JP4256238B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device to which speed sensorless control applied to an electric vehicle or an electric vehicle drive device is applied, and in particular, when starting an inverter from a state where an electric motor is rotating at a low speed including a stopped state, the mechanical The present invention relates to a power conversion apparatus that can be started stably and smoothly without causing any vibration or disturbance.

  For example, in electric vehicle control, the operation is stopped by stopping the gate of the inverter while stopping at the station, and the coasting period for stopping the operation of the inverter and stopping the operation completely during traveling between stations is provided. is there.

  In general, the speed sensorless control that controls the torque and speed of the motor without detecting the rotational speed of the motor estimates the rotational speed, that is, the rotor frequency based on the magnetic flux or induced voltage of the motor. Or during coasting, the speed of the motor cannot be accurately grasped, and it is not even known whether the vehicle is currently stopped or rotating at high speed.

  On the other hand, when starting an inverter by a command such as powering or braking in electric vehicle control, it is indispensable to start electrically and mechanically stable and smooth due to the influence on ride comfort and signal system. It is necessary to start with the inverter output frequency matched to the rotational speed or rotor frequency.

  Under such a request, the power conversion device to which the vector control method with speed sensor provided with the speed detector is applied can be started by outputting an inverter output frequency that matches the rotor frequency.

  However, if an appropriate inverter output frequency is not given at the start of the inverter, as described above, system instability, overcurrent, overvoltage, sudden torque change, etc. may occur, resulting in deterioration of ride comfort or in the worst state. May lead to protection.

  As means for solving these problems, a power conversion device to which speed sensorless control is applied includes a control period for estimating the approximate rotor frequency, which is different from the rotational speed estimation method during normal operation when starting the inverter. There is a case. When the approximate value of the rotor frequency can be estimated, normal operation is started based on the estimated value of the rotor frequency.

  FIG. 11 shows an example of a power conversion device to which conventional speed sensorless control that implements such a control mode is applied.

  In FIG. 11, the main circuit includes an inverter 1, a filter capacitor 2, and an induction motor 3. A current detector 4 detects currents Iu and Iw flowing through the motor 3, and a coordinate converter 7 converts the DQ axis currents Id and Iq. Is converted to

The voltage calculation unit 5 receives the excitation current command IdRef and the excitation current Id given from the outside, and calculates and outputs the output voltage commands Vd ^* and Vq ^* so that the torque current command IqRef and the torque current Iq coincide with each other. .

The coordinate converter 6 converts the DQ-axis output voltage commands Vd ^* , Vq ^* into three-phase voltage commands Vu ^* , Vv ^* , Vw ^* and outputs them.

  Based on the three-phase voltage command, the PWM control unit 9 generates a gate command by, for example, triangular wave comparison PWM control, and drives and controls the inverter 1.

The first inverter output frequency calculation unit 26 is for estimating an outline of the rotation speed of the motor, that is, the rotor frequency immediately after the inverter is started, and the second inverter frequency calculation unit 27 is a first inverter frequency calculation unit. The normal control is performed based on the approximate rotor frequency estimated value ωRH ^* calculated at 26, specifically, the approximate rotor frequency is set to the initial value of the inverter output frequency.

The second inverter output frequency calculation unit 26 includes a D-axis induced voltage calculation unit 15 and an inverter output frequency control unit 16 shown in FIG. The D-axis induced voltage calculation unit 15 calculates and outputs the D-axis induced voltage Ed from the DQ-axis voltage commands Vd ^* and Vq ^* and the DQ-axis currents Id and Iq. The inverter output frequency control unit 16 controls and outputs the inverter output frequency command ω1 ^* so that the input D-axis induced voltage Ed becomes zero.

  The inverter frequency command calculation unit 15 is known as speed sensorless vector control, and there are various other methods. Other examples of the first inverter output frequency calculation unit 26 are disclosed in Patent Document 1, Patent Document 2, and Patent Document 3.

