KR101694539B1 - Apparatus for dirving compressor of an air conditioner and method for driving the same - Google Patents

Abstract

The present invention relates to a method for providing a compensating torque at an optimum phase compensation angle, in particular when compensating for the load torque of a compressor of an air conditioner, in particular a single rotary compressor, which is optimized for the phase current and frequency of a given motor, That is, the phase compensation angle that minimizes the speed ripple is measured and stored as a table. In actual operation, the compensation torque having the optimal phase compensation angle can be applied with reference to the table.

Description

TECHNICAL FIELD [0001] The present invention relates to a compressor driving apparatus for an air conditioner,

The present invention relates to an apparatus for driving a compressor of an air conditioner and a driving method thereof.

More specifically, the present invention relates to a method of providing a compensating torque having an optimal phase-compensating angle when compensating for the load torque of a compressor of an air conditioner, in particular a single rotary compressor, The optimum phase compensation angle, which minimizes the speed ripple, is measured and stored as a table. In actual operation, the compensating torque with the optimal phase compensation angle can be applied with reference to the table.

The air conditioner is disposed in a room such as a room, a living room, an office or a business store, and is capable of maintaining a comfortable indoor environment by controlling the temperature, humidity, cleanliness and airflow of the air.

The air conditioner is generally divided into an integral type and a separated type. The integral type and the separate type are the same as the functional type, but the integral type is formed by integrating the functions of cooling and heat dissipation to form a hole in the wall of the house or by hanging the device on the window. Side, an outdoor unit that performs heat dissipation and compression functions is installed, and the two devices separated from each other are connected by a refrigerant pipe.

On the other hand, a motor, such as a compressor or a fan, is used in the air conditioner, and a driving device for driving the motor is used. The motor driving apparatus receives commercial AC power and converts the DC voltage into a DC voltage, converts the DC voltage into a commercial AC power of a predetermined frequency, and supplies the AC power to the motor so as to drive a motor such as a compressor or a fan.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of applying a compensating torque having an optimal phase compensation angle capable of minimizing a speed ripple of a motor driving a compressor of an air conditioner.

An apparatus for driving a compressor of an air conditioner is provided according to an embodiment of the present invention. The compressor driving device includes: a motor for rotating the compressor; An inverter having a plurality of switching elements and outputting an AC power having a predetermined phase and a predetermined amplitude by a switching operation to drive the motor; And a controller for detecting a frequency and a phase current of the motor for the compressor, reading a phase compensation angle corresponding to the frequency or phase current, and compensating for a load torque of the motor using the read phase compensation angle.

According to another embodiment of the present invention, a method of controlling a compressor driving apparatus of an air conditioner is provided. The control method includes: detecting a frequency of the motor for the compressor; Detecting a phase current of the motor for the compressor; Reading a phase compensation angle corresponding to the frequency or phase current; And compensating the load torque of the motor using the read phase compensation angle.

According to the present invention, for each air conditioner driving motor, it is possible to provide a compensating torque having an optimal phase compensation angle that can minimize the speed ripple of the motor.

1 is a schematic view of an air conditioner related to the present invention.
2 is a circuit diagram showing an apparatus for driving a compressor of an air conditioner according to an embodiment of the present invention.
3 to 6 show a method of controlling a compressor driving apparatus according to an embodiment of the present invention.
7 is a graph illustrating an optimal phase compensation angle for each frequency while fixing the phase current of the motor to a certain value and changing the frequency of the motor according to an embodiment of the present invention.
8 is a graph illustrating an optimal phase compensation angle for each phase current while fixing the motor frequency to a certain value and changing the phase current of the motor according to an embodiment of the present invention.
FIG. 9 is a table generated based on the measurement result of FIG. 7, and FIG. 10 is a table generated based on the measurement result of FIG.
11 is a flow chart illustrating a method of compensating for load torque at an optimal phase compensation angle, in accordance with an embodiment of the present invention.

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

1 is a schematic view of an air conditioner related to the present invention.

Referring to the drawings, the air conditioner 50 is largely divided into an indoor unit (I) and an outdoor unit (O).

