CN106712631B - Permanent magnet synchronous motor system and its method and a device for controlling weak magnetism - Google Patents
Permanent magnet synchronous motor system and its method and a device for controlling weak magnetism Download PDFInfo
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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
- 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
- H02P27/06—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 using dc to ac converters or inverters
- H02P27/08—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 using dc to ac converters or inverters with pulse width modulation
- H02P27/12—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 using dc to ac converters or inverters with pulse width modulation pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control
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Abstract
The invention discloses a kind of permanent magnet synchronous motor system and its method and a device for controlling weak magnetism, the described method comprises the following steps: obtaining the D axis output voltage u under the rotating coordinate system of the permanent magnet synchronous motor systemdWith Q axis output voltage uq；Output voltage threshold limit is obtained, and Q shaft voltage threshold limit is obtained according to the D axis output voltage and the output voltage threshold limit；According to the Q axis output voltage uqWeak magnetoelectricity stream is generated with the Q shaft voltage threshold limit, and the weak magnetoelectricity stream is superimposed to the D shaft current closed loop of the permanent magnet synchronous motor system, to carry out weak magnetic control to permanent magnet synchronous motor.The weak magnetic control for carrying out closed loop feedback using Q shaft voltage error as a result, keeps the perfect tracking of D shaft current, it is unstable in the case where input ac voltage cyclic swing characteristic itself and the fluctuation of load to can be avoided D shaft current, improves weak magnetic control performance.
Description
Technical Field
The invention relates to the technical field of motor control, in particular to a flux weakening control method of a permanent magnet synchronous motor system, a flux weakening control device of the permanent magnet synchronous motor system and the permanent magnet synchronous motor system.
Background
Permanent magnet synchronous motors have been widely used in various industries due to their characteristics of good control performance, high power density, energy saving, etc. Among them, in many application occasions, the permanent magnet synchronous motor is required to operate in a high frequency range and then operate in a weak magnetic range, such as a variable frequency compressor based on the permanent magnet synchronous motor, a fan based on the permanent magnet synchronous motor, and the like.
The flux weakening control method in the related art mostly adopts closed-loop feedback of the output voltage amplitude to carry out flux weakening current regulation. However, the problem is that the weak magnetic current (D-axis current) cannot be well tracked due to the limitation of the D-axis voltage, which affects the weak magnetic control performance.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide a flux weakening control method for a permanent magnet synchronous motor system, which can maintain complete tracking of D-axis current and improve flux weakening control performance.
Another object of the present invention is to provide a field weakening control apparatus for a permanent magnet synchronous motor system. It is a further object of the present invention to provide a permanent magnet synchronous motor system.
In order to achieve the above object, an embodiment of the present invention provides a method for controlling field weakening of a permanent magnet synchronous motor system, including the following steps: obtaining D-axis output voltage u under a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uq(ii) a Acquiring an output voltage limiting threshold, and acquiring a Q-axis voltage limiting threshold according to the D-axis output voltage and the output voltage limiting threshold; according to the Q-axis output voltage uqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor.
According to the flux weakening control method of the permanent magnet synchronous motor system provided by the embodiment of the invention, the D-axis output voltage u under the rotating coordinate system of the permanent magnet synchronous motor system is firstly obtaineddAnd Q-axis output voltage uqThen obtaining an output voltage limiting threshold, obtaining a Q-axis voltage limiting threshold according to the D-axis output voltage and the output voltage limiting threshold, and further obtaining a Q-axis output voltage u according to the Q-axis output voltageqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor. Thus, the method of embodiments of the present invention uses the Q-axis voltageThe error carries out the flux weakening control of closed-loop feedback, keeps the complete tracking of the D-axis current, can avoid the instability of the D-axis current under the conditions of the periodic fluctuation characteristic and the load fluctuation of the input alternating voltage, and improves the flux weakening control performance.
According to one embodiment of the invention, obtaining the output voltage limit threshold comprises: obtaining D-axis output voltage u under a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd outputs a voltage u according to the D axisdAnd Q-axis output voltage uqObtaining a desired output voltage usOr according to the α output voltage uαAnd β Axis output Voltage uβObtaining a desired output voltage us(ii) a According to the desired output voltage usAnd calculating the output voltage limit threshold value according to the direct current bus voltage of the permanent magnet synchronous motor system.
According to one embodiment of the invention, the output voltage limit threshold is less than or equal to the dc bus voltage of the permanent magnet synchronous motor systemAnd (4) doubling.
According to an embodiment of the present invention, the Q-axis voltage limit threshold is obtained according to the following formula:
wherein u isqlimLimiting a threshold value for the Q-axis voltage, ulimLimiting a threshold value for said output voltage udAnd outputting voltage for the D axis.
According to an embodiment of the invention, the output voltage u is based on the Q-axisqAnd the Q-axis voltage limit threshold generates a field weakening current, comprising: obtainingThe Q-axis voltage limit threshold and the Q-axis output voltage uqThe voltage difference between the magnitudes of (a); and generating the weak magnetic current according to the voltage difference value and a preset PI control model.
According to one embodiment of the invention, the output voltage u is based on the Q axisqAnd after the Q-axis voltage limit threshold generates a field weakening current, the method further comprises: and limiting the weak magnetic current according to a preset amplitude limiting model so that the permanent magnet synchronous motor system performs weak magnetic control according to the weak magnetic current after amplitude limiting.
According to one embodiment of the present invention, the field weakening control bandwidth is smaller than the D-axis current closed loop bandwidth and greater than 2 times the frequency of the ac power input to the permanent magnet synchronous motor system.
In order to achieve the above object, an embodiment of the present invention provides a field weakening control device for a permanent magnet synchronous motor system, including: a first obtaining module for obtaining the D-axis output voltage u under the rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uq(ii) a The second acquisition module is used for acquiring an output voltage limit threshold; a weak magnetic control module for obtaining a Q-axis voltage limit threshold according to the D-axis output voltage and the output voltage limit threshold, and outputting a Q-axis output voltage u according to the Q-axis output voltage uqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor.
