Method for distinguishing between switch open circuit and open phase open circuit of PMSM driver

Abstract

The present application relates to a kind of PMSM driver switch open circuit and open circuit of phase distinction method, make the subdivision of two kinds of open circuit phenomenon caused by fault to driver itself.First, the current prediction model after the fault of establishing switch open circuit is obtained to obtain the estimated value of switch open circuit fault current.Subsequently, by the current sampling method suitable for the state of health, switch open circuit fault, open circuit fault of phase obtains actual phase current value, and the residual between estimated value and actual value is solved.Finally, according to the polarity relationship and relative amplitude relationship between estimated value, actual value, residual distinguishes whether the fault phase is in switch open circuit fault or open circuit fault of phase.Different from existing driver open circuit diagnostic method, the present application realizes the distinction of open circuit phase fault mode, and can distinguish the driver open circuit caused by switch open circuit fault and the driver open circuit caused by open circuit fault of phase.

Description

Technical Field

[0001] The invention belongs to the field of PMSM drive system fault diagnosis and relates to a method for distinguishing between a PMSM driver switch open circuit and a phase-failure open circuit. Background Art

[0002] As an industrial application where both reliability and cost are crucial, improving the reliability and maintainability of permanent magnet synchronous motors and their drives has become a key research focus. However, with the rise in voltage levels, power density, and integration levels, failure modes in permanent magnet synchronous motors and their drives are becoming increasingly diverse, resulting in time-consuming maintenance. Accurate fault location technology plays a crucial role in improving maintenance efficiency and ensuring the correct fault tolerance approach is implemented.

[0003] Failures occurring in different locations can cause similar fault phenomena. The most typical example is an open circuit fault, which is also the most typical fault phenomenon in motor drives. This open circuit phenomenon can be caused by connection failures, such as connector failure or phase winding damage. This type of fault is called a phase failure. Furthermore, failure of the power switch in the drive can also cause an open circuit phenomenon. This can be caused by failures in the driver chip or the power switch connection line, which is called a switch open circuit fault. After a phase failure occurs, the fault phase current loses its conduction path. However, after a switch open circuit fault, the fault phase current is not zero due to the presence of a freewheeling diode in parallel with the power switch.

[0004] However, open-switch faults and phase-loss faults are currently categorized as the same fault type, making it difficult to distinguish them. This makes it difficult to determine whether the open circuit occurs on the inverter side or the motor side. The reason for categorizing open-switch faults and phase-loss faults is that the motor driver cannot detect the fault current after an open-switch fault. As a result, open-switch faults and phase-loss faults exhibit the same fault phenomenon: zero current in the faulted phase. Summary of the Invention

[0005] Technical problems to be solved

[0006] In order to avoid the shortcomings of the existing technology, the present invention proposes a method for distinguishing between open circuit and phase open circuit of a PMSM driver switch, so as to improve the reliability and maintainability of the permanent magnet synchronous motor and its driver, reduce the time consumption during the maintenance process, and provide correct fault diagnosis information after a fault.

[0007] Technical Solution

[0008] A method for distinguishing between a PMSM driver switch open circuit and a phase open circuit, characterized by the following steps:

[0009] Step 1: Establish a current prediction model after a switch open fault occurs to obtain an estimated value of the switch open fault current;

[0010] At the fault opposite potential V bemfX >0, the fault current estimate is

[0011] At the fault opposite potential V bemfX <0, the fault current estimate is

[0012] Where: t u7 for The action time, L s is the phase inductance, the opposite potential V bemfX >0, u D is the forward conduction voltage of the upper arm freewheeling diode; t u0 for The action time of the fault opposite potential V bemfX <0,u D is the forward conduction voltage of the freewheeling diode of the lower bridge arm;

