JPH0556683A - Load sharing controller for motor - Google Patents

Abstract

PURPOSE:To prevent operation miss by determining the sharing amount of sub-motor upon switching to load sharing control and varying the sharing ratio slowly. CONSTITUTION:Upon switching of a sub-motor 6 to load sharing control, sharing ratio is varied according to a ramp function upto a value operated based on an actual load sharing ratio. In other words, actual sharing ratio of speed current reference between a main motor 1 and the sub-motor 6 before switching to load sharing control, i.e., during speed control, is employed as an initial value immediately after switching to load sharing control. Load sharing control is then carried out by gradually varying the sharing ratio from the initial value upto a set ratio operated based on mechanical conditions according to a ramp function thus suppressing speed variation at the time of switching to load sharing control. According to the invention, operation miss can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load sharing control device for an electric motor which switches control methods.

[0002]

2. Description of the Related Art Generally, when a mechanical restraining force is exerted between a plurality of electric motors, a conventional electric motor control device performs speed control such that one electric motor serves as a main electric motor so that an actual speed matches a speed reference. Load sharing control is performed in which other electric motors are used as slave electric motors to supply currents obtained by multiplying the electric currents of the main electric motors by a set sharing ratio to perform current control.

However, when there is no mechanical restraining force between the electric motors, the slave motor is also operated by speed control so that the actual speed matches the speed reference as in the main motor.

Therefore, under a mechanical condition in which the mechanical restraining force changes from a state without a force to a state with a mechanical restraint force, the actual share ratio with the main motor and the set share ratio for current control during speed control of the slave motor are different. In this case, even if the current reference of the secondary motor changes when the load sharing control is switched, the current reference of the main motor does not change immediately.Therefore, if the current reference of the slave motor changes, the current reference of the main motor and the slave motor changes. The sum changes and acts as a disturbance on the speed control system of the main motor, causing speed fluctuations. For example, increasing the sum of the current references accelerates the motor, and operation of the speed control amplifier of the traction motor causes the current reference to decrease until the actual speed equals the speed reference.

As described above, in the conventional control device, if there is a difference between the sharing ratio during speed control and the setting sharing ratio during load sharing control,
Speed change occurred when switching to load sharing control.

[0006]

In order to reduce the speed fluctuation at the time of switching to the load sharing control, the speed fluctuation response and the time until the fluctuation converge can be reduced by increasing the speed control response. In a continuous processing plant in which one process line is formed by a large number of electric motors, there is a problem of uniform speed, and the response of speed control cannot be easily changed. Also, while the set share ratio is uniquely determined for various machine conditions, it is currently set by a human system by the operator, so there are problems such as setting the share ratio difference too large. It was

When the speed control is switched to the load sharing control in an operating state like a paper machine of a paper manufacturing plant, if the speed fluctuation is large, the product will be adversely affected.

According to the present invention, in order to reduce the speed fluctuation when switching to the load sharing control, the sharing amount of the slave motor during the load sharing control is calculated and the load sharing of the electric motor is gradually changed. An object is to provide a control device.

[0009]

According to the present invention, a rotation speed detector for detecting the rotation speed of a main motor, and a deviation value between an actual rotation speed output from the rotation speed detector and a preset reference rotation speed are calculated. A speed control amplifier that amplifies, a main circuit current control amplifier that controls so that the current reference value output from this speed control amplifier and the main circuit current that flows in the drive main circuit of the main motor match, and this main circuit current control A main circuit power converter that supplies power to the main motor according to an instruction from the amplifier, a slave motor that is normally speed-controlled by the same operation as the main motor, and a calculator that calculates the load sharing ratio of the slave motor and the main motor. , A first computing device that computes a sharing ratio when the slave motor is under load sharing control from a predetermined machine condition, and a load sharing ratio and a divider that are set by the first computing device. Actually A ramp function generator that gently changes the sharing ratio difference with the ratio, a second computing device that multiplies the sharing ratio output from the ramp function generator by the reference speed current of the main motor, and the second computing device. And a slave circuit current control amplifier that controls the slave circuit current flowing in the drive slave circuit of the slave motor to match, and a slave circuit power converter that supplies power to the slave motor according to a command from the slave circuit current control amplifier. A load sharing control device for an electric motor, comprising: an output circuit of the divider, an output circuit of the second arithmetic device, and a switch that opens and closes the drive slave circuit, respectively, according to the speed control method of the slave motor.