According to the flux-weakening control device of the permanent magnet synchronous motor system provided by the embodiment of the invention, the D-axis output voltage u under the rotating coordinate system of the permanent magnet synchronous motor system is obtained through the first obtaining moduledAnd Q-axis output voltage uqAnd the output voltage limiting threshold is obtained through the second obtaining module, the weak magnetic control module obtains the Q-axis voltage limiting threshold according to the D-axis output voltage and the output voltage limiting threshold, and the Q-axis output voltage u is obtained according to the Q-axis output voltage uqAnd a Q-axis voltage limiting threshold value generates weak magnetic current, andand the flux weakening current is superposed to a D-axis current closed loop of the permanent magnet synchronous motor system so as to carry out flux weakening control on the permanent magnet synchronous motor. Therefore, the device provided by the embodiment of the invention adopts the Q-axis voltage error to carry out the flux weakening control of closed-loop feedback, keeps the complete tracking of the D-axis current, can avoid the instability of the D-axis current under the conditions of the periodic fluctuation characteristic and the load fluctuation of the input alternating voltage, and improves the flux weakening control performance.
According to an embodiment of the invention, the second obtaining module is further configured to obtain a D-axis output voltage u in a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd outputs a voltage u according to the D axisdAnd Q-axis output voltage uqObtaining a desired output voltage usOr according to the α output voltage uαAnd β Axis output Voltage uβObtaining a desired output voltage usAnd according to said desired output voltage usAnd calculating the output voltage limit threshold value according to the direct current bus voltage of the permanent magnet synchronous motor system.
According to one embodiment of the invention, the output voltage limit threshold is less than or equal to the dc bus voltage of the permanent magnet synchronous motor systemAnd (4) doubling.
According to one embodiment of the invention, the weak magnetic control module obtains the Q-axis voltage limit threshold according to the following formula:
wherein u isqlimLimiting a threshold value for the Q-axis voltage, ulimLimiting a threshold value for said output voltage udAnd outputting voltage for the D axis.
According to an embodiment of the present invention, the weak magnetic control module is further configured to obtain the Q-axis voltage limit threshold and the Q-axis output voltage uqAnd generating the flux weakening current according to the voltage difference value and a preset PI control model.
According to one embodiment of the invention, the output voltage u is based on the Q axisqAnd after the Q-axis voltage limiting threshold value generates weak magnetic current, the weak magnetic control module limits the weak magnetic current according to a preset amplitude limiting model, so that the permanent magnet synchronous motor system performs weak magnetic control according to the weak magnetic current after amplitude limiting.
According to one embodiment of the present invention, the field weakening control bandwidth is smaller than the D-axis current closed loop bandwidth and greater than 2 times the frequency of the ac power input to the permanent magnet synchronous motor system.
In order to achieve the above object, a permanent magnet synchronous motor system according to another embodiment of the present invention includes a field weakening control device of the permanent magnet synchronous motor system.
According to the permanent magnet synchronous motor system provided by the embodiment of the invention, the flux weakening control device is adopted to perform flux weakening control of closed-loop feedback by adopting the Q-axis voltage error, so that the complete tracking of the D-axis current is kept, the instability of the D-axis current under the conditions of the periodic fluctuation characteristic and the load fluctuation of the input alternating voltage can be avoided, and the flux weakening control performance is improved.
Drawings
Fig. 1 is a flowchart of a field weakening control method of a permanent magnet synchronous motor system according to an embodiment of the present invention;
fig. 2 is a topological schematic of a control circuit of a permanent magnet synchronous machine according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a rotating coordinate system in relation to a stationary coordinate system in accordance with one embodiment of the present invention;
FIG. 4 is a schematic diagram of spatial voltage modulation according to one embodiment of the present invention;
FIG. 5 is a schematic diagram of spatial voltage modulation according to another embodiment of the present invention;
fig. 6 is a control block diagram of a field weakening control method of a permanent magnet synchronous motor system according to one embodiment of the present invention;
fig. 7 is a vector control block diagram of a permanent magnet synchronous motor system according to an embodiment of the present invention, wherein the permanent magnet synchronous motor is a surface mount permanent magnet synchronous motor;
fig. 8 is a vector control block diagram of a permanent magnet synchronous motor system according to an embodiment of the present invention, wherein the permanent magnet synchronous motor is an in-line permanent magnet synchronous motor; and
fig. 9 is a block schematic diagram of a field weakening control arrangement of a permanent magnet synchronous motor system according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The field weakening control method of the permanent magnet synchronous motor system, the field weakening control device of the permanent magnet synchronous motor system, and the permanent magnet synchronous motor system according to the embodiment of the present invention will be described below with reference to the accompanying drawings.
Fig. 1 is a flowchart of a field weakening control method of a permanent magnet synchronous motor system according to an embodiment of the present invention. As shown in fig. 1, the method comprises the steps of:
s1: obtaining D-axis output voltage u under rotating coordinate system of permanent magnet synchronous motor systemdAnd Q-axis output voltage uq。
According to an embodiment of the present invention, as shown in fig. 2, a permanent magnet synchronous motor system may include a control chip, a driving unit, an electrolytic capacitor, and a permanent magnet synchronous motor. The electrolytic capacitor is connected in parallel with the input end of the driving unit, the output end of the driving unit is connected with the permanent magnet synchronous motor, and the driving unit is used for driving the permanent magnet synchronous motor; the control chip is used for detecting the phase current of the permanent magnet synchronous motor through the current detection unit and outputting a driving signal to the driving unit according to the phase current of the permanent magnet synchronous motor so as to control the operation of the permanent magnet synchronous motor through the driving unit. According to a specific example of the present invention, the current detection unit may include three (or two) current sensors. The driving unit may be a three-phase bridge driving circuit composed of 6 IGBTs, or a three-phase bridge driving circuit composed of 6 MOSFETs, or an intelligent power module IPM is employed, with each IGBT or MOSFET having a corresponding anti-parallel diode.
