JP2010124585A - Motor-driving inverter control device and air-conditioner having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small, light-weight, and low-cost motor-driving inverter control device. <P>SOLUTION: The small, light-weight, and low-cost motor-driving inverter control device can be attained by using a small-capacity reactor 11, a small-capacity capacitor 12, and further, a bidirectional switch. Even when the motor drive is difficult or impossible due to large variations in the inverter input voltage, an inverter is operated by a motor voltage command correcting means 17, such that the voltage applied to a motor is maintained at a substantially fixed level, thus motor drive is maintained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor drive inverter control device using a small capacity reactor and a small capacity capacitor, and further relates to an air conditioner using a motor drive inverter control device as an inverter device.

  As a general induction motor drive inverter control device used in a general-purpose inverter or the like, a V / F control type induction motor drive inverter control device as shown in FIG. 11 is well known (for example, non-patent). Reference 1).

  In FIG. 11, the main circuit is composed of a DC power supply device 113, an inverter 3 and an induction motor 4, and the DC power supply device 113 is connected to the AC power supply 1, the rectifier circuit 2, and the DC voltage source of the inverter 3. For this purpose, a smoothing capacitor 112 that accumulates electric energy and a power factor improving reactor 111 of the AC power source 1 are included.

On the other hand, in the control circuit, the V / F control pattern 13 which determines the motor voltage applied to the induction motor 4 based on the speed command omega ^* of the induction motor 4, a motor voltage value that is determined from the V / F control pattern 13 From the motor voltage creating means 14 for creating the motor voltage command value of the induction motor 4 based on the motor voltage and the PWM control means 18 for creating the PWM signal of the inverter 3 based on the motor voltage command value created from the motor voltage creating means 14 It is configured.

  An example of a general V / F control pattern 13 is shown in FIG.

As shown in FIG. 12, the motor voltage value applied to the induction motor 4 is uniquely determined with respect to the speed command ω ^* . Generally, the speed command ω ^* and the motor voltage value are stored as table values in the memory of a computing device such as a microcomputer, and for speed commands ω ^* other than the table values, linear interpolation is performed from the table values. The motor voltage value is derived.

  Here, when the AC power supply 1 is 220 V (AC power supply frequency 50 Hz), the input of the inverter 3 is 1.5 kW, and the smoothing capacitor 112 is 1500 μF, the harmonics of the AC power supply current when the power factor improving reactor 111 is 5 mH and 20 mH. FIG. 13 shows the relationship between the wave component and the order with respect to the AC power supply frequency.

  FIG. 13 is shown together with the IEC (International Electrotechnical Commission) standard. When the power factor improving reactor 111 is 5 mH, the third harmonic component greatly exceeds that of the IEC standard. In the case of, it is understood that the IEC standard is cleared in the harmonic components up to the 40th order.

  For this reason, it is necessary to take measures such as further increasing the inductance value of the power factor improving reactor 111 in order to clear the IEC standard even when the load is high, increasing the size and weight of the inverter device, and further increasing the cost. There was an inconvenience of inviting.

  Therefore, for example, a DC power supply device as shown in FIG. 14 has been proposed as a DC power supply device that suppresses an increase in the inductance value of the power factor improving reactor 111 and achieves a reduction in power harmonic components and an increase in power factor. .

  In FIG. 14, the AC power supply voltage of the AC power supply 1 is applied to the AC input terminal of the full-wave rectifier circuit formed by bridge-connecting the diodes D1 to D4, and the output is charged to the intermediate capacitor C via the reactor Lin. The electric charge of the intermediate capacitor C is discharged to the smoothing capacitor CD, and a DC voltage is supplied to the load resistor RL. In this case, the transistor Q1 is connected to the positive and negative DC current path connecting the load side of the reactor Lin and the intermediate capacitor C, and the transistor Q1 is driven by the base drive circuit G1.

