Phase sequence detection method based on back electromotive force

Abstract

The invention discloses a phase sequence detection method based on back electromotive force, and belongs to the technical field of motor control, and the method comprises the steps: collecting the three-phase output current of a motor driver; acquiring an electrical angular speed and an electrical angle of the motor; converting the three-phase current into a static two-phase coordinate system by using the electrical angle to obtain a d-axis current and a q-axis current; obtaining a d-axis given voltage and a q-axis given voltage through a current loop controller; d-axis back electromotive force is calculated; calculating q-axis back electromotive force; and comparing the q-axis counter electromotive force with the d-axis counter electromotive force, if the q-axis counter electromotive force is greater than the d-axis counter electromotive force, determining that the phase sequence is correct, otherwise, determining that the phase sequence is wrong. According to the invention, the phase sequence can be rapidly and actively detected before the motor is started or at the initial operation stage without waiting for fault occurrence or generation of dangerous large current, so that operation risks and equipment potential safety hazards are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor phase sequence detection, in particular to a phase sequence detection method based on back electromotive force. BACKGROUND

[0002] When the servo drive system is first installed or maintained, it is crucial to connect the three-phase power lines (usually marked as A, B, C) of the motor to the output terminals (usually marked as U, V, W) of the driver in the correct phase sequence. There are theoretically six combinations of wiring between the driver and the motor, three of which are positive sequence connections, and three of which are reverse sequence connections. If the phase sequence is connected incorrectly, the servo driver will not be able to control the motor normally, causing the motor to run out of control (such as "flywheel"), overcurrent, overload, and a series of abnormal conditions such as locked rotor, which not only may damage the motor and associated equipment, but also poses a threat to the safety of the operator.

[0003] Currently, the conventional method for servo drivers to detect phase sequence errors mainly relies on protection mechanisms triggered after a fault occurs, such as monitoring abnormal signals such as overcurrent, locked rotor, overload, or excessive speed deviation. However, these detection methods have significant drawbacks: locked rotor, overload, and excessive speed deviation alarms usually need to experience a certain duration of fault operation before they can be triggered and confirmed, while overcurrent alarms, although they respond relatively quickly, still require the system to generate a dangerous large current within a short period of time to reach the protection threshold. This passive detection method based on fault consequences essentially intervenes only after the incorrect wiring has caused a harmful operating state, and it cannot effectively and quickly identify and prevent the occurrence of phase sequence errors during the initial power-up phase or early operation. This approach has a response lag and relies on the severity of the fault, posing a safety hazard. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art and provide a phase sequence detection method based on back electromotive force, which can quickly and actively determine whether the wiring phase sequence is correct before the motor starts or during the initial operation stage, without waiting for a fault to occur or a dangerous large current to be generated, thereby effectively avoiding the risk of operation and safety hazards caused by phase sequence errors.

[0005] To solve the above problems, the present application provides a phase sequence detection method based on back electromotive force, comprising the following steps:

[0006] S1: obtaining the three-phase output current of the motor driver through the current acquisition module;

[0007] S2: obtaining the electrical angular velocity ω of the motor through the encoder module e and the electrical angle θ e ;

[0008] S3: setting a coordinate transformation matrix for converting the coordinates of the three-phase output current in a three-phase coordinate system to the coordinates in a static two-phase coordinate system where the d-axis and q-axis are located, inputting the electrical angle into the coordinate transformation matrix, and transforming the three-phase output current through the coordinate transformation matrix to obtain the d-axis stator current i d and the q-axis stator current i q ;

[0009] S4: obtaining the d-axis given voltage u d and the q-axis given voltage u q ;

[0010] S5: obtaining the d-axis back electromotive force wherein R is a stator resistance constant, L d is a d-axis inductance constant, L q is a q-axis inductance constant, is the derivative of the d-axis current with respect to time;

[0011] S6: obtaining the q-axis back electromotive force wherein, is the derivative of the q-axis current with respect to time;

[0012] S7: judging whether the wiring phase sequence of the motor is correct by comparing the size of and When is greater than , it indicates that the wiring phase sequence of the motor is correct, otherwise, it indicates that the wiring phase sequence of the motor is incorrect.

[0013] Compared with the prior art, the present application has the beneficial effects that: the present application acquires the three-phase output current of the motor driver and the electrical angle and electrical angular velocity of the motor in real time, and calculates the key parameters d-axis back electromotive force and q-axis back electromotive force based on the coordinate transformation and back electromotive force estimation formula, which represent the actual running state of the motor, and then directly compares and The phase sequence is determined by the magnitude of the phases. This detection method, based on the inherent electromagnetic characteristics (back electromotive force) of the motor, can complete the determination at the initial stage of motor startup or at extremely low speeds. The response speed is significantly faster than traditional methods that rely on fault phenomena such as overcurrent and stalled rotor. It effectively solves the problem of lag in response of existing technologies. More importantly, this method does not require the motor to generate dangerously large currents sufficient to trigger overcurrent protection or experience abnormal operating conditions such as stalled rotor or runaway rotor that may damage the equipment during the detection process. It is a proactive and preventive detection method that fundamentally avoids the operational risks and safety threats to equipment and personnel that may be caused by incorrect phase sequence wiring, and significantly improves the safety and reliability of system initialization and operation.

