A control method for maximum torque current ratio of a permanent magnet synchronous reluctance motor

Abstract

The application relates to a control method for maximum torque current ratio of a permanent magnet synchronous reluctance motor, and belongs to the technical field of motor control, which comprises the following steps: step S01: collecting permanent magnet synchronous reluctance motor operation state information, including a speed feedback signal, a stator current feedback signal and a stator current reference amplitude output by a speed controller, and obtaining a current MTPA current angle; and step S02: generating a MTPA current angle feedforward value corresponding to a current operation condition according to a pre-established stator current reference amplitude and MTPA current angle mapping relationship. The application combines current amplitude feedforward, unit current torque evaluation and online search correction, constructs a permanent magnet synchronous reluctance motor MTPA online optimization control mechanism suitable for a speed closed loop PI operation condition, reduces the influence of current amplitude variation on online search evaluation results, improves MTPA current angle search precision and dynamic response speed, and balances system dynamic performance and steady-state performance.

Description

Technical Field

[0001] This invention relates to a control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor, belonging to the field of motor control technology. Background Technology

[0002] The Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSynRM) combines the high efficiency and high power density of permanent magnet synchronous motors with the simple structure and good speed regulation performance of synchronous reluctance motors, making it widely applicable in new energy vehicles, power tools, industrial servo systems, and high-performance drives. In the vector control system of a permanent magnet synchronous reluctance motor, to fully utilize the motor's reluctance torque and improve the electromagnetic torque generated per unit current, a maximum torque per ampere (MTPA) control strategy is typically adopted. This involves optimizing the stator current vector angle to ensure the motor operates in the optimal current distribution state.

[0003] Currently, the control methods for permanent magnet synchronous reluctance motors (MTPA) mainly include analytical calculation methods based on motor parameter models and optimization methods based on online search. Model-based methods typically require establishing an electromagnetic torque model using motor flux linkage and inductance parameters, and then calculating the optimal current angle. However, during motor operation, factors such as magnetic saturation, temperature rise, and load changes can cause changes in motor parameters, leading to a deviation between the MTPA operating point calculated based on a fixed-parameter model and the actual optimal operating point, thus reducing control accuracy.

[0004] Chinese invention patent CN115085608B discloses an MTPA control method based on a permanent magnet synchronous motor. This method obtains the direct-axis inductance and stator resistance through a model reference adaptive system, establishes the torque equation based on parameter identification results, and simultaneously uses high-frequency signal injection to obtain the current angle corresponding to the MTPA operating point, thus achieving MTPA control of the motor. This method improves the accuracy of torque model calculation through online parameter identification and reduces the impact of parameter variations on the control effect. However, this method requires additional parameter identification and high-frequency signal injection processes, increasing the computational complexity of the control system. Furthermore, high-frequency signal injection may cause current fluctuations, affecting the stable operation of the system.

[0005] Chinese invention patent CN118842365A discloses a method and device for controlling a permanent magnet synchronous motor (MTPA) based on an extreme value search algorithm. This method uses the extreme value search algorithm to track the minimum value of the stator current amplitude. By combining sliding mode extreme value search with astable oscillation extreme value search, it achieves rapid convergence and steady-state optimization of the MTPA operating point. While this method uses an online search approach to reduce dependence on the motor parameter model, its search target is primarily the minimum value of the stator current amplitude. During the speed closed-loop PI control process, the speed regulator adjusts the current amplitude in real time according to load changes, causing the current amplitude change and current angle change to be coupled during the search process. This makes it difficult for the evaluation index to accurately reflect the current angle optimization effect, affecting the accuracy of the MTPA search and its dynamic response capability.

[0006] Therefore, existing MTPA control methods for permanent magnet synchronous reluctance motors still have problems such as the search evaluation index being greatly affected by changes in current amplitude under closed-loop PI operation, insufficient current angle adjustment speed when the load changes, and limited steady-state operation performance. There is a need for a control method for the maximum torque-current ratio of permanent magnet synchronous reluctance motors to improve the dynamic response speed, search accuracy, and operational stability of MTPA control. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a control method for the maximum torque-current ratio of a permanent magnet synchronous reluctance motor (MTPA) to improve the dynamic response speed, search accuracy and operation stability of the MTPA control.

