Ferrite permanent magnet auxiliary synchronous reluctance motor rotor electric angle compensation method and system

Abstract

The application discloses a ferrite permanent magnet auxiliary synchronous reluctance motor rotor electric angle compensation method and system, belongs to the motor vector control technical field, and is used for solving the problem that a larger magnetic field deviation angle caused by the armature reaction magnetic field due to a weak permanent magnet magnetic field under a maximum torque current ratio control strategy influences rotor magnetic field orientation control positioning precision in a ferrite permanent magnet auxiliary synchronous reluctance motor vector control technology based on a Hall position sensor. The application pre-establishes a compensation curve of the magnetic field deviation angle changing with the effective value of the stator current; the magnetic field deviation angle corresponding to the measured effective value of the stator current is obtained according to the compensation curve, the rotor electric angle is compensated based on the magnetic field deviation angle and the installation error angle to obtain the compensated rotor electric angle, the rotor electric angle is aligned with the d-axis only by using a low-cost Hall position sensor and relying on a pure software algorithm, the magnetic field orientation precision is ensured, the effectiveness of the rotor magnetic field orientation control is maintained, and the motor is stably operated under load.

Description

Technical Field

[0001] This invention relates to a method and system for compensating the rotor electrical angle of a ferrite permanent magnet assisted synchronous reluctance motor, belonging to the field of motor vector control technology. Background Technology

[0002] Permanent magnet assisted synchronous reluctance motors combine the simple structure and high reliability of synchronous reluctance motors with the high efficiency and high power density of permanent magnet motors. While improving overall performance, they effectively reduce dependence on rare earth resources, making them an important development direction for high-efficiency motors. Currently, this type of motor is mainly divided into two categories: rare earth permanent magnet motors and ferrite permanent magnet assisted synchronous reluctance motors, allowing for flexible selection based on application scenarios.

[0003] Rare-earth permanent magnet motors have strong permanent magnet magnetic fields, and the magnetic field generated by the armature current has little impact on the triggering time of the Hall position sensor, resulting in a basically fixed electrical zero position for the Hall signal. However, they are expensive. In contrast, ferrite permanent magnet assisted synchronous reluctance motors can significantly reduce motor costs while meeting certain performance requirements, and have broad market prospects.

[0004] However, in practical applications and control, there are fundamental differences between motors using ferrite and rare-earth permanent magnets in Hall position sensor-based control. For ferrite permanent magnet assisted synchronous reluctance motors, due to the weak remanence of ferrite materials, the permanent magnet magnetic field in the motor's air gap is relatively weak. Under the maximum torque-to-current ratio control mode, the strong armature reaction significantly distorts the synthesized magnetic field in the air gap, and the synthesized magnetic field dynamically changes with the magnitude of the armature current. Currently, the control of ferrite permanent magnet assisted synchronous reluctance motors often uses low-cost Hall position sensors to detect the rotor position. Faced with this dynamic change in the magnetic field, the timing of the Hall position sensor's trigger edge also dynamically changes with the magnitude of the armature current. This results in a dynamically changing angular difference between the electrical zero position sensed by the Hall signal and the actual magnetic field axis of the rotor, known as the "magnetic field offset angle."

[0005] The existence of the "magnetic field offset angle" leads to inaccurate rotor magnetic field orientation, which causes distortion of the quadrature axis current and direct axis current calculated by coordinate transformation in the current loop control, resulting in current turbulence. This leads to a decrease in the accuracy of the current loop closed-loop control and a deterioration in the control effect, specifically manifested as difficulty in motor starting, abnormal torque output, insufficient load-carrying capacity, or even inability to operate normally under load.

[0006] A search revealed that Chinese patent CN120357803A discloses a regional optimization control strategy for excitation current. In the constant torque region, the excitation current corresponding to MTPA is used to improve efficiency, while in the field weakening region, voltage control is combined to dynamically adjust the excitation current to ensure high dynamic response. The core contribution of this technology lies in optimizing the current distribution strategy of the motor in different operating regions, aiming to achieve global high efficiency and rapid response. However, the effective implementation of this strategy depends entirely on a fundamental premise: that the rotor position information used by the control system is accurate, thereby ensuring that the current vector is accurately decomposed and tracked in the correct dq-axis coordinate system.

[0007] Chinese patent CN104852663A addresses the challenge of accurately determining the N / S polarity of the rotor magnetic poles before starting a permanent magnet assisted synchronous reluctance motor. Its core technology lies in applying a series of specific voltage vectors and utilizing the asymmetry of the dq-axis current response to infer the polarity of the permanent magnet. This method contributes by avoiding starting reversal or failure due to polarity misjudgment, a crucial prerequisite for reliable motor starting. However, it does not resolve the impact of the "magnetic field offset angle."

[0008] Existing angle compensation technologies mostly focus on observer error correction or rotor initial position detection, lacking consideration for the magnetic field deformation caused by armature reaction under maximum torque-current ratio control. This fails to solve the problem of systematic offset of the reference signal of low-cost Hall position sensors, resulting in poor control performance of ferrite permanent magnet assisted synchronous reluctance motors (MTPA) based on Hall position sensors. Consequently, these technologies are difficult to promote and apply in industrial settings, and the advantages of this low-cost solution cannot be fully realized. Summary of the Invention

[0009] To address the aforementioned problems, or one of them, the present invention aims to provide a rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor. This method solves the problem of inaccurate Hall position sensor observations caused by armature reaction in ferrite permanent magnet assisted synchronous reluctance motors. By establishing a compensation relationship between the magnetic field offset angle and the stator current, and combining it with installation error correction, the rotor electrical angle is dynamically compensated in real time. This ensures that the rotor angle information obtained by the motor is aligned with the d-axis, guarantees accurate magnetic field orientation, and ensures the effectiveness of rotor magnetic field orientation control based on the MTPA control strategy and stable operation of the motor under load.

