JP5068292B2 - Electric motor drive device and air conditioner - Google Patents

Description

  The present invention relates to an electric motor drive device that drives an electric motor (motor) while controlling a voltage. In particular, in an air conditioner that is a refrigeration cycle apparatus, an apparatus that drives an electric motor that rotates an outdoor fan (blower) that blows air to an outdoor heat exchanger that becomes a condenser or the like during heating operation to exchange heat with air It is suitable for.

  Conventionally, a drive device having inverter means or the like controls a voltage (power to be supplied) applied to the electric motor, and causes the electric motor to perform a desired drive. For example, an air conditioner has a blower and efficiently exchanges heat between a refrigerant flowing through a heat exchanger and, for example, air. At this time, the rotation of the fan is controlled by applying a voltage to the electric motor that rotates the fan motor via the inverter means.

  In a conventional air conditioner, a DC voltage is switched by an inverter means and applied to a fan motor to control the fan motor to a target rotational speed, while the target rotational speed can be varied by a predetermined value according to the input current of the inverter means. There is something like that (see, for example, Patent Document 1).

  In addition, when frost formation on the outdoor heat exchanger is detected or estimated during heating operation, fan control during frost formation to reduce the rotation speed of the outdoor fan is performed before the defrost operation, and heating operation is continued. Some of them (for example, refer to Patent Document 2).

JP-A-11-51454 (first page, FIG. 1) Japanese Unexamined Patent Publication No. 2009-58222 (first term, FIG. 1)

  However, in the technique described in Patent Document 1, the input current of the inverter means pulsates at a frequency six times the frequency output from the inverter means. When such a pulsating current is detected to control the inverter means to control the rotation of the fan, there is a problem that the control is not stable and the rotational speed becomes unstable, for example, noise is generated.

  Moreover, in the technique of Patent Document 2, the frosting speed changes depending on the outside air temperature, the outside air humidity, and the rotational speed of the outdoor fan motor, so that it is difficult to accurately detect and estimate the amount of frosting. For this reason, the rotational speed cannot be reduced with respect to the increase in the ventilation resistance of the heat exchanger, the current of the outdoor fan motor increases, and performance degradation due to motor demagnetization or shutdown due to overcurrent interruption is a problem.

  Furthermore, even if the load on the outdoor fan motor is increased due to external factors such as strong winds, the number of revolutions cannot be controlled, so the current flowing through the outdoor fan motor increases. For this reason, performance deterioration due to operation stoppage due to motor demagnetization or overcurrent interruption becomes a problem.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain an electric motor or the like that can be driven optimally and stably by stably controlling the inverter means. .

An electric motor driving apparatus according to the present invention includes an inverter unit that converts a DC voltage from a DC power source and applies an AC voltage to the motor, a shunt resistor connected between the DC power source and the inverter unit, and both ends of the shunt resistor. Charging means for charging and holding the peak value of the voltage in the capacitor; discharging means for discharging the charge charged in the charging means with a first time constant; and current detection value correction means The current flowing through the shunt resistor is detected by correcting the error based on the power factor of the motor, and the inverter means is applied to the motor so that the current detected by the current detecting means becomes a predetermined value. And an inverter control means for controlling the frequency of the alternating voltage.

  In the electric motor drive device of the present invention, the charging means holds the peak voltage at the terminal voltage of the shunt resistor, and the current value and the motor rotation speed are determined based on the peak voltage. Can be detected stably, and the motor can be controlled by calculating a rotational speed command value or the like. For this reason, the rotation speed of the motor of the electric motor can be stabilized, and stable electric motor control such as prevention of noise generation and constant current control can be performed.

It is a block diagram of the air conditioning apparatus which shows Embodiment 1 of this invention. 3 is a diagram showing a configuration of a voltage holding unit 15. FIG. FIG. 6 is a diagram illustrating a voltage relationship according to the operation of the voltage holding unit 15. 3 is a diagram showing a configuration of inverter control means 11. FIG. FIG. 6 is a diagram showing the operation of the position / speed estimation means 19. FIG. 3 is a diagram showing a configuration of current detection means 20. 3 is a diagram showing a configuration of a rotation speed command calculation means 21. FIG. 3 is a diagram showing a configuration of a voltage control means 22. FIG. FIG. 6 is a diagram illustrating an operation of the voltage control unit 22. It is a figure which shows the control action of Embodiment 1 of this invention. It is a figure which shows the structure of the electric current detection means 20 of Embodiment 2 of this invention. It is a figure which shows the output of the electric current detection means 20 of Embodiment 2 of this invention. It is a figure which shows the structure of the electric current detection means 20 of Embodiment 3 of this invention. FIG. 6 is a diagram showing the operation of the peak hold means 31. It is a figure which shows the output of the electric current detection means 20 of Embodiment 3 of this invention. It is a figure which shows the relationship between the pulse Duty of shunt voltage, and an error. It is a figure which shows the relationship between a voltage vector and a current vector. It is a figure which shows the operation | movement at the time of the electric current detection error generation of this invention. It is a figure which shows the structure of the inverter control means 11 of Embodiment 4 of this invention. It is a figure which shows the structure of the electric current detection means 20 of Embodiment 4 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an air conditioner centering on a motor drive device according to Embodiment 1 of the present invention. In this embodiment, a separate type air conditioner will be described as an example.

