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Claims  |
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What is claimed is:
1. A vector control apparatus for an induction motor comprising:
a) a current command calculating section for receiving a torque command (T*), a magnetic flux command (.lambda. .sub.2 *), and an estimated secondary magnetic flux component(.vertline. .lambda..sub.2 /M.vertline.) and for outputting a primary
current command vector (i.sub.1 *.sup.e) according to the torque command, the magnetic flux command, and the estimated secondary magnetic flux component;
b) a current controlling section for receiving the primary current command vector from the current command calculating section, for detecting a primary current vector (i.sub.1) flowing through the induction motor, for generating a primary voltage
vector (v.sub.1) according to a deviation between the primary current command vector and the primacy current vector, and for outputting the primary current vector to the induction motor according to the generated primacy voltage vector; and,
c) a magnetic flux observer of a full order for receiving the primary voltage vector and the primary current vector from the current controlling section and for generating a vector variable ( .lambda..sub.2 or .lambda..sub.2 /M) related to the
estimated secondary magnetic flux component to be supplied to the current command calculating section and related to an estimated rotation phase ( .theta.) of a rotary coordinate system to be supplied to the current controlling section based on the
primary voltage vector and the primary current vector, the magnetic flux observer of the full order having a plurality of coefficients expressed in circuit constants of a T-I type equivalent circuit of the induction motor.
2. A vector control apparatus for an induction motor as claimed in claim 1, which further comprises a velocity determinator for determining a rotation velocity (.omega.r) of a rotor of the induction motor and outputting the determined velocity
of the rotor to the magnetic flux observer of the full order wherein the magnetic flux observer of the full order is based on a state equation as follows: ##EQU2## wherein .alpha.r.sub.11 =-(R.sub.1 /L.sigma.+R.sub.2 '/L.sigma.), .alpha.r.sub.12
=1/L.sigma. *M/L.sub.2 *.omega.r, .alpha.i.sub.12 =-L.sigma.*M/L.sub.2 *.omega.r, .alpha.r.sub.21 =M/.tau..sub.2, .alpha.r.sub.22 =-1/.tau..sub.2, .alpha.i.sub.22 =.omega.r, b.sub.1 =1/.sigma.L.sub.1 =1/L.sigma.,
g.sub.1 =(k-1)[-1/L.sigma.*(R.sub.1 +R.sub.2 ')-1/.tau..sub.2 ],
g.sub.2 =(k-1)(.omega.r),
g.sub.3 =(k.sup.2 -1)L.sub.2 /M(-R.sub.1)+(k-1)*L.sub.2 /M[(R.sub.1 +R.sub.2 ')+L.sigma./.tau..sub.2 ],
g.sub.4 =(k-1)L.sub.2 /M(-r*L.sigma.),
and wherein R.sub.1 denotes a primary resistance of the T-I type equivalent circuit to the induction motor, R.sub.2 '=(M/L.sub.2).sup.2 *R.sub.2, wherein M denotes an exciting impedance in a T type equivalent circuit, L.sub.2 denotes a secondary
inductance, and R.sub.2 denotes a secondary resistance, L.sigma.=.sigma.L.sub.1 =L.sub.1 -M.sup.2 /L.sub.2 wherein .sigma.=1-M.sup.2 /L.sub.1 L.sub.2, wherein L.sub.1 denotes a primary inductance, and .tau.=L.sub.2 /R.sub.2.
3. A vector control apparatus for an induction motor as claimed in claim 1, wherein the magnetic flux observer of the full order is based on a state equation expressed as follows: ##EQU3## wherein g.sub.1 =(k-1)[-1/L.sigma.*(R.sub.1 +R.sub.2
')-1/.tau..sub.2 ], g.sub.2 =(k-1)(.omega.r),
g.sub.3 =(k-1)1/M'[(R.sub.1 +R.sub.2 ')+L.sigma.*1/.tau..sub.2 ]-(k.sup.2 -1)1/M'*R.sub.1,
g.sub.4 =(k-1).notident./M'(-.omega.rL.sigma.), wherein M' denotes an exciting impedance in the T-I type equivalent circuit, and wherein the estimated secondary magnetic flux component ( .lambda..sub.2) of the magnetic flux observer of the full
order in the state equation is changed to an estimated exciting current component ( .lambda..sub.2 /M).
4. A vector control apparatus for an induction motor as claimed in claim 2, wherein the estimated magnetic flux ( .lambda..sub.2) of the magnetic flux observer of the full order is changed to an exciting current component ( .lambda..sub.2 /M)
and a part of a secondary circuit of the T-I equivalent circuit of the induction motor is transformed into a rotary coordinate system.
5. A vector control apparatus for an induction motor as claimed in claim 4, wherein the estimated magnetic flux observer includes a secondary voltage vector (v.sub.2) in the T-I type equivalent circuit divided by an iron loss resistance (Rn) to
derive an iron loss current component (iRn) in a steady state term, the iron loss component being subtracted from the primary current vector and being transferred into a secondary current vector of the T-I type equivalent circuit.
