KR101634640B1 - Apparatus for dirving motor of air conditioner and method for driving the same - Google Patents

Abstract

The present invention relates to an electric motor driving apparatus for an air conditioner and a driving method thereof. A method of driving an electric motor of an air conditioner according to an embodiment of the present invention includes the steps of driving an electric motor in accordance with a constant speed command and operating the motor in accordance with a speed command or a speed command and a first and a second mechanical angle corresponding to a reference speed within a predetermined range Calculating a maximum speed mechanical angle corresponding to a maximum speed ripple of the electric motor based on the detected first and second mechanical angles; And selecting an optimal load pattern table that minimizes the ripple. This makes it possible to calculate an optimum load pattern table at a constant speed operation.

Electric motors, drives, machine angles

Description

[0001] The present invention relates to an electric motor driving apparatus for an air conditioner,

The present invention relates to an electric motor driving apparatus for an air conditioner and a driving method thereof, and more particularly to an electric motor driving apparatus for an air conditioner capable of calculating an optimum load pattern table at a constant speed operation will be.

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, a fan, and the like, and a motor driving device for driving the motor is used. The motor drive unit receives the 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 the motor such as a compressor or a fan.

An object of the present invention is to provide an electric motor drive apparatus for an air conditioner capable of calculating an optimum load pattern table at a constant speed operation.

According to another aspect of the present invention, there is provided a method of driving an electric motor of an air conditioner, including the steps of: driving an electric motor in accordance with a constant speed command; comparing a speed command or a speed command with a reference speed Calculating a maximum speed mechanical angle corresponding to the maximum speed ripple of the electric motor on the basis of the detected first and second mechanical angles; And selecting an optimal load pattern table that minimizes the speed ripple according to the maximum speed mechanical angle of the load torque pattern.

According to an aspect of the present invention, there is provided an apparatus for driving an electric motor of an air conditioner, including an electric motor and a plurality of switching elements, And controls the motor so as to drive the motor in accordance with a constant speed command, and sequentially detects the first and second mechanical angles corresponding to the speed command or the speed command and the reference speed within a predetermined range, The maximum speed mechanical angle corresponding to the maximum speed ripple of the electric motor is calculated on the basis of the first and second mechanical angles of the plurality of load torque patterns, And a control unit for selecting the table.

As described above, in the motor driving apparatus and the driving method of the air conditioner according to the present invention, the load pattern table is arranged according to the maximum speed mechanical angle calculated at the constant speed operation, It is possible to calculate an optimum load pattern table that is the minimum.

This makes it possible to simply and significantly reduce the speed ripple due to the load torque during constant speed operation.

It is also possible to accurately calculate the maximum speed mechanical angle at the constant speed operation by judging the presence or absence of abnormality of the plurality of sequentially calculated mechanical angles and correcting the abnormality.

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).

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.

The electric motor in the electric motor driving apparatus of the air conditioner according to the embodiment of the present invention may be the electric motor 2b for operating the compressor 2 of the air conditioner as shown in the figure.

1 shows only one indoor unit I and one outdoor unit O. However, the motor driving apparatus of the air conditioner according to the embodiment of the present invention is not limited to this and includes 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 electric motor driving apparatus of an air conditioner according to an embodiment of the present invention.

The electric motor driving apparatus of the air conditioner according to the embodiment of the present invention may be an electric 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. Various types of compressors are possible. Hereinafter, a single-rotary type compressor will be described as an example of a motor drive apparatus for driving the compressor.

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, And a detection unit 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. This will be described later with reference to FIG.

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). 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.

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 is a simplified block diagram of the inside of the control unit of FIG.

The control unit 230 includes an estimation unit 305, a current command generation unit 310, a voltage command generation unit 320, a torque compensation unit 325, and a switching control signal output unit 330 ).

On the other hand, the figure, although not shown, it is also possible to convert the three-phase output current (i _o) to the d-axis, q-axis current, or further comprising an axis conversion for converting the d-axis, q-axis current to the three-phase current.

Estimation unit 305, based on the detected output current (i _o) to estimate the 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 305 may also estimate the position of the rotor based on the detected output current _io . The location of such a simulator 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, has a relationship, if the number of poles 4 poles of the motor 250, 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 generation section 310 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 unit 310 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 310 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.

