JPH0526953Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a device for controlling an elevator driven by an AC motor.

Some elevator cars use an induction motor as the motor to drive the car, and connect it to a variable voltage/variable frequency device using voltage type slip frequency control to control the speed. In this case, when the car is accelerated, when a heavy load is raised, or when a light load is lowered, electric power is supplied to the electric motor through the inverter, and the electric motor runs in power. However, during deceleration, when a light load increases, or when a heavy load decreases, the electric motor enters a regenerative braking state, and regenerative power flows into the inverter. This energy accumulates in the smoothing capacitor and increases this voltage, potentially destroying elements within the inverter.
Therefore, a power regeneration inverter is used to return this regenerated power to the AC side and protect the inverter, but this inevitably increases the cost of the device. In order to make this cheaper, the power regeneration inverter is omitted and the regenerated power is consumed by a resistor.

However, in high-speed, large-capacity elevators, the regenerative power is large, and large resistors must be used.
On the contrary, it becomes expensive and impractical.

This idea is to improve the above-mentioned problems.By increasing the slip of the induction motor, a part of the regenerated power is consumed inside the motor, and the resistance for consuming the regenerated power can be made smaller. The purpose is to provide a control device.

An embodiment of this invention will be described below with reference to FIGS. 1 to 4.

In the figure, 1 is a three-phase AC power supply, 2 is an electromagnetic contactor contact that is connected to power supply 1 and closes when the car 12 (described later) starts and opens when it stops, 3 is a converter connected to contact 2, and 4 is a converter. A smoothing capacitor connected to the DC side of 3 to smooth the DC output,
5 is a regenerative power control device that is connected to both ends of the smoothing capacitor 4 and generates an output when the DC side voltage rises due to regenerative power; 6 is a transistor that is controlled by the output of the control device 5; and 7 is connected in series with the transistor 6. 8 is a well-known inverter that is connected to both ends of the smoothing capacitor 4 and is composed of transistors and diodes and converts direct current into alternating current with variable voltage and frequency. A three-phase induction motor connected to the AC side of the inverter 8, 10 is a motor 9
A main cable 11 is wound around the sheave 10 and has a car 12 and a counterweight 13 connected to both ends, respectively. A main rope 14 is directly connected to the electric motor 9 and outputs a speed signal 14a. A generator for the speedometer, 15 a speed command signal, 16 an adder that outputs a deviation signal between the speed command signal 15 and the speed signal 14a, and 17 a transfer function Gs, which has the function of improving the response of the speed control system. Compensation element, 18 is a comparator that outputs an output when the output of compensation element 17 becomes negative, 19 is a switching relay that is energized by the output of comparator 18, and 19a and 19b are contacts a when switching relay 19 is energized. 20 is a gain adjuster that adjusts the gain of the output of the compensation element 17; 21 is an adder that adds the output of the contact 19a and the speed signal 14a; 22 is an adder 21; 23 is a voltage command generator that also generates a voltage command, 24 is a gain adjuster that adjusts the gain of the output of the voltage command generator 23, and 25 is a voltage command generator that generates a frequency command from the output of the voltage command generator 23. This is an inverter control device that controls the inverter 8 according to a frequency command.

Next, the operation of this embodiment will be explained.

First, the principle of this invention will be explained with reference to FIGS. 2 to 4. In order to simplify the explanation, the excitation component is omitted in FIG. 2.

In Figure 2, mechanical energy Pg and electric motor 9
The energy Pi consumed inside is as follows.

Pg=[V/Z] ²・[1-S/S]r ₂ ... Pi=[V/Z] ²・(r ₁ + r ₂ ) ... However, Z=√{ ₀ ( ₁ + ₂ )} ² + ( ₁ + ₂ ) ² ...
Here, V: AC input voltage ω ₀ : Angular velocity of AC input s: Slip of motor 9 Z: Total impedance of motor 9 r ₁ , r ₂ : Primary resistance and secondary resistance of motor 9 (primary conversion value) ₁ + ₂ : Primary leakage inductance and secondary leakage inductance (primary conversion value) of the motor 9 In the formula, the mechanical energy Pg is the slip s
When is positive, it is equal to the mechanical output, and when it is negative, it is equal to the mechanical input, or regenerative energy. Now, the ratio η between the regenerated energy and the energy consumed by the winding inside the electric motor 9 is given by the formula: η=P ₁ /Pg=[r ₁ +r ₂ /r ₁ ]・[s/1−s ]......

