A method for detecting open circuit fault state of inverter based on stator current

Abstract

The present invention discloses a method for detecting an inverter open circuit fault state based on stator current. The method comprises: under the condition of an inverter open circuit fault, applying an action vector to the inverter through a controller and collecting three-phase stator current to obtain a vector action distribution time; when the inverter fault phase current generates commutation, judging the vector state after commutation, and then judging the intermittent condition of the inverter; obtaining the periodic fault phase current of the inverter under commutation and intermittent conditions; comparing the three-phase stator current of the inverter to be detected with the periodic fault phase current and the healthy three-phase stator current, and finally realizing open circuit fault state detection. The method of the present invention unifies the inverter and the controller, takes into account the essential characteristic of controller regulation that causes current distortion, can realize high-precision analysis of fault current, has strong generalization ability, strong versatility and scalability, and a wider range of application, and provides theoretical support for rapid fault state detection.

Description

Technical Field

[0001] The invention relates to a method for detecting an open circuit fault state of an inverter, and relates to the technical field of intelligent perception and operation and maintenance of electric power equipment, and in particular to a method for detecting an open circuit fault state of an inverter based on stator current. Background Art

[0002] Inverter open circuit is one of the most common fault types in motor drive systems, which has a serious impact on the long-term operation of the inverter and motor and the stability of the system. Accurate fault feature extraction and recognition is an important prerequisite for the development of online monitoring and fault diagnosis technology of motor drive system operation status, which has very important theoretical and practical significance.

[0003] Most of the current motor drive systems are closed-loop controlled, and the fault characteristics are closely related to the operating conditions and are affected by the controller's regulation.

[0004] As a highly nonlinear high-order system, coupled with the variable actual operating conditions, the complexity of accurately modeling the system is higher, the computing power is greatly increased and it is difficult to achieve accurate analysis, which is inconsistent with the development trend of fault diagnosis technology in pursuit of efficiency and universality, and the practicality of the analytical model method has deteriorated.

[0005] There is a transition process between the moment of fault occurrence and the stable state after the fault. This transition process is greatly affected by the control parameters. The fault characteristics have changed compared with the open-loop controller. The existing theory ignores the influence of the controller regulation and operating conditions, and the obtained diagnostic threshold does not match the actual effect. More importantly, the transition process corresponding to different controllers is not the same, the regularity of the characteristics becomes weaker, and the problem of difficult threshold selection in the signal processing method is further amplified. The problem that the current change under closed-loop conditions is affected by the feedback regulation of the controller has received less attention. Although the simplified model that ignores feedback regulation can reduce the amount of calculation when analyzing the fault current, the simplified model will cause the loss of fault characteristics. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention provides a method for detecting an inverter open circuit fault state based on stator current.

[0007] The technical solution adopted by the present invention is:

[0008] The inverter open circuit fault state detection method based on stator current of the present invention comprises:

[0009] Step 1: Under the condition of an inverter open circuit fault, a preset action vector is applied to the inverter through a controller and the three-phase stator current of the inverter is collected at the same time, so as to obtain the modulation degree under the condition of the inverter open circuit fault, and then obtain the action distribution time of the preset action vector.

[0010] Step 2: Determine whether there is commutation and discontinuity in the fault phase current of the inverter. When the fault phase current of the inverter generates commutation, determine the vector state of the preset action vector after commutation according to the fault phase current of the inverter; if the normal current flow path under the action of the current vector includes the faulty device, the current flow path will be changed and commutated to other devices, otherwise no commutation will occur.

[0011] Step 3: After the fault phase current of the inverter is commutated, it is determined whether the fault phase current of the inverter is intermittent according to the vector state after the commutation of the preset action vector and the action distribution time of the preset action vector.

[0012] Step 4: When the fault phase current of the inverter generates commutation and discontinuity, obtain the three-phase current change rate of the inverter, and then obtain the fault phase current of the inverter at the next vector switching moment, and repeat steps 4-5 to obtain the periodic fault phase current of the inverter.

[0013] Step 5: The three-phase stator current of the inverter to be detected is collected through the controller, and compared with the periodic fault phase current for consistency, and then compared with the three-phase stator current of the inverter in a healthy state to determine the degree of fault, and finally realize the inverter open circuit fault state detection.

