KR20210088346A - Apparatus and mothod for motor control and conditioner using the same - Google Patents

Abstract

The present invention relates to an air conditioner. According to an embodiment of the present invention, an air conditioner comprises: a link capacitor connected between an output terminal of a converter and an input terminal of an inverter; a link voltage detecting unit detecting a link voltage that is a voltage between both terminals of the link capacitor; and a control unit controlling a motor to be driven by decreasing an operating frequency of the motor according as a voltage size of the link voltage decreases. Accordingly, there is an effect for stably providing a cooling function even when an input voltage is unstable.

Description

Electric motor control device, control method, and air conditioner using the same {APPARATUS AND MOTHOD FOR MOTOR CONTROL AND CONDITIONER USING THE SAME}

The present invention relates to a motor control apparatus and control method capable of stably providing a cooling function even in an unstable state of input voltage, and an air conditioner using the same.

The air conditioner is installed to provide a more comfortable indoor environment for humans by discharging hot and cold air into the room to create a comfortable indoor environment, controlling the indoor temperature, and purifying the indoor air. In general, an air conditioner includes an indoor unit configured as a heat exchanger and installed indoors, and an outdoor unit configured as a compressor and a heat exchanger and supplying a refrigerant to the indoor unit.

Such an air conditioner is controlled separately from an indoor unit composed of a heat exchanger and an outdoor unit composed of a compressor and a heat exchanger, and is operated by controlling power supplied to the compressor or the heat exchanger. Also, at least one indoor unit may be connected to the outdoor unit, and the air conditioner may be operated in a cooling or heating mode by supplying refrigerant to the indoor unit according to a requested operating state.

In an environment in which the input voltage is unstable, the air conditioner stops the operation for a certain period of time in order to ensure the stability of the operation of the air conditioner. That is, in an environment in which the external input power is not constant, the DC link voltage in the electric motor for operating the compressor of the air conditioner is not sufficiently charged and a voltage drop occurs. In this case, the DC link voltage is sufficiently charged by forcing the air conditioner to idle for several minutes.

However, in the conventional case, there is a problem in that the idle state of the air conditioner frequently occurs in a region such as a developing country where voltage instability occurs frequently, and the cooling effect is reduced accordingly.

Patent Publication No. 10-2004-0041405 Registered Patent No. 10-1809964

SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor control apparatus and control method capable of stably providing a cooling function even in a state where an input voltage is unstable, and an air conditioner using the same.

Another object of the present invention is to provide a motor control device capable of stably operating an air conditioner even when the DC link voltage is changed within a certain range by varying the operating frequency of the motor according to the magnitude of the DC link voltage of the motor control device. and a control method, and an air conditioner using the same.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned may be understood by the following description, and will be more clearly understood by the examples of the present invention. Moreover, it will be readily apparent that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The motor control device according to the present invention is a motor control device included in an air conditioner and controlling an electric motor for driving a compressor, and includes a link capacitor connected between an output terminal of a converter and an input terminal of an inverter, and between both ends of the link capacitor. and a link voltage detection unit detecting a link voltage that is a voltage of , and a control unit controlling an operating frequency of the motor to decrease as the voltage level of the link voltage decreases to control the motor to be driven.

In addition, the controller may control the driving of the motor by dividing the link voltage based on a normal voltage and a lower limit voltage lower than the fixed voltage.

In addition, the control unit controls to drive the motor at a normal operating frequency when the link voltage is equal to or greater than the normal voltage, and when the link voltage is equal to or greater than the lower limit voltage and less than the normal voltage, the lower limit operating frequency is lower than the normal operating frequency. It can be controlled to drive the electric motor.

In addition, when the link voltage is less than the lower limit voltage, the controller may control the compressor to stop for a predetermined time and then restart the starting process.

