KR101655799B1 - Motor driver of air conditioner - Google Patents

Abstract

The present invention relates to an electric motor driving apparatus for an air conditioner. A motor driving apparatus for an air conditioner according to an embodiment of the present invention includes a filter unit for limiting harmonics of an input AC power source and a converter for rectifying AC power from the filter unit to output rectified power, A smoothing capacitor for smoothing a rectified power supply, and an inverter for receiving a direct current power from a smoothing capacitor, converting the smoothed capacitor into an alternating current power of a predetermined frequency by a switching operation of the switching element, and supplying the smoothed capacitor to the three-phase motor do. As a result, the harmonics of the input AC power can be limited.

Description

Technical Field [0001] The present invention relates to a motor driver of an air conditioner,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor driving apparatus for an air conditioner, and more particularly, to an electric motor driving apparatus of an air conditioner capable of limiting harmonics of an input AC power source.

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, in an air conditioner, a motor is used for a compressor and the like, and a motor drive device for driving the motor is used. Since the electric motor driving apparatus drives the electric motor by using a power source of several hundred V, the limitation of the harmonic current to the system may be a problem.

For each of these harmonic harmonic currents, each country has a separate regulatory approach, for example, the European Union (EU) EN 6100-3-12 has established regulations for harmonic harmonic current regulation for currents above 16 A have.

Accordingly, various attempts have been made to secure the efficiency and stability of the motor driving apparatus of the air conditioner.

An object of the present invention is to provide an electric motor drive apparatus for an air conditioner capable of limiting harmonics of an input AC power source.

Another object of the present invention is to provide an electric motor drive apparatus for an air conditioner capable of increasing the voltage of an output terminal of a converter.

According to an embodiment of the present invention, there is provided an apparatus for driving an electric motor of an air conditioner, comprising: a filter unit that limits harmonics of an input AC power source; and a diode device, A smoothing capacitor for smoothly smoothing the rectified power; and a plurality of switching elements. The smoothing capacitor is supplied with a direct current power of the smoothing capacitor and is supplied with an alternating current power of a predetermined frequency To the three-phase motor.

As described above, the motor driving apparatus of the air conditioner according to the embodiment of the present invention can limit the harmonic current of the harmonic of the input AC power source by using the filter unit, so that it can cope with the harmonic regulation.

Further, since the AC power is rectified by using a diode element which is a passive element, electromagnetic interference (EMI) such as noise due to the switching operation and the input power factor can be improved.

Further, by using the step-up capacitor, it becomes possible to step up the dc step voltage which is the output stage of the converter.

In addition, since the operation of the inverter is restricted when the input current or dc voltage is detected by the input current detection unit or the dc voltage detection unit, it is possible to protect circuit elements and the like in the drive unit.

1 is a schematic view of an air conditioner related to the present invention.
2 is a circuit diagram showing an electric motor driving apparatus of an air conditioner according to an embodiment of the present invention.
3 is a diagram illustrating frequency components of the input alternating current of FIG.
4 is a timing diagram illustrating the waveform of the input current of FIG.
5 is a timing chart illustrating the waveform of the dc step voltage in Fig.
FIG. 6 is a simplified block diagram of the control unit of FIG. 2. FIG.
7 is a circuit diagram showing an electric motor driving apparatus of an air conditioner according to another 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 (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 heat exchanger 4 and composed of an outdoor fan 5a for accelerating the heat radiation of the refrigerant and an electric motor 5b for rotating the outdoor fan 5a, An accumulator 3 for temporarily storing the gasified refrigerant to remove moisture and foreign substances, and then supplying a refrigerant of a certain pressure to the compressor, a compressor 6 for compressing the refrigerant, a cooling / heating switching valve 10 for changing the flow path of the compressed refrigerant, And the like.

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 an electric motor 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).

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

Meanwhile, the electric motor in the electric motor driving apparatus of the air conditioner according to the embodiment of the present invention may be an electric motor 2b, 5b, 9b for operating an outdoor fan, a compressor or an indoor fan as shown in the figure.

