JP2023153612A - Motor control device - Google Patents

Abstract

To shorten a time from input of an operation command to re-activation of an induction motor by minimizing shock at the time of re-activation even in a case where a residual voltage is attenuated in a configuration where a voltage detector is disposed at an output side of a power converter.SOLUTION: A motor control device comprises: a power converter configured to convert a DC voltage into a three-phase AC voltage of a variable voltage and a variable frequency and supply it to an induction motor; an inter-phase time detection section configured to detect an inter-phase voltage of the induction motor for two or more phase intervals; a current detection section configured to detect a phase current of the induction motor; a current adjustment section configured to calculate a voltage command value so that a component obtained by converting a detected current value onto a synchronous coordinate axis matches a current command value; and a re-activation control section. Therein, the re-activation control section is configured to: when activating the induction motor from a state where an initial velocity is generated, implement an excitation operation for velocity estimation to give a stepwise current command value of a predetermined magnitude to the current adjustment section for a predetermined time; after cutting off output of the power converter, perform convergence arithmetic processing for obtaining a rotation velocity and a rotation speed of the induction motor and a phase of a residual secondary magnetic flux using the detected values of the inter-phase voltages for two or more phase intervals; and restart control of the induction motor.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a motor control device that estimates a rotor speed when starting an induction motor from a state where it has an initial speed.

Variable speed motor drive devices that drive motors at variable speeds using power converters are applied to various fields. Among electric motors, induction motors are widely used because they have a relatively simple and robust structure. In addition, even if the control device should fail, there is the advantage that it can be operated by directly connecting to a commercial power source as a backup.

When restarting such an induction motor during a period in which the rotor is free-running, such as after a momentary power outage or when switching from commercial operation, the mechanical shock at startup is reduced. Therefore, it is desirable to obtain the rotor speed, match the output frequency to the rotor speed, and restart.

In order to obtain the speed of the rotor during free running, it is possible to use the induced voltage generated by the secondary magnetic flux remaining in the rotor. Even if the residual magnetic flux is minute, a relatively large induced voltage can be obtained if the rotational speed is high. However, when the secondary magnetic flux decreases to near zero after a long period of time has passed since the operation was stopped, the induced voltage can no longer be observed.

Furthermore, depending on the installation environment, a small voltage may be induced in the wiring of the motor due to the influence of the wiring of large power capacity equipment that is close to the motor to be controlled due to space constraints. If such a voltage is observed to be larger than the amplitude of the residual voltage of the motor, there is a possibility that the rotor speed cannot be estimated correctly.

As a method of obtaining rotor speed in a free running state using residual magnetic flux, for example, there is Patent Document 1. According to this, when it is determined that the residual magnetic flux is small and speed estimation is difficult, a direct current is applied to the motor, and while the direct current is being applied, the input voltage vector of the induction motor is detected or estimated. Then, the secondary magnetic flux is obtained by integrating the result of subtracting the voltage drop due to the primary resistance of the induction motor and the voltage drop due to leakage inductance from the voltage vector, and the center of the vector is determined from the change in the vector at three points. Estimate the rotational angular frequency from the relationship between progress and phase.

In this method, when the rotor is rotating at a low speed, it takes a long time to obtain the vector locus of the secondary magnetic flux. During this time, time passes while DC current continues to flow through the induction motor, so it is thought that a brake torque proportional to the rotational speed is generated.

To address this problem, in Patent Document 2, as a method to shorten the time of applying DC current, the voltage drop due to the primary resistance is subtracted from the induced voltage when DC current is applied to an induction motor in a free-running state. The secondary magnetic flux is estimated by integrating the value, and the rotational speed is estimated using the twice differentiated value of the estimated value of the q-axis component of the secondary magnetic flux. The second differential value of the estimated secondary magnetic flux immediately after the inverter that drives the induction motor starts operating includes a component proportional to the rotation speed. Therefore, the rotation speed can be estimated by dividing the above twice differentiated value by the result of multiplication of the excitation inductance, the reciprocal of the quadratic time constant, and the excitation current.

Patent No. 3535735 Patent No. 6447183

Since the methods disclosed in these patent documents all use the amount of magnetic flux generated when current is passed through the motor, it is assumed that the initial residual magnetic flux is near zero. For example, when these methods are used when a relatively large amount of magnetic flux remains, such as when a motor with a relatively long secondary time constant is restarted shortly after free-run, the magnetic flux information used for speed estimation can be There is a possibility that torque disturbance may occur due to the current applied to obtain the torque and the remaining secondary magnetic flux.

Furthermore, these methods estimate only the rotation speed and rotation direction, and when restarting with relatively large residual magnetic flux, the estimation is performed according to the difference between the induced voltage due to the residual magnetic flux and the initial voltage at restart. There is a risk that a rush current may flow.

When controlling the torque of an electric motor, it is assumed that the operating state and the free run state are switched relatively frequently, or that the motor is restarted in a short time after being set to the free run state. In order to suppress current disturbance during restart, it is necessary to apply an output voltage as an initial value that takes into account the magnitude and phase of the induced voltage due to residual secondary magnetic flux, and restart the system.

In order to accurately obtain the residual voltage without causing torque disturbance, it is desirable to provide a voltage detector on the output side of the power converter. However, as time passes after the free run, the residual voltage attenuates and the induced voltage becomes lower than the noise component in the installed environment, making it difficult to accurately estimate the speed.

Therefore, in a configuration in which a voltage detector is placed on the output side of the power converter, even if the residual voltage attenuates, the shock at restart is minimized, noise resistance is ensured, and the power converter is restarted after an operation command is input. Provided is a motor control device that can shorten the time required to start up the motor.

The motor control device of the embodiment includes a power converter that converts a DC voltage into a three-phase AC voltage of variable voltage and variable frequency and supplies the voltage to an induction motor;
a phase-to-phase voltage detection unit that detects phase-to-phase voltage of the induction motor between two or more phases;
a current detection unit that detects a phase current of the induction motor;
a current adjustment unit that calculates a voltage command value such that a component obtained by converting the detected value of the phase current onto a synchronous coordinate axis matches the current command value;
When starting the induction motor from a state where an initial speed is generated,
carrying out an excitation operation for speed estimation that gives a step-like current command value of a predetermined magnitude to the current adjustment unit for a predetermined time;
After cutting off the output of the power converter, convergence calculation processing is performed to obtain the rotational speed and rotational direction of the induction motor and the phase of residual secondary magnetic flux using the detected values of the interphase voltage between two or more phases. , and a restart control unit that restarts control of the induction motor.
Further, the motor control device of the embodiment includes a power converter to a current adjustment unit similar to the above,
When the induction motor is in an operating state, when a coast-to-run operation stop request is input, or when the main circuit potential of a power converter that drives the induction motor is lowered and it is determined that operation is difficult and the motor shifts to a coast-to-run state, Make sure to always perform convergence calculation processing,
When the operation command is input again or the main circuit potential is restored, the induction motor and a restart control unit that restarts the control of the controller.

