阅读说明：本技术 一种三相电压源逆变器桥臂开路故障实时检测方法 (Real-time detection method for open-circuit fault of bridge arm of three-phase voltage source inverter ) 是由 赵金 周洋 宋宇金 于 2020-04-10 设计创作，主要内容包括：本发明公开了一种三相电压源逆变器桥臂开路故障实时检测方法,包括以下步骤：S1、采集当前时刻的a、b、c三相电流数据；S2、根据所得当前时刻的a、b、c三相电流数据,更新三相电流向量；S3、根据所得三相电流向量,构建每两相电流向量间的Gram矩阵；S4、计算各Gram矩阵的行列式以及各电流向量的模,并根据所得各Gram矩阵的行列式以及各电流向量的模,计算每两相电流间的无关性系数；S5、通过比较每两相电流间的无关性系数与阈值th的大小,得到各相桥臂的故障检测结果。该方法不需要对电流信号进行滤波、降噪等数据处理过程,计算量较小,实时性好,具有较好的鲁棒性,有利于快速定位到故障桥臂,为逆变器的快速检修或容错控制提供基础。(The invention discloses a real-time detection method for open-circuit faults of a bridge arm of a three-phase voltage source inverter, which comprises the following steps of: s1, collecting current data of three phases a, b and c at the current moment; s2, updating three-phase current vectors according to the obtained current data of the three phases a, b and c at the current moment; s3, constructing a Gram matrix between every two phases of current vectors according to the obtained three-phase current vectors; s4, calculating the determinant of each Gram matrix and the modulus of each current vector, and calculating the independence coefficient between each two phases of currents according to the determinant of each Gram matrix and the modulus of each current vector; and S5, obtaining the fault detection result of each phase bridge arm by comparing the irrelevance coefficient between each two phases of currents with the threshold th. The method does not need data processing processes such as filtering, noise reduction and the like on the current signal, has small calculated amount, good real-time performance and good robustness, is favorable for quickly positioning a fault bridge arm, and provides a basis for quick maintenance or fault-tolerant control of the inverter.)

1. A real-time detection method for an open-circuit fault of a bridge arm of a three-phase voltage source inverter is characterized by comprising the following steps: the method comprises the following steps:

s1, collecting current a, b and c three-phase current data i_a、i_bAnd i_c；

S2, updating the three-phase current vector I according to the obtained current data of the three phases a, b and c at the current moment_a、I_bAnd I_c；

S3, constructing a Gram matrix G (I) between every two phase current vectors according to the obtained three phase current vectors_b，I_c)、G(I_a，I_c) And G (I)_a，I_b)；

S4, calculating the determinant of each Gram matrix and the modulus of each current vector, and calculating the independence coefficient between each two phases of currents according to the determinant of each Gram matrix and the modulus of each current vector;

and S5, obtaining the fault detection result of each phase bridge arm by comparing the irrelevance coefficient between each two phases of currents with the threshold th.

2. The method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter according to claim 1, wherein the current vector of the mth phase at the kth moment is as follows:

I_m(k)＝[i_m(t)，i_m(t+1)，…，i_m(k)]^T

where m is a, b, c, t is k-L-1, k is the current sampling time,is the current vector dimension, n_pIs the number of pole pairs of the motor, w is the motor speed, T_sIs the sampling time.

3. The method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter according to claim 1, wherein the irrelevance coefficient between the m-phase current and the n-phase current is a coefficientWhere, m, n ≠ a, b, c, m ≠ n.

4. The method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter in real time according to claim 1, wherein the method for determining the threshold value comprises the following steps:

s01, calculating independence coefficients between each two phases of currents when the inverter normally operates and when the inverter fails respectively; the inverter faults comprise faults of double tubes in a single bridge arm of the inverter and faults of single tubes of the single bridge arm;

and S02, taking the minimum value of the irrelevance coefficient between every two phases of currents when the inverter normally operates as the maximum value of the threshold value, and taking the maximum value of the irrelevance coefficient between the other two normal phases of currents when one phase of the inverter fails as the minimum value of the threshold value.

