JPH09117200A - Induction motor control device - Google Patents

Abstract

(57) Abstract: In an induction motor control device, steady-state and transient losses are minimized, and a transition from power running to regeneration and regeneration to power running is performed quickly. SOLUTION: Steady loss minimum magnetic flux calculation unit 11, target magnetic flux calculation unit 12, excitation current calculation unit 13, torque current calculation unit 1
5, slip frequency calculation unit 16, motor rotation speed calculation unit 1
7. An induction motor control device that includes an integration calculation unit 18, calculates a current command value according to a torque command value and a rotation speed of the induction motor, and drives the induction motor with a polyphase alternating current corresponding to the current command value. In the above, when the polarity change detection unit 30 that detects a change in the polarity of the torque command value Te ′ and outputs the polarity change timing signal Cp and the polarity change timing signal Cp as a reset signal are input, the transfer function is The target torque calculation unit 31 that resets the output target torque Tm to 0 is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high-efficiency drive control device for an induction motor, and more particularly to a drive control technique for an induction motor that performs power running and regeneration.

[0002]

2. Description of the Related Art As a conventional high-efficiency driving method for an induction motor, for example, there are methods described in Japanese Patent Application Laid-Open No. 7-31178 and Japanese Patent Application No. 5-207418.
In this control method, the rotor magnetic flux is constantly controlled to minimize the steady loss at the given torque command value, and transiently the magnetic flux response is set to the optimum value according to the torque response. It is configured to reduce steady loss and transient loss.

Specifically, the configuration is as shown in FIGS. 7 and 8. 7 is a block diagram showing the configuration of the entire system, and FIG. 8 is a block diagram showing details of the high-efficiency drive control calculation unit 1 in FIG. First, in FIG. 7, reference numeral 1 denotes a high-efficiency drive control calculation unit, for example, a torque command value Te ′ corresponding to an operation amount of an accelerator pedal or the like of an electric vehicle and a motor rotation speed N (rp) detected by a rotation speed sensor 5.
m) is input to calculate and output the exciting current command value iΦ ′, the torque current command value iT ′, and the phase angle θ of the current.
Further, 2 is a coordinate conversion unit, which is the above-mentioned exciting current command value iΦ ′ calculated in the coordinate system rotating at the electric motor power source frequency,
The torque current command value iT ′ and the current phase angle θ are converted into three-phase alternating current command values iu ′, iv ′, iw ′. A current control PWM inverter 3 causes the three-phase alternating currents iu ′, iv ′, iw ′ flowing in the induction motor 4 to follow the respective command values. Reference numeral 5 is a rotation speed sensor for detecting the rotation speed of the induction motor 4, and 6 is a current control PWM inverter 3.
DC power supply to the.

Next, in FIG. 8, 11 is a minimum steady-state loss magnetic flux calculating section for calculating the rotor magnetic flux Φr 'which minimizes the steady-state loss of the induction motor at a given torque command value Te', and 14 is a torque command value. A target torque calculation unit that calculates the target torque Tm of the induction motor based on a transfer function having a predetermined low-pass characteristic with Te 'as an input, and 12 is a steady-state minimum magnetic flux Φr' and the low-pass used in the target torque calculation unit 14. In terms of characteristics, a target magnetic flux calculating unit for calculating the target magnetic flux Φr and the first-order derivative dΦr / dt of the target magnetic flux based on a transfer function having a low-pass characteristic that minimizes the transient loss of the induction motor, 13 is an exciting current calculating unit, 15 Is a torque current calculator, 16 is a slip frequency calculator, 17 is a motor speed calculator, and 18 is an integral calculator. That is, the steady loss minimum magnetic flux calculation unit 11, the target magnetic flux calculation unit 12, and the target torque calculation unit 14 are added to a general vector control calculation unit, and the torque response and the magnetic flux response are independently variable. By doing so, the above effect is achieved.

