Fault-tolerant control method, device and storage medium for open-circuit fault of alternating current motor

Abstract

The present application relates to the field of motor control, and more particularly to a fault-tolerant control method, device, computer equipment and computer storage medium for open-circuit fault of an alternating current motor. The method comprises: A, under the condition of considering the change of motor cross-axis current and direct-axis current with motor rotor electric angle, constructing a fault-tolerant control optimization model, wherein the fault-tolerant control optimization model comprises a cost equation generated based on a motor torque equation and a restriction condition constituted by one or more of a fault phase current equation, a motor phase current limit equation and a motor phase voltage limit equation; and B, determining a phase current reference value at the current motor rotor electric angle by using the fault-tolerant control optimization model.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor control, and more particularly, to a fault-tolerant control method, device, computer equipment and computer storage medium for open-circuit fault of an alternating current motor. BACKGROUND

[0002] Electric drive systems applied in the field of vehicles often have high safety and reliability requirements. At present, for the open-circuit fault of a three-phase alternating current motor inverter, a relatively common fault-tolerant strategy is to modify the topology structure of a three-phase full-bridge inverter. For example, a spare bridge arm is added on the basis of a three-phase full-bridge inverter, or the neutral point of a three-phase winding is connected to the middle of two voltage division capacitors on the DC side through a bidirectional thyristor, or the neutral point of the three-phase winding of the motor is opened, and two sets of three-phase full-bridge inverters are used to drive through the open winding method. Although such strategies can achieve fault-tolerant control, they cannot be directly applied to existing three-phase alternating current motor drive system products due to the need to modify the hardware circuit structure. In addition, the change of the hardware circuit also means an increase in cost and system complexity.

[0003] For the open-circuit fault of a three-phase alternating current motor inverter, there are few fault-tolerant strategies that do not change the hardware circuit structure of the motor and the inverter. Some existing technologies achieve fault-tolerant control by modifying the action time of each voltage vector in space vector modulation (SVPWM), but the actual torque control effect of this method is not good, and the speed application range of this method may be limited due to the failure to adjust the current reference under fault; some existing technologies achieve fault-tolerant control of the motor by reconstructing the motor model under fault state combined with model prediction method, but such control strategy is not only complex but also has low control precision; some existing technologies treat the current reference of the fault phase as a second harmonic form of the normal phase current to achieve fault-tolerant control of the motor, but this second harmonic form of the phase current limits the torque output capability under fault, and cannot be applied to the high-speed field weakening region of the motor. In addition, the peak value of the phase current in some fault-tolerant strategies is large, which increases the copper loss of the system, reduces the efficiency, and may affect the stability of the control system. SUMMARY

[0004] To solve or at least alleviate one or more of the above problems, the present application proposes a fault-tolerant control method, device, computer equipment and computer storage medium for open-circuit fault of an alternating current motor, to improve the reliability of the electric drive system and reduce the loss of motor torque caused by fault.

[0005] According to a first aspect of the present application, there is provided a fault-tolerant control method for open-circuit fault of an AC motor driven by an inverter, the method comprising the following steps: A, constructing a fault-tolerant control optimization model under the condition that the d-axis and q-axis currents of the motor vary with the rotor electrical angle of the motor, wherein the fault-tolerant control optimization model comprises a cost equation generated based on a motor torque equation and a constraint condition constituted by one or more of a fault phase current equation, a motor phase current limit equation, and a motor phase voltage limit equation; and B, determining a phase current reference value at the current rotor electrical angle of the motor by using the fault-tolerant control optimization model.

[0006] As an alternative or supplement to the above solution, the method according to an embodiment of the present application further comprises: C, determining a fault phase and an open-circuit fault type of the AC motor based on fault state information of the AC motor and an inverter driving the AC motor, wherein the open-circuit fault type comprises a first fault type and a second fault type.

[0007] As an alternative or supplement to the above solution, in the method according to an embodiment of the present application, in step C, when the fault state information indicates that there is an open-circuit fault in the inverter, and there is only a single-phase open-circuit fault in the inverter and the windings of the AC motor as a whole, and wherein the fault phase bridge arm of the inverter satisfies one of the following conditions: the two switching elements of the upper and lower bridge arms simultaneously have an open-circuit fault; the two diodes of the upper and lower bridge arms simultaneously have an open-circuit fault; the switching element and the diode of the upper bridge arm simultaneously have an open-circuit fault; the switching element and the diode of the lower bridge arm simultaneously have an open-circuit fault; and the total number of switching elements and diodes having an open-circuit fault is more than two, the open-circuit fault type is determined as the first fault type.

[0008] As an alternative or supplement to the above solution, in the method according to an embodiment of the present application, in step C, when the fault state information indicates that there is an open-circuit fault in the windings of the AC motor, and there is only a single-phase open-circuit fault in the inverter and the windings of the AC motor as a whole, the open-circuit fault type is determined as the first fault type.

[0009] As an alternative or supplement to the above solution, in the method according to an embodiment of the present application, in step C, when the fault state information indicates that there is no fault in the windings of the AC motor, and there is an open-circuit fault in only a single-phase bridge arm and satisfies one of the following conditions: the total number of switching elements and diodes having an open-circuit fault is one; the switching element of the upper bridge arm and the diode of the lower bridge arm simultaneously have an open-circuit fault; and the switching element of the lower bridge arm and the diode of the upper bridge arm simultaneously have an open-circuit fault, the open-circuit fault type is determined as the second fault type.