[0014] In the step 1, the actual dq axis current of the inverter is first obtained by the three-phase stator current of the inverter collected by the controller, and then the current error is obtained according to the difference between the actual dq axis current of the inverter and the reference current. The dq axis voltage of the inverter is obtained according to the current error using a proportional integral PI (Proportional Integral) regulator, and the modulation degree of the inverter under the open circuit fault condition is obtained according to the dq axis voltage of the inverter. m ,as follows:

[0015] m =(3( v df 2 + v qf 2 )) 1 / 2 / V dc

[0016] in, v df and v qf are the dq axis voltages of the inverter respectively; V dc is the DC voltage of the inverter.

[0017] In step 1, the action vector is presetV j The role distribution time is as follows:

[0018] T i = mT s sin(π / 3- θ λs )

[0019] T e = mT s sin θ λs

[0020] T 0= T s [1- m sin( θ λs +π / 3)]

[0021] in, T i , T e and T 0 are preset action vectors V j The starting vector action time, terminal vector action time and zero vector action time; m is the modulation index under the inverter open circuit fault condition; T s is the switching cycle of the controller; θ λs The preset action vector V j The angle with the initial boundary of the current sector. Preset action vector V j Enter λ ( λ =I, ..., VI) The vector of the sector is the initial boundary of the current sector.

[0022] In the step 2, the vector state after commutation of the preset action vector is determined according to the fault phase current of the inverter, as follows:

[0023] When the fault phase current of the inverter meets the following conditions:

[0024] i x > e x / R -(2 S x -S y - S z ) V dc / 6 R

[0025] in, i x is the fault x-phase current of the inverter. When the fault x-phase current of the inverter is the a-phase current, the y-phase current and the z-phase current of the inverter are the b-phase current and the c-phase current respectively. When the fault x-phase current of the inverter is the b-phase current, the y-phase current and the z-phase current of the inverter are the a-phase current and the c-phase current respectively. When the fault x-phase current of the inverter is the c-phase current, the y-phase current and the z-phase current of the inverter are the a-phase current and the b-phase current respectively. e x is the fault x back electromotive force of the inverter; R is the stator winding resistance; S x , S y and S z In the preset action vector V j The vector after commutation V jf The vector states of the x-phase, y-phase and z-phase currents of the inverter under action; V dc is the DC voltage of the inverter.

[0026] Then determine the preset action vector V j The vector after commutation V jf is the forward vector of the fault x-phase current of the inverter.

[0027] When the fault phase current of the inverter meets the following conditions:

[0028] i x < e x / R -(2 S x - S y - S z ) V dc / 6 R

[0029] Then determine the preset action vector V jThe vector after commutation V jf is the reverse vector of the fault x-phase current of the inverter.

[0030] When the fault phase current of the inverter meets the following conditions:

[0031] i x +(2 S x - S y - S z ) V dc / 6 R - e x / R =0

[0032] Then determine the preset action vector V j The vector after commutation V jf is the zero direction vector of the fault x-phase current of the inverter.

[0033] In the step 3, it is determined whether the fault phase current of the inverter is intermittent according to the vector state after the commutation of the preset action vector and the action distribution time of the preset action vector, as follows:

[0034] When the preset action vector V j The vector after commutation V jf The expected working vector generated by the controller is in phase with the fault phase current of the inverter, and the fault phase current of the inverter is judged to be non-intermittent. V j The vector after commutation V jf The desired working vector generated by the controller is an anti-phase vector when the following conditions are met:

[0035] [ k xf T j + i x (0)] i x (0)<0

[0036] in, k xf is the current change rate after commutation of the fault x-phase current of the inverter, and the fault x-phase current of the inverter is the a-phase current, the b-phase current or the c-phase current; Tj Allocate time for the action of a preset action vector, j = i , e and 0, T i , T e and T 0 are preset action vectors V j The starting vector action time, terminal vector action time and zero vector action time; i x (0) is the initial value of the fault x-phase current of the inverter.

[0037] Then the fault x-phase current of the inverter appears to have a current zero crossing point, that is, it is judged that the fault phase current of the inverter is intermittent.

[0038] In step 4, the fault phase current of the inverter at the next vector switching moment is as follows:

[0039] i x ( r )= i x ( r -1)+ k xf T jf + k x0 T j0 + k xn T jn

[0040] in, i x ( r )and i x ( r -1) are respectively the inverter at the next vector switching moment r and the current vector switching moment r -1 fault x phase current; k xf , k x0 and k xn are the current change rates of commutation, intermittent flow and normal flow generated by the faulty x-phase current of the inverter, respectively. The faulty x-phase current of the inverter is the a-phase current, the b-phase current or the c-phase current; T jf is the time for the fault x-phase current to commutate, Tj0 is the intermittent time of the fault x-phase current, T jn It is the time during which the current of fault x phase flows normally.

