KR101272450B1 - Control device of ac motor and refrigerating air conditioner using the same - Google Patents

Abstract

The present invention precisely detects a linear bus current and drives an AC motor with high performance even when the modulation rate is low, such as when the AC motor is used in a low load or low speed region. In the inverter for converting the supplied DC power to AC power, the inverter control circuit for controlling the switch element included in the inverter, the DC bus current detector for detecting the DC bus current flowing through the inverter, the DC bus current detector A low pass filter for smoothing the detected direct current bus current and a compensator for correcting the attenuation of the direct current bus current smoothed by the low pass filter.

Description

CONTROL DEVICE OF AC MOTOR AND REFRIGERATING AIR CONDITIONER USING THE SAME}

The present invention relates to a control device for an AC motor, and more particularly, to a method for estimating a motor current based on a DC bus current of an inverter.

If the motor current flowing through the AC motor can be accurately estimated and used for controlling the AC motor, the AC motor can be driven with higher performance.

In patent document 1, the electric current of two phases is detected from the DC bus current of an inverter, and a motor current is estimated based on this detection value. To this end, it is necessary to detect the current twice within one carrier cycle, and a high speed A / D converter is required.

In Patent Literature 2, unlike Patent Literature 1 in which a current of two phases must be detected, the motor current can be estimated only by the detection value of one phase. However, in order to estimate the motor current once, it is necessary to detect the DC bus current a plurality of times in a predetermined period, and the need for a high speed A / D converter is not improved.

Japanese Patent Application Laid-Open No. 2002-95263 Japanese Patent Application Publication No. 2007-221999

When the AC motor is driven in a low load or low speed region, in order to lower the modulation rate, the energization period of the DC bus current of the inverter is shortened. When the energization period of the DC bus current is short, it is difficult to detect the DC bus current multiple times within the energization period. In the conventional technique, an error occurs in the detection of the DC bus current, and the motor current cannot be accurately estimated. The problem that an AC motor cannot be driven with high performance arises.

An object of the present invention is to provide a method of accurately estimating a motor current and driving an AC motor with high performance by accurately detecting a linear bus current even when the inverter has a short current duration.

 DC power supply, an inverter for converting DC power supplied from the DC power supply into AC power, an inverter control circuit for controlling switch elements included in the inverter, and a DC bus current detector for detecting a DC bus current flowing through the inverter And a low pass filter for smoothing the DC bus current detected by the DC bus current detector, and a compensator for correcting the attenuation of the DC bus current smoothed by the low pass filter.

According to the present invention, even when the modulation rate is low, the linear bus line current can be detected accurately. For this reason, the AC motor can be driven with high performance even in a low load or low speed region.

1 is a configuration diagram of a control device of Embodiment 1. FIG.
Fig. 2 is a diagram of voltage and current waveforms in the control device of Example 1;
FIG. 3 is a vector diagram showing respective components of voltage and current in the control device of Example 1. FIG.
4 is a waveform diagram of a logical DC bus current IDC in the control device of Example 1. FIG.
5 is a waveform diagram of a DC bus current when the modulation rate is low in the control device of Example 1. FIG.
6 is a waveform diagram of a DC bus current when the modulation rate is high in the control device of Example 1. FIG.
FIG. 7 is a waveform diagram showing switching of current detection phase in Example 3. FIG.
8 is a waveform diagram showing the followability of DC bus current detection in Example 4. FIG.
9 is a schematic view of a fifth embodiment;
10 is a waveform diagram of linear busbar currents when the filter time constant of Example 5 is switched;
11 is a schematic view of a sixth embodiment;

EMBODIMENT OF THE INVENTION Hereinafter, each Example of this invention is described using drawing.

Example 1

The control apparatus of Example 1 is demonstrated using FIGS. In FIG. 1, the AC motor 1 outputs torques corresponding to three-phase alternating currents Iu, Iv, and Iw applied from the inverter 2. The inverter 2 is provided with switch elements Sup, Sun, Svp, Svn, Swp, and Swn. The inverter 2 applies three-phase AC voltages Vu, Vv, Vw to the AC motor 1, and supplies AC power. The DC power supply 3 applies DC voltage VDC to the inverter 2, and supplies DC power. The DC bus current detector 4 detects the DC bus current IDC of the inverter 2. The low pass filter 5 smoothes the detection value of the direct current bus current detector 4. The corrector 6 corrects the attenuation of the detected value by the low pass filter 5. The inverter control circuit 7 controls on / off of the switch elements Sup, Sun, Svp, Svn, Swp, Swn. In addition, the detail of the PWM signal generation part 7a, the vector control part 7b, and the current estimation part 7c in the inverter control circuit 7 is demonstrated in Example 2. As shown in FIG.