[0008] The technical solution adopted by this invention to solve the above problems is as follows: a control method for the maximum torque-current ratio of a permanent magnet synchronous reluctance motor, applied in a vector control system for a permanent magnet synchronous reluctance motor, comprising the following steps: Step S01: Collect the operating status information of the permanent magnet synchronous reluctance motor, including the speed feedback signal, the stator current feedback signal, and the stator current reference amplitude output by the speed controller, and obtain the current MTPA current angle; Step S02: Based on the pre-established mapping relationship between stator current reference amplitude and MTPA current angle, generate the MTPA current angle feedforward value corresponding to the current operating condition, and determine whether to start feedforward correction based on the deviation between the feedforward angle and the current MTPA current angle. Step S03: When the feedforward correction condition is met, perform a local online search near the feedforward corrected current angle; when the feedforward correction condition is not met, keep the current MTPA current angle unchanged. Step S04: Apply a search disturbance near the current MTPA current angle, obtain the motor operating status information before and after the disturbance, and construct a unit current torque evaluation index; Step S05: Calculate the gradient of the evaluation index based on the change of the unit current torque evaluation index during two consecutive search processes, and filter the gradient to obtain a stable gradient estimation result. Step S06: Adaptively adjust the search step size based on the gradient estimation result, correct the MTPA current angle online, and impose boundary constraints on the corrected MTPA current angle; Step S07: Calculate the d-axis current reference value and q-axis current reference value based on the corrected MTPA current angle and stator current reference amplitude, and input them into the current controller to complete the current closed-loop control; Step S08: Repeat steps S01 to S07 to achieve online real-time optimization of the MTPA current angle during the operation of the permanent magnet synchronous reluctance motor.

[0009] Preferably, the unit current torque evaluation index is calculated based on the electromagnetic torque and stator current information obtained during motor operation, and the electromagnetic torque generated by the unit current is used as the basis for online MTPA search evaluation.

[0010] Preferably, the online search correction involves applying a disturbance near the current MTPA current angle, calculating the gradient of the evaluation index based on the change in the unit current torque evaluation index, and correcting the MTPA current angle online based on the gradient estimation result.

[0011] Preferably, the permanent magnet synchronous reluctance motor vector control system includes a speed regulation module, an MTPA control module based on unit current torque evaluation and current amplitude feedforward, a current regulation module, a coordinate transformation module, an SVPWM module, a three-phase inverter, a permanent magnet synchronous reluctance motor, and a position and speed detection module. All functional modules together constitute a closed-loop vector control system.

[0012] Preferably, during the operation of the permanent magnet synchronous reluctance motor vector control system, the position and speed detection module collects the motor rotor position and speed information in real time, and feeds back the detection results to the coordinate transformation module and the speed adjustment module to realize the motor rotor magnetic field orientation control and speed closed-loop PI control.

[0013] Preferably, in the speed closed-loop PI, the motor speed setpoint is compared with the actual feedback speed, and the current reference amplitude Is* is output after calculation by the speed regulator. The current reference amplitude Is* output by the speed regulator is input to the MTPA control module based on unit current torque evaluation and current amplitude feedforward. This module completes the initialization, online optimization and real-time correction of the MTPA current angle, and outputs the optimal MTPA current angle β under the current operating condition.

[0014] Preferably, the MTPA control module calculates the direct-axis current reference value Id-ref and the quadrature-axis current reference value Iq-ref based on the output optimal current angle β and the current reference amplitude Is*, and the calculation relationship is as follows: Id-ref=Is*cosβ Iq-ref=Is*sinβ The calculated Id-ref and Iq-ref are used as reference inputs for the inner current loop, respectively. They are compared with the current feedback value and calculated by the d-axis and q-axis current regulators to obtain the corresponding voltage commands Ud and Uq. Then, after inverse Park transformation, SVPWM modulation, and three-phase inverter driving of permanent magnet synchronous reluctance motor, the current closed-loop control is realized.

[0015] Preferably, during motor operation, the position and speed detection module continuously acquires operating status information such as motor rotor position, motor speed, and stator current, and completes coordinate transformation from a three-phase stationary coordinate system to a two-phase rotating coordinate system to obtain d-axis current Id and q-axis current Iq. Meanwhile, the current electromagnetic torque Te is calculated based on the motor feedback information, and Te, Id, and Iq are fed back to the MTPA control module for unit current torque evaluation and online current angle search and correction. As a preferred option, the unit current torque evaluation module first collects the electromagnetic torque Te, direct-axis current Id, and quadrature-axis current Iq of the current control cycle, calculates the current stator current amplitude Is based on the feedback current, and constructs the unit current torque evaluation index.

[0016] As a preferred option, the formula for calculating Is is as follows;

[0017] The formula for calculating the electromagnetic torque generated by a unit stator current is as follows;

[0018] After calculating the evaluation index for the current control cycle, the current evaluation index (J(k)) is compared with the evaluation index (J(k-1)) for the previous control cycle, and the following conditions are met: .