[0010] As an alternative or in addition to the above solutions, in the method according to an embodiment of the application, if the AC motor is a permanent magnet synchronous motor and the inverter is a three-phase full-bridge inverter, the cost equation is a first cost equation J1 or a second cost equation J2, wherein,

[0011]

[0012] wherein T ref is a torque reference value, N p is a number of motor pole pairs, θ e is a motor rotor electrical angle, i d is a direct-axis current and a function of θ e , i q is a quadrature-axis current and a function of θ e , λ m is a permanent magnet flux linkage, L d is a direct-axis inductance, L q is a quadrature-axis inductance, i max is a maximum limit value of a phase current, and ρ is a penalty coefficient and depends on motor operating efficiency.

[0013] As an alternative or in addition to the above solutions, in the method according to an embodiment of the application, step A further comprises: A1, generating a first algorithm model based on the cost equation and a restriction condition constituted by the fault phase current equation; A2, generating a second algorithm model based on a restriction condition constituted by the fault phase current equation and a motor phase current limit equation; and A3, generating a third algorithm model based on a restriction condition constituted by the fault phase current equation and a motor phase voltage limit equation.

[0014] As an alternative or in addition to the above solutions, in the method according to an embodiment of the application, wherein, if the AC motor is a permanent magnet synchronous motor and the inverter is a three-phase full-bridge inverter, the first algorithm model satisfies the following equation:

[0015]

[0016] wherein θ e is a motor rotor electrical angle, i d is a direct-axis current and a function of θ e , i q is a quadrature-axis current and a function of θ e , T ref is a torque reference value, N p is a number of motor pole pairs, λ m is a permanent magnet flux linkage, L d is a direct-axis inductance, L q is a quadrature-axis inductance, and θ1 is a preset value and depends on a fault phase.

[0017] As an alternative or supplement to the above solution, in the method according to an embodiment of the application, if the AC motor is a permanent magnet synchronous motor and the inverter is a three-phase full-bridge inverter, the first algorithm model satisfies the following equation:

[0018]

[0019] where θ is the motor rotor electrical angle, i is the direct-axis current and is a function of θ, i is the quadrature-axis current and is a function of θ, T is the torque reference value, N is the motor pole pair number, λ is the permanent magnet flux linkage, L is the direct-axis inductance, L is the quadrature-axis inductance, θ1 is a preset value and depends on the fault phase, i is the maximum limit value of the phase current, and ρ is a penalty coefficient and depends on the motor operating efficiency. e d e q e ref p m d q max

[0020] As an alternative or supplement to the above solution, in the method according to an embodiment of the application, step B includes: B1, acquiring the current motor speed, the torque reference value, the motor rotor electrical angle, and the maximum limit values of the phase voltage and the phase current; B2, determining the rotor electrical angle range for fault-tolerant control based on the open-circuit fault type; and B3, determining the phase current reference value at the current motor rotor electrical angle based on the current motor speed, the torque reference value, the motor rotor electrical angle, and the maximum limit values of the phase voltage and the phase current, using the fault-tolerant control optimization model within the rotor electrical angle range for fault-tolerant control.

[0021] As an alternative or supplement to the above solution, in the method according to an embodiment of the application, step B2 includes: if the open-circuit fault type is a first fault type, the rotor electrical angle range for fault-tolerant control is determined as the entire rotor electrical angle period; and if the open-circuit fault type is a second fault type, the rotor electrical angle range for fault-tolerant control is determined as half the rotor electrical angle period or the entire rotor electrical angle period.

[0022] ​​​​​​​​​​​As an alternative or supplement to the above solutions, in the method according to an embodiment of the present application, step B3 comprises: determining a first phase current reference value by using a first algorithm model based on the torque reference value and the motor rotor electric angle; if the current amplitude under the first phase current reference value is less than or equal to the maximum limit value of the phase current and the voltage amplitude is less than or equal to the maximum limit value of the phase voltage, determining the first phase current reference value as the current phase current reference value; if the current amplitude under the first phase current reference value is greater than the maximum limit value of the phase current and the voltage amplitude is less than or equal to the maximum limit value of the phase voltage, determining the current phase current reference value by using a second algorithm model; and if the voltage amplitude is greater than the maximum limit value of the phase voltage, determining the current phase current reference value by using a third algorithm model.

[0023] As an alternative or supplement to the above solutions, the method according to an embodiment of the present application further comprises one or more of the following steps: D, controlling the AC motor according to the determined phase current reference value within the rotor electric angle range for fault-tolerant control; and E, if the open-circuit fault type is the second fault type and the rotor electric angle range for fault-tolerant control is half a rotor electric angle period, controlling the AC motor according to the phase current reference value obtained under the non-fault state control strategy within the other half rotor electric angle period.

[0024] According to a second aspect of the present application, there is provided a fault-tolerant control device for an open-circuit fault of an AC motor, the AC motor being driven by an inverter, the fault-tolerant control device comprising: a model establishing module configured to construct a fault-tolerant control optimization model by taking into account the variation of motor cross-axis and direct-axis currents with the motor rotor electric angle, wherein the fault-tolerant control optimization model comprises a cost equation generated based on a motor torque equation and a restriction condition constituted by one or more of a fault phase current equation, a motor phase current limit equation and a motor phase voltage limit equation; and a current determining module configured to determine a phase current reference value at a current motor rotor electric angle by using the fault-tolerant control optimization model.

[0025] As an alternative or supplement to the above solutions, the device according to an embodiment of the present application further comprises: a fault determining module configured to determine a fault phase and an open-circuit fault type of the AC motor based on fault state information of the AC motor and an inverter driving the AC motor, wherein the open-circuit fault type comprises a first fault type and a second fault type.

