Method and device for detecting open phase of motor

Abstract

The invention discloses an open-phase detection method and device for a motor, and relates to the field of fault detection, and the method comprises the steps: obtaining the three-phase current of the motor, and determining the counter electromotive force value of the motor according to the three-phase current; determining the running state of the motor according to the back electromotive force value, wherein the back electromotive force value is positively correlated with the rotating speed of the motor; when the motor is in a static state, pre-positioning current is input to the motor so as to control the motor to return; if the pre-positioning current is not equal to the A-phase current of the motor in the static state, determining that the motor has an open-phase fault; and when the motor is in the starting state and the ratio of the maximum value to the minimum value in the three-phase current exceeds a preset multiple, determining that the motor has an open-phase fault. The three-phase current of the motor not only can reflect the running state of the motor, but also can judge whether the motor is open-phase or not when the motor is in a static state and a starting state based on the sampled three-phase current, thereby avoiding the damage of the open-phase fault model of the motor, and improving the running safety of the motor.

Description

Technical Field

[0001] The present invention relates to the field of fault detection, and in particular to a method and device for detecting phase loss of a motor. Background Art

[0002] Permanent magnet synchronous motors are widely used in industrial production and the automotive industry, and the fault detection function of motors is becoming increasingly important. Among them, phase loss is one of the more common and most harmful faults. It is usually caused by aging of the motor power line, internal winding short circuit, poor contact of connectors, etc. If it is not discovered in time, the power devices in the motor and motor controller may be damaged at the least, and the motor may suffer from severe unbalanced vibration, damaging the equipment and causing personal injury. Therefore, in order to detect the operating status and safety protection of permanent magnet synchronous motors, it is very necessary to have a phase loss fault detection function for permanent magnet synchronous motors in the entire speed range to avoid further damage caused by motor phase loss. Summary of the invention

[0003] The purpose of the present invention is to provide a method and device for detecting phase loss of a motor, which can determine whether the motor is phase-lost based on the three-phase current obtained by sampling when the motor is in a stationary state and a starting state, thereby avoiding damage caused by phase loss of the motor and improving the safety of motor operation.

[0004] In order to solve the above technical problems, the present invention provides a method for detecting phase loss of a motor, comprising:

[0005] Acquire the three-phase current of the motor, and determine the back electromotive force value of the motor according to the three-phase current;

[0006] Determining the running state of the motor according to the back electromotive force value, wherein the back electromotive force value is positively correlated with the rotation speed of the motor, and the running state includes starting and stationary;

[0007] When the motor is in a stationary state, inputting a pre-positioning current into the motor so as to control the motor to return to the normal position;

[0008] If the pre-positioning current is not equal to the A-phase current of the motor in a stationary state, it is determined that the motor has a phase failure;

[0009] When the motor is in the starting state, when the ratio between the maximum value and the minimum value in the three-phase current exceeds a preset multiple, it is determined that the motor has a phase failure, and the preset multiple is a value greater than 1.

[0010] On the other hand, obtaining the three-phase current of the motor and determining the back electromotive force value of the motor according to the three-phase current includes:

[0011] Sampling the A-phase current and the B-phase current of the motor;

[0012] According to Kirchhoff's law, the C phase current I of the motor is determined c =-I a -I b ;

[0013] Among them, I a is the A phase current, I b is the B phase current, I c is the C phase current;

[0014] The three-phase current is filtered according to a filtering relation, and the filtering relation is:

[0015] ;

[0016] Among them, I a_lpf is the fundamental value of phase A current after filtering, I b_lpf is the fundamental value of the B-phase current after filtering, I c_lpf is the fundamental value of the C phase current after filtering, I a_lpf_last is the fundamental value of the A phase current after the last sampling and filtering, I b_lpf_last is the fundamental value of the B-phase current after the last sampling and filtering, I c_lpf_last is the fundamental value of the C-phase current after the last sampling and filtering, and α is the filtering coefficient;

[0017] The back electromotive force value of the motor is determined according to the filtered three-phase current.

[0018] On the other hand, determining the running state of the motor according to the back electromotive force value includes:

[0019] When the back electromotive force value is less than a first threshold value, determining that the motor is in a stationary state or an extremely low speed state;

[0020] When the back electromotive force is greater than a second threshold, determining that the motor is in a starting state;

[0021] When the back electromotive force is greater than the second threshold value and less than a third threshold value, determining that the motor enters a stalled state;

[0022] Among them, the first threshold is the smallest, and the second threshold is the largest.

