TWI403747B - System and method for detecting phase failure of the brushless motor and a brushless motor control system with the phase failure detection - Google Patents

Abstract

The present invention is a system and method for detecting phase failure of the brushless motor and a brushless motor control system with the phase failure detection. The system for detecting phase failure has a micro-controller, a voltage divider and a virtual neutral point circuit being composed of a plurality of resistors. The voltage divider and the virtual neutral point circuit detect the three phase voltages of the brushless motor and transmit the detected three phase voltages to the micro-controller. The micro-controller determines whether the phase failure occurs based on the characteristics of the three phase voltages. Therefore, phase failure can be easily recognized and the motor can be protected without using any electric current sensor.

Description

Phase loss diagnosis system and method for brushless motor and brushless motor control system with phase loss diagnosis function

The invention relates to a phase loss diagnosis system of a brushless motor, in particular to a technology capable of judging whether a phase loss fault of a frequency converter or a phase loss of a motor winding occurs without using a current sensing component.

In the past, the phase-deficient diagnostic method applied to the permanent magnet brushless motor uses the three-phase current of the detecting motor as a basis for diagnosis. The disadvantages and limitations are as follows:

1. In order to obtain the three-phase current value of the motor, it is often necessary to connect several expensive current sensing components to the respective phases of the motor, but in a low-cost application, this architecture will be difficult to adopt.

2. The traditional phase detection method for detecting current is usually required to input the current sampling data measured by each current sensor to a controller, and perform complex mathematical operations through the controller to obtain average current and three-phase current imbalance. Rate, so the controller must be implemented with a higher-order control chip, which also reduces the overall processing efficiency of the controller.

3, due to a variety of factors causing motor current anomalies, such as the operation of abnormal loads, and the current reference value for determining the phase loss is usually determined by the rule of thumb, so there will be doubts about misjudgment.

The main object of the present invention is to provide a phase loss diagnosis system for a brushless motor, which can diagnose the presence or absence of a motor winding according to the basic characteristics of the sum of the three-phase voltages of the motor without presuming sampling of the three-phase current of the motor. The inverter that blocks or controls the motor fails and forms a phase loss state.

In order to achieve the foregoing objective, the phase loss diagnosis system of the brushless motor of the present invention comprises: a microcontroller outputting a commutation signal for controlling the brushless motor; and a virtual neutral point circuit comprising a plurality of resistors. The virtual neutral point circuit is connected to the three-phase wiring of the brushless motor; a voltage dividing circuit is connected between the virtual neutral point circuit and the microcontroller to feedback the three-phase of the brushless motor The terminal voltage data is given to the microcontroller; wherein the microcontroller determines whether the inverter phase loss occurs according to whether the three-phase terminal voltage of the brushless motor is within a predetermined range, and also according to the three-phase end of the brushless motor Whether the voltage is greater than a predetermined value determines whether the motor winding phase loss occurs.

Another object of the present invention is to provide a brushless motor control system with a phase loss diagnostic function, comprising: a microcontroller outputting a commutation signal for controlling a brushless motor; and an inverter receiving the micro control The commutation signal outputted by the device is composed of a plurality of power transistors, and the three-arm structure is a U-phase arm, a V-phase arm and a W-phase arm; and a brushless motor is an AC three-phase permanent magnet. The brushless motor is operated by the inverter, and the three-phase wiring is respectively connected to the U-phase arm, the V-phase arm and the W-phase arm of the inverter, and the three-phase terminal voltages are V _ug , V _vg and V _{wg respectively}

a virtual neutral point circuit is composed of a plurality of resistors, and the virtual neutral point circuit is connected to the three-phase wiring of the brushless motor to sense the voltages of the three-phase terminals thereof are V _ug , V _vg and Vw _{g respectively} ; a voltage dividing circuit is connected between the virtual neutral point circuit and the microcontroller to feedback the three-phase terminal voltage data of the brushless motor to the microcontroller; wherein the microcontroller is based on the brushless Whether the three-phase terminal voltage of the motor is within a predetermined range determines whether the phase loss of the inverter occurs, and whether the motor winding phase loss occurs according to whether the three-phase terminal voltage of the brushless motor is greater than a predetermined value.