The voltage command generation unit 320 generates the voltage command values v ^* _d and v ^* _q based on the detected output current i _o and the calculated current command values i ^* _d and i ^* _q . For example, the voltage command generation unit 320 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 generate a voltage command value v ^* _d , v ^* _q ). To this end, the voltage command generation unit 320 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 torque compensating unit 325 compensates the torque command v ^* of the mechanical angle? _M estimated by the estimating unit 250 or the first and second torque commands v ^* and v ^* The second machine angles? _Me1 and? _Me2 are sequentially detected and the maximum speed mechanical angle? _M is calculated based on the detected first and second machine angles? _Me1 and? _Me2 , The optimum load pattern table which minimizes the speed ripple according to the maximum speed mechanical angle (? _M ) of the load torque pattern is selected.

On the other hand, the torque compensating unit 325 compares the magnitudes of the first and second mechanical angles? _Me1 and? _Me2 so that when the first mechanical angle? _Me1 is larger, ([theta] _Me1 , [theta] _Me2 ) to calculate the maximum speed mechanical angle [theta] _M corresponding to the maximum speed ripple of the electric motor 250 based on the compensated machine angle. As described above, it is possible to accurately calculate the maximum speed mechanical angle [theta] _M at the constant speed operation by judging the presence or absence of abnormality of the plurality of machine angles sequentially calculated at the constant speed operation and correcting them.

On the other hand, the torque compensating unit 325 generates and outputs the compensation current instruction value i ^* _c in accordance with the calculated maximum speed mechanical angle [theta] _M so as to compensate the speed ripple at the constant speed operation due to the load torque . For example, the compensation current command value i ^* _c at the calculated maximum speed mechanical angle [theta] _M may correspond to the minimum value.

Accordingly, the current command generation section 310 can generate and output a final current command value by summing the current command value (i ^* _d , i ^* _q ) generated and outputted and the compensation current command value i ^* _c described above . As a result, the current command for the load torque compensation is changed, so that the voltage commands v ^* _d and v ^* _q and the output Sic of the switching control signal output unit are changed. As a result, the compensation of the load torque makes it possible to accurately apply the predetermined pattern, and the speed ripple due to the load torque at the constant speed operation can be simply and significantly reduced.

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.

4 is a diagram showing a load torque according to the speed of the electric motor.

Referring to the drawings, Fig. 4 (a) is a view showing the rotational speed of the electric motor 250. Fig. During the initial startup, the electric motor 250 gradually increases its rotational speed, maintains a constant speed at the retention frequency, and then increases its rotational speed again. At this time, the retention frequency may be, for example, approximately 35 Hz.

In the embodiment of the present invention, the first and second machine angles corresponding to the speed command or the speed command and the reference speed within the predetermined range are sequentially detected in accordance with the constant speed command at the retention frequency, Thereby accurately detecting the second mechanical angle.

4 (b) shows the speed ripple when the motor 250 is driven according to the constant speed command. For example, in the case where the constant speed command is v ₁ , the speed ripple curve is obtained by multiplying the mechanical angle (? _Me ) by 360 ° as the speed estimate v ^* ₁ estimated by the estimator 305 It can be expressed in the form of a periodic curve such as a shape of a sine function correspondingly.

At this time, when the load of the electric motor 250 is, for example, a single rotary type compressor, it can be expressed by a load torque T _L as shown in the drawing by one cycle of suction and discharge.

On the other hand, in Fig. 4 (b), the maximum speed mechanical angle? _M is a mechanical angle corresponding to the point (v _1p ) at which the speed estimation value v ^* ₁ becomes the maximum. Various methods can be tried as a method of calculating the maximum speed mechanical angle ([theta] _M ). For example, the speed reference (v ₁₎ and by using the two reference speed within a predetermined range, can be calculated using the proportional relationship, or the speed command (v ₁₎ or the speed reference (v ₁₎ to the desired It is possible to calculate by using the proportional relationship, that is, the average, using one reference speed within the range. In the embodiment of the present invention, it is described that the maximum speed mechanical angle? _M is calculated using the average among them, but the present invention is not limited to this.

5 is a diagram referred to explain the embodiment of the present invention.