[0014] The specific steps of step S3 are as follows:

[0015] S3-1: Construct the coordinate transformation matrix T,

[0016]

[0017] S3-2: Obtain the d-axis stator current and q-axis stator current in a stationary two-phase coordinate system. Among them, i a i is the A-phase current in the three-phase output current. b i is the B-phase current in the three-phase output current. c This refers to the C-phase current in the three-phase output current. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0019] A phase sequence detection method based on back electromotive force includes the following steps:

[0020] S1: Obtain the three-phase output current of the motor driver through the current acquisition module;

[0021] S2: Obtain the electric angular velocity ω of the motor through the encoder module. e and electrical angle θ e ;

[0022] S3: Set the coordinate transformation matrix to transform the coordinates of the three-phase output current in the three-phase coordinate system to the coordinates of the stationary two-phase coordinate system containing the d-axis and q-axis. Input the electrical angle into the coordinate transformation matrix, and use the coordinate transformation matrix to transform the three-phase output current to obtain the d-axis stator current i in the stationary two-phase coordinate system. d and q-axis stator current i q ;

[0023] S4: Obtain the d-axis given voltage u in the stationary two-phase coordinate system through the current loop controller.d and q-axis given voltage u q ;

[0024] S5: Obtain d-axis back electromotive force wherein, R is stator resistance constant, L d is d-axis inductance constant, L q is q-axis inductance constant, is the derivative of d-axis current with respect to time;

[0025] S6: Obtain q-axis back electromotive force wherein, is the derivative of q-axis current with respect to time;

[0026] S7: Determine whether the connection phase sequence of the motor is correct by comparing and When is greater than , it indicates that the connection phase sequence of the motor is correct, otherwise, it indicates that the connection phase sequence of the motor is incorrect.

[0027] The coordinate transformation method of converting the three-phase current coordinate system into the stationary two-phase coordinate system belongs to the mature prior art in the field of motor control, and the specific operation steps of step S3 are:

[0028] S3-1: Construct the coordinate transformation matrix T,

[0029]

[0030] S3-2: Obtain the d-axis stator current and q-axis stator current in the stationary two-phase coordinate system, wherein, i a is the A-phase current in the three-phase output current, i b is the B-phase current in the three-phase output current, and i c is the C-phase current in the three-phase output current.

[0031] There are six cases in total for the connection of the driver and the motor, three positive sequences and three negative sequences, which are: positive sequence UVW-ABC, UVW-BCA, UVW-CAB; negative sequence UVW-ACB, UVW-BAC, UVW-CBA, assuming that the output current of the driver in the d-q coordinate system is wherein, I s is the current amplitude, The driver and the motor under different connection modes are specifically represented as:

[0032] When the connection is UVW-ABC, for the motor, the d-q axis current The current is consistent with the driver current, the motor rotates forward, at this time, the d-axis current is less than the q-axis current, i d , q The encoder electric angular velocity is greater than 0, that is: ω e >0, the d-axis back electromotive force calculated by the back electromotive force estimation module is less than the q back electromotive force, that is: Therefore, it is judged that the motor and the driver are correctly wired.

[0033] When the wiring is UVW-BCA, for the motor, the d-q axis current The current is (+d, -q), the motor reverses, at this time, the d-axis current is greater than the q-axis current, i d >i q The encoder electric angular velocity is less than 0, that is: ω e <0, the d-axis back electromotive force calculated by the back electromotive force estimation module is greater than the q back electromotive force, that is: Therefore, it is judged that the motor and the driver are incorrectly wired.

[0034] When the wiring is UVW-CAB, for the motor, the d-q axis current The current is (-d, -q), the motor reverses, at this time, the d-axis current and the q-axis current are simultaneously less than 0, i d <0, i q <0, the encoder electric angular velocity is less than 0, that is: ω e <0, the d-axis back electromotive force calculated by the back electromotive force estimation module is greater than the q back electromotive force, that is: Therefore, it is judged that the motor and the driver are incorrectly wired.

[0035] When the wiring is UVW-ACB, for the motor, the d-q axis current The current will change with the electric angle, and finally the motor shaft will stop and lock at the electric angle θ e =±π / 4, at this time, the encoder electric angular velocity is 0, that is: ω e =0, the d-axis back electromotive force calculated by the back electromotive force estimation module is greater than the q back electromotive force, that is: Therefore, it is judged that the motor and the driver are incorrectly wired.

