CN112234870A - Method and system for controlling starting of alternating current asynchronous motor during galloping - Google Patents

Method and system for controlling starting of alternating current asynchronous motor during galloping Download PDF

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Publication number
CN112234870A
CN112234870A CN202011106186.0A CN202011106186A CN112234870A CN 112234870 A CN112234870 A CN 112234870A CN 202011106186 A CN202011106186 A CN 202011106186A CN 112234870 A CN112234870 A CN 112234870A
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motor
current
frequency
frequency converter
voltage
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Inventor
瞿李锋
孙建军
任红
习楠
詹恒
赵珊
金祖勇
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Wuhan Keliyuan Electric Co ltd
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Wuhan Keliyuan Electric Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P1/00—Arrangements for starting electric motors or dynamo-electric converters
    • H02P1/16—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters
    • H02P1/26—Arrangements for starting electric motors or dynamo-electric converters for starting dynamo-electric motors or dynamo-electric converters for starting an individual polyphase induction motor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/22—Current control, e.g. using a current control loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/34—Arrangements for starting
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage

Abstract

The invention discloses a method and a system for controlling the runaway starting of an alternating current asynchronous motor, wherein the method comprises the steps of carrying out constant current control on the motor in the starting process of driving the motor by a frequency converter so as to enable a stator and a rotor of the motor to be equivalent in circuit; the frequency converter applies a target current signal with constant amplitude and frequency gradually decreased according to the preset step change frequency to the motor, so that the target current signal acts on the motor; the frequency converter collects the voltage and current values of a motor at the motor end, and the controller calculates the equivalent inductance of the motor according to the voltage and current values of the motor and the applied angular frequency; and the frequency converter performs frequency sweeping control, when the applied angular frequency reaches the rotor frequency range of the motor, the equivalent inductance value of the motor is judged to be the maximum, the searched maximum inductance value of the motor is used as the searched target rotor frequency, the rotating speed tracking is successfully realized based on the target rotor frequency, and the runaway starting is realized.

Description

Method and system for controlling starting of alternating current asynchronous motor during galloping
Technical Field
The invention relates to the technical field of motors, in particular to a method and a system for controlling starting of an alternating current asynchronous motor during galloping.
Background
The motor stator is a static part of the motor, when the motor stator is separated from a frequency converter or a power frequency power grid, the motor stator is passive, the motor rotor is still in a rotating state, but the rotating speed is random and uncertain, if the motor is restarted, the current rotating speed of the motor must be obtained, otherwise, the over-current tripping operation is generated due to large rotating difference or the capacitor direct voltage is increased and tripped due to the fact that the rotating speed of the rotor is high, and the motor is in a generating state.
The common method for starting the runaway includes controlling a frequency converter to output search voltage and frequency to enable a stator to generate current, carrying out vector decomposition on the current to obtain a torque current component, when the speed of a stator rotating magnetic field is the same as the rotating speed of a motor, enabling the torque current component to be about zero, searching for the rotor frequency when the torque current is observed to be the minimum value and close to zero, and then controlling the output voltage of the frequency converter to complete the runaway starting according to a V/F curve by using the current frequency.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
The invention mainly aims to provide a method and a system for controlling the runaway starting of an alternating-current asynchronous motor, and aims to solve the technical problems that the current is uncontrollable and the motor is not stably started enough in the runaway starting process of the motor controlled by a frequency converter.
The method for controlling the runaway starting of the alternating current asynchronous motor comprises the following steps:
in the starting process of a frequency converter driving motor, the frequency converter performs constant current control on the motor, so that a stator and a rotor of the motor are equivalent in circuit;
the frequency converter applies a target current signal with constant amplitude and frequency gradually decreased according to preset step change frequency to the motor, so that the target current signal acts on the motor; wherein the motor is an alternating current asynchronous motor;
the frequency converter collects the voltage and the current value of a motor at the motor end, and the controller calculates the equivalent inductance of the motor according to the voltage, the current value and the applied angular frequency of the motor;
and when the applied angular frequency reaches the rotor frequency range of the motor, the frequency converter judges that the equivalent inductance value of the motor is the maximum, the searched maximum inductance value of the motor is used as the searched target rotor frequency, and the motor is started by the runaway based on the target rotor frequency.
