JP2011067023A - Current detection method, inverter device and converter device utilizing current detection method, motor drive equipped with such device, and refrigeration and air-conditioning equipment - Google Patents

Abstract

A current detection method capable of stable operation even in an overmodulation region, an inverter device and a converter device using the current detection method, a low-cost motor drive device, and a refrigerating and air-conditioning apparatus are provided.
An AC motor, an inverter for driving the AC motor, current detection means for detecting a bus current or each arm current on the inverter DC side, and control means for controlling the AC motor using the detected current detection value In the motor drive apparatus having the above-described configuration, the AC motor current reference value is calculated from the past detection value of the current obtained from the current detection means or the current command value of the control means, and the current detection means is used for one phase of the AC motor current. When only the current of the current can be detected, an error between the current detection value for one phase and the current reference value is calculated, and the AC motor current of the phase that cannot be detected is estimated using the error.
[Selection] Figure 6

Description

  The present invention relates to a current detection method, and more particularly to a current detection method suitable for current detection in a conversion device such as an inverter device that converts direct current to alternating current or a converter device that converts alternating current to direct current. The present invention also relates to an inverter device and a converter device, and further relates to a motor driving device and a refrigerating and air-conditioning apparatus provided with the device. Note that. Hereinafter, the inverter device and the converter device are collectively referred to as a “conversion device”.

  Motor drive inverter devices that convert direct current to three-phase alternating current and converter devices that convert three-phase alternating current to direct current are widely applied in the fields of industrial equipment and home appliances. In particular, motor-driven inverter devices that convert direct current into three-phase alternating current are widely used in refrigeration and air conditioning equipment (for example, air conditioners, refrigeration and refrigeration systems, and water heaters) that place importance on energy saving performance and comfort. .

  In these refrigeration and air-conditioning equipment, in order to reduce the cost, current detection means (specifically, shunt resistance, current sensor, etc.) provided on the inverter's DC bus or each arm is used, and three-phase AC current is generated. Many methods to reproduce are adopted. In particular, in a motor drive device using an inverter device, stable overmodulation PWM control is desired in order to reduce the loss of the switching element (improve efficiency) and further expand the motor drive range.

  However, as will be described in detail below, generally, in the above-described overmodulation region, within a certain period of time, depending on the current detection means, only a current for one phase of a plurality of phases (for example, three phases) can be obtained. The phenomenon that it cannot be detected occurs. When such a phenomenon occurs, the reproduction error in the alternating current generated by the inverter device increases, and the control by the motor drive device may become unstable, and it is difficult to actually employ the overmodulation control described above. Met.

  For example, according to Patent Document 1 below, as a countermeasure when a three-phase alternating current cannot be detected from a bus current, any two values of the three-phase voltage command values are close to each phase. Even if this current cannot be detected, a processing method is disclosed in which the current in the rotational coordinate system obtained last time is regarded as the current in the current rotational coordinate system and the three-phase voltage command value and phase are calculated based on the current.

  Further, according to the following Patent Document 2, it is also proposed to use a past motor current already detected in a detectable phase as an alternating current reproduction processing method when only a current for one phase can be detected.

JP 2007-312511 A JP 2004-64903 A

  However, in the above-described conventional technology, a section in which only one phase current of the conversion device in the overmodulation region can be detected becomes long, so that the detection error of the three-phase alternating current becomes large and the control becomes unstable. There was a problem of becoming.

  Therefore, the present invention has been made in view of the above-described prior art, and more specifically, a current detection method capable of more reliably obtaining a three-phase alternating current even in the above-described overmodulation region. An object of the present invention is to provide an inverter device capable of stabilizing control by using the device, and a motor driving device and a refrigerating and air-conditioning apparatus including the device. .

  In order to achieve the above object, according to the present invention, first, in a power conversion circuit for supplying power converted from three-phase alternating current to direct current or from direct current to three-phase alternating current to a load, In the current detection method for detecting the current of each phase of the three-phase alternating current, when only the current for the one phase can be detected, the current detection value for the one phase, the current reference value, A current detection method is provided in which an error in the other phase is calculated and an AC current of another phase that cannot be detected is calculated using the error.