[0010] To address the aforementioned problems or one of them, the second objective of this invention is to provide a rotor electrical angle compensation system for a ferrite permanent magnet assisted synchronous reluctance motor. This system aims to solve the problem of inaccurate Hall position sensor readings caused by armature reaction in ferrite permanent magnet assisted synchronous reluctance motors. By establishing a compensation relationship between the magnetic field offset angle and the stator current, combined with installation error correction, the rotor electrical angle is dynamically compensated in real time. This ensures that the rotor angle information obtained by the motor is aligned with the d-axis, guarantees accurate magnetic field orientation, and ensures the effectiveness of rotor magnetic field orientation control based on the MTPA control strategy and stable operation of the motor under load.

[0011] To achieve one of the above objectives, the first technical solution of the present invention is as follows: A method for compensating the rotor electrical angle of a ferrite permanent magnet assisted synchronous reluctance motor includes the following steps: Based on the Hall position sensor, the estimated value of the rotor electrical angle at time t is obtained; Determine the installation error angle of the Hall position sensor; Based on the maximum torque-current ratio curve, a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current is pre-established. Obtain the measured effective value of the stator current at time t; Based on the compensation curve, the magnetic field offset angle corresponding to the measured effective value of the stator current is obtained, and the rotor electrical angle is compensated based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle at time t.

[0012] As a preferred technical measure: The method for obtaining the estimated rotor electrical angle at time t based on the Hall position sensor is as follows: Based on a three-phase Hall position sensor, six electrical angles corresponding to Hall state transitions are obtained as discrete reference values. The position of the rotor is detected using a Hall position sensor, and the electrical angular velocity of the rotor is calculated. Based on the rotor's electrical angular velocity and discrete reference values, a continuous function of the electrical angle value changing with time is obtained, and the electrical angle value at time t in the continuous function is used as the estimated value of the rotor's electrical angle at that time.

[0013] As a preferred technical measure: Based on the Hall position sensor, other methods for obtaining the rotor electrical angle estimate at time t include: When a Hall state transition is detected, the corresponding discrete reference value is used as the estimated rotor electrical angle at that moment.

[0014] As a preferred technical measure: The method for measuring the electric angular velocity of the rotor is to obtain the time interval between two adjacent discrete reference values ​​of the rotor. The electric angular velocity of the rotor is obtained by dividing the angle difference between two adjacent discrete reference values ​​by the time interval. Alternatively / and, based on the rotor's electrical angular velocity and discrete reference values, the method for obtaining a continuous function of the electrical angle value changing with time is as follows: The electrical angle period of the motor is divided into six sectors based on six discrete reference values; When a Hall state transition is detected, the discrete reference value corresponding to the state transition is used as the initial value of the current sector. Based on the rotor electric angular velocity of the previous sector, the current sector is integrated and linearly interpolated to obtain a continuous function of the electric angle value changing with time.

[0015] As a preferred technical measure: The method for establishing a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current, based on the maximum torque-current ratio curve, is as follows: Obtain the maximum torque-to-current ratio curve and select multiple effective current values ​​from the curve; The rotor electrical angle is measured simultaneously using a rotary transformer and a Hall position sensor; Coordinate transformation is performed based on the rotor electrical angle read from the rotary transformer, and rotor field orientation control of the motor is performed based on the maximum torque-current ratio control strategy. For each effective current value, the load is gradually adjusted so that the measured stator current equals the effective current value; the zero electrical angle of the Hall position sensor is obtained and the difference between it and the actual d-axis angle of the rotor is calculated to obtain the magnetic field offset angle under the current operating condition; thus, a data point corresponding to the effective stator current value and the magnetic field offset angle is obtained. By iterating through the effective values ​​of each stator current, multiple discrete data points are obtained; By fitting the discrete data points, a continuous compensation curve of the stator current effective value and the magnetic field offset angle is obtained.

[0016] As a preferred technical measure: The method for generating the maximum torque-to-current ratio curve is as follows: Calibration is performed by scanning point by point, and multiple stator current effective values ​​are set sequentially. A test platform is built by connecting the motor and the dynamometer. For each set stator current effective value, the motor is controlled to run at a constant speed at that current effective value. The current lead angle is gradually adjusted and the output torque is detected to determine the optimal current lead angle that maximizes the output torque. The maximum torque operating point under that current effective value is obtained. Multiple operating points are obtained by traversing different stator current effective values, and the maximum torque-current ratio curve corresponding to the stator current effective value and the output torque is generated accordingly.

[0017] By converting the parameters at each operating point into the direct-axis current and quadrature-axis current required for vector control, a mapping relationship between the direct-axis current, quadrature-axis current, and output torque is finally established.

[0018] As a preferred technical measure, the method for determining the installation error angle of the Hall position sensor is as follows: Under no-load conditions, by selecting the rotor main pole N as the d-axis and comparing the phase relationship of the rising edge of the A-phase Hall signal, the difference between the estimated Hall angle zero point and the d-axis is obtained. This difference is the installation error angle.