A diagram showing the configuration of a motor control device, which is an embodiment Functional block diagram showing the configuration of the convergence calculation processing unit Diagram showing the relationship between rotor magnetic flux and induced voltage Diagram showing DQ synchronous coordinate axis and MT synchronous coordinate axis Diagram explaining how to observe the phase difference between two phase voltages Signal waveform diagram showing transition from stop mode to initial speed estimation mode A diagram showing the waveforms of phase-to-phase voltage and torque current when the induction motor is restarted from a coasting state. Waveform diagram showing the change in secondary magnetic flux when a current command value is given for a predetermined period of time Flowchart showing the processing content of the control device Pre-start speed estimation operation: Type 1, speed estimation excitation operation: Valid, pre-start excitation operation: Disabled, timing chart showing the case where inter-phase voltage level judgment becomes NG Pre-start speed estimation operation: Type 1, excitation operation for speed estimation: Valid, pre-start excitation operation: Timing chart showing the case where inter-phase voltage level judgment becomes NG in the case of Valid. Timing chart showing a case where the interphase voltage phase difference determination is NG in the same case as in FIG. 10 Flowchart showing the processing content of the control device Timing chart showing the case of pre-start speed estimation operation: Type 2, excitation operation for speed estimation: valid, excitation operation for pre-start: valid

An embodiment will be described below. As shown in FIG. 1, each phase terminal of a three-phase AC power supply 1 is connected to an AC input terminal of a full-wave rectifier circuit 2 consisting of a diode bridge. A smoothing capacitor 3 and a power converter 4 are connected between the DC output terminals of the full-wave rectifier circuit 2. Each phase output terminal of the power converter 4, which is an inverter, is connected to each phase winding terminal of the induction motor 5.

The control device 6, which is a restart control section, controls the power converter 4 to convert the DC voltage into a three-phase AC voltage with variable voltage and variable frequency. Current detection units 7U and 7W are arranged at the U-phase and W-phase output terminals of the power converter 4, and the U-phase and W-phase currents i _u and i _w detected by these are detected by the UVW/dq converter. 8 is entered. The UVW/dq converter 8 converts the three-phase current into a dq-axis current in vector control, and inputs it to the current adjustment section 9 and the speed estimation processing section 10.

Each phase output terminal of the power converter 4 is connected to an input terminal of an interphase voltage detection section 11. The inter-phase voltage detection section 11 detects the UV inter-phase voltage v _uv and the WV inter-phase voltage v _wv , and inputs these to the convergence calculation processing section 12 , the inter-phase voltage level determination section 13 , and the inter-phase voltage phase difference determination section 14 . The gate drive permission signal is applied to one input terminal of an AND gate 16 via a NOT gate 15, and the speed estimation operation command is applied to the other input terminal of the AND gate 16. The output signal of the AND gate 16 is input to the convergence calculation processing section 12 as a convergence calculation execution command.

The convergence calculation processing unit 12 performs a convergence calculation process, which will be described later, on the input phase-to-phase voltage to obtain the initial secondary magnetic flux command value φ _{rd_ref_Init} , the initial speed command value ω _{re_ref_Init} , and the initial output voltage phase value θ _{re_Init} . Generate and output. The secondary magnetic flux command value initial value φ _{rd_set_Init} is input to the magnetic flux/current command generation unit 17 , and the speed command initial value ω _{re_ref_Init} is input to the speed command generation unit 18 . The output voltage phase initial value θ _{re_Init} is input to the integrator 27 .

The phase-to-phase voltage level determination section 13 compares the input phase-to-phase voltage with a threshold value and outputs a determination result of OK/NG to the restart processing section 19 . The phase-to-phase voltage phase difference determining section 14 compares the input phase difference between the phase-to-phase voltages with a threshold value and outputs a determination result of OK/NG to the restart processing section 19 .

Further, the magnetic flux/current command generation unit 17 is inputted with a secondary magnetic flux target value φ _{rd_set} and a secondary magnetic flux command value initial value φ _{rd_ref_Init} . Based on these input values, the magnetic flux/current command generation unit 17 generates a d-axis current target value i _{sd_set} , a filtered secondary magnetic flux target value φ _{rd_set_Filt} , and a filtered d-axis current target value i _{sd_set_Filt} as described below. Generate and output. Further, the secondary magnetic flux target value φ _{rd_set} is output as is.

Further, the speed target value ω _{re_set} is input to the speed command generation unit 18 . The speed command generation section 18 generates a speed command value ω _{re_ref} based on these input values, and outputs it to the speed control section 20 . The speed estimation value ω _{re_est} output from the speed estimation processing section 10 is input to the speed control section 20 .

In addition, the restart processing unit 19 includes a driving command "ON/OFF", a pre-start speed estimation operation "Type 1/Type 2/invalid", a pre-start speed estimation operation == an operation for Type 2 "enable/invalid", and a pre-start speed estimation operation "Enable/Invalid". Excitation operation "valid/invalid" is input. Based on these input signals, the restart processing unit 19 generates a speed estimation excitation operation command "ON/OFF", a pre-start excitation operation command "ON/OFF", a speed control operation command "ON/OFF", a speed It generates and outputs signals such as an estimated operation command "ON/OFF", excitation current setting i _{mag_1} for speed estimation, and switch setting selection. The speed estimation excitation operation command, the pre-start excitation operation command, and the speed control operation command are given to input terminals of the three-input OR gate 21. The output signal of the OR gate 21 is input to the power converter 4 and the NOT gate 15 as a gate drive permission signal.

Changeover switches 22 and 23 are connected to two input terminals of the current adjustment section 9, respectively. The movable contact of the changeover switch 22 is switched between fixed contact AB and fixed contact CD by the above-described switch setting selection. The fixed contact AB is given a speed estimation excitation current setting i _{mag_1} , and the fixed contact CD is given a d-axis current target value i _{sd_set} as i _{mag_2} . The symbols A, B, C, and D attached to the fixed contacts mean the contact symbols of the switches selected in the processing of the control device shown in FIGS. 9 and 13.

The movable contacts of the changeover switch 23 are switched between fixed contacts ABC and fixed contacts D by selecting switch settings. The fixed contact ABC is given a zero value, and the fixed contact D is given the output signal of the speed control section 20. The signals input to the current adjustment unit 9 via the changeover switches 22 and 23 are a D-axis current command i _{sd_ref} and a Q-axis current command i _{sq_ref} , respectively.

The Q-axis current command i _{sq_ref} is input to the slip calculation section 24 . Further, a secondary magnetic flux command φ _{rd_ref} is input to the slip calculation unit 24 . The slip calculation unit 24 calculates the _slip frequency ω slip of the induction motor 5 based on these input values, and outputs it to the adder 25 . A movable contact of a changeover switch 26 is connected to the adder 25, and the movable contact is switched to fixed contacts A, BC, and D by selecting a switch setting. A zero value is given to the fixed contact A, a speed command initial value ω _{re_ref_Init} is given to the fixed contact BC, and an estimated speed value ω _{re_est} is given to the fixed contact D.