The outdoor unit (O) includes a compressor (2) serving to compress refrigerant, a compressor drive unit (2b) for driving the compressor, an outdoor heat exchanger (4) serving to dissipate the compressed refrigerant, An outdoor fan 5 disposed at one side of the outdoor heat exchanger 4 and composed of an outdoor fan 5a for accelerating the heat radiation of the refrigerant and a drive device 5b for rotating the outdoor fan 5a, An accumulator (10) for temporarily storing the gasified refrigerant to remove water and foreign matter, and supplying refrigerant of a certain pressure to the compressor 3).

The indoor unit I includes an indoor heat exchanger 8 disposed inside the room and performing a cooling / heating function, an indoor fan 9a disposed at one side of the indoor heat exchanger 8 for promoting heat radiation of the refrigerant, And an indoor air blower 9 composed of a drive device 9b for rotating the fan 9a.

At least one indoor heat exchanger 8 may be installed. At least one of an inverter compressor and a constant speed compressor can be used as the compressor (2).

Further, the air conditioner 50 may be constituted by a cooling unit that cools the room, or a heat pump that cools or heats the room.

Meanwhile, the compressor driving apparatus of the air conditioner according to the embodiment of the present invention may be each driving apparatus 2b for operating the compressor 2 of the air conditioner as shown in the drawing.

1 shows only one indoor unit I and one outdoor unit O. However, the compressor driving apparatus of the air conditioner according to the embodiment of the present invention is not limited to this, and may include a plurality of indoor units and an outdoor unit The present invention is also applicable to an air conditioner having a multi-type air conditioner, a single indoor unit, and a plurality of outdoor units.

2 is a circuit diagram showing an apparatus for driving a compressor of an air conditioner according to an embodiment of the present invention.

The compressor driving apparatus of the air conditioner according to the embodiment of the present invention may include a motor for operating the compressor as described above. In particular, it may be a compressor having a large variation depending on a load, for example, a single rotary type compressor. A variety of compressors are possible, but in the following, a driving device for driving the compressor is described taking a single-rotary type compressor as an example.

2 according to an embodiment of the present invention includes a converter 210, an inverter 220, a control unit 230, an input current detection unit A, (E). The motor driving apparatus 200 of FIG. 2 may further include a reactor L, a smoothing capacitor C, a dc voltage detection unit B, and the like.

The reactor L is disposed between the commercial AC power supply 205 and the converter 210 to perform a power factor correcting or boosting operation. The reactor L may also function to limit the harmonic current due to the fast switching of the converter 210. [

The input current detection section A can detect the input current (i _s ) input from the commercial AC power source 205. For this, a current sensor, a current transformer (CT), a shunt resistor, or the like may be used. The detected input current i _s is a discrete signal in the form of a pulse and can be input to the controller 230 for estimation of the input voltage v _s and generation of the converter switching control signal Scc have.

The converter 210 converts the commercial AC power source 205 that has passed through the reactor L into DC power and outputs the DC power. Although the commercial AC power source 205 is shown as a single-phase AC power source in the figure, it may be a three-phase AC power source. The internal structure of the converter 210 also changes depending on the type of the commercial AC power source 205. For example, in the case of a single-phase AC power source, a half-bridge type converter in which two switching elements and four diodes are connected may be used, and in the case of a three-phase AC power source, six switching elements and six diodes may be used.

The converter 210 includes a switching element, and performs a boost operation, a power factor correction, and a DC power conversion by a switching operation. Meanwhile, the converter 210 may be a diode or the like and may perform a rectifying operation without a separate switching operation.

The smoothing capacitor C is connected to the output terminal of the converter 210. The converted DC power outputted from the converter 210 is smoothed. Hereinafter, the output terminal of the converter 210 is referred to as a dc stage or a dc link stage. At the dc stage, a smoothed direct current voltage is applied to the inverter 220.

The dc voltage detection unit B can detect the dc voltage Vdc at both ends of the smoothing capacitor C. [ For this purpose, the dc voltage detection unit B may include a resistance element, an amplifier, and the like. The dc terminal voltage Vdc detected is a dc terminal voltage Vdc that is detected is a discrete signal in the form of a pulse and is used to estimate the input voltage v _s and to generate the converter switching control signal Scc And may be input to the control unit 230.