6. A vector control apparatus for an induction motor as claimed in claim 3, wherein the estimated magnetic flux observer includes a secondary voltage vector (v.sub.2) in the T-I type equivalent circuit divided by an iron loss resistance (Rn) to
derive an iron loss current component (iRn) in a steady state term, the iron loss component being subtracted from the primary current vector and being transferred into a secondary current vector of the T-I type equivalent circuit.
7. A vector control apparatus for an induction motor as claimed in claim 2, wherein the magnetic flux observer of the full order includes: a) a first subtractor (S64) for receiving the primary voltage vector (v.sub.1) at its plus input end; b)
a second subtractor (S69) for receiving the primary current vector (i.sub.1) at its minus input end and receiving an estimated primary current ( i.sub.1) to output a subtraction result of ( i.sub.1 -i.sub.1) thereof; c) a first adder (S65) for adding an
output subtraction result of the first subtractor (S64) to a first coefficient of R.sub.2 ' from a first coefficent block (190); d) a third subtractor (S66) for receiving an output addition result of the first adder at its plus input end and receiving a
second coefficient of (R.sub.1+R.sub.2 ') at its minus input end from a second coefficient block (19B) to output a subtraction result thereof; e) a second adder (S67) for adding the subtraction result of the third subtractor to a third coefficient of M
from a third coefficient block (19I) to output an addition result thereof to a fourth coefficient block (19H); f) a third adder (S68) for adding a fourth coefficient (.DELTA.T/L.sigma.), wherein .DELTA.T denotes a sampling period of the magnetic flux
observer from the fourth coefficient block to a z-.sup.1 operator from a z.sup.-1 operator block (19I), wherein z.sup.-1 denotes a z transform operator and a superscript of -1 denotes a delay corresponding to the sampling period, to output an addition
result thereof to an input end of the z.sup.-1 operator block and to the estimated primary current output end ( i.sub.1); g) a fourth adder (S73) for adding the first coefficient of (R.sub.1 +R.sub.2 ') from a fifth coefficient block (19C) connected
with the output subtraction result of the second subtractor to a fifth coefficient of (1/.tau..notident.2* .omega.rJ)L.sigma. from a sixth coefficient block (19D) to output an addition result thereof; h) a fourth subtractor (S70) for receiving a sixth
coefficent of (k-1), wherein k denotes a constant used to multiply poles that the induction motor inherently has, at its plus end thereof and receiving an output of a coefficient of R.sub.1 *(k.sup.2 -1) from a combination of a seventh coefficient block
(19G) of (k.sup.2 -1) and an eighth coefficient block (19F) of R.sub.1 connected with the output subtraction result of the second subtractor (S69) to output a subtraction result (.DELTA.v.sub.2) thereof; h) a fifth adder (S71) for adding the subtraction
result (.DELTA.v.sub.2) from the fourth subtractor (S70) to a seventh coefficient of R.sub.2 ' from a ninth coefficient block (19A) connected to the estimated primary current output end ( i.sub.1); i) a fifth subtractor (S72) for receiving the addition
result of the fifth adder at its plus input end and receiving the first coefficient (R.sub.2 ') from the first coefficient block at its minus input end to output a subtraction result thereof to an eighth coefficient of 1/M', wherein M'=M.sup.2 /L.sub.2
and M' denotes an exciting impedance in the T-I type equivalent circuit, from a tenth coefficient block (19L); j) a sixth subtractor (S75) for receiving an output of a rotary coordinate transform matrix block (19M) at is plus input end and receiving a
first input of the rotary coordinate transform matrix block (19M) at its minus input end to output a subtraction result thereof to the second adder (S67) via a coefficient block (19J) of M; k) a sixth adder (S74) for adding the output of the rotary
coordinate transform matrix block (19M) and the eighth coefficient of 1/M' from the tenth coefficient block (19L) to output its addition result as ( .lambda..sub.2 /M; 1) another z.sup..sup.-1 operator block (19P) connected between the input end of the
rotary coordinate transform matrix block (19M) and both of the output addition result of the sixth adder (S74) and the first coefficient block (190); and m) an eleventh coefficient block (19E) of (k-1) connected between the output addition result of the
fourth adder (S73) and both of a minus input end of the first subtractor (S64) and a plus input end of the fourth subtractor (S70), a second input end of the rotary coordinate transform matrix block (19M) receiving a rotation phase angle of
.DELTA..theta. from a block (19N) of the rotation velocity (.omega.r) expressed as .DELTA..theta.=.omega.r* .DELTA.T.
