JP7563306B2 - Motor Control Device - Google Patents

Description

The present invention relates to a motor control device.

For example, rolling equipment used in steel plants often uses inverters that control the frequency of the power supplied to a motor (synchronous motor), thereby controlling the rotational speed of the motor.

A synchronous motor drive system is also known in which a speed controller converts the speed deviation, which is the difference between a speed reference and the actual speed of the motor, into a torque reference, and controls the inverter based on the torque reference (see, for example, Patent Document 1).

In addition, a technology is known in which the speed deviation, which is the difference between a speed reference and the actual speed of the motor, is converted into a torque reference, and then drooping control is performed with a set drooping rate (drooping gain) to adjust the speed deviation so that it is eliminated.

Japanese Patent Publication No. 2014-239612

As mentioned above, in recent years, speed control, including torque system control, has been put to practical use to control the rotational speed of a motor. However, if torque system corrections such as inertia compensation, mechanical loss compensation, and submerged compensation are overcompensated, the speed control will act to reduce the torque in the negative direction.

In other words, in conventional motor rotation speed control, drooping control acts only on the torque reference converted from the speed deviation, so even though the torque is ultimately controlled to be positive, drooping can sometimes act in the direction of acceleration (reverse polarity).

The present invention has been made to solve the above-mentioned problems, and aims to provide a motor control device that can control the rotation speed of a motor by correcting the polarity of the speed reference to the correct polarity even when the torque system is affected by external disturbances.

A motor control device according to one aspect of the present invention is a motor control device that includes an inverter for driving a motor and controls the rotational speed of the motor, and is characterized by having a speed control unit that controls the rotational speed of the motor via the inverter by outputting a torque reference for the motor based on a speed command that is a speed reference for the motor, a torque control unit that controls the torque of the motor via the inverter by outputting a torque command for the motor based on the torque reference output by the speed control unit, a current control unit that outputs a current command for the inverter so as to control the frequency of the power supplied to the motor by the inverter based on the torque command output by the torque control unit, and a torque command correction unit that corrects the speed command for the speed control unit by multiplying the torque command output by the torque control unit by a drooping gain.

In addition, the motor control device according to one aspect of the present invention is preferably characterized in that the torque command correction unit has a variable coefficient unit that multiplies the drooping gain by a coefficient so as to increase or decrease the drooping gain depending on the operating status of the motor.

According to the present invention, even when the torque system is affected by external disturbances, the motor rotation speed can be controlled by correcting the polarity of the speed reference to the correct one.

FIG. 1 is a diagram illustrating a configuration example of a rolling system. 1 is a block diagram illustrating a configuration of a motor control device according to an embodiment and its surroundings. FIG. FIG. 4 illustrates an example of the configuration of a speed control unit. FIG. 4 is a diagram illustrating an example of the configuration of a torque control unit. FIG. 4 is a diagram illustrating an example of the configuration of a calculated torque correction unit. FIG. 4 illustrates an example of the configuration of a torque command correction unit;

The following describes a motor control device according to one embodiment, taking as an example a motor control device used in a rolling system, with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration example of a rolling system 1. As shown in FIG. 1, the rolling system 1 includes, for example, a hot rolling line 2, a controller 3, and a rolling control device 4.

The hot rolling line 2 includes, for example, a heating furnace 20, a roughing mill 21, a finishing mill 22, a water cooling device 23, a cutting machine 24, and a winding machine 25.

In the hot rolling line 2, the rough rolling mill 21 performs rough rolling on the slabs output by the heating furnace 20, and sends the raw material (rolled material) to the finishing rolling mill 22. Then, in the hot rolling line 2, the finishing rolling mill 22 further rolls the roughly rolled rolled material to a specified specification, and after it is cooled by the water cooling device 23, the cutter 24 cuts it to a specified length, and the winder 25 winds it up.

For example, the roughing mill 21 is provided with multiple synchronous motors 21a, each of whose rotational speeds is controlled by the motor control device 5 described later.

The controller 3 is, for example, a programmable logic controller (PLC) and controls the rolling control device 4.

The rolling control device 4 includes, for example, a motor control device 5, and controls each part of the hot rolling line 2 according to the control by the controller 3. The motor control device 5 includes a drooping correction unit 6, and controls the rotation speed of the synchronous motor 21a.

Next, the motor control device 5 will be further described using Figures 2 to 6. Figure 2 is a block diagram illustrating the configuration of the motor control device 5 and its surroundings according to one embodiment.

As shown in FIG. 2, the motor control device 5 has a speed reference output unit 50, a speed control unit 51, a torque control unit 52, a current control unit 53, an inverter 54, and a drooping correction unit 6, and controls the rotation speed of the synchronous motor (motor) 21a by controlling the inverter 54.

The speed reference output unit 50 outputs a speed command regarding the rotational speed of the synchronous motor 21a to the speed control unit 51.

