A phase sequence detection method based on back electromotive force

Abstract

The application discloses a phase sequence detection method based on back electromotive force, and belongs to the technical field of motor control. The method comprises the following steps: collecting three-phase output currents of a motor driver; obtaining an electrical angular velocity and an electrical angle of the motor; transforming the three-phase currents to a stationary two-phase coordinate system by using the electrical angle to obtain d-axis current and q-axis current; obtaining d-axis given voltage and q-axis given voltage through a current loop controller; calculating d-axis back electromotive force; calculating q-axis back electromotive force; comparing the size of the q-axis back electromotive force and the d-axis back electromotive force, if the q-axis back electromotive force is greater than the d-axis back electromotive force, the phase sequence is correct, otherwise, the phase sequence is incorrect. The application can quickly and actively detect the phase sequence before the motor starts or in the initial running stage, without waiting for the fault to occur or the dangerous large current to be generated, so as to avoid the running risk and the equipment safety hidden danger.

Description

Technical Field

[0001] This invention relates to the field of motor phase sequence detection technology, and more specifically, to a phase sequence detection method based on back electromotive force. Background Technology

[0002] When installing or maintaining a servo drive system for the first time, it is crucial to connect the motor's three-phase power lines (usually marked A, B, and C) to the driver's output terminals (usually marked U, V, and W) in the correct phase sequence. Theoretically, there are six possible wiring combinations between the driver and the motor, three of which are in the correct sequence and three are in the reverse sequence. If the wiring phase sequence is incorrect, the servo drive will be unable to control the motor properly, causing a series of abnormal operating conditions such as uncontrolled motor operation (e.g., "runaway"), overcurrent, overload, and stall. This may not only damage the motor and related equipment but also pose a threat to the safety of the operators.

[0003] Currently, conventional servo drive detection of phase sequence errors mainly relies on protection mechanisms triggered after a fault occurs, such as monitoring abnormal signals like overcurrent, stalled rotor, overload, or excessive speed deviation. However, these detection methods have significant drawbacks: alarms such as stalled rotor, overload, and excessive speed deviation usually require a certain period of continuous operation before they can be triggered and confirmed. While overcurrent alarms respond relatively quickly, they still require the system to generate a dangerously large current sufficient to reach the protection threshold within a short period. This passive detection method based on the consequences of a fault essentially intervenes only after incorrect wiring has caused a hazardous operating condition. It cannot effectively and quickly identify and prevent phase sequence errors during the initial power-on phase or early operation, resulting in safety hazards such as delayed response and dependence on the severity of the fault. Summary of the Invention

[0004] The purpose of this invention is to overcome the deficiencies in the prior art and provide a phase sequence detection method based on back electromotive force. This phase sequence detection method can quickly and proactively determine whether the wiring phase sequence is correct before the motor starts or during the initial operation phase, without waiting for a fault to occur or for a dangerous large current to be generated, thereby effectively avoiding operational risks and equipment safety hazards caused by incorrect phase sequence.

[0005] To address the above problems, this invention provides a phase sequence detection method based on back electromotive force, comprising the following steps: S1: Obtain the three-phase output current of the motor driver through the current acquisition module; S2: Obtain the motor's electrical angular velocity via the encoder module. and electrical angle ; 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 d-axis and q-axis in the two-phase rotating coordinate system. 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 in the two-phase rotating coordinate system. and q-axis stator current ; S4: Obtain the given voltage along the d-axis in the two-phase rotating coordinate system via a current loop controller. and q-axis given voltage ; S5: Obtain the d-axis back electromotive force , ,in, The stator resistance is constant. Let d be the inductance constant. Let be the q-axis inductance constant. This is the derivative of the d-axis stator current with respect to time; S6: Obtain the q-axis back electromotive force , ,in, This is the derivative of the q-axis stator 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.

[0006] Compared with the prior art, the advantages of this invention are: This invention 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 parameter characterizing the actual operating state of the motor, the d-axis back electromotive force, based on coordinate transformation and back electromotive force estimation formula. and q-axis back electromotive force And thus directly compare 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 slow response in 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.

[0007] The specific steps of step S3 are as follows: S3-1: Constructing the coordinate transformation matrix T , ; S3-2: Obtain the d-axis stator current and q-axis stator current in a two-phase rotating coordinate system. ,in, This refers to the A-phase current in the three-phase output current. This refers to the B-phase current in the three-phase output current. This refers to the C-phase current in the three-phase output current. Detailed Implementation

[0008] 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 with reference to the accompanying drawings.

[0009] A phase sequence detection method based on back electromotive force includes the following steps: S1: Obtain the three-phase output current of the motor driver through the current acquisition module; S2: Obtain the motor's electrical angular velocity via the encoder module. and electrical angle ; 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 d-axis and q-axis in the two-phase rotating coordinate system. 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 in the two-phase rotating coordinate system. and q-axis stator current ; S4: Obtain the given voltage along the d-axis in the two-phase rotating coordinate system via a current loop controller. and q-axis given voltage ; S5: Obtain the d-axis back electromotive force , ,in, The stator resistance is constant. Let d be the inductance constant. Let be the q-axis inductance constant. This is the derivative of the d-axis stator current with respect to time; S6: Obtain the q-axis back electromotive force , ,in, This is the derivative of the q-axis stator 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.