8. A vector control apparatus for an induction motor as claimed in claim 2, wherein the magnetic flux observer of the full order includes: a) a first subtractor (S64) for receiving the primary voltage vector (v.sub.1) at its plus input end; b)
a second subtractor (S69) for receiving the primary current vector (i.sub.1) at its minus input end and receiving an estimated primary current ( i.sub.1) to output a subtraction result of ( i.sub.1 -i.sub.1) thereof; c) a first adder (S65) for adding an
output subtraction result of the first subtractor (S64) to a first coefficient of R.sub.2 ' from a first coefficient block (190); d) a third subtractor (S66) for receiving an output addition result of the first adder at its plus input end and receiving
a second coefficient of (R.sub.1 +R.sub.2 ') at its minus input end from a second coefficient block (19B) to output a subtraction result thereof; e) a second adder (S67) for adding the subtraction result of the third subtractor to a third coefficient of
M from a third coefficient block (19I) to output an addition result thereof to a fourth coefficient block (19H); f) a third adder (S68) for adding a fourth coefficient (.DELTA.T/L.sigma.), wherein .DELTA.T denotes a sampling period of the magnetic flux
observer from the fourth coefficient block to a z.sup.-1 operator from a z.sup.-1 operator block (19I), wherein z.sup.-1 denotes a z transform operator and a superscript of -1 denotes a delay corresponding to the sampling period, to output an addition
result thereof to an input end of the z.sup.-1 operator block and to the estimated primary current output end ( i.sub.1); g) a fourth adder (S73) for adding the first coefficient of (R.sub.1 +R.sub.2 ') from a fifth coefficient block (19C) connected
with the output subtraction result of the second subtractor to a fifth coefficient of (1/.tau.2*.omega.rJ)L.sigma. from a sixth coefficient block (19D) to output an addition result thereof; h) a fourth subtractor (S70) for receiving a sixth coefficient
of (k-1), wherein k denotes a constant used to multiply poles that the induction motor inherently has, at its plus end thereof and receiving an output of a coefficient of R.sub.1 *(k.sup.2 -1) from a combination of a seventh coefficient block (19G) of
(k.sup.2 -1) andaneighthcoefficient block (19F) of R.sub.1 connected with the output subtraction result of the second subtractor (S69) to output a subtraction result (.DELTA.v.sub.2) thereof; h) a fifth adder (S71) for adding the subtraction result
(.DELTA.v.sub.2) from the fourth subtractor (S70) to a seventh coefficient of R.sub.2 ' from a ninth coefficient block (19A) connected to the estimated primary current output end ( i.sub.1); i) a fifth subtractor (S72) for receiving the addition result
of the fifth adder at its plus input end and receiving the first coefficient (R.sub.2 ') from the first coefficient block at its minus input end to output a subtraction result thereof to an eighth coefficient of 1/M', wherein M'=M.sup.2 /L.sub.2 and M'
denotes an exciting impedance in the T-I type equivalent circuit, from a tenth coefficient block (19L); j) a sixth subtractor (S75) for receiving an output of a rotary coordinate transform matrix block (19M) at is plus input end and receiving a first
input of the rotary coordinate transform matrix block (19M) to output a subtraction result thereof to the second adder (S67) via a coefficient block (19J) of M; k) a sixth adder (S76) for adding another z.sup.-1 operator of another z.sup.-1 operator
block (19P) and the eighth coefficient of 1/M' from the tenth coefficient block (19L) to output its addition result to a minus input end of the sixth subtractor (S75) and the first input end of the rotary coordinate transform matrix block (19M); 1) the
other z.sup.-1 operator block (19P) connected between both of the output end of the rotary coordinate transform matrix block (19M) and the .lambda..sub.2 /M output end and both of the plus input end of the sixth adder (S76) and the first coefficient
block (190); and m) an eleventh coefficient block (19E) of (k-1) connected between the output addition result of the fourth adder (S73) and both of a minus input end of the first subtractor (S64) and a plus input end of the fourth subtractor (S70), a
second input end of the rotary coordinate transform matrix block (19M) receiving a rotation phase angle of .DELTA..theta. from a block (19N) of the rotation velocity (.omega.r) expressed as .DELTA..theta.=.omega.r* .DELTA.T.
