An Open - Circuit Fault Tolerant Control Method for an On - Vehicle Integrated Charging System

Abstract

The present invention discloses an open-circuit fault tolerance control method for an in-vehicle integrated charging system. The method is applicable to the application of a six-phase permanent magnet motor including a surface-mounted permanent magnet rotor and an interior permanent magnet rotor in an integrated charging system. The stator of the six-phase permanent magnet motor includes two sets of three-phase symmetrical windings. The method realizes the control of the motor by establishing a mathematical model of the six-phase permanent magnet motor control system, and then, according to the established model and the collected and given motor signals, successively passing through a phase-locked loop, a VSD transformation, a current controller, a VSD inverse transformation, and SPWM, so as to achieve the charging operation under the open-circuit fault of the in-vehicle integrated charging system. The present invention effectively ensures that the motor does not generate mechanical torque under the open-circuit fault during the charging operation, and achieves a charging performance similar to that during the normal operation, and can well realize the fault tolerance control of the open-circuit fault of the in-vehicle integrated charging system, and is suitable for occasions such as electric vehicles and plug-in hybrid vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and particularly to an open-circuit fault tolerance control method for an in-vehicle integrated charging system. Background Art

[0002] With the rapid development of the electric vehicle market, the application of in-vehicle integrated charging systems is becoming increasingly widespread. In electric vehicles and plug-in hybrid vehicles, in-vehicle integrated charging systems are required to supply power for charging. Therefore, the in-vehicle integrated charging system is not only an important part of electric vehicles, but also one of the key technologies to promote the popularization of electric vehicles and the construction of charging infrastructure. With the development of the electric vehicle market and the progress of technology, it is expected that the application scope of in-vehicle integrated charging systems will continue to expand. The in-vehicle integrated charging system provides a better charging experience for electric vehicles by offering convenient charging methods, high charging efficiency, space savings, safety assurance, strong versatility, etc., and promotes the popularization and development of electric vehicles.

[0003] During the motor charging process, the charging current passes through the motor winding and then flows through the inverter to charge the in-vehicle battery. According to statistics, among the motor system failures, the open-circuit fault of the motor winding caused by the failure of the inverter switching tube accounts for about 30% of the total motor system failures. During the integrated charging operation, if an open-circuit fault occurs and is not dealt with in time, a series of more serious faults such as the power grid, the motor body, the inverter, the DC / DC converter, and the battery will occur. Therefore, it is particularly important to ensure that the battery can continue to be charged under open-circuit faults and to implement an open-circuit fault tolerance control method for the in-vehicle integrated charging system.

[0004] The open-circuit fault tolerance control technology is a method to ensure the safety and reliability of the motor system. When an open circuit occurs between one or more phases of the motor, causing the motor to malfunction, this control method is adopted to ensure the stable operation and safety of the motor system. When an open-circuit fault occurs in the motor winding, by controlling the state of the switching element, the switching of different windings can be achieved to keep the motor working normally. By adjusting the working parameters and control strategies of the motor driver, the changes in the open-circuit winding can be adapted to reduce the impact on the system. By controlling the output power and control strategy of the motor driver, the additional load can be distributed to the normally working windings to maintain the balance of the entire system. At the same time, in solving problems such as unnecessary torque generation, increased losses, current distortion, and reduced power factor of the power grid caused by open-circuit faults during the charging process, there is not much research on this type of control method at present, and there is still room for further improvement in achieving system reliability and fault tolerance.

[0005] An on-vehicle integrated charging system is a system that utilizes the existing traction system hardware of an electric vehicle, such as an electric motor and an inverter, etc., to charge the on-vehicle battery as a charging circuit during vehicle charging. In an on-vehicle integrated charging system, a six-phase permanent magnet motor uses windings of six phases, usually driven by six independent current suppliers. This motor structure has a relatively high power density and efficiency, and can provide a higher output torque and speed range. A single-phase on-vehicle integrated charging system refers to a device integrated with a charging function in an electric vehicle, which can convert AC electrical energy into DC electrical energy through an external power source for charging the battery. This integrated design enables the vehicle to no longer require an additional charger, thereby reducing the cost, weight, and volume of the vehicle charger. However, during the motor charging process, the charging current passes through the motor windings, resulting in the generation of unnecessary torque. Eliminating this unnecessary torque and improving the charging efficiency and performance are of great significance in an on-vehicle integrated charging system. Summary of the Invention

