JPH07143798A - Speed sensorless vector controller - Google Patents

Abstract

PURPOSE:To make the rotation of a motor smooth by stabilizing the control in ultra-low speed region or low speed region. CONSTITUTION:A monitoring circuit 11 checks an estimated speed value LAMBDAomegaR' from a speed estimating/operating section 7 to decide whether it is lower than a preset lower limit. If a decision is made that the estimated speed value LAMBDAomegaR' is lower than the lower limit set value, a switch 12 is turned oppositely to the direction shown on the drawing. The switch 12 is inserted into an estimated speed supply path and when the switch 12 is turned, an estimated speed value LAMBDAomegar generated from a function generator 13 is fed to an adder 9 where it is added to a slip frequency omegas to produce an output frequency omega1 which is then fed to a voltage type vector operating section 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention calculates an estimated speed by using a detected motor current, and uses the estimated speed to perform a vector control by asynchronous PWM control on a three-phase induction machine in an extremely low speed range or a low speed range. The present invention relates to a speed sensorless vector control device for stabilizing control in a range.

[0002]

2. Description of the Related Art Generally, speed sensorless vector control of an induction motor is to control the speed of an electric motor without using a speed sensor by detecting the electric current of the electric motor, performing rotation orthogonal coordinate conversion, estimating the electric motor speed by calculation. Is.

A conventional speed sensorless vector control device is disclosed in Japanese Patent Laid-Open No. 262887/1990. In this control device, a motor model voltage is calculated from a magnetic flux current command, a torque current command, a motor (motor) constant, and a speed command, and asynchronous PWM calculation is performed from this model voltage to perform inverter control. At this time, the torque current is detected, the error component from the torque current command is calculated, and the speed is estimated from this error component.

However, in the speed sensorless vector control, the error of the estimated speed becomes large as the motor speed approaches zero. As a result, the state becomes uncontrollable or unstable. Such a state is a problem peculiar to the sensorless vector control in any method, and therefore, it has been conventionally applied to an application where the operation is not performed in the extremely low speed range or the low speed range.

[0005]

As described above, in the conventional speed sensorless control, the output voltage value becomes a very small value in an extremely low speed range such as when starting. This is because the sensorless vector control uses an inverter (INV) that uses a power transistor or the like. That is, in INV, an error occurs between the command value and the actual value of the output voltage due to the forward voltage drop of the power device such as a power transistor and the short-circuit prevention time of the upper and lower arms. Therefore, the smaller the command voltage is, the more the voltage error due to the above causes occurs. Will be greatly affected. For this reason, control in the low speed range may become unstable. Therefore, in order to solve the above problems, a means for performing forward voltage drop compensation and dead time compensation is also adopted, but control in an extremely low speed region has not been improved yet.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a speed sensorless vector control device for smoothing the rotation of a motor by stabilizing the control in an extremely low speed region or a low speed region. And

[0007]

In order to achieve the above-mentioned object, the present invention calculates the estimated speed by using the detected motor current, and calculates the estimated speed, the exciting current command and the torque current command. The excitation voltage command and the torque voltage command are obtained by performing vector calculation using the device that controls the three-phase induction machine using these excitation voltage command and torque voltage command, and the lower limit value of the preset estimated speed and A monitoring circuit that compares the estimated speed values calculated by calculation,
The function generator for obtaining the estimated speed used for calculating the output frequency and the supply path for the estimated speed calculated by using the electric motor current are inserted in the speed generator calculated by the comparison result of the monitoring circuit. A switching device that switches to the estimated speed output from the function generator in a low speed range where it is possible is provided.

The second invention is characterized in that the lower limit value of the monitoring circuit is set to a set value having the same polarity as the direction of the exciting current command.

A third aspect of the present invention is characterized in that the maximum output value of the function generator is set to the same value as the set value of the monitoring circuit.

A fourth aspect of the present invention is characterized in that the output value of the function generator starts from zero at the time of starting and rises up to the maximum value with a cushion.

[0011]

When the monitoring circuit detects that the speed estimated value calculated by the calculation is less than or equal to the lower limit of the preset estimated speed, the switch operates to output the speed estimated output from the function generator. Supplied to perform vector operations. Thereby, the control in the extremely low speed range or the low speed range is stably performed.

[0012]

Embodiments of the present invention will be described below. Figure 1
Shows a motor control device according to this embodiment. The voltage type vector calculation unit 1 uses the motor excitation current command I _1d *, the motor torque current command I _1q * and the inverter output frequency to determine the motor primary d-axis and q-axis winding voltage commands v _id * and v _iq.
Calculate *. The arithmetic expression at this time is shown by the following Expression 1.