S2: and acquiring an output voltage limit threshold, and acquiring a Q-axis voltage limit threshold according to the D-axis output voltage and the output voltage limit threshold.
Wherein, the output voltage limit threshold u can be set according to the DC bus voltage and the modulation method of the permanent magnet synchronous motor systemlimFor example, the output voltage limit threshold u is set according to the maximum voltage amplitude that can be output by the driver correspondence control method and the modulation methodlim. Output voltage limiting threshold ulimThe specific acquisition mode of (a) is described in the following examples.
Specifically, the Q-axis voltage limit threshold may be obtained according to the following equation:
wherein u isqlimLimiting the threshold for the Q-axis voltage, ulimLimiting the threshold value for the output voltage udOutputting the voltage for the D axis.
S3: according to Q-axis output voltage uqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor.
That is, the voltage u can be output according to the D axisdAnd an output voltage limiting threshold ulimCalculating a Q-axis voltage limit threshold uqlimI.e. byThen outputs a voltage u according to the Q axisqAnd Q-axis voltage limit threshold uqlimAnd carrying out field weakening control.
According to an embodiment of the present invention, the output voltage u is outputted according to the Q-axisqAnd a Q-axis voltage limit threshold generating a field weakening current, comprising: obtaining a Q-axis voltage limiting threshold and a Q-axis output voltage uqThe voltage difference between the magnitudes of (a); and generating weak magnetic current according to the voltage difference value and a preset PI control model.
It should be noted that the proportional parameter in the preset PI control model may be zero, and at this time, the preset PI control model is only an integral model, and integral control may be performed on the voltage difference value; the proportional parameter in the preset PI control model may also be non-zero, and at this time, the preset PI control model is a proportional-integral model and may perform proportional-integral control on the voltage difference.
That is, as shown in fig. 6, the voltage u may be output according to the D axisdAnd an output voltage limiting threshold ulimCalculating a Q-axis voltage limit threshold uqlimI.e. byThe Q-axis voltage is then limited to a threshold uqlimMinus the Q-axis voltage uqTo obtain a flux-weakening controlled voltage difference Deltau, i.e.Δu＝uqlim-uqAnd performing pure integral control or proportional-integral control on the voltage difference value delta u to adjust the field weakening current.
Further, according to an embodiment of the present invention, the voltage u is output according to the Q-axisqAnd after the Q-axis voltage limiting threshold value generates weak magnetic current, the method further comprises the following steps: and limiting the weak magnetic current according to a preset amplitude limiting model so that the permanent magnet synchronous motor system performs weak magnetic control according to the limited weak magnetic current.
That is to say, the weak magnetic current output by the preset PI control model can be limited by the preset limiting model, i.e. the limiting link, to obtain the limited weak magnetic current ifwcAnd then according to the weak magnetic current i after amplitude limitingfwcPerforming field weakening control, e.g. limiting field weakening current ifwcD-axis current closed loop superposed to the permanent magnet synchronous motor system, wherein the upper limit of the amplitude limiting link can be zero, and the lower limit of the amplitude limiting link can be the minimum value i of the D-axis currentd_min。
Obtaining the output voltage limiting threshold u is described belowlimTwo examples of (2).
In one embodiment of the present invention, the output voltage limit threshold u may be set according to the DC bus voltagelim. In particular, the output voltage limiting threshold is less than or equal to the DC bus voltage of the PMSM systemAnd (4) doubling. Wherein,
that is, the output voltage limit threshold ulimCan be set not to exceed the DC bus voltage udcA value of 0.577 times, i.e., ulim≤0.577udc。
In another embodiment of the invention, the output can be based on the D axis under the rotating coordinate systemVoltage udAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβSetting an output voltage limiting threshold ulim. Specifically, obtaining the output voltage limit threshold comprises: obtaining D-axis output voltage u under rotating coordinate system of permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd outputs a voltage u according to the D axisdAnd Q-axis output voltage uqObtaining a desired output voltageOr output voltage u according to axis ααAnd β Axis output Voltage uβObtaining a desired output voltageAccording to desired output voltageAnd calculating an output voltage limit threshold value according to the direct current bus voltage of the permanent magnet synchronous motor system.
Wherein, as shown in FIG. 3, the rotating coordinate system can have d axis (direct axis) and q axis (quadrature axis), and the desired output voltageCan be D-axis output voltage u on D-axisdAnd Q-axis output voltage u on Q-axisqThe resultant voltage vector. In addition, the estimated angle theta of the rotor of the permanent magnet synchronous motor is usedeOutput voltage u to D axisdAnd Q-axis output voltage uqInverse park coordinate conversion is performed to obtain α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβThe static coordinate system can have α axes and β axes, and the expected output voltageCan also output power for α shaftPress uαAnd β axis output voltage uβThe resultant voltage vector. Specifically, the output voltage u is output according to a rotating coordinate systemd/uqOr the output voltage u in a stationary coordinate systemα/uβCalculating the expected output voltageAmplitude u ofsIn order to realize the purpose,
further, the voltage is output according to the desireAnd calculating an output voltage limit threshold value by using the direct current bus voltage of the permanent magnet synchronous motor system, wherein the output voltage limit threshold value comprises the following steps: obtaining expected output voltage under a rotating coordinate systemMaximum output voltage in the vector direction of (1) or desired output voltage in a stationary coordinate systemThe maximum output voltage in the vector direction of (a); taking the maximum output voltage in a rotating coordinate system or the maximum output voltage in a static coordinate system as an output voltage limiting threshold ulim。
Specifically, the voltage of the direct current bus can be 2/3 times that of the direct current busConstructing a voltage space for the basic voltage vector, as shown in fig. 4 and 5, the regular hexagonal boundary and its inner region are voltage spaces from which a desired output voltage can be obtained(or is represented by u)d/uqOr watchIs shown as uα/uβ) The maximum voltage that can be output in the vector direction, i.e., the desired output voltageThe magnitude of the voltage vector formed by the intersection with the voltage space boundary (regular hexagon).
