JP2000308400A - Vector controller for induction motor of elevator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vector controller in which comfortableness is prevented from deteriorating due to torque follow-up lag because of elevator cage is possibly deteriorated when a maximum efficiency operation is attained by varying the ratio between an exciting current command and a torque current command is varied depending on the load in vector control. SOLUTION: A maximum efficiency control section 18 obtains a flux command λ* from a torque command T*, an exciting current operating section 21 obtains an exciting current command id* from the flux command and a flux estimating section 22 estimates the flux of an induction motor from the exciting current command id*. A torque current operating section 23 enhances the follow-up performance of torque by obtaining a torque current command iq* from the torque command using an estimated flux λe from the flux estimating section. The invention also includes an arrangement for estimating the flux directly from the flux command λ* and obtaining the exciting current command, and an arrangement where the maximum efficiency control section 18 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control apparatus for an induction motor for an elevator, and more particularly to a control of a torque current for obtaining a good ride quality of an elevator car.

[0002]

2. Description of the Related Art When an induction motor is used as a drive source of an elevator, the induction motor is generally driven by a vector control type inverter in order to satisfy the requirements of the elevator car landing accuracy and riding comfort.

FIG. 3 is a block diagram of a vector control device for an elevator induction motor. Inverter 2 to drive the induction motor 1 is controlled current source is a voltage-controlled by PWM exciting current command i _d * and the torque current command i _q * voltage control signal by a digital calculation result of the current control unit 3 for v _u , V _v , v _w .

[0004] The current control system for the current control section 3 and the central portion is obtained even if the signal current i _v currents i _u two-phase induction motor 1 is in the feedback signal, the subtraction unit 4 from the detection signal of the i _w These three-phase current signals are converted into d- and q-axis two-phase currents by a three-phase / two-phase converter 5, and further converted into coordinate converters 6.
Rotational phase θ in the combined current detection signal i _d of the induction motor 1, a fixed / rotating coordinate conversion to i _q performed by.

The operation result of the current control unit 3 becomes two-axis voltage commands v _d and v _q of _d and _q . These voltage commands are subjected to rotation / fixed coordinate conversion by the coordinate conversion unit 7 in accordance with the phase θ. Are further converted into three-phase voltage control signals v _u , v _v , v _w by a two-phase / three-phase converter 8.

[0006] The speed control system of the induction motor 1 has a speed detection unit including a pulse pickup 9 and a speed detection circuit 10 to perform feedback control. The position controller 11 responds not only to the acceleration command according to the elevator car floor and the landing floor, but also to the acceleration command at the start of ascending and descending and the number of occupants (weight measurement) in addition to the speed command in a pattern consisting of a constant speed and a deceleration area. Generates a load command. Speed control unit 12 obtains a digital calculating the speed setting value from the speed command and the acceleration command and the load command from the position controller 11, proportional integral (PI) calculation for the deviation of the speed setting value and the speed detection signal omega _r The result is obtained as a torque command T *.

The magnetic flux / current command calculator 13 separates the torque command T * into a secondary magnetic flux command λ * and a torque current command _iq *, and the torque current command _iq * is directly sent to the current controller 3. and then, the correction by the speed detection signal ω _r in the secondary flux command λ *. The exciting current calculation unit 14 outputs the secondary magnetic flux command λ *
, An excitation current command _id * is obtained as a command to the current control unit 3.

[0008] Slip angular frequency arithmetic unit 15, flux lambda (or excitation current command i _d *) and the torque current command iq * and the slip angular frequency from the secondary time constant tau ₂ of the motor ω determined by the excitation current calculation unit 14 _Ask for _s . The adder 16 obtains the primary angular frequency omega by adding the slip angular frequency omega _s and the speed detection signal omega _r. The integrator 17 calculates the rotational phase θ by integrating the primary angular frequency ω.

[0009]

In the conventional vector control apparatus, in order to prevent torque fluctuation in a transient state, the magnetic flux / current command calculation unit 13 excludes a constant output operation region except for a constant output operation region.
The secondary magnetic flux command λ * (excitation current command _id *) is always kept constant regardless of the operation state. Therefore, even when the load is light (in an elevator, when the car is operating at a constant speed with the weight of the car and the weight of the counterweight balanced), the same exciting current flows as when the load is heavy, and the light load At times, the ratio of iron loss increases, and the electric-mechanical conversion efficiency of the motor decreases.