[0023] On the other hand, when the motor is in a stationary state, inputting a pre-positioning current to the motor so as to control the motor to return to the normal position comprises:

[0024] The pre-positioning current is determined based on a coordinate transformation relationship, and the coordinate transformation relationship is:

[0025] ;

[0026] The expression of the pre-positioning current is ;

[0027] where, I d is the actual value of the d-axis current of the motor, I q is the actual value of the q-axis current of the motor, I a is the phase-A current, I b is the phase-B current, I c is the phase-C current.

[0028] On the other hand, if the pre-positioning current is not equal to the phase-A current of the motor in the stationary state, it is determined that the motor has a phase loss fault, including:

[0029] Start timing when the pre-positioning current output value is sent to the motor;

[0030] After waiting for a time T1, sample the phase-A current N1 times, and integrate and sum to obtain the sum of the phase-A current I act_sum1 ;

[0031] where, T / 2 < T1 < T, T is the pre-positioning time, N1×T pwm < T / 2, T pwm is the PWM wave generation period of the power device sent to the motor controller;

[0032] Sample the pre-positioning current N1 times, and integrate and sum to obtain the sum of the pre-positioning current I ref_sum1 ;

[0033] If in k consecutive samplings, there is a preset multiple of the sum of the phase-A current less than the sum of the pre-positioning current, it is determined that the motor has a phase loss fault, k is an integer greater than 1, and the preset multiple is a number greater than 1.

[0034] On the other hand, when the motor is in the starting state, when the ratio between the maximum value and the minimum value of the three-phase current exceeds the preset multiple, it is determined that the motor has a phase loss fault, including:

[0035] Sample the three-phase current n rounds, and each round of sampling collects N2 times;

[0036] where, , f pwm is the PWM wave generation frequency of the power device sent to the motor controller, f n_max is the maximum rotation frequency of the motor, f n_min is the lowest rotation frequency for the motor to enter closed-loop speed regulation;

[0037] Select the maximum value from the N2 three-phase currents in each round of sampling;

[0038] Integrate the maximum values ​​in n rounds;

[0039] Select the maximum integral value and the minimum integral value from the maximum integral values;

[0040] If the preset multiple of the minimum integral value is smaller than the maximum integral value, it is determined that a phase failure occurs in the motor.

[0041] On the other hand, after performing n rounds of sampling on the three-phase current, each round of sampling is performed N2 times, the method further includes:

[0042] The three-phase current sampled in n rounds is modulated according to a modulation relationship, and the modulation relationship is:

[0043] ;

[0044] in, is the fundamental value of phase A current after modulation and filtering, is the fundamental value of phase B current after modulation and filtering, is the fundamental value of phase C current after modulation and filtering, I a_lpf is the fundamental value of phase A current after filtering, I b_lpf is the fundamental value of phase B current after filtering, I c_lpf is the fundamental value of phase C current after filtering;

[0045] The maximum value is selected from the N2 three-phase currents in each round of sampling, including:

[0046] Select the maximum value I among the N2 three-phase currents in each round of sampling after modulation a_max ,I b_max and I c_max ;

[0047] The selected maximum value is filtered using a filtering relation;

[0048] The three-phase current is filtered according to a filtering relation, and the filtering relation is:

[0049] ;

[0050] Among them, I a_peak_pos is the maximum current of phase A after filtering, I b_peak_pos is the maximum value of phase B current after filtering, I c_peak_pos is the maximum value of phase C current after filtering, I a_peak_pos_last is the maximum current of phase A after the last sampling and filtering, I b_peak_pos_last is the maximum value of the B-phase current after the last sampling and filtering, I c_peak_pos_last is the maximum value of the C phase current after the last sampling and filtering, I a_maxis the maximum value of the N2 A-phase currents in each round of sampling, I b_max is the maximum value of the N2 B-phase currents in each round of sampling, I c_max is the maximum value of the N2 C-phase currents in each round of sampling, and α is the filter coefficient.

[0051] On the other hand, integrating the maximum values ​​in n rounds includes:

[0052] Integrate and sum the maximum values ​​of the three-phase currents in each round to obtain the three-phase current integral value;

[0053] Among them, the expression of the integral value of phase A current is: , the expression of the integral value of phase B current is , the expression of the integral value of phase C current is ;

[0054] Among them, I a_peak_pos_sum is the integral value of phase A current, I b_peak_pos_sum is the integral value of B current, I c_peak_pos_sum is the integrated value of C current, I a_peak_pos(i) is the maximum value of the A phase current sampled in the i-th round, I b_peak_pos(i) is the maximum value of the B-phase current sampled in the i-th round, I c_peak_pos(i) is the maximum value of the C-phase current sampled in the i-th round, where i is a positive integer less than n;

[0055] Select the maximum value of the integral and the minimum value of the integral after integration, including:

[0056] Determine the integral maximum value I according to the maximum value selection relation peak_pos_sum_max , the maximum value selection relationship is:

[0057] ;

[0058] Determine the integral minimum value I according to the minimum value selection relation peak_pos_sum_min , the minimum value selection relationship is:

[0059] .