Referring to the drawings, FIG. 5 (a) specifically shows a velocity curve according to the machine angle of FIG. 4 (b). That is, the maximum speed mechanical angle? _M is calculated using the speed command v ₁ and one reference speed v _r1 within a predetermined range. P1 and P2 denote positions that match the reference speed v _r1 in the estimated speed (v ₁ ) curve. On the other hand, Pa and Pb represent positions matched to the first reference velocity v _r1 and the second reference velocity v _r2 in the estimated velocity (v ₁ ) curve, respectively.

5 (b) shows the first and second machine angles? _A1 and? _A2 at positions P1 and P2 that match the speed command and the reference speed within a predetermined range. It can be seen that the first and second mechanical angles? _A1 and? _A2 , which are sequentially detected at this time, are sequentially detected when their magnitudes are viewed. Accordingly, the maximum speed mechanical angle [theta] _M can be calculated by the average of the first and second mechanical angles [theta] _a1 and [theta] _a2 as shown in the following equation ( ₂ ).

Next, FIG. 5 (c) shows the first and second machine angles? _B1 and? _B2 at positions P1 and P2 that match the speed command and the reference speed within a predetermined range. The magnitude of the first and second mechanical angles? _B1 and? _B2 sequentially detected at this time is such that the magnitude of the first mechanical angle? _B1 is different from the magnitude of the second mechanical angle? _B2 ) ≪ / RTI > This occurs when the position of the machine angle is continuously repeated by 360 degrees and the cycle is repeated between the reference speed (v _r1 ) and the increment. In this case, if the maximum speed mechanical angle? _M is simply calculated as the average of the first and second machine angles? _B1 and? _B2 , the different values are calculated.

In the embodiment of the present invention, in order to correct this, when the first mechanical angle? _B1 is larger than the second mechanical angle? _B2 and the difference value between the first mechanical angle and 360 占 is smaller than the second mechanical angle |? _b1 - 360? | <? _b2 ), and compensates the first mechanical angle? _b1 .

That is, the maximum speed mechanical angle? _M is calculated by the difference between the first machine angle and 360 ° (? _B1 - 360?) And the second machine angle? _A2 as shown in the following equation .

Next, FIG. 5 (d) shows the first and second machine angles? _C1 and? _C2 at positions P1 and P2 that match the speed command and the reference speed within a predetermined range. The magnitude of the first and second mechanical angles? _C1 and? _C2 sequentially detected at this time is set such that the magnitude of the first mechanical angle? _Cl is different from the magnitude of the second mechanical angle? _C2 ) &Lt; / RTI &gt; This occurs when the position of the machine angle is continuously repeated by 360 degrees and the cycle is repeated between the reference speed (v _r1 ) and the increment. In this case, if the maximum speed mechanical angle? _M is simply calculated as the average of the first and second machine angles? _C1 and? _C2 , the different value is calculated.

In the embodiment of the present invention, in order to correct this, when the first mechanical angle? _C1 is larger than the second mechanical angle? _C2 and the difference value between the first mechanical angle and 360 ° is larger than the second mechanical angle |? _c1 - 360? |? _c2 ), and compensates the second mechanical angle? _c2 .

That is, the maximum speed mechanical angle? _M is calculated by the average of the first mechanical angle? _C1 and the addition value? _C2 + 360 占 between the second mechanical angle and 360 占 as shown in the following equation (4) .

In this way, by compensating at least one of the detected first and second machine angles, it is possible to accurately calculate the maximum speed mechanical angle at the constant speed operation.

FIG. 6 is a flowchart illustrating a method of driving an electric motor of an air conditioner according to an embodiment of the present invention, and FIGS. 7 and 8 are views referred to explain the driving method of FIG.

Referring to the drawings, the controller 230 controls the motor 250 to drive according to the speed command v ^* (S610). For example, as described above with reference to FIG. 4, the motor 250 is controlled to be driven at a constant speed command corresponding to a retention frequency (approximately 35 Hz). Accordingly, the controller 250 outputs the corresponding inverter switching control signal Sic to the inverter 220.

Next, the first and second machine angles corresponding to the speed command or the speed command and the reference speed within the predetermined range are sequentially detected (S620). 5, the control unit 230 uses the reference speed v _r1 within the predetermined range of the speed command v ^* ₁ at P1 and P2 corresponding to the reference speed v _r1 The first and second mechanical angles of the first and second sensors are detected. The detection of the first and second mechanical angles may be performed in the estimating unit 305 and the torque compensating unit 325 described above.