[0019] Compared with the prior art, the advantages of the present invention are as follows: This invention discloses a control method for the maximum torque-to-current ratio (MTPA) of a permanent magnet synchronous reluctance motor (PMSM). It combines current amplitude feedforward, unit current torque evaluation, and online search correction to construct an online optimization control mechanism for the MTPA under closed-loop PI operation conditions. This reduces the impact of current amplitude variations on the online search evaluation results, improves the MTPA current angle search accuracy and dynamic response speed, and balances both dynamic and steady-state performance of the system. It possesses good parameter adaptability and engineering application value. Attached Figure Description

[0020] Figure 1 This is a structural diagram of a permanent magnet synchronous reluctance motor (MTPA) control system based on unit current torque evaluation and current amplitude feedforward. Figure 2 This is a flowchart of a control method for the maximum torque-current ratio of a permanent magnet synchronous reluctance motor according to the present invention; Figure 3 Here is a flowchart of the current amplitude feedforward module's workflow; Figure 4 Here is a flowchart of the unit current torque evaluation module. Figure 5 Workflow diagram for the online search correction module; Figure 6 A comparison chart of the current angle β variation curves under the analytical formula method; Figure 7 A comparison chart of the current angle β variation curves under the traditional online search method; Figure 8 This is a comparison chart of the current angle β variation curves under the control method of the present invention; Figure 9 A comparison of the current angle β response curves under experimental conditions using the traditional online search method; Figure 10 This is a comparison of the current angle β response curves under experimental conditions for the control method of this invention; Figure 11 A comparison of dq-axis current response curves under the analytical formula method; Figure 12 A comparison chart of dq-axis current response curves under the traditional online search method; Figure 13 This is a comparison chart of the dq-axis current response curves under the control method of the present invention; Figure 14 A comparison of dq-axis current response curves under experimental conditions using the traditional online search method; Figure 15 This is a comparison chart of the dq-axis current response curves under the control method of the present invention; Figure 16 This is a structural diagram of a traditional permanent magnet synchronous reluctance motor (MTPA) control system. Detailed Implementation

[0021] like Figure 1 As shown in this embodiment, a control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor is applied in a vector control system for the permanent magnet synchronous reluctance motor, and includes the following steps: Includes the following steps: Step S01: Collect the operating status information of the permanent magnet synchronous reluctance motor, including the speed feedback signal, the stator current feedback signal, and the stator current reference amplitude output by the speed controller, and obtain the current MTPA current angle; Step S02: Based on the pre-established mapping relationship between stator current reference amplitude and MTPA current angle, generate the MTPA current angle feedforward value corresponding to the current operating condition, and determine whether to start feedforward correction based on the deviation between the feedforward angle and the current MTPA current angle. Step S03: When the feedforward correction condition is met, perform a local online search near the feedforward corrected current angle; when the feedforward correction condition is not met, keep the current MTPA current angle unchanged. Step S04: Apply a search disturbance near the current MTPA current angle, obtain the motor operating status information before and after the disturbance, and construct a unit current torque evaluation index; Step S05: Calculate the gradient of the evaluation index based on the change of the unit current torque evaluation index during two consecutive search processes, and filter the gradient to obtain a stable gradient estimation result. Step S06: Adaptively adjust the search step size based on the gradient estimation result, correct the MTPA current angle online, and impose boundary constraints on the corrected MTPA current angle; Step S07: Calculate the d-axis current reference value and q-axis current reference value based on the corrected MTPA current angle and stator current reference amplitude, and input them into the current controller to complete the current closed-loop control; Step S08: Repeat steps S01 to S07 to achieve online real-time optimization of the MTPA current angle during the operation of the permanent magnet synchronous reluctance motor.

[0022] The current amplitude feedforward strategy generates a corresponding MTPA current angle feedforward value based on a pre-established mapping relationship between the stator current reference amplitude and the MTPA current angle. It then determines whether to initiate feedforward correction based on the deviation between the feedforward angle and the current MTPA current angle. When changes in system load cause variations in the stator current reference amplitude, feedforward correction enables the current MTPA current angle to quickly approach the target operating point, thereby reducing the time required for re-searching using traditional online search methods and improving the system's dynamic response speed.

[0023] The unit current torque evaluation index is calculated based on the electromagnetic torque and stator current information obtained during motor operation, using the electromagnetic torque generated per unit current as the evaluation basis for online MTPA search. Compared to the traditional method that directly uses electromagnetic torque as the search criterion, this invention can reduce the impact of current amplitude changes during speed closed-loop PI operation on the search results, improve the sensitivity of the evaluation index to changes in the MTPA current angle, and thus improve the accuracy of search direction determination.