[0010] The coordinate transformation method for converting a three-phase current coordinate system to a two-phase rotating coordinate system is a mature existing technology in the field of motor control. The specific operation steps of step S3 are as follows: S3-1: Constructing the coordinate transformation matrix T , ; S3-2: Obtain the d-axis stator current and q-axis stator current in a two-phase rotating coordinate system. ,in, This refers to the A-phase current in the three-phase output current. This refers to the B-phase current in the three-phase output current. This refers to the C-phase current in the three-phase output current.

[0011] There are six possible connections between the driver and the motor: three forward sequences and three reverse sequences. The forward sequences are UVW-ABC, UVW-BCA, and UVW-CAB; the reverse sequences are UVW-ACB, UVW-BAC, and UVW-CBA. Assume the driver's output current in the dq coordinate system is... ,in, The current amplitude, The driver and motor behave differently depending on the connection method: When the wiring is UVW-ABC, for the motor, the dq axis stator current... When the current is the same as the driver current, the motor rotates in the forward direction. At this time, the d-axis stator current is less than the q-axis stator current. The encoder's electrical angular velocity is greater than 0, that is: The back electromotive force (EMF) calculated by the back EMF estimation module is less than the back EMF q, that is: This allows us to determine that the wiring between the motor and the driver is correct.

[0012] When the wiring is UVW-BCA, for the motor, the dq axis stator current... The current is (+d, -q). When the motor reverses direction, the d-axis stator current is greater than the q-axis stator current. The encoder's electrical angular velocity is less than 0, that is: The back electromotive force (EMF) calculated by the back EMF estimation module is greater than the back EMF q, that is: This led to the conclusion that the wiring between the motor and the driver was incorrect.

[0013] When the wiring is UVW-CAB, for the motor, the dq axis stator current... The current is (-d, -q). When the motor reverses direction, both the d-axis stator current and the q-axis stator current are less than 0. The encoder's electrical angular velocity is less than 0, that is: The back electromotive force (EMF) calculated by the back EMF estimation module is greater than the back EMF q, that is: This led to the conclusion that the wiring between the motor and the driver was incorrect.

[0014] When the wiring is UVW-ACB, for the motor, the dq axis stator current... The current will change with the electrical angle, and eventually the motor shaft will stop and lock at the electrical angle. At this point, the encoder's electrical angular velocity is 0, that is: The back electromotive force (EMF) calculated by the back EMF estimation module is greater than the back EMF q, that is: This led to the conclusion that the wiring between the motor and the driver was incorrect.

[0015] When the wiring is UVW-BAC, for the motor, The current will change with the electrical angle, and eventually the motor shaft will stop and lock at the electrical angle. or At this point, the encoder's electrical angular velocity is 0, that is: The back electromotive force (EMF) calculated by the back EMF estimation module is greater than the back EMF q, that is: This led to the conclusion that the wiring between the motor and the driver was incorrect.

[0016] When the wiring is UVW-CBA, for the motor, The current will change with the electrical angle, and eventually the motor shaft will stop and lock at the electrical angle. or At this point, the encoder's electrical angular velocity is 0, that is: The back electromotive force (EMF) calculated by the back EMF estimation module is greater than the back EMF q, that is: This led to the conclusion that the wiring between the motor and the driver was incorrect.

[0017] Table 1 below shows the detection results of the traditional phase sequence detection method and the phase sequence detection method of this embodiment when the wiring between the motor and the driver is incorrect: Table 1

[0018] According to the data in Table 1, the phase sequence detection method based on back EMF in this embodiment has a significantly shorter detection response time (15ms–40ms) than the traditional method (20ms–300ms) in various incorrect wiring scenarios. Especially in the case of UVW-BCA wiring errors, this method reduces the detection time from approximately 300ms required by the traditional stall alarm to 15ms, improving the response speed by approximately 95%. More importantly, the traditional method relies on the occurrence of faults such as stall or overcurrent to trigger the alarm, while this method can proactively identify phase sequence errors in a very short time, effectively avoiding the risk of equipment damage caused by dangerous operating conditions such as stall or overcurrent, fundamentally improving the safety and reliability of the system.

[0019] This embodiment 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 parameter characterizing the actual operating state of the motor, the d-axis back EMF, based on coordinate transformation and back EMF estimation formula. and q-axis back electromotive force And thus directly compare 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 slow response in 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.

[0020] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

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 motor's electrical angular velocity via the encoder module. and electric angle ; 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 d-axis and q-axis in the two-phase rotating coordinate system. 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 in the two-phase rotating coordinate system. and q-axis stator current ; S4: Obtain the given voltage along the d-axis in the two-phase rotating coordinate system via a current loop controller. and q-axis given voltage ; S5: Obtain the d-axis back electromotive force , ,in, The stator resistance is constant. Let d be the inductance constant. Let be the q-axis inductance constant. This is the derivative of the d-axis stator current with respect to time; S6: Obtain the q-axis back electromotive force , ,in, This is the derivative of the q-axis stator 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 based on back electromotive force according to claim 1, characterized in that, The specific operation steps of step S3 are as follows: S3-1: Constructing the coordinate transformation matrix T , ; S3-2: Obtain the d-axis stator current and q-axis stator current in a two-phase rotating coordinate system. ,in, This refers to the A-phase current in the three-phase output current. This refers to the B-phase current in the three-phase output current. This refers to the C-phase current in the three-phase output current.

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