[0036] When the wiring is UVW-BAC, for the motor, The current will change with the electric angle, and finally the motor shaft will stop and lock at the electric angle θ e =π / 12 or θ e =7π / 12, at this time, the encoder electric angular velocity is 0, that is: ω e =0, the d-axis back electromotive force calculated by the back electromotive force estimation module is greater than the q back electromotive force, that is: Thus, it is judged that the motor and the driver are connected in error.

[0037] When the connection is UVW-CBA, for the motor, The current will change with the electrical angle, and finally the motor shaft will stop and be locked at the electrical angle θ e = 5π / 12 or θ e = 11π / 12, at this time, the encoder electrical angular velocity is 0, that is, ω e = 0, the d-axis back-EMF calculated by the back-EMF estimation module is greater than the q-axis back-EMF, that is, Thus, it is judged that the motor and the driver are connected in error.

[0038] The following Table 1 shows the detection results of the traditional phase sequence detection method and the phase sequence detection method of the embodiment when the motor and the driver are connected in error:

[0039] Table 1

[0040]

[0041] According to the data in Table 1, it is shown that the phase sequence detection method based on back-EMF of the embodiment has a detection response time (15ms-40ms) which is significantly shorter than that (20ms-300ms) of the traditional method in various error connection scenarios. Especially when the connection is UVW-BCA, the detection time of the method is shortened from about 300ms required by the traditional stall alarm to 15ms, and the response speed is improved by about 95%. More importantly, the traditional method needs to rely on the occurrence of stall or overcurrent and other faults to trigger the alarm, while the method can actively identify the phase sequence error in a very short time, effectively avoiding the risk of equipment damage caused by stall, overcurrent and other dangerous working conditions, and fundamentally improving the safety and reliability of the system.

[0042] The embodiment calculates the key parameters d-axis back-EMF and q-axis back-EMF characterizing the actual running state of the motor based on the real-time acquisition of the three-phase output current of the motor driver and the electrical angle and electrical angular velocity of the motor, and the coordinate transformation and back-EMF estimation formula and The method can judge the phase sequence according to the size relationship, the detection method based on the inherent electromagnetic characteristics (counter electromotive force) of the motor can complete the judgment at the initial stage of motor starting or at extremely low speed, the response speed is significantly faster than the traditional method triggered by relying on overcurrent, locked rotor and other fault phenomena, effectively solves the problem of response lag in the prior art, more importantly, the method does not need the motor to generate a dangerous large current enough to trigger the overcurrent protection or experience abnormal working conditions such as locked rotor, flywheel and the like which may cause damage to the equipment during the detection process, is a kind of active and preventive detection means, fundamentally avoids the operation risk and safety threat to equipment and personnel caused by phase sequence error wiring, significantly improves the safety and reliability of system initialization and operation.

[0043] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited to this. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present disclosure.

Claims

1. A phase sequence detection method based on back electromotive force, characterized in that, Includes the following steps: S1: Obtain the three-phase output current of the motor driver through the current acquisition module; S2: Obtain the electric angular velocity ω of the motor through the encoder module. e and electrical angle θ e ; S3: Set the coordinate transformation matrix to transform the coordinates of the three-phase output current in the three-phase coordinate system to the coordinates of the stationary two-phase coordinate system containing the d-axis and q-axis. Input the electrical angle into the coordinate transformation matrix, and use the coordinate transformation matrix to transform the three-phase output current to obtain the d-axis stator current i in the stationary two-phase coordinate system. d and q-axis stator current i q ; S4: Obtain the d-axis given voltage u in the stationary two-phase coordinate system through the current loop controller. d and q-axis given voltage u q ; S5: Obtain the d-axis back electromotive force Where R is the stator resistance constant, L d L is the d-axis inductance constant. q Let q be the q-axis inductance constant. This is the derivative of the d-axis current with respect to time; S6: Obtain the q-axis back electromotive force in, This is the derivative of the q-axis current with respect to time. S7: By comparison and The size of the motor determines whether the wiring phase sequence is correct. Greater than If the phase sequence is 1, it indicates that the motor wiring phase sequence is correct; otherwise, it indicates that the motor wiring phase sequence is incorrect.

2. The phase sequence detection method for back electromotive force according to claim 1, characterized in that, The specific steps of step S3 are as follows: S3-1: Construct the coordinate transformation matrix T, S3-2: Obtain the d-axis stator current and q-axis stator current in a stationary two-phase coordinate system. Among them, i a i is the A-phase current in the three-phase output current. b i is the B-phase current in the three-phase output current. c This refers to the C-phase current in the three-phase output current.

Images