Predictive Current Control Method and System for GaN-based Permanent Magnet Synchronous Motors

Abstract

This invention discloses a predictive current control method and system for a GaN-based permanent magnet synchronous motor. The method includes: predicting the current of each voltage vector among multiple voltage vectors of the inverter based on a predictive current model to obtain multiple predicted currents; filtering the multiple voltage vectors according to the multiple predicted currents and a first cost function to obtain candidate voltage vectors; determining the duration of action of the candidate voltage vectors; if there are multiple candidate voltage vectors, filtering them according to the duration of action of the multiple candidate voltage vectors and a second cost function to obtain the optimal voltage vector; and controlling the inverter according to the optimal voltage vector and its duration to control the operation of the permanent magnet synchronous motor. This improves the overall steady-state performance of the motor while reducing the computational load, thus lowering the complexity of the control method.

Description

Technical Field

[0001] This invention relates to the field of motor control, and in particular to a predictive current control method and system for a GaN-based permanent magnet synchronous motor. Background Technology

[0002] In the field of electric motors, permanent magnet synchronous motors (PMSMs) have significant advantages over traditional motors, such as high power density, large torque-to-inertia ratio, and fast dynamic response, making them highly promising for modern industrial applications. However, traditional field-oriented control methods for PMSMs suffer from slow dynamic response and require complex PID parameter tuning and decoupling algorithms. Direct torque control methods, on the other hand, exhibit large steady-state torque ripple and less than ideal low-speed characteristics. Therefore, new control algorithms are needed for PMSMs. One such algorithm predicts the stator flux linkage under the action of multiple voltage vectors from the inverter, finds the optimal voltage vector through differentiation, and employs a deadbeat control strategy to adjust the control step size of this voltage vector, thereby improving the steady-state performance of the control system.

[0003] The drawback of the control algorithms mentioned above is that the optimal control time for multiple voltage vectors needs to be calculated during the control process. This type of calculation is quite cumbersome, which makes the control algorithm more complex and difficult to implement. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, the first objective of this invention is to propose a predictive current control method for a permanent magnet synchronous motor. This method involves setting two levels of cost functions. Based on the predictive current model and the first cost function, multiple voltage vectors of the inverter are screened to determine candidate voltage vectors, and the duration of each candidate voltage vector's action is determined. When multiple candidate voltage vectors are included, the optimal voltage vector is determined based on the duration of each candidate voltage vector and the second cost function. The inverter is then controlled using the optimal voltage vector and its duration to control the motor operation. This allows the motor to operate according to the optimal voltage vector and optimal action time determined based on control requirements, thereby improving the overall steady-state performance of the motor. Simultaneously, when determining the action time, only the duration of the candidate voltage vector needs to be calculated, reducing the computational load and thus lowering the complexity of the method, achieving optimization of the control method.

[0005] A second objective of this invention is to provide a computer-readable storage medium.

[0006] The third objective of this invention is to provide a predictive current control system for a permanent magnet synchronous motor.

[0007] The fourth objective of this invention is to provide a predictive current control device for a permanent magnet synchronous motor.

[0008] To achieve the above objectives, a first aspect of the present invention proposes a predictive current control method for a permanent magnet synchronous motor. The method includes: predicting the current of each voltage vector among multiple voltage vectors of an inverter based on a predictive current model to obtain multiple predicted currents; filtering the multiple voltage vectors according to the multiple predicted currents and a first cost function to obtain candidate voltage vectors; determining the duration of action of the candidate voltage vectors; if there are multiple candidate voltage vectors, filtering the multiple candidate voltage vectors according to the duration of action of the multiple candidate voltage vectors and a second cost function to obtain an optimal voltage vector; and controlling the inverter according to the optimal voltage vector and the duration of action of the optimal voltage vector to control the operation of the permanent magnet synchronous motor.

[0009] According to the predictive current control method for permanent magnet synchronous motors of the present invention, current prediction is performed on each of the multiple voltage vectors of the inverter based on a predictive current model to obtain multiple predicted currents. Candidate voltage vectors and their durations are determined based on the multiple predicted currents and a first cost function. When multiple candidate voltage vectors are included, the optimal voltage vector is selected based on the duration of the candidate voltage vectors and a second cost function. Finally, the permanent magnet synchronous motor is controlled to operate according to the optimal voltage vector and its duration. This enables the motor to operate according to the optimal voltage vector and optimal duration in the inverter determined according to control requirements, thereby improving the overall steady-state performance of the motor. Simultaneously, when determining the duration, only the duration of the candidate voltage vectors needs to be calculated, reducing the computational load and thus lowering the complexity of the method, achieving optimization of the control method.

[0010] According to one embodiment of the present invention, the method further includes: if there is one candidate voltage vector, then the candidate voltage vector is determined as the optimal voltage vector.

[0011] According to one embodiment of the present invention, multiple voltage vectors are screened based on multiple predicted currents and a first cost function to obtain candidate voltage vectors, including: inputting multiple predicted currents into the first cost function for calculation to obtain multiple first cost function values, wherein the first cost function is used to characterize the degree of deviation between the predicted current and the given current; if the first cost function value is equal to zero, then the voltage vector corresponding to the first cost function value is determined as a candidate voltage vector; if multiple first cost function values ​​are not equal to zero, then the minimum value of the multiple first cost function values ​​is obtained, and the voltage vector corresponding to the minimum value is taken as a candidate voltage vector.

[0012] According to one embodiment of the present invention, the first cost function is:

[0013]

[0014]

[0015]

[0016] Where f1 is the value of the first cost function, and μ1 and μ2 are the weights. These are the d-axis and q-axis components of the nth predicted current at time t0+T', respectively. Let i be the d-axis component and q-axis component of the given current at time t0+T', where t0 is the current time and T' is the duration of the voltage vector. d,offset i q,offset These represent the maximum fluctuation values ​​of the d-axis component and the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

[0017] According to one embodiment of the present invention, determining the duration of action of a candidate voltage vector includes: if there are multiple candidate voltage vectors, or if there is one candidate voltage vector that corresponds to zero, then the duration of action of the candidate voltage vector is determined based on the rate of change of current corresponding to the candidate voltage vector and the actual current fluctuation range of the permanent magnet synchronous motor; if there is one candidate voltage vector that corresponds to the minimum value, then the duration of action of the candidate voltage vector is the minimum allowable duration of action.

[0018] According to one embodiment of the present invention, the duration of action of the candidate voltage vector is determined by the following method:

[0019] T ac,n =maxT'

[0020]

[0021] Among them, T ac,n The duration of the nth voltage vector as a candidate voltage vector, where max represents the maximum value to be obtained. The d-axis and q-axis components of the nth predicted current at time t0+T' are respectively, k d,n (t0), k q,n (t0) represents the d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0, respectively. Let i be the d-axis component and q-axis component of the given current at time t0+T', where t0 is the current time and T' is the duration of the voltage vector. d,offset i q,offset These represent the maximum fluctuation values ​​of the d-axis component and the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

[0022] According to one embodiment of the present invention, the optimal voltage vector is obtained by filtering multiple candidate voltage vectors based on the duration of action of multiple candidate voltage vectors and a second cost function. The method includes: inputting the duration of action of multiple candidate voltage vectors into the second cost function for calculation to obtain multiple second cost function values; wherein the second cost function is used to characterize the degree of deviation between the actual current of the permanent magnet synchronous motor and the given current within the duration of action; obtaining the minimum value of the multiple second cost function values, and taking the candidate voltage vector corresponding to the minimum value as the optimal voltage vector.

