WO2009064050A2

WO2009064050A2 - Motor controller of air conditioner

Info

Publication number: WO2009064050A2
Application number: PCT/KR2008/002445
Authority: WO
Inventors: Sun Ho Hwang; Han Su Jung; Chung Hun Lee
Original assignee: Lg Electronics Inc.
Priority date: 2007-11-14
Filing date: 2008-04-30
Publication date: 2009-05-22
Also published as: WO2009064050A3; KR20090049856A

Abstract

The present invention relates to a motor controller of an air conditioner, including an inverter including a plurality of switching elements and adapted to convert input DC power into specific AC power, the inverter driving a motor including a stator coil and a rotor, output current detection means for detecting an output current flowing through the inverter, a parameter correction unit that corrects an inductance value of the motor based on the detected output current, and a microcomputer that outputs a switching control signal to drive switching elements within the inverter based on the corrected inductance value and the output current. Accordingly, accurate control can be performed by varying an inductance value, that is, a motor parameter according to an output current.

Description

MOTOR CONTROLLER OF AIR CONDITIONER

Technical Field

[1] The present invention relates to a motor controller of an air conditioner, and more specifically to a motor controller of an air conditioner, which can be controlled accurately depending on an output current. Background Art

[2] An air conditioner is an apparatus disposed in space, such as rooms, dining rooms, office rooms, and shops, and adapted to control an output current, moisture, cleaning and air stream of the air in order to maintain pleasant indoor environments.

[3] An air conditioner is generally divided into a unit type and a separate type. The unit type and the separate type are identical in terms of their functions. The unit type includes an integrated cooling and heat-dissipation function and is installed in a wall of a house or hung on a wall. In the separate type, an indoor unit having the cooling/ heating functions is installed indoors and an outdoor unit having the heat-dissipation and compression functions is installed outdoors and thereafter both the units are connected by refrigerant ducts.

[4] Meanwhile, the air conditioner uses motors in a compressor, fans, and so on and includes a motor controller for driving them. The motor controller of the air conditioner converts input commercial AC power into DC power, converts the DC power into commercial AC power having a specific frequency, and supplies the AC power to the motors in order to control the motors for the compressor, fans, and so on.

[5] To control this air conditioner, a sensorless method has been used for the purpose of saving expenses. In the case in which the motor of the air conditioner is controlled based on this sensorless method, the accuracy of control is required. Disclosure of Invention Technical Problem

[6] An object of the present invention is to provide a motor controller of an air conditioner, which enables accurate control by varying motor parameters depending on an output current. Technical Solution

[7] A motor controller of an air conditioner according to an embodiment of the present invention includes an inverter including a plurality of switching elements and adapted to convert input DC power into specific AC power, the inverter driving a motor including a stator coil and a rotor, output current detection means for detecting an output current flowing through the inverter, a parameter correction unit that corrects an inductance value of the motor based on the detected output current, and a microcomputer that outputs a switching control signal to drive switching elements within the inverter based on the corrected inductance value and the output current.

[8] A motor controller of an air conditioner according to an embodiment of the present invention includes an inverter including a plurality of switching elements and adapted to convert input DC power into specific AC power, the inverter driving a motor including a stator coil and a rotor, output current detection means for detecting an output current flowing through the inverter, a parameter correction unit that corrects an inductance value of a motor based on current command values, and a microcomputer that outputs a switching control signal to drive switching elements within the inverter based on the corrected inductance value and the output current. Advantageous Effects

[9] A motor controller of an air conditioner in accordance with an eirbodiment of the present invention can correct motor parameters depending on an output current. Accordingly, a control operation within the controller, as well as velocity estimation, can be performed accurately.