[0013]

[Equation 1]

The PWM control inverter 2 speed-controls the squirrel-cage induction motor 3 based on the voltage commands v _id * and v _iq *. The current detector 4 is a phase current I _U , I _V , I _W of the motor 3.
Then, the coordinate conversion unit 5 converts the phase currents I _U , I _V , and I _W into the currents I _1d and I _1q based on the rotational coordinates dq. Of the converted currents, torque current detection I _1q and torque current command I
₁ q * is given to the deviation device 6 to obtain an error current component at its output. This error current component is input to the speed estimation calculation unit 7. The speed estimation calculation unit 7 obtains a speed estimation error component from the error current component, calculates this speed estimation error component, and obtains an estimated speed value ∧ω _r (hereinafter, the estimated value is denoted by a ∧ symbol).

Reference numeral 8 is a slip frequency calculation unit, and this calculation unit 8
_{Sends the} slip frequency ω _s to the output according to the excitation current command I _1d * and the torque current command I _1q *. The sent slip frequency ω _s and the estimated speed value ∧ω _r are added by the adder 9 and the output frequency ω ₁ is sent to the output. This output frequency ω ₁
Is supplied to the voltage vector calculator 1 and is also input to the conversion circuit 10 for converting the output frequency ω ₁ into the phase angle θ. The phase angle θ obtained in the conversion circuit 10 is supplied to the PWM control inverter 2.

Reference numeral 11 is a monitoring circuit for monitoring whether the estimated speed value ∧ω _r 'from the speed estimation calculation unit 7 is a preset lower limit value. This monitoring circuit 11 sets the estimated speed value ∧ω _r ' and the lower limit setting. The value is compared with the value, and when it is determined from the comparison result that the value is equal to or less than the set value, the switch 12 is switched in the opposite direction to that shown in the drawing. This switching device 12 is inserted in the estimated speed supply passage, and when the switching device 12 is switched, the estimated speed value ∧ω _r generated by the function generator 13 is given to the adder 9, and this addition device 9 The output frequency ω ₁ is calculated by adding the slip frequency ω _s .

The speed estimation calculation unit 7 continues to execute the error current component from the deviation device 6, and switches when the estimated speed value ∧ω _r 'of the speed estimation calculation unit 7 becomes equal to or higher than the lower limit set value of the monitoring circuit 11. The device 12 is switched to the position shown in the figure, and the estimated speed value ∧ω _r is supplied from the speed estimation calculation unit 7 to the adder 9.

The lower limit set value of the monitoring circuit is set so as to be monitored in both the forward rotation direction and the reverse rotation direction of the motor. When the operation command is the forward rotation command, the lower limit set value in the forward rotation direction is set. Is used.

[0019]

According to the present invention, with the above-described structure, the following effects can be obtained.

With respect to claim 1, the following effects (1) and (2) can be obtained. (1) In an extremely low speed range or a low speed range where the speed cannot be estimated, the estimated speed value generated by the function generator is used instead of the estimated speed, so the output frequency is stable, , The rotation of the electric motor becomes smooth. (2) When the estimated speed is output from the function generator, the slip frequency corresponding to the torque command is added to this value, so that the desired torque can be generated, and the problem of insufficient torque does not occur. .

With respect to claim 2, the following effect (3) can be obtained. (3) By setting the polarity of the set value of the monitoring circuit to be the same as that of the operation command of the inverter, there is an effect of preventing the motor from rotating in the reverse direction different from the operation command direction.

With respect to claim 3, the following effect (4) can be obtained. (4) By making the maximum output value of the function generator the same as the setting value of the estimated speed monitoring circuit, the speed output data used for the output frequency calculation does not become discontinuous and the motor accelerates smoothly even when the motor is started. be able to.

With respect to claim 4, the following effect (5) can be obtained. (5) At the time of starting, the estimated speed is output as a cushion from the function generator, so that an overcurrent trip can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a speed sensorless vector control device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Voltage vector calculation part 2 ... PWM control inverter 3 ... Induction motor 5 ... Coordinate conversion part 6 ... Deviation device 7 ... Speed estimation calculation part 8 ... Slip frequency calculation part 9 ... Adder 11 ... Monitoring circuit 12 ... Switching device 13 ... Function generator

Claims (4)

[Claims] 1. An estimated speed is calculated using the detected motor current, and a vector operation is performed using the estimated speed, an excitation current command and a torque current command to obtain an excitation voltage command and a torque voltage command, and the excitation voltage command and the torque voltage command are calculated. In a device that controls a three-phase induction machine using a voltage command and a torque voltage command, a monitoring circuit that compares the preset lower limit value of the estimated speed with the estimated speed value calculated by calculation, and the output frequency calculation The function generator for obtaining the estimated speed to be used and the supply passage for the estimated speed calculated by using the electric motor current are inserted so that the speed calculated by the comparison result of the monitoring circuit cannot be estimated. A speed sensorless vector control device comprising: a switch that switches to an estimated speed output from the function generator in a low speed range. 2. The speed sensorless vector control device according to claim 1, wherein the lower limit value of the monitoring circuit is set to a set value having the same polarity as the direction of the exciting current command. 3. The maximum output value of the function generator is set to the same value as the set value of the monitoring circuit.
The speed sensorless vector control device described. 4. The speed sensorless vector control device according to claim 1, wherein the output value of the function generator starts from zero and rises up to a maximum value with a cushion at the time of starting.