KR102558382B1 - Apparatus and method for controlling of motor - Google Patents

Abstract

According to an embodiment of the present invention, the inverter converts the DC voltage into a three-phase AC voltage and supplies it to the motor; a detector for measuring the phase current of the motor; and a control unit controlling the inverter to apply a zero (0) vector at a phase switching time point in a synchronous acceleration section of the motor.

Description

Motor control device and method {APPARATUS AND METHOD FOR CONTROLLING OF MOTOR}

The present invention relates to a motor control apparatus and method, and more particularly, to a motor control apparatus and method applicable to a brushless direct current (BLDC) motor.

BLDC 　 motor uses a commutation circuit composed of switching elements instead of mechanical elements such as brushes and commutators. This BLDC　motor does not require replacement of brushes due to wear and is characterized by low electromagnetic interference and low driving noise.

The BLDC motor is supplied with power through a power conversion device that converts commercial AC power into pulsed multi-phase AC power (typically three-phase). The controller that controls the speed of the BLDC motor controls the rotational speed of the BLDC motor based on the phase current information of the multi-phase AC power supplied to the BLDC motor from the power converter and the position and speed information of the rotor. The control unit controls the rotational speed of the BLDC motor to follow the speed command input from the outside.

BLDC = In order to derive optimal efficiency from a motor, the position of the rotor and the timing of commutation of the phase current must be precisely matched. To this end, a device for detecting the position of the rotor is required. In general, a position detection sensor such as an encoder is used to detect the position of the rotor. Since the encoder is bulky and expensive, a method of detecting the position of the rotor using an electric circuit has been sought. As a result, the position of the rotor is detected through the zero crossing point of the counter electromotive force of the motor. Electric circuits are widely used. An operation mode in which the position of the rotor is detected using an electric circuit instead of a position detection sensor such as an encoder is referred to as a sensorless operation mode.

For the sensorless operation of a BLDC = motor, a predetermined initial startup is required prior to starting the sensorless operation. That is, system initialization is performed to initialize the inverter and control variables, and 2-phase (in the case of a 3-phase motor) is excited to forcibly align the rotor. When the alignment of the rotor is completed, the “synchronous” acceleration of the motor is performed by increasing the phase voltage and driving frequency to a preset value. When the driving frequency and phase voltage reach a certain level due to synchronous acceleration, the driving frequency is fixed and the phase voltage is varied, and the operation mode is switched to detect the zero crossing point of the counter electromotive force generated at this time. A sensorless driving mode in which the phase current is switched and the rotational speed of the motor is controlled using the zero crossing point detected in this process is implemented.

In this initial starting stage, since the actual position of the rotor is unknown due to weak counter-electromotive force, a voltage is arbitrarily applied to the stator winding to synchronously accelerate the rotor. In the synchronous acceleration section, noise is generated at the time of phase change. There is a problem.

A technical problem to be achieved by the present invention is to provide a motor control device and method capable of reducing noise generated when a phase current rapidly decreases at a phase switching time in a synchronous acceleration section.

According to an embodiment of the present invention, the inverter converts the DC voltage into a three-phase AC voltage and supplies it to the motor; a detector for measuring the phase current of the motor; and a control unit controlling the inverter to apply a zero (0) vector at a phase switching time point in a synchronous acceleration section of the motor.

The control unit may control the application of the zero vector until the phase current measured by the detection unit converges to 0 [A].

According to an embodiment of the present invention, aligning the position of the rotor by supplying current to any two phases of the motor; accelerating and rotating the rotor of the motor up to a certain speed by varying the magnitude and driving frequency of the phase voltage applied to the motor; applying a zero (0) vector by controlling an inverter at a phase switching time point; fixing the driving frequency and varying the phase voltage when the driving frequency and the voltage reach preset values; estimating rotor position information from back electromotive force information of the motor; and switching phase currents and controlling the rotational speed of the motor according to the estimated rotor position information.

The applying of the zero (0) vector may include measuring a phase current of the motor; and controlling to apply the zero vector until the measured phase current converges to 0 [A].

The motor control apparatus and method according to the present invention can reduce noise generated as the phase current rapidly decreases at the point of phase current switching in the synchronous acceleration section.