The addition result of the adder 25 is input to the integrator 27 as the output frequency ω _stat . The integration result of the integrator 27 is input to the UVW/dq converter 8 and the dq/UVW converter 28 as an output voltage phase θ _{re_c} . D and Q axis currents i _d and i _q are inputted to the current adjustment unit 9 from the UVW/dq converter 8 . The current adjustment section 9 generates a compensation voltage by performing, for example, proportional-integral calculation on the difference between the input current command value and the currents i _d , i _q , and outputs it to the voltage calculation section 29 . The voltage calculation unit 29 generates voltage commands v _{sd_ref} and v _{sq_ref} based on the compensation voltage and the equation of the induction motor, and outputs them to the dq/UVW converter 28 . The dq/UVW converter 28 converts the input voltage command into a three-phase voltage command, generates a PWM signal, and outputs it to the power converter 4.

FIG. 2 is a functional block diagram showing the internal configuration of the convergence calculation processing section 12. As shown in FIG. When the phase-to-phase voltages v _uv , v _wv are converted into three-phase voltages by the UV, WV/UVW converter 31 , the d-axis voltages v _dc , It is converted into the q-axis voltage v _qc . These voltages v _dc and v _qc are input to an error calculator 34 and a sum of squares calculator 35 . The error calculator 34 calculates the phase error θ _err using equation (8). The phase error θ _err is given a sign (-) by the encoder 36, and is multiplied by the proportional gains K _{P_PLL} and K _{I_PLL} by the gain adders 37P and 37I.

The output terminal of the gain giver 37P is connected to the START side fixed contact of the changeover switch 38P, and the output terminal of the gain giver 37I is connected to the START side fixed contact of the changeover switch 38I via the Δt giver 39. A zero value is given to the fixed contact STOP side of the switch 38. A movable contact of the switch 38P is connected to one input terminal of the adder 41. The movable contact of switch 38I is connected to the other input terminal of adder 41 via another adder 40.

The output signal of the adder 40 is fed back to the added value input of the adder 40 via the unit delay element 42. Switching of the changeover switch 38 is performed by a convergence calculation execution command signal.

The output signal of the adder 41 becomes the estimated speed ω _{re_est_PLL} , and is input to the adder 44 via the Δt adder 43 . The output signal of the adder 44 is input to the αβ/dq converter 33 as the estimated phase θ _{re_est_PLL} , and is outputted to the outside as the output voltage phase initial value θ _{re_Init} . Further, the output signal of the adder 44 is fed back to the added value input of the adder 44 via a unit delay element 45. The estimated speed ω _{re_est_PLL} is input to the input B of the divider 46, and is outputted to the outside as the speed command initial value ω _{re_ref_Init} . The output signal of the sum of squares calculator 35 is input to the input A of the divider 46 . The divider 46 outputs the division result A/B to the outside as a secondary magnetic flux command initial value _{φrd_ref_Init} .

Next, a method for estimating speed in this embodiment will be explained. When the rotor magnetic flux of an induction motor is subjected to vector control, as shown in Fig. 3, if the direction of the magnetic flux is defined as the M-axis and the phase advanced by 90 degrees from there is defined as the T-axis, the induced voltage is Occurs in the T-axis direction. The integral value of θ _re, which corresponds to the actual rotor speed and electrical angle, is taken as the phase and position information representing the M-axis direction. Since the M axis is the direction of magnetic flux, it is assumed to be θ _flux .

In order to estimate the speed and residual magnetic flux direction of a rotor having an initial speed, first, a DQ synchronous coordinate axis corresponding to the estimated MT synchronous coordinate axis is defined. FIG. 4 shows the relationship between the estimated DQ synchronous coordinate axes calculated within the controller and the MT synchronous coordinate axes in the actual motor. The DQ synchronization coordinate axis defines the currently recognized estimated speed as ω _{re_est_PLL} and the direction of the estimated phase θ _{re_est_PLL} corresponding to its time integral value as the D axis.

The induced voltage is observed and converted to the DQ synchronous coordinate axes using the estimated phase θ _{re_est_PLL} . D and Q axis components v _dc and v _qc are obtained as values of the DQ synchronous coordinate axes. If the MT synchronization axis and the DQ synchronization axis match, only v _qc can be obtained, so speed estimation may be performed so that v _dc becomes 0.

Next, the above calculation processing of the convergence calculation processing section 12 will be explained. Detection of the phase-to-phase voltages v _uv and v _wv involves detecting the U and W phase potentials based on the V phase potential.

２相線間電圧（ｖ_ｕｖ，ｖ_ｗｖ）から３相静止軸上の電圧（ｖ_ｕ，ｖ_ｖ，ｖ_ｗ）には、以下の式で変換できる。

The two-phase line-to-line voltage (v _uv , v _wv ) can be converted into the voltage on the three-phase stationary axis (v _u , v _v , v _w ) using the following formula.

３相静止軸上の電圧から２相静止軸上の電圧（ｖ_α，ｖ_β）への変換は、以下の式による。

Conversion from the voltage on the 3-phase stationary axis to the voltage (v _α , v _β ) on the 2-phase stationary axis is based on the following equation.

The voltages (v _α , v _β ) are converted into voltage values (v _dc , v _qc ) on the synchronous coordinate axes using a conversion formula using position information θ _{re_est_PLL} corresponding to the time integral value of the estimated rotor speed ω _{re_est_PLL} . Convert.

The purpose of this estimation operation is to make the DQ synchronous coordinate axis, which is the estimated MT synchronous coordinate axis calculated in the calculator, match the MT synchronous coordinate axis of the actual motor. If there is no error between θ _{re_est_PLL} and θ _flux , only the Q-axis component of the induced voltage is observed. If the DQ synchronous coordinate axis has an error θ _err in the advancing direction than the MT synchronous coordinate axis in the actual motor, a positive value is observed as the D-axis component in the controller. If the error between θ _{re_est_PLL} and θ _flux is small, the following approximate expression can be used for the induced voltage.

または、以下のように近似しても良い。

Alternatively, it may be approximated as follows.

A PLL (Phase Locked Loop) tracking operation is performed by PI control as shown in FIG. As shown in Fig. 4, the estimated DQ synchronous coordinate axis is in the forward direction of the MT synchronous coordinate axis in the actual motor by θ _err , so the estimated DQ synchronous coordinate axis is aligned with the MT synchronous coordinate axis. In order to get closer, PI compensation is performed by changing the sign of θ _err .

ＰＩ制御のゲインＫ_{Ｐ＿ＰＬＬ}、Ｋ_{Ｉ＿ＰＬＬ}は、以下のように設定する。
Ｋ_{Ｐ＿ＰＬＬ}＝２ζω_ＰＬＬ，Ｋ_{Ｉ＿ＰＬＬ}＝ω_ＰＬＬ ^２ …（１０）

The PI control gains K _{P_PLL} and K _{I_PLL} are set as follows.
K _{P_PLL} =2ζω _PLL , K _{I_PLL} =ω _PLL ² ...(10)

Note that ζ is a damping ratio. The sum of squares calculator 35 calculates the magnitude |v _dq | of the detected voltage and transmits it to the phase-to-phase voltage level determination unit 13. If it is lower than a predetermined voltage determination value, speed estimation using the residual voltage is performed. It was determined that it could not be implemented stably and was rejected. Note that the magnitude of the voltage may be calculated from the component on the αβ stationary axis.