In order to solve this problem, in a vector control device for an induction motor for an electric vehicle, there has been proposed a method of maximizing the efficiency by changing an exciting current according to a load. This method focuses on the current ratio between the exciting component current and the torque component current from the motor equivalent circuit at the time of vector control taking into account iron loss, and derives a simple conditional expression that maximizes the efficiency for any load. The maximum efficiency control is obtained based on this conditional expression. The maximum efficiency control method will be described below in principle.

FIG. 4 shows an equivalent circuit when the induction motor is controlled by the vector. Each part constant here is
It becomes constant in a normal T-type equivalent circuit, L ₁ the primary self-inductance, L ₂ a secondary self-inductance, equivalent iron loss resistance R _m, mutual inductance, primary resistance R ₁ to M,
Assuming that R ₂ is a secondary resistance, the following equation is obtained.

[0012]

Lσ = (L ₁ L ₂ −M ² ) / L ₂ RC = α {(ωM) ² / R _m } (1) R ₂ ′ = α ² R ₂ M ′ = αM α = M / L ₂ omega: in power supply angular frequency above the equivalent circuit, the exciting component current i _d, as torque current i _q, Doing vector control in consideration of iron loss,
The primary current I ₁ and the slip angle frequency ω _S are given by the following equations.

[0013]

(Equation 2)

Here, _ic is the iron loss current, and is given by the following equation.

[0015]

Equation 3] _{i c = ωM'i d / R c} = R m i d / (ωM) ... (4) In addition, the torque T, when the pole pairs p, becomes the following equation.

[0016]

Equation 4] _{T = 3pM'i d i q ... (} 5) exciting current i _d takes into account the constant output range, a constant value i _dmax in the base speed omega ₀ or less, the terminal of the motor at higher speed Field weakening control is performed by the following equation so that the voltage becomes substantially constant.

[0017]

Equation 5] _{i d = i dmax × ω 0} / ω r ... (6) ω r: rotor speed also for total loss W _total of the induction motor, equivalent circuits above and (2) in FIG. 4 expression and From the expression (4), it is expressed by the following expression (7). However, it is assumed that R _m ² ≪ (ωM) ² .

[0018]

[6] ^{_{W total = 3R 1 I 1 2}} + 3R 2 'i q 2 + 3R C i c 2 + W m = 3 _{[(R 1 + R 2')} i q 2 + (R 1 + R m ') i d 2 +2 _{{R m / (ωM)}} R 1 i d i q ] _{+ W m ... (7) W} m: mechanical loss R _m '= [alpha] R _m Incidentally, the equivalent iron loss resistance R _m will vary by power frequency,
Assuming that the power loss frequency is proportional to the 1.6th power and the iron loss resistance R _m0 at the rated frequency f ₀ , the following relationship is obtained.

[0019]

R _m = R _m0 × (f / f ₀ ) ^1.6 (8) Further, it is assumed that the mechanical loss is proportional to the square of the rotor angular velocity as in the following equation.

[0020]

W _m = K _m × ω _r ² (9) From these relationships and the equivalent circuit of FIG. 4, the loss of the motor can be obtained for an arbitrary speed and load torque.

On the other hand, the shaft output P _out of the motor is given by the following equation.

[0022]

P _out = ω _r × T−W _m (10) Accordingly, the efficiency η (%) of the motor is given by the following equation.

[0023]

Η = 100 × P _out / (P _out + W _total ) (11) Here, assuming that the ratio between the torque component current and the excitation component current is A,

[0024]

A = ( _iq / _id ) (12) From the torque of the above equation (5), the following equation is obtained.

[0025]

Equation 12] _{i d i q = T / 3pM} '... (13) i q 2 = (T / 3pM') A ... (14) i d 2 = T / (3pM'A) ... (15) wherein these Substituting into equation (7), the motor loss W
_total can be expressed as a function of the ratio A.

