JPH0712895B2 - AC elevator control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a control device for an AC elevator that controls an elevator driven by an induction motor.

[Conventional technology]

An induction motor is used as an electric motor for driving a car of an elevator, and by controlling the slip frequency of the induction motor, the torque of the electric motor is controlled to operate the car.
This is shown in FIGS. 4 and 5.

In the figure, (1) is a three-phase AC power supply terminal, (2) is a terminal (1)
A magnetic contactor contact that is connected to and that is closed when the car (11) is started and opened when stopped, (3) is a converter that is composed of a rectifier circuit that rectifies three-phase AC voltage into DC through the contact (2), (4) is a smoothing capacitor connected to the DC side of the converter (3), (5) is a resistor having one end connected to one end of the smoothing capacitor (4), and (6) is smoothed with the other end of the resistor (5). A transistor connected to the other end of the capacitor (4),
(7) is an inverter known as a pulse width modulation system which is connected to both ends of the smoothing capacitor (4) and is composed of a transistor and a diode to convert a constant DC voltage into an AC of an arbitrary voltage and an arbitrary frequency, and (8) is an inverter A three-phase induction motor driven by (7), (9) a drive sheave of a hoist driven by the electric motor (8), (10) a main rope wound around the sheave (9), ( 11) and (12) are cages and counterweights that are respectively coupled to both ends of the main rope (10), and (13) is a speed signal (13a) that is coupled to the electric motor (8) and indicates the rotational speed of the electric motor (8). Generator for speed meter, (14) for speed command signal, (15) for speed command signal (1
4) and an adder that outputs the deviation signal of the speed signal (13a),
(16) is a compensation element connected to the adder (15) for improving the response of the speed control system, G (S) is a transfer function, and (16)
a) is the output of the compensation element (16) and is the slip frequency command signal, (1
7) is an adder that outputs the added value of the slip frequency command signal (16a) and the speed signal (13a), (18) is a voltage command generator that issues a voltage command signal (18a) from the output of the adder (17), (1
Similarly, 9) is a frequency command generator that issues a frequency command signal (19a), and (20) is an inverter that controls the output voltage and output frequency of the inverter (7) based on the voltage command signal (18a) and the frequency command signal (19a). It is a control device.

In such a configuration, the compensation element (16) outputs the slip frequency command signal (16a) corresponding to the deviation between the speed command signal (14) and the speed signal (13a), and the slip frequency command signal (16a) outputs the torque. It corresponds to the command signal, and the adder (1
2) By adding the speed signal (13a),
The voltage command signal (18a) and the frequency command signal (19a) are determined so as to satisfy the relationship that the voltage / frequency is substantially constant. According to these command values, the control device (20) causes the inverter (7) (when the converter (8) is composed of a thyristor or the like, depending on the case, the converter (3)).
The element of () is controlled by switching to generate a torque corresponding to the slip frequency command signal (16a) in the electric motor (8). Thus, the electric motor (8) is activated and the car (11) runs, and its speed is automatically controlled with high accuracy.

FIG. 5 shows a torque curve (21) with respect to the rotation speed of the electric motor (8). Here, n ₀ is a synchronous speed, which is a rotational speed corresponding to the output frequency of the inverter (7)
Is the operating point when is rotated. Generally, an induction machine has a torque at a slip frequency (e.g., n ₀ −n ₁ , near synchronous speed n ₀ ,
Or equivalent to n ₀ −n ₂ ). Therefore, the torque can be controlled by controlling the amount n ₀ −n ₁ corresponding to slip × frequency.

[Problems to be solved by the invention]

However, in the case of an elevator, when decelerating and stopping the car (11) and when descending at a constant speed under heavy load,
Braking force must be generated in the electric motor (8). If this is shown in FIG. 5, this is the case where the required braking torque is T ₂ . In this case, the rotation speed n ₂ of the electric motor (8) is
It becomes higher than the synchronization speed n ₀ . In such an operation, mechanical energy is converted into electrical energy via the electric motor (8), and regenerative power is returned to the DC side through the inverter (7). Therefore, the DC voltage rises, which may damage the elements in the inverter (7). The resistor (5) protects this, and the regenerative power is consumed by the resistor (5) due to the conduction of the transistor (6). There is also a device in which a regenerative inverter is provided instead of the resistor (5) to return regenerative power to the power supply side.