[0019] As a preferred technical measure: The rotor electrical angle compensation method for the ferrite permanent magnet assisted synchronous reluctance motor is used for MTPA control of the ferrite permanent magnet assisted synchronous reluctance motor. The MTPA control method includes: The rotor electrical angle is estimated based on the Hall position sensor; Real-time acquisition of motor stator current; Based on the compensation curve of the magnetic field offset angle as a function of the stator current effective value, the magnetic field offset angle corresponding to the measured stator current effective value is obtained. The rotor electrical angle is estimated based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle. Based on the compensated rotor electrical angle, the stator current is transformed by coordinate transformation to calculate the feedback signals of direct-axis current and quadrature-axis current. With the current command output from the maximum torque-current ratio curve as the target, and combined with the calculated direct-axis current and quadrature-axis current feedback signals, real-time tracking and adjustment are achieved through current closed-loop control, so that the motor operating point always tracks the maximum torque-current ratio curve and ensures that the motor outputs maximum torque.

[0020] This MTPA control method, based on measurable stator current, utilizes an offline calibrable compensation curve showing the change of the magnetic field offset angle with the effective value of the stator current. It calculates and actively superimposes the angle compensation in real time to counteract the magnetic field offset caused by armature reaction, which varies with the current. This feedforward dynamic compensation effectively eliminates the angle deviation, ensures the magnetic field orientation accuracy, and enables the motor to operate stably at the optimal operating point of MTPA across the entire current range, fully leveraging the high efficiency and high power density advantages of ferrite permanent magnet assisted synchronous reluctance motors.

[0021] To achieve one of the above objectives, the second technical solution of the present invention is as follows: A rotor electrical angle compensation system for a ferrite permanent magnet assisted synchronous reluctance motor includes the following modules: The electrical angle estimation module is used to obtain the estimated value of the rotor electrical angle at time t based on the Hall position sensor. The installation error determination module is used to determine the installation error angle of the Hall position sensor; The compensation curve establishment module is used to pre-establish a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current, based on the maximum torque-current ratio curve. The current acquisition module is used to acquire the effective value of the stator current measured at time t. The electrical angle compensation module is used to obtain the magnetic field offset angle corresponding to the measured effective value of the stator current according to the compensation curve, and to compensate the estimated value of the rotor electrical angle based on the magnetic field offset angle and the installation error angle, so as to obtain the rotor electrical angle at time t.

[0022] To achieve one of the above objectives, the third technical solution of the present invention is as follows: An electronic device includes a processing unit and a storage device for storing one or more programs; characterized in that when the processing unit executes the one or more programs, it implements the rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in any one of claims 1 to 8.

[0023] The storage device can be internal memory, external memory, cache memory, or other special memory.

[0024] The processing unit has signal processing capabilities and can be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, an off-the-shelf programmable gate array, or other programmable logic devices.

[0025] Compared with existing technologies, this invention offers the following advantages: In vector control, the d-axis is the reference axis for magnetic field orientation. Only when the rotor electrical angle, upon which coordinate transformation depends, is strictly aligned with the true d-axis of the rotor can the direct-axis current and quadrature-axis current be accurately decoupled, achieving precise MTPA control. Addressing the problem of dynamic offset of the Hall position sensor's observation angle caused by armature reaction during MTPA operation of a ferrite permanent magnet assisted synchronous reluctance motor, this method establishes a compensation relationship between the magnetic field offset angle and the effective value of the stator current through offline calibration. Combined with Hall installation error correction, it corrects the rotor electrical angle online in real time, ensuring it always approximates the true d-axis position. This solution requires only a low-cost Hall position sensor and relies on pure software algorithms to ensure the rotor electrical angle is aligned with the d-axis, guaranteeing magnetic field orientation accuracy, the effectiveness of rotor magnetic field orientation control based on the MTPA control strategy, and stable motor operation under load. It eliminates the need for high-resolution encoders or complex state observers, significantly reducing system hardware costs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the installation of a three-phase Hall position sensor; Figure 2 This is a diagram showing the three-phase Hall signal and the square wave output of the Hall 6 sector; Figure 3This is the average rotor speed of each sector in Example 2. Waveform diagram; Figure 4 This is a discrete angular position waveform diagram of the Hall position sensor angular position estimation in Example 2; Figure 5 This is a continuous angular position waveform diagram with integral interpolation and error correction introduced in Example 2; Figure 6 This is the maximum torque-to-current ratio control curve of the motor under different effective values ​​of stator current in Example 2, calibrated offline.

[0027] Figure 7 In Example 2, under no-load conditions, the Hall signal zero position (marked by the rising edge of phase A) and the position in a stationary orthogonal coordinate system are... Fixed installation deviation angle between shafts The vector graph.

[0028] Figure 8 It is a vector diagram of the air gap composite magnetic field offset under the influence of stator current under the control of maximum torque current ratio; Figure 9 This refers to the offline calibration of the stator current RMS value in Example 2. With offset angle Mathematical model; Figure 10 This is a control block diagram of the MTPA control strategy with magnetic field offset angle compensation proposed in this invention; Figure 11 This is a flowchart of the present invention; Figure 12 This is a control block diagram of the existing MTPA control strategy. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application. This invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined by the claims.