If an induced voltage due to the residual magnetic flux generated in the induction motor is observed in the detected phase-to-phase voltages v _uv and v _wv , ideally a phase difference of 60 degrees will occur between the phase-to-phase voltages of the two phases. There is. When the amplitude of the induced voltage becomes small and there is no difference from the detected offset amount, or when the amplitude of the induced voltage becomes smaller than the size of noise, the phase difference becomes a value far away from 60 degrees. When the inter-phase voltage phase difference determining unit 14 detects this state, it determines that the speed estimation using the two-phase line voltage cannot be stably estimated, and the result is NG.

FIG. 5 shows an outline of a method for detecting a phase difference carried out by the phase-to-phase voltage phase difference determination unit 14. CounterVal is reset when the polarity of the WV phase is switched.
CNT_A: Time difference between rising timings between WV and UV; CNT_B: Time difference between rising timing between UV and falling timing between WV. If the initial value of sign recognition is made to match the sign of the detected voltage value and the estimation operation is started, CounterVal is reset to 0 at the first WV phase polarity switching, and the second The count value up to polarity switching is stored in CNT_A.

However, at this time, since CNT_B has not yet been saved and has an initial value of 0, the phase cannot be calculated correctly. At the third polarity switch, "CNT_(A+B)" corresponding to "CNT_A+CNT_B" is saved, and CNT_B can be calculated using the previously obtained CNT_A.
CNT_B=CNT_(A+B)-CNT_A
Therefore, the phase from the second polarity switch to the third polarity switch (between the rising edge of UV and the falling edge of WV) is calculated using the following formula.
Phase=180×CNT_B/CNT_(A+B)

When the polarity switches for the fourth time, if CNT_B obtained from the third polarity switch is used, CNT_(A+B) can be obtained by the following formula.
CNT_(A+B)=CNT_A+CNT_B
The phase from the third polarity switch to the fourth polarity switch, that is, the period from the fall of UV to the rise of WV, is calculated using the following formula.
Phase=180×CNT_A/CNT_(A+B)
By performing the above-described repeated processing, it becomes possible to correctly recognize the phase difference from the third polarity switch in the figure. The operation is such that two values are obtained alternately, such as 120 [deg] in the third time, 60 [deg] in the fourth time, and 120 [deg] in the fifth time.

Next, the principle of generating secondary magnetic flux by applying DC excitation to a free-running motor will be explained. The mathematical model of an induction motor can be expressed as follows.

ｉ_ｓｄ［Ａ］：一次電流のＤ軸成分 Ｒ_ｓ［Ω］：一次抵抗
ｉ_ｓｑ［Ａ］：一次電流のＱ軸成分 σＬ_ｓ［Ｈ］：一次インダクタンス
φ_ｒｄ［Ｗｂ］：二次磁束のＤ軸成分 Ｍ［Ｈ］：相互インダクタンス
φ_ｒｑ［Ｗｂ］：二次磁束のＱ軸成分 Ｌ_ｒ［Ｈ］：二次インダクタンス

i _sd [A]: D-axis component of primary current R _s [Ω]: Primary resistance i _sq [A]: Q-axis component of primary current σL _s [H]: Primary inductance φ _rd [Wb]: Secondary magnetic flux D-axis component M [H]: Mutual inductance φ _rq [Wb]: Q-axis component of secondary magnetic flux L _r [H]: Secondary inductance

When DC excitation is performed, current control is performed on the DQ synchronization axis with the control phase θ _re =0, that is, a fixed phase. When the rotor is stopped, ω _re =0, and the command value of the applied current is a DC amount given in steps, so the primary frequency ω _stat , which is the output frequency, is also ω _stat =0. Considering that, when ω _re =ω _stat =0, the slip frequency is also treated as 0. Furthermore, since the response of the current controller is set to be sufficiently faster than the secondary time constant, it can be considered that the voltage command is given so that the current value matches the current command value. That is, the command current i _sd is constant.

Considering the above, the equation of the induction motor when DC excitation is performed can be expressed as follows.

直流励磁実施時の二次磁束の挙動を求めるために、３行目と４行目を書き出し整理すると、

In order to find the behavior of the secondary magnetic flux during DC excitation, write out and organize the 3rd and 4th lines, as follows:

The current value is given as a constant value i _sd only to the D-axis in an almost step-like manner, sufficiently early in response to changes in the secondary magnetic flux by current control. From the equation of the D-axis component shown in equation (13), when the initial value of the secondary magnetic flux is set to φ _rd (0)=0 and Laplace transform is performed, the following is obtained.

これを整理すると（１６）式となり、（１６）式を逆ラプラス変換すると（１７）式となる。

When this is rearranged, the equation (16) is obtained, and when the equation (16) is subjected to inverse Laplace transform, the equation (17) is obtained.

From this, it can be seen that by applying a current to the D axis, the secondary magnetic flux proportional to the current value rises as a final value as a first-order delayed response of a second-order time constant. When a current value equivalent to a no-load current is given as a current command, the secondary magnetic flux becomes approximately equivalent to the rated magnetic flux. Regarding the Q-axis component, since the Q-axis current is controlled to 0, φ _rq =0. If the voltage command value at this time is organized from the first and second lines, the D-axis voltage command value is as follows. Note that the command value on the Q-axis side is omitted because i _sq =0.

From this, until the secondary magnetic flux φ _rd reaches the value of Mi _sd , the second term is generated as a positive value, so the voltage value larger than the voltage drop R _s i _sd due to the winding resistance is It can be seen that it is applied as a voltage command.

Next, the case where the rotor has an initial speed will be described. Since the rotor is not stopped, ω _re ≠0. Since the command value of the current to be applied is a DC amount given in steps, the primary frequency, which is the output frequency, is considered to be ω _S =0, and the slip frequency ω _slip has an absolute value equal to the rotor speed and a reverse polarity. It is believed that there is. That is, ω _slip =−ω _re . Also, like when it is stopped, the response of the current controller is set sufficiently faster than the secondary time constant, so it is assumed that the voltage command is given so that the current value matches the current command value. good. That is, the command current i _sd is constant.

Considering the above, the equation for the induction motor can be expressed as follows.

磁束の挙動を求めるために、３行目と４行目を書き出して整理すると、

In order to find the behavior of magnetic flux, write out and organize the 3rd and 4th lines.

Laplace transform is applied to equation (22). The current value is given as a constant value i _sd only to the D-axis by current control in a substantially step manner in response to changes in the secondary magnetic flux, the rotation speed is also constant, and the initial value of the secondary magnetic flux is set to 0. Then, it can be organized as follows.

これを具体的に計算すると、以下のようになる。

A concrete calculation of this is as follows.