The inverter output frequency command ω1 ^* , which is the output of the inverter output frequency calculation unit 10, is added with the inverter output frequency initial value ω1ini and the inverter output frequency receding correction value ω1cmp by the adder 12 and the adder 13, respectively. ω1.

  The integrator 8 integrates the inverter output frequency ω1, and generates and outputs the phase angle θ of the D axis with respect to the reference axis A axis of the stationary coordinate system used in the coordinate converters 6 and 7.

The slip frequency calculation unit 11 calculates the slip frequency reference ωs ^* based on the excitation current command IdRef and the torque current command IqRef. The subtracter 14 subtracts the slip frequency reference ωs ^* from the inverter output frequency ω1 to generate the rotor frequency estimated value ωRH.
JP 11-285300 A JP 11-346500 A JP 2000-253506 A

  As described above, in the power conversion device to which the conventional speed sensorless control is applied, even if the approximate rotor frequency is estimated by the first inverter output frequency calculation unit 26, the electric motor is accurately rotated when the motor is rotating at a low speed. It is difficult to estimate the rotor frequency, and an estimation error is likely to occur. When the control shifts to the normal operation based on the estimated rotor frequency value having an error, mechanical vibration or disturbance is induced depending on conditions.

  When such a power conversion device is a train driving device, the ride comfort at the start of the inverter may deteriorate. In particular, such a situation becomes conspicuous when a torque in the direction opposite to the direction of rotation is generated, for example, when it is assumed that the vehicle is stopped or moved forward but is erroneously moved backward.

  Further, when it is erroneously estimated that the rotor frequency is forward and low-speed rotation in a state where the vehicle is moving backward, a predetermined torque is not generated, which may cause an acceleration failure or electrical vibration.

  An object of the present invention is to provide a power conversion device capable of suppressing electrical and mechanical vibrations and disturbances and starting stably and smoothly when starting an inverter from a state where an electric motor rotates at a low speed. It is to provide.

In order to achieve the above object, the present invention provides an inverter for applying an AC voltage having a variable voltage and a variable frequency to a motor, and a speed for driving the motor by estimating a rotational speed of the motor and controlling an output voltage of the inverter. In a power converter having a sensorless control means,
Enter a first inverter output frequency calculation unit that estimates a schematic speed of said motor immediately after starting the inverter, a schematic speed of the electric motor estimated by the first inverter output frequency calculating unit is the estimated If it is determined that the approximate speed is low, the initial value of the frequency output from the inverter is set to a non-zero value in the direction in which the rotation is desired , and if it is determined that the estimated approximate speed is high, And a second inverter output frequency calculation unit that sets the estimated approximate speed as an initial value of the frequency output by the inverter .

In order to achieve the above object, the present invention drives an electric motor by applying an AC voltage of variable voltage and variable frequency to the electric motor, and estimating the rotational speed of the electric motor and controlling the output voltage of the inverter. In a power converter having a speed sensorless control means for
Enter a first inverter output frequency calculation unit that estimates a schematic speed of said motor immediately after starting the inverter, a schematic speed of the electric motor estimated by the first inverter output frequency calculating unit is the estimated If it is determined that the approximate speed is low, the initial value of the frequency output by the inverter is set to be larger in the direction in which it is desired to rotate than the rotational frequency of the motor , and it is determined that the estimated approximate speed is high. In this case, a second inverter output frequency calculation unit that sets the estimated approximate speed as an initial value of the frequency output from the inverter is provided.

  According to the present invention, when starting an inverter from low-speed rotation, which is difficult to estimate speed, it is difficult to generate torque in the direction opposite to the direction in which it is desired to rotate. Therefore, vibration caused by resonance, backlash, etc. existing in the mechanical load. -Suppresses disturbance and realizes a stable and smooth start, and when used in a drive device for trains and electric vehicles, an improvement in ride comfort can be expected.