In addition, the control unit receives the magnitude of the link voltage from the link voltage detection unit, and determines whether the link voltage belongs to any one of a normal range, a lower limit range, and an unstable range based on the normal voltage and the lower limit voltage. and a frequency setting unit configured to change the operating frequency of the motor to a normal operating frequency or a lower limit operating frequency lower than the normal operating frequency according to the range of the link voltage provided from the determining unit and the voltage determining unit.

In addition, the voltage determining unit may set the link voltage to belong to the normal range when the level of the link voltage is equal to or greater than the normal voltage, and to belong to the lower limit range when the level of the link voltage is less than the normal voltage and equal to or greater than the lower limit voltage.

The frequency setting unit may set the operating frequency as the normal operating frequency when the link voltage is within the normal range, and may set the operating frequency as the lower limit operating frequency when the link voltage is within the lower limit range.

In addition, the voltage determining unit, if the level of the link voltage is less than the lower limit voltage, sets it to belong to the unstable range, and the frequency setting unit forces the motor to an idle state for a predetermined time if the link voltage is in the unstable range can be set.

The motor control method according to the present invention is a motor control method for controlling an electric motor included in an air conditioner and driving a compressor, and a link voltage that is a voltage between both ends of a link capacitor connected between an output terminal of a converter and an input terminal of an inverter is detected. and controlling the motor to be driven by reducing the operating frequency of the motor as the voltage level of the link voltage decreases.

In addition, the controlling to drive the motor may include determining whether the link voltage belongs to any one of a normal range, a lower limit range, or an unstable range based on a normal voltage and a lower limit voltage. If the link voltage is in the normal range, The method may include setting the operating frequency as a normal operating frequency and setting the operating frequency as a lower limit operating frequency when the link voltage is within the lower limit range.

Also, the motor control method may further include setting the motor to be forced into an idle state for a predetermined time when the link voltage is in the unstable range.

An air conditioner according to the present invention includes a compressor for compressing a refrigerant, an electric motor for driving the compressor, and an electric motor control device for controlling driving of the electric motor. The motor control device includes a link capacitor connected between an output terminal of the converter and an input terminal of the inverter, a link voltage detector detecting a link voltage that is a voltage between both ends of the link capacitor, and as the voltage level of the link voltage decreases, the and a control unit for controlling the motor to drive the motor by reducing the operating frequency of the motor.

The motor control apparatus and control method according to the present invention, and an air conditioner using the same, have an effect of stably providing a cooling function even in a state in which an input voltage is unstable.

In addition, the motor control apparatus and control method according to the present invention, and the air conditioner using the same, operate by varying the operating frequency of the motor according to the magnitude of the DC link voltage of the motor control device, thereby changing the DC link voltage within a certain range. It also has the effect of stably operating the air conditioner.

In addition, the electric motor control apparatus and control method according to the present invention, and an air conditioner using the same, have an effect of preventing a decrease in cooling efficiency by removing unnecessary idle operation.

In addition to the above-described effects, the specific effects of the present invention will be described together while describing specific details for carrying out the invention below.

1 is a diagram illustrating the configuration of an air conditioner according to an embodiment of the present invention.
FIG. 2 is a view for explaining the outdoor unit and the indoor unit shown in FIG. 1 .
3 is a block diagram of an apparatus for controlling an electric motor according to an embodiment of the present invention.
4 is a block diagram illustrating a control unit of the motor control device shown in FIG. 3 .
5 is a view for explaining a motor control method according to an embodiment of the present invention.
6 and 7 are diagrams for explaining a driving state by motor control according to an embodiment of the present invention.

The above-described objects, features and advantages will be described below in detail with reference to the accompanying drawings, and accordingly, those of ordinary skill in the art to which the present invention pertains will be able to easily implement the technical idea of the present invention. In describing the present invention, if it is determined that a detailed description of a known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

Although the first, second, etc. are used to describe various elements, these elements are not limited by these terms, of course. These terms are only used to distinguish one component from other components, and unless otherwise stated, the first component may be the second component, of course.