ラプラス逆変換を行うことで、電流印加後の磁束の挙動を得ることができる。電流は電流制御されているので一定値とする。

By performing Laplace inverse transformation, the behavior of magnetic flux after current application can be obtained. Since the current is current controlled, it is kept at a constant value.

Ｑ軸電流ｉ_ｓｑは０に制御されているので、生成される二次磁束は以下のように示すことができる。

Since the Q-axis current i _sq is controlled to 0, the generated secondary magnetic flux can be expressed as follows.

（２５）式は、初速ω_ｒｅで回転子が回転している誘導電動機に対し、直流を印加開始から時刻ｔ［ｓ］経過した時点で生じている磁束を表している。

Equation (25) represents the magnetic flux generated at a time point t [s] after the start of applying direct current to an induction motor whose rotor is rotating at an initial speed ω _re .

Assuming that the current application is finished at time t=t1, the secondary magnetic flux generated in the rotor at that time is shown as follows.

磁束量を具体的に算出するため、（２６）式をオイラーの公式を用いて極座標に書き換える。

In order to specifically calculate the amount of magnetic flux, equation (26) is rewritten into polar coordinates using Euler's formula.

（２７）式を計算すると、

Calculating equation (27), we get

（２７）式と（２８）式より、（２６）式は以下のように表現できる。

From equations (27) and (28), equation (26) can be expressed as follows.

時間関数部と、回転子速度依存で変化するゲインと位相に分けて表現すると、以下のようになる。

When expressed separately in the time function part and the gain and phase that change depending on the rotor speed, it is as follows.

Although the rotor speed is an unknown quantity, the second-order time constant can be obtained by off-line tuning, etc., so it is desirable to determine the time for applying current depending on the second-order time constant. As a guideline for the application time, considering the behavior of the magnetic flux when the rotor is stopped, it is sufficient to set ω _re =0 in equation (30).

となり、（３１）式より、以下のように求められる。

From equation (31), it is obtained as follows.

This corresponds to Equation (17), which is the behavior of the magnetic flux obtained assuming that the rotor is stopped. It can be seen that when the rotor speed is 0, the level of magnetic flux to be generated can be adjusted by the application time and the applied current value. These amounts are set in advance.
Next, a specific method of calculating the initial value of the voltage command value will be explained. From equation (11), if we take only the stationary term and write the voltage on the left side, we get

電動機がフリーラン中は電流が流れないことに留意し、成分で表すと、

Keeping in mind that no current flows while the motor is free-running, expressed in terms of components,

検出電圧のＤＱ軸上の値の２乗和を計算すると、

Calculating the sum of squares of the detected voltage values on the DQ axis,

これより、残留二次磁束の大きさは、以下のように求められる。

From this, the magnitude of the residual secondary magnetic flux is determined as follows.

電動機に与える理想電圧は、電動機の式から定常状態として算出し、ＤＱ軸の成分で表すと以下のようになる。

The ideal voltage to be applied to the motor is calculated as a steady state from the equation of the motor, and expressed by the components of the DQ axis as follows.

（３５）、（３６）式で表される電圧指令値を、再起動時においては、具体的に以下の条件として算出する。
・条件１：速度制御として再起動する場合を想定し、初期トルク指令を０として、トルク電流であるＱ軸電流ｉ_ｓｑの初期値は０と考える。
・条件２：残留二次磁束は定格磁束より低い状態から再起動させることとする。すなわち、励磁電流ｉ_ｓｄは、残留二次磁束と同等の磁束を生成する励磁電流となるように初期値を設定する。

At the time of restart, the voltage command value expressed by equations (35) and (36) is specifically calculated under the following conditions.
- Condition 1: Assuming a case of restarting as speed control, the initial torque command is set to 0, and the initial value of the Q-axis current i _sq , which is the torque current, is considered to be 0.
・Condition 2: The residual secondary magnetic flux shall be restarted from a state lower than the rated magnetic flux. That is, the initial value of the excitation current i _sd is set so that it becomes an excitation current that generates a magnetic flux equivalent to the residual secondary magnetic flux.

When restarting a motor in a free-running state, as a result of convergence calculation processing using the induced voltage due to residual secondary magnetic flux, the initial value ω _{re_est_Init} of the rotor speed command, which becomes the initial value of the rotor angular velocity ω _{re_est} , and the output The phase θ _{re_Init} of the secondary magnetic flux, which is the initial value of the voltage phase θ _{re_c} , is determined.

The magnitude of the induced voltage is determined from the voltage detection value, and using ω _{re_ref_Init} as the initial value of the rotor speed command, the initial value φ _{rd_ref_Init} of the secondary magnetic flux command value can be obtained as follows.

回転速度が十分に速い時は、以下のように近似してもよい。

When the rotation speed is sufficiently high, it may be approximated as follows.

Regarding the current value to flow at startup, if the secondary magnetic flux can be tracked to the D-axis side by convergence calculation processing, the D-axis current i _{sd_ref_Init} that generates the residual secondary magnetic flux is as follows. It can be calculated.
i _{sd_ref_Init} =φ _{rd_ref_Init} /M…(39)

Using these values, the output voltage command value at restart can be calculated as follows. Since the torque command immediately after startup is 0, the torque current i _sq is 0, and the slip frequency is also 0. Considering that the output frequency ω _stat will be the same value as the initial speed command value ω _{re_ref_Init} , the following is obtained. You can give it like this.

After giving the initial value, if the D-axis current is controlled with a magnetic flux equivalent to the rated magnetic flux of the motor, the rated magnetic flux is generated, for example, as a current command i _{sd_set_Filt} that passes through a filter equivalent to the leakage time constant T _leak . By applying a level D-axis current, unnecessary vibration elements can be eliminated. The initial value of the filter immediately after restarting may be the i _{sd_ref_Init} shown above. Note that _Tc is the control period.

Regarding the command value of the secondary magnetic flux, since the magnetic flux is not set as the target magnetic flux at the time of restart, if the behavior is to gradually reach the rated magnetic flux at a time equivalent to the secondary time constant T _r , the magnetic flux command value should be set to By using the secondary magnetic flux command φ _{rd_set_Filt} passed through a filter equivalent to the constant T _r , unnecessary vibrations are not induced. The initial value of the filter immediately after restarting may be the above-mentioned _{φrd_ref_Init} .

A voltage command is calculated from the thus obtained secondary magnetic flux command and the D-axis current command. As the value equivalent to the rotor speed, ω _{re_est} obtained from the speed estimation value in sensorless vector control may be used. As the initial value, it is preferable to use the speed command initial value ω _{re_ref_Init} , which is the final value of the estimated speed ω _{re_est_PLL} in the convergence calculation processing section. Furthermore, when a Q-axis current command is given from a torque command obtained from speed control, the component of the Q-axis current command is also added in the same way as the D-axis current. When a Q-axis current occurs, the primary frequency needs to be set to ω _stat , which is the sum of the slip frequency.

FIG. 7 shows an example in which the initial value of the voltage command and subsequent voltage commands are given as described above and restarted. It can be seen that the torque current is completely undisturbed and a shock-free restart is possible.