[0006] The object of the present invention is to address the deficiencies of the above-mentioned existing technologies. The present invention provides a fault-tolerant control method for open-circuit faults of an on-vehicle integrated charging system, which is simple and easy to implement, enables the system to have high reliability and strong fault tolerance, and can well achieve the fault-tolerant control of open-circuit faults in the system.

[0007] The present invention adopts the following technical solutions to solve the above technical problems:

[0008] A fault-tolerant control method for open-circuit faults of an on-vehicle integrated charging system, including a six-phase permanent magnet motor, a phase-locked loop, a VSD conversion module, a current controller, a VSD inverse conversion module, and an SPWM module; the VSD is vector space decomposition;

[0009] The stator of the six-phase permanent magnet motor includes two sets of independent symmetric three-phase armature windings, namely three-phase windings A, B, C and three-phase windings X, Y, Z, and each set of windings is driven by a set of three-phase full-bridge drive circuits; the rotor of the motor can be a surface-mounted permanent magnet rotor or an interior permanent magnet rotor.

[0010] Furthermore, its fault-tolerant control method includes the following steps:

[0011] Step 21: Establish a mathematical model of the air-gap synthetic magnetomotive force for the six-phase permanent magnet motor during integrated charging operation. When current flows through each phase of the stator winding, pulsating magnetomotive forces are generated in the three-phase windings A, B, C and the three-phase windings X, Y, Z respectively, and the magnetomotive force generated by each phase is:

[0012]

[0013] Where:

[0014] F A ,FB , F C , F X , F Y , F Z The magnetomotive forces generated by each phase are the magnetomotive forces generated by each phase, N c is the equivalent number of turns of each phase winding, θ is the angle of the motor air-gap circumference, i A , i B , i C , i X , i Y , i Z are the phase currents of the six-phase permanent magnet motor respectively, α is the phase difference between the two sets of three-phase windings, and this formula takes the axis of the magnetomotive force generated by the A-phase winding as the starting point;

[0015] According to the above formula, the resultant magnetomotive forces of the three-phase windings A, B, C and the three-phase windings X, Y, Z are:

[0016]

[0017] During normal integrated charging operation, the single-phase power grid is connected to the neutral points of the two sets of windings respectively. Due to the symmetry of the two sets of three-phase windings, the phase currents are respectively:

[0018] i A = i B = i C = i g / 3, i X = i Y = i Z = -i g / 3

[0019] Where:

[0020] i g is the current on the grid side;

[0021] Substituting the phase currents during the above normal integrated charging operation into the resultant magnetomotive force formula, it can be obtained that the magnetomotive forces of the three-phase windings A, B, C and the three-phase windings X, Y, Z cancel each other out and synthesize, that is, the magnetomotive force F is 0. Using the VSD method to analyze the phase currents during normal operation, and decomposing the phase currents into three different spaces through the VSD transformation, namely the αβ space (electromechanical energy conversion space), the xy space (harmonic space) and the zero-sequence space, and then performing the transformation from the stationary coordinate system to the rotating coordinate system on the variables in these three spaces, it can be obtained that no electromagnetic torque is generated during normal operation;

[0022] Step 22: When a fault occurs in the inverter switch tube, causing the bridge arm to disconnect, an open-circuit fault occurs in one or more phases of the motor winding. The resultant magnetomotive force of the remaining healthy windings in the motor air gap no longer cancels each other out, but instead forms a pulsating magnetomotive force and a pulsating magnetic field. If the position of the motor rotor remains unchanged, this pulsating magnetic field will generate a non-zero electromagnetic torque on the rotor. To avoid the generation of this torque, the direct axis of the motor rotor needs to be aligned with the axis of the pulsating magnetic field, so that the rotor is in a balanced position.