Specifically, as shown in FIG. 4, if an output voltage is desiredWithin the voltage space, the modulated output voltage and the expected output voltageConsistent, output voltage limiting threshold ulimCan be a desired output voltageThe vector magnitude of the intersection of the extension line and the voltage space boundary (regular hexagon).
As shown in fig. 5, if an output voltage is desiredOut of the voltage space, the modulated output voltage and the expected output voltageNot identical, the output voltage limit threshold ulimCan be a desired output voltageVector magnitude at the intersection with the voltage space boundary (regular hexagon).
It should be noted that the two kinds of the above-mentioned output voltage limiting threshold u are obtainedlimThe above-mentioned methods can be implemented individually or in combination. When implemented in combination, the selection can be made according to whether the permanent magnet synchronous motor system is in an overmodulation regionAnd selecting a corresponding acquisition mode.
Specifically, the voltage may be output as desiredAmplitude u ofsAnd judging whether the permanent magnet synchronous motor system is in an overmodulation region. When the desired output voltage usIs greater than the DC bus voltage udcWhen the voltage is 0.577 times, judging that the permanent magnet synchronous motor system is in an overmodulation region; when the desired output voltage usIs less than or equal to the DC bus voltage udcAnd when the time is 0.577 times, judging that the permanent magnet synchronous motor system is in a linear modulation region.
If the permanent magnet synchronous motor system is in the overmodulation region, the output voltage u is output according to the D axis under the rotating coordinate system in combination with the embodiments of fig. 4 and 5dAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβSetting an output voltage limiting threshold ulim(ii) a If the permanent magnet synchronous motor system is in the linear modulation region, an output voltage limit threshold u is set according to the voltage of the direct current buslimE.g. setting ulim≤0.577udc. Thus, the field weakening control is divided into field weakening control in a linear modulation region and field weakening control in an overmodulation region, and when a space vector pulse width modulation algorithm is adopted and the driver operates in the linear modulation region without overmodulation, the output voltage is limited by a threshold ulimIs set as ulim≤0.577udcAnd limiting the threshold u based on the output voltage corresponding to the linear modulation regionlimCarrying out weak magnetic control; limiting the output voltage by a threshold u when space vector pulse width modulation algorithm is used and the drive can operate in the overmodulation regionlimSet to the desired output voltage usAnd the maximum voltage that can be output in the vector direction of (1) and the threshold value u is limited based on the output voltage corresponding to the overmodulation regionlimAnd carrying out field weakening control.
The flux weakening control flow of the permanent magnet synchronous motor system is described in detail with reference to fig. 6 to 8, in this embodiment, sensorless vector control of the permanent magnet synchronous motor is taken as an example for description, and sensorless vector control of the permanent magnet synchronous motor is not different from this embodiment and is not described again.
In vector control of a permanent magnet synchronous motor, a speed correction unit corrects a speed of the permanent magnet synchronous motor based on a given rotation speedAnd to the estimated rotation speedSpeed correction, e.g. proportional-integral adjustment, to achieve a given torque
In a surface-mounted permanent magnet synchronous motor, the torque is set according to a given torqueAnd the torque current coefficient KtCalculating a given torque current (i.e. a given Q-axis current)Given direct axis current (i.e. given D axis current)By a field weakening current ifwcTo decide, for exampleIn an embedded permanent magnet synchronous motor, a torque control unit controls a torque according to a given torqueCoefficient of torque current KtAnd a weak magnetic current ifwcCalculating to obtain a given quadrature axis current (a given Q axis current) through maximum torque current control (MTPA)And given direct axis current (given D axis current)
The current correction unit is based on a given D-axis currentAnd a given Q-axis currentRespectively to the direct-axis feedback current idAnd quadrature axis feedback current iqCurrent correction to obtain a direct axis voltage udAnd quadrature axis voltage uq. Then, the inverse park coordinate conversion unit estimates the angle based on the estimated angleTo direct axis voltage udAnd quadrature axis voltage uqInverse park coordinate conversion was performed to obtain α axis voltage uαAnd β axis voltage uβThe space vector modulation unit then couples α axis voltages uαAnd β axis voltage uβPerforming SVM (Space vector Modulation) Modulation to generate a PWM driving signal; the driving unit drives the permanent magnet synchronous motor according to the PWM driving signal.
The three-phase current of the permanent magnet synchronous motor is collected through the current detection unit, and the clarke coordinate conversion unit carries out clarke coordinate conversion on the three-phase current to obtain two-phase current iα/iβ(ii) a The park coordinate conversion unit estimates the angle based on the angleFor two-phase current iα/iβPerforming park coordinate conversion to obtain a direct-axis (D-axis) feedback current idQuadrature axis (Q-axis) feedback current iq. The position estimation unit, e.g. a speed flux observer, is based on the output voltage uα/uβAnd twoPhase current iα/iβAnd motor parameters (motor resistance R)sStraight axis inductor LdAnd quadrature axis inductance Lq) Estimating the position and speed of the rotor by a sensorless estimation algorithm to obtain an estimated rotational speedAnd estimating the electrical angle
In addition, according to an embodiment of the present invention, the field-weakening control bandwidth is smaller than the D-axis current closed-loop bandwidth and greater than 2 times the frequency of the ac power input to the permanent magnet synchronous motor system. Specifically, the proportional control parameter and the integral control parameter of the preset PI control model may be set according to the weak magnetic control bandwidth.
In the weak magnetic control, the weak magnetic current i is exemplified in the embodiment of fig. 7fwcSuperposed to the D-axis current closed loop according to the weak magnetic current ifwcTo D axis feedback circuit idThe regulation is carried out, so that the flux weakening control is realized, and meanwhile, the speed closed loop still depends on the given rotating speedAnd to the estimated rotation speedSpeed correction to obtain a given torqueAccording to a given torqueAnd the torque current coefficient KtCalculating a given Q-axis currentThe Q-axis current closed loop is still based on the given Q-axis currentTo quadrature axis feedback current iqAnd (6) carrying out adjustment.