[0030] Example 1 like Figure 11 As shown in the figure, this embodiment describes a method for compensating the rotor electrical angle of a ferrite permanent magnet assisted synchronous reluctance motor, including the following steps: Based on the Hall position sensor, the estimated value of the rotor electrical angle at time t is obtained; Determine the installation error angle of the Hall position sensor; Based on the maximum torque-current ratio curve, a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current is pre-established. Obtain the measured effective value of the stator current at time t; Based on the compensation curve, the magnetic field offset angle corresponding to the measured effective value of the stator current is obtained, and the rotor electrical angle is compensated based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle at time t.

[0031] This rotor electrical angle compensation method for ferrite permanent magnet assisted synchronous reluctance motors addresses the problem of dynamic offset of the Hall position sensor observation angle caused by armature reaction during MTPA operation. This method establishes a compensation relationship between the magnetic field offset angle and the effective value of the stator current through offline calibration, and combines Hall installation error correction to correct the rotor electrical angle online in real time, ensuring it always approximates the true d-axis position. This solution requires only a low-cost Hall position sensor and relies on a pure software algorithm to ensure the rotor electrical angle is aligned with the d-axis, guaranteeing magnetic field orientation accuracy, the effectiveness of rotor magnetic field orientation control based on the MTPA control strategy, and stable motor operation under load. It eliminates the need for high-resolution encoders or complex state observers, significantly reducing system hardware costs.

[0032] Furthermore, based on the Hall position sensor, the method for obtaining the estimated rotor electrical angle at time t is as follows: Based on a three-phase Hall position sensor, six electrical angles corresponding to Hall state transitions are obtained as discrete reference values. The position of the rotor is detected using a Hall position sensor, and the electrical angular velocity of the rotor is calculated. Based on the rotor's electrical angular velocity and discrete reference values, a continuous function of the electrical angle value changing with time is obtained, and the electrical angle value at time t in the continuous function is used as the estimated value of the rotor's electrical angle at that time.

[0033] Furthermore, in order to eliminate accumulated errors, the method for obtaining the rotor electrical angle estimate at time t based on the Hall position sensor may also include: when a Hall state transition is detected, the corresponding discrete reference value is used as the rotor electrical angle estimate at that time, ensuring that the rotor electrical angle is precisely aligned with the reference position at each Hall transition edge.

[0034] Furthermore, The method for measuring the electric angular velocity of the rotor is to obtain the time interval between two adjacent discrete reference values ​​of the rotor. The electric angular velocity of the rotor is obtained by dividing the angle difference between two adjacent discrete reference values ​​by the time interval. Furthermore, based on the rotor's electrical angular velocity and discrete reference values, the method for obtaining a continuous function of the electrical angle value changing with time is as follows: The electrical angle period of the motor is divided into six sectors based on six discrete reference values; When a Hall state transition is detected, the discrete reference value corresponding to the state transition is used as the initial value of the current sector. Based on the rotor electric angular velocity of the previous sector, the current sector is integrated and linearly interpolated to obtain a continuous function of the electric angle value changing with time.

[0035] Furthermore, based on the maximum torque-to-current ratio curve, the method for establishing a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current is as follows: Obtain the maximum torque-to-current ratio curve and select multiple effective current values ​​from the curve; The rotor electrical angle is measured simultaneously using a rotary transformer and a Hall position sensor; Coordinate transformation is performed based on the rotor electrical angle read from the rotary transformer, and rotor field-oriented control of the motor is performed based on the maximum torque-current ratio control strategy; rotor field-oriented control of the motor based on the maximum torque-current ratio control strategy is what is commonly referred to in this field as MTPA control.

[0036] For each effective current value, the load is gradually adjusted so that the measured stator current equals the effective current value; the zero electrical angle of the Hall position sensor is obtained and the difference between it and the actual d-axis angle of the rotor is calculated to obtain the magnetic field offset angle under the current operating condition; thus, a data point corresponding to the effective stator current value and the magnetic field offset angle is obtained. By iterating through the effective values ​​of each stator current, multiple discrete data points are obtained; By fitting the discrete data points, a continuous compensation curve of the stator current effective value and the magnetic field offset angle is obtained.

[0037] A test platform can be used that connects the motor to the dynamometer, and the load can be gradually adjusted from light load to heavy load using the dynamometer.

[0038] Furthermore, the method for generating the maximum torque-to-current ratio curve is as follows: Calibration was performed by point-by-point scanning, sequentially setting multiple effective values ​​for the stator current. A test platform was built using a motor and dynamometer docking. For each set effective stator current value, the motor was controlled to run at a constant speed at that current value. The current lead angle was gradually adjusted, and the output torque was measured to determine the optimal current lead angle that maximized the output torque, thus obtaining the maximum torque operating point at that current value. Multiple operating points were obtained by traversing different effective stator current values, and a maximum torque-current ratio curve corresponding to the effective stator current value and the output torque was generated (e.g., fitted). By converting the parameters of each operating point into the direct-axis and quadrature-axis currents required for vector control, a mapping relationship between the direct-axis current, quadrature-axis current, and output torque was finally established.

[0039] Furthermore, the method for determining the installation error angle of the Hall position sensor is as follows: Under no-load conditions, by selecting the rotor main pole N as the d-axis and comparing the phase relationship of the rising edge of the A-phase Hall signal, the difference between the estimated Hall angle zero point and the d-axis is obtained. This difference is the installation error angle.