A further object of the present invention is to provide a phase loss diagnosis method for a brushless motor, the method comprising: sensing a three-phase terminal voltage V _ug , V _vg and V _{wg of} a brushless motor; calculating a virtual neutral point Voltage (V _s ), wherein the virtual neutral point voltage is Determining whether the neutral point voltage (V _s ) is in a predetermined range V _min ~V _max , wherein the preset range is V _dc is the constant current chain voltage. If the neutral point voltage (V _s ) is not within the preset range, it is determined that the inverter has a phase loss fault. Determining whether the neutral point voltage (V _s ) is constant less than a predetermined value during the previous commutation period, wherein the predetermined value is And ε is a small value, and if it is less than the predetermined value, it is determined that the motor winding has a phase loss fault.

With the foregoing system and method, the microcontroller of the present invention can realize the purpose of phase loss diagnosis without sampling the current for complicated mathematical operations, so that the system requirements can be achieved by using a low-order microcontroller to be widely applicable to low The price of the product market, while avoiding the use of the rule of thumb to determine the current reference value can reduce the probability of false positives, so the invention can effectively reduce the cost and increase the reliability of the system.

Referring to the first figure, the present invention can detect whether an abnormality occurs in the operation of a three-phase brushless motor (30) connected to the frequency converter (20), wherein the frequency converter (20) receives the microcontroller ( 10) The commutation signal that is output.

As shown in the second figure, the frequency converter (20) can be composed of six power transistors to form a three-arm structure, and each power transistor has a bypass diode, and the three-arm structure is a U-phase arm (21), V, respectively. Phase arm (22) and W phase arm (23); the brushless motor (30) is an AC three-phase permanent magnet brushless motor, which is operated by the control of the frequency converter (20), and the three-phase wiring thereof is respectively The U-phase arm (21), the V-phase arm (22), and the W-phase arm (23) of the inverter (20) are connected, and the three-phase terminal voltages thereof are represented as V _ug , V _{vg ,} and V _{wg , respectively} .

The circuit structure of the phase loss diagnosis system of the present invention comprises: a microcontroller (10) whose output controls the commutation signal of the motor, the microcontroller (10) has a built-in inverter phase loss diagnostic program and a brushless Motor winding phase loss diagnostic program; a virtual neutral point circuit (40) consisting of three resistors, one end of which is connected to the three phase between the brushless motor (30) and the inverter (20) Wiring; a voltage dividing circuit (50) is connected between the virtual neutral point circuit (40) and the microcontroller (10), and is composed of a first resistor (51) and a second resistor (52). And a capacitor (53); one end of the first resistor (51) is connected to the other end of each resistor of the virtual neutral circuit (40), and the other end is simultaneously connected to the input end of the microcontroller (10) and The second resistor (52) and the capacitor (53), the second resistor (52) and the other end of the capacitor (53) are grounded, and the voltage dividing circuit (50) is coupled with the virtual neutral point circuit (40) for sensing. The three-phase terminal voltages V _ug , V _vg and V _{wg of the} brushless motor (30) are returned to the microcontroller (10).

In the foregoing system architecture, the present invention can diagnose whether the brushless motor (30) or the inverter (20) is missing according to the three-phase terminal voltage of the brushless motor (30) without using the current sensor. The phase failure is determined by the following methods:

A, inverter phase loss detection

The phase loss of the inverter (20) can be divided into two cases: the upper arm phase loss (A) and the lower arm phase loss (B), as shown in the second figure. Under the influence of the bypass diode of the power transistor, the terminal voltage of the brushless motor (30) is limited between the DC bus voltage V _dc and the ground. Under normal driving, the three-phase terminal voltage V _ug , V _vg and V _wg two phases must respectively connected to the positive terminal and the negative terminal of the power supply, it can be deduced the sum of the three-phase terminal voltage as to satisfy the following formula (1), occurs when the inverter phase, three-phase terminal voltage The sum will exceed this range.