[0013] Step 2: Calculate the estimated value and the actual phase current value i under three conditions X_samp The residual between Among them: actual phase current value i X_samp The actual phase current values ​​obtained by the current sampling method in the three states of healthy, open switch fault, and open phase fault; Step 3: Distinguish whether the fault phase is in an open switch fault or an open phase fault based on the polarity and relative amplitude relationship between the estimated value, actual value, and residual;

[0014] when i X_samp and The polarity is opposite, and i X_resi The magnitude is greater than When , it is determined that this phase is in a healthy state;

[0015] when i X_samp and The polarity is the same, and i X_resi The magnitude is less than When , it is determined that this phase is in the power switch open state;

[0016] when i X_resi and The polarity is the same, and i X_resi The magnitude is equal to When , it is determined that this phase is in the phase-off open circuit state.

[0017] In step 1, t u0 and tu7 They all account for half of the zero vector action time of the current switching cycle, and are uniformly expressed as t u0=t u7 =T s (1-R v1 -R v2 ) / 2, where T s is the switching period, R v1 With R v2 It indicates the proportion of the action time of the two effective vectors in each switching cycle.

[0018] The switch open circuit fault is any failure condition in which only the power switch cannot be turned on, including but not limited to failure of the driving signal or damage of the power switch.

[0019] The open-phase fault is a failure in which all power switches and freewheeling diodes cannot conduct, including but not limited to power module damage, connector connection failure, wiring harness failure or phase winding failure.

[0020] Beneficial effects

[0021] The present invention proposes a method for distinguishing between a PMSM driver switch open circuit and a phase open circuit, which enables the driver itself to achieve a subdivision of the two faults that cause the open circuit phenomenon. First, a current prediction model after the switch open circuit fault occurs is established to obtain an estimated value of the switch open circuit fault current. Subsequently, the actual phase current value is obtained by a current sampling method applicable to the three states of health, switch open circuit fault, and phase open circuit fault, and the residual between the estimated value and the actual value is calculated. Finally, the polarity relationship and relative amplitude relationship between the estimated value, the actual value, and the residual are used to distinguish whether the fault phase is in a switch open circuit fault or a phase open circuit fault. Different from the existing driver open circuit diagnosis method, this method realizes the distinction between the open circuit phase fault mode and can successfully distinguish between the driver open circuit caused by the switch open circuit fault and the driver open circuit caused by the phase open circuit fault.

[0022] The present invention achieves the distinction between power switch open circuit fault and phase open circuit fault in the PMSM driver, so that the fault type and fault location causing the open circuit phenomenon can be accurately located;

[0023] The diagnostic method proposed in the present invention based on the relationship between the polarity and relative amplitude of the diagnostic variable can obtain reliable diagnostic results within half a fundamental wave cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of a method for distinguishing between a switch open circuit and a phase-fail open circuit in a PMSM driver according to the present invention;

[0025] Figure 2 This is a waveform diagram of the experimental results of the present invention;

[0026] Figure 3 This is a waveform diagram of the experimental results of the present invention;

[0027] Figure 4 This is a waveform diagram of the experimental results of the present invention. DETAILED DESCRIPTION

[0028] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0029] The following will clearly describe the technical solution of the present invention in combination with the embodiments and experimental results. The described embodiments are only part of the embodiments of the present invention, not all of them. Figure 1 This is a schematic diagram of the fault differentiation method proposed in the present invention. Taking the failure of phase A of the PMSM driver as an example, the specific implementation is as follows:

[0030] Step (1) establishes a current prediction model for the fault phase under a switch open circuit fault and obtains an estimated value of the fault current:

[0031] Step (1.1) can be analyzed to know that, in the fault opposite potential V bemfA >0, the switch open circuit fault current is only When the vector is on, the freewheeling diode on the upper bridge arm is turned on, and the forward conduction voltage of the diode is u D , the phase inductance is L s , The action time is t u7 , then we can get V bemfA The estimated fault current when >0 is

