CN112448654A - Method and system for controlling magnetic suspension motor - Google Patents
Method and system for controlling magnetic suspension motor Download PDFInfo
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- CN112448654A CN112448654A CN201910815673.5A CN201910815673A CN112448654A CN 112448654 A CN112448654 A CN 112448654A CN 201910815673 A CN201910815673 A CN 201910815673A CN 112448654 A CN112448654 A CN 112448654A
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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
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
- H02P29/028—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the motor continuing operation despite the fault condition, e.g. eliminating, compensating for or remedying the fault
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
- H02H7/09—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors against over-voltage; against reduction of voltage; against phase interruption
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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
- H02P27/085—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 wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
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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
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/032—Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/72—Electric energy management in electromobility
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Abstract
The invention discloses a method and a system for controlling a magnetic suspension motor, comprising the following steps: when the network voltage drop phenomenon occurs, acquiring and detecting the direct current bus voltage and/or the feedback rotating speed of the magnetic suspension motor in real time, and determining the type of the current network voltage drop phenomenon based on the direct current bus voltage and/or the feedback rotating speed; according to the network voltage drop phenomenon type, a coping drive instruction which is consistent with the network voltage drop phenomenon type is generated in a self-adaptive manner; the frequency converter performs voltage closed-loop control on the direct current bus voltage by using the coping drive instruction and performs speed closed-loop control on the real-time rotating speed of the magnetic suspension motor, so that the magnetic suspension motor can avoid undervoltage fault and safely operate or be controlled to stop under the control of obtaining an input voltage signal after voltage closed-loop control. The invention enhances the power grid adaptability of the magnetic suspension motor, protects the magnetic suspension motor bearing when the network voltage drops, and prolongs the service life of the device.
Description
Technical Field
The invention relates to the technical field of photoelectric motor control, in particular to a method and a system for controlling a magnetic suspension motor when network voltage drops.
Background
The network voltage drop problem becomes one of the most serious dynamic power quality problems affecting the normal and safe operation of many electric equipment. The network voltage drop is caused by severe weather (such as lightning strike, storm and the like), system faults (such as system single-phase-to-ground faults and the like) and sudden start of some large loads (such as large motors, steel-making electric arc furnaces and the like) along with serious current distortion phenomena and the like, and the abnormal work or the faults of the equipment caused by factors which can not be reached by manpower need to be controlled reasonably aiming at the special condition to ensure that the equipment is safe for passing the network voltage drop period.
For expensive electric equipment such as a magnetic suspension motor, manufacturers or users usually start the magnetic suspension motor through a frequency converter in a soft mode, and the magnetic suspension motor is driven in a variable frequency mode and normal operation of the magnetic suspension motor is guaranteed. However, the magnetic suspension motor is sensitive to network voltage drop, and when the frequency converter is stopped due to failure caused by network voltage drop, the magnetic suspension motor loses the control of the frequency converter, and a magnetic suspension bearing of the magnetic suspension motor touches and rubs the inner wall of the motor to cause the motor to be damaged. Particularly, when the magnetic suspension motor is still in a high-speed state during the network voltage drop, the conventional variable-frequency driving magnetic suspension motor stops the magnetic suspension motor in an undervoltage fault mode, and at the moment, the magnetic suspension bearing is greatly damaged by the fault stop in an uncontrolled state, so that the service life is influenced.
At present, aiming at the abnormal work or fault of equipment caused by the non-manpower accessible factor of network voltage drop, a frequency converter often stops a magnetic suspension motor in the form of under-voltage fault. In addition, in the prior art, a related technical scheme for controlling a magnetic suspension motor to enable the magnetic suspension motor to stably pass through the network voltage drop period is not provided.
Disclosure of Invention
One of the technical problems to be solved by the invention is to provide a control strategy for a magnetic suspension motor when the network voltage drops, so that the magnetic suspension motor can be ensured to be in a safe state when the network voltage drops continuously, magnetic suspension motor equipment can safely pass the network voltage drop period, and the adaptability and reliability of a power grid are enhanced.
In order to solve the above technical problem, the present invention provides a method for controlling a magnetic levitation motor, including: step one, when a network voltage drop phenomenon occurs, acquiring and detecting the direct current bus voltage and/or the feedback rotating speed of a magnetic suspension motor in real time, and determining the type of the current network voltage drop phenomenon based on the direct current bus voltage and/or the feedback rotating speed; step two, adaptively generating a coping drive instruction which is consistent with the type of the network pressure drop phenomenon according to the type of the network pressure drop phenomenon; and thirdly, the frequency converter performs voltage closed-loop control on the direct-current bus voltage by using the corresponding driving instruction and performs speed closed-loop control on the real-time rotating speed of the magnetic suspension motor connected with the frequency converter, so that the magnetic suspension motor is prevented from running safely or stopping in a controlled manner due to undervoltage faults under the control of obtaining an input voltage signal after the voltage closed-loop control.
Preferably, in step two, the method comprises the following steps: when the network voltage drop phenomenon type is short-time unrecoverable, generating a deceleration driving control instruction containing preset deceleration rate and minimum running speed information, so that the frequency converter respectively performs voltage closed-loop control and speed closed-loop control by using the deceleration driving control instruction, and the magnetic suspension motor is controlled to perform deceleration running at the deceleration rate; and further generating a pulse-sealing driving control instruction when the feedback rotating speed is detected to reach the minimum operating speed, so that the frequency converter respectively performs the voltage closed-loop control and the speed closed-loop control by using the pulse-sealing driving control instruction, and the magnetic suspension motor is controlled to stop.
Preferably, in the second step, the method further comprises: and when the network voltage drop phenomenon type is short-time restorable, generating a low-voltage ride through drive control command, so that the frequency converter respectively performs the voltage closed-loop control and the speed closed-loop control by using the low-voltage ride through drive control command, thereby controlling the magnetic suspension motor to safely operate at a low speed.