[0010]

In the load sharing control device for the electric motor according to the present invention, the rotational speed of the main electric motor is detected, and the deviation value between the actual rotational speed output from the rotational speed detector and the previously set reference rotational speed is amplified, Control is performed so that the current reference value output from the speed control amplifier and the main circuit current flowing in the drive main circuit of the main motor match, and power is supplied to the main motor according to the command from the main circuit current control amplifier. The speed of the electric motor is controlled by the same operation as the main motor, the load sharing ratio of the slave motor and the main motor is calculated, and the share ratio when the slave motor is in the load sharing control is calculated from the predetermined machine condition. 1) Gradually change the sharing ratio difference between the load sharing ratio set by the computing device and the actual sharing ratio from the divider, and multiply the sharing ratio output from the ramp function generator by the reference speed current of the main motor. , The second operation The output of the slave circuit and the slave circuit current flowing in the slave circuit of the slave motor are controlled to match, power is supplied to the slave motor according to the command of the slave circuit current control amplifier, and the divider is controlled by the speed control method of the slave motor. And the drive circuit of the second arithmetic unit are opened and closed.

[0011]

EXAMPLE An example of the present invention will be described below. FIG. 1 shows a rotation speed detector 2 that detects the rotation speed of the main motor _1, and a speed that amplifies the deviation value between the actual rotation speed W ₁ output from the rotation speed detector 2 and the preset reference rotation speed W _2. The control amplifiers 3, 14 and the main circuit current control amplifier 4 for controlling so that the current reference value I _1R output from the speed control amplifiers 3, 14 and the main circuit current flowing through the drive main circuit 20 of the main motor 1 match. And a main circuit power converter 5 that supplies power to the main motor 1 in accordance with a command from the main circuit current control amplifier 4.
When the slave electric motor 6 that is always speed-controlled by the same operation as the main electric motor 1, the calculator 7 that calculates the load sharing ratio of the slave electric motor 6 and the main electric motor 1, and the slave electric motor 6 is under load sharing control Of the load sharing ratio set by the first computing device 8 and the computing device 8 for calculating the sharing ratio of the load factor from the predetermined machine condition, and the sharing ratio difference between the actual sharing ratio from the divider 7 is gradually changed. A ramp function generator 9 is operated, a sharing device output from the ramp function generator 9 is multiplied by a reference speed current of the main motor 1, and an output of the calculation device 10 and a drive slave circuit 21 of the slave motor 6 are supplied. The slave circuit current control amplifier 11 that controls the slave circuit currents to match each other, the slave circuit power converter 12 that supplies power to the slave motor 6 according to a command from the slave circuit current control amplifier 11, and the speed control of the slave motor 6. Depending on the method, the divider 7 Shows a load sharing control device forces the circuit and the computation unit 10 outputs the circuit and to open and close the drive sub circuit 21 respectively switch 13 and the electric motor formed by including the.

That is, the speed detector 2 for detecting the speed of the main motor 1 and the speed control amplifier 3 for amplifying the deviation between the actual speed output from the speed detector 2 and the preset speed reference.
And a main circuit current control amplifier 4 that controls so that the current reference output from the speed control amplifier 3 and the actually measured actual current match, and power is supplied to the main motor 1 according to a command from the main circuit current control amplifier 4. A main circuit power converter 5 and a slave electric motor 6 whose speed is always controlled by the same operation as the main electric motor 1.
A computing device 8 for computing the load sharing ratio when the slave motor 6 is in current control; and a computing device 10 for multiplying the load sharing ratio set by the computing device 8 by the current reference of the main motor 1.
A slave circuit current control amplifier 11 that controls the output from the arithmetic unit 10 and the actual current of the slave motor 6 to match, and a slave circuit power converter that supplies power to the slave motor 6 according to a command from the slave circuit current control amplifier 11. A load sharing control device for an electric motor, which includes a switch 12 for opening and closing an output circuit of the arithmetic unit 8, an output circuit of the arithmetic unit 10, and an input side circuit of the slave circuit current control amplifier 11. , The main motor 1 whose speed is controlled so that the actual speed of the electric motor matches the speed reference, and the slave electric motor 6 which is supplied with a current obtained by multiplying the speed current reference of the main electric motor 1 by the calculated set share ratio and whose current is controlled. In the load sharing control device for a motor configured as described above, when the slave motor 6 is busy with the load sharing control, the sharing ratio is changed by the ramp function from the previous actual load sharing ratio to the calculated sharing ratio. A load sharing control unit for causing.