5. The method according to claim 4, wherein the threshold th ∈ [0.612, 0.866] is set as the threshold th.

6. The method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter in real time according to the claim 3, wherein the step S5 includes:

when r is_bc< th, and r_abNot less than th, and r_acWhen the phase a is not less than th, the bridge arm of the phase a has a fault; otherwise, the a-phase bridge arm has no fault;

when r is_ac< th, and r_abNot less than th, and r_bcWhen the phase b is not less than th, the bridge arm of the phase b has a fault; otherwise, the b-phase bridge arm has no fault;

when r is_ab< th, and r_acNot less than th, and r_bcWhen the phase c bridge arm is larger than or equal to th, the phase c bridge arm has a fault; otherwise, the c-phase bridge arm has no fault.

7. A storage medium, characterized in that when the instructions are read by a computer, the instructions cause the computer to execute the method for real-time detection of open-circuit fault of bridge arm of three-phase voltage source inverter according to any one of claims 1 to 6.

Technical Field

The invention belongs to the technical field of online detection, and particularly relates to a real-time detection method for an open-circuit fault of a bridge arm of a three-phase voltage source inverter.

Background

The three-phase voltage source inverter is widely applied to the fields of industry, electric traffic, household appliances, motor transmission and the like, and has important significance on the healthy operation of the system as an important component of the system. For example, in a traction system of a high-speed rail locomotive, an inverter is a core component of a power conversion system, and once a fault occurs and cannot be repaired in time, the fault of a power system can be caused and even evolves to become a serious accident of vehicle damage and death; in industrial production, an inverter is a core component of a motor drive system, and if a fault occurs, the inverter may cause a machine such as a lathe to stop, and if the fault occurs, a production accident may be caused. In the inverter, due to the influence of factors such as overvoltage, overcurrent and thermal stress, the power tube is easy to have faults, particularly open-circuit faults, so that the research of the open-circuit fault detection method for the bridge arm of the three-phase voltage source inverter is of great significance.

The existing inverter bridge arm fault diagnosis method comprises a hardware-based bridge arm fault diagnosis method and a system information-based bridge arm fault diagnosis method. The hardware-based bridge arm fault diagnosis method is characterized in that an additional diagnosis circuit or other sensors are added for fault diagnosis, and the method is high in cost and complexity in an industrial system, so that the method cannot be widely applied. The bridge arm fault diagnosis method based on system information, particularly the current-based method, usually adopts a mode identification method to diagnose after filtering and denoising a signal, and the mode identification process usually has large calculation amount, occupies more DSP processor resources, has long diagnosis time and poor real-time performance; the method can be well applied in post analysis or offline diagnosis, but in practical application, particularly in fault-tolerant control of an induction motor driving system, a fault bridge arm needs to be quickly and automatically replaced by a redundant bridge arm after the fault bridge arm is detected, or a system control method (such as a shared bridge arm and the like) is changed to realize fault-tolerant control, so that the requirement on the speed of fault detection is high, the fault-tolerant control is not implemented yet due to overlong detection time, and an accident occurs already.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides a real-time detection method for the open-circuit fault of a bridge arm of a three-phase voltage source inverter, which is used for solving the technical problem of poor real-time performance caused by large calculated amount due to the adoption of a mode identification method in the prior art.

In order to achieve the above object, in a first aspect, the present invention provides a method for detecting an open-circuit fault of a bridge arm of a three-phase voltage source inverter in real time, including the following steps:

s1, collecting current a, b and c three-phase current data i_a、i_bAnd i_c；

S2, updating the three-phase current vector I according to the obtained current data of the three phases a, b and c at the current moment_a、I_bAnd I_c；

S3, constructing a Gram matrix G (I) between every two phase current vectors according to the obtained three phase current vectors_b，I_c)、G(I_a，I_c) And G (I)_a，I_b) Wherein, in the step (A),

s4, calculating the determinant of each Gram matrix and the modulus of each current vector, and calculating the independence coefficient between each two phases of currents according to the determinant of each Gram matrix and the modulus of each current vector;

and S5, obtaining the fault detection result of each phase bridge arm by comparing the irrelevance coefficient between each two phases of currents with the threshold th.

Further preferably, the m-th phase current vector at the k-th time is:

I_m(k)＝[i_m(t)，i_m(t+1)，…，i_m(k)]^T

where m is a, b, c, t is k-L-1, k is the current sampling time,is the current vector dimension, n_pIs the number of pole pairs of the motor, w is the motor speed, T_sIs the sampling time.

Further preferably, the m-phase current and the n-phase current have a coefficient of independenceWhere, m, n ≠ a, b, c, m ≠ n.

