KR20110092055A - Apparatus for dirving compressor of an air conditioner and method for driving the same - Google Patents

Abstract

PURPOSE: A device for driving a compressor of an air conditioner and a driving method thereof are provided to measure a phase compensating angle minimizing speed ripples, store it as a table, and apply compensation torque with an optimal phase compensating angle with reference to the table in operation. CONSTITUTION: A device for driving a compressor of an air conditioner comprises a motor, an inverter(220) and a control unit(230). The motor rotates a compressor. The inverter comprises a plurality of switching elements. The inverter outputs AC power with a given phase and a given amplitude by switching operation to drive the motor. The control unit detects the frequency and phase current for the compressor. The control unit reads a phase compensating angle corresponding to the frequency or the phase current. The control unit compensates the load torque of the motor using the read phase compensating angle.

Description

Apparatus for dirving compressor of an air conditioner and method for driving the same}

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

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

An air conditioner is a device that is disposed in a room, a living room, an office, or a business store to adjust a temperature, humidity, cleanliness, and airflow of an air to maintain a comfortable indoor environment.

Air conditioners are generally divided into one-piece and separate types. The integrated type and the separate type are functionally the same, but the integrated type integrates the functions of cooling and heat dissipation to install a hole in the wall of the house or hang the device on the window. On the side, an outdoor unit that performs heat dissipation and compression functions was installed, and two separate devices were connected by refrigerant pipes.

Meanwhile, a motor is used in an air conditioner such as a compressor and a fan, and a driving device for driving the air conditioner is used. The motor driving device receives a commercial AC power, converts the DC voltage into DC voltage, converts the DC voltage into commercial AC power having a predetermined frequency, and supplies the same to the motor, thereby controlling a motor such as a compressor or a fan.

It is an object of the present invention to provide a method of applying a compensation torque having an optimum phase compensation angle that can minimize the speed ripple of a motor driving a compressor of an air conditioner.

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

According to another embodiment of the present invention, a method for controlling a compressor drive 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 compressor motor; Reading a phase compensation angle corresponding to the frequency or phase current; And compensating for 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 compensation torque having an optimum phase compensation angle capable of minimizing the speed ripple of the motor.

1 is a schematic diagram of an air conditioner according to the present invention.
2 is a circuit diagram illustrating a compressor driving apparatus of an air conditioner according to an embodiment of the present invention.
3 to 6 illustrate a method of controlling a compressor driving apparatus according to an embodiment of the present invention.
7 is a graph in which the phase current of the motor is fixed to an arbitrary value and the optimum phase compensation angle for each frequency is measured while changing the frequency of the motor according to one embodiment of the present invention.
8 is a graph in which an optimal phase compensation angle is measured for each phase current while fixing the frequency of the motor to an arbitrary value and changing the phase current of the motor according to one embodiment of the present invention.
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. 8.
11 is a flowchart illustrating a method of compensating load torque at an optimal phase compensation angle according to 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 diagram of an air conditioner according 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) for compressing a refrigerant, a compressor driving device (2b) for driving a compressor, an outdoor side heat exchanger (4) for dissipating a compressed refrigerant, An outdoor blower 5 disposed on one side of the outdoor heat exchanger 4 and including an outdoor fan 5a for promoting heat dissipation of the refrigerant and a driving device 5b for rotating the outdoor fan 5a, and expanding the condensed refrigerant Expansion mechanism (6), cooling / heating switching valve (10) for changing the flow path of the compressed refrigerant, and accumulator for temporarily storing the gasified refrigerant to remove moisture and foreign matter and supplying a refrigerant of a constant pressure to the compressor ( 3) and the like.

The indoor unit (I) is disposed inside the indoor heat exchanger (8) performing cooling / heating functions, and the indoor fan (9a) and the indoor disposed at one side of the indoor heat exchanger (8) to promote heat dissipation of the refrigerant. And an indoor blower 9 made of a drive device 9b for rotating the fan 9a.

At least one indoor side heat exchanger (8) may be installed. The compressor 2 may be at least one of an inverter compressor and a constant speed compressor.