1 is a configuration diagram showing the main configuration of a motor control device according to an embodiment of the present invention.
2 is a schematic diagram of the configuration of a motor according to an embodiment of the present invention;
3 is a diagram for explaining an inverter control operation of a control unit according to an embodiment of the present invention.
4 is a diagram for explaining the operation of the motor control device according to an embodiment of the present invention.
5 is a diagram for explaining a method of detecting a position of a motor rotor according to an embodiment of the present invention.
6 is a flowchart of a motor control method according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, the technical spirit of the present invention is not limited to some of the described embodiments, but can be implemented in a variety of different forms, and within the scope of the technical spirit of the present invention, one or more of the components among the embodiments can be selectively combined, replaced, and used.

In addition, the terms (including technical and scientific terms) used in the embodiments of the present invention, unless specifically defined and described, can be interpreted in a meaning that can be generally understood by those skilled in the art to which the present invention belongs, and commonly used terms, such as terms defined in a dictionary, will be able to interpret their meaning in consideration of the contextual meaning of the related art.

Also, terms used in the embodiments of the present invention are for describing the embodiments and are not intended to limit the present invention.

In this specification, the singular form may also include the plural form unless otherwise specified in the phrase, and when described as "at least one (or more than one) of A and (and) B and C" A, B, It may include one or more of all combinations that can be combined with C.

Also, terms such as first, second, A, B, (a), and (b) may be used to describe components of an embodiment of the present invention.

These terms are only used to distinguish the component from other components, and the term is not limited to the nature, order, or order of the corresponding component.

In addition, when a component is described as being 'connected', 'coupled', or 'connected' to another component, the component may be directly connected, coupled, or connected to the other component, as well as a case where the component is 'connected', 'coupled', or 'connected' due to another component between the component and the other component.

In addition, when it is described as being formed or disposed "upper (above) or lower (below)" of each component, the upper (above) or lower (below) includes not only a case where two components are in direct contact with each other, but also a case where one or more other components are formed or disposed between the two components. In addition, when expressed as "up (up) or down (down)", it may include the meaning of not only an upward direction but also a downward direction based on one component.

Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings, but the same or corresponding components regardless of reference numerals are given the same reference numerals, and overlapping descriptions thereof will be omitted.

1 is a configuration diagram showing the main configuration of a motor control device according to an embodiment of the present invention.

Referring to FIG. 1 , a motor control device 100 according to the present invention may include an inverter 120, a detection unit 130, and a control unit 140.

In an embodiment of the present invention, the motor 110 to be controlled may have a rotor, receive power from the inverter 120 and rotate the rotor to provide rotational force. Here, the motor 110 may include a BLDC motor, and may have a three-phase winding that generates an inductance component.

That is, the BLDC motor has a structure without an insulated conductor such as a carbon brush for transmitting power. There is a magnet on the motor shaft and a coil on the inner wall of the motor case, so that the power supply for the motor to rotate is supplied to the coil attached to the non-rotating motor inner wall. As it is supplied to the coil, it does not require a brush.

2 is a structural schematic diagram of a motor according to an embodiment of the present invention. Referring to FIG. 2 , a motor according to an embodiment of the present invention may include a stator 3 and a rotor 5 .

The stator 3 may be fixed within the housing 31 constituting the outer body. The stator 3 is a driving part that creates a rotational driving force together with the rotor 5 mounted coaxially on the inside, and as a kind of electromagnet, the stator core 25 fixedly mounted on the inner circumferential surface of the housing 31 by press-fitting, etc. And the coil 33 wound around the stator core 25. The stator core 25 is a hollow cylindrical member as shown in the figure, and has a through hole through which the rotor 5 is inserted on the central axis, and a plurality of ribs protrude radially inward on the inner circumferential surface of the stator core 25 and are arranged at regular intervals in the circumferential direction to form a through hole, and the ribs extend along the axial direction of the stator core 25 to wind the coil 33.

As mentioned above, the rotor 5 is a part coaxially mounted on the inside of the stator 3 and driven to rotate, and may be rotatably inserted into the through hole in the center of the stator core 25 of the stator 3. The rotor 5 may be composed of a rotating shaft 37 arranged long along the central axis and a permanent magnet 27 attached to an outer circumferential surface of the rotating shaft 37 . The permanent magnets 27 are alternately arranged with two N poles and two S poles at 90 ° intervals around the rotation shaft 37, and the rotor 5 can be rotated and driven by interaction with the stator 3 according to the driving principle of the motor when the stator 3 is excited.

