Method and system for detecting three-phase imbalance of motor

Abstract

The invention provides a motor three-phase imbalance detection method and system, and relates to the technical field of motor detection. The method comprises the following steps: determining a running state of a motor and an unbalance monitoring parameter associated with the running state; determining whether the motor has three-phase imbalance according to the running state and the imbalance monitoring parameters; and under the condition that the three-phase imbalance occurs in the motor, determining the occurrence reason of the three-phase imbalance according to the imbalance monitoring parameters, and performing imbalance compensation on the motor according to the imbalance compensation processing mode. According to the invention, three-phase imbalance monitoring is carried out on the motor according to the running state of the motor and the associated imbalance monitoring parameters, the reliability and accuracy of three-phase imbalance detection of the motor are improved, the three-phase imbalance condition of the motor can be quickly found, imbalance compensation can be carried out on the motor in time, and the reliability of the motor is improved. Long-time abnormal operation of the motor is avoided, overall safety of the system is improved, stability and reliability of the motor are improved, and service life of the motor is prolonged.

Description

Technical Field

[0001] The present disclosure relates to the technical field of motor detection, and particularly to a method and system for detecting three-phase imbalance of a motor. Background Art

[0002] In recent years, motors have been widely used in various fields such as industry, agriculture, military, and household applications. However, motors may malfunction during actual operation, such as output imbalance, phase loss, or three-phase imbalance caused by different operating conditions of the motor. Without effective detection and protection measures, abnormal operation of three-phase imbalance often leads to serious consequences, such as increased vibration, abnormal noise, decreased speed, increased current, increased temperature, motor burnout, etc., and will also have an adverse impact on electrical equipment and the entire power grid. In addition, there are often moments when the current value is zero or close to zero in motor control itself, and it is easy to misjudge the three-phase imbalance situation caused by current phase loss of the motor based on the current values collected at these moments during three-phase imbalance detection. Summary of the Invention

[0003] The present disclosure aims to solve at least one of the technical problems in the related art to some extent.

[0004] To this end, a first aspect embodiment of the present disclosure provides a method for detecting three-phase imbalance of a motor, which is characterized by including the following steps:

[0005] Determine the operating state of the motor;

[0006] Obtain the imbalance monitoring parameter associated with the operating state;

[0007] Determine whether the motor has three-phase imbalance according to the operating state and the imbalance monitoring parameter;

[0008] In the case where the motor has three-phase imbalance, determine the cause of the three-phase imbalance according to the imbalance monitoring parameter, and perform imbalance compensation on the motor according to the imbalance compensation processing method.

[0009] In some embodiments of the present disclosure, the unbalance monitoring parameters include: the voltages of the three-phase busbars and the three-phase currents; wherein, determining whether the motor has three-phase unbalance according to the operating state and the unbalance monitoring parameters includes: when the operating state is the stationary state, and the voltages of the three-phase busbars are within the normal operating range of the busbar voltages, and the unbalance degree of the three-phase currents is less than the unbalance degree threshold, determining that the motor does not have three-phase unbalance; or, when the operating state is the stationary state, and the voltages of the three-phase busbars are not within the normal operating range of the busbar voltages or the unbalance degree of the three-phase currents is greater than or equal to the unbalance degree threshold, determining that the motor has three-phase unbalance.

[0010] In some embodiments of the present disclosure, the unbalance monitoring parameters further include the control current, the level values of the current signals on the three phase lines, and the code value of the speed sensor encoder; wherein, determining the cause of the three-phase unbalance according to the unbalance monitoring parameters includes: when the three-phase currents have a first value, and it is determined based on the level values that the current signals on the three phase lines all exist, determining that the cause of the three-phase unbalance is that the three-phase currents have a zero-crossing phenomenon; or, when the three-phase currents have a first value, and it is determined based on the level values that there is a missing current signal among the current signals on the three phase lines, and there is a broken wire state in the line connection of the motor, determining that the cause of the three-phase unbalance is poor line contact; or, when the three-phase currents have a first value, and it is determined based on the level values that there is a missing current signal among the current signals on the three phase lines, and the line connection of the motor has no broken wire, and the control current exceeds the control current threshold range, determining that the cause of the three-phase unbalance is that there is an abnormality at the position where the motor drive unit is connected to the three phases of the motor; or, when the three-phase currents have a first value, and it is determined based on the level values that there is a missing current signal among the current signals on the three phase lines, and the line connection of the motor has no broken wire, and the control current does not exceed the control current threshold range, determining that the cause of the three-phase unbalance is that there is a broken wire inside the motor; or, when the three-phase currents do not have the first value and the three-phase currents have an abnormal increase, and the code value is not within the preset code value range, determining that the cause of the three-phase unbalance is an encoder failure; or, when the three-phase currents do not have the first value and the three-phase currents have an abnormal increase, and the code value is within the preset code value range, determining that the cause of the three-phase unbalance is that there is a broken wire or a short circuit inside the motor.

[0011] In some embodiments of the present disclosure, the unbalance monitoring parameters include: three-phase current, control current, and motor speed; wherein, determining whether the motor has three-phase unbalance according to the operating state and the unbalance monitoring parameters includes: when the operating state is a non-stationary state, determining that the load state of the motor is no-load according to the three-phase current, the control current, and the motor speed; when the voltage of the three-phase bus is within the normal operating range of the bus voltage and the unbalance degree of the three-phase current is less than the unbalance degree threshold, determining that the motor has no three-phase unbalance; or, when the voltage of the three-phase bus is not within the normal operating range of the bus voltage, or the unbalance degree of the three-phase current is greater than or equal to the unbalance degree threshold, determining that the motor has three-phase unbalance.

[0012] In some embodiments of the present disclosure, the unbalance monitoring parameters further include current signals on three phase lines. Determining the cause of the three-phase unbalance according to the unbalance monitoring parameters includes: when there is a missing current signal among the current signals on the three phase lines, determining that the cause of the three-phase unbalance is a phase loss; or, when the current signals on the three phase lines all exist and the three-phase current is detected to exceed the preset normal threshold range at least twice, determining that the cause of the three-phase unbalance is a circuit fault of the motor.

[0013] In some embodiments of the present disclosure, the unbalance monitoring parameters include: three-phase current, control current, and motor speed; wherein, determining whether the motor has three-phase unbalance according to the operating state and the unbalance monitoring parameters includes: when the operating state is a non-stationary state, determining that the load state of the motor is loaded according to the three-phase current, the control current, and the motor speed; when the three-phase current does not exceed the preset normal threshold range, determining that the motor has no three-phase unbalance; or, when the three-phase current exceeds the preset normal threshold range, determining that the motor has three-phase unbalance.

