Open-circuit fault-tolerant control method and system for three-level open-winding permanent magnet synchronous motor

Abstract

This invention discloses an open-circuit fault-tolerant control method and system for a three-level open-winding permanent magnet synchronous motor. The invention includes: when an open-circuit fault occurs in the three-level open-winding permanent magnet synchronous motor, acquiring the current of the non-faulty phases and the rotor speed and position; based on the acquired non-faulty phase currents and rotor speed and position, performing current prediction using the stator voltage of the faulty phase based on the original motor mathematical model; selecting the space voltage vector and corresponding switching state within a diamond modulation range based on the current prediction results; and reducing torque ripple through quadrature-axis current injection to achieve open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor. This invention considers the effects of the fundamental back EMF and the third-order back EMF of the faulty phase and optimizes the voltage vector selection process of the three-level converter, which can improve the accuracy of current prediction, achieve accurate tracking of the stator current, reduce motor torque ripple, and reduce motor noise.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet synchronous motor control technology, specifically relating to an open-circuit fault-tolerant control method and system for a three-level open-winding permanent magnet synchronous motor. Background Technology

[0002] For high-power, high-reliability motor systems, the high-power characteristics of three-level converters and the strong fault-tolerant operation capability of open-winding motors can be utilized to form a high-power three-level converter-open-winding motor system. In a three-level open-winding permanent magnet motor with a common DC bus, after a phase-loss fault, the remaining two normal phases can continue to operate and generate electromagnetic torque. However, due to the presence of zero-sequence path and third-order back EMF harmonics, the motor output torque exhibits significant torque ripple, affecting the motor's safe and stable operation. To address the fault-tolerant operation and torque ripple issues after a phase loss, traditional methods reconstruct a new coordinate transformation through current reconstruction to achieve vector control. Without considering the third-order back EMF harmonics, this can generate relatively stable torque. However, the new coordinate transformation constructed by this method is relatively complex, resulting in a more complex mathematical model of the motor, and torque ripple cannot be effectively suppressed when the third-order back EMF is large. Another method can use the model before the open-circuit fault for fault-tolerant control, but it does not consider the stator voltage influence of the faulty phase, leading to poor current tracking accuracy, and there is still room for improvement in torque ripple suppression. Summary of the Invention

[0003] The technical problem to be solved by this invention is as follows: Addressing the aforementioned problems in the prior art, this invention provides an open-circuit fault-tolerant control method and system for a three-level open-winding permanent magnet synchronous motor. The invention aims to address the issue of phase loss faults in high-power three-level open-winding permanent magnet synchronous motor systems. Under the premise of unchanged original motor mathematical model, it considers the effects of the fundamental back electromotive force and the third-order back electromotive force of the fault phase and optimizes the voltage vector selection process of the three-level converter. This improves current prediction accuracy, achieves precise tracking of stator current, reduces motor torque ripple, and lowers motor noise.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for open-circuit fault-tolerant control of a three-level open-winding permanent magnet synchronous motor includes the following steps:

[0006] S1: When an open-circuit fault occurs in any phase of a three-level open-winding permanent magnet synchronous motor, the current of the non-faulty phase, as well as the rotor speed and position of the motor, are collected.

[0007] S2, based on the collected non-faulty phase currents and the motor rotor speed and position, when a fault occurs, the stator voltage of the faulty phase is considered to predict the current.

[0008] S3, selects the space voltage vector and corresponding switching state within the diamond modulation range based on the current prediction result;

[0009] S4 reduces torque ripple through quadrature-axis current injection to achieve open-circuit fault-tolerant control of a three-level open-winding permanent magnet synchronous motor.

[0010] Optionally, step S2 includes:

[0011] S2.1 Calculate the estimated value of the quadrature and direct axis current at the next moment based on the current at the current moment and the voltage at the previous moment, determine the stator voltage of the fault phase, and calculate the slope of the quadrature and direct axis current when the zero voltage vector is applied and the slope of the quadrature and direct axis current when two non-zero voltage vectors are applied, based on the stator voltage of the fault phase.