[0060] On the other hand, if the preset multiple of the minimum integral value is less than the maximum integral value, it is determined that the motor has a phase failure, including:

[0061] Determine the amplitude requirement value of the three-phase current, the expression of the amplitude requirement value is:

[0062] ;

[0063] Among them, I s is the amplitude requirement value, Id_ref is the d-axis demand current, I q_ref is the q-axis demand current;

[0064] If the preset multiple of the minimum integral value is smaller than the maximum integral value for k consecutive times, it is determined that the phase corresponding to the minimum integral value is out of phase;

[0065] If the preset multiple of the minimum integral value is greater than the maximum integral value, and I a_peak_pos ,I b_peak_pos and I c_peak_pos The difference between the amplitude requirement value and the amplitude requirement value is greater than the preset difference, I a_peak_pos ,I b_peak_pos and I c_peak_pos When all are 0, it is determined that the three phases are missing at the same time.

[0066] In order to solve the above technical problems, the present invention further provides a motor phase loss detection device, comprising:

[0067] Memory for storing computer programs;

[0068] A processor is used to implement the steps of the above-mentioned motor phase loss detection method when executing the computer program.

[0069] The present invention discloses a method and device for detecting phase loss of a motor, which relates to the field of fault detection, including: obtaining the three-phase current of the motor, and determining the back electromotive force value of the motor according to the three-phase current; determining the running state of the motor according to the back electromotive force value, the back electromotive force value is positively correlated with the speed of the motor, and the running state includes starting and stationary; when the motor is in a stationary state, inputting a pre-positioning current to the motor so as to control the motor to return to the normal state; if the pre-positioning current is not equal to the A-phase current of the motor in the stationary state, it is determined that the motor has a phase loss fault; when the motor is in a starting state, when the ratio between the maximum value and the minimum value in the three-phase current exceeds a preset multiple, it is determined that the motor has a phase loss fault. The three-phase current of the motor can not only reflect the running state of the motor, but also can judge whether the motor is phase-lost based on the three-phase current obtained by sampling when the motor is in a stationary state and a starting state, so as to avoid the damage of the motor phase loss fault modeling and improve the safety of motor operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0071] Figure 1 A flow chart of a method for detecting phase loss of a motor provided by the present invention;

[0072] Figure 2 A flow chart for judging the running state of a motor provided by the present invention;

[0073] Figure 3 A flow chart of a motor phase loss detection before starting provided by the present invention;

[0074] Figure 4 A flow chart of a motor phase loss detection after starting provided by the present invention;

[0075] Figure 5 A schematic structural diagram of a motor phase loss detection device provided by the present invention. DETAILED DESCRIPTION

[0076] The core of the present invention is to provide a motor phase loss detection method and device, which can determine whether the motor is phase-lost based on the three-phase current obtained by sampling when the motor is in a stationary state and a starting state, thereby avoiding damage caused by the motor phase loss fault and improving the safety of motor operation.

[0077] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] Three-phase permanent magnet synchronous motors are widely used in industrial production and the automotive industry, and the fault detection function of the inverter is becoming more and more important. Among them, phase loss is one of the more common and most harmful faults. It is usually caused by aging of the motor power line, short circuit of the internal winding of the motor, poor contact of the connector caused by vibration, etc. If it is not discovered in time, the motor and the power devices in the motor controller may be damaged at the least, and the motor may suffer from severe unbalanced vibration, damaging the equipment and causing personal injury. Therefore, in view of the operating status detection and safety protection of permanent magnet synchronous motors, it is very necessary to have a phase loss fault detection function for the full speed range of permanent magnet synchronous motors to avoid further damage caused by motor phase loss.

[0079] Figure 1 A flow chart of a motor phase loss detection method provided by the present invention, the motor phase loss detection method comprising:

[0080] S11: Obtain the three-phase current of the motor, and determine the back electromotive force value of the motor according to the three-phase current;

[0081] S12: determining the running state of the motor according to the back electromotive force value, the back electromotive force value is positively correlated with the speed of the motor, and the running state includes starting and stationary;

[0082] The motor current can be obtained by sampling the three-phase line. After the three-phase current is collected, the current motor back electromotive force value is calculated according to the enhanced sliding mode algorithm. The back electromotive force value can represent the working state of the motor. When the motor running state is divided by starting, it is divided into the static state before starting and the starting running state.