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

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

Meanwhile, although FIG. 1 illustrates one indoor unit (I) and one outdoor unit (O), the compressor driving apparatus of the air conditioner according to the embodiment of the present invention is not limited thereto, and includes a plurality of indoor units and outdoor units. Of course, the present invention can be applied to a multi-type air conditioner, an air conditioner having one indoor unit and a plurality of outdoor units.

2 is a circuit diagram illustrating a compressor driving apparatus 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, the compressor may vary greatly depending on the load, for example, a single rotary compressor. Various compressors are possible. Hereinafter, a driving apparatus for driving the compressor will be described using a single rotary compressor as an example.

Referring to the drawings, the driving device 200 of FIG. 2 according to an embodiment of the present invention includes a converter 210, an inverter 220, a controller 230, an input current detector A, and an output current detector. (E). In addition, the motor driving apparatus 200 of FIG. 2 may further include a reactor L, a smoothing capacitor C, a dc terminal voltage detector B, and the like.

The reactor L is disposed between the commercial AC power supply 205 and the converter 210 to perform power factor correction or step-up operation. In addition, the reactor L may perform a function of limiting harmonic currents due to the fast switching of the converter 210.

The input current detector A may detect an input current i _s input from the commercial AC power supply 205. To this end, a current sensor, CT (current trnasformer), shunt resistor, or the like can be used. The detected input current i _s is a discrete signal in the form of a pulse and may 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 passed through the reactor L into a DC power source and outputs the DC power source. Although the commercial AC power supply 205 is shown as a single phase AC power supply in the figure, it may be a three phase AC power supply. The internal structure of the converter 210 also varies according to the type of the commercial AC power source 205. For example, in the case of a single phase AC power supply, 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 supply, six switching elements and six diodes may be used.

The converter 210 includes a switching element and performs a boosting operation, a power factor improvement, and a DC power conversion by a switching operation. On the other hand, the converter 210 may be made of a diode or the like to perform rectification without a separate switching operation.

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

The dc end voltage detector B may detect a dc end voltage Vdc that is both ends of the smoothing capacitor C. To this end, the dc terminal voltage detector B may include a resistor, an amplifier, and the like. The detected dc terminal voltage Vdc is detected, and the detected dc terminal voltage Vdc is a discrete signal in the form of a pulse, which estimates the input voltage v _s and generates the converter switching control signal Scc. For example, the control unit 230 may be input to the controller 230.

The inverter 220 includes a plurality of inverter switching elements, converts a smoothed DC power source into a three-phase AC power source having a predetermined frequency by on / off operation of the switching element, and outputs the same to the three-phase electric motor 250.

Inverter 220 is a pair of upper arm switching elements (Sa, Sb, Sc) and lower arm switching elements (S'a, S'b, S'c) connected in series with each other, a total of three pairs of upper and lower arms The switching elements are connected in parallel with each other (Sa & S'a, Sb & S'b, Sc & S'c). Diodes are connected in anti-parallel to each of the switching elements Sa, S'a, Sb, S'b, Sc, and 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 supply having the predetermined frequency is output to the three-phase electric motor 250.

The output current detector E detects the output current i _o flowing between the inverter 220 and the three-phase motor 250. In other words, the current flowing through the motor 250 is detected. The output current detector E may detect the output current of each phase, or may detect the output current of one or two phases by using three-phase equilibrium.

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

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

The controller 230 may estimate the position of the motor 250, that is, the position of the rotor of the motor 250, based on the output current i _o detected by the output current detector E. The rotational speed of 250 can be calculated. 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, thereby generating and outputting an inverter switching control signal Sic having a variable pulse width. .

In this way, the output current is detected without using a separate motor position detecting element or the like, the position and speed of the motor 250 are estimated according to the output current, and the feedback control is performed so that the estimated speed follows the speed command. This is called control by a sensorless algorithm. The control operation by the sensorless algorithm may not be performed at the time of initial startup of the motor 250, but may be performed when the rotation speed of the motor 250 is greater than or equal to a predetermined value.