The inverter 220 includes a plurality of inverter switching elements and converts the smoothed direct current power to a three-phase alternating current power having a predetermined frequency by the on / off operation of the switching element and outputs the three-

The inverter 220 includes a pair of upper arm switching elements Sa, Sb and Sc and lower arm switching elements S'a, S'b and S'c connected in series to each other, The switching elements are connected to each other in parallel (Sa & S a, Sb & S'b, Sc & S'c). Diodes are connected in anti-parallel to each switching element Sa, S'a, Sb, S'b, Sc, S'c.

The switching elements in the inverter 220 perform ON / OFF operations of the respective switching elements based on the inverter switching control signal Sic from the controller 230. [ As a result, the three-phase AC power source having the predetermined frequency is output to the three-phase motor 250.

An output current detector (E) detects the inverter 220 and the output current (i _o) flowing between a three-phase motor 250. That is, the current flowing in the electric motor 250 is detected. The output current detection unit E can detect all the output currents of the respective phases or can detect the output currents of one or two phases using the three-phase balance.

The output current detection unit E may be located between the inverter 220 and the motor 250. A current sensor, a current transformer (CT), a shunt resistor, or the like may be used for detecting the current. For example, one end of the shunt resistor may be connected to the three lower arm switching elements S'a, S'b, S'c of the inverter 220, respectively.

The detected output current i ₀ can be applied to the control unit 230 as a discrete signal in a pulse form and is used to estimate the input current based on the detected output current i ₀ Can be used. In addition, the detected output current (i _o) is, may be used to generate the inverter switching control signal (Sic).

Controller 230, the location of the output current (i _o) motor 250 on the basis of the detection at the output current detector (E), that is can estimate the position of the rotor of the motor 250, and the electric motor It is possible to calculate the rotation speed of the rotor 250. In addition, based on the estimated position and rotation speed, various control operations are performed to drive the motor 250 according to the speed command to generate and output an inverter switching control signal Sic having a variable pulse width .

In this manner, the output current is detected without using a separate motor position detecting element, etc., and the position and speed of the electric motor 250 are estimated in accordance with the output current, and the feedback control is performed so that the estimated speed follows the speed command This is called control by a sensor algorithm. The control operation by the sensorless algorithm can be performed from the time when the rotation speed of the electric motor 250 is equal to or greater than a predetermined value, while the electric motor 250 is not initially started.

Meanwhile, the control unit 230 controls the motor to be driven in accordance with the constant speed command, controls the motor 250 to drive in accordance with the constant speed command, The first and second mechanical angles corresponding to the speed command or the speed command and the reference speed within the predetermined range are sequentially detected by the output current i _o of the electric motor 250, Calculates the maximum speed mechanical angle according to the machine angle. Maximum speed Select an optimal load pattern table that minimizes the speed ripple among a plurality of load torque patterns calculated according to the machine angle.

The control unit 230 can compensate the load torque of the electric motor 250 according to the selected optimum load pattern table. This makes it possible to simply and significantly reduce the speed ripple due to the load torque during constant speed operation.

On the other hand, the control unit 230 can determine whether the first and second detected angles are in the normal range. Corrects at least one of the first and second machine angles, and calculates a maximum speed mechanical angle under a constant speed based on the first and second machine angles.

For example, the control unit 230 estimates the position of the rotor based on the output current ( _io ) of the electric motor 250, and accordingly, the first and second mechanical angles of the electric motor 250 are sequentially . Then, the maximum speed mechanical angle corresponding to the maximum speed ripple of the electric motor 250 is calculated using the first and second mechanical angles sequentially detected. At this time, the maximum speed mechanical angle can be calculated using the average of the detected first and second mechanical angles. If the magnitudes of the sequentially detected first and second mechanical angles are not sequential, it is preferable that the magnitude of the first mechanical angle is larger than the magnitude of the second mechanical angle.

On the other hand, the control unit 230 controls the switching operation of the inverter 220. To this end, the control unit 230, receives the output current (i _o) detected by the output current detector (E), generates the inverter switching control signal (Sic), and outputs it to the inverter 220. The The inverter switching control signal Sic may be a switching control signal for pulse width modulation (PWM).

On the other hand, the control unit 230 can also control the switching operation of the converter 210. [ The controller 230 may receive the dc terminal voltage Vdc detected by the dc terminal voltage detector B to generate a converter switching control signal Scc and output the converter switching control signal Scc to the converter 210. The converter switching control signal Scc may be a PWM switching control signal.

