JPWO2014162579A1 - AC motor drive system and power system - Google Patents

Abstract

As a method for realizing stable drive from a low speed range without using the rotor position sensor of the AC motor, it is versatile enough to support various motors regardless of the characteristics of the structure and materials used of the AC motor. A high drive device is proposed. A circuit that detects a virtual neutral point potential for the AC motor and a circuit that generates a reference voltage different from this potential are provided, and by amplifying the difference between them, an electromotive voltage due to a change in the position of the rotor is obtained. By switching the energization phase of the AC motor based on the electromotive voltage, this can be realized by stably driving the AC motor at a constant speed. The value of the electromotive voltage varies depending on the type and specification of the motor, but it can be used universally by adjusting the gain of the amplifier.

Description

  The present invention relates to a motor drive technology used for applications such as rotational speed control of a motor drive device such as a fan, pump, compressor, spindle motor, etc., positioning control of a mechanical device, and torque control such as an electric assist. .

  In fields such as home appliances, industry, and automobiles, for example, rotational speed control for fans, pumps, compressors, conveyors, elevators, etc., torque assist devices such as electric power steering, and motor drive devices for positioning control in manufacturing equipment Is used. In motor drive devices in these fields, permanent magnet type synchronous motors (hereinafter referred to as “PM motors”), which are small and highly efficient AC motors, are widely used. However, in order to drive the PM motor, information on the magnetic pole position of the rotor of the motor is required, and therefore a position sensor such as a resolver or a Hall IC is indispensable. In recent years, sensorless control that performs rotational speed and torque control of a PM motor without using this position sensor has been widespread.

  Realization of sensorless control can reduce the cost of the position sensor (the cost of the sensor itself, the cost of the sensor wiring, the cost of the sensor installation and adjustment work), and the size of the device is reduced by the amount that the sensor is unnecessary. There are also merits such as being able to be used in poor environments.

  Currently, sensorless control of PM motors directly detects the induced voltage (speed electromotive force) generated by the rotation of the rotor and drives the PM motor as rotor position information, or from the PM motor mathematical model A position estimation technique for estimating and calculating the rotor position is employed.

  As a sensorless method based on an induced voltage (speed electromotive voltage) generated by a PM motor, there is a method based on a zero cross of an induced voltage (for example, Patent Document 1). In this method, the PM motor is driven by energization at 120 degrees, the voltage of a phase that is not energized is detected, the timing at which the voltage crosses zero is obtained by a comparator, and phase information is obtained. Further, in Patent Document 1, a virtual neutral point circuit is provided, and a zero cross signal of an induced voltage of a non-conduction phase is detected from the virtual neutral point potential to obtain phase information. By introducing a virtual neutral point circuit, one comparator can be provided.

  Similarly, as a sensorless drive method using a virtual neutral point potential detection circuit, there is a method of Patent Document 2 for sine wave drive.

  A major problem with these sensorless control systems is the position detection method during low-speed operation. As long as it is based on the induced voltage (speed electromotive voltage) generated by the PM motor, the sensitivity is lowered in the low speed region where the induced voltage is small, and the position information is buried in noise. In addition, position detection in a completely stopped state is physically impossible.

  On the other hand, a position sensorless system that does not use a speed electromotive force has been proposed, and a position sensorless system in a zero speed region in which no speed electromotive voltage is generated has been disclosed (Patent Document 3).

  Since Patent Document 3 is a technique deeply related to the present invention, the details will be described with reference to FIGS.

  FIG. 18 is a configuration diagram of an AC motor drive device based on Patent Document 3. As shown in FIG. In the figure, the inverter 3 is driven by a signal from the controller 1, and the AC motor 4 (PM motor) which is a load of the inverter 3 is driven without a position sensor. The principle of position sensorless determines which phase is energized by detecting the terminal voltage of the PM motor 4. The energization algorithm is performed by detecting the magnitude of an electromotive voltage (this is called a magnetic saturation electromotive voltage) generated in an open phase (a phase that is not energized).

  This magnetic saturation electromotive voltage will be briefly described.