[0083] S13: When the motor is in a stationary state, input a pre-positioning current to the motor so as to control the motor to return to the normal position;

[0084] S14: If the pre-positioning current is not equal to the A-phase current of the motor in the static state, it is determined that the motor has a phase failure;

[0085] The motor needs to be pre-positioned in the static state before starting, that is, a certain pre-positioning current is input to return the motor to the correct position. In actual calculation, the pre-positioning current is completely consistent with the A-phase current in the static state. When a phase is missing, it will affect the A-phase current. Therefore, in the pre-positioning state, whether the A-phase current is abnormal can be detected to determine the current fault state.

[0086] S15: When the motor is in the starting state, when the ratio between the maximum value and the minimum value of the three-phase current exceeds a preset multiple, it is determined that the motor has a phase failure, and the preset multiple is a value greater than 1.

[0087] After the motor is started, the ratio between the three-phase currents should not be too large. This application adopts the method of selecting the maximum value and the minimum value among the three-phase currents for comparison. If the ratio of the maximum value to the minimum value reaches a preset multiple, it means that one of the items may have failed. At this time, it is determined that the motor has a phase failure.

[0088] Furthermore, in order to improve the accuracy of detection, multiple sampling can often be used when determining a fault, and then the samples can be integrated and processed to avoid directly determining that the motor is faulty due to a single abnormal value, which leads to incorrect judgment, reduced accuracy of judgment, and affected safety of motor operation.

[0089] The present invention discloses a method and device for detecting phase loss of a motor, which relates to the field of fault detection, including: obtaining the three-phase current of the motor, and determining the back electromotive force value of the motor according to the three-phase current; determining the running state of the motor according to the back electromotive force value, the back electromotive force value is positively correlated with the speed of the motor, and the running state includes starting and stationary; when the motor is in a stationary state, inputting a pre-positioning current to the motor so as to control the motor to return to the normal state; if the pre-positioning current is not equal to the A-phase current of the motor in the stationary state, it is determined that the motor has a phase loss fault; when the motor is in a starting state, when the ratio between the maximum value and the minimum value in the three-phase current exceeds a preset multiple, it is determined that the motor has a phase loss fault. The three-phase current of the motor can not only reflect the running state of the motor, but also can judge whether the motor is phase-lost based on the three-phase current obtained by sampling when the motor is in a stationary state and a starting state, so as to avoid the damage of the motor phase loss fault modeling and improve the safety of motor operation.

[0090] Based on the above embodiments:

[0091] In some embodiments, obtaining the three-phase current of the motor and determining the back electromotive force value of the motor according to the three-phase current includes:

[0092] Sampling the A-phase current and B-phase current of the motor;

[0093] Determine the motor's C phase current I according to Kirchhoff's law c =-I a -I b ;

[0094] Among them, I a is the phase A current, I b is the B phase current, I c is the C phase current;

[0095] The three-phase current is filtered according to the filtering relationship, which is:

[0096] ;

[0097] Among them, I a_lpf is the fundamental value of phase A current after filtering, I b_lpf is the fundamental value of phase B current after filtering, I c_lpf is the fundamental value of the C phase current after filtering, I a_lpf_last is the fundamental value of the A phase current after the last sampling and filtering, I b_lpf_last is the fundamental value of the B-phase current after the last sampling and filtering, I c_lpf_last is the fundamental value of the C-phase current after the last sampling and filtering, and α is the filtering coefficient;

[0098] The back electromotive force value of the motor is determined based on the filtered three-phase current.

[0099] Before detecting the motor phase loss, the three-phase current is first filtered to remove the interference phase in the current fundamental wave to avoid affecting subsequent processing. To save hardware costs, usually only the A-phase and B-phase currents are sampled, and the C-phase is calculated using Kirchhoff's law. In the filtering process, the fundamental wave value after the last sampling and filtering is used to improve the accuracy of the fundamental wave value used in subsequent calculations.

[0100] Figure 2 A flow chart for judging the running state of a motor provided by the present invention;

[0101] In some embodiments, determining the operating state of the motor according to the back electromotive force value includes:

[0102] When the back electromotive force value is less than the first threshold value, it is determined that the motor is in a stationary state or an extremely low speed state;

[0103] When the back electromotive force is greater than a second threshold, determining that the motor is in a starting state;

[0104] When the back electromotive force is greater than the second threshold value and less than the third threshold value, determining that the motor enters a stalled state;

[0105] Among them, the first threshold is the smallest and the second threshold is the largest.

[0106] The current motor back electromotive force value EMF is calculated according to the enhanced sliding mode algorithm. When the EMF is less than the first threshold value EMF1, it is considered that the current system is in a stationary state or a very low speed state. Pre-positioning can be performed first, and phase loss fault detection before startup can be performed. Then open-loop startup and closed-loop control can be performed, and phase loss fault detection after startup can be performed at the same time. Open-loop startup is a strategy for the motor controller to slowly start the motor by controlling the current and speed. Closed-loop control means that the motor control system enters a control state where both current and angle are closed-loop controlled. If the EMF is greater than the second threshold value EMF2, the pre-positioning and open-loop startup state can be skipped, and the closed-loop speed regulation state can be directly entered. If the EMF is less than the third threshold value EMF3 in the closed-loop speed regulation state, it is judged that the system enters a stalled state.