  The circuit further includes pulse generation circuits I1 and I2 for applying a pulse voltage to the base drive circuit G1, and a dummy resistor Rdm. The pulse generation circuits I1 and I2 are circuits for detecting a zero cross point of the AC power supply voltage, respectively. From the detection of the zero cross point, the pulse current circuit is configured to flow a pulse current through the dummy resistor Rdm until the instantaneous value of the AC power supply voltage becomes equal to the voltage across the intermediate capacitor C.

  Here, the pulse generation circuit I1 generates a pulse voltage in the first half of the half cycle of the AC power supply voltage, and the pulse generation I2 generates a pulse voltage in the second half of the half cycle of the AC power supply voltage.

  When the transistor Q1 is turned on and a current is forced to flow through the reactor Lin, a backflow prevention diode D5 is connected so that the charge of the intermediate capacitor C is not discharged through the transistor Q1, and further, the intermediate capacitor C A backflow prevention diode D6 and a reactor Ldc for enhancing the smoothing effect are connected in series to a path for discharging the electric charge of the current to the smoothing capacitor CD.

With the above configuration, the transistor Q1 is turned on in a part or all of the phase interval in which the instantaneous value of the AC power supply voltage does not exceed the voltage across the intermediate capacitor C, thereby suppressing the increase in size of the device and the harmonics. Component reduction and higher power factor can be achieved.
JP-A-9-266684 Refer to pages 661 to 711 of "Inverter Drive Handbook", Inverter Drive Handbook Editorial Committee, 1995 First Edition, published by Nikkan Kogyo Shimbun.

  However, the above-described conventional configuration still has the smoothing capacitor CD having a large capacity and the reactor Lin (described in the simulation result at 1500 μF and 6.2 mH in Patent Document 1), and further the intermediate capacitor. C, transistor Q1, base drive circuit G1, pulse generation circuits I1 and I2, dummy resistor Rdm, backflow prevention diodes D5 and D6, and a reactor Ldc that enhances the smoothing effect, thereby increasing the size of the device and the number of parts. There has been a problem of incurring a cost increase accompanying the increase.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a motor drive inverter control device that is small, light, and low in cost.

In order to solve the above-described problems, the present invention provides an inverter control device including a bidirectional switch that converts AC power from an AC power source into AC power having a desired frequency and a desired voltage and supplies the AC power to a motor. A predetermined small-capacitance capacitor for absorbing the regenerative energy of the motor is provided between the predetermined small-capacity reactor connected to the AC input line, and the motor of the motor is based on the speed command value of the motor. Motor voltage command creating means for creating a voltage command value, input voltage detecting means for detecting an input voltage value of the inverter, and the inverter that obtains a preset input voltage reference value of the inverter from the input voltage detecting means An input voltage correction coefficient is derived by dividing by the input voltage detection value of the input voltage, and when the input voltage detection value is zero, the input voltage correction coefficient Those having an input voltage correction means for setting a predetermined maximum value of the input voltage correction coefficient, and a motor voltage command correcting means for producing a motor voltage command correction value of the motor.

  The motor voltage command correction means for creating the motor voltage command correction value for the motor multiplies the motor voltage command value obtained from the motor voltage command creation means by the input voltage correction coefficient that is the output value of the input voltage correction means. It is obtained by combining them.

  With the above configuration, a small-capacity capacitor and a small-capacity reactor can be used. Further, since a rectifier circuit is not required by using a bidirectional switch, a small, lightweight, low-cost motor drive inverter control device can be realized. Even when the inverter input voltage fluctuates significantly and it becomes difficult or impossible to drive the motor, it is possible to operate the inverter so that the voltage applied to the motor becomes almost constant and to keep the motor driven. .

  With the above configuration, it is possible to maintain the motor drive even when the inverter input voltage fluctuates significantly and becomes zero.

  The input voltage correction means has an input voltage correction coefficient having at least a preset upper limit value or lower limit value.

  With the above configuration, it is possible to maintain the motor drive even when the inverter input voltage fluctuates significantly, and to suppress fluctuations in the AC power supply current by having a preset upper or lower limit value. Thus, the AC power factor can be improved and the harmonic component of the AC power supply current can be suppressed.

  Further, the input voltage correction means increases the input voltage correction coefficient in proportion to the input voltage detection value when the input voltage detection value is larger than the input voltage reference value.