  According to the present invention, there is also provided a motor driving apparatus for driving a three-phase AC motor using the current detection method, the inverter driving the three-phase AC motor, and a bus on the DC side of the inverter. Current detection means for detecting the current of each arm of the inverter from current, and control means for controlling the current supplied to the three-phase AC motor using the current detection value detected by the current detection means If the control means can detect only the current for one phase of the three-phase AC motor current, the motor drive apparatus estimates the AC motor current of the phase that cannot be detected by the current detection method described above. Is provided.

  In the present invention, in the motor drive device described above, the control unit reproduces the AC motor current by using the current detection value obtained from the current detection unit, converts it to motor rotation coordinates, and It is preferable to calculate the AC motor current reference value by processing the converted current signal with a low-pass filter or averaging means and inversely transforming it into fixed coordinates, or the control means is the current detection means Using the current detection value obtained from the above, the AC motor current is reproduced and converted into motor rotation coordinates, and the motor current detection value is controlled to coincide with the motor current command value at the motor rotation coordinates, and It is preferable to calculate the AC motor current reference value by inversely converting the motor current command value into fixed coordinates. Alternatively, the control means calculates an error between the current detection value for one phase and the current reference value, and uses the current reference value corresponding to the phase that cannot be detected and the error to exchange the phase that cannot be detected. It is preferable to calculate the motor current.

  Further, according to the present invention, in order to achieve the above-mentioned object, the alternating current of the configuration in which the input side is connected to the three-phase AC power source via the reactor and the smoothing capacitor is connected between the DC terminals on the output side is converted into direct current. A converter circuit, a current detection means for detecting a bus current or each arm current of the converter circuit, and a control means for controlling the converter circuit using a current detection value of the current detection means. The control means calculates a three-phase input current reference value using the current detection value of the current detection means or the current command value of the control means, and the current detection means calculates 1 of the three-phase input current. When only the current for the phase can be detected, the converter device that estimates the AC current of the phase that cannot be detected by the current detection method according to claim 1 is provided.

  Furthermore, according to the present invention, in order to achieve the above object, an inverter circuit for converting a direct current of a configuration in which the direct current side is connected to a direct current power supply and the alternating current side is connected to a three-phase alternating current power supply through a reactor to an alternating current; In the system connection inverter device, comprising: current detection means for detecting a bus current or each arm current of the inverter circuit; and control means for controlling the inverter circuit using a current detection value of the current detection means, The control means calculates a three-phase alternating current reference value using the current detection value of the current detection means or the current command value of the control means, and the current detection means for one phase of the three-phase alternating current. When only the current can be detected, an inverter device is provided that estimates the AC current of the phase that cannot be detected by the current detection method described in claim 1.

  According to the present invention, in order to achieve the above object, a compressor, a heat exchanger connected to the compressor by piping, an AC motor built in the compressor, and the AC motor are provided. The inverter circuit includes a driving inverter circuit, and the inverter circuit further includes a current detection unit that detects a bus current on the DC side or each arm current, and a current generated by the current detection unit. In the apparatus including a control unit that controls the AC motor using a detection value, the control unit of the inverter circuit uses a past detection value of the current obtained from the current detection unit or a current command value of the control unit. When the AC motor current reference value is calculated and only the current for one phase of the three-phase AC current can be detected by the current detection means, the current described in claim 1 is used. The output method, refrigeration and air conditioning equipment that supplies three-phase alternating current to the AC motor by estimating the AC motor current can not be detected phase are provided.

  According to the current detection method of the present invention described above, the three-phase alternating current can be obtained more reliably even in the overmodulation region. Therefore, by utilizing this, stable motor control becomes possible according to the present invention, so that the motor drive device that achieves both high efficiency and high output can further provide a refrigeration air conditioner. Exhibits excellent effects. In addition, by using the present invention, it is possible to provide a converter and a system-connected inverter that can reduce distortion (harmonics) and ripple current without using complex modulation processing, and thereby expand the output range. Demonstrates the excellent effect of being possible.