[0023] According to one embodiment of the present invention, the second cost function is:

[0024]

[0025] Where f2 is the value of the second cost function, i q (t0) represents the q-axis component of the actual current of the permanent magnet synchronous motor at time t0. ac,n Let k be the duration of the nth voltage vector as a candidate voltage vector. q,n (t0) represents the rate of change of the q-axis current corresponding to the nth voltage vector at time t0. For t0+T ac,n The q-axis component of the given current is given at any given time, where t0 is the current time.

[0026] According to one embodiment of the present invention, the predicted current model is constructed in the following manner: a current model of a permanent magnet synchronous motor is constructed in the dq axis coordinate system; the current model is then discretized and linearized sequentially to obtain the predicted current model.

[0027] According to one embodiment of the present invention, the predicted current model is expressed in the following manner:

[0028]

[0029]

[0030] in, The d-axis and q-axis components of the nth predicted current at time t0+T' are respectively, k d,n (t0), k q,n (t0) represent the d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0, respectively. d (t0), i q (t0) represents the d-axis and q-axis components of the actual current of the permanent magnet synchronous motor at time t0, where t0 is the current time, T' is the duration of the voltage vector, and u d (t0), u q(t0) represents the d-axis and q-axis components of the actual voltage of the permanent magnet synchronous motor at time t0, respectively. S L S These are the stator resistance and stator inductance of a permanent magnet synchronous motor, ω. e The electrical angular frequency of the permanent magnet synchronous motor. These are the d-axis and q-axis components of the stator flux linkage of the permanent magnet synchronous motor at time t0, respectively.

[0031] According to one embodiment of the present invention, the range of variation of the operating duration is determined based on the maximum allowable switching frequency of the inverter and the computing power of the processor.

[0032] According to one embodiment of the present invention, the range of variation in the duration of action is expressed in the following manner:

[0033]

[0034] Among them, T c,min T is the minimum permissible duration of action. c,max For the maximum permissible duration of action, T min =1 / f max f max T is the maximum permissible switching frequency of the inverter. cal This represents the processor's maximum computational latency.

[0035] According to one embodiment of the present invention, the upper limit of the minimum permissible operating time is determined based on the actual current fluctuation range and DC bus voltage of the permanent magnet synchronous motor.

[0036] According to one embodiment of the present invention, the upper limit of the minimum permissible duration of action is expressed in the following manner:

[0037]

[0038] Among them, T c,min U is the minimum permissible duration of action. dc i is the DC bus voltage. d,offset i q,offset These are the maximum d-axis and q-axis fluctuation values ​​of the actual current of the permanent magnet synchronous motor, respectively. S This is the stator inductance of a permanent magnet synchronous motor.

[0039] According to one embodiment of the present invention, the switching transistor in the inverter is a gallium nitride switching transistor.

[0040] To achieve the above objectives, a second aspect of the present invention provides a computer-readable storage medium having a program stored thereon that, when executed by a processor, implements the aforementioned method.

[0041] According to the computer-readable storage medium of the present invention, the aforementioned method enables the motor to operate according to the optimal voltage vector and optimal operating time in the inverter determined according to control requirements, thereby improving the overall steady-state performance of the motor and reducing the amount of computation and the complexity of the control method.

[0042] To achieve the above objectives, a third aspect of the present invention provides a predictive current control system for a permanent magnet synchronous motor, comprising: a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the aforementioned method.

[0043] According to the predictive current control system of the permanent magnet synchronous motor of the present invention, the motor can be made to operate according to the optimal voltage vector and optimal action time in the inverter determined according to the control requirements by means of the aforementioned method, thereby improving the overall steady-state performance of the motor and reducing the amount of calculation and the complexity of the control method.

[0044] To achieve the above objectives, a fourth aspect of the present invention provides a predictive current control device for a permanent magnet synchronous motor. The device includes: a prediction module for predicting the current of each voltage vector among multiple voltage vectors of an inverter based on a predictive current model, thereby obtaining multiple predicted currents; a first screening module for screening the multiple voltage vectors according to the multiple predicted currents and a first cost function, thereby obtaining candidate voltage vectors; a duration determination module for determining the duration of action of the candidate voltage vectors; a second screening module for screening the multiple candidate voltage vectors according to the duration of action of the multiple candidate voltage vectors and a second cost function if multiple candidate voltage vectors are included, thereby obtaining an optimal voltage vector; and a control module for controlling the inverter according to the optimal voltage vector and the duration of action of the optimal voltage vector, thereby controlling the operation of the permanent magnet synchronous motor.

[0045] According to an embodiment of the present invention, a predictive current control device for a permanent magnet synchronous motor predicts the current of each voltage vector among multiple voltage vectors of the inverter based on a predictive current model by a prediction module, obtaining multiple predicted currents. A first screening module then determines candidate voltage vectors based on the multiple predicted currents and a first cost function. Simultaneously, a duration determination module determines the duration of action of the candidate voltage vectors. When multiple candidate voltage vectors are included, a second screening module further selects the optimal voltage vector based on the duration of action of the candidate voltage vectors and a second cost function. Finally, a control module controls the permanent magnet synchronous motor to operate according to the optimal voltage vector and its duration of action. This enables the motor to operate according to the optimal voltage vector and optimal duration of action in the inverter determined according to control requirements, thereby improving the overall steady-state performance of the motor. Furthermore, when determining the duration of action, only the duration of action of the candidate voltage vectors needs to be calculated, reducing the computational load and thus lowering the complexity of the method, achieving optimization of the control method.

[0046] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0047] Figure 1 A circuit diagram of an inverter according to an embodiment of the present invention;

[0048] Figure 2 A flowchart of a predictive current control method for a permanent magnet synchronous motor according to an embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of multiple voltage vectors and a given voltage vector of an inverter according to an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of multiple predicted currents and given currents of an inverter according to an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram illustrating the direction of a given voltage vector according to an embodiment of the present invention;

[0052] Figure 6 This is a geometrical diagram of a given voltage vector and the voltage vector of an inverter according to an embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram comparing the d-axis component variation of motor current when a motor is controlled by a control method according to an embodiment of the present invention and related technologies.

[0054] Figure 8This is a schematic diagram comparing the q-axis component variation of the motor current when the control method according to an embodiment of the present invention controls the motor with related technologies.

[0055] Figure 9 A schematic diagram of a predictive current control system for a permanent magnet synchronous motor according to an embodiment of the present invention;

[0056] Figure 10 This is a schematic diagram of the predictive current control device for a permanent magnet synchronous motor according to an embodiment of the present invention. Detailed Implementation

[0057] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0058] The following description, with reference to the accompanying drawings, outlines the predictive current control method and apparatus for permanent magnet synchronous motors, a storage medium, and a predictive current control system for permanent magnet synchronous motors, as proposed in embodiments of the present invention.

[0059] It should be noted that the predictive current control method for permanent magnet synchronous motors in this embodiment of the invention can be applied to... Figure 1 In the inverter shown, reference Figure 1 As shown, the inverter 100 is connected to the DC power supply Vdc and the motor 200 respectively. The inverter 100 includes: a first switching transistor S1 to a sixth switching transistor S6.