[0041] When the fault x-phase current of the inverter does not produce commutation, the commutation time of the fault x-phase current is T jf =0, when the fault x-phase current of the inverter does not produce discontinuity, the discontinuity time of the fault x-phase current is T j0 =0.

[0042] In step 5, the three-phase stator current of the inverter to be detected collected by the controller is compared with the periodic fault phase current for consistency, so as to judge the fault condition of the inverter to be detected and determine the fault phase current in the three-phase stator current of the inverter.

[0043] In the step 5, when it is determined that the inverter to be detected has a fault phase current, the three-phase stator current of the inverter to be detected collected by the controller is operated in steps 4-5, and then the periodic fault phase current of the inverter to be detected is obtained, and the periodic fault phase current of the inverter to be detected is compared with the three-phase stator current of the inverter in a healthy state. The greater the difference between the periodic fault phase current of the inverter to be detected and the three-phase stator current of the inverter in a healthy state, the greater the fault degree of the inverter is.

[0044] The electronic device of the present invention comprises: a memory and a processor coupled to each other, wherein the memory stores program data, and the processor calls the program data to execute the method as described above.

[0045] The computer-readable storage medium of the present invention stores program data thereon, and is characterized in that the program data implements the method described above when executed by a processor.

[0046] The beneficial effects of the present invention are:

[0047] 1) The method of the present invention starts from the essential operating characteristics of the motor and its drive system, unifies the inverter and the controller, has strong integrity, is more practical, will not cause distortion of fault characteristics, and realizes high-precision analysis of fault current for the first time, which can solve the problem of lack of high-precision fault phase current state detection.

[0048] 2) The method of the present invention proposes the feature of discontinuous fault phase current and reveals the fundamental cause of fault current distortion.

[0049] 3) The method of the present invention takes into account the essential characteristic of controller regulation that causes current distortion, can more accurately describe the law of fault current distortion, and has strong generalization ability under different control parameters.

[0050] 4) The method of the present invention takes error integration as the core and only requires basic electrical parameters as system input. It has strong versatility and scalability and a wider range of applications.

[0051] 5) The method of the present invention can perform multi-step estimation of the fault current, obtain a priori fault current characteristics, and provide theoretical support for rapid fault state detection.

[0052] In summary, the method of the present invention has low sensitivity to motor speed changes and load changes, and can be applied in different control cycles, different open-circuit devices and different topological structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 FIG. 1 is a topological structure diagram of a converter in an embodiment of the method of the present invention, wherein: Figure 1 (a) is the topology diagram of the two-level inverter. Figure 1 (b) is a topological diagram of a neutral point clamped NPC (Neutral Point Clamped) three-level inverter;

[0054] Figure 2 It is the work flow chart of the method of the present invention;

[0055] Figure 3 The upper bridge arm device S of the a phase of the two-level inverter in the embodiment of the method of the present invention is a1 Phase b current diagram after opening the circuit;

[0056] Figure 4 The device S of the upper bridge arm of the a phase of the NPC three-level inverter in the embodiment of the method of the present invention is a1 Three-phase current diagram after opening the circuit;

[0057] Figure 5 Schematic diagram of three-phase currents obtained when a phase current fault occurs in a two-level inverter in an embodiment of the method of the present invention. DETAILED DESCRIPTION

[0058] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] The present invention takes a 4.5kW surface-mounted permanent magnet synchronous motor as an embodiment, wherein the stator winding resistance of the surface-mounted permanent magnet synchronous motor is 0.559Ω, the stator winding inductance is 4.24mH, the permanent magnet flux is 0.339Wb, the sampling frequency is 4kHz, the motor speed is 1000r / min, the pole pair number is 4, the DC voltage is 450V, the power factor angle is 11.5°, and the current amplitude is 17.3A. Figure 1 (a) and Figure 1 As shown in (b), the topology of the two-level inverter and the NPC three-level inverter for open circuit fault state detection in the embodiment of the present invention is shown. The inverter open circuit fault state detection method based on stator current of the present invention is used to detect the open circuit fault state of the inverter, as shown in FIG. Figure 2 As shown, the details are as follows:

[0060] First, under the condition of an inverter open circuit fault, the controller applies a preset action vector to the inverter and simultaneously collects the three-phase stator current of the inverter. At the moment of the fault, the a-phase current is 0 and the rotor position angle is 0, then the b-phase current is -15A and the c-phase current is 15A. The three-phase stator current and rotor position angle of the inverter collected by the controller are used to obtain the actual dq axis current of the inverter, which are 0 and 17.3A respectively. Then, the current error is obtained based on the difference between the actual dq axis current of the inverter and the reference current. The proportional-integral PI regulator is used to obtain the dq axis voltage of the inverter based on the current error. The proportional coefficient of the proportional-integral PI regulator is 3.5, and the integral coefficient is 462. The reference voltage vector in the proportional-integral PI regulator is located in the Vth sector, and the effective vector is V 5(001) and V 6(101)), from V 6(101) and the output dq axis voltages are -30.715V and 151.68V respectively. The modulation index under the inverter open circuit fault condition is obtained according to the dq axis voltage of the inverter. m ,as follows:

[0061] m =(3( v df 2 + v qf 2 )) 1 / 2 / V dc

[0062] v df = v d0 + K id (Δ i df* / s )+ K pd Δ i df *

[0063] v qf = v q0 + K iq (Δ i qf * / s )+ K pq Δ i qf *

[0064] in, v df and v qf are the dq axis voltages of the inverter respectively; V dc is the DC voltage of the inverter; v d0 and v q0 are the dq axis steady-state voltages of the inverter respectively; K id and K iq are the first and second integral coefficients of the proportional-integral PI regulator, K pd and K pq are the first and second proportional coefficients of the proportional-integral PI regulator respectively; Δ i df * and Δ i qf * They are the differences between the reference value and the actual value of the inverter's dq axis current respectively.

[0065] The modulation index under the inverter open circuit fault condition is finally obtained m It is 0.5957.

[0066] Then according to the modulation index under the inverter open circuit fault condition m Get the preset action vector V j The role of the distribution time is as follows:

[0067] T i = mT s sin(π / 3- θ λs )

[0068] T e = mT s sin θ λs

[0069] T 0= T s [1- m sin( θ λs +π / 3)]

[0070] in, T i , T e and T 0 are preset action vectors V j The starting vector action time, terminal vector action time and zero vector action time; m is the modulation index under the inverter open circuit fault condition; T s is the switching cycle of the controller; θ λs The preset action vector V j The angle with the initial boundary of the current sector. Preset action vector V j Enter λ ( λ =I, ..., VI) The vector of the sector is the initial boundary of the current sector.

[0071] The final preset action vector V j The starting vector action time T0 = 0.10405ms, the terminal vector action time T5 = 0.047354ms, and the zero vector action time T6 = 0.098598ms.

[0072] Then determine whether the inverter's faulty a-phase current has commutation and discontinuity. If the normal current flow path under the current vector includes the faulty device, the current flow path will be changed and commutated to other devices. Otherwise, no commutation will occur. In specific implementation, the expected a-phase current change rate is 35377A / s. Determine the current vector V 6(101) Fault phase a current of the inverter i ais the forward vector, once i a >0, the flow will be switched to S immediately a2 anti-parallel diodes, so there is commutation.

[0073] When the faulty a-phase current of the inverter generates commutation, the vector state after commutation of the preset action vector is determined according to the faulty a-phase current of the inverter, as follows:

[0074] When the inverter's fault a phase current meets the following conditions:

[0075] i a > e a / R -(2 S a - S b - S c ) V dc / 6 R

[0076] in, i a is the fault phase a current of the inverter; e a is the reverse electromotive force of the inverter fault a; R is the stator winding resistance; S a , S b and S c In the preset action vector V j The vector after commutation V jf The vector states of the a-phase, b-phase and c-phase currents of the inverter under action; V dc is the DC voltage of the inverter.

[0077] Then determine the preset action vector V j The vector after commutation V jf is the forward vector of the fault a-phase current of the inverter.

[0078] When the inverter's fault a phase current meets the following conditions:

[0079] i a < e a / R -(2S a - S b - S c ) V dc / 6 R

[0080] Then determine the preset action vector V j The vector after commutation V jf is the reverse vector of the fault a phase current of the inverter.