It is a figure which shows schematic structure of the motor drive device which uses the electric current detection method of this invention which becomes one Embodiment. It is a control functional block diagram in the said motor drive device. It is a functional block diagram which shows the structure of the speed & phase estimator in the said motor drive device. It is a wave form diagram which shows the PWM carrier wave, the three-phase modulation wave, and the bus current waveform on the inverter DC side together with the energization mode of the inverter. It is the waveform figure which expanded the partial time which shows the three-phase modulation wave in an overmodulation area | region, and the bus current waveform on the inverter DC side. It is a functional block diagram which shows the structure of the electric current reproduction calculator in the said motor drive device. It is a flowchart figure which shows the detail of the electric current reproduction calculation process in the said motor drive device. It is a control function block diagram which shows the modification of the said motor drive device. It is a block diagram of the converter apparatus which becomes other embodiment of this invention. It is a functional block diagram which shows the structure of the control part of the said converter apparatus. It is a block diagram of the system | strain connection inverter apparatus which becomes further another embodiment of this invention. It is a block diagram of the refrigeration air conditioning equipment to which this invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The current detection method according to the present invention will be described in detail in the description of the motor driving device using the current detection method described in detail below.
<< Motor drive device >>

<Device configuration>
FIG. 1 is a configuration diagram of a motor drive device for a three-phase motor according to an embodiment of the present invention. As is apparent from the figure, this motor drive device is a converter that converts alternating current into direct current. (Rectifier etc.) 2, DC capacitor 3, inverter 4 for converting DC to AC, current detection means 6 for detecting the bus current on the inverter DC side, voltage detection means 7 for detecting DC voltage, and controller Therefore, it receives power from the AC power source 1 and drives the AC motor 5. The current detection means 6 for detecting the bus current on the inverter DC side includes a shunt resistor 61, as is apparent from the figure.

<Overall control configuration>
The controller 8 constituting the motor driving device is configured by using, for example, a semiconductor arithmetic element such as a microcomputer or a DSP (digital signal processor), and the detection signals of the current detecting means 6 and the voltage detecting means 7 are detected. As a result, an on / off control signal for a semiconductor power element such as an IGBT that constitutes the inverter 4 is output.

  Details of the controller 8 configured using the semiconductor arithmetic element will be described with reference to the functional block diagram of FIG. Each of these functions is realized by an arithmetic processing program stored in advance in the storage device of the controller. As is apparent from the figure, the controller 8 calculates a voltage command signal to be applied to the motor by so-called vector control, and generates an inverter PWM control signal. More specifically, the d-axis A current command generator 11, a speed controller 12, a voltage command controller 13, a voltage 2-axis / 3-phase converter 14, a speed & phase estimator 15, a current 3-phase / 2-axis converter 16, A current reproduction calculator 17, a PWM controller 18, a low-pass filter 19, and a current 2-axis / 3-phase converter 20 are provided.

  Further, details of the above-described functional blocks will be described below with reference to FIG.

<Configuration of three-phase current reproduction and dq converter>
The current reproduction calculator 17 receives the detection signal (Ish) from the bus current detection means 6, the three-phase voltage command values (Vu ^* , Vv ^* , Vw ^* ), and the current 2-axis / 3-phase converter 20. The motor current (Iu, Iv, Iw) is reproduced using the three-phase AC current signals (Iu_r, Iv_r, Iw_r). The details of the current reproduction process will be described later.

Based on the reproduced motor current and the estimated phase information (θ _dc ), the three-phase / two-axis converter 16 calculates the dc axis current (Idc) and qc as shown in the following equation (1). The shaft current (Iqc) is converted. The dc-qc axis is an estimation axis of the control system, the dq axis is a motor rotor axis, and the axis error between the dq axis and the dc-qc axis is defined as (Δθc).