[0012] S2.2, the duration of each voltage vector is determined based on the slopes of the quadrature-direct-axis currents when the zero voltage vector is applied and the slopes of the quadrature-direct-axis currents when the two non-zero voltage vectors are applied:

[0013] ,

[0014] ,

[0015] ,

[0016] In the above formula, The duration of the zero voltage vector. The sampling period is The duration of the first non-zero voltage vector. For the duration of the second non-zero voltage vector, and These are the reference values ​​for the direct and quadrature axis currents, respectively. and These are the estimated values ​​of the quadrature and direct-axis currents at time k+1, respectively. and These are the slopes of the currents along the quadrature and direct axes when the zero voltage vector is applied. and These are the slopes of the quadrature and direct-axis currents when the first non-zero voltage vector is applied. and These are the slopes of the quadrature and direct-axis currents when the second non-zero voltage vector is applied. The number of the first selected voltage vector. The number of the selected second voltage vector. Let be an intermediate variable, and we have:

[0017] ;

[0018] S2.3, Current prediction is performed according to the following formula:

[0019] ,

[0020] In the above formula, and These are the predicted values ​​of the quadrature and direct axis currents at time k+2, respectively. and These are the estimated values ​​of the quadrature and direct axis currents at time k+1, respectively.

[0021] Optionally, the functional expression for determining the stator voltage of the faulty phase in step S2.1 is:

[0022] ,

[0023] In the above formula, The stator voltage of the faulty phase. The electric angular velocity of the motor. It is a permanent magnet flux chain. The rotor position angle of the motor. It is a permanent magnet with a three-stage magnetic flux linkage.

[0024] Optionally, the functional expressions for calculating the slope of the quadrature-direct axis current under zero voltage vector action and the slope of the quadrature-direct axis current under two non-zero voltage vector actions in step S2.1, based on the stator voltage of the fault phase, are as follows:

[0025] ,

[0026] ,

[0027] ,

[0028] In the above formula, and These are the slopes of the currents along the quadrature and direct axes when the zero voltage vector is applied. For stator resistance, and These are the direct and quadrature axis currents, respectively. The electric angular velocity of the motor. The stator voltage of the faulty phase. It is a permanent magnet flux chain. The rotor position angle of the motor. and These are the direct and quadrature axis inductors, and These are the slopes of the quadrature and direct-axis currents when the first non-zero voltage vector is applied. and These are the components of the selected first voltage vector on the perpendicular and perpendicular axes, respectively. The number of the first selected voltage vector. and These are the slopes of the quadrature and direct-axis currents when the second non-zero voltage vector is applied. and These are the components of the selected second voltage vector on the perpendicular and perpendicular axes, respectively. The number of the selected second voltage vector.

[0029] Optionally, step S3 includes:

[0030] S3.1, Reconstruct the space voltage vector diagram after an open-circuit fault occurs in a three-level open-winding permanent magnet synchronous motor, and determine the switching state configuration with the fewest switching times in each small sector;

[0031] S3.2, perform large sector identification, traverse each large sector, predict the current through the boundary large vector, and determine the large sector by minimizing the preset cost function:

[0032] S3.3, perform small sector judgment, traverse each small sector within the selected large sector, and select the vector according to the switching state configuration with the fewest switching times in each small sector determined in S3.1. The small sector is determined by minimizing the preset cost function to obtain the optimal voltage vector and switching state.

[0033] Optionally, the preset cost function is expressed as follows:

[0034] ,

[0035] In the above formula, This represents the preset cost function. and These are the reference values ​​for the direct and quadrature axis currents, respectively. and These are the predicted values ​​of the quadrature and direct axis currents at time k+2, respectively.

[0036] Optionally, in step S4, when torque ripple is reduced by injecting quadrature-axis current to achieve open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor, the functional expression of the injected quadrature-axis current is:

[0037] ,

[0038] In the above formula, For the injected quadrature-axis current, Zero-axis current, For quadrature axis current, The rotor position angle of the motor. The electric angular velocity of the motor. The sampling period is It is a permanent magnet with a three-stage magnetic flux linkage. It is a permanent magnet flux linkage.

[0039] Furthermore, the present invention also provides an open-circuit fault-tolerant control system for a three-level open-winding permanent magnet synchronous motor, including a microprocessor and a memory interconnected thereto, wherein the microprocessor is programmed or configured to execute the open-circuit fault-tolerant control method for the three-level open-winding permanent magnet synchronous motor.

[0040] Furthermore, the present invention also provides a computer-readable storage medium storing a computer program or instructions that are programmed or configured to execute the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor via a processor.

[0041] In addition, the present invention also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the open-circuit fault-tolerant control method for the three-level open-winding permanent magnet synchronous motor via a processor.