  In FIG. 1, a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an expansion valve 4 and an indoor heat exchanger 5 are attached via a refrigerant pipe 6 to constitute a refrigerant circuit for circulating various refrigerants. Then, when the refrigerant evaporates and condenses, the air conditioning operation is performed while changing the pressure of the refrigerant passing through the pipe by utilizing heat absorption and heat dissipation with respect to the air to be heat exchanged. .

  Moreover, the air conditioning apparatus of this Embodiment has the ventilation fan 7 for ventilating the outdoor heat exchanger 3 and performing heat exchange with a refrigerant | coolant and air, and the electric motor 8 which operates this. . The inverter means 9 that drives the electric motor 8 by applying a voltage is a circuit (device) having switching elements 9a to 9f. A conversion operation is performed by supplying power from the DC power supply 10, and a voltage is applied to the electrically connected motor 8 to supply power. The inverter means 9 has a control input terminal connected to the inverter control means 11, and the operation is controlled by the inverter control means 11.

  Furthermore, it has DC voltage detection means 12 for detecting the DC voltage value Vdc from the DC power supply 10 and magnetic pole position detection means 13 for detecting the magnetic pole positions (Hu, Hv, Hw) of the electric motor 8. In addition, voltage holding means 15 is provided for detecting and holding the peak voltage Vc of the terminal voltage Vsh of the shunt resistor 14 provided between the inverter means 9 and the DC power supply 10.

  The inverter control means 11 generates PWM signals (UP, VP, WP, UN, VN, WN) based on the outputs of the DC voltage detection means 12, the magnetic pole position detection means 13, and the voltage holding means 15. In the inverter means 9, the switching elements 9 a to 9 f that are bridge-connected are driven to control the voltage applied to the electric motor 8.

  FIG. 2 is a diagram illustrating a configuration example of the voltage holding unit 15. Here, the terminal voltage Vsh of the shunt resistor 14 changes intermittently according to the switching timing of the switching elements 9 a to 9 f in the inverter means 9 and the current flowing through the motor 8. Therefore, for example, if it is attempted to directly detect the peak value of the current by a microcomputer or the like based on the terminal voltage Vsh, it is necessary to detect it in synchronization with the switching timing. This complicates the detection method and requires an expensive microcomputer with a high processing speed.

  Therefore, as shown in FIG. 2, the voltage holding means 15 of the present embodiment detects and holds the peak voltage Vc by the backflow prevention means 16, the charging means 17 and the discharging means 18. In the voltage holding unit 15, the charge supplied based on the terminal voltage Vsh is charged into the charging unit 17 through the backflow preventing unit 16. Thereby, the charging means 17 can hold | maintain the peak voltage Vc of the terminal voltage Vsh which changes intermittently as a voltage which concerns on charge. The backflow prevention means 16 prevents the current from flowing back to the input side due to the peak voltage Vc. Therefore, it is possible to improve reliability. Here, the charging means 17 remains charged unless discharged. If this is left, it may continue to be held at a high voltage even when the load is light and the voltage drops, or when noise or the like occurs. Therefore, the discharging unit 18 is provided in parallel with the charging unit 17 so that the electric charge stored in the charging unit 17 is discharged at a predetermined timing. For this reason, it is possible to eliminate the influence of the voltage related to the voltage drop of the terminal voltage Vsh, noise, etc., and to improve the reliability.

  FIG. 3 is a diagram showing a voltage relationship for explaining the operation of the voltage holding means 15. As shown in FIG. 3, the voltage holding means 15 can detect the peak voltage Vc of the shunt voltage Vsh regardless of the switching timing of the switching elements 9a to 9f. For this reason, even if the peak value of the current is detected using an inexpensive microcomputer having a low processing capability in the high-level means, the peak value of the current can be detected without any problem, thereby reducing the cost. be able to.

  Here, as shown in FIG. 2, it is possible to realize the backflow preventing means 16 as a diode and the charging means 17 as a capacitor. As for the discharging means 18, a discharging resistor can be connected in parallel with the charging means 17. Further, it is possible to discharge the charge stored in the charging means 17 by providing a short-circuit means in parallel with the charging means 17. Although representative means have been described this time, other means may be used as long as they have other similar functions.

  Here, when the charging means 17 is constituted by a capacitor and the discharging means 18 is constituted by a resistor, the product of the capacitance C of the capacitor and the resistance value R of the resistor is set as a first time constant, and the charge stored in the capacitor is Discharge occurs. For this reason, if the first time constant is too small, the charge accumulated in the capacitor is immediately discharged, and the peak voltage Vc cannot be detected accurately. Also, as shown in FIG. 3, the envelope of the terminal voltage Vsh pulsates at a frequency six times the current flowing through the motor 8, so that if the first time constant is small, the waveform of the peak voltage Vc also pulsates. May appear. Therefore, an electrostatic capacity C, a capacitor having a resistance value R, and a resistance are provided so that the first time constant is 1/6 times or more of the operation cycle of the electric motor 8.

