JP3260071B2 - AC elevator control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved AC elevator control device for controlling an elevator speed by driving an induction motor with a general-purpose inverter.

[0002]

2. Description of the Related Art At present, inverter devices are widely used to control an AC motor such as an induction motor or a synchronous motor at a variable speed. Recently, among these inverter devices, what is generally called “general-purpose inverter”
The application range is being expanded by the high performance and high functionality accompanying the recent performance improvement of switching elements and microprocessors.

As a control method for this general-purpose inverter, V / f control has been widely adopted. V / f control is an open-loop control method, and there is no need to detect the rotation speed of the electric motor. For this reason, even in the case of an existing AC motor, it is not necessary to attach a speed detector to the motor, and variable speed operation is possible by simply connecting a general-purpose inverter between the AC power supply and the motor. Therefore, if speed control is performed using this general-purpose inverter without a speed sensor,
The trouble of mounting the speed detector can be omitted, a simple control configuration can be realized, and the cost merit is great.

When this general-purpose inverter without a speed sensor is applied to elevator control, in an elevator, the load applied to the motor fluctuates depending on the loading condition of a car, and the speed varies. Therefore, when the actual traveling speed is higher than a set value,
There is a risk that the car will plunge into the destination floor. In order to avoid this danger, when the vehicle reaches a predetermined distance before the destination floor, the speed is reduced from the rated speed to a low speed by a predetermined deceleration, and the vehicle travels at a low speed until reaching the destination floor.

[0005] In addition, although the speed varies even when the vehicle is traveling at a low speed, if the actual traveling speed is lower than the set value, the vehicle cannot reach the destination floor, and there is a risk of causing a stop or a reverse run. The set speed during running could not be lowered, and good stopping performance (stop shock, landing level accuracy) could not be obtained.

However, a recent general-purpose inverter has a control function (slip frequency compensation control) for estimating a load applied to the motor from a detection signal of a motor current or the like and compensating for speed variations in order to compensate for the disadvantage of speed sensorlessness. It is becoming. In this slip frequency compensation control, the slip frequency obtained by calculation from the estimated load is added to a predetermined speed command, and this is used as a frequency command for the inverter output. If the actual speed is lower than the command value, the command frequency is increased. If the actual speed is higher than the command value, the control is performed so that the command frequency is lowered so that the actual speed matches the speed command.

[0007]

By applying an inverter having the above-described slip frequency compensation control function to an elevator, speed variations due to load fluctuations are reduced, and low-speed traveling time can be reduced, so that driving efficiency is improved. You can do it. In addition, the stopping performance can be improved by lowering the low-speed setting speed.However, this general-purpose inverter without a speed sensor does not have high calculation accuracy of the slip compensation control at a low speed, and therefore, when the output frequency of the inverter becomes low. That is, when the value of the frequency command becomes low (particularly several Hz
Below), it is easy to fall into an unstable state such as insufficient torque. For this reason, it is necessary to make the value of the frequency command during low-speed traveling higher than the lowest frequency at which the inverter can control stably.

In the elevator control, the regenerative operation frequently occurs depending on the load condition. However, in the regenerative operation, the actual speed is higher than the speed command. Works. For this reason, if the low speed portion of the speed command is set low, especially when the regenerative load is large, the value of the frequency command becomes a command frequency even lower than the lowest frequency at which the inverter can control stably. If the frequency is set to be higher than the lowest frequency, the low speed setting of the speed command cannot be set too low. This is shown in FIG.

FIG. 6A shows a conventional speed command.
(B) is a diagram showing a relationship between a command frequency, a slip frequency, a car speed, and the like at each load when a speed command is set to a low speed. As shown in FIG.
If the low speed setting of the speed command is lowered, the command frequency = the output frequency enters an unstable region where the regenerative load is large. Therefore, the low speed setting cannot be made lower than the value shown in FIG. As a result, there has been a problem that the speed of the car cannot be sufficiently reduced, and the stop shock when the brake is engaged increases.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to improve the stopping performance with a simple configuration even when the slip frequency compensation control of a general-purpose inverter is applied to an elevator. It is intended.

The present invention relates to a control device for an AC elevator in which a general-purpose inverter is used and the speed of the elevator is controlled by a slip frequency compensation control without a speed sensor. And a lower limit frequency limiter that sets the lower limit frequency to a value slightly higher than the lowest frequency at which the inverter operates stably with respect to the frequency command obtained by adding the slip frequency command obtained by estimating the load.