Preferably, the step of performing constant current control on the motor by the frequency converter specifically includes:
the frequency converter collects three-phase current at the stator side of the motor, converts the three-phase current into d-axis current and q-axis current under a two-phase rotating coordinate system through abc-dq conversion, performs difference on the d-axis current and a given current amplitude value, sends the difference to a PI (proportional integral) regulator, performs difference on the q-axis current and 0, and sends the difference result to the PI regulator, so that the PI regulator forms current closed-loop control, wherein the stator current I is kept when different angular frequencies are applied in the constant current control processSThe amplitude is a given value.
Preferably, the transformed rotational phase θ is applied during said abc-dq transformationkTo obtain a varying angular frequency wkLower feedback current Id(k)、Iq(k)。
Preferably, the step of the controller calculating the equivalent inductance of the motor from the motor voltage, the current value, and the applied angular frequency comprises:
the controller estimates an inductance curve of the motor, and the equivalent circuit impedance of the motor is Z-Rs+L*f(ws) The terminal voltage U ═ I (R)s+L*f(ws) Then equivalent inductance)
Figure BDA0002727028180000021
Wherein U is the terminal voltage of the motor, I is the current value, RsIs the stator resistance of the machine, f (w)s) Is the applied angular frequency.
Preferably, the step of estimating, by the controller, an inductance curve of the motor further includes:
calculating the inductance value of the current frequency sweep frequency band and the inductance variation of the frequency sweep frequency band at the last moment, and if the inductance variation of the current frequency sweep frequency band is delta LkGreater than 0, and the inductance variation Delta L of the next scanning frequency bandk+1If the frequency is less than 0, namely when the peak inflection point appears in L, the current frequency is judged to be the rotor frequency.
Preferably, the preset step change frequency is 55Hz to 0 Hz.
In addition, in order to achieve the above purpose, the invention further provides a runaway starting control system for the alternating current asynchronous motor, wherein the control system comprises a frequency converter, an analog quantity sampling circuit, a controller, a driving module and a motor, and the motor is the alternating current asynchronous motor;
the alternating current input end of the frequency converter is connected with a power grid, and the output end of the frequency converter is connected with the motor through a cable, so that the frequency converter is equivalent to a constant current source, and a stator circuit and a rotor circuit of the motor are equivalent;
wherein the content of the first and second substances,
the frequency converter is used for outputting a current signal to the stator side of the motor;
the analog quantity sampling circuit is respectively connected with the frequency converter and the controller and is used for acquiring the current signal and the voltage signal output by the frequency converter, conditioning the current signal and the voltage signal and outputting a conditioning signal of current and voltage to the controller;
the controller is used for carrying out analog-to-digital conversion on the conditioning signal of the current and the voltage, carrying out Park conversion on the three-phase currents Ia, Ib and Ic obtained through the analog-to-digital conversion, and obtaining the current I of the d axisdAnd q-axis current Iq；
The controller is also used for aiming at the current IdAnd the current IqExecuting frequency sweep control and current closed-loop control to synthesize a modulation wave PWM signal, and outputting the PWM signal to the driving module;
the driving module is used for outputting the PWM signal to drive the IGBT of the frequency converter, controlling the frequency converter to apply a target current signal which has constant amplitude and gradually decreased frequency according to preset step change frequency to the motor, and enabling the target current signal to act on the motor, wherein the target current signal and equivalent impedance of the frequency converter enable a stator side of the motor to generate a target voltage signal;
the analog quantity sampling circuit is also used for acquiring the target voltage signal, conditioning the target voltage signal and then sending the target voltage signal to the controller;
and the controller is used for estimating the inductance of the motor according to the target voltage signal and the target current signal, executing inductance maximum value query through frequency sweep control, and taking the searched maximum value inductance as the searched target rotor frequency when the inductance maximum value is searched.
Preferably, the frequency converter is provided with a plurality of bridge arms, and each bridge arm in the first direction is connected with the motor through a cable.