[0024] The online search correction applies a small perturbation near the current MTPA current angle, calculates the gradient of the evaluation index based on the change in the unit current torque evaluation index, and corrects the MTPA current angle online based on the gradient estimation result. Simultaneously, it combines adaptive step size adjustment, filtering, and boundary constraints to improve the stability of the search process, reducing search perturbations and system oscillations while ensuring search speed.

[0025] The d-axis current reference value and q-axis current reference value are calculated based on the corrected MTPA current angle and stator current reference amplitude. The calculated reference values ​​are then input into the current closed-loop controller to achieve maximum torque-current ratio control of the permanent magnet synchronous reluctance motor, so that the motor can maintain a better current distribution state under different operating conditions.

[0026] During motor operation, the system continuously acquires operating status information and repeatedly executes current amplitude feedforward, unit current torque evaluation, and online search and correction processes, enabling the MTPA current angle to be updated in real time as the operating conditions change, thus achieving continuous online optimization of the MTPA operating point of the permanent magnet synchronous reluctance motor.

[0027] The permanent magnet synchronous reluctance motor vector control system includes a speed regulation module, an MTPA control module based on unit current torque evaluation and current amplitude feedforward, a current regulation module, a coordinate transformation module, a space vector pulse width modulation (SVPWM) module, a three-phase inverter, a permanent magnet synchronous reluctance motor, and a position and speed detection module. All functional modules together constitute a closed-loop vector control system. During the operation of the vector control system for permanent magnet synchronous reluctance motor, the position and speed detection module collects the motor rotor position and speed information in real time, and feeds the detection results back to the coordinate transformation module and the speed regulation module to realize the magnetic field orientation control of the motor rotor and the closed-loop PI control of the speed. In the speed closed-loop PI controller, the motor speed setpoint is compared with the actual feedback speed, and the speed regulator calculates and outputs a current reference amplitude Is*. Unlike traditional MTPA control methods that directly calculate the current angle based on lookup tables or analytical models, this embodiment inputs the current reference amplitude Is* output by the speed regulator into the MTPA control module based on unit current torque evaluation and current amplitude feedforward proposed in this invention. This module completes the initialization, online optimization, and real-time correction of the MTPA current angle, and outputs the optimal MTPA current angle β under the current operating conditions.

[0028] The MTPA control module calculates the direct-axis current reference value Id-ref and the quadrature-axis current reference value Iq-ref based on the output optimal current angle β and the current reference amplitude Is*. The calculation relationship is as follows: Id-ref=Is*cosβ Iq-ref=Is*sinβ The calculated Id-ref and Iq-ref are used as reference inputs for the inner current loop, respectively. They are compared with the current feedback value and calculated by the d-axis and q-axis current regulators to obtain the corresponding voltage commands Ud and Uq. Then, after inverse Park transformation, SVPWM modulation, and three-phase inverter driving of permanent magnet synchronous reluctance motor, the current closed-loop control is realized.

[0029] During motor operation, the position and speed detection module continuously acquires operating status information such as rotor position, motor speed, and stator current, and performs coordinate transformation from a three-phase stationary coordinate system to a two-phase rotating coordinate system to obtain the d-axis current Id and q-axis current Iq. Simultaneously, it calculates the current electromagnetic torque Te based on motor feedback information and feeds Te, Id, and Iq back to the MTPA control module for unit current torque evaluation and online current angle search and correction. Because the MTPA control module always evaluates and corrects based on the real-time operating status of the motor, it reduces the dependence on the accuracy of motor parameters, enabling dynamic adjustment of the optimal current angle. This improves the system's control accuracy and robustness under parameter variations and load disturbances.

[0030] In this embodiment, the MTPA control module based on unit current torque evaluation and current amplitude feedforward is the core functional module of the entire control system. Its inputs include the current reference amplitude Is* output by the speed regulation module and motor operation feedback information. Its output is the optimal MTPA current angle β, and further generates direct axis and quadrature axis current reference values ​​to realize MTPA control of permanent magnet synchronous reluctance motor under different operating conditions.

[0031] Compared to traditional MTPA control methods, this invention introduces current amplitude feedforward to quickly determine the initial current angle and combines it with unit current torque evaluation to achieve online current angle search and correction. This improves the tracking accuracy of the MTPA operating point while ensuring the system's dynamic response speed, thus laying the foundation for subsequent overall control processes (such as...). Figure 2 (as shown) and each functional module (such as Figures 3-5 The implementation (shown) provides the foundation.