[0026]

W _total = (R ₁ + R ₂ ') (T / 3 pM') A + (R ₁ + R _m ') T / (3 pM'A) +2 ｛R _m / (ωM)｝ R ₁ T / ( pM ′) + W _m (16) Here, in order to maximize the efficiency of the electric motor in an arbitrary load state, it is sufficient to minimize the loss in the operating state. Therefore, assuming that ∂W _total / ∂A = 0, A
By solving for (= _iq / _id ), a condition that maximizes the efficiency can be obtained, and is expressed by the following equation.

[0027]

[Equation 14]

However, in the derivation of the above equation (17), strictly speaking, ω and R _m also become functions of A and are affected by the differentiation. However, when the rotation speed is fixed, these values are almost constant. Value.

Therefore, the torque current _iq and the exciting current _id
The ratio A can be determined by the above equation (17) of, for a given torque command T, becomes maximum efficiency current command value i _q, i _d
Is obtained by the following equation.

[0030]

(Equation 15)

FIG. 5 is a block diagram of an elevator vector control device for performing maximum efficiency control. In FIG. 5, a portion different from FIG. 3 is a maximum efficiency control portion 18 instead of the magnetic flux / current command calculation portion 13. The maximum efficiency control unit 18 provides the torque command T * with the above (18), (1)
9) For the performs computation (exciting current i _d seek flux λ Alternatively) that is, always perform vector control in the maximum efficiency.

In FIG. 5, the exciting current calculator 1 shown in FIG.
4 is provided with a high-speed magnetic flux control section 14A. The control section 14A improves the response delay of the torque with respect to the change in the exciting current.

That is, the response of the secondary magnetic flux to the change of the exciting current is delayed, and as a result, the response of the torque is delayed.
In order to improve the response delay of the secondary magnetic flux, the high-speed magnetic flux controller 14A pseudo-differentiates the magnetic flux command λ * to obtain an excitation current command _id *.

For example, the high-speed magnetic flux control section 14A is configured as an operation block shown in FIG. In the figure, the relationship between the magnetic flux command λ * and the magnetic flux estimation value λe is as follows.

[0035]

(Equation 16)

By appropriately selecting the value of the proportional gain G in this equation, the time constant of the secondary magnetic flux response can be set to 1 / (1 + G) of the secondary time constant τ ₂ , thereby improving the torque response. Is done.

As described above, the conventional device attempts to improve the torque tracking delay by providing the high-speed magnetic flux controller 14A in the maximum efficiency controller 18, but cannot reduce the torque tracking delay to zero. The occurrence of the delay in following the torque may deteriorate ride comfort when the maximum efficiency control is employed in the vector control device for the elevator.

An object of the present invention is to provide a vector control device which prevents a decrease in ride quality due to a delay in following a torque.

[0039]

SUMMARY OF THE INVENTION The present invention estimates the magnetic flux of an electric motor from a magnetic flux command or an exciting current command, and obtains a torque current command using the estimated magnetic flux, thereby improving the followability of torque and improving ride comfort. Which is characterized by the following configuration.

A vector control device for an induction motor for an elevator, wherein an induction motor is used as a drive source of the elevator, and a torque current command and an excitation current command of the induction motor are obtained based on a torque command obtained by a speed control system to vector-control the induction motor. A magnetic flux estimating unit for estimating a magnetic flux of the induction motor from a magnetic flux command obtained from the torque command or an exciting current command obtained from the magnetic flux command; and a torque current command from the torque command using the magnetic flux estimated by the magnetic flux estimating unit. And a torque current calculation unit for determining

In order to obtain the magnetic flux command from the torque command, a maximum efficiency control unit for obtaining a maximum efficiency operation by changing a ratio between the torque current command and the exciting current command according to the load of the induction motor. It is characterized by having.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a block diagram of a vector control device showing an embodiment of the present invention. This figure differs from FIG. 5 in that the high-speed magnetic flux control unit 14A
, The magnetic flux estimating unit 22 estimates the magnetic flux λe
The torque current calculation unit 23 uses the torque current command _iq *
The point is to seek.

The excitation current calculation unit 21 includes the maximum efficiency control unit 1
8 to the excitation current command i from the maximum efficiency flux command λ *
_d * is obtained, and an excitation current command to the current control unit 3 is obtained.

The magnetic flux estimator 22 obtains the estimated magnetic flux λe from the exciting current command i _d * determined by the excitation current calculation unit 21.
In this magnetic flux estimation, similarly to the block configuration of the high-speed magnetic flux control unit in FIG. 6, the magnetic flux of the electric motor is estimated with a small delay by using a magnetic flux model.