[0040] The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor described in this embodiment is used for MTPA control of a ferrite permanent magnet assisted synchronous reluctance motor. The MTPA control method includes: The rotor electrical angle is estimated based on the Hall position sensor; Real-time acquisition of motor stator current; Based on the compensation curve of the magnetic field offset angle as a function of the stator current effective value, the magnetic field offset angle corresponding to the measured stator current effective value is obtained. The rotor electrical angle is estimated based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle. Based on the compensated rotor electrical angle, the stator current is transformed by coordinate transformation to calculate the feedback signals of direct-axis current and quadrature-axis current. With the current command output from the maximum torque-current ratio curve as the target, and combined with the calculated direct-axis current and quadrature-axis current feedback signals, real-time tracking and adjustment are achieved through current closed-loop control, so that the motor operating point always tracks the maximum torque-current ratio curve and ensures that the motor outputs maximum torque.

[0041] This MTPA control method, based on measurable stator current, utilizes an offline calibrable compensation curve showing the change of the magnetic field offset angle with the effective value of the stator current. It calculates and actively superimposes the angle compensation in real time to counteract the magnetic field offset caused by armature reaction, which varies with the current. This feedforward dynamic compensation effectively eliminates the angle deviation, ensures the magnetic field orientation accuracy, and enables the motor to operate stably at the optimal operating point of MTPA across the entire current range, fully leveraging the high efficiency and high power density advantages of ferrite permanent magnet assisted synchronous reluctance motors.

[0042] Example 2 like Figures 1-11 As shown in the figure, this embodiment describes a method for compensating the rotor electrical angle of a ferrite permanent magnet assisted synchronous reluctance motor, including the following steps: S01: Based on the Hall position sensor, obtain the estimated value of the rotor electrical angle at time t; The physical premise of this embodiment is that the permanent magnet assisted synchronous reluctance motor uses ferrite as the permanent magnet. The material was measured using a Hall effect position sensor; ferrite permanent magnets have the inherent characteristic of low remanence, resulting in a low permanent magnet flux linkage. It is significantly weaker than rare-earth permanent magnets such as neodymium iron boron. The Hall position sensor outputs a low-resolution discrete position signal. The primary task of this embodiment is to convert the low-resolution discrete position signal output by the Hall position sensor into continuous rotor position and speed information that meets the requirements of vector control.

[0043] Based on the precise mapping relationship between the digital signal transition edge of the Hall position sensor and the absolute spatial position of the rotor, an angular reference can be provided for the entire control system, such as... Figure 1 As shown, if the Hall position sensor is installed without error, the duty cycle of the three Hall signals with a phase difference of 120° electrical angle is 50%. One electrical cycle can be divided into 6 uniform intervals using XOR logic, as shown below. Figure 2 As shown, its rising and falling edges evenly divide one electrical cycle into six 60° sectors. By aligning the rotor shaft to a known position (e.g., using d-axis positioning), the absolute electrical angle value corresponding to the boundary of each sector can be determined. These six angles constitute the absolute reference points for rotor position observation; Between two adjacent Hall effect transitions, the rotor rotates a fixed electrical angle of 60°. The time interval between these two transitions is measured using a high-precision timer. You can then use the formula The average electrical angular velocity within this interval is calculated, thus achieving low-cost velocity measurement using the edge moments of the Hall signal. Although the output is stepped, subsequent processing can provide the system with basic velocity closed-loop capability.

[0044] Ideally, based on the Hall transition signal, the continuous rotor electrical angle... It can be shown by formula (1).

[0045] (1) in, Electric angular velocity; For the previous Hall transition moment The corresponding accurate electrical angle; Will exist Taylor expansion is performed at each time step, as shown in formula (2).

[0046] (2) The higher the order of formula (2), the more accurate the estimation. However, considering the real-time computing power of digital controllers, the zero-order or first-order approximation is most commonly used.

[0047] In specific implementations of this invention, such as Figure 3 , Figure 4 , Figure 5 As shown, an average velocity algorithm (i.e., a first-order approximation) is used for angle interpolation. Its basic principle is based on the characteristic that the mechanical dynamic response of an electric motor is much slower than that of electrical control. It can be approximated that within a whole sector (60° electrical angle) defined by two adjacent Hall effect transitions, the electrical angular velocity... Keep constant. For example... Figure 4 , Figure 5 The Hall angle estimation principle shown is that when the rotor enters the i-th Hall sector, the estimated electrical angular velocity in that sector is... The average electric angular velocity calculated in the previous sector (sector i-1) is used. .

[0048] The calculation formula is shown in formula (3).

[0049] (3) in, For a fixed sector electrical angle difference, The time interval between adjacent Hall transition edges is obtained by capturing the timer. and Let i and i be the times when the (i-1)th and i-th Hall transitions occur, respectively. and These are the calibrated absolute discrete electrical angle reference values ​​corresponding to these two moments.

[0050] Obtaining the average electric angular velocity Then, it can be performed in the i-th sector. The rotor electrical angle is calculated using linear interpolation. The estimated rotor electrical angle at any time t is... As shown in formula (4).

[0051] (4) in, The starting absolute reference angle of the current sector. Within each PWM control cycle, the above formula can be equivalent to formula (5).

[0052] (5) Where k is the PWM cycle count after entering the current sector.

[0053] The above integration process can accumulate errors due to speed estimation errors or timing deviations. To address this issue, this embodiment performs direct correction and amplitude limiting. When the next Hall transition edge is... When the moment arrives, the system will immediately use the estimated angle value calculated according to formula (4). Forced correction to the starting absolute reference angle of the next sector , that is to say This operation eliminates accumulated errors. It prevents errors caused by calculation errors within sectors. Exceeding in advance or below Update each time formula (4) is used. After that, it needs to be limited, as shown in formula (6).