(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration of the power conversion device according to the first embodiment of the present invention.

  In the present embodiment, torque control of an induction motor is performed by known speed sensorless vector control.

  In FIG. 1, a filter capacitor 2 is connected to the DC input side of the VVVF inverter 1, and an induction motor 3 is connected to the AC output side. A DC voltage source (not shown) is provided on the DC input side of the VVVF inverter 1.

  The current detector 4 detects currents Iu and Iw flowing through the induction motor 3, and the detected currents Iu and Iw are converted into DQ axis currents Id and Iq by the coordinate converter 7.

In the voltage calculation unit 5, an excitation current command IdRef and an excitation current Id are given from the outside, and the DQ-axis output voltage command Vd is set so that the excitation current command IdRef and the excitation current Id coincide with the torque current command IqRef and the torque current Iq. ^{* And} Vq ^* are calculated and output.

The coordinate converter 6 converts the DQ-axis output voltage commands Vd ^* , Vq ^* into three-phase voltage commands Vu ^* , Vv ^* , Vw ^* and outputs them.

  Based on the three-phase voltage command from the coordinate converter 6, the PWM control unit 9 generates a gate command by, for example, triangular wave comparison PWM control, and drives and controls the inverter 1.

  Regarding the calculation of the inverter output frequency ω1, the first inverter output frequency calculation unit 26 for estimating the approximate rotational speed, that is, the rotor frequency immediately after the inverter is started, and the rotor for the normal speed sensorless control operation after the inverter is started. A second inverter output frequency calculation unit 27 that estimates the frequency and calculates the inverter output frequency is provided.

The first inverter output frequency calculation unit 26 calculates and estimates the approximate rotor frequency ωRH ^* immediately after the start of the inverter, and the second inverter frequency calculation unit 27 normally performs estimation based on the estimated approximate rotor frequency ωRH ^*. Transition to driving.

  Details of the second inverter output frequency calculation unit 27 are shown in FIG.

As shown in FIG. 2, the second inverter output frequency calculation unit 27 includes a D-axis induced voltage calculation unit 15 and an inverter output frequency control unit 16 in order to perform a normal speed sensorless control operation. The D-axis induced voltage calculation unit 15 calculates and outputs the D-axis induced voltage Ed from the DQ-axis voltage commands Vd ^* and Vq ^* and the DQ-axis currents Id and Iq. The inverter output frequency control unit 16 controls and outputs the inverter output frequency command ω1 ^* so that the input D-axis induced voltage Ed becomes zero. The inverter frequency command calculation unit 15 is known as speed sensorless vector control, and there are various other methods.

Further, the second inverter frequency calculation unit 27 has a function of determining an initial value of the inverter output frequency by using the approximate rotor frequency ωRH ^* that is the output of the first inverter output frequency calculation unit 26 as an input. The absolute value of the approximate rotor frequency ωRH ^* is calculated by the absolute value calculator 29 and compared with a predetermined value by the comparator 30. If it is equal to or greater than the predetermined value, it is determined that the rotation is at a high speed, and the approximate rotor frequency ωRH ^* is set as the initial value ω1ini of the inverter output frequency.

On the other hand, the absolute value of the rotor frequency OmegaRH ^* Summary is, when it is less than the predetermined value, a predetermined alpha [Hz] rather schematic of the rotor frequency OmegaRH ^* as an initial value ω1ini the inverter output frequency (claim 2).

  Here, the predetermined value α is set to about 5 Hz. However, in the present embodiment, the inverter output frequency at which the output voltage of the inverter 1 is maximum is 50 Hz, and here, the inverter is started on the assumption that it wants to move forward (frequency is in the positive direction). When going backwards (frequency is negative), it is necessary to reverse the sign of each numerical value.

  The initial value ω1ini of the inverter output frequency is added and corrected in the adder 12 to the output of the inverter output frequency control unit 16.