[0014] In some embodiments of the present disclosure, the unbalance monitoring parameters further include current signals on three phase lines; wherein, determining the cause of the three-phase unbalance according to the unbalance monitoring parameters includes: when there is a missing current signal among the current signals on the three phase lines, determining that the cause of the three-phase unbalance is a phase loss; or, when the current signals on the three phase lines all exist and the three-phase current and the motor speed meet a preset condition, determining that the cause of the three-phase unbalance is a change in the load of the motor; or, when the current signals on the three phase lines all exist and the three-phase current and the motor speed do not meet the preset condition, determining that the cause of the three-phase unbalance is a short circuit inside the motor.

[0015] In some embodiments of the present disclosure, the unbalance compensation processing method includes: using a motor control algorithm simulation system to open-circuit the first set of windings of the motor, performing simulation research and analysis on the second set of windings under an unbalanced state, and using a quasi-resonant controller to suppress the double-frequency harmonics of the motor control system.

[0016] In some embodiments of the present disclosure, the unbalance compensation processing method includes: sampling the three-phase current of the motor, calculating the compensation target value and compensation value of the three-phase unbalance current in each electrical frequency cycle, calculating the unbalance compensation voltage of the motor three-phase inductance according to the compensation target value and compensation value of the three-phase unbalance current, and performing current unbalance compensation on the motor according to the unbalance compensation voltage of the motor three-phase inductance.

[0017] A second aspect embodiment of the present disclosure provides a detection system for three-phase unbalance of a motor, characterized in that the system includes:

[0018] An acquisition unit, configured to acquire unbalance monitoring parameters associated with the operating state of the motor;

[0019] A main control unit, configured to execute the method described in the foregoing first aspect.

[0020] The detection method for three-phase unbalance of the motor provided by the present disclosure monitors the three-phase unbalance of the motor according to the operating state of the motor and its associated unbalance monitoring parameters, improves the reliability and accuracy of the three-phase unbalance detection of the motor, helps to quickly discover the three-phase unbalance situation of the motor, and timely performs unbalance compensation on the motor according to the unbalance compensation processing method, avoiding the motor from being in an abnormal operating state for a long time, enhancing the overall safety of the system, and improving the stability, reliability and service life of the motor. In addition, the present disclosure further details the unbalance detection of the motor to analyze the cause of the unbalance according to the unbalance monitoring parameters, providing a reliable reference for subsequent maintenance or repair work of the motor.

[0021] Additional aspects and advantages of the present disclosure will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present disclosure. Description of the Drawings

[0022] The above-mentioned and / or additional aspects and advantages of the present disclosure will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, where:

[0023] Figure 1 is a schematic flowchart of a method for detecting three-phase imbalance of an electric motor provided by an embodiment of the present disclosure;

[0024] Figure 2 is a schematic diagram of a simulation model of a single-three-phase winding power drive part provided by an embodiment of the present disclosure;

[0025] Figure 3 is a schematic diagram of current under open-loop control of a single winding provided by an embodiment of the present disclosure;

[0026] Figure 4 is a Bode diagram of a quasi-resonant controller provided by an embodiment of the present disclosure;

[0027] Figure 5 is a schematic diagram of compensating current imbalance of an electric motor provided by an embodiment of the present disclosure;

[0028] Figure 6 is a schematic flowchart of a method for detecting three-phase imbalance of an electric motor in a stationary state provided by an embodiment of the present disclosure;

[0029] Figure 7 is a schematic flowchart of a method for detecting three-phase imbalance of an electric motor in a non-stationary state provided by an embodiment of the present disclosure;

[0030] Figure 8 is a schematic diagram of a detection system for three-phase imbalance of an electric motor provided by an embodiment of the present disclosure. Detailed Embodiments

[0031] The embodiments of the present disclosure will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0032] Specifically, the method and system for detecting three-phase imbalance of an electric motor according to the embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0033] Figure 1 is a schematic flowchart of a method for detecting three-phase imbalance of an electric motor provided by an embodiment of the present disclosure. AsFigure 1 As shown in the figure, the method for detecting three-phase imbalance of the motor may include the following steps:

[0034] S101, determine the operating state of the motor.

[0035] Among them, the operating state of the motor may include a stationary state and a non-stationary state. The stationary state refers to the state of the motor when it is not powered on or not under the action of an external force, and the motor does not rotate at this time. The non-stationary state refers to the state of the motor being in a loaded state or an unloaded state.

[0036] S102, obtain the imbalance monitoring parameters associated with the operating state.

[0037] It should be noted that different motor operating states are associated with different imbalance monitoring parameters, which are used to detect whether three-phase imbalance occurs in different motor operating states and the causes of the imbalance.

[0038] S103, determine whether the motor has three-phase imbalance according to the operating state and the imbalance monitoring parameters.

[0039] In some embodiments of the present disclosure, when the motor is in a stationary state, the motor can be powered on, and after power-on, the voltages and three-phase currents of the three-phase busbars of the motor are used as the imbalance monitoring parameters to determine whether the motor has three-phase imbalance. When the motor is in a non-stationary state, the voltages, three-phase currents, control current, and motor speed of the three-phase busbars of the motor can be used as the imbalance monitoring parameters to distinguish whether the motor is loaded, and according to the load condition of the motor, as well as the three-phase current and / or the voltage of the three-phase busbar, it is determined whether the motor has three-phase imbalance.

[0040] It should be noted that the parameters of three-phase imbalance of the motor have different characteristics in different operating states. Therefore, the imbalance detection of the motor can be performed by determining whether the imbalance monitoring parameters meet the parameter requirements for three-phase imbalance of the motor in the current operating state. Using the corresponding imbalance monitoring parameters based on different operating states of the motor can provide reliable data support for the detection of three-phase imbalance of the motor and more accurately detect the three-phase imbalance situation of the motor.

[0041] S104, in the case of three-phase imbalance of the motor, determine the cause of the three-phase imbalance according to the imbalance monitoring parameters, and perform imbalance compensation on the motor according to the imbalance compensation processing method.

[0042] In some embodiments of the present disclosure, when a three-phase imbalance occurs in the motor, the imbalance conditions caused by different reasons also have corresponding parameter characteristics. Therefore, the cause of the three-phase imbalance can be determined by judging whether the imbalance monitoring parameters meet the parameter requirements of the imbalance cause under the corresponding operating state. Among them, under the same motor operating state, the imbalance monitoring parameters used to judge whether the motor has a three-phase imbalance and the imbalance monitoring parameters used to judge the cause of the motor imbalance may have parameter overlap.