In the case of an electric vehicle, the torque command value Te 'is calculated according to the operation amount of the accelerator pedal and the forward / reverse shift switch. For example, the torque command calculator 20 shown in FIG.
Coefficient circuit 201 for calculating the torque corresponding to, an inverting circuit 202 for inverting the sign of the output of the coefficient circuit 201,
The coefficient circuit 201 according to the backward shift switch signal F / R
Alternatively, it is composed of a multiplexer 203 that outputs one of the outputs of the inverting circuit 202 as a torque command value Te ′. Here, when F / R is 0, it is forward, and when it is 1, it is backward, and the multiplexer 203 selects the output of the coefficient circuit 201 when F / R is 0 and the output of the inverting circuit 202 when it is 1. There is. Therefore, the torque command calculation unit 20 outputs a positive torque command value Te 'when the shift switch moves forward and a negative torque command value Te' when the shift switch moves backward according to the operation amount of the accelerator pedal.

[0006]

Conventionally, a DC electric motor has been used as a traveling electric motor of an electric forklift truck, but an induction motor is required because maintenance of brushes and the like is not necessary and the efficiency of the electric motor is improved. Is being adopted. In a forklift, for example,
During the forward power running, the shift switch is set to the reverse side, the vehicle is decelerated by regenerative braking, and the operation shifts to the reverse power running as it is, which is not an ordinary operation in an electric vehicle. FIG. 10 shows the operation when such an operation is performed using the conventional high-efficiency drive control method for an induction motor. The output torque of the electric motor is Te.

In this example, the operation amount α of the accelerator pedal is operated from 0 to α1 with the forklift stopped and the shift switch F / R in the forward position. Along with this, the torque command value Te ′ increases from 0 to T1. The target torque Tm has a predetermined low-pass characteristic with respect to the torque command value Te 'and rises from 0 to T1.
Further, the value of the steady loss minimum magnetic flux Φr ′ with respect to the value T1 of the torque command value Te ′ is Φ1, and the target magnetic flux Φr has a low-pass characteristic that minimizes the transient loss and rises from 0 to Φ1. At that time, the three-phase alternating current of the electric motor is controlled like iu, the output torque Te of the electric motor is also controlled according to the target torque Tm, and the electric motor rotation speed N is accelerated.

Next, at time t1, the shift switch F / R is switched to the reverse position while the accelerator pedal operation amount remains α1. Then, the torque command value Te ′ is −T
The target torque Tm has a predetermined low-pass characteristic and falls from T1 to −T1. Further, since the absolute value does not change between the value T1 of the torque command value Te ′ and −T1,
The value of the minimum steady-state loss magnetic flux Φr ′ remains Φ1, and thus the target magnetic flux Φr also remains Φ1. The three-phase AC current of the electric motor is controlled like iu, the output torque Te of the electric motor is also controlled according to the target torque, and the electric motor rotation speed N is decelerated. Here, regenerative control is performed in a region where the rotational speed N is positive, and power running is performed in a negative region.

As described above, since the target torque Tm is the output of the transfer function having the low-pass characteristic with respect to the torque command value Te ', the polarity of the torque command value Te' for switching the shift switch F / R is reversed. At this time, the target torque Tm
The polarity of does not immediately reverse. Therefore, even if the operator switches the shift switch in an attempt to decelerate while the vehicle is moving forward, the vehicle will accelerate for a while. Therefore, there arises a problem that the vehicle moves differently from the operator's intention and the response is unsatisfactory.

Further, the above problem does not occur only when the shift switch of the forklift is changed, but when the drive mode of a general induction motor shifts from power running to regeneration or from regeneration to power running, that is, the polarity of the torque command value changes. This is what happens when you flip.

The present invention has been made in order to solve the conventional problems as described above, and it is an induction motor that promptly shifts from power running to regeneration and from regeneration to power running while minimizing steady and transient losses. It is an object of the present invention to provide a control device of.