Also, when it is described that a component is "connected", "coupled" or "connected" to another component, the components may be directly connected or connected to each other, but other components are "interposed" between each component. It is to be understood that “or, each component may be “connected,” “coupled,” or “connected” through another component.

Also, as used herein, the singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "consisting of" or "comprising" should not be construed as necessarily including all of the various components or various steps described in the specification, some of which components or some steps are It should be construed that it may not include, or may further include additional components or steps.

Hereinafter, a motor control apparatus and a control method according to some embodiments of the present invention, and an air conditioner using the same will be described.

1 is a diagram illustrating the configuration of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 1 , an air conditioner 100 according to an embodiment of the present invention includes an indoor unit 10 , at least one outdoor unit 20 connected to the indoor unit 10 , and the indoor unit 10 and the outdoor unit 20 . It may include a controller (not shown) for controlling the.

A controller (not shown) may be connected to the indoor unit 10 and the outdoor unit 20 to monitor and control the operation thereof. In this case, the controller (not shown) may be connected to a plurality of indoor units to perform operation setting, lock setting, schedule control, and the like for the indoor units. The controller (not shown) may have a structure included in the indoor unit 10 or the outdoor unit 20 . A controller (not shown) may be included in the indoor unit 10 or the outdoor unit 20 .

The air conditioner 100 is applicable to any of a stand-type air conditioner, a wall-mounted air conditioner, a ceiling-type air conditioner, and a duct-type air conditioner, but for convenience of description below, a stand-type air conditioner is used as an example. Explain.

The outdoor unit 20 selects a compressor that receives and compresses a refrigerant, an outdoor heat exchanger that exchanges heat between the refrigerant and outdoor air, an accumulator that extracts a gaseous refrigerant from the supplied refrigerant and supplies it to the compressor, and a refrigerant flow path according to the heating operation. It may include a four-way valve that In addition, it may further include a plurality of sensors, valves and an oil recovery unit.

The outdoor unit 20 operates a provided compressor and an outdoor heat exchanger to compress or heat exchange the refrigerant according to a setting to supply the refrigerant to the indoor unit 10 . The outdoor unit 20 is driven at the request of a controller (not shown) or the indoor unit 10, and as the cooling/heating capacity is changed in response to the driven indoor unit 10, the number of compressors installed in the outdoor unit 20 increases. become variable.

The indoor unit 10 is connected to the outdoor unit 20, receives a refrigerant, and discharges hot or cold air to an air conditioning target. The indoor unit 10 may include an indoor heat exchanger, an indoor unit fan, an expansion valve through which the supplied refrigerant is expanded, and a plurality of sensors.

At this time, the outdoor unit 20 and the indoor unit 10 are connected to each other through a communication line to transmit and receive data. The outdoor unit and the indoor unit are connected to a controller (not shown) through a communication line and operate under the control of the controller (not shown).

A remote controller (not shown) may be connected to the indoor unit 10 , input a user's control command to the indoor unit 10 , and receive and display status information of the indoor unit 10 . In this case, the remote controller (not shown) communicates with the indoor unit 10 by wire or wirelessly depending on the connection type. To this end, the remote controller (not shown) may include a communication module capable of transmitting or receiving data.

For example, a user may input a target temperature through a remote controller (not shown). In this case, the remote controller (not shown) receives the user input for the target temperature and transmits it to the controller (not shown).

FIG. 2 is a view for explaining the outdoor unit and the indoor unit shown in FIG. 1 .

Referring to FIG. 2 , the air conditioner 100 is largely divided into an indoor unit 10 and an outdoor unit 20 .

