1. A motor speed regulation inverter open circuit fault diagnosis method based on self-adaptive mean value calculation relates to a circuit topology structure comprising a direct current power supply E, a main inverter circuit and a permanent magnet synchronous motor PMSG;

the main inverter circuit is a voltage source type two-level inverter circuit and comprises three-phase bridge arms, each phase of bridge arm comprises 2 switching tubes with reverse parallel diodes, namely the three-phase bridge arms comprise 6 switching tubes with reverse parallel diodes, and the 6 switching tubes with the reverse parallel diodes are respectively marked as switching tubes S_voljWherein, vol represents the phase sequence, vol is a, b, c, j represents the serial number of the switching tube, and j is 1, 2; in each phase arm, a switching tube S_vol1And a switching tube S_vol2After being connected in series, the switching tube S is connected between a direct current positive bus and a direct current negative bus of a direct current power supply E_vol1And a switching tube S_vol2Is marked as point P_volVol is a, b, c, point P_aPoint P_bPoint P_cRespectively connected with three phases of a PMSG (permanent magnet synchronous generator);

the open-circuit fault diagnosis method is characterized by comprising the following steps of:

step 1, sampling three-phase output current of a permanent magnet synchronous motor PMSG for N times in a set sampling period to obtain three-phase output current sampling signals of N permanent magnet synchronous motors PMSG, and sampling the three-phase output current of the permanent magnet synchronous motor PMSG obtained by the nth timeThe output current sampling signal is recorded as the three-phase output currentN is the maximum sampling frequency in the sampling period, and N is a positive integer;

step 2, obtaining current components under alpha and beta coordinates by utilizing Park vector transformationAndthe expression is as follows:

using current components in alpha beta coordinatesAndfor three-phase output currentNormalization is carried out to obtain normalized three-phase output currentThe expression is as follows

Step 3, self-adaptively judging the phase current period

Setting a judgment threshold thr, and recording the three-phase output current reversing flag bit asvol is a, b, c, k is the number of commutation of phase current, k is 1,2,3, …, three-phase output current commutation flag bitThe calculation is as follows:

if it isAnd isIndicating that the three-phase output current is reversed and indicating the three-phase output current reversing flag bit

Wherein the content of the first and second substances,for the (n + 1) th three-phase output currentOutputting current by three phases after normalization;

step 4, calculating the periodic mean value of the normalized three-phase output current

Step 4.1, when k is equal to 2, a complete period current signal of the three-phase output current is obtained, and the k-1 th three-phase output current period signal when k is equal to or larger than 2 is recorded as T_k-1，At this time, the average value of the normalized three-phase output current period is taken as the average valuevol is a, b, c, mean valueThe expression of (a) is:

at this time, the number of samples in one current period is M,

step 4.2, if k is not changed, the mean value of the normalized three-phase output current is updated, and the updated mean value is recorded as an updated mean valuevol is a, b, c, updating the mean valueThe expression of (a) is:

during the mean value update, the number of samples M in one current period remains unchanged,

if k changes, the number of samples M in a current cycle changes,

step 5, recording an open circuit fault detection variable as D, wherein the expression is as follows:

step 6, according to the set open-circuit fault detection threshold value T_safeSet open-circuit fault locating threshold I_safeAnd 5, performing open-circuit fault diagnosis on the open-circuit fault detection variable D obtained in the step 5, wherein the diagnosis result is as follows:

D＜T_safeindicating no fault;

D≥T_safeand is andand isAnd isSwitch tube S_a1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_a2A failure;

D≥T_safeand is andand isAnd isSwitch tube S_b1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_b2A failure;

D≥T_safeand is andand isAnd isSwitch tube S_c1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_c2And (4) failure.

Background

In the motor control, compared with the traditional contactor control, the inverter control can realize the motor soft start with low mechanical equipment impact force and low starting current and can realize the high and stable speed change of the motor under the complex condition, thereby being widely applied to the motor motion control. At present, in order to ensure the operation safety of motor equipment, various perfect fault protection functions are integrated in most inverters so as to realize active fault reporting when a motor or a power supply fails, but online diagnosis for faults of the inverters is relatively less.