[0042] Compared with existing technologies, the present invention has the following main advantages: The open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor employs a three-vector model predictive current control strategy after a phase loss fault occurs. While maintaining the motor's mathematical model, it considers the influence of the back electromotive force (EMF) and compensates for the stator voltage of the faulty phase in the control algorithm. This is equivalent to the back EMF and mutual inductance voltage acting together on the faulty phase, achieving decoupling control of the faulty phase during the control process. In model predictive current control with an unchanged motor mathematical model, it eliminates the current tracking error caused by coupling between the faulty and normal phases. Through quadrature-axis current harmonic injection, it ensures that the actual motor current tracks the reference current, improving torque ripple suppression. The present invention reconstructs the voltage vector distribution of the two-sided three-level converters after a phase loss and fully utilizes the advantages of the three-level converters. It achieves a five-level effect through the two-sided three-level converters, optimizes voltage vector selection, and selects voltage within the diamond modulation range, rather than just the regular hexagonal range, utilizing all voltage vectors. Simultaneously, it configures the switching state of the voltage vectors according to the principle of minimizing switching frequency, significantly reducing the number of power device switching operations. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the basic process of the method of this invention.

[0044] Figure 2 This is a schematic diagram of the open-winding motor control principle of the method of the present invention.

[0045] Figure 3 This is a schematic diagram of the remaining normal phase space vector distribution of a three-level open-winding motor according to an example method of the present invention.

[0046] Figure 4 This is a schematic diagram of the normal phase space vector distribution large sector division of the method of this invention.

[0047] Figure 5 This is a schematic diagram of the first major sector division of the normal phase space vector distribution in the example method of the present invention.

[0048] Figure 6 The method of this invention considers the motor output torque before and after the fault phase voltage.

[0049] Figure 7 The Fourier analysis results of the motor output torque before considering the fault phase voltage are presented in the example method of this invention.

[0050] Figure 8 The Fourier analysis results of the motor output torque after considering the fault phase voltage in the example method of this invention. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] like Figure 1 As shown, the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor in this embodiment includes the following steps:

[0053] S1: When an open-circuit fault occurs in any phase of a three-level open-winding permanent magnet synchronous motor, the current of the non-faulty phase, as well as the rotor speed and position of the motor, are collected.

[0054] S2, based on the collected non-faulty phase currents and the motor rotor speed and position, when a fault occurs, the stator voltage of the faulty phase is considered to predict the current.

[0055] S3, selects the space voltage vector and corresponding switching state within the diamond modulation range based on the current prediction result;

[0056] S4 reduces torque ripple through quadrature-axis current injection to achieve open-circuit fault-tolerant control of a three-level open-winding permanent magnet synchronous motor.

[0057] like Figure 2 As shown, the three-level open-winding permanent magnet synchronous motor in this embodiment uses a common DC bus connection. Each of the first and second ends of the motor windings is connected to a three-level three-phase converter, and the two converters share a single DC power supply. (See figure.) Indicates the direct-axis current of the motor. Indicates the quadrature-axis current of the motor. Indicates the zero-axis current of the motor. Indicates the direct-axis current reference value. Indicates the reference value of the quadrature axis current. Indicates the injection of harmonic current. S b1 , S c1 , S b2 , S c2 This indicates the switching status of the B and C phase windings. Compared to a normal motor, an open-winding motor opens the neutral point of the windings, providing a path for zero-sequence current. Therefore, the tertiary flux linkage of the motor will affect its operation. Since the three phase windings of an open-winding motor are independent, a phase loss fault will not affect the remaining normal phases. This embodiment, using a model-based predictive fault-tolerant control method considering the stator voltage of the faulty phase, does not require changes to the coordinate transformation and the motor's mathematical model. It considers the faulty phase voltage within the original motor mathematical model, improving current prediction accuracy, achieving precise stator current tracking, improving current control performance, and reducing motor torque ripple.

[0058] In step S1 of this embodiment, when collecting the current of the non-faulty phases and the speed and position of the motor rotor, it is assumed that when phase a fails, the non-faulty phases are phases b and c. In addition, the speed and position of the motor rotor are obtained by the motor encoder.

[0059] like Figure 3 As shown, the spatial voltage vector distribution of the two converters under a phase loss fault in the motor is reconstructed. The voltage vector selection method is optimized to utilize all voltage vectors. At the same time, the switching states of the converters are optimized to minimize the switching frequency and reduce the number of switching operations of the power devices. In the figure, N state represents the switching states of the four power devices as 0, 0, 1, 1; O state represents the switching states as 0, 1, 1, 0; and P state represents the switching states as 1, 1, 0, 0. For example, PN-OP means that phase B of the first-end converter is in state P and phase C is in state N, while phase B of the last-end converter is in state O and phase C is in state P.

[0060] When a phase-loss fault occurs in an open-winding motor (assuming the fault occurs in phase a), with the coordinate transformation and the motor's mathematical model remaining unchanged, the expression for the output torque of the motor considering the third harmonic of the current is:

[0061] ,

[0062] in, This indicates the output torque of the motor. Indicates the number of pole pairs of the motor. This indicates fundamental frequency magnetic therapy. This indicates the third flux linkage of the motor. This represents the component of the motor's fundamental current on the zero axis. The motor rotor position is shown. From the torque expression after a phase loss, it can be seen that the torque ripple is divided into two parts: the torque ripple caused by the third zero-sequence current and the torque ripple caused by the fundamental frequency zero-sequence component. This part of the torque ripple exhibits two forms: second-order ripple and fourth-order ripple. Therefore, to suppress torque ripple, it is necessary to address this part of the torque ripple.

[0063] ,

[0064] The torque expression for an open-winding motor after a phase loss can be derived by injecting a current at the quadrature axis (Q-axis) reference value. The torque generated by this injected current is used to counteract the torque pulsation. The magnitude of the injected current is as follows:

[0065] ,

[0066] ,

[0067] Due to the controller's one-beat delay, delay compensation is needed for the injected current. Considering the very short control cycle and As a combination of high direct traffic and low communication traffic, it can be considered that... The amplitude of the current injection changes very little within a control cycle, and this amplitude change has little impact on the motor control process. Therefore, the influence of the phase during the controller's one-step delay is mainly considered. Thus, the zero-sequence current in the injection current expression is corrected as follows:

[0068] ,

[0069] Similarly, .

[0070] Model predictive control is designed based on a discretized mathematical model of the motor. In a synchronous rotating coordinate system, the current state equation of the open-winding motor is:

[0071] ,

[0072] in This represents the stator resistance of the motor. , , These represent the quadrature-axis, direct-axis, and zero-axis inductances, respectively. , , Let T represent the AC, DC, and zero-axis voltages, respectively. Assume the system sampling period is T. s Discretizing the above state equations yields the discretized current state equations:

[0073] ,

[0074] Where k is the sampling period kT s The discrete values, k+1 is the sampling period (k+1)T s The discrete values.

[0075] In practical control systems, the motor-related information sampled at time k needs to undergo one cycle of calculation before being emitted at time k+1 and applied to the motor. In predictive control, the voltage vector selected at time k is actually emitted at time k+1, thus requiring compensation for a one-cycle delay in the control. Based on the sampled motor current and position information at time k, the voltage vector acting at time k+1 is calculated. Therefore, the predicted current value at time k+1 needs to be calculated based on the voltage vector acting at time k, and the voltage vector at time k+1 is calculated using this predicted value. Considering the controller's one-cycle delay, the current sample value at time k corresponds to the voltage value at time k-1. The above equation, after discretization, yields:

[0076] ,

[0077] Under normal operation of an open-winding motor, because the AC / DC axis and zero axis are decoupled, the AC / DC axis (DQ axis) current cannot affect the third-order zero-sequence current. That is, under normal circumstances, AC / DC axis (DQ axis) current control cannot affect the zero-sequence current. Therefore, additional zero-axis current control is needed to suppress the zero-sequence current under normal conditions. However, under a-phase fault conditions, the zero axis (0 axis) and AC / DC axis (DQ axis) are coupled. Therefore, AC / DC axis (DQ axis) current control will affect the zero-sequence current, reducing the degrees of freedom of current control to two. In this case, only the AC / DC axis (DQ axis) current needs to be controlled. Additionally:

[0078] ,

[0079] In model predictive current control, the duration of each voltage vector needs to be determined based on the voltage vector combination. Based on the deadbeat control principle, three-voltage vector predictive control is used in each control cycle. The predicted value of the current at the next moment along the direct-quadrature axis (DQ axis) is equal to the given value. The prediction formula for the direct-quadrature axis (DQ axis) is as follows:

[0080] ,

[0081] in, and These are the predicted values ​​of the quadrature and direct axis currents at time k+2, respectively. and These are the estimated values ​​of the quadrature and direct-axis currents at time k+1, respectively. , , , , , This represents the slope of the current perpendicular to the direct axis when three voltage vectors are applied. , , This indicates the duration of action of the three voltage vectors. , This is the reference value for the direct and quadrature axis currents.

[0082] In this embodiment, step S2 includes:

[0083] S2.1 Calculate the estimated value of the quadrature and direct axis current at the next moment based on the current at the current moment and the voltage at the previous moment, determine the stator voltage of the fault phase, and calculate the slope of the quadrature and direct axis current when the zero voltage vector is applied and the slope of the quadrature and direct axis current when two non-zero voltage vectors are applied, based on the stator voltage of the fault phase.

[0084] S2.2, the duration of each voltage vector is determined based on the slopes of the quadrature-direct-axis currents when the zero voltage vector is applied and the slopes of the quadrature-direct-axis currents when the two non-zero voltage vectors are applied:

[0085] ,

[0086] ,

[0087] ,

[0088] In the above formula, The duration of the zero voltage vector (U0) is... The sampling period is For the first non-zero voltage vector (U) i The duration of action of ) For the second non-zero voltage vector (U) j The duration of action of ) and These are the reference values ​​for the direct and quadrature axis currents, respectively. and These are the estimated quadrature and direct-axis currents at time k+1, respectively. and These are the slopes of the currents along the quadrature and direct axes when the zero voltage vector is applied. and These are the slopes of the quadrature and direct-axis currents when the first non-zero voltage vector is applied. and These are the slopes of the quadrature and direct-axis currents when the second non-zero voltage vector is applied. The number of the first selected voltage vector. The number of the selected second voltage vector. Let be an intermediate variable, and we have:

[0089] ;

[0090] S2.3, based on the discretized mathematical model of the motor in the synchronous rotating coordinate system, considering the delay of one control cycle, the prediction formula for the quadrature-direct (dq) axis current is obtained. Based on the concept of deadbeat current control, three-voltage vector predictive control is used in each control cycle. The predicted value of the quadrature-direct axis current at the next moment is equal to the given value. Therefore, in this embodiment, current prediction is performed according to the following formula:

[0091] ,

[0092] In the above formula, and These are the predicted values ​​of the quadrature and direct axis currents at time k+2, respectively. and These are the estimated values ​​of the direct and quadrature axis currents at time k+1. Substituting these vectors and their corresponding times into the formula allows for current prediction.

[0093] Since the mutual inductance voltage amplitude is very small, its impact on motor control is negligible. Therefore, the functional expression for determining the stator voltage of the faulty phase in step S2.1 of this embodiment is:

[0094] ,

[0095] In the above formula, The stator voltage of the faulty phase. The electric angular velocity of the motor. It is a permanent magnet flux chain. The rotor position angle of the motor. The permanent magnet has a third flux linkage. The influence of the a-phase stator voltage on the model's predicted current control is calculated using Park and Clark transforms. Considering the faulty phase stator voltage, the functional expressions for calculating the quadrature-direct axis current slopes under zero voltage vector action and under two non-zero voltage vector action in step S2.1 of this embodiment are as follows:

[0096] ,

[0097] ,

[0098] ,

[0099] In the above formula, and These are the slopes of the currents along the quadrature and direct axes when the zero voltage vector is applied. For stator resistance, and These are the direct and quadrature axis currents, respectively. The electric angular velocity of the motor. The stator voltage of the faulty phase. It is a permanent magnet flux chain. The rotor position angle of the motor. and These are the direct and quadrature axis inductors, and These are the slopes of the quadrature and direct-axis currents when the first non-zero voltage vector is applied. and These are the components of the selected first voltage vector on the perpendicular and perpendicular axes, respectively. The number of the first selected voltage vector. and These are the slopes of the quadrature and direct-axis currents when the second non-zero voltage vector is applied. and These are the components of the selected second voltage vector on the perpendicular and perpendicular axes, respectively. The selected second voltage vector is assigned a number. Based on the slope of the direct-axis current under the action of the zero voltage vector, the slope of the DQ-axis current under the action of the two selected voltage vectors is calculated. Using the slopes of the direct-axis current under the action of the zero vector and the two selected voltage vectors respectively, the action time of the three voltage vectors is calculated. Finally, the optimal vector acting on the motor is selected through the current cost function.

[0100] In this embodiment, the selection rule for the voltage vector is as follows: the spatial voltage vectors of the remaining two normal phases are divided into eight large sectors, and each large sector is further divided into several small sectors. The vector action sequence and switching state corresponding to each small sector are determined by the minimum switching frequency. First, by traversing the large vectors of each large sector, the large sector is determined based on the selected optimal large vector. Then, all small sectors in the selected large sector are traversed to obtain the small sector where the optimal voltage vector is located, and the switching state and action time of the voltage vector are determined simultaneously. Specifically, step S3 in this embodiment includes:

[0101] S3.1, Reconstruct the space voltage vector diagram after an open-circuit fault occurs in a three-level open-winding permanent magnet synchronous motor, and determine the switching state configuration with the fewest switching times in each small sector;

[0102] S3.2, perform large sector identification, traverse each large sector, predict the current through the boundary large vector, and determine the large sector by minimizing the preset cost function:

[0103] S3.3, perform small sector judgment, traverse each small sector within the selected large sector, and select the vector according to the switching state configuration with the fewest switching times in each small sector determined in S3.1. The small sector is determined by minimizing the preset cost function to obtain the optimal voltage vector and switching state.

[0104] In this embodiment, the preset cost function is expressed as follows:

[0105] ,

[0106] In the above formula, This represents the preset cost function. and These are the reference values ​​for the direct and quadrature axis currents, respectively. and These are the predicted values ​​of the AC and DC axis currents at time k+2. The phase voltage of the open-winding motor is generated by the combined action of the converters on both sides. When a fault occurs in phase A of the motor, it no longer participates in the modulation of the motor voltage. At this time, the voltage vector of the motor is generated by phases B and C. The voltage vector diagram in the two-phase stationary coordinate system is as follows: Figure 4 As shown, the horizontal axis is the α axis and the vertical axis is the β axis. The voltage vector is divided into eight small sectors. When selecting a vector, the large sector is first determined. Each large sector is traversed to select the large sector containing the required voltage vector. Then, all small sectors within the corresponding large sector are traversed until a voltage vector combination that meets the requirements is obtained, at which point the loop exits. Simultaneously, the selected vector must satisfy the basic characteristics of a three-level converter; the switching state of each phase cannot directly switch from N to P or from P to N.

[0107] Based on the cost function that minimizes current error, the switching states are further configured according to the principle of minimizing the number of switching operations of power devices. The following example uses the first sector to configure the switching states corresponding to the voltage vectors. First, the large sectors are determined. Each large sector is traversed. In the first large sector, two large voltage vectors are selected (the two red boundary vectors in the diagram). To reduce the number of switching operations, the zero vector is chosen as the starting and ending point. U1 is the first vector, and U2 is the second vector. The vector arrangement is as follows... Figure 5Here, Uref represents the reference voltage vector, and U1-U5 are five non-zero vectors within the first major sector. U1 corresponds to a switch state of ON-OP, and U2 corresponds to a switch state of NN-PP. It's important to note that this calculation only determines the major sector where the voltage vector resides and does not actually affect the motor. After determining the voltage vector in the first major sector, each sub-sector within that sector is traversed. When the voltage vector is in sub-sectors 1 and 2, U3 is selected as the first vector and U4 as the second vector, with U3 corresponding to a switch state of ON-OO and U2 corresponding to a switch state of NN-OO. In this case, only two sets of power device switch states change within the cycle. When the voltage vector is in sub-sector 3, U4 is selected as the first vector and U5 as the second vector, with U4 corresponding to a switch state of NN-OO and U5 corresponding to a switch state of NN-OP. In this case, only three sets of power device switch states change within the cycle. When the voltage vector is in sub-sector 4, U3 is selected as the first vector and U5 as the second vector, with U3 corresponding to a switch state of ON-OO. When the switching state corresponding to U5 is selected as NN-OP or ON-PP, only three sets of power device switching states change within the cycle. When the voltage vector is located in sector 5, U5 is selected as the first vector and U2 as the second vector, where U5 corresponds to either NN-OP or ON-PP, and U2 corresponds to NN-PP. In this case, four sets of power device switching states change within the cycle. When the voltage vector is located in sector 6, U1 is selected as the first vector and U5 as the second vector, where U1 corresponds to ON-OP, and U5 corresponds to either NN-OP or ON-PP. In this case, only three sets of power device switching states change within the cycle. The switching states in other sectors are similar. Through the above optimization of voltage vector selection and corresponding switching states, a maximum of 8+5=13 cycles are executed per cycle, greatly reducing the calculation speed and improving the selection speed. At the same time, by utilizing the redundancy of the dual three-level converter, a voltage vector may correspond to multiple switching states. By optimizing the selection of switching states, the number of switching changes is greatly reduced, lowering the switching frequency and losses.