The three-phase motor 250 has a stator and a rotor, and alternating current power of a predetermined frequency is applied to the coils of the stator of each phase, so that the rotor rotates. As the type of the electric motor 250, various types such as a BLDC (blushless DC) electric motor and synRM (Synchronous Reluctance Motor) can be used.

The three-phase electric motor 250 may be a compressor motor for the air conditioner. In particular, it may be a single rotary type compressor with a large load fluctuation.

Meanwhile, the control unit 230 may be an outdoor unit control unit, and may further perform communication with an indoor unit control unit that can be separately arranged in the indoor unit. The outdoor unit control unit receives the operation command by communication with the indoor unit control unit, and can determine a speed command value to be described later based on the received operation command.

In addition, the controller 230 of the motor driving apparatus 200 of the air conditioner described above can simultaneously control the fan motor and the compressor motor 250 used in the outdoor unit.

3 to 6, a method of controlling a compressor driving apparatus according to the present invention will be described.

Fig. 3 shows the angular velocity change of the motor for a single rotary compressor. Ideally, the angular speed of the motor should be constant. However, as shown in FIG. 3, the speed of the motor driving the compressor is not constant but changes. That is, there is a speed ripple. The cause of velocity ripple is not known exactly but it is assumed that it is caused by various factors of surrounding environment such as load change and current size.

In order to eliminate such a speed ripple, a method of compensating the load torque is used.

Fig. 4 shows the relationship between the motor torque TM and the load torque TL of the motor for a single rotary compressor. The motor torque TM refers to the torque for driving the motor, and the load torque TL refers to the torque due to the load applied to the motor. The motor is accelerated when the motor torque TM is larger than the load torque TL and decelerated when the motor torque TM is smaller than the load torque TL. In addition, the motor torque TM must be larger than the load torque TL for the motor to be driven in the stopped state.

As shown in Fig. 4, the motor torque TM has a slight ripple, but exhibits a substantially constant pattern. The load torque of the motor for the single rotary compressor shows a large variation, and in particular, the load torque of the large-capacity single rotary compressor is greatly changed.

In order to compensate for the change in the load torque, a compensation torque TL 'equal in magnitude and opposite to the load torque TL is applied as shown in Fig. Substantially, the compensating torque TL 'can be applied by raising the motor torque TM by adjusting the magnitude and frequency of the phase current applied to the motor torque TM.

Ideally, the compensation torque TL 'should be in the opposite direction to the load torque TL as shown in Fig. 4, and its phase should be the same. However, even if the phase current and phase for generating the compensating torque TL 'having the same pattern as the load torque are applied after the measurement of the load torque TL, Lt; RTI ID = 0.0 > TL '< / RTI > This is because, even if a specific phase current and phase are input, an accurate compensation torque TL 'does not occur due to a mechanical error, an electrical error, or a load change.

In particular, the phase error of the compensation torque TL 'is substantially problematic in many cases. That is, even if the phase current and the phase angle are inputted to apply the compensating torque TL 'for compensating the load torque TL as shown in Fig. 6, substantially phase error occurs and the ideal compensating torque TL (TL '' ') or a compensation torque (TL' '') is applied.

In the present invention, the phase compensation angle at which the frequency and the phase current value of the motor are fixed and the speed ripple is minimized at that time is calculated without calculating the phase error from the load torque TL, The phase of the compensation torque TL 'to be applied is determined by referring to the table.

That is, the phase compensation angle which minimizes the speed ripple for each frequency while fixing the phase current of the motor to an arbitrary value and changing the frequency is measured. Then, the phase compensation angle that minimizes the speed ripple of the motor is measured for each phase current value while the motor frequency is fixed to an arbitrary value and the phase current of the motor is changed. Then, when driving the motor, instead of applying the compensation torque TL 'with reference to the load torque TL of the motor, the optimum phase compensation angle corresponding to the frequency and the phase current applied to the motor, that is, The phase compensation angle is minimized.

7 is a graph illustrating an optimal phase compensation angle for each frequency while fixing the phase current of the motor to a certain value and changing the frequency of the motor according to an embodiment of the present invention.

