JP4730997B2 - Induction motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an industrial machine drive induction motor represented by a fan pump.
[0002]
[Prior art]
For example, FIG. 8 shows a reference V: for operating an induction motor in a conventional inverter device described in p209 to p210 of Reference Document: Yamamura, Ohno et al. 1 is a general configuration diagram of a constant / f control device, in which 1 is a commercial power source, 2 is a rectifier, 3 is an inverter main circuit, 4 is an induction motor, 5 is a load machine, 6 is a V / f controller, 7 Is a main circuit drive signal generator.
[0003]
The outline of the operation will be described below. The rectifier 2 converts AC power supplied from the commercial power source 1 into DC power. The inverter main circuit 3 converts the DC voltage supplied from the rectifier 2 into an AC voltage based on the drive signal output from the main circuit drive signal generator 7 and outputs the AC voltage to the induction motor 4. Voltage amplitude command value | V | * and voltage frequency command value ω for the AC voltage output from the inverter main circuit 3_Vf* Indicates the rotation speed command value (rotation frequency command value) ω of the induction motor input from the outside_m* In the V / f controller 6 according to *.
[0004]
  In the V / f controller 6, the calculation is generally performed as in the following formulas (1) and (2), and the voltage amplitude command value | V | * and the voltage frequency command value ω_Vf* Is output to the main circuit drive signal generator 7. K_VfIs the voltage amplitude command value | V | * and the voltage frequency command value ω calculated in consideration of the rating of the induction motor_VfThe ratio of *.
          ω_Vf* = ω_m* ----------------- (1)
          | V | * = K_Vf・ Ω_Vf* ----------------- (2)
That is, the V / f constant control is a voltage amplitude command value | V | * and a voltage frequency command value ω._Vf* Ratio K_{V f}As a constant, induction motor4This means that the AC voltage applied to the is controlled.
[0005]
In the V / f controller 6, the upper limit of the frequency of the AC voltage output from the inverter main circuit 3, that is, the upper limit ω of the inverter output frequency._VfmaxIs set in consideration of the rotational speed region of the induction motor 4. And the upper limit ω of the inverter output frequency_VfmaxWhen a rotation frequency command value exceeding is input to the V / f controller,
In equation (1), ω_Vf* = ω_VfmaxBy calculating *, the rotation speed of the induction motor 4 is prevented from exceeding the limit speed for safe operation.
[0006]
The main circuit drive signal generator 7 has a voltage amplitude command value | V | * and a voltage frequency command value ω._Vf* Is converted into an inverter drive signal and output to the inverter main circuit 3. Thus, the inverter main circuit 3 has the voltage amplitude command value | V | * and the voltage frequency command value ω._VfThe AC voltage according to * is output to the induction motor 4, and the induction motor 4 rotates according to the operating characteristics under the V / f constant control described later. With this configuration, the upper limit ω of the inverter output frequency_VfmaxAny rotational speed command value ω within a range not exceeding_m* Variable speed operation of the induction motor 4 according to is possible.
[0007]
Next, the operating characteristics of the induction motor 4 under constant V / f control will be described from the aspect of the physical relationship with the load machine 5. For simplicity of explanation, the number of pole pairs of the induction motor 4 is treated as 1 throughout this specification.
[0008]
FIG. 9 is a Bode diagram illustrating the frequency characteristics of the physical relationship between the induction motor 4 and the load machine 5 under the constant V / f control in consideration of the above. Gmeca is the rotational speed fluctuation Δω from the torque fluctuation Δτ in the load machine 5._mTransfer characteristics up to. G_IMIs the rotational speed fluctuation Δω in the induction motor 4 under constant V / f control._mTo the torque fluctuation Δτ.
[0009]
When the torque fluctuation Δτ is input to the load machine 5, the load machine 5 is accelerated or decelerated based on the transfer characteristic Gmeca in the load machine 5, and the rotational speed fluctuation Δω._mIs output. And rotational speed fluctuation Δω_mIs input to the induction motor 4, the transfer characteristic G in the induction motor 4_IMBased on this, the induction motor 4 outputs a torque fluctuation Δτ. Therefore, the load machine 5 and the induction motor 4 have a rotational speed variation Δω._mThere is a physical loop based on the input / output relationship of torque fluctuation Δτ.
[0010]
Here, the transfer characteristic G in the induction motor 4_IMThe important basic characteristics of will be described. The induction motor 4 has a voltage frequency command value ω that is the frequency of the AC voltage output from the inverter main circuit 3._Vf* And rotational speed ω_mTorque τ that is basically proportional to the difference is output. Therefore rotation speed ω_mIs the rotational speed fluctuation Δω_mIs accompanied by a torque fluctuation Δτ that appears in the torque τ generated through the slip._mIs the opposite sign.
[0011]
That is, the rotational speed ω_mIs the voltage frequency command value ω_Vf* When kept in the vicinity, rotational speed fluctuation Δω_mWhen this occurs, the induction motor 4 causes the transfer characteristic G_IMRotational speed fluctuation Δω according to_mIs generated and output to the load machine 5. This torque fluctuation Δτ is the original rotational speed fluctuation Δω for the load machine 5._mSpeed change Δω after the output of the transfer characteristic Gmeca_mIs the original rotational speed fluctuation Δω_mSmaller than. And Δω_mTransfer characteristic G in the induction motor 4 due to the decrease of_IMAs a result, the transfer characteristic G in the induction motor 4 decreases._IMThe torque fluctuation Δτ, which is the output of, also decreases. Thus, the rotational speed fluctuation Δω_mAnd a physical loop made up of torque fluctuation Δτ include rotational speed fluctuation Δω_m, And has a stable characteristic that tries to converge both torque fluctuations Δτ to 0, and again the rotational speed ω_mIs the voltage frequency command value ω_Vf* Remains nearby.