<Voltage control>
In the voltage command controller 13, the dc axis current command value (Idc *) given from the d axis current command generator 11, the qc axis current command value (Iqc *) given from the speed controller 12, and the dc axis current detection. Using the value (Idc), the qc-axis current detection value (Iqc), the speed command value (ω1 *), and the motor constant, the dc-axis voltage command value (Vdc ^* ) and the qc-axis voltage command value (Vqc ^* ) Is calculated. Finally, based on the dc-axis voltage command value (Vdc ^* ), the qc-axis voltage command value (Vqc ^* ) and the estimated phase information (θ _dc ), the three-phase voltage of the motor is calculated from the following equation (2). Command values (Vu ^* , Vv ^* , Vw ^* ) are output.

<Phase sensorless>
Subsequently, a speed & phase estimation method for realizing position sensorless control will be described in detail below.

  FIG. 3 is a detailed functional block diagram of the speed & phase estimator 15. As shown in FIG. 3, the phase estimator 15 calculates the rotor position and the rotational speed by the motor rotor position sensorless control method. To estimate. Specifically, an axis error calculator 21 that calculates an axis error between the motor axis (dq axis) and the control system axis (dc-qc axis), a speed estimator 22 that estimates the motor rotation speed, and a phase And an arithmetic unit 23.

The axis error calculator 21 includes the dc axis voltage command value (Vdc ^* ), the qc axis command voltage value (Vqc ^* ), the dc axis current value (idc), the qc axis current value (iqc), and the motor constant 24 (winding). From the resistance (r), the q-axis inductance (Lq)), and the estimated motor rotation speed value (ω1), the axis error (Δθc) is calculated using the following (Equation 3).

The speed estimator 22 processes the shaft error (Δθc) output from the shaft error calculator 21 using a so-called PI controller, and outputs an estimated value (ω1) of the motor rotation speed. Here, the PI controller performs PLL control so as to eliminate the estimated axis error (Δθc) between the motor shaft (dq axis) and the control system axis (dc-qc axis). Further, the phase calculator 23 integrates the estimated motor rotation speed (ω1) to calculate the control system phase (θ _dc ).

<Current reproduction>
Next, a method for reproducing the AC motor current from the bus current on the inverter DC side will be described with reference to FIGS. FIG. 4 shows a PWM carrier wave 31, three-phase modulated waves 32, 33, and 34, a bus current waveform 35 on the inverter DC side, and an energization mode of the inverter.

  As shown in FIG. 4, the bus current Ish corresponds to the current for one phase of the motor depending on the energization mode of the inverter (see the bridge circuit at the bottom of the figure), so the sampling timing of the A / D converter ( By appropriately adjusting “◯” in the figure according to the magnitude of the modulated wave, the three-phase alternating current can be reproduced from the bus current. That is, when the U-phase and V-phase IGBTs of the upper arm and the W-phase IGBT of the lower arm are on, the current iw flows, the V-phase IGBT of the upper arm, and the U-phase and W of the lower arm Since the current iv flows when the phase IGBT is on, these currents iv and iw are respectively detected as is1 by the current detection means 6 including the shunt resistor 61 for detecting the bus current on the inverter DC side. The The remaining current iu is obtained using the fact that the sum of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw is 0 (Iu + Iv + Iw = 0).

However, as shown in FIG. 5, three-phase modulated waves 32, 33, and 34 that normally have different values in a part of the overmodulation region are one of them (in this example, W-phase The modulated wave Vw ^* : 34) has a predetermined value (0 V in this example), but becomes a modulated wave (Vu ^* : 32, Vv ^* : 33) that has no difference between the other two phases. A phenomenon occurs in which the corresponding phase current of the three-phase modulated wave cannot be detected. That is, the current detection value in this section can only detect the current for one phase (for example, only for the W phase), and as described above, the reproduction error in the alternating current generated by the inverter device becomes large, Control by the motor drive device becomes unstable.