[0043] In some embodiments of the present disclosure, when the motor operating state is the stationary state and a three-phase imbalance occurs, the numerical values of the three-phase currents can be used to distinguish between two cases: the current value is zero / close to zero and the numerical values of the three-phase currents are abnormal. For the case where the current value is zero / close to zero, it can be determined whether the motor is phase-loss according to the current signals of the three phase lines. If there is a missing current signal among the current signals of the three phase lines, the cause of the motor imbalance is motor phase-loss, and the cause of the phase-loss is further investigated for the phase-loss problem. If there is no missing current signal among the current signals of the three phase lines, there is a zero-crossing phenomenon in the motor.

[0044] Among them, the zero-crossing phenomenon is a normal phenomenon in the three-phase AC power system, which means that the current just passes through the zero point during the imbalance detection, and it does not belong to the three-phase imbalance caused by motor faults. By comprehensively judging the cause of the imbalance through the three-phase current values and current signals, the misjudgment of the normal zero-crossing phenomenon of the motor as a motor phase-loss fault can be avoided, and the accuracy of motor imbalance detection can be improved. If the numerical values of the three-phase currents are abnormal, it can be further determined whether the three-phase imbalance is caused by a motor problem or an encoder problem through the code value of the speed sensor encoder.

[0045] In some embodiments of the present disclosure, when the motor operating state is a non-stationary state and a three-phase imbalance occurs, two cases of the motor being loaded and unloaded can be distinguished. When the motor is unloaded, it can be determined whether the cause of the imbalance is motor phase-loss or motor circuit fault by distinguishing whether the current signals of the three phase lines are missing. When the motor is loaded, the two causes of the imbalance of phase-loss and non-phase-loss are distinguished according to the current signals. If the cause is non-phase-loss, further analysis can be carried out based on the three-phase currents and the motor speed to investigate other causes of the imbalance.

[0046] In some embodiments of the present disclosure, when it is determined that the motor has a three-phase imbalance, there can be various imbalance compensation processing methods to compensate for the imbalance of the motor.

[0047] In a possible implementation manner, the first set of windings of the motor can be opened based on the motor control algorithm simulation system, and the simulation research and analysis under the imbalance state can be carried out on the second set of windings, and a quasi-resonant controller is used to suppress the second harmonic of the motor control system.

[0048] Figure 2Schematic diagram of a simulation model for the power drive part of a single - three - phase winding. As Figure 2 shown, based on the Simulink motor control algorithm simulation system, one set of windings of a 1.1kW dual - three - phase permanent magnet synchronous motor is open - circuited, and the other set of windings is simulated and analyzed under unbalanced conditions. In the dashed block diagram, it shows that the second set of windings is completely removed, and all the PWM2 signals output by the control algorithm are off signals. Figure 3 Schematic diagram of current under single - winding open - loop control provided by an embodiment of the present disclosure. Among them, Figure 3 (a) in it is the waveform diagram of I d1 and I q1 . Figure 3 (b) in it is the schematic diagram of harmonic current content analysis. As Figure 3 shown, the dual - three - phase permanent magnet synchronous motor operates in single - set three - phase open - loop, that is, the u d_1 and u q_1 values at rated operation are given. At this time, the unbalanced condition of the motor is the most serious. The electrical cycle of the 1.1kW simulation prototype at rated speed is about 0.046s. Figure 3 Two stable I d1 and I q1 electrical - cycle waveforms after open - loop control are intercepted. The second - harmonic component in the current is obvious. The rated I q1_DC = 3A, and the amplitude of the second - harmonic has reached about 0.5A. Analyzing the harmonic content of the current on the q - axis, it is found that the proportion of the second - harmonic current reaches 17%. The torque is generated by the interaction between the q - axis current component and the permanent - magnet flux. If there is a large amount of second - harmonic current in I q1 , there will also be a large - amplitude second - harmonic pulsation in the torque. Among them, the amplitude of the second - harmonic torque reaches 12.4 Nm, causing a large vibration interference to the operation of the motor system.

[0049] The current PI (proportional - integral) and feed - forward decoupling controllers in the control algorithm of the dual - three - phase permanent magnet synchronous motor are used to achieve fast and stable control of the motor current.

[0050] The proportional link reflects the signal deviation of the system in proportion in real - time and compensates it in time, which can improve the dynamic performance of current control. The integral link eliminates the static error by continuously integrating the error, improving the steady - state performance of current control. The proportional link in the PI controller can partially compensate for the current deviation caused by the second - harmonic current in the single - winding operation mode. The feed - forward decoupling module has nothing to do with the second - harmonic current in the single - winding operation mode of the dual - three - phase permanent magnet synchronous motor. Therefore, the influence of the feed - forward decoupling module is not considered in the following comparison of various second - harmonic current suppression algorithms, and it is default to be connected in parallel with the PI controller to improve the regulation effect of the PI controller on the DC components of the d - axis current and q - axis current.

[0051] The PI controller used in the traditional inner current loop control of motors has infinite gain at a frequency of 0 and can achieve static error-free tracking and elimination of DC signals. However, the PI controller cannot track and eliminate the second-harmonic current existing in the single-winding operation mode of a dual-three-phase permanent magnet synchronous motor well, and there is still a second-harmonic component in the steady state. If a second-harmonic selection coordinate system is established and a new PI controller is added, the tracking and elimination of the second-harmonic component can be achieved. However, this method increases the computational complexity of coordinate transformation, requires an increase in the number of PI controllers, and raises the system complexity. To meet the requirement of suppressing harmonics, a resonant controller can achieve the tracking of a specific periodic signal and eliminate the components of a specified harmonic order through integration. The resonant controller has two imaginary poles and has infinite gain at the resonant angular frequency ω0, enabling static error-free tracking of the harmonic quantity with a frequency of ω0.

[0052] The speed of the motor changes with the load, power output, etc. Due to the influence of factors such as the detection accuracy of the encoder, the algorithm accuracy of the positionless controller, and the accuracy of the digital control system, there may be an error between the actual resonant angular frequency and the given resonant angular frequency of the resonant controller, resulting in poor application effects of the ideal resonant controller in the actual motor control system. Therefore, in the present disclosure, the resonant controller is improved to adopt a quasi-resonant controller.

[0053] Figure 4 The Bode diagram of a quasi-resonant controller provided by an embodiment of the present disclosure is shown as Figure 4 follows. Compared with the resonant controller, the gain of the quasi-resonant controller drops significantly at the resonant angular frequency, but the gain near the resonant angular frequency increases. The quasi-resonant controller can effectively suppress the second-harmonic of the actual motor control system.