[0012]
Rotational speed fluctuation Δω under V / f constant control shown above_mAnd the characteristic of the physical loop composed of torque fluctuation Δτ, the transfer characteristic G inherent to the induction machine_IMIn a variable speed driving application that is sufficiently gentler than the response of the V / f constant control device having a simple device configuration that does not use a rotational speed sensor, the voltage frequency command value ω_Vf* Is the rotational speed command value ω_mIf given as *, an arbitrary rotation speed command value ω_m* Rotational speed control according to
[00013]
[Problems to be solved by the invention]
However, when the load machine has a resonance characteristic in the conventional V / f control device, depending on the conditions of the machine resonance frequency and the operation frequency of the induction motor, a large amplitude self-excited vibration is generated and persists. was there.
[0014]
The present invention has been made to solve the above-described problems, and has as its object to improve the frequency characteristics of an induction motor and stably operate an induction motor and a load machine while avoiding the occurrence of vibration.
[0015]
[Means for Solving the Problems]
  The induction motor control device according to the present invention converts a rotation frequency command value input from the outside into a first voltage amplitude command value and a first voltage frequency command value for the output voltage of the inverter main circuit. A voltage amplitude compensation command value and a voltage frequency compensation command value based on the input current of the induction motor or the DC bus current of the inverter, and the voltage amplitude compensation command value from the first voltage amplitude command value. A subtractor a that subtracts the value and outputs a second voltage amplitude command value; and a subtractor b that subtracts the voltage frequency compensation command value from the first voltage frequency command value and outputs a second voltage frequency command value. And a main circuit drive signal generator that converts the second voltage amplitude command value and the second voltage frequency command value into drive signals for the inverter main circuit, and the compensation calculation unit includes:The phase characteristic in the transmission characteristic from the torque fluctuation to the rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], andBelow the rotation frequency command valueMachine that isAt the resonance frequency, the calculation is performed so that the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor is corrected to −270 [deg] or more.
[0016]
  A V / f controller that converts a rotation frequency command value input from the outside into a first voltage amplitude command value and a first voltage frequency command value for the output voltage of the inverter main circuit; a voltage amplitude compensation command value; A compensation calculation unit for computing a voltage frequency compensation command value based on an input current of the induction motor or a DC bus current of the inverter, and a second voltage amplitude by subtracting the voltage amplitude compensation command value from the first voltage amplitude command value A subtractor a that outputs a command value; a subtractor b that subtracts the voltage frequency compensation command value from the first voltage frequency command value and outputs a second voltage frequency command value; and the second voltage amplitude command. A main circuit drive signal generator that converts a value and the second voltage frequency command value into a drive signal for the inverter main circuit, and the compensation calculation unit includes:The phase characteristic in the transmission characteristic from the torque fluctuation to the rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], andBelow the rotation frequency command valueMachine that isAt the resonance frequency, the calculation is performed so that the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor is corrected from −270 [deg] or less to −270 [deg] or more.
[0017]
  In addition, the compensation calculation unit is configured to output the first voltage frequency command value under any condition where the first voltage frequency command value takes any value from 0 to an upper limit value of the inverter output frequency set in the V / f controller. All frequency range below the command valueThe phase characteristic of the transfer characteristic from torque fluctuation to rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], and the rotation In the machine resonance frequency that is below the frequency command value,The calculation is performed so that the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor becomes −270 [deg] or more.
[0018]
The compensation calculation unit receives an input current of the induction motor or a DC bus current of the inverter and estimates and outputs a torque current of the induction motor, and the torque current estimator outputs And a compensation command value calculator for calculating a voltage amplitude compensation command value and a voltage frequency compensation command value based on the torque component current.
[0019]
The compensation calculation unit calculates the ratio between the voltage amplitude compensation command value and the voltage frequency compensation command value to be the same as the ratio between the first voltage amplitude command value and the first voltage frequency command value. .
[0020]
The compensation command value calculator calculates a voltage frequency compensation command value using a high-pass filter and a proportional gain based on the torque component current.
[0021]
The compensation command value calculator calculates a voltage frequency compensation command value using a high-pass filter, a low-pass filter, and a proportional gain based on the torque component current.
[0022]
Furthermore, the compensation command value calculator is used for the cutoff frequency ω of the high-pass filter.₁The value of the proportional gain Kp is set by the following equation to calculate the voltage frequency compensation command value.
ω₁= {Tan (β)}²・ Ωσ
Kp = (ω_Vfmax ²+ Ω₁ ²) / (Ω_Vfmax・ Tan (β) ・ k_G)
Where β, ωσ, ω_Vfmax, K_GIs a setting constant defined below.
β = 90−α [deg], α = 20 [deg] or more,
ωσ: (secondary resistance value / secondary leakage reactance value) of the induction motor,
ω_Vfmax: Maximum value in operating condition of voltage frequency,
k_G: Induction motor (secondary magnetic flux primary conversion value / primary leakage reactance value)
[0023]
Embodiment
Embodiment 1 FIG.
FIG. 1 shows a control apparatus for an induction motor according to Embodiment 1 of the present invention. The same reference numerals as those in FIG. 8 of the conventional apparatus denote the same or corresponding parts. The rectifier 2 converts AC power supplied from the commercial power source 1 into DC power. The inverter main circuit 3 converts the DC voltage supplied from the rectifier 2 into an AC voltage based on the drive signal output from the main circuit drive signal generator 7, outputs the AC voltage to the induction motor 4, and operates the load machine 5. Voltage amplitude command value | V | * and voltage frequency command value ω for the AC voltage output from the inverter main circuit 3_Vf* Indicates the rotation speed command value (rotation frequency command value) ω of the induction motor input from the outside_m* In the V / f controller 6 according to *.