Based on this, the weak magnetic control loop can limit the Q-axis voltage to a threshold value uqlimMinus the Q-axis voltage uqThe obtained voltage difference value delta u is input to the input end of a weak magnetic PI controller, and weak magnetic current i is output through the weak magnetic PI controller, namely a preset PI control modelfwc(ii) a Weak magnetic current ifwcA D-axis current control model to a D-axis feedback circuit i superposed to the D-axis current closed loop and passing through the D-axis current closed loopdAnd (6) carrying out adjustment. The bandwidth of the weak magnetic control loop, namely the weak magnetic control bandwidth, is less than the bandwidth of the D-axis current closed loop and more than 2 times of the frequency of an alternating current power supply input to the permanent magnet synchronous motor system. Therefore, proportional control parameters and integral control parameters of the preset PI control model are set to meet the condition that the bandwidth of the weak magnetic control loop is lower than the bandwidth of the direct-axis current closed loop and higher than the frequency of an input power supply by 2, and therefore the weak magnetic control can make a fast enough response to the voltage fluctuation of the direct-current bus.
In summary, according to the flux-weakening control method of the permanent magnet synchronous motor system provided by the embodiment of the invention, the D-axis output voltage u under the rotating coordinate system of the permanent magnet synchronous motor system is firstly obtaineddAnd Q-axis output voltage uqThen obtaining an output voltage limiting threshold, obtaining a Q-axis voltage limiting threshold according to the D-axis output voltage and the output voltage limiting threshold, and further obtaining a Q-axis output voltage u according to the Q-axis output voltageqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor. Therefore, the method provided by the embodiment of the invention adopts the Q-axis voltage error to carry out the flux weakening control of closed-loop feedback, keeps the complete tracking of the D-axis current, can avoid the instability of the D-axis current under the conditions of the periodic fluctuation characteristic and the load fluctuation of the input alternating voltage, and improves the flux weakening control performance.
Fig. 9 is a block schematic diagram of a field weakening control arrangement of a permanent magnet synchronous motor system according to an embodiment of the present invention. According to an embodiment of the present invention, as shown in fig. 2, the permanent magnet synchronous motor system may include a control chip 1, a driving unit 2, an electrolytic capacitor EC, and a permanent magnet synchronous motor 3. The electrolytic capacitor EC is connected in parallel with the input end of the driving unit 2, the output end of the driving unit 2 is connected with the permanent magnet synchronous motor 3, and the driving unit 2 is used for driving the permanent magnet synchronous motor 3; the control chip 1 is used for detecting the phase current of the permanent magnet synchronous motor 3 through the current detection unit 4, and outputting a driving signal to the driving unit 2 according to the phase current of the permanent magnet synchronous motor 3 so as to control the operation of the permanent magnet synchronous motor 3 through the driving unit 2. According to a specific example of the present invention, the current detection unit 4 may include three (or two) current sensors. The driving unit 2 may be a three-phase bridge driving circuit composed of 6 IGBTs, or a three-phase bridge driving circuit composed of 6 MOSFETs, or an intelligent power module IPM, with each IGBT or MOSFET having a corresponding anti-parallel diode.
As shown in fig. 9, the field weakening control apparatus 100 according to the embodiment of the present invention includes: a first acquisition module 10, a second acquisition module 20 and a field weakening control module 30.
The first obtaining module 10 is configured to obtain a D-axis output voltage u in a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uq(ii) a The second obtaining module 20 is configured to obtain an output voltage limit threshold; the weak magnetic control module 30 is used for obtaining a Q-axis voltage limit threshold according to the D-axis output voltage and the output voltage limit threshold, and obtaining a Q-axis output voltage u according to the Q-axis output voltageqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor.
The second obtaining module 20 may set the output voltage limit threshold u according to the dc bus voltage and the modulation method of the pmsm systemlimFor example, the output voltage limit threshold u is set according to the maximum voltage amplitude that can be output by the driver correspondence control method and the modulation methodlim. Limit of output voltageThreshold value ulimThe specific acquisition mode of (a) is described in the following examples.
Specifically, the field weakening control module 30 may obtain the Q-axis voltage limit threshold according to the following formula:
wherein u isqlimLimiting the threshold for the Q-axis voltage, ulimLimiting the threshold value for the output voltage udOutputting the voltage for the D axis.
That is, the field-weakening control module 30 may output the voltage u according to the D-axisdAnd an output voltage limiting threshold ulimCalculating a Q-axis voltage limit threshold uqlimI.e. byThen outputs a voltage u according to the Q axisqAnd Q-axis voltage limit threshold uqlimAnd carrying out field weakening control.
According to an embodiment of the present invention, the field-weakening control module 30 is further configured to obtain the Q-axis voltage limiting threshold and the Q-axis output voltage uqAnd generating a flux weakening current according to the voltage difference and a preset PI control model.
It should be noted that the proportional parameter in the preset PI control model may be zero, and at this time, the preset PI control model is only an integral model, and integral control may be performed on the voltage difference value; the proportional parameter in the preset PI control model may also be non-zero, and at this time, the preset PI control model is a proportional-integral model and may perform proportional-integral control on the voltage difference.
That is, as shown in fig. 6, the field-weakening control module 30 may output a voltage u according to the D-axisdAnd an output voltage limiting threshold ulimCalculating a Q-axis voltage limit threshold uqlimI.e. byThe Q-axis voltage is then limited to a threshold uqlimMinus the Q-axis voltage uqTo obtain a flux-weakening controlled voltage difference value delta u, i.e. delta u-uqlim-uqAnd performing pure integral control or proportional-integral control on the voltage difference value delta u to adjust the field weakening current.
Further, according to an embodiment of the present invention, the voltage u is output according to the Q-axisqAnd after the Q-axis voltage limiting threshold generates the weak magnetic current, the weak magnetic control module 30 further limits the weak magnetic current according to a preset amplitude limiting model, so that the permanent magnet synchronous motor system performs weak magnetic control according to the limited weak magnetic current.