Preferably, cables for connecting the motor and each bridge arm are provided with a voltage sensor and a current sensor;
the analog quantity sampling circuit comprises a voltage sampling module and a current sampling module;
and the voltage sensor is used for transmitting the voltage signal to a voltage sampling module of the analog quantity sampling circuit for conditioning and then transmitting the conditioned voltage signal to the controller for voltage signal processing.
And the current sensor is used for transmitting the current signal to a current sampling module of the analog quantity sampling circuit, conditioning the current signal and then transmitting the conditioned current signal to the controller for current signal processing.
The invention has the beneficial effects that: the frequency converter controls the motor to be controllable in current in the process of galloping starting, and the rotor frequency can be quickly searched, so that the motor is stably started; the frequency converter searches the frequency of the motor rotor in a constant-current control mode, so that the current amplitude is controllable, no overcurrent phenomenon exists, the working is safe and reliable, and the characteristic is good.
Drawings
FIG. 1 is a circuit structure connection diagram of the runaway starting control system of the AC asynchronous motor of the invention;
FIG. 2 is a motor impedance equivalent circuit model of the flying start control system of the AC asynchronous motor of the present invention;
FIG. 3 is a schematic block diagram of a controller implementing the runaway start control of an embodiment of the invention;
fig. 4 is a schematic flow chart of the method for controlling the runaway starting of the alternating current asynchronous motor according to the invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example one
Referring to fig. 1, fig. 1 is a circuit structure connection diagram of an alternating current asynchronous motor runaway starting control system of the invention;
the runaway starting control system of the alternating current asynchronous motor comprises a frequency converter 10, an analog quantity sampling circuit 20, a controller 30, a driving module 40 and a motor 50; the motor 50 is an alternating current asynchronous motor;
the alternating current input end of the frequency converter 10 is connected with a power grid, and the output end of the frequency converter is connected with the motor 50 through a cable, so that the frequency converter 10 is equivalent to a constant current source, and a stator circuit and a rotor circuit of the motor 50 are equivalent;
wherein the content of the first and second substances,
the frequency converter 10 is used for outputting a current signal to the stator side of the motor 50;
the analog sampling circuit 20 is respectively connected to the frequency converter 10 and the controller 30, and is configured to obtain the current signal and the voltage signal output by the frequency converter 10, perform signal conditioning on the current signal and the voltage signal, and output a conditioning signal of current and voltage to the controller 30;
the controller 30 is configured to perform analog-to-digital conversion on the conditioning signal of the current and voltage, perform Park conversion on the three-phase currents Ia, Ib, and Ic obtained through the analog-to-digital conversion, and obtain a current I of the d-axisdAnd q-axis current Iq；
The controller 30 is further configured to target the current IdAnd the current IqPerforming frequency sweep control and current closed-loop control to synthesize a modulation wave (PWM) signal, and outputting the PWM signal to the driving module 40;
the driving module 40 is configured to output the PWM signal to drive an IGBT (Insulated Gate Bipolar Transistor) of the frequency converter 10, and control the frequency converter 10 to apply a target current signal, which has a constant amplitude and a frequency that decreases in steps according to a preset step change frequency, to the motor 50, so that the target current signal acts on the motor 50, where the preset step change frequency is 55Hz to 0Hz, and the target current signal and an equivalent impedance of the frequency converter 10 enable a stator side of the motor 50 to generate a target voltage signal;
the analog quantity sampling circuit 20 is further configured to obtain the target voltage signal, condition the target voltage signal, and send the target voltage signal to the controller 30;
the controller 30 is configured to estimate the inductance of the motor 50 according to the target voltage signal and the target current signal, execute inductance maximum value query through frequency sweep control, and use the maximum inductance value as the searched target rotor frequency when the inductance maximum value is found.
In a specific implementation, the frequency converter 10 is provided with a plurality of bridge arms, and each bridge arm in a first direction (the first direction is a horizontal direction in fig. 1) is connected to the motor 50 through a cable;
the analog quantity sampling circuit 20 comprises a voltage sampling module 022 and a current sampling module 021;
cables for connecting the motor 50 and each bridge arm are provided with a voltage sensor and a current sensor;
the voltage sensor is used for transmitting the voltage signal to a voltage sampling module 022 of the analog quantity sampling circuit 20 for conditioning, and then transmitting the conditioned voltage signal to the controller 30 for voltage signal processing;
the current sensor is configured to transmit the current signal to the current sampling module 021 of the analog sampling circuit 20, condition the current signal, and send the conditioned current signal to the controller 30 for current signal processing.