[0024]
8 is an induction machine current detector, 9a is a torque component current estimation calculator, 10 is a compensation command value calculator, 11a is a subtractor a, and 11b is a subtractor b. Further, the torque current estimation calculator 9a and the compensation command value calculator 10 are collectively referred to as a compensation calculator 20a.
[0025]
The operation will be described below. The induction machine current detector 8 detects induction machine currents Iu, Iv, Iw flowing through the induction motor 4. In the torque component current estimation calculator 9a, the induction machine currents Iu, Iv, Iw output from the induction machine current detector 8 and the ω output from the V / f controller 6 are output._VfBased on *, the torque equivalent current iq of the induction motor 4 is estimated and calculated by calculating the following formulas (3) and (4).
θ^*= ∫ω_Vf* dt ----------------- (3)
iq = -Iu.cos (θ^*) -Iv · cos (θ^*―120)
―Iw · cos (θ^*―240) ----------------- (4)
[0026]
The compensation command value calculator 10 receives the torque component current iq from the torque component current estimation calculator 9a, and performs compensation calculations of equations (6) and (7) including the transfer characteristics represented by the following equation (5). . Where s is the Laplace operator and ω₁Is the cutoff frequency of the high-pass filter, Kp is the proportional gain,_VfIs the voltage amplitude command value | V | * and the voltage frequency command value ω_VfThe ratio of *.
Gh = Kp.s / (s + ω₁----------------- (5)
Δω_Vf* (S) = Gh • iq (s) ----------------- (6)
Δ | V | * (s) = K_Vf・ Δω_Vf* (S) ---------- (7)
[0027]
In this way, the compensation command value calculator 10 supplies the voltage amplitude compensation command value Δ | V | * to the subtractor a11a and the voltage frequency compensation command value Δω._Vf* Is output to the subtracter b11b.
In the subtractor a11a, the difference between the first voltage amplitude command value | V | * output from the V / f controller 6 and the voltage amplitude compensation command value Δ | V | * is determined as the second voltage amplitude command value | V | Calculate as ** and output to main circuit drive signal generator 7. Similarly, the subtractor b11b also outputs the first voltage frequency command value ω output from the V / f controller 6._Vf* And voltage frequency compensation command value Δω_Vf* Is the second voltage frequency command value ω_VfCalculated as ** and output to the main circuit drive signal generator 7.
[0028]
In order to explain the principle that the problem can be solved by the first embodiment, first, self-excitation that depends on the mechanical resonance frequency ωmeca of the load machine 5 and the operating condition of the induction motor 4, which is a problem in the conventional V / f constant control. The principle of generating vibration will be described. For this purpose, the transfer characteristic G in the induction motor 4 shown in FIG._IM31 and a physical loop constituted by the transfer characteristic Gmeca30 in the load machine 5 -G_IM・ It is necessary to pay attention to the frequency characteristics of Gmeca. Here, as described in the description of FIG. 9, the transfer characteristic G in the induction motor 4._IMRotational speed fluctuation Δω of the transfer characteristic Gmeca of the load machine 5_mSince the characteristic of the feedback cancels out, the characteristic of the discussion regarding stability is as follows. For the transfer characteristic in the induction motor 4, −1 is multiplied by −G_IMThe phase characteristics will be described as follows.
[0029]
FIG. 9C shows the physical loop-G._IM-It is a Bode diagram explaining the frequency characteristic of Gmeca.
FIG. 9 (a) shows the torque fluctuation Δτ in the load machine 5 to the rotational speed fluctuation Δω._mIt is a Bode diagram of transfer characteristic Gmeca until. As an example, the case where the mechanical resonance frequency ωmeca is 40 [Hz] is shown. Gmeca has a mechanical resonance frequency ωmeca with a very large peak in gain, and a characteristic in which the phase changes from +90 [deg] to -90 [deg].
[0030]
FIG. 9B shows the voltage frequency command value ω by the constant V / f control._Vf* = Rotational speed fluctuation Δω in an induction motor driven at 50 [Hz]_mTo G of torque fluctuation Δτ_IMTransfer characteristic -G multiplied by -1_IMIt is a Bode diagram. -G_IMCan be described as follows by linearizing the voltage equation of the induction motor.
-G_IM  ≒ {K_T・ Kg / (s + ωσ)} · {(s²+ B₁s + ω_Vf*²) / (S²+ A₁s + ωp²)} ----------------- (8)
K_T, Kg, b₁, A₁, Ωp are all values determined from the constants of the induction motor, and the following relationship holds.
ωp ≒ ω_Vf* ---------------- (9)
a₁≒ 2b₁            ----------------- (10)
[0031]
From above -G_IMThe characteristic is that the voltage frequency command value ω_Vf* A gain change of about -5 [dB] in the vicinity and a steep phase change of ± 20 [deg] are added. Therefore, depending on the induction machine circuit constants and operating conditions, the voltage frequency command value ω as shown in the example of FIG._Vf* Due to steep phase lag in the following frequency range,_IMAppears in the frequency region X where the phase of the phase is less than −90 [deg].
[0032]
FIG. 9C shows a physical loop-G._IM・ Gmeca's Bode diagram. In the case where the mechanical resonance frequency ωmeca shown in FIG. 9A and the frequency region X shown in FIG. 9B overlap due to the mutual frequency characteristics of the induction motor 4 and the load machine 5, the phase in the physical loop is − It can be seen that in the frequency region below 180 [deg], the gain is 0 [dB] or more due to the peak due to resonance. Therefore physical loop-G_IM-Since Gmeca becomes unstable, vibration is generated and sustained between the load machine 5 and the induction motor 4.