  When a pulse voltage is applied to two phases of the PM motor (see FIGS. 19 (a) and 19 (b)), a voltage corresponding to the position of the rotor of the PM motor is generated in the open phase that is not energized. (In FIG. 19, the U phase becomes the open phase). This voltage (magnetic saturation electromotive voltage) is a voltage that is generated when the inductance in the motor changes minutely due to the relationship between the permanent magnet magnetic flux attached to the rotor of the PM motor and the energization current. It is also observable at.

  Therefore, by observing this magnetic saturation electromotive voltage, the position (angle) of the rotor can be detected, and position sensorless driving in a low speed region is possible. In order to distinguish this electromotive force from the speed electromotive force generated by the rotation of the rotor, the magnetic saturation electromotive force is called. Since the magnetic saturation electromotive voltage is a voltage generated in the open phase, it is necessary to select the detection phase on the control side and read the voltage.

  FIG. 21 shows the relationship between the energized phase, the open phase, and the magnetic saturation electromotive voltage with respect to the rotor position θd. As the energized phase, two phases having the largest rotational force are selected by θd. Switching the energized phase should be performed at the time when a predetermined value (each threshold value on the positive side and negative side) is reached while observing the magnitude of the magnetic saturation electromotive voltage of the open phase. The drive without the position sensor can be realized.

  FIG. 22A to FIG. 22C are magnetic saturation electromotive voltage detection circuits described in Patent Document 3. FIG. In FIG. 22A, the three-phase voltage is detected and amplified by the three amplifiers 5 with reference to the neutral point of the stator winding of the PM motor. After that, the open phase is selected by a switch in the microcomputer, and the magnetic saturation electromotive voltage is read into the controller. In FIG. 22B, a virtual neutral point circuit is provided, and three-phase voltages are detected using the neutral point potential as a reference potential. In this case, it is not necessary to detect the winding neutral point potential of the PM motor. FIG. 22 (c) detects the potential difference between the virtual neutral point potential and the neutral point of the PM motor stator winding, and information on the magnetic saturation electromotive force can be obtained with one amplifier. After all, it is necessary to extract the potential of the winding neutral point from the PM motor.

Japanese Patent Laid-Open No. 5-15189 JP 2006-67667 A JP 2009-189176 A

  The one described in Patent Document 1 can be realized by one comparator by detecting the virtual neutral point potential, but since it is based on the speed electromotive voltage, the PM motor can be driven in the stop / low speed range. Can not. In the low-speed range, the induced voltage is almost zero, so the output of the comparator flutters.

  The device described in Patent Document 2 uses the virtual neutral point potential for creating the detection timing of the DC bus current, and still cannot realize high torque driving in the stop / low speed region.

  The thing of patent document 3 can emit a driving force, without stepping out, when a motor is a stop and low speed state. However, the method disclosed in Patent Document 3 has the following problems.

  When the detection circuits shown in FIGS. 22A and 22B are used, three amplifiers are required, and the circuit becomes complicated. Further, these three amplifier circuits need to have the same characteristics, and time is required for gain adjustment and offset adjustment. Further, when the specification of the PM motor is changed, it is necessary to readjust these three gains and offsets, and further adjustment time is required.

  Also, when targeting a PM motor of 100V or more, it may be necessary to insulate the detection circuit from the control circuit for safety reasons. However, in this case, three expensive isolation amplifiers must be prepared. is there.

  In the case of FIG. 22 (c), the number of amplifiers can be realized by one, but the neutral point potential of the stator winding of the PM motor needs to be drawn out of the motor, and the versatility is poor. Since a general PM motor is a three-wire type, a dedicated motor for this control is required. Further, when the motor characteristics are changed, it is necessary to readjust the gain and offset of the amplifier, which is a problem.

  An object of the present invention is to provide an AC motor drive system capable of realizing a position control system and a speed control system that are highly responsive and highly stable from near zero speed to a high speed range.