[0026] According to a third aspect of the present application, there is provided a computer device comprising: a memory; a processor; and a computer program stored on the memory and executable on the processor, the execution of the computer program causing any one of the methods according to the first aspect of the present application to be performed.

[0027] According to a fourth aspect of the present application, a computer storage medium is provided, which comprises instructions that, when executed, perform any of the methods according to the first aspect of the present application.

[0028] The fault-tolerant control scheme for open-circuit fault of an AC motor according to the present application can be directly applied to an existing AC motor drive system product (i.e., a standard three-phase full-bridge inverter and a three-phase AC motor) without changing any hardware circuit or structure of the electric drive system or adding any additional device, thereby reducing the cost of fault-tolerant control of the system and improving the iterability of the fault-tolerant control scheme (for example, the functionality can be configured for old products by software installation, and the functionality can be continuously upgraded by software update).

[0029] The fault-tolerant control scheme for open-circuit fault of an AC motor according to some embodiments of the present application can also make full use of the remaining healthy power elements to achieve fault-tolerant control, thereby improving the reliability of the electric drive system, increasing the torque output capability under motor open-circuit fault, and reducing the motor torque loss caused by the fault, and is suitable for the full speed range of the electric drive system.

[0030] The fault-tolerant control scheme for open-circuit fault of an AC motor according to some embodiments of the present application can also reduce the current peak value and effective value under fault on the basis of meeting the fault motor torque output, reduce the copper loss of the electric drive system, and thereby improve the system efficiency and stability.

[0031] The fault-tolerant control scheme for open-circuit fault of an AC motor according to some embodiments of the present application can also reduce motor torque fluctuation and avoid the generation of unintended reverse torque under motor fault state, for example, no negative torque is generated when the reference torque value is positive, and no positive torque is generated when the reference torque value is negative. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above and / or other aspects and advantages of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements throughout. In the drawings:

[0033] Figure 1 a flowchart of a fault-tolerant control method for open-circuit fault of an AC motor according to one or more embodiments of the present application;

[0034] Figure 2 a topological circuit diagram of a three-phase full-bridge inverter for driving a three-phase AC motor according to one or more embodiments of the present application;

[0035] Figure 3Block diagram of the fault-tolerant control device 30 for open-circuit fault of an AC motor according to one or more embodiments of the present application; and

[0036] Figure 4 Block diagram of the computer device 40 according to one or more embodiments of the present application. DETAILED DESCRIPTION

[0037] The following detailed description is merely exemplary in nature and is not intended to limit the disclosed technology or the application and uses of the disclosed technology. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

[0038] In the following detailed description of embodiments, numerous specific details are set forth in order to provide a more thorough understanding of the disclosed technology. However, it will be apparent to one of ordinary skill in the art having the benefit of this disclosure that the disclosed technology can be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0039] The terms such as "comprise" and "include" mean that the technology of the present application does not exclude the presence of other elements and steps not directly and explicitly expressed in the specification. The terms such as "first" and "second" do not mean the order of the units in time, space, size, etc., but only distinguish the units.

[0040] Electric drive systems applied in the field of vehicles often have high safety and reliability requirements. In order to ensure that the vehicle can work stably for a long time when a fault occurs, the electric drive system often needs to have good fault tolerance capability. As described above, the existing fault-tolerant control scheme usually needs to change the hardware circuit structure of the motor and the inverter, or has the disadvantages of limited speed application range, complex control strategy, low control precision, limited torque output capability, etc. In view of this, the present application proposes a fault-tolerant control scheme for open-circuit fault of an AC motor, so as to seek to improve the reliability of the electric drive system and reduce the loss of motor torque without changing the hardware structure of the motor and the inverter and without adding additional devices.

[0041] In the following, exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings.

[0042] Figure 1 Flow chart of the fault-tolerant control method 10 for open-circuit fault of an AC motor according to one or more embodiments of the present application.

[0043] As Figure 1As shown, optionally, in step S110, the faulty phase and open-circuit fault type of the AC motor are determined based on the fault status information of the inverter and AC motor windings. Exemplarily, the fault status information may indicate whether an open-circuit fault exists in each phase winding of the AC motor and in each power device (e.g., switching element, diode) in the inverter used to drive the AC motor. It should be noted that the diagnostic method for the fault status information can be based on diagnostic methods known in the art, and the present invention does not specifically limit this.

[0044] For example, the aforementioned AC motor can be a three-phase AC motor such as a permanent magnet synchronous motor, an asynchronous motor, or a synchronous reluctance motor. Correspondingly, the aforementioned inverter can be a three-phase full-bridge inverter commonly used in the field of motor control. The following will use a three-phase AC motor and a three-phase full-bridge inverter as examples to describe the fault-tolerant control scheme in detail. It should be noted that the fault-tolerant control scheme according to the present invention can be applied to other types of AC motors (e.g., five-phase AC motors) and other types of inverters using the same or similar principles. The examples and implementation methods shown should be considered illustrative rather than restrictive.

