KR20190059362A - Control method and apparatus for electric motor - Google Patents

Abstract

Disclosed are an electric compressor and a control method thereof and, more specifically, to an electric compressor and a control method thereof, wherein the control method comprises the following steps of: primarily reducing a speed of an electric motor after receiving a stop command; and secondarily reducing a current flowing to the electric motor. Accordingly, noise generated when components collide with each other by rotary inertia is reduced and, at the same time, durability of the components is improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electric compressor,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric compressor, and more particularly, to an electric compressor that suppresses noise generated after receiving a stop command of an electric compressor and improves the durability of the component, and a control method thereof.

The car has a car air conditioner to control the temperature of the car interior. The automotive air conditioner includes an electric compressor. The electric compressor includes a system that sucks refrigerant and discharges high-pressure refrigerant through a compression unit. The compression unit of the motor-driven compressor is driven through an electric motor. The electric motor controls the torque of the motor through the inverter and adjusts the rotation speed. That is, when the compression section rotates, the compression load of the refrigerant is formed due to the pressure of the discharge port through which the refrigerant is discharged.

However, such an electric compressor is disadvantageous in that operational noise is generated when the electric compressor is stopped. More specifically, in order to stop the motor compressor in operation, the motor is stopped by interrupting the current applied to the motor, which is provided in the motor compressor. In this case, when the rotation torque of the motor of the motor compressor is momentarily lost, Noise and vibration are generated due to the momentary impact between the mechanical components of the motor-driven compressor, which is moving due to the load and the inertia.

In the case of an electric compressor used in a car air conditioner, normal control is performed such that the electric compressor is repeatedly turned on / off when a set target temperature is reached. In this case, for example, There is a problem that the noise is repeated due to the impact caused by the inertia between the parts due to the above-described reasons, and thus the performance of the motor-driven compressor is affected.

1 is a graph showing noise caused by repetition of operation and stop of a conventional motor-driven compressor.

As shown in FIG. 1, it can be seen that the noise of the motor-driven compressor is increased at the operation stop time T2 after the operation start time T1. This is an impact noise due to the inertia between the parts due to the stop of the motor, as described above.

In addition, there is a problem that the passengers in the car are irritated by the noise and vibration generated in the electric compressor and are very uncomfortable. The drawback of this problem is that the ride environment and the comfort of the vehicle are significantly deteriorated.

Accordingly, it is an object of the present invention to solve the above-mentioned problems, and it is an object of the present invention to solve the above problems by providing a motor control apparatus for a motor vehicle in which a speed of an electric motor is firstly reduced after receiving a stop command, And to improve the durability of components, and a control method therefor.

According to another aspect of the present invention, there is provided a control method for an electric compressor including an electric motor controlled by a control unit, the control method comprising: a deceleration control step of decelerating a rotation speed of the electric motor by the control unit after receiving a stop command; And reducing the current flowing to the electric motor by the control unit.

In the deceleration control step, a current larger than the magnitude of the current applied to the electric motor before the stop command is received may be applied by the controller.

Also, in the deceleration control step, a current larger than the magnitude of the current applied to the electric motor before the stop command is received is applied by the control unit, so that the torque of the electric motor can be increased.

In the deceleration control step, the rotational speed of the electric motor may be reduced by the control unit.

In the deceleration control step, the synchronous frequency of the current applied to the electric motor by the control unit may be gradually reduced.

An initial deceleration information calculation step of calculating initial deceleration information of the electric motor based on the electric motor rotation speed, the phase current applied to the electric motor, and the allowable stop time of the predetermined electric motor before the stop command is received from the controller And the deceleration control step may decelerate the electric motor by the control unit based on the initial deceleration information.

Also, the initial deceleration information may include an initial deceleration current, an initial deceleration synchronization speed, and an initial deceleration synchronization angle applied to the electric motor.

A deceleration discrimination step of discriminating whether the rotational speed of the electric motor has reached a target rotational speed and an initial decelerating current, an initial decelerating synchronizing speed and an initial decelerating synchronizing angle applied to the electric motor, and repeating the decelerating control step Time deceleration information calculation step.

Also, in the decreasing current performing step, the magnitude of the final decelerating current applied to the electric motor in the deceleration control step may be reduced by the controller.