8 is a graph illustrating an optimal phase compensation angle for each phase current while fixing the motor frequency to a certain value and changing the phase current of the motor according to an embodiment of the present invention.

Fig. 9 shows the results of the measurement in Fig. 7, and Fig. 10 shows the results of the measurements of Fig.

For example, when the motor for the compressor is driven, the controller of the compressor measures the phase current and the frequency applied to the motor, detects an optimal phase compensation value corresponding to each phase current and frequency from FIG. 9 or 10, The compensation torque TL 'is applied using the phase compensation angle.

According to the embodiment, when the optimum phase compensation angle corresponding to the phase current of the driving motor and the optimal phase compensation angle corresponding to the frequency are different, an average of the two phase compensation angles can be used.

Compressor motors produced in the same production line also exhibit different load torque characteristics during operation. The method proposed in the present invention generates a table showing the relationship between the phase current and the frequency and the optimal phase compensation angle for each motor that has been produced and stores the table in a storage device readable by the control unit or the control unit of the compressor, TL) can be compensated optimally.

11 is a flow chart illustrating a method of compensating for load torque at an optimal phase compensation angle, in accordance with an embodiment of the present invention.

In step S11, the frequency of the compressor motor of the air conditioner is detected. In step S12, the phase current of the motor is detected. In step S13, a phase compensation angle corresponding to the phase current and frequency detected from the stored table is read. In step S14, the compensated torque is generated using the read phase compensation angle. That is, the load torque is compensated. In some embodiments, if the phase compensation angle corresponding to the detected phase current is different from the phase compensation angle corresponding to the detected frequency, the average value of these can be used.

Although the present invention has been described with reference to various embodiments, the present invention is not limited to these embodiments. Those skilled in the art will appreciate that various modifications may be made to the embodiments described above, and these variations are also included within the scope of the present invention.

O: outdoor unit I: indoor unit
2: compressor 2b: driving device
4: outdoor heat exchanger
5a: outdoor fan (5a) 5b: driving device
5: outdoor blower 6: expansion device
10: switching valve 3: accumulator
8: indoor heat exchanger 9a: indoor fan
9b: drive device 9: indoor blower
210: converter 220: inverter
230:

Claims (10)

A compressor driving apparatus for an air conditioner,
A motor for rotating the compressor;
An inverter having a plurality of switching elements and outputting an AC power having a predetermined phase and a predetermined amplitude by a switching operation to drive the motor; And
A controller for detecting a frequency and a phase current of the motor for the compressor, reading out a phase compensation angle corresponding to the frequency or phase current, and compensating for a load torque of the motor using the read phase compensation angle, . The method according to claim 1,
Wherein the phase compensation angle is an average of a phase compensation angle corresponding to the frequency and a phase compensation angle corresponding to the phase current.
The method according to claim 1,
Wherein the controller reads a phase compensation angle corresponding to the frequency or phase current from a table generated based on previously measured data. The method of claim 3,
Wherein the phase compensation angle corresponding to the frequency is a phase compensation angle that minimizes the speed ripple of the motor with respect to the frequency of the specific motor while setting the phase current to a constant value. The method of claim 3,
Wherein the phase compensation angle corresponding to the phase current is a phase compensation angle that minimizes a speed ripple of the motor with respect to a specific phase current value of the motor while the frequency is set to a constant value. A method for controlling a compressor driving apparatus of an air conditioner,
Detecting a frequency of the motor for the compressor;
Detecting a phase current of the motor for the compressor;
Reading a phase compensation angle corresponding to the detected frequency or phase current; And
And compensating the load torque of the motor using the read phase compensation angle.
The method according to claim 6,
Wherein the phase compensation angle is an average of a phase compensation angle corresponding to the frequency and a phase compensation angle corresponding to the phase current. The method according to claim 6,
Wherein the phase compensation angle corresponding to the frequency or the phase current is read from a table generated based on previously measured data. 9. The method of claim 8,
Wherein the phase compensation angle corresponding to the frequency minimizes the speed ripple of the motor with respect to the frequency of the specific motor while setting the phase current to a constant value. 9. The method of claim 8,
Wherein the phase compensation angle corresponding to the phase current minimizes the speed ripple of the motor with respect to a specific phase current value of the motor while the frequency is set to a constant value.

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