Next, setting of the current application time will be explained. From equation (25), write out the third line to find the behavior of the secondary magnetic flux when DC excitation is performed.

This equation is the same as a first-order lag filter with a time constant T _r whose input is M _sd .

The change in magnetic flux when i _sd is controlled to be constant in the current regulator 9 can be obtained by the following equation. If _Tc is expressed in discrete time as the control period, it becomes equivalent to equation (43).

As shown in FIG. 8, the initial value of _{φrd_set_Filt} may be equal to the value shown in equation (38). The secondary magnetic flux φ _{rd_set_Filt} shown in equation (48) is calculated while applying i _{sd_set} , and the time T _{mag_2} and i _{sd_set} are applied until the value reaches the command value φ _{rd_set} of the secondary magnetic flux. If the applied current i _{sd_set} is set to be equivalent to a no-load current, the increase in secondary magnetic flux requires time equivalent to a secondary time constant. However, if the no-load current is made larger than the no-load current, the time for the magnetic flux to reach the target value can be shortened, so the delay until startup can be shortened.

Next, the operation of this embodiment will be explained. The flowchart shown in FIG. 9 shows the processing in the restart processing section when the operation command is switched from the operation command OFF state to the operation command ON and a restart request is received. Further, the flowchart shown in FIG. 13 shows the processing in the restart processing section when the state of the driving command ON is switched to the driving command OFF, and the state is free run, that is, the power converter output is turned OFF.

In these flowcharts, two types of excitation operations for speed estimation are provided. "Speed estimation excitation operation Type 2" is activated when it is detected that the phase-to-phase voltage is smaller than the threshold value in the free run state after the operation command is turned OFF, or when the phase difference between the phase-to-phase voltages is detected to be smaller than the threshold value. If it is detected and it is determined that speed estimation cannot be performed, an excitation operation for speed estimation is automatically performed so that speed estimation can be performed again. On the other hand, "excitation operation type 1 for speed estimation" does not have the function of type 2, and when it is determined that speed estimation cannot be performed, the excitation operation is not performed automatically and speed estimation is terminated. Then, it enters a standby state with the operation command ON. The excitation operation is performed after receiving the operation command ON.

The flow when the driving command is switched from the driving command OFF state to the driving command ON will be explained using FIG. 9 . In the initial state, all commands output by the restart processing unit 19 are OFF. First, the restart processing unit 19 determines whether the following condition 1 is satisfied (S1).
{(Pre-startup speed estimation operation==Type1)or
(Pre-startup speed estimation operation==Type2) and (speed estimation operation counter==0)}
If condition 1 is not satisfied (no), the process moves to step S13, and if condition 1 is satisfied (yes), it is determined whether condition 2 below is satisfied (S2).
{(Excitation operation for speed estimation == valid) and
(Phase-to-phase voltage level judgment ==NG) or (Phase-to-phase voltage phase difference judgment ==NG)}
Note that NG indicates that each detection is smaller than the threshold value.

If condition 2 is not satisfied (no), the process moves to step S8, and if condition 2 is satisfied (yes), the following process A1 is executed (S3).
Switch setting selection: A
Excitation time setting for speed estimation: Timer=T _{mag_1}
Excitation current setting for speed estimation: i _{sd_ref} =I _{mag_1} (i _{sq_ref} =0)
Excitation operation command for speed estimation: ON
Then, the current application process is performed until the Timer subtracted by Δt in step S6 becomes zero (S4; yes) (S5).

When the Timer becomes zero (S4; no), the excitation operation command for speed estimation is turned off as process A2 (S7), and then the following process B1 is executed (S8).
Speed estimation time setting: Timer=T _spdest
Speed estimation operation command: ON
In subsequent steps S9 to S11, the speed estimation processing unit 10 performs speed estimation processing in the same manner as steps S4 to S6 (S10).

When the Timer becomes zero (S9; no), the following process B2 is executed (S12).
Speed command initialization: ω _{re_ref_Init1} = ω _{re_ref_Init}
Control axis phase initialization: θ _{re_Init1} = θ _{re_Init1}
Secondary magnetic flux calculation initialization: φ _{r_ref_Init1} = φ _{r_ref_Init1}
Speed command initialization: ω _{re_ref} = ω _{re_ref_Init1}
Control axis phase initialization: θ _{re_c} = θ _{re_Init1}
Secondary magnetic flux calculation initialization: φ _{r_ref} = φ _{r_ref_Init1}
Speed estimation operation command: OFF

Furthermore, in step S13, the following process B3 is executed. Note that this process is performed when the determination in step S1 is "no", so the pre-startup speed estimation operation corresponds to Type 2.
Speed command initialization: ω _{re_ref} = ω _{re_ref_Init2}
Control axis phase initialization: θ _{re_c} = θ _{re_Init2}
Secondary magnetic flux calculation initialization: φ _{r_ref} = φ _{r_ref_Init2}
When step S12 or S13 is executed, the following condition 3 is determined (S14).
{(Speed command value initial value < threshold value) or (pre-start excitation operation == valid)}

If condition 3 is not satisfied (no), the process moves to step S20, and if condition 3 is satisfied (yes), the following process C1 is performed (S15).
Switch setting selection: C
(At startup) Excitation time setting: Timer=T _{mag_2}
(At startup) Excitation current setting: i _{sd_ref} =I _{mag_2}
Pre-start excitation operation command: ON

Subsequent steps S16 to S18 perform the same processing as steps S4 to S6. Then, when the Timer becomes zero (S16; no), the pre-start excitation operation command is turned off as process C2 (S19). Then, the switch setting selection is set to D and the speed control operation command is turned on to start speed control (S20).

Next, the flow when switching from the driving command ON state to the driving command OFF state will be described using FIG. 13. In the initial state, all commands output by the restart processing unit 19 are OFF. The restart processing unit 19 determines whether the following condition 1 is satisfied (S21).
(Pre-startup speed estimation operation ==Type1 or Type2)
If condition 1 is not satisfied (no), the process moves to step S36, and if condition 1 is satisfied (yes), the following process A1 is executed (S22).
Switch setting selection: A
Excitation time setting for speed estimation: Timer=T _spdest
Speed estimation operation counter: Count=0
Speed estimation operation command: ON

Then, while the driving command is OFF (S23; yes), the speed estimation processing unit 10 performs speed estimation processing (S25) until the Timer subtracted by Δt in step S26 becomes zero (S24; yes). .
When the Timer becomes zero (S24; no), the following process A2 is executed (S27).
Speed estimation operation counter: Count+=1
Excitation interval setting for speed estimation: Timer=Δt

Then, it is determined whether the following condition 2 is satisfied (S28).
{(Phase-to-phase voltage level judgment==NG) or (Phase-to-phase voltage phase difference judgment==NG)}
If condition 2 does not hold (no), the process returns to step S23, and if it does (yes), it is determined whether condition 3 below holds (S29).
{(Excitation operation for speed estimation==valid) and (speed estimation operation before startup==Type2)}

If condition 3 is not satisfied (no), the process moves to step S36, and if it is satisfied (yes), the following process B1 is performed (S30).
Switch selection setting: B
Speed estimation operation command: OFF
Excitation time setting for speed estimation: Timer=T _{mag_1}
Excitation current setting for speed estimation: i _{sd_ref} =I _{mag_1}
Excitation operation command for speed estimation: ON

In subsequent steps S31 to S33, current application processing is performed in the same manner as steps S4 to S6 (S32). When the Timer becomes zero (S31; no), the following process B2 is executed (S34).
Excitation operation command for speed estimation: OFF
Excitation time setting for speed estimation: Timer=T _spdest
Speed estimation operation command: ON
Then, the process returns to step S23.