9. A vector control apparatus for an induction motor as claimed in claim 2, wherein the magnetic flux observer of the full order includes: a) a first subtractor (S64) for receiving the primary voltage vector (v.sub.1) at its plus input end; b)
a second subtractor (S69) for receiving the primary current vector (i.sub.1) at its minus input end and receiving an estimated primary current ( i.sub.1) to output a subtraction result of ( i.sub.1 -i.sub.1) thereof; c) a first adder (S65) for adding an
output subtraction result of the first subtractor (S64) to a first coefficient of R.sub.2 ' from a first coefficent block (190); d) a third subtractor (S66) for receiving an output addition result of the first adder at its plus input end and receiving a
second coefficient of (R.sub.1 +R.sub.2 ') at its minus input end from a second coefficient block (19B) to output a subtraction result thereof; e) a second adder (S67) for adding the subtraction result of the third subtractor to a third coefficient of M
from a third coefficient block (19I) to output an addition result thereof to a fourth coefficient block (19H); f) a third adder (S68) for adding a fourth coefficient (.DELTA.T/L.sigma.), wherein .DELTA.T denotes a sampling period of the magnetic flux
observer from the fourth coefficient block to a z.sup.-1 operator from a z.sup.-1 operator block (19I), wherein z.sup.-1 denotes a z transform operator and a superscript of -1 denotes a delay corresponding to the sampling period, to output an addition
result thereof to an input end of the z.sup.-1 operator block and to the estimated primary current output end ( i.sub.1); g) a fourth adder (S73) for adding the first coefficient of (R.sub.1 +R.sub.2 ') from a fifth coefficient block (19C) connected
with the output subtraction result of the second subtractor to a fifth coefficient of (1/.tau.2*.omega.rJ)L.sigma. from a sixth coefficient block (19D) to output an addition result thereof; h) a fourth subtractor (S70) for receiving a sixth coefficent
of (k-1), wherein k denotes a constant used to multiply poles that the induction motor inherently has, at its plus end thereof and receiving an output of a coefficient of R.sub.1 *(k.sup.2 -1) from a combination of a seventh coefficient block (19G) of
(k.sup.2 -1) and an eighth coefficient block (19F) of R.sub.1 connected with the output subtraction result of the second subtractor (S69) to output a subtraction result (.DELTA.v.sub.2) thereof; h) a fifth adder (S71) for adding the subtraction result
(.DELTA.v.sub.2) from the fourth subtractor (S70) to a seventh coefficient of R.sub.2 ' from a ninth coefficient block (19A) connected to the estimated primary current output end ( i.sub.1); i) a fifth subtractor (S72) for receiving the addition result
of the fifth adder at its plus input end and receiving the first coefficient (R.sub.2 ') from the first coefficient block at its minus input end to output a subtraction result thereof to an eighth coefficient of 1/M', wherein M'=M.sup.2 /L.sub.2 and M'
denotes an exciting impedance in the T-I type equivalent circuit, from a tenth coefficient block (19L); j) a sixth subtractor (S75) for receiving an output of a rotary coordinate transform matrix block (19M) at is plus input end and receiving a first
input of the rotary coordinate transform matrix block (19M) at its minus input end to output a subtraction result thereof to the second adder (S67) via a coefficient block (19J) of M; k) a sixth adder (S77) for adding the output of the rotary coordinate
transform matrix block (19M) and the eighth coefficient of 1/M' from the tenth coefficient block (19L) via a first weight block (21C) of (1-.alpha.), wherein a denotes a weight coefficient and 0.ltoreq..alpha..ltoreq.0, to output its addition result as
.lambda..sub.2 /M; 1) a seventh adder (S76) for adding the eighth coefficient of 1/M' from the tenth coefficient block (19L) via a second weight block (21A) of .alpha. and the z.notident.-1 operator from another z.notident.-1 operator block (19P) to
output its addition result to the first input end of the rotary coordinate transform block (19M); m) the other z.sup.-1 operator block (19P) connected between the output addition result of the seventh adder (S76) which is the .lambda..sub.2 /M output
end and both of the plus input end of the sixth adder (S76) and the first coefficient block (190) of R.sub.2 '; and n) an eleventh coefficient block (19E) of (k-1) connected between the output addition result of the fourth adder (S73) and both of a
minus input end of the first subtractor (S64) and a plus input end of the fourth subtractor (S70), a second input end of the rotary coordinate transform matrix block (19M) receiving a rotation phase angle of .DELTA..theta. from a block (19N) of the
rotation velocity (.omega.r) expressed as .DELTA..theta.=.omega.r* .DELTA.T.
10. A vector control apparatus for an induction motor as claimed in claim 9, wherein the rotary coordinate transform matrix block (19M) is expressed as: ##EQU4##
11. A vector control apparatus for an induction motor as claimed in claim 10, which further comprises a pole coordinate transform block (22D) which receives the .lambda.2/M output from the magnetic flux observer of the full order at its .lambda. input end, outputs the secondary magnetic flux component of .vertline. .lambda..sub.2 /M.vertline. at its .vertline.R.vertline. output end to the current command calculating section (22A), and outputs an estimated rotation phase ( .theta.) to the
current controlling section (22B).
12. A vector control method for an induction motor, the vector control method comprising the steps of: a) receiving a torque command (T*), a magnetic flux command (.lambda..sub.2 *), and an estimated secondary magnetic flux component(.vertline.