Preferably, in the first step, if the dc bus voltage is lower than a preset dc bus safe voltage threshold, and the dc bus voltage cannot be maintained at the dc bus safe voltage threshold within a preset bus safe voltage maintaining time threshold, it is determined that the current network voltage drop phenomenon is in a short-time unrecoverable state; and if the direct-current bus voltage is lower than the direct-current bus safe voltage threshold and the direct-current bus voltage can be maintained at the direct-current bus safe voltage threshold or is lifted to be higher than the direct-current bus safe voltage threshold within the bus safe voltage maintaining time threshold, judging that the type of the current network voltage drop phenomenon is a short-time restorable state.
Preferably, in the step one, the method further comprises: and when the network voltage drop phenomenon does not occur at present, generating a normal operation instruction, so that the frequency converter continues to drive the magnetic suspension motor to operate according to the original control strategy under the instruction of the normal operation instruction.
The invention also provides a system for controlling the magnetic suspension motor, which utilizes the method to realize the protection function of avoiding the magnetic suspension motor from being damaged due to undervoltage fault when the network voltage drops, and the system comprises: the network voltage drop protection control device is used for acquiring and detecting the direct-current bus voltage and/or the feedback rotating speed of the magnetic suspension motor in real time when the network voltage drop phenomenon occurs, determining the type of the current network voltage drop phenomenon based on the acquisition and detection, and then adaptively generating a response driving instruction which is consistent with the type of the network voltage drop phenomenon according to the type of the network voltage drop phenomenon; and the frequency converter is connected with the network voltage drop protection control device and is used for performing voltage closed-loop control on the direct-current bus voltage by utilizing the coping drive instruction and performing speed closed-loop control on the real-time rotating speed of the magnetic suspension motor connected with the frequency converter, so that the magnetic suspension motor is prevented from undervoltage fault and running safely or stopping in a controlled manner under the control of obtaining an input voltage signal after the voltage closed-loop control.
Preferably, the network pressure drop protection and control device comprises: the first strategy generation module is configured to generate a deceleration driving control instruction containing preset deceleration rate and minimum operating speed information when the network voltage drop phenomenon type is short-time unrecoverable, so that the frequency converter performs the voltage closed-loop control and the speed closed-loop control respectively by using the deceleration driving control instruction, thereby controlling the magnetic suspension motor to perform deceleration operation at the deceleration rate, and further generates a pulse-sealing driving control instruction when it is detected that the feedback rotation speed reaches the minimum operating speed, so that the frequency converter performs the voltage closed-loop control and the speed closed-loop control respectively by using the pulse-sealing driving control instruction, thereby controlling the magnetic suspension motor to stop under control.
Preferably, the network pressure drop protection and control device further comprises: and the second strategy generation module is used for generating a low-voltage ride-through driving control command when the network voltage drop phenomenon type is short-time recoverable, so that the frequency converter respectively performs the voltage closed-loop control and the speed closed-loop control by using the low-voltage ride-through driving control command, thereby controlling the low-speed safe operation of the magnetic suspension motor.
Preferably, the network pressure drop protection and control device further comprises: the network voltage drop type identification module is used for determining the type of the current network voltage drop phenomenon, wherein if the direct-current bus voltage is lower than a preset direct-current bus safety voltage threshold value and the direct-current bus voltage cannot be maintained at the direct-current bus safety voltage threshold value within a preset bus safety voltage maintenance time threshold value, the type of the current network voltage drop phenomenon is judged to be in a short-time unrecoverable state; further, in the present invention,
and if the direct-current bus voltage is lower than the direct-current bus safe voltage threshold and the direct-current bus voltage can be maintained at the direct-current bus safe voltage threshold or is lifted to be higher than the direct-current bus safe voltage threshold within the bus safe voltage maintaining time threshold, judging that the type of the current network voltage drop phenomenon is a short-time restorable state.
Preferably, the network voltage drop type identification module is further configured to generate a normal operation instruction when a network voltage drop phenomenon does not occur currently, so that the frequency converter continues to drive the magnetic suspension motor to operate according to an original control strategy under the instruction of the normal operation instruction.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
the invention provides a method and a system for controlling a magnetic suspension motor during network voltage drop, which can self-adaptively select a magnetic suspension motor control strategy in a network voltage drop period according to the current network voltage condition by introducing a network voltage drop protection control device, and can seamlessly switch the control mode according to the network voltage recovery condition. The magnetic suspension motor control strategy provided by the invention enhances the power grid adaptability of the magnetic suspension motor when the grid voltage drops, protects the magnetic suspension motor bearing when the grid voltage drops, and prolongs the service life of the magnetic suspension motor.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a step diagram of a method for controlling a magnetic levitation motor according to an embodiment of the present application.
Fig. 2 is a detailed flowchart of a method for controlling a magnetic levitation motor according to an embodiment of the present application.
Fig. 3 is a schematic diagram illustrating a control principle of a frequency converter for a magnetic levitation motor when a network voltage drops in the method for controlling a magnetic levitation motor according to the embodiment of the present application.
Fig. 4 is a schematic structural diagram of a system for controlling a magnetic levitation motor according to an embodiment of the present application.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
The network voltage drop problem becomes one of the most serious dynamic power quality problems affecting the normal and safe operation of many electric equipment. The network voltage drop is caused by severe weather (such as lightning strike, storm and the like), system faults (such as system single-phase-to-ground faults and the like) and sudden start of some large loads (such as large motors, steel-making electric arc furnaces and the like) along with serious current distortion phenomena and the like, and the abnormal work or the faults of the equipment caused by factors which can not be reached by manpower need to be controlled reasonably aiming at the special condition to ensure that the equipment is safe for passing the network voltage drop period.
