Vector control apparatus for induction motor

Claim 2

An induction motor vector control apparatus as set forth in claim 1, characterised in that said first means (1, 2) derives the target value i 1d * as follows: i 1d *= ( λ 2d * M* ) · 1 A Mn + S · M'* R 2 '* · λ 2d * M* wherein A Mn = ΔV 1 δI n /M 2 */L 2 *·ω on ·λ 2d */M*, Δv 1 δ n denotes an arror voltage in the δ axis at a measuring point n, ω on denotes a primary angular frequency at the measuring point n, S denotes differential operator, M'* denotes the target value of the exciting inductance, L 2 * denotes the target value of the second inductance L 2 and R 2 '* denotes the target value of R 2 ' = (M/L 2 ) 2 ·R 2 , R 2 denoting the second resistance.

Claim 3

An induction motor vector control apparatus as set forth in claim 1, characterised in that it further includes an iron loss compensation circuit (14) which is so constructed as to caclulate a value derived from the target value λ 2d * in the d-axis component of the secondary magnetic flux according to the rotor angular frequency of the induction motor divided by the target value M* of the exciting inductance and the variation of the exciting inductance so that the calculated output of the iron loss compensation circuit (14) and the derived i 1q * are added to the first coordinate conversion block (5 1 ) as a torque instruction value i 1q '*.

Claim 4

An induction motor vector control apparatus as set forth in claim 2, characterised in that said exciting inductance M' is formatted in a data table with respect to the primary angular frequency ω o .

Claim 5

An induction motor vector control apparatus as set forth in claim 4, characterised in that said exciting inductance variation A Mn is formatted in a data table with respect to an exciting instruction λ 2d */M*

Claim 6

An induction motor vector control apparatus as set forth in claim 5, characterised in that said first-order advance element calculation block (1 2 ) receives a division value of the exciting instruction λ 2d */M* using the data table formatted exciting inductance variation A Mn and outputs the division value of the primary current target value i id *.

Claim 7

An induction motor vector control apparatus as set forth in claim 5, characterised in that said first means (1) derives the target value i id * of the primary current by dividing the exciting instruction λ 2d */M* using the data table formatted exciting inductance variation A Mn and adding the derived divided value to a differential term of the first-order advance element calculation block (1 2 ).

Claim 8

An induction motor vector control apparatus as set forth in claim 5, characterised in that said iron loss compensation circuit (14) receives the exciting instruction λ 2d */M* and the data table formatted exciting inductance variation A Mn and calculates the torque instruction value i 1q '* by the addition of the derived output thereof to the target value i 1q * of the primary current.

Claim 9

An induction motor vector control apparatus as set forth in claim 1, further characterised by a) detecting means (4 3 ) for detecting a rotor angular frequency ω r of the induction motor; b) secondary magnetic instruction amplifying means (1 1 ) for deriving a ratio of a target value of a secondary magnetic flux in a d-axis component to a target value of an exciting inductance λ 2d */M* according to the rotor angular frequency ω r ; c) the first-order advance element calculation block (1 2 ) calculating as follows: i 1d * = λ 2d */M* (1 + L 2 */R 2 * ·S), wherein i 1d * denotes a target value of a primary current in the induction motor in the d-axis component, L 2 * denotes a target value of a secondary inductance, and R 2 * denotes a target value of a secondary resistance, S denotes differential operator; d) the first coordinate conversion block (5 1 ) being so constructed as to receive i 1d * and i 1q '* (a target value of the primary current in the induction motor in a q-axis component) and as to calculate the following phase difference φ, i 1γ *, sinφ, and cosφ: tan -1 (i 1q '*/i 1d *) = φ i 1d ​ *2 + i 1q' *2 = I 1 , wherein I 1 denotes a primary current of the induction motor, I 1 comprises an i 1γ * component and i 1 δ* component in γ-δ axes of γ-δ coordinate system with the primary current I 1 as a reference axis; e) an ideal voltage calculation block (5 2 ) as the second means being so constructed as to calculate the following: v 1γ * = R 1 i 1γ * + M 2 */L 2 * · ω o · λ 2d */M*· sinφ v 1δ * = L σ ω o i 1γ * M 2 */L 2 * · ω o · λ 2d */M*· cosφ wherein Lσ = (L 1 L 2 -M 2 )·L 2 , L 1 and L 2 denote the primary and secondary inductance respectively, ωo denotes a power supply angular frequency and R 1 denotes the primary resistance; f) the slip angular frequency calculation block (3 4 ) being so constructed as to calculate the slip angular frequency ω s * on the basis of i 1q * and λ 2d */M*; g) a secondary resistance R 2 compensation amplifying means (10) for calculating a secondary resistance variation K on the basis of Δv 1 δ, wherein Δv 1 δ denotes an error voltage of the primary voltage v 1 in the δ axis; h) an M' compensator (12) which is so constructed as to calculate a variation in an exciting inductance on the basis of the following equation: A Mn = Δv 1 δ In /M 2 */L 2 *·ω on · λ 2d */M* , wherein Δv 1 δ In denotes δ-axis error voltage at a measuring point n of the speed during no load operation, ω o denotes a primary angular frequency at the measuring point n from the slip angular frequency calculation block; and i) a divider (13) which receives both λ 2d */M* from the secondary magnetic flux instruction amplifier (1 1 ) and A Mn from the M' compensator (12) and carries out a division so that a variation in the exciting inductance is compensated for i 1d *.

Claim 10

An induction motor vector control apparatus as set forth in claim 9, characterised in that said slip angle frequency calculation block (3 4 ) calculates ω s * as follows: ω s * = R' 2 */M'* · i 1q */λ 2d */M*, wherein R' 2 = (M/L 2 ) 2 ·R 2 , M' = M 2 /L 2 .

Claim 11

An induction motor vector control apparatus as set forth in claim 9, characterised in that said first-order advance element calculation block (1 2 ) calculates i 1d * = λ 2d */M* x (1 + S·M'*/R' 2 *).

Claim 12

An induction motor vector control apparatus as set forth in claim 11, characterised in that said first-order advance element calculation block (1 2 ) calculates i 1d * = (λ 2d */M*) · 1/A Mn + S · M'*/R' 2 * · λ 2d */M*.

Claim 13

An induction motor vector control apparatus as set forth in claim 12, characterised in that it further includes an iron loss compensator (14) which is so constructed as to calculate the iron loss compensation formula as: T RM = R m */M* x 1/A Mn x λ 2d */M* x 1/A Mn x 1/ω o .

Claim 14

An induction motor vector control apparatus as set forth in claim 13, characterised in that said slip angular frequency calculation block (3 4 ) calculates a follows: ω sn = (1 + K n ) · ω s(n-1) and in that ω sn is derived as ω s is added to the detected rotor angular frequency ω r to derive ω o which is a target value of the power supply angular frequency and is supplied to the M' compensator (12) and iron loss compensator (14), K n denoting the secondary resistance variation in the n-th order.