FIG. 3 is a graph of the equation with the slip s on the horizontal axis and the ratio η on the vertical axis. In this figure, it can be seen that the absolute value of the ratio η increases with the absolute value of the slip s both in the region of s>0 and in the region of s<0. At s=1, η
=∞, indicating that the mechanical output is zero when the electric motor 9 is started. Furthermore, it can be seen that when s=-r ₂ /r ₁ , η=-1, that is, all the regenerative energy is consumed inside the electric motor 9. Therefore, if we control so that s=-r ₂ /r ₁ at all times,
All of the regenerated power will be consumed by the electric motor 9, and the resistor 7 will be unnecessary. However, in this case, Z = ω ₀ ( ₁ + ₂ ) from the formula, and the torque T of the electric motor 9 changes the angular velocity of the electric motor 9 by ω = ω ₀
Assuming (1-s)..., and calculating from the formula, T=K・Pg/ω=K[V/Z] ²・[1-s/s]・r ₂
/ω (However, K is a constant proportional) =KV ² /ω ₀ ² ( ₁ + ₂ ) ²・r ₂ /ω ₀ s =KV ³ /ω ₀ ³・r ₂ / ( ₁ + ₂ ) ² ...... , S=-r ₂ /r ₁ , even if V/ω ₀ is constant, the torque T is inversely proportional to ω ₀ and becomes nonlinear, resulting in poor controllability. Also, electric motors generally have r ₁
≒r ₂ , so when S=-r ₂ /r ₁ , S≒-1, which is in the region of anti-characteristics on the right side of ω _s2 in Figure 4, which also reduces controllability. I understand that. Therefore, smooth control becomes difficult, resulting in an unfavorable ride quality of the car 12.

Therefore, this improvement measure will be explained below.
Figure 4 shows the torque characteristics when the applied voltage V and the applied frequency ω ₀ of the motor are constant, where ω ₀ is the synchronous angular velocity, and ω _s1 and ω _s2 are the synchronous angular velocity when the motor is running and when braking, respectively. shows the motor rotational angular velocity when stall torque is generated. As is clear from this figure, when the rotational angular velocity of the motor is between ω _s1 and ω _s2 , the torque of the motor is equal to the slip angular velocity ω _s ,
That is, it can be seen that it is approximately proportional to the difference between the synchronous angular velocity ω ₀ and the rotational angular velocity ω of the motor. This is the formula,
This will be explained using a formula. Generally, when the rotational angular velocity of the electric motor is between ω _s1 and ω _s2 , r ₂ /s >> r ₁ ,
r ₂ /s >> ω ₀ (1 ₁ +1 ₂ ) holds true. From this, Z=(r ₂ /s) shown in the formula. At this time, the motor torque T is calculated from the formula: T=K・Pg/ω=KV ² /(r ₂ /s) ²・1−s/
s・r ₂ /ω =K/r ₂・sV ²・1−s/ω=K/r ₂・sV ²・1
/ω ₀ =K/r ₂・[V/ω ₀ ] ²・sω ₀ =K/r ₂・[V
/ω ₀ ] ² ω _s ω _s =sω ₀ , ω ₀ =ω/(1−s). From the equation, when the rotational angular velocity of the electric motor is between ω _s1 and ω _s2 and V/ω ₀ is controlled to be constant, the torque T of the electric motor is proportional to ω _s .

On the other hand, the relationship between the slip s and the current I flowing through the motor is I=V/Z. Here, if the voltage V and slip s are determined from the formula and formula, s=T・ω ₀・r ₂ /K・V ² . Assuming that Z=r ₂ /s is the region, from Eqs. and Eqs. becomes. From the equation, braking torque T and angular velocity ω ₀
Under certain conditions, it is clear that as the slip s increases, the current I increases. Therefore, the energy consumption within the electric motor 9 increases. It can be seen from the equation that in order to increase the slip s, the voltage V or V/ω ₀ can be decreased. That is, the larger the slip angular velocity ω _s is, the more current flows through the motor 9, and the more energy is consumed by the internal windings of the motor 9.

Therefore, if this slip angular velocity ω _s is set to a value close to ω _s2 when the motor stalls torque is generated, while maintaining the linearity of the torque T and the slip angular velocity ω _s ,
The energy consumed inside the electric motor 9 can be increased, and as a result, the energy consumed by the resistor 7 during regeneration is reduced.

In order to set this slip angular velocity ω _s to a value close to ω _s2 when the motor stalls torque is generated, V/ω ₀ expressed by the equation should be controlled to a small constant value.

However, in this case, the gain of torque T with respect to the slip angular velocity ω _s (here, the gain of torque T on the right side of the equation
(value of V/ω ₀ ) ² ) decreases, so the open loop gain of the speed control system also decreases. Therefore, it is necessary to correct this gain.