Again, referring to FIG. 1 , the inverter 120 may convert the DC voltage into a 3-phase AC voltage and supply it to the motor 110 . In the inverter 120, each of the power switching elements S1 to S6 is connected to the three-phase (U, V, and W) windings as shown in FIG. That is, the inverter 120 includes a three-phase switching element, and may include, for example, an upper three-phase FET and a lower three-phase FET.

The detector 130 may detect the phase current of the motor. In an embodiment of the present invention, the detection unit 130 may measure the phase current generated when the zero vector is applied. In addition, the detector 130 may measure counter electromotive force of each phase U, V, and W from the three-phase output terminal of the three-phase inverter 120 . The detection unit 130 may include a voltage and current detection sensor. For example, the detection unit 130 may include at least one of a current transformer and a transformer.

The control unit 140 may control the inverter to apply the zero (0) vector at the time of phase change in the synchronous acceleration section of the motor. The control unit 130 turns on all the three-phase switches at the top of the inverter 120 or turns on all the three-phase switches at the bottom of the inverter 120 to control the zero (0) vector to be applied to the motor 100.

In an embodiment of the present invention, the phase switching time point may mean a time point at which a phase for applying a phase voltage is changed. For example, during forced alignment, it may mean the time to switch to the U-W phase if the U-V phase winding is excited, or the time to excite the V-W phase winding if the U-W phase winding is excited.

In addition, the controller may control the application of the zero vector until the phase current measured by the detector converges to 0 [A]. That is, the control unit applies a zero vector by controlling the inverter from the phase change point to the point when the phase current converges to 0 [A] using the phase current measured by the detector, thereby effectively reducing noise generated at the point of phase change.

3 is a diagram for explaining an inverter control operation of a control unit according to an embodiment of the present invention.

Referring to FIGS. 1 and 3 , in the inverter 120 according to the present invention, power switching elements FETs S1 to S6 are connected to windings of three phases (U, V, and W).

At this time, the power factor correction capacitors 210 may be connected in parallel to each other on a connection line between the inverter unit 120 and the three-phase winding of the motor 110 . That is, among the three phases of the power factor correction capacitor 210 at the output terminal of the inverter 120, three may be connected in parallel between U and V phases, between V and W phases, and between W and U phases, respectively. Also, the capacitance size of the power factor correction capacitor 210 may be set to be the same as that of the inductance component of the motor 110 .

The controller 130 applies a switching driving signal of each of the power switching devices S1 to S6 to the inverter 120 . That is, the control unit 130 controls the switching operation of each switching element S1 to S6 of the inverter 120 according to the user's operation to control the start, operation and speed of the motor 110, and generates a switching drive signal for switching each switching element S1 to S6 and applies it to the inverter 120.

The controller 140 turns on all three-phase switches at the top of the inverter 120 or turns on all the three-phase switches at the bottom of the inverter 120 so that the zero vector is applied to the motor 100. Can be controlled.

In addition, the control unit 140 may estimate rotor position information from counter electromotive force information of the motor 110, and may control switching of phase current and rotation speed of the motor according to the estimated rotor position information. The control unit 140 is electrically connected to the outside of the stator to drive or stop the rotation of the rotor by disengaging the stator.

The motor control device 100 according to an embodiment of the present invention may be provided by applying a cooling fan for cooling a heat exchanger including a motor rotor provided in the motor 110 and a fan connected to a rotational shaft of the motor rotor.

4 is a diagram for explaining the operation of the motor control device according to an embodiment of the present invention.

4(a) shows a graph of phase voltages and phase currents measured according to phase transition points in the prior art. Referring to FIG. 4(a), a sudden change in phase current occurs at each phase change point, and this sudden change in phase current causes noise.

Referring to FIGS. 1 and 4(b) , the control unit 140 may control the inverter to apply a zero (0) vector at the time of phase change in the synchronous acceleration section of the motor. Referring to a portion highlighted by a red circle in FIG. 4 , the control unit 140 applies a zero vector by controlling the inverter at the time of phase conversion to excite the U-V phase in a state in which the U-W phase winding is energized. Due to the zero vector applied at the time of phase conversion, the phase current shows a relatively gentle change. Comparing FIGS. 4(a) and 4(b), it can be seen that the phase current in the comparative example to which the zero vector is not applied shows a current change close to an impulse, whereas in the example to which the zero vector is applied, the measured phase current change shows a relatively gentle slope. These differences in the embodiments can effectively reduce noise generated from the motor at the time of phase change.

