JP4706716B2 - Induction motor control method - Google Patents

Description

  The present invention relates to a control method for driving and controlling an inverter-controlled induction motor by speed sensorless vector control.

  As a method for realizing speed sensorless vector control of an induction motor, for example, as described in Patent Document 1 below, by performing current control so that a detected value of torque current matches a command value, the rotational speed of the motor There is a way to estimate

JP 2001-238497 A

  In the control method according to the prior art, since the amount corresponding to the induced voltage of the motor is calculated and used for speed estimation, the speed estimation accuracy deteriorates due to the influence of the voltage control error in the low speed range where the induced voltage becomes small, Control becomes unstable.

  An object of the present invention is to provide a control method capable of operating an induction motor stably even in a low speed range.

  In the control method for the induction motor according to the present invention, in the low speed range, the output of the first speed estimating means for estimating the speed from the detected value of the torque current is masked, and the second is used for estimating the speed from the excitation current command and the torque current command. The speed is estimated by the speed estimation means.

Further, the first excitation current command i _d ^* and the first torque current command i _q ^* are switched to the second excitation current command i _d2 ^* and the second torque current command i _q2 ^* by the current command switching means, and stable. Drive at the correct operating point.

  According to the present invention, the induction motor can be stably operated even in a low speed range including reverse activation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1
The control system for the induction motor of this embodiment is shown in FIG. The control system for an induction motor according to the present invention converts an inverter controller 1 into an AC voltage having a variable voltage and a variable frequency in accordance with three-phase voltage commands v _u ^* , v _v ^* , v _w ^* sent from the inverter controller 1. The inverter 2 drives the induction motor 4, the induction motor 4, and the current detector 3 that detects the current flowing from the inverter 2 to the induction motor 4.

The inverter controller 1 inputs the excitation current command i _d ^* , the torque current command i _q ^*, and the three-phase current detection values i _u , i _v , i _w detected by the current detector 3 to input the three-phase The voltage commands v _u ^* , v _v ^* , v _w ^* are output to the inverter 2.

The detailed configuration of the inverter controller 1 will be described below. The magnetizing controller 103 receives the first excitation current command i _d ^* and the first torque current command i _q ^* and inputs the second excitation current command i _d2 ^* and the second torque current according to an algorithm described later. Convert to command i _q2 ^* .

The current converter 102 inputs the three-phase current detection values i _u , i _v , i _w and the phase command θ ^* , and converts the three-phase current detection values i _u , i _v , i _w into the excitation current i _d and torque. It is converted into current i _q and output.

The current controllers 105a and 105b provide a voltage compensation value Δv _d0 ^* and a voltage compensation value Δv so that the excitation current command i _d ^* and the excitation current i _d , and the torque current command i _q ^* and the torque current i _q coincide with each other. _q0 ^* is generated and output.

The output gains 112a and 112b receive the voltage compensation values Δv _d0 ^* and Δv _q0 ^* output from the current controllers 105a and 105b and G ₁ (ω _r ^) which is a function of the estimated speed, and the voltage compensation values Δv _d0. Voltage compensation values Δv _d ^* and Δv _q ^* are generated and output by multiplying ^* and Δv _q0 ^* by G ₁ (ω _r ^) which is a function of the estimated speed.

  The speed estimator 113 includes a current controller 111, an output gain 112c, a reference accelerator 107, an adder 116, and an integrator 110.

The current controller 111 receives a deviation between the torque current command i _q2 ^* and the torque current i _q, and generates and outputs an estimated acceleration α ₁₀ based on the deviation.

Output gain 112c inputs the estimated acceleration alpha _10, multiplied by G ₂ (ω _r ^), and generates an estimated acceleration alpha _1, and outputs.

The reference accelerator 107 receives the excitation current command i _d2 ^* and the torque current command i _q2 ^* , generates the estimated acceleration α ₂ based on the product of the excitation current command i _d2 ^* and the torque current command i _q2 ^* , Output.

The adder 116 adds α ₁ and the estimated acceleration α ₂ , inputs the added value to the integrator 110, integrates it with the integrator 110, and generates and outputs an estimated speed ω _r ^.