[0032] like Figure 2 As shown, the MTPA control method for permanent magnet synchronous reluctance motors proposed in this invention, based on unit current torque evaluation and current amplitude feedforward, achieves rapid initialization of the MTPA current angle through current amplitude feedforward, and dynamically tracks the optimal current angle by combining unit current torque evaluation and online search correction, ensuring that the motor maintains a state close to the maximum torque-to-current ratio under different operating conditions. The entire control method is executed cyclically according to a fixed control cycle, and after the control cycle ends, it re-enters the next cycle, continuously completing the current angle optimization process.

[0033] After system startup, the control parameters are first initialized, and motor operating status information is collected in real time, including rotor position, motor speed, d-axis current, q-axis current, and electromagnetic torque feedback quantities. The speed regulation module calculates the current reference amplitude Is* for the current control cycle based on the deviation between the speed setpoint and the actual feedback speed, which serves as the input variable for the MTPA control module of this invention, providing a reference for subsequent current angle optimization.

[0034] Unlike traditional MTPA control methods that directly use analytical models or fixed lookup tables to calculate the current angle, this invention utilizes a current amplitude feedforward module to quickly determine the corresponding initial MTPA current angle βff based on the current current reference amplitude. This allows the system to quickly enter the vicinity of the optimal operating point, thereby effectively shortening the online search time and improving the system's dynamic response speed.

[0035] After acquiring the initial current angle, the system enters the unit current torque evaluation stage. Based on the electromagnetic torque and current feedback information collected during the current control cycle, a unit current torque evaluation index is constructed to evaluate the current MTPA operating point in real time. This evaluation index reflects the ability of a unit stator current to generate electromagnetic torque and serves as an important basis for determining whether the current angle should continue to be optimized.

[0036] Unlike traditional search methods that optimize based solely on current change trends, this invention uses unit current torque as the evaluation target, enabling the evaluation results to directly reflect the energy utilization efficiency at the current operating point and improving the targeting and control accuracy of the search process.

[0037] After obtaining the evaluation results for the current control cycle, the system enters the online search and correction phase. Based on the changes in the evaluation indicators over two consecutive control cycles, it determines whether the current search direction can further improve the unit current torque. When the evaluation indicator increases, the current angle is corrected while maintaining the current search direction; when the evaluation indicator decreases, the search direction is changed, and the current angle update value is readjusted. Boundary constraint checks are performed after each current angle update. If the update result exceeds the preset current angle range, it is limited to the allowable range to ensure stable operation throughout the online search process. Subsequently, the corrected MTPA current angle is used as the optimal current angle for the current control cycle, and the system proceeds to the next step of current reference value calculation.

[0038] Based on the optimized MTPA current angle β and the current reference amplitude Is* output by the speed regulation module, the direct-axis current reference value Id and the quadrature-axis current reference value Iq are calculated and used as reference inputs for the inner-loop current controller to achieve closed-loop current control. After the current control is completed, the system re-acquires the motor operating status information and returns to the current amplitude feedforward stage to begin online optimization for the next control cycle, thus forming a continuous closed-loop search process, enabling the MTPA operating point to be adjusted in real time according to the operating conditions.

[0039] The control method proposed in this invention employs a three-stage collaborative optimization strategy: "current amplitude feedforward + unit current torque evaluation + online search correction". Specifically, current amplitude feedforward is used to quickly determine the initial search position; unit current torque evaluation is used to judge the quality of the current operating point in real time; and online search correction is used to continuously optimize the MTPA current angle based on the evaluation results. These three components work together to ensure that the system balances rapid response capability with steady-state control accuracy, avoiding the problems of long initial search time, susceptibility to parameter changes, and insufficient steady-state optimization accuracy inherent in traditional search algorithms.

[0040] The above process constitutes the overall execution process of the MTPA control method of this invention. Among them, the current amplitude feedforward module is used to acquire the initial current angle, and its specific implementation process is as follows: Figure 3 As shown; the unit current torque evaluation module is used to complete the performance evaluation of the current operating point, and its specific implementation process is as follows. Figure 4 As shown; the online search and correction module is used to perform real-time optimization of the current angle, and its specific implementation process is as follows. Figure 5 As shown, the three functional modules execute sequentially and run in a loop to jointly complete the MTPA control method for permanent magnet synchronous reluctance motors proposed in this invention, which is based on unit current torque evaluation and current amplitude feedforward.