  FIG. 4 is a diagram showing the configuration of the inverter control means 11. As shown in FIG. 4, the inverter control means 11 of the present embodiment includes a position / speed estimation means 19, a current detection means 20, a rotation speed command calculation means 21, and a voltage control means 22. Based on the DC voltage Vdc detected by the DC voltage detecting means 12, the outputs (Hu, Hv, Hw) detected by the magnetic pole position detecting means 13, and the peak voltage Vc from the voltage holding means 15, six types of PWM Signals (UP, VP, WP, UN, VN, WN) are output. Here, the inverter control means 11 is not particularly limited, but can be constituted by, for example, a microcomputer having a CPU (Central Processing Unit) or the like. At this time, the processing procedure of each means is stored as a program in a storage device (not shown), and the function of each means is realized by executing the program.

  FIG. 5 is a diagram showing the configuration of the position / velocity estimation means 19. Here, the operation of the position / velocity estimation means 19 when the magnetic pole position detection means 13 is a Hall sensor will be described. As for the output of the Hall sensor, HIGH (= 1) and LOW (= 0) are repeated approximately every 180 [deg] according to the magnetic pole position of the rotor of the electric motor 8. Then, signals having a phase difference of 120 degrees are output in the U phase, the V phase, and the W phase. Here, it is assumed that the period from the rising edge of the U phase to the next rising edge is one electrical cycle (operation cycle), and n times of control is performed at the cycle Ts during that period. At this time, one period of electricity can be expressed by n × Ts, and the electric frequency can be obtained by taking the reciprocal thereof. Then, by multiplying the electrical frequency by 2π, the rotational electrical angular frequency ω of the motor 8 that is the electrical angular frequency can be obtained. Furthermore, it is also possible to obtain the mechanical rotational speed by multiplying the number of pole pairs of the electric motor 8.

  Next, how to determine the magnetic pole position θ when the rise of the U-phase Hall sensor output Hu is set to 0 degrees will be described. When the rise of the U-phase Hall sensor output Hu is set to 0 degree, 0 [deg] is obtained when (Hu, Hv, Hw) = (1, 0, 1), and 60 [[1, 0, 0] is obtained. deg],..., (0, 0, 1) is 300 [deg], and θh is detected. Since θh is stepped, an angle to be added for each control cycle Ts is obtained based on the obtained rotational electrical angular frequency ω and added to θh. As a result, as shown in FIG. 5, a magnetic pole position θ that changes linearly from 0 [deg] to 360 [deg] can be obtained.

  FIG. 6 is a diagram showing the configuration of the current detection means 20. The current detection means 20 of this embodiment includes a voltage / current conversion means 23 and a restriction means 24. Based on the peak voltage Vc from the voltage holding means 15 and the resistance value Rsh of the shunt resistor 14, the voltage / current converter 23 converts the peak value of the current flowing through the shunt resistor 14 according to Ohm's law (I = Vc / Rsh). Ask. The obtained current may be an unexpected current that exceeds the overcurrent cutoff value due to noise or the like. By limiting the current exceeding the overcurrent cutoff value in the limiting means 24, the current value I is finally detected.

  Here, the current value is obtained by the voltage / current conversion means 23 and then the current value is restricted by the restriction means 24. For example, after the restriction means 24 restricts the peak voltage Vc to a predetermined voltage value, the voltage current The conversion unit 23 may detect the current I.

  FIG. 7 is a diagram showing the configuration of the rotational speed command calculating means 21. The rotational speed command calculating means 21 includes a constant current rotational speed calculating means 25 and a rotational speed command limiting means 26. The constant current rotation number calculation means 25 is connected to the shunt resistor 14 by a proportional integral (PI) control method based on a deviation between the current value I output from the current detection means 20 and a preset current control value I *. A rotation speed command value is determined so that the current peak value becomes the current control value I *. Here, the current control value I * needs to be set to a value lower than the overcurrent cutoff value so as not to fall into the overcurrent cutoff.

  Further, in order to prevent the motor rotational speed from causing a concern about noise and a decrease in driving performance, in the present embodiment, the rotational speed is limited within the rotational speed range requested by the rotational speed command restricting means 26. For this reason, it is possible to rotate at the optimum rotational speed command value ω * according to the current, and the operation stop due to overcurrent interruption occurs even under conditions where the load of the motor 8 such as outside wind or frosting increases. Stable operation is possible without doing so.

  Here, in the present embodiment, the method for obtaining the rotational speed command value by the proportional integral control method has been described. However, any other control method may be used as long as it is a method for keeping the current constant. It goes without saying that there is nothing.