The inverter 2 applies the three-phase AC voltages Vu, Vv, and Vw of Equation 1 to the AC motor 1, and the three-phase AC current Iu of Equation 2 is applied to the AC motor 1. Iv, Iw flow. The three-phase alternating voltage of (Equation 1) is shown in Fig. 2A, and the three-phase alternating current of Equation 2 is shown in Fig. 2B.

In Equations 1 and 2, V1 is a motor voltage, I1 is a motor current, θv is a voltage phase based on the U axis, and φ is a voltage / current phase difference.

Next, each component of voltage current is demonstrated using FIG. In FIG. 3, the U axis | shaft shows the U phase coil direction of the stator of the AC motor 1. As shown in FIG. The components in the U-axis direction of the motor voltage V1 and the motor current I1 are defined as the U phase voltage Vu and the U phase current Iu, respectively. Similarly, although abbreviate | omitted in FIG. 3, the component of a V-axis direction is made into V phase voltage Vv and V phase current Iv, and the component of a W-axis direction is made into W phase voltage Vw and W phase current Iw. In addition, the component of the motor voltage V1 direction of the motor current I1 is made into the effective current Ia, and the component orthogonal to it is made into the reactive current Ir.

The direct current bus current detector 4 detects any one of the three-phase alternating currents Iu, Iv, and Iw as the direct current bus current IDC. Which of the three-phase alternating currents is detected depends on a combination of on / off of the switch elements Sup, Sun, Svp, Svn, Swp, Swn. 4, the relationship between the on / off combination of the switch element and the theoretical waveform of the DC bus current IDC will be described in detail.

4A is a carrier signal of a carrier period Tc. Here, an example in which a triangular wave is used as a carrier signal is shown, but a high wave may be used.

The inverter control circuit 7 compares the carrier signals with the command values Vu *, Vv *, Vw * of the three-phase AC voltage, and determines on / off of the switch elements Sup, Sun, Svp, Svn, Swp, Swn. .

Hatching of Su in FIG. 4B corresponds to a period in which the carrier signal becomes Vu * or less, and represents a period in which the switch element Sup is turned on. Similarly, hatching of Sv in FIG. 4C corresponds to a period during which the carrier signal becomes Vv * or less, and indicates a period in which the switch element Svp is turned on. Hatching of Sw in FIG. 4D is It corresponds to a period during which the carrier signal becomes Vw * or less, and represents a period in which the switch element Swp is turned on.

The switch elements Sup and Sun shown in FIG. 1 operate complementarily, respectively, and when one is on, the other is off. Similarly, the switch elements Svp and Svn, Swp and Swn also operate complementarily, and when one is on, the other is off. However, in order to prevent the short circuit of the inverter 2, you may set the dead time which turns off both.

As shown in Fig. 4, when all of Sup, Svp, and Swp are on and all are off, the DC bus current IDC does not flow. On the other hand, in the period Tu in which only Sup is on, the U-phase current Iu flows in the forward direction, and in the period Tw in which Sup and Svp are on, the W-phase current Iw flows in the reverse direction. As a result, logically, the DC bus current IDC shown in Fig. 4E is obtained.

Next, the detection method of the DC bus current IDC by the DC bus current detector 4 is demonstrated concretely using FIG.4 (e). The DC bus current detector 4 detects the U-phase current Iu at timing A after Ts from Sup on when the carrier signal descends. The reason for setting Ts will be described later. In addition, instead of the example shown here, the U phase current may be detected at the timing B at the time of carrier signal up, and the W phase current Iw may be detected.

Next, an example of detecting the DC bus current IDC actually observed will be described with reference to FIGS. 5 and 6. 5 is a waveform diagram of the DC bus current IDC when the modulation rate is low and the period Tu is short, and FIG. 6 is a waveform diagram of the DC bus current IDC when the modulation rate is high and the period Tu is long.