Therefore, in the present invention, the current reproduction calculator 17 can detect the corresponding phase current of the above-described three-phase modulated wave in the overmodulation region. The detailed configuration of the current reproduction calculator 17 is shown in the attached functional block diagram of FIG. 6, which reproduces the three-phase AC currents Iu, Iv, Iw from the bus current Ish, and is an A / D converter. 41, a current detection information calculator 42, a current reproduction unit 43, and a current error correction processing unit 44. More specifically, the input signal of the current reproduction computing unit 17 includes a detected bus current signal (Ish), a three-phase modulated wave (Vu ^* , Vv ^* , Vw ^* ), and a three-phase alternating current reference value ( Iu_r, Iv_r, Iw_r). These three-phase AC current reference values (Iu ^* = Iu_r, Iv ^* = Iv_r, Iw ^* = Iw_r) convert the detected AC motor current into a dc-qc axis as shown in FIG. These values (Idc, Iqc) are processed by the low-pass filter 19 and reversely converted into a three-phase current using a current 2-axis / 3-phase converter 20.

The current detection information calculator 42 uses the three-phase modulated wave (Vu ^* , Vv ^* , Vw ^* ) to distribute the A / D activation timing and the A / D converted current value to the three-phase current. Necessary information and a necessity flag output by the current error correction processing unit 44 are given to each functional block. That is, as shown in the flowchart of FIG. 7 attached, three-phase modulated waves (Vu ^* , Vv ^* , Vw ^* ) are input (step S71), and a difference from the voltage command value is calculated (step S72). Thereafter, the information of the current detection phase is calculated (step S73), and it is determined whether the phase capable of detecting the current is only one phase or whether the current for two phases can be detected (step S73). S74).

  As a result of the determination in step S74, if it is possible to detect currents for two phases, as described above with reference to FIG. Minute AC motor current (Iu, Iv, Iw) can be reproduced (so-called normal reproduction: step S75).

  On the other hand, as shown in FIG. 5 described above, when only one phase of current can be detected, for example, in a partial section of the overmodulation region, the AC motor current (Iu, Iv, Iw) is as follows: Calculate.

First, a current error is calculated (step S75). Specifically:
(1) When only U-phase current (Iu) is detected:
ΔI = Iu_r−Iu
Iv = Iv_r + ΔI × Kv
Iw = Iw_r + ΔI × Kw
(2) When only V-phase current (Iv) is detected:
ΔI = Iv_r−Iv
Iu = Iu_r + ΔI × Ku
Iw = Iw_r + ΔI × Kw
(3) When only the W-phase current (Iw) is detected:
ΔI = Iw_r−Iw
Iu = Iu_r + ΔI × Ku
Iv = Iv_r + ΔI × Kv

Here, the current error (ΔI) is the difference between the current reference value (Iu ^* or Iv ^* or Iw ^* ) of the same phase and the detected current (Iu or Iv or Iw). The phase current that cannot be detected is also calculated from the corresponding current reference value and the current error as described above.

  Next, a detected value of a current that cannot be detected is calculated from the error obtained as described above and a detected value in the past (step S76), and the process ends.

  In general, in order to simplify the arithmetic processing, it is only necessary to correct the phase current that cannot be detected by halving the current error. That is, the correction gains (Ku, Kv, Kw) may be set to Ku = 1/2, Kv = 1/2, and Kw = 1/2.

In order to further improve the correction accuracy, the correction gain (Ku, Kv, Kw) may be calculated using the current reference value as in the following equation.
(1) When only U-phase current is detected:
Kv = | Iv_r | / (| Iv_r | + | Iw_r |)
Kw = | Iw_r | / (| Iv_r | + | Iw_r |)
(2) When only V-phase current is detected:
Ku = | Iu_r | / (| Iu_r | + | Iw_r |)
Kw = | Iw_r | / (| Iu_r | + | Iw_r |)
(3) When only W-phase current is detected:
Ku = | Iu_r | / (| Iu_r | + | Iv_r |)
Kv = | Iv_r | / (| Iu_r | + | Iv_r |)

As described above, the current error is estimated from the detected current of the phase that can be detected (Iu or Iv or Iw) and the current reference value of the same phase (Iu ^* or Iv ^* or Iw ^* ), and By correcting the current error of the phase that cannot be detected, it is possible to improve the detection accuracy of the reproduced three-phase current, thereby improving the stability of motor control during overmodulation.

