JP6207953B2 - Power conversion device and power conversion method - Google Patents

Description

  The present invention relates to a power conversion device and a power conversion method.

  As a background art of this technical field, there is JP-A-11-75394 (Patent Document 1). In this publication, “on / off signals are generated and output for an inverter that operates a motor such as a permanent magnet synchronous motor and a semiconductor switching element that constitutes the inverter in order to control the winding current of the motor to a predetermined value. The present invention relates to a power conversion device for an AC rotating machine such as an electric motor driving device provided with a control device, and at the time of the rotor idling of the electric motor, at least one of the semiconductor switching elements of the inverter is turned on by the idling restart control unit. The line is short-circuited, and the position of the rotor is estimated based on the winding current flowing at that time, and the motor is restarted via the inverter. "(See summary).

JP-A-11-75394

  Patent Document 1 describes a method for restarting an electric motor. However, in the restart method disclosed in Patent Document 1, for example, when an induction motor is used for a fan, current flows even if the induction motor causes the winding to short-circuit during idling due to external force (wind or the like). Therefore, the rotor position and frequency cannot be estimated. Further, for example, even in a permanent magnet synchronous motor, when the rotational frequency during idling of the rotor is low, the current value when the winding is short-circuited is low, so the rotor position and frequency cannot be estimated with high accuracy.

  Therefore, the present invention, compared with the prior art including the invention disclosed in Patent Document 1, is the rotation during idling even when the current does not flow when the winding is short-circuited or when the rotation frequency is low. A power conversion device capable of estimating a child position and frequency is provided.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present application includes a plurality of means for solving the above-mentioned problems. For example, an AC motor including a semiconductor switching element and converting a DC voltage into an arbitrary voltage by a combination of ON and OFF of the semiconductor switching element. A power converter that drives the power converter, a control device that controls a semiconductor switching element of the power converter and applies an arbitrary voltage to the AC motor from the power converter, and detects a current flowing through the AC motor Or an estimation current detector, and the control device applies an arbitrary voltage from the power converter to the AC motor when the AC motor idles or stops, and applies a current and a voltage flowing through the AC motor. The induced voltage frequency / phase of the AC motor is derived based on the determined time, and the AC motor is restarted using the derived induced voltage frequency / phase. It is a conversion apparatus.

  According to the present invention, even when no current flows when the winding is short-circuited during idling of the rotor or when the rotational frequency is low, the rotor position and frequency during idling are estimated, and restartable power conversion is possible. An apparatus can be provided.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of the block diagram of the power converter device in Example 1. FIG. 3 is an example of a restart control unit of the power conversion device according to the first embodiment. It is a modification of the block diagram of the power converter device in Example 1. FIG. 3 is an example of a restart control unit of the power conversion device according to the first embodiment. 3 is an example of a restart control unit of the power conversion device according to the first embodiment. 3 is an example of an arbitrary AC voltage applied from the power conversion device according to the first embodiment. It is an example of the electric current detection timing at the time of applying arbitrary DC voltages to the power converter device in Example 1, and an electric current change. It is an example of the rotation direction estimation timing of the power converter device in Example 1. It is an example of the restart control part of the power converter device in Example 1. It is an example of the block diagram of the power converter device in Example 2. FIG. It is an example of the restart control part of the power converter device in Example 2. It is an example which raised the arbitrary DC voltage applied from the power converter device in Example 2 gradually. It is an example which gradually raised the amplitude of the arbitrary alternating voltage applied from the power converter device in Example 2. FIG. 6 is an example of a two-phase induced voltage of the power conversion device according to the second embodiment.

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

  In the present embodiment, an example of the configuration of a power conversion device capable of estimating the rotor position and frequency of an AC motor that is idling will be described.

  FIG. 1 is an example of a configuration diagram of the power conversion device according to the first embodiment.

  A power conversion device 101 that drives a permanent magnet synchronous motor 105 includes a smoothing capacitor 102, a power converter 103, a current detector 104, and a control device 106.