The outdoor unit 20 includes a compressor 102a serving to compress the refrigerant, an electric motor 102b driving the compressor, an outdoor heat exchanger 104 serving to radiate heat from the compressed refrigerant, and an outdoor heat exchanger. An outdoor blower 105 comprising an outdoor fan 105a disposed on one side of 104 to promote heat dissipation of the refrigerant and an electric motor 105b for an outdoor fan rotating the outdoor fan 105a, and expansion to expand the condensed refrigerant The mechanism 106, the cooling/heating switching valve 110 for changing the flow path of the compressed refrigerant, and the accumulator 103 for temporarily storing the vaporized refrigerant to remove moisture and foreign substances and then supplying the refrigerant at a constant pressure to the compressor etc.

The indoor unit 10 includes an indoor heat exchanger 108 for cooling, heating, or dehumidification, and an indoor fan 109a for facilitating heat dissipation of the refrigerant, which is disposed on one side of the indoor heat exchanger 108. and an indoor blower 109 including an electric motor 109b for rotating the indoor fan 109a.

At least one indoor heat exchanger 108 may be installed. Compressor 102a, various compression methods such as an inverter compressor and a constant speed compressor may be applied.

In addition, the air conditioner 50 may be configured as an air conditioner for cooling a room, or may be modified as a heat pump for cooling or heating the room.

Meanwhile, although FIG. 2 shows one indoor unit 10 and one outdoor unit 20, the driving device of the air conditioner according to the embodiment of the present invention is not limited thereto, and a multi-type having a plurality of indoor units and outdoor units. Of course, it is applicable to an air conditioner, an air conditioner including one outdoor unit and a plurality of indoor units.

Hereinafter, each configuration will be described based on the cooling operation of the air conditioner 100, but it is obvious to those skilled in the art that the heating operation, the dehumidifying operation, or the blowing operation are also included in the scope of the present invention.

Meanwhile, in the following description, unless otherwise specified, the compressor refers to the compressor 102a included in the outdoor unit 20 . In addition, the electric motor refers to the compressor motor 102b included in the outdoor unit 20 .

3 is a block diagram of an apparatus for controlling an electric motor for a compressor according to an embodiment of the present invention.

Referring to FIG. 3 , the compressor 102a motor control device 200 of the air conditioner 100 according to an embodiment of the present invention includes a converter 202 , an inverter 230 , an output terminal of the converter, and the inverter. It includes a link capacitor C connected between the input terminals, a link voltage detection unit 205 , a current detection unit 210 , and a control unit 260 . The motor control apparatus 200 according to an embodiment of the present invention may further include a reactor (L).

The reactor L is disposed between the commercial AC power supply and the converter 202 to perform power factor correction or step-up operation. In addition, the reactor L may perform a function of limiting the harmonic current caused by the high-speed switching of the converter 202 .

The converter 202 converts commercial AC power passing through the reactor L into DC power and outputs it. Although the drawing shows the commercial AC power as a single-phase AC power, it may also be a three-phase AC power. The internal structure of the converter 202 also varies according to the type of commercial AC power. For example, in the case of a single-phase AC power supply, a half-bridge converter in which two switching elements and four diodes are connected may be used, and in the case of a three-phase AC power supply, six switching elements and six diodes may be used. The converter 202 includes a plurality of switching elements, and performs step-up, power factor improvement, or DC power conversion by a switching operation.

The link capacitor C is connected to the output terminal of the converter 202 . It may serve to smooth the converted DC power output from the converter 202 . The voltage smoothed by the link capacitor C is input to the inverter 230 . Accordingly, since the voltage across the link capacitor C (hereinafter referred to as 'link voltage') becomes the input voltage of the inverter 230, when the voltage stored in the link capacitor C is not sufficient, the The operation may be operated incompletely. Accordingly, the control unit 230 uses the link voltage detected by the link voltage detection unit 205 to control the inverter.

The link voltage detector 205 may detect the voltage Vdc stored in the link capacitor C. To this end, the link voltage detection unit 205 may include a voltage transformer (VT) or a resistance element. The detected link voltage Vdc is provided to the controller 260 .