Further preferably, the method for determining the threshold value includes the following steps:

s01, calculating independence coefficients between each two phases of currents when the inverter normally operates and when the inverter fails respectively; the inverter faults comprise faults of double tubes in a single bridge arm of the inverter and faults of single tubes of the single bridge arm;

and S02, taking the minimum value of the irrelevance coefficient between every two phases of currents when the inverter normally operates as the maximum value of the threshold value, and taking the maximum value of the irrelevance coefficient between the other two normal phases of currents when one phase of the inverter fails as the minimum value of the threshold value.

Further preferably, the threshold th ∈ [0.612, 0.866] is described above.

Further preferably, when r_bc< th, and r_abNot less than th, and r_acWhen the phase a is not less than th, the bridge arm of the phase a has a fault; otherwise, the a-phase bridge arm has no fault;

when r is_ac< th, and r_abNot less than th, and r_bcWhen the phase b is not less than th, the bridge arm of the phase b has a fault; otherwise, the b-phase bridge arm has no fault;

when r is_ab< th, and r_acNot less than th, and r_bcWhen the phase c bridge arm is larger than or equal to th, the phase c bridge arm has a fault; otherwise, the c-phase bridge arm has no fault.

In a second aspect, the present invention provides a storage medium, which when the computer reads the instructions, causes the computer to execute the method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter in real time provided by the first aspect of the present invention.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

1. the invention provides a real-time detection method for open-circuit faults of bridge arms of a three-phase voltage source inverter, which is characterized in that after an independence coefficient between every two phases of currents is obtained based on Gram matrix calculation, the obtained independence coefficient between every two phases of currents is compared with a threshold value to obtain a fault detection result of each phase of bridge arm.

2. The real-time detection method for the open-circuit fault of the bridge arm of the three-phase voltage source inverter has the advantages that the average diagnosis time is only 1/2 current fundamental wave periods, the detection speed is higher than that of most diagnosis methods at present, and the detection speed is high.

3. According to the method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter in real time, the current signal is not required to be filtered, subjected to noise reduction and the like, and only based on the three-phase current original data, a diagnosis result can be still rapidly and accurately given when the single sudden change of the motor load is within 30% of the rated load, the misdiagnosis rate is low, and the robustness is good.

4. The method for detecting the open-circuit fault of the bridge arm of the three-phase voltage source inverter in real time is applied to fault-tolerant control of an induction motor driving system, can quickly locate the fault bridge arm, provides a basis for quick maintenance or fault-tolerant control of the inverter, and improves the reliability of the induction motor driving system.

Drawings

Fig. 1 is a flowchart of a method for detecting an open-circuit fault of a bridge arm of a three-phase voltage source inverter in real time according to the present invention;

fig. 2 is a topology structure diagram of a motor vector control system with a fault detection module according to an embodiment of the present invention;

fig. 3 is a waveform diagram of each phase current of an inverter provided by an embodiment of the present invention, which operates in a normal state, an a-phase bridge arm double-tube fault state, and an a-phase bridge arm single-tube fault state; wherein, the diagram (a) is a three-phase current waveform diagram of the inverter working in a normal state; the diagram (b) is a three-phase current waveform diagram of the inverter working in a state of a double-tube fault of an a-phase bridge arm; the graph (c) is a three-phase current waveform diagram of the inverter working in the single-tube fault state of the a-phase bridge arm;

fig. 4 is a current waveform diagram of a phase a bridge arm single tube fault, and a waveform diagram of change of an independence coefficient and characteristic quantities representing each phase fault with time, provided by the embodiment of the present invention; wherein, the graph (a) is a current waveform graph when a single tube of an a-phase bridge arm fails; the graph (b) is a waveform diagram of the change of the independence coefficients among the phases along with the time when the single tube of the a-phase bridge arm fails; the graph (c) is a waveform diagram representing the change of characteristic quantities of all phases of faults along with time when a single tube of the a-phase bridge arm has a fault;

fig. 5 is a waveform diagram of a current when a dual-tube fault occurs in the a-phase bridge arm, and a waveform diagram of a change of an independence coefficient and a characteristic quantity representing each phase fault along with time, which are provided by the embodiment of the present invention; wherein, the graph (a) is a current waveform graph when a phase-a bridge arm double-tube fails; the graph (b) is a waveform diagram of the change of the irrelevance coefficients of all phases along with time when a phase bridge arm double-tube fails; the graph (c) is a waveform diagram representing the change of characteristic quantity of each phase fault along with time when the a-phase bridge arm double-tube fault occurs;