Further comprising an initial decrease current information calculation step of calculating a decrease current applied to the electric motor during a predetermined allowable stop time based on a magnitude of a final deceleration current applied to the motor in the deceleration control step, The reduction current performing step includes:

The control unit may decrease the current applied to the electric motor based on the decrease current calculated in the initial decrease current information calculation step.

A reduction current discrimination step of discriminating whether a deceleration current applied to the electric motor has reached a target deceleration current, a real time reduction current information calculation step of calculating a reduction current applied to the electric motor, As shown in FIG.

In order to achieve the above object, the present invention provides an electric compressor having an electric motor controlled by a control unit, comprising: a control unit for decelerating a rotational speed of the electric motor after receiving a stop command, And an electric motor.

Also, the control unit may apply a current larger than a current applied to the electric motor before decelerating the rotational speed of the electric motor before the stop command is received.

The control unit may control the motor so that the deceleration rate at the time of decelerating the rotation speed of the electric motor is constantly reduced.

According to the motor compressor and the control method of the present invention described above, after the stop command is received, the speed of the electric motor is reduced, and then the electric current flowing through the electric motor is reduced. It is possible to suppress the noise generated while hitting and improve the durability of the parts, and in particular, in the case of an electric vehicle, there is an effect that the noise sensitive to a quiet room can be remarkably reduced.

1 is a graph showing noise caused by repetition of operation and stop of a conventional motor-driven compressor.
FIG. 2 is a graph showing the rotational speed of an electric motor to which a stopping logic is applied to a conventional electric compressor and the amount of current applied to the electric motor.
3 is a flowchart illustrating a method of controlling an electric compressor according to an embodiment of the present invention.
4 is a graph showing the rotational speed of an electric motor driven by the control method of the electric compressor of the present invention and the phase current applied to the electric motor.
5 is a perspective view showing an electric motor having a clearance.

For a better understanding of the present invention, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. The embodiments of the present invention may be modified into various forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. The present embodiments are provided to enable those skilled in the art to more fully understand the present invention. Therefore, the shapes and the like of the elements in the drawings can be exaggeratedly expressed to emphasize a clearer description. It should be noted that in the drawings, the same members are denoted by the same reference numerals. Further, detailed descriptions of well-known functions and configurations that may be unnecessarily obscured by the gist of the present invention are omitted.

The control method of the motor-driven compressor according to the present invention is designed to catch noise caused by movement of components due to inertia during operation of the motor. The motor-driven compressor according to the present invention includes an electric motor A step of decelerating a rotational speed of the electric motor, and a step of reducing a current flowing to the electric motor secondarily after the motor is provided. The control method may be implemented by a control unit provided on one side of the air conditioner of the vehicle.

In order to easily understand the contents of the present invention, the electric motor is operated by a three-phase current. Meanwhile, the electric motor to which the present invention is applied needs to be able to sense the position, speed, and the like of the rotor of the electric motor. To provide a separate sensor, there is a problem of electric motor size and cost increase. Thus, recently, the electric compressor has no sensor, and senses the position and speed through the sensorless operation.

In addition, the present invention performs the motor stopping logic 100 even when receiving a normal stop command as well as an emergency stop condition for stopping the motor, that is, preventing damage due to high temperature or impact.

FIG. 2 is a graph showing the rotational speed of an electric motor to which a stopping logic is applied to a conventional electric compressor and the amount of current applied to the electric motor.

For example, as shown in FIG. 2, when the stop condition is satisfied, a stop command is received from the control unit, and the current applied to the instantaneous electric motor is momentarily blocked. This is the same as the conventional stopping method, and the part having a certain clearance (refer to FIG. 5) associated with the motor is hit by the rotational inertia to generate noise. Especially in the case of an electric vehicle, it causes inconvenience in a quiet interior.

FIG. 2 is a diagram showing only three phase currents applied to a three-phase AC motor in order to facilitate understanding of the invention. This is also applied to the example of FIG. 4 to be described later.

3 is a flowchart illustrating a method of controlling an electric compressor according to an embodiment of the present invention.