On the other hand, the control unit 230, according to the embodiment of the present invention, controls to drive the motor in accordance with a constant speed command, and controls to drive the motor 250 in accordance with this constant speed command, by a sensory algorithm That is, the first and second machine angles corresponding to the speed command or the speed command and the reference speed within a predetermined range are sequentially detected by the output current i _o of the motor 250, and the first and second detected The maximum speed machine angle is calculated according to the machine angle. Among the plurality of load torque patterns calculated according to the maximum speed machine angle, an optimum load pattern table with minimum speed ripple is selected.

The controller 230 may compensate the load torque of the motor 250 according to the selected optimal load pattern table. This makes it possible to simply and significantly reduce the speed ripple due to the load torque during constant speed operation.

The controller 230 may determine whether the detected first and second machine angles are in the normal range. If it is determined not to be in the normal range, at least one of the first and second machine angles is corrected, and based on the first and second machine angles, the maximum speed machine angle under a constant speed is calculated.

For example, the controller 230 estimates the position of the rotor based on the output current i _{o of} the motor 250, thereby sequentially calculating the first and second machine angles of the motor 250. Detect. 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 machine angle can be calculated using the average of the detected first and second machine angles. On the other hand, when the magnitudes of the first and second machine angles which are sequentially detected are not sequential, it is preferable to compensate for this when the size of the first machine angle is larger than that of the second machine angle.

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

The controller 230 may also control a switching operation of the converter 210. To this end, the controller 230 may receive the dc terminal voltage Vdc detected by the dc terminal voltage detector B, 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 switching control signal for PWM.

Three-phase electric motor 250 is provided with a stator and a rotor, each phase AC power of a predetermined frequency is applied to the coil of each stator, the rotor is rotated. The type of the motor 250 may be a variety of forms, such as a brushless DC (BLDC) motor, a synchronous reluctance motor (synRM).

The three-phase electric motor 250 may be a compressor electric motor of an air conditioner. In particular, it may be a single rotary compressor with a high load fluctuation.

On the other hand, the control unit 230 is an outdoor unit control unit, it is also possible to perform further communication with the indoor unit control unit that can be disposed separately. The outdoor unit control unit receives a driving command by communication with the indoor unit control unit, and can determine a speed command value to be described later based on the received driving command.

In addition, the controller 230 of the electric motor drive device 200 of the air conditioner described above may simultaneously control the fan motor and the compressor motor 250 used in the outdoor unit.

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

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

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

4 shows the relationship between the motor torque TM and the load torque TL of the motor for a single rotary compressor. Motor torque TM refers to the torque for driving the motor, and load torque TL refers to torque due to the load applied to the motor. The motor is accelerated when the motor torque TM is greater than the load torque TL, and decelerated when the motor torque TM is less than the load torque TL. In addition, the motor torque TM must always be greater than the load torque TL in order for the motor to run in a stationary state.

As shown in FIG. 4, the motor torque TM has some ripple, but exhibits a nearly constant pattern. The load torque of the motor for a single rotary compressor shows a large amount of change, especially in a large capacity single rotary compressor.

In order to compensate for the change in the load torque, as shown in FIG. 5, a compensation torque TL ′ opposite to the load torque TL and having the same magnitude is applied. Substantially, the compensation 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 'is in the direction opposite to the load torque TL as shown in Fig. 4, and the phase should be the same. However, substantially, even after measuring the load torque TL, even if the phase current and the phase for generating the compensation torque TL 'having the same pattern as the load torque are applied, the magnitude opposite to the exact load torque TL is obtained. Compensation torque TL 'with is not generated. This is because even when a specific phase current and phase are input, the corresponding compensation torque (TL ') does not occur due to mechanical errors, electrical errors, or load changes.

In particular, the phase error of the compensation torque TL 'is often problematic. That is, as shown in FIG. 6, even when the phase current and the phase angle are input to apply the compensation torque TL 'for compensating the load torque TL, a phase error substantially occurs and thus the ideal compensation torque ( TL '), which is faster in phase (TL' ') or slower (TL' ''), is applied.

In the present invention, such a phase error is not calculated from the load torque TL, and the frequency and phase current values of the motor are fixed, and then the phase compensation angle that minimizes the speed ripple is measured, and this is made into a table. A method of determining the phase of the compensation torque TL 'to be applied with reference to the table is used.