[0060] The positive terminal of the DC power supply Vdc is connected to the first terminals of the first switch S1, the third switch S3, and the fifth switch S5, respectively. The negative terminal of the DC power supply Vdc is connected to one end of the bus sampling resistor R, and the other end of the bus sampling resistor R is connected to the second terminals of the second switch S2, the fourth switch S4, and the sixth switch S6, respectively. The second terminal of the first switch S1 is connected to the first terminal of the second switch S2 and phase A of the motor 200, the second terminal of the third switch S3 is connected to the first terminal of the fourth switch S4 and phase B of the motor 200, and the second terminal of the fifth switch S5 is connected to the first terminal of the sixth switch S6 and phase C of the three-phase motor. Each of the first switch S1 to the sixth switch S6 has a parasitic diode (D1 to D6). By controlling the conduction and cutoff of the first switch S1 to the sixth switch S6, the DC power supply Vdc can be inverted into AC power to drive the motor 200.

[0061] Figure 2 The flowchart below shows a predictive current control method for a permanent magnet synchronous motor according to an embodiment of the present invention. (Refer to...) Figure 2As shown, the method includes:

[0062] S11, based on the predicted current model, performs current prediction on each of the multiple voltage vectors of the inverter to obtain multiple predicted currents.

[0063] Specifically, refer to Figure 1 As shown, the inverter includes three bridge arms: phase A, phase B, and phase C. Depending on the on / off state of these three bridge arms, the inverter can output multiple voltage vectors, including six basic voltage vectors and two zero-voltage vectors, such as... Figure 3 As shown, by constructing a predictive current model, inputting multiple voltage vectors into the predictive current model, and simultaneously setting the duration of action of these multiple voltage vectors to the same duration, multiple predictive currents can be predicted.

[0064] In some embodiments, the predicted current model is constructed as follows: a current model of a permanent magnet synchronous motor is constructed in the dq-axis coordinate system; the current model is then discretized and linearized sequentially to obtain the predicted current model.

[0065] Furthermore, the predicted current model is expressed in the following way:

[0066]

[0067]

[0068] in, The d-axis and q-axis components of the nth predicted current at time t0+T' are respectively, k d,n (t0), k q,n (t0) represent the d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0, respectively. d (t0), i q (t0) represents the d-axis and q-axis components of the actual current of the permanent magnet synchronous motor at time t0, where t0 is the current time, T' is the duration of the voltage vector, and u d (t0), u q (t0) represents the d-axis and q-axis components of the actual voltage of the permanent magnet synchronous motor at time t0, respectively. S L S These are the stator resistance and stator inductance of a permanent magnet synchronous motor, ω. e The electrical angular frequency of the permanent magnet synchronous motor. These are the d-axis and q-axis components of the stator flux linkage of the permanent magnet synchronous motor at time t0, respectively.

[0069] Specifically, refer to Figure 3As shown, the motor current can be decoupled using the dq-axis method to calculate the motor current components separately. Assuming the inverter's A, B, and C phase windings are perfectly symmetrical, and disregarding non-ideal characteristics of the switching transistors and motor magnetic saturation, etc., the following approach is adopted. Figure 1 The current model of the inverter-driven motor during operation can be constructed according to the following formula (3):

[0070]

[0071] in, i dq (t), Let R represent the voltage vector, current vector, and flux linkage of the stator of the permanent magnet synchronous motor, respectively, and all three are vectors. S and L S ω represents the resistance and inductance of the motor stator, respectively. e The electric angular frequency of the motor, n p T represents the number of pole pairs of the motor. e This refers to the output electromagnetic torque of the motor. Additionally, the magnetic flux linkage... Through the current vector i dq The calculation yields the specific formula shown in formula (4) below:

[0072]

[0073] Where, φ m L represents the flux linkage of a permanent magnet. S i represents the inductance of the motor stator. dq (t) represents the current vector of the stator of the permanent magnet synchronous motor.

[0074] Subsequently, when the duration of the voltage vector is short, the effect of the change in motor angle caused by it can be ignored. At the same time, assuming that the motor speed remains constant during the duration of the voltage vector, the above current model can be discretized to obtain the following formula (5):

[0075]

[0076] in, It is the predicted current vector at the end of the k-th control cycle, i.e., the predicted current vector at the beginning of the (k+1)-th control cycle; i dq (k) is the current value sampled and measured at the beginning of the k-th control cycle. It is the stator flux linkage, which can be obtained through sampling. dq (k) Input the above formula (4) to calculate and obtain T. c It is the duration of the inverter's voltage vector, u dq (k) is the voltage vector of the inverter, R Sand L S ω represents the resistance and inductance of the motor stator, respectively. e This indicates the electrical angular frequency of the motor.

[0077] Typically, during the motor control process, at the beginning of the kth control cycle, the inverter acquires the given voltage vector. There are errors between the given voltage vector and multiple voltage vectors of the inverter, such as... Figure 3 As shown, the inverter's voltage vectors include eight vectors, V0 to V7, where the vector directions of V1 to V6 are as follows: Figure 3 As shown, V0 and V7 are zero-voltage vectors (not illustrated). Figure 3 Δu dq (k) represents the voltage vector V1 of the inverter and the given voltage vector. The difference will also be reflected in the predicted current vector. Multiple voltage vectors of the inverter can be input into the above formula (5) to predict multiple current vectors under multiple voltage vectors V0 to V7. like Figure 4 As shown, where This is the given current for the k-th control cycle, which is the motor stator current at the end of the k-th cycle determined according to the control requirements. Figure 4 The thin dashed line shown represents the difference between the given current and multiple predicted current vectors.

[0078] Meanwhile, since the d-axis current component and q-axis current component of the motor are coupled during actual operation, the above formula (5) can be linearized to further improve the accuracy of the predicted current. Therefore, the predicted current of the motor can be expressed according to the above formula (1), where the rate of change k d,n (t0), k q,n (t0) can be calculated by transforming the above formula (3) to obtain the above formula (2). From the above formulas (1) to (2), it can be seen that when the fixed parameters such as the stator inductance and resistance of the motor are obtained, the d-axis component and q-axis component of the nth predicted current of the motor can be accurately predicted by the above formulas (1) to (2) after the nth voltage vector output by the inverter starts from time t0 and lasts for time T'.

[0079] In some embodiments, the range of variation in duration is determined based on the inverter’s maximum allowable switching frequency and the processor’s computing power.

[0080] Furthermore, the range of variation in duration of action is expressed by the following formula (6):

[0081]

[0082] Among them, T c,minT is the minimum permissible duration of action. c,max T is the maximum permissible duration of action. min =1 / f max f max T is the maximum permissible switching frequency of the inverter. cal This represents the processor's maximum computational latency.

[0083] Specifically, when determining the predicted current in S11, it is necessary to determine the duration of the voltage vector, which is limited by various parameters within the motor. For example, the allowable duration of the voltage vector is limited by the switching frequency of the inverter's switching transistors. Therefore, referring to formula (6), the minimum allowable duration of the voltage vector needs to be greater than the minimum allowable switching period T of the inverter. min Meanwhile, since the control method in this embodiment of the invention adopts single-step delay compensation, that is, each voltage vector transformation of the motor is calculated to determine its optimal action duration, the action duration of the motor needs to be greater than the maximum calculation delay of the processor. Thus, the range of values ​​for the minimum allowable action duration can be determined. Subsequently, based on actual experimental experience, the motor control effect is best when the maximum allowable action duration of the voltage vector is set to about four times the minimum allowable action duration. Therefore, the maximum allowable action duration can be set to four times the minimum allowable action duration to obtain the best control effect.