[10] Further, a motor controller of an air conditioner in accordance with an embodiment of the present invention can improve the accuracy of control by correcting motor parameters depending on current command values. Brief Description of the Drawings

[11] FIG. 1 is a schematic view of an air conditioner pertinent to the present invention;

[12] FIG. 2 is a block diagram showing a motor controller of an air conditioner in accordance with an eπi>odiment of the present invention;

[13] FIG. 3 is a graph showing the relationship between an output current and an inductance value;

[14] FIG. 4 is an internal block diagram of a microcomputer of FIG. 2;

[15] FIG. 5 is a block diagram showing a motor controller of an air conditioner in accordance with an embodiment of the present invention; and

[16] FIG. 6 is an internal block diagram of a microcomputer of FIG. 5.

Mode for the Invention

[17] Hereafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [18] FIG. 1 is a schematic view of an air conditioner pertinent to the present invention.

[19] Referring to the drawing, an air conditioner 50 is largely divided into an indoor unit

I and an outdoor unit O.

[20] The outdoor unit O includes a compressor 2 functioning to compress refrigerant, a motor 2b for the compressor for driving the compressor, an outdoor-side heat exchanger 4 functioning to dissipate heat of compressed refrigerant, an outdoor ventilation fan 5, including an outdoor fan 5a disposed on one side of the outdoor heat exchanger 5 and configured to accelerate heat dissipation of refrigerant and a motor 5b for rotating the outdoor fan 5a, an expansion mechanism 6 for expanding condensed refrigerant, a cooling/heating switching valve 10 for switching the flow passage of compressed refrigerant, an accumulator 3 for temporarily storing vaporized refrigerant, removing moisture and alien substance from the refrigerant and supplying refrigerant of a specific pressure to the compressor, and so on.

[21] The indoor unit I includes an indoor-side heat exchanger 8 disposed indoor and performing a cooling/heating function, an indoor ventilation fan 9 disposed on one side of the indoor-side heat exchanger 8 and including an indoor fan 9a for accelerating heat dissipation of refrigerant and a motor 9b for rotating the indoor fan 9a, and so on.

[22] At least one indoor-side heat exchanger 8 can be installed. The compressor 2 can employ at least one of an inverter compressor and a constant speed compressor. Further, the air conditioner 50 can be constructed as a cooling device for cooling the indoor or a heat pump for cooling or heating the indoor.

[23] Meanwhile, the motor in the motor controller of the air conditioner in accordance with an embodiment of the present invention can be each of motor 2b, 5b,and 9b for operating the compressor, the outdoor fan, and the indoor fan.

[24] FIG. 2 is a block diagram showing the motor controller of the air conditioner in accordance with an embodiment of the present invention and FIG. 3 is a graph showing the relationship between an output current and an inductance value.

[25] Referring to FIGS. 2 and 3, the motor controller 200 of the air conditioner in accordance with an errbodiment of the present invention includes an inverter 220, a microcomputer 230, a parameter correction unit 270, and output current detection means E. The motor controller 200 may further include a converter 210, a reactor L, a smoothing capacitor C, and so on.

[26] The reactor L is disposed between cαrmercial AC power and the converter 210 and performs power factor correction or a boosting operation. The reactor L can also function to limit the harmonic current through high-speed switching of the converter 210.

[27] The converter 210 converts the commercial AC power, passing through the reactor

L, into DC power and outputs converted DC power. Although, in the drawing, the commercial AC power has been illustrated as single-phase AC power, it may be three- phase AC power. An internal configuration of the converter 210 may vary depending on the type of commercial AC power. For example, in the case of single-phase AC power, a half-bridge type converter having two switching elements and four diodes connected may be used. In the case of three-phase AC power, six switching elements and six diodes may be used. The converter 210 includes a plurality of switching elements and performs a boosting operation, power factor improvements and DC power conversion through the switching operation.

[28] The smoothing capacitor C is connected to the output terminal of the converter 210 and functions to smooth converted DC power output from the converter 210. The output terminal of the converter 210 is hereinafter referred to as a dc terminal or a dc link terminal. The DC voltage smoothed at the dc terminal is applied to the inverter 220.

[29] The inverter 220 includes a plurality of inverter switching elements. The inverter

220 converts the smoothed DC power into commercial AC power having a specific frequency through the on/off operations of the switching elements and outputs the converted AC power. More specifically, an upper arm switching element and a lower arm switching element, which are connected in series, forms one pair. A total of three pairs of the upper and lower arm switching elements are connected in parallel.