[0081] When the inverter's fault a phase current meets the following conditions:

[0082] i a +(2 S a - S b - S c ) V dc / 6 R - e a / R =0

[0083] Then determine the preset action vector V j The vector after commutation V jf is the zero direction vector of the fault a phase current of the inverter.

[0084] After the inverter fault a phase current generates commutation, the actual action vector is V 5(001), action vector V 5(001) Fault phase a current of the inverter i a It is a negative vector. The actual action vector and the expected vector after commutation are opposite vectors.

[0085] After the inverter's faulty a-phase current is commutated, it is determined whether the inverter's faulty a-phase current is intermittent based on the vector state after commutation of the preset action vector and the action distribution time of the preset action vector, as follows:

[0086] When the preset action vector V j The vector after commutation V jfIf the expected working vector generated by the controller is in phase with the inverter fault a phase current, the inverter fault a phase current is judged to be non-intermittent. V j The vector after commutation V jf The desired working vector generated by the controller is an anti-phase vector when the following conditions are met:

[0087] [ k af T j + i a (0)] i a (0)<0

[0088] in, k af is the current change rate of the inverter's fault phase a current after commutation; T j Allocate time for the action of a preset action vector, j = i , e and 0, T i , T e and T 0 are preset action vectors V j The starting vector action time, terminal vector action time and zero vector action time; i a (0) is the initial value of the fault phase a current of the inverter.

[0089] Then the faulty a-phase current of the inverter appears to have a current zero crossing point, that is, it is judged that the faulty a-phase current of the inverter is intermittent.

[0090] In specific implementation, due to the initial value of the current i a (0) = 0, clamping will occur and the intermittent state will be entered immediately, that is, in the action vector V 6. Fault phase a current of the inverter in the action state i a It remains zero continuously and has a zero crossing point, so it is judged that the fault a phase current of the inverter is intermittent.

[0091] When the fault phase a current of the inverter generates commutation and discontinuity, the three-phase current change rate of the inverter is obtained, and then the fault phase a current of the inverter at the next vector switching moment is obtained, as follows:

[0092] i a ( r)= i a ( r -1)+ k af T jf + k a0 T j0 + k an T jn

[0093] in, i a ( r )and i a ( r -1) are respectively the inverter at the next vector switching moment r and the current vector switching moment r -1 fault phase a current; k af and k an are the current change rates after commutation and discontinuity of the faulty a-phase current of the inverter respectively; T jf is the time for the current commutation of fault phase a, T j0 is the intermittent time of the fault phase a current, T jn It is the time during which the current of fault phase a flows normally.

[0094] When the inverter's fault phase a current does not commutate, the commutation time of the fault phase a current is T jf =0, when the fault phase a current of the inverter does not produce discontinuity, the discontinuity time of the fault phase a current is T j0 =0.

[0095] The three-phase current change rate is as follows:

[0096]

[0097] in, L is the stator winding inductance.

[0098] Since the commutation time is 0, the discontinuous state is entered immediately, so only the three-phase current change rate under the discontinuous condition needs to be considered. k a0 =0, k b0 -22086A / s.

[0099] Intermittent time of fault phase a current T j0 as follows:

[0100] T j0 = T j + i a (0) / k af

[0101] The interruption time of the fault phase a current of the inverter can be obtained to be 0.098598ms.

[0102] Since the vector in the current sampling period V 6, all are intermittent, then the commutation time is 0, the normal time is 0, then we can get i a (2)=0, i b (2) = -17.1A. Since the sum of the three-phase currents is 0, i c (2) = 17.1A.

[0103] Repeat the above steps to obtain the inverter's periodic fault a-phase current. Figure 3 As shown, the upper bridge arm device S of the a phase of the two-level inverter a1 Taking open circuit as an example, the b-phase current is obtained, where i bf To experimentally measure the b-phase current waveform, i bf_e is the b-phase current waveform obtained by the method of the present invention, i bn is the b-phase current waveform in a healthy state, i bf_e1 is the b-phase current waveform obtained based on the Fourier decomposition method. Figure 4 As shown, the upper arm outer device S of phase a of the three-level inverter is a1 Take open circuit as an example, and obtain the three-phase current. Figure 5 As shown, the three-phase current shown in the shaded part can be obtained according to the above steps. Repeating the steps can obtain Figure 5 The periodic fault phase current in i bf is the difference between the reference value and the actual value of the b-phase current after inverter commutation, Δ i bn It is the difference between the reference value and the actual value of the b-phase current after the inverter is discontinuous.