However, in either case, the device for regenerative power processing becomes expensive and the control device becomes large.

A method of solving this drawback is a method of consuming regenerative electric power inside the motor as shown in JP-A-59-17879 and JP-A-58-36866.

In this method, since the regenerative power is processed in the motor without any special device, the control device may be small in size at low cost, but the heat generated in the motor is large and the size of the motor is increased. It is possible to invite

Further, when the torque command is switched from the power running to the braking in the deceleration process as in the case of the heavy load increase operation in the car or the light load decrease operation, the speed command at the stop is as shown in FIG. Since the speed is gentle, the power running torque command is generated again when the vehicle is stopped, which may deteriorate the riding comfort.

The present invention has been made to solve the above problems, and is to suppress the heat generation of a motor within an allowable range and to make a regenerative power consumption device small and inexpensive.

[Means for solving problems]

A control device for an AC elevator according to the present invention connects a DC power supply to an inverter, converts DC power into AC power having a variable voltage and a variable frequency, and drives the induction motor with the converted AC power to drive a car. In the above, the regenerative power consumption device connected to the DC power source, the first means for controlling the torque of the electric motor by the torque command signal according to the deviation between the speed command signal and the speed signal of the electric motor, the torque. A second command for controlling the braking torque by controlling the amplitude command of the primary voltage or the primary current of the electric motor based on the command signal and generating a frequency command such that the electric motor does not generate regenerative electric power based on the speed signal. Means and when the torque command signal changes from positive to negative when the torque command signal is positive or in the deceleration range of the car. In the following, the first means is also used, and a switching means is provided for switching to the second means when the torque command becomes negative while the speed command signal does not output the deceleration command. Is.

[Action]

In the control device for the AC elevator according to the present invention,
When the torque command signal changes from positive to negative when the torque command signal is positive or in the deceleration range of the car, even after that, the speed command signal is changed by the first means based on the switching control of the switching means. When the torque command signal corresponding to the deviation of the speed signal of the electric motor controls the torque of the electric motor, and the torque command becomes negative in the state where the speed command signal does not output the deceleration command, the first control is performed based on the switching control of the switching means. The second means generates a frequency command based on the speed signal so that the electric motor does not generate regenerative electric power, and the braking torque is controlled. Therefore, when braking torque is required such as during deceleration of the elevator, regeneration is performed. The electric power is consumed within the motor within the allowable range of heat generation by the motor, and is consumed by the regenerative resistance beyond that, and the speed command generates the deceleration command. Becomes a braking state, there is no possibility that the electric motor is in the power running state until just before stopping, not the riding comfort of deterioration.

〔Example〕

 Examples of the present invention will be described below.

First, the principle of the present invention will be described.

FIG. 2 shows an electric motor (8) for briefly explaining the present invention.
Is a simple equivalent circuit of.

Here, the mechanical input P _G during the regenerative operation is the predetermined slip value S ′.
Is expressed as an absolute value with S ′ = − S, However, S '> 0 during regenerative operation.

On the other hand, the loss P _M consumed by the winding resistances r ₁ and r ₂ (r ₁ : primary resistance) inside the motor is P _M = (r ₁ + r ₂ ) I ² (2) Power converted to and consumed by regenerative resistor P _R
Is Here, the ratio η between the power P _R consumed by the regenerative resistor and the power P _M consumed by the motor is Therefore, it has no relation to the magnitude of the current, and is a function only for slip. The relationship with respect to the slip S is shown in FIG.

As is clear from the figure, Then, the amount consumed by the regenerative resistor becomes 0, so η =
It is 0.

or, Then, η = 1, that is, the power consumed by the motor and the power consumed by the regenerative resistor become substantially equal.

In the region where the absolute value of the slip S is sufficiently small, FIG. 3 is far from the actual condition, but in the region where the regenerative electric power is large, it is in good agreement with the actual condition.

According to the present invention, the heat generated in the motor is set as a sufficiently allowable loss from the viewpoint of insulation and life, and the slip S is selected so that the remainder is consumed by the resistance. It is designed to be within the allowable value.

A concrete embodiment of the present invention is shown in FIG.