[0054] Both the resonant controller and the quasi-resonant controller need to be used in parallel with the PI controller. The PI controller plays a role in regulating and controlling the DC component, while the resonant controller or the quasi-resonant controller plays a role in regulating and controlling the harmonic component. The quasi-resonant controller adopted in the present invention is used in parallel with the PI controller and is called a proportional integral quasi-resonant controller. The proportional integral quasi-resonant controller can, while regulating the DC component of the inner current loop, suppress the second-harmonic current and reduce the imbalance problem in the single-winding operation mode. In the simulation, the resonant suppression frequency ω o is set to be twice the fundamental frequency ω e of the motor. When the motor runs at the rated speed, the resonant suppression frequency is 268 rad / s. After adding the quasi-resonant module, the second-harmonic content in the q-axis current of the motor drops to 0.93%, and the amplitude of the second-harmonic current decreases significantly. Compared with the PI controller, the second-harmonic pulsation in the torque waveform under the proportional integral quasi-resonant controller drops significantly, and the unbalanced operation problem is effectively controlled.

[0055] When there is an offset between the given resonant angular frequency input to the resonant controller and the quasi-resonant controller and the actual double-frequency angular frequency, the double-frequency harmonic content increases as the absolute value of the resonant angular frequency offset increases, and the suppression effect of the resonant controller decreases faster than that of the quasi-resonant controller. Therefore, using a quasi-resonant controller can not only achieve a better harmonic current suppression effect at the accurate resonant angular frequency point, but also has a strong harmonic current suppression ability when there is a small deviation in the given resonant angular frequency.

[0056] In another possible implementation, for a three-phase unbalanced resistive-inductive load, reactive power compensation can be performed separately on its positive and negative sequence components to improve the utilization efficiency of the grid active power, reduce the three-phase unbalance degree of the grid at the same time, and minimize the power loss caused by excessive reactive power content in the system due to the existence of the three-phase asymmetric resistive-inductive load. Figure 5 A schematic diagram for compensating current imbalance of a motor provided by an embodiment of the present disclosure.

[0057] As an example, the positive and negative half-wave peaks of each three-phase current can be determined by real-time monitoring and sampling the three-phase current waveform of the motor: the positive half-wave peaks I A_max 、I B_max 、I C_max , and the negative half-wave peaks I A_min 、I B_min 、I C_min . Within a 2π period of the motor current, the following judgment is made for each ADC interruption, and the positive and negative half-wave peaks of the three-phase current are updated according to the three-phase current of the motor: If I A >0, I A >I A_max , then I A_max =I A ; If I A <0, I A <I A_min , then I A_min =I A . The positive half-wave peaks I B_max 、I C_max and the negative half-wave peaks I B_min 、I C_min of phase B and phase C are obtained by the same method. After a 2π period of the current waveform ends, the updated positive and negative half-wave peaks of the three-phase current I A_max , I B_max , I C_max , I A_min , I B_min , I C_min are obtained. The compensation value of the three-phase unbalanced current is obtained according to the positive and negative half-wave peaks. Among them, the target value of the three-phase unbalanced current compensation and the compensation value of the three-phase unbalanced current compensation can be obtained through the following formula:

[0058] I_unb = [(I A_max - I A_min ) × 0.5 + (I B_max - I B_min ) × 0.5 + (I C_max - I C_min ) × 0.5] / 3

[0059] I_unbaaim = (I A_max - I A_min ) × 0.5 - I_unb

[0060] I_unbbaim = (I B_max - I B_min ) × 0.5 - I_unb

[0061] I_unbcaim = -(I_unbaaim + I_unbbaim)

[0062] I_unb_a = I_unb_a + I_unbaaim × λ

[0063] I_unb_b = I_unb_b + I_unbbaim × λ

[0064] I_unb_c = I_unb_c + I_unbcaim × λ

[0065] Among them, I_unb is the average value of the three-phase unbalance amount, I_unbaaim, I_unbbaim, and I_unbcaim are the target values of the three-phase unbalanced current compensation respectively, I_unb_a, I_unb_b, and I_unb_c are the compensation values of the three-phase unbalanced current respectively, λ is the compensation step size of the current unbalance amount, the value range of λ is from 0 to 1, and the larger λ is, the faster the unbalance compensation is.

[0066] Based on the compensation values of the three-phase unbalanced current, the three-phase inductance unbalance compensation voltages U A_unb , U B_unb and U C_unb are obtained:

[0067] U A_unb = ωL × I_unb_a × cos(θ - 900)

[0068] U B_unb = ωL × I_unb_b × cos(θ - 900 + 1200)

[0069] U C_unb = ωL × I_unb_c × cos(θ - 900 - 1200)

[0070] Among them, 900 represents the angle by which the inductor current lags the voltage.

[0071] In the three-phase voltages U A , U B , U C generated by the CLARKE inverse transformation, add U A_unb , U B_unb , U C_unb respectively to complete the current imbalance compensation for the motor.

[0072] By implementing the embodiments of the present disclosure, the three-phase imbalance of the motor is monitored according to the operating state of the motor and its associated imbalance monitoring parameters, improving the reliability and accuracy of the three-phase imbalance detection of the motor, helping to quickly detect the three-phase imbalance under different motor operating conditions, and timely compensating for the imbalance of the motor according to the imbalance compensation processing method, avoiding the motor from being in an abnormal operating state for a long time, enhancing the overall safety of the system, and improving the stability, reliability and service life of the motor. In addition, the present disclosure also refines the imbalance detection of the motor to analyze the cause of the imbalance according to the imbalance monitoring parameters, providing a reliable reference for the subsequent maintenance or repair work of the motor.

[0073] Figure 6 It is a schematic flowchart of a method for detecting three-phase imbalance in the static state of a motor provided by an embodiment of the present disclosure. As Figure 6 shown, the method may include:

[0074] S601, determine that the operating state of the motor is the static state.

[0075] S602, obtain the imbalance monitoring parameters associated with the static state, including: the voltages of the three-phase busbars, the three-phase currents, the control current, the level values of the current signals on the three phase lines, and the code values of the speed sensor encoder.

[0076] Among them, the code value of the speed sensor encoder refers to the number of pulses output by the encoder during rotation or linear motion, and these pulses can be used to represent the displacement or speed of the mechanical component.

[0077] S603, determine whether the voltages of the three-phase busbars and the three-phase currents satisfy: the voltages of the three-phase busbars are within the normal operating range of the busbar voltage, and the imbalance degree of the three-phase currents is less than the imbalance degree threshold.

[0078] Among them, the normal operating range of the busbar voltage can be determined according to the power supply standard or equipment requirements, and the calculation formula for the imbalance degree of the three-phase currents is as follows for reference:

[0079] E=(I max -I min )×100%

[0080] Among them, Imax is the maximum current value among the three-phase currents, I min is the minimum current value among the three-phase currents.