[0104] Finally, the controller collects the three-phase stator current of the inverter to be detected and compares it with the periodic fault phase current for consistency, so as to judge the fault condition of the inverter to be detected and determine the fault phase current in the three-phase stator current of the inverter. When it is judged that the inverter to be detected has a fault phase current, the three-phase stator current of the inverter to be detected collected by the controller is operated in the above steps to obtain the periodic fault phase current of the inverter to be detected, and the periodic fault phase current of the inverter to be detected is compared with the three-phase stator current of the inverter in a healthy state. When the difference between the periodic fault phase current of the inverter to be detected and the three-phase stator current of the inverter in a healthy state is greater, it is judged that the fault degree of the inverter is greater, and finally the fault degree of the inverter to be detected is determined to realize the open circuit fault state detection of the inverter.

[0105] According to the above embodiments, the present invention starts from the current distortion characteristics after the inverter has an open circuit fault, unifies the inverter and the controller, and then analyzes the three-phase current distortion law after the inverter has an open circuit fault, so as to clarify the cause of the fault characteristics. The present invention takes into account the influence of the controller feedback adjustment when detecting the inverter open circuit fault state, can be applied to a variety of topological structures, and the detection accuracy is higher than that of the existing detection method.

[0106] It should be understood by those skilled in the art that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present application may be implemented in various computer languages. The present application is described according to the flowcharts of the methods, systems and computer program products of the embodiments of the present application.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting an inverter open circuit fault state based on stator current, characterized in that: include: Step 1: Under the condition of an inverter open circuit fault, a preset action vector is applied to the inverter through a controller and the three-phase stator current of the inverter is collected at the same time, so as to obtain the modulation degree under the condition of the inverter open circuit fault, and then obtain the action distribution time of the preset action vector; Step 2: when the fault phase current of the inverter generates commutation, the vector state of the preset action vector after commutation is determined according to the fault phase current of the inverter; Step 3: After the fault phase current of the inverter is commutated, it is determined whether the fault phase current of the inverter is intermittent according to the vector state after the commutation of the preset action vector and the action distribution time of the preset action vector; Step 4: When the fault phase current of the inverter generates commutation and discontinuity, obtain the three-phase current change rate of the inverter, and then obtain the fault phase current of the inverter at the next vector switching moment, and repeat steps 4-5 to obtain the periodic fault phase current of the inverter; Step 5: The three-phase stator current of the inverter to be detected is collected through the controller, and compared with the periodic fault phase current for consistency, and then compared with the three-phase stator current of the inverter in a healthy state to determine the degree of fault, and finally realize the inverter open circuit fault state detection.

2. The method for detecting an inverter open circuit fault state based on stator current according to claim 1, characterized in that: In the step 1, the actual dq axis current of the inverter is first obtained by the three-phase stator current of the inverter collected by the controller, and then the current error is obtained according to the difference between the actual dq axis current of the inverter and the reference current. The dq axis voltage of the inverter is obtained according to the current error using a proportional integral PI regulator, and the modulation degree of the inverter under the open circuit fault condition is obtained according to the dq axis voltage of the inverter. m ,as follows: m =(3( v df 2 + v qf 2 )) 1 / 2 / V dc in, v df and v qf are the dq axis voltages of the inverter respectively; V dc is the DC voltage of the inverter.

3. The inverter open circuit fault state detection method based on stator current according to claim 1, characterized in that: In step 1, the action vector is preset V j The role distribution time is as follows: T i = mT s sin(π / 3- θ λs ) T e = mT s sin θ λs T 0= T s [1- m sin( θ λs +π / 3)] in, T i , T e and T 0 are preset action vectors V j The starting vector action time, terminal vector action time and zero vector action time; m is the modulation index under the inverter open circuit fault condition; T s is the switching cycle of the controller; θ λs The preset action vector V j The angle with the initial boundary of the current sector.