[0023] Further, the specific steps of the open-circuit fault tolerance control method are as follows:

[0024] Step 31: During the integrated charging operation, when the charging current of the AC power supply remains unchanged, the open-circuit fault current distribution strategy of the on-vehicle integrated charging system for different winding open-circuit faults:

[0025] When the motor has a single-phase open circuit: When the faulty phase is A, B, or C, the current in the healthy windings of the ABC phase group is i g / 2, and the current in the healthy windings of the XYZ phase group is -i g / 3. When the faulty phase is X, Y, or Z, the current in the healthy windings of the ABC phase group is i g / 3, and the current in the healthy windings of the XYZ phase group is -i g / 2;

[0026] When the motor has a two-phase open circuit: When the faulty phases are AB, AC, or BC, the current in the healthy windings of the ABC phase group is i g , and the current in the healthy windings of the XYZ phase group is -i g / 3. When the faulty phases are XY, XZ, or YZ, the current in the healthy windings of the ABC phase group is i g / 3, and the current in the healthy windings of the XYZ phase group is -i g , when the faulty phases are AX, AY, AZ, BX, BY, BZ, CX, CY, or CZ, the current in the healthy windings of the ABC phase group is i g / 2, and the current in the healthy windings of the XYZ phase group is -i g / 2;

[0027] When the motor has a three-phase open circuit: When the faulty phases are ABX, ABY, ABZ, ACX, ACY, ACZ, BCX, BCY, or BCZ, the current in the healthy windings of the ABC phase group is i g , and the current in the healthy windings of the XYZ phase group is -i g / 2. When the faulty phases are AXY, AXZ, AYZ, BXY, BXZ, BYZ, CXY, CXZ, or CYZ, the current in the healthy windings of the ABC phase group is i g / 2, and the current in the healthy windings of the XYZ phase group is -i g ;

[0028] When the motor is in a four-phase open circuit: When the faulty phases are ABXY, ABXZ, ABYZ, ACXY, ACXZ, ACYZ, BCXY, BCXZ, BCYZ, the current in the healthy windings of the ABC phase group is i g , and the current in the healthy windings of the XYZ phase group is -i g ;

[0029] The windings of each phase of the motor are not strictly symmetrical. In order to make the currents flowing through the remaining non-faulty phases of each three-phase winding be distributed according to the open-circuit fault current distribution strategy of the on-vehicle integrated charging system, it is necessary to control the current in the healthy windings. According to the type of fault, substitute the currents of each phase into the magnetomotive force synthesis formula according to the current distribution strategy to obtain the synthesized pulsating magnetomotive force. The axis of this pulsating magnetomotive force is the reference line that the rotor direct axis needs to align with. According to the current distribution strategy, substitute the currents into the magnetomotive force of each phase of the stator winding and the synthesis magnetomotive force formulas of the three-phase windings A, B, C and the three-phase windings X, Y, Z to calculate the total synthesized magnetomotive force of each phase of the healthy winding under the open-circuit fault. The included angle between the axis of the magnetomotive force and the magnetomotive force of the A-phase winding is the rotor position information φ at this time;

[0030] Step 32: After the rotor position is rebalanced, project the currents of each phase of the current distribution strategy corresponding to the open-circuit fault onto the zero-sequence space by using the above VSD transformation, and calculate the reference signals of the three space currents under this fault. The components of the currents of each healthy phase under the fault projected onto the three planes are all non-zero. Only the current i q in the αβ space is 0, which ensures that the electromagnetic torque of the motor is 0 and guarantees that integrated charging can still be carried out when the inverter fails and causes the motor to open circuit. In order to make the current after the fault follow the current distribution strategy, it is necessary to control the charging current of the motor after the fault. For the quadrature-axis current i q in the αβ space, the reference signal of the current it controls is a direct current, so a traditional proportional-integral (PI) controller is used for control. For other current signals, the reference signal is an alternating component, so a proportional-resonant (PR) controller is used for control. Its z-domain transfer function G PR (z) is:

[0031]

[0032] Where:

[0033] k p is the proportional link coefficient of the PR controller, k i is the resonant link coefficient of the PR controller, H r (z) is the transfer function of the z-domain resonant filter, and a0, a1, a2, b0, b1, b2 are the coefficients of each item of the resonant filter transfer function. These coefficients can be calculated from the parameters of the motor and the performance parameters of the required designed PR resonant controller;

[0034] The real-time currents of each phase after VSD transformation and the current reference signal are input into the current fault-tolerant controller to achieve the control and balance of each space current, ensuring adjustment according to the current distribution strategy;

[0035] Step 33: According to the sampled grid voltage signal, obtain its phase information through a phase-locked loop. Combine the reference value of the grid current amplitude and the open-circuit fault current distribution strategy of the on-vehicle integrated charging system to determine the reference value of the current of each phase of the motor under fault conditions. Then use VSD transformation to convert the current reference signal into three spaces. Input the real-time currents of each phase after VSD transformation and the current reference signal into the current fault-tolerant controller to achieve the control and balance of each space current, ensuring adjustment according to the current distribution strategy. The output result of the current fault-tolerant controller is the reference voltage of the three spaces. Then generate the reference signal of each phase voltage through VSD inverse transformation, and finally generate the SPWM signal to drive the inverter to realize the charging operation under the open-circuit fault of the on-vehicle integrated charging system.

[0036] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0037] (1) An open-circuit fault-tolerant control method for an on-vehicle integrated charging system provided by the present invention. The fault-tolerant control method effectively ensures that the motor does not generate electromagnetic torque under open-circuit faults during charging operation, and achieves charging performance similar to that during normal operation, including a high grid power factor, etc.;

[0038] (2) An open-circuit fault-tolerant control method for an on-vehicle integrated charging system provided by the present invention. The fault-tolerant control method provides reliable protection and stable operation for the charging system, ensures the safety and efficiency of the charging process, and further improves the performance and reliability of the on-vehicle integrated charging system;

[0039] (3) An open-circuit fault-tolerant control method for an on-vehicle integrated charging system provided by the present invention. The system control method establishes a mathematical model for open-circuit fault-tolerant control of the on-vehicle integrated charging system, and then according to the established model and the collected and given motor signals, generates the reference signal of each phase voltage through VSD inverse transformation, and finally generates the SPWM signal to drive the inverter to realize the charging operation under the open-circuit fault of the on-vehicle integrated charging system;

[0040] (4) An open-circuit fault-tolerant control method for an on-vehicle integrated charging system provided by the present invention. It has high reliability and strong fault tolerance, and can well realize the fault-tolerant control operation of the on-vehicle integrated charging system under open-circuit faults during charging operation, and is applicable to application scenarios such as pure electric vehicles and plug-in hybrid vehicles equipped with integrated charging systems. Description of the Drawings

[0041] Figure 1 Result diagram of a single-phase on-vehicle integrated charging system based on a six-phase permanent magnet motor;

[0042] Figure 2 Electromagnetic vector diagrams of each phase of the six-phase permanent magnet motor;

[0043] Figure 3 Current control strategies on three planes under open-circuit faults during integrated charging operation;

[0044] Figure 4 Fault-tolerant control block diagram of the on-vehicle integrated charging system during charging operation under open-circuit faults. Detailed implementation manners

[0045] The present invention will be further explained below with reference to the accompanying drawings.

[0046] As Figure 1 shown is the result diagram of a single-phase on-vehicle integrated charging system based on a six-phase permanent magnet motor. During electric operation, the on-vehicle battery is connected to the DC bus through a DC / DC converter and drives the six-phase permanent magnet motor through a six-bridge-arm two-level inverter;

[0047] During charging operation, a single-phase AC power supply is connected to the stator of the motor through the two neutral points of the two sets of three-phase windings of the six-phase permanent magnet motor, the ABC phase group and the XYZ phase group. At this time, the inverter connected to the stator winding operates in the synchronous rectifier mode, converts the input alternating current into direct current and outputs it to the DC bus, and then the DC / DC converter charges the on-vehicle battery;

[0048] As Figure 2 shown are the electromagnetic vector diagrams of each phase of the six-phase permanent magnet motor, where the phase difference between the two sets of three-phase windings is α.