.lambda..sub.2 /M.vertline.);
b) outputting a primary current command vector (i.sub.1 *.sup.e) according to the torque command, the magnetic flux command, and the estimated secondary magnetic flux component;
c) receiving the primary current command vector;
d) detecting a primary current vector (i.sub.1) flowing through the induction motor, for generating a primary voltage vector (v.sub.1) according to a deviation between the primary current command vector and the primacy current vector;
e) outputting the primary current vector to the induction motor according to the generated primacy voltage vector;
f) providing a magnetic flux observer of a full order for receiving the primary voltage vector and the primary current vector and for generating a vector variable ( .lambda..sub.2 or .lambda..sub.2 /M) related to the estimated secondary magnetic
flux component and related to an estimated rotation phase ( .theta.) of a rotary coordinate system based on the primary voltage vector and the primary current vector, the magnetic flux observer of the full order having a plurality of coefficients
expressed in circuit constants of a T-I type equivalent circuit of the induction motor. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to vector control apparatus and method for controlling torque and speed of an induction motor through a vector control type inverter in which a magnetic flux observer of a full order is expressed in a state equation
and has a plurality of coefficients expressed in circuit constants in a T-I type equivalent circuit to the induction motor.
b) Description of the Related Art
There are some kinds of vector control methods for an induction motor. There is a certain kind of vector control method for the induction motor in which a secondary magnetic flux of the induction motor is estimated using a flux observer and the
induction motor is controlled on the basis of the estimated magnetic flux.
In addition, Japanese technical papers describing the application of the full order magnetic flux observer so as to add a compensation for a temperature variation of the secondary resistance of the induction motor and/or to achieve a speed
control of the induction motor without use of a speed sensor.
That is to say, there are four published papers listed below:
1) a first Literature (Literature 1); "Adaptive Flux Observer of Induction Motor and its Stability" in T.IEE Japan Volume 111-D, No. 3 published on Mar. 3, 1991 and authored by Hisao Kubota and Kouki Matuse.
2) a second Literature (Literature 2); "Performance of a Torque Control for Induction Motor Using State Observer" published on 1987 in National Meeting of Industrial Application Department on Japan Electrical Society and authored by Hideki
Hashimoto, Yukou Ohno, Seiji Kondo, and Fumio Harashima.
3) a third literature (Literature 3); "Direct Field Oriented Control of Induction Motor Without Speed Sensors using Adaptive Flux Observer" published on November of 1991 in a paper D of a Japan Electrical Engineering Society, Volume 111, No. 11
and authored by Hisao Kubota, Masanori Ozaki, and Kouki Matsuse.
4) a fourth literature (Literature 4); "Hyperstability of the Full Order Adaptive Observer for Vector Controlled-Induction Motor Drive Without Speed Sensor" in a paper D of the Japan Electric Engineering Society published on January 1992, Volume
112, No. 11 and authored by Gung Yang and Tung-Hai Chin.
Equations concerned with the full order magnetic flux observer are known from the above-listed literatures 1 and 2.
The literature 1 recites that the observer is constituted by the equations in a time-continuous system to which a numerical value integration such as an Euler method is applied.
On the other hand, the literature 2 recites that the observer is constituted by equations in a time-discrete system using a time-discrete model to reduce computation errors.
A general concept on the equation in the time-continuous system recited in the literature 1 will briefly be described below.
A state equation on stator coordinates of the induction motor is given by an equation (1) in TABLE 1.
In the TABLE 1, i.sub.1 denotes a primary current of the induction motor, v.sub.1 denotes a primary voltage, and .lambda..sub.1 denotes a secondary magnetic flux.
Furthermore, TABLE 2 shows respective coefficients (2-1) through (2-11) recited in the equation (1).
In the equation (1), the current, voltage, and magnetic constants are two-axis components but are expressed in terms of vectors to simplify the expressions of equation. Actually, the primary current, the primary voltage, and secondary magnetic
flux mean two-axis components of .alpha.-.beta..
That is to say, the primary current, the primary voltage, and the secondary magnetic flux are expressed in three equations (3) in TABLE 3.
Constants (circuit constants) in the induction motor are represented as follows:
R.sub.1 : Primary Voltage;
R.sub.2 : Secondary Resistance;
L.sub.1 : Primary Inductance;
L.sub.2 : Secondary Resistance; and
M: Mutual (Exciting) Inductance in a T type equivalent circuit to the induction motor;
The magnetic flux observer of the full order recited in the literature 1 is expressed in the case where a pole arrangement of the observer is set to be k times as large as the pole arrangement hat the induction motor inherently has.
On the other hand, the magnetic flux observer provided in the vector control method can also be constituted by an equation (4) in TABLE 4. An estimation variable is represented by a superscript of .
In addition, feedback gains of the observer are expressed in equations (5-1), (5-2), (5-3), (5-4), and (5-5) in TABLE 5.
Utilizing the magnetic flux observer of the full order, induction motor drives without a rotor speed sensor such as a rotary encoder has been proposed in the literatures 3 and 4. In each of the literatures 3 and 4, in order to estimate the rotor
speed, an adaptive control for the rotor speed has been carried out using the following speed estimation equations.
That is to say, error components between a model current and an actual current such as an excitation current or a torque current are defined in equations (6-1) and (6-2) in TABLE 6.
It is noted that the model current is a current flowing through a Model Reference Adaptive System (MRAS) recited in the literature 4 and a superscript of denotes an estimated value in the MRAS side.