[0084] In some embodiments, the upper limit of the minimum permissible operating time is determined based on the actual current fluctuation range of the permanent magnet synchronous motor and the DC bus voltage.

[0085] Furthermore, the upper limit of the minimum allowed duration of action is expressed in the following way:

[0086]

[0087] Among them, T c,min U is the minimum permissible duration of action. dc i is the DC bus voltage. d,offset i q,offset These are the maximum d-axis and q-axis fluctuation values ​​of the actual current of the permanent magnet synchronous motor, respectively. S This is the stator inductance of a permanent magnet synchronous motor.

[0088] Specifically, when controlling the motor, it is necessary to first obtain the given voltage vector according to the control requirements of the motor, and then calculate the given current at the next moment based on the given voltage vector at the current moment, the duration of the voltage vector, and the motor current at the current moment. The specific formula is shown in the following formula (8):

[0089]

[0090] in, The given voltage vector u of the motor at time t0 * Under the influence of (t0), at t0+T c,min The predicted current at time t, which is the given current t0 is the current time, T c,min R is the minimum permissible duration of the voltage vector. S and L S ω represents the resistance and inductance of the motor stator, respectively. e Indicates the electrical angular frequency of the motor. This represents the magnetic flux linkage of the motor. Based on the above formula (8), the corresponding given current can be determined from the given voltage vector. Typically, the given voltage vector and given current of the motor are given by the outer loop PID controller of the predictive control system. Meanwhile, at t0+T... c,min At any given moment, if the difference between the predicted current and the given current's d-axis or q-axis component exceeds the corresponding maximum fluctuation value, the stable operation of the motor will be disturbed, thus affecting its steady-state performance. Typically, for common surface-mounted permanent magnet synchronous motors, the q-axis component of the motor current is used to output electromagnetic torque, while the d-axis component is generally set to zero to improve the overall system power factor and reduce the coupling effect between the d-axis and q-axis components, facilitating decoupling. Therefore, in this embodiment of the invention, the maximum fluctuation value i of the actual current's d-axis component of the permanent magnet synchronous motor can be set. d,offset The maximum fluctuation value i of the q-axis component is greater than or equal to q,offset Both are greater than zero.

[0091] Since the motor current is affected by the duration of the voltage vector, the minimum allowable duration of the voltage vector is also limited by the actual current fluctuation range of the permanent magnet synchronous motor, thus yielding the above formula (7). The specific derivation process of formula (7) is as follows:

[0092] First, assuming the inverter's DC bus voltage is sufficiently high and undervoltage does not occur, then during the motor's steady-state operation, the given voltage vector must fall within the hexagonal region formed by the six effective voltage vectors of the inverter. Figure 5 As shown, for reference Figure 5 As shown, the six voltage vectors of the inverter can be divided into six sectors (SV1 to SV6), and a given voltage vector can be... Figure 5 shown One of them can also fall in other sectors. When a given voltage vector is determined, the voltage vector of the inverter closest to it can be determined based on the given voltage vector. For ease of expression, the cost function can be set as shown in the following formula (9):

[0093]

[0094] Where g1 is the cost function value, Given a current, For the motor at t0+T c,min The predicted current is obtained by combining multiple voltage vectors of the inverter with the minimum allowable duration T. c,min By inputting formula (1), multiple predicted currents can be obtained. Inputting these multiple predicted currents into formula (9) yields multiple cost function values, which represent the degree of error between the inverter's voltage vector and the given voltage vector. Let u be the voltage vector with the smallest cost function value. dq (t0), then the voltage vector u dq (t0) and given voltage vector u dq * The geometric relationship of (t0) can be as follows: Figure 6 As shown, for reference Figure 6 As shown, given voltage vector u dq * If (t0) falls within sector SV2 of the inverter, then the voltage vector V2 is u. dq (t0), at this time, given voltage vector u dq * Possible cases of (t0) are as follows Figure 6 As shown in the figure, from the geometric figures of the two, it can be seen that when the given voltage vector coincides with the voltage vector SV2, the difference between the given voltage vector and the inverter voltage vector is |Δu dq | is zero when the given voltage vector is Figure 5 When the solid line at the edge of the sector in the diagram represents the difference |Δu dq The maximum value is the difference between the given voltage vector and the inverter's voltage vector. Figure 6 The vector |Δu dq | max Furthermore, based on the geometric relationship between the given voltage vector and the inverter voltage vector at this time, the following formula (10) can be obtained:

[0095]

[0096] Where, |Δu dq | is the difference between the given voltage vector and the inverter's voltage vector, u dq (t0) is the voltage vector that minimizes the cost function value g1 among multiple voltage vectors of the inverter, u dq * (t0) is the given voltage vector at time t0, U dc This refers to the DC bus voltage of the inverter, and the coefficient of the DC bus voltage is calculated based on the constant amplitude Clarke transform, which converts the three-phase current into the two-phase stationary current. Figure 5 and Figure 6The α and β coordinate system in the diagram. It should be noted that in... Figure 5 In the other sectors shown, due to the given voltage vector and voltage vector u dq The geometric relationship of (t0) is similar, so the above formula (10) still holds.

[0097] At the same time, based on the above formula (8), the following formula (11) can be obtained:

[0098]

[0099] in, This indicates that the motor is in voltage vector u dq Under the influence of (t0), at t0+T c,min The predicted current at time t is given. The meanings of the other physical quantities are the same as in formula (8) above, and will not be repeated here. Combining formulas (10) and (11) above, we can obtain the following formula (12):

[0100]

[0101] in, This represents the difference between the predicted current and the given current. Indicates at t0+T c,min Predicted current when multiple voltage vectors act on the motor at any given time. For a given current, U dc This is the DC bus voltage of the inverter.

[0102] Meanwhile, since the motor rotor is constantly rotating, that is, the d-axis component and q-axis component of the motor current are constantly changing, the above formula (12) can be extended to the following formula (13):

[0103]

[0104] Among them, i d and i q These are the d-axis and q-axis components of a given current, respectively. Indicates at t0+T c,min Predicted current U when multiple voltage vectors act on the motor at any given time dc This is the DC bus voltage of the inverter. Based on the aforementioned information, the motor operates at t0+T. c,min The predicted current at any given time needs to be less than the maximum current change value to ensure steady-state operation of the motor, thus enabling the above formula (7).

[0105] Therefore, by setting the upper limit of the minimum allowable operating time of the motor according to the above formula (7), the operating time of the inverter's voltage vector is made to be greater than the upper limit, thus ensuring the stable operation of the motor and improving the steady-state performance of the motor.

[0106] In some embodiments, the switching transistors in the inverter are gallium nitride (GaN) transistors.

[0107] Specifically, since the dead-time effect of gallium nitride (GaN) switches is significantly reduced compared to traditional inverters, and their switching characteristics are closer to ideal switches, the motor current generated by inverters using GaN switches is closer to the linearized predicted current model, thus making the predicted current model of the motor more accurate.