In the figure (29), the torque command is positive and the speed command signal (1
When the torque command is positive when 4) issues the deceleration command, the inverter (7) is controlled by the conventionally known torque control device (30) even if the torque command becomes negative thereafter. A switch (29a) is connected to the switch to switch to a new control means when the torque command becomes negative while the speed command signal does not output the deceleration command. The determined slip S '(=-S)
The frequency command circuit that determines the output frequency of the inverter (7) so as to drive the motor with (32) is the current value command circuit that determines the absolute value of the current from the torque command, and (33) is the absolute value and frequency of the current. This command value is output in the following manner in the current command synthesis circuit that gives the current to be output from the inverter (7) as an instantaneous value across each phase.

R phase I _1R = I ₁ sin ω ₀ t S phase I _1S = I ₁ sin (ω ₀ t + 2 / 3π) T phase I _1T = I ₁ sin (ω ₀ t + 4 / 3π) Also, (34) is the above command current. In contrast, a current detector that detects the current (motor current) actually output from the inverter (7) for each phase, (35) is a comparator that compares the current command value with the actual measurement value, and (36) is this comparator. A well-known PWM that controls the transistor of the inverter (7) according to the output of the comparator
(Pulse width control) device. Further, (37) is a preset voltage command value, (38) is a comparator, and (39) is a transistor base drive circuit.

In the above configuration, when the elevator is started, the output of the compensating element (16) generates a power running torque command, so in this case, the elevator is operated by a known control device. If the braking torque command is generated from the compensation element (16) before the deceleration process, the absolute value of the current according to the torque command is output from the current value command circuit (32), and it is necessary from the motor speed. Frequency command is output from the frequency command circuit (31). Therefore, the current command synthesizing circuit (33) synthesizes these and outputs the command value of the output current of the inverter (7) (current that should flow to the motor). This value is compared with the actual current, and the PWM device (36) controls the transistor of the inverter (7) so that a current close to the command value is passed.

On the other hand, in this embodiment, the regenerated electric power is returned, but when the electric power is returned to the DC side, the DC side voltage rises. This DC voltage is compared with a predetermined DC voltage command value (37) with a comparator (38), and if the DC voltage is high, the transistor (6) is made conductive through the transistor base drive circuit (39). Regenerative power is consumed by the resistor (5).

That is, in the above embodiment, the speed command signal (14)
When the torque command signal from the compensating element (16) changes from positive to negative when the deceleration command is issued by the torque control device (30), the torque control device (30) is also controlled based on the switching control of the switching means (29). ), The torque of the electric motor (8) is controlled by the torque command signal according to the deviation between the speed command signal (14) and the speed signal of the electric motor (8), and the speed command signal (14) does not output the deceleration command. If the torque command becomes negative, the current value command circuit (32) controls the amplitude command of the primary current of the electric motor (8) based on the torque command signal based on the switching control of the switching means (29). With
The frequency command circuit (31) generates a frequency command based on the speed signal so that the electric motor (8) does not generate regenerative electric power, thereby controlling the braking torque, thereby requiring a braking torque for deceleration of the elevator. In this case, the regenerative electric power is consumed in the electric motor (8) within the range where the heat generation of the motor is allowable, and is consumed by the regenerative resistor (5) beyond that, and the speed command signal (14) generates the deceleration command. The electric motor (8) remains in the braking state until the car stops, and the electric motor does not become in the power running state immediately before the stop, so that the riding comfort is not deteriorated.

Here, if the torque command signal becomes negative while the speed command signal (14) does not issue the deceleration command, that is, if the torque command signal becomes negative when the speed command issues the acceleration or constant speed command. This state occurs when the car is under a light load and is rising, or when the car is under a heavy load and is descending. At this time, the speed command signal (14) generates a deceleration command and the car The motor (8) remains in the braking state until the motor stops (the torque command signal becomes negative), and as shown in FIG. 6, the motor (8) does not power until immediately before the stop. Even if the control by the circuit (31) and the current value command circuit (32) is used, the riding comfort does not deteriorate.