[0033]
Next, by adding the induction machine current detector 8, the torque component current estimation calculator 9a, the compensation command value calculator 10, and the subtractors 11a and 11b in the first embodiment, self-excited vibration, which has been a problem in the past, is added. The direct principle that can avoid the occurrence will be described.
[0034]
FIG. 3 is a diagram illustrating the frequency characteristics of the physical loop when the compensation calculation unit 20a is added as in the first embodiment. FIG. 3A shows the rotational speed fluctuation Δω from the torque fluctuation Δτ in the load machine 5._mFIG. 10 is a Bode diagram of the transfer characteristic Gmeca up to and is the same as FIG.
[0035]
FIG. 3B illustrates the voltage frequency command value ω after the phase advance / delay compensation is performed by the compensation calculation unit 20a._Vf* = Rotational speed fluctuation Δω in induction motor when driven at 50 [Hz]_mTo G of torque fluctuation Δτ_IMTransfer characteristic h multiplied by -1 -G_IMIt is a Bode diagram of h.
[0036]
FIG. 3C shows a physical loop −G after the compensation is applied._IMh • An example of a Gmeca Bode diagram.
[0037]
Compensation command value calculator 10 uses parameters Kp and ω in equation (5).₁Is set as described below, so that the conventional physical loop -G in FIG._IM-Transfer characteristics related to the induction motor 4 in which the phase is -90 [deg] or less in the destabilization region in Gmeca, that is, in the frequency region including the mechanical resonance frequency ωmeca -G_IMTransfer characteristic with a phase of −90 [deg] or more in the same frequency region −G_IMCompensation calculation is performed so that h. In other words, the transfer characteristic G of the induction motor 4 in the frequency region including the mechanical resonance frequency ωmeca._IMIs compensated so that the phase of the phase becomes −270 [deg] or more.
[0038]
Due to this compensation, the physical loop -G as shown in FIG._IMh In Gmeca, it is possible to stabilize by eliminating the frequency region where the phase is less than 180 [deg] and the gain is 0 [dB] or more. It is possible to operate the load machine 5.
[0039]
Next, the transfer command G of the induction motor 4 is calculated by the compensation command value calculator 10._IMG_IMExplain why it can be modified to h. The voltage frequency compensation command value Δω from the torque component current iq in the compensation command value calculator 10_Vf* Transfer characteristic Gh up to * Cutoff frequency ω₁A high-pass filter and a proportional gain Kp, and voltage amplitude compensation command value Δ | V | * and voltage frequency compensation command value Δω_Vf* Ratio of voltage amplitude command value | V | * and voltage frequency command value ω_Vf* Ratio K_VfAn example in which the calculation by the compensation command value calculator is represented by formulas (5), (6), and (7) will be described.
[0040]
FIG. 4 is a block diagram relating to the input / output of the state quantity of the induction motor 4 used for the explanation of the constant setting. However, assuming that the response of the inverter is ideal, the voltage amplitude compensation command value Δ | V | * and the voltage frequency compensation command value Δω with respect to the equations (5), (6), and (7)._Vf* Actual inverter output amplitude variation Δ | V |, which varies depending on *, inverter output frequency variation Δω_VfAre the voltage amplitude compensation command value Δ | V | * and the voltage frequency compensation command value Δω, respectively._VfExplain that it matches *.
[0041]
Gwm is the rotation speed fluctuation Δω in the induction motor._mTo the torque current fluctuation Δiq. Gw is a voltage amplitude compensation command value Δ | V | * and a voltage frequency compensation command value Δω as in equations (6) and (7)._Vf* Ratio of voltage amplitude command value | V | * and voltage frequency command value ω_Vf* Ratio K_VfInverter output frequency oscillation Δω_VfTo the torque current fluctuation Δiq. K_TIs a torque constant.
[0042]
Rotational speed fluctuation Δω in the conventional case without the compensation command value calculator 10_mTo G of torque fluctuation Δτ_IMIs
G_IM= K_TGwm ----------------- (11)
It can be expressed as. This G_IMThe Bode diagram obtained by multiplying -1 by 1 is as shown in FIG. 9 (b). The phase is more extreme than -90 [deg] in the lower region of the inverter frequency depending on the induction machine circuit constants and operating conditions. There is a frequency region that lags behind.
[0043]
When a loop of the compensation command value calculator 10 is added to such characteristics, the rotational speed fluctuation Δω is obtained by the compensation effect Gmod including Gh and Gw as in the following equation (12)._mTo the torque fluctuation Δτ is G_IMTo G_IMIt can be compensated to change to h.
Gmod = (1 + Gh · Gw)^-1  ------------- (12)
G_IMh = Gmod ・ G_IM          ------------- (13)
[0044]
Next, a method is described in which the compensation effect Gmod is set to have a phase lead compensation characteristic for stabilizing the physical loop, and self-excitation can be avoided. Hereinafter, description will be made by paying attention to the cut-off frequency and DC gain of Gh and Gw constituting Gmod. Globally, Gw can be approximated as a combination of a first-order lag of the cutoff frequency ωσ and a proportional gain as in the following equation.
Gw≈Kg / (s + ωσ) = Gσ ----------- (14)
On the other hand, the characteristic Gh in the compensation command value calculation is the cut-off frequency ω as shown in Equation (5).₁, And a proportional gain Kp.
[0045]
FIG. 5 shows a compensation effect Gmod = (1 + Gh · Gw) composed of Gw and Gh.^-1It is an example of a Bode diagram. Focusing on the phase characteristics, ωσ and ω on the frequency logarithmic axis₁Midpoint, that is, (ωσ · ω₁)^1/2It can be confirmed that the phase lag / lead compensation is centered on. That is, the phase lead compensation region is the parameter of the compensation command value calculator ω₁It can be changed by adjusting the setting. The phase compensation amount can be set by the proportional gain Kp.