When the driving command is turned ON (S23; no), the following process C1 is executed (S35) and the process ends.
Speed command initialization: ω _{re_ref_Init2} = ω _{re_ref_Init}
Control axis phase initialization: θ _{re_Init2} = θ _{re_Init1}
Secondary magnetic flux calculation initialization: φ _{r_ref_Init2} = φ _{r_ref_Init1}
Speed estimation operation command: OFF

Furthermore, in step S36, the following process C2 is executed, and then the process ends.
Speed command initialization: ω _{re_ref_Init2} = 0
Control axis phase initialization: θ _{re_Init2} = 0
Secondary magnetic flux calculation initialization: φ _{r_ref_Init2} = 0
Speed estimation operation command: OFF

FIGS. 10 to 12 show an example of the operation when the speed estimation excitation operation Type 1 is used. FIG. 10 is a timing chart showing a case where the interphase voltage level determination is NG in the case of pre-start speed estimation operation: Type 1, speed estimation excitation operation: valid, pre-start excitation operation: invalid, and FIG. is a timing chart showing a case in which pre-start speed estimation operation: Type 1, speed estimation excitation operation: valid, and pre-start excitation operation: valid. Moreover, FIG. 12 shows a case similar to FIG. 10 in which the inter-phase voltage phase difference determination is NG.

As described above, according to this embodiment, the power converter 4 converts a DC voltage into a three-phase AC voltage of variable voltage and variable frequency, and supplies the voltage to the induction motor 5. The interphase voltage detection section 11 detects interphase voltages v _uv and v _wv of the induction motor 5 , and the current detection section 7 detects phase currents i _u and i _w of the induction motor 5 . The current adjustment unit 9 calculates the voltage command values v _{sd_ref and} v sq_ref so that the components obtained by converting the detected values of each phase current onto the DQ synchronous coordinate axis match the current command values i _{sd_ref} and i _{sq_ref} .

When the induction motor 5 is in an operating state, the control device 6 receives a coast-to-run operation stop request, or when the main circuit potential of the power converter 4 that drives the induction motor 5 is determined to be difficult to operate, When transitioning to the state, convergence calculation processing is always performed. Then, when the operation command is input again or the main circuit potential is restored, the induction motor is Restart the control.

In other words, if the main circuit potential cannot be maintained due to a free run stop request from the host controller or a momentary power failure, the convergence calculation process is started when the power converter 4 stops and shifts to the free run state, and the free run is stopped. By continuing to perform convergence calculations during operation, no matter when an operation command is input or when a momentary power outage condition is resolved, the rotational speed estimated at that time is used as the speed command, so that the speed command can be set immediately. A reboot is possible.

Further, in the excitation operation Type 1 for speed estimation, when it is determined that speed estimation cannot be performed, the speed estimation is ended and a standby state is entered where the driving command is turned on. Upon receiving the operation command ON, the control device 6 sets a step current command value of a predetermined magnitude to the current adjustment section 9 in advance when starting the induction motor 5 from a state where an initial speed is generated. After carrying out the excitation operation for speed estimation for a certain period of time and cutting off the output of the power converter 4, the rotational speed and rotational direction of the induction motor 5 and the phase of the residual secondary magnetic flux are determined using the phase-to-phase voltages v _uv and v _wv . Convergence calculation processing is performed to obtain , and the control of the induction motor 5 is restarted. That is, in order to bring the residual voltage to an estimable level, excitation for speed estimation is performed, then speed estimation is performed, and the induction motor 5 is restarted.

With this configuration, in a configuration in which the phase-to-phase voltage detection section 11 is disposed on the output side of the power converter 4, speed estimation is performed even when the residual voltage is attenuated, thereby minimizing the shock that occurs at restart, and improving durability. The noise level is improved and the time from receiving a driving command to actually restarting can be shortened.

Further, the control device 6 performs the excitation operation for speed estimation on the condition that the peak value or effective value of the phase-to-phase voltage detected by the phase-to-phase voltage detection unit 11 is determined to be smaller than a predetermined determination value, After cutting off the output of the power converter 4, convergence calculation processing is performed and the control of the induction motor 5 is restarted. That is, by performing excitation for speed estimation when the detected phase-to-phase voltage is smaller than the determination value, speed estimation using voltage detection can be appropriately performed.

Further, the control device 6 also performs the excitation operation for speed estimation when the phase difference between the two phase voltages is determined to be smaller than the determination value in the phase difference determination unit 14, and similarly performs the excitation operation for speed estimation of the induction motor 5. Since the control is restarted, speed estimation can be performed appropriately in this case as well.

Furthermore, the control device 6 sets the rotation speed ω _{re_est_PLL} and the initial value ω _{re_ref_Init} of the speed command value from the rotation direction in the convergence calculation processing unit 12, and sets the phase of the residual secondary magnetic flux obtained by the convergence calculation process to the D axis. Then, the DQ synchronized coordinate axis with the phase advanced by 90 degrees from the D axis as the Q axis is rotated at a frequency based on the rotation speed ω _{re_est_PLL} , and the initial values of the voltage commands v _sd and v _sq are set immediately before the end of the convergence calculation process. It is determined using the initial value φ _{re_ref_Init} of the secondary magnetic flux calculated from the phase-to-phase voltage value and rotation speed. In other words, the direction of the residual secondary magnetic flux, that is, the phase, is set as the D-axis, the voltage command value v _sq of the Q-axis is adjusted to the phase-to-phase voltage, and the initial value of the secondary magnetic flux used for torque calculation and voltage command value calculation is also adjusted. and restart it. This makes it possible to suppress current disturbances during restart.

In addition, the control device 6 calculates the deviation between the initial value of the secondary magnetic flux and the command value of the secondary magnetic flux, calculated from the interphase voltage value and rotational speed immediately before the end of the convergence calculation process, and the D-axis current of a predetermined magnitude. Based on the command value, the application time of the D-axis current command value is determined, and the current adjustment section 9 sets a time for applying the current in the D-axis direction according to the D-axis current command value and its application time. The level of the magnetic flux applied for speed estimation is set to, for example, about 25% of the rated magnetic flux in order to minimize disturbances during application. At the time of restart, the magnetic flux level has further decreased, so if there is a large torque request immediately after startup, the current value will be used to gain torque due to the lack of magnetic flux, and even a small torque command will cause the current to become excessive. There is a risk that Therefore, by setting the magnetic flux level at restart to a state close to the rated value, the increase in current can be suppressed.