In this way, in the method in which all the regenerative power generated during braking of the electric motor (8) is consumed inside the electric motor (8), the magnetic flux of the electric motor (8) has a ratio of rated voltage / rated frequency to the electric motor (8). In the method of controlling almost constant, it becomes smaller than that in the case of power running. Therefore, when the electric motor (8) is once braked and the control for consuming all the regenerated electric power inside the electric motor (8) is performed, even after that, the electric motor (8) becomes power running and the normal control is performed. Since the magnetic flux of the electric motor (8) is very small, and the magnetic flux has a first-order lag of the second-order time constant of the electric motor (8), the magnetic flux has a normal value during power running, that is, the rated voltage and the rated frequency of the electric motor (8). It cannot immediately return to the magnetic flux when given. In other words, the power running torque is not immediately generated, and as a result, when the electric motor (8) is in power running immediately before the stop as shown in FIG. 6, the electric motor (8) actually generates the running torque. Is delayed, the car speed suddenly becomes zero at this time, and the speed command signal (14)
As described above, the vehicle cannot be smoothly decelerated and the riding comfort is deteriorated. However, in the above-described embodiment, when the electric motor (8) is braking for the first time during deceleration, the electric motor (8) becomes power running again immediately before the stop. In such a case, even if the electric motor (8) is braked, the control of consuming all the regenerated electric power inside the electric motor (8) is not performed, and the deterioration of the riding comfort can be prevented. In the method in which the torque of the electric motor (8) is given by the product of the magnetic flux and the electric current, and the regenerative power is consumed inside the electric motor (8), the regenerative electric power is consumed by the primary and secondary resistances of the electric motor. As a result, when the same braking torque is generated, the magnetic flux of the motor is smaller in this system than in the system in which the voltage / frequency ratio to the motor (8) is controlled to be substantially constant.

〔The invention's effect〕

As described above, according to the present invention, the switching control of the switching means is performed even when the torque command signal changes from positive to negative when the torque command signal is positive and in the deceleration range of the car. Based on the above, the first means controls the torque of the electric motor by the torque command signal according to the deviation between the speed command signal and the speed signal of the electric motor, and makes the torque command negative when the speed command signal does not give the deceleration command. In this case, based on the switching control of the switching means, the second means generates a frequency command such that the electric motor does not generate regenerative electric power based on the speed signal to control the braking torque. When braking torque is required when decelerating, the regenerative power is consumed within the motor within the range where the heat generation of the motor is allowable, and the regenerative power is consumed by the regenerative resistance and the speed command is reduced. Motor until the car generates a command to stop much becomes braking state, without the motor until just before stopping is powering state, thus ride rather than deteriorate, the size of the apparatus can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control device for an AC elevator according to an embodiment of the present invention, FIGS. 2 and 3 are for explaining the principle of the present invention, and FIG. 2 is an equivalent circuit diagram of an electric motor. Three
The figure is a slip characteristic curve diagram, and Fig. 4 is the configuration diagram of the conventional example, the fifth diagram.
4 is a torque characteristic curve diagram of the electric motor of FIG. 4, and FIG. 6 is a speed correspondence curve diagram of the torque command. In the figure, (3) is a converter, (5) is a resistor, (6) is a transistor, (7) is an inverter, (8) is an electric motor,
(13) is a generator for speedometer, (16) is compensation element, (29) is switching means, (30) is torque control device, (31) is frequency command circuit, (32) is current value command circuit, ( 33) is a current command synthesis circuit, (36) is a pulse width controller, (38) is a comparator,
(39) is a transistor base drive circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A system in which a DC power source is connected to an inverter to convert DC power into AC power of variable voltage and variable frequency, and the converted AC power drives an induction motor to drive a car. A first means for controlling the torque of the electric motor by a torque command signal according to a deviation between a speed command signal and a speed signal of the electric motor, the regenerative power consumption device connected to the DC power supply, based on the torque command signal Second means for controlling the braking torque by controlling the amplitude command of the primary voltage or the primary current of the electric motor and generating a frequency command such that the electric motor does not generate regenerative electric power based on the speed signal, and the torque. When the torque command signal changes from positive to negative when the command signal is positive and in the deceleration range of the car, the first means is used even after that. It is with, if the speed command signal is torque command is negative in a state that does not emit deceleration command controller for an AC elevator characterized by comprising a switching means for switching to the second means.