FIG. 6 is a waveform of current when a 30% load is suddenly applied to a motor, and waveforms of the independence coefficient and the characteristic quantity representing each phase fault along with time; wherein, the graph (a) is a current waveform graph when the motor is suddenly loaded by 30 percent; the graph (b) is a waveform diagram of the change of each interphase independence coefficient along with time when the motor is suddenly loaded by 30 percent; and (c) is a waveform diagram of the characteristic quantity of each phase fault along with the change of time when the motor is suddenly loaded by 30 percent.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In order to achieve the above object, the present invention provides a method for detecting an open fault of a power tube of a three-phase voltage source inverter in real time, as shown in fig. 1, including the following steps:

s1, collecting current a, b and c three-phase current data i_a、i_bAnd i_c；

S2, updating the three-phase current vector I according to the obtained current data of the three phases a, b and c at the current moment_a、I_bAnd I_c；

S3, constructing a Gram matrix G (I) between every two phase current vectors according to the obtained three phase current vectors_b，I_c)、G(I_a，I_c) And G (I)_a，I_b) Wherein, in the step (A),

s4, calculating the determinant of each Gram matrix and the modulus of each current vector, and calculating the independence coefficient between each two phases of currents according to the determinant of each Gram matrix and the modulus of each current vector;

and S5, obtaining the fault detection result of each phase bridge arm by comparing the irrelevance coefficient between each two phases of currents with the threshold th.

For clearly describing the method for detecting the open fault of the power tube of the three-phase voltage source inverter in real time, the following embodiments are described in detail:

as shown in fig. 2, the topology structure diagram of the motor vector control system with the fault detection module in the present invention is composed of power tubes (T1, T2, T3, T4, T5, T6), corresponding freewheeling diodes, filter capacitors (C1, C2), an induction motor, a vector control module, and a fault diagnosis module; and the direct-current voltage output after rectification is Ud.

Specifically, the method for detecting the open fault of the power tube of the three-phase voltage source inverter in real time comprises the following steps:

s1, collecting three-phase current data i of a, b and c at the current moment_a、i_bAnd i_c；

S2, obtaining the current timeUpdating three-phase current vector I_a、I_bAnd I_c(ii) a Wherein, the m phase current vector at the kth moment is:

I_m(k)＝[i_m(t)，i_m(t+1)，…，i_m(k)]^T

where m is a, b, c, t is k-L-1, k is the current sampling time,is the current vector dimension, n_pIs the number of pole pairs of the motor, w is the motor speed, T_sIs the sampling time.

S3, constructing a Gram matrix G (I) between every two phase current vectors according to the obtained three phase current vectors_b，I_c)、G(I_a，I_c) And G (I)_a，I_b) Wherein, in the step (A), in particular, a Gram matrix is often used for representing the correlation between a group of vectors, and the fault diagnosis is carried out by analyzing the independence between each two phases of current by the aid of the Gram matrix.

S4, calculating the determinant of each Gram matrix and the modulus of each current vector, and calculating the independence coefficient between each two phases of currents according to the determinant of each Gram matrix and the modulus of each current vector;

specifically, the irrelevance coefficient between the phase-a current and the phase-b currentCoefficient of independence between a-phase current and c-phase currentCoefficient of independence between phase b current and phase c current

S5, obtaining a fault detection result of each phase of bridge arm by comparing the irrelevance coefficient between each two phases of currents with the threshold th;

specifically, the method for determining the threshold value includes the following steps:

s01, calculating independence coefficients between each two phases of currents when the inverter normally operates and when the inverter fails respectively; the inverter faults comprise faults of double tubes in a single bridge arm of the inverter and faults of single tubes of the single bridge arm;

specifically, taking the a-phase bridge arm diagnosis process as an example, as shown in fig. 3, the graphs (a) and (b) and (c) are three-phase current waveform diagrams of the inverter operating in a normal state, a two-tube fault state of the a-phase bridge arm, and a single-tube fault state of the a-phase bridge arm, respectively. According to the symmetry of current waveform in each state of the inverter, the embodiment divides a current period into 6 sub-intervals, so that three-phase current vectors can be decomposed into 3 sub-vectors I₁、I₂、I₃To greatly simplify the calculation of current independence values under different conditions.