  It is an object of the present invention to provide a magnetic saturation electromotive voltage detection circuit capable of realizing a low speed region driving characteristic near zero speed for a motor having any characteristic in a PM motor driving apparatus without a position sensor. .

  The technique of Patent Document 3 can obtain good control performance when the motor is stopped and at a low speed, but has a problem that the number of parts of the detection circuit is large. In particular, for a PM motor having a small magnetic saturation electromotive voltage, since an individual amplifier is attached to the electromotive voltage detection circuit, it takes time to adjust the amplification gain and offset. In addition, the system with few amplifiers, which is another proposal described in this known example, requires the extraction of the stator winding of the PM motor, and has a great problem in versatility.

  The present invention provides a detection circuit capable of solving these problems and a position sensorless driving method.

  A 120-degree energization method for driving the PM motor by sequentially selecting two phases among the three-phase stator windings of the PM motor is implemented. In this case, the principle that the open phase electromotive voltage (magnetic saturation electromotive voltage) changes depending on the rotor position is applied. The open-phase electromotive voltage is detected by providing a virtual neutral point circuit and detecting the virtual neutral point potential as a difference from an independent reference potential. A magnetic saturation electromotive force is obtained by appropriately amplifying the detected value. By switching the energized phase based on this magnetic saturation electromotive voltage, a highly versatile position sensorless drive system can be realized with a simple circuit.

  The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

  According to the present invention, by using a simple voltage detection circuit, it is possible to realize a drive device capable of stopping a PM motor having various characteristics and positionless from a low speed range.

  The control configuration remains almost the same as that of the conventional 120-degree energization sensorless system, and highly accurate and stable speed control or position control can be realized over a wide range from the stop state to the high speed range.

It is a figure showing the structure of the drive device of the alternating current motor which concerns on 1st Embodiment. It is a figure which shows the relationship between the energization phase to the motor which concerns on 1st Embodiment, and an open phase. It is a figure which shows the electric potential of the virtual neutral point electric potential detection part which concerns on 1st Embodiment. It is a wave form diagram regarding a detection potential concerning a 1st embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 2nd Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 3rd Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 4th Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 5th Embodiment. It is a circuit diagram which shows the amplifier of the control apparatus of the alternating current motor which concerns on 5th Embodiment. It is a flowchart of the reference voltage adjustment method which concerns on 6th Embodiment. It is a figure which shows the rotor position at the time of the electricity supply which concerns on 6th Embodiment. It is a flowchart of the amplifier gain adjustment method which concerns on 7th Embodiment. It is a figure which shows the rotor position at the time of the electricity supply which concerns on 7th Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 8th Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 9th Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on 10th Embodiment. It is a figure showing the structure of the air conditioning machine which concerns on 11th Embodiment. It is a figure showing the structure of the drive device of the alternating current motor which concerns on a conventional system. It is a figure which shows the voltage application to the alternating current motor which concerns on a conventional system. It is a figure which shows the position dependence of the magnetic saturation electromotive force of the alternating current motor which concerns on a conventional system. It is a figure which shows the change of the open phase voltage which concerns on a conventional system, and energization mode switching by it. It is a figure which shows the structure of the detection circuit of the open phase voltage which concerns on a conventional system. It is a figure which shows the structure of the detection circuit of the open phase voltage which concerns on a conventional system. It is a figure which shows the structure of the detection circuit of the open phase voltage which concerns on a conventional system.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The AC motor drive apparatus according to the first embodiment of the present invention will be described with reference to FIGS.

  This device is intended to drive a three-phase AC motor 4, and is roughly divided into an inverter including a controller 1, a virtual neutral point detection circuit 2, a DC power source 31, an inverter main circuit 32, and a gate driver 33. 3. An AC motor (PM motor) 4 to be driven, an amplifier 5, and a reference voltage generator 6 are configured.

  In this embodiment, a PM motor is taken as an example of a drive target. However, other types of AC motors can be used as long as they are motors that can obtain magnetic saturation characteristics with respect to the rotor position.