Next, the rotor speed .omega.r is estimated from an equation (7) in TABLE 7 using the magnetic flux and error current components.
SUMMARY OF THE INVENTION
However, in the state equations (1) and (4) each constituting the magnetic flux observer of the full order, constants in a T type equivalent equation has been used as the constants in the induction motor.
When the rotor speed of an actual induction motor is controlled using the vector control method, a separation between a primary leakage current and a secondary leakage current cannot be made. Hence, values on the secondary resistance L.sub.2 and
mutual (exciting) inductance M cannot be determined.
It is therefore necessary to alter the constants in the above-described equations (1) and (4) into those in another equivalent circuit.
If the constants in a T-I type equivalent circuit could be represented, those constants could easily be measured and would easily correspond to physical quantities such as magnetic flux and torque current and would be convenient.
Next, in the equations (1) and (4), the secondary magnetic flux has been used as a second-order variable. However, in the vector control method, the division of magnetic flux by the mutual inductance M is often used. This division corresponds
to an excitation current so that it is convenient in the vector control method.
In the vector control method, magnetic flux and currents on rotary coordinates are often given as commands. It is convenient for the estimated magnetic flux in the magnetic flux observer to be enabled to be converted into the rotary coordinates.
The full order magnetic flux observer recited in each literature ignores an iron loss component although the induction motor includes the iron loss current component. Hence, an error occurs in the estimated magnetic flux component and/or rotor
speed in the vector control method without use of the rotor speed sensor.
It is therefore an object of the present invention to provide improved vector control apparatus and method for an induction motor in which at least a magnetic flux observer of a full order whose elements in state equations can be represented by
the constants in the T-I type equivalent circuit.
According to one aspect of the present invention, there is provided with a vector control apparatus for an induction motor comprising: a) a current command calculating section for receiving a torque command (T*), a magnetic flux command
(.lambda..sub.2 *), and an estimated secondary magnetic flux component(.vertline. .lambda..sub.2 /M.vertline.) and for outputting a primary current command vector (i.sub.1 *.sup.e) according to the torque command, the magnetic flux command, and the
estimated secondary magnetic flux component; b) a current controlling section for receiving the primary current command vector from the current command calculating section, for detecting a primary current vector (i.sub.1) flowing through the induction
motor, for generating a primary voltage vector (v.sub.1) according to a deviation between the primary current command vector and the primacy current vector, and for outputting the primary current vector to the induction motor according to the generated
primacy voltage vector; and, c) a magnetic flux observer of a full order for receiving the primary voltage vector and the primary current vector from the current controlling section and for generating a vector variable ( .lambda..sub.2 or .lambda..sub.2
/M) related to the estimated secondary magnetic flux component to be supplied to the current command calculating section and related to an estimated rotation phase ( .theta.) of a rotary coordinate system to be supplied to the current controlling section
based on the primary voltage vector and the primary current vector, the magnetic flux observer of the full order having a plurality of coefficients expressed in circuit constants of a T-I type equivalent circuit of the induction motor.
According to another aspect of the present invention, there is provided with a vector control method for an induction motor, the vector control method comprising the steps of: a) receiving a torque command (T*), a magnetic flux command
(.lambda..sub.2 *), and an estimated secondary magnetic flux component(.vertline. .lambda..sub.2 /M.vertline.); b) outputting a primary current command vector (i.sub.1 *.sup.e) according to the torque command, the magnetic flux command, and the
estimated secondary magnetic flux component; c) receiving the primary current command vector; d) detecting a primary current vector (i.sub.1) flowing through the induction motor, for generating a primary voltage vector (v.sub.1) according to a deviation
between the primary current command vector and the primacy current vector; e) outputting the primary current vector to the induction motor according to the generated primacy voltage vector; f) providing a magnetic flux observer of a full order for
receiving the primary voltage vector and the primary current vector and for generating a vector variable ( .lambda..sub.2 or .lambda..sub.2 /M) related to the estimated secondary magnetic flux component and related to an estimated rotation phase (
.theta.) of a rotary coordinate system based on the primary voltage vector and the primary current vector, the magnetic flux observer of the full order having a plurality of coefficients expressed in circuit constants of a T-I type equivalent circuit of
the induction motor.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit block diagram of a first preferred embodiment of a vector control apparatus for an induction motor especially representing a magnetic flux observer of a full order in the first embodiment according to the present invention.
FIG. 2 is a circuit block diagram of a second preferred embodiment of the induction motor vector control apparatus especially representing a magnetic flux observer of the full order in the second preferred embodiment.
FIG. 3 is a circuit block diagram of a third preferred embodiment of the induction motor vector control apparatus especially representing a magnetic flux observer of the full order in the third embodiment.
FIG. 4 is a circuit block diagram of a portion enclosed by a dot line of FIG. 3.