[0049] As Figure 3 shown are the current control strategies on three planes under open-circuit faults during the integrated charging operation described in the present invention, namely the αβ plane, the xy plane and the zero-sequence plane.

[0050] As Figure 4 shown is the fault-tolerant control block diagram of the on-vehicle integrated charging system during charging operation under open-circuit faults described in the present invention, and its specific implementation steps are as follows:

[0051] Step 1: According to the sampled voltage and current signals i A 、i B 、i C 、i X 、i Y 、i Z , when there is current flowing through each phase of the stator winding, the magnetomotive force generated in the motor air gap is calculated as:

[0052]

[0053] The resultant magnetomotive forces of the three-phase windings A, B, C and the three-phase windings X, Y, Z are as follows:

[0054]

[0055] Among them, F A , F B , F C , F X , F Y , F Z are the magnetomotive forces generated by each phase respectively. N c is the equivalent number of turns of each phase winding, and θ is the angle of the motor air-gap circumference. This formula assumes that the axis of the magnetomotive force generated by the A-phase winding is the starting point.

[0056] Step 2: Using the VSD method, decompose the parameters and variables of each phase into several different spaces through coordinate transformation, namely the αβ space (electromechanical energy conversion space), the xy space (harmonic space) and the zero-sequence space:

[0057] Step 2-1: Use the VSD transformation to convert the current reference signal into three spaces:

[0058]

[0059] Step 2-2: Transform the stationary coordinate system into a rotating coordinate system:

[0060]

[0061] The VSD is the vector space decomposition;

[0062] Step 3: Combine the reference value of the grid current amplitude and the current distribution strategy for each phase under the open-circuit fault in Table 1 to determine the reference value of the current of each phase of the motor under the fault condition;

[0063] Table 1 Open-circuit fault current distribution strategy of on-vehicle integrated charging system

[0064]

[0065] Step 4: Input the real-time current of each phase after the VSD transformation and the current reference signal into the current fault-tolerant controller to achieve the control and balance of the current in each space, and ensure the adjustment according to the current distribution strategy in Table 1.

[0066] Step 4-1: Calculate the reference signals of the currents in the three spaces under this fault according to the currents of each phase in the current distribution strategy corresponding to the open-circuit fault:

[0067] [i d 0 i xi y i 01 i 02 T = T dq T vsd [i A i B i C i X i Y i Z T

[0068] Step 4-2: If the reference signal of the controlled quantity is a DC quantity such as iq, a traditional PI controller is used for control. If the reference signal of the controlled quantity is an AC component, a proportional-resonant (PR) controller is used for control, and its transfer function is:

[0069]

[0070] Where:

[0071] k p is the proportional link coefficient of the PR controller, k i is the resonant link coefficient of the PR controller, H r (z) is the transfer function of the z-domain resonant filter, and a0, a1, a2, b0, b1, b2 are the coefficients of each item of the transfer function of the resonant filter. These coefficients can be calculated from the parameters of the motor and the performance parameters of the required designed PR resonant controller;

[0072] Step 5: The output result of the current fault-tolerant controller is the reference voltage in three spaces, and the reference signals of each phase voltage are generated through the inverse VSD transformation.

[0073] Step 6: The finally generated SPWM signal is used to drive the inverter to realize the charging operation under the open-circuit fault of the on-vehicle integrated charging system. It is ensured that under the open-circuit fault during the charging operation, the motor will not generate mechanical torque effectively in this case, and the charging performance similar to that during normal operation is achieved, including a high power factor of the power grid, etc.