[0107] Figure 3 A flow chart of a motor phase loss detection before starting provided by the present invention;

[0108] In some embodiments, when the motor is in a stationary state, inputting a pre-positioning current to the motor so as to control the motor to return to the normal position includes:

[0109] The pre-positioning current is determined based on the coordinate transformation relationship, which is:

[0110] ;

[0111] The expression of the pre-position current is ;

[0112] Among them, I d is the actual value of the d-axis current of the motor, and I q is the actual value of the q-axis current of the motor, and I a is the current of phase A, and I b is the current of phase B, and I c is the current of phase C.

[0113] Before the motor starts, for the detection of open phase, when the system enters the pre-positioning state, the controller injects a d-axis current with a certain amplitude and time into the motor at an electrical angle of 0 degrees, and the d-axis current at this time obtained through coordinate transformation is the current value of phase A.

[0114] In the traditional sliding mode observer-based position control system of a permanent magnet synchronous motor, before the motor starts and when the system enters the pre-positioning state, the controller injects a d-axis current with a certain amplitude and time into the motor at an electrical angle of 0 degrees to make the rotor position of the motor return to normal.

[0115] When the electrical angle of the motor rotor is 0°, I d = I a . It can be seen from this that the d-axis current at this time is exactly the same as the current of phase A, and when there is an open phase, it will affect the current of phase A. Therefore, detecting whether there is an abnormality in the current of phase A in the pre-positioning state can determine the current fault state.

[0116] In some embodiments, if the pre-positioning current is not equal to the current of phase A of the motor in the stationary state, it is determined that the motor has an open-phase fault, including:

[0117] Start timing when the pre-positioning current output value is sent to the motor;

[0118] After waiting for a time T1, sample the current of phase A N1 times, and integrate and sum to obtain the sum of the currents of phase A and I act_sum1 ;

[0119] Among them, T / 2 < T1 < T, T is the pre-positioning time, and N1×T pwm < T / 2, and T pwm is the PWM wave generation period of the power device sent to the motor controller;

[0120] Sample the pre-positioning current N1 times, and integrate and sum to obtain the sum of the pre-positioning currents and I ref_sum1 ;

[0121] If in k consecutive samplings, there is a preset multiple of the sum of the currents of phase A less than the sum of the pre-positioning currents, it is determined that the motor has an open-phase fault, k is an integer greater than 1, and the preset multiple is a number greater than 1.

[0122] When performing phase loss detection in the pre-position state, in order to avoid errors caused by unstable current when the motor is just connected to the current, first, wait for T1 and wait for the current amplitude to stabilize. Then, sample (sum) Ia N1 times and integrate to obtain I act_sum1 , Similarly, the preset demand current value is sampled and integrated N1 times to obtain I ref_sum1 If I act_sum1 < I ref_sum1 / 10, then the count is increased by 1, and two consecutive I act_sum1 < I ref_sum1 / 10, a phase failure fault is reported and the tube is shut down. Otherwise, the count is restarted. This method can be used if any of the three phases is missing.

[0123] Figure 4 A flow chart of a motor phase loss detection after starting provided by the present invention;

[0124] In some embodiments, when the motor is in a starting state, when the ratio between the maximum value and the minimum value of the three-phase current exceeds a preset multiple, determining that the motor has a phase failure includes:

[0125] Perform n rounds of sampling on the three-phase current, with each round of sampling collecting N2 times;

[0126] in, , f pwm is the PWM frequency of the power device sent to the motor controller, f n_max is the maximum rotation frequency of the motor, f n_min The minimum rotation frequency of the motor to enter closed-loop speed regulation;

[0127] Select the maximum value among the N2 three-phase currents in each round of sampling;

[0128] Integrate the maximum values ​​in n rounds;

[0129] Select the maximum integral value and the minimum integral value from the maximum integral values;

[0130] If the preset multiple of the minimum integral value is less than the maximum integral value, it is determined that the motor has a phase failure.