[0081] S604, if the voltage of the three-phase bus is within the normal operating range of the bus voltage and the unbalance degree of the three-phase currents is less than the unbalance degree threshold, it is determined that the motor has no three-phase unbalance.

[0082] S605, if the voltage of the three-phase bus is not within the normal operating range of the bus voltage, or the unbalance degree of the three-phase currents is greater than or equal to the unbalance degree threshold, it is determined that the motor has three-phase unbalance, and it is determined whether there is a first value in the three-phase currents.

[0083] Wherein, the first value can be a zero value, or can also be a value lower than a preset threshold, and the preset threshold is a relatively small value close to 0.

[0084] S606, if there is a first value in the three-phase currents, it is determined whether there is a missing current signal among the current signals on the three phase lines based on the level values of the current signals on the three phase lines.

[0085] In some embodiments of the present disclosure, it can be determined whether there is a missing current signal by the magnitude of the level values of the current signals on the three phase lines. For example, when the level value of the current signal on a certain phase line is less than or equal to a second value (such as a 0 value, or a relatively small value close to 0), it is determined that there is a missing current signal on that phase line. If the level value of the current signal on a certain phase line is greater than the second value, it is determined that the current signal on that phase line exists. Whether there is a missing current signal is further used to determine whether the first value in the three-phase currents is caused by a phase loss or a zero-crossing phenomenon.

[0086] S607, if there is no missing current signal among the current signals on the three phase lines, it is determined that the cause of the three-phase unbalance is the zero-crossing phenomenon of the three-phase currents.

[0087] If there is no missing current signal among the current signals on the three phase lines, that is, current signals are detected on all three phase lines, it is determined that the cause of the three-phase unbalance is the zero-crossing phenomenon of the three-phase currents.

[0088] S608, if there is a missing current signal among the current signals on the three phase lines, it is determined whether there is a broken wire in the line connection of the motor.

[0089] The phase that causes the abnormality can be determined by the missing current signal, and the line connection condition of the phase line with the missing current signal can be determined. Optionally, the line connection condition can be determined by the line signal or visual observation of the three-phase motor. In some embodiments of the present disclosure, once the phase line with phase loss is determined, corresponding measures can be taken for the motor through the main control unit of the motor, such as stopping the motor operation, issuing an alarm, or attempting to restore balance, to ensure that the motor can stop running safely when a fault occurs and prevent further damage.

[0090] S609, if the line connection condition is that there is a broken line in the motor line, determine that the cause of the three-phase imbalance is poor line contact.

[0091] S610, if the line connection condition is that there is no broken line in the line, determine whether the control current exceeds the control current threshold range.

[0092] S611, if the control current exceeds the control current threshold range, determine that the cause of the three-phase imbalance is an abnormality at the position where the motor's drive unit is connected to the three phases of the motor.

[0093] Wherein, the drive unit is used to drive the motor.

[0094] S612, if the control current does not exceed the control current threshold range, determine that the cause of the three-phase imbalance is a broken line inside the motor.

[0095] S613, if the first value does not exist in the three-phase current and it is determined that there is an abnormal increase in the three-phase current, determine whether the code value of the speed sensor encoder is within the preset code value range.

[0096] Among them, the abnormal increase situation includes: the difference between the three-phase currents is greater than the preset difference, and / or at least one of the three-phase currents exceeds the preset normal threshold range. The difference between the three-phase currents being greater than the preset difference means that the current of a certain phase in the three phases shows an abnormal increase, while the currents of the other two phases may be normal or change little. For example, the current difference between phase A and phase C (or phase B) is greater than the preset difference, that is, the current of phase A is significantly higher than the current of phase C (or phase B). At least one of the three-phase currents exceeding the preset normal threshold range means that one or more of I A 、I B 、I C exceeds the preset normal threshold range. It should be noted that the two abnormal increase situations of the difference between the three-phase currents being greater than the preset difference and at least one of the three-phase currents exceeding the preset normal threshold range may exist simultaneously. For example, an abnormal increase in the current of a certain phase may cause the currents of other phases to be affected as well.

[0097] S614, if the code value is not within the preset code value range, determine that the cause of the three-phase imbalance is an encoder fault.

[0098] S615, if the code value is within the preset code value range, determine that the cause of the three-phase imbalance is a break or short circuit inside the motor.

[0099] By implementing the embodiments of the present disclosure, when the motor is in a stationary state, it is identified whether the motor has a three-phase imbalance through the bus voltage and three-phase current. And when a three-phase imbalance occurs, it is successively detected whether the motor is missing a phase and the cause of the imbalance according to the values of the three-phase current, the current signal, and the code value of the speed sensor encoder. The cause of the imbalance of the motor is accurately located based on the imbalance monitoring parameters when the motor is in a stationary state, providing a reliable reference for subsequent motor maintenance or repair work, so as to quickly restore the motor performance.

[0100] Figure 7 The flowchart of a method for detecting three-phase imbalance of a motor in a non-stationary state provided by the embodiments of the present disclosure. As Figure 7 shown, the method may include:

[0101] S701, determine that the operating state of the motor is a non-stationary state.

[0102] S702, obtain the imbalance monitoring parameters associated with the non-stationary state, including: three-phase current, control current, and motor speed.

[0103] S703, judge the load state of the motor according to the three-phase current, control current, and motor speed of the motor.

[0104] S704, if the load state of the motor is no-load, determine whether the voltage of the three-phase bus and the three-phase current satisfy: the voltage of the three-phase bus is within the normal operating range of the bus voltage, and the unbalance degree of the three-phase current is less than the unbalance degree threshold.

[0105] S705, if the voltage of the three-phase bus is within the normal operating range of the bus voltage, and the unbalance degree of the three-phase current is less than the unbalance degree threshold, determine that the motor has no three-phase imbalance.

[0106] S706, if the voltage of the three-phase bus is not within the normal operating range of the bus voltage, or the unbalance degree of the three-phase current is greater than or equal to the unbalance degree threshold, determine that the motor has a three-phase imbalance, determine that the imbalance monitoring parameters further include the current signals on the three phase lines, and determine whether there is a missing current signal among the current signals on the three phase lines.

[0107] S707, if there is a missing current signal among the current signals on the three phase lines, determine that the cause of the three-phase imbalance is a missing phase.

[0108] In some embodiments of the present disclosure, after determining that the cause of the three-phase imbalance is a missing phase, the PWM duty cycle can be reduced, and the motor can be slowly stopped to reduce the inertia of the motor.

[0109] S708, if current signals on all three phase lines exist and at least twice the detected three-phase current exceeds the preset normal threshold range, determine that the cause of the three-phase imbalance is a circuit fault in the motor.