  The controller 1 controls the rotation speed or torque of the PM motor 4 via the inverter 3. At that time, the difference between the virtual neutral point potential E1 detected by the virtual neutral point detection circuit 2 and Eb generated by the reference voltage generator 6 is differentially amplified by the amplifier 5 and the amplification result is controlled. Input to the A / D converter (analog / digital converter) of device 1 and read the value.

  The controller 1 uses the obtained voltage as an open-phase magnetic saturation electromotive voltage for switching the energized phase. The energized phase is switched by comparing the magnitude relationship between the obtained magnetic saturation electromotive force and a preset threshold value. Details are described in Patent Document 3 which has already been published, and therefore will be omitted.

  FIG. 2 shows a state in which energization from the V phase to the W phase is performed as an example. When this voltage is applied, a magnetic saturation electromotive force is generated in the U phase that is an open phase. Specifically, the magnetic saturation electromotive force is detected by the circuit connection as shown in FIG. In FIG. 3, the U-phase voltage Eu, which is an open phase, basically has a value in the vicinity of the intermediate potential (VDC / 2) of the DC voltage VDC. However, as described in Patent Document 3, since the inductance slightly fluctuates depending on the position of the rotor, it varies depending on the rotor position as shown in FIG. The rate of change varies greatly depending on the characteristics of the PM motor. In the case of an embedded rotor structure using a rare earth magnet or the like, the dependence on the rotational position is very strong and the sensitivity is high. However, in the case of a structure in which a ferrite magnet is arranged on the rotor surface (non-salient pole structure), the change in inductance is small and the position dependency is small.

  In the case of this slight change in inductance, it is necessary to amplify the detected value, but in the conventional circuit, it is necessary to provide an amplifier for each of the three phases.

  In the present embodiment, as shown in FIG. 1, a virtual neutral point circuit 2 is provided to detect the open phase voltage. As shown in FIG. 1, the virtual neutral point detection circuit 2 connects a resistor Z1 to each phase terminal of the motor 4, and further supplies the potential at the common connection point (that is, the virtual neutral point potential E0). The voltage is divided by the two resistors Z2 and Z3, and the voltage is detected as the potential E1 from the ground level.

  As shown in FIG. 4, since the effect of Eu fluctuation occurs in the virtual neutral point potential E0, even if this virtual neutral point potential is observed, it is possible to observe the magnetic saturation electromotive voltage of the open phase. Is possible. In the present embodiment, in order to amplify the fluctuation by the electronic circuit, the voltage is once detected by dividing it into a low pressure. As shown in FIG. 4B, the output E1 of the voltage dividing circuit shows the same change as E0. The average value at this time is defined as Eb. Since E1 fluctuates around Eb, the magnetic saturation electromotive force can be detected with high sensitivity by amplifying the difference between them.

  Therefore, the reference voltage generator 6 sets Eb corresponding to the average value of E1, amplifies it by the amplifier 5, and inputs it to the A / D converter of the controller 1. If the input range of the A / D converter is 0 to 5V, it is possible to detect the magnetic saturation electromotive voltage with high sensitivity by setting the output reference potential of the amplifier 5 to 2.5V. (FIG. 4C). If the A / D converter of the controller 1 is 12 bits, a digital value centered on 2048 [digit] is obtained as shown in FIG.

If the magnetic saturation electromotive voltage of the target PM motor 4 is weak, it can be detected with high sensitivity by increasing the amplification gain of the amplifier 5. In any case, the use of the AC motor driving apparatus according to the present embodiment provides an advantage that it can be applied to a motor having any magnetic saturation electromotive voltage characteristic by simply changing the gain setting of one amplifier. .
(Second Embodiment)
Next, with reference to FIG. 5, a description will be given of an AC motor driving apparatus according to the second embodiment of the present invention.

  FIG. 5 has substantially the same configuration as that of the driving apparatus of FIG. 1, but is different from FIG. 1 in that an amplifier 5B is included in the controller 1B.