[0074] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.​​

Claims

1. An open - circuit fault - tolerant control method for an in - vehicle integrated charging system, characterized in that It includes a six-phase permanent magnet motor, a phase-locked loop, a VSD conversion module, a current controller, a VSD inverse conversion module, and an SPWM module; where VSD is vector space decomposition. The stator of the six-phase permanent magnet motor includes two sets of independent symmetrical three-phase armature windings, namely three-phase windings A, B, C and three-phase windings X, Y, Z. Each set of windings is driven by a set of three-phase full-bridge drive circuits. The rotor of the motor can be a surface-mounted permanent magnet rotor or an interior permanent magnet rotor. The specific steps of the open-circuit fault tolerance control method are as follows: Step 11: During the integrated charging operation, when the charging current of the AC power supply remains unchanged, the open-circuit fault current distribution strategy of the in-vehicle integrated charging system for different winding open-circuit faults: When the motor has a single-phase open circuit: When the faulty phase is A, B, or C, the current i in the healthy windings of the ABC phase group ABC_nf equals i g / 2, and the current i in the healthy windings of the XYZ phase group XYZ_nf equals -i g / 3. When the faulty phase is X, Y, or Z, the current i in the healthy windings of the ABC phase group ABC_nf equals i g / 3, and the current i in the healthy windings of the XYZ phase group XYZ_nf equals -i g / 2; When the motor has two open phases: When the faulty phases are AB, AC, or BC, the current \(i\) in the healthy windings of the ABC phase group ABC_nf equals \(i\) g , and the current \(i\) in the healthy windings of the XYZ phase group XYZ_nf equals \(-i\) g / 3. When the faulty phases are XY, XZ, or YZ, the current \(i\) in the healthy windings of the ABC phase group ABC_nf equals \(i\) g / 3, and the current \(i\) in the healthy windings of the XYZ phase group XYZ_nf equals \(-i\) g . When the faulty phases are AX, AY, AZ, BX, BY, BZ, CX, CY, or CZ, the current \(i\) in the healthy windings of the ABC phase group ABC_nf equals \(i\) g / 2, and the current \(i\) in the healthy windings of the XYZ phase group XYZ_nf equals \(-i\) g / 2; When the motor is in a three-phase open circuit: When the faulty phases are ABX, ABY, ABZ, ACX, ACY, ACZ, BCX, BCY, BCZ, the current i of the healthy winding of the ABC phase group ABC_nf is equal to i g , and the current i of the healthy winding of the XYZ phase group XYZ_nf is equal to -i g / 2. When the faulty phases are AXY, AXZ, AYZ, BXY, BXZ, BYZ, CXY, CXZ, CYZ, the current i of the healthy winding of the ABC phase group ABC_nf is equal to i g / 2, and the current i of the healthy winding of the XYZ phase group XYZ_nf is equal to -i g ; When the motor is in a four-phase open circuit: When the faulty phases are ABXY, ABXZ, ABYZ, ACXY, ACXZ, ACYZ, BCXY, BCXZ, BCYZ, the current i of the healthy winding of the ABC phase group ABC_nf is equal to i g , and the current i of the healthy winding of the XYZ phase group XYZ_nf is equal to -i g ; The said i g is the current on the grid side; The windings of each phase of the motor are not strictly symmetrical. In order to make the currents flowing through the remaining non-faulty phases of each three-phase winding be distributed according to the open-circuit fault current distribution strategy of the in-vehicle integrated charging system, it is necessary to control the current of the healthy windings. According to the type of fault, substitute the phase currents into the magnetomotive force synthesis formula according to the current distribution strategy to obtain the synthesized pulsating magnetomotive force. The axis of this pulsating magnetomotive force is the reference line that the rotor direct axis needs to align with. According to the current distribution strategy, substitute the current into the magnetomotive force of each phase of the stator winding and the synthesis magnetomotive force formula of the three-phase windings A, B, C and the three-phase windings X, Y, Z to calculate the total synthesis magnetomotive force of each phase of the healthy winding under open-circuit fault. The included angle between the magnetomotive force axis and the magnetomotive force of phase A winding is the rotor position information φ at this time. Step 12: After rebalancing the rotor position, project the phase currents of the current distribution strategy corresponding to the open-circuit fault into the zero-sequence space using the VSD transformation, and calculate the reference signals of the three space currents under this fault. The projected components of the phase currents of the healthy phases under the fault in all three planes are not zero, and only the current i q in the αβ space is 0, ensuring that the electromagnetic torque of the motor is 0 and guaranteeing that integrated charging can still be carried out when the inverter fault causes the motor to open circuit. In order to make the current after the fault follow the current distribution strategy, it is necessary to control the charging current of the motor after the fault. For the quadrature-axis current i q in the αβ space, the reference signal of the current it controls is a direct current, so a traditional proportional-integral (PI) controller is used for control. For other current signals, the reference signal is an AC component, so a proportional-resonant controller is used for control. Its transfer function G PR (z) is as follows: where k p is the proportional link coefficient of the proportional-resonant controller, and k i is the resonant link coefficient of the proportional-resonant controller, H r (z) is the transfer function of the z-domain resonant filter, and a0, a1, a2, b0, b1, b2 are the coefficients of the transfer function of the resonant filter; Input the real-time currents of each phase after VSD conversion and the current reference signal into the current fault tolerance controller to achieve the control and balance of each space current, and ensure adjustment according to the current distribution strategy. Step 13: According to the sampled grid voltage signal, obtain its phase information through the phase-locked loop. Combine the reference value of the grid current amplitude and the open-circuit fault current distribution strategy of the in-vehicle integrated charging system to determine the reference value of the current of each phase of the motor under fault conditions. Then use VSD conversion to convert the current reference signal into three spaces. Input the real-time currents of each phase after VSD conversion and the current reference signal into the current fault tolerance controller to achieve the control and balance of each space current, and ensure adjustment according to the current distribution strategy. The output result of the current fault tolerance controller is the reference voltage of the three spaces. Then generate the reference signal of each phase voltage through VSD inverse conversion, and finally generate the SPWM signal to drive the inverter to achieve the charging operation under the open-circuit fault of the in-vehicle integrated charging system.