[0131] When the motor starts, that is, in the open-loop start-up and closed-loop speed regulation stages, the same algorithm is used for phase loss detection, the three-phase current is modulated, and then the fundamental amplitude of the three-phase current waveform is extracted. The three-phase current is sampled N2 times, and the maximum value is extracted from it. The value of N2 is used to ensure that the three-phase current amplitude can be collected when the motor runs at a high speed and the rotation frequency is high, and at the same time, the amount of calculation when the motor runs at a low speed and the rotation frequency is low. Then, the maximum value of the three-phase current collected is filtered. The final three-phase current amplitude I is obtained. a_peak_pos ,I b_peak_pos and I c_peak_pos , and perform integration processing to obtain the integral value I of the three-phase current amplitude a_peak_pos_sum ,I b_peak_pos_sum and I c_peak_pos_sum . Extract the maximum and minimum values ​​in the integral and compare them.

[0132] In some embodiments, the three-phase current is sampled n times, and each round of sampling is performed after N2 times, and further includes:

[0133] The three-phase current sampled in n rounds is modulated according to the modulation relationship, and the modulation relationship is:

[0134] ;

[0135] in, is the fundamental value of phase A current after modulation and filtering, is the fundamental value of phase B current after modulation and filtering, is the fundamental value of phase C current after modulation and filtering, I a_lpf is the fundamental value of phase A current after filtering, I b_lpf is the fundamental value of phase B current after filtering, I c_lpf is the fundamental value of phase C current after filtering;

[0136] The maximum value is selected from the N2 three-phase currents in each round of sampling, including:

[0137] Select the maximum value I among the N2 three-phase currents in each round of sampling after modulation a_max ,I b_max and I c_max ;

[0138] The selected maximum value is filtered using a filtering relation;

[0139] The three-phase current is filtered according to the filtering relationship, which is:

[0140] ;

[0141] Among them, I a_peak_pos is the maximum current of phase A after filtering, Ib_peak_pos is the maximum value of phase B current after filtering, I c_peak_pos is the maximum value of phase C current after filtering, I a_peak_pos_last is the maximum current of phase A after the last sampling and filtering, I b_peak_pos_last is the maximum value of the B-phase current after the last sampling and filtering, I c_peak_pos_last is the maximum value of the C phase current after the last sampling and filtering, I a_max is the maximum value of the N2 A-phase currents in each round of sampling, I b_max is the maximum value of the N2 B-phase currents in each round of sampling, I c_max is the maximum value of the N2 C-phase currents in each round of sampling, and α is the filter coefficient.

[0142] When the motor starts, that is, the open-loop start-up and closed-loop speed regulation stages, the same algorithm is used for phase loss detection. First, the three-phase current is modulated. , and It only contains the positive half-axis waveform, which is conducive to subsequent processing and reduces the difficulty of data processing. θ is the electrical angle of the motor rotor.

[0143] The filtering method is the same as above and will not be described again here.

[0144] In some embodiments, integrating the maximum values ​​in n rounds includes:

[0145] Integrate and sum the maximum values ​​of the three-phase currents in each round to obtain the three-phase current integral value;

[0146] Among them, the expression of the integral value of phase A current is: , the expression of the integral value of phase B current is , the expression of the integral value of phase C current is ;

[0147] Among them, I a_peak_pos_sum is the integral value of phase A current, I b_peak_pos_sum is the integral value of B current, I c_peak_pos_sum is the integrated value of C current, I a_peak_pos(i) is the maximum value of the A phase current sampled in the i-th round, I b_peak_pos(i) is the maximum value of the B-phase current sampled in the i-th round, I c_peak_pos(i) is the maximum value of the C-phase current sampled in the i-th round, where i is a positive integer less than n;

[0148] Select the maximum value of the integral and the minimum value of the integral after integration, including:

[0149] Determine the maximum value of the integral I according to the maximum value selection relationship peak_pos_sum_max , the maximum value selection relationship is:

[0150] ;

[0151] Determine the integral minimum value I according to the minimum value selection relation peak_pos_sum_min , the minimum value selection relationship is:

[0152] .

[0153] Each round collects N2 three-phase currents, selects the largest one among the N2 in each round for integration, that is, accumulates the n maximum values ​​and finds the maximum value I peak_pos_sum_max and minimum value I peak_pos_sum_min .

[0154] In some embodiments, if the preset multiple of the minimum integral value is less than the maximum integral value, it is determined that the motor has a phase failure, including:

[0155] Determine the amplitude requirement of the three-phase current. The expression of the amplitude requirement is:

[0156] ;

[0157] Among them, I s is the amplitude requirement, I d_ref is the d-axis demand current, I q_ref is the q-axis demand current;

[0158] If the preset multiple of the minimum integral value is smaller than the maximum integral value for k consecutive times, it is determined that the phase corresponding to the minimum integral value is out of phase;

[0159] If the preset multiple of the minimum integral value is greater than the maximum integral value, and I a_peak_pos ,I b_peak_pos and I c_peak_pos The difference between the amplitude requirement value and the amplitude requirement value is greater than the preset difference, I a_peak_pos ,I b_peak_pos and I c_peak_pos When all are 0, it is determined that the three phases are missing at the same time.