[0045] Figure 2 A topology diagram of a three-phase full-bridge inverter for driving a three-phase AC motor according to one or more embodiments of the present invention is shown. Figure 2 As shown, this three-phase full-bridge inverter includes three bridge arms, each of which can be divided into an upper bridge arm and a lower bridge arm. Each upper bridge arm and lower bridge arm each includes one switching element and one diode. The A-phase winding of the three-phase motor is connected to the switching element T. A1 T A2 and diode D A1 D A2 Connected, the B-phase winding of the three-phase motor is connected to the switching element T. B1 T B2 and diode D B1 D B2 Connected, the C-phase winding of the three-phase motor is connected to the switching element T. C1 T C2 and diode D C1 D C2 Interconnected. Typically, the failure probability of inverters (e.g., switching elements, diodes) in an electric drive system is much higher than that of the windings in an AC motor. For three-phase full-bridge inverters, open-circuit faults in switching elements caused by bond wire detachment or driver chip failure are more common. For example, open-circuit fault types can be divided into two categories: a first fault type and a second fault type.

[0046] Optionally, when the fault status information indicates that the inverter has an open-circuit fault, and the winding of the AC motor and the inverter as a whole has only a single-phase open-circuit fault (for example, only the inverter A-phase bridge arm has an open-circuit fault, or the motor A-phase winding and the inverter A-phase bridge arm have open-circuit faults at the same time), and wherein the fault phase bridge arm of the inverter satisfies one of the following conditions, the open-circuit fault type is determined to be the first fault type: the two switching elements (for example, T A1 , T A2 ) of the upper and lower bridge arms have open-circuit faults at the same time; the two diodes (for example, D A1 , D A2 ) of the upper and lower bridge arms have open-circuit faults at the same time; the switching element and the diode (for example, T A1 , D A1 ) of the upper bridge arm have open-circuit faults at the same time; the switching element and the diode (for example, T A2 , D A2 ) of the lower bridge arm have open-circuit faults at the same time; and the total number of switching elements and diodes of the single-phase bridge arm having open-circuit faults is more than two (for example, T A1 , T A2 , D A1 , D A2 ).

[0047] Optionally, when the fault status information indicates that the winding of the AC motor has an open-circuit fault, and the inverter and the winding of the AC motor as a whole has only a single-phase open-circuit fault (for example, only the motor A-phase winding has an open-circuit fault, or the motor A-phase winding and the inverter A-phase bridge arm have open-circuit faults at the same time), the open-circuit fault type is determined to be the first fault type.

[0048] Optionally, when the fault status information indicates that the winding of the AC motor has no fault, and only a single-phase bridge arm of the inverter has an open-circuit fault (for example, all switching elements and diodes of the B-phase and C-phase bridge arms are working normally, and only the A-phase bridge arm has an open-circuit fault), and one of the following conditions is satisfied, the open-circuit fault type is determined to be the second fault type: the total number of switching elements and diodes having open-circuit faults is one (for example, only the upper bridge arm switching element T A1 has an open-circuit fault, or only the lower bridge arm switching element T A2 has an open-circuit fault, or only the upper bridge arm diode D A1 has an open-circuit fault, or only the lower bridge arm diode D A2 has an open-circuit fault); the switching element of the upper bridge arm and the diode of the lower bridge arm (for example, T A1 , D A2 ) have open-circuit faults at the same time; and the switching element of the lower bridge arm and the diode of the upper bridge arm (for example, T A2 , D A1 ) have open-circuit faults at the same time.

[0049] In step S120, a fault-tolerant control optimization model is constructed under the condition that the motor cross-axis and direct-axis currents vary with the motor rotor electric angle, wherein the fault-tolerant control optimization model includes a cost equation generated based on a motor torque equation and a limit condition constituted by one or more of a fault phase current equation, a motor phase current limit equation, and a motor phase voltage limit equation. The construction steps of the fault-tolerant control optimization model will be described in detail below by taking a three-phase permanent magnet synchronous motor as an example.

[0050] Alternatively, the cost equation constituting the fault-tolerant control optimization model can be a first cost equation J1 generated based on a motor torque equation or a second cost equation J2 generated under the condition that the motor operating efficiency is considered. In one example, the first cost equation J1 and the second cost equation J2 satisfy the following equation:

[0051]

[0052]

[0053] where T ref is a torque reference value, N p is the number of motor pole pairs, θ e is the motor rotor electric angle, i d is the direct-axis current and is a function of θ e , i q is the cross-axis current and is a function of θ e , λ m is the permanent magnet flux linkage, L d is the direct-axis inductance, L q is the cross-axis inductance, i max is the maximum limit value of the phase current, and ρ is a penalty coefficient. Specifically, in the second cost equation J2, when ρ is zero, it represents that the motor efficiency optimization is not considered, in which case the torque output capability is the largest under motor failure, but the phase current amplitude and effective value are the highest, and the motor efficiency is relatively low; when ρ is greater than zero, it represents that the phase current amplitude and effective value are considered (copper loss is reduced, and the motor efficiency is optimized). The greater the value of ρ represents the lower the phase current amplitude and effective value, and the higher the motor efficiency, but the lower the torque output capability. The specific value of ρ can be determined according to the difference between the actual output torque of the motor and the reference torque and the motor operating efficiency requirement.

[0054] Alternatively, the limit condition of the cost equation constituting the fault-tolerant control optimization model can be represented as:

[0055]

[0056] where u maxThe maximum limit value of the phase voltage is θ1, which is a preset value and depends on the fault phase determined in step S110, i.e., θ1 is 0 when the fault phase is A phase, θ1 is -2π / 3 when the fault phase is B phase, and θ1 is +2π / 3 when the fault phase is C phase. The above motor torque equation uses the inductance representation method, and can also use the flux linkage representation method.