2. The open-circuit fault tolerance control method for an in-vehicle integrated charging system according to claim 1, characterized in that, Its fault tolerance control method includes the following steps: Step 21: Establish a mathematical model of the air-gap synthesis magnetomotive force for the six-phase permanent magnet motor during integrated charging operation. When there is current flowing through each phase of the stator winding, pulsating magnetomotive forces are generated in the three-phase windings A, B, C and the three-phase windings X, Y, Z respectively. The magnetomotive force generated by each phase is: Where: F A ,F B ,F C ,F X ,F Y ,F Z are the magnetomotive forces generated by each phase, N c is the equivalent number of turns of each phase winding, θ is the angle of the motor air-gap circumference, i A ,i B ,i C ,i X ,i Y ,i Z are the phase currents of the six-phase permanent magnet motor respectively, α is the phase difference between the two sets of three-phase windings, and this formula takes the axis of the magnetomotive force generated by the A-phase winding as the starting point; According to the above formula, the synthesis magnetomotive force of the three-phase windings A, B, C and the three-phase windings X, Y, Z is: During normal integrated charging operation, the single-phase power grid is connected to the neutral points of the two sets of windings respectively. Due to the symmetry of the two sets of three-phase windings, the currents of each phase are: i A = i B = i C = i g / 3, i X = i Y = i Z = -i g / 3 Where: i g is the current on the grid side; Substituting the phase currents during normal integrated charging operation into the resultant magnetomotive force formula, it can be obtained that the magnetomotive forces of the three-phase windings A, B, C and the three-phase windings X, Y, Z cancel each other out synthetically, that is, the magnetomotive force F is 0. Using the VSD method to analyze the phase currents during normal operation, the phase currents are decomposed into three different spaces through the VSD transformation, namely the αβ space, the xy space and the zero-sequence space. Then, by performing the transformation from the stationary coordinate system to the rotating coordinate system on the variables in these three spaces, it can be concluded that no electromagnetic torque is generated during normal operation; Step 22: When a fault occurs in the inverter switch tube resulting in an open circuit of the bridge arm, an open circuit fault occurs in one or more phases of the motor winding. The resultant magnetomotive force of the remaining healthy windings in the motor air gap no longer cancels each other out but is a pulsating magnetomotive force and a pulsating magnetic field. If the rotor position of the motor remains unchanged, this pulsating magnetic field will cause the rotor to generate a non-zero electromagnetic torque. To avoid the generation of this torque, the direct axis of the motor rotor needs to be aligned with the axis of the pulsating magnetic field to keep the rotor in an equilibrium position.

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