[0160] When the d-axis current and q-axis current can follow their required values ​​well, the three-phase current amplitude required value I s It is obtained by synthesizing the dq axis demand values. If I appears twice in a row peak_pos_sum_min peak_pos_sum_max / 10, then determine the motor I peak_pos_sum_min The place where the phase is missing.

[0161] When I peak_pos_sum_min >I peak_pos_sum_max / 10 condition, first determine whether one of the three phases is missing. If the three-phase current amplitudes are all equal to I s ​When the phase difference is large and close to 0, it means that there is no current in the three-phase circuits and they are all in an open circuit state. Therefore, it is determined that the three phases are missing.

[0162] Figure 5 The present invention provides a schematic diagram of the structure of a motor phase loss detection device, the motor phase loss detection device comprising:

[0163] A memory 51, used for storing computer programs;

[0164] The processor 52 is used to implement the steps of the above-mentioned motor phase loss detection method when executing the computer program.

[0165] For the introduction of the motor phase loss detection device provided in the present application, please refer to the above embodiments and will not be repeated here.

[0166] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0167] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0168] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting phase loss of a motor, characterized in that: include: Acquire the three-phase current of the motor, and determine the back electromotive force value of the motor according to the three-phase current; Determining the running state of the motor according to the back electromotive force value, wherein the back electromotive force value is positively correlated with the rotation speed of the motor, and the running state includes starting and stationary; When the motor is in a stationary state, inputting a pre-positioning current into the motor so as to control the motor to return to the normal position; If the pre-positioned current is not equal to the A-phase current of the motor in a stationary state, it is determined that the motor has a phase failure; When the motor is in the starting state, when the ratio between the maximum value and the minimum value in the three-phase current exceeds a preset multiple, it is determined that the motor has a phase failure, and the preset multiple is a value greater than 1.

2. The method for detecting phase loss of a motor according to claim 1, characterized in that: Acquiring the three-phase current of the motor and determining the back electromotive force value of the motor according to the three-phase current, including: Sampling the A-phase current and the B-phase current of the motor; According to Kirchhoff's law, the C phase current I of the motor is determined c =-I a -I b ; Among them, I a is the A phase current, I b is the B phase current, I c is the C phase current; The three-phase current is filtered according to a filtering relation, and the filtering relation is: ； Among them, I a_lpf is the fundamental value of phase A current after filtering, I b_lpf is the fundamental value of phase B current after filtering, I c_lpf is the fundamental value of the C phase current after filtering, I a_lpf_last is the fundamental value of the A-phase current after the last sampling and filtering, I b_lpf_last is the fundamental value of the B-phase current after the last sampling and filtering, I c_lpf_last is the fundamental value of the C-phase current after the last sampling and filtering, and α is the filtering coefficient; The back electromotive force value of the motor is determined according to the filtered three-phase current.

3. The method for detecting phase loss of a motor according to claim 1, characterized in that: Determining the running state of the motor according to the back electromotive force value includes: When the back electromotive force value is less than a first threshold value, determining that the motor is in a stationary state or an extremely low speed state; When the back electromotive force is greater than a second threshold, determining that the motor is in a starting state; When the back electromotive force is greater than the second threshold value and less than a third threshold value, determining that the motor enters a stalled state; Among them, the first threshold is the smallest, and the second threshold is the largest.

4. The method for detecting phase loss of a motor according to claim 1, characterized in that: When the motor is in a stationary state, inputting a pre-positioning current to the motor so as to control the motor to return to the normal position comprises: The pre-positioning current is determined based on a coordinate transformation relationship, and the coordinate transformation relationship is: ； The expression of the pre-position current is: ; Among them, I d is the actual value of the d-axis current of the motor, I q is the actual value of the q-axis current of the motor, I a is the A phase current, I b is the B phase current, I c is the C phase current, and θ is the electrical angle of the motor rotor.

5. The method for detecting phase loss of a motor according to claim 1, characterized in that: If the pre-positioning current is not equal to the A-phase current of the motor in a stationary state, it is determined that the motor has a phase failure, including: Start timing when the predetermined current output value is set to the motor; After waiting for T1 time, the A phase current is sampled N1 times, and the integral sum is obtained to obtain the A phase current and I act_sum1 ; Among them, T / 2 < T1 < T, where T is a predetermined time, and N1×T pwm < T / 2, T pwm is the PWM wave generation period of the power device sent to the motor controller; The pre-position current is sampled N1 times, and the pre-position current and I are obtained by integrating and summing. ref_sum1 ; If for k consecutive samplings, the preset multiple of the sum of the A-phase current is less than the preset current sum, it is determined that the motor has a phase loss fault, k is an integer greater than 1, and the preset multiple is a number greater than 1.