  The smoothing capacitor 102 is a smoothing capacitor for smoothing the DC voltage, but the DC voltage may be directly input without being smoothed. The power converter 103 converts the DC voltage into an arbitrary voltage according to the combination of ON / OFF of the semiconductor switching element.

  The current detector 104 is, for example, a shunt resistor or a Hall CT, and detects the three-phase output current of the power converter 103. Since only two phases are detected and the sum of the three-phase alternating current is zero, the remaining one phase may be calculated. Further, a shunt resistor may be arranged at the positive electrode or negative electrode of the input of the power converter 103, and the three-phase output current may be estimated from the current flowing through the shunt resistor.

  The control device 106 includes an AC motor control unit 107, a restart control unit 108, and a gate signal control unit 109.

  The AC motor control unit 107 outputs a voltage command based on the three-phase output current in order to arbitrarily control the speed or torque of the permanent magnet synchronous motor 105. The restart control unit 108 receives the cutoff level setting value, the AC motor constant setting value, and the three-phase output current detected by the current detector 104, and sets the frequency, phase, and rotation direction to the AC motor control unit 107, and the cutoff command. Is output to the gate signal control unit 109.

  The gate signal control unit 109 receives a voltage command from the AC motor control unit 107 and controls on / off of the semiconductor switching element so that a voltage based on the voltage command is applied to the permanent magnet synchronous motor 105. When the gate signal control unit 109 receives a cutoff command from the restart control unit 108, the gate signal control unit 109 turns off all the semiconductor switching elements so as to interrupt the voltage application to the permanent magnet synchronous motor 105.

  Here, a method for estimating the magnetic pole position and the rotational angular velocity of the permanent magnet synchronous motor 105 from the current flowing when an arbitrary voltage is applied will be described. In order to restart the permanent magnet synchronous motor 105 from the idling state, it becomes an overcurrent state and cannot be normally restarted. Therefore, the amplitude, phase and frequency of the output voltage of the power converter 103 are set to the permanent magnet at the time of restarting. It is necessary to make the value approximately equal to those of the induced voltage of the synchronous motor 105. It is also necessary to know the rotation direction of the permanent magnet synchronous motor 105.

FIG. 2 is an example of a restart control unit of the power conversion apparatus illustrated in FIG. For example, when three-phase output currents i _u , i _v , i _w are input to the restart control unit 108, the peak current generation unit 201 generates a peak current. At this time, the voltage application processing unit 202 applies an arbitrary voltage when the generated peak current is below the current cutoff level. When the peak current generated from the current flowing by applying an arbitrary voltage exceeds the current interruption level, the arbitrary voltage application is interrupted to avoid overcurrent.

  FIG. 3 is a modification of the configuration diagram of the power conversion device according to the first embodiment.

  As shown in FIG. 3, the power conversion device 301 includes a DC voltage detector 310 that detects a DC voltage, and the DC voltage detected using the DC voltage detector 310 is input to the restart control unit 308 in the control device 306. .

  FIG. 4 is an example of a restart control unit of the power conversion device according to the first embodiment.

  As shown in FIG. 4, the voltage application processing unit 402 can determine arbitrary voltage application and interruption so as to avoid overvoltage based on the DC voltage input to the restart control unit 308.

  FIG. 5 is an example of a restart control unit of the power conversion device according to the first embodiment.

  As shown in FIG. 5, any voltage application and interruption may be determined using both peak current and DC voltage.

  The frequency / phase estimation processing unit 203 receives the three-phase output current and the AC motor constant, and outputs the frequency, phase, and rotation direction.

  As an internal process of the frequency / phase estimation processing unit 203, for example, a current difference value is first calculated from the current value and the previous value of the three-phase output current detected by the differential operation unit 204. Next, each phase induced voltage instantaneous value is calculated in the induced voltage estimation processing unit 205 from the current difference value of each phase and the AC motor constant known in advance. Next, the frequency calculation processing unit 206 calculates the frequency from the estimated phase induced voltage instantaneous value, the phase calculation processing unit 207 calculates the phase, and the rotation direction determination processing unit 208 estimates the rotation direction from the phase. . The estimated frequency, phase, and rotation direction are output to the AC motor control unit 107 and controlled based on these, whereby the power converter 101 is restarted.