First, the case where the modulation rate is low is demonstrated using FIG. In an actual circuit having a delay or nonlinear characteristic in the switch element, the waveform of the DC bus current IDC does not become the ideal shape shown in FIG. 4E, but is represented by the solid line in FIG. 5B. Pulsating. For this reason, in order to detect U phase current Iu correctly, it is necessary to detect a current after a pulsation is settled. However, when the modulation rate is low, the period Tu is short because the three-phase voltages Vu, Vv, and Vw are near zero, and the next switching is performed before ringing is settled, so that the U-phase current Iu cannot be detected accurately.

Therefore, in the present embodiment, as shown in Fig. 1, the low pass filter 5 having the characteristic shown in (Equation 3) is provided at the rear end of the DC bus line current detector 4. Here, in (Equation 3), Tf is a time constant. By using the low pass filter 5 having the characteristic (Equation 3), the DC bus current IDC shown by the solid line is smoothed to the filter value IDC 'indicated by the dotted line. In addition, the characteristic of the low pass filter 5 shown by Formula (3) is an example, and a higher order low pass filter may be sufficient as it.

When the modulation rate is low as shown in Fig. 5, since the period Tu is short with respect to the carrier period Tc, the pulsation converges early and the filter value IDC 'at timing C which is the timing at which the waveform of the DC bus current IDC rises is zero. Can be approximated by Moreover, timing C is ideally the time of Sup at the time of carrier signal falling in FIG. At this time, the detection value Iu 'of the U-phase current Iu can be obtained from Equation (4).

 In addition, the correction coefficient epsilon of (4) is (5).

Next, the case where the modulation rate is high is demonstrated using FIG. In FIG. 5, the filter value IDC 'at timing C can be approximated to zero. In FIG. 6, since the period Tu is long with respect to the carrier period Tc, the pulsation does not converge even at timing C, and the filter value IDC' Do not converge to zero. In this case, it is preferable to accurately calculate the filter value IDC 'at timing C without approximating to zero.

Therefore, in the present embodiment, as shown in FIG. 1, the corrector 6 is provided at the rear end of the low pass filter 5. The corrector 6 substitutes the correction coefficient ε into (Equation 4) and inverts the U-phase current Iu from the U-phase current detection value Iu '. Thereby, the attenuation of the low pass filter 5 can be corrected. The inverter control circuit 7 controls the on / off of the switch elements Sup, Sun, Svp, Svn, Swp, Swn based on the three-phase alternating currents Iu, Iv, and Iw thus obtained, so that the AC motor 1 Can be driven stably.

As described above, according to the configuration of the present embodiment using the low pass filter 5 and the compensator 6, it is possible to accurately detect the current whether the modulation rate is low or high. Therefore, the AC motor 1 can be driven with high performance even in a low load or low speed region, and the driving range can be wide ranged.

[Example 2]

Example 2 is demonstrated using FIG. In addition, description about the point equivalent to Example 1 is abbreviate | omitted.

As shown in FIG. 1, the present embodiment includes a PWM signal generator 7a, a vector controller 7b, and a current estimator 7c in the inverter control circuit 7. The current I1 is estimated and vector control of the AC motor 1 is performed. Hereinafter, each will be described in detail.

The current estimating unit 7c estimates the reactive current Ir and the effective current Ia described in FIG. 3 based on the output from the corrector 6, and estimates the amplitude and phase of the motor current I1. This estimation principle is described below.

As is clear from Fig. 3, the reactive current Ir and the effective current Ia are represented by the equations (6) and (7), respectively.

Substituting Equation 6 and Equation 7 into Equation 2, Equation 8 is obtained.

In addition, the U-phase current detection value Iu 'represented by (Equation 4) is integrated into the period Q1 (θv1 ≦ θv ≦ θv2) shown in FIG. 2, and the integral value S1 of Equation 9 is obtained. Similarly, it integrates with Q2 ((theta) v2 <= (theta) v <= (theta) v3), and the integral value S2 of (10) is calculated | required.

Substituting (Equation 4) and (Equation 8) into (Equation 9) and (Equation 10), (Equation 11) and (Equation 12) are obtained.

In addition, k _r1 , Δk _r1 , k _a1 , and Δk _a1 in Equation 11 are defined by Equation 13, and k _r2 , Δk _r2 , k _a2 , Δk _a2 in Equation 12 are represented by Equation (Equation 12): 14).