As shown in FIG. 3, when the stop command of the electric motor is received during the operation of the electric motor, the controller performs the motor stop logic 100. The motor stop logic 100 includes a step of largely decelerating the speed of the electric motor and a step of reducing the current flowing in the electric motor thereafter. That is, it is possible to flexibly reduce the inertia by flexibly reducing the speed of the electric motor in the first place. When the rotational speed of the electric motor is secondarily decreased to zero, the electric current flowing in the electric motor To reduce the amount.

More specifically, the motor stop logic 100 performed by the control unit includes an initial deceleration information calculation step 110 for calculating a current applied to the electric motor so as to decelerate the rotation speed of the electric motor based on initial information of the electric motor. A deceleration control step (120) for gradually decelerating the speed of the electric motor; A deceleration discrimination step (130) for discriminating whether deceleration of the electric motor is completed to a certain level; A real-time deceleration information calculation step (140) for calculating a current applied to the electric motor in real time for deceleration of the electric motor; An initial reduced current information calculation step (150) for calculating a reduced current to reduce the current applied to the initial electric motor after deceleration of the electric motor; A step 160 of gradually reducing the current applied to the electric motor; A decreasing current discrimination step 170 for discriminating whether the current applied to the electric motor has been reduced and a real time reduced current information calculation step 180 for calculating the decreasing current in real time to reduce the current applied to the electric motor.

The configuration of the control method of the motor-driven compressor according to the present invention will now be described in detail with reference to FIG.

4 is a graph showing the rotational speed of an electric motor driven by the control method of the electric compressor of the present invention and the phase current applied to the electric motor.

- initial deceleration information calculation step 110,

First, in the initial deceleration information calculation step 110, before the deceleration control of the rotational speed of the electric motor is performed, the rotational speed of the electric motor at the time of receiving the stop command from the controller, the phase current applied to the electric motor, Calculate the initial deceleration information of the electric motor based on the allowable stop time of the motor. The initial deceleration information of the motor includes an initial decelerating current, an initial decelerating synchronizing speed and an initial decelerating synchronizing angle applied to the electric motor after receiving the stop command for linear deceleration of the electric motor.

In this case, in the initial deceleration information calculation step 110, the initial deceleration current may be determined through a pre-calculated deceleration current table using the peak value of the phase current flowing through the electric motor at the time of receiving the stop command from the controller . At this time, the initial deceleration current has a larger value than the phase current at the time of receiving the stop command from the control section, and the deceleration current table may be previously determined (may vary depending on the capacity or type of the electric motor) by the experiment and stored in the control section. Further, the determined deceleration current may be kept constant until the deceleration control is completed.

In this case, if the electric motor is provided with a separate sensor as described above, the above-described calculation step is not necessary. However, the present invention takes into consideration a case where no separate sensor is provided in the electric motor.

On the other hand, before the stop command is received from the control unit, the rotational speed of the electric motor driven by the sensorless logic and the rotational speed of the electric motor can be calculated without the sensor by the phase current applied to the electric motor. That is, when controlling the electric motor before the stop command is received, it is not necessary to provide a separate sensor, and both the rotational speed of the electric motor and the position of the rotor can be calculated. Therefore, Motor control is possible.

- deceleration control step 120,

In the deceleration control step 120, the control unit applies a current to the electric motor based on the initial deceleration current, the initial deceleration synchronizing speed, and the initial deceleration synchronizing angle calculated in the initial deceleration information calculating step 110.

More specifically, as shown in FIG. 4, in this deceleration control step 120, linear deceleration control is performed on the rotational speed of the electric motor. When a stop command is received from the control unit, the calculated initial deceleration current And applies deceleration control to the motor. In this case, in this step, a current larger than the current applied to the motor is applied to the motor before the stop command is received, and at the same time, the synchronous frequency of the current, that is, the synchronous speed is controlled to be gradually decreased.

On the other hand, before the stop command is received, as described above, the angular position of the motor rotor can be calculated by the sensorless logic based on the rotational speed of the motor being driven and the phase current applied to the motor. However, the angular position of the rotor of the motor calculated by the sensorless logic is based on the current flowing in the motor. If the amount of current flowing as the rotation speed of the motor decreases, tracking is performed at each position of the rotor of the motor Which is extremely difficult.