That is, the phase current of the motor is fixed to an arbitrary value, and the phase compensation angle for minimizing the speed ripple is measured for each frequency while changing the frequency. Then, the frequency of the motor is fixed to an arbitrary value, and the phase compensation angle that minimizes the speed ripple of the motor is measured for each phase current value while changing the phase current of the motor. 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 phase current applied to the motor, that is, speed ripple The phase compensation angle is minimized.

7 is a graph in which the phase current of the motor is fixed to an arbitrary value and the optimum phase compensation angle for each frequency is measured while changing the frequency of the motor according to one embodiment of the present invention.

8 is a graph in which an optimal phase compensation angle is measured for each phase current while fixing the frequency of the motor to an arbitrary value and changing the phase current of the motor according to one embodiment of the present invention.

The results of FIG. 7 are tabulated in FIG. 9, and the results of FIG. 8 are tabulated in FIG. 10.

For example, when driving a compressor motor, the control unit of the compressor measures the phase current and frequency applied to the motor, detects the optimum phase compensation value corresponding to each phase current and frequency from FIG. 9 or FIG. The compensation torque TL 'is applied using the phase compensation angle.

According to an exemplary embodiment, when the optimal phase compensation angle corresponding to the phase current of the driving motor is different from the optimum phase compensation angle corresponding to the frequency, the average of the two phase compensation angles may be used.

Compressor motors produced on the same production line also exhibit different load torque characteristics when driven substantially. The method proposed in the present invention generates a table representing the relationship between the phase current and frequency and the optimum phase compensation angle for each motor in which the production is completed, and stores the table in the control unit of the compressor or a storage device that can be read by the control unit. TL) can be optimally compensated.

11 is a flowchart illustrating a method of compensating load torque at an optimal phase compensation angle according to 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, the phase compensation angle corresponding to the detected phase current and frequency is read from the stored table. In step S14, the compensation torque is generated using the read phase compensation angle. That is, the load torque is compensated for. According to an embodiment, when the phase compensation angle corresponding to the detected phase current and the phase compensation angle corresponding to the detected frequency are different, these average values may be used.

Although the present invention has been described above with reference to various embodiments, the present invention is not limited to these embodiments. Those skilled in the art will understand that various modifications can be made to the above embodiments, which are included in the scope of the present invention.

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

Claims (10)

In the compressor drive device of the air conditioner,
A motor for rotating the compressor;
An inverter having a plurality of switching elements and outputting an AC power source having a predetermined phase and a predetermined amplitude by a switching operation to drive the motor; And
And a controller for detecting a frequency and phase current of the compressor motor, reading a phase compensation angle corresponding to the frequency or phase current, and compensating for the load torque of the motor using the read phase compensation angle. . The method of claim 1,
And the phase compensation angle is an average of the phase compensation angle corresponding to the frequency and the phase compensation angle corresponding to the current. The method of claim 1,
The controller is configured to read 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,
And a phase compensation angle corresponding to the frequency is a phase compensation angle for minimizing a speed ripple of the motor with respect to a frequency of a specific motor while setting the phase current to a constant value. The method of claim 3,
And a phase compensation angle corresponding to the phase current is a phase compensation angle for minimizing a speed ripple of the motor with respect to a specific phase current value of the motor while setting the frequency to a constant value. In the compressor drive device control method of the air conditioner,
Detecting a frequency of the compressor motor;
Detecting a phase current of the compressor motor;
Reading a phase compensation angle corresponding to the speed or current; And
Compensating for the load torque of the motor using the read phase compensation angle. The method of claim 6,
And the phase compensation angle is an average of the phase compensation angle corresponding to the frequency and the phase compensation angle corresponding to the current. The method of claim 6,
And a phase compensation angle corresponding to the frequency or phase current is read from a table generated based on previously measured data. The method of claim 8,
And a phase compensation angle corresponding to the frequency is a phase compensation angle for minimizing a speed ripple of the motor with respect to a frequency of a specific motor while setting the phase current to a constant value. The method of claim 8,
And a phase compensation angle corresponding to the phase current is a phase compensation angle for minimizing a speed ripple of the motor with respect to a specific phase current value of the motor while setting the frequency to a constant value.

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