The inverter 230 includes a plurality of switching devices for inverters, and converts DC power smoothed by on/off operation of the switching devices into three-phase AC power of a predetermined frequency and outputs the converted power. For example, an upper-arm switching element and a lower-arm switching element connected in series with each other may be a pair, and a total of three pairs of upper-arm switching elements and lower-arm switching elements may be connected to each other in parallel.

The three-phase AC power output from the inverter 230 is applied to each phase (u, v, w) of the three-phase motor 250 . Here, the electric motor 102b is a three-phase electric motor, having a stator and a rotor, and each phase AC power of a predetermined frequency is applied to the coils of each phase, and the rotor rotates. As the type of the three-phase motor 250, various types such as a BLDC motor and a synRM motor are possible.

The controller 260 controls the inverter 230 to control the driving of the electric motor.

The controller 260 may generate and output the switching control signal Sic of the inverter based on the output current output from the inverter 230 or the link voltage detected by the link voltage detector 205 . For example, the inverter switching control signal Sic may be a pulse width modulation (PWM) switching control signal. For example, the controller 260 may control the inverter 230 through PWM duty ratio control.

The controller 260 may control the driving of the inverter 230 so that the operating frequency of the motor is varied according to the magnitude of the link voltage Vdc. This will be described in more detail below with reference to FIG. 4 .

The current detector 210 may detect the output current io flowing between the inverter 420 and the motor 102b. That is, the current flowing through the electric motor 102b is detected. For example, the output current detection unit E may detect the output currents iu, iv, iw on u, v, and w.

The current detector 210 may be positioned between the inverter 230 and the motor 102b, and a current transformer (CT), a shunt resistor, or the like may be used for detecting the current.

4 is a block diagram illustrating a control unit of the motor control device shown in FIG. 3 .

Referring to FIG. 4 , the motor control apparatus 200 for the compressor 102a includes a link voltage detection unit 205 , a current detection unit 210 , a memory 220 , an inverter 230 , and a control unit 260 .

The link voltage detector 205 may detect the voltage Vdc stored in the link capacitor C. To this end, the link voltage detection unit 205 may include a voltage transformer (VT) or a resistance element. The detected dc terminal voltage Vdc may be input to the controller 260 .

The current detector 210 senses the u-phase, v-phase and w-phase currents applied to the motor 102b. The current detector 210 may be positioned between the inverter 230 and the motor 102b, and a current transformer (CT), a shunt resistor, or the like may be used to detect the current.

The memory 220 is electrically connected to the controller 260 . The memory 220 may store basic data for the unit, control data for operation control of the unit, and input/output data. The memory 220 may be various storage devices such as ROM, RAM, EPROM, flash drive, hard drive, and the like.

The inverter 230 includes a plurality of inverter switching elements, converts the smoothed DC power (Vdc) by the on/off operation of the switching elements into three-phase AC power of a predetermined frequency, and outputs it to the three-phase motor 102b. have. The inverter 230 controls the driving of the compressor 102a through PWM duty ratio control of the power applied to the motor 102b. Here, the electric motor 102b is a three-phase electric motor, it has a stator and a rotor, and each phase AC power of a predetermined frequency is applied to the coils of each phase, and the rotor rotates. As the type of the three-phase motor 250, various types such as a BLDC motor and a synRM motor are possible.

The inverter 230 may control the driving of the compressor 102a by dividing it into a plurality of steps according to an operating frequency for driving the motor 102b. According to the control of the controller 260 , the inverter 230 may control the operating frequency by dividing the operating frequency into a plurality of ranges.

The controller 260 may control to reduce the operating frequency of the motor and drive it as the voltage level of the link voltage Vdc decreases. That is, the controller 260 may control the inverter 230 to change the operating frequency of the motor according to a change in the link voltage Vdc.

The controller 260 may control the driving of the motor by dividing the current link voltage Vdc based on a lower limit voltage lower than a normal voltage and a fixed voltage.