For expensive electric equipment such as a magnetic suspension motor, manufacturers or users usually start the magnetic suspension motor through a frequency converter in a soft mode, and the magnetic suspension motor is driven in a variable frequency mode and normal operation of the magnetic suspension motor is guaranteed. However, the magnetic suspension motor is sensitive to network voltage drop, and when the frequency converter is stopped due to failure caused by network voltage drop, the magnetic suspension motor loses the control of the frequency converter, and a magnetic suspension bearing of the magnetic suspension motor touches and rubs the inner wall of the motor to cause the motor to be damaged. Particularly, when the magnetic suspension motor is still in a high-speed state during the network voltage drop, the conventional variable-frequency driving magnetic suspension motor stops the magnetic suspension motor in an undervoltage fault mode, and at the moment, the magnetic suspension bearing is greatly damaged by the fault stop in an uncontrolled state, so that the service life is influenced.
At present, aiming at the abnormal work or fault of equipment caused by the non-manpower accessible factor of network voltage drop, a frequency converter often stops a magnetic suspension motor in the form of under-voltage fault. In addition, in the prior art, a related technical scheme for controlling a magnetic suspension motor to enable the magnetic suspension motor to stably pass through the network voltage drop period is not provided.
In order to solve the technical problem, the invention provides a method and a system for controlling a magnetic suspension motor when the net pressure drops. The method and the system can utilize the network voltage drop protection control device to identify whether the network voltage drop phenomenon occurs currently, determine the type of the phenomenon when the phenomenon occurs, adaptively select the control strategy of the magnetic suspension motor when the network voltage drops, and seamlessly switch the control mode according to the recovery condition of the network voltage, so that the magnetic suspension motor can be controlled to decelerate and stop when the network voltage continuously drops and can not be recovered in a short time, and the magnetic suspension motor is stopped by low-speed safe power failure; and after the low voltage ride through of the magnetic suspension motor can be controlled when the network voltage continuously drops and can be recovered in a short time, the network voltage is recovered to the normal network voltage in time and continuously and stably operates, the network voltage dropping period is safely passed, the network adaptability of the magnetic suspension motor is enhanced, and the bearing of the magnetic suspension motor is protected.
It should be noted that the conventional magnetic levitation motor control system (i.e., the frequency converter 20) includes: the magnetic suspension type alternating current motor comprises a direct current voltage control link, a speed link, a current link, a torque link, a flux weakening link, a modulation link, a rectification unit, an inversion unit and the like, wherein an external three-phase alternating current power supply (a power grid power supply) can be supplied to the inversion unit through a public direct current bus in a middle direct current loop after being rectified, and the inversion unit inverts direct current into three-phase alternating current (the following input voltage signal) with adjustable frequency and voltage and supplies power to the alternating current magnetic suspension motor so as to meet the requirement of motor driving. Based on the above, the invention provides a method and a system for controlling a magnetic suspension motor during network voltage drop, which is characterized in that a network voltage drop protection control device 10 is added on the basis of the existing frequency converter control system, and the network voltage drop protection control device 10 is used for adaptively selecting a control mode during network voltage drop. The network voltage drop protection control device 10 of the present invention may be configured in an upper computer for controlling the frequency converter 20, and may also be integrated in a dc voltage control link (dc voltage acquisition link) inside the frequency converter 20, which is not specifically limited in the present invention. In addition, in the embodiment of the present invention, the frequency converter 20 driving the magnetic levitation motor to be controlled may be in a diode rectification mode, or may be in a four-quadrant rectification mode, which is not particularly limited by the present invention.
Fig. 1 is a step diagram of a method for controlling a magnetic levitation motor according to an embodiment of the present application. As shown in fig. 1, the magnetic levitation motor control method of the present invention includes the following steps: step S110, when the network voltage drop protection control device 10 determines that the current network voltage drop phenomenon occurs, the direct current bus voltage and/or the feedback rotating speed of the magnetic suspension motor are/is acquired and detected in real time, and based on the acquired direct current bus voltage and/or the feedback rotating speed, the type of the current network voltage drop phenomenon is determined; step S120, the network voltage drop protection control device 10 generates a corresponding driving instruction which is in accordance with the current network voltage drop phenomenon type in a self-adaptive manner according to the network voltage drop phenomenon type; then, step S130, the frequency converter 20 receives the corresponding driving instruction generated in step S120, and performs voltage closed-loop control on the dc bus voltage in the frequency converter 20 and speed closed-loop control on the real-time rotation speed of the magnetic levitation motor 30 (to be controlled) connected to the frequency converter 20 by using the current corresponding driving instruction, so that the magnetic levitation motor 30 can avoid undervoltage fault and operate safely or stop under control under the control of obtaining the input voltage signal after the voltage closed-loop control.
Fig. 2 is a detailed flowchart of a method for controlling a magnetic levitation motor according to an embodiment of the present application. The magnetic levitation motor control method according to the present invention will be described in detail with reference to fig. 1 and 2.
First, in step S110, the determination process of the current network voltage drop phenomenon type is completed through the following steps S201 to S205.
Specifically, in step S201, the grid voltage drop protection control device 10 collects and detects the grid voltage in real time. Then, in step S202, the network voltage drop protection and control device 10 determines whether a network voltage drop phenomenon occurs currently according to the collected network voltage. If the current grid voltage is continuously lower than the preset grid safe operation voltage threshold and is not recovered within the preset grid detection time threshold, the current grid voltage drop phenomenon occurs, and the step S203 is performed; otherwise (if the current grid voltage is continuously higher than the grid safe operation voltage threshold within the grid detection time threshold, or if the current grid voltage is lower than the grid safe operation voltage threshold but recovers within the grid detection time threshold), the grid voltage drop phenomenon does not occur, and the process proceeds to step S205. It should be noted that, the power grid detection time threshold and the power grid safe operation voltage threshold are not specifically limited, and those skilled in the art can set the thresholds according to actual situations.