6. The method for detecting phase loss of a motor according to any one of claims 1 to 5, characterized in that: When the motor is in a starting state, when the ratio between the maximum value and the minimum value of the three-phase current exceeds a preset multiple, determining that the motor has a phase failure includes: Perform n rounds of sampling on the three-phase current, with each round of sampling collecting N2 times; in, , f pwm is the PWM frequency of the power device sent to the motor controller, f n_max is the maximum rotation frequency of the motor, f n_min The minimum rotation frequency of the motor to enter closed-loop speed regulation; Select the maximum value among the N2 three-phase currents in each round of sampling; Integrate the maximum value in n rounds; Select the maximum integral value and the minimum integral value from the maximum integral values; If the preset multiple of the minimum integral value is smaller than the maximum integral value, it is determined that a phase failure occurs in the motor.

7. The method for detecting phase loss of a motor according to claim 6, characterized in that: The three-phase current is sampled n times, and each round of sampling is performed after N2 times, and further includes: The three-phase current sampled in n rounds is modulated according to a modulation relationship, and the modulation relationship is: ； in, is the fundamental value of phase A current after modulation and filtering, is the fundamental value of phase B current after modulation and filtering, is the fundamental value of phase C current after modulation and filtering, I a_lpf is the fundamental value of phase A current after filtering, I b_lpf is the fundamental value of phase B current after filtering, I c_lpf is the fundamental value of the C-phase current after filtering, and θ is the electrical angle of the motor rotor; The maximum value is selected from the N2 three-phase currents in each round of sampling, including: Select the maximum value I among the N2 three-phase currents in each round of sampling after modulation a_max ,I b_max and I c_max ; The selected maximum value is filtered using a filtering relation; The three-phase current is filtered according to a filtering relation, and the filtering relation is: ； Among them, I a_peak_pos is the maximum current of phase A after filtering, I b_peak_pos is the maximum value of phase B current after filtering, I c_peak_pos is the maximum value of phase C current after filtering, I a_peak_pos_last is the maximum current of phase A after the last sampling and filtering, I b_peak_pos_last is the maximum value of the B-phase current after the last sampling and filtering, I c_peak_pos_last is the maximum value of the C phase current after the last sampling and filtering, I a_max is the maximum value of the N2 A-phase currents in each round of sampling, I b_max is the maximum value of the N2 B-phase currents in each round of sampling, I c_max is the maximum value of the N2 C-phase currents in each round of sampling, and α is the filter coefficient.

8. The method for detecting phase loss of a motor according to claim 7, characterized in that: Integrate the maximum value in n rounds, including: Integrate and sum the maximum values ​​of the three-phase currents in each round to obtain the three-phase current integral value; Among them, the expression of the integral value of phase A current is: , the expression of the integral value of phase B current is , the expression of the integral value of phase C current is ; Among them, I a_peak_pos_sum is the integral value of phase A current, I b_peak_pos_sum is the integral value of B current, I c_peak_pos_sum is the integrated value of C current, I a_peak_pos(i) is the maximum value of the A phase current sampled in the i-th round, I b_peak_pos(i) is the maximum value of the B-phase current sampled in the i-th round, I c_peak_pos(i) is the maximum value of the C-phase current sampled in the i-th round, where i is a positive integer less than n; Select the maximum value of the integral and the minimum value of the integral after integration, including: Determine the integral maximum value I according to the maximum value selection relation peak_pos_sum_max , the maximum value selection relationship is: ； Determine the integral minimum value I according to the minimum value selection relation peak_pos_sum_min , the minimum value selection relationship is: 。 9. The method for detecting phase loss of a motor according to claim 8, characterized in that: If the preset multiple of the minimum integral value is less than the maximum integral value, determining that the motor has a phase failure includes: Determine the amplitude requirement value of the three-phase current, the expression of the amplitude requirement value is: ； Among them, I s is the amplitude requirement value, I d_ref is the d-axis demand current, I q_ref is the q-axis demand current; If the preset multiple of the minimum integral value is smaller than the maximum integral value for k consecutive times, it is determined that the phase corresponding to the minimum integral value is out of phase; If the preset multiple of the minimum integral value is greater than the maximum integral value, and I a_peak_pos ,I b_peak_pos and I c_peak_pos The difference between the amplitude requirement value and the amplitude requirement value is greater than the preset difference, I a_peak_pos ,I b_peak_pos and I c_peak_pos When all are 0, it is determined that the three phases are missing at the same time.

10. A motor phase loss detection device, characterized in that: include: Memory for storing computer programs; A processor is used to implement the steps of the motor phase loss detection method as claimed in any one of claims 1 to 9 when executing the computer program.

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