[0046]
Therefore, −G in the frequency region including the machine resonance frequency ωmeca of the load machine 5 as a setting guideline._IMThe phase of h is greater than -90 [deg], that is, G_IMThe parameter ω of Gh in the compensation command value calculator is obtained so that Gmod having a phase of h of −270 [deg] or more can be obtained.₁If Kp is set, physical loop -G_IMh Since Gmeca is stabilized, it is possible to stably operate the induction motor 4 and the load machine 5 without generating self-excited vibration.
[0047]
The design principle of the compensation command value calculator 10 has been developed, and the voltage frequency command value ω_Vf* Is the upper limit ω of the inverter output frequency set in the V / f controller 6 from 0_VfmaxThe transfer characteristic G of the induction motor 4 after compensation under any of the following conditions_IMTransfer characteristic h multiplied by -1 -G_IMThe phase characteristic at h is the voltage frequency command value ω_Vf* In the following, the transmission characteristic G of the induction motor 4 after compensation is set so that it is always more than −90 [deg]._IMThe phase characteristic at h is the voltage frequency command value ω_Vf* If the compensation command value calculator 10 is set so that it is always −270 [deg] or more, the physical loop −G_IMh ・ Gmeca is the upper limit of the inverter output frequency ω_VfmaxVoltage frequency command value ω in all frequency ranges below_Vf* In any case, the phase becomes −180 [deg] or more, so that the phase is stable, and the voltage resonance command value ωmeca of the load machine 5 is any value and the voltage frequency command value ω_Vf* Is 0 or more, upper limit ω_VfmaxWith any of the following values, the induction motor 4 and the load machine 5 can be stably operated without generating self-excited vibration.
[0048]
Here, when the equations (5), (6), and (7) are used as the compensation command value calculator 10, the compensation command value calculator internal parameter ω₁An example of a specific method for setting Kp will be described below.
[0049]
First, design guidelines are made simpler and more specific. Rotational speed fluctuation Δω of induction motor before compensation_mTo G of torque fluctuation Δτ_IMVoltage frequency command value ω_Vf* Assume that a steep phase lag in the vicinity can be estimated as ± α [deg]. So G_IM-G multiplied by -1_IMIs the voltage frequency command value ω_Vf* Global first-order lag characteristic K independent of_TConsidering only Kg / (s + ωσ), from the frequency ω2 at which the phase delay becomes (−90 + α) [deg], the upper limit ω of the inverter output frequency_VfmaxConsider the design of the transfer characteristic of Gh in the compensation command value calculator so that the compensation effect Gmod that always gives a margin of −90 [deg] to + α [deg] in the region up to.
[0050]
From this design guideline, the cutoff frequency ω of the high-pass filter in the compensation command value calculator₁The value of the proportional gain Kp is obtained as follows.
ω₁= {Tan (β)}²ωσ ---------------- (15)
Kp = (ω_Vfmax ²+ Ω₁ ²) / (Ω_Vfmax・ Tan (β) ・ k_G(16)
Where β, ωσ, ω_Vfmax, K_GIs a setting constant defined below.
β = 90−α [deg], α = 20 [deg] or more,
ωσ: (secondary resistance value / secondary leakage reactance value) of the induction motor,
ω_Vfmax: Maximum value in operating condition of voltage frequency,
k_G: Induction motor (secondary magnetic flux primary conversion value / primary leakage reactance value)
It is.
In the case of the normal induction motor shown in the examples of FIGS. 3 and 4, a in equations (9) and (11)₁, B₁Therefore, α = 20 [deg]. Therefore, if α is set to 20 [deg] or more and the settings of (15) and (16) are performed, the rotational speed fluctuation Δω in the induction motor after compensation is set._mTo G of torque fluctuation Δτ_IMTransfer characteristic h multiplied by -1 -G_IMFor h, from ω2 to ω_VfmaxVoltage frequency command value ω in all frequency ranges up to_Vf* Even if there is a sudden phase change in the vicinity, the phase can always be −90 [deg] or more. As a result, physical loop-G_IMh. Since Gmeca is stabilized, it is possible to stably operate the induction motor 4 and the load machine 5 without generating self-excited vibration.
[0051]
As shown in the above explanation of the compensation principle, the compensation command value computing unit 10 is_IMFor the purpose of obtaining a phase lead compensation characteristic for the above, a design having a high-pass characteristic is applied. However, when mounting, a low-pass filter can be added in a frequency range that does not affect the stabilization design. That is, the high-frequency noise is removed by this low-pass filter and the stability of the compensation loop Gh · Gw is secured while the physical loop -G_IMh ・ Gmeca can be stabilized.
[0052]
Embodiment 2. FIG.
6 shows an induction motor control apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. 12 is a DC bus current detector, and 9b is a torque component current estimation calculator. In the second embodiment, the functions of the induction machine current detector 8 and the torque component current estimation calculator 9a in the first embodiment are replaced by the DC bus current detector 12 and the torque component current estimation calculator 9b.
[0053]
The operation will be described below. The operations of the component parts 1 to 7 are the same as the operations of FIG. 8 of the conventional example and FIG. 1 of the first embodiment. The DC bus current detector 12 detects the DC bus current idc flowing from the rectifier 2 to the inverter main circuit 3 and inputs it to the torque current estimation calculator 9b. In the torque component current estimation calculator 9b, the DC bus current idc obtained by the DC bus current detector 12 and the voltage frequency command value ω._VfBased on **, the following equation (17) is calculated. Note that Vdc is the value of the DC bus voltage, and in the present invention, using the rated value instead of the actually measured value does not affect the accuracy of the effect of the invention. Kr is a torque constant.
iq = (Vdc · idc) / (Kr · ω_Vf*) --------- (17)
[0054]
Iq calculated in the torque current estimation calculator 9b is input to the compensation command value calculator 10. The operations of the subsequent stage, the compensation command value calculator 10, the subtractor a11a, and the subtractor b11b are the same as those in the first embodiment. Therefore, the physical loop -G is set by setting the compensation command value calculator 10 in the same manner._IMh ・ Gmeca is stabilized, generation of self-excited vibration is suppressed, and the induction motor 4 and the load machine 5 can be operated stably.