Then, when the network voltage drop protection control device 10 determines that the current drop phenomenon occurs, the process proceeds to step S203. Step S203, the network voltage drop protection control device 10 acquires and detects the dc bus voltage in the frequency converter 20 and/or the real-time rotation speed (feedback rotation speed) fed back by the magnetic levitation motor 30 to be controlled connected to the current frequency converter 20 in real time, so as to enter step S204. Referring to fig. 3, in general, in the case of the existing variable frequency driving magnetic levitation motor, the driving of the magnetic levitation motor 30 by the frequency converter 20 includes two aspects: one is the closed-loop control of the voltage on the dc bus (not shown) of the intermediate dc link and the other is the closed-loop control of the operating speed of the motor 30 to be controlled. Therefore, the network voltage drop protection control device 10 can acquire the real-time rotating speed fed back by the magnetic suspension motor 30 to be controlled in real time through the output of the frequency converter 20 for closed-loop control of the operating speed of the motor 30 to be controlled. In the embodiment of the present invention, the collection mode of the motor speed signal collected in the speed closed-loop control process may be an encoder mode or a non-encoder mode, which is not specifically limited in the present invention.
Step S204, the network voltage drop protection control device 10 determines the type of the current network voltage drop phenomenon according to the real-time collected dc bus voltage and/or the real-time feedback rotation speed of the magnetic suspension motor 30 to be controlled. In the embodiment of the present invention, the types of the net pressure drop phenomenon include: a short unrecoverable state and a short recoverable state.
Specifically, in one embodiment, if the network voltage drop protection control device 10 detects that the current dc bus voltage is lower than the preset dc bus safe voltage threshold, and the dc bus voltage cannot be maintained at the dc bus safe voltage threshold within the preset bus safe voltage maintaining time threshold, it determines that the current network voltage drop phenomenon is in the short-time unrecoverable state. In another embodiment, if the network voltage drop protection control device 10 detects that the current dc bus voltage is lower than the dc bus safe voltage threshold, and the dc bus voltage can be maintained at the dc bus safe voltage threshold within the bus safe voltage maintaining time threshold, or quickly rises above the dc bus safe voltage threshold (that is, reaches the bus voltage when the frequency converter normally works), it determines that the current network voltage drop phenomenon is in a short-time recoverable state. It should be noted that, the safety voltage threshold of the dc bus (i.e. the lowest safety voltage of the dc bus when the frequency converter 20 normally operates) and the bus safety voltage maintaining time threshold are not specifically limited in the present invention, and those skilled in the art can set the safety voltage threshold according to actual situations.
In addition, step S110 in the present invention further includes step S205. Step S205 is that when the network voltage drop protection control device 10 determines that the current drop phenomenon does not occur, the network voltage drop protection control device 10 generates a normal operation instruction and sends the normal operation instruction to the frequency converter 20, so that the frequency converter 20 continues to drive the current magnetic suspension motor 30 to be controlled to normally operate according to the original control strategy under the instruction of the current normal operation instruction. The original control strategy is selected from one of the overall control modes of the motor, such as a vector control strategy, direct torque control and the like.
Thus, the present invention determines whether the network voltage drop phenomenon occurs currently through the above-mentioned manner, and further determines the type of the network voltage drop phenomenon after determining that the network voltage drop phenomenon occurs, so that the network voltage drop protection control device 10 adaptively selects a corresponding control strategy according to different phenomenon types through the following steps S120 and S130, and protects the magnetic suspension motor 30 to be controlled, so that the magnetic suspension motor can safely and stably pass through the network voltage drop period.
In step S120, the following steps S206 to S207 complete the adaptive generation process of the coping strategy when the current network voltage drops.
Specifically, in step S206, when the network voltage drop protection control device 10 determines that the current network voltage drop phenomenon type is short-term unrecoverable, the network voltage drop protection control device 10 adaptively generates a deceleration driving control command including information of a preset (first) deceleration rate and a preset minimum motor operating speed (the minimum motor operating speed is determined according to the intrinsic operating parameters of the current motor 30 to be controlled), so that the frequency converter 20 respectively performs the voltage closed-loop control and the speed closed-loop control by using the current deceleration driving control command, thereby controlling the current magnetic suspension motor 30 to be controlled to perform deceleration operation at the first deceleration rate. Then, when the network voltage drop protection control device 10 detects that the current feedback rotation speed reaches the minimum operation speed in real time, it further generates a pulse-sealing driving control instruction in a self-adaptive manner, so that the frequency converter 20 performs the voltage closed-loop control and the speed closed-loop control respectively by using the current pulse-sealing driving control instruction, thereby controlling the controlled shutdown of the magnetic suspension motor 30.
Fig. 3 is a schematic diagram illustrating a control principle of a frequency converter for a magnetic levitation motor when a network voltage drops in the method for controlling a magnetic levitation motor according to the embodiment of the present application.
When the network voltage drops continuously and cannot recover for a short time, the intermediate dc voltage (dc bus voltage) U on the dc bus in the frequency converter 20 will be generateddc_rtAppear to be fixedThe degree of falling is not maintained at the safe voltage threshold U of the direct current busdc_holdTo (3). At this time, as shown in fig. 3, after receiving the deceleration drive control command, the inverter 20 uses the deceleration drive control command to realize the dc bus voltage U according to the (first) deceleration rate and the minimum operating speeddc_rtVoltage closed-loop control of and the output N to the rotational speed (feedback speed, speed closed-loop control according to the invention) of the magnetic levitation motorr_backSo that U is controlleddc_rt<Udc_holdAnd feed back the rotational speed Nr_backDecelerating to a minimum operating speed N with a certain sloper_min. The frequency converter 20 then drives the control command after receiving the seal pulse, i.e., Nr_back≤Nr_minAt this time, the frequency converter 20 performs the pulse-sealing control under the instruction of the current pulse-sealing driving control instruction, so that the current magnetic suspension motor 30 to be controlled is controlled at the low speed Nr_minAnd the controlled shutdown is not the undervoltage fault high-speed shutdown, so that the magnetic suspension bearing damage caused by the uncontrolled state fault shutdown of the magnetic suspension motor 30 to be controlled in the high-speed running state is avoided.