It can be understood that, referring to fig. 2, fig. 2 is a motor impedance equivalent circuit model of the ac asynchronous motor runaway starting control system of the present embodiment; in the present embodiment, an equivalent circuit is connected to the inverter 10 and the motor 50, the inverter 10 is equivalent to a constant current source, the motor 50 is a load, and the equivalent impedance is Z ═ Rs+L*f(ws) The motor inductance parameter is not a constant but a non-linear parameter. The relation between the stator induction voltage vector and the input current, the equivalent impedance and the equivalent rotor voltage vector exists in an expression 1, wherein USAs terminal voltage, ISTerminal input current, UΨrIs an equivalent rotor voltage vector, LσFor total leakage inductance, R, of stator and rotorsIs the stator resistance.
Figure BDA0002727028180000061
Figure BDA0002727028180000062
The relationship of equation 1 is simplified to the following equation:
Figure BDA0002727028180000063
Figure BDA0002727028180000064
according to equation 4, if the motor voltage, motor input current, applied angular velocity are known, the motor equivalent inductance can be estimated. The input end of the motor applies a variable frequency signal, the angular speed is a variable, the current rotating speed n of the rotor and the slip is s, when the frequency difference between the applied frequency and the rotor is smaller, the inductance value estimated by the formula 4 is larger, and when the applied frequency is lower than or higher than the rotor frequency, the inductance value is smaller. Therefore, under the condition of applying constant current and in a frequency scanning mode, the maximum value of the inductance can be estimated according to the collected terminal voltage and current, and the rotor frequency can be locked.
Fig. 3 is a schematic block diagram of the controller of the present embodiment executing the runaway start control. Because the stator side of the motor is free of voltage in the initial state, the rotor rotates freely, and the stator winding forms a current path through constant-current variable-frequency control. The specific control steps are as follows:
(1) the set initial frequency of 55Hz was set. The initial phase θ is obtained by integrating the angular velocity:
Figure BDA0002727028180000071
collecting three-phase current at the stator side, carrying out alpha beta transformation from a three-phase static coordinate system to a two-phase vertical coordinate system on the three-phase current Ia, Ib and Ic, and obtaining an initial angle theta through integration1For current component i under two-phase static coordinate systemα、iβPerforming Park conversion to obtain feedback current Id、Iq。
(2) Setting frequency change step delta f and time change step delta t, and changing the frequency of the frequency converter from 55Hz to 0Hz to w according to the set stepk＝wk-1+ Δ w, p.v.The angular velocity integration of the conversion is used for obtaining the rotating angle required by Park conversion
Figure BDA0002727028180000072
At the rotation angle thetakThe dq conversion in the step (1) is repeated next to obtain the variation angular frequency wkLower feedback current Id(k)、Iq(k)。
Figure BDA0002727028180000073
(3) The frequency converter gives the designated current Id (I) and Iq (0) of the dq axis, and the frequency converter rotates at the angle theta of the sweep frequencykLower pair of currents Id(k)、Iq(k)Performing PI closed loop control to detect feedback current Id(k)Feeding the difference to PI regulator, and detecting the feedback current Iq(k)And a given current of 0 is fed to the PI regulator. At rotation angle theta of frequency sweepkAnd carrying out dq inverse transformation on output values of the two PI regulators to obtain a modulation wave, wherein the modulation wave acts on an IGBT (insulated gate bipolar translator) of the frequency converter, and the amplitude of the current at the input side of the motor is kept constant.
(4) Collecting terminal induction voltage U under sampling frequencysAnd current ISAnd sequentially estimating the inductance of the motor in the sweep frequency range of 55Hz-0Hz according to the nonlinear relation between the inductance and the voltage, the current and the angular frequency in the formula (4), and storing.