That is to say, the weak magnetic current output by the preset PI control model can be limited by the preset limiting model, i.e. the limiting link, to obtain the limited weak magnetic current ifwcAnd then according to the weak magnetic current i after amplitude limitingfwcPerforming field weakening control, e.g. limiting field weakening current ifwcD-axis current closed loop superposed to the permanent magnet synchronous motor system, wherein the upper limit of the amplitude limiting link can be zero, and the lower limit of the amplitude limiting link can be the minimum value i of the D-axis currentd_min。
Obtaining the output voltage limiting threshold u is described belowlimTwo examples of (2).
In an embodiment of the invention, the second obtaining module 20 may set the output voltage limit threshold u according to the dc bus voltagelim. In particular, the output voltage limiting threshold is less than or equal to the DC bus voltage of the PMSM systemAnd (4) doubling. Wherein,
that is, the output voltage limit threshold ulimCan be set to be not more thanOver-direct current bus voltage udcA value of 0.577 times, i.e., ulim≤0.577udc。
In another embodiment of the present invention, the second obtaining module 20 is further configured to obtain the D-axis output voltage u in the rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd outputs a voltage u according to the D axisdAnd Q-axis output voltage uqObtaining a desired output voltage usOr output voltage u according to axis ααAnd β Axis output Voltage uβObtaining a desired output voltage usAnd outputs the voltage u according to the desiredsAnd calculating an output voltage limit threshold value according to the direct current bus voltage of the permanent magnet synchronous motor system.
Wherein, as shown in FIG. 3, the rotating coordinate system can have d axis (direct axis) and q axis (quadrature axis), and the desired output voltageCan be D-axis output voltage u on D-axisdAnd Q-axis output voltage u on Q-axisqThe resultant voltage vector. In addition, the estimated angle theta of the rotor of the permanent magnet synchronous motor is usedeOutput voltage u to D axisdAnd Q-axis output voltage uqInverse park coordinate conversion is performed to obtain α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβThe static coordinate system can have α axes and β axes, and the expected output voltageCan also be α shaft output voltage uαAnd β axis output voltage uβThe resultant voltage vector. Specifically, the output voltage u is output according to a rotating coordinate systemd/uqOr the output voltage u in a stationary coordinate systemα/uβCalculating the expected output voltageAmplitude u ofsIn order to realize the purpose,
further, the second obtaining module 20 is configured to obtain a desired output voltage under a rotating coordinate systemMaximum output voltage in the vector direction of (1) or desired output voltage in a stationary coordinate systemAnd the maximum output voltage in the rotating coordinate system or the maximum output voltage in the stationary coordinate system is used as the output voltage limit threshold ulim。
Specifically, the voltage of the direct current bus can be 2/3 times that of the direct current busConstructing a voltage space for the basic voltage vector, as shown in fig. 4 and 5, the regular hexagonal boundary and its inner region are voltage spaces from which the second obtaining module 20 can obtain the desired output voltage(or is represented by u)d/uqOr is represented by uα/uβ) The maximum voltage that can be output in the vector direction, i.e., the desired output voltageThe magnitude of the voltage vector formed by the intersection with the voltage space boundary (regular hexagon).
Specifically, as shown in FIG. 4, if an output voltage is desiredAt voltage nullIn the middle, the modulated output voltage and the expected output voltageConsistent, output voltage limiting threshold ulimCan be a desired output voltageThe vector magnitude of the intersection of the extension line and the voltage space boundary (regular hexagon).
As shown in fig. 5, if an output voltage is desiredOut of the voltage space, the modulated output voltage and the expected output voltageNot identical, the output voltage limit threshold ulimCan be a desired output voltageVector magnitude at the intersection with the voltage space boundary (regular hexagon).
It should be noted that the two kinds of the above-mentioned output voltage limiting threshold u are obtainedlimThe above-mentioned methods can be implemented individually or in combination. When the two are combined together, the corresponding acquisition mode can be selected according to whether the permanent magnet synchronous motor system is in the overmodulation region or not.
Specifically, the second obtaining module 20 may output the voltage according to the desired output voltageAmplitude u ofsAnd judging whether the permanent magnet synchronous motor system is in an overmodulation region. When the desired output voltage usIs greater than the DC bus voltage udcWhen the voltage is 0.577 times, judging that the permanent magnet synchronous motor system is in an overmodulation region; when the desired output voltage usIs less than or equal to the DC busLine voltage udcAnd when the time is 0.577 times, judging that the permanent magnet synchronous motor system is in a linear modulation region.
If the pm synchronous motor system is in the overmodulation region, the second obtaining module 20 outputs the voltage u according to the D-axis output voltage u in the rotational coordinate system, in conjunction with the embodiments of fig. 4 and 5dAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβSetting an output voltage limiting threshold ulim(ii) a If the permanent magnet synchronous motor system is in the linear modulation region, the second obtaining module 20 sets the output voltage limit threshold u according to the dc bus voltagelimE.g. setting ulim≤0.577udc. Thus, the field weakening control is divided into field weakening control in a linear modulation region and field weakening control in an overmodulation region, and when a space vector pulse width modulation algorithm is adopted and the driver operates in the linear modulation region without overmodulation, the output voltage is limited by a threshold ulimIs set as ulim≤0.577udcAnd limiting the threshold u based on the output voltage corresponding to the linear modulation regionlimCarrying out weak magnetic control; limiting the output voltage by a threshold u when space vector pulse width modulation algorithm is used and the drive can operate in the overmodulation regionlimSet to the desired output voltage usAnd the maximum voltage that can be output in the vector direction of (1) and the threshold value u is limited based on the output voltage corresponding to the overmodulation regionlimAnd carrying out field weakening control.
The flux weakening control flow of the permanent magnet synchronous motor system is described in detail with reference to fig. 6 to 8, in this embodiment, sensorless vector control of the permanent magnet synchronous motor is taken as an example for description, and sensorless vector control of the permanent magnet synchronous motor is not different from this embodiment and is not described again.