Specifically, referring to fig. 3, first, the grid voltage drop protection control device 10 determines the current bus voltage real-time value U according to the current bus voltage real-time value Udc_rtWhether the voltage is lower than a bus safety voltage threshold value Udc_holdJudging whether to perform motor deceleration control, if Udc_rt<Udc_holdThen the control of the magnetic levitation motor 30 to be controlled to decelerate by the frequency converter 20 is started.
The DC voltage closed loop control input into the inverter 20 is then the current bus voltage real time value Udc_rtAnd the feedback rotating speed N of the magnetic suspension motorr_backThe output quantity is the stator current isAnd obtaining the AC and DC axis current reference instruction i through current loop distribution (maximum torque current ratio control and flux weakening control)q_refAnd id_ref(wherein, the quadrature axis current instruction i output by the maximum torque current ratio control link is obtained after the maximum torque current ratio controlq_mtpaAnd a direct-axis current instruction i output by the maximum torque-current ratio control linkd_mtpa) And further passing a current PI control (reference command I for alternating and direct axis currentq_refAnd id_refRespectively with quadrature axis current feedback value i processed by coordinate transformationq_backDirect axis current feedback value id_backAfter differential processing, current PI control is carried out, and corresponding quadrature axis voltage instruction u is outputq_refAnd direct axis voltage command ud_ref) Optimal regulation strategy control (through quadrature axis voltage command u)q_refAnd direct axis voltage command ud_refAnd receives the rotor position angle theta of the motor 30 to be controlled detected in real time, and performs modulation control according to the information to obtain a corresponding three-phase PWM pulse signal Sa、Sb、Sc) And inverter control for distributing the three-phase modulation voltages (input voltage signals acquired by the magnetic levitation motor 30 to be controlled) Ua, Ub, Uc at this time to drive the magnetic levitation motor 30. Wherein U isdc_rtFor determining whether motor deceleration control is required, Nr_backFor the minimum operation speed stop judgment, in this case, the motor deceleration control process is to decelerate from the current rotating speed to the minimum operation speed N according to a fixed slope (a certain first deceleration rate K1)r_min。
Further, the first deceleration rate is expressed by the following expression (1):
wherein N isr_ratedFor the rated rotation speed of the magnetic levitation motor 30 to be controlled, Δ t is the deceleration time corresponding to the deceleration control in the short-time unrecoverable state, and the deceleration time is adjusted according to the actual demand, thereby adjusting the deceleration change frequency.
Subsequently, the magnetic levitation motor 30 to be controlled is decelerated to a minimum operating speed N under the control of the frequency converter 20r_minThen, the network voltage drop protection control device 10 performs closed-loop control on the passing speed (the closed-loop control of the speed is that A, B phase output current i of the magnetic suspension motor 30 to be controlled is monitored in real timea、ibAnd the rotor position angle theta is subjected to coordinate transformation processing, so that a quadrature axis current feedback value i is obtainedq_backDirect axis current feedback value id_backThen according to quadrature axis current feedback value iq_backDirect axis current feedback value id_backAnd the AC/DC axis voltage command u outputted by the sum current PI controlq_ref、ud_refCalculating the feedback rotating speed to obtain the real-time feedback rotating speed Nr_back) The obtained real-time feedback speed is judged, and whether the feedback rotating speed of the magnetic suspension motor meets N is specifically judgedr_back≤Nr_minCondition, i.e. whether the stop controlled condition is satisfied, is based on the feedback speed N of the magnetic levitation motorr_backTo select whether to perform pulse-sealing control when N isr_back≤Nr_minAt this time, the output of the modulated voltage pulse in the frequency converter 20 is blocked by the blocking pulse drive control command.
Further, in step S207, when the network voltage drop protection control device 10 determines that the current network voltage drop phenomenon type is short-term recoverable, the network voltage drop protection control device 10 adaptively generates a low-voltage ride-through drive control instruction containing information of a low-voltage ride-through low-speed value and a low-voltage ride-through deceleration rate, so that the frequency converter 20 respectively performs the voltage closed-loop control and the speed closed-loop control by using the current low-voltage ride-through drive control instruction, thereby controlling the current to-be-controlled magnetic levitation motor 30 to perform deceleration operation at the low-voltage ride-through deceleration rate, performing low-speed safe operation after reaching a rotation speed conforming to the low-voltage ride-through low-speed value until the network voltage is recovered to normal, and then controlling the magnetic levitation motor 30 by using the frequency converter 20 according to the original closed-loop control strategy under the instruction of the normal operation, so that the magnetic suspension motor 30 to be controlled is stable in the network voltage falling period.
Referring to fig. 3, when the grid voltage drops for a short time and recovers to the normal grid voltage in time, the intermediate dc voltage (dc bus voltage) on the dc bus in the frequency converter 20 will drop to a certain extent, but can be maintained at least at the dc bus safety voltage threshold Udc_holdTo (3). At this time, as shown in fig. 3, after receiving the low voltage ride through drive control command, the frequency converter 20 uses the low voltage ride through drive control command to perform the low voltage ride through according to the low voltage ride through commandThe more the speed reduction rate and the low voltage ride through the low speed value, the DC bus voltage U is realizeddc_rtVoltage closed-loop control and control of the speed (feedback speed) N of a magnetic levitation motorr_backThe speed closed-loop control of the motor enables the magnetic suspension motor 30 to be controlled to firstly carry out speed reduction operation according to the low-voltage ride-through speed reduction rate and carry out low-speed safe operation at the rotating speed which is consistent with the low-voltage ride-through low-speed value until the network voltage returns to normal and the intermediate direct-current voltage U isdc_rtAnd (4) recovering the normal value (namely at least reaching the safe voltage threshold value of the direct current bus), thereby controlling the magnetic suspension motor 30 to continue to normally operate and stabilizing the grid voltage falling period.