And (Equation 11) and (Equation 12) obtain (Equation 15).

The current estimating unit 7c can estimate the reactive current Ir and the effective current Ia from Equation 15 obtained above. In addition, the coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 in Equation 15 correspond to the attenuation of the DC bus current IDC by the low pass filter 5, and the compensator 6 determines the attenuation. In order to correct the influence, the DC bus current IDC is corrected using coefficients Δk _r1 , Δk _r2 , Δk _a1 , Δk _a2 stored in advance or calculated using (Equation 13) and (Equation 14). do.

In addition, although the example using the U phase current detection value Iu 'integrated value of the continuous sections Q1 and Q2 was demonstrated above, you may calculate the integrated value of the non-continuous sections Q1 and Q2, and perform current estimation in this way. In this way, the timing for performing the calculation process can be distributed, and the concentration of the calculation load can be prevented. Further, three or more sections Q1, Q2,... The integrated value of Qn may be obtained, and the current can be estimated using more integrated values, so that suitable current estimation can be performed even when noise is mixed. In the case where current estimation is performed by these methods, it is possible to respond simply by changing the integration section of Equations 13 and 14 to the section where the current is actually detected.

The vector control unit 7b provided at the rear end of the current estimation unit 7c calculates the voltage commands Vu *, Vv *, Vw * from the amplitude and phase of the motor current I1 based on the vector control. The control signals of the switching elements Sup, Sun, Svp, Svn, Swp, and Swn are output based on the voltage commands Vu *, Vv *, and Vw * from the PWM signal generator 7a and the vector controller 7b. As a result, the inverter 2 is PWM controlled, and the AC motor 1 is driven.

As described above, according to the configuration of the present embodiment, the attenuation of the DC bus current IDC by the low pass filter 5 can be corrected, and the reactive current Ir and the effective current Ia can be estimated. Thereby, the AC motor 1 can be driven with high performance compared with the structure which does not correct the attenuation by the low pass filter 5.

[Example 3]

Example 3 is demonstrated using FIG. In addition, description about the point equivalent to Example 2 is abbreviate | omitted.

As can be seen from (Equation 13) and (Equation 14), the coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 depend on the voltage phases θv1, θv2 and θv3 shown in FIG. 2. Since the voltage phase θv advances with the drive of the AC motor 1, the coefficients Δk _r1 , Δk _r2 , Δk _a1 , Δk _a2 are recalculated using (Equation 13) and (Equation 14) for each current estimation. In this case, a large computational load is applied to the compensator 6. In the case where coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 are stored in advance, the compensator 6 must include a large capacity memory that stores all coefficients.

Therefore, the present embodiment unifies the coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 of Equation (15) to reduce the computational load or the storage capacity of the corrector 6.

In order to unify the coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 , the current detection value has periodicity, and the current estimation may be performed in synchronization with this. When the current phase to be detected is appropriately switched in accordance with the voltage phase θv, the current detection value has a periodicity.

As shown in Table 1, the case where the current detection phase is switched will be described. Here, -U denotes detecting -Iu 'in which the negative phase of the U-phase current detection value Iu' is reversed. The same applies to the V phase and the W phase. In addition, Table 1 shows one embodiment of the present embodiment, in which, when the current detection value has periodicity and current can be estimated in synchronization with this, instead of the example shown in Table 1, various sections, voltage phases, and detection phases are used. Combinations may be used.

The current detection value at this time is shown by the solid line in FIG. The current detection value has periodicity, for example, detecting the U phase in the section D is the same as detecting the -V phase in the section C. FIG. The same applies to other sections, and the coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 may be calculated based on any one of the sections.

In the present embodiment described above, the coefficients Δk _r1 , Δk _r2 , Δk _a1 , and Δk _a2 can be unified, so that the calculation load of the current estimation unit 7c is also reduced.

Example 4

Example 4 is demonstrated using FIG. In addition, description is abbreviate | omitted about the point equivalent to the Example demonstrated previously.

In general, the larger the time constant Tf, the lower the response of the filter value IDC 'to the linear bus line current IDC is. At this time, the response of the current estimated value to the actual current decreases, and the control of the AC motor 1 also deteriorates.

