A calibration method for an induction motor

Abstract

This invention discloses a calibration method for an induction motor, including optimal flux linkage calibration: dividing the torque into several equal parts based on the motor's maximum output torque, and sequentially increasing the torque; given a first base speed, adjusting the flux linkage value at each torque, and using the flux linkage value corresponding to the highest torque accuracy and efficiency of the motor drive system as the initial flux linkage value; and completing the optimal flux linkage calibration at each torque based on the initial flux linkage value. This invention, by allocating flux linkage at a fixed speed, has the advantages of systematically optimizing torque-flux linkage characteristics, improving operating accuracy and efficiency across the entire speed range, and balancing high-precision torque output and high-efficiency operation.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a calibration method for an induction motor. Background Technology

[0002] With the rapid development of the electric vehicle industry, the performance requirements for drive motors are increasing. Induction motors, as one of the commonly used drive motors in electric vehicles, directly affect the power, economy, and comfort of the vehicle. In electric vehicle drive systems, accurate motor calibration is crucial to ensuring efficient and stable motor operation. However, traditional induction motor calibration methods often suffer from the following technical problems: First, the calibration process lacks a systematic approach, making it difficult to achieve global optimization of torque-flux characteristics; second, traditional calibration techniques are insufficient in compensating for flux errors, resulting in limited torque control accuracy. These problems severely restrict the performance of induction motors in electric vehicle applications, especially under complex operating conditions requiring both high-precision torque output and high-efficiency operation.

[0003] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a calibration method for induction motors, which has the advantages of systematically optimizing torque-flux characteristics, improving operating accuracy and efficiency across the entire speed range, and balancing high-precision torque output and high-efficiency operation.

[0005] The technical solution adopted in this invention is: a calibration method for an induction motor, including optimal flux linkage calibration: Divide the torque into several equal parts based on the motor's maximum output torque, and increase the torque in sequence. Given a first base speed, the flux linkage value is adjusted under each torque, and the initial flux linkage value is the one that corresponds to the highest torque accuracy of the motor drive system and the highest efficiency of the motor drive system. The optimal flux linkage is calibrated for each torque based on the initial flux linkage value.

[0006] Furthermore, the step of calibrating the optimal flux linkage under each torque based on the initial flux linkage value includes: Multiple verification speeds were selected. At each torque, using the initial flux linkage value as a reference, it was determined whether the torque accuracy and efficiency of the motor drive system at the corresponding verification speed met the requirements. If satisfied, the initial flux linkage value is determined to be the optimal flux linkage under the corresponding torque. If the initial flux linkage value is not met, the flux linkage is fine-tuned based on the initial flux linkage value. The flux linkage value corresponding to the condition that the torque accuracy and efficiency of the motor drive system meet the requirements at all verified speeds is the optimal flux linkage for the corresponding torque.

[0007] Furthermore, the first basic rotational speed is 1 / 3 × n max ~2 / 3×n max n max This is the motor's maximum base speed.

[0008] Furthermore, the plurality of verification speeds includes a low verification speed and a high verification speed, wherein the low verification speed is less than 1 / 3×n. max The high verification speed is greater than 2 / 3×n max n max This is the motor's maximum base speed.

[0009] Furthermore, the requirement that the torque accuracy and efficiency of the motor drive system meet the requirements at all verified speeds means that the torque accuracy and efficiency of the motor drive system are within the set range at each verified speed.

[0010] Furthermore, it also includes flux linkage correction calibration: Divide the torque into several equal parts based on the motor's maximum output torque, and increase the torque in sequence. Given a second base speed, the flux linkage error value is adjusted for each torque, and the flux linkage error value corresponding to the highest torque accuracy of the motor drive system is used as the initial flux linkage error value. The flux linkage correction calibration is performed for each torque based on the initial flux linkage error value.

[0011] Furthermore, the step of performing flux correction calibration under each torque based on the initial flux error value includes: Multiple corrected speeds are selected, and at each torque, the torque accuracy of the motor drive system at the corresponding corrected speed is determined based on the initial flux linkage error value to see if it meets the requirements. If satisfied, then determine the flux correction value under the torque corresponding to the initial flux error value; If not, the flux linkage error is fine-tuned based on the initial flux linkage error value, and the flux linkage error value corresponding to the torque accuracy of the motor drive system at each corrected speed is determined as the corrected flux linkage error value. The average of the initial flux linkage error value and multiple corrected flux linkage error values ​​is taken as the flux linkage correction value under the corresponding torque.

[0012] Furthermore, the second basic rotational speed is 1 / 3 × n max ~2 / 3×n max n maxThis is the motor's maximum base speed.

[0013] Furthermore, the plurality of corrected speeds includes low-correction speeds and high-correction speeds, wherein the low-correction speed is less than 1 / 3×n. max The high-correction speed is greater than 2 / 3×n max n max This is the motor's maximum base speed.

[0014] Furthermore, after determining the flux linkage correction value under the corresponding torque, the corresponding q-axis current is recorded. Based on the determined data, the flux linkage error-q-axis current curve is fitted to obtain the flux linkage correction table.

[0015] The beneficial effects of this invention are as follows: This invention, by distributing flux at a fixed speed, has the advantages of systematically optimizing torque-flux characteristics, improving operating accuracy and efficiency across the entire speed range, and balancing high-precision torque output with high-efficiency operation. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the calibration process for the optimal magnetic flux linkage of this invention.

[0017] Figure 2 This is a flowchart of the calibration process for magnetic flux correction in this invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0019] This invention proposes a calibration method for induction motors, including optimal flux linkage calibration, such as... Figure 1 As shown: Divide the torque into several equal parts according to the maximum output torque of the motor, and increase the torque in turn; Given a first base speed, adjust the flux linkage value under each torque, and take the flux linkage value corresponding to the highest efficiency of the motor drive system that meets the torque accuracy requirements as the initial flux linkage value; Use the initial flux linkage value as the reference to complete the optimal flux linkage calibration under each torque.

[0020] Optimal flux linkage calibration refers to obtaining a set of flux linkage parameters that balances torque accuracy and system efficiency through systematic testing. This can be achieved using a piecewise optimization algorithm to ensure that each torque segment reaches its optimal operating state. Dividing the torque range into several equal parts involves discretizing the torque range, which can be achieved using linear or nonlinear partitioning to form a calibration point matrix covering the entire operating range. The first base speed is the benchmark test speed used to determine the initial flux linkage value. This can be achieved by selecting the middle value of the motor's base speed, serving as