[0110] If at least twice the detected three-phase current does not all exceed the preset normal threshold range, it can be determined that the current unbalanced situation of the motor is not caused by a fault and is a normal situation. As a possible implementation, the three-phase current can be detected multiple times, such as three times. If the three-phase current exceeds the preset normal threshold range in each detection, it can be determined that the cause of the three-phase imbalance is a circuit fault in the motor.

[0111] S709, if the load state of the motor is loaded, determine whether the three-phase current exceeds the preset normal threshold range.

[0112] S710, if the three-phase current does not exceed the preset normal threshold range, determine that the motor has not experienced a three-phase imbalance.

[0113] S711, if the three-phase current exceeds the preset normal threshold range, determine that the motor has a three-phase imbalance, determine that the unbalance monitoring parameters also include the current signals on the three phase lines, and determine whether there is a missing current signal among the current signals on the three phase lines.

[0114] S712, if there is a missing current signal among the current signals on the three phase lines, determine that the cause of the three-phase imbalance is a phase loss.

[0115] In some embodiments of the present disclosure, after determining that the cause of the three-phase imbalance is a phase loss, the PWM duty cycle can be reduced and the motor can be slowly stopped to reduce the inertia of the motor. It should be noted that in Figure 7 the illustrated embodiment, after determining that the cause of the three-phase imbalance is a phase loss when the motor is not in a stationary state, the steps of reducing the PWM duty cycle and slowly stopping the motor can be independently implemented from the steps of performing unbalance compensation on the motor according to the unbalance compensation processing method, so there is no conflict between the two steps.

[0116] S713, if current signals exist on all three phase lines, determine whether the three-phase current and the motor speed meet the preset conditions.

[0117] Among them, the preset conditions are: the three-phase current and the motor speed are negatively correlated, and there are no identical frequency components in the spectrum of the three-phase current and the motor speed, and the three-phase current does not exceed the preset normal threshold range and the motor speed does not exceed the preset normal speed range.

[0118] It should be noted that under normal circumstances, there is a certain relationship between the current and speed of the motor:

[0119] Increasing current: When the load increases, the motor requires a greater torque to drive the load, resulting in an increase in current. If the rotational speed remains constant or decreases slightly, it indicates that the motor is operating within the normal range.

[0120] Rotational speed fluctuation: The change in rotational speed is usually related to load changes, power supply voltage fluctuations, or the response of the motor control system. Rotational speed fluctuations may be related to changes in current, but the specific relationship depends on the motor control method and load characteristics.

[0121] It is possible to collect real-time data of the three-phase current and rotational speed of the motor, plot the three-phase current and rotational speed data on the same time axis as a time series graph, and perform time series analysis on the three-phase current and motor rotational speed. Determine the correlation between the three-phase current and the motor rotational speed based on the time series graph:

[0122] Negative correlation: If the rotational speed decreases when the current increases, it indicates that the load has increased. The motor requires a greater torque to drive the load, resulting in an increase in current. The decrease in rotational speed is because the motor is overcoming a greater load, and the motor is operating normally.

[0123] Positive correlation: If the rotational speed also increases when the current increases, there is an abnormal situation. There may be problems with the control system or sudden load changes, resulting in unstable motor output power. It is necessary to check the control system. If it is found that there is a problem with the control system, the control parameters can be adjusted or the control equipment can be replaced.

[0124] In some embodiments of the present disclosure, Fourier transform can be performed on the three-phase current and motor rotational speed to analyze their spectral components and determine whether there are the same frequency components in the spectra of the three-phase current and motor rotational speed. If there are the same frequency components in the current and rotational speed at certain specific frequencies, it indicates that the motor may have mechanical resonance or electrical resonance problems. Resonance causes periodic changes in the motor load, affecting the current and rotational speed. Mechanical resonance analysis can be performed on the motor and corresponding measures can be taken, such as checking the mechanical components of the motor and the load and making necessary adjustments or replacements.

[0125] S714, if the three-phase current and motor rotational speed meet the preset conditions, determine that the cause of the three-phase imbalance is a change in the motor load.

[0126] When the three-phase current and motor rotational speed meet the preset conditions, it means that there is a negative correlation between the three-phase current and the motor rotational speed, and there are no same frequency components in the spectra of the three-phase current and the motor rotational speed, and the three-phase current does not exceed the preset normal threshold range and the motor rotational speed does not exceed the preset normal rotational speed range, which is a normal situation. In some embodiments of the present disclosure, the PID parameters can be appropriately adjusted to reduce the imbalance caused by load changes. The load distribution can also be optimized to ensure balanced load distribution and avoid overloading of single-phase loads.

[0127] S715. If the three-phase current and the motor speed do not meet the preset conditions, it is determined that the cause of the three-phase imbalance is a fault inside the motor.

[0128] The three-phase current and the motor speed not meeting the preset conditions means that at least one of the following is satisfied: the three-phase current and the motor speed have a non-negative correlation (positive correlation or no obvious correlation), there are the same frequency components in the spectrum of the three-phase current and the motor speed, the three-phase current exceeds the preset normal threshold range and the motor speed does not exceed the preset normal speed range, which is an abnormal situation. In some embodiments of the present disclosure, a fault such as a short circuit inside the motor can reduce the PWM duty cycle, cause a slow shutdown, and reduce the inertia of the motor.

[0129] Alternatively, the abnormal cause and the corresponding solution can be further determined according to the three-phase current and the motor speed. For example, if the three-phase current and the motor speed are positively correlated, and when the three-phase current increases, the motor speed also increases, it is determined that there is a problem with the control system, resulting in unstable motor output power, and the control system of the motor can be checked. If there are the same frequency components in the spectrum of the three-phase current and the motor speed (resonance occurs at a specific frequency), it is determined that mechanical resonance causes periodic changes in the motor load, affecting the current and speed, and mechanical resonance analysis can be performed and corresponding measures can be taken.

[0130] By implementing the embodiments of the present disclosure, when the motor is in a non-stationary state, according to the load state of the motor, corresponding unbalance monitoring parameters are used to identify whether the motor has a three-phase imbalance and the cause of the imbalance when the three-phase imbalance occurs. It realizes the accurate positioning of the cause of the motor imbalance based on the unbalance monitoring parameters when the motor is in a non-stationary state, provides a reliable reference for the subsequent maintenance or repair work of the motor, so as to quickly restore the motor performance.

[0131] Figure 8 This is a schematic diagram of a detection system for three-phase imbalance of a motor provided by an embodiment of the present disclosure. As Figure 8 shown, the detection system for three-phase imbalance of the motor includes: an acquisition unit 801 and a main control unit 802.

[0132] Among them, the acquisition unit 801 is used to acquire unbalance monitoring parameters associated with the operating state of the motor.