In the vector control of the permanent magnet synchronous motor, the speed correction unit 101 corrects the speed according to a given rotation speedAnd to the estimated rotation speedSpeed correction, e.g. proportional-integral adjustment, to achieve a given torque
In a surface-mounted permanent magnet synchronous motor, the torque is set according to a given torqueAnd the torque current coefficient KtCalculating a given torque current (i.e. a given Q-axis current)Given direct axis current (i.e. given D axis current)By a field weakening current ifwcTo decide, for exampleIn the interior permanent magnet synchronous motor, the torque control unit 102 controls the torque according to a given torqueCoefficient of torque current KtAnd a weak magnetic current ifwcCalculating to obtain a given quadrature axis current (a given Q axis current) through maximum torque current control (MTPA)And given direct axis current (given D axis current)
The current correction unit 103 corrects the current according to the given D-axis currentAnd a given Q-axis currentRespectively to the direct-axis feedback current idAnd quadrature axis feedback current iqCurrent correction to obtain a direct axis voltage udAnd quadrature axis voltage uq. Then, the inverse park coordinate conversion unit 104 converts the angle based on the estimated angleTo direct axis voltage udAnd quadrature axis voltage uqInverse park coordinate conversion was performed to obtain α axis voltage uαAnd β axis voltage uβThe space vector modulation unit 105 then couples α axis voltages uαAnd β axis voltage uβPerforming SVM (Space vector modulation) modulation to generate a PWM driving signal; the driving unit 2 drives the permanent magnet synchronous motor 3 according to the PWM driving signal.
The three-phase current of the permanent magnet synchronous motor 3 is collected through the current detection unit 4, and the clarke coordinate conversion unit 106 performs clarke coordinate conversion on the three-phase current to obtain a two-phase current iα/iβ(ii) a park coordinate conversion unit 107 from the estimated angleFor two-phase current iα/iβPerforming park coordinate conversion to obtain a direct-axis (D-axis) feedback current idQuadrature axis (Q-axis) feedback current iq. The position estimation unit 108, e.g. a speed flux linkage observer, is based on the output voltage uα/uβAnd two-phase current iα/iβAnd motor parameters (motor resistance R)sStraight axis inductor LdAnd quadrature axis inductance Lq) Estimating the position and speed of the rotor by a sensorless estimation algorithm to obtain an estimated rotational speedAnd estimating the electrical angle
In addition, according to an embodiment of the present invention, the field-weakening control bandwidth is smaller than the D-axis current closed-loop bandwidth and greater than 2 times the frequency of the ac power input to the permanent magnet synchronous motor system. Specifically, the proportional control parameter and the integral control parameter of the preset PI control model may be set according to the weak magnetic control bandwidth.
In the weak magnetic control, the weak magnetic current i is exemplified in the embodiment of fig. 7fwcSuperposed to the D-axis current closed loop according to the weak magnetic current ifwcTo D axis feedback circuit idThe regulation is carried out, so that the flux weakening control is realized, and meanwhile, the speed closed loop still depends on the given rotating speedAnd to the estimated rotation speedSpeed correction to obtain a given torqueAccording to a given torqueAnd the torque current coefficient KtCalculating a given Q-axis currentThe Q-axis current closed loop is still based on the given Q-axis currentTo quadrature axis feedback current iqAnd (6) carrying out adjustment.
Based on this, the weak magnetic control loop can limit the Q-axis voltage to a threshold value uqlimMinus the Q-axis voltage uqThe obtained voltage difference value delta u is input to the input end of a weak magnetic PI controller, and weak magnetic current i is output through the weak magnetic PI controller, namely a preset PI control modelfwc(ii) a Weak magnetic current ifwcA D-axis current control model to a D-axis feedback circuit i superposed to the D-axis current closed loop and passing through the D-axis current closed loopdAnd (6) carrying out adjustment. The bandwidth of the weak magnetic control loop, namely the weak magnetic control bandwidth, is less than the bandwidth of the D-axis current closed loop and more than 2 times of the frequency of an alternating current power supply input to the permanent magnet synchronous motor system. Therefore, proportional control parameters and integral control parameters of the preset PI control model are set to meet the condition that the bandwidth of the weak magnetic control loop is lower than the bandwidth of the direct-axis current closed loop and higher than the frequency of an input power supply by 2, and therefore the weak magnetic control can make a fast enough response to the voltage fluctuation of the direct-current bus.
In summary, according to the field weakening control apparatus of the permanent magnet synchronous motor system provided by the embodiment of the present invention, the first obtaining module first obtains the D-axis output voltage u of the permanent magnet synchronous motor system in the rotating coordinate systemdAnd Q-axis output voltage uqAnd the output voltage limiting threshold is obtained through the second obtaining module, the weak magnetic control module obtains the Q-axis voltage limiting threshold according to the D-axis output voltage and the output voltage limiting threshold, and the Q-axis output voltage u is obtained according to the Q-axis output voltage uqAnd generating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system so as to perform weak magnetic control on the permanent magnet synchronous motor. Therefore, the device provided by the embodiment of the invention adopts the Q-axis voltage error to carry out the flux weakening control of closed-loop feedback, keeps the complete tracking of the D-axis current, can avoid the instability of the D-axis current under the conditions of the periodic fluctuation characteristic and the load fluctuation of the input alternating voltage, and improves the flux weakening control performance.
Finally, the embodiment of the invention also provides a permanent magnet synchronous motor system which comprises the flux weakening control device of the permanent magnet synchronous motor system of the embodiment.
According to the permanent magnet synchronous motor system provided by the embodiment of the invention, the flux weakening control device is adopted to perform flux weakening control of closed-loop feedback by adopting the Q-axis voltage error, so that the complete tracking of the D-axis current is kept, the instability of the D-axis current under the conditions of the periodic fluctuation characteristic and the load fluctuation of the input alternating voltage can be avoided, and the flux weakening control performance is improved.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (15)
1. A flux weakening control method of a permanent magnet synchronous motor system is characterized by comprising the following steps:
obtaining D-axis output voltage u under a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uq；
Acquiring an output voltage limiting threshold, and acquiring a Q-axis voltage limiting threshold according to the D-axis output voltage and the output voltage limiting threshold;
according to the Q-axis output voltage uqGenerating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system to perform weak magnetic control on the permanent magnet synchronous motor;
when the permanent magnet synchronous motor system is in an overmodulation region, outputting a voltage u according to a D axis under a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβSetting the output voltage limit threshold; and when the permanent magnet synchronous motor system is in a linear modulation region, setting the output voltage limit threshold according to the direct current bus voltage of the permanent magnet synchronous motor system.