Then, the load sharing control device for the electric motor according to the present invention switches the actual sharing ratio of the speed current reference of the main motor 1 and the slave motor 6 to the load sharing control before switching to the load sharing control, that is, during speed control. The initial value immediately after crossing, the load sharing control is performed by gradually changing the sharing ratio by the ramp function from this initial value to the set sharing ratio calculated by the machine condition, and the speed fluctuation amount at the time of switching to the load sharing control is set. Reduce.

For example, when a mechanical restraining force that pressurizes between the rolls 15 is applied, when the speed control of both the main motor 1 and the slave motor 6 is performed, the motor set to a high roll rotation speed causes the motor set to the other motor load. Will also be driven and it will be out of control.

In this case, before the mechanical restraint force is applied to the roll 15, that is, the actual share ratio when both of them are under speed control is calculated by the divider 7 every moment and stored by the ramp function generator 9. Keep it.

Since the switch 13 is brought into an operating state by the generation of mechanical restraining force, the slave circuit current control amplifier 11 is provided.
The signal from the speed control amplifier 14 that was output to
Instead, the actual share ratio during speed control of the slave motor 6 stored in the ramp function generator 9 and the set share ratio from the arithmetic unit 10 are changed at a rate determined by the ramp function, and the arithmetic unit 10 is changed. Then, the product of the speed current reference I _1R of the main motor ₁ and the current reference signal of the slave motor 6 is used.

Therefore, the current reference value I _2R of the slave motor 6, which can be obtained by multiplying the current reference value I _1R of the main motor ₁ by the ramp function output K, does not suddenly change at the time of switching to the load sharing control, and the setting sharing is performed. Since it changes to a value corresponding to the ratio, the sum of the current references of the main motor 1 and the slave motor 6 does not change significantly,
The amount of speed fluctuation can be reduced by reducing the disturbance to the speed control system. Therefore, according to the present embodiment, the provision of the arithmetic unit 8, the ramp function generator 9, and the divider 7 makes it possible to reduce the automatic share ratio setting and the reduction of the speed fluctuation amount.

[0018]

According to the present invention, when the load sharing control is switched to, the load sharing ratio is changed from the actual sharing ratio immediately before switching to the automatically set sharing ratio by a ratio, so that the disturbance to the speed control system is disturbed. This reduces the amount of speed fluctuations and prevents operational errors.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a load sharing control device showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Main motor 3 ... Speed control amplifier 4 ... Main circuit current control amplifier 5 ... Main circuit power converter 6 ... Slave motor 7 ... Divider 8 ... First arithmetic unit 9 ... Ramp function generator 10 ... Second Arithmetic device 13 ... Switch

Claims (1)

[Claims] 1. A rotation speed detector for detecting a rotation speed of a main motor, and a speed control amplifier for amplifying a deviation value between an actual rotation speed output from the rotation speed detector and a reference rotation speed set in advance. A main circuit current control amplifier that controls so that the current reference value output from this speed control amplifier and the main circuit current flowing in the drive main circuit of the main motor match, and the main circuit current control amplifier commands the main circuit current control amplifier. A main circuit power converter for supplying electric power to the electric motor, a slave electric motor whose speed is normally controlled by the same operation as the main electric motor, a calculator for calculating a load sharing ratio of the slave electric motor and the main electric motor, and the slave A first computing device that computes a sharing ratio when the electric motor is in a load sharing control based on a predetermined machine condition, a load sharing ratio set by the first computing device, and an actual value from the divider. Minute A ramp function generator that gently changes the share ratio difference from the share ratio, a second computing device that multiplies the share ratio output from the ramp function generator by the reference speed current of the main motor, and the second computing device. A slave circuit current control amplifier for controlling the output of the arithmetic unit and the slave circuit current flowing in the drive slave circuit of the slave motor, and a slave circuit for supplying power to the slave motor according to a command from the slave circuit current control amplifier. A motor comprising an electric power conversion device and a switch for opening and closing the output circuit of the divider, the output circuit of the second arithmetic unit, and the drive slave circuit according to the speed control method of the slave motor. Load sharing control device.