When the inverter operates in a normal state, according to the symmetry of the current waveform, as shown in (a) of fig. 3, the three-phase current can be decomposed into:

therefore, the method has the advantages that,

under normal conditions, the three-phase current is a sine wave, so the modulus of the current vector is as follows:

the determinant values of the Gram matrix (Gram matrix) are:

therefore, the irrelevance coefficient between the a-phase current and the b-phase currentAnd further according to the symmetry of the light,

when both the upper and lower transistors in the inverter a-phase arm fail, as shown in fig. 3 (b), i is the time when_aTheoretical value 0, due in fact to the action of the antiparallel diode, i_aNot exactly 0, i.e.And i_bThe waveform is approximate to a sine wave although distorted, and the waveforms of the positive half period and the negative half period are antisymmetric, so thatSo there is a quantitative relationship as follows:

the phase-to-phase independence of the failed a-phase current from the normal b-phase current is,

from the symmetry, the phase-to-phase independence of the a-phase current and the c-phase current is also 1, and it is known that, when an open fault occurs in a certain phase, the phase-to-phase independence of the fault phase current and the normal phase current increases. For normal two-phase current I_bAnd I_cDeterminant of Gram matrix between two phase currents:

therefore, when a double-tube fault occurs to the phase a, the independence between the phase currents b and c is 0, namely the independence between the normal current of the other two phases and the independence between the normal phase and the fault phase can be reduced to 0, and the independence between the normal phase and the fault phase can be increased to 1.

When a single-tube fault occurs in the a-phase bridge arm, according to the diagram (c) in fig. 3, each current vector is approximated as:

thus, the integration can be performed using a sine trigonometric function

According to symmetry, r_ac＝r_ab0.9354. For the independence of the currents between the two phases b and c, the first positive half period of the single-tube fault is similar to the condition of the double-tube fault, and no current (r) exists in the bridge arm_bc0); the second half period is similar to the normal condition, and the current in the bridge arm normally passes throughTherefore, when a phase bridge arm has a single tube fault, the fault occurs

And S02, taking the minimum value of the irrelevance coefficient between every two phases of current in normal operation of the inverter as the maximum value of the threshold, and taking the maximum value of the irrelevance coefficient between the other two phases of normal current when one phase of the inverter fails as the minimum value of the threshold, and obtaining the value range of the threshold th as th ∈ [0.612, 0.866 ].

Specifically, the relationship between the inverter operation and the current independence in different states can be summarized according to the above analysis and calculation as shown in table 1:

TABLE 1

From the analysis in Table 1 and above, it can be seen that r is the normal operating condition of the inverter_bcNot less than 0.866; when the inverter fails, r_bcLess than or equal to 0.612 (r when a-phase double-tube fails_bc0, single tube fault time r_bc0.612), therefore, r may be adopted_bcThe method for judging whether the inverter b and c phases have faults is the same as the method for judging whether the a phase has faults, and the method is not repeated here, the minimum value of the irrelevance coefficient between every two phases of current when the inverter normally operates is taken as the maximum value of the threshold, the maximum value of the irrelevance coefficient between the other two normal phases of current when the inverter has faults at one phase is taken as the minimum value of the threshold, and the value range of the threshold th is obtained as th ∈ [0.612, 0.866]]。

Further, the independence coefficient is compared with the threshold value th, the characteristic quantity of the characteristic fault at the current moment is obtained, whether each bridge arm has the fault or not is judged, and the fact that when a certain phase has the fault, the independence between the other two phases of current is reduced is found through specific calculation, so that when r is the fault_bc< th, and r_abNot less than th, and r_acCharacteristic quantity F for characterizing a-phase fault when the value is more than or equal to th_A1, the a-phase bridge arm has a fault; otherwise, F_A0, a phase bridge armThere is no fault;

when r is_ac< th, and r_abNot less than th, and r_bcCharacteristic quantity F for characterizing phase b fault when being more than or equal to th_B1, a b-phase bridge arm has a fault; otherwise, F_BThe b-phase bridge arm has no fault when the phase is 0;

when r is_ab< th, and r_acNot less than th, and r_bcCharacteristic quantity F for characterizing phase c fault when being more than or equal to th_C1, the c-phase bridge arm has a fault; otherwise, F_CAnd when the phase c bridge arm is 0, no fault exists. In this embodiment, the selected threshold th is 0.62.

Finally, steps S1-S5 may be repeated to continuously output the fault detection results of the respective phase legs at each time.