The inverter output frequency command ω1 ^* , which is the output of the second inverter output frequency calculation unit 27, is added with the inverter output frequency receding correction value ω1cmp by the adder 13, and becomes the inverter output frequency ω1.

  Here, the inverter output frequency receding correction unit 21 is configured as shown in FIG.

  As shown in FIG. 3, the inverter output frequency receding correction unit 21 calculates the time that has elapsed since the inverter was started by the timer 17. However, the timer 17 may be not the time that has elapsed since the start of the inverter but the time that has elapsed since the torque command was started.

  The comparator 18 outputs 1 when the elapsed time after starting the inverter, which is the output of the timer 17, is larger than the predetermined value Tset, and 0 when it is smaller. The rise detector 23 outputs 1 only when the output of the comparator 18 as an input changes from 0 to 1 (instant), and otherwise outputs 0.

  The comparator 22 compares the inverter output frequency ω1 with the set frequency ω1set for reverse detection, and outputs 1 if ω1 <ω1set, and 0 otherwise.

  The AND circuit 24 takes an AND of the output of the comparator 22 and the output of the rising detector 23 and outputs the result. In the RS flip-flop 25, when the output of the AND circuit 24 is 1, the output is set to 1, and when the operation command Gst_ of the inverter is 1 indicating operation stop, 0 is output as the RearDet. RearDet = 1 indicates a state in which a backward movement is detected.

  The switch 19 outputs 0 when RearDet = 0, and outputs ω1Rear when RearDet = 1.

  The change rate limiter 20 outputs a value following the input as the inverter output frequency correction amount ω1 cmp while limiting the output change rate. Here, ω1rear is set to about −5 Hz.

  The integrator 8 integrates the inverter output frequency ω1, and generates and outputs the phase angle θ of the D axis (relative to the reference axis A axis of the stationary coordinate system) used in the coordinate converters 6 and 7.

Further, the rotational speed, that is, the rotor frequency can be estimated as follows. The slip frequency calculation unit 11 calculates the slip frequency reference ωs ^* based on the excitation current command IdRef and the torque current command IqRef. The subtracter 14 subtracts the slip frequency reference ωs ^* from the inverter output frequency ω1 to generate the rotor frequency estimated value ωRH.

  The effects of the power conversion device of the present embodiment configured as described above will be shown below.

Immediately after starting the inverter, the first inverter output frequency calculation unit 26 estimates the approximate rotor frequency ωRH ^* . When the actual rotational speed, that is, the rotor frequency is high, the accuracy of the approximate rotor frequency estimation value is high, and the reliability of this estimation result is high. In the second inverter output frequency calculation unit 27, when it is determined that the approximate rotor frequency estimated value exceeds the predetermined value and the rotation speed is high, the value is set as an initial value of the inverter output frequency.

  On the other hand, when the actual rotor frequency is low, since the approximate rotor frequency estimation accuracy estimated by the first inverter output frequency calculation unit 26 is low, the second inverter output frequency calculation unit 27 does not use this value, Α [Hz] is set as the initial value of the inverter output frequency.

  When the first inverter output frequency calculation unit 26 is configured as Japanese Patent Application Laid-Open No. 2002-281605, the operation shown in FIG. 4 is performed when the inverter is started from the state where the electric motor 3 is stopped. Immediately after the inverter is started, the first inverter output frequency calculator 26 acts on the inverter output frequency ω1. The inverter output frequency ω1 is given an appropriate initial value, and is adjusted in a direction in which an evaluation index such as a D-axis induced voltage decreases.