At present, a main circuit of an inverter for motor speed regulation is usually a bridge circuit composed of a plurality of power switches IGBT, and according to statistics, the fault of a power device accounts for more than 70% of the fault of a frequency converter, so that the fault diagnosis of the inverter is mainly the fault diagnosis of the power switch tube IGBT. Faults of the power switching tube IGBT generally comprise short-circuit faults and open-circuit faults, the short-circuit faults are generally protected by an integrated current limiting device, and the open-circuit faults cannot be directly diagnosed.

There have been relevant studies aiming at power switch tube IGBT open-circuit fault diagnosis research, such as

The invention has the following patents: a two-level three-phase voltage source inverter bridge arm open-circuit fault diagnosis method (CN111381188B) provides a current-based power switch tube open-circuit fault diagnosis method aiming at two-level three-phase voltage source inverter bridge arm open-circuit faults.

The invention has the following patents: a real-time detection method (CN111413646B) for the open-circuit fault of a three-phase voltage source inverter bridge arm is characterized in that a current-based open-circuit fault diagnosis method is also adopted for the open-circuit fault of the three-phase voltage source inverter bridge arm, and when the dimension of a current vector for detecting the open-circuit fault is calculated, the rotating speed of a motor is also introduced to eliminate the influence of the change of current frequency.

The invention has the following patents: an NPC three-level inverter open-circuit fault diagnosis method (CN111077471B) based on instantaneous frequency aims at open-circuit fault diagnosis of a photovoltaic inverter switching tube, aims at fixed-frequency periodic current, and adopts a phase current mean value method in fault location, which is the mainstream open-circuit fault location method at present.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and particularly provides a threshold-based phase current commutation detection strategy for phase current signals with variable frequency, wherein a phase current sample between two commutations is selected as a period sample, the adaptive mean value updating of the phase current is realized according to the number of samples in the current period sample until the phase current is commutated again, and a period sample is reselected and the number of samples in the period sample is updated for the adaptive mean value updating of the phase current.

The invention aims to realize the method, and provides a self-adaptive mean value calculation-based open-circuit fault diagnosis method for a motor speed regulation inverter, wherein a circuit topology structure related to the diagnosis method comprises a direct-current power supply E, a main inverter circuit and a permanent magnet synchronous motor PMSG;

the main inverter circuit is a voltage source type two-level inverter circuit and comprises three-phase bridge arms, each phase of bridge arm comprises 2 switching tubes with reverse parallel diodes, namely the three-phase bridge arms comprise 6 switching tubes with reverse parallel diodes, and the 6 switching tubes with the reverse parallel diodes are respectively marked as switching tubes S_voljWherein, vol represents the phase sequence, vol is a, b, c, j represents the serial number of the switching tube, and j is 1, 2; in each phase arm, a switching tube S_vol1And a switching tube S_vol2After being connected in series, the switching tube S is connected between a direct current positive bus and a direct current negative bus of a direct current power supply E_vol1And a switching tube S_vol2Is marked as point P_vol，vol＝a, b, c, point P_aPoint P_bPoint P_cRespectively connected with three phases of a PMSG (permanent magnet synchronous generator);

the open-circuit fault diagnosis method comprises the following steps:

step 1, sampling three-phase output current of a permanent magnet synchronous motor PMSG for N times in a set sampling period to obtain three-phase output current sampling signals of N permanent magnet synchronous motors PMSG, and recording the three-phase output current sampling signals of the permanent magnet synchronous motor PMSG obtained by sampling for the nth time as three-phase output currentN is the maximum sampling frequency in the sampling period, and N is a positive integer;

step 2, obtaining current components under alpha and beta coordinates by utilizing Park vector transformationAndthe expression is as follows:

using current components in alpha beta coordinatesAndfor three-phase output currentNormalization is carried out to obtain normalized three-phase output currentThe expression is as follows

Step 3, self-adaptively judging the phase current period

Setting a judgment threshold thr, and recording the three-phase output current reversing flag bit ask is the number of commutations of phase current, k is 1,2,3, …, three-phase output current commutations flag bitThe calculation is as follows:

if it isAnd isIndicating that the three-phase output current is reversed and indicating the three-phase output current reversing flag bit