2. The field weakening control method of a permanent magnet synchronous motor system according to claim 1, wherein obtaining the output voltage limit threshold comprises:
obtaining D-axis output voltage u under a rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd outputs a voltage u according to the D axisdAnd Q-axis output voltage uqObtaining a desired output voltage usOr according to the α output voltage uαAnd β Axis output Voltage uβObtaining a desired output voltage us；
According to the desired output voltage usAnd calculating the output voltage limit threshold value according to the direct current bus voltage of the permanent magnet synchronous motor system.
3. The field weakening control method of a permanent magnet synchronous motor system according to claim 1, wherein said output voltage limit threshold is less than or equal to a dc bus voltage of said permanent magnet synchronous motor systemAnd (4) doubling.
4. The field weakening control method of a permanent magnet synchronous motor system according to claim 1, wherein said Q-axis voltage limit threshold is obtained according to the following formula:
wherein u isqlimLimiting a threshold value for the Q-axis voltage, ulimLimiting a threshold value for said output voltage udAnd outputting voltage for the D axis.
5. The field weakening control method of a permanent magnet synchronous motor system according to claim 1, wherein said output voltage u is outputted according to said Q-axisqAnd the Q-axis voltage limit threshold generates a field weakening current, comprising:
obtaining the Q-axis voltage limit threshold and the Q-axis output voltage uqThe voltage difference between the magnitudes of (a);
and generating the weak magnetic current according to the voltage difference value and a preset PI control model.
6. The field weakening control method of a permanent magnet synchronous motor system according to claim 1 or 5, wherein a voltage u is outputted according to said Q axisqAnd after the Q-axis voltage limit threshold generates a field weakening current, the method further comprises: and limiting the weak magnetic current according to a preset amplitude limiting model so that the permanent magnet synchronous motor system performs weak magnetic control according to the weak magnetic current after amplitude limiting.
7. The field weakening control method of a permanent magnet synchronous motor system according to claim 1, wherein a field weakening control bandwidth is smaller than the D-axis current closed loop bandwidth and is greater than 2 times a frequency of an alternating current power supply input to the permanent magnet synchronous motor system.
8. A flux weakening control device of a permanent magnet synchronous motor system is characterized by comprising:
a first obtaining module for obtaining the D-axis output voltage u under the rotating coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uq；
The second acquisition module is used for acquiring an output voltage limit threshold;
a weak magnetic control module for obtaining a Q-axis voltage limit threshold according to the D-axis output voltage and the output voltage limit threshold, and outputting a Q-axis output voltage u according to the Q-axis output voltage uqGenerating weak magnetic current by the Q-axis voltage limiting threshold, and superposing the weak magnetic current to a D-axis current closed loop of the permanent magnet synchronous motor system to perform weak magnetic control on the permanent magnet synchronous motor;
the second obtaining module is used for outputting a voltage u according to a D-axis output voltage u under a rotating coordinate system of the permanent magnet synchronous motor system when the permanent magnet synchronous motor system is in an overmodulation regiondAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd setting the output voltage limit threshold, and when the permanent magnet synchronous motor system is in a linear modulation region, setting the output voltage limit threshold according to the direct current bus voltage of the permanent magnet synchronous motor system.
9. The flux weakening control device of the permanent magnet synchronous motor system according to claim 8, wherein the second obtaining module is further configured to obtain a D-axis output voltage u in a rotation coordinate system of the permanent magnet synchronous motor systemdAnd Q-axis output voltage uqOr α -axis output voltage u in a stationary coordinate systemαAnd β Axis output Voltage uβAnd outputs a voltage u according to the D axisdAnd Q-axis output voltage uqObtaining a desired output voltage usOr according to the α output voltage uαAnd β Axis output Voltage uβObtaining a desired output voltage usAnd outputting electricity according to the desirePress usAnd calculating the output voltage limit threshold value according to the direct current bus voltage of the permanent magnet synchronous motor system.
10. The field weakening control device of a permanent magnet synchronous motor system according to claim 8, wherein said output voltage limit threshold is equal to or less than a dc bus voltage of said permanent magnet synchronous motor systemAnd (4) doubling.
11. The field weakening control device of a permanent magnet synchronous motor system according to claim 8, wherein said field weakening control module obtains said Q-axis voltage limiting threshold according to the following formula:
wherein u isqlimLimiting a threshold value for the Q-axis voltage, ulimLimiting a threshold value for said output voltage udAnd outputting voltage for the D axis.
12. The flux weakening control device of a permanent magnet synchronous motor system according to claim 8, wherein said flux weakening control module is further configured to obtain said Q-axis voltage limiting threshold and said Q-axis output voltage uqAnd generating the flux weakening current according to the voltage difference value and a preset PI control model.
13. The field weakening control device of a permanent magnet synchronous motor system as claimed in claim 8 or 12, wherein a voltage u is outputted according to said Q axisqAfter the weak magnetic current is generated by the Q-axis voltage limiting threshold, the weak magnetic control module also feeds the weak magnetic current according to a preset amplitude limiting modelAnd limiting the line to enable the permanent magnet synchronous motor system to perform flux weakening control according to the flux weakening current after amplitude limiting.
14. The field weakening control device of a permanent magnet synchronous motor system according to claim 8, wherein a field weakening control bandwidth is smaller than the D-axis current closed loop bandwidth and is greater than 2 times the frequency of an alternating current power supply input to the permanent magnet synchronous motor system.
15. A permanent magnet synchronous motor system, characterized in that it comprises a field weakening control device of a permanent magnet synchronous motor system according to any of the claims 8-14.
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