Specifically, referring to fig. 3, first, the grid voltage drop protection control device 10 determines the current bus voltage real-time value U according to the current bus voltage real-time value Udc_rtWhether the voltage is lower than a bus safety voltage threshold value Udc_holdAnd can be maintained at the safe voltage threshold U of the direct current bus within the safe voltage maintenance time threshold of the busdc_holdOr quickly raising the voltage to be higher than the safe voltage threshold of the direct current bus (namely, the bus voltage in normal work), and selecting whether to carry out low voltage ride through control.
The DC voltage closed loop control input into the inverter 20 is then the current bus voltage real time value Udc_rtAnd the feedback rotating speed N of the magnetic suspension motorr_backThe output quantity is the stator current isAnd obtaining the given value i of the quadrature-direct axis current through current loop distribution (maximum torque current ratio control and flux weakening control)d_refAnd iq_refAnd then the modulation voltages (input voltage signals) Ua, Ub and Uc at the moment are distributed through optimal regulation strategy control and inversion control to drive the magnetic suspension motor. If the current bus voltage real-time value Udc_rtLower than the bus safety voltage threshold Udc_holdAt this time, the grid voltage sag protection control device 10 starts deceleration control to generate a low voltage ride through drive control command including a low voltage ride through low speed value and low voltage ride through deceleration rate information, so that the magnetic levitation motor 30 to be controlled is decelerated to the low voltage ride through low speed value at a fixed slope (low voltage ride through deceleration rate K2) under the control of the frequency converter 20. Wherein, the low-voltage ride-through low-speed value is larger than the magnetic levitation potential to be controlledMinimum operating speed N of the engine 30r_min。
Further, the low-voltage ride-through deceleration rate is expressed by the following expression (2):
wherein N isr_ratedFor the rated rotation speed of the magnetic levitation motor 30 to be controlled, Δ t is the deceleration time corresponding to the deceleration control in the short-time restorable state, and the deceleration time is adjusted according to the actual requirement, thereby adjusting the real-time output rotation speed of the magnetic levitation motor 30 to be controlled.
At this time, after the grid voltage is slowly recovered, the current dc bus voltage bus reaches the normal operation level, that is, it is safe that the grid voltage drop phenomenon does not occur, the frequency converter 20 recovers the original control strategy, and distributes the stator current i through the dc voltage closed-loop controlsThen obtaining the given value i of the quadrature-direct axis current according to the current loop distributiond_refAnd iq_refAnd then the modulation voltages (input voltage signals) Ua, Ub and Uc at the moment are distributed through optimal regulation strategy control and inversion control to drive the magnetic suspension motor. Further, in the process of gradually recovering the voltage of the power grid, the current real-time feedback rotating speed Nr_backIs less than the preset safety threshold value N of the real-time rotating speed fed back by the running of the magnetic suspension motor 30 to be controlled in the original control strategy mode before the network voltage fallsr_setIn (1). Therefore, in this case, the network voltage drop protection control device 10 needs to send an acceleration operation control command containing information of the acceleration rate returning to the normal state to the frequency converter 20, so that the magnetic levitation motor 30 to be controlled is accelerated to operate at a preset fixed acceleration slope (i.e. the acceleration rate returning to the normal state) under the control of the frequency converter 20, thereby causing N to be detectedr_backAcceleration is adjusted to the above-mentioned safety threshold Nr_set。
Next, after determining the corresponding coping control strategy, the network voltage drop protection control device 10 proceeds to step S130, and completes the driving control process of the magnetic suspension motor 30 to be controlled when the frequency converter 20 drops the network voltage through the following steps S208 to S210.
Specifically, when the network voltage drop phenomenon type is short-term unrecoverable, the frequency converter 20 receives and analyzes the deceleration driving control instruction sent by the network voltage drop protection control device 10 in step S208, performs voltage closed-loop control on the dc bus voltage and performs speed closed-loop control on the rotational speed of the magnetic levitation motor 30 to be controlled connected to the frequency converter 20 according to the (first) deceleration rate and the minimum operating speed in the current analysis result, and provides the input voltage signal subjected to the current voltage closed-loop control to the magnetic levitation motor 30 to be currently controlled, so that the magnetic levitation motor 30 to be currently controlled performs deceleration operation at the current (first) deceleration rate by using the input voltage signal, and then the operation proceeds to step S209. Step S209 is to further receive and analyze the pulse-closed driving control command sent by the network voltage drop protection control device 10, perform voltage closed-loop control on the dc bus voltage and perform speed closed-loop control on the rotation speed of the magnetic levitation motor 30 to be controlled connected to the frequency converter 20 under the instruction of the current pulse-closed driving control command, and provide the input voltage signal after current voltage closed-loop control to the magnetic levitation motor 30 to be controlled, so that the magnetic levitation motor 30 to be controlled is controlled to stop by using the input voltage signal.
When the network voltage drop phenomenon type is short-time restorable, step S210 the frequency converter 20 receives and analyzes the low voltage ride through drive control command sent by the network voltage drop protection control device 10, according to the low voltage ride through low speed value and the low voltage ride through deceleration rate in the current analysis result, performs voltage closed-loop control on the dc bus voltage, performs speed closed-loop control on the rotation speed of the magnetic levitation motor 30 to be controlled connected with the frequency converter 20, and provides an input voltage signal subjected to current voltage closed-loop control to the magnetic levitation motor 30 to be controlled, so that the magnetic levitation motor 30 to be controlled uses the input voltage signal to firstly perform deceleration operation according to the low voltage ride through deceleration rate, and performs low-speed safe operation after reaching a feedback rotation speed corresponding to the low voltage ride through low speed value, until the magnetic levitation motor 30 to be controlled returns to normal operation under the instruction after the network voltage returns to a steady state, so that the magnetic levitation motor 30 currently to be controlled smoothly passes through a network voltage drop period of this type.
Thus, by the above technical solution, in the embodiment of the present invention, when the net pressure continuously drops and cannot be recovered in a short time, the magnetic suspension motor 30 is controlled to decelerate to a low speed for controlled shutdown; when the net pressure falls for a short time and can be recovered for a short time, low voltage ride through control is carried out, after the net pressure is timely recovered to the normal net pressure, the magnetic suspension motor 30 continues to operate normally, the net pressure falls for a stable degree, and the magnetic suspension motor bearing is protected.
On the other hand, the present invention is based on the above-mentioned magnetic levitation motor control method (method for controlling a magnetic levitation motor), and also provides a system for controlling a magnetic levitation motor, which can realize a protection function for preventing the magnetic levitation motor 30 to be controlled from being damaged due to an undervoltage fault when the grid voltage drops. Fig. 4 is a schematic structural diagram of a system for controlling a magnetic levitation motor according to an embodiment of the present application. As shown in fig. 4, the system includes: a network voltage drop protection control device 10 and a frequency converter 20 for controlling a magnetic levitation motor 30.
Specifically, the network voltage drop protection and control device 10, implemented according to the method described in the above step S110 and step S120, is configured to acquire and detect the dc bus voltage and/or the feedback rotation speed of the magnetic suspension motor in real time when the network voltage drop phenomenon occurs, determine the type of the current network voltage drop phenomenon based on the acquired feedback rotation speed, and then adaptively generate a response driving instruction according to the type of the network voltage drop phenomenon. The frequency converter 20, implemented according to the method described in step S130 above, is configured to perform voltage closed-loop control on the dc bus voltage in the frequency converter 20 and perform speed closed-loop control on the rotational speed of the magnetic levitation motor 30 connected to the frequency converter 20 by using the response driving command sent by the network voltage drop protection control device 10, so that the magnetic levitation motor 30 can avoid undervoltage fault and operate safely or stop under control under the control of obtaining the input voltage signal after the voltage closed-loop control.
Further, the above-mentioned net pressure drop protection and control device 10 includes: the network voltage drop type identification module 11, the first strategy generation module 12 and the second strategy generation module 13.
The network voltage drop type identifying module 11, implemented according to the method described in the above step S201 to step S205, is configured to collect and detect a network voltage in real time, determine whether a network voltage drop phenomenon occurs currently according to the collected network voltage, and further determine the type of the current network voltage drop phenomenon when it is determined that the current network voltage drop phenomenon occurs. The network voltage drop type identification module 11 is configured to determine that the current network voltage drop phenomenon is in a short-time unrecoverable state if it is detected that the dc bus voltage is lower than a preset dc bus safe voltage threshold and the dc bus voltage cannot be maintained at the dc bus safe voltage threshold within a preset bus safe voltage maintenance time threshold. And the network voltage drop type identification module 11 is further configured to determine that the current network voltage drop phenomenon is in a short-time recoverable state if it is detected that the dc bus voltage is lower than the dc bus safe voltage threshold and the dc bus voltage can be maintained at the dc bus safe voltage threshold or quickly rises above the dc bus safe voltage threshold within the bus safe voltage maintenance time threshold.
In addition, the network voltage drop type identification module 11 is further configured to generate a normal operation instruction when the network voltage drop phenomenon does not occur currently, so that the frequency converter 20 continues to drive the magnetic suspension motor 30 to operate normally according to the original control strategy under the instruction of the normal operation instruction.
Further, the first policy generating module 12, implemented according to the method described in the foregoing step S206 to step S207, is configured to generate a deceleration driving control instruction containing preset (first) deceleration rate and minimum operating speed information when the network voltage drop phenomenon type is short-term unrecoverable, so that the frequency converter 20 performs voltage closed-loop control and speed closed-loop control respectively by using the deceleration driving control instruction, thereby controlling the magnetic levitation motor 30 to perform deceleration operation at the (first) deceleration rate, and further generates a pulse-sealing driving control instruction when detecting that the feedback rotation speed reaches the minimum operating speed, so that the frequency converter 20 performs voltage closed-loop control and speed closed-loop control respectively by using the pulse-sealing driving control instruction, thereby controlling the magnetic levitation motor 30 to stop under control.
Further, the second strategy generating module 13, implemented according to the method described in the above step S208, is configured to generate a low voltage ride through driving control instruction when the network voltage drop phenomenon type is short-term recoverable, so that the frequency converter 20 performs voltage closed-loop control and speed closed-loop control respectively by using the low voltage ride through driving control instruction, thereby controlling the magnetic levitation motor to operate safely at a low speed.
The invention provides a method and a system for controlling a magnetic levitation motor when a network voltage drops. The invention introduces the network voltage drop protection control device, can self-adaptively select the magnetic suspension motor control strategy in the network voltage drop period according to the current network voltage condition by utilizing the device, and can seamlessly switch the control mode according to the network voltage recovery condition. Specifically, aiming at the condition that the network voltage continuously drops and cannot be recovered in a short time, the method ensures that the magnetic suspension motor is controlled to decelerate to a low-speed controlled stop rather than an undervoltage fault high-speed stop through the direct-current bus voltage closed-loop control and the speed closed-loop control; aiming at the condition that the network voltage drops in a short period and recovers to the normal network voltage in time, the low voltage ride through in the short-period network voltage drop period is carried out through the direct current bus voltage closed-loop control and the speed closed-loop control until the network voltage recovers to be normal, so that the magnetic suspension motor continues to operate normally and the network voltage drop period is stably passed. Therefore, the magnetic suspension motor control strategy provided by the invention enhances the power grid adaptability of the magnetic suspension motor when the grid voltage drops, protects the magnetic suspension motor bearing when the grid voltage drops, and prolongs the service life of the magnetic suspension motor.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method for controlling a magnetically levitated motor, comprising:
step one, when a network voltage drop phenomenon occurs, acquiring and detecting the direct current bus voltage and/or the feedback rotating speed of a magnetic suspension motor in real time, and determining the type of the current network voltage drop phenomenon based on the direct current bus voltage and/or the feedback rotating speed;
step two, adaptively generating a coping drive instruction which is consistent with the type of the network pressure drop phenomenon according to the type of the network pressure drop phenomenon;
and thirdly, the frequency converter performs voltage closed-loop control on the direct-current bus voltage by using the corresponding driving instruction and performs speed closed-loop control on the real-time rotating speed of the magnetic suspension motor connected with the frequency converter, so that the magnetic suspension motor is prevented from running safely or stopping in a controlled manner due to undervoltage faults under the control of obtaining an input voltage signal after the voltage closed-loop control.