[0041] like Figure 3As shown, the current amplitude feedforward module in this embodiment is used to quickly determine the initial value of the MTPA current angle based on the current reference amplitude of the current cycle, providing an initial search point for subsequent unit current torque evaluation and online search correction. The current reference amplitude is output by the speed regulation module and serves as the input to the current amplitude feedforward module, enabling the system to quickly obtain an initial current angle close to the optimal operating point before entering the online search.

[0042] Once the current reference amplitude Is* is obtained, it is first determined whether the system meets the MTPA control conditions. If it does, the pre-established current amplitude-current angle (Is-β) mapping database is searched to obtain the corresponding initial MTPA current angle βff. After obtaining the effective current reference amplitude, the corresponding feedforward angle is calculated according to the mapping relationship.

[0043] Subsequently, the obtained initial current angle is judged for its range. If it exceeds the preset allowable range, it is limited; otherwise, it is directly used as the initial current angle output of the online search module in the current control cycle.

[0044] The initial current angle obtained from the Is-β database is only used as the initial value for online search and is not directly used as the final MTPA current angle. Since this initial value is close to the optimal MTPA operating region, subsequent online searches only need to be corrected within a local range to complete the tracking of the optimal current angle, thereby reducing search time and improving the dynamic response performance of the system.

[0045] This embodiment introduces current amplitude feedforward, combining current amplitude information with the Is-β database to achieve rapid initialization of the MTPA current angle, providing a reliable initial search point for the unit current torque evaluation module. The system then enters... Figure 4 The unit current torque evaluation module shown provides real-time evaluation of the current operating point and offers an evaluation basis for subsequent online search and correction.

[0046] like Figure 4 As shown, the unit current torque evaluation module in this embodiment is used to perform real-time performance evaluation of the current MTPA operating point and generate evaluation results based on the changing trend of the evaluation index, providing a decision-making basis for subsequent online search and correction. This module uses the real-time electromagnetic torque and current information fed back by the motor as input, and quantitatively evaluates the operating state corresponding to the current angle β by constructing a unit current torque evaluation index.

[0047] The unit current torque evaluation module first collects the electromagnetic torque Te, direct-axis current Id, and quadrature-axis current Iq of the current control cycle, calculates the current stator current amplitude Is based on the feedback current, and constructs the unit current torque evaluation index. The formula for calculating Is is is as follows;

[0048] The formula for calculating the electromagnetic torque generated by a unit stator current is as follows;

[0049] Where J represents the electromagnetic torque generated by a unit stator current. The larger the value of J, the closer the MTPA operating point corresponding to the current angle β is to the optimal operating state.

[0050] After calculating the evaluation index for the current control cycle, compare the current evaluation index J(k) with the evaluation index J(k-1) of the previous control cycle; when the following conditions are met:

[0051] If the current angle adjustment direction can increase the unit current torque, the output evaluation result is "search direction maintained"; otherwise, if the current search direction fails to increase the unit current torque, the output evaluation result is "search direction adjusted", and this evaluation result is sent to the online search correction module as an important basis for subsequent current angle updates.

[0052] Unlike traditional MTPA control methods that optimize based on motor mathematical models or current amplitude changes, this invention uses unit current torque as the evaluation target, directly reflecting the actual operating efficiency corresponding to the current angle β. The evaluation process can be completed using only real-time feedback information from the motor, without relying on precise motor parameters. Therefore, it can reduce the impact of parameter changes on control performance and improve the system's adaptability and robustness under different operating conditions.

[0053] In this embodiment, the unit current torque evaluation module is only responsible for evaluating the performance at the current operating point and outputting the evaluation results; it does not directly participate in the correction of the current angle β. The online search and correction module further optimizes the current angle online based on the evaluation results output by this module, enabling the evaluation module and the search module to operate independently yet collaboratively, jointly achieving continuous optimization of the MTPA operating point. Subsequently, the system enters... Figure 5 The online search and correction module shown updates the current angle β in real time.

[0054] like Figure 5 As shown, the online search and correction module in this embodiment is used to optimize the current angle β of the current cycle online based on the evaluation results output by the unit current torque evaluation module. This module adjusts the search direction and update method of the current angle in real time according to the evaluation results, so that the MTPA operating point continuously approaches the direction of maximum unit current torque, achieving dynamic tracking of the optimal current angle under different operating conditions.

[0055] The online search correction module receives the evaluation results output by the unit current torque evaluation module and determines whether the current search direction can increase the unit current torque. When the evaluation result shows that the current search direction is effective, the current search direction is maintained and the current angle β is updated; when the evaluation result shows that the current search direction is ineffective, the search direction is changed and the current angle β is updated again, so that the search process always proceeds in the direction of increasing unit current torque.