Therefore, in order to overcome the shortcomings of the sensorless logic, the deceleration control step 120 tracks the position of the rotor by using the sensorless method described above, so that current is not flowed to the electric motor, The current is applied to pull the rotor of the motor strongly by the magnetic force of the magnetic field by the current to prevent the step-out.

Further, in the deceleration control step 120, as the electric motor rotates at a low speed, a torque corresponding to the movement of the electric motor is required. Particularly in the case of the electric compressor, when the discharge and compression of the refrigerant are repeated, Therefore, even if the rotational speed of the electric motor is the same, a difference in torque required for rotation due to repetition of the discharge and extrusion of the scroll is generated. Therefore, in this step, It is necessary to synchronize the rotational speed by applying a larger torque to the reduced rotational speed of the motor. On the other hand, if the current applied to the electric motor and the rotation of the motor are not synchronized, there is a problem that the phase lag phenomenon may occur and cause a louder noise.

As a result, the deceleration control step 120 of this step controls the generation theta of the motor. At this time, since the position of the rotor of the electric motor can not be detected, a larger phase current value is allowed to flow, It is possible to prevent out-of-phase. In this step, since it is difficult to calculate the real-time rotor position through the sensorless logic, deceleration is performed by controlling the synchronous rotation angle of the rotor of the motor in order to prevent noise when the motor stops.

- deceleration discrimination step (130)

In the deceleration determining step 130, it is determined whether the rotational speed of the motor has reached the target rotational speed. If it is determined that the rotational speed has reached the deceleration determining step 130, the reduction current calculating step 150 is performed. 140). In this case, the target rotation speed is preferably zero.

- real-time deceleration information calculation step 140,

In the real-time deceleration information calculation step 140, when the deceleration discrimination step 130 determines that the electric motor does not reach the target rotation speed, the deceleration synchronization speed and the deceleration synchronization angle of the electric motor are calculated again based on the electric current flowing in the electric motor And the deceleration control step 120 is repeatedly performed. That is, in the initial deceleration information calculation step 110, the deceleration synchronization speed value is calculated through the motor speed through the sensorless logic and the stop allowable time upon receipt of the stop command. In this step, the sensorless logic is not used, And calculates the deceleration synchronization angle of the motor based on the information. The calculated current value is again applied to the electric motor in the deceleration control step (120).

In this case, it may be implemented as a pulse width modulation (PWM) control that performs deceleration control until the rotational speed of the electric motor reaches the target rotational speed.

- initial reduction current information calculation step 150,

The initial reduction current information calculation step 150 is a step of calculating a reduction current to be applied to the motor by using a predetermined allowable stop time based on the final deceleration current after the deceleration control of the electric motor is completed.

- the step of performing the decreasing current (160)

In the decreasing current performing step 160, the final synchronizing angle position of the motor is maintained, and at the same time, the current amplitude is gradually reduced to the motor. If the current applied to the motor is momentarily blocked, even if the rotational speed of the motor is the target speed and there is almost no rotational movement, the magnetic field applied to the motor instantaneously disappears, so that not only the rotor but also other motors related to the motor An impact due to the inertia of the component of the full drive unit may be generated and noise may be generated.

Therefore, in this step, the magnitude of the current applied to the motor is gradually reduced for a predetermined allowable time, thereby gradually reducing the magnetic field applied to the synchronous angle position of the electric motor. Accordingly, it is possible to remove the mechanical impact on the parts of the electric motor, thereby reducing the physical impact generated repeatedly on / off and improving the durability of the parts.

- Decreasing current discrimination step 170:

In the decreasing current discrimination step 170, it is determined whether the deceleration current applied to the electric motor has reached the target value. If it is determined that the deceleration current has reached the completion value, the completion step 190 is performed. Step 180 is performed.

- a real-time reduced current information calculation step 180,

In the real-time reduced current information calculation step 180, when it is determined in the decreasing current determination step 170 that the electric motor does not reach the target reduced current value, the reduced current is calculated again, and the reduced current performing step 160 is repeated .

Accordingly, a current of a reduced magnitude for each control loop is updated and applied to the final stopped synchronous angle position through the deceleration current and the predetermined stop permission time. That is, the reduction current control is performed until the target reduction current is reached based on the final deceleration synchronization angle.