5 is a diagram for explaining a method of detecting a position of a motor rotor according to an embodiment of the present invention.

Referring to FIG. 5, when the motor rotates, the counter electromotive force generated in the stator coil of each phase is extracted, and the position information of the rotor and the switching time of each phase current can be estimated using the zero crossing (ZC) point of the counter electromotive force.

In the high-speed section, the detection unit measures the voltage of the three-phase (U, V, and W) terminals to obtain the counter electromotive force, and the neutral point is calculated as the average value of the counter electromotive force, and the ZC point where the neutral point and the counter electromotive force intersect is obtained.

Since the ZC point occurs 6 times per 1 electrical rotation (360°) of the BLDC motor, it is the basis for detecting the position at 60° intervals, so the ZC point can be used to detect the position.

6 is a flowchart illustrating a control method of a brushless DC motor according to an embodiment of the present invention, and shows a control method from initial startup of the brushless DC motor to switching to a sensorless operation mode.

First, for the sensorless operation of a BLDC motor, a predetermined initial startup is required prior to starting the sensorless operation. That is, system initialization is performed to initialize the inverter and control variables (S601).

Next, current is supplied to any two phases of the motor to align the rotor position. That is, if the brushless DC motor has 3 phases, 2 of them are excited to forcibly align the rotor (S602).

Next, the magnitude of the phase voltage applied to the motor and the driving frequency are varied to accelerate and rotate the rotor of the motor up to a certain speed. That is, when the alignment of the rotor is completed, the "synchronous" acceleration of the motor is performed to increase the phase voltage and the driving frequency to a preset value (S603).

Next, when synchronous acceleration starts, phase switching is performed. For example, if the U-V phase winding is excited during forced alignment, the phase is switched to the U-W phase to excite the U-W phase winding (S604).

Next, a zero vector is applied at the time of phase change. The zero vector can be applied by turning on all three-phase switches at the top of the inverter or by turning on all the three-phase switches at the bottom of the inverter (S605).

At this time, the zero vector is applied until the phase current measured in the synchronous acceleration section becomes 0 [A] (S606).

Next, when the driving frequency and the voltage reach preset values, the driving frequency is fixed and the phase voltage is varied. That is, when the driving frequency and the phase voltage reach a certain level by synchronous acceleration, the driving frequency is fixed and the phase voltage is varied (S607).

Next, rotor position information is estimated from the counter electromotive force information of the motor. That is, position information is estimated using the zero crossing point of counter electromotive force generated when the phase voltage is varied (S608).

Next, switching of the phase current and controlling the rotational speed of the motor according to the estimated rotor position information. That is, a sensorless driving mode is implemented in which switching of phase currents and controlling the rotational speed of the motors are performed according to the rotor position information (S609).

The term '~unit' used in this embodiment means software or a hardware component such as a field-programmable gate array (FPGA) or ASIC, and '~unit' performs certain roles. However, '~ part' is not limited to software or hardware. '~bu' may be configured to be in an addressable storage medium and may be configured to reproduce one or more processors. Thus, as an example, '~unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Functions provided within components and '~units' may be combined into smaller numbers of components and '~units' or further separated into additional components and '~units'. In addition, components and '~units' may be implemented to play one or more CPUs in a device or a secure multimedia card.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be understood that it can be changed.

100: motor control device
110: motor
120: inverter
130: detection unit
140: control unit

Claims (4)

an inverter that converts DC voltage into 3-phase AC voltage and supplies it to the motor;
a detector for measuring the phase current of the motor; and
A control unit controlling the inverter to apply a zero (0) vector at a phase switching time point in a synchronous acceleration section of the motor;
wherein the control unit applies the zero vector by controlling the inverter from a point in time when phase switching is performed using the phase current measured by the detector unit to a point in time when the phase current converges to 0 [A].
delete Aligning the position of the rotor by supplying current to any two phases of the motor;
accelerating and rotating the rotor of the motor to a predetermined speed by varying the magnitude and driving frequency of the phase voltage applied to the motor;
measuring the phase current of the motor;
applying a zero vector by controlling an inverter from the point at which phase switching is performed using the phase current to the point at which the phase current converges to 0 [A]; fixing the driving frequency and varying the phase voltage when the driving frequency and the voltage reach preset values;
estimating rotor position information from back electromotive force information of the motor; and
A motor control method comprising switching a phase current and controlling a rotational speed of a motor according to the estimated rotor position information.
delete

Images