2. The method according to claim 1, characterized in that in step two, it comprises:
when the network voltage drop phenomenon type is short-time unrecoverable, generating a deceleration driving control instruction containing preset deceleration rate and minimum running speed information, so that the frequency converter respectively performs voltage closed-loop control and speed closed-loop control by using the deceleration driving control instruction, and the magnetic suspension motor is controlled to perform deceleration running at the deceleration rate;
and further generating a pulse-sealing driving control instruction when the feedback rotating speed is detected to reach the minimum operating speed, so that the frequency converter respectively performs the voltage closed-loop control and the speed closed-loop control by using the pulse-sealing driving control instruction, and the magnetic suspension motor is controlled to stop.
3. The method according to claim 1 or 2, characterized in that in step two, further comprising:
and when the network voltage drop phenomenon type is short-time restorable, generating a low-voltage ride through drive control command, so that the frequency converter respectively performs the voltage closed-loop control and the speed closed-loop control by using the low-voltage ride through drive control command, thereby controlling the magnetic suspension motor to safely operate at a low speed.
4. A method according to any one of claims 1 to 3, wherein, in the first step,
if the direct-current bus voltage is lower than a preset direct-current bus safe voltage threshold value, and the direct-current bus voltage cannot be maintained at the direct-current bus safe voltage threshold value within a preset bus safe voltage maintaining time threshold value, judging that the type of the current network voltage drop phenomenon is a short-time unrecoverable state;
and if the direct-current bus voltage is lower than the direct-current bus safe voltage threshold and the direct-current bus voltage can be maintained at the direct-current bus safe voltage threshold or is lifted to be higher than the direct-current bus safe voltage threshold within the bus safe voltage maintaining time threshold, judging that the type of the current network voltage drop phenomenon is a short-time restorable state.
5. The method according to claim 4, wherein in the step one, further comprising:
and when the network voltage drop phenomenon does not occur at present, generating a normal operation instruction, so that the frequency converter continues to drive the magnetic suspension motor to operate according to the original control strategy under the instruction of the normal operation instruction.
6. A system for controlling a magnetic levitation motor, wherein the system implements a protection function for preventing the magnetic levitation motor from being damaged by an undervoltage fault when a network voltage drops by using the method of any one of claims 1 to 5, the system comprising:
the network voltage drop protection control device is used for acquiring and detecting the direct-current bus voltage and/or the feedback rotating speed of the magnetic suspension motor in real time when the network voltage drop phenomenon occurs, determining the type of the current network voltage drop phenomenon based on the acquisition and detection, and then adaptively generating a response driving instruction which is consistent with the type of the network voltage drop phenomenon according to the type of the network voltage drop phenomenon;
and the frequency converter is connected with the network voltage drop protection control device and is used for performing voltage closed-loop control on the direct-current bus voltage by utilizing the coping drive instruction and performing speed closed-loop control on the real-time rotating speed of the magnetic suspension motor connected with the frequency converter, so that the magnetic suspension motor is prevented from undervoltage fault and running safely or stopping in a controlled manner under the control of obtaining an input voltage signal after the voltage closed-loop control.
7. The system of claim 6, wherein the network pressure drop protection control device comprises: a first policy generation module, wherein,
the first strategy generation module is configured to generate a deceleration driving control instruction containing preset deceleration rate and minimum operating speed information when the network voltage drop phenomenon type is short-term unrecoverable, so that the frequency converter performs the voltage closed-loop control and the speed closed-loop control respectively by using the deceleration driving control instruction, thereby controlling the magnetic levitation motor to perform deceleration operation at the deceleration rate, and further generates a pulse-sealing driving control instruction when it is detected that the feedback rotation speed reaches the minimum operating speed, so that the frequency converter performs the voltage closed-loop control and the speed closed-loop control respectively by using the pulse-sealing driving control instruction, thereby controlling the magnetic levitation motor to stop in a controlled manner.
8. The system of claim 6 or 7, wherein the network pressure drop protection control device further comprises: a second policy generation module, wherein,
and the second strategy generation module is used for generating a low-voltage ride-through driving control instruction when the network voltage drop phenomenon type is short-time restorable, so that the frequency converter respectively performs the voltage closed-loop control and the speed closed-loop control by using the low-voltage ride-through driving control instruction, thereby controlling the magnetic suspension motor to safely operate at a low speed.
9. The system according to any one of claims 6 to 8, wherein the network pressure drop protection control device further comprises:
the network voltage drop type identification module is used for determining the type of the current network voltage drop phenomenon, wherein if the direct-current bus voltage is lower than a preset direct-current bus safety voltage threshold value and the direct-current bus voltage cannot be maintained at the direct-current bus safety voltage threshold value within a preset bus safety voltage maintenance time threshold value, the type of the current network voltage drop phenomenon is judged to be in a short-time unrecoverable state; further, in the present invention,
and if the direct-current bus voltage is lower than the direct-current bus safe voltage threshold and the direct-current bus voltage can be maintained at the direct-current bus safe voltage threshold or is lifted to be higher than the direct-current bus safe voltage threshold within the bus safe voltage maintaining time threshold, judging that the type of the current network voltage drop phenomenon is a short-time restorable state.
10. The system of claim 9,
and the network voltage drop type identification module is also used for generating a normal operation instruction when the network voltage drop phenomenon does not occur at present, so that the frequency converter continues to drive the magnetic suspension motor to operate according to the original control strategy under the instruction of the normal operation instruction.
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