[0012]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, in the invention described in claim 1, in the same configuration as the conventional one, the target torque calculation unit calculates the target torque of the induction motor from the torque command value based on a predetermined transfer function, and the polarity of the torque command value. When is reversed, the target torque is set to the value of the torque command value. The target torque calculation unit corresponds to, for example, the target torque calculation unit 32 in the embodiment of FIG. 3 described later. In a second aspect of the invention, in the same configuration as the conventional one, the target torque calculation unit calculates the target torque of the induction motor from the torque command value based on a predetermined transfer function, and the polarity of the torque command value is reversed. At this time, the target torque is set as the output initial value, and the output initial value is calculated as a function of the torque command value in the output initial value setting unit. The target torque calculation unit and the output initial value setting unit correspond to, for example, the target torque calculation unit 33 and the output initial value setting unit 34 in the embodiment of FIG. 5 described later. According to a third aspect of the invention, in the same configuration as the conventional one, the target torque calculation unit calculates the target torque of the induction motor from the torque command value based on a predetermined transfer function, and the polarity of the torque command value is reversed. At this time, the target torque is set to 0. The target torque calculation unit corresponds to, for example, the target torque calculation unit 31 in the embodiment of FIG. 1 described later. According to the invention described in claim 4, the function for calculating the output initial value according to claim 3 is variable.

[0013]

First, the operation of the invention will be described. As described above, in the present invention, by adopting the configuration described in claim 1, the response of the torque at the time of transition from power running to regeneration or from regeneration to power running is improved as compared with the configuration described in claim 3. Further, with the configuration described in claim 2, it becomes possible to set the response of the torque. Further, with the configuration according to the third aspect, it is possible to minimize the loss during steady state and transient state, while the transition from power running to regeneration or from regeneration to power running is quick. Further, by having the configuration according to claim 4,
The torque responsiveness setting is variable.

(Embodiment) The present invention will be described below with reference to the drawings. FIG. 1 is a first embodiment of the present invention.
FIG. 9 is a block diagram showing the overall configuration of the electric motor system for traveling of the electric forklift truck, which is the same as FIG. 7 described in the prior art, and the command calculation unit for outputting the torque command value Te ′ in FIG. Since it is the same as No. 9, it is omitted here. FIG. 1 is a block diagram showing details of the high-efficiency drive control calculation unit 1 in FIG.

Reference numeral 30 denotes a polarity change detector for detecting a change in polarity of the torque command value Te 'and outputting a polarity change timing signal Cp. Reference numeral 31 denotes a torque command value T as an input of a transfer function.
Polarity change timing signal Cp using e ′ as a reset signal
Is input as an initial output value at reset, and the target torque T of the induction motor is set based on a transfer function having a predetermined low-pass characteristic with respect to the torque command value Te ′.
m is a target torque calculation unit that resets the transfer function when the polarity timing signal Cp is input and sets the output target torque Tm to 0. In addition, since the blocks having the same numbers as those in FIG. 8 described in the related art have the same functions, description thereof will be omitted here.

Next, the operation will be described. The characteristic portions of the first embodiment will be described in detail with reference to the waveform chart shown in FIG. The waveform diagram shown in FIG. 2 shows the operation amount α of the accelerator pedal when the forklift is stopped and the shift switch F / R is in the forward position as in the case of the conventional technique.
After operating from 0 to α1, the shift switch F is operated at time t1 while the accelerator pedal operation amount α remains at α1.
This is when / R is switched to the retracted position.

Until the time t1, the same as in the prior art,
When the shift switch F / R is switched to the reverse position, FIG.
Torque command value T, which is the output of the torque command calculator 20 of
e ′ changes from T1 to −T1. Then, the polarity of the torque command value Te ′ changes, so that the polarity change timing signal Cp is output from the polarity change detection unit 30. Therefore, the output of the transfer function of the target torque calculation unit 31 is reset to 0, and the value of the torque command value Te ′ that is the input of the transfer function is −T1, the value of the target torque Tm becomes 0, and thereafter, 0 to -T with predetermined low-pass characteristics
Get down to 1. Further, the value of the torque command value Te 'is T
Since the absolute value does not change between 1 and -T1, the value of the steady loss minimum magnetic flux Φr ′ remains Φ1, and therefore the target magnetic flux Φr also remains Φ1. The three-phase AC electric motor is i
The output torque Te of the electric motor is controlled according to the target torque, and the electric motor rotation speed N is decelerated. Here, regenerative control is performed in the region where the rotation speed N is positive,
Negative areas are powering. As described above, in the first embodiment, the control of the rotor magnetic flux in the steady state and the transient state is the same as that in the conventional technique, that is, the steady loss and the transient loss are minimized. Moreover, when the polarity of the torque command value changes, the power running operation is quickly changed to the regenerative operation. 10 and 2, the time when the rotation speed N becomes 0 from the time t1 is obviously short in the first embodiment. In the first embodiment, description has been given by taking the shift switch switching during forward traveling of the electric forklift truck as an example. The effects of the present invention can be obtained.