(5) Interrogating the application of a constant current frequency w to a motorkTime motor inductance estimated value LKAnd applying a constant current frequency wk-1Time motor inductance estimated value LK-1Calculating the inductance difference value delta L of the current scanning frequency bandk＝Lw(k)-Lw(k-1)Is recorded as the sweep frequency segment wkThe inductance variation is calculated in turn for each sweep frequency band between 55Hz and 0Hz, if the sweep frequency band w is currently in usekLower DeltaLkGreater than 0, and the next scanning frequency band wk+1Lower DeltaLk+1If the L is less than 0, namely the peak inflection point appears, judging the current angular frequency wkIs the rotor frequency.
The beneficial effect of this embodiment lies in: the frequency converter controls the motor to be controllable in current in the process of galloping starting, and the rotor frequency can be quickly searched, so that the motor is stably started; the frequency converter searches the frequency of the motor rotor in a constant-current control mode, so that the current amplitude is controllable, no overcurrent phenomenon exists, the working is safe and reliable, and the characteristic is good.
Example two
In this embodiment, the method for controlling the flying start of the ac asynchronous motor mainly includes the following technical steps: and carrying out constant current control, frequency sweep control of a frequency converter, detection of terminal voltage, estimation of motor inductance value and search of rotor frequency on the motor. Firstly, in the starting process of a frequency converter driving motor, the frequency converter is equivalent to a constant current source, a motor stator and a motor rotor are equivalent in circuit, and the frequency converter applies a current signal with constant amplitude and frequency gradually decreased from 55 to 0Hz according to setting; and then the frequency converter collects the terminal voltage of the motor, the equivalent inductance of the motor is estimated according to the voltage value, when the applied frequency is close to the vicinity of the rotor frequency, the equivalent inductance of the motor is the largest, the inductance is about small when the frequency is far away from the rotor frequency, the maximum inductance value is recorded during frequency sweeping, the rotor frequency searching is completed at the moment, the current frequency is recorded, and the motor is started in an aerocar.
Referring to fig. 4, fig. 4 is a schematic flow chart of a method for controlling the flying start of an ac asynchronous motor according to the present invention, the method for controlling the flying start of an ac asynchronous motor includes:
step S10 (frequency converter constant current control), in the starting process of a frequency converter driving motor, the frequency converter performs constant current control on the motor to enable the stator and the rotor of the motor to perform circuit equivalence; the motor is an alternating current asynchronous motor;
it can be understood that when the motor rotor does not stop rotating and the frequency converter detects that the motor has no voltage, the frequency converter executes a constant current control strategy and outputs a current signal with constant amplitude and an initial frequency of 55 Hz. The constant current control strategy comprises the steps of collecting three-phase current at the stator side, converting the three-phase current into d-axis current and q-axis current under a two-phase rotating coordinate system through Park conversion of abc-dq, wherein the initial value of the Park conversion angle is an angle theta obtained by integrating the angular frequency of 55Hz1The d-axis current and the given current amplitude are differenced and sent to a PI regulator, and the q-axis current and 0 are differenced and sent to the PI regulatorThe PI regulator forms current closed-loop control, and the stator current I is always kept in the constant current control processSThe amplitude is a given value.
Step S20 (frequency sweep control of the motor) in which the frequency converter applies a target current signal with constant amplitude and gradually decreased frequency according to a preset step change frequency to the motor so that the target current signal acts on the motor;
preferably, the preset step change frequency of the present embodiment is 55Hz to 0 Hz;
understandably, the frequency converter performs frequency sweep control from 55Hz to 0Hz according to the set frequency step delta f and the time step delta t, and the angular velocity w is obtained when the frequency and the time are uniformly changedkUniformly changing, and integrating angular velocity to obtain the rotation angle required by Park conversion
Figure BDA0002727028180000081
And d-axis and q-axis components under different frequencies are sequentially solved and are respectively sent to the PI controllers, so that frequency-sweep mode down-conversion constant-current control is realized.