Now, when a starting command is issued to the car 12, the electromagnetic contactor contact 2 is closed, and the converted AC power is supplied to the electric motor 9 via the converter 3, smoothing capacitor 4, and inverter 8. The electric motor 9 is now activated and the car 12 runs. The deviation signal between the speed command signal 15 and the speed signal 14a passes through the compensation element 17 and becomes a torque command. This value is contact 1
It is added to the speed signal 14a by the adder 21 via the adder 9a, and a frequency command is generated from the frequency command generator 22. On the other hand, the output of the adder 21 is input to the voltage command generator 23, where a voltage command is generated and output via the contact 19b. Based on these voltage commands and frequency commands, the inverter control device 25
controls the inverter 8, and its output voltage and frequency are adjusted. With this, the speed of the electric motor 9, that is, the traveling speed of the car 12, is automatically controlled with high precision.

When the electric motor 9 is in a regenerative operation state, the speed signal 14a is larger than the speed command signal 15, and the output of the adder 16 becomes negative. Now, comparator 18
emits an output, the switching relay 19 is energized, and the contacts 19a and 19b are switched from contact a to contact b.

Therefore, the slip angular velocity ω _s of the motor, which is the output of the compensation element 17, is adjusted by the gain adjuster 20 and input to the adder 21 via the contact 19a. Then, the output of the voltage command generator 23 is lowered by the gain adjuster 24 compared to during power running. Therefore, V/ω ₀ = a constant value is lower than during power running. As this V/ω ₀ becomes smaller, as is clear from the equation, the torque relative to ω _s becomes smaller, so the gain adjuster 20 adjusts the torque. Since ω _s is increased in a range approximately proportional to ω _s to compensate for the torque, the power consumed within the motor increases. On the other hand, when the voltage of the smoothing capacitor 4 increases due to the inflow of regenerative power, the regenerative power control device 5
produces an output, transistor 6 conducts, and resistor 7
Regenerative power is allowed to flow in through the However, as described above, since the regenerated power is consumed by the electric motor 9, the amount consumed by the resistor 7 is reduced, and the resistor 7 can be small. or,
If the value of V/ω ₀ is reduced, the excitation of the motor becomes smaller, and therefore the magnetic flux density becomes lower, which also has the effect of reducing the noise of the motor.

Note that during regenerative operation, the gain adjuster 24 acts to lower the gain, and the gain of the speed control system is lowered. The gain adjuster 20 corrects this, thereby keeping the gain of the speed control system substantially constant during regenerative operation.

As explained above, this invention converts commercial AC power into DC using a converter, smooths this using a smoothing capacitor, and converts it into variable voltage/variable frequency AC power using an inverter to drive an induction motor that drives a car. When driving a motor, when the deviation signal between the speed command signal and the speed signal becomes negative, the control torque of the motor is controlled and the excitation of the motor is lowered than during power running, so a part of the regenerated power is used inside the motor. This allows the resistor for regenerative power consumption to be made smaller. Further, there is an effect that the noise of the electric motor can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of an AC elevator control device according to this invention, Fig. 2 is an equivalent circuit diagram of an induction motor showing the principle of Fig. 1, and Fig. 3 is a diagram showing the difference between consumed energy and regenerated energy. The ratio characteristic curve diagram, FIG. 4, is also a torque characteristic curve diagram. 3...Converter, 4...Smoothing capacitor, 5
...Regenerative power control device, 6...Transistor, 7
... Resistor for regenerative power consumption, 8 ... Inverter, 9
...Three-phase induction motor, 12...Cage, 14a...
Speed signal, 15...Speed command signal, 18...Comparator, 19...Switching relay (switching means), 22...
Frequency command generator, 23... Voltage command generator, 2
4...gain adjuster, 25...inverter control device.

Claims (1)

[Scope of utility model registration request] Convert commercial AC power to DC using a converter, smooth this DC using a smoothing capacitor,
This is converted into AC power by an inverter, and this inverter is controlled by a deviation signal between the speed command signal and the speed signal corresponding to the speed of the car, and the converted AC power is used to drive the induction motor to operate the car. In a control device for an AC elevator, the controller is configured to consume regenerative power through a resistor connected to the DC side of the inverter during operation and braking of the electric motor, which is in a first state when the polarity of the deviation signal is positive. , a switching means that switches to the second state when the switching means is in the first state, a power running control means that controls the power running torque of the electric motor when the switching means is in the first state, and a switching means that switches to the second state when the switching means is in the second state. is between the rotational speed of the stall torque during regenerative braking of the electric motor and the synchronous rotational speed, and within the range where the slip angular frequency and braking torque of the electric motor maintain approximately linearity, a first gain regulator that lowers the voltage applied to the motor so that the absolute value of the slip angular frequency increases; and a first gain regulator that adjusts the slip angular frequency so as to suppress an increase in the deviation signal due to the operation of the first gain regulator. 1. A control device for an AC elevator, characterized in that it is equipped with a 2-gain adjuster.