As shown in FIG. 3, the speed control unit 51 calculates the difference between the speed command output by the speed reference output unit 50 and the speed feedback detected as the actual speed of the synchronous motor 21a as the speed deviation. The speed control unit 51 then performs PI control on the speed deviation using the speed control AMP, and outputs the speed control final calculation torque (PI control result) to the torque control unit 52.

The speed control final calculation torque is a torque reference for the torque of the synchronous motor 21a. In other words, the speed control unit 51 controls the rotation speed of the synchronous motor 21a via the inverter 54 by outputting the torque reference for the synchronous motor 21a based on a speed command that is the speed reference for the synchronous motor 21a.

As shown in FIG. 4, the torque control unit 52 outputs a torque command to the current control unit 53 based on the final speed control calculation torque output by the speed control unit 51 and an external torque assistance reference input from, for example, the controller 3.

In other words, the torque control unit 52 controls the torque of the synchronous motor 21a via the inverter 54 by outputting a torque command to the synchronous motor 21a based on the torque reference output by the speed control unit 51.

The current control unit 53 outputs a current command to the inverter 54 so that the inverter 54 controls the frequency of the power supplied to the synchronous motor 21a based on the torque command output by the torque control unit 52.

The inverter 54 drives the synchronous motor 21a while controlling the rotation speed by controlling the frequency of the power supplied to the synchronous motor 21a.

The drooping correction unit 6 has a calculated torque correction unit 60 and a torque command correction unit 62, and performs drooping correction.

Specifically, as shown in FIG. 5, the calculated torque correction unit 60 multiplies the speed control final calculated torque output by the speed control unit 51 by a drooping gain related to the torque input from the controller 3 and then inverts the result to calculate the drooping command.

For example, if a negative speed control final calculation torque is input to the calculation torque correction unit 60, a positive drooping command is calculated.

The calculated torque correction unit 60 also multiplies the speed reference input from the controller 3 by a predetermined rate, adds the calculated drooping command, and outputs the resulting speed command to the speed reference output unit 50.

As shown in FIG. 6, the torque command correction unit 62 has a variable coefficient unit 620 that multiplies the drooping gain by a coefficient so as to increase or decrease the drooping gain depending on the operating status of the inverter 54.

For example, the variable coefficient unit 620 multiplies the coefficient so as to reduce the drooping gain when the synchronous motor 21a is started, and multiplies the coefficient so as to increase the drooping gain when the synchronous motor 21a is in normal operation.

The torque command correction unit 62 multiplies the torque command output by the torque control unit 52 by the drooping gain obtained by multiplying the drooping gain related to the torque input from the controller 3 by the coefficient obtained by the variable coefficient unit 620, and then inverts the result to calculate a drooping command. The torque command correction unit 62 also multiplies the speed reference input from the controller 3 by a predetermined rate, adds the calculated drooping command to the speed reference output unit 50, and outputs the speed command obtained by adding the calculated drooping command to the speed reference output unit 50.

In other words, the torque command correction unit 62 corrects the speed command for the speed control unit 51 by multiplying the torque command output by the torque control unit 52 by the drooping gain.

In this way, the motor control device 5 corrects the torque command output by the torque control unit 52 by multiplying it by the drooping gain, so that even when the torque system is affected by a disturbance, the motor rotation speed can be controlled by correcting the polarity to the correct speed reference.

Note that each function of the motor control device 5 may be configured in part or in whole by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1...Rolling system, 2...Hot rolling line, 3...Controller, 4...Rolling control device, 5...Motor control device, 6...Dropping correction unit, 20...Heating furnace, 21...Rough rolling mill, 21a...Synchronous motor (motor), 22...Finishing rolling mill, 23...Water cooling device, 24...Cutting machine, 25...Winding machine, 50...Speed reference output unit, 51...Speed control unit, 52...Torque control unit, 53...Current control unit, 54...Inverter, 60...Calculated torque correction unit, 62...Torque command correction unit, 620...Variable coefficient unit

Claims (2)

A motor control device including an inverter that drives a motor and controls a rotation speed of the motor,
a speed control unit that controls a rotation speed of the motor via the inverter by outputting a torque reference of the motor based on a speed command that is a speed reference of the motor;
a torque control unit that controls the torque of the motor via the inverter by outputting a torque command for the motor based on the torque reference output by the speed control unit;
a current control unit that outputs a current command to the inverter so as to control a frequency of the electric power supplied from the inverter to the motor based on the torque command output by the torque control unit;
a torque command correction unit that corrects a speed command for the speed control unit by multiplying the torque command output by the torque control unit by a first drooping gain;
a calculation torque correction unit that corrects a speed command for the speed control unit by multiplying a torque reference output by the speed control unit by a second drooping gain;
A motor control device comprising: The torque command correction unit is
2. The motor control device according to claim 1, further comprising a variable coefficient unit that multiplies the first drooping gain by a coefficient so as to increase or decrease the first drooping gain depending on an operating condition of the motor.

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