  FIG. 8 is a diagram showing the configuration of the voltage control means 22. The voltage control unit 22 includes a voltage command amplitude calculation unit 27, a three-phase voltage command calculation unit 28, and a PWM generation unit 29. The voltage command calculation means 27 obtains the voltage command amplitude V * by, for example, proportional integral control based on the deviation between the rotating electrical angular frequency ω and the rotational speed command value ω *. As a result, the operation can be performed at the rotational electrical angular frequency ω that matches the rotational speed command value ω *.

  FIG. 9 is a diagram for illustrating the operation of the voltage control means 22 (particularly, the three-phase voltage command calculation means 28 and the PWM generation means 29). Based on the voltage command amplitude V *, the DC voltage value Vdc, and the magnetic pole position θ, the three-phase voltage command calculation means 28 calculates voltage command values Vu *, Vv *, and Vw * to be applied to each phase of the motor 8 by the following formula ( It calculates | requires based on 1)-(3). Here, θv represents the applied voltage phase, and is represented by the sum of the magnetic pole position θ and the leading phase angle θf with respect to the magnetic pole position θ. By setting this θf optimally, it is possible to apply a voltage with an optimal phase, which can contribute to an improvement in the operating efficiency of the electric motor 8.

  Here, as a basic voltage command value generation method, the method of obtaining the voltage command value based on the formulas (1) to (3) has been described, but third-order harmonic superposition modulation, space vector modulation, three-phase modulation Needless to say, there is no problem even if the voltage command value is obtained by two-phase modulation or the like.

  The PWM generator 29 generates a PWM signal (UP) based on the magnitude relationship between the three-phase voltage command values Vu *, Vv *, Vw * obtained by the equations (1) to (3) and a triangular wave carrier having an amplitude of 1. , VP, WP, UN, VN, WN). A voltage based on a voltage command value can be applied to the electric motor 8 by switching the switching elements 9a to 9f of the inverter means 9 with this PWM signal.

  FIG. 10 is a diagram showing the relationship between the motor rotation speed and control of the electric motor 8 according to the first embodiment. For example, during the heating operation of the air conditioner, since the ambient temperature of the outdoor unit is generally low and the air density is high, the output torque of the electric motor 8 necessary for driving the blower fan 7 increases and the flowing current also increases. . In addition, if the outdoor heat exchanger 3 is frosted, the air flow path (air passage) is blocked, and thus the torque required to drive the blower fan 7 increases with the passage of drive time.

  In the conventional control, as shown in FIG. 10 (a), the motor 8 is controlled so that the rotation speed is constant. For example, according to the amount of frost that progresses with the elapse of the drive time, The value increased from I0 to I1. Therefore, it is necessary to maintain the rotation speed of the electric motor 8 at N0 so as not to reach the overcurrent cutoff value, and it is difficult to improve the heating capacity due to an increase in the rotation speed or the like.

  Therefore, as shown in FIG. 10B, by controlling so that the current supplied to the electric motor 8 is constant, the current that does not reach the overcurrent cutoff value even at a light load where frosting does not progress. Consider that the heating capacity is improved by supplying I1 and increasing the rotational speed of the electric motor 8 accordingly. As described above, in the present embodiment, stable current peak value detection can be performed, so that control is performed to keep the current value constant (for example, I1 constant) so as not to reach the overcurrent cutoff value. Is possible. For this reason, it becomes possible to increase the rotation speed at the time of the light load in which frost formation does not advance from the conventional N0 to the maximum N1. Thereby, the efficiency of heat exchange in the outdoor heat exchanger can be improved, and an air conditioner capable of improving the heating capacity can be obtained.

  In addition, for example, when the wind in the direction opposite to the blowing direction (so-called head wind) blows to the blower fan 7, the load on the electric motor 8 may increase. In the case of conventional control, since the current value is increased and the motor speed of the electric motor 8 is kept constant, the electric motor 8 stops due to overcurrent interruption, and heat exchange cannot be performed efficiently, resulting in reduced capacity. It was. In the air conditioner of Embodiment 1, since the current supplied to the electric motor 8 is controlled to be constant, for example, even if a head wind occurs and the rotational speed decreases, the current value does not increase. When the wind stops, the operation can be continued by increasing the rotation speed in accordance with the current value. For this reason, it is possible to obtain an air conditioner that is highly reliable and capable of improving its performance.

  Furthermore, even when the outdoor heat exchanger 3 becomes blocked due to aging, accumulation of dust, etc., and the torque required to drive the blower fan 7 increases, the outdoor heat exchanger 3 can be operated at an optimum rotational speed at which the current value is constant. Therefore, it is possible to obtain an air conditioner that is highly reliable and capable of improving its performance.

  As described above, in the electric motor drive device according to the first embodiment, the voltage holding unit 15 holds the peak voltage Vc of the terminal voltage Vsh of the shunt resistor 14. The means 23 converts the peak voltage Vc and the resistance value of the shunt resistor 14 to the peak value of the current flowing through the shunt resistor 14 (current supplied to the electric motor 8) regardless of the switching timing in the inverter means 9. It is possible to control the electric motor 8 by detecting the current value I and calculating the rotational speed command value and the like. For this reason, at least the current detection means 20 does not need to perform high-speed processing, and can perform processing with a low-cost microcomputer.