[0055]
Embodiment 3 FIG.
In the explanation of the compensation principle in the first embodiment, the structure of the compensation command value calculator 10 is a combination of a high-pass filter of order 1 and a proportional gain. As another example of the compensation command value calculator 10, an inverter frequency ω_VfAn example in which vibration can be avoided even if a filter having a structure in which the resonance characteristics change due to the above will be described.
[0056]
The compensation command value calculator at this time performs the calculations of the following equations (18), (19), and (20). However, Kh, c₁, D₁, D₂Is a constant determined from the circuit constant of the induction motor. Also, the voltage amplitude compensation command value Δ | V | * and the voltage frequency compensation command value Δω_Vf* The ratio of the voltage amplitude command value | V | * and the voltage frequency command value ω is the same as the setting example in the first embodiment._Vf* Ratio K_VfSame as
Gh₂= -Kh * (s²+ D₁s + d₂) / (S²+ C₁s + ω_Vf ²(18)
Δω_Vf* (S) = Gh₂・ Iq (s) ---------------- (19)
Δ | V | * (s) = K_Vf・ Δω_Vf* (S) --------------- (20)
Expressions (19) and (20) are the same as Expressions (6) and (7) in the description of the setting in the first embodiment.
[0057]
Therefore, inverter output frequency fluctuation Δω_VfTo the torque component current fluctuation Δiq is exactly the same as in the first embodiment. Therefore, when the present embodiment is compared with the first embodiment in accordance with the block diagram relating to the input / output of the state quantity of the induction motor 4 shown in FIG. 4, the transfer characteristics in the compensation command value calculator are Gh and Gh.₂Other than this point, the concept of compensation setting in the first embodiment can be applied to this example.
[0058]
Transfer characteristic Gh₂Is added to the compensation command value calculator 10 using₁, D₁, D₂Is ideally set, the transfer characteristic Gh shown in the following equation (21)₂, And the compensation effect Gmod including the transfer characteristic Gw₂Can be obtained. However, Gwm is the rotational speed variation Δω in the induction motor 4 as described in the description of the first embodiment and the description of FIG._mAnd Gσ is a first order lag characteristic determined by the circuit constant of the induction motor 4 as shown in the equation (14). This compensation effect Gmod₂Includes an inverse characteristic of Gwm, and therefore, rotational speed fluctuation Δω in Gwm and induction motor 4_mTo G of torque fluctuation Δτ_IMVoltage frequency command value ω_Vf* It has the effect of canceling out the steep phase change of about ± 20 [deg] in the vicinity.
[0059]
Figure 7 shows Gmod₂Is a diagram illustrating a specific design method when a notch filter that changes characteristics according to an inverter frequency is used as a compensation calculator when phase lead / lag compensation is performed on an induction motor. is there. G in Fig. 9 (b)_IMVoltage frequency command value ω_Vf* It can also be seen from the top of the figure that the relationship between the steep advance and delay of each phase characteristic in the vicinity is exactly reversed.
Gmod₂= (1 + Gh₂・ Gw)^-1≒ Gσ ・ (-Gwm^-1---- (21)
[0060]
Therefore, the compensation effect Gmod₂To transfer the transfer characteristic of the induction motor 4 to G_IMTo G based on the simple first-order lag characteristic shown in Equation (22)._IMh₂It can be modified as follows. Therefore, the voltage frequency command value ω_Vf* Transfer characteristics G under any condition_IMh₂Transfer characteristic -G multiplied by -1_IMh₂Is always at least −90 [deg].
[0061]
G_IMh₂= Gmod₂・ G_IM≒ -K_T・ Gσ --------- (22)
As a result, the corrected physical loop -G_IMh₂・ By always setting the phase of Gmeca to -180 [deg] or more, physical loop -G_IMh₂-Since Gmeca becomes stable, it is possible to suppress the occurrence of self-excited vibration and to stably operate the induction motor 4 and the load machine 5.
[0062]
Embodiment 4 FIG.
In the first embodiment shown in FIG. 1, in the compensation command value computing unit 10, the voltage amplitude compensation command value Δ | V | * and the voltage frequency compensation command value Δω_Vf* Ratio of voltage amplitude command value | V | * and voltage frequency command value ω_Vf* Ratio K_VfHowever, this is not particularly limited. For example, Δ | V | * may be always 0.
[0063]
Even in such a case, the voltage frequency compensation command value Δω is calculated from the torque current iq in the compensation command value calculator 10._Vf* The transfer characteristics up to * are set appropriately, and the rotation frequency command ω_m* At the machine resonance frequency ωmeca of the load machine 5 below, the rotational speed fluctuation Δω of the induction motor 4_mBy calculating so as to correct the phase of the transfer characteristic from to −270 [deg] from −270 [deg] or more to −270 [deg] or more, the physical loop composed of the induction motor 4 and the load machine 5 can be stabilized. It is possible to suppress the occurrence of self-excited vibration and to stably operate the induction motor 4 and the load machine 5.