For example, when the link voltage Vdc is equal to or greater than the normal voltage, the controller 260 may control the motor to be driven at the normal operating frequency. Alternatively, when the link voltage Vdc is higher than the lower limit voltage and less than the normal voltage, the motor may be controlled to be driven at a lower limit operating frequency lower than the normal operating frequency.

For example, the normal voltage may be 150V, the lower limit voltage may be 130V, and the normal operating frequency may be 45Hz to 58Hz. The lower limit operating frequency may be 25 Hz. Therefore, when the link voltage Vdc is 155V, the motor may be driven at any one of 45Hz to 58Hz depending on the normal operating frequency. On the other hand, when the link voltage Vdc is 133V, the motor may be driven at 25Hz, which is the lower limit operating frequency.

On the other hand, when the link voltage (Vdc) is less than the lower limit voltage, for example, when it is 120V, the control unit 260 forcibly stops the motor, that is, the compressor, for a predetermined time so that the link voltage (Vdc) is charged and boosted. It is possible to re-perform the starting process of the motor.

As a result, when the link voltage Vdc does not reach the normal voltage but is higher than the lower limit voltage, the control unit 260 drives the motor at a lower operating frequency than normal, thereby preventing the forced idle of the motor even in an unstable state of power supply. and enable continuous operation. In addition, even when the motor is started, even when the lower limit voltage is lower than the normal voltage, the idle state of the air conditioner can be minimized by lowering the frequency of the motor to operate the compressor, so that cooling can be performed faster.

The control unit 260 may include a voltage determining unit 261 and a frequency setting unit 263 . According to an embodiment, the control unit 260 may further include a frequency detection unit 262 .

The voltage determining unit 261 receives the magnitude of the link voltage Vdc from the link voltage detection unit 205 and sets the current link voltage to any one of a normal range, a lower limit range, or an unstable range based on the normal voltage and the lower limit voltage. belonging can be determined.

For example, the voltage determining unit 261 may set the link voltage to belong to the normal range when the level of the link voltage is equal to or greater than the normal voltage, and set it to belong to the lower limit when the level of the link voltage is less than the normal voltage and equal to or greater than the lower limit voltage.

Also, the voltage determining unit 261 may set the link voltage to be within the unstable range when the level of the link voltage is less than the lower limit voltage.

The frequency setting unit 263 may set the operating frequency of the motor to be changed to a normal operating frequency or a lower limit operating frequency according to the range of the link voltage provided from the voltage determining unit 261 . Here, the lower limit operating frequency is a frequency lower than the normal operating frequency.

If the link voltage is in the normal range, the frequency setting unit 263 may set the operating frequency of the motor as the normal operating frequency, and if the link voltage is in the lower limit range, set the operating frequency of the motor as the lower limit operating frequency.

Here, the normal operating frequency may be a frequency range of a predetermined range, for example, the normal voltage is 150V, the normal range is 150V or more, and the normal operating frequency may be 45Hz to 58Hz. The lower limit voltage may be 130V, the lower limit range may be 130V or more and less than 150V, and the lower limit operating frequency may be 25Hz.

In the lower limit range in which the link voltage is lower than the normal range, the motor cannot be driven at the normal operating frequency, but the motor can be driven at a lower operating frequency lower than that.

Therefore, when the input voltage is somewhat unstable and the link voltage is not within the normal range but falls within the lower limit range, the operating range of the air conditioner is increased by lowering the idle range of the motor by lowering the frequency of the motor to drive, and thus the overall operating range of the air conditioner is increased. It can improve cooling performance.

On the other hand, when the link voltage is lower than the lower limit range, that is, in the unstable range, the driving of the motor may operate unstable, so the frequency setting unit 263 may set the motor to be forced into an idle state for a predetermined time.

Using the current detected by the current detector 210 , the frequency detector 262 may detect the current operating frequency of the motor.

The frequency setting unit 263 may change the operating frequency of the motor using the magnitude of the link voltage currently detected by the link voltage detection unit 205 and the current operating frequency detected by the frequency detection unit 262 .