Wherein the content of the first and second substances,for the (n + 1) th three-phase output currentOutputting current by three phases after normalization;

step 4, calculating the periodic mean value of the normalized three-phase output current

Step 4.1, setting that when k is 2, three-phase output current is obtainedThe k-1 th three-phase output current periodic signal when k is more than or equal to 2 is marked as T_k-1，At this time, the average value of the normalized three-phase output current period is taken as the average valueMean valueThe expression of (a) is:

at this time, the number of samples in one current period is M,

step 4.2, if k is not changed, the mean value of the normalized three-phase output current is updated, and the updated mean value is recorded as an updated mean valueUpdating mean valuesThe expression of (a) is:

during the mean value update, the number of samples M in one current period remains unchanged,

if k changes, the number of samples M in a current cycle changes,

step 5, recording an open circuit fault detection variable as D, wherein the expression is as follows:

step 6, according to the set open-circuit fault detection threshold value T_safeSet open-circuit fault locating threshold I_safeAnd 5, performing open-circuit fault diagnosis on the open-circuit fault detection variable D obtained in the step 5, wherein the diagnosis result is as follows:

D<T_safeindicating no fault;

D≥T_safeand is andand isAnd isSwitch tube S_a1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_a2A failure;

D≥T_safeand is andand isAnd isSwitch tube S_b1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_b2A failure;

D≥T_safeand is andand isAnd isSwitch tube S_c1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_c2And (4) failure.

Compared with the prior art, the invention has the beneficial effects that:

1. the current signal acquisition does not need an additional sensor, so the fault characteristic quantity for extracting the open-circuit fault characteristic of the motor speed regulation inverter is simple to obtain;

2. the self-adaptive mean value calculation method can simultaneously realize open-circuit fault detection and positioning, excessive auxiliary judgment variables are not needed, and the algorithm is simple and effective to realize;

3. the self-adaptive mean value algorithm provided by the invention can realize the mean value self-adaptive calculation of the current signal with frequency change, so that the rapid detection and positioning of the open-circuit fault of the inverter under various conditions can be effectively realized.

Drawings

FIG. 1 is a flow chart of a fault diagnosis method of the present invention;

FIG. 2 is a topology of an inverter for motor speed regulation in an embodiment of the present invention;

FIG. 3 is a simulated waveform diagram of a sampled current sample according to an embodiment of the present invention;

FIG. 4 is a diagram showing the calculation result of the open circuit fault detection variable D in the embodiment of the present invention;

FIG. 5 is the average value of the normalized three-phase output current period in the embodiment of the present inventionThe calculation result graph of (2);

FIG. 6 shows an inverter controlled lower switch tube S according to an embodiment of the present invention_a1And (5) an open-circuit fault diagnosis result graph.

Detailed Description

The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.

Fig. 2 is a topology diagram of an inverter for motor speed regulation according to an embodiment of the present invention, and as can be seen from fig. 2, a circuit topology structure related to the open-circuit fault diagnosis method according to the present invention includes a direct current power supply E, a main inverter circuit, and a permanent magnet synchronous motor PMSG.

The main inverter circuit is a voltage source type two-level inverter circuit and comprises three-phase bridge arms, each phase of bridge arm comprises 2 switching tubes with reverse parallel diodes, namely the three-phase bridge arms comprise 6 switching tubes with reverse parallel diodes, and the 6 switching tubes with the reverse parallel diodes are respectively marked as switching tubes S_voljWherein, vol represents the phase sequence, vol is a, b, c, j represents the serial number of the switch tube, and j is 1, 2. In each phase arm, a switching tube S_vol1And a switching tube S_vol2Direct current positive bus connected to direct current power supply E after series connectionBetween the line and the DC negative bus, a switch tube S_vol1And a switching tube S_vol2Is marked as point P_volVol is a, b, c, point P_aPoint P_bPoint P_cAre respectively connected with the three phases of the PMSG.