[0056] The online search correction does not employ a fixed-direction continuous search, but rather adjusts the search direction in real time based on the unit current torque evaluation results, achieving closed-loop coordination between evaluation and search, and improving the accuracy and stability of online current angle optimization.

[0057] After updating the current angle β, boundary constraints are applied to the update result. If the updated current angle β exceeds the preset allowable range, it is limited to the corresponding boundary value; if the current angle β is within the allowable range, it is directly used as the optimal current angle output for the current control cycle.

[0058] Subsequently, the direct-axis current reference value and quadrature-axis current reference value are calculated based on the updated current angle β and current reference amplitude, and sent to the current control module to complete the current control of this control cycle.

[0059] After completing the control cycle, the system re-acquires the motor operating status information and enters the next control cycle, repeating the unit current torque evaluation and online search correction process, so that the current angle β can be continuously dynamically optimized as the motor operating status changes, realizing real-time tracking of the MTPA operating point.

[0060] Since the current angle update is always based on the real-time evaluation results, it can effectively adapt to load changes and motor parameter changes, thereby improving the MTPA control performance under different operating conditions.

[0061] This embodiment achieves rapid initialization, real-time evaluation, and dynamic optimization of the MTPA current angle through the coordinated operation of three modules: current amplitude feedforward, unit current torque evaluation, and online search and correction. Specifically, current amplitude feedforward is used to quickly determine the initial search point, unit current torque evaluation is used to judge the performance at the current operating point, and online search and correction is used to continuously optimize the current angle β based on the evaluation results. These three modules form a complete closed-loop optimization process, enabling the permanent magnet synchronous reluctance motor to maintain optimal unit current torque output capability under different operating conditions.

[0062] To analyze the current angle variation process under different MTPA control methods, the analytical formula method, the traditional online search method, and the method of this invention are compared. Figures 6 to 8 As shown, the current angle β variation curves corresponding to the three methods are given respectively.

[0063] Analytical formulas can calculate the theoretical current angle based on motor parameters; traditional online search methods gradually approximate the target operating point by perturbing the current angle, which involves an iterative adjustment process. The method of this invention utilizes current amplitude feedforward to obtain the initial current angle and combines it with unit current torque evaluation for online correction, enabling the current angle to quickly enter the corresponding MTPA operating region.

[0064] To analyze the control effect under actual operating conditions, an experimental platform for a permanent magnet assisted synchronous reluctance motor was built, and comparative experiments were conducted between the traditional online search method and the method of this invention. Figures 9 to 10 As shown, the current angle response curves of the two methods during load changes are presented.

[0065] Figure 9 The results are from experiments using the traditional online search method. As shown in the figure, the traditional method searches step by step from the initial current angle, and requires continuous adjustment of the current angle to find the MTPA operating point during load changes.

[0066] Figure 10 These are the experimental results of the method of this invention. This method uses current amplitude feedforward to obtain an initial angle close to the MTPA operating point, and completes further correction through unit current torque evaluation, thus shortening the current angle adjustment process during load changes.

[0067] Depend on Figures 11 to 13 It is known that the analytical model method can determine the corresponding current distribution based on the motor parameters; the traditional online search method requires iterative adjustment of the current angle to redistribute the d-axis and q-axis currents. The method of this invention uses current amplitude feedforward to determine the initial current angle and combines it with online search correction to enable the d-axis and q-axis currents to be quickly adjusted to the corresponding MTPA operating state.

[0068] Compared with traditional online search methods, the method of this invention obtains the initial current angle by current amplitude feedforward, reduces the iterative adjustment process of the current angle, and enables the d-axis and q-axis currents to reach a new steady-state distribution state more quickly. In summary, by combining current amplitude feedforward, unit current torque evaluation, and online search correction, an online optimization control mechanism for permanent magnet synchronous reluctance motors (MTPA) suitable for speed closed-loop PI operation is constructed. This mechanism reduces the impact of current amplitude variations on the online search evaluation results, improves the current angle search accuracy and dynamic response speed of MTPA, and balances the dynamic and steady-state performance of the system. It has good parameter adaptability and engineering application value.