The slip calculator 108 calculates and outputs a slip frequency command ω _s ^* from the current command i _d2 ^* and the current command i _q2 ^* based on the equation (1).

Where R ₂ is the secondary resistance of the motor, and L ₂ is the secondary self-inductance of the motor.

Adder 114 adds the motor speed ω _r ^ and the slip frequency command ω _s ^* in, to produce the inverter frequency command ω ₁ ^*. The inverter frequency command ω ₁ ^* is integrated by the integrator 109 to generate a phase command θ ^* .

The voltage command calculator 104 calculates the voltage command v from the excitation current command i _d2 ^* , the torque current command i _q2 ^*, and the inverter frequency command ω ₁ ^* based on the equations (2) and (3). _d0 ^* and _vq0 ^* are calculated and output.

Where R ₁ is the primary resistance of the motor, M is the mutual inductance of the motor, and l _σ is the primary equivalent leakage inductance of the motor.

Further, the voltage commands v _d0 ^* and v _q0 ^* output from the voltage command calculator 104 and the voltage compensation values Δv _d ^* and Δv _q ^* output from the output gains 112a and 112b are respectively added by the adders 115a and 115b. The voltage commands v _d ^* and v _q ^* are generated and output. The voltage command converter 106 converts the input voltage commands v _d ^* , v _q ^* into three-phase voltage commands v _u ^* , v _v ^* , v _w ^* based on the phase command θ ^* .

  Next, an example of operation | movement of the inverter controller 1 of a present Example is demonstrated using the time chart shown in FIG. FIG. 4 shows an operation waveform when the induction motor 4 is started from a state where the induction motor 4 is reversing at a low speed, passes through zero speed and accelerates in the forward direction.

In the low speed range (period T ₀ ) where the estimated speed is equal to or less than ω _r1 , G ₂ of the output gain 112c in FIG. As a result, the estimated acceleration α ₁ generated by the output gain 112 c based on the estimated acceleration α ₁₀ output from the current controller 111 becomes 0, and the motor speed is determined based only on the estimated acceleration α ₂ generated by the reference accelerator 107. presume. As a result, the motor speed can be estimated without being affected by the voltage control error in the low speed range.

In this embodiment, as shown in FIG. 4, in the low speed range (period T ₀ ) where the estimated speed is ω _r1 or less, G ₁ of the output gains 112a and 112b in FIG. The voltage compensation values Δv _d0 ^* and Δv _q0 ^* output from the output 105b are made to coincide with the voltage compensation values Δv _d ^* and Δv _q ^* output from the output gains 112a and 112b. As a result, in the low speed region (period T ₀ ) where the estimated speed is equal to or less than ω _r1 , the excitation current and the torque current are controlled to match the command values. Note that the magnetizing controller 103 sets the excitation current command to i _d2 ^* and the torque current command to i _q2 ^* in the low speed region (period T ₀ ) where the estimated speed is equal to or less than ω _r1 .

On the other hand, since the induced voltage increases in a high speed region where the estimated speed is equal to or higher than ω _r1, it is desirable to reduce the exciting current _id to reduce the magnetic flux inside the induction motor and to reduce the induced voltage. Therefore, when the estimated speed reaches ω _r1 , switching to an operating point A in FIG. 2 described later is started. During the switching period T ₁ , the magnetizing controller 103 in FIG. 1 changes the excitation current command from i _d2 ^* to i _d ^* and the torque current command from i _q2 ^* to i _q ^* , as shown in FIG. Switch to the correct lamp shape.

Further, during the switching period T ₁ , G 1 of the output gains 112a and 112b in FIG. ₁ is switched in a ramp shape from 1 to 0 as shown in FIG. 4, and the voltage compensation value Δv output from the current controllers 105a and 105b. Mask _d0 ^* and Δv _q0 ^* . Further, during the switching period T ₁ , G _{2 of the} output gain 112c is switched from 0 to 1 in a ramp shape as shown in FIG. 4, and speed estimation based on the estimated acceleration α ₁₀ output from the current controller 111 is performed. .

In the period T _2, continue to operate at a speed sensorless vector control. This makes it possible to perform good control even in a high speed range.