[0057] It should be noted that the fault-tolerant control optimization model composed of the above cost equation (i.e., the first cost equation J1 or the second cost equation J2) and the constraint condition (i.e., equation 3) can reduce motor torque fluctuations and avoid the generation of unintended reverse torque in the motor fault state, for example, no negative torque is generated when the reference torque value is positive; no positive torque is generated when the reference torque value is negative.

[0058] Optionally, step S120 includes generating a first algorithm model based on the cost equation (e.g., the first cost equation J1 or the second cost equation J2) and the constraint condition composed of the fault phase current equation. In one example, if the cost equation is the first cost equation J1, the first algorithm model satisfies the following equation in consideration of the minimum difference between the motor torque output and the torque reference:

[0059]

[0060] In another example, if the cost equation is the second cost equation J2, the first algorithm model satisfies the following equation in consideration of the motor torque output and the operating efficiency at the same time:

[0061]

[0062] Optionally, step S120 further includes generating a second algorithm model based on the constraint condition composed of the fault phase current equation and the motor phase current limit equation. In one example, the second algorithm model constructed based on the constraint condition satisfies the following equation:

[0063]

[0064] Optionally, step S120 further includes generating a third algorithm model based on the constraint condition composed of the fault phase current equation and the motor phase voltage limit equation. In one example, the third algorithm model constructed based on the constraint condition satisfies the following equation:

[0065]

[0066] where R s is the winding resistance of the motor, and ω e is the motor speed. The above motor phase voltage limit equation uses the inductance representation method, and can also use the flux linkage representation method. If the winding resistance R sThen, the motor phase voltage limit equation can be simplified, and the simplified third algorithm model satisfies the following equation:

[0067]

[0068] Next, in step S130, the phase current reference value at the current motor rotor electrical angle is determined by using the fault-tolerant control optimization model. Alternatively, the phase current reference value at the current motor rotor electrical angle can be determined by using the first algorithm model, the second algorithm model, or the third algorithm model based on the open-circuit fault type determined in step S110.

[0069] Alternatively, step S130 comprises obtaining the current motor speed, the torque reference value, the motor rotor electrical angle, and the maximum limit values of the phase voltage and the phase current.

[0070] Alternatively, step S130 further comprises determining the rotor electrical angle range for the fault-tolerant control based on the open-circuit fault type. Alternatively, if the open-circuit fault type is the first fault type, the rotor electrical angle range for the fault-tolerant control is determined as the entire rotor electrical angle period; and if the open-circuit fault type is the second fault type, the rotor electrical angle range for the fault-tolerant control is determined as half of the rotor electrical angle period or the entire rotor electrical angle period.

[0071] In one example, if the fault phase determined in step S110 is phase A and the open-circuit fault type is the first fault type, the rotor electrical angle range for the fault-tolerant control is [0, 2π]. That is, if the open-circuit fault type is the first fault type, the fault-tolerant control strategy is adopted to obtain the phase current reference value in the entire rotor electrical angle range.

[0072] In one example, if the fault phase is phase A and the open-circuit fault type is the second fault type, only half of the rotor electrical angle range (for example, [0, π] or [π, 2π]) can be regarded as the fault state, and then the fault-tolerant control strategy is adopted for this half of the rotor electrical angle range, and the non-fault state control strategy is adopted for the other half of the rotor electrical angle period (i.e., the non-fault state). Specifically, in this example, for one of the following cases of the second fault type, the rotor electrical angle range for the fault-tolerant control is [0, π] (i.e., the motor is regarded as being in the fault state when the rotor electrical angle is in [0, π]): only the lower bridge arm switching element (for example, T A2 ) has an open-circuit fault; only the upper bridge arm diode (for example, D A1 ) has an open-circuit fault; the lower bridge arm switching element and the upper bridge arm diode (for example, T A2 , D A1) open-circuit fault of upper bridge arm switch element (e.g., T A1 ) open-circuit fault of lower bridge arm diode (e.g., D A2 ) open-circuit fault of upper bridge arm switch element and lower bridge arm diode (e.g., T A1 , D A2 ) open-circuit fault of upper bridge arm switch element and lower bridge arm diode. In this way, the remaining healthy power elements can be fully utilized to implement fault-tolerant control, thereby improving the torque output capability and reducing torque fluctuation of the motor under open-circuit fault.

[0073] Alternatively, in another example, if the fault phase is phase A and the open-circuit fault type is the second fault type, the entire rotor electrical angle range [0, 2π] can also be determined as the rotor electrical angle range for fault-tolerant control. That is, if the open-circuit fault type is the second fault type, the fault-tolerant control strategy can also be adopted in the entire rotor electrical angle range to obtain the phase current reference value. It can be understood that compared with the above-mentioned fault-tolerant control strategy only for half of the rotor electrical angle range and the non-fault state control strategy for the other half of the rotor electrical angle period, the fault-tolerant control strategy for the second fault type in the entire rotor electrical angle range will correspondingly reduce the torque output capability of the system and increase the torque fluctuation.

[0074] It needs to be further explained that the fault-tolerant control method 10 as shown in Figure 1 may be implemented without determining the open-circuit fault type, for example, all possible open-circuit fault conditions can be classified as the first fault type, and the rotor electrical angle range for fault-tolerant control is determined as the entire rotor electrical angle period.

[0075] Optionally, step S130 further comprises: based on the obtained current motor speed, torque reference value, motor rotor electrical angle, and maximum limit values of phase voltage and phase current, determining the phase current reference value at the current motor rotor electrical angle by using the fault-tolerant control optimization model in the rotor electrical angle range for fault-tolerant control. Exemplarily, the determination process of the phase current reference value includes steps S131-S134.