  With the above configuration, it is possible to maintain the drive of the motor even when the inverter input voltage fluctuates significantly, and further increase the input voltage correction coefficient when the inverter input voltage is larger than the input voltage reference value. Thus, it is possible to improve the output torque of the motor.

  Also, the inverter operating frequency is steadily fixed within a frequency range in which the inverter operating frequency is an even multiple of the AC power supply frequency and a frequency range that is set in front of and behind the resonant frequency. This is to avoid this.

  With the above configuration, it is possible to prevent unstable operation of the motor by avoiding the resonance phenomenon between the inverter frequency and the AC power supply frequency, and to realize stable driving.

  The combination of the small-capacity reactor and the small-capacitance capacitor is determined so that the resonance frequency of the small-capacity reactor and the small-capacitance capacitor is larger than 40 times the AC power supply frequency.

  With the above configuration, it is possible to suppress the harmonic component of the AC power supply current and clear the IEC standard.

Further, the capacitance of the small capacitor is determined so that the maximum value of the detected input voltage that increases when the inverter stops is smaller than the withstand voltage of the electric element included in the peripheral circuit of the inverter.

  With the above configuration, it is possible to prevent the inverter drive elements and peripheral circuits from being destroyed.

  Further, the carrier frequency of the inverter is determined so as to satisfy a preset AC power source power factor value.

  With the above configuration, it is possible to satisfy a preset AC power source power factor value, and by setting the minimum necessary carrier frequency, it is possible to suppress the inverter loss to the minimum necessary.

  As is apparent from the above, the present invention provides an inverter control device including a bidirectional switch that converts AC power from an AC power source into AC power having a desired frequency and a desired voltage and supplies the AC power to an AC input side. A predetermined small-capacitance capacitor for absorbing the regenerative energy of the motor is provided between the predetermined small-capacity reactor connected to the AC input line, and the motor of the motor is based on the speed command value of the motor. Motor voltage command creating means for creating a voltage command value, input voltage detecting means for detecting an input voltage value of the inverter, and the inverter that obtains a preset input voltage reference value of the inverter from the input voltage detecting means An input voltage correction coefficient is derived by dividing by the input voltage detection value of the input voltage, and when the input voltage detection value is zero, the input voltage correction coefficient Those having an input voltage correction means for setting a predetermined maximum value of the input voltage correction coefficient, and a motor voltage command correcting means for producing a motor voltage command correction value of the motor. The motor voltage command correction means for creating a motor voltage command correction value for the motor includes the motor voltage command value obtained from the motor voltage command creation means and an input voltage correction coefficient that is an output value of the input voltage correction means. By using this configuration, a rectifier circuit becomes unnecessary by using a small-capacitor and a small-capacitor, and by using a bidirectional switch. A low-cost inverter control device for motor drive can be realized, and the inverter is operated so that the voltage applied to the motor is almost constant even when the inverter input voltage fluctuates significantly and it becomes difficult or impossible to drive the motor. And driving the motor can be maintained.

  Further, according to the present invention, the input voltage correction means derives the input voltage correction coefficient by dividing the input voltage reference value by the input voltage detection value, and when the input voltage detection is zero, the input voltage correction coefficient is preset to the input voltage correction coefficient. The maximum value of the input voltage correction coefficient is set. According to this configuration, it is possible to maintain the motor drive even when the inverter input voltage fluctuates and becomes zero. Play.

  Further, according to the present invention, the input voltage correction means has an input voltage correction coefficient having at least a preset upper limit value or lower limit value. According to this configuration, even when the inverter input voltage fluctuates significantly, It is possible to maintain the drive of the motor, and further suppress the fluctuation of the AC power supply current by having a preset upper limit value or lower limit value, improve the AC power supply power factor and reduce the harmonic component of the AC power supply current There is an effect that it can be suppressed.