2 V _dc > V _ug + V _vg + V _wg > V _dc (1)

In order to simplify the circuit architecture, the present invention obtains the correlation signal of the sum of the three-phase terminal voltages V _ug , V _vg and V _wg by the virtual neutral point voltage V _s formed by three resistors, as shown in the following formula (2), in combination with the 1) It can be seen that in the case of normal driving, the virtual neutral point voltage (V _s ) should satisfy the formula (3), and when it is detected that the virtual neutral point voltage (V _s ) does not satisfy the formula (3), It is judged that the inverter is out of phase. As shown in the waveform diagram of Annex 1, it is shown that the problem of the upper arm phase loss occurs according to the virtual neutral point voltage (V _s ), so the inverter phase loss diagnosis signal is low level. Turned to high level; as shown in Annex 2, it is shown that the problem of the lower arm phase loss occurs according to the virtual neutral point voltage (V _s ), so the inverter phase loss diagnostic signal changes from low level to high. Level.

B, brushless motor winding phase loss

When the winding of the brushless motor (30) is out of phase, the virtual neutral point voltage (V _s ) is fixed at one-half DC link voltage (V _dc ) in the interval where the phase-deficient winding is un-excited. The level is such that a predetermined value (V _o ) is one-half of the DC link voltage (V _dc ) plus a small value ε, as shown in the following equation (4), when any conduction interval is detected If the virtual neutral point voltage (V _s ) is less than the predetermined value (V _o ) for a long time, it can be judged that the motor winding is out of phase, and the third is the actual diagnosis waveform diagram. When the motor winding is out of phase, It is determined that the virtual neutral point voltage (V _s ) is less than a predetermined value (V _o ).

The foregoing determination of whether the inverter (20) and the brushless motor (30) are out of phase can be realized by the inverter phase loss diagnosis program of the microcontroller (10) and the brushless motor winding phase loss diagnosis program, respectively. All are interrupt programs, wherein the inverter phase loss diagnostic program is set to trigger execution at a fixed frequency, and the brushless motor winding phase loss diagnostic program can be triggered by a Hall signal that detects the rotor position of the motor.

Please refer to the third figure. When the inverter phase loss diagnostic program is executed, first read the sample value of the virtual neutral point voltage (V _s ) (301) to further determine whether the neutral point voltage (V _s ) is located. A preset range V _min ~V _max (302), if the judgment result is no, it indicates that the inverter (20) has a phase loss fault, so the microcontroller (10) outputs a control brushless motor (30) to stop. The instruction (303) further determines whether the virtual neutral point voltage (V _s ) is greater than a predetermined value (V _o ) (304) if the determination result is within the preset range V _min ~ V _max , if greater than a predetermined value (V) _o ) The number of times Vs>Vo is counted by a variable N (305). If it is less than, the inverter phase loss diagnostic program is directly terminated.

Please refer to the fourth figure. When the Hall signal changes and triggers the microcontroller (10) to execute the brushless motor winding phase loss diagnostic program, it is judged that the virtual neutral point voltage (V _s ) is in the previous commutation. Whether it is less than the predetermined value (V _o ) during the period (ie, the case of N=0) (401), if it is less than the predetermined value (V _o ), it is judged that the motor winding has a phase loss fault, and after the fault occurs, the microcontroller ( 10) Output a control command to stop the brushless motor (30), and immediately stop the operation (402) to achieve the protection function. If it is greater than the predetermined value (V _o ), the variable N is restored to 0 (403).

In summary, the advantages of the present invention can be summarized as follows:

1. Because the system hardware architecture only needs a few resistors and a voltage divider circuit, the use of current sensing components is not required, which can effectively reduce the cost and volume of the system.

2. Since it is not necessary to use complicated mathematical expressions, it is only necessary to compare the three-phase terminal voltage obtained by the feedback with the fixed-level voltage value to diagnose the fault, so that the lower-order control chip can be used to realize the diagnostic control. The purpose.

(10). . . Microcontroller

(20). . . Frequency converter

(twenty one). . . U-phase arm

(twenty two). . . V-phase arm

(twenty three). . . W phase arm

(30). . . Brushless motor

(40). . . Virtual neutral point circuit

(50). . . Voltage dividing circuit

(51). . . First resistance

(52). . . Second resistance

(53). . . capacitance

(V _dc ). . . DC link voltage

(V _ug )(V _vg) (V _wg ). . . Three-phase terminal voltage

First figure: Circuit diagram of the phase loss diagnosis system of the brushless motor of the present invention.

Second figure: Circuit diagram of the frequency converter of the invention.