In the above description, the current command and the gain are switched as a function of time within the preset switching period T _1. However, the switching end speed ω _r2 larger than the estimated speed ω _r1 is set separately, and the estimated speed is ω _{Between r1} and _ωr2 , the current command and gain may be similarly switched as a function of speed.

Next, a method for setting the excitation current command i _d2 ^* and the torque current command i _q2 ^* output from the magnetization increasing controller 103 in FIG. 1 will be described with reference to FIGS. 2 and 3. FIG. 2 shows the relationship between the slip frequency of the induction motor and the generated torque when the magnitude of the primary current is constant.

First, the operation at the operating point A in FIG. 2 used in the vector control in the period T _{2 in} FIG. 4 will be described. At the operating point A, the excitation current command i _d2 ^* = i _d ^* , the torque current command i _q2 ^* = i _q ^* , and the slip ω _s0 . If a speed estimation error occurs and the estimated speed exceeds the actual speed, the slip increases due to the difference between the estimated speed and the actual speed, and the generated torque decreases. As a result, the induction motor cannot generate the required torque, the actual speed acceleration becomes smaller than the estimated speed acceleration, and the speed estimation error increases. The same applies when the estimated speed falls below the actual speed. Thus, at the operating point A, a stable induction motor cannot be operated.

Next, the operation at the operation point B in FIG. 2 where the same torque as the operation point A can be generated will be described. At the operating point B in FIG. 2, it is assumed that the excitation current command i _d2 ^* = i _q ^* , the torque current command i _q2 ^* = i _d ^* , and the slip ω _s1 . At the operating point B, as the slip increases, the torque also increases. Therefore, when a speed estimation error occurs, the torque changes in a direction to reduce the speed estimation error. Thus, the motor can be stably accelerated at the operating point B.

  That is, in FIG. 2, when the slope of the torque change graph with respect to the slip change is positive, it is stable in a range where the slip is smaller than the operating point C which is the maximum value of the torque change graph, and conversely, It can be seen that in the range where the slope of is negative and the slip is larger than the operating point C, it becomes unstable.

Next, the relationship between the operating point A and the operating point B and the current vector will be described with reference to FIG. FIG. 3 shows current vectors at the operating point A and the operating point B in FIG. 2, and the current vectors have the same magnitude. Area of the rectangle O-i _d -A-I _q and O-i _d2 -B-i _q2 shown in FIG. 3 is proportional to the operating point A, the torque generated by the B. As described in FIG. 2, the operating point A and the operating point B have the same torque. In the description of FIG. 3, the influence of magnetic flux saturation is ignored.

Further, as shown in FIG. 3, the operating point C in FIG. 2 at which the torque is maximum is an intersection of a one-dot chain line indicating that the excitation current i _d and the torque current i _q are equal to an arc indicating a constant current. It is.

As described above, the excitation current command i _d2 ^* output from the magnetizing controller 103 in FIG. 1 is set to be larger than the torque current command i _q2 ^* , that is, the excitation current command in the hatched area in FIG. If the _selection is made so that i _d2 ^* and torque current command i _q2 ^* are entered, the induction motor can be controlled stably.

Further, the excitation current command i _d2 ^* output from the magnetization controller 103 is equal to the torque current command i _q ^* input to the magnetization controller 103, and the torque current command i _q2 ^* output from the magnetization controller 103 is If it is selected to be equal to the excitation current command i _d ^* input to the magnetizing controller 103, the torque generated by the induction motor is changed to the torque corresponding to the excitation current command i _d ^* and the torque current command i _q ^* . It is possible to equalize and control not only stably, but also the occurrence of transient speed estimation errors can be suppressed.

Further, the product of the excitation current command i _d2 ^* and torque current command i _q2 ^* output from the magnetizing controller 103 is the product of the excitation current command i _d ^* and torque current command i _q ^* input to the magnetizing controller 103. The torque generated by the induction motor can be made equal to the torque corresponding to the excitation current command i _d ^* and the torque current command i _q ^* . In this case, the magnitude of the motor current can be reduced without changing the torque generated by the induction motor by appropriately selecting the combination of the excitation current command i _d2 ^* and the torque current command i _q2 ^* .