[30] The three-phase AC power output from the inverter 220 is applied to each phase of a three-phase motor 250. The three-phase motor 250 is equipped with a stator and a rotor. Each phase AC power having a specific frequency is applied to the coils of the stator of each phase, so that the rotor is rotated. Types of the three-phase motor 250 can be various such as an induction motor, a BLDC motor, and a synRM motor.

[31] The output current detection means E detects an output current i flowing through the motor 250. The output current detection means E may be located between the inverter 220 and the motor 250. The output current detection means E may employ a current sensor, a current transformer (CT), a shunt resistor or the like for current detection in order to detect current. Further, the output current detection means E may be a shunt resistor having one terminal connected to each of the three lower arm switching elements of the inverter 220. The detected output current i is input to the microcomputer 230 in order to generate a switching control signal Sc. [32] The detected output current i is also input to the parameter correction unit 270 and used to correct motor parameters depending on the detected output current i .

[33] The parameter correction unit 270 corrects motor parameters depending on the detected output current i . The motor parameters can be divided into mechanical parameters of a motor and electrical parameters of a motor. The motor parameters can include an inductance value L , an equivalent resistance value R of a motor, equivalent a a inductance L of a motor, and so on. a

[34] In an eirbodiment of the present invention, the inductance value L of the motor a parameters are corrected depending on an output current. An electrical equation of a motor, which is related to the electrical parameter of the motor, is expressed by the following Equation 1. [35] MathFigure 1

L- ,,dai±--

V 'aa == F ^f^Ua'iaa + + e

[36] where V denotes a terminal voltage, R denotes the equivalent resistance, L a a a denotes the equivalent inductance, i is current, and e denotes counter electromotive a force. [37] Meanwhile, referring to FIG. 3, the inductance value L has a decreasing value as a the output current i detected in the output current detection means E increases. The parameter correction unit 270 corrects the inductance value L depending on the output a current i by employing this characteristic. Meanwhile, correction of the inductance value L depending on the output current i is also possible through a calculation a o operation, but not limited thereto. Such correction of the inductance value L a depending on the output current i is also possible by employing a previously stored look-up table. [38] A motor parameter Sv including the corrected inductance value L is input to the a microcomputer 230 and used to generate a switching control signal Sc. [39] The microcomputer 230 can output the switching control signal Sc in order to control the inverter 220. The switching control signal Sc is a switching control signal for PWM and is generated based on the output current i detected in the output current detection means E and the motor parameter Sv including the corrected inductance value La.

[40] A detailed operation of the microcomputer 230 is described later on with reference to FIG. 4. [41] Meanwhile, the motor controller 200 of the air conditioner in accordance with an eirbodiment of the present invention may further include dc terminal voltage detection means for detecting a dc terminal voltage across the smoothing capacitor C. The detected dc terminal voltage is used to generate a converter switching control signal to control the switching operation of the converter. Here, the converter switching control signal can be generated in the same microcomputer as the microcomputer 230, but may be generated in a microcomputer different from the microcomputer 230.

[42] FIG. 4 is an internal block diagram of a microcomputer of FIG. 2.

[43] Referring to the drawing, the microcomputer 230 includes an estimation unit 405, a current command generator 410, a voltage command generator 420, and a switching control signal output unit 430.

[44] The estimation unit 405 estimates a rotor velocity v of the motor based on the detected output current i and the corrected inductance value La. The velocity estimation algorithm is based on the above Equation 1. The velocity v is estimated by employing this algorithm. The velocity v of the rotor can be estimated accurately by correcting the inductance value, which varies depending on a change of an output current.