  FIG. 6 is an example of an arbitrary AC voltage applied from the power conversion device according to the first embodiment.

  In this embodiment, for example, a method for estimating the frequency and phase based on the current flowing when an arbitrary DC voltage is applied will be described. However, the applied voltage may be an arbitrary AC voltage as shown in FIG. By using an alternating voltage, the load of each semiconductor switching element can be made uniform.

First, a method for estimating an induced voltage instantaneous value will be described. For example, a current that flows when an arbitrary DC voltage is applied during idling of the rotor is detected or estimated as a three-phase current. Assuming that the current of each phase of u, v, and w is i _u , i _v , and i _w , the induced voltage instantaneous values e _u , e _v , and e _w of each phase can be obtained from the voltage equation according to Equation 1. In Equation 1, v is an arbitrary applied voltage, R is the winding resistance of the permanent magnet synchronous motor 105, L is the winding inductance of the permanent magnet synchronous motor 105, the subscripts u, v, and w are the u-axis of each quantity. , V-axis and w-axis components.

Here, assuming that the voltage application time is extremely short, since R can be ignored, Equation 2 can be obtained.

Note that using either at least several 1 or Formula 2, each phase of the induced voltage instantaneous value e _u, e _v, may be calculated e _w. Further, although Equations 1 and 2 calculate three phases, only the two phases may be calculated, and the total of the three-phase alternating current may be zero, so that the remaining one phase may be calculated.

  As can be seen from Equation 2, time differentiation of the current is required to estimate the induced voltage instantaneous value. For example, in the case of software, the calculation is performed by obtaining the current increment value Δi per current sampling time Δt.

FIG. 7 is an example of current detection timing and current change when an arbitrary DC voltage is applied to the power conversion device according to the first embodiment. For example, after an arbitrary DC voltage is applied, when the current grows and reaches a cutoff level, the voltage application is interrupted. In the meantime, the current is acquired at an arbitrary sampling interval, and an incremental value of the current is obtained by taking the difference from the previously acquired current value as shown in Equation 3. For this reason, at least two points of current sampling are required.

Note that the subscript n represents the number of times of current sampling per voltage application, and n> 0.

Assuming that the current sampling time is Δt, Expression 2 can be expressed as Expression 4.

Next, a method for estimating the induced voltage frequency will be described. Assuming that ω is an angular velocity, the induced voltage constant _Ke and the induced voltage amplitude value E ₁ have a relationship of Formula 5.

When the induced voltage frequency is f, Equation 5 can be expressed as Equation 6 from ω = 2πf.

Further, when the induced voltage instantaneous value is used, the induced voltage amplitude value can be obtained by Equation 7.

From the equations 6 and 7, the induced voltage frequency can be derived from the estimated induced voltage instantaneous values e _u , e _v , e _{w of} each phase.

  As described above, the induced voltage frequency of the permanent magnet synchronous motor 105 can be derived by detecting currents at least at two points.

  Next, a method for estimating the induced voltage phase will be described.

First, the induced voltage instantaneous values e _α , e _{β obtained} by converting the instantaneous induced voltage values e _u , e _v , e _{w of} each phase derived from Eq. Is derived.

The induced voltage phase θ is obtained by the following equation (9) from the induced voltage instantaneous values e _α and e _β .

Finally, a method for estimating the rotation direction of the permanent magnet synchronous motor 105 will be described. The relationship between the angular velocity ω and the induced voltage phase θ is expressed by equation (10).

The rotational direction of the permanent magnet synchronous motor 105 can be determined by the sign of the angular velocity ω, that is, the rotational direction can be estimated in the incremental direction per unit time of the phase obtained in Equation 9.