For example, when the link voltage is in the lower limit range and the current operating frequency of the motor corresponds to the normal range, the frequency setting unit 263 may set the operating frequency of the motor to be changed to the lower limit operating frequency.

Alternatively, when the link voltage is in the normal range and the current operating frequency of the motor corresponds to the lower limit operating frequency, the frequency setting unit 263 may set the operating frequency of the motor to be changed to the normal operating frequency.

Alternatively, when the link voltage is in an unstable range, the frequency setting unit 263 may set the motor to be forced into an idle state for a predetermined time regardless of the current frequency state of the motor.

In the above, various examples of the air conditioner according to an embodiment of the present invention have been described with reference to FIGS. 1 to 4 . Hereinafter, a method of controlling an air conditioner according to an embodiment of the present invention will be described with reference to FIG. 5 . However, since the control method of the air conditioner to be described below is performed in the air conditioner described above with reference to FIGS. 1 to 4 , it can be easily understood with reference to the description described above with respect to FIGS. 1 to 4 .

5 is a flowchart illustrating a control method of an air conditioner according to an embodiment of the present invention.

The motor control device 200 is included in the air conditioner and controls the motor for driving the compressor.

The motor control device 200 detects a link voltage that is a voltage between both ends of a link capacitor connected between an output terminal of the converter and an input terminal of the inverter ( S510 ).

The motor control apparatus 200 may control the motor to be driven by reducing the operating frequency of the motor as the voltage level of the link voltage decreases.

For example, the motor control device 200 may determine whether the link voltage belongs to any one of a normal range, a lower limit range, or an unstable range based on the normal voltage and the lower limit voltage.

The motor control apparatus 200 may set the operating frequency of the motor to the normal operating frequency when the link voltage is equal to or greater than the normal voltage, that is, in the normal range (S520, Yes) (S541). Here, the normal operating frequency may be a frequency range of a predetermined range.

If the link voltage is lower than the normal voltage but falls within the lower limit range higher than the lower limit voltage (S530, Yes), the motor control device 200 may set the operating frequency as the lower limit operating frequency (S542).

If the link voltage is in an unstable range lower than the lower limit voltage, the motor control device 200 stops the compressor by forcing the motor to be idle for a predetermined time, and after a predetermined time has elapsed, the starting process of the motor is performed again. It can be (S543).

6 and 7 are diagrams for explaining a driving state by motor control according to an embodiment of the present invention.

FIG. 6 corresponds to a conventional control method that immediately enters an idle state when the link voltage is out of a normal range.

As shown, the link voltage 610 between both ends of the current link capacitor C is indicated by a dotted line, and the motor is driven only when the link voltage 610 is higher than the normal voltage Vnrm (611, 612). It can be seen that it is becoming

On the other hand, according to an embodiment of the present invention, when the link voltage is within the lower limit range even if it is out of the normal range, FIG. 7 shows the case of driving the motor at a low frequency (lower limit operating frequency) without immediately entering the idle state. applicable.

As shown, the link voltage 610 between both ends of the current link capacitor C is indicated by a dotted line, and when the link voltage 710 is higher than the normal voltage Vnrm, the motor is driven at the normal operating frequency ( 711, 712).

On the other hand, when the link voltage 610 is lower than the normal voltage Vnrm but higher than the lower limit voltage Vlim, the motors are driven 721 and 722 at the lower limit operating frequency.

As a result, in FIG. 7 , even when the link voltage changes, the driving range of the motor, that is, the compressor is extended, so that the air conditioner does not unconditionally enter the idle state even in a situation where the input voltage is unstable, and can operate as stable as possible. it can be seen that there is

As described above, the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed in this specification, and various methods can be obtained by those skilled in the art within the scope of the technical spirit of the present invention. It is obvious that variations can be made. In addition, although the effects according to the configuration of the present invention are not explicitly described and described while describing the embodiments of the present invention, it is natural that the effects predictable by the configuration should also be recognized.