[45] The current command generator 410 generates d,q-axis current command values i ,

_* ^d i based on the estimated velocity v and a velocity command value v*. For example, q the current command generator 410 may include a PI controller (not shown) for

_{* *} generating the d,q-axis current command values i , i based on the estimated velocity d q v and the velocity command value v*, and a d,q-axis current command limit unit (not shown) for limiting the levels of the d,q-axis current command values i , i so that the

• . ^d i d,q-axis current command values i , i do not exceed specific values. d i [46] The voltage command generator 420 generates d,q-axis voltage command values v

_{* * *}

, v based on the d,q-axis current corrmand values i , i and a detected output d q d q current i . For example, the voltage command generator 420 may include a PI

⁰ . _* controller (not shown) for generating the d,q-axis voltage command values v ,v

. . ^d 9 based on the d,q-axis current command values i , i and the detected output current i , d q o and a d,q-axis voltage command limit unit (not shown) for limiting the levels of the

_{* *} d,q-axis voltage command values v ,v so that the d,q-axis voltage command values v * . ^d i

,v do not exceed specific values. d q

[47] The switching control signal output unit 430 outputs the switching control signal

_{* *}

Sc based on the d,q-axis voltage command values v , v in order to drive the inverter d q switching elements. The switching control signal Sc is applied to the gate terminals of the inverter (220) switching elements and controls on/off of the inverter switching elements. [48] Meanwhile, it has been shown in the drawing that the output current i is input to the voltage command generator 420, but the present invention is not limited thereto. The output current i may be a value that has been transformed into rotating reference frames of the d,q axes.

[49] FIG. 5 is a block diagram showing a motor controller of an air conditioner in accordance with an eirbodiment of the present invention.

[50] Referring to the drawing, the motor controller 500 of the air conditioner in accordance with an embodiment of the present invention includes an inverter 520, a microcomputer 530, a parameter correction unit 570, and output current detection means E. The motor controller 500 of the air conditioner in accordance with an eirbodiment of the present invention may further include a converter 510, a reactor L, a smoothing capacitor C, and so on.

[51] The motor controller 500 of the air conditioner of FIG. 5 is almost similar to the motor controller 200 of the air conditioner of FIG. 2. That is, the converter 510, the inverter 520, the microcomputer 530, the output current detection means E, the reactor L, and the smoothing capacitor C have the same functions as those of FIG. 2. Hereinafter, description is given on the basis of a difference between the motor controller 500 of FIG. 5 and the motor controller 200 of FIG. 2.

[52] The output current detection means E detects an output current i flowing through a motor 550, as described with reference to FIG. 2. However, the detected output current i is not input to the parameter correction unit 570 but only to the microcomputer 530.

[53] The parameter correction unit 570 corrects motor parameters depending on the current comrand values i , i generated from a microcomputer 530 to be described d q later on. In particular, in an embodiment of the present invention, the inductance value

_{* *}

L f the motor parameters is corrected according to the current command values i , i an o _f d q

. For example, the inductance value L can be corrected according to an amount I of

♦ * a * * ♦ the current command values i , i . The amount I of the current command values i , i d q d q can be calculated by the following Equation 2. [54] MathFigure 2

_*

[55] Snilarly to FIG. 3, the inductance value L decreases as the amount I of the a current command values increases. The parameter correction unit 570 corrects the inductance value L such that the inductance value L decreases as the amount I of the a a current conmand values increases by employing this characteristic. Meanwhile, correction of the inductance value L depending on the amount I of the current a command values is also possible through a calculation operation, but not limited

_* thereto. Such correction of the inductance value L depending on the amount I of the a current command values is also possible by employing a previously stored look-up table. [56] The motor parameter Sv including the corrected inductance value La is input to the microcomputer 530 and used to generate the switching control signal Sc. [57] The microcomputer 530 can output the switching control signal Sc in order to control the inverter 520. The switching control signal Sc is a switching control signal for PWM and is generated based on the output current i , detected in the output current detection means E, and the motor parameter Sv including the corrected inductance value L . a

[58] A detailed operation of the microcomputer 530 is described later on with reference to FIG. 6.