  Further, when the voltage holding means 15 is configured by connecting capacitors and resistors in parallel, the first time constant, which is the product of the capacitance and the resistance value, becomes 1/6 times or more of the operation cycle of the motor 8. Since it did in this way, the pulsation component in the terminal voltage Vsh can be suppressed and the stable peak voltage Vc can be obtained. Furthermore, since a stable peak value of the current can be obtained, the rotation speed of the motor of the electric motor 8 can be stabilized and the occurrence of noise and the like can be prevented. Moreover, the drive of the inverter means 9 can be controlled so that the electric current supplied to the electric motor 8 becomes constant, and the electric motor 8 can be driven optimally and stably. For this reason, energy saving can be achieved in driving the electric motor 8.

  When the motor drive device of the present embodiment is used for driving the motor 8 that rotates the blower fan 7 that feeds air to the outdoor heat exchanger 3 in the air conditioner, constant current control is performed. Thus, for example, when the outdoor heat exchanger 3 is performing a heating operation in which it becomes a condenser or the like, it is possible to increase the rotation speed at a light load when frosting on the outdoor heat exchanger 3 is not progressing. It becomes. For this reason, efficient heat exchange is possible in the outdoor heat exchanger 3, and an air conditioner capable of improving the heating capacity can be obtained. In addition, stable operation can be performed by performing constant current control so as not to stop the electric motor 8 and the air conditioner due to overcurrent interruption. Further, by suppressing the pulsation of current, stable control can be performed, and an air conditioner with less noise can be obtained.

  Further, even when wind blows to the blower fan 7 in the direction opposite to the blow direction and the load of the electric motor 8 increases, the constant current control is performed, so that the operation can be continued. Further, even when the air passage is blocked due to aging deterioration or accumulation of dust in the outdoor heat exchanger 3 and the torque required to drive the blower fan 7 increases, the optimum rotational speed that keeps the current value constant. It is possible to drive with. From the above, it is possible to obtain an air conditioner that is highly reliable and capable of improving its performance. Here, although the outdoor heat exchanger 3 was demonstrated as a condenser, a gas cooler etc. may be sufficient, for example.

Embodiment 2. FIG.
In the motor drive device in the air conditioning apparatus of the first embodiment, the first time constant in the voltage holding means 15 that detects and holds the peak voltage Vc in the shunt resistor 14 is 1/6 times or more the operating cycle of the motor 8. It was made to become. Here, it is sufficient if the voltage holding means 15 can be designed so as to have a desired first time constant. However, in order to suppress the pulsating flow component if there is a restriction in the selection of the capacitance or resistance value of the capacitor, for example. It may be difficult to obtain the required first time constant. In that case, there is a possibility that a pulsation component having a frequency 6 times the operation frequency of the inverter appears remarkably in the peak voltage Vc. At this time, the current value I detected by the current detecting means 20 also pulsates, and the rotational speed command value ω * calculated based on the pulsating current value I also pulsates, and there is a concern about deterioration of controllability and noise. Is done.

  Therefore, the drive device of the second embodiment aims to solve the above-described problem, and suppresses the pulsating component in the detected current so that a stable current value can be detected. Here, the basic configuration of the air-conditioning apparatus of Embodiment 2 is the same as the configuration of FIG.

  FIG. 11 is a diagram showing the configuration of the current detection means 20 according to Embodiment 2 of the present invention. The current detection unit 20 according to the present embodiment is different from the first embodiment in that a low-pass filter unit 30 is provided between the voltage / current conversion unit 23 and the limiting unit 24.

  In the current detection unit 20 of the first embodiment, the voltage / current conversion unit 23 detects the peak voltage Vc that is the output of the voltage holding unit 15 and converts it to a current value, and the limiting unit 24 limits the current value. It was. In the present embodiment, the current value related to the conversion of the voltage / current conversion means 23 is removed by the low-pass filter means 30 having the second time constant to remove a frequency component that is six times the operating frequency of the inverter means 9. Therefore, the pulsation of the current value I is suppressed by limiting by the limiting means 24. As a result, it is possible to further ensure control stability and improve noise.

  FIG. 12 is a diagram showing the relationship of currents due to the operation of the current detection means 20. The low-pass filter unit 30 needs to suppress the pulsating component that the voltage holding unit 15 cannot suppress. For this reason, the pulsation component is suppressed in the current detection means 20 by setting the second time constant to a time constant higher than the first time constant. In this manner, by controlling the current supplied to the electric motor 8 to be constant based on the current value I in which the pulsation component is suppressed, as in the first embodiment, a highly stable air conditioner can be obtained. Obtainable.

  However, as can be seen from FIG. 12, the pulsation component can be suppressed by providing the low-pass filter means 30, but the peak of the current is also suppressed, compared with the waveform as it is converted from the peak voltage Vc to the current value I. A difference ΔI from the original peak value occurs. With respect to the difference ΔI, for example, by adding an average difference ΔI obtained experimentally in advance and taking into account the correction, the current value detection error can be reduced.