In this case, when the inverter is started from the state where the electric motor is stopped, the inverter output frequency ω1 converges in the 0 Hz direction. The inverter output frequency ω1 after a predetermined time has elapsed is set as the approximate rotor frequency ωRH ^* . The approximate rotor frequency ωRH ^* is input to the second inverter output frequency calculation unit 27, and if it does not exceed the predetermined value, it is determined that the rotation is at a low speed. When it is determined that the rotation speed is low, the initial value ω1ini of the inverter output frequency reference ω1 ^* is set to 5 Hz (= αHz). Since the actual rotor frequency is 0 Hz, the inverter output frequency ω 1 converges from the initial value 5 Hz to 0 Hz by the action of the inverter frequency control unit 16 of the second inverter output frequency calculation unit 27.

FIG. 5 shows an operation in which the inverter is started while the electric motor is rotating at a high speed. Immediately after the inverter is started, the first inverter output frequency calculator 26 acts on the inverter output frequency ω1. The inverter output frequency ω1 is given an appropriate initial value, and is adjusted in a direction in which an evaluation index such as a D-axis induced voltage decreases. The inverter output frequency ω1 converges to the true rotor frequency. The inverter output frequency ω1 after a lapse of a predetermined time is used as an approximate rotor frequency ωRH ^* . Since this exceeds a predetermined value, it is determined that the rotation speed is high. When it is determined that the rotation speed is high, the second inverter output frequency calculation unit 27 sets the initial value of the inverter output frequency reference ω1 ^{* to} the approximate estimated rotor frequency value ωRH ^* , and then the inverter output frequency ω1 is set to an appropriate value. Converge to the value.

FIG. 6 shows the inverter started in a state where the electric motor is rotating in the low speed and forward direction. The first inverter output frequency calculation unit 26 determines that the approximate rotor frequency ωRH ^* is smaller than a predetermined value and is a low speed rotation, and the initial value of the inverter output frequency ω1 is set to 5 Hz. By the action of the inverter frequency control unit 16 of the second inverter output frequency calculation unit 27, the speed immediately converges to the actual rotor rotational frequency.

  FIG. 7 shows an example in which the inverter is started from a state in which the electric motor is rotating at a low speed in the reverse direction (the direction opposite to the direction in which the motor is desired to rotate). As in the case of FIG. 6, it is determined that the rotation speed is low, and the initial value of the inverter output frequency ω <b> 1 is set to 5 Hz. By the action of the inverter frequency control unit 16 of the second inverter output frequency calculation unit 27, the inverter output frequency ω1 converges to zero Hz. When the inverter output frequency becomes zero Hz, no induced voltage is generated (because the induced voltage is magnetic flux × inverter output frequency), and information on the rotor frequency cannot be obtained completely. After this, it cannot be guaranteed that the inverter output frequency will converge to the rotor frequency. The inverter output frequency backward correction unit 21 compares the inverter output frequency ω1 with the set frequency ω1set for backward detection when the elapsed time since the start of the inverter exceeds Tset. For example, if ω1set is set to a plus number Hz, it is determined that the vehicle is moving backward (RearDet = 1). The inverter output frequency correction amount ω1 cmp gradually decreases (in this case, increases in the minus direction) by the action of the switch 19 and the change rate limiter 20, and eventually reaches ω1rear. The inverter output frequency ω1 increases in the minus direction by the correction amount ω1 cmp, but when an induced voltage is generated, the operation of the inverter frequency control unit 16 of the second inverter output frequency calculation unit 27 It converges to the vicinity of the sum of the rotor frequency and the slip frequency, and appropriate torque is generated.

  As described above, according to the present embodiment, stable and smooth start-up can be realized when the electric motor is stopped, moving forward at low speed, and moving backward at low speed. In particular, the motor is stopped or rotating at a very low speed, and the induced voltage is difficult to accurately capture (the induced voltage is small because the inverter output frequency is small. Since it is buried in other error voltages, the accurate induced voltage is calculated. In particular, when the inverter output frequency is zero, the induced voltage = 0, so that it cannot be estimated in principle, and conversely, if the rotational speed is small, the information accuracy of the induced voltage is high. Therefore, in the situation where the convergence of the inverter output frequency is high and unnecessary torque is unlikely to be generated), the initial value of the inverter output frequency is set so that the inverter output frequency> the rotor frequency (assuming to move forward).