  Note that the rotation direction of the permanent magnet synchronous motor 105 may not be accurately estimated depending on the timing. FIG. 8 is an example of the rotation direction estimation timing of the power conversion device according to the first embodiment. For example, when the phase of the timing of T1 is used as a reference as shown in FIG. 8, the rotation direction can be correctly estimated by using the phase of the T2 timing after t seconds, but the phase of the T2 ′ timing after t ′ seconds is used. If the direction of rotation is estimated, it is erroneously estimated.

  However, in the present application, since the induced voltage frequency of the permanent magnet synchronous motor 105 can be derived by detecting at least two currents as described above, the derivation timing of the induced voltage phase θ using the derived frequency. Can be accurately estimated.

  Furthermore, in this application, FIG. 9 is an example of the restart control unit of the power conversion device according to the first embodiment. It is also possible to determine whether or not the permanent magnet synchronous motor 105 is stopped or rotating at low speed based on the cutoff command time, that is, the voltage application interruption time, in the AC motor state determination unit 909 of FIG. The AC motor state determination unit 909 compares the shutoff command time with the arbitrarily set stop judgment time or the low speed judgment time, and when the shutoff command time exceeds the stop judgment time or the low speed judgment time, the motor is stopped or slow Judged as medium. The stop determination and the low speed determination may be performed at the same time. Further, the stop determination time and the low speed determination time may be set individually.

  When it is determined that the permanent magnet synchronous motor 105 is rotating at a low speed, an arbitrary DC voltage is applied to the permanent magnet synchronous motor 105 to brake and stop the permanent magnet synchronous motor 105, thereby stopping the permanent magnet synchronous motor. It is also possible to restart 105 smoothly. The DC voltage applied when braking the permanent magnet synchronous motor 105 may be zero voltage.

  As described above, the frequency, phase, and rotation direction of the induced voltage can be estimated from each phase current obtained by applying an arbitrary DC voltage and a known AC motor constant.

  In the present embodiment, portions common to the first embodiment will be described using the same reference numerals, and different portions will be described in detail.

  FIG. 10 is an example of a configuration diagram of the power conversion device according to the second embodiment.

  A power converter 1001 that drives the permanent magnet synchronous motor 105 includes a smoothing capacitor 102, a power converter 103, a current detector 104, and a controller 1006.

  The control device 1006 includes an AC motor control unit 107, a restart control unit 1008, and a gate signal control unit 109.

  The restart control unit 1008 receives a cutoff level setting value, an AC motor constant setting value, and a three-phase output current, and outputs a frequency, a phase, and a rotation direction to the AC motor control unit 107, and outputs a cutoff command to the gate signal control unit 109. To do.

  FIG. 11 is an example of a restart control unit of the power conversion device according to the second embodiment.

The rotation direction determination processing unit 1108 in the frequency / phase estimation processing unit 1103 can estimate the rotation direction from the relationship between the induced voltage instantaneous values of at least two phases derived each time.
FIG. 12 is an example of an arbitrary DC voltage applied from the power conversion device according to the second embodiment.

  In this embodiment, for example, the induced voltage frequency / phase of the permanent magnet synchronous motor 105 is estimated based on the current that flows when an arbitrary DC voltage is gradually applied as shown in FIG. By applying an arbitrary DC voltage gradually, when the permanent magnet synchronous motor 105 is idling at a high rotational speed, for example, rapid current growth can be suppressed. In addition, when the induced voltage generated by the permanent magnet synchronous motor 105 is very small, that is, when the permanent magnet synchronous motor 105 is idling at a low rotation speed, the current growth is moderated by gradually applying the voltage. That is, it is possible to estimate without reducing the rotational speed of the permanent magnet synchronous motor 105.

  FIG. 13 is an example in which the amplitude of an arbitrary AC voltage applied from the power converter in Example 2 is gradually increased.

  Similar effects can be obtained by gradually applying an AC voltage as shown in FIG.