  As described above, according to the motor drive device of the second embodiment, the current detection unit 20 includes the low-pass filter unit 30 to suppress the pulsation component included in the current value related to the conversion of the voltage-current conversion unit 23, In addition, since the correction is performed using the difference ΔI, as in the first embodiment, the motor rotation speed of the motor 8 can be stabilized by the stable current value I, and the occurrence of noise and the like can be prevented. Moreover, the drive of the inverter means 9 can be controlled so that the electric current supplied to the electric motor 8 becomes constant, and the electric motor 8 can be driven optimally and stably.

  For this reason, even when the electric motor drive device of the present embodiment is used for driving the electric motor 8 that rotates the blower fan 7 that feeds air to the outdoor heat exchanger 3 in the air conditioner, the electric motor drive device according to the first embodiment is used. It is possible to obtain an air conditioner that exhibits the same effect as described.

  Here, the current detection means 20 as in the present embodiment is provided when the first time constant of 1/6 or more of the operation cycle of the motor 8 cannot be obtained in the setting in the voltage holding means 15. The most effective. However, it is possible to apply even if the first time constant is 1/6 times or more of the operation cycle of the electric motor 8.

Embodiment 3 FIG.
In the air conditioner of the second embodiment, the voltage detector 15 is provided in the current detector 20 when it is difficult to obtain the necessary first time constant due to restrictions on the capacitance and resistance of the capacitor. The low-pass filter means 30 is used to improve control stability. Here, as described above, the low-pass filter means 30 can suppress the peak value of the current in order to suppress the pulsating component in the current value. For this reason, in the second embodiment, the difference ΔI is added to obtain the current peak value. However, if the difference ΔI is estimated differently, an overcurrent interruption or the like may occur if the current detection error increases.

  Therefore, the air conditioner of Embodiment 3 enables the current detection means 20 to detect the peak value of the current with higher accuracy. Here, the basic configuration of the air-conditioning apparatus of Embodiment 3 is the same as the configuration of FIG.

  FIG. 13 is a diagram showing the configuration of the current detection means 20 according to Embodiment 3 of the present invention. The current detection unit 20 according to the present embodiment is different from the second embodiment in that a peak hold unit 31 is provided between the voltage / current conversion unit 23 and the limiting unit 24 instead of the low-pass filter unit 30. .

  In the present embodiment, the peak hold means 31 has a calculation means such as a microcomputer, for example, and determines the peak value of the current converted by the voltage / current conversion means 23 and stores it in a storage device (not shown). A process of storing (holding) is performed. Further, in order not to keep the peak value of the current temporarily increased due to noise or the like, the current peak value is attenuated based on the set third time constant τ.

  For example, in the first embodiment, the current detection unit 20 detects the peak voltage Vc, which is the output of the voltage holding unit 15, by the voltage / current conversion unit 23 and converts it to a current value, and the limiting unit 24 determines the current value. There were restrictions. In the present embodiment, the peak value of the current flowing through the shunt resistor 14 is held by the peak hold unit 31 with respect to the current value related to the conversion of the voltage / current conversion unit 23 so that the detection error of the peak value of the current is reduced. It is to make. Thereby, it becomes possible to prevent the air conditioner from being stopped due to overcurrent interruption and to obtain a highly reliable air conditioner.

  FIG. 14 is a flowchart showing the processing operation of the peak hold means 31. For example, when the current Ibuf converted and output by the voltage-current converter 23 is input (S1), the current Ibuf is compared with the current peak value Ip with an initial value of 0 (S2). If it is determined that the current Ibuf is larger than the current peak value Ip, a process of setting Ip = Ibuf, t = 0 (S3), and holding the current peak value Ip is performed (S5).

  For example, a high current Ibuf may be instantaneously input from the voltage / current converter 23 due to the influence of noise or the like. If the current due to such noise is kept as it is, the reliability of the control is lowered. Therefore, in the present embodiment, a countermeasure is taken by setting a third time constant τ and attenuating with the third time constant τ. Here, regarding the third time constant τ, it is necessary to prevent the peak value of the current from pulsating. For this reason, the third time constant is set to be larger than the first time constant.

If it is determined in S2 that the current Ibuf is not larger than the current peak value Ip (the current peak value Ip is equal to or less than Ibuf), the current peak value Ip is attenuated with a time constant τ as time t passes, for example. The current peak value Ip is calculated as in the following equation (4) (S4).
Ip = Ip × exp (−t / τ) (4)

  FIG. 15 is a diagram showing the relationship of currents due to the operation of the current detection means 20. The peak hold means 31 can finally detect the current value I without causing pulsation by holding the peak value Ip of the current flowing through the shunt resistor 14. Further, by performing the attenuation process so as not to pulsate the peak current value Ip, it is possible to increase the reliability of the control without continuing to maintain the peak current value Ip temporarily increased due to noise or the like.