[0069] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for controlling the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor, characterized in that: Applied to the vector control system of permanent magnet synchronous reluctance motor, the following steps are included: Step S01: Collect the operating status information of the permanent magnet synchronous reluctance motor, including the speed feedback signal, the stator current feedback signal, and the stator current reference amplitude output by the speed controller, and obtain the current MTPA current angle; Step S02: Based on the pre-established mapping relationship between stator current reference amplitude and MTPA current angle, generate the MTPA current angle feedforward value corresponding to the current operating condition, and determine whether to start feedforward correction based on the deviation between the feedforward angle and the current MTPA current angle. Step S03: When the feedforward correction condition is met, perform a local online search near the feedforward corrected current angle; when the feedforward correction condition is not met, keep the current MTPA current angle unchanged. Step S04: Apply a search disturbance near the current MTPA current angle, obtain the motor operating status information before and after the disturbance, and construct a unit current torque evaluation index; Step S05: Calculate the gradient of the evaluation index based on the change of the unit current torque evaluation index during two consecutive search processes, and filter the gradient to obtain a stable gradient estimation result. Step S06: Adaptively adjust the search step size based on the gradient estimation result, correct the MTPA current angle online, and impose boundary constraints on the corrected MTPA current angle; Step S07: Calculate the d-axis current reference value and q-axis current reference value based on the corrected MTPA current angle and stator current reference amplitude, and input them into the current controller to complete the current closed-loop control; Step S08: Repeat steps S01 to S07 to achieve online real-time optimization of the MTPA current angle during the operation of the permanent magnet synchronous reluctance motor.

2. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 1, characterized in that: The unit current torque evaluation index is calculated based on the electromagnetic torque and stator current information obtained during motor operation, and the electromagnetic torque generated by unit current is used as the basis for online MTPA search evaluation.

3. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 1, characterized in that: The online search correction applies a disturbance near the current MTPA current angle, calculates the gradient of the evaluation index based on the change in the unit current torque evaluation index, and corrects the MTPA current angle online based on the gradient estimation result.

4. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 1, characterized in that: The permanent magnet synchronous reluctance motor vector control system includes a speed regulation module, an MTPA control module based on unit current torque evaluation and current amplitude feedforward, a current regulation module, a coordinate transformation module, an SVPWM module, a three-phase inverter, a permanent magnet synchronous reluctance motor, and a position and speed detection module. All functional modules together constitute a closed-loop vector control system.

5. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 4, characterized in that: During the operation of the permanent magnet synchronous reluctance motor vector control system, the position and speed detection module collects the motor rotor position and speed information in real time, and feeds back the detection results to the coordinate transformation module and the speed adjustment module to realize the motor rotor magnetic field orientation control and speed closed-loop PI control.

6. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 4, characterized in that: In the speed closed-loop PI controller, the motor speed setpoint is compared with the actual feedback speed. After calculation by the speed regulator, a current reference amplitude Is* is output. The current reference amplitude Is* output by the speed regulator is input to the MTPA control module based on unit current torque evaluation and current amplitude feedforward. This module completes the initialization, online optimization and real-time correction of the MTPA current angle, and outputs the optimal MTPA current angle β under the current operating condition.

7. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 6, characterized in that: The MTPA control module calculates the direct-axis current reference value Id-ref and the quadrature-axis current reference value Iq-ref based on the output optimal current angle β and the current reference amplitude Is*. The calculation relationship is as follows: Id-ref=Is*cosβ Iq-ref=Is*sinβ The calculated Id-ref and Iq-ref are used as reference inputs for the inner current loop, respectively. They are compared with the current feedback value and calculated by the d-axis and q-axis current regulators to obtain the corresponding voltage commands Ud and Uq. Then, after inverse Park transformation, SVPWM modulation, and three-phase inverter driving of permanent magnet synchronous reluctance motor, the current closed-loop control is realized.

8. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 7, characterized in that: During motor operation, the position and speed detection module continuously acquires operating status information such as motor rotor position, motor speed, and stator current, and completes coordinate transformation from a three-phase stationary coordinate system to a two-phase rotating coordinate system to obtain d-axis current Id and q-axis current Iq. Simultaneously, the current electromagnetic torque Te is calculated based on the motor feedback information, and Te, Id, and Iq are fed back to the MTPA control module for unit current torque evaluation and online current angle search and correction.

9. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 8, characterized in that: The unit current torque evaluation module first collects the electromagnetic torque Te, direct-axis current Id, and quadrature-axis current Iq of the current control cycle, calculates the current stator current amplitude Is based on the feedback current, and constructs the unit current torque evaluation index.

10. The control method for the maximum torque-to-current ratio of a permanent magnet synchronous reluctance motor according to claim 9, characterized in that: The formula for calculating Is is is as follows; ； The formula for calculating the electromagnetic torque generated by a unit stator current is as follows; ； After calculating the evaluation index for the current control cycle, the current evaluation index J(k) is compared with the evaluation index J(k-1) of the previous control cycle, and the following conditions are met: .

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