[59] Meanwhile, the motor controller 500 of the air conditioner in accordance with an eirbodiment of the present invention may further include dc terminal voltage detection means for detecting a dc terminal voltage across the smoothing capacitor C. The detected dc terminal voltage is used to generate a converter switching control signal to control the switching operation of the converter. Here, the converter switching control signal can be generated in the same microcomputer as the microcomputer 530, but may be generated in a separate microcomputer from the microcomputer 530.

[60] FIG. 6 is an internal block diagram of a microcomputer of FIG. 5.

[61] Referring to the drawing, the microcomputer 530 of FIG. 6 has the same constituent elements as those of the microcomputer 230 of FIG. 4. That is, the microcomputer 530 of FIG. 6 includes an estimation unit 605, a current command generator 610, a voltage command generator 620, and a switching control signal output unit 630.

[62] The estimation unit 605, the current command generator 610, the voltage command generator 620, and the switching control signal output unit 630 have the same operations as those of FIG. 4. However, the current command generator 610 outputs generated current command values i , i to the parameter correction unit 570 as well d q as to the voltage command generator 620. Accordingly, accurate estimation of the velocity v and subsequent accurate control of the inverter are made possible. [63] While the invention has been described in connection with the embodiments with reference to the accompanying drawings, it will be understood that those skilled in the art can implement the technical constructions of the present invention in various forms without departing from the technical spirit or indispensable characteristics of the present invention. Therefore, the above-described erribodiments should be construed to be illustrative and limitative from all aspects. Furthermore, the scope of the present invention is defined by the appended claims rather than the above detailed description. Thus, the present invention should be construed to cover all modifications or variations induced from the meaning and range of the appended claims and their equivalents. Industrial Applicability

[64] The motor controller of the air conditioner in accordance with the present invention can be employed to correct motor parameters depending on an output current.

[65]

Claims

[1] A motor controller of an air conditioner, comprising: an inverter including a plurality of switching elements and adapted to convert input DC power into specific AC power, the inverter driving a motor including a stator coil and a rotor; output current detection means for detecting an output current flowing through the inverter; a parameter correction unit that corrects an inductance value of the motor based on the detected output current; and a microcomputer that outputs a switching control signal to drive switching elements within the inverter based on the corrected inductance value and the output current. [2] The motor controller of the air conditioner according to claim 1, wherein the parameter correction unit corrects the inductance value such that an amount of the inductance value decreases as the detected output current increases. [3] The motor controller of the air conditioner according to claim 1, wherein the parameter correction unit comprises a look-up table in which an amount of the inductance value is previously stored according to the detected output current. [4] The motor controller of the air conditioner according to claim 1, wherein the microcomputer comprises: an estimation unit that estimates a velocity based on the corrected inductance value and the output current; a current command generator that generates current command values based on the estimated velocity and a velocity corrmand value; a voltage command generator that generates a voltage corrmand value based on the current command values and the output current; and a switching control signal output unit that outputs the switching control signal to drive the switching elements within the inverter based on the voltage command value. [5] A motor controller of an air conditioner, comprising: an inverter including a plurality of switching elements and adapted to convert input DC power into specific AC power, the inverter driving a motor including a stator coil and a rotor; output current detection means for detecting an output current flowing through the inverter; a parameter correction unit that corrects an inductance value of a motor based on current ccrrmand values; and a microcomputer that outputs a switching control signal to drive switching elements within the inverter based on the corrected inductance value and the output current. [6] The motor controller of the air conditioner according to claim 5, wherein the parameter correction unit corrects the inductance value such that an amount of the inductance value decreases as the detected output current increases. [7] The motor controller of the air conditioner according to claim 5, wherein the parameter correction unit comprises a look-up table in which an amount of the inductance value is previously stored according to the current command values. [8] The motor controller of the air conditioner according to claim 5, wherein the microcomputer comprises: an estimation unit that estimates a velocity based on the corrected inductance value and the output current; a current command generator that generates current cαnmand values based on the estimated velocity and a velocity ccrrmand value; a voltage command generator that generates a voltage command value based on the current command values and the output current; and a switching control signal output unit that outputs the switching control signal to drive the switching elements within the inverter based on the voltage conmand value.