  As a value at which voltage application starts, a value to which voltage is applied may be determined from the relationship between the winding resistance of the AC motor constant and the current interruption level value. Moreover, by starting voltage application from a value that is half the rated voltage of the permanent magnet synchronous motor 105, the maximum potential difference from the instantaneous value of the induced voltage generated by the permanent magnet synchronous motor 105 can be minimized. Furthermore, when current sampling is performed a plurality of times as shown in FIG. 7, for example, the voltage value to be applied next time is determined from the induced voltage frequency or induced voltage amplitude value of the permanent magnet synchronous motor 105 estimated at the previous current sampling. Good.

In the present embodiment, the method for estimating the induced voltage frequency / phase of the permanent magnet synchronous motor 105 is the same as that in the first embodiment, and is therefore omitted.
FIG. 14 is an example of two-phase induced voltages of the power conversion device according to the second embodiment.

  Ta in FIG. 14 is a timing at which the u-phase induced voltage changes from positive to negative. The other induced voltage is a v-phase induced voltage. At this timing, the rotational direction is estimated from the direction of increase of the two-phase induced voltage derived next. In the case of Ta, for example, if the u-phase induced voltage increases to the negative side and the v-phase induced voltage increases to the positive side, it is determined as normal rotation. Conversely, the u-phase induced voltage increases to the positive side, and the v-phase induced voltage increases. If it increases to the negative side, it is determined to be reverse.

  Tb in FIG. 14 is timing when the u-phase induced voltage is the maximum amplitude value (negative side). At this timing, if the v-phase induced voltage increases to the negative side, it is determined as normal rotation, and conversely, if the v-phase induced voltage increases to the positive side, it is determined to be reverse.

  Tc in FIG. 14 is a timing at which the u-phase induced voltage changes from negative to positive. At this timing, if the u-phase induced voltage increases to the positive side and the v-phase induced voltage increases to the negative side, it is determined as normal rotation. Conversely, the u-phase induced voltage increases to the negative side, and the v-phase induced voltage is positive. If it increases to the side, it is determined as reverse rotation.

  Td in FIG. 14 is the timing when the u-phase induced voltage is the maximum amplitude value (positive side). At this timing, if the v-phase induced voltage increases to the positive side, it is determined to be normal rotation. Conversely, if the v-phase induced voltage increases to the negative side, it is determined to be reverse.

Although this rotational direction determination method may not be accurately estimated depending on the determination timing, as in the rotational direction determination method described in the first embodiment, if the rotational direction determination timing is determined using the derived frequency. In the above embodiment, the case where the present invention is applied to a permanent magnet synchronous motor is described. However, for example, an induction voltage such as an induction motor or a synchronous motor that does not use a permanent magnet for a rotor is described. The present invention is applicable to an electric motor that is rotating or stopped by an external force in a state where no is generated.

  The present application is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 101 ... Power converter, 102 ... Smoothing capacitor, 103 ... Power converter, 104 ... Current detector, 105 ... Permanent magnet synchronous motor, 106 ... Control device, 107 ... AC motor control part, 108 ... Restart control part, 109 DESCRIPTION OF SYMBOLS ... Gate signal control part 201 ... Peak current generation part 202 ... Voltage application processing part 203 ... Frequency / phase estimation processing part 204 ... Differentiation calculation part 205 ... Induced voltage estimation processing part 206 ... Frequency calculation processing part, 207 ... Phase calculation processing unit, 208 ... Rotational direction determination processing unit, 301 ... Power conversion device, 306 ... Control device, 308 ... Restart control unit, 310 ... DC voltage detector, 402 ... Voltage application processing unit, 502 ... Voltage Application processing unit, 909 ... AC motor state determination unit, 1001 ... power conversion device, 1006 ... control device, 1008 ... restart control unit, 1103 ... frequency and position Estimation processing unit, 1108 ... rotational direction determination unit

Claims (16)