[0108] In step S4 of this embodiment, when reducing torque ripple through quadrature-axis current injection to achieve open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor, the zero-axis current is obtained through coordinate transformation based on the sampled current in S1. The harmonic current to be injected into the quadrature axis is obtained from the motor torque expression, and considering a one-cycle delay, the functional expression of the injected quadrature-axis current is:

[0109] ,

[0110] In the above formula, For the injected quadrature-axis current, Zero-axis current, For quadrature axis current, The rotor position angle of the motor. The electric angular velocity of the motor. The sampling period is It is a permanent magnet with a three-stage magnetic flux linkage. This is a permanent magnet flux linkage. The aforementioned current is injected into the quadrature axis current reference value, and the torque generated by this injected current counteracts the torque pulsation.

[0111] Figure 6 The simulation results show the motor output torque before and after considering the fault phase voltage in this example. Before 0.2s, the fault phase voltage was not considered, and the torque ripple was large at this time; after considering the fault phase voltage from 0.2s onwards, the motor torque ripple was effectively suppressed. Figure 7 The Fourier analysis results of the motor output torque before considering the fault phase voltage are presented in the example method of this invention. Figure 8 This is the Fourier analysis result of the motor output torque considering the fault phase voltage in the method of this invention. See also Figure 7 and Figure 8 It can be seen that after considering the fault phase voltage, the total harmonic distortion rate of the output torque is reduced, and the motor torque pulsation is significantly suppressed.

[0112] In summary, the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor in this embodiment employs a three-vector model predictive current control strategy after a phase-loss fault occurs in the three-level common DC bus open-winding motor. While keeping the motor's mathematical model unchanged, it considers the influence of back EMF and mutual inductance voltage, compensating for the stator voltage of the faulty phase in the control algorithm. This is equivalent to the back EMF and mutual inductance voltage acting together on the faulty phase, achieving decoupling control of the faulty phase during the control process. In model predictive current control with an unchanged motor mathematical model, the current tracking error caused by stator voltage coupling of the faulty phase is eliminated. Through Q-axis current harmonic injection, accurate stator current tracking is achieved, improving torque ripple suppression. The voltage vector distribution of the two-sided three-level converters after phase loss was reconstructed, and the advantages of the three-level converters were fully utilized. The five-level effect was achieved through the two-sided three-level converters. The voltage vector selection was optimized, and the voltage selection was performed within the diamond modulation range instead of just the regular hexagon range. All voltage vectors were utilized. At the same time, the switching state of the voltage vector was configured according to the principle of minimizing the number of switching operations, which greatly reduced the number of switching operations of the power devices.

[0113] Furthermore, this embodiment also provides an open-circuit fault-tolerant control system for a three-level open-winding permanent magnet synchronous motor, including a microprocessor and a memory interconnected thereto, wherein the microprocessor is programmed or configured to execute the open-circuit fault-tolerant control method for the three-level open-winding permanent magnet synchronous motor.

[0114] This embodiment also provides a computer-readable storage medium storing a computer program or instructions that are programmed or configured to execute the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor via a processor.

[0115] This embodiment also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the open-circuit fault-tolerant control method for the three-level open-winding permanent magnet synchronous motor via a processor.