FIG. 3 is a diagram showing a second embodiment of the present invention, in which the target torque calculating section 3 of the first embodiment shown in FIG.
1 is changed to the target torque calculation unit 32. The target torque calculation unit 32 uses the torque command value Te ′ as a reset signal as the input of the transfer function and the polarity change timing signal C
Torque command value T with p as the initial output value at reset
The target torque Tm of the induction motor is calculated on the basis of a transfer function having a predetermined low-pass characteristic with respect to the torque command value Te ', and the transfer is performed when the polarity timing signal Cp is input. Reset the function,
The target torque Tm which is the output is set to the torque command value T at that time.
It is the value of e '.

Next, the operation will be described with reference to the waveform chart shown in FIG. The waveform diagram shown in FIG. 4 is the same as the description of the first embodiment, with the forklift stopped and the shift switch F.
/ R is in the forward position, the accelerator pedal operation amount α is operated from 0 to α1, and at time t1, the accelerator pedal operation amount α is maintained at α1 and the shift switch F / R is moved to the backward position. It is when switching to. Until time t1, the same as in the first embodiment, but when the shift switch F / R is switched to the reverse position, the torque command value Te ′ output from the torque command calculator 20 in FIG. 9 changes from T1 to −T1. To do. Then, the polarity of the torque command value Te ′ changes, so that the polarity change timing signal Cp is output from the polarity change detection unit 30. Therefore, the output of the transfer function of the target torque calculation unit 32 is reset to the value -T1 of the torque command value Te 'at that time, and the value of the torque command value Te' that is the input of the transfer function is -T1, so the target The value of the torque Tm becomes −T1 and thereafter remains −T1. Further, the value of the torque command value Te 'is T1 and -T.
Since the absolute value does not change at 1, steady-state minimum magnetic flux Φr '
Remains at Φ1 and therefore the target magnetic flux Φr remains at Φ1. The three-phase AC electric drive of the electric motor is controlled like iu, the output torque Te of the electric motor is also controlled according to the target torque, and the electric motor rotation speed N is decelerated. Here, regenerative control is performed in a region where the rotational speed N is positive, and power running is performed in a negative region.

As described above, in the second embodiment, the control of the rotor magnetic flux in the steady state and the transient state is the same as that in the conventional technique, that is, the steady loss and the transient loss are minimized. In addition, when the polarity of the torque command value changes, the power running operation quickly shifts to the regenerative operation, and the output torque Te of the electric motor quickly follows the torque command value Te '. 2 and 4, the rotation speed N is 0 from time t1.
The time required for this is obviously short in this embodiment. Although the second embodiment has been described by taking the shift switch switching during forward traveling of the electric forklift truck as an example, when the induction motor shifts from the power running operation to the regenerative operation or from the regenerative operation to the power running operation, The effect of the invention can be obtained.

FIG. 5 is a diagram showing a third embodiment of the present invention, in which the target torque calculation unit 3 in FIG. 1 of the first embodiment is used.
1 is changed to a target torque calculation unit 33 and an output initial setting unit 34. The output initial setting unit 34 determines the torque command value T
The output initial value Tre is obtained by a predetermined calculation using e ′ as an input.
The target torque calculation unit 33 inputs the torque command value Te ′ as the input of the transfer function, the polarity change timing signal Cp as the reset signal, and the output initial value Tres as the output initial value at reset. , A target torque Tm of the induction motor is calculated based on a transfer function having a predetermined low-pass characteristic with respect to the torque command value Te ′, and when the polarity timing signal Cp is input, the transfer function is reset and output. The target torque Tm is set as the output initial value Tres at that time.