  The above is the configuration of the motor drive device according to the present invention and the control principle thereof. In the above embodiment, an example has been described in which a method of detecting a bus current on the inverter DC side using a shunt resistor is used as a current detection method. However, instead of this, a current sensor may be used. Absent. However, the use of the shunt resistor can reduce the cost of the sensor as compared with the direct detection method of the three-phase alternating current. Of course, the above-described current reproduction process is not limited to the above-described motor driving device, and can be similarly applied to, for example, a motor driving device with a position / speed sensor. On the other hand, when the current sensor is used, the AC motor current can be reproduced using three resistors or current sensors provided on the lower arm of the switching element constituting the inverter.

<Modification of controller>
Next, FIG. 8 attached herewith shows a modified example of the controller 8 shown in FIG. The controller 8 according to this modification is basically the same as that shown in FIG. 2, and the same reference numerals as those in FIG. 2 indicate functional blocks that perform the same operations. The difference from FIG. 2 is that the calculation of the three-phase alternating current reference values (Iu ^* = Iu_r, Iv ^* = Iv_r, Iw ^* = Iw_r) converts the detected motor current into the dc-qc axis conversion value. Instead, the dc-qc axis current command value (Idc ^* , Iqc ^* ) is used. However, as a precondition for such control to be valid, for example, it is possible to perform control so that the current command and the actual current substantially coincide. The current reproduction process is the same as that in the embodiment shown in FIG.
<< Converter device >>

  Subsequently, FIG. 9 attached is a diagram showing an example of a configuration when the current detection method of the present invention is used in a converter device instead of the motor drive device of FIG. 1 described above.

  As shown in FIG. 9, the converter device includes a converter circuit 104 connected to a three-phase AC power supply 101 via a ripple filter 102 and a reactor 103, and a smoothing capacitor 105 connected to a DC output terminal of the converter circuit 104. The control unit 106 for controlling the converter circuit 104, the shunt resistor 1071 for detecting the bus current, the current detection circuit 107, and the DC voltage detection are connected between the smoothing capacitor 105 and the converter circuit 104. Circuit 108. The control unit 106 is configured by using a semiconductor arithmetic element such as a microcomputer or a DSP (digital signal processor) as in FIG.

<Control system configuration>
Next, in FIG. 10 attached, the configuration related to the converter control of the control unit 106 in the converter device described above, in particular, is shown by functional blocks as in FIG. As apparent from the figure, the control unit 106 uses the voltage controller 110 to determine the q-axis current command value from the deviation between the voltage signal (Ed) from the DC voltage detection circuit 108 and the DC voltage command value (Ed ^* ). (Iq ^* ) is created. The d-axis current command value (id ^* ) is set to 0 in order to minimize the reactive current component of the input current.

<Current reproduction process>
The current reproduction processing unit 118 includes a bus DC current detection signal (Ish) from the bus current detection circuit 107, an output command voltage signal (Vr ^* , Vs ^* , Vt ^* ), and a three-phase AC current reference value (Ir_r, The three-phase alternating current (Ir, Is, It) is reproduced using Is_r, It_r).

<Command voltage calculation processing>
The vector control system converts the three-phase alternating current (Ir, Is, It) reproduced above into a value (id, iq) on the dq-axis coordinate by the three-phase / 2-axis conversion 114, and each command value ( The deviation from ⁽ id ^* , iq ^* ) is obtained, and the command voltage (Vd *, Vq *) on the dq axis is calculated via the vector controller 111.

Further, using the calculated dq-axis command voltage (Vd ^* , Vq ^* ) and the phase information (θdc) from the phase estimation controller 112, the two-phase / 3-phase conversion 113 performs a three-phase command voltage (Vr ^* , Vs). ^* , Vt ^* ) is calculated. Since the processing in the phase estimation controller 112 uses the power sensorless control method disclosed in Patent Document 3 described above, detailed description thereof is omitted here.

  The three-phase alternating current reference values (Ir_r, Is_r, It_r) are obtained by processing the dq axis values (Id, Iq) of the detected current with a low-pass filter 116 as shown in the attached FIG. Calculated by three-phase conversion 117. Naturally, if the control is performed so that the dq axis current command value and the detected value substantially coincide with each other, the dq axis current command value (Id, Iq) is used as in the process shown in FIG. Current reference values (Ir_r, Is_r, It_r) may be calculated.