  This is a state where slip frequency> 0, and is a state where positive torque (torque in the direction of rotation) is generated. Therefore, even if the true rotor frequency cannot be accurately estimated immediately after the inverter is started, it is possible to avoid reverse rotation caused by the occurrence of torque in the direction opposite to the direction of rotation. Applying a torque opposite to the direction of rotation is to inject reverse (kinetic) energy into the mechanical load connected to the motor, and vibration and disturbance caused by mechanical resonance and backlash. It is easy to induce. When applied to a drive device for an electric vehicle, riding comfort is degraded by reverse torque. Further, according to the present embodiment, it is possible to avoid the occurrence of the reverse torque, so that stable and smooth start can be expected.

  The inverter output frequency initial value ω1ini is set to 5 Hz for the following reason. In general, errors in the inverter output voltage (such as element voltage drop and dead time effects) affect the estimation of the induced voltage, and the speed sensorless vector control that estimates the rotor frequency has a great influence on the inverter. When the inverter output frequency (base frequency) that outputs the maximum voltage is considered as 100%, the frequency is approximately 10% or less. Therefore, when the inverter output frequency initial value is set higher, the inverter output frequency can be quickly converged (speed estimation) when the rotation speed is higher, while time is required during the low speed rotation. Therefore, a frequency of about 10% is appropriate.

  In the present embodiment, the inverter frequency backward correction unit 21 determines the backward detection based on the inverter frequency ω <b> 1, but the same effect can be obtained even if it is determined based on the estimated rotor frequency ωRH. The inverter frequency ω1 and the estimated rotor frequency ωRH are different from each other by the slip frequency reference value calculated by the slip frequency calculation unit 11. Therefore, in a situation where the acceleration is poor due to insufficient torque and the inverter frequency does not gradually increase, the rotor frequency estimated value ωRH also does not gradually increase. Therefore, it can be determined that the acceleration is poor, that is, the vehicle is moving backward, based on the estimated rotor frequency.

  Although the present embodiment shows a configuration based on an induction motor, a similar effect can be obtained with a permanent magnet motor, a permanent magnet reluctance motor, or the like.

(Second Embodiment)
FIG. 8 is a block diagram showing a schematic configuration of the second embodiment of the present invention.

  Since the present embodiment is different from the first embodiment only in the inverter output frequency receding correction unit 21, the description will be omitted.

  Details of the inverter output frequency receding correction unit 21 are shown in FIG. Since the input to the comparator 22 is different from the inverter output frequency receding correction unit 21 of the first embodiment shown in FIG.

The inverter output frequency receding correction unit 21 receives the DQ axis voltage commands Vd ^* and Vq ^* , the DQ axis currents Id and Iq, and the inverter output frequency ω1. The Q-axis induced voltage calculation unit 32 calculates a Q-axis induced voltage E2Q that is a Q-axis component of the induced voltage. The Q-axis induced voltage E2Q can be calculated by the following equation, for example.

E2Q = Vq ^* −R1 × Iq−σ × L1 × ω1 × Id (1)
Where R1: primary resistance value,
σ: leakage coefficient (= 1−M × M / L1 / L2),
L1: A primary self-inductance.

On the other hand, the inverter output frequency ω1 is input to the Q-axis induced voltage reference calculation unit 33, and for example, the reference amount E2Q ^* of the Q-axis induced voltage is calculated and output as in the following equation.

E2Q ^* = ω1 × M2 / L2 × Id (2)
The subtracter 34 subtracts the Q-axis induced voltage E2Q from the Q-axis induced voltage reference E2Q ^* . The subtractor 34 is input to the absolute value calculation unit 35, and the absolute value is calculated. The output of the absolute value calculator 35 is input to the comparator 22.