Furthermore, the method for detecting the open fault of the power tube of the three-phase voltage source inverter in real time has small calculated amount and good real-time property. Specifically, for the current chain table with the data size n, the number of times of calculation in one control cycle includes: (1) i | |_aThe number of times of calculating | is 3 × (2n-1) (including n-times of multiplication and n-1 times of addition), (2) the number of times of calculating the determinant of the Gram matrix is 3 × (2n-1) (including n-times of multiplication and n-1 times of addition, the calculation result of the vector inner product can be shared, so that the calculation of the determinant can be reduced by half), and (3) the irrelevance coefficient r between the m-th phase and the n-th phase_mnThe calculation times of (1) is 3 times of division and 3 times of root-opening number calculation times (the calculation amount of one root-opening number is larger than that of one multiplication, but the magnitude is still smaller than n)); the total number is about 12n times, namely the algorithm time complexity is O (n), the calculated amount is small, the real-time performance is good, and the method is suitable for being applied to an industrial DSP processor.

Further, in order to verify the detection speed of the present invention, the present embodiment adopts a method of shielding the control signal of the transistor to simulate a corresponding fault, wherein the system sampling frequency is 5 kHz. The motor speed was 500 rpm (with 15% rated load). Specifically, the waveform diagram of the single-tube fault of the a-phase bridge arm (T2 fault) is shown in (a) diagram in fig. 4, and it can be seen that the fault occurs at 0.10 s. The method for detecting the open-circuit fault of the bridge arm of the inverter in real time is adopted for detection, wherein the threshold th is selected to be 0.75. The waveform diagram of the change of the independence coefficient of each phase with time when the single tube of the a-phase bridge arm fails is shown as (b) diagram in fig. 4, wherein the abscissa represents time, the ordinate represents the independence coefficient, and the fundamental wave period of the motor phase current is 0.06 s. As shown in fig. 4 (c), the waveform of the change with time of the characteristic quantity characterizing each phase fault when the single tube of the a-phase bridge arm has a fault is shown, wherein the abscissa represents time, the ordinate represents the characteristic quantity characterizing the fault, the characteristic quantity is 1 representing the fault, and the characteristic quantity is 0 representing no fault. As can be seen, the fault was diagnosed at 0.121s, with a diagnostic time of 0.021s, about 35% current cycle. Fig. 5 (a) shows a waveform diagram of a double-tube fault of an a-phase bridge arm, which is detected by the inverter bridge arm open-circuit fault real-time detection method provided by the invention, and the threshold th is selected to be 0.75. The waveform diagram of the change of the irrelevance coefficient of each phase with time when the double-tube of the a-phase bridge arm fails is shown as a graph (b) in fig. 5, wherein the abscissa represents time, the ordinate represents the irrelevance coefficient, and the fundamental wave period of the motor phase current is 0.06 s. As shown in fig. 5 (c), the waveform of the change with time of the characteristic quantity indicating the failure of each phase when the a-phase arm double tube fails is shown, in which the abscissa indicates time, the ordinate indicates the characteristic quantity indicating the failure, the characteristic quantity is 1 indicating the failure, and the characteristic quantity is 0 indicating no failure. It can be seen from the figure that the fault occurred at 0.10s and was diagnosed at 0.124s, with a diagnostic time of 0.024s, about 40% current cycle. Therefore, the average diagnosis time of the real-time detection method for the open-circuit fault of the bridge arm of the three-phase voltage source inverter provided by the invention is only 1/2 current fundamental wave periods, which is faster than that of most diagnosis methods at present (most of the current fundamental wave periods are about 1, and a small part of the current fundamental wave periods reach 2/3 current fundamental wave periods), and the detection speed is fast.

Further, in order to prove the robustness of the real-time detection method for open faults of the power tube of the three-phase voltage source inverter provided by the invention, in the embodiment, the motor initially operates at 500 rpm and 15% of rated load, and then 30% of load is suddenly added to 45% of rated load at 0.6s, as shown in fig. 6, wherein a graph (a) is a current waveform diagram when the motor suddenly adds 30% of load, a graph (b) is a waveform diagram of the change of each phase independence coefficient along with time when the motor suddenly adds 30% of load, and a graph (c) is a waveform diagram of the change of characteristic quantities representing faults of each phase along with time when the motor suddenly adds 30% of load (the characteristic quantity is 1 represents a fault, and the characteristic quantity is 0 represents no fault). It can be seen from the figure that although the waveform amplitude of each phase of current is obviously increased, the waveform change trends of each phase of current are similar, the independence between the phase of current has certain fluctuation but larger margin according to the threshold value, and misdiagnosis does not occur, which indicates that the method provided by the invention has better robustness to load disturbance.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.