FIG. 2 is a circuit diagram showing an apparatus for driving an electric motor of an air conditioner according to an embodiment of the present invention. FIG. 3 is a diagram illustrating frequency components of an input AC current in FIG. 2, Fig. 5 is a timing chart illustrating the waveform of the dc step voltage in Fig. 2; Fig.

The motor driving apparatus 200 of an air conditioner according to an embodiment of the present invention includes a filter unit 206, a boost capacitor unit 208, a converter 210, a smoothing capacitor C, An inverter 220, a controller 230, and the like. The motor driving apparatus 200 of the air conditioner may further include an input current detection unit A, a dc voltage detection unit B, an output current detection unit E, and the like.

The filter unit 206 is disposed between the commercial AC power source and the converter 210 for removing the harmonic current. In the figure, a three-phase AC power source is exemplified as a commercial AC power source. It is also possible that the commercial AC power source is a single-phase AC power source, which will be described later with reference to FIG.

The filter unit 206 may include inductors Lf1, Lf2, and Lf3 and capacitors Cf1, Cf2, and Cf3 that are connected in parallel to each other on each phase of three-phase commercial AC power. In the figure, it is illustrated that the inductors Lf1, Lf2, Lf3 and the capacitors Cf1, Cf2, Cf3 are connected in parallel to the AC power of each phase.

 It is preferable that the inductance and the capacitance of each of the inductors Lf1, Lf2 and Lf3 and the capacitors Cf1, Cf2 and Cf3 are within a range for limiting the third harmonic or more of the commercial AC power supply. For example, if the frequency of the commercial AC power source is 50 Hz or 60 Hz, the inductance of the inductor Lf1 and the capacitance of the capacitor Cf1 may be determined according to Equation (1) below for the third harmonic limitation.

The product (Lf1Cf1) of the inductance of the inductor Lf1 and the capacitance of the capacitor Cf1 may be in the range of approximately 4 to 9 * 10 < ^-7 >. The range of the other inductors Lf2, Lf3 and the capacitors Cf2, Cf3 can also be determined within the above-described range.

On the other hand, the third harmonic, the fifth harmonic, and a seventh capacitance product of the limit to the harmonics, such as an inductor the inductance and the capacitor (Cf1) of (Lf1) (Lf1Cf1) is in the range of about 1 to 2.5 * ^10-7 Lt; / RTI >

3 illustrates that harmonics of the commercial AC power supply are limited. As described above, when the product (Lf1Cf1) of the inductance of the inductor Lf1 and the capacitance of the capacitor Cf1 is approximately in the range of 1 to 2.5 * 10 ^-7 , as shown in Fig. 3, .

Fig. 3 shows that the level with respect to the frequency component is the largest at around 60 Hz, which is the first harmonic, and that there is almost no level for the frequency components at 180 Hz as the third harmonic, 300 Hz as the fifth harmonic, and 420 Hz as the seventh harmonic For example.

As described above, by using the filter unit 206 for limiting harmonics,

It is possible to limit the harmonic current of the harmonic of the circle, and it is possible to cope with the harmonic regulation.

The step-up capacitor unit 208 includes a boost capacitor that stores at least a part of the AC power filtered through the filter unit 206 and supplies the AC power to the converter 210. In the drawing, step-up capacitors Cr1, Cr2, and Cr3 connected between two of three phases are illustrated.

Since the three-phase AC power source is supplied with an electrical angle of 120 degrees, the potential difference corresponding to the corresponding phase difference is stored using the boost capacitors Cr1, Cr2, and Cr3 connected between the two phases of the three phases. Then, at least a part of the stored potential difference is added to the AC power of each phase and supplied to the converter 210. As a result, the DC terminal voltage Vdc, which is the output terminal of the converter 210, can be boosted.

The converter 210 includes a diode element and rectifies an AC power source through the filter unit 206 and the boost capacitor unit 208 to output a rectified power source. Specifically, the pair of the upper-arm diode elements Da, Db, and Dc and the lower-arm diode elements D'a, D'b, and D'c are connected in series to each other, and three pairs of upper and lower- Are connected to each other in parallel (Da & D'a, Db & D'b, Dc & D'c).