  The comparator 22 compares AbsE2Q, which is the output of the absolute value calculator 35, with a predetermined set value AbsE2Qset. 1 is output when AbsE2Q is larger than AbsE2Qset, and 0 is output when AbsE2Q is smaller.

With the above configuration, it is possible to detect that the electric motor is moving backward by the Q-axis induced voltage. Immediately after shifting to normal sensorless control, the inverter output frequency is positive, and therefore the slip frequency is not appropriate when the motor is started from a retracted state. At this time, since the magnetic flux does not increase to the target value and is maintained at a small value, the magnitude of the Q-axis induced voltage is smaller than the original magnitude, that is, the Q-axis induced voltage reference. Therefore, the Q-axis induced voltage E2Q is compared with the reference value E2Q ^*, and when the deviation is large, it can be detected that the vehicle is moving backward.

  In the present embodiment, the Q-axis induced voltage is referred to as a backward index. However, in the vector control, since the D-axis induced voltage is controlled to be zero, the magnitude of the induced voltage (vector length of the DQ-axis induced voltage) can be similarly used instead of the Q-axis induced voltage. Advantageous effects can be obtained.

Further, the deviation of the Q-axis induced voltage output and calculated by the subtracter 34 can be calculated by the following configuration. FIG. 10 shows details of the voltage control unit 5. There is a feedforward (FF) voltage calculation unit 36 that calculates the voltage in a feedforward manner so that a current that matches the predetermined excitation current command IdRef and the torque current command IqRef flows using the motor constant. There is also a current control unit 37 that corrects the DQ axis output voltage by PI control or the like so that the actual DQ axis current value matches the current command. The output of the feedforward voltage calculation unit 36 and the output of the current control unit 37 are added by adders 40 and 41 to become output voltage commands Vd ^* and Vq ^* .

Here, the Q-axis voltage correction amount VqPI of the current control unit 37 is input to the absolute value calculation unit 35. The Q-axis voltage calculation amount VqPI has an effect of compensating for a difference between the actual Q-axis induced voltage E2Q and the Q-axis induced voltage reference E2Q ^* . Therefore, it is also possible to detect the backward movement based on the Q-axis voltage correction amount VqPI that is the output of this current control.

  Similarly, when starting from reverse, appropriate slip cannot be maintained, and the magnetic flux is small, so the magnitude of the induced voltage is small. At this time, the phase difference between the voltage and current applied to the motor also shows different values. Therefore, it is possible to determine that the vehicle is moving backward from the phase difference between the voltage and current applied to the motor, that is, the power factor of the motor.

  Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention at the stage of implementation. In addition, the embodiments may be appropriately combined as much as possible, and in that case, combined effects can be obtained. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, when an invention is extracted by omitting some constituent elements from all the constituent elements shown in the embodiment, when the extracted invention is implemented, the omitted part is appropriately supplemented by a well-known common technique. It is what is said.