4. The inverter open circuit fault state detection method based on stator current according to claim 1, characterized in that: In the step 2, the vector state after commutation of the preset action vector is determined according to the fault phase current of the inverter, as follows: When the fault phase current of the inverter meets the following conditions: i x ＞ e x / R -(2 S x - S y - S z ) V dc / 6 R in, i x is the fault x-phase current of the inverter. When the fault x-phase current of the inverter is the a-phase current, the y-phase current and the z-phase current of the inverter are the b-phase current and the c-phase current respectively. When the fault x-phase current of the inverter is the b-phase current, the y-phase current and the z-phase current of the inverter are the a-phase current and the c-phase current respectively. When the fault x-phase current of the inverter is the c-phase current, the y-phase current and the z-phase current of the inverter are the a-phase current and the b-phase current respectively. e x is the fault x back electromotive force of the inverter; R is the stator winding resistance; S x , S y and S z In the preset action vector V j The vector after commutation V jf The vector states of the x-phase, y-phase and z-phase currents of the inverter under action; V dc is the DC voltage of the inverter; Then determine the preset action vector V j The vector after commutation V jf is the forward vector of the fault x-phase current of the inverter; When the fault phase current of the inverter meets the following conditions: i x ＜ e x / R -(2 S x - S y - S z ) V dc / 6 R Then determine the preset action vector V j The vector after commutation V jf is the reverse vector of the fault x-phase current of the inverter; When the fault phase current of the inverter meets the following conditions: i x +(2 S x - S y - S z ) V dc / 6 R - e x / R =0 Then determine the preset action vector V j The vector after commutation V jf is the zero direction vector of the fault x-phase current of the inverter.

5. The inverter open circuit fault state detection method based on stator current according to claim 1, characterized in that: In the step 3, it is determined whether the fault phase current of the inverter is intermittent according to the vector state after the commutation of the preset action vector and the action distribution time of the preset action vector, as follows: When the preset action vector V j The vector after commutation V jf The expected working vector generated by the controller is in phase with the fault phase current of the inverter, and the fault phase current of the inverter is judged to be non-intermittent. V j The vector after commutation V jf The desired working vector generated by the controller is an anti-phase vector when the following conditions are met: [ k xf T j + i x (0)] i x (0)<0 in, k xf is the current change rate after commutation of the fault x-phase current of the inverter, and the fault x-phase current of the inverter is the a-phase current, the b-phase current or the c-phase current; T j Allocate time for the action of a preset action vector, j = i , e and 0, T i , T e and T 0 are preset action vectors V j The starting vector action time, terminal vector action time and zero vector action time; i x (0) is the initial value of the fault x-phase current of the inverter; Then the fault x-phase current of the inverter appears to have a current zero crossing point, that is, it is judged that the fault phase current of the inverter is intermittent.

6. The method for detecting an inverter open circuit fault state based on stator current according to claim 1, characterized in that: In step 4, the fault phase current of the inverter at the next vector switching moment is as follows: i x ( r )= i x ( r -1)+ k xf T jf + k x0 T j0 + k xn T jn in, i x ( r )and i x ( r -1) are respectively the inverter at the next vector switching moment r and the current vector switching moment r -1 fault x-phase current; k xf , k x0 and k xn are the current change rates of commutation, intermittent flow and normal flow generated by the faulty x-phase current of the inverter, respectively. The faulty x-phase current of the inverter is the a-phase current, the b-phase current or the c-phase current; T jf is the time for the fault x-phase current to commutate, T j0 is the intermittent time of the fault x-phase current, T jn The time during which the fault x-phase current flows normally; When the fault x-phase current of the inverter does not produce commutation, the commutation time of the fault x-phase current is T jf =0, when the fault x-phase current of the inverter does not produce discontinuity, the discontinuity time of the fault x-phase current is T j0 =0.

7. The method for detecting an inverter open circuit fault state based on stator current according to claim 1, characterized in that: In step 5, the three-phase stator current of the inverter to be detected collected by the controller is compared with the periodic fault phase current for consistency, so as to judge the fault condition of the inverter to be detected and determine the fault phase current in the three-phase stator current of the inverter.

8. The method for detecting an inverter open circuit fault state based on stator current according to claim 1, characterized in that: In the step 5, when it is determined that the inverter to be detected has a fault phase current, the three-phase stator current of the inverter to be detected collected by the controller is operated in steps 4-5, and then the periodic fault phase current of the inverter to be detected is obtained, and the periodic fault phase current of the inverter to be detected is compared with the three-phase stator current of the inverter in a healthy state. The greater the difference between the periodic fault phase current of the inverter to be detected and the three-phase stator current of the inverter in a healthy state, the greater the fault degree of the inverter is.

9. An electronic device, characterized in that: include: A memory and a processor coupled to each other, wherein the memory stores program data, and the processor calls the program data to execute the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having program data stored thereon, characterized in that: When the program data is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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