(Example 2)
An electric vehicle of the present embodiment is shown in FIG. In FIG. 5, an inverter controller 1, an inverter 2, a current detector 3, and an induction motor 4 have the same configuration as that of the first embodiment shown in FIG. 1, and are mounted on an electric vehicle.

  In the present embodiment, a DC voltage received from the overhead wire 201 and the track 207 via the current collector 202 and the wheel 206 is input to the inverter 2 via the power receiving filter 203. The power receiving filter 203 includes a filter reactor 203a and a filter capacitor 203b.

The master controller 211 converts the driver's notch operation into a notch command α ^* and outputs it. The notch command α ^* is input to the current command generator 214, and the current command generator 214 generates and outputs an excitation current command i _d ^* and a torque current command i _q ^* . An excitation current command i _d ^* and a torque current command i _q ^* are input to the inverter controller 1, and the inverter controller 1 outputs a three-phase voltage command v _uvw ^* to the inverter 2 as in the first embodiment. The induction motor 4 generates torque by the AC voltage supplied from the inverter 2 and drives the wheels 206 via a gear (not shown). Although FIG. 5 shows the case where there is one induction motor 4, two to four induction motors 4 are connected in parallel to the output of one inverter 2, and the detected value of the output current of the inverter 2 is shown. May be input to the inverter controller 1 and controlled similarly to the first embodiment.

  According to the present embodiment, it is possible to configure an electric vehicle drive system that can be stably operated even in a low speed range including reverse activation.

Explanatory drawing of the control system of the induction motor of Example 1. FIG. Explanatory drawing which shows the relationship between the slip frequency of an induction motor, and generated torque when a frequency and the magnitude | size of a primary current are constant. Explanatory drawing of the relationship between an electric current command and stability. 3 is a time chart illustrating an example of the operation of the inverter controller according to the first embodiment. Explanatory drawing of the control block of the electric vehicle of Example 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inverter controller, 2 ... Inverter, 3 ... Current detector, 4 ... Induction motor, 103 ... Magnetization controller, 104 ... Voltage command calculator, 113 ... Speed estimator.

Claims (5)

In a control method for controlling an induction motor with an alternating voltage having a variable voltage and a variable frequency calculated based on an input first excitation current command and a first torque current command,
A first control step of inputting a first excitation current command and a first torque current command, and outputting a second excitation current command and a second torque current command;
A second control step of inputting the second excitation current command and the second torque current command and outputting a first speed estimated value;
A third control step for inputting a current value flowing through the induction motor and the second torque current command and outputting a second estimated speed value;
In a region where the speed of the induction motor is low, the magnitude of the second excitation current command is controlled to be equal to or greater than the magnitude of the second torque current command, and the variable is based on the first speed estimation value. Voltage variable frequency is controlled,
In a region where the speed of the induction motor is high, control is performed so that the first excitation current command and the second excitation current command match, and the first torque current command and the second torque current command match. And the variable voltage variable frequency is controlled based on the second speed estimation value,
The magnitude of the product of the second excitation current command and the second torque current command is controlled to be greater than the magnitude of the product of the first excitation current command and the first torque current command,
Between the region where the speed of the induction motor is low and the region where the speed of the induction motor is high, a second excitation current command is set as the first excitation current command, and a second torque current command is set as the first torque current command. An induction motor control method comprising a switching period for switching to a torque current command. In the control method of the induction motor according to claim 1,
When the estimated speed generated based on the first speed estimated value and the second speed estimated value reaches a predetermined first estimated value (ω _r1 ) in the switching period, the switching start point A method for controlling an induction motor, characterized in that: In the control method of the induction motor according to claim 2,
A control method for an induction motor, characterized in that, in the switching period, a point in time when the estimated speed reaches a predetermined second estimated value (ω _r2 ) greater than the first estimated value is a switching end point. . In the control method of the induction motor according to claim 1,
In the switching period, the current command is switched as a function of time or a function of speed. The method for controlling an induction motor according to claim 1 is provided,
An electric vehicle wherein wheels are driven by the induction motor.

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