoto 2-1, Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Yasukawa Electric Co., Ltd.

Claims (3)

[Claims] 1. A current value obtained by converting the primary current of an induction motor in a fixed coordinate system. , And the voltage value obtained by converting the primary voltage in the fixed coordinate system Current estimated value [3] Estimated value of the secondary interlinkage magnetic flux converted in and the stator coordinate system [External 4] And the estimated value of the secondary interlinkage magnetic flux Square the sum of the squares of each and add 1 / Lm
Absolute value of field current derived by multiplying (Lm: mutual inductance) Using, the speed estimation value A method for estimating the speed of an induction motor, which corrects the error. 2. The outside 8 And [outside 9] Estimated speed by deviation of The speed estimation method according to claim 1, wherein 3. A speed command value [11]And speed estimate [External 12]Input the deviation from the
Feedback controller and speed command value [External 13]And field current command [External 14]And the output of the speed feedback controller
Feedforward controller, the output of the speed feedback controller and the q-axis current
Estimated value [External 15]Torque current feedback controller to input deviation of
LA and field current command [External 16]And d-axis current estimated value [Ex. 17]Field current feedback controller to input deviation of
And the output of the feedforward controller and the torque
The added value of the output of the current feedback controller.
Q-phase voltage command [External 18]And the output of the feedforward controller and
With the added value of the output of the excitation current feedback controller
A certain d-phase voltage command [External 19]And the magnetic flux position are input to the induction motor via the inverter.
Three-phase primary voltage v_u , V _v , V_w Applying a vector system
And the primary voltage v_u , V_v , V_w And flow to the front induction motor
Three-phase primary current i_u , I_v , I_w Enter the α-axis primary
Pressure [Outside 20]And β-axis primary voltage [External 21]And α-axis primary current [External 22]And β-axis primary current [External 23]A three-phase / two-phase converter that outputs theAnd the α-axis and β-axis component estimated values of the primary current derived last timeAnd the estimated values of the α-axis and β-axis components of the secondary magnetic fluxUsing [external 27][Outside 28]It is obtained through the low-pass filter with the time constant ofAnd field current absolute value [External 30]Then, the speed estimation valueIs calculated and corrected by the method according to claim 1,
(K + 1) T_s (K = 0, 1, 2, ..., T_s Is sun
Pulling time) Seconds [External 32]And calculateAnd a magnetic flux velocity all-dimensional observer that outputs the magnetic flux position
Induction motor drive device.