Step S30 (estimating motor inductance), wherein the frequency converter collects motor voltage and current value at the motor end, and the controller calculates the equivalent inductance of the motor according to the motor voltage, the current value and the applied angular frequency;
it can be understood that the equivalent circuit impedance of the motor is Z-R under the application of the signals of the step S10 and the step S20s+L*f(ws) The terminal voltage U ═ I (R)s+L*f(ws) Then, then
Figure BDA0002727028180000082
The motor voltage, current and frequency are nonlinear functions, and if the voltage and current are known, the motor inductance value can be estimated. Collecting terminal voltage and current by a frequency converter, and estimating an equivalent inductance L of the motor according to the voltage and current values;
in a specific implementation, the terminal induction voltage U is collected under the sampling frequencysAnd current ISSequentially estimating the inductance of the motor in the sweep frequency range of 55Hz-0Hz according to the nonlinear relation of the inductance, the voltage, the current and the angular frequency in the formula (4), and performingAnd (5) storing.
Step S40 (find inductance maximum tracking rotor frequency): and when the applied angular frequency reaches the rotor frequency range of the motor, the frequency converter judges that the equivalent inductance value of the motor is the maximum, the searched maximum inductance value of the motor is used as the searched target rotor frequency, and the motor is started by the runaway based on the target rotor frequency.
It should be noted that, at a constant current, when the inverter sweep frequency is in the vicinity of the rotor frequency, the motor inductance value becomes large, and when the sweep frequency is higher or lower than the rotor frequency, the motor inductance becomes smaller.
Understandably, under constant current frequency sweep, a motor inductance curve is estimated according to the nonlinear function relationship of voltage, current and frequency, and the difference value delta L of the inductance value under the current frequency sweep frequency and the inductance value under the last moment frequency sweep frequency is judgedk＝Lw(k)-Lw(k-1)If the current scanning frequency band is Δ LkGreater than 0, and the next scanning frequency band is Delta Lk+1If the frequency is less than 0, namely when the peak inflection point appears in L, judging that the current frequency is the rotor frequency. Therefore, when the peak inflection point of the inductance at the machine end is detected, the rotor frequency is considered to be searched.
The beneficial effect of this embodiment lies in: the frequency converter controls the motor to be controllable in current in the process of galloping starting, and the rotor frequency can be quickly searched, so that the motor is stably started; the frequency converter searches the frequency of the motor rotor in a constant-current control mode, so that the current amplitude is controllable, no overcurrent phenomenon exists, the working is safe and reliable, and the characteristic is good.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments. The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (9)

1. A method for controlling the runaway starting of an alternating current asynchronous motor is characterized by comprising the following steps:
in the starting process of a frequency converter driving motor, the frequency converter performs constant current control on the motor, so that a stator and a rotor of the motor are equivalent in circuit;
the frequency converter applies a target current signal with constant amplitude and frequency gradually decreased according to preset step change frequency to the motor, so that the target current signal acts on the motor; wherein the motor is an alternating current asynchronous motor;
the frequency converter collects the voltage and the current value of a motor at the motor end, and the controller calculates the equivalent inductance of the motor according to the voltage, the current value and the applied angular frequency of the motor;
and when the applied angular frequency reaches the rotor frequency range of the motor, the frequency converter judges that the equivalent inductance value of the motor is the maximum, the searched maximum inductance value of the motor is used as the searched target rotor frequency, and the motor is started by the runaway based on the target rotor frequency.
2. The method for controlling the runaway starting of the alternating current asynchronous motor according to claim 1, wherein the step of performing constant current control on the motor by the frequency converter specifically comprises:
the frequency converter collects three-phase current at the stator side of the motor, converts the three-phase current into d-axis current and q-axis current under a two-phase rotating coordinate system through abc-dq conversion, performs difference on the d-axis current and a given current amplitude value, sends the difference to a PI (proportional integral) regulator, performs difference on the q-axis current and 0, and sends the difference result to the PI regulator, so that the PI regulator forms current closed-loop control, wherein the stator current I is kept when different angular frequencies are applied in the constant current control processSThe amplitude is a given value.
3. The method of controlling a runaway start in an AC asynchronous motor of claim 2, wherein the abc-dq transformation applies a transformed rotational phase θkTo obtain a varying angular frequency wkLower feedback current Id(k)、Iq(k)。
4. The method of controlling an ac asynchronous motor coaster start of claim 1 wherein the step of the controller calculating the equivalent inductance of the motor from the motor voltage, the current value, and the applied angular frequency comprises:
the controller estimates an inductance curve of the motor, and the equivalent circuit impedance of the motor is Z-Rs+L*f(ws) The terminal voltage U ═ I (R)s+L*f(ws) Then equivalent inductance)
Figure FDA0002727028170000021
Wherein U is the terminal voltage of the motor, I is the current value, RsIs the stator resistance of the machine, f (w)s) Is the applied angular frequency.