FIG. 5 is a circuit block diagram of the circuit portion shown in FIG. 4 in which inputs i.sub.1 and .DELTA.v.sub.2 and output of v.sub.2 of FIG. 4 are rotary coordinate transformed and a term of s is replaced with (s+.omega..sub.1 j).
FIG. 6 is a circuit block diagram of the circuit portion shown in FIG. 5 in which a block related to a slip is clarified and a torque current component i.sub.T (=i.sub.1 -i.sub.2) is defined.
FIG. 7 is a circuit block diagram of a modification of the third embodiment shown in FIG. 3.
FIG. 8 is an approximation equivalent circuit in a T-I type equivalent circuit including an iron loss resistance of the induction motor.
FIG. 9 is a circuit block diagram of the vector control apparatus for the induction motor especially representing the magnetic flux observer in a fourth embodiment according to the present invention.
FIG. 10 is a circuit block diagram of a modification of the magnetic flux observer of the full order in the fourth embodiment shown in FIG. 9.
FIG. 11 is a circuit block diagram of the magnetic flux observer based on equations recited in TABLE 11 and TABLE 12.
FIG. 12 is a circuit block diagram of the magnetic flux observer of the full order shown in FIG. 11 and in which a z.sup.-1 operator is used.
FIG. 13 is a circuit block diagram of the magnetic flux observer of the full order shown in FIG. 11 and in which feedback terms related to integration terms of a secondary circuit are separated into I and J terms.
FIG. 14 is a circuit block diagram of the magnetic flux observer of the full order shown in FIG. 13 and in which whole M' related components are rearranged to R.sub.2 ' related components.
FIGS. 15A and 15B are an explanatory view of a rotation vector and a circuit block diagram representing a portion enclosed by a dot line of A in FIG. 14.
FIGS. 16A and 16B are an explanatory view of a concept of a rotary (rotor) coordinate transformation and a circuit block diagram embodying the rotary coordinate transformation shown in FIG. 15A.
FIG. 17 is a circuit block diagram of a circuit portion enclose by a dot line of A in FIG. 14.
FIGS. 18A, 18B, and 18C are circuit block diagrams of a combination of the circuit portion shown in FIG. 17 with the circuit block diagram of the rotary coordinate transformation shown in FIG. 16B.
FIGS. 19, 20, and 21 are circuit block diagrams of the magnetic flux observer in the vector control apparatus for the induction motor according to the present invention especially representing the magnetic flux observer in a fifth preferred
embodiment related to FIG. 18A, in a modification of the fifth embodiment related to FIG. 18B, and in another modification of the fifth embodiment related to FIG. 18C, respectively.
FIG. 22 is a circuit block diagram of an example of the vector control apparatus to which the magnetic flux observer described in each embodiment is applicable.
BEST MODE FOR CARRYING OUT THE INVENTION
Reference will hereinafter be made to the drawings in order to facilitate a better understanding of the present invention.
(First Embodiment)
FIG. 1 shows a first preferred embodiment of a vector control apparatus for an induction motor according to the present invention.
That is to say, FIG. 1 shows a block diagram of a magnetic flux observer using constants in a T-I type equivalent circuit of the induction motor. It is noted that the T-I type equivalent circuit is exemplified by an European Patent Application
Publication No. EP 0 790 701 A2 which corresponds to a U.S. patent application Ser. No. 08/800,171 which has already been allowed (, the disclosure of which is herein incorporated by reference).
In the first embodiment, in order to replace each coefficient in each of state equations (1) and (4) recited in TABLE 1 and TABLE 4 with the constants in the constants in the T-I type equivalent circuit, conversion equations (8-1), (8-2), (8-3),
and (8-4) in TABLE 8 are substituted into each of the state equations (1) and (4) to derive equations (9-1), (9-2), (9-3), (9-4), (9-5), (9-6), and (9-7) in TABLE 9.
Next, TABLE 10 shows feedback terms g.sub.1, g.sub.2, g.sub.3, and g.sub.4 of the observer represented by the constants of the induction motor T-I type equivalent circuit.
Hence, using the state equations of (1) and (4) in which the constants in the T-I equivalent circuit are adopted and the equations of (9-1) through (9-7) in which the constants in the T-I type equivalent circuit are adopted, the magnetic observer
of the full order in the first embodiment shown in FIG. 1 is achieved.