  As described above, according to the motor driving apparatus of the third embodiment, the peak detection unit 31 is provided in the current detection unit 20 to hold the peak value of the current value related to the conversion of the voltage / current conversion unit 23. Even if a pulsating component is included in the current value, as in the first embodiment, by detecting the stable current value I, the rotational speed of the motor of the electric motor 8 is stabilized and the occurrence of noise and the like is prevented. be able to. Moreover, the drive of the inverter means 9 can be controlled so that the electric current supplied to the electric motor 8 becomes constant, and the electric motor 8 can be driven optimally and stably. Also, in the peak hold means 31, a third time constant τ is set, and when the current peak value cannot be updated, the current value is attenuated. Therefore, it is possible to prevent the current value that has been increased from being maintained.

  As described above, even when the electric motor drive device of the present embodiment is used for driving the electric motor 8 that rotates the blower fan 7 that feeds air to the outdoor heat exchanger 3 in the air conditioner, the electric motor drive device according to the first embodiment is used. It is possible to obtain an air conditioner that exhibits the same effect as described. Here, the current detection unit 20 as in the present embodiment can be applied even if the first time constant in the voltage holding unit 15 is 1/6 times or more of the operation cycle of the electric motor 8.

Embodiment 4 FIG.
In the air conditioners of the second and third embodiments described above, the current detection unit 20 is provided with the low-pass filter unit 30 and the peak hold unit 31 to detect the voltage value I with the pulsation component suppressed.

  FIG. 16 is a diagram showing the relationship between the duty and the error in the shunt voltage. For example, the voltage holding means 15 repeats the charging of the charging means 17 and the discharging of the discharging means 18, but at this time, the voltage value at a point where the speed at which the charging means 17 is charged and the speed at which the discharging means 18 discharges is balanced. Is stable. Here, while the electrostatic capacitance C and the resistance value R of the elements in the charging unit 17 and the discharging unit 18 are constant, the ratio (Duty) of the voltage zero section to the pulse voltage generation section in the terminal voltage Vsh is large. The discharge time becomes longer with respect to the charge time. For this reason, as shown in FIG. 16, the current detection error based on the shunt resistor 14 increases.

  FIG. 17 is a diagram showing the relationship between the voltage vector and the current vector. As shown in FIG. 17, for example, when a current vector exists on the U-phase axis where the current supplied to the U-phase is maximum (a switching pattern (UP, VN, WN = ON) by a PWM signal related to the U-phase) The current relating to the U phase flows through the shunt resistor 14. However, if the phase difference φ of the voltage vector is significantly different from the current vector (the power factor is reduced), when the voltage vector is decomposed into each element, the current related to the U phase is as shown in FIG. The element of the voltage vector for flowing through the shunt resistor 14 is reduced. For this reason, the switching time for flowing the current relating to the U phase on the shunt resistor 14 is shortened, and the pulse width is narrowed. And the error of the voltage holding means 15 becomes large, and it becomes difficult to detect the peak value with high accuracy.

  FIG. 18 is a diagram for illustrating a relationship between control of the electric motor 8 according to the fourth embodiment and time. During heating operation or the like, the load on the electric motor 8 increases with time due to the influence of frost formation. Therefore, as shown in FIG. 18, when the rotational speed decreases with time (FIG. 18 (a)), The power factor decreases (FIG. 18 (b)). Therefore, as described above, the current detection error increases with the deterioration of the power factor (FIG. 18C), and it becomes difficult to keep the current value constant (here, FIG. 18C shows voltage holding means). 15 shows that the peak voltage Vc held by the voltage 15 is lower than the original peak voltage and the error is widened. Further, when the error becomes large, an overcurrent interruption may occur depending on the operation state, so that the operation may not be continued.

  FIG. 19 is a diagram showing the configuration of the inverter control means 11 according to the fourth embodiment of the present invention. In the present embodiment, the current value obtained based on the peak voltage Vc is corrected in order to prevent overcurrent interruption due to an increase in current detection error. Therefore, the present embodiment is different from the first embodiment in that the rotational electrical angular frequency ω of the electric motor 8 related to the output of the position / velocity estimation means 19 is output to the current detection means 20 as shown in FIG.

  FIG. 20 is a diagram showing the configuration of the current detection means 20 according to Embodiment 4 of the present invention. The current detection unit 20 of the present embodiment is different from that of the first embodiment in that a current detection value correction unit 32 is provided between the voltage / current conversion unit 23 and the limiting unit 24.

  As described above, the rotational electrical angular frequency ω increases or decreases according to the load status of the electric motor 8. Here, when the rotational electrical angular frequency ω decreases, the load is high and the power factor is poor. For this reason, the current detection value correction means 32 has a storage device, and the relationship between the rotational electrical angular frequency ω and the current detection error is stored in advance in the storage device as data. Then, according to the rotational electrical angular frequency ω output from the position / velocity estimation means 19, the current value obtained by the voltage-current conversion means 23 is corrected from the data stored in the storage device. As described above, it is possible to correct the current value with a simple process.