The smoothing capacitor C is connected to the output terminal of the converter 210. From converter 210

And the output rectified power is smoothed to the direct current power. Hereinafter, the output terminal of the converter 210 is referred to as a dc stage or a dc link stage. A smoothed DC voltage on the dc stage is applied to the inverter 220.

The dc terminal voltage Vdc of the smoothing capacitor C may be harmonic limitation, power factor improvement, and boosted DC power through the filter 206, the boost capacitor 208 and the converter 210 .

The inverter 220 includes a plurality of switching elements and converts the smoothed direct current power into a three-phase alternating current power having a predetermined frequency by the on / off operation of the switching element and outputs the converted direct current power to the motor 250.

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 Sa, S'a, Sb, S'b, Sc and S'c in the inverter 220 are connected to the switching elements Sa, Sb, Sc and S'c based on the inverter switching control signal Sic from the controller 230, , S'a, Sb, S'b, Sc, S'c). For example, PWM (Pulse Width Modulation) switching is performed by the space vector on / off operation of the switching element, and a three-phase AC power having a predetermined frequency can be output to the three-phase motor 250.

The three-phase AC power outputted from the inverter 220 is applied to each phase of the three-phase motor 250. Here, the three-phase motor 250 has a stator and a rotor, and each phase alternating current power of a predetermined frequency is applied to a coil of each stator so that the rotor rotates. The three-phase motor 250 may be of various types such as a BLDC motor, a synRM motor, and an induction motor. The three-phase motor 250 may be classified into a compressor-use electric motor 2b used in a compressor of an air conditioner and a fan-use electric motor 5b or 9b for driving a fan.

On the other hand, the control unit 230 outputs the inverter switching control signal Sic to the inverter 220 to control the switching operation of the inverter. Switching control signal (Sic) is a switching control signal for PWM, it is generated based on the detected output current (i _o), which is outputted to the inverter 230. The To this end, an output current detection unit E may be provided.

An output current detector (E) detects an output current (i _o) flowing through the outdoor fan motor 250. 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 disposed between the inverter 220 and the motor 250 as shown in the figure and may be disposed between the three lower arm switching elements S'a and S 'b, S'c) connected to each end of the shunt resistor.

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). The detailed operation of the output of the inverter switching control signal Sic in the control unit 230 will be described later with reference to Fig.

Meanwhile, an apparatus for driving an electric motor 200 of an air conditioner according to an embodiment of the present invention includes an input current detector A for detecting an input current i _i from a commercial AC power source for detecting an abnormality of a converter stage, , And a dc voltage detection unit (B).

The input current detecting unit A may be located between the three-phase AC power source and the filter unit 206, but the present invention is not limited thereto. The input current detecting unit A may be disposed between the filter unit 206 and the boosting capacitor unit 208, 208 and the converter 210. As shown in FIG. For current detection, a current sensor, a current transformer (CT), a shunt resistor, or the like may be used.

Fig. 4 shows an example of the detected input current i _i . As described above, since the motor driving apparatus 200 of the air conditioner includes the filter unit 206, the third harmonic and the fifth harmonic other than the first harmonic (approximately 60 Hz) are limited.

Input current detection section (A) can be detected instantaneously by the input current (i _i), the detected input current (i _i) is applied to the controller 230.

The control unit 230 compares the detected input current i _i with a predetermined reference value to limit the operation of the inverter 220 when the detected input current i _i is determined to be either an overcurrent or a low current can do. For example, it is possible to output the switching control signal Sic to the inverter 220, or to output the switching control signal Sic to turn off all the switching elements. Further, it may be controlled to stop the supply of commercial AC power.

On the other hand, the dc short-circuit voltage detection unit B may include a resistance element or the like positioned between both ends of the dc stage.

the dc short voltage detection unit B can detect the dc short voltage Vdc on an average or momentary basis and the detected dc short voltage Vdc can be applied to the control unit 230. [

Fig. 5 shows an example of the detected dc voltage (Vdc). As described above, the dc voltage source Vdc is stably secured by the filter unit 206, the step-up capacitor unit 208, the converter 210, and the smoothing capacitor C, as described above.