In recent years, some microprocessors used for motor control have built-in differential analog amplifiers. The controller 1B of FIG. 5 has such a differential amplifier 5B built in the microprocessor. In this case, the same effect as that of the embodiment of FIG. 1 can be obtained. Furthermore, the differential amplifier gain can be set by the software of the microprocessor, making it possible to more easily handle various PM motors.
(Third embodiment)
Next, with reference to FIG. 6, an AC motor drive apparatus according to the third embodiment of the present invention will be described.

  6 has almost the same configuration as that of the driving apparatus of FIG. 1, but the reference voltage generator 6B is different from that of FIG. The reference voltage generator 6B includes a DC voltage dividing circuit 61 that divides the voltage value of the DC voltage 31 of the inverter 3B. The DC voltage dividing circuit 61 sets a voltage dividing ratio so as to coincide with the reference voltage Eb in FIG.

  The reference voltage generator 6 in FIG. 1 outputs a constant voltage Eb irrespective of the DC voltage VDC. For this reason, when the DC voltage VDC fluctuates, the average value of E1 may fluctuate and deviate from the set value of Eb. At this time, if the gain of the amplifier 5 is large, the deviation (offset value) is amplified, which may depart from the dormitory range for the A / D converter.

  According to the present embodiment, when the DC voltage VDC varies, the divided voltage Eb also changes accordingly. That is, the reference value Eb also changes in conjunction with the fluctuation of E1, and no offset amount is generated. As a result, even if the gain of the amplifier 5 is set large, the magnetic saturation electromotive voltage can be detected with high sensitivity.

Thus, according to the present embodiment, it is possible to realize an AC motor driving apparatus that is robust against DC voltage fluctuations.
(Fourth embodiment)
Next, with reference to FIG. 7, an AC motor driving apparatus according to the fourth embodiment of the present invention will be described.

  7 has substantially the same configuration as that of the driving apparatus of FIG. 6, but a controller 1C and a reference voltage generator 6C are different from those of FIG. The controller 1C is a processor having a D / A converter (digital / analog converter) output, and the output of the reference voltage generator 6C is corrected by the output. The reference voltage generator 6C creates a reference voltage by adding the D / A output value of the controller 1C to the detected value of the DC voltage divided by the voltage dividing circuit 61 by the adder 62.

  The third embodiment (FIG. 6) described above is an embodiment that can cope with fluctuations in the DC voltage VDC. However, for example, a detection error due to the influence of the voltage dividing resistor 62 and the temperature drift of the amplifier 5 occurs. There is a fear. In addition, due to the influence of the component variation of the virtual neutral point circuit, the average value of E0 does not necessarily match Eb, and an offset may occur.

  In contrast, in the present embodiment, the voltage value input to the controller 1C is observed, and the D / A converter output is adjusted so that the average value becomes an intermediate value in the AD input range. As a result, the reference voltage Eb is adjusted, and the deviation of the average value due to drift can be corrected.

  In the correction by the D / A converter, there is no problem even if the effect value E1 of the virtual neutral point potential is corrected. Further, instead of the correction by “addition” as in this embodiment, the voltage division ratio may be corrected. Regarding the correction method, the resistance value may be switched by an analog switch or the like without using the D / A converter.

Thus, according to this embodiment, it becomes possible to adjust the detection error (offset amount) due to temperature drift or individual variation, and a more practical drive device can be realized.
(Fifth embodiment)
Next, an AC motor driving apparatus according to the fifth embodiment of the present invention will be described with reference to FIGS.

  8 has substantially the same configuration as that of the driving apparatus of FIG. 7, but a controller 1D and an amplifier 5D are different from those of FIG. The controller 1D outputs the gain control signal Gset to the amplifier 5D, and the amplifier 5D sets the amplification gain based on the gain control signal Gset.

  The amplifier 5D is composed of an electronic circuit shown in FIG. In the figure, operational amplifiers 50a to 50b constitute a differential amplifier, and the amplification factor is determined by resistors 51a, 51b, 52a, 52b, 53a, 53b, and 54. The resistor 54 can switch the four resistors R11 to R14 with switches. This switch is an analog switch and is switched by a gain control signal Gset from the controller 1D. In order to select one of the four resistors, the switch may be switched with a 2-bit signal. This circuit gain is represented by the mathematical formula shown in FIG. 9, and the gain increases as the resistor 54 (R1) is lowered, and the gain decreases as the resistor 54 is increased.