[0064]
【The invention's effect】
  As described above, according to the induction motor control apparatus of the present invention, the rotation frequency command value input from the outside is converted into the first voltage amplitude command value and the first voltage frequency command value for the output voltage of the inverter main circuit. A V / f controller for converting to a voltage amplitude compensation command value and a voltage frequency compensation command value based on the input current of the induction motor or the DC bus current of the inverter, and the first voltage amplitude command A subtractor a that subtracts the voltage amplitude compensation command value from the value and outputs a second voltage amplitude command value; and a second voltage frequency command that subtracts the voltage frequency compensation command value from the first voltage frequency command value. A subtractor b for outputting a value; and a main circuit drive signal generator for converting the second voltage amplitude command value and the second voltage frequency command value into drive signals for the inverter main circuit, and the compensation The arithmetic unit isThe phase characteristic in the transmission characteristic from the torque fluctuation to the rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], andBelow the rotation frequency command valueMachine that isSince the calculation is performed so that the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor is corrected to −270 [deg] or more at the resonance frequency, the physical loop composed of the induction motor and the load machine is stabilized, Generation of self-excited vibration can be suppressed, and the load machine and the induction motor can be operated stably.
[0065]
  A V / f controller that converts a rotation frequency command value input from the outside into a first voltage amplitude command value and a first voltage frequency command value for the output voltage of the inverter main circuit; a voltage amplitude compensation command value; A compensation calculation unit for computing a voltage frequency compensation command value based on an input current of the induction motor or a DC bus current of the inverter, and a second voltage amplitude by subtracting the voltage amplitude compensation command value from the first voltage amplitude command value A subtractor a that outputs a command value; a subtractor b that subtracts the voltage frequency compensation command value from the first voltage frequency command value and outputs a second voltage frequency command value; and the second voltage amplitude command. A main circuit drive signal generator that converts a value and the second voltage frequency command value into a drive signal for the inverter main circuit, and the compensation calculation unit includes:The phase characteristic in the transmission characteristic from the torque fluctuation to the rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], andBelow the rotation frequency command valueMachine that isSince the calculation is performed so that the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor is corrected from -270 [deg] or less to -270 [deg] or more at the resonance frequency, the induction motor and the load machine are included. It is possible to stabilize the physical loop, suppress the occurrence of self-excited vibration, and operate the load machine and the induction motor stably.
[0066]
  In addition, the compensation calculation unit is configured to output the first voltage frequency command value under any condition where the first voltage frequency command value takes any value from 0 to an upper limit value of the inverter output frequency set in the V / f controller. All frequency range below the command valueThe phase characteristic of the transfer characteristic from torque fluctuation to rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], and the rotation In the machine resonance frequency that is below the frequency command value,Since the calculation for correcting the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor to be −270 [deg] or more is performed, the first resonance frequency can be obtained regardless of the mechanical resonance frequency of the load machine. Stabilize the physical loop consisting of the induction motor and the load machine, suppress the occurrence of self-excited vibration, and operate the load machine and the induction motor stably can do.
[0067]
The compensation calculation unit receives an input current of the induction motor or a DC bus current of the inverter and estimates and outputs a torque current of the induction motor, and the torque current estimator outputs A compensation command value calculator that calculates a voltage amplitude compensation command value and a voltage frequency compensation command value based on the torque component current to be used. Rotational speed fluctuation Δω in the induction motor using the transfer characteristics inside the induction motor that can be grasped with physical meaning._mIt is possible to manipulate the transfer characteristic from torque to torque fluctuation.
[0068]
In addition, the compensation calculation unit calculates the ratio between the voltage amplitude compensation command value and the voltage frequency compensation command value to be the same as the ratio between the first voltage amplitude command value and the first voltage frequency command value. Since the transfer characteristics inside the induction motor required to stabilize the frequency characteristics of the loop can be obtained with a simple structure, the frequency of the physical loop consisting of the load machine and the induction motor can be determined by simple compensation calculations and parameter settings. Stabilization of characteristics can be achieved, generation of self-excited vibration can be suppressed, and stable load machine and induction motor operation can be achieved.
[0069]
Also, the compensation command value calculator calculates the voltage frequency compensation command value using the high-pass filter and proportional gain based on the torque component current, so it can be easily adjusted by adjusting the cutoff frequency and proportional gain value of the high-pass filter. It is possible to manipulate the transfer characteristics from the rotational speed fluctuation to the torque fluctuation in the induction motor.
[0070]
The compensation command value calculator calculates the voltage frequency compensation command value based on the torque component current using the high-pass filter, low-pass filter, and proportional gain, so the low-pass filter can improve the stability of the compensation loop and eliminate sensor noise. While obtaining, by adjusting the cutoff frequency of the high-pass filter and the value of the proportional gain, it is possible to manipulate the transfer characteristics from the rotational speed fluctuation to the torque fluctuation in the induction motor.
[0071]
Furthermore, the compensation command value calculator is used for the cutoff frequency ω of the high-pass filter.₁And the value of proportional gain Kp is set by the following formula and the voltage frequency compensation command value is calculated.
ω₁= {Tan (β)}²・ Ωσ
Kp = (ω_Vfmax ²+ Ω₁ ²) / (Ω_Vfmax・ Tan (β) ・ k_G)
From the frequency at which the phase lag in the case of approximating the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor to the global first order lag characteristic independent of the inverter frequency is (−270 + α) [deg], the inverter operating frequency Upper limit frequency ω_VfmaxIn this region, it is possible to perform phase lead compensation that always gives a margin of −270 [deg] to + α [deg]. When α is set to 20 [deg] or more, the mechanical resonance frequency of the load machine is Regardless of the frequency range, the physical loop composed of the induction motor and the load machine can be stabilized, the occurrence of self-excited vibration can be suppressed, and the load machine and the induction motor can be operated stably.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an induction motor control apparatus according to Embodiment 1 of the present invention;
FIG. 2 is a diagram showing a physical relationship between an induction motor and a load machine under V / f control.
FIG. 3 is a diagram for explaining an improvement in the stability of a physical loop according to the present invention.
FIG. 4 is a diagram for explaining the concept of performing phase lead / lag compensation on the transfer characteristics of an induction motor according to the present invention.