  In this case as well, the current reproduction process when only the current for one phase can be detected is performed in the same manner as the process in the current reproduction calculator 17 described in detail above.

  By the way, especially in the case of a converter, there is a section where the difference between the two-phase modulated waves is small even in the linear modulation region. Therefore, if a special modulation method (for example, a modulation wave shift process for each PWM carrier half cycle) is not used, only one phase of current can be detected within a certain time. However, if the above-described special modulation method is adopted, distortion (harmonic) and ripples of the input current are generated. Therefore, it is desirable not to use such a special modulation method as much as possible.

On the other hand, if the current reproduction process of the present invention described above is used, the current detection error in the section in which only the one-phase current can be detected can be corrected without using the above-described special modulation method. In addition, reduction of current ripple can be realized. In addition, since the control performance of the overmodulation region can be improved, it is possible to reduce the loss of the switching element and expand the DC voltage range as the output.
<< System-connected inverter device >>

  Further, FIG. 11 shows a configuration when the current detection method of the present invention is applied to a system-connected inverter device. Also in FIG. 11, the same reference numerals as those shown in FIG. 9 indicate the constituent elements having the same functions.

  This embodiment is equivalent to the case where the power conversion direction in the converter device described above is reversed, that is, from the power source 202 (rectifier, storage battery, solar cell, fuel cell, etc.) connected to the DC side to the AC power source side. It shows the usage form of power conversion.

The control system in this embodiment has the same configuration as above except that the voltage controller 110 in the control system shown in FIG. 10 is not necessary. The current reproduction process is also the same as that of the current reproduction calculator 17 described in detail above.
<< Refrigeration and air-conditioning equipment >>

  The attached FIG. 12 shows what is called a refrigerating air conditioner such as an air conditioner or a refrigerator, for example, for driving the compressor motor using the motor driving device (see FIG. 1 above). It is a figure which shows the structure of an apparatus.

  In the figure, a refrigerating and air-conditioning apparatus 400 is a device that harmonizes the temperature in a room or cools air in a storage, and includes heat exchangers 401 and 402, fans 403 and 404, a compressor 405, and piping 406. And a motor driving device 407. The compressor motor 408 is configured using a permanent magnet synchronous motor or a three-phase induction motor, and is disposed inside the compressor 405. The motor driving device 407 receives power from the AC power source and drives the compressor motor 406.

  In such a refrigerating and air-conditioning apparatus, by using the above-described motor driving device (see FIG. 1 above), as is clear from the above, it is possible to improve the control stability of the overmodulation region at a relatively low cost. Therefore, vibration and noise during high-speed rotation of the motor can be reduced, thereby improving the performance of the air conditioner and the refrigerator. Especially for low-speed efficiency-oriented motors required to improve APF, loss reduction and DC voltage utilization can be improved by overmodulation control, ensuring output during high-speed operation and the output range of air conditioners and refrigerators An excellent effect that can be expanded.

DESCRIPTION OF SYMBOLS 1 ... AC power source, 2 ... Converter, 3 ... DC capacitor, 4 ... Inverter, 5 ... AC motor, 6 ... Current detection means, 61 ... Shunt resistance, 7 ... Voltage detection means, 8 ... Controller, 41 ... A / D Converter: 42 ... Current detection information computing unit, 43 ... Current reproduction unit, 44 ... Current error correction processor, 101 ... AC power supply, 102 ... Ripple filter, 103 ... Reactor, 104 ... Inverter, 105 ... DC capacitor, 107 ... Converter / inverter controller 108 ... Voltage detection means 109 ... Load 110 ... Voltage controller 111 ... Vector controller 112 ... Phase estimator 113 ... 2-axis / 3-phase conversion 114 ... 3-phase / 2-axis Conversion 115 ... PWM controller 116 ... Low pass filter 117 ... 2-axis / 3-phase conversion 201 ... Inverter controller 202 ... DC power supply 400 ... Refrigeration air conditioner 401, 402 ... heat exchanger, 403, 404 ... fan, 405 ... compressor, 406 ... piping, 407 ... motor driving device, 408 ... motor for compressor.