In the present invention, the input voltage correction means increases the input voltage correction coefficient in proportion to the input voltage detection value when the input voltage detection value is larger than the input voltage reference value. Even when the inverter input voltage fluctuates significantly, it is possible to maintain the motor drive, and when the inverter input voltage is larger than the input voltage reference value, the input voltage correction coefficient is increased to increase the motor The output torque can be improved.

  Further, according to the present invention, the inverter operating frequency is steady within a frequency range in which the inverter operating frequency is an even multiple of the AC power supply frequency and a frequency range set in advance around the resonant frequency. According to this configuration, it is possible to prevent unstable operation of the motor by avoiding the resonance phenomenon between the inverter frequency and the AC power supply frequency, and realize stable driving. The effect that it is.

  The present invention also determines the combination of the small-capacity reactor and the small-capacitance capacitor so that the resonance frequency of the small-capacity reactor and the small-capacitance capacitor is greater than 40 times the AC power supply frequency. It is possible to suppress the harmonic component of the AC power supply current and to clear the IEC standard.

  Further, according to the present invention, the capacitance of the small-capacitance capacitor is determined so that the maximum value of the input voltage detection value that rises when the inverter stops is smaller than the withstand voltage of the electric element included in the peripheral circuit of the inverter. Therefore, according to this configuration, there is an effect that it is possible to prevent each drive element and peripheral circuit of the inverter from being destroyed.

  Further, the present invention determines the carrier frequency of the inverter so as to satisfy a preset AC power source power factor value. According to this configuration, the preset AC power source power factor value can be satisfied. It becomes possible, and there is an effect that the inverter loss can be suppressed to the minimum necessary by setting the minimum necessary carrier frequency.

  Embodiments of the present invention will be described below with reference to the drawings. In the following embodiment, the induction motor drive inverter control device is described. However, the present invention is not limited to the induction motor drive inverter control device, and can be applied to all motor drive inverter control devices. is there.

(Embodiment 1)
FIG. 1 shows a system configuration diagram of an induction motor driving inverter control apparatus showing a first embodiment of the present invention. In FIG. 1, the main circuit of the inverter control device is an AC power source 1, a small-capacity reactor 11 of 2 mH or less, a small-capacitance capacitor 12 of 100 μF or less, and a bidirectional that converts AC power into AC power of variable voltage and variable frequency. The inverter 3 includes a switch, and the induction motor 4 is driven by AC power converted by the inverter 3.

On the other hand, the control circuit determines a motor voltage value to be applied to the induction motor 4 based on the speed command ω ^* of the induction motor 4 and a motor voltage value determined from the V / F control pattern 13. Motor voltage generating means 14 for generating a motor voltage command value for the induction motor 4 based on the input voltage, input voltage detecting means 15 for detecting the input voltage value of the inverter 3, and a preset input voltage reference value of the inverter 3 and input. The input voltage correction means 16 for deriving the ratio of the input voltage detection value of the inverter 3 obtained from the voltage detection means 15, the motor voltage command value obtained from the motor voltage command creation means 14, and the output value of the input voltage correction means 16. The motor voltage command value is corrected by multiplying it with a certain input voltage correction coefficient to reduce the induction mode. Motor voltage command correction means 17 for creating a motor voltage command correction value for the motor 4 and PWM control means 18 for generating a PWM signal for the inverter 3 based on the motor voltage command correction value created from the motor voltage command correction means 17 It is configured.

  Since the V / F control pattern 13 has been described in the above-described conventional technology, the description thereof is omitted here (the inverter control device for driving an induction motor of the V / F control method in FIG. 11).

  Hereinafter, a specific method will be described.

The motor voltage command creating means 14 creates motor voltage command values v _u ^* , v _v ^* , v _w ^* by the calculation represented by the formula (1).

Here, V _m is a motor voltage value determined from the V / F control pattern 13, and θ ₁ is derived by time-integrating the speed command ω ^* as expressed by the equation (2).

FIG. 2 is a diagram showing a first embodiment of the input voltage correction means 16 according to the present invention. In the input voltage correction means 16, the input voltage reference value _{Vpn0 of} the inverter 3 set in advance and the input voltage detection means are shown. deriving the input voltage correcting coefficient k _pn as in equation (3) using the input voltage detection value v _pn of inverter 3 obtained from 15.