The controller 230 compares the detected dc terminal voltage Vdc with a predetermined reference value to limit the operation of the inverter 220 when the detected dc terminal voltage Vdc is determined to be an overvoltage or a low voltage . For example, it is possible to output the switching control signal Sic to the inverter 220, or to output the switching control signal Sic to turn off all the switching elements. Further, it may be controlled to stop the supply of commercial AC power.

As described above, since the operation of the inverter 220 and the like in the abnormal state is restricted by using the input current detection unit A and the dc voltage detection unit B, the stability of the circuit element in the drive system 200 can be secured .

FIG. 6 is a simplified block diagram of the control unit of FIG. 2. FIG.

Referring to the drawings, the controller 230 outputs a switching control signal Sic for controlling on / off operations of the switching elements in the inverter 220. The control unit 230 includes an estimation unit 605, a current command generation unit 610, a voltage command generation unit 620, and a switching control signal output unit 630.

Estimation unit 605, on the basis of the output current (i _o) detected can be estimated speed (v) of the motor. For example, the mechanical and electric equations of the electric motor 250 can be compared with each other, and the speed v of the electric motor can be estimated accordingly.

The estimator 605 may estimate the position of the rotor based on the detected output current _io . The position of this rotor can estimate the electrical angle, or the machine angle, of the electric motor 250. The relationship between the mechanical angle and the electrical angle is normally such that the period of the mechanical angle has a relationship of the number of poles of the electric motor 250 / twice as compared with the electrical angle.

Here, θ _Me represents the mechanical angle, and θ _e represents the electrical angle. For example, if the six poles of poles of the motor 250, and has a relation of θ _Me = 3θ _e, have a relationship in a case where the number of poles of the motor 250 4 poles, θ _Me = 2θ _e.

That is, when the six poles of poles of the motor 250, the machine in each (θ _Me) 360˚, an electrical angle (θ _e) of 120˚ cycle is presented a corresponding three, four poles of poles of the electric motor 250 , Two electrical angles? _E of 180 占 cycle correspond to each other within 360 占 of the mechanical angle? _Me .

The current command generator 610 generates the current command value i ^* _d , i ^* _q based on the estimated speed v and the speed command value v ^* . For example, the current command generation section 610 performs PI control based on the difference between the estimated speed v and the speed command value v ^* to generate the current command value i ^* _d , i ^* _q . To this end, the current command generator 610 may include a PI controller (not shown). It is also possible to further include a limiter (not shown) for limiting the current command value (i ^* _d , i ^* _q ) so that it does not exceed the allowable range.

Voltage command generation unit 620 based on the detected output current (i _o) and the calculated current command value ^{_{(i * d, i * q}} ) to generate a voltage command value ^{_{(v * d, v * q}} ). For example, the voltage command generation unit 620 performs PI control based on the difference between the detected output current i _o and the calculated current command value i ^* _d , i ^* _q to obtain a voltage command value v ^* _d , v ^* _q ). To this end, the voltage command generation unit 620 may include a PI controller (not shown). It is also possible to further include a limiter (not shown) for limiting the level so that the voltage command values v ^* _d and v ^* _q do not exceed the permissible range.

The switching control signal output unit 330 generates an inverter switching control signal Sic as a PWM signal based on the voltage command values v ^* _d and v ^* _q and outputs the switching control signal Sic to the inverter 220. Accordingly, the switching elements Sa, S'a, Sb, S'b, Sc, and S'c in the inverter 220 perform on / off switching operations.

The controller 230 compares the detected input current i _i and the dc voltage Vdc with the reference value to determine whether there is an abnormality or not. When the abnormality is determined, Can be limited.

7 is a circuit diagram showing an electric motor driving apparatus of an air conditioner according to another embodiment of the present invention.

Referring to the drawings, an electric motor driving apparatus 700 of an air conditioner according to an embodiment of the present invention is substantially the same as the driving apparatus 200 of the air conditioner of FIG. Accordingly, the filter unit 706, the boost capacitor unit 708, the converter 710, the smoothing capacitor C, the inverter 720, the control unit 730, the input current detection unit A, the dc step voltage detection unit B ), An output current detection unit (E), and the like.