The block diagram which shows the power converter device of 1st Embodiment of this invention. The block diagram of the 2nd inverter output frequency calculating part in the embodiment. The block diagram of the inverter output frequency backward correction | amendment part in the embodiment. The figure which shows the operation | movement when the electric motor in the embodiment starts an inverter from rotation stop. The figure which shows operation | movement when the electric motor in the embodiment starts an inverter from forward high speed rotation. The figure which shows the operation | movement at the time of the electric motor in the same embodiment starting an inverter from a forward low speed rotation. The figure which shows the operation | movement at the time of the electric motor in the same embodiment starting an inverter from reverse low speed rotation. The block diagram which shows the power converter device of 2nd Embodiment of this invention. The block diagram of the inverter output frequency backward correction | amendment part in the embodiment. The figure which shows the structural example of the Q-axis induced voltage deviation calculation in the same embodiment. The figure which shows an example of the conventional power converter device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inverter, 2 ... Filter capacitor, 3 ... Induction motor, 4 ... Current detector, 5 ... Voltage calculating part, 6 ... Coordinate converter, 7 ... Coordinate converter, 8 ... Integrator, 9 ... PWM control part, 11 ... Slip frequency calculation unit, 12 ... Adder, 13 ... Adder, 14 ... Adder, 15 ... D-axis induced voltage calculation unit, 16 ... Inverter output frequency control unit, 17 ... Timer, 18 ... Comparator, 19 ... Switch , 20 ... change rate limiter, 21 ... inverter output frequency receding correction unit, 22 ... comparator, 23 ... rise detector, 24 ... AND circuit, 25 ... RS flip-flop, 26 ... first inverter output frequency calculation unit, 27 2nd inverter output frequency calculation unit, 28 ... switch, 29 ... absolute value calculator, 30 ... comparator, 31 ... switch, 32 ... Q-axis induced voltage calculation unit, 33 ... Q-axis induced voltage reference calculation , 34 ... subtractor, 35 ... absolute value calculating section, 36 ... feed-forward (FF) voltage calculating unit, 37 ... current control unit, 38 ... subtractor, 39 ... subtractor, 40 ... adder, 41 ... adder.

Claims (8)

In an electric power converter comprising: an inverter that applies an AC voltage of variable voltage and variable frequency to an electric motor; and a speed sensorless control unit that estimates the rotational speed of the electric motor and controls the output voltage of the inverter to drive the electric motor.
A first inverter output frequency calculation unit that estimates an approximate speed of the electric motor immediately after starting the inverter;
Type a schematic speed of the electric motor estimated by the first inverter output frequency calculating unit, when the outline speed as the estimated is determined to be slow, want to rotate the initial value of the frequency of the inverter output A second inverter output frequency that sets the estimated approximate speed as an initial value of the frequency output by the inverter when it is determined that the estimated approximate speed is high. A power conversion device comprising: an arithmetic unit . The power conversion device according to claim 1,
The initial value of the output frequency of the inverter when it is determined that the estimated approximate speed is low is 10% or less of the output frequency when the output voltage of the inverter is saturated. apparatus. In an electric power converter comprising: an inverter that applies an AC voltage of variable voltage and variable frequency to an electric motor; and a speed sensorless control unit that estimates the rotational speed of the electric motor and controls the output voltage of the inverter to drive the electric motor.
A first inverter output frequency calculation unit that estimates an approximate speed of the electric motor immediately after starting the inverter;
Type a schematic speed of the electric motor estimated by the first inverter output frequency calculating unit, when the outline speed as the estimated is determined to be slow, the initial value of the frequency of the inverter output, the If the rotation speed is set to be larger than the rotation frequency of the motor and the estimated approximate speed is determined to be high, the estimated approximate speed is set as an initial value of the frequency output by the inverter . An inverter output frequency calculation unit and a power conversion device. In the power converter device according to claim 1 or 3,
A reverse detection means for determining that the inverter is moving backward when the rotational speed does not exceed the predetermined value based on the estimated rotational speed after a predetermined time has elapsed after starting the inverter;
A power converter comprising: means for correcting the output frequency of the inverter in a direction opposite to the direction in which the output frequency is desired to be rotated when the reverse detection is detected by the reverse detection means. The power conversion device according to claim 4,
The power conversion device, wherein the reverse detection means determines reverse according to the output frequency of the inverter instead of the estimated value of the rotation speed. The power conversion device according to claim 4,
The power conversion device according to claim 1, wherein the reverse detection means does not determine the reverse after the start of the inverter but determines the reverse based on an elapsed time from the start of applying the torque command. The power conversion device according to claim 4,
The reverse detection means calculates an induced voltage instead of the estimated value of the rotational speed, and determines reverse based on the calculated induced voltage. The power conversion device according to claim 4,
The power conversion device, wherein the reverse detection means determines reverse based on a phase difference between a voltage and a current applied to the electric motor instead of the estimated value of the rotation speed.

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