Here, in the present invention because of the use of small-capacity capacitor, because when the input voltage detection value v _pn becomes zero occurs, it is necessary to set a small term [delta] ₀ for zero divide prevented.

Instead of the small term δ ₀ of the number (3), when the input voltage detection value v _pn is zero, the input voltage correction coefficient k _pn is set to the maximum value of the preset input voltage correction coefficient to zero. It is possible to prevent splitting.

That is, the input voltage correction coefficient k _pn may be derived as shown in _Equation (4).

Here, k _{pn — max} is a preset maximum value of the input voltage correction coefficient.

Further, the motor voltage command correction means 17 uses the motor voltage command values v _u ^* , v _v ^* , v _w ^* and the input voltage correction coefficient k _pn to _{express the} motor voltage command correction values v _uh ^* , v _vh ^* and v _wh ^* are derived.

  As described above, an inverter controller for driving an induction motor that is small, light, and low-cost can be realized by using a small-capacity reactor and a small-capacitance capacitor, and the inverter input voltage varies greatly, making it difficult or impossible to drive the induction motor. Even in this case, the inverter can be operated so that the voltage applied to the induction motor is substantially constant, and the drive of the induction motor can be maintained.

  The present invention is not limited to the induction motor drive inverter control device by V / F control as in the above-described embodiment, and the present invention is also applied to the induction motor drive inverter control device by well-known vector control. Is possible.

  It should be noted that the present invention is applicable both when a speed sensor such as a pulse generator cannot be used, such as a compressor drive motor in an air conditioner, or when a speed sensor can be provided, such as a servo drive. Is applicable.

(Embodiment 2)
FIG. 3 shows a second embodiment of the input voltage correcting means according to the present invention. In FIG. 3, an input voltage correction coefficient k _pn has an upper limit value k _pn1 and a lower limit value k _pn2 set in advance, and is expressed as the number (6).

Here, V _pn1 and V _pn2 are input voltage value detection values at the upper limit value k _pn1 and the lower limit value k _pn2 of the input voltage correction coefficient, respectively.

Note that the input voltage correction coefficient k _pn does not necessarily have both the upper limit value k _pn1 and the lower limit value k _pn2 as shown in FIG. 3, and may have only one of them depending on the operating conditions.

  In addition, in the conventional inverter control device for driving the induction motor (including the inverter control device for driving the induction motor using the DC power supply of Patent Document 1), the electric energy stored in the electrolytic capacitor having a large capacity exceeding 1000 μF is used. It is possible to maintain the drive of the induction motor under load conditions within the operating range, but in the present invention, a small-capacity reactor and a small-capacitance capacitor are used, and the electrical energy stored in the small-capacitance capacitor is small. In order to maintain the drive of the induction motor even when there is a shortage of electrical energy, the magnetic energy of the small-capacity reactor must be used together, so the drive characteristics of the induction motor and the electrical characteristics of the AC power supply are in a trade-off relationship. is there.

  Therefore, when there is a margin in the limit load withstand capacity of the induction motor, it is possible to improve the electrical characteristics of the AC power supply by suppressing excessive voltage correction.

Here, FIG. 5 and FIG. 6 show the results of operating the induction motor driving inverter control device of the present invention. Figure 5 is a operation result when both the upper and lower limit values in the input voltage correcting coefficient k _pn not set, Both upper limit value k _pn1 and the lower limit k _{pn 2} in FIG. 6 input voltage correcting coefficient k _pn This is an operation result in the case of being set, and the effect is obvious if the reactor current waveforms in FIGS. 5 and 6 are compared.

  The specifications at this time are as follows: the inductance value of the small capacity reactor is 2 mH, the capacity of the small capacity capacitor is 25 μF, the AC power supply is 220 V (50 Hz), the inverter operating frequency is 57 Hz (here, the number of poles of the motor is two) Therefore, the inverter operating frequency is equal to the motor speed command value), and the inverter carrier frequency is 5 kHz.