Next, the control unit 230 calculates the maximum speed mechanical angle [theta] _M (S630). The maximum speed mechanical angle [theta] _M can be calculated as an average of the first and second mechanical angles, as shown in the above-mentioned equation (2).

Next, the control unit 230 selects an optimum load pattern table that minimizes the speed ripple among a plurality of load torque patterns according to the calculated maximum speed mechanical angle [theta] _M (S640).

For example, the control unit 230, particularly, the torque compensating unit 325 may be configured to match the maximum speed mechanical angles? _M calculated to the lowest value among the plurality of load torque patterns, And outputs the compensation current instruction value i ^* _c according to the corresponding load torque pattern. Accordingly, the current command generation unit 310 can generate and output the final current command value by adding the current command value (i ^* _d , i ^* _q ) generated and output to the compensation current command value i ^* _c described above have. As a result, the current command for the load torque compensation is changed, so that the voltage commands v ^* _d and v ^* _q and the output Sic of the switching control signal output unit are changed. Each of the switching control signals Sic is output for each of the plurality of load torque patterns to drive the electric motor 250 and the speed of the electric motor 250 is estimated again to select a load torque pattern that minimizes the speed ripple .

7 shows examples of the load patterns A, B, and C (patterns A, B, and C) with a plurality of load patterns, but the present invention is not limited to these examples.

Fig. 8 shows estimated speeds estimated by the estimating unit 305 according to the load pattern of Fig. 7, and shows respective speed ripples thereof. 8 (a) shows the speed ripple Rva according to the load pattern A, FIG. 8 (b) shows the speed ripple Rvb according to the load pattern B, Gt; Rvc &lt; / RTI &gt;

As a result of comparison between the speed ripples, Rva <Rvb <Rvc, the controller 230 selects the load pattern A with the optimum load pattern. As a result, the compensation of the load torque makes it possible to accurately apply the predetermined pattern, and the speed ripple due to the load torque at the constant speed operation can be simply and significantly reduced.

Meanwhile, the load torque is compensated according to the selected load pattern table (S650). As described above, the control unit 230 outputs the compensation current instruction value i ^* _c . Accordingly, the current command generation unit 310 can generate and output the final current command value by adding the current command value (i ^* _d , i ^* _q ) generated and output to the compensation current command value i ^* _c described above have. As a result, the current command for the load torque compensation is changed, so that the voltage commands v ^* _d and v ^* _q and the output Sic of the switching control signal output unit are changed.

Although not shown in the drawing, a step of correcting the detected first and second mechanical angles may be further performed between step 620 (S630) and step 630 (S630).

For example, when the second machine angle of the first and second machine angles detected sequentially is larger, it is determined that the second machine angle is normal. Thus, as in the above-described equation (2) 1 and the second mechanical angle.

Next, when the first machine angle of the first machine angle and the second machine angle is larger, it is determined that the first machine angle is abnormal, and the controller 230 can compensate for any one of the first and second machine angles. Then, the control unit 230 can calculate the maximum speed mechanical angle [theta] _M based on the compensated first and second machine angles.

For example, the control unit 230, a first mechanical angle and when the difference value between 360˚ is less than the second mechanical angle _{(| θ 1 - 360˚ | <} θ 2), a first compensating for mechanical angle (θ ₁₎ can do. That is, 360 degrees is subtracted from the first machine angle. Accordingly, the average of the compensated first and second machine angles can be calculated as the maximum speed machine angle, as in Equation (3).

Also, the controller 230 can compensate the second machine angle? ₂ when the difference between the first machine angle and 360 ° is larger than the second machine angle (|? ₁ - 360? |>? ₂ ) have. That is, 360 ° is added at the second machine angle. Accordingly, the average of the compensated first and second machine angles can be calculated by the maximum speed machine angle, as in Equation (4).

Although not shown in the drawing, a speed stability determination step for determining whether or not the electric motor is driven stably can be further performed.