[0108] S12, based on multiple predicted currents and the first cost function, multiple voltage vectors are filtered to obtain candidate voltage vectors;

[0109] In some embodiments, the method further includes: if there is one candidate voltage vector, then determining the candidate voltage vector as the optimal voltage vector.

[0110] Furthermore, based on multiple predicted currents and a first cost function, multiple voltage vectors are screened to obtain candidate voltage vectors. This includes: inputting multiple predicted currents into the first cost function for calculation to obtain multiple first cost function values, wherein the first cost function is used to characterize the degree of deviation between the predicted current and the given current; if the first cost function value is equal to zero, then the voltage vector corresponding to the first cost function value is determined as a candidate voltage vector; if multiple first cost function values ​​are not equal to zero, then the minimum value of the multiple first cost function values ​​is obtained, and the voltage vector corresponding to the minimum value is taken as a candidate voltage vector.

[0111] Specifically, the first cost function is used to characterize the degree of deviation between the predicted current and the given current. The given current is calculated based on the given voltage vector and the given duration of action using the above formula (8). The given duration of action is the same as the duration of action input in the above formulas (1) to (2). Therefore, after inputting the multiple predicted currents calculated by S11 into the first cost function, the magnitude of the multiple first cost function values ​​can represent the degree of deviation between the multiple voltage vectors of the inverter and the given voltage vector. When one or more first cost function values ​​are equal to zero, it means that the deviation between the voltage vector corresponding to these one or more cost function values ​​and the target voltage vector is within the acceptable range. When multiple first cost function values ​​are not equal to zero, it means that the degree of deviation between the multiple voltage vectors and the target voltage vector is outside the acceptable range. At this time, the minimum value of the multiple first cost function values ​​can be obtained, and the voltage vector corresponding to the minimum value can be used as the candidate voltage vector, so that the predicted current corresponding to the candidate voltage vector is closest to the given current.

[0112] Meanwhile, when there is only one candidate voltage vector determined by the above method, it means that the candidate voltage vector is the one that is closest to the target voltage vector among the multiple voltage vectors output by the inverter. At this time, the candidate voltage vector can be determined as the optimal voltage vector to obtain the best control effect on the motor.

[0113] In some embodiments, the first cost function may be the following formula (13):

[0114]

[0115] Where f1 is the value of the first cost function, and μ1 and μ2 are the weights. These are the d-axis and q-axis components of the nth predicted current at time t0+T', respectively. Let i be the d-axis component and q-axis component of the given current at time t0+T', where t0 is the current time and T' is the duration of the voltage vector. d,offset i q,offset These represent the maximum fluctuation values ​​of the d-axis component and the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

[0116] Specifically, a suitable minimum permissible action time T can be selected within the range of the minimum permissible action time determined by the above formulas (6) to (7). c,min As the duration of action T', the minimum allowable duration of action T c,min By inputting the multiple voltage vectors of the inverter one by one into the above formula (14), the d-axis component of the nth predicted current at time t0+T' can be obtained. when d-axis component of a given current The difference is less than the maximum fluctuation value i of the d-axis component of the actual current of the permanent magnet synchronous motor. d,offset When t0+T', the weight μ1 is zero; otherwise, the weight μ1 is 1. Similarly, when the nth predicted current q-axis component is at time t0+T', the weight μ1 is zero. With respect to the q-axis component of the given current The difference is less than the maximum fluctuation value i of the q-axis component of the actual current of the permanent magnet synchronous motor. q,offsetWhen the predicted current is within the maximum fluctuation range of the actual motor current, the weight μ2 is zero; otherwise, the weight μ2 is 1. Therefore, when both the d-axis and q-axis components of the predicted current are within the maximum fluctuation range of the actual motor current, the first cost function value f1 is zero. When one or more of the d-axis and q-axis components of the predicted current exceed the corresponding maximum fluctuation range, the first cost function value f1 is equal to the square of the difference between the predicted current and the given current in that axis component (referring to the d-axis component or q-axis component of the predicted current that exceeds the corresponding maximum fluctuation range). The larger the difference between the predicted current and the given current in that axis component, that is, the greater the deviation between the predicted current and the given current, the larger the corresponding first cost function value. Thus, the first cost function can characterize the degree of deviation between the predicted current and the given current.

[0117] S13, determine the duration of action of the candidate voltage vector;

[0118] In some embodiments, determining the duration of action of a candidate voltage vector includes: if there are multiple candidate voltage vectors, or if there is one candidate voltage vector that corresponds to zero, then the duration of action of the candidate voltage vector is determined based on the rate of change of current corresponding to the candidate voltage vector and the actual current fluctuation range of the permanent magnet synchronous motor; if there is one candidate voltage vector that corresponds to the minimum value, then the duration of action of the candidate voltage vector is the minimum allowable duration of action.

[0119] Specifically, after determining the candidate voltage vector, it is also necessary to determine the duration of its action to ensure better motor control. The method is as follows: When the candidate voltage vector includes a single voltage vector corresponding to the minimum value, it indicates that when this voltage vector acts on the motor for the minimum allowable duration, the predicted current determined by the predicted current model will exceed the maximum fluctuation range of the motor current, thus affecting the normal operation of the motor. Therefore, the duration of this voltage vector should be shortened as much as possible to reduce its impact on the motor. Thus, the duration of this candidate voltage vector can be determined as the minimum allowable duration. When the candidate voltage vector includes multiple voltage vectors or includes a single voltage vector corresponding to zero, it indicates that when this candidate voltage vector acts on the motor for the minimum allowable duration, the predicted current is within the maximum fluctuation range of the motor current. In this case, the most suitable duration can be selected based on the current change rate corresponding to the candidate voltage vector and the actual current fluctuation range of the permanent magnet synchronous motor to optimize the motor control effect.

[0120] Furthermore, the duration of action of the candidate voltage vector is determined using the following formula (15):

[0121]

[0122] Among them, T ac,nThe duration of the nth voltage vector as a candidate voltage vector, where max represents the maximum value to be obtained. The d-axis and q-axis components of the nth predicted current at time t0+T' are respectively, k d,n (t0), k q,n (t0) represents the d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0, respectively. Let i be the d-axis component and q-axis component of the given current at time t0+T', where t0 is the current time and T' is the duration of the voltage vector. d,offset i q,offset These represent the maximum fluctuation values ​​of the d-axis component and the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

[0123] Specifically, when the candidate voltage vector includes multiple voltage vectors or the candidate voltage vector includes one voltage vector corresponding to zero, the duration of action can be calculated using the above formula (15). The d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0 can be calculated using the above formula (2). The above formula (15) can determine the set of all durations of action that can limit the d-axis and q-axis components of the predicted current to the maximum fluctuation range. Subsequently, the maximum value in this set can be selected as the duration of action of the candidate voltage vector, thereby minimizing the operating frequency of the switching transistors in the inverter and reducing the switching losses of the inverter without reducing the control effect on the motor.

[0124] In related technologies, it is usually necessary to calculate the duration of action of multiple voltage vectors of the inverter. As mentioned above, the calculation of the duration of action of voltage vectors is complex and computationally intensive, which increases the complexity of the motor control method. However, in this embodiment of the invention, after preliminary screening of multiple voltage vectors of the inverter through a first cost function, it is only necessary to determine the duration of action of the candidate voltage vectors that have passed the screening, thereby significantly reducing the amount of computation and simplifying the control method. At the same time, preliminary screening of the number of voltages of the inverter through the first cost function can also remove some voltage vectors with poor control effect, avoiding these voltage vectors from interfering with subsequent vector selection, thereby improving the accuracy of the control method in determining the optimal voltage vector and thus optimizing the control effect on the motor.