5. The method for controlling the runaway start of an AC asynchronous motor as claimed in claim 4 wherein the step of the controller predicting the inductance curve of the motor further comprises:
calculating the inductance value of the current frequency sweep frequency band and the inductance variation of the frequency sweep frequency band at the last moment, and if the inductance variation of the current frequency sweep frequency band is delta LkGreater than 0, and the inductance variation Delta L of the next scanning frequency bandk+1If the frequency is less than 0, namely when the peak inflection point appears in L, the current frequency is judged to be the rotor frequency.
6. The method for controlling the runaway of an AC asynchronous motor as claimed in any one of claims 1 to 5 wherein the predetermined step change frequency is from 55Hz to 0 Hz.
7. The control system is characterized by comprising a frequency converter, an analog quantity sampling circuit, a controller, a driving module and a motor, wherein the motor is an alternating current asynchronous motor;
the alternating current input end of the frequency converter is connected with a power grid, and the output end of the frequency converter is connected with the motor through a cable, so that the frequency converter is equivalent to a constant current source, and a stator circuit and a rotor circuit of the motor are equivalent;
wherein the content of the first and second substances,
the frequency converter is used for outputting a current signal to the stator side of the motor;
the analog quantity sampling circuit is respectively connected with the frequency converter and the controller and is used for acquiring the current signal and the voltage signal output by the frequency converter, conditioning the current signal and the voltage signal and outputting a conditioning signal of current and voltage to the controller;
the controller is used for carrying out analog-to-digital conversion on the conditioning signal of the current and the voltage, carrying out Park conversion on the three-phase currents Ia, Ib and Ic obtained through the analog-to-digital conversion, and obtaining the current I of the d axisdAnd q-axis current Iq；
The controller is also used for aiming at the current IdAnd the current IqExecuting frequency sweep control and current closed-loop control to synthesize a modulation wave PWM signal, and outputting the PWM signal to the driving module;
the driving module is used for outputting the PWM signal to drive the IGBT of the frequency converter, controlling the frequency converter to apply a target current signal which has constant amplitude and gradually decreased frequency according to preset step change frequency to the motor, and enabling the target current signal to act on the motor, wherein the target current signal and equivalent impedance of the frequency converter enable a stator side of the motor to generate a target voltage signal;
the analog quantity sampling circuit is also used for acquiring the target voltage signal, conditioning the target voltage signal and then sending the target voltage signal to the controller;
and the controller is used for estimating the inductance of the motor according to the target voltage signal and the target current signal, executing inductance maximum value query through frequency sweep control, and taking the searched maximum value inductance as the searched target rotor frequency when the inductance maximum value is searched.
8. An alternating current asynchronous motor coaster start control system as claimed in claim 7 wherein the frequency converter is provided with a plurality of arms, each arm in the first direction being connected to the motor by a respective cable.
9. The flying start control system for the alternating current asynchronous motor as claimed in claim 7, wherein cables for connecting the motor and each bridge arm are provided with a voltage sensor and a current sensor;
the analog quantity sampling circuit comprises a voltage sampling module and a current sampling module;
and the voltage sensor is used for transmitting the voltage signal to a voltage sampling module of the analog quantity sampling circuit for conditioning and then transmitting the conditioned voltage signal to the controller for voltage signal processing.
And the current sensor is used for transmitting the current signal to a current sampling module of the analog quantity sampling circuit, conditioning the current signal and then transmitting the conditioned current signal to the controller for current signal processing.
CN202011106186.0A 2020-10-16 2020-10-16 Method and system for controlling starting of alternating current asynchronous motor during galloping Pending CN112234870A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113507237A (en) * 2021-07-21 2021-10-15 中冶赛迪工程技术股份有限公司 Method for optimizing frequency converter runaway starting

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113507237A (en) * 2021-07-21 2021-10-15 中冶赛迪工程技术股份有限公司 Method for optimizing frequency converter runaway starting

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