[0076] In step S131, based on the obtained torque reference value and the motor rotor electrical angle, a first phase current reference value is determined by using a first algorithm model. Exemplarily, the obtained torque reference value, the motor rotor electrical angle, and the permanent magnet flux linkage are brought into the solution of the first algorithm model as shown in formula 4 or formula 5 to obtain the first direct-axis current reference value i d1and the first quadrature-axis current reference value i q1 Exemplarily, the first algorithm model as shown in equation 4 can be solved by using Newton method, the process is as follows:

[0077] The fault phase current equation is brought into the motor torque equation to obtain the following equation:

[0078]

[0079] According to the above equation 9, the following cost equation is constructed:

[0080]

[0081] That is, the solution of the first algorithm model is converted into solving the minimum value of the cost equation f. Next, the Jacobian matrix J and the Hessian matrix H of the cost equation f with respect to i d are calculated:

[0082]

[0083]

[0084] Finally, the above matrix is brought into the direct-axis current i d iteration formula based on Newton method solution:

[0085] i d(k) = i d(k-1) - H -1 J (equation 13)

[0086] It should be noted that the above Newton method solving process is only illustrative but not restrictive, and other numerical analysis methods or other ways can be used to determine the phase current reference value. In addition, the same or similar method can be used to solve the first algorithm model as shown in equation 5, which will not be described here. It should be further noted that in the generation process of the phase current reference value, the motor nonlinear parameter values such as the permanent magnet flux linkage λ m , the direct-axis inductance L d , the quadrature-axis inductance L q , and the winding resistance R s may be obtained by table lookup method or online estimation method.

[0087] In step S132, based on the first phase current reference value obtained in step S131, the current amplitude i s1 and the voltage amplitude u s1 under the first phase current reference value are calculated, and compared with the maximum limit value i max of the phase current and the maximum limit value u max of the phase voltage, respectively.

[0088] If the current amplitude under the first phase current reference value is less than or equal to the maximum limit value of the phase current, and the voltage amplitude is less than or equal to the maximum limit value of the phase voltage (i.e., i s1 ≤ i max and u s1 ≤ u max ), the first phase current reference value (i.e., i d1 and i q1 ) is determined as the current phase current reference value. If the current amplitude under the first phase current reference value is greater than the maximum limit value of the phase current, and the voltage amplitude is less than or equal to the maximum limit value of the phase voltage (i.e., i s1 > i max and u s1 ≤ u max ), the step S133 is continued. If the voltage amplitude under the first phase current reference value is greater than the maximum limit value of the phase voltage (i.e., u s1 > u max ), the step S134 is continued.

[0089] In the step S133, the current phase current reference value is further determined by using the second algorithm model. Exemplarily, the motor rotor electric angle is brought into the second algorithm model as shown in equation 6 to solve the second direct-axis current reference value i d2 and the second quadrature-axis current reference value i q2 under the current rotor electric angle, so as to obtain the current phase current reference value.

[0090] In the step S134, the current phase current reference value is determined by using the third algorithm model. Exemplarily, the motor rotor electric angle, the winding resistance of the alternating current motor, the motor speed, and the permanent magnet flux linkage are brought into the third algorithm model as shown in equation 7 or 8 to solve the third direct-axis current reference value i d3 and the third quadrature-axis current reference value i q3 under the current rotor electric angle, so as to obtain the current phase current reference value.

[0091] Exemplarily, the Newton method can also be used to solve the second and third algorithm models, and the specific solving process is not described herein. It should be noted that the current phase current reference value obtained according to the above steps S131-S134 is only applicable to the rotor electric angle range for the fault-tolerant control as described above.

[0092] For the first fault type, the current phase current reference value obtained by the steps S131-S134 can be applicable to the entire rotor electric angle period, that is, the fault phase current in the entire rotor electric angle period should satisfy the fault phase current equation.

[0093] For the second fault type, the current phase current reference value obtained by steps S131-S134 can only be applied to half of the rotor electrical angle period (e.g., [0, π] or [π, 2π]), and for the other half of the rotor electrical angle period, the remaining healthy power elements in the fault bridge arm can be fully utilized to achieve the same control effect as the non-fault state. That is, only the fault phase current in half of the rotor electrical angle period should satisfy the fault phase current equation, and in the other half of the rotor electrical angle period, the phase current reference value can be obtained by using the control strategy of the non-fault state.

[0094] Alternatively, for the second fault type, the current phase current reference value obtained by steps S131-S134 can also be applied to the entire rotor electrical angle period, that is, the fault phase current in the entire rotor electrical angle period should satisfy the fault phase current equation.

[0095] Optionally, the method 10 further comprises a step S140: controlling the motor according to the determined current phase current reference value (e.g., the above i d1 and i q1 , or i d2 and i q2 , or i d3 and i q3 ) in the rotor electrical angle range for fault-tolerant control; and if the open-circuit fault type is the second fault type and the rotor electrical angle range for fault-tolerant control is half of the rotor electrical angle period, the alternating current motor can be controlled according to the phase current reference value obtained under the non-fault state control strategy in the other half of the rotor electrical angle period. Illustratively, the above phase current reference value can be obtained by online calculation in the motor controller, or offline calculation according to pre-set motor parameters, pre-set working conditions, and pre-set fault conditions, and then obtained by table lookup method.