The third figure: the flowchart of the phase loss diagnosis program of the inverter of the present invention.

Fourth: Flow chart of the brushless motor winding phase loss diagnostic program of the present invention.

(10). . . Microcontroller

(20). . . Frequency converter

(30). . . Brushless motor

(40). . . Virtual neutral point circuit

(50). . . Voltage dividing circuit

(51). . . First resistance

(52). . . Second resistance

(53). . . capacitance

(V _dc ). . . DC link voltage

(V _ug )(V _vg) (V _wg ). . . Three-phase terminal voltage

Claims (15)

A phase loss diagnosis system for a brushless motor, comprising: a microcontroller outputting a commutation signal for controlling a brushless motor; and a virtual neutral point circuit comprising a plurality of resistors, the virtual neutral point circuit Connecting a three-phase wiring between the brushless motor and the frequency converter; a voltage dividing circuit is connected between the virtual neutral point circuit and the microcontroller to feedback the three-phase terminal voltage of the brushless motor The data is given to the microcontroller; wherein the microcontroller determines whether the inverter phase loss occurs according to whether the three-phase terminal voltage outputted from the inverter to the brushless motor is within a predetermined range, and is also output according to the inverter. Whether the three-phase terminal voltage of the brushless motor is less than a predetermined value determines whether the motor winding phase loss occurs. For example, in the phase loss diagnosis system of the brushless motor according to the first aspect of the patent application, the three-phase voltage of the inverter output to the brushless motor is V _ug , V _vg and V _wg , wherein it is determined whether the inverter phase loss occurs. The preset range is V _min ~V _max . If the preset range is exceeded, the inverter phase loss occurs. The preset range is: among them It is a virtual neutral point voltage, and V _dc is the _DC link voltage. The phase loss diagnosis system of the brushless motor according to claim 1 or 2, wherein the three-phase voltage of the brushless motor is V _ug , V _vg and V _wg , which is used to determine whether the motor winding phase is missing. The predetermined value is V _o . If the predetermined value is less than the predetermined value, it is determined that the motor winding phase loss occurs, and the predetermined value is: Where ε is a small value and V _dc is the constant current chain voltage. The phase loss diagnosis system of the brushless motor according to claim 3, wherein the microcontroller stores a frequency converter phase loss diagnosis program and a brushless motor winding phase loss diagnosis program to respectively determine the inverter phase loss and the motor. The winding is out of phase. The phase-defining diagnostic system of the brushless motor according to claim 4, wherein the virtual neutral circuit comprises three resistors, and one end of each resistor is connected to one of the three-phase wiring of the brushless motor. The other ends of the three resistors are connected in common to the voltage dividing circuit. The phase-defining circuit of the brushless motor according to claim 5, wherein the voltage dividing circuit comprises a first resistor, a second resistor and a capacitor; one end of the first resistor is connected to the virtual neutral circuit Each of the resistors is connected to the input end of the microcontroller and the second resistor and capacitor at the other end. The second resistor and the other end of the capacitor are grounded. The phase loss diagnosis system of the brushless motor according to claim 4, wherein: the inverter phase loss diagnosis program is executed at a fixed frequency, and includes: reading a virtual neutral point voltage (V _s ) sampling a value; determining whether the neutral point voltage (V _s ) is within the preset range; if the determination result is no, the microcontroller outputs a control command for stopping the brushless motor; and if the judgment result is in a preset range Further determining whether the virtual neutral point voltage (V _s ) is greater than the predetermined value, and if greater than the predetermined value, incrementing a variable N by one; the brushless motor winding phase loss diagnostic program is based on a Hall signal of the brushless motor The executing includes: determining whether the virtual neutral point voltage (V _s ) is less than the predetermined value during the previous commutation period; if less than the predetermined value, determining that the motor winding has a phase loss fault, the microcontroller is outputting A control command for stopping the brushless motor; if greater than the predetermined value, the variable N is restored to zero. A brushless motor control system with a phase loss diagnosis function includes: a microcontroller outputting a commutation signal for controlling a brushless motor; and an inverter receiving a commutation signal output by the microcontroller, The three-arm structure is composed of a plurality of power transistors, wherein the three-arm structure is a U-phase arm, a V-phase arm and a W-phase arm; and a brushless motor is an AC three-phase permanent magnet brushless motor, which is controlled by a frequency