Therefore, according to the present embodiment, the gain of the amplifier 5D can be changed by the gain control signal Gset in accordance with the magnetic saturation electromotive voltage characteristic of the target PM motor 4, and the drive device for the AC motor with higher versatility can be obtained. Can be realized.
(Sixth embodiment)
Next, an AC motor drive device according to a sixth embodiment of the present invention will be described with reference to FIGS. In the fourth embodiment shown in FIG. 7, it has been shown that the reference voltage Eb can be adjusted. This reference voltage Eb may be adjusted before driving when the PM motor 4 is driven. A specific algorithm for automatically performing the adjustment work will be described in this embodiment.

FIG. 10 is a chart showing a procedure for automatic adjustment of the reference voltage Eb. In the figure, the flow from S01 to S03 describes the operation of the Eb automatic adjustment routine. When the adjustment work is started, the offset adjustment is performed according to the following procedure.
(1) S01: Two phases out of three phases are selected and energized to move the rotor. For example, power is supplied from the V phase to the W phase.
(2) S02: The rotor rotates by being attracted by electromagnetic force generated by energization. A predetermined time until the rotation due to the energization stops is waited. When power is supplied from the V phase to the W phase, the rotor is fixed at a position as shown in FIG. 11 (the phase angle θd = 90 [deg] when the U phase stator position is used as a reference). .
(2) S03: Observe the open-phase electromotive voltage (magnetic saturation electromotive voltage) in this state, and adjust the D / A of the controller 1C so that the value matches the intermediate value (VADmax / 2) of the A / D converter. What is necessary is just to adjust the value of a converter. Thereby, the adjustment of the reference voltage Eb is completed.

  When energized from the V phase to the W phase, the rotor moves to a position of 90 degrees in electrical angle and is fixed. At that time, the magnetic saturation electromotive force becomes “zero” in principle (the positive pulse electromotive force in FIG. 20 becomes zero when θd = 90 [deg]). Therefore, if the value of Eb is adjusted in this state, the average value is adjusted.

  By such a procedure (FIG. 10), automatic adjustment of Eb (adjustment of offset amount) becomes possible. This algorithm may be executed before the PM motor 4 is actually operated, or may be performed while looking at intervals during operation.

As described above, according to the sixth embodiment of the present invention, the reference voltage is automatically adjusted, and the PM motor can be driven more simply and reliably.
(Seventh embodiment)
Next, an AC motor driving apparatus according to the seventh embodiment of the invention will be described with reference to FIGS. In the fifth embodiment shown in FIG. 8, it has been shown that the gain of the amplifier 5D can be adjusted. The amplification factor may be adjusted before driving when the PM motor 4 is driven. A specific algorithm for automatically performing the adjustment work will be described in this embodiment.

FIG. 12 is a chart showing a procedure for automatic adjustment of amplification gain. In the figure, the flow from T01 to T06 means the operation of the automatic gain adjustment routine. When the adjustment work is started, the adjustment is performed according to the following procedure.
(1) T01: Temporarily set the amplification factor of the proposed differential amplifier 5D to the minimum value.
(2) T02: Energize two phases and move the rotor. For example, the rotor is moved by passing a current from the U phase to the W phase.
(3) T03: Wait for a predetermined time until the rotation stops. When power is supplied from the U phase to the W phase, the rotor is fixed at a position (θd = 30 [deg]) as shown in FIG.
(4) T04: In this state, the energized phase is switched (the U phase → W phase is switched from the V phase to the W phase energized), and the open phase electromotive voltage immediately after the switch (in this case, the U phase becomes the open phase) Remember.