The control device 6 also controls the speed so that the result of converting the phase-to-phase voltage onto a synchronous axis configured to use the time integral value of the speed estimate as the phase during coordinate conversion is only the Q-axis component. Adjust estimates.

FIG. 14 is a timing chart showing a case where the speed estimation operation before startup is Type 2, the excitation operation for speed estimation is valid, and the excitation operation for pre-startup is valid. In pre-startup speed estimation operation Type 2, a free-run operation stop request is input while the induction motor 5 is in the operating state, or the main circuit potential of the power converter 4 that drives the induction motor 5 has decreased and it is determined that operation is difficult. When the control device 6 shifts to the free run state, the control device 6 performs convergence calculation processing, but it is determined that the peak value or effective value of the phase-to-phase voltage detected by the phase-to-phase voltage detection unit 11 is smaller than a predetermined determination value. Then, the convergence calculation process is stopped, and when the current adjustment section 8 is caused to give a step current command value of a predetermined magnitude for a predetermined time, the convergence calculation process is restarted. As a result, when speed estimation continues during free running, when the interphase voltage level decreases, excitation for speed estimation is performed, and the residual magnetic flux can be maintained at a level that allows speed estimation.

Furthermore, while constantly performing the convergence calculation process, if it is determined that the phase difference between the two phase-to-phase voltages detected by the phase-to-phase voltage detection unit 11 is smaller than a predetermined determination value, the control device 6 performs the convergence calculation process. When the current controller 8 is caused to give a step-like current command value of a predetermined magnitude for a predetermined time, the convergence calculation process is restarted. This makes it possible to maintain residual magnetic flux at a level that allows speed estimation even when the phase difference between phase voltages becomes small while speed estimation continues during free running.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

In the drawing, 1 is a three-phase AC power supply, 2 is a full-wave rectifier circuit, 3 is a smoothing capacitor, 4 is a power converter, 5 is an induction motor, 6 is a control device, 7 is a current detection section, 9 is a current adjustment section, 10 is a speed estimation processing section, 11 is an inter-phase voltage detection section, 12 is a convergence calculation processing section, 13 is an inter-phase voltage level determination section, and 14 is an inter-phase voltage phase difference determination section.

Claims (10)

a power converter that converts the DC voltage into a variable voltage variable frequency three-phase AC voltage and supplies it to the induction motor;
a phase-to-phase voltage detection unit that detects phase-to-phase voltage of the induction motor between two or more phases;
a current detection unit that detects a phase current of the induction motor;
a current adjustment unit that calculates a voltage command value such that a component obtained by converting the detected value of the phase current onto a synchronous coordinate axis matches the current command value;
When starting the induction motor from a state where an initial speed is generated,
carrying out an excitation operation for speed estimation that gives a step-like current command value of a predetermined magnitude to the current adjustment unit for a predetermined time;
After cutting off the output of the power converter, convergence calculation processing is performed to obtain the rotational speed and rotational direction of the induction motor and the phase of residual secondary magnetic flux using the detected values of the interphase voltage between two or more phases. and a restart control unit that restarts control of the induction motor. The restart control unit performs the speed estimation excitation operation on the condition that the peak value or effective value of the phase-to-phase voltage detected by the phase-to-phase voltage detection unit is determined to be smaller than a predetermined determination value. 2. The motor control device according to claim 1, wherein the convergence calculation process is performed after cutting off the output of the power converter, and the control of the induction motor is restarted. an inter-phase voltage phase difference determination unit that calculates a phase difference between two or more phases of the inter-phase voltage detected by the inter-phase voltage detection unit and compares it with a predetermined determination value;
The restart control unit also performs the speed estimation excitation operation when the interphase voltage phase difference determination unit determines that the phase difference is smaller than the determination value, and shuts off the output of the power converter. 3. The motor control device according to claim 2, wherein the convergence calculation process is performed after the calculation is performed, and the control of the induction motor is restarted. a power converter that converts the DC voltage into a variable voltage variable frequency three-phase AC voltage and supplies it to the induction motor;
a phase-to-phase voltage detection unit that detects phase-to-phase voltage of the induction motor between two or more phases;
a current detection unit that detects a phase current of the induction motor;
a current adjustment unit that calculates a voltage command value such that a component obtained by converting the detected value of the phase current onto a synchronous coordinate axis matches the current command value;
When the induction motor is in an operating state, when a coast-to-run operation stop request is input, or when the main circuit potential of a power converter that drives the induction motor is lowered and it is determined that operation is difficult and the motor shifts to a coast-to-run state, Make sure to always perform convergence calculation processing,
When the operation command is input again or the main circuit potential is restored, the induction motor and a restart control unit that restarts control of the motor. The restart control unit is configured to perform a restart control unit, when it is determined that the peak value or effective value of the phase-to-phase voltage detected by the phase-to-phase voltage detection unit is smaller than a predetermined determination value while constantly performing the convergence calculation process. 5. The electric motor control device according to claim 4, wherein the convergence calculation process is restarted when the convergence calculation process is stopped and the current adjustment section is caused to give a step-like current command value of a predetermined magnitude for a predetermined time. an inter-phase voltage phase difference determination unit that calculates a phase difference between two or more phases of the inter-phase voltage detected by the inter-phase voltage detection unit and compares it with a predetermined determination value;
6. The electric motor control device according to claim 5, wherein the restart control unit stops the convergence calculation process even when the interphase voltage phase difference determination unit determines that the phase difference is smaller than the determination value. The restart control unit sets an initial value of the speed command value from the rotation speed and rotation direction,
Rotating a DQ synchronized coordinate axis in which the phase of the residual secondary magnetic flux obtained by the convergence calculation process is defined as the D axis, and the phase advanced by 90 degrees from the D axis is defined as the Q axis, at a frequency based on the rotation speed,
The induction according to any one of claims 1 to 6, wherein the voltage command initial value is determined using an initial value of the secondary magnetic flux calculated from the interphase voltage value and rotation speed immediately before the end of the convergence calculation process. Electric motor control device. The restart control unit calculates a deviation between the initial value of the secondary magnetic flux and the command value of the secondary magnetic flux, which is calculated from the phase-to-phase voltage value and the rotational speed immediately before the end of the convergence calculation process, and a predetermined magnitude of D. determining the application time of the D-axis current command value based on the axis current command value;
The induction motor control device according to claim 7, wherein the current adjustment section sets a time for applying the current in the D-axis direction according to the D-axis current command value and its application time. The restart control unit converts the phase-to-phase voltage onto a synchronized axis configured to use a time integral value of the estimated speed value as a phase during coordinate conversion, so that the result is only a Q-axis component. The induction motor control device according to claim 7, wherein the estimated speed value is adjusted. The restart control unit converts the phase-to-phase voltage onto a synchronized axis configured to use a time integral value of the estimated speed value as a phase during coordinate conversion, so that the result is only a Q-axis component. The induction motor control device according to claim 8, wherein the estimated speed value is adjusted.

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