[0054] (6) Constrain it to satisfy .

[0055] The amplitude limiting is directly corrected by interpolation using the average velocity method and the jump edge, as described above. Figure 4 and Figure 5 As shown, the system ultimately obtains a continuous and high-precision rotor position function, based on which the estimated rotor electrical angle value at each moment can be obtained. .

[0056] S02: Determine the installation error angle of the Hall position sensor; Due to the inherent low remanence of ferrite permanent magnet materials, the provided permanent magnet flux linkage It is significantly weaker than rare-earth permanent magnet materials. This fundamental difference leads to a unique magnetic field sensing bias phenomenon. For example... Figure 8 As shown, under no-load conditions, due to the relatively weak magnetic field of the ferrite permanent magnet, there is an inherent deviation angle between the zero-crossing point of the air gap synthetic magnetic field sensed by the Hall position sensor (i.e., the transition edge of the Hall signal) and the Hall trigger zero position of the rare-earth permanent magnet material. This deviation angle It is determined by both the sensor's installation location and the characteristics of the weak magnetic field distribution.

[0057] Under no-load conditions, by selecting the main pole N as the d-axis and comparing the phase relationship of the rising edge of the A-phase Hall signal, the difference between the estimated Hall angle zero point and the actual d-axis is obtained, which is the installation error angle. .

[0058] S03: Based on the maximum torque-current ratio curve, a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current is pre-established. At a constant rotational speed, the effective values ​​of different stator currents were calibrated using a point-by-point scanning method. The corresponding maximum torque current vector lead angle This ultimately forms the maximum torque-to-current ratio (MTPA) control curve for the motor. The MTPA fitting curve is shown below. Figure 6 As shown, the results were obtained through offline calibration: on a platform where the motor and dynamometer are connected, the motor is controlled to run at a constant speed, and the effective values ​​of the stator current are obtained for different... Find the optimal current lead angle that maximizes the output torque. And then fit to obtain , Mapping relationship with torque. Current lead angle. That is, the stator current vector and The included angle of the axis, then , The expression for the shaft current is shown in formula (7).

[0059] (7) The expression for the electromagnetic torque is further obtained as shown in formula (8).

[0060] (8) Where: Te is the torque, P is the number of pole pairs of the motor, Ld is the direct-axis inductance, and Lq is the quadrature-axis inductance; When the motor is operating under the MTPA control strategy, the control system injects a component including direct-axis demagnetization. and generate cross-axis armature reaction magnetic field current stator current RMS value The armature reaction magnetic field generated by this current interacts with the originally weak permanent magnet magnetic field, significantly altering the spatial vector direction of the resultant magnetic field in the air gap. For example... Figure 8 As shown, for ferrite permanent magnet motors, the weak permanent magnet field cannot provide sufficient remanence to resist the torsional effect of the armature reaction magnetic field, causing the axis of the synthesized magnetic field to shift further relative to its no-load position. Therefore, a current-dependent magnetic field is generated between the Hall position sensor triggering the electrical zero position and the rotor's actual d-axis direction. The dynamically changing error offset angle, i.e., the magnetic field offset angle defined in this invention. Without compensation, the control system will perform coordinate transformation based on the position signal with deviation, resulting in abnormal motor torque output and inability to start and operate under load normally. The compensation method described in this invention is precisely for online dynamic compensation of this dynamic offset angle caused by current, and for finding the accurate magnetic field offset angle. .

[0061] The core of this invention lies in establishing offline calibration. and A precise quantization model.

[0062] Based on the calibrated MTPA curve, determine the value at each calibration current. Below, the difference between the zero electrical angle of the Hall position sensor and the actual d-axis angle of the rotor is the magnetic field offset angle. Through multiple groups By fitting the data points to a curve, a mapping relationship between the magnetic field offset angle and the effective value of the stator current can be established. Compensation curve.

[0063] On a controllable test platform, the rotor electrical angle is measured simultaneously using a rotary transformer and a Hall position sensor. Coordinate transformation is performed based on the actual rotor electrical angle read from the resolver, allowing the motor to operate at different steady-state operating points determined by the MTPA control strategy. The position information corresponding to the actual rotor d-axis read from the resolver is recorded at this point, and the difference between the two is the current effective value of the stator current. Magnetic field deflection angle generated under action The measured value; By traversing multiple different ranges from light load to overload The working point, through testing, yields a set of discrete data points. The data set is processed using a curve fitting algorithm to generate a continuous compensation curve, i.e. Functional model. The compensation curve reveals that the distortion of the air gap magnetic field of the permanent magnet assisted synchronous reluctance motor by the armature reaction magnetic field is systematic and related to the effective value of the stator current. The complex magnetic field coupling effect is transformed into a clear and quantifiable mapping relationship between the magnetic field offset angle and the effective value of the stator current, providing a direct basis for online real-time compensation. For example... Figure 9 As shown, the compensation curve quantitatively describes the variation of magnetic field sensing offset with load current in a specific ferrite permanent magnet assisted synchronous reluctance motor.

[0064] S04: Obtain the measured effective value of the stator current at time t; During the online operation of the motor, the effective value of the stator current is acquired in real time. .

[0065] S05: Based on the compensation curve, obtain the magnetic field offset angle corresponding to the measured effective value of the stator current, and compensate the estimated value of the rotor electrical angle based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle at time t.