[0133] The main control unit 802 is used to execute the method provided by the foregoing embodiment. In addition, after the main control unit 802 executes the method provided by the foregoing embodiment, it can also send corresponding control commands to the drive unit.

[0134] Figure 8The drive unit 803 therein can perform data analysis according to the control commands of the main control unit, adjust the PID (Proportional-Integral-Derivative) parameters, and drive and control the motor through the drive unit to ensure that the motor has different drive modes under different working conditions. This improves the stability and response speed of the entire control system.

[0135] In some embodiments of the present disclosure, when the operating state of the motor is the stationary state (corresponding to the Figure 6 illustrated embodiment), the PID parameters can be adjusted in the following manner:

[0136] Proportional (P) parameter: In the stationary state, the proportional parameter is mainly used to quickly respond to changes in the set value. The initial value can be set to a medium level (such as 1.0), and then adjusted according to the system response.

[0137] Integral (I) parameter: In the stationary state, the integral parameter is used to eliminate the steady-state error. The initial value can be set to a low level (such as 0.1) to avoid integral saturation.

[0138] Derivative (D) parameter: In the stationary state, the derivative parameter is mainly used to suppress overshoot. The initial value can be set to a low level (such as 0.01) to avoid excessive amplification of noise.

[0139] In some embodiments of the present disclosure, when the operating state of the motor is the non-stationary state (loaded / unloaded) (corresponding to the Figure 7 illustrated embodiment), the PID parameters can be adjusted in the following manner:

[0140] Proportional (P) parameter: In the non-stationary state, the proportional parameter needs to be adjusted according to the load condition. When loaded, the proportional parameter can be appropriately increased to improve the response speed; when unloaded, the proportional parameter can be appropriately decreased to avoid oscillation.

[0141] Integral (I) parameter: In the non-stationary state, the integral parameter needs to be adjusted according to the dynamic characteristics of the system. When loaded, the integral parameter can be appropriately increased to eliminate the steady-state error; when unloaded, the integral parameter can be appropriately decreased to avoid integral saturation.

[0142] Derivative (D) parameter: In the non-stationary state, the derivative parameter needs to be adjusted according to the dynamic characteristics of the system. When loaded, the derivative parameter can be appropriately increased to suppress overshoot; when unloaded, the derivative parameter can be appropriately decreased to avoid excessive amplification of noise.

[0143] For different working conditions of the motor, the control commands issued by the main control unit and the drive mode of the motor can be determined with reference to the following method:

[0144] When the main control unit determines that the cause of the three-phase imbalance is a phase loss, the control command: Immediately issue a shutdown command and send an alarm signal. Driving method: The drive unit stops the motor operation according to the shutdown command and performs fault diagnosis and repair.

[0145] When the main control unit determines that the cause of the three-phase imbalance is a load change, the control command: The main control unit adjusts the PID parameters in real time according to the load change situation to maintain the system stability and response speed. Driving method: The drive unit adjusts the output torque and speed of the motor in real time according to the adjusted PID parameters to adapt to the load change.

[0146] When the main control unit determines that the cause of the three-phase imbalance is a line fault, the control command: After the main control unit detects the line fault, it immediately issues a shutdown command and sends an alarm signal. Driving method: The drive unit stops the motor operation according to the control command and performs fault diagnosis and repair.

[0147] When the main control unit determines that the cause of the three-phase imbalance is a motor fault, the control command: After the main control unit detects the motor fault, it immediately issues a shutdown command and sends an alarm signal. Driving method: The drive unit stops the motor operation according to the control command and performs fault diagnosis and repair.

[0148] When the main control unit determines that the cause of the three-phase imbalance is a connection fault, the control command: After the main control unit detects the connection fault, it immediately issues a shutdown command and sends an alarm signal. Driving method: The drive unit stops the motor operation according to the control command and performs fault diagnosis and repair.

[0149] In some embodiments of the present disclosure, the PID parameters and the driving method can also be adjusted based on the real-time parameters of the motor, including:

[0150] (1) Real-time monitoring

[0151] Sensor data: The current, voltage, speed, torque and other parameters of the motor are real-time monitored through sensors.

[0152] Data analysis: The main control unit performs real-time analysis on the sensor data to judge the system state.

[0153] (2) PID parameter adjustment

[0154] Adaptive control: An adaptive control algorithm is adopted to adjust the PID parameters in real time according to the system state.

[0155] Fuzzy control: A fuzzy control algorithm is adopted to adjust the PID parameters according to the empirical rules.

[0156] (3) Driving method adjustment

[0157] Vector control: When high-precision control is required, the vector control method is adopted.

[0158] Direct torque control: When fast response is required, the direct torque control method is adopted.

[0159] Variable frequency control: When adjusting the rotational speed is required, the variable frequency control method is adopted.

[0160] Among them, the specific implementation of adjusting the PID parameters and the drive mode based on the real-time parameters of the motor can refer to the following steps:

[0161] S1, Initialization: Set the initial PID parameters and the drive mode.

[0162] S2, Real-time monitoring: Real-time monitor the motor status through sensors.

[0163] S3, Status judgment: The main control unit performs real-time analysis on the sensor data to judge the system status.

[0164] S4, PID parameter adjustment: Adjust the PID parameters in real time according to the system status.

[0165] S5, Drive mode adjustment: Adjust the drive mode in real time according to the system status.

[0166] S6, Execute control command: The drive unit executes the corresponding control operations according to the control command.

[0167] S7, Fault handling: When a fault is detected, immediately stop the machine and give an alarm, and perform fault diagnosis and repair.

[0168] Through the above steps, precise adjustment and fault handling of the motor control system can be achieved, ensuring the stability and reliability of the system.

[0169] To implement the above embodiments, the present disclosure also proposes an electronic device, including: a processor, and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the method provided in the foregoing embodiments.

[0170] To implement the above embodiments, the present disclosure also proposes a computer-readable storage medium, in which computer-executable instructions are stored, and when the computer-executable instructions are executed by a processor, they are used to implement the method provided in the foregoing embodiments.

[0171] To implement the above embodiments, the present disclosure also proposes a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the method provided in the foregoing embodiments.

[0172] In the description of the foregoing embodiments, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0173] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0174] Any process or method description in a flowchart or described in other ways herein can be understood to represent a module, segment, or portion of code including one or more executable instructions for implementing a customized logic function or process, and the scope of the preferred embodiments of the present disclosure includes additional implementations, where the functions may be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0175] The logic and / or steps represented in the flowchart or otherwise described herein can, for example, be considered as a definitional sequence list of executable instructions for implementing logical functions, which can be embodied specifically in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in conjunction with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other suitable processing as necessary, and then stored in a computer memory.