[0032] Step (1.2) can be analyzed to know that, in the fault opposite potential V bemfA <0, the switch open circuit fault current is only When the vector is on, the freewheeling diode of the lower bridge arm is turned on. The action time is t u0 , then we can get V bemfA The estimated fault current when <0 is

[0033] Step (2) uses a current sampling method suitable for the three states of healthy, open circuit, and phase failure to continuously sample the phase current. The sampling results in the three states are the actual phase current values ​​i at this time. A_samp , and find the residual between the actual value and the estimated value

[0034] Step (3) When i A_samp and The polarity is opposite, and i A_resi The magnitude is greater than When , it is determined that this phase is in a healthy state;

[0035] Step (4) When iA_samp and The polarity is the same, and i A_resi The magnitude is less than When , it is determined that this phase is in the power switch open state;

[0036] Step (5) When i A_resi and The polarity is the same, and i A_resi The magnitude is equal to When , it is determined that this phase is in the phase-off open circuit state;

[0037] The overall effect of the proposed fault differentiation method is as follows: Figure 2 , Figure 3 , Figure 4 As shown. Figure 2 In the health state, i A_samp and Opposite polarity, i A_resi Amplitude greater than exist Figure 3 When the switch is open, it can be seen A_samp and Same polarity, i A_resi Amplitude less than exist Figure 4 In the phase-open state, it can be seen that i A_resi and The polarity is the same, and i A_resi The magnitude is equal to

[0038] The current sampling method in step 2 in the three states of switch open circuit and phase failure is:

[0039] Step (1) Based on the equivalent circuit after the switch open circuit fault, the conditions for the freewheeling diode to conduct after the fault are obtained:

[0040] Step (1.1) The post-fault conduction condition of the freewheeling diode of the upper half bridge arm of the fault phase is: the voltage u across the diode is XP Greater than the forward conduction voltage u of the diode D .u XP Depends on the phase voltage of the fault phase, that is, the voltage difference u from the fault phase terminal to the neutral point of the motor XN , and the voltage difference u from the DC bus positive pole to the neutral point PN . And because the fault phase voltage u XN Equal to the fault reverse potential V bemfX Therefore, the condition for the upper half bridge arm freewheeling diode to be turned on can be expressed as: u XP =u XN -u PN =V bemfX -u PN >uD ;

[0041] Step (1.2) The post-fault conduction condition of the freewheeling diode of the lower half bridge arm of the fault phase is: the voltage u across the diode is OX Greater than the forward conduction voltage u of the diode D .u OX Depends on the phase voltage of the fault phase, that is, the voltage difference u from the fault phase terminal to the neutral point of the motor XN , and the voltage difference u from the negative pole of the DC bus to the neutral point ON . And because the fault phase voltage u XN Equal to the fault reverse potential V bem f X Therefore, the condition for the upper half bridge arm freewheeling diode to be turned on can be expressed as: u OX =u ON -u XN =u ON -V bemfX >u D ;

[0042] Step (2) determines the voltage vector that can achieve the above conduction conditions, which is called the activation vector:

[0043] Step (2.1) To achieve the conduction of the upper arm diode of the fault phase, V bemfX Need to be greater than 0, and considering u PN Only when it is equal to 0 can u be guaranteed XP >u D It is always true, so it is necessary to connect the phase winding that has not experienced a fault to the positive pole of the busbar. bemfX >0, only It can realize the conduction of the bridge arm diode on the fault phase, and because of the effect of phase inductance, the conduction current is It has been growing approximately linearly.

[0044] Step (2.2) To achieve the conduction of the lower bridge arm diode of the fault phase, V bemfX Need to be less than 0, and considering u ON Only when it is equal to 0 can u be guaranteed OX >u D It is always true, so it is necessary to connect the phase winding that has not experienced a fault to the negative pole of the busbar. bemfX <0, only It can realize the conduction of the bridge arm diode on the fault phase, and because of the effect of phase inductance, the conduction current is It has been growing approximately linearly.