[0125] S14. If there are multiple candidate voltage vectors, the multiple candidate voltage vectors are filtered according to the duration of action of the multiple candidate voltage vectors and the second cost function to obtain the optimal voltage vector.

[0126] In some embodiments, the optimal voltage vector is obtained by filtering multiple candidate voltage vectors based on the duration of action of multiple candidate voltage vectors and a second cost function. This includes: inputting the duration of action of multiple candidate voltage vectors into the second cost function for calculation to obtain multiple second cost function values; wherein the second cost function is used to characterize the degree of deviation between the actual current of the permanent magnet synchronous motor and the given current within the duration of action; obtaining the minimum value of the multiple second cost function values, and taking the candidate voltage vector corresponding to the minimum value as the optimal voltage vector.

[0127] Furthermore, the second cost function is given by the following formula (16):

[0128]

[0129] Where f2 is the value of the second cost function, i q (t0) represents the q-axis component of the actual current of the permanent magnet synchronous motor at time t0. ac,n Let k be the duration of the nth voltage vector as a candidate voltage vector. q,n (t0) represents the rate of change of the q-axis current corresponding to the nth voltage vector at time t0. For t0+T ac,n The q-axis component of the given current is given at any given time, where t0 is the current time.

[0130] Specifically, when the candidate voltage vectors and their durations are determined, the rate of change k of the q-axis current corresponding to the nth voltage vector at time t0 is... q,n (t0) can be calculated using the formula (2) above, t0+T ac,n q-axis component of the given current at any given time It can be calculated using the above formula (8), or obtained directly from the outer loop PID controller.

[0131] The second cost function value is used to describe, based on the aforementioned predicted current model, when the nth voltage vector is used as a candidate voltage vector and continues for the duration determined by the above formula (15), the q-axis component of the actual motor current and the time at t0+T ac,n The average value of the difference between the q-axis components of the given current at time t0 is used to calculate the second cost function. Therefore, when there are multiple candidate voltage vectors, the multiple candidate voltage vectors and the determined duration of action can be input into the above formula (16) for calculation. The smaller the calculated value of the second cost function, the closer the average value of the actual current generated by the candidate voltage vector within the duration of action is to the q-axis component of the given current at time t0. The better the control effect of the candidate voltage vector is, the better the control effect of the candidate voltage vector is. Thus, the second cost function can be used to characterize the degree of deviation between the actual current of the permanent magnet synchronous motor and the given current within the duration of action.

[0132] When multiple candidate voltage vectors exist, the corresponding second cost function value can be calculated using the action duration and the second cost function determined in S13. Since the second cost function is used to characterize the deviation between the actual current of the permanent magnet synchronous motor and the given current within the action duration, and the smaller the value of the second cost function, the smaller the deviation between the actual current and the given current when the candidate voltage vector corresponding to the second cost function value acts on the motor, the minimum value among multiple second cost function values ​​can be obtained, and the candidate voltage vector corresponding to the minimum value can be used as the optimal voltage vector, so that the actual current generated by the voltage vector of the inverter is closer to the given current, thereby obtaining the optimal control effect on the motor and enhancing the steady-state performance of the motor.

[0133] S15 controls the inverter based on the optimal voltage vector and the duration of the optimal voltage vector to control the operation of the permanent magnet synchronous motor.

[0134] Specifically, once the optimal voltage vector and its duration are determined, the inverter can be controlled to continuously output the optimal vector for the determined duration, thereby minimizing the difference between the actual current of the motor and the given current, achieving optimal control of the motor, and improving the motor's steady-state performance.

[0135] As a concrete example, see reference Figures 7-8 As shown, in related technologies, when a fixed-step prediction method is used to control motor operation, the motor current is prone to exceeding the maximum variation range due to incorrect selection of the optimal voltage vector. Figure 7 As shown by the solid line; or because the duration of the voltage vector's action is too short, the switching frequency of the switching transistor is too high, resulting in high switching losses, such as... Figure 8 As shown by the solid line, in this embodiment of the invention, the optimal voltage vector can be determined in real time, and the duration of the optimal voltage vector can be extended as much as possible within the allowable fluctuation range of the motor current, such as... Figures 7-8 As shown by the dotted line, this not only ensures that the motor current fluctuation is within the maximum allowable range, improving the motor's steady-state performance, but also reduces the switching frequency of the switching transistor under the same control level, thereby reducing switching losses.

[0136] In summary, according to the embodiments of the present invention, by predicting the predicted current corresponding to multiple voltage vectors of the inverter based on the predicted current model, and by discretizing and linearizing the current model during its construction to determine the current change slope, the influence of current coupling on the current change rate is reduced, thereby improving the accuracy of current prediction. Simultaneously, by setting a first cost function to characterize the degree of deviation between the predicted current and the given current, multiple voltage vectors are initially screened to determine candidate voltage vectors and calculate the corresponding optimal action duration. This reduces the computational load in determining the action duration, lowers the complexity of the control method, and avoids introducing non-linearity. The optimal control method improves the steady-state performance of the control method. Secondly, when determining the candidate voltage vector, the action time of the candidate voltage vector is set to the maximum value within the allowable range, thereby reducing the switching frequency and switching losses under the same control level. In addition, when there are multiple candidate voltage vectors, a second cost function is set to characterize the difference between the average value of the predicted current and the given current within the action time, thereby selecting the candidate voltage vector with the best motor control effect from multiple candidate voltage vectors as the optimal voltage vector to control the inverter, and then control the motor operation, further improving the steady-state performance of the motor and realizing the optimization of the motor control method.

[0137] Corresponding to the above embodiments, this embodiment of the invention also provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the aforementioned method.

[0138] According to the computer-readable storage medium of the present invention, the aforementioned method enables the motor to operate according to the optimal voltage vector and optimal operating duration among multiple voltage vectors of the inverter, thereby improving the overall steady-state performance of the motor, reducing the amount of computation, lowering the complexity of the control method, reducing the switching frequency, and reducing switching losses, thus achieving comprehensive optimization of the motor control method.

[0139] Corresponding to the above embodiments, this invention also provides a predictive current control system for a permanent magnet synchronous motor, referencing... Figure 9 As shown, the system 200 includes: a memory 210, a processor 220, and a program stored in the memory 210 and executable on the processor 220. When the processor 220 executes the program, it implements the aforementioned method.

[0140] According to the predictive current control system of the permanent magnet synchronous motor of the present invention, the motor can operate according to the optimal voltage vector and the optimal operating time among the multiple voltage vectors of the inverter through the aforementioned method, thereby improving the overall steady-state performance of the motor, reducing the amount of calculation, reducing the complexity of the control method, reducing the switching frequency, reducing the switching loss, and realizing a comprehensive optimization of the motor control method.

[0141] Corresponding to the above embodiments, this embodiment of the invention also provides a predictive current control device 300 for a permanent magnet synchronous motor, see reference. Figure 10 As shown, the device 300 includes: a prediction module 310, a first screening module 320, a duration determination module 330, a second screening module 340, and a control module 350.

[0142] The system includes a prediction module 310 for predicting the current of each voltage vector in the inverter based on a predicted current model, resulting in multiple predicted currents; a first screening module 320 for screening multiple voltage vectors based on multiple predicted currents and a first cost function, resulting in candidate voltage vectors; a duration determination module 330 for determining the duration of action of the candidate voltage vectors; a second screening module 340 for screening multiple candidate voltage vectors based on their duration and a second cost function if multiple candidate voltage vectors are included, resulting in an optimal voltage vector; and a control module 350 for controlling the inverter based on the optimal voltage vector and its duration, thereby controlling the operation of the permanent magnet synchronous motor.

[0143] According to one embodiment of the present invention, the second screening module 340 is further configured to: if the candidate voltage vector includes one, then determine the candidate voltage vector as the optimal voltage vector.

[0144] According to an embodiment of the present invention, the first screening module 320 is further configured to: input multiple predicted currents into a first cost function for calculation to obtain multiple first cost function values, wherein the first cost function is used to characterize the degree of deviation between the predicted current and the given current; if the first cost function value is equal to zero, then determine the voltage vector corresponding to the first cost function value as a candidate voltage vector; if multiple first cost function values ​​are not equal to zero, then obtain the minimum value of the multiple first cost function values, and take the voltage vector corresponding to the minimum value as a candidate voltage vector.

[0145] According to one embodiment of the present invention, the first cost function is:

[0146]

[0147]

[0148]

[0149] Where f1 is the value of the first cost function, and μ1 and μ2 are the weights. These are the d-axis and q-axis components of the nth predicted current at time t0+T', respectively. Let i be the d-axis component and q-axis component of the given current at time t0+T', where t0 is the current time and T' is the duration of the voltage vector.d,offset i q,offset These represent the maximum fluctuation values ​​of the d-axis component and the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

[0150] According to one embodiment of the present invention, the duration determination module 330 is further configured to: if the candidate voltage vector includes multiple candidates, or if the candidate voltage vector includes one candidate voltage vector and is a voltage vector corresponding to zero, then determine the duration of action of the candidate voltage vector based on the current change rate corresponding to the candidate voltage vector and the actual current fluctuation range of the permanent magnet synchronous motor; if the candidate voltage vector includes one candidate voltage vector and is a voltage vector corresponding to the minimum value, then the duration of action of the candidate voltage vector is the minimum allowable duration of action.

[0151] According to one embodiment of the present invention, the duration of action of the candidate voltage vector is determined by the following method:

[0152] T ac,n =maxT'

[0153]

[0154] Among them, T ac,n The duration of the nth voltage vector as a candidate voltage vector, where max represents the maximum value to be obtained. The d-axis and q-axis components of the nth predicted current at time t0+T' are respectively, k d,n (t0), k q,n (t0) represents the d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0, respectively. Let i be the d-axis component and q-axis component of the given current at time t0+T', where t0 is the current time and T' is the duration of the voltage vector. d,offset i q,offset These represent the maximum fluctuation values ​​of the d-axis component and the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

[0155] According to one embodiment of the present invention, the second screening module 340 is further configured to: input the duration of action of multiple candidate voltage vectors into the second cost function for calculation to obtain multiple second cost function values; wherein, the second cost function is used to characterize the degree of deviation between the actual current of the permanent magnet synchronous motor and the given current within the duration of action; obtain the minimum value of the multiple second cost function values, and take the candidate voltage vector corresponding to the minimum value as the optimal voltage vector.

[0156] According to one embodiment of the present invention, the second cost function is:

[0157]

[0158] Where f2 is the value of the second cost function, iq (t0) represents the q-axis component of the actual current of the permanent magnet synchronous motor at time t0. ac,n Let k be the duration of the nth voltage vector as a candidate voltage vector. q,n (t0) represents the rate of change of the q-axis current corresponding to the nth voltage vector at time t0. For t0+T ac,n The q-axis component of the given current is given at any given time, where t0 is the current time.

[0159] According to one embodiment of the present invention, the predicted current model is constructed in the following manner: a current model of a permanent magnet synchronous motor is constructed in the dq axis coordinate system; the current model is then discretized and linearized sequentially to obtain the predicted current model.

[0160] According to one embodiment of the present invention, the predicted current model is expressed in the following manner:

[0161]

[0162]

[0163] in, The d-axis and q-axis components of the nth predicted current at time t0+T' are respectively, k d,n (t0), k q,n (t0) represent the d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time t0, respectively. d (t0), i q (t0) represents the d-axis and q-axis components of the actual current of the permanent magnet synchronous motor at time t0, where t0 is the current time, T' is the duration of the voltage vector, and u d (t0), u q (t0) represents the d-axis and q-axis components of the actual voltage of the permanent magnet synchronous motor at time t0, respectively. S L S These are the stator resistance and stator inductance of a permanent magnet synchronous motor, ω. e The electrical angular frequency of the permanent magnet synchronous motor. These are the d-axis and q-axis components of the stator flux linkage of the permanent magnet synchronous motor at time t0, respectively.

[0164] According to one embodiment of the present invention, the range of variation of the operating duration is determined based on the maximum allowable switching frequency of the inverter and the computing power of the processor.

[0165] According to one embodiment of the present invention, the range of variation in the duration of action is expressed in the following manner:

[0166]

[0167] Among them, T c,min T is the minimum permissible duration of action. c,max T is the maximum permissible duration of action. min =1 / f max f max T is the maximum permissible switching frequency of the inverter. cal This represents the processor's maximum computational latency.

[0168] According to one embodiment of the present invention, the upper limit of the minimum permissible operating time is determined based on the actual current fluctuation range and DC bus voltage of the permanent magnet synchronous motor.

[0169] According to one embodiment of the present invention, the upper limit of the minimum permissible duration of action is expressed in the following manner:

[0170]

[0171] Among them, T c,min U is the minimum permissible duration of action. dc i is the DC bus voltage. d,offset i q,offset These are the maximum d-axis and q-axis fluctuation values ​​of the actual current of the permanent magnet synchronous motor, respectively. S This is the stator inductance of a permanent magnet synchronous motor.

[0172] According to one embodiment of the present invention, the switching transistor in the inverter is a gallium nitride switching transistor.

[0173] It should be noted that, regarding the predictive current control device of the present invention, please refer to the description of the predictive current control method in this application, and the specific details will not be repeated here.

[0174] According to an embodiment of the present invention, the predictive current control device for a permanent magnet synchronous motor predicts the predicted current corresponding to multiple voltage vectors of the inverter based on the predicted current model of the prediction module. During the construction of the current model, the current model is discretized and linearized to determine the current change slope, reducing the influence of current coupling on the current change rate and thus improving the accuracy of current prediction. Simultaneously, by setting a first cost function in the first screening module to characterize the degree of deviation between the predicted current and the given current, multiple voltage vectors are initially screened to determine candidate voltage vectors. The optimal operating duration is then determined by the duration determination module. This reduces the computational load in determining the operating duration, lowers the complexity of the control method, and avoids introducing non-optimal control methods. First, by setting the duration of the candidate voltage vector to the maximum value within the allowable range, the switching frequency can be reduced and switching losses can be decreased under the same control level. Second, when multiple candidate voltage vectors exist, a second cost function is set in the second screening module 340 to characterize the difference between the average value of the predicted current and the given current within the duration of the action. This allows the candidate voltage vector with the best motor control effect to be selected as the optimal voltage vector to control the inverter. The control module then controls the motor operation according to the optimal voltage vector, further improving the steady-state performance of the motor and thus optimizing the motor control method.