[0066] During the online operation of the motor, the control system collects the effective value of the stator current in real time. Query the above The compensation curve is used to obtain the real-time effective value of the stator current. Corresponding real-time magnetic field offset angle ; and the installation error angle and magnetic field offset angle The compensated rotor electrical angle is applied to the obtained estimated rotor electrical angle to form the final compensated rotor electrical angle used for coordinate transformation. The specific formula is as follows: ; in, This refers to the installation error angle; This is an estimated value for the rotor electrical angle; This is the magnetic field offset angle; like Figure 10 As shown, the MTPA control method using the ferrite permanent magnet assisted synchronous reluctance motor rotor electrical angle compensation method described in this embodiment achieves dynamic closed-loop correction of the rotor position angle within each control cycle. In the current closed-loop regulation stage, three-phase current sensors collect the motor phase currents in real time, and obtain feedback values ​​id and iq through Clarke transformation and Park transformation. The deviation between the MTPA command currents id* and iq* and the feedback currents is sent to the d-axis and q-axis current PI regulators, outputting the corresponding d-axis voltage command ud and q-axis voltage command uq. Subsequently, the voltage command in the synchronous rotating coordinate system is converted to the stationary two-phase coordinate system through inverse Park transformation, generating ualpha and ubeta. Then, the voltage vector is synthesized through the space vector pulse width modulation (SVPWM) algorithm, driving the three-phase inverter to generate the actual voltage applied to the motor stator windings. The rotor electrical angle is used for Park transformation and inverse Park transformation.

[0067] Compared with existing technologies, this embodiment reveals and solves the magnetic field offset problem caused by the dynamic control current of MTPA, which is strongly correlated with the current amplitude. The core of this invention lies in establishing an offset angle model that reflects the internal electromagnetic characteristics of the motor by combining offline MTPA calibration with offset angle calibration. During online operation, high-precision dynamic compensation can be achieved simply by looking up a table and performing calculations based on the real-time current. A proprietary solution is provided directly to address the dynamic magnetic field offset caused by the coupling of the weak magnetic properties of ferrite materials and MTPA control, making it possible to use a low-cost position sensing scheme for this type of motor. Through advanced algorithm compensation, high-precision rotor position sensing and magnetic field orientation control can be achieved using only low-resolution, low-cost Hall sensors, eliminating the need for high-precision position sensors. This breaks the traditional constraint that high-performance vector control must rely on high-precision hardware, significantly reducing hardware costs while ensuring system control accuracy and dynamic performance. Furthermore, this invention is simple and reliable, does not rely on uniform motor speed operation, is easy to implement and promote in engineering, and significantly improves the performance and reliability of permanent magnet assisted synchronous reluctance motor systems using ferrite and Hall sensors.

[0068] Example 3 This embodiment describes a rotor electrical angle compensation system for a ferrite permanent magnet assisted synchronous reluctance motor, which includes the following modules: The electrical angle estimation module is used to obtain the estimated value of the rotor electrical angle at time t based on the Hall position sensor. The installation error determination module is used to determine the installation error angle of the Hall position sensor; The compensation curve establishment module is used to pre-establish a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current, based on the maximum torque-current ratio curve. The current acquisition module is used to acquire the effective value of the stator current measured at time t. The electrical angle compensation module is used to obtain the magnetic field offset angle corresponding to the measured effective value of the stator current according to the compensation curve, and to compensate the estimated value of the rotor electrical angle based on the magnetic field offset angle and the installation error angle, so as to obtain the rotor electrical angle at time t.

[0069] The module in this application is an object that uses physical or virtual representation to form an objective description of form and structure. The object is not the same as a physical object, and is not limited to physical or virtual. It can be a data processing function, software program, processing mode, usage method, operation mode, workflow, application process, electronic hardware, circuit module, processing system, system imitation or simulation object.

[0070] Example 4 This embodiment describes an electronic device, which includes a processing unit and a storage device. The storage device is used to store one or more programs. When the processing unit executes the one or more programs, it implements the rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in Embodiment 1 or 2 above.

[0071] The storage device can be internal memory, external memory, cache memory, or other special memory.

[0072] The processing unit has signal processing capabilities and can be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, an off-the-shelf programmable gate array, or other programmable logic devices.

[0073] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features within the scope of the technology disclosed in the present invention; and these modifications or substitutions will not cause the substance of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. Any modifications or equivalent substitutions that do not deviate from the spirit and scope of the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for compensating the rotor electrical angle of a ferrite permanent magnet assisted synchronous reluctance motor, characterized in that, Includes the following steps: Based on the Hall position sensor, the estimated value of the rotor electrical angle at time t is obtained; Determine the installation error angle of the Hall position sensor; Based on the maximum torque-current ratio curve, a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current is pre-established. Obtain the measured effective value of the stator current at time t; Based on the compensation curve, the magnetic field offset angle corresponding to the measured effective value of the stator current is obtained, and the rotor electrical angle is compensated based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle at time t.

2. The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in claim 1, characterized in that, The method for obtaining the estimated rotor electrical angle at time t based on the Hall position sensor is as follows: Based on a three-phase Hall position sensor, six electrical angles corresponding to Hall state transitions are obtained as discrete reference values. The position of the rotor is detected using a Hall position sensor, and the electrical angular velocity of the rotor is calculated. Based on the rotor's electrical angular velocity and discrete reference values, a continuous function of the electrical angle value changing with time is obtained, and the electrical angle value at time t in the continuous function is used as the estimated value of the rotor's electrical angle at that time.