[0116] Those skilled in the art will understand that the technical solutions provided by the embodiments of this application may be in the form of a method, system, or computer program product. Therefore, this application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application may take the form of a computer program product embodied on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create an implementation for the process. Figure 1 One or more processes and / or boxes Figure 1 The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0117] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for open-circuit fault-tolerant control of a three-level open-winding permanent magnet synchronous motor, characterized in that, Includes the following steps: S1: When an open-circuit fault occurs in any phase of a three-level open-winding permanent magnet synchronous motor, the current of the non-faulty phase, as well as the rotor speed and position of the motor, are collected. S2, based on the collected non-faulty phase currents and the motor rotor speed and position, when a fault occurs, the stator voltage of the faulty phase is considered to predict the current. S3, select the space voltage vector and corresponding switching state within the diamond modulation range based on the current prediction result; S4 reduces torque ripple through quadrature axis current injection to achieve open-circuit fault-tolerant control of a three-level open-winding permanent magnet synchronous motor; Step S2 includes: S2.1 Calculate the estimated value of the dq-axis current at the next moment based on the current at the current moment and the voltage at the previous moment, determine the stator voltage of the fault phase, and calculate the dq-axis current slope when the zero voltage vector is applied and the dq-axis current slope when two non-zero voltage vectors are applied, based on the stator voltage of the fault phase. S2.2, the duration of each voltage vector is calculated based on the dq-axis current slope when the zero voltage vector is applied and the dq-axis current slope when the two non-zero voltage vectors are applied: ； ； ； In the above formula, The duration of the zero voltage vector. The sampling period is The duration of the first non-zero voltage vector. For the duration of the second non-zero voltage vector, and These are the reference values ​​for the dq axis currents, and These are the estimated values ​​of the dq-axis current at time k+1. and These are the dq-axis current slopes when the zero voltage vector is applied. and These represent the dq-axis current slopes when the first non-zero voltage vector is applied. and These are the dq-axis current slopes when the second non-zero voltage vector is applied. The number of the first selected voltage vector. The number of the selected second voltage vector. Let be an intermediate variable, and we have: ； S2.3, Current prediction is performed according to the following formula: ； In the above formula, and These are the predicted values ​​of the dq-axis current at time k+2. and These are the estimated values ​​of the dq-axis current at time k+1.

2. The open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that, The functional expression for determining the stator voltage of the faulty phase in step S2.1 is: ； In the above formula, The stator voltage of the faulty phase. The electric angular velocity of the motor. It is a permanent magnet flux linkage. The rotor position angle of the motor. It is a permanent magnet with a three-stage magnetic flux linkage.

3. The open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that, In step S2.1, the functional expressions for calculating the dq-axis current slope under zero voltage vector action and the dq-axis current slope under two non-zero voltage vector action, based on the stator voltage of the fault phase, are as follows: ； ； ； In the above formula, and These are the dq-axis current slopes when the zero voltage vector is applied. For stator resistance, and These are the dq-axis currents, respectively. The electric angular velocity of the motor. The stator voltage of the faulty phase. It is a permanent magnet flux linkage. The rotor position angle of the motor. and These are the d-q axis inductors, and These represent the dq-axis current slopes when the first non-zero voltage vector is applied. and These are the components of the selected first voltage vector on the dq axis. The number of the first selected voltage vector. and These are the dq-axis current slopes when the second non-zero voltage vector is applied. and These are the components of the selected second voltage vector on the dq axis. The number of the selected second voltage vector.

4. The open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that, Step S3 includes: S3.1, Reconstruct the space voltage vector diagram after an open-circuit fault occurs in a three-level open-winding permanent magnet synchronous motor, and determine the switching state configuration with the fewest switching times in each small sector; S3.2, perform large sector identification, traverse each large sector, predict the current through the boundary large vector, and determine the large sector by minimizing the preset cost function: S3.3, perform small sector judgment, traverse each small sector within the selected large sector, and select the vector according to the switching state configuration with the fewest switching times in each small sector determined in S3.

1. The small sector is determined by minimizing the preset cost function to obtain the optimal voltage vector and switching state.

5. The open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor according to claim 4, characterized in that, The function expression of the preset cost function is: ； In the above formula, This represents the preset cost function. and These are the reference values ​​for the dq axis currents, and These are the predicted values ​​of the dq-axis currents at time k+2.

6. The open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor according to claim 1, characterized in that, In step S4, when torque ripple is reduced by injecting quadrature-axis current to achieve open-circuit fault-tolerant control of the three-level open-winding permanent magnet synchronous motor, the functional expression of the injected quadrature-axis current is: ； In the above formula, For the injected quadrature-axis current, Zero-axis current, For quadrature axis current, The rotor position angle of the motor. The electric angular velocity of the motor. The sampling period is It is a permanent magnet with a three-stage magnetic flux linkage. It is a permanent magnet flux linkage.

7. A three-level open-winding permanent magnet synchronous motor open-circuit fault-tolerant control system, comprising a microprocessor and a memory interconnected, characterized in that, The microprocessor is programmed or configured to execute the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor according to any one of claims 1 to 6.

8. A computer-readable storage medium storing a computer program or instructions, characterized in that, The computer program or instructions are programmed or configured to execute, via a processor, the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor as described in any one of claims 1 to 6.

9. A computer program product, comprising a computer program or instructions, characterized in that, The computer program or instructions are programmed or configured to execute, via a processor, the open-circuit fault-tolerant control method for a three-level open-winding permanent magnet synchronous motor as described in any one of claims 1 to 6.

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