The rotor is at a position of θd = 30 [deg] by the process of T03, and when energization from the V phase to the W phase is performed in this state, the open-phase electromotive voltage is the positive pulse electromotive voltage of FIG. A value at 30 [deg] is observed. Since this value is a value at the time of switching the energized phase, it is the voltage itself necessary for switching the energized phase. Therefore, it is possible to determine whether or not the gain of the amplifier 5D is appropriate from the magnitude of the voltage detection.
(5) T05: Determine whether the detection sensitivity is sufficient. If the sensitivity is sufficient, the gain setting value is OK. If the sensitivity is insufficient, the gain of the amplifier 5D is adjusted from the controller 1D via the gain control signal Gset and adjusted again from TO2.

  Such a procedure (FIG. 12) enables automatic gain adjustment of the amplifier 5D. This algorithm may be executed before the PM motor 4 is actually operated, or may be performed while looking at intervals during operation.

As described above, according to the seventh embodiment of the present invention, the amplifier gain of the amplifier 5D is automatically adjusted, and the PM motor can be driven more simply and reliably.
(Eighth embodiment)
Next, with reference to FIG. 14, an AC motor drive device according to an eighth embodiment of the present invention will be described.

14 has substantially the same configuration as that of the driving apparatus of FIG. 1, but an amplifier 5E is different from that of FIG. The amplifier 5E is an amplifier having a structure in which an input unit and an output unit are electrically insulated. The controller 1 may be directly touched by a user depending on the system, and when the operating voltage of the inverter 3 becomes a high voltage exceeding 100 V, it is desirable to be electrically insulated from these. The gate signal of the inverter 3 can be insulated by a photocoupler, but the virtual neutral point potential needs to use an insulation amplifier. However, according to the present invention, since the open-phase electromotive voltage can be detected by detecting the virtual neutral point potential, the electromotive voltage information for three phases can be obtained by using one insulation amplifier. For this reason, there is an advantage that an expensive insulation amplifier can be minimized.
(Ninth embodiment)
Next, with reference to FIG. 15, a description will be given of an AC motor drive device according to a ninth embodiment of the present invention.

  FIG. 15 has substantially the same configuration as that of the third embodiment shown in FIG. 6, except that a winding neutral point potential detection circuit 7 and a changeover switch 8 are newly added.

  As described above, when the PM motor 4 to be driven is driven by 120 degrees energization, detection of the open phase electromotive voltage can be realized by detecting the virtual neutral point potential. However, when the neutral point of the stator winding of the PM motor 4 is drawn, the rotor position can be detected by detecting the potential. Therefore, if the winding neutral point potential detection circuit 7 is provided in advance and the winding neutral point potential of the target motor can be detected (that is, if the winding neutral point potential is extracted), Use it, otherwise use the virtual neutral point potential. Which one is used is switched by the switch 8. In FIG. 15, when the switch 8 is set to the “0” side, the sensorless driving using the virtual neutral point potential is performed similarly to the previous embodiments, and when the switch 8 is set to the “1” side, the stator winding of the PM motor is used. Position sensorless driving using the neutral point potential is possible.

Therefore, according to the ninth embodiment of the present invention, an appropriate sensorless driving method can be selected according to the winding structure of the motor, and a higher-performance driving method can be realized.
(Tenth embodiment)
Next, a tenth embodiment of the present invention will be described.

  FIG. 16 is an actual view of AC motor drive device 41 according to the present embodiment. In this figure, the control device is packaged inside the PM motor as one system. By integrating everything in this way, wiring between the motor and the inverter can be eliminated. As shown in FIG. 16, the wiring of the integrated drive system is only a power line to the inverter 3 and a communication line for returning the rotation speed command and the operation state.

In the present invention, since sensorless driving that eliminates the rotor position sensor can be realized, the integrated system can be extremely compact and can be downsized.
(Eleventh embodiment)
Next, an eleventh embodiment of the present invention will be described.