[0012]

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present application, the inverter stably responds to a frequency command obtained by adding a frequency-converted predetermined speed command and a slip frequency command obtained by estimating a motor load from the output of the inverter. By providing a lower limit frequency limiter with a lower limit frequency slightly higher than the lowest operating frequency, the command frequency after passing the limiter does not fall below the lowest frequency at which the inverter operates stably even at a large regenerative load. , The speed setting of the speed command can be reduced.

[0014]

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a basic diagram for achieving the effects of the present invention.
FIG .

In FIG. 1, 1 is a three-phase AC power supply, 2 is a converter for converting an AC power supply to DC, 3 is a smoothing capacitor for smoothing the output of this converter, and 4 is a converter 2
An inverter for converting the output of the inverter into an alternating current having a variable voltage and a variable frequency; 5 a current detector for detecting the output current of each phase of the inverter 4; 6 an induction motor fed by the inverter 4 to drive the elevator; and 7 an induction motor 6 The hoisting sheave driven by the sheaves, 8 is an electromagnetic brake, 9 is a main rope wound around the sheave 7, 10 is a car connected to the main rope 9,
1 is a counterweight, and 12 is a car position detector that detects the position of the car 10 and outputs a car position signal 12a.
Reference numeral 3 denotes an inverter control device constituted by a microcomputer, and 14 determines a car position based on a car position signal 12a, and a signal 14a indicates that the car has reached a predetermined distance before the landing level.
The car position determination unit 15 outputs a signal 14b when the vehicle reaches the landing level. The car position determination unit 15 generates a predetermined speed command 15a together with an elevator operation start command.
4a, a speed command generator for switching from the first stage low speed setting to the second stage low speed setting;
A predetermined time has passed since a was switched to the low speed setting of the second stage, or a brake engagement command generator 17 that outputs a brake engagement command 16a when a signal 14b is input.
Is a frequency converter that outputs a speed command 17a obtained by frequency-converting the speed command 15a, and 18 is a frequency converter that calculates a compensation amount according to the motor load from the inverter output current.
The slip frequency calculation unit 19 outputs a as a speed command 1
7a and the slip frequency command 18a, and the frequency command 1
An adder 9a outputs a required voltage, 20 calculates a required voltage so that the output frequency of the inverter matches the command frequency 19a, and generates a PWM signal corresponding thereto. This is a base drive circuit that controls a switching element such as a transistor that constitutes an inverter.

The operation of the above configuration will be described . When an elevator operation start command (not shown) is output, the speed command generator 15 outputs a speed command 15a, and the frequency converter 17 converts the speed command 15a into a frequency signal speed command 17a. On the other hand, the output of the inverter 4 is detected by the current detector 5, and the slip frequency is calculated by using the detection signal.
Is calculated by The slip frequency command 18a is output from the adder 1
At 9, it is added to the speed command 17 a to become a frequency command 19 a and input to the voltage / frequency calculation unit 20. As a result, the output of the inverter is controlled to match the frequency command 19a, and as a result, the speed of the car is reduced to the speed command 15a.
Driven to match.

Here, the speed command 15a consists of two stages of low speed settings as shown in FIG. 2. After the car has passed the deceleration start point and decelerated to the first low speed set value, the car is landed. When the signal reaches a predetermined distance before the level, the speed command is switched to the second low speed setting by the signal 14a. Thereafter, when the car reaches the landing level or when a certain period of time has elapsed from the low speed setting of the second stage, the brake engagement signal 16a is output, and the car stops at the landing level.

All of the above processing is realized by software in a microcomputer constituting the inverter control device 13, and FIG. 3 shows a flowchart of a main part of the software.

First, after starting operation as in the conventional case,
After decelerating to the low speed setting of the stage, it is determined in step S1 whether or not the car has reached a predetermined distance before the landing level, and if so, the speed command is switched to the low speed setting of the second stage in step S2. After the car has further started to decelerate toward the second-stage low speed setting, it is determined in step S3 whether or not the car has reached the landing level.
In step 5, a brake engagement command is output to stop the car. Also, even if the car does not reach the landing level, step S
If it is detected that a predetermined time has elapsed since the switching to the second-stage low-speed setting in step 4, a brake engagement command is also output in step S5 to stop the car.