Next, the operation will be described with reference to the waveform chart shown in FIG. The waveform diagram shown in FIG. 6 is the same as in the first embodiment, when the forklift is stopped and the shift switch F / R is in the forward position, the accelerator pedal operation amount α is operated from 0 to α1, and At t1, the accelerator switch operation amount α remains α1, and the shift switch F /
This is when R is switched to the retracted position. Time t1
Up to the same as conventional technology, but shift switch F / R
Is switched to the retracted position, the torque command calculation unit 2 of FIG.
The torque command value Te ′, which is an output of 0, changes from T1 to −T1. Then, the polarity of the torque command value Te ′ changes, so that the polarity change timing signal Cp is output from the polarity change detection unit 30. Therefore, the target torque calculation unit 3
The output of the transfer function 3 is reset to the value of the output initial value Tres at that time. Now, assuming that the calculation contents of the output initial setting unit 34 are as shown in Expression 1, the output initial value T at this point is
Since the value of res is −T1 / 2, the value of the target torque Tm is −T1 / 2, and the value of the torque command value Te ′ that is the input of the transfer function is −T1, so that after that, the predetermined low-pass characteristic is obtained. And falls from -T1 / 2 to -T1. Further, since the absolute values of the torque command value Te 'do not change between T1 and -T1, the value of the minimum steady loss magnetic flux Φr' remains Φ1, and therefore the target magnetic flux Φr also remains Φ1. The three-phase AC electric drive of the electric motor is controlled like iu, the output torque Te of the electric motor is also controlled according to the target torque, and the electric motor rotation speed N is decelerated. Here, regenerative control is performed in a region where the rotational speed N is positive, and power running is performed in a negative region.

Tres = Te ′ × 0.5 (Equation 1) As described above, in the third embodiment, the control of the rotor magnetic flux during the steady state and the transient state is the same as that of the first embodiment, that is, the steady loss is also present. Transient losses are also minimal. Moreover, when the polarity of the torque command value changes, it is possible to quickly shift from the power running operation to the regenerative operation. Further, by making the target torque at the time of transition a function of the torque command value, it is possible to set the torque response at the time of switching the system switch.

In the third embodiment, the function of the output initializing section 34 is fixed, but in the first embodiment, the function is considered to be, for example, the expression 2, and the second function is also used. In the embodiment of FIG.
It is thought to be something like.

Tres = Te ′ × 0 (Equation 2) Tres = Te ′ × 1 (Equation 3) That is, by making the function variable, the torque response when the shift switch is switched can be made variable. For example, the shift shock felt by the operator can be automatically adjusted by changing the load capacity of the forklift.

[0026]

As described above, in the present invention, when the polarity of the torque command value is reversed, the output of the transfer function that calculates the target torque is set to 0. Therefore, from power running to regeneration or from regeneration to power running. It is possible to minimize the loss in steady state and transient state while performing the transition quickly. Also, when the polarity of the torque command value is reversed,
If the output torque command value of the transfer function that calculates the target torque is made equal, the effect that the output torque of the electric motor can quickly follow the command value is further achieved, and the polarity of the torque command value is If the output of the transfer function that calculates the target torque is set to the function of the torque command value when reversing, the torque responsiveness during power running to regeneration or transition from power running to regeneration can be set variable. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a high-efficiency drive control calculation unit according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing an operation in the first embodiment of the present invention.

FIG. 3 is a block diagram showing a high-efficiency drive control calculation unit according to the second embodiment of the present invention.

FIG. 4 is a waveform diagram showing an operation in the second embodiment of the present invention.

FIG. 5 is a block diagram showing a high-efficiency drive control calculation unit according to the third embodiment of the present invention.

FIG. 6 is a waveform diagram showing an operation in the third embodiment of the present invention.

FIG. 7 is a block diagram showing an entire system in a conventional example.

FIG. 8 is a block diagram showing a high-efficiency drive control calculation unit in a conventional example.

FIG. 9 is a block diagram showing a torque command calculation unit in a conventional example.