  FIG. 17 is an actual view of an air conditioner outdoor unit 50 using an AC motor drive device according to the present embodiment. In this figure, the compressor 51 of the air conditioner has a built-in PM motor 4 to be driven, and the controller 1, the virtual neutral point circuit 2, the inverter 3, the amplifier 5, and the reference voltage generator 6 are located above the outdoor unit. is set up. In order to realize an energy saving operation, the air conditioner needs to be driven at a low speed as much as possible. For this purpose, the low speed sensorless drive in the present invention is important. Further, since the PM motor to be driven is designed with priority given to efficiency, it is not always possible to obtain sufficient magnetic saturation electromotive voltage characteristics, and it is necessary to amplify the electromotive voltage. Therefore, if the drive device of the present invention is applied, sensorless drive from low speed can be applied to a motor designed with priority on efficiency, and system merit can be obtained.

  Not only the compressor drive of an air conditioner but a fan, a pump (water pump, oil pump), etc. are applicable similarly.

  Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the scope of the invention.

  As described above, the present invention is a technique for constructing a motor drive device that is premised on position sensorlessness. This motor can be used for positioning applications in machine tools and industrial machines, including rotational speed control for fans, pumps (hydraulic pumps, water pumps), compressors, spindle motors, air conditioning equipment, disk drivers, etc. It is.

DESCRIPTION OF SYMBOLS 1 ... Controller, 2 ... Neutral point potential detection circuit, 3 ... Inverter, 4 ... Permanent magnet type synchronous motor,
DESCRIPTION OF SYMBOLS 5 ... Amplifier, 6 ... Reference voltage generator, 31 ... DC power supply, 32 ... Inverter main circuit, 33 ... Gate driver

Claims (11)

AC motor,
An inverter for driving the AC motor;
Means for detecting a virtual neutral point potential for the AC motor;
A controller for controlling the AC motor;
Reference potential generating means for generating a reference potential for the virtual neutral point potential;
In an AC motor drive system comprising: an amplifying unit that amplifies a difference between the virtual neutral point potential and the reference potential;
The AC motor drive system characterized in that the controller reads the output of the amplifying means and controls the energization phase of the AC motor based on the output value of the amplifying means. AC motor,
An inverter for driving the AC motor;
Means for detecting a virtual neutral point potential for the AC motor;
A microprocessor that controls the AC motor and incorporates a differential analog amplifier;
In an AC motor drive system comprising: a reference potential generating means for generating a reference potential for the virtual neutral point potential;
The microprocessor is configured to differentially amplify the virtual neutral point potential and the reference potential by the analog amplifier, and control an energization phase of the AC motor based on the amplification result. system. In the drive system of the alternating current motor according to claim 1 or 2,
The drive system for an AC motor, wherein the reference potential is a potential based on a detected value of a DC voltage of the inverter. In the drive system of the alternating current motor according to claim 1 or 2,
At least one of the detecting means and the reference potential generating means includes an adjusting means for adjusting an offset amount of the detecting means or the reference potential generating means based on a signal from the controller. Driving system. In the drive system of the AC motor according to claim 1,
The amplifying unit adjusts an amplification factor of the amplifying unit based on a signal from the controller. In the drive system of the alternating current motor according to claim 1 or 2,
A drive system for an AC motor, comprising: means for automatically adjusting an offset amount of at least one of the detection means or the reference potential generation means when the controller energizes the AC motor. In the drive system of the AC motor according to claim 1,
An AC motor drive system comprising: means for automatically adjusting the amplification factor of the amplifying means when the controller energizes the AC motor. In the drive system of the AC motor according to claim 1,
An AC motor drive system characterized by having a circuit configuration in which electrical coupling is isolated at the input or output of the amplifier. In the drive system of the alternating current motor according to claim 1 or 2,
The drive system for an AC motor, wherein the reference potential is selectable between a detected value of a DC voltage of the inverter and a potential based on a connection neutral point of a stator winding of the AC motor. . In the drive system of the alternating current motor according to claim 1 or 2,
A drive system for a three-phase AC motor, characterized in that the AC motor, the inverter, and the controller are integrated, and the inverter, the power supply line of the controller, and a signal line to the controller are drawn to the outside. A power system including the AC motor drive system according to claim 1 or 2,
A power system that drives a compressor, a pump, or a fan as a load of the three-phase AC motor.

Images