converter. Controlled and operated, the three-phase wiring is respectively connected to the U-phase arm, the V-phase arm and the W-phase arm of the inverter, and the three-phase terminal voltages are V _ug , V _vg and V _{wg -} a virtual neutral point circuit, respectively. Constructed by a plurality of resistors, the virtual neutral circuit is connected to the three-phase wiring between the brushless motor and the inverter to sense the three-phase terminal voltages V _ug , V _vg and V _wg ; a voltage dividing circuit, Connected between the virtual neutral point circuit and the microcontroller to feedback the three-phase terminal voltage data of the brushless motor to the microcontroller; wherein the microcontroller is output to the brushless according to the inverter output Whether the three-phase terminal voltage of the motor is within a predetermined range to determine whether the inverter phase loss occurs, According to whether the output from the inverter to the three-phase brushless motor terminal voltage is less than a predetermined value is determined presence or absence of phase windings of the motor. For example, the brushless motor control system with the phase loss diagnosis function described in claim 8 of the patent scope, wherein the preset range of the inverter phase loss is determined to be V _min ~V _max , if the preset range is exceeded, the frequency conversion occurs. The phase is missing, the preset range is: among them It is a virtual neutral point voltage, and V _dc is the DC link voltage supplied to one of the inverters. The brushless motor control system with the phase loss diagnosis function described in claim 8 or 9 of the patent application, the predetermined value for determining whether the motor winding phase loss occurs is V _o , and if it is less than the predetermined value, it is determined that the motor is generated. The winding is out of phase, the predetermined value is: Where ε is a small value and V _dc is the DC link voltage supplied to one of the frequency converters. For example, in the brushless motor control system with the phase loss diagnosis function described in claim 10, the microcontroller stores a frequency converter phase loss diagnosis program and a brushless motor winding phase loss diagnosis program to respectively determine the inverter shortage. Phase and motor winding phase loss. The virtual neutral circuit includes three resistors, one end of each resistor is connected to one of the three-phase wiring of the brushless motor, as in the brushless motor control system with the phase loss diagnosis function described in claim 11 of the patent scope. The line is connected, and the other end of the three resistors are connected to the voltage dividing circuit. The brushless motor control system with a phase loss diagnostic function according to claim 12, wherein the voltage dividing circuit comprises a first resistor, a second resistor and a capacitor; one end of the first resistor is connected to the virtual Each resistor of the circuit, the other end is simultaneously connected to the input end of the microcontroller and the second resistor And the capacitor, the second resistor and the other end of the capacitor are grounded. A brushless motor control system with a phase loss diagnostic function according to claim 11 wherein: the inverter phase loss diagnostic program is executed at a fixed frequency, and includes: reading a virtual neutral point voltage (V _s a sampling value; determining whether the neutral point voltage (V _s ) is within the preset range; if the determination result is no, the microcontroller outputs a control command for stopping the brushless motor; and if the judgment result is In the preset range, it is further determined whether the virtual neutral point voltage (V _s ) is greater than the predetermined value, and if it is greater than the predetermined value, a variable N is incremented by one; the brushless motor winding phase loss diagnostic program is one of the brushless motors. Executing the Hall signal, comprising: determining whether the virtual neutral point voltage (V _s ) is less than the predetermined value during the previous commutation period; if less than the predetermined value, determining that the motor winding is out of phase failure, the micro control The device outputs a control command for stopping the brushless motor; if it is greater than the predetermined value, the variable N is restored to 0. A phase loss diagnosis method for a brushless motor, comprising: sensing a three-phase terminal voltage V _ug , V _vg and V _wg outputted from a frequency converter to a brushless motor; calculating a virtual neutral point voltage (V _s ), Where the virtual neutral point voltage is Determining whether the neutral point voltage (V _s ) is in a predetermined range V _min ~V _max , wherein the preset range is V _dc is the constant current chain voltage. If the neutral point voltage (V _s ) is not within the preset range, it is determined that the inverter has a phase loss fault; determining the neutral point voltage (V _s ) is changed in the previous time. Whether the phase period is less than a predetermined value, wherein the predetermined value is And ε is a small value, and if it is less than the predetermined value, it is judged that the motor winding has a phase loss fault.