The difference is that the three-phase AC power supply is used as the commercial AC power supply in the driving apparatus 200 of FIG. 2, but the single-phase AC power supply is used as the driving apparatus 700 of FIG. In the following, the difference will be mainly described.

The filter unit 706 includes an inductor L1 and a capacitor C1 that are connected to one end of a single-phase AC power source 705 and are connected in parallel with each other. 2, it is preferable that the inductance of the inductor L1 and the capacitance of the capacitor C1 are within a range for limiting the third harmonic or more of the commercial AC power supply. For example, for the third harmonic limitation, the product L1C1 of the inductance of inductor L1 and the capacitance of capacitor C1 may range from approximately 4 to 9 * 10 <" ⁷ >. In order to limit the third harmonic, the fifth harmonic and the seventh harmonic, the product L1C1 of the inductance of the inductor L1 and the capacitance of the capacitor C1 is approximately 1 to 2.5 * 10 ^{- 7} < / RTI >

The booster capacitor unit 708 includes a boost capacitor that stores at least a part of the AC power filtered through the filter unit 706 and supplies the AC power to the converter 710. In the figure, a step-up capacitor (Cr) connected between both ends of a single-phase AC power source is exemplified.

The converter 710 has a diode element and rectifies the alternating current power through the filter unit 706 and the boosting capacitor unit 708 to output the rectified power. Specifically, two pairs of the upper and lower laminated diode elements D1 and D2 and the lower arm diode elements D'1 and D'2 are connected in series, 1, D2 & D'2).

On the other hand, the control unit 730 outputs the inverter switching control signal Sic to the inverter 720 in order to control the switching operation of the inverter. Switching control signal (Sic) is a switching control signal for PWM, it is generated based on the detected output current (i _o), which is outputted to the inverter 730. The To this end, an output current detection unit E may be provided.

Further, the control unit 730 receives the detected input current i _i and the dc step voltage Vdc

It is possible to judge whether there is an abnormality or not and to limit the operation of the inverter 720 as described above.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (10)

A filter portion including an inductor and a capacitor;
A converter having a diode element and rectifying an AC power from the filter unit to output a rectified power;
A boosting capacitor disposed between the filter unit and the converter for storing at least a part of the AC power filtered through the filter unit and supplying the AC power to the converter;
A smoothing capacitor connected to an output terminal of the converter and smoothing the power output from the converter; And
And an inverter which is provided with a plurality of switching elements and is supplied with a DC power of the smoothing capacitor and is converted into an AC power of a predetermined frequency by a switching operation of the switching element to supply the AC power to the three-
The converter includes:
And rectifies and outputs AC power fed through the filter unit and the boost capacitor. delete delete The method according to claim 1,
The filter unit includes:
And limits at least the third harmonic of the input AC power. The method according to claim 1,
Wherein the input AC power source is a three-phase AC power source,
Wherein the converter comprises a pair of upper and lower arm diode elements connected in series to each other and a pair of upper and lower arm diode elements connected in parallel to each other. The method according to claim 1,
The input AC power source is a single-phase AC power source,
Wherein the converter comprises a pair of upper and lower arm diode elements connected in series to each other, and a pair of upper and lower arm diode elements are connected in parallel to each other. The method according to claim 1,
And a controller for controlling the switching operation of the inverter. 8. The method of claim 7,
Further comprising an input current detection unit for detecting an input current from the input AC power supply,
Wherein the control unit determines an abnormality based on the detected input current and limits the operation of the inverter when the abnormality is determined. 8. The method of claim 7,
Further comprising a dc voltage detection unit detecting a dc voltage at the output of the converter,
Wherein the control unit determines an abnormality based on the detected dc voltage and limits the operation of the inverter when the abnormality is determined. 8. The method of claim 7,
Wherein,
A speed estimator for estimating a speed of the electric motor based on an output current detected from an output terminal of the inverter;
A current command generator for generating a current command value based on the estimated speed and command speed;
A voltage command generator for generating a voltage command value based on the current command value and the detection output current; And
And a switching control signal output unit for outputting a switching control signal for driving a switching element in the inverter.

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