Thus, in the present embodiment, the filter constant IDC 'defines the time constant Tf of (Equation 3) in relation to the carrier period Tc so that the linear bus current IDC follows a sufficient response speed, thereby preventing deterioration in control responsiveness. .

8 shows waveform diagrams of the DC bus currents IDC and IDC '. It is assumed that the filter value IDC 'is detected once per carrier period Tc. Here, IDC0 represents the rated value of the DC bus current IDC, and DC bus current IDC is set to the rated value IDC0 or less. In addition, let IDC1 detect the filter value IDC 'in a certain energization period, and let IDC2 filter value IDC' immediately before the next energization period. IDCm represents the minimum resolution of the DC bus current detector 4, and zero is detected when the filter value IDC 'is equal to or less than IDCm.

At this time, if the filter value IDC 'can vary from the rated value IDC0 to less than the minimum resolution IDCm within the carrier period Tc, the delay of the low pass filter 5 can be ignored. This condition is represented by (16).

Here, with respect to IDC1 and IDC2, (Equation 17) holds.

(Equation 18) is obtained from (Equation 16) and (Equation 17).

In this embodiment, by using the time constant Tf satisfying Equation (18), a filter value IDC 'having a sufficient response speed can be obtained, and the AC motor 1 is controlled based on this filter value IDC'. The fall of the control responsiveness of the motor 1 can be prevented.

[Example 5]

Example 5 is demonstrated using FIG. 9, FIG. In addition, description is abbreviate | omitted in the point equivalent to the Example demonstrated previously.

In this embodiment, the accuracy of current estimation is improved by adjusting the time constant Tf in accordance with the modulation rate of the inverter 2.

9 is a configuration diagram of the low pass filter 5 used in the fifth embodiment. As shown here, the low pass filter 5 incorporates a plurality of low pass filters 5a, 5b, and 5c, and the multiplexer 5d can switch the low pass filter to be used. The low pass filter 5a combines a predetermined resistor and a capacitor to form a filter having a predetermined time constant. The other low pass filters 5b and 5c have the same configuration, but resistors and capacitors are selected to form filters having different time constants, respectively. In this case, it is assumed that the time constant decreases in the order of the low pass filters 5a, 5b, 5c.

The period Tu described in FIG. 4 becomes longer as the modulation rate is higher, and the low pass filter 5 eliminates the need for smoothing the DC bus current IDC. Therefore, as shown in Fig. 10, the multiplexer 5d is switched so that the time constant Tf becomes smaller as the modulation rate is higher. Accordingly, the viscosity of the current estimation can be achieved by using a low pass filter 5a when the modulation rate is the highest and a low pass filter 5c when the modulation rate is the smallest. Can improve.

In addition, although a low pass filter is always used here, when the modulation rate is high enough and the threshold value is exceeded, the low pass filter 5 and the compensator 6 may be avoided, and direct DC bus current may be observed. do. In this embodiment, the time constant Tf may be changed in accordance with the modulation rate by using a configuration other than FIG. 9. For example, by providing a short circuit in parallel with the capacitor of the low pass filter 5 and controlling the amount of discharge, the time constant Tf may be changed continuously in accordance with the modulation rate.

[Example 6]

Example 6 is demonstrated using FIG. The sixth embodiment is an embodiment in which any one of the control devices described in the first to fifth embodiments is applied to a drive device for a refrigeration air conditioner.

These drive devices are often driven under operating conditions in which the load decreases as the speed decreases. The lower the speed, the smaller the induced voltage of the AC motor 1, and the smaller the load, the smaller the motor current I1. For this reason, the modulation rate at ultra low speed is extremely small. Therefore, by applying the control device described in any one of the first to fifth embodiments to the drive device of the refrigerating and air conditioning device, such as the fan drive device or the compressor drive device, the drive range can be widened. By applying the present invention to the drive device, current detection is possible even when the modulation rate is extremely small, and the drive device can be controlled from the ultra low speed.