[0096] The method 10 according to one or more embodiments of the present application can be directly applied to the existing AC motor drive system product (i.e., the standard three-phase full-bridge inverter and the three-phase AC motor) without changing the hardware structure of the motor and the inverter and without adding additional devices, thereby reducing the fault-tolerant control cost of the system while improving the iterability of the fault-tolerant control scheme. Meanwhile, in some embodiments, the method 10 can make full use of the remaining healthy power elements to achieve fault-tolerant control, thereby improving the reliability of the electric drive system, increasing the torque output capability under the open-circuit fault of the motor, and reducing the torque loss of the motor caused by the fault, which is applicable to the full speed range of the electric drive system. Moreover, in some embodiments, the method 10 can reduce the current peak value and the effective value under the fault on the basis of meeting the fault motor torque output, thereby reducing the copper loss of the electric drive system and improving the system efficiency and stability. In addition, in some embodiments, the method 10 can reduce the motor torque fluctuation and avoid the generation of unintended reverse torque under the motor fault state, for example, no negative torque is generated when the reference torque value is positive, and no positive torque is generated when the reference torque value is negative.

[0097] Figure 3 A block diagram of the fault-tolerant control device 30 for the open-circuit fault of the AC motor according to one or more embodiments of the present application is shown in FIG. 3. As shown in FIG. 3, the fault-tolerant control device 30 includes a model establishing module 320 and a current determining module 330. Optionally, the fault-tolerant control device 30 further includes a fault determining module 310. Figure 3

[0098] Optionally, the fault determining module 310 is configured to determine the fault phase and the open-circuit fault type of the AC motor based on the fault state information of the windings of the inverter and the AC motor, wherein the open-circuit fault type includes a first fault type and a second fault type. The determination process of the fault type can refer to the description of step S110 above, which will not be repeated here.

[0099] The model establishing module 320 is configured to construct a fault-tolerant control optimization model under the condition of considering the variation of the motor cross-axis and direct-axis currents with the motor rotor electric angle, wherein the fault-tolerant control optimization model includes a cost equation generated based on a motor torque equation and a restriction condition constituted by one or more of a fault phase current equation, a motor phase current limitation equation, and a motor phase voltage limitation equation. The construction process of the fault-tolerant control optimization model can refer to the description of step S120 above, which will not be repeated here.

[0100] The current determining module 330 is configured to determine the phase current reference value at the current motor rotor electric angle by using the fault-tolerant control optimization model. The determination process of the phase current reference value can refer to the description of step S130 above, which will not be repeated here.

[0101] Continuing to refer to​Figure 4 Figure 4 is a block diagram of a computer device 40 according to one or more embodiments of the present application.

[0102] As shown in Figure 4 , the computer device 40 comprises a communication unit 410, a memory 420, a processor 430, a computer program 440 stored on the memory 420 and executable on the processor 430.

[0103] The communication unit 410 is configured as a communication interface to establish a communication connection between the computer device and an external device (e.g. a current controller, a motor sensor) or a network.

[0104] The memory 420 stores the computer program 440 executable by the processor 430. The processor 330 is configured to execute the computer program 440 to implement the method as shown in Figure 1 .

[0105] According to a fourth aspect of the present application, there is also provided a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method 10 as shown in Figure 1 . The computer readable storage medium can include random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read only memory (EEPROM), FLASH memory, other known storage media, and / or the like.

[0106] Where applicable, the various embodiments provided by the present application can be implemented using hardware, software, or combinations of hardware and software. Also, where applicable, the various hardware components and / or software components set forth herein can be combined into composite components comprising software, hardware, and / or both, where applicable. It will depend from the application and design combinations of the hardware and software components can be implemented. Additionally, where applicable, it is contemplated that software components can be implemented as hardware components and vice versa.

[0107] Software, such as program code and / or data, according to the present application, can be stored on one or more computer storage media. It is also contemplated that software identified herein can be implemented using one or more general purpose or special purpose computers and / or computer systems, networked and / or otherwise. Where applicable, the order of the blocks of the processes can be changed, combined into composite blocks and / or separated into sub-blocks to provide features described herein.

[0108] ​The embodiments and examples set forth herein are presented to best explain the embodiments of the application and its specific application to provide those skilled in the art with the information needed to best utilize the application and its application. However, those skilled in the art will appreciate that the description and examples are provided for the purpose of illustration and example only. It is not intended to limit the aspects of the application to the precise form described.

Claims

1. A fault-tolerant control method for open-circuit faults in AC motors, characterized in that, The AC motor is driven by an inverter, and the method includes the following steps: C. Based on the fault status information of the AC motor and the inverter driving the AC motor, determine the fault phase and open circuit fault type of the AC motor, wherein the open circuit fault type includes a first fault type and a second fault type. A. Considering the variation of the AC and DC axis currents of the motor with the electric angle of the motor rotor, construct a fault-tolerant control optimization model. The fault-tolerant control optimization model includes a cost equation generated based on the motor torque equation and a constraint condition composed of one or more of the fault phase current equation, the motor phase current limiting equation, and the motor phase voltage limiting equation. B. Use the fault-tolerant control optimization model to determine the phase current reference value under the current motor rotor electrical angle; D. Within the rotor electrical angle range for fault-tolerant control, the AC motor is controlled according to the determined phase current reference value; and E. If the open-circuit fault type is the second fault type and the rotor electrical angle range for fault-tolerant control is half a rotor electrical angle cycle, then the AC motor is controlled in the other half rotor electrical angle cycle according to the phase current reference value obtained under the non-fault state control strategy.