10: indoor unit
20: outdoor unit
200: motor control device
205: link voltage detection unit
220: memory
230: inverter
260: control unit
261: voltage discrimination unit
262: frequency detection unit
263: frequency setting unit

Claims (12)

An electric motor control device included in an air conditioner and controlling an electric motor for driving a compressor, the motor control device comprising:
a link capacitor connected between an output terminal of the converter and an input terminal of the inverter;
a link voltage detector detecting a link voltage that is a voltage between both ends of the link capacitor; and
a control unit controlling the motor to be driven by decreasing the operating frequency of the motor as the voltage level of the link voltage decreases;
A motor control device comprising a.
According to claim 1, wherein the control unit
A motor control device for controlling driving of the motor by dividing the link voltage based on a normal voltage and a lower limit voltage lower than the fixed voltage.
According to claim 2, wherein the control unit
When the link voltage is greater than or equal to the normal voltage, control to drive the motor at a normal operating frequency, and when the link voltage is above the lower limit voltage and less than the normal voltage, drive the motor at a lower operating frequency lower than the normal operating frequency. Motor control unit that controls.
According to claim 2, wherein the control unit
When the link voltage is less than the lower limit voltage, the motor control apparatus controls to restart the starting process after stopping the compressor for a predetermined time.
According to claim 2, wherein the control unit
a voltage determining unit receiving the level of the link voltage from the link voltage detecting unit and determining whether the link voltage belongs to any one of a normal range, a lower limit range, or an unstable range based on the normal voltage and the lower limit voltage; and
a frequency setting unit configured to change the operating frequency of the motor to a normal operating frequency or a lower limit operating frequency lower than the normal operating frequency according to the range of the link voltage provided from the voltage determining unit;
A motor control device comprising a.
The method of claim 5, wherein the voltage determining unit
If the magnitude of the link voltage is greater than or equal to the normal voltage, it is set to belong to the normal range, and when the magnitude of the link voltage is less than the normal voltage and greater than or equal to the lower limit voltage, it is set to belong to the lower limit range.
The method of claim 6, wherein the frequency setting unit
When the link voltage is in the normal range, the operating frequency is set to the normal operating frequency, and when the link voltage is in the lower limit range, the operating frequency is set to the lower limit operating frequency.
The method of claim 5, wherein the voltage determining unit
If the magnitude of the link voltage is less than the lower limit voltage, it is set as belonging to the unstable range,
The frequency setting unit
If the link voltage is in the unstable range, the motor control device is configured to force the motor to an idle state for a predetermined time.
A motor control method for controlling an electric motor included in an air conditioner and driving a compressor, the motor control method comprising:
detecting a link voltage that is a voltage between both ends of a link capacitor connected between an output terminal of the converter and an input terminal of the inverter; and
controlling the motor to be driven by reducing the operating frequency of the motor as the voltage level of the link voltage decreases;
A motor control method comprising a.
The method of claim 9, wherein the controlling to drive the electric motor comprises:
determining whether the link voltage belongs to any one of a normal range, a lower limit range, or an unstable range based on the normal voltage and the lower limit voltage;
setting the operating frequency to a normal operating frequency when the link voltage is in the normal range; and
setting the operating frequency as a lower limit operating frequency when the link voltage is within the lower limit range;
A motor control method comprising a.
11. The method of claim 10,
setting the motor to be in an idle state for a predetermined time when the link voltage is in the unstable range;
Motor control method further comprising a.
a compressor that compresses the refrigerant;
an electric motor driving the compressor; and
Including a motor control device for controlling the driving of the motor,
The motor control device is
a link capacitor connected between an output terminal of the converter and an input terminal of the inverter;
a link voltage detector detecting a link voltage that is a voltage between both ends of the link capacitor; and
a control unit controlling the motor to be driven by decreasing the operating frequency of the motor as the voltage level of the link voltage decreases;
An air conditioner comprising a.

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