The torque current calculator 23 is provided with the speed controller 12
A torque current command _iq * is obtained from the torque command T * obtained by. By using the magnetic flux λe estimated by the magnetic flux estimating unit 22 in the torque current calculation, a torque current command calculation with a reduced delay can be performed. Note that the estimated magnetic flux λe of the magnetic flux estimating unit 22 is also used as an input to the slip angle frequency calculating unit 15.

According to the present embodiment, in addition to increasing the power conversion efficiency by the maximum efficiency control, the torque current command _iq * is obtained by using the magnetic flux estimated by the magnetic flux estimating unit 22. Vector control can be performed using _iq * and the excitation current command _id *. To obtain the torque required for the motor, reduce the delay of the torque current command, that is, reduce the torque generated by the motor with respect to the torque command. It is possible to enhance the followability and prevent a decrease in ride comfort.

(Second Embodiment) FIG. 2 is a block diagram showing another embodiment of the present invention. 1 differs from FIG. 1 in that a high-speed magnetic flux control unit 24 is provided instead of the exciting current calculation unit 21 and the magnetic flux estimation unit 22.

The high-speed magnetic flux controller 24 is constituted by a block diagram equivalent to the FIG. 6 is obtained from the flux command lambda * from the maximum efficiency control unit 18 and the estimated flux λe excitation current command i _d *.
The estimated magnetic flux λe is used in the torque current calculation in the torque current calculation unit 23 and is also used in the slip angle frequency calculation in the slip angle frequency calculation unit 15.

In the first embodiment, since the estimated magnetic flux λe includes the delay of the excitation current command by the excitation current calculation unit 21, this delay is determined by the torque current calculation unit 2.
3 is also included in the torque current calculation.

On the other hand, in the present embodiment, the estimated magnetic flux λe does not include the delay in the exciting current calculator 21, and the delay in the torque current calculation in the torque current calculator 23 is further reduced. And the riding comfort can be further improved.

In the above embodiments, the case where the maximum efficiency control unit 18 applies the magnetic flux command or the excitation current command to the device for maximizing the efficiency has been described. The present invention can be applied to a device that calculates magnetic flux and torque current from T *. In this case, although the efficiency is inferior, the followability of the torque is excellent and the riding comfort can be improved.

[0052]

As described above, according to the present invention, the magnetic flux of the electric motor is estimated from the magnetic flux command or the excitation current command, and the torque current command is obtained using the estimated magnetic flux. Performance and the ride comfort of the elevator car can be improved.

Further, by combining this with the maximum efficiency control, a comfortable and efficient vector control can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an elevator vector control device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an elevator vector control device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional general elevator vector control device.

FIG. 4 is an equivalent circuit of an induction motor at the time of vector control.

FIG. 5 is a block diagram of a conventional vector control device for an elevator using maximum efficiency control.

FIG. 6 is a block diagram of a high-speed magnetic flux controller in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Induction motor 2 ... Inverter 3 ... Current control part 11 ... Position controller 12 ... Speed control part 13 ... Magnetic flux / current command calculation part 14 ... Excitation current calculation part 18 ... Maximum efficiency control part 21 ... Excitation current calculation part 22 ... Magnetic flux estimator 23 ... Torque current calculator 24 ... Maximum efficiency controller

Claims (2)

[Claims] 1. A drive source for an elevator is an induction motor,
A vector control device for an elevator induction motor for vector-controlling the induction motor by obtaining a torque current command and an excitation current command of the induction motor based on a torque command obtained by a speed control system, wherein a magnetic flux command or the magnetic flux obtained from the torque command A magnetic flux estimating unit for estimating a magnetic flux of the induction motor from an exciting current command obtained from the command, and a torque current calculating unit for obtaining the torque current command from the torque command using the magnetic flux estimated by the magnetic flux estimating unit. A vector control device for induction motors for elevators. 2. A maximum efficiency control unit for obtaining a maximum efficiency operation by changing a ratio between the torque current command and the excitation current command according to a load of an induction motor to obtain the magnetic flux command from the torque command. The vector control device for an induction motor for an elevator according to claim 1, further comprising: