Loss-of-field detection method and system for permanent magnet motor and related components
阅读说明：本技术 一种永磁电机的失磁检测方法、系统及相关组件 (Loss-of-field detection method and system for permanent magnet motor and related components ) 是由 沈文 王二峰 吴轩钦 王宇 于 2020-06-30 设计创作，主要内容包括：本申请公开了一种永磁电机的失磁检测方法,应用于驱动永磁电机运行的变频器,包括：当永磁电机处于停机过程,获取永磁电机对应的参考电压和转速；根据参考电压和转速计算实际转子磁链；利用实际转子磁链确定永磁电机的状态,状态包括失磁状态或未失磁状态。本申请通过电机控制系统中既有的变频器实现永磁电机的失磁检测,不需要额外的硬件和仪器设备,也不需要提前对永磁电机进行标定,工程实用性强,且在每次永磁电机的停机过程中,均可以对永磁电机进行失磁检测,实现重复检测的目的,提高永磁电机运行的可靠性和安全性。本申请还公开了一种永磁电机的失磁检测装置、电子设备及计算机可读存储介质,具有以上有益效果。(The application discloses a method for detecting loss of field of a permanent magnet motor, which is applied to a frequency converter for driving the permanent magnet motor to operate and comprises the following steps: when the permanent magnet motor is in a shutdown process, acquiring a reference voltage and a rotating speed corresponding to the permanent magnet motor; calculating an actual rotor flux linkage according to the reference voltage and the rotating speed; and determining the state of the permanent magnet motor by utilizing the actual rotor flux linkage, wherein the state comprises a loss-of-field state or a non-loss-of-field state. This application realizes permanent magnet motor's demagnetization through existing converter among the motor control system and detects, does not need extra hardware and instrument and equipment, also need not mark permanent magnet motor in advance, and the engineering practicality is strong, and at permanent magnet motor's the shut down in-process at every turn, all can carry out the demagnetization to permanent magnet motor and detect, realizes the purpose of repeated detection, improves permanent magnet motor reliability and security of operation. The application also discloses a loss of field detection device of the permanent magnet motor, electronic equipment and a computer readable storage medium, which have the beneficial effects.)
1. A method for detecting loss of field of a permanent magnet motor is applied to a frequency converter for driving the permanent magnet motor to operate, and comprises the following steps:
when the permanent magnet motor is in a shutdown process, acquiring a reference voltage and a rotating speed corresponding to the permanent magnet motor;
calculating an actual rotor flux linkage according to the reference voltage and the rotating speed;
and determining the state of the permanent magnet motor by utilizing the actual rotor flux linkage, wherein the state comprises a loss-of-field state or a non-loss-of-field state.
2. The method for detecting loss of field according to claim 1, wherein before obtaining the reference voltage and the rotation speed corresponding to the permanent magnet motor, the method further comprises:
when the permanent magnet motor is in a shutdown process, judging whether the running state of the permanent magnet motor meets a loss-of-field detection condition;
correspondingly, the process of acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor specifically comprises the following steps:
and when the running state meets the loss-of-field detection condition, acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor.
3. The method according to claim 2, wherein the step of determining whether the operating state of the permanent magnet motor meets the condition for detecting loss of field specifically comprises:
acquiring the running state of the permanent magnet motor, wherein the running state comprises the state of a stator winding of the permanent magnet motor;
and when the state of the stator winding is an open circuit state, judging that the running state of the permanent magnet motor meets the loss-of-field detection condition.
4. The method for detecting loss of field according to claim 1, wherein the process of obtaining the reference voltage and the rotating speed corresponding to the permanent magnet motor specifically comprises:
acquiring reference voltage and rotating speed corresponding to the permanent magnet motor according to a preset period;
correspondingly, the process of calculating the actual rotor flux linkage according to the reference voltage and the rotating speed specifically includes:
calculating the rotor flux linkage corresponding to the current acquisition period according to the reference voltage and the rotating speed acquired by the current acquisition period, and updating the rotor flux linkage calculation times;
and when the calculation times of the rotor flux linkages reach preset times, calculating the average value of all the rotor flux linkages, and taking the average value as the actual rotor flux linkages.
5. The method according to claim 1, wherein the process of determining the state of the permanent magnet motor using the actual rotor flux linkage specifically comprises:
determining a target rotor flux linkage;
judging whether the difference value of the actual rotor flux linkage and the target rotor flux linkage is in a preset range or not;
if so, judging that the state of the permanent magnet motor is the non-loss-of-field state;
and if not, judging that the state of the permanent magnet motor is the field loss state.
6. The method according to claim 5, wherein the process of determining the target rotor flux linkage specifically comprises:
judging whether the permanent magnet motor is a new motor or not;
if so, determining the rated rotor flux linkage of the permanent magnet motor as the target rotor flux linkage;
if not, determining the reference rotor flux linkage of the permanent magnet motor as the target rotor flux linkage, wherein psip＝k·ψrN，ψpFor said reference rotor flux linkage, psirNK is more than 0 and less than or equal to 1 for the rated rotor flux linkage.
7. A method of detecting loss of field according to any of claims 1-6, wherein the shutdown process comprises a free shutdown process or a slowed down shutdown process;
correspondingly, the reference voltage corresponding to the motor is the line voltage of the output end of the frequency converter.
8. The loss of field detection method of claim 7, further comprising:
when the permanent magnet motor is in the deceleration shutdown process, the reference current of the d axis and the reference current of the q axis are both set to be 0, and the state of the stator winding of the permanent magnet motor is in an open circuit state through the adjustment of a current loop PI.
9. The utility model provides a permanent-magnet machine's loss of field detection device which characterized in that is applied to the converter that drives the permanent-magnet machine operation, this loss of field detection device includes:
the acquisition module is used for acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor when the permanent magnet motor is in a shutdown process;
the calculation module is used for calculating the actual rotor flux linkage according to the reference voltage and the rotating speed;
and the field loss judging module is used for determining the state of the permanent magnet motor by utilizing the actual rotor flux linkage, wherein the state comprises a field loss state or a non-field loss state.
10. An electronic device, comprising:
a memory for storing a computer program;
a processor for implementing the steps of the method of detecting loss of field of a permanent magnet machine according to any of claims 1-8 when executing said computer program.
11. A computer-readable storage medium, characterized in that the computer-readable storage medium has stored thereon a computer program which, when being executed by a processor, carries out the steps of the method of detecting loss of field of a permanent magnet machine according to any one of claims 1-8.
Technical Field
The present disclosure relates to the field of permanent magnet motors, and more particularly, to a method and a system for detecting loss of field of a permanent magnet motor, and related components.
Background
The permanent magnet synchronous motor has the advantages of small volume, high power density, high efficiency, high power factor and the like, and along with the more mature frequency conversion technology, the application of the permanent magnet synchronous motor is more and more extensive. The rotor magnetic field of the permanent magnet synchronous motor is generated by permanent magnet materials, and the permanent magnet materials lose magnetism due to application of high temperature, weak magnetism and the like. The electromagnetic torque output by the permanent magnet synchronous motor is closely related to the strength of a rotor magnetic field, the loss of the rotor can cause the torque output by the motor to be reduced, the current can be rapidly increased under the same load, so that the copper consumption of a stator is increased, the efficiency of the motor is reduced, the temperature of the motor is increased, the rotor is further lost of the magnetic field, a vicious circle is entered, and finally the motor is damaged.
At present, in order to solve the technical problems, generally, a current value is increased when a permanent magnet synchronous motor is in a steady state, and a torque change measured by a dynamometer is compared with a calibrated current and torque meter to judge whether the permanent magnet synchronous motor loses magnetism.
Therefore, how to provide a solution to the above technical problem is a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The application aims to provide a method and a device for detecting loss of magnetism of a permanent magnet motor, electronic equipment and a computer readable storage medium, the loss of magnetism of the permanent magnet motor is detected through an existing frequency converter in a motor control system, extra hardware and instrument equipment are not needed, the permanent magnet motor is not needed to be calibrated in advance, engineering practicability is high, loss of magnetism of the permanent magnet motor can be detected in the shutdown process of the permanent magnet motor every time, the purpose of repeated detection is achieved, and the reliability and the safety of the operation of the permanent magnet motor are improved.
In order to solve the technical problem, the present application provides a method for detecting a loss of field of a permanent magnet motor, which is applied to a frequency converter for driving the permanent magnet motor to operate, and the method for detecting a loss of field comprises the following steps:
when the permanent magnet motor is in a shutdown process, acquiring a reference voltage and a rotating speed corresponding to the permanent magnet motor;
calculating an actual rotor flux linkage according to the reference voltage and the rotating speed;
and determining the state of the permanent magnet motor by utilizing the actual rotor flux linkage, wherein the state comprises a loss-of-field state or a non-loss-of-field state.
Preferably, before the reference voltage and the rotating speed corresponding to the permanent magnet motor are obtained, the method for detecting loss of field further includes:
when the permanent magnet motor is in a shutdown process, judging whether the running state of the permanent magnet motor meets a loss-of-field detection condition;
correspondingly, the process of acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor specifically comprises the following steps:
and when the running state meets the loss-of-field detection condition, acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor.
Preferably, the process of determining whether the operating state of the permanent magnet motor meets the loss-of-field detection condition specifically includes:
acquiring the running state of the permanent magnet motor, wherein the running state comprises the state of a stator winding of the permanent magnet motor;
and when the state of the stator winding is an open circuit state, judging that the running state of the permanent magnet motor meets the loss-of-field detection condition.
Preferably, the process of acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor specifically includes:
acquiring reference voltage and rotating speed corresponding to the permanent magnet motor according to a preset period;
correspondingly, the process of calculating the actual rotor flux linkage according to the reference voltage and the rotating speed specifically includes:
calculating the rotor flux linkage corresponding to the current acquisition period according to the reference voltage and the rotating speed acquired by the current acquisition period, and updating the rotor flux linkage calculation times;
and when the calculation times of the rotor flux linkages reach preset times, calculating the average value of all the rotor flux linkages, and taking the average value as the actual rotor flux linkages.
Preferably, the process of determining the state of the permanent magnet motor by using the actual rotor flux linkage specifically includes:
determining a target rotor flux linkage;
judging whether the difference value of the actual rotor flux linkage and the target rotor flux linkage is in a preset range or not;
if so, judging that the state of the permanent magnet motor is the non-loss-of-field state;
and if not, judging that the state of the permanent magnet motor is the field loss state.
Preferably, the process of determining the target rotor flux linkage specifically includes:
judging whether the permanent magnet motor is a new motor or not;
if so, determining the rated rotor flux linkage of the permanent magnet motor as the target rotor flux linkage;
if not, determining the reference rotor flux linkage of the permanent magnet motor as the target rotor flux linkage, wherein psip＝k·ψrN，ψpFor said reference rotor flux linkage, psirNK is more than 0 and less than or equal to 1 for the rated rotor flux linkage.
Preferably, the shutdown process comprises a free shutdown process or a decelerated shutdown process;
correspondingly, the reference voltage corresponding to the motor is the line voltage of the output end of the frequency converter.
Preferably, the method for detecting loss of field further comprises:
when the permanent magnet motor is in the deceleration shutdown process, the reference current of the d axis and the reference current of the q axis are both set to be 0, and the state of the stator winding of the permanent magnet motor is in an open circuit state through the adjustment of a current loop PI.
In order to solve the above technical problem, the present application further provides a magnetic loss detection device for a permanent magnet motor, which is used for driving a frequency converter operated by the permanent magnet motor, and the magnetic loss detection device includes:
the acquisition module is used for acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor when the permanent magnet motor is in a shutdown process;
the calculation module is used for calculating the actual rotor flux linkage according to the reference voltage and the rotating speed;
and the field loss judging module is used for determining the state of the permanent magnet motor by utilizing the actual rotor flux linkage, wherein the state comprises a field loss state or a non-field loss state.
In order to solve the above technical problem, the present application further provides an electronic device, including:
a memory for storing a computer program;
a processor for implementing the steps of the method of detecting loss of field of a permanent magnet machine as claimed in any one of the preceding claims when executing said computer program.
In order to solve the above technical problem, the present application further provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the steps of the method for detecting loss of field of a permanent magnet motor according to any one of the above.
The application provides a method for detecting the loss of field of a permanent magnet motor, which considers the condition that the terminal voltage of the motor can be equivalent to back electromotive force when the motor stops, therefore, the application acquires the corresponding reference voltage and the corresponding rotating speed of the permanent magnet motor in the motor stopping process, therefore, the actual rotor flux linkage of the permanent magnet motor is calculated, the actual rotor flux linkage can determine whether the rotor magnetic field of the permanent magnet motor is normal or not, thereby judging whether the permanent magnet motor is demagnetized, realizing the demagnetization detection of the permanent magnet motor through the existing frequency converter in the motor control system without additional hardware and instrument equipment and calibrating the permanent magnet motor in advance, having strong engineering practicability, in addition, in the process of stopping the permanent magnet motor every time, the loss of field detection can be carried out on the permanent magnet motor, the purpose of repeated detection is achieved, and the reliability and the safety of the operation of the permanent magnet motor are improved. The application also provides a device for detecting the loss of magnetism of the permanent magnet motor, electronic equipment and a computer readable storage medium, and the device has the same beneficial effects as the method for detecting the loss of magnetism of the permanent magnet motor.
Drawings
In order to more clearly illustrate the embodiments of the present application, the drawings needed for the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained by those skilled in the art without inventive effort.
Fig. 1 is a main circuit topology structure diagram of a frequency converter driving permanent magnet synchronous motor provided in the present application;
fig. 2 is a flowchart illustrating steps of a method for detecting loss of field of a permanent magnet motor according to the present disclosure;
FIG. 3 is a schematic structural diagram of a control system for controlling a winding current to be 0 based on a vector provided by the present application;
fig. 4 is a schematic structural diagram of a loss-of-field detection device of a permanent magnet motor according to the present application.
Detailed Description
The core of the application is to provide a method and a device for detecting loss of magnetism of a permanent magnet motor, electronic equipment and a computer readable storage medium, the loss of magnetism of the permanent magnet motor is detected through an existing frequency converter in a motor control system, extra hardware and instrument equipment are not needed, the permanent magnet motor does not need to be calibrated in advance, the engineering practicability is high, in the shutdown process of the permanent magnet motor at each time, loss of magnetism of the permanent magnet motor can be detected, the purpose of repeated detection is achieved, and the reliability and the safety of the operation of the permanent magnet motor are improved.
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
To facilitate understanding of the method for detecting loss of field of a permanent magnet motor provided in the present application, a control system to which the method for detecting loss of field is applied is described below, and referring to fig. 1, fig. 1 is a main circuit topology structure diagram of a frequency converter driven permanent magnet synchronous motor provided in the present application. As shown in fig. 1, the frequency converter includes an
Generally, in a general frequency converter product, a rotating speed tracking hardware circuit is usually configured, a motor back electromotive force and a motor rotating speed of a permanent magnet motor can be measured, and a back electromotive force phase and amplitude and a motor rotating speed after the motor is free to stop are calculated in real time, so that when the permanent magnet motor is in a rotating state and needs to be started immediately, a frequency converter can send a voltage with the same amplitude and phase as a back electromotive force, and then a normal operation mode is switched into, and no current impact occurs. In this application, permanent magnet motor can be permanent magnet synchronous motor, also can be permanent magnet direct current brushless motor.
The following describes a method for detecting loss of field of a permanent magnet motor in detail.
Referring to fig. 2, fig. 2 is a flowchart illustrating steps of a method for detecting a loss of field of a permanent magnet motor according to the present application, where the method for detecting a loss of field of a permanent magnet motor includes:
s101: when the permanent magnet motor is in a shutdown process, acquiring a reference voltage and a rotating speed corresponding to the permanent magnet motor;
as a preferred embodiment, the shutdown process comprises a free shutdown process or a decelerated shutdown process;
correspondingly, the reference voltage corresponding to the motor is the line voltage of the output end of the frequency converter.
Specifically, the shutdown process of the permanent magnet motor may include a free-stop process and a deceleration shutdown process. Two shut-down procedures are described below:
specifically, the permanent magnet motor can be controlled to enter the free stop process through the frequency converter, when the frequency converter receives a stop instruction, the drive signal is not output to the permanent magnet motor any more, and at the moment, the permanent magnet motor enters the free stop process. It should be noted that, when the permanent magnet motor enters the free stop process, the amplitude of the inter-phase back electromotive force of the permanent magnet motor is lower than that of the bus bar voltage, and when no current flows through the stator winding of the permanent magnet motor, the terminal voltage of the permanent magnet motor can be equivalent to back electromotive force. When the permanent magnet motor is in the free stop process, the reference voltage corresponding to the permanent magnet motor is the line voltage of the output end of the frequency converter, the purpose of the step is to obtain the line voltage of the output end of the frequency converter and the rotating speed of the motor, so that the terminal voltage of the motor can be calculated through the line voltage, the amplitude of the back electromotive force can be calculated, and the rotor flux linkage can be calculated through the amplitude and the rotating speed of the motor. The present embodiment may obtain the rotation speed of the motor and the line voltage at the output end of the frequency converter according to a preset obtaining period, and may also obtain the rotation speed of the motor and the line voltage at the output end of the frequency converter after receiving the obtaining instruction, where the triggering condition for obtaining the rotation speed of the motor and the line voltage at the output end of the frequency converter is not limited herein.
Considering that the frequency converter may receive a shutdown instruction at any time, before the permanent magnet motor enters a free shutdown process, the motor power of the permanent magnet motor is uncertain, and a situation that the obtained terminal voltage of the permanent magnet motor cannot be directly equivalent to a back electromotive force may exist, so that the accuracy of subsequent permanent magnet motor demagnetization detection is influenced. Therefore, as a preferred embodiment, when the permanent magnet motor is in a free shutdown process, before performing the demagnetization judgment, the application judges whether the operation state of the permanent magnet motor meets the demagnetization detection condition, and if the operation state of the permanent magnet motor meets the demagnetization detection condition, it indicates that the obtained terminal voltage of the permanent magnet motor can be directly equivalent to back electromotive force, and at this time, the motor rotation speed and the line voltage at the output end of the frequency converter are obtained. It can be understood that the running state of the permanent magnet motor is monitored, when the running state meets the condition of field loss detection, the rotating speed of the motor and the line voltage of the output end of the frequency converter are immediately obtained to carry out field loss detection, the response speed is higher, and the detection efficiency can be improved.
The running state of the permanent magnet motor can comprise the state of a stator winding of the permanent magnet motor, when the permanent magnet motor is in the free stop process and the stator winding of the permanent magnet motor is in an open circuit state, the rotating speed of the motor and the line voltage of the output end of the frequency converter are obtained at the moment, so that the terminal voltage of the permanent magnet motor obtained through the line voltage can be directly equivalent to back electromotive force, and the accuracy of subsequent demagnetization judgment is improved. Specifically, in the free stop process of the permanent magnet motor, when the current value is 0, the stator winding of the permanent magnet motor is judged to be in an open circuit state through current sampling.
Of course, it may be determined whether the permanent magnet motor meets the demagnetization detection condition according to the above manner, or a preset waiting time may be set, where the preset waiting time is reached to indicate that the demagnetization detection condition is met, that is, after the permanent magnet motor enters the free shutdown process, the preset waiting time is waited to obtain the motor rotation speed and the line voltage at the output end of the frequency converter, so as to ensure that no current flows through the stator winding of the permanent magnet motor, and the terminal voltage of the permanent magnet motor may be directly equivalent to the back electromotive force.
In the embodiment, the rotating speed of the motor and the line voltage of the output end of the frequency converter can be obtained based on the rotating speed tracking hardware circuit of the frequency converter, hardware and instruments such as an air switch, a relay, a contactor and a measuring instrument do not need to be additionally arranged, and the detection mode is simple, efficient and reliable.
Certainly, on the occasion of not configuring a rotation speed tracking hardware circuit, when the permanent magnet motor is in the process of deceleration and shutdown, the reference currents of the d axis and the q axis may be set to 0, and the stator winding current of the permanent magnet motor is controlled to be approximately 0 through the current loop PI regulation, that is, the stator winding of the permanent magnet motor is controlled to be approximately in an open-circuit state, and a specific control system schematic diagram is shown in fig. 3. It will be appreciated that the line voltage at the output of the inverter can be approximated equivalently by the reference voltage of the current loop PI regulator (the output voltage of the permanent magnet machine in this case) neglecting the non-linear effect of the dead zone.
According to the above assumptions, the reference voltage is approximately equivalent to a back electromotive force:
in the formula, Eα，EβIs the back electromotive force, U, of the motor under a two-phase static coordinate systemα，UβThe reference voltage is under a two-phase static coordinate system;
the source of the rotating speed of the motor can be obtained by the speed measurement of an encoder and the calculation of a non-speed observer, and can also be obtained by the calculation of reference voltage, and the application is not specifically limited herein;
s102: calculating an actual rotor flux linkage according to the reference voltage and the rotating speed;
specifically, when the permanent magnet motor is in the free stop process, the line voltage U at the output end of the frequency converter can be detected through a rotating speed tracking hardware circuit configured in the frequency converteruv，UvwAnd assuming that three-phase windings of the permanent magnet motor are symmetrical, and calculating the amplitude E of the back electromotive force between lines through UV phase-to-phase voltage and Fourier analysis. Considering that the rotating speed tracking hardware circuit only calculates the back electromotive force and the rotating speed of the permanent magnet motor at the current rotating speed, and does not calculate the rotor flux linkage of the permanent magnet motor, whether the rotor magnetic field of the permanent magnet motor is normal or not cannot be judged. Therefore, the present embodiment can track the motor rotation speed ω detected by the hardware circuit according to the rotation speed through the frequency converterrAnd calculating to obtain an actual rotor flux linkage by combining the amplitude E of the back electromotive force, and judging whether the rotor magnetic field of the permanent magnet motor is normal or not through the actual rotor flux linkage so as to determine whether the permanent magnet motor is demagnetized or not.
In the case of a hardware speed tracking circuit, the actual rotor flux linkage can be calculated by the following formula:
wherein psirIs the actual rotor flux linkage.
Correspondingly, in the occasion without a hardware rotating speed tracking circuit and in the process of deceleration shutdown,
s103: and determining the state of the permanent magnet motor by utilizing the actual rotor flux linkage, wherein the state comprises a loss-of-field state or a non-loss-of-field state.
Specifically, whether the rotor is demagnetized or not is judged according to comparison between the calculated actual rotor flux linkage and a target rotor flux linkage prestored in the frequency converter. As a preferred embodiment, a difference between an actual rotor flux linkage and a target rotor flux linkage is obtained, whether the difference is within a preset range is judged, if so, the motor is considered to have no field loss phenomenon and to be in a non-field loss state, and if not, the motor is considered to have the field loss phenomenon and to be in the field loss state, and the permanent magnet motor needs to be overhauled, so as to improve the operation safety of the permanent magnet motor. The preset range may be set according to actual engineering requirements, and this embodiment is not specifically limited herein.
As a preferred embodiment, the target rotor flux linkage needs to be selected according to actual conditions, and for a newly-used permanent magnet motor, that is, a new motor, and a permanent magnet motor that has been used for a period of time, the respective target rotor flux linkages of the new-used permanent magnet motor and the new motor are not necessarily the same, and the target rotor flux linkage should be selected specifically according to the use condition of the permanent magnet motor, so as to further improve the accuracy of detecting the loss of field of the permanent magnet motor. Based on this, the present embodiment determines the usage of the permanent magnet motor by determining whether the current loss detection is the first loss detection, if the current loss detection is the first loss detection, the corresponding motor is the motor that is newly put into use, then the rated rotor flux linkage of the permanent magnet motor is used as the target rotor flux linkage, and if the current permanent magnet motor is not the motor that is newly put into use, that is, the current detection is not the first detection, then the reference rotor flux linkage is determined as the target rotor flux linkage, where ψp＝k·ψrN，ψpFor said reference rotor flux linkage, psirNK is more than 0 and less than or equal to 1 for the rated rotor flux linkage, and the reference rotor flux linkage is less than or equal to the target rotor flux linkage so as to avoid the condition of misjudgment. Wherein, k isThe value can be determined according to the actual engineering requirement, and the application is not specifically limited herein.
It can be seen that, in the present embodiment, when the motor is stopped, there is a situation that the terminal voltage of the motor may be equivalent to the back electromotive force, therefore, in the present application, the reference voltage and the rotation speed corresponding to the permanent magnet motor in the motor stopping process are obtained, so as to calculate the actual rotor flux linkage of the permanent magnet motor, and the actual rotor flux linkage may determine whether the rotor magnetic field of the permanent magnet motor is normal, thereby determining whether the permanent magnet motor is demagnetized.
On the basis of the above-described embodiment:
as a preferred embodiment, the process of obtaining the reference voltage and the rotation speed corresponding to the permanent magnet motor specifically includes:
acquiring reference voltage and rotating speed corresponding to the permanent magnet motor according to a preset period;
correspondingly, the process of calculating the actual rotor flux linkage according to the reference voltage and the rotating speed specifically comprises the following steps:
calculating the rotor flux linkage corresponding to the current acquisition period according to the reference voltage and the rotating speed acquired by the current acquisition period, and updating the rotor flux linkage calculation times;
and when the calculation times of the rotor flux linkage reach the preset times, calculating the average value of all the rotor flux linkages, and taking the average value as the actual rotor flux linkage.
It can be understood that, due to the reason of the sensor itself or the influence of other factors on the signal transmission process, there may be an error in the detected data, and in order to improve the accuracy of the loss of magnetization detection, the data is further processed in this embodiment. Firstly, presetting an acquisition period for acquiring line voltage and motor rotation speed and times for acquiring the line voltage and the motor rotation speed, assuming that the preset times is 5 times, the acquisition period is 5ms, namely acquiring the motor rotation speed and the line voltage at the output end of a frequency converter every 5ms, then calculating rotor flux linkages according to the acquired line voltage and the motor rotation speed, and when the times for acquiring the line voltage and the motor rotation speed reach the preset times, namely the calculation times of the rotor flux linkages reach the preset times, obtaining 5 rotor flux linkages, at the moment, calculating the average value of the 5 rotor flux linkages, and performing magnetic loss detection by taking the average value of the rotor flux linkages as an actual rotor flux linkage to prevent misjudgment, thereby further improving the accuracy of the magnetic loss detection.
As a preferred embodiment, the method for detecting loss of field further includes:
and when the state of the permanent magnet motor is a field loss state, generating an alarm signal.
Specifically, when the permanent magnet motor is in a loss-of-field state, a corresponding alarm signal is generated and sent to the human-computer interaction device, and the alarm signal is displayed through the human-computer interaction device, so that an operator can find the loss-of-field phenomenon of the permanent magnet motor in time, overhaul the lost-field permanent magnet motor, and improve the reliability of loss-of-field detection.
To sum up, this application utilizes the in-process that permanent-magnet machine freely shut down on current converter hardware basis, and stator winding opens a way, and the motor end voltage equivalence is the characteristics of back electromotive force, and automatic rapid measurement permanent-magnet machine's back electromotive force and motor speed calculate the rotor flux linkage of motor, compares with permanent-magnet machine's target rotor flux linkage, judges whether the motor has the phenomenon of losing magnetism to the staff in time handles the permanent-magnet machine who loses magnetism, prevents to force the overload start-up and the operation leads to permanent-magnet machine overheat burnout. This application only can realize through converter software, does not need extra hardware and instrument and equipment, also need not the manual work to carry out off-line analysis to the signal, can repeated detection moreover, and is irrelevant with motor power, whether the motor is changed, can both detect out the motor fast and lose magnetism, and the algorithm is simple, and the engineering practicality is strong.
Referring to fig. 4, fig. 4 is a schematic structural diagram of a loss of excitation detection device of a permanent magnet motor provided in the present application, which is applied to a frequency converter for driving the permanent magnet motor to operate, and the loss of excitation detection device of the permanent magnet motor includes:
the acquisition module 11 is used for acquiring a reference voltage and a rotating speed corresponding to the permanent magnet motor when the permanent magnet motor is in a shutdown process;
the calculation module 12 is used for calculating the actual rotor flux linkage according to the reference voltage and the rotating speed;
and the field loss judging module 13 is configured to determine a state of the permanent magnet motor by using the actual rotor flux linkage, where the state includes a field loss state or a non-field loss state.
It can be seen that, in the present embodiment, when the motor is stopped, there is a situation that the terminal voltage of the motor may be equivalent to the back electromotive force, therefore, in the present application, the reference voltage and the rotation speed corresponding to the permanent magnet motor in the motor stopping process are obtained, so as to calculate the actual rotor flux linkage of the permanent magnet motor, and the actual rotor flux linkage may determine whether the rotor magnetic field of the permanent magnet motor is normal, thereby determining whether the permanent magnet motor is demagnetized.
As a preferred embodiment, the obtaining module 11 is specifically configured to:
when the permanent magnet motor is in a shutdown process, judging whether the running state of the permanent magnet motor meets a loss-of-field detection condition;
and when the running state meets the loss-of-field detection condition, acquiring the reference voltage and the rotating speed corresponding to the permanent magnet motor.
As a preferred embodiment, the process of determining whether the operating state of the permanent magnet motor satisfies the loss-of-field detection condition specifically includes:
acquiring the running state of the permanent magnet motor, wherein the running state comprises the state of a stator winding of the permanent magnet motor;
and when the state of the stator winding is an open circuit state, judging that the running state of the permanent magnet motor meets the loss-of-field detection condition.
As a preferred embodiment, the process of obtaining the reference voltage and the rotation speed corresponding to the permanent magnet motor specifically includes:
acquiring reference voltage and rotating speed corresponding to the permanent magnet motor according to a preset period;
correspondingly, the calculation module 12 is specifically configured to:
calculating the rotor flux linkage corresponding to the current acquisition period according to the reference voltage and the rotating speed acquired by the current acquisition period, and updating the rotor flux linkage calculation times;
and when the calculation times of the rotor flux linkage reach the preset times, calculating the average value of all the rotor flux linkages, and taking the average value as the actual rotor flux linkage.
As a preferred embodiment, the demagnetization determining module 13 specifically includes:
a determination unit for determining a target rotor flux linkage;
and the judging unit is used for judging whether the difference value of the actual rotor flux linkage and the target rotor flux linkage is in a preset range, judging that the state of the permanent magnet motor is in a non-loss-of-field state if the difference value is in the preset range, and judging that the state of the permanent magnet motor is in a loss-of-field state if the difference value is not in the preset range.
As a preferred embodiment, the determining unit is specifically configured to:
judging whether the permanent magnet motor is a new motor or not;
if so, determining the rated rotor flux linkage of the permanent magnet motor as the target rotor flux linkage;
if not, determining the reference rotor flux linkage of the permanent magnet motor as a target rotor flux linkage, wherein psip＝k·ψrN，ψpFor reference rotor flux linkage, #rNIs rated rotor flux linkage, k is more than 0 and less than or equal to 1.
As a preferred embodiment, the shutdown process includes a free shutdown process or a decelerated shutdown process;
correspondingly, the reference voltage corresponding to the motor is the line voltage of the output end of the frequency converter.
As a preferred embodiment, the method for detecting loss of field further includes:
when the permanent magnet motor is in the process of deceleration and shutdown, the reference current of the d axis and the reference current of the q axis are both set to be 0, and the state of the stator winding of the permanent magnet motor is in an open circuit state through the adjustment of a current loop PI.
In another aspect, the present application further provides an electronic device, including:
a memory for storing a computer program;
a processor for implementing the steps of the method for detecting loss of field of a permanent magnet motor as described in any one of the above embodiments when executing the computer program.
For an introduction of an electronic device provided in the present application, please refer to the above embodiments, which are not described herein again.
The electronic equipment has the same beneficial effects as the loss of field detection method of the permanent magnet motor.
In another aspect, the present application further provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the steps of the method for detecting loss of field of a permanent magnet motor as described in any one of the above embodiments.
For the introduction of a computer-readable storage medium provided in the present application, please refer to the above embodiments, which are not described herein again.
The computer-readable storage medium has the same beneficial effects as the loss-of-field detection method of the permanent magnet motor.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
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