As described above, the input voltage correction coefficient k _pn has at least a preset upper limit value k _pn1 or lower limit value k _pn2 , thereby suppressing fluctuations in the AC power supply current, improving the AC power supply power factor, and increasing the AC power supply current harmonics. Wave components can be suppressed.

(Embodiment 3)
FIG. 4 shows a third embodiment of the input voltage correcting means according to the present invention. In FIG. 4, when the input voltage detection value v _pn is larger than the input voltage reference value V _pn0, the input voltage correction coefficient k _pn is increased in proportion to the input voltage detection value v _pn . It is expressed as follows.

Here, δ ₀ is a minute term for preventing zero _division , and in the region where the input voltage detection value v _pn is V _{pn0 to} V _pn3 , the input voltage correction coefficient k _pn is prevented so that the input voltage correction coefficient k _pn does not change suddenly. set the switch grace period _pn the resolve operation, the input voltage detection value v _pn is in the region beyond the V _pn4 have a maximum value k _pn4 at increasing input voltage correcting coefficient k _pn.

Note that the switching grace period and the upper limit value k _pn4 do not necessarily have to be set, and may not be set according to the driving situation.

Further, it is generally known that the output torque of the induction motor is proportional to the square of the voltage applied to the motor (for example, see page 33 of “Inverter Drive Handbook”, edited by Inverter Drive Handbook Editorial Committee, 1995). First edition, Nikkan Kogyo Shimbun issued), in the case of insufficient exposure limit tolerance induction motor, the motor applied by the input voltage detection value k _pn performs further voltage correction at a greater interval than the input voltage reference value V _PN0 It is possible to increase the voltage and maintain the drive of the induction motor.

Thus, it is possible to improve the output torque of the induction motor by the input voltage detection value v _pn is larger input voltage correcting coefficient k _pn is greater than the input voltage reference value V _PN0.

(Embodiment 4)
A specific method for setting the inverter operating frequency according to the present invention will be described below.

Since the induction motor driving inverter control apparatus of the present invention uses a small-capacitance capacitor, the inverter input voltage pulsates greatly at twice the frequency of the AC power supply frequency f _S as shown in FIG. 5 or FIG.

Therefore, the frequency of the inverter operating frequency f ₁ is an even multiple of the AC power source frequency f _S, synchronous resonance (twice the frequency of the AC power source frequency f _S) and the frequency inverter input voltage pulsates it occurs.

Here, FIG. 7 shows the result when the inverter control device for driving the induction motor of the present invention is operated. FIG. 7 shows an operation result when the inverter operating frequency f ₁ is twice the AC power supply frequency f _S , and a resonance phenomenon occurs in synchronization with the frequency at which the inverter input voltage pulsates.
It can be seen that a negative DC component is superimposed on the motor current.

  Therefore, brake torque is generated in the induction motor, and adverse effects such as a decrease in output torque and an increase in motor loss occur.

  The specifications at this time are as follows: the inductance value of the small capacity reactor is 0.5 mH, the capacity of the small capacity capacitor is 10 μF, the AC power source is 220 V (50 Hz), the inverter operating frequency is 100 Hz (here, the number of poles of the motor is Because of the two poles, the inverter operating frequency is equal to the motor speed command value), and the inverter carrier frequency is 5 kHz.

Therefore, in the setting of the inverter operation frequency f _1, the inverter operating frequency f ₁ is required to avoid being constantly fixed case such that the number (8).

  Here, n is an integer, Δf is a preset frequency width, and the frequency width Δf is basically set so that the influence of the resonance phenomenon described above is reduced.

Further, when the inverter operating frequency f ₁ exceeds the resonance frequency obtained by the equation (8), it is avoided that the inverter operating frequency f ₁ is changed at a stroke in a transient state such as acceleration or deceleration and fixed at the resonance frequency.

  Note that the frequency width Δf does not necessarily need to be set, and may not be set depending on the driving condition (such as during light load) (in this case, Δf = 0 may be set).

  As described above, by avoiding the resonance phenomenon between the inverter frequency and the AC power supply frequency, unstable operation of the induction motor can be prevented and stable driving can be realized.