Claims (8)

Current detection for detecting the current of each phase of the three-phase AC current from the bus current on the DC side in the power conversion circuit that supplies the load with the power converted from the three-phase AC to the DC or from the DC to the three-phase AC A method,
When only the current for one phase can be detected, an error between the current detection value for the one phase and the current reference value is calculated, and the AC current of the other phase that cannot be detected is calculated using the error. What is claimed is: 1. A current detection method characterized by: A motor driving device for driving a three-phase AC motor,
An inverter for driving the three-phase AC motor;
Current detection means for detecting the current of each arm of the inverter from the bus current on the DC side of the inverter;
With a control means for controlling the current supplied to the three-phase AC motor using the current detection value detected by the current detection means,
The control means estimates an AC motor current of a phase that cannot be detected by the current detection method according to claim 1, when only the current for one phase of the three-phase AC motor current can be detected. A motor drive device.   In the motor drive device according to claim 2, the control unit reproduces the AC motor current by using a current detection value obtained from the current detection unit, converts the AC motor current into a motor rotation coordinate, and the conversion is performed. A motor driving device characterized in that the AC motor current reference value is calculated by processing a current signal with a low-pass filter or averaging means and inversely transforming it into fixed coordinates.   3. The motor driving apparatus according to claim 2, wherein the control means reproduces the AC motor current using the current detection value obtained from the current detection means and converts it into motor rotation coordinates, and the motor rotation coordinates. The motor current detection value is controlled so as to coincide with the motor current command value, and the AC motor current reference value is calculated by inversely converting the motor current command value into a fixed coordinate. Drive device.   3. The motor driving apparatus according to claim 2, wherein the control means calculates an error between a current detection value for one phase and the current reference value, and a current reference value corresponding to a phase that cannot be detected and the error. The motor driving device is characterized in that the AC motor current of the phase that cannot be detected is calculated using. A converter circuit for converting alternating current into direct current with a configuration in which the input side is connected to a three-phase alternating current power supply via a reactor and a smoothing capacitor is connected between the direct current terminals on the output side;
Current detecting means for detecting a bus current or each arm current of the converter circuit;
A converter device comprising control means for controlling the converter circuit using a current detection value of the current detection means,
The control means calculates a three-phase input current reference value using a current detection value of the current detection means or a current command value of the control means, and
2. A converter characterized by estimating an undetectable phase AC current by the current detection method according to claim 1, when the current detection means can detect only a current of one phase of a three-phase input current. apparatus. An inverter circuit that converts direct current of a configuration in which the direct current side is connected to a direct current power supply and the alternating current side is connected to a three-phase alternating current power supply via a reactor;
Current detecting means for detecting a bus current or each arm current of the inverter circuit;
In the inverter device for system connection comprising the control means for controlling the inverter circuit using the current detection value of the current detection means,
The control means calculates a three-phase alternating current reference value using a current detection value of the current detection means or a current command value of the control means, and
An inverter characterized in that an alternating current of a phase that cannot be detected is estimated by the current detection method according to claim 1 when the current detecting means can detect only one phase of a three-phase alternating current. apparatus. A compressor,
A heat exchanger connected to the compressor by piping;
An AC motor built in the compressor;
A refrigerating and air-conditioning apparatus provided with an inverter circuit for driving the AC motor,
The inverter circuit has current detection means for detecting the bus current on the DC side or each arm current, and control means for controlling the AC motor using a current detection value by the current detection means. In
The control means of the inverter circuit calculates an AC motor current reference value using a past detection value of the current obtained from the current detection means or a current command value of the control means, and
In the case where the current detection means can detect only the current for one phase of the three-phase AC current, the current detection method according to claim 1 estimates the AC motor current of the phase that cannot be detected and supplies the current to the AC motor. A refrigerating and air-conditioning apparatus that supplies a three-phase alternating current.

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