FIG. 10 is a waveform diagram showing an operation in a conventional example.

[Explanation of symbols]

 11 Steady Loss Minimum Flux Calculation Section 12 Target Flux Calculation Section 13 Excitation Current Calculation Section 15 Torque Current Calculation Section 16 Slip Frequency Calculation Section 17 Motor Rotation Speed Calculation Section 18 Integral Calculation Section 30 Polarity Change Detection Section 31 Target Torque Calculation Section 32 Target Torque Calculation unit 33 Target torque calculation unit 34 Output initial value setting unit

Claims (4)

[Claims] 1. A controller for an induction motor which calculates a current command value according to a torque command value and a rotation speed of the induction motor and drives the induction motor with a polyphase alternating current corresponding to the current command value. The minimum steady-state magnetic flux calculation unit that calculates the rotor magnetic flux that minimizes the steady-state loss of the induction motor at the specified torque command value, and the minimum steady-state magnetic flux described above are input, and the target magnetic flux and target based on the transfer function having the low-pass characteristic are input. A target magnetic flux calculation unit that calculates the first-order differential value of the magnetic flux, and a target torque when the target torque of the induction motor is calculated from the torque command value based on a predetermined transfer characteristic and the polarity of the torque command value is reversed. Based on the circuit constant of the induction motor, the target magnetic flux, the first derivative of the target magnetic flux, the target torque, and the rotation of the induction motor. And a vector control calculation unit that calculates the current command value according to the electric current and a motor drive unit that causes the current flowing in the induction motor to follow the current command value.The output torque of the induction motor is set to the target torque. A control device for an induction motor that controls to a value corresponding to. 2. A control device for an induction motor which calculates a current command value according to a torque command value and a rotation speed of the induction motor and drives the induction motor with a polyphase alternating current corresponding to the current command value. The minimum steady-state magnetic flux calculation unit that calculates the rotor magnetic flux that minimizes the steady-state loss of the induction motor at the specified torque command value, and the minimum steady-state magnetic flux described above are input, and the target magnetic flux and target based on the transfer function having the low-pass characteristic are input. A target magnetic flux calculation unit that calculates the first-order differential value of the magnetic flux, and a target torque when the target torque of the induction motor is calculated from the torque command value based on a predetermined transfer characteristic and the polarity of the torque command value is reversed. A target torque calculation unit that sets the above-mentioned torque command value as a value, and based on the circuit constant of the induction motor, the target magnetic flux, the first derivative of the target magnetic flux, and the target torque. An output torque of the induction motor, which includes a vector control calculation unit that calculates the current command value according to the rotation speed of the induction motor, and a motor drive unit that causes the current flowing in the induction motor to follow the current command value. Is a control device for an induction motor, which controls so as to have a value corresponding to the target torque. 3. A controller for an induction motor, which calculates a current command value according to a torque command value and a rotation speed of the induction motor, and drives the induction motor with a polyphase alternating current corresponding to the current command value. The minimum steady-state magnetic flux calculation unit that calculates the rotor magnetic flux that minimizes the steady-state loss of the induction motor at the specified torque command value, and the minimum steady-state magnetic flux described above are input, and the target magnetic flux and target based on the transfer function having the low-pass characteristic are input. A target magnetic flux calculation unit that calculates a first-order differential value of the magnetic flux, an output initial value setting unit that calculates an output initial value from the torque command value based on a predetermined function, and a predetermined transfer characteristic from the torque command value based on a predetermined transfer characteristic. A target torque calculation unit that calculates the target torque of the induction motor and sets the target torque to the value of the output initial value when the polarity of the torque command value is reversed, and the rotation speed of the induction motor. Based on a constant, a vector control calculation unit that calculates the current command value according to the target magnetic flux, the first-order derivative value of the target magnetic flux, the target torque, and the rotation speed of the induction motor, and a current flowing through the induction motor. And a motor drive unit that causes the current command value to follow, and controls the output torque of the induction motor to a value corresponding to the target torque. 4. The control device for an induction motor according to claim 3, wherein the function of the output initial value setting unit is variable according to various conditions.