[0176] It should be understood that various parts of the present disclosure can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0177] Those of ordinary skill in the art of this technology can understand that all or part of the steps carried by the method of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0178] In addition, in each embodiment of the present disclosure, each functional unit may be integrated in a processing module, may exist physically separately for each unit, or two or more units may be integrated in one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0179] The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disc, etc. Although the embodiments of the present disclosure have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A detection method for three-phase imbalance of an electric motor, characterized in that, Including the following steps: Determine the operating state of the motor; Obtain the unbalance monitoring parameters associated with the operating state; Determine whether three-phase unbalance occurs in the motor according to the operating state and the unbalance monitoring parameters; In the case that three-phase unbalance occurs in the motor, determine the cause of the three-phase unbalance according to the unbalance monitoring parameters, and perform unbalance compensation on the motor according to the unbalance compensation processing method.

2. The method according to claim 1, characterized in that, The unbalance monitoring parameters include: the voltage and three-phase current of the three-phase bus; wherein, determining whether three-phase unbalance occurs in the motor according to the operating state and the unbalance monitoring parameters includes: In the case that the operating state is a stationary state, the voltage of the three-phase bus is within the normal operating range of the bus voltage, and the unbalance degree of the three-phase current is less than the unbalance degree threshold, it is determined that three-phase unbalance does not occur in the motor; or, In the case that the operating state is a stationary state, the voltage of the three-phase bus is not within the normal operating range of the bus voltage or the unbalance degree of the three-phase current is greater than or equal to the unbalance degree threshold, it is determined that three-phase unbalance occurs in the motor.

3. The method according to claim 2, wherein The unbalance monitoring parameters further include the control current, the level values of the current signals on the three phase lines, and the code value of the speed sensor encoder; wherein, determining the cause of the three-phase unbalance according to the unbalance monitoring parameters includes: In the case that the three-phase current has a first value and it is determined based on the level value that the current signals on the three phase lines all exist, it is determined that the cause of the three-phase unbalance is that the three-phase current has a zero-crossing phenomenon; or, In the case that the three-phase current has a first value and it is determined based on the level value that there is a missing current signal among the current signals on the three phase lines, and there is a broken wire state in the line connection of the motor, it is determined that the cause of the three-phase unbalance is poor line contact; or, In the case that the three-phase current has a first value and it is determined based on the level value that there is a missing current signal among the current signals on the three phase lines, the line connection of the motor has no broken wire, and the control current exceeds the control current threshold range, it is determined that the cause of the three-phase unbalance is an abnormality at the position where the motor three-phase is connected in the drive unit of the motor; or, In the case that the three-phase current has a first value and it is determined based on the level value that there is a missing current signal among the current signals on the three phase lines, the line connection of the motor has no broken wire, and the control current does not exceed the control current threshold range, it is determined that the cause of the three-phase unbalance is a broken wire inside the motor; or, In the case that the three-phase current does not have the first value and the three-phase current has an abnormal increase, and the code value is not within the preset code value range, it is determined that the cause of the three-phase unbalance is an encoder fault; or, When the first value does not exist in the three-phase current and the three-phase current shows an abnormal increase, and the code value is within the preset code value range, it is determined that the cause of the three-phase imbalance is a break or short circuit inside the motor.

4. The method according to claim 1, wherein The imbalance monitoring parameters include: three-phase current, control current, and motor speed; among them, determining whether the motor has a three-phase imbalance according to the operating state and the imbalance monitoring parameters includes: When the operating state is a non-stationary state, determine that the load state of the motor is no-load according to the three-phase current, the control current, and the motor speed. When the voltage of the three-phase bus is within the normal operating range of the bus voltage and the imbalance degree of the three-phase current is less than the imbalance degree threshold, it is determined that the motor does not have a three-phase imbalance; or, When the voltage of the three-phase bus is not within the normal operating range of the bus voltage, or the imbalance degree of the three-phase current is greater than or equal to the imbalance degree threshold, it is determined that the motor has a three-phase imbalance.

5. The method according to claim 4, characterized in that, The imbalance monitoring parameters further include current signals on three phase lines. Determining the cause of the three-phase imbalance according to the imbalance monitoring parameters includes: When there is a missing current signal among the current signals on the three phase lines, it is determined that the cause of the three-phase imbalance is a phase loss; or, When the current signals on the three phase lines all exist and the three-phase current is detected to exceed the preset normal threshold range at least twice, it is determined that the cause of the three-phase imbalance is a circuit fault in the motor.

6. The method according to claim 1, characterized in that, The imbalance monitoring parameters include: three-phase current, control current, and motor speed; among them, determining whether the motor has a three-phase imbalance according to the operating state and the imbalance monitoring parameters includes: When the operating state is a non-stationary state, determine that the load state of the motor is loaded according to the three-phase current, the control current, and the motor speed. When the three-phase current does not exceed the preset normal threshold range, it is determined that the motor does not have a three-phase imbalance; or, When the three-phase current exceeds the preset normal threshold range, it is determined that the motor has a three-phase imbalance.

7. The method according to claim 6, characterized in that, The imbalance monitoring parameters further include current signals on three phase lines; among them, determining the cause of the three-phase imbalance according to the imbalance monitoring parameters includes: When there is a missing current signal among the current signals on the three phase lines, it is determined that the cause of the three-phase imbalance is a phase loss; or, When the current signals on the three phase lines all exist and the three-phase current and the motor speed meet the preset conditions, it is determined that the cause of the three-phase imbalance is a change in the load of the motor; or, When the current signals on the three phase lines all exist and the three-phase current and the motor speed do not meet the preset conditions, it is determined that the cause of the three-phase imbalance is a short circuit inside the motor.

8. The method according to any one of claims 1-7, characterized in that The imbalance compensation processing method includes: Using a simulation system based on a motor control algorithm, open the first set of windings of the motor, and conduct simulation research and analysis on the second set of windings under unbalanced conditions. Use a quasi-resonant controller to suppress the double-frequency harmonics of the motor control system.

9. The method according to any one of claims 1 to 7, characterized in that The unbalance compensation processing method includes: Sampling the three-phase current of the motor, calculating the compensation target value and compensation value of the three-phase unbalanced current in each electrical frequency cycle, and calculating the unbalance compensation voltage of the three-phase inductance of the motor according to the compensation target value and compensation value of the three-phase unbalanced current, and compensating the current unbalance of the motor according to the unbalance compensation voltage of the three-phase inductance of the motor.

10. A detection system for three-phase imbalance of a motor, characterized in that, The system includes: An acquisition unit for acquiring unbalance monitoring parameters associated with the operating state of the motor; A main control unit for executing the method according to any one of claims 1-9.

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