  Here, in the present embodiment, the current value is corrected by the rotational electrical angular frequency ω related to the output of the position / velocity estimation means 19, but the parameters related to the correction are not limited to the rotational electrical angular frequency ω. For example, it goes without saying that there is no problem even if the current value is corrected based on the power factor, the pulse width, and the like obtained by calculation or the like.

  As described above, according to the motor drive device of the fourth embodiment, the current detection value correction unit 32 is provided in the current detection unit 20, and the current related to the conversion of the voltage-current conversion unit 23 based on the rotational electrical angular frequency ω. Since the value is corrected, a stable current value I can be detected as in the first embodiment by correcting the error based on, for example, the state of the load and the power factor. For this reason, for example, when used for driving the electric motor 8 that rotates the blower fan 7 of the air conditioner, the electric motor 8 and the air conditioner are not stopped in order to block overcurrent due to an error, and stable operation is performed. Can do. As described above, it is possible to obtain an air conditioner that exhibits the same effect as described in the first embodiment.

Embodiment 5 FIG.
In Embodiments 1 to 4 described above, the electric motor 8 is controlled based on the output of the magnetic pole position sensor, but there is no problem even if this control is performed using the magnetic pole position sensorless control based on the phase current detection of the motor. Needless to say.

  In each of the above-described embodiments, description has been given of driving the electric motor 8 that rotates the blower fan 7 that sends air to the outdoor heat exchanger 3 included in the heat source unit of the air conditioner by using the driving device of the present invention. . According to each of the embodiments described above, it can be seen that the effect of the drive device can be effectively exhibited when the drive device of the present invention is applied to the outdoor unit of the air conditioner, particularly during heating operation. However, the application of the drive device of the present invention is not limited to the air conditioner. For example, as an application example of the drive device of the present invention, it can be applied not only to an air conditioner but also to a device using a blower fan, a screw or the like rotated by an electric motor, such as a heat pump water heater or a vacuum cleaner.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 Four way valve, 3 Outdoor heat exchanger, 4 Expansion valve, 5 Indoor heat exchanger, 6 Refrigerant piping, 7 Blower fan, 8 Electric motor, 9 Inverter means, 9a-9f Switching element, 10 DC power supply, 11 Inverter control means, 12 DC voltage detection means, 13 magnetic pole position detection means, 14 shunt resistance, 15 voltage holding means, 16 backflow prevention means, 17 charging means, 18 discharge means, 19 position / speed estimation means, 20 current detection means, 21 Rotation speed command calculation means, 22 Voltage control means, 23 Voltage current conversion means, 24 Limiting means, 25 Constant current rotation speed calculation means, 26 Rotation speed command restriction means, 27 Voltage command amplitude calculation means, 28 Three-phase voltage command calculation Means, 29 PWM generation means, 30 low-pass filter means, 31 peak hold means, 32 current detection value correction means

Claims (11)

Inverter means for converting a DC voltage from a DC power source and applying an AC voltage to the motor;
A shunt resistor connected between the DC power source and the inverter means;
Charging means having a capacitor, and causing the capacitor to hold a peak value of the voltage across the shunt resistor by charging;
Discharging means connected in parallel with the capacitor and discharging the charge charged in the capacitor with a first time constant;
Current detection means having current detection value correction means, and detecting the current flowing through the shunt resistor with error correction based on the power factor of the motor ;
An electric motor drive device comprising: inverter control means for controlling a frequency of an alternating voltage applied to the electric motor by the inverter means so that the current detected by the current detection means becomes a predetermined value.   2. The motor driving device according to claim 1, wherein the first time constant is 1/6 times or more of a period of an AC voltage applied to the electric motor by the inverter unit.   The motor driving device according to claim 1, wherein the current detection unit detects a current based on a peak value of the both-ends voltage and a resistance value of the shunt resistor.   4. The electric motor drive according to claim 1, wherein the current detection unit further includes a low-pass filter unit that smoothes the detected current by a low-pass filter having a second time constant. apparatus.   The motor driving device according to claim 4, wherein the second time constant is larger than the first time constant.   6. The motor driving apparatus according to claim 4, wherein the low-pass filter unit further corrects the current smoothed by the low-pass filter.   The current detection means further includes a maximum value detection means for detecting a maximum value of the current related to detection, and an attenuation means for attenuating the maximum value of the current detected by the maximum value detection means with a third time constant. The drive device for an electric motor according to any one of claims 1 to 3.   The motor driving device according to claim 7, wherein the third time constant is larger than the first time constant. Current detection value correcting means, said inverter means based on the frequency of the AC voltage applied to the motor, the motor driving device according to claim 1, characterized in that to correct the value of the current. Motor driving device according to any one of claims 1 to 9, characterized in that driving the motor for rotating the fan. An air conditioner comprising the electric motor drive device according to any one of claims 1 to 10 for driving an electric motor that rotates a blower fan that promotes heat exchange in a heat exchanger provided in an outdoor unit. .

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