FIG. 5 is a diagram for explaining a specific design method when a high-pass filter and a proportional gain are used as a compensation calculator when phase lead / lag compensation is performed on an induction motor according to the present invention.
FIG. 6 is a block diagram showing an induction motor control apparatus according to Embodiment 2 of the present invention;
FIG. 7 is a diagram for explaining a specific design method when a notch filter whose characteristics are changed according to an inverter frequency is used as a compensation calculator when phase lead / lag compensation is performed on an induction motor according to the present invention.
FIG. 8 is a configuration diagram of a conventional V / f constant control device.
FIG. 9 is an explanatory diagram of frequency characteristics of a physical loop in conventional V / f constant control.
[Explanation of symbols]
1 Commercial power supply 2 Rectifier
3 Inverter main circuit 4 Induction motor
5 Load machine 6 V / f controller
7 Main circuit drive signal generator 8 Induction machine current detector
9a, 9b Torque component current estimation calculator 10 Compensation command value calculator
11a subtractor a 11b subtractor b
12 Bus current detector 20a Compensation calculation part.

Claims (8)

A V / f controller for converting a rotation frequency command value input from the outside into a first voltage amplitude command value and a first voltage frequency command value for the output voltage of the inverter main circuit;
A compensation calculation unit for calculating a voltage amplitude compensation command value and a voltage frequency compensation command value based on the input current of the induction motor or the DC bus current of the inverter;
A subtractor a that subtracts the voltage amplitude compensation command value from the first voltage amplitude command value and outputs a second voltage amplitude command value;
A subtractor b for subtracting the voltage frequency compensation command value from the first voltage frequency command value and outputting a second voltage frequency command value;
A main circuit drive signal generator for converting the second voltage amplitude command value and the second voltage frequency command value into a drive signal for the inverter main circuit;
The compensation calculation unit has a characteristic that a phase characteristic in a transmission characteristic from torque fluctuation to rotation speed fluctuation of a load machine mechanically connected to the induction motor changes from +90 [deg] to −90 [deg], and An induction motor that performs a calculation so as to correct a phase of a transfer characteristic from a rotational speed fluctuation to a torque fluctuation of the induction motor to -270 [deg] or more at a mechanical resonance frequency that is equal to or less than the rotational frequency command value. Control device. A V / f controller for converting a rotation frequency command value input from the outside into a first voltage amplitude command value and a first voltage frequency command value for the output voltage of the inverter main circuit;
A compensation calculation unit for calculating a voltage amplitude compensation command value and a voltage frequency compensation command value based on the input current of the induction motor or the DC bus current of the inverter;
A subtractor a that subtracts the voltage amplitude compensation command value from the first voltage amplitude command value and outputs a second voltage amplitude command value;
A subtractor b for subtracting the voltage frequency compensation command value from the first voltage frequency command value and outputting a second voltage frequency command value;
A main circuit drive signal generator for converting the second voltage amplitude command value and the second voltage frequency command value into a drive signal for the inverter main circuit;
The compensation calculation unit has a characteristic that a phase characteristic in a transmission characteristic from torque fluctuation to rotation speed fluctuation of a load machine mechanically connected to the induction motor changes from +90 [deg] to −90 [deg], and At a mechanical resonance frequency that is equal to or less than the rotational frequency command value, calculation is performed so that the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor is corrected from −270 [deg] or less to −270 [deg] or more. An induction motor control apparatus characterized by the above. The compensation calculation unit is configured to output the first voltage frequency command value under any condition where the first voltage frequency command value takes any value between 0 and the upper limit of the inverter output frequency set in the V / f controller. In all frequency ranges below ,
The phase characteristic of the transfer characteristic from torque fluctuation to rotational speed fluctuation of the load machine mechanically connected to the induction motor has a characteristic that changes from +90 [deg] to −90 [deg], and the rotational frequency command value The calculation for correcting the phase of the transfer characteristic from the rotational speed fluctuation to the torque fluctuation of the induction motor to be −270 [deg] or more is performed at a mechanical resonance frequency which is the following. Induction motor controller. The compensation calculation unit inputs an input current of the induction motor or a DC bus current of the inverter, and estimates and outputs a torque component current of the induction motor; and a torque component current estimator,
4. The compensation command value calculator for calculating a voltage amplitude compensation command value and a voltage frequency compensation command value based on the torque component current output by the torque component current estimator. Induction motor controller. The compensation calculation unit calculates the ratio between the voltage amplitude compensation command value and the voltage frequency compensation command value so as to be the same as the ratio between the first voltage amplitude command value and the first voltage frequency command value. The control apparatus for an induction motor according to claim 4. 6. The control apparatus for an induction motor according to claim 5, wherein the compensation command value computing unit computes a voltage frequency compensation command value using a high-pass filter and a proportional gain based on the torque component current. 7. The induction motor control device according to claim 6, wherein the compensation command value computing unit computes a voltage frequency compensation command value by a high-pass filter, a low-pass filter, and a proportional gain based on the torque component current. 8. The compensation command value calculator calculates a voltage frequency compensation command value by setting values of a cutoff frequency ω ₁ and a proportional gain Kp of the high-pass filter according to the following equations. Induction motor control device.
ω ₁ = {tan (β)} ² · ωσ
Kp = (ω _Vfmax ² + ω ₁ ² ) / (ω _Vfmax · tan (β) · k _G )
However, in the above equation, β, ωσ, ω _Vfmax and k _G are set constants defined below.
β = 90−α [deg], α = 20 [deg] or more,
ωσ: (secondary resistance value / secondary leakage reactance value) of the induction motor,
ω _Vfmax : Maximum value under operating conditions of voltage frequency,
k _G : (Induction motor primary side converted value / primary leakage reactance value)

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