(Embodiment 5)
A specific method for determining the specifications of the small-capacity capacitor and small-capacity reactor according to the present invention will be described below.

In the inverter control apparatus for driving an induction motor according to the present invention, the resonance frequency f _LC (LC resonance frequency) of the small capacitor and the small reactor is set to suppress the harmonic component of the AC power supply current and to clear the IEC standard. The combination of the small-capacity capacitor and the small-capacity reactor is determined so as to be larger than 40 times the AC power supply frequency f _S.

Here, when the capacitance of the small-capacitance capacitor is C [F] and the inductance value of the small-capacity reactor is L [H], the LC resonance frequency f _LC is expressed by the following equation (9).

That is, the combination of the small-capacitance capacitor and the small-capacity reactor is determined so as to satisfy f _LC > 40 f _S (because the IEC standard specifies the 40th harmonic in the harmonic component of the AC power supply current). .

  As described above, by determining the combination of the small-capacitance capacitor and the small-capacity reactor, the harmonic component of the AC power supply current can be suppressed and the IEC standard can be cleared.

  Next, determination of the capacitance of the small capacitor will be described below.

  When the inverter stops, the small-capacitance capacitor absorbs the regenerative energy of the induction motor (the magnetic energy stored in the inductance component of the induction motor until just before the stop) and the input voltage value of the inverter rises. The capacity of the small-capacitance capacitor is determined so that the maximum value of the input voltage becomes smaller than the breakdown voltage of the element.

  With the above configuration, it is possible to prevent the peripheral circuit from being destroyed by determining the capacity of the small-capacitance capacitor so that the maximum value of the inverter input voltage is smaller than the withstand voltage of each driving element.

  The inductance value of the small capacity reactor can be automatically determined by the above-described method.

  A specific method for setting the inverter carrier frequency according to the present invention will be described below.

  In the inverter control apparatus for driving an induction motor according to the present invention, as described in the second embodiment, since the electrical energy stored in the small-capacitance capacitor is small, the drive of the induction motor is maintained even when the electrical energy is insufficient. Therefore, the reactor current waveform is greatly influenced by the carrier frequency of the inverter.

  Therefore, in the inverter control apparatus for driving an induction motor according to the present invention, the carrier frequency of the inverter is set so as to satisfy a preset AC power source power factor value.

  Here, the results when the induction motor driving inverter control apparatus of the present invention is operated are shown in FIGS. 8 shows the operation results when the carrier frequency is 3.3 kHz, FIG. 9 shows the operation result at 5 kHz, and FIG. 10 shows the operation result at 7.5 kHz. When the reactor current waveforms are compared, the reactor current (or AC power supply current) is the carrier frequency. It turns out that the dependence by is large.

  Further, when each AC power factor value was measured with a digital power meter, it was 0.878 when the carrier frequency in FIG. 8 was 3.3 kHz, 0.956 when 5 kHz in FIG. 9, and 7.5 kHz in FIG. It was 0.962.

  The specifications at this time are as follows: the inductance value of the small capacity reactor is 0.5 mH, the capacity of the small capacity capacitor is 10 μF, the AC power supply is 220 V (50 Hz), the inverter operating frequency is 57 Hz (here, the number of poles of the motor is The inverter operating frequency and the motor speed command value are equal because of two poles), and the input power in the AC power supply is 900W.

Here, for example, when the preset AC power factor value is 0.9, the carrier frequency may be set between 3.3 kHz and 5 kHz, and finally the preset AC power source is set. While satisfying the power factor value (0.9 in this case), the carrier frequency is determined to be the lowest.

  As described above, the preset AC power source power factor value can be satisfied, and the inverter loss can be suppressed to the minimum necessary by setting the minimum necessary carrier frequency.

  In the above-described embodiment, the induction motor has been described. However, the present invention can also be applied to other motors.

  INDUSTRIAL APPLICABILITY The present invention provides a small, light, and low cost motor drive inverter control device, and is useful as a motor control device used in an air conditioner or the like.