- completion step 190,

In the completion step 190, the current flowing to the electric motor is finally cut off when the target decrease current is reached. For example, the output of the three-phase PWM device of the inverter connected to the electric motor is cut off. Accordingly, there is an effect that noise can be reduced by receiving the stop command from the control unit to the electric motor, and at the same time, the physical impact can be reduced to improve the durability.

The control method of the motor-driven compressor according to the present invention is performed by a control unit provided at one side of the motor-driven compressor, thereby eliminating noise caused by frequent stopping and driving of the motor, and enhancing durability of the motor.

The embodiments of the motor-driven compressor and the control method thereof according to the present invention described above are merely illustrative and those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. . Therefore, it is to be understood that the present invention is not limited to the above-described embodiments. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims. It is also to be understood that the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

100: Motor stop logic
110: initial deceleration information calculation step
120: Deceleration control step
130: deceleration discrimination step
140: Real-time deceleration information calculation step
150: initial reduction current information calculation step
160: Reduced current performing step
170: Decrease current discrimination step
180: Real-time reduction current information calculation step
190: Completion phase

Claims (14)

A control method for an electric compressor including an electric motor controlled by a control unit,
A deceleration control step (120) of decelerating the rotational speed of the electric motor by the control unit after receiving the stop command,
And a decrease current execution step (160) for reducing a current flowing in the electric motor by the control unit after the deceleration control step (120). The method according to claim 1,
The deceleration control step (120)
Wherein the control unit applies a current larger than the magnitude of the current applied to the electric motor before the stop command is received. The method of claim 2,
The deceleration control step (120)
Wherein a current larger than a magnitude of a current applied to the electric motor before the stop command is received is applied by the controller to increase the torque of the electric motor. The method according to claim 1,
The deceleration control step (120)
Wherein the rotational speed of the electric motor is constantly reduced by the controller. The method of claim 4,
The deceleration control step (120)
Wherein the synchronous frequency of the current applied to the electric motor is gradually reduced by the controller. The method according to claim 1,
An initial deceleration information calculation step of calculating initial deceleration information of the electric motor based on the electric motor rotation speed, the phase current applied to the electric motor, and the allowable stop time of the predetermined electric motor before receiving the stop command from the controller 110)
Wherein the deceleration control step (120) decelerates the electromotive motor by the control unit based on the initial deceleration information. The method of claim 6,
Wherein the initial deceleration information includes:
The initial deceleration current, the initial deceleration synchronizing speed, and the initial deceleration synchronizing angle applied to the electric motor. The method of claim 7,
A deceleration determining step (130) for determining whether the rotational speed of the electric motor has reached a target rotational speed;
And a real-time deceleration information calculation step (140) of calculating an initial deceleration current, an initial deceleration synchronization speed and an initial deceleration synchronization angle applied to the electric motor and repeating the deceleration control step (120) Way. The method according to claim 1,
The step of performing the decreasing current (160)
Wherein the control unit decreases the magnitude of the final deceleration current applied to the electric motor in the deceleration control step (120). The method of claim 9,
An initial reduction current information calculation step (150) for calculating a reduction current applied to the electric motor during a predetermined stop permission time based on a magnitude of a final deceleration current applied to the motor in the deceleration control step (120) Further comprising:
The step of performing the decreasing current (160)
Wherein the control unit reduces the current applied to the electric motor based on the reduced current calculated in the initial reduced current information calculation step (150). The method of claim 10,
A decreasing current discrimination step (170) for discriminating whether a decelerating current applied to the electric motor has reached a target decelerating current;
Further comprising a real-time reduced current information calculation step (180) of calculating a reduction current applied to the electric motor and performing the decreasing current performing step (160) repeatedly. In an electric compressor provided with an electric motor controlled by a control unit,
And a control unit for decreasing the current flowing through the electric motor after decelerating the rotational speed of the electric motor after receiving the stop command. The method of claim 12,
Wherein,
Wherein a current larger than a current applied to the electric motor is applied before decelerating the rotation speed of the electric motor before the stop command is received. 14. The method of claim 13,
Wherein,
And the deceleration speed at the deceleration of the rotational speed of the electric motor is reduced to be constant.

Images