For example, as shown in Fig. 5 (a), before calculating the first and second machine angles, the machine angles at the points Pa and Pb corresponding to different reference velocities v _r1 and v _r2 are determined, If the angular range is within the permissible range, the speed stability can be judged. Alternatively, it is possible to estimate the speed ripple before the first and second mechanical angle calculations, analyze the components of the speed ripple, and determine that the speed is unstable if the speed ripple exceeds the allowable range.

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.

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 simplified block diagram of the inside of the control unit of FIG.

4 is a diagram showing a load torque according to the speed of the electric motor.

5 is a diagram referred to explain the embodiment of the present invention.

6 is a flowchart illustrating a method of driving an electric motor according to an embodiment of the present invention.

FIGS. 7 and 8 are views referred to explain the driving method of FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

210: converter 220: inverter

230: control unit 305:

310: current command generator 320: voltage command generator

325: Torque compensating unit 330: Switching control signal output unit

Claims (14)

Driving an electric motor in accordance with a constant speed command; Estimating a mechanical angle of the electric motor based on a current flowing in the electric motor; Sequentially detecting first and second machine angles corresponding to the speed command or the speed command and the reference speed within a predetermined range among the estimated machine angles; Compensating at least one of the first and second machine angles if the first one of the detected first and second machine angles is greater than the first machine angle; Calculating a maximum speed mechanical angle corresponding to a maximum speed ripple of the electric motor based on the compensated first and second mechanical angles; And selecting an optimal load pattern table having a minimum speed ripple according to the maximum speed mechanical angle among the plurality of load torque patterns. The method according to claim 1, And driving the motor by compensating the load torque of the motor according to the selected load pattern table. delete The method according to claim 1, Wherein the maximum speed mechanical angle calculating step comprises: If the detected first machine angle is greater, by an average of the compensated first and second machine angles, And when the detected second mechanical angle is larger, it is calculated by the average of the detected first and second mechanical angles. The method according to claim 1, Wherein the maximum speed mechanical angle calculating step comprises: Compensating the first machine angle when the detected first machine angle is larger and the difference value between the first machine angle and 360 ° is smaller than the second machine angle, And compensates the second mechanical angle when the detected first mechanical angle is larger and the difference value between the first mechanical angle and 360 ° is larger than the second mechanical angle. . delete Electric motor; An inverter having a plurality of switching elements and outputting an AC power having a predetermined frequency and a predetermined magnitude by a switching operation to drive the motor; And And estimates a mechanical angle of the electric motor on the basis of a current flowing in the electric motor, calculates a speed command or a speed command from the estimated machine angle and a reference speed in a predetermined range At least one of the first and second machine angles, when the first one of the detected first and second machine angles is greater than the first machine angle, And calculates a maximum speed mechanical angle corresponding to the maximum speed ripple of the electric motor based on the compensated first and second mechanical angles, And a controller configured to select an optimum load pattern table to be used for driving the air conditioner. 8. The method of claim 7, Wherein, And controls the motor to be driven by compensating the load torque of the motor according to the selected load pattern table. delete 8. The method of claim 7, Wherein, If the detected first machine angle is greater, calculating the maximum speed machine angle calculation by an average of the compensated first and second machine angles, When the second mechanical angle is larger, calculates the maximum speed mechanical angle by an average of the first and second detected mechanical angles. 8. The method of claim 7, Wherein, Wherein when the first machine angle is larger and the difference value between the first machine angle and 360 占 is smaller than the second machine angle, And compensates the second mechanical angle when the first mechanical angle is larger and the difference value between the first mechanical angle and 360 ° is larger than the second mechanical angle. delete 8. The method of claim 7, Wherein, An estimating unit that estimates a speed of the electric motor based on an output current flowing to the electric motor; A current command generator for generating a current command value based on the estimated speed and the speed command value; A voltage command generator for generating a voltage command value based on the current command value and the detected output current; And And a switching control signal output unit for generating and outputting the inverter switching control signal based on the voltage command value. 14. The method of claim 13, Wherein, Calculating a maximum speed mechanical angle on the basis of the mechanical angle of the electric motor estimated by the estimating section and selecting an optimum load pattern table having a minimum speed ripple according to the maximum speed mechanical angle among the plurality of load torque patterns And a torque compensation unit for compensating a load torque of the electric motor according to the selected load pattern table to generate a compensation current command value, Wherein the current command generator generates and outputs a final current command value using the current command value and the compensation current command value.

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