A power converter that includes a semiconductor switching element, converts a DC voltage into an arbitrary voltage by a combination of ON and OFF of the semiconductor switching element, and drives an AC motor;
And a control device, wherein the controlling the semiconductor switching elements of the power converter is controlled to apply an arbitrary voltage to the AC motor from the power converter,
And a current detector for detecting or estimating the current flowing through the AC motor,
Wherein the controller, an arbitrary voltage from the power converter during idle or stopping of the AC motor is applied to the AC motor, the induced voltage frequency of the AC motor based on the current flowing through the AC motor and time of applying a voltage and phase derives, restart the AC motor using the induced voltage frequency and phase that the derived,
The voltage application to the AC motor is interrupted when the current flowing through the AC motor exceeds a predetermined current value, or the voltage application to the AC motor is performed when the current flowing through the AC motor falls below a predetermined current value. Resume
The combination of voltage application and voltage application interruption is performed at least once for the AC motor, and the voltage application interruption time until the next time is determined using at least one of the induced voltage frequencies of the AC motor derived so far. The power converter characterized by doing . A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power converter that converts a DC voltage into an arbitrary voltage and drives an AC motor;
A control device that controls a semiconductor switching element of the power converter and controls the application of an arbitrary voltage from the power converter to the AC motor;
A current detector for detecting or estimating a current flowing through the AC motor,
The control device applies an arbitrary voltage from the power converter to the AC motor when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on the current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
A DC voltage detector for detecting a DC voltage input to the power converter;
When the detected DC voltage exceeds a predetermined voltage value, the voltage application to the AC motor is interrupted,
When the detected DC voltage falls below a predetermined voltage value, voltage application to the AC motor is resumed,
The combination of voltage application and voltage application interruption is performed at least once for the AC motor, and the voltage application interruption time until the next time is determined using at least one of the induced voltage frequencies of the AC motor derived so far. The power converter characterized by doing. A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power converter that converts a DC voltage into an arbitrary voltage and drives an AC motor;
A control device that controls a semiconductor switching element of the power converter and controls the application of an arbitrary voltage from the power converter to the AC motor;
A current detector for detecting or estimating a current flowing through the AC motor,
The control device applies an arbitrary voltage from the power converter to the AC motor when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on the current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
The voltage application to the AC motor is interrupted when the current flowing through the AC motor exceeds a predetermined current value, or the voltage application to the AC motor is performed when the current flowing through the AC motor falls below a predetermined current value. Resume
The power converter according to claim 1, wherein the AC motor is determined to be stopped or rotating at a low speed according to a time until voltage application to the AC motor is interrupted. A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power converter that converts a DC voltage into an arbitrary voltage and drives an AC motor;
A control device that controls a semiconductor switching element of the power converter and controls the application of an arbitrary voltage from the power converter to the AC motor;
A current detector for detecting or estimating a current flowing through the AC motor,
The control device applies an arbitrary voltage from the power converter to the AC motor when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on the current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
A DC voltage detector for detecting a DC voltage input to the power converter;
When the detected DC voltage exceeds a predetermined voltage value, the voltage application to the AC motor is interrupted,
The power converter according to claim 1, wherein the AC motor is determined to be stopped or rotating at a low speed according to a time until voltage application to the AC motor is interrupted. The power conversion device according to claim 3 or 4,
When it is determined that the AC motor is rotating at a low speed, an arbitrary DC voltage is applied to the AC motor for braking. The power converter according to any one of claims 1 to 4,
The voltage applied to the AC motor from the power converter when the AC motor is idling or stopped is a voltage of an arbitrary frequency that gradually increases the voltage value. A power converter according to any one of claims 1 to 4,
Power conversion apparatus and estimates the direction of rotation of the AC motor using at least one of the induced voltage phase of the derived the AC motor each time. A power converter according to any one of claims 1 to 4,
Wherein based on the current flowing to the AC motor and time voltage is applied to derive an induced voltage instantaneous value of the ac motor, with at least two phases of the induced voltage instantaneous value of the AC motor derived in each time of the AC motor A power converter characterized by estimating a rotation direction. A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power conversion process for converting a DC voltage into an arbitrary voltage and driving an AC motor;