2. The method according to claim 1, in step C, when the fault status information indicates that the inverter has an open-circuit fault, and the windings of the inverter and the AC motor as a whole have only a single-phase open-circuit fault, and the faulty phase bridge arm of the inverter meets one of the following conditions, the open-circuit fault type is determined as the first fault type: Both switching elements of the upper and lower bridge arms experienced open-circuit faults simultaneously; Both diodes in the upper and lower bridge arms simultaneously experienced open-circuit faults; The switching elements and diodes in the upper bridge arm both experience open-circuit faults. The switching elements and diodes in the lower bridge arm both experience open-circuit faults. as well as The total number of switching elements and diodes that experience open-circuit faults is more than two.

3. The method according to claim 1, in step C, when the fault status information indicates that the winding of the AC motor has an open circuit fault, and there is only a single-phase open circuit fault in the overall winding of the inverter and the AC motor, the open circuit fault type is determined as the first fault type.

4. The method according to claim 1, in step C, when the fault status information indicates that the windings of the AC motor are fault-free, and only a single-phase bridge arm of the inverter has an open-circuit fault, and one of the following conditions is met, the open-circuit fault type is determined as a second fault type: The total number of switching elements and diodes experiencing an open-circuit fault is one. The switching element in the upper bridge arm and the diode in the lower bridge arm both experience open-circuit faults simultaneously; and The switching element in the lower bridge arm and the diode in the upper bridge arm both experienced open-circuit faults.

5. The method according to claim 1, wherein, If the AC motor is a permanent magnet synchronous motor and the inverter is a three-phase full-bridge inverter, then the cost equation is either the first cost equation J1 or the second cost equation J2, where, Among them, T ref For torque reference value, N p Let θ be the number of pole pairs of the motor. e i is the electrical angle of the motor rotor. d It is a direct-axis current and is θ e The function, i q It is the quadrature-axis current and is θ e The function, λ m For permanent magnet flux linkage, L d For a direct-axis inductor, L q For quadrature axis inductance, i max ρ is the maximum limit value of the phase current, and ρ is the penalty coefficient that depends on the motor operating efficiency.

6. The method according to claim 1, wherein, Step A further includes: A1. Based on the cost equation and the constraints formed by the fault phase current equation, a first algorithm model is generated; A2. Based on the constraints formed by the fault phase current equation and the motor phase current limiting equation, a second algorithm model is generated; and A3. Based on the constraints formed by the fault phase current equation and the motor phase voltage limiting equation, a third algorithm model is generated.

7. The method according to claim 6, wherein, If the AC motor is a permanent magnet synchronous motor and the inverter is a three-phase full-bridge inverter, the first algorithm model satisfies the following equation: Where, θ e i is the electrical angle of the motor rotor. d It is a direct-axis current and is θ e The function, i q It is the quadrature-axis current and is θ e The function, T ref For torque reference value, N p λ is the number of pole pairs of the motor. m For permanent magnet flux linkage, L d For a direct-axis inductor, L q It is a quadrature-axis inductance, and θ1 is a preset value that depends on the faulty phase.

8. The method according to claim 6, wherein, If the AC motor is a permanent magnet synchronous motor and the inverter is a three-phase full-bridge inverter, the first algorithm model satisfies the following equation: Where, θ e i is the electrical angle of the motor rotor. d It is a direct-axis current and is θ e The function, i q It is the quadrature-axis current and is θ e The function, T ref For torque reference value, N p λ is the number of pole pairs of the motor. m For permanent magnet flux linkage, L d For a direct-axis inductor, L q For quadrature axis inductance, θ1 is a preset value and depends on the faulty phase, i max ρ is the maximum limit value of the phase current, and ρ is the penalty coefficient that depends on the motor operating efficiency.

9. The method according to claim 1, wherein, Step B includes: B1. Obtain the current motor speed, torque reference value, motor rotor electrical angle, and maximum limit values ​​of phase voltage and phase current; B2. Based on the open-circuit fault type, determine the rotor electrical angle range for fault-tolerant control; and B3. Based on the current motor speed, the torque reference value, the motor rotor electrical angle, and the maximum limits of the phase voltage and phase current, determine the phase current reference value under the current motor rotor electrical angle using the fault-tolerant control optimization model within the rotor electrical angle range for fault-tolerant control.

10. The method according to claim 9, wherein, Step B2 includes: If the open-circuit fault type is the first fault type, then the rotor electrical angle range for fault-tolerant control is determined to be the entire rotor electrical angle cycle; and If the open-circuit fault type is the second fault type, then the rotor electrical angle range for fault-tolerant control is determined to be half a rotor electrical angle cycle or the entire rotor electrical angle cycle.

11. The method according to claim 9, wherein, Step B3 includes: Based on the torque reference value and the electric angle of the motor rotor, the first phase current reference value is determined using the first algorithm model; If the current amplitude under the first phase current reference value is less than or equal to the maximum limit value of the phase current and the voltage amplitude is less than or equal to the maximum limit value of the phase voltage, then the first phase current reference value is determined as the current phase current reference value. If the current amplitude at the first phase current reference value is greater than the maximum limit of the phase current, and the voltage amplitude is less than or equal to the maximum limit of the phase voltage, then the current phase current reference value is determined using the second algorithm model; and If the voltage amplitude is greater than the maximum limit of the phase voltage, the current phase current reference value is determined using the third algorithm model.

12. A computer device, characterized in that, It comprises: a memory; a processor; and a computer program stored in the memory and executable on the processor, the execution of which causes the method according to any one of claims 1-11 to be performed.

13. A computer storage medium, characterized in that, The computer storage medium includes instructions that, when executed, perform the method according to any one of claims 1-11.

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