[0045] In step (3), the sampling hold time of the analog-to-digital conversion circuit is subtracted from the end of the activation vector action time to obtain the count value of the trigger sampling opportunity, which is the count value CNT when the upper bridge arm diode is turned on. v7samp , and the count value CNT when the lower bridge arm diode is turned on v0samp :

[0046] Step (3.1) Find the maximum duty cycle DR in each phase of the current control cycle in the PWM calculation max With the minimum duty cycle DR min , then DR max The total value CNT of the switching cycle ts The product of At the end of the effect time, DR min *CNT ts for End of action time;

[0047] Step (3.2) Since PWM uses up and down counting to achieve symmetrical modulation, the sampling and holding time of the digital-to-analog conversion circuit is set to CNT delay , so in The timing of sampling fault current is CNT v7samp =DR min *CNT ts +CNT delay , and in The timing of sampling the current after the fault is CNT v0samp =DR max *CNT ts -CNT delay ;

[0048] Step (4) in V bemfX >0, when the PWM time base counter is equal to CNT v7samp Trigger sampling at the same time; bemfX <0, when the PWM time base counter is equal to CNT v0samp The sampling is triggered at the same time.

[0049] The experimental conditions of this embodiment are: DC bus voltage 200V, the number of pole pairs of the motor is 4, L d =L q =2.4mH, winding resistance 0.306Ω, permanent magnet flux 0.281Wb, operating speed 100rpm, inverter switching frequency 10kHz, control chip is TMS320F28335, and the IGBT module used in the inverter is FUJI 7MBR25VA120.

Claims

1. A method for distinguishing between a PMSM driver switch open circuit and a phase open circuit, characterized in that Here are the steps: Step 1: Establish a current prediction model after a switch open fault occurs to obtain an estimated value of the switch open fault current; At the fault opposite potential V bemfX >0, the fault current estimate is At the fault opposite potential V bemfX <0, the fault current estimate is Where: t u7 for The action time, L s is the phase inductance, the opposite potential V bemfX >0, u sD is the forward conduction voltage of the upper arm freewheeling diode; t u0 for The action time of the fault opposite potential V bemfX <0,u xD is the forward conduction voltage of the freewheeling diode of the lower bridge arm; Step 2: Calculate the estimated value and the actual phase current value i under three conditions X_samp The residual between Among them: actual phase current value i X_samp The actual phase current values ​​obtained by the current sampling method in the three states of healthy, open switch fault, and open phase fault; Step 3: Distinguish whether the fault phase is in an open switch fault or an open phase fault based on the polarity and relative amplitude relationship between the estimated value, actual value, and residual; when i X_samp and The polarity is opposite, and i X_resi The magnitude is greater than When , it is determined that this phase is in a healthy state; when i X_samp and The polarity is the same, and i X_resi The magnitude is less than When , it is determined that this phase is in the power switch open state; when i X_resi and The polarity is the same, and i X_resi The amplitude is equal to When , it is determined that this phase is in the phase-off open circuit state.

2. The method for distinguishing between a PMSM driver switch open circuit and a phase open circuit according to claim 1, characterized in that: In step 1, t u0 Both tu7 and tu8 occupy half of the zero vector action time of the current switching cycle, and are uniformly expressed as t u0 =t u7 =T s (1-R v1 -R v2 ) / 2, where T s is the switching period, R v1 With R v2 It indicates the proportion of the action time of the two effective vectors in each switching cycle.

3. The method for distinguishing between a PMSM driver switch open circuit and a phase open circuit according to claim 1, characterized in that: The switch open circuit fault is any failure condition in which only the power switch cannot be turned on, including but not limited to failure of the driving signal or damage of the power switch.

4. The method for distinguishing between a PMSM driver switch open circuit and a phase open circuit according to claim 1, characterized in that: The open-phase fault is a failure in which all power switches and freewheeling diodes cannot conduct, including but not limited to power module damage, connector connection failure, wiring harness failure or phase winding failure.

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