A control step of controlling the semiconductor switching element of the power converter, and controlling to apply an arbitrary voltage from the power converter to the AC motor;
A current detection step of detecting or estimating a current flowing through the AC motor,
In the control step, an arbitrary voltage is applied to the AC motor from the power conversion step when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on a current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
The voltage application to the AC motor is interrupted when the current flowing through the AC motor exceeds a predetermined current value, or the voltage application to the AC motor is performed when the current flowing through the AC motor falls below a predetermined current value. Resume
The combination of voltage application and voltage application interruption is performed at least once for the AC motor, and the voltage application interruption time until the next time is determined using at least one of the induced voltage frequencies of the AC motor derived so far. A power conversion method characterized by: A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power conversion process for converting a DC voltage into an arbitrary voltage and driving an AC motor;
A control step of controlling the semiconductor switching element of the power converter, and controlling to apply an arbitrary voltage from the power converter to the AC motor;
A current detection step of detecting or estimating a current flowing through the AC motor,
In the control step, an arbitrary voltage is applied to the AC motor from the power conversion step when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on a current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
A DC voltage detection step of detecting a DC voltage input to the power conversion step;
  When the detected DC voltage exceeds a predetermined voltage value, the voltage application to the AC motor is interrupted,
When the detected DC voltage falls below a predetermined voltage value, voltage application to the AC motor is resumed,
The combination of voltage application and voltage application interruption is performed at least once for the AC motor, and the voltage application interruption time until the next time is determined using at least one of the induced voltage frequencies of the AC motor derived so far. A power conversion method characterized by: A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power conversion process for converting a DC voltage into an arbitrary voltage and driving an AC motor;
A control step of controlling the semiconductor switching element of the power converter, and controlling to apply an arbitrary voltage from the power converter to the AC motor;
A current detection step of detecting or estimating a current flowing through the AC motor,
In the control step, an arbitrary voltage is applied to the AC motor from the power conversion step when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on a current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
The voltage application to the AC motor is interrupted when the current flowing through the AC motor exceeds a predetermined current value, or the voltage application to the AC motor is performed when the current flowing through the AC motor falls below a predetermined current value. Resume
The power conversion method according to claim 1, wherein the AC motor is determined to be stopped or rotating at a low speed according to a time until voltage application to the AC motor is interrupted. A semiconductor switching element is provided, and the semiconductor switching element is turned on / off in combination.
A power conversion process for converting a DC voltage into an arbitrary voltage and driving an AC motor;
A control step of controlling the semiconductor switching element of the power converter, and controlling to apply an arbitrary voltage from the power converter to the AC motor;
A current detection step of detecting or estimating a current flowing through the AC motor,
In the control step, an arbitrary voltage is applied to the AC motor from the power conversion step when the AC motor is idling or stopped, and an induced voltage frequency of the AC motor is based on a current and voltage applied to the AC motor. Deriving the phase, restarting the AC motor using the derived induced voltage frequency and phase,
A DC voltage detection step of detecting a DC voltage input to the power conversion step;
When the detected DC voltage exceeds a predetermined voltage value, the voltage application to the AC motor is interrupted,
The power conversion method according to claim 1, wherein the AC motor is determined to be stopped or rotating at a low speed according to a time until voltage application to the AC motor is interrupted. The power conversion method according to claim 11 or 12,
A power conversion method comprising applying an arbitrary DC voltage to the AC motor and applying braking when it is determined that the AC motor is rotating at a low speed. A power conversion method according to any one of claims 9 to 12,
The voltage applied to the AC motor from the power conversion step when the AC motor is idling or stopped is a voltage of an arbitrary frequency that gradually increases the voltage value. A power conversion method according to any one of claims 9 to 12,
A power conversion method, wherein the rotational direction of the AC motor is estimated using at least one of the induced voltage phases of the AC motor derived each time. A power conversion method according to any one of claims 9 to 12,
An induced voltage instantaneous value of the AC motor is derived based on a time during which the current and voltage flowing to the AC motor are applied, and at least two phases of the induced voltage instantaneous values of the AC motor derived at each time are used. A power conversion method characterized by estimating a rotation direction.

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