3. The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in claim 2, characterized in that, Based on the Hall position sensor, other methods for obtaining the rotor electrical angle estimate at time t include: When a Hall state transition is detected, the corresponding discrete reference value is used as the estimated rotor electrical angle at that moment.

4. The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in claim 2, characterized in that, The method for calculating the electric angular velocity of the rotor is as follows: Obtain the time interval between two adjacent discrete reference values ​​of the rotor; The electric angular velocity of the rotor is obtained by dividing the angle difference between two adjacent discrete reference values ​​by the time interval. Alternatively / and, based on the rotor's electrical angular velocity and discrete reference values, the method for obtaining a continuous function of the electrical angle value changing with time is as follows: The electrical angle period of the motor is divided into six sectors based on six discrete reference values; When a Hall state transition is detected, the discrete reference value corresponding to the state transition is used as the initial value of the current sector. Based on the rotor electric angular velocity of the previous sector, the current sector is integrated and linearly interpolated to obtain a continuous function of the electric angle value changing with time.

5. The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in claim 1, characterized in that, The method for establishing a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current, based on the maximum torque-current ratio curve, is as follows: Obtain the maximum torque-to-current ratio curve and select multiple effective current values ​​from the curve; The rotor electrical angle is measured simultaneously using a rotary transformer and a Hall position sensor; Coordinate transformation is performed based on the rotor electrical angle read from the rotary transformer, and rotor field orientation control of the motor is performed based on the maximum torque-current ratio control strategy. For each effective value of current, the load is gradually adjusted until the measured stator current equals that effective value of current; Obtain the zero-position electrical angle of the Hall position sensor and calculate the difference between it and the actual d-axis angle of the rotor to obtain the magnetic field offset angle under the current operating condition; thereby obtaining a data point corresponding to the effective value of the stator current and the magnetic field offset angle. By iterating through the effective values ​​of each stator current, multiple discrete data points are obtained; By fitting the discrete data points, a continuous compensation curve of the stator current effective value and the magnetic field offset angle is obtained.

6. The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in claim 5, characterized in that, The method for generating the maximum torque-to-current ratio curve is as follows: Calibration is performed by scanning point by point, and multiple effective values ​​of stator current are set sequentially. A test platform is built by connecting the motor and the dynamometer. For each set effective value of stator current, the motor is controlled to run at a constant speed at that effective value of current. The current lead angle is gradually adjusted and the output torque is detected to determine the optimal current lead angle that maximizes the output torque and obtain the maximum torque operating point under that effective value of current. Multiple operating points are obtained by traversing different effective values ​​of stator current, and the maximum torque-current ratio curve corresponding to the effective value of stator current and the output torque is generated accordingly.

7. The rotor electrical angle compensation method for a ferrite permanent magnet assisted synchronous reluctance motor as described in claim 2, characterized in that, The method for determining the installation error angle of a Hall position sensor is as follows: Under no-load conditions, by selecting the rotor main pole N as the d-axis and comparing the phase relationship of the rising edge of the A-phase Hall signal, the difference between the estimated Hall angle zero point and the d-axis is obtained. This difference is the installation error angle.

8. A method for compensating the rotor electrical angle of a ferrite permanent magnet assisted synchronous reluctance motor as described in any one of claims 1 to 7, characterized in that, It is used for MTPA control of ferrite permanent magnet assisted synchronous reluctance motors, and the control method of the MTPA control includes: The rotor electrical angle is estimated based on the Hall position sensor; Real-time acquisition of motor stator current; Based on the compensation curve of the magnetic field offset angle as a function of the stator current effective value, the magnetic field offset angle corresponding to the measured stator current effective value is obtained. The rotor electrical angle is estimated based on the magnetic field offset angle and the installation error angle to obtain the compensated rotor electrical angle. Based on the compensated rotor electrical angle, the stator current is transformed by coordinate transformation to calculate the feedback signals of direct-axis current and quadrature-axis current. With the current command output from the maximum torque-current ratio curve as the target, and combined with the calculated direct-axis current and quadrature-axis current feedback signals, real-time tracking and adjustment are achieved through current closed-loop control, so that the motor operating point always tracks the maximum torque-current ratio curve and ensures that the motor outputs maximum torque.

9. A rotor electrical angle compensation system for a ferrite permanent magnet assisted synchronous reluctance motor, characterized in that, Includes the following modules: The electrical angle estimation module is used to obtain the estimated value of the rotor electrical angle at time t based on the Hall position sensor. The installation error determination module is used to determine the installation error angle of the Hall position sensor; The compensation curve establishment module is used to pre-establish a compensation curve for the magnetic field offset angle as a function of the effective value of the stator current, based on the maximum torque-current ratio curve. The current acquisition module is used to acquire the effective value of the stator current measured at time t. The electrical angle compensation module is used to obtain the magnetic field offset angle corresponding to the measured effective value of the stator current according to the compensation curve, and to compensate the estimated value of the rotor electrical angle based on the magnetic field offset angle and the installation error angle, so as to obtain the rotor electrical angle at time t.

10. An electronic device comprising a processing unit and a storage device, the storage device being used to store one or more programs; characterized in that, When the one or more programs are executed by the processing unit, the rotor electrical angle compensation method of the ferrite permanent magnet assisted synchronous reluctance motor as described in any one of claims 1 to 8 is implemented.

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