With the above arrangement, the car is decelerated toward the second low speed setting lower than the first low speed setting, and then the brake is engaged.
The stop shock is smaller. In addition, although the output of the inverter may be unstable and torque may be insufficient due to lowering the low-speed setting of the second stage, even in such a case, the brake is engaged after a certain period of time after switching to the low-speed setting of the second stage. As a result, the vehicle can be stopped almost at the landing level without impairing safety.

Next, an embodiment of the present invention will be described. FIG. 4 is an overall configuration diagram, and the same or corresponding components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 4, reference numeral 14 denotes a car position judging unit which judges a car position based on a car position signal 12a and outputs a signal 14b when the car reaches a landing level, and 16 denotes a brake engagement command which outputs a brake engagement command 16a by input of the signal 14b. Generator, 15
Is a speed command generator that generates a predetermined speed command 15a as shown in FIG. 6A in response to an elevator operation start command, and 22 sets a lower limit value of the frequency command 19a to a minimum frequency at which the inverter operates stably. The lower limit frequency limiter is set to a higher value.

In the above configuration, when an elevator operation start command (not shown) is output, the speed command generator 1
5 outputs a speed command 15a, and the frequency converter 17 converts the speed command 15a into a speed command 17a of a frequency signal. On the other hand, the output of the inverter 4 is detected by the current detector 5, and the slip frequency is calculated by the slip frequency calculator 18 using the detection signal. The slip frequency command 18a is added to the speed command 17a by the adder 19, and is added to the lower limit frequency limiter 22 as a frequency command 19a. By setting the lower limit of the lower limit frequency limiter to a value slightly higher than the lowest frequency at which the inverter operates stably, even if the value of the frequency command 19a falls below the lowest frequency, the lower limit of the lower limit frequency limiter 22 is set. The output 22a can be limited so that it does not always fall below the lower limit set value. This is shown in FIG.

FIG. 5 shows the relationship between the command frequency and the car speed for each load when the speed command is set to a low speed. As is clear from FIG. 5, the provision of the lower limit frequency limiter prevents the command frequency 22 a from dropping below the minimum frequency where the load on the regenerative side is large even when the low-speed set value is set lower than the conventional value. . As a result, even if the low-speed setting is set lower than before, the inverter can always be operated in a stable state regardless of the load condition, and by setting the low-speed setting low, the speed of the car when the brake is engaged can be reduced. Particularly, it becomes lower on the power running side, and the stop shock can be reduced.

[0025]

According to the present invention, even when the slip frequency compensation control without a speed sensor is performed using a general-purpose inverter, the value of the low speed setting of the speed command can be set low with a simple configuration, and Stop shock can be reduced without impairing the performance.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram which is a basis for achieving the effects of the present invention.

FIG. 2 is a diagram showing a speed command in FIG. 1;

FIG. 3 is a flowchart showing an operation of a main part in FIG. 1;

FIG. 4 is an overall configuration diagram showing one embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a command frequency and a car speed for each load when a speed command is set to a low speed.

FIG. 6A is a diagram showing a conventional speed command, and FIG.
FIG. 3 is a diagram showing a relationship between a command frequency, a slip frequency, a car speed, and the like at each load when a speed command is set to a low speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-phase AC power supply 2 Converter 3 Smoothing capacitor 4 Inverter 5 Current detector 6 Induction motor 8 Electromagnetic brake 10 Car 12 Car position detector 13 Inverter control unit 14 Car position determination unit 15 Speed command generation unit 16 Brake engagement command generation unit 17 Frequency converter 18 Slip frequency calculator 19 Adder 20 Voltage / frequency calculator 22 Lower limit frequency limiter

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B66B 1/00-1/52

Claims (3)

(57) [Claims] 1. An AC elevator control device which uses a general-purpose inverter to control the speed of an elevator by a slip frequency compensation control without a speed sensor, comprising the steps of: The inverter operates stably in response to the frequency command obtained by adding the slip frequency command obtained by estimating the load.
A control device for an AC elevator, comprising: a lower frequency limiter that sets a lower limit frequency to a value slightly higher than a lowest frequency to be performed. 2. The control device for an AC elevator according to claim 1, wherein the predetermined speed command has a low speed portion in two stages after deceleration. 3. The control device for an AC elevator according to claim 2, wherein when the car reaches a predetermined distance before the landing level, the low speed portion of the first stage is switched to the low speed portion of the second stage.