1: AC motor
2: inverter
3: DC power
4: DC bus current detector
5: low pass filter
5d: multiplexer
6: compensator
7: inverter control circuit
7a: PWM signal generator
7b: vector control unit
7c: current estimator
VDC: DC voltage
IDC: DC Bus Current
Sup, Sun, Svp, Svn, Swp, Swn: Switching Elements
Vu, Vv, Vw: U phase voltage, V phase voltage, W phase voltage
Vu *, Vv *, Vw *: U phase voltage command, V phase voltage command, W phase voltage command
V1: motor voltage
I1: motor current
Ir: Reactive Current
Ia: active current
θv: voltage phase
φ: voltage / current phase difference

Claims (7)

With DC power supply,
An inverter for converting direct current power supplied from the direct current power source into alternating current power;
An inverter control circuit for controlling the switch elements provided in the inverter,
A DC bus current detector for detecting a DC bus current flowing through the inverter;
A low pass filter for smoothing the DC bus current detected by the DC bus current detector;
A compensator for correcting the attenuation of the DC bus current smoothed in this low pass filter,
The correction amount by the corrector is dependent on the time constant of the low pass filter and the timing of detecting the DC bus current. The method of claim 1,
The inverter control circuit,
Current estimation means for estimating the amplitude and phase of an alternating current flowing through the alternating current motor from a plurality of direct current bus currents detected by the direct current bus current detector;
Vector control means for calculating a voltage command of the inverter control circuit based on the output of the current estimation means;
And a PWM signal generating means for PWM controlling the switch element on the basis of the output of the vector control means. The method of claim 2,
And the current estimating means estimates the amplitude and phase of the alternating current flowing through the alternating current motor in synchronization with the periodicity of the detected value of the direct current bus current detector. With DC power supply,
An inverter for converting direct current power supplied from the direct current power source into alternating current power;
An inverter control circuit for controlling the switch elements provided in the inverter,
A DC bus current detector for detecting a DC bus current flowing through the inverter;
A low pass filter for smoothing the DC bus current detected by the DC bus current detector;
A compensator for correcting the attenuation of the DC bus current smoothed in this low pass filter,
The inverter control circuit,
Current estimation means for estimating the amplitude and phase of an alternating current flowing through the alternating current motor from a plurality of direct current bus currents detected by the direct current bus current detector;
Vector control means for calculating a voltage command of the inverter control circuit based on the output of the current estimation means;
PWM signal generating means for PWM controlling the switch element based on the output of the vector control means,
The time constant Tf of the low pass filter is
[Equation 1]

Where Tf: time constant, Tc: carrier period of the inverter control circuit, IDC0: rated value of linear bus current, IDCm: minimum resolution of DC bus current detector
It is a control device of an AC motor. With DC power supply,
An inverter for converting direct current power supplied from the direct current power source into alternating current power;
An inverter control circuit for controlling the switch elements provided in the inverter,
A DC bus current detector for detecting a DC bus current flowing through the inverter;
A low pass filter for smoothing the DC bus current detected by the DC bus current detector;
A compensator for correcting the attenuation of the DC bus current smoothed in this low pass filter,
The inverter control circuit,
Current estimation means for estimating the amplitude and phase of an alternating current flowing through the alternating current motor from a plurality of direct current bus currents detected by the direct current bus current detector;
Vector control means for calculating a voltage command of the inverter control circuit based on the output of the current estimation means;
PWM signal generating means for PWM controlling the switch element based on the output of the vector control means,
And a time constant of the low pass filter in accordance with the modulation rate of the inverter. With DC power supply,
An inverter for converting direct current power supplied from the direct current power source into alternating current power;
An inverter control circuit for controlling the switch elements provided in the inverter,
A DC bus current detector for detecting a DC bus current flowing through the inverter;
A low pass filter for smoothing the DC bus current detected by the DC bus current detector;
A compensator for correcting the attenuation of the DC bus current smoothed in this low pass filter,
The inverter control circuit,
Current estimation means for estimating the amplitude and phase of an alternating current flowing through the alternating current motor from a plurality of direct current bus currents detected by the direct current bus current detector;
Vector control means for calculating a voltage command of the inverter control circuit based on the output of the current estimation means;
PWM signal generating means for PWM controlling the switch element based on the output of the vector control means,
And the direct current bus current detector avoids the low pass filter and the compensator when the modulation rate of the inverter is equal to or greater than a threshold value, and directly detects the direct bus current flowing through the inverter. The refrigeration air conditioner of any one of Claims 1-6 which made the control apparatus of the AC motor the control apparatus of the AC motor used for a fan or a compressor.

Images