In FIG. 1, S1 denotes a first subtractor connected between a first coefficient block 1A of v1 by 1/L.sigma. and a second coefficient block 1B by 1/L.sigma., S2 denotes a first adder connected between the first subtractor S1 and a third
coefficient block 1C by 1/L.sigma., S3 denotes a second subtractor connected between the first adder S2 and a fourth coefficient block 1F by 1/L.sigma., S4 denotes a third subtractor connected between 0 and a fifth coefficient block 1I by L.sub.2 /M, S5
denotes a second adder connected between the third subtractor S4 and a sixth coefficient block 1L by L.sub.2 /M, S6 denotes a third adder connected between the second adder S5 and a seventh coefficient block 1E by M/.tau..sub.2, S7 denotes a fourth
subtractor connected between the third adder S6 and an eighth coefficient block 1P by (1/.tau..sub.2 -.omega..sub.r J), S8 denotes a fifth subtractor connected between an estimated model current i.sub.1 and an actual primary current i.sub.1. In
addition, the second coefficient block 1B is connected to a ninth coefficient block 1M, the third coefficient block 1C is connected to a tenth coefficient block 1D, the fourth coefficient block 1F is connected to an eleventh coefficient block 1G by
(R.sub.1 +R.sub.2 '), a first integrator 1H is connected to the second subtractor S3, a twelfth coefficient block 1E is connected between the first integrator 1H and the third adder S6, the eleventh coefficient block 1G is connected to the first
integrator 1H, the fifth coefficient block 1I is connected to a thirteenth coefficient block 1J by (k.sup.2 -1), the thirteenth coefficient block 1J is connected to a fourteenth coefficient block 1K, the fourteenth coefficient block 1K is connected to
the fifth subtractor S8, the ninth coefficient block 1M is connected to a fifteenth coefficient block 1N by {(R.sub.1 +R.sub.2 ')I+(1/.tau..sub.2 I-.omega..sub.r J) L .sigma., the fifteenth coefficient block 1N is connected to the fifth subtractor S8,
the tenth coefficient block 1D is connected to the eighth coefficient block 1P, and a second integrator 10 is connected between the fourth subtractor S7 and an estimated secondary magnetic flux .lambda..sub.2.
Consequently, it becomes unnecessary to separate between the primary leakage inductance and the secondary leakage inductance so that the apparatus for controlling the torque and speed of the induction motor in terms of vector control method in
which the constants measured from the actual induction motor to be controlled are directly used can be achieved.
(Second Embodiment)
FIG. 2 shows a second preferred embodiment of the vector apparatus for the induction motor according to the present invention.
That is to say, FIG. 2 shows a circuit block diagram of the magnetic flux observer of the full order in the second embodiment whose secondary magnetic flux .lambda..sub.2 is changed to the secondary current i.sub.2.
In order to alter the secondary magnetic flux into the excitation current component (.lambda..sub.2 /M), the elements in the second column of the state equation (4) recited in TABLE 4 are multiplied by M and those in the second column are
multiplied by 1/M to derive an equation (11-1) of TABLE 11. If the equation (11-1) of TABLE 11 is arranged, an equation of (11-2) of TABLE 11 can be derived.
In addition, the feedback terms of g.sub.1 through g.sub.4 of the observer are derived as equations (21-1), (12-2), (21-3), and (12-4) in TABLE 12.
Hence, the equation (11-2) of TABLE 11 constitutes the magnetic flux observer of the full order shown in FIG. 2 when 1/L.sigma. and 1/M' are arranged immediately before integration terms of the equation (11-2).
In FIG. 2, S9 denotes a first subtractor connected between the input voltage value v.sub.1 and a first coefficient block 2 G by (k-1), S10 denotes a first adder connected between the first subtractor S9 and a second coefficient block 2I, S11
denotes a second subtractor connected between the first adder S11 and a third coefficient block 2B by (R.sub.1 +R.sub.2 ')I, S12 denotes a third subtractor connected between the third subtractor S12 and the first coefficient block 2G, S14 denotes a third
adder connected between the second adder S13 and a fifth coefficient block 2A by R.sub.2 'I, S15 denotes a fourth subtractor connected between a sixth coefficient block 2J and a seventh coefficient block 2L, and S16 denotes a fifth subtractor connected
between i.sub.1 output end and i.sub.1 input end.
In addition, in FIG. 2, an eighth coefficient block 2F is connected between the fourth coefficient block 2E and the fifth subtractor S16, a ninth coefficient block 2H is connected between the first coefficient block 2G and the fifth subtractor
S16, a twelfth coefficient block 2I is connected between the first adder S10 and the seventh coefficient block 2L, a first integrator 2k is connected between the fourth subtractor S15 and an .lambda..sub.2 /M output end, an eleventh coefficient block 2C
is connected between the first adder S11 and a second integrator 2D, a twelfth coefficient block 2B is connected between the second subtractor S11 and the second integrator 2D, and the fifth coefficient block 2A is connected between the third adder S14
and the second integrator 2D.
In FIG. 2, a portion enclosed by a dot line indicates the feedback term of the magnetic flux observer and a portion enclosing the fifth coefficient block 2A, the second subtractor S11, the twelfth coefficient block 2B, the eleventh coefficient
block 2C, and the second integrator 2D indicates an induction motor model.
Hence, the estimated results of i.sub.1 and .lambda..sub.2 /M are obtained and are used to perform the vector control for the induction motor as variables. The induction motor drives can easily be achieved.
(Third Embodiment)
FIG. 3 shows a third preferred embodiment of the vector control apparatus for the induction motor according to the present invention.
That is to say, FIG. 3 is a circuit block diagram of the magn | | |