[0175] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0176] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0177] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0178] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0179] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0180] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A predictive current control method for a permanent magnet synchronous motor, characterized in that, The method includes: Based on the predicted current model, current prediction is performed on each of the multiple voltage vectors of the inverter to obtain multiple predicted currents; Based on the multiple predicted currents and the first cost function, the multiple voltage vectors are filtered to obtain candidate voltage vectors; Determine the duration of action of the candidate voltage vector; If there are multiple candidate voltage vectors, the multiple candidate voltage vectors are filtered according to the duration of action of the multiple candidate voltage vectors and the second cost function to obtain the optimal voltage vector; The inverter is controlled based on the optimal voltage vector and the duration of the optimal voltage vector to control the operation of the permanent magnet synchronous motor. The step of filtering the multiple voltage vectors based on the multiple predicted currents and the first cost function to obtain candidate voltage vectors includes: The multiple predicted currents are respectively input into the first cost function for calculation to obtain multiple first cost function values, wherein the first cost function is used to characterize the degree of deviation between the predicted current and the given current; If the first cost function value is equal to zero, then the voltage vector corresponding to the first cost function value is determined as the candidate voltage vector; If all of the multiple first cost function values ​​are not equal to zero, then the minimum value of the multiple first cost function values ​​is obtained, and the voltage vector corresponding to the minimum value is taken as the candidate voltage vector; The second cost function is: in, The value of the second cost function. for The q-axis component of the actual current of the permanent magnet synchronous motor at the specified time. The duration of the nth voltage vector as a candidate voltage vector. for The rate of change of q-axis current corresponding to the nth voltage vector at time n. for The q-axis component of the given current at any given time. This refers to the current moment.

2. The method according to claim 1, characterized in that, The method further includes: If the candidate voltage vector includes only one, then the candidate voltage vector is determined as the optimal voltage vector.

3. The method according to claim 1, characterized in that, The first cost function is: in, The first cost function value, , As weight, , They are respectively The d-axis and q-axis components of the predicted current at time n. , They are respectively Given the d-axis and q-axis components of the current at any given time, For the current moment, The duration of the voltage vector's action. , These are the maximum fluctuation values ​​of the d-axis component and the maximum fluctuation value of the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

4. The method according to claim 1, characterized in that, Determining the duration of action of the candidate voltage vector includes: If the candidate voltage vector includes multiple vectors, or if the candidate voltage vector includes one voltage vector corresponding to zero, then the duration of action of the candidate voltage vector is determined based on the current change rate corresponding to the candidate voltage vector and the actual current fluctuation range of the permanent magnet synchronous motor. If the candidate voltage vector includes a voltage vector that corresponds to the minimum value, then the duration of action of the candidate voltage vector is the minimum allowable duration of action.

5. The method according to claim 4, characterized in that, The duration of action of the candidate voltage vector is determined in the following manner: in, The duration of the nth voltage vector as a candidate voltage vector, where max represents the maximum value to be obtained. , They are respectively The d-axis and q-axis components of the predicted current at time n. , They are respectively The d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time n. , They are respectively Given the d-axis and q-axis components of the current at any given time, For the current moment, The duration of the voltage vector's action. , These are the maximum fluctuation values ​​of the d-axis component and the maximum fluctuation value of the q-axis component of the actual current of the permanent magnet synchronous motor, respectively.

6. The method according to claim 1, characterized in that, The step of filtering multiple candidate voltage vectors based on their duration and a second cost function to obtain the optimal voltage vector includes: The duration of action of multiple candidate voltage vectors is input into the second cost function for calculation to obtain multiple second cost function values; wherein, the second cost function is used to characterize the degree of deviation between the actual current of the permanent magnet synchronous motor and the given current within the duration of action; Obtain the minimum value of the plurality of second cost function values, and take the candidate voltage vector corresponding to the minimum value as the optimal voltage vector.

7. The method according to claim 1, characterized in that, The predicted current model is constructed in the following way: In the dq axis coordinate system, construct the current model of the permanent magnet synchronous motor; The current model is discretized and linearized sequentially to obtain the predicted current model.

8. The method according to claim 1, characterized in that, The predicted current model is expressed in the following way: in, , They are respectively The d-axis and q-axis components of the predicted current at time n. , They are respectively The d-axis current change rate and q-axis current change rate corresponding to the nth voltage vector at time n. , They are respectively The d-axis and q-axis components of the actual current of the permanent magnet synchronous motor at the specified time. For the current moment, The duration of the voltage vector's action. , They are respectively The d-axis and q-axis components of the actual voltage of the permanent magnet synchronous motor at the specified time. , These are the stator resistance and stator inductance of the permanent magnet synchronous motor, respectively. The electrical angular frequency of the permanent magnet synchronous motor is given. , They are respectively The d-axis and q-axis components of the stator flux linkage of the permanent magnet synchronous motor at the specified time.

9. The method according to claim 1, characterized in that, The range of variation in the duration of operation is determined based on the maximum allowable switching frequency of the inverter and the computing power of the processor.

10. The method according to claim 9, characterized in that, The range of variation in the duration of action is expressed in the following way: in, For the minimum permissible duration of action, For the maximum permissible duration of action, , The maximum permissible switching frequency of the inverter. This represents the maximum computational latency of the processor.

11. The method according to claim 10, characterized in that, The upper limit of the minimum allowable operating time is determined based on the actual current fluctuation range and DC bus voltage of the permanent magnet synchronous motor.

12. The method according to claim 11, characterized in that, The upper limit of the minimum allowable duration of action is expressed in the following way: in, The minimum permissible duration of action, The DC bus voltage is... , These are the maximum d-axis fluctuation value and the maximum q-axis fluctuation value of the actual current of the permanent magnet synchronous motor, respectively. is the stator inductance of the permanent magnet synchronous motor.

13. The method according to any one of claims 1-12, characterized in that, The switching transistors in the inverter are gallium nitride switching transistors.

14. A computer-readable storage medium, characterized in that, It stores a program that, when executed by a processor, implements the method according to any one of claims 1-13.

15. A predictive current control system for a permanent magnet synchronous motor, characterized in that, include: A memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the method according to any one of claims 1-13.

16. A predictive current control device for a permanent magnet synchronous motor, characterized in that, The apparatus is used to implement the method according to any one of claims 1-13, comprising: The prediction module is used to predict the current for each of the multiple voltage vectors of the inverter based on the prediction current model, so as to obtain multiple predicted currents. The first screening module is used to screen the multiple voltage vectors based on the multiple predicted currents and the first cost function to obtain candidate voltage vectors; The duration determination module is used to determine the duration of action of the candidate voltage vector; The second filtering module is used to filter the multiple candidate voltage vectors according to the duration of action of the multiple candidate voltage vectors and the second cost function if the candidate voltage vectors include multiple ones, so as to obtain the optimal voltage vector. The control module is used to control the inverter based on the optimal voltage vector and the duration of the optimal voltage vector, so as to control the operation of the permanent magnet synchronous motor.

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