The system block diagram of the inverter control apparatus for induction motor drive which shows the 1st Embodiment of this invention The figure which shows 1st Embodiment of the input voltage correction means which concerns on this invention The figure which shows 2nd Embodiment of the input voltage correction means which concerns on this invention. The figure which shows 3rd Embodiment of the input voltage correction means which concerns on this invention. The figure which shows the 1st operation result of the inverter control apparatus for induction motor drive of this invention The figure which shows the 2nd operation result of the inverter control apparatus for induction motor drive of this invention The figure which shows the 3rd operation result of the inverter control apparatus for induction motor drive of this invention The figure which shows the 4th operation result of the inverter control apparatus for induction motor drive of this invention The figure which shows the 5th operation result of the inverter control apparatus for induction motor drive of this invention The figure which shows the 6th operation result of the inverter control apparatus for induction motor drive of this invention System configuration diagram of a conventional inverter control device for driving an induction motor The figure which shows an example of the conventional V / F control pattern The diagram which showed the relationship between the harmonic component of alternating current power supply current in the inverter apparatus for induction motor drive of FIG. 11, and the order with respect to alternating current power supply frequency Conventional DC power supply

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 3 Inverter 4 Induction motor 11 Small capacity reactor 12 Small capacity capacitor 13 V / F control pattern 14 Motor voltage command preparation means 15 Input voltage detection means 16 Input voltage correction means 17 Motor voltage command correction means 18 PWM control means

Claims (9)

In an inverter control device including a bidirectional switch that converts AC power from an AC power source into AC power having a desired frequency and a desired voltage and supplies the AC power to the motor, a predetermined small-capacity reactor connected to the AC input side; Between the AC input lines, a capacitor with a predetermined small capacity for absorbing the regenerative energy of the motor is provided,
Motor voltage command creating means for creating a motor voltage command value of the motor based on the speed command value of the motor;
Input voltage detecting means for detecting an input voltage value of the inverter;
An input voltage correction coefficient is derived by dividing a preset input voltage reference value of the inverter by the input voltage detection value of the inverter obtained from the input voltage detection means, and when the input voltage detection value is zero Is an input voltage correction means for setting a maximum value of the input voltage correction coefficient preset in the input voltage correction coefficient,
A motor drive inverter control device comprising motor voltage command correction means for creating a motor voltage command correction value for the motor. The motor voltage command correction means for creating a motor voltage command correction value for the motor includes the motor voltage command value obtained from the motor voltage command creation means and an input voltage correction coefficient that is an output value of the input voltage correction means. 2. An inverter control apparatus for driving a motor according to claim 1, wherein the inverter control apparatus is obtained by multiplication. 2. The motor drive inverter control device according to claim 1, wherein the input voltage correction means has at least an upper limit value or a lower limit value set in advance for the input voltage correction coefficient. The input voltage correction means increases the input voltage correction coefficient in proportion to the input voltage detection value when the input voltage detection value is larger than the input voltage reference value. Inverter control device for motor drive. The inverter operating frequency is steadily fixed within a frequency range in which the inverter operating frequency is an even multiple of the AC power supply frequency and a frequency range set in front of and behind the resonant frequency. The inverter control apparatus for driving a motor according to claim 1, wherein: 2. The motor according to claim 1, wherein a combination of the small-capacity reactor and the small-capacitance capacitor is determined so that a resonance frequency between the small-capacity reactor and the small-capacitance capacitor is larger than 40 times the AC power supply frequency. Drive inverter control device. The capacity of the small-capacitance capacitor is determined so that the maximum value of the input voltage detection value that rises when the inverter is stopped is smaller than the withstand voltage of the electric element included in the peripheral circuit of the inverter. The inverter control device for driving a motor according to claim 1. The motor drive inverter control device according to claim 1, wherein the carrier frequency of the inverter is determined so as to satisfy a preset AC power source power factor value. A compressor for compressing the refrigerant;
A motor for driving the compressor;
An air conditioner comprising: the inverter control device according to claim 1, wherein AC power from an AC power source is converted into AC power of variable voltage and variable frequency and supplied to the motor.

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