Fig. 1 is a flow chart of the fault diagnosis method of the present invention, and as can be seen from fig. 1, the steps of the open-circuit fault diagnosis method of the present invention are as follows:

step 1, sampling three-phase output current of a permanent magnet synchronous motor PMSG for N times in a set sampling period to obtain three-phase output current sampling signals of N permanent magnet synchronous motors PMSG, and recording the three-phase output current sampling signals of the permanent magnet synchronous motor PMSG obtained by sampling for the nth time as three-phase output currentN is the maximum sampling frequency in the sampling period, and N is a positive integer;

step 2, obtaining current components under alpha and beta coordinates by utilizing Park vector transformationAndthe expression is as follows:

using current components in alpha beta coordinatesAndfor three-phase output currentNormalization is carried out to obtain normalized three-phase output currentThe expression is as follows

Step 3, self-adaptively judging the phase current period

Setting a judgment threshold thr, and recording the three-phase output current reversing flag bit ask is the number of commutations of phase current, k is 1,2,3, …, three-phase output current commutations flag bitThe calculation is as follows:

if it isAnd isIndicating that the three-phase output current is reversed and indicating the three-phase output current reversing flag bit

Wherein the content of the first and second substances,for the (n + 1) th three-phase output currentOutputting current by three phases after normalization;

step 4, calculating the periodic mean value of the normalized three-phase output current

Step 4.1, when k is equal to 2, a complete period current signal of the three-phase output current is obtained, and the k-1 th three-phase output current period signal when k is equal to or larger than 2 is recorded as T_k-1，At this time, the average value of the normalized three-phase output current period is taken as the average valueMean valueThe expression of (a) is:

at this time, the number of samples in one current period is M,

step 4.2, if k is not changed, the mean value of the normalized three-phase output current is updated, and the updated mean value is recorded as an updated mean valueUpdating mean valuesThe expression of (a) is:

during the mean value update, the number of samples M in one current period remains unchanged,

if k changes, the number of samples M in a current cycle changes,

step 5, recording an open circuit fault detection variable as D, wherein the expression is as follows:

step 6, according to the set open-circuit fault detection threshold value T_safeSet open-circuit fault locating threshold I_safeAnd 5, performing open-circuit fault diagnosis on the open-circuit fault detection variable D obtained in the step 5, wherein the diagnosis result is as follows:

D<T_safeindicating no fault;

D≥T_safeand is andand isAnd isSwitch tube S_a1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_a2A failure;

D≥T_safeand is andand isAnd isSwitch tube S_b1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_b2A failure;

D≥T_safeand is andand isAnd isSwitch tube S_c1A failure;

D≥T_safeand is andand isAnd isSwitch tube S_c2And (4) failure.

In order to verify the technical effect of the invention, the invention is simulated.

FIG. 3 is a simulated waveform of a current sample obtained by sampling according to an embodiment of the present inventionIt can be seen from the figure that, in order to simulate the variable frequency speed regulation process of the motor, the analog input of the motor changes from 0.02 second to 0.05 second, namely corresponding to the three-phase output currentIs changed. After 0.02 s, the a-phase output currentThe part with positive amplitude is completely lost, and the switch tube G under the control of analog frequency conversion₁Open circuit fault, at which bc phase output currentAndstill approximates a full sine wave.

Fig. 4 is a graph of the calculation result of the open circuit fault detection variable D in the embodiment of the present invention, and it can be seen from the graph that after 0.023 seconds, the open circuit fault detection variable D is greater than the set open circuit fault detection threshold T_safeWhen the open circuit fault is detected, the value is 0.01.

FIG. 5 is a graph showing the average value of the normalized three-phase output current period according to the embodiment of the present inventionAs can be seen from the graph of the calculation results of (a), after 0.023 seconds, the average value of the abc three-phase currentsAll change relative to the mean value of bc phase currentAndmean value of a-phase currentThe most obvious change is caused, so that the open-circuit fault occurs to the switching tube of the a-phase bridge arm, and meanwhile, the average value of the a-phase current isLess than open circuit fault location threshold-I_safeIs-0.02, and shows that the switching tube G of the upper bridge arm of the a phase₁An open circuit fault occurs.

FIG. 6 shows an inversion-controlled lower switch tube S according to an embodiment of the present invention_a1Open-circuit fault diagnosis result chart, and it can be seen from the chart that after 0.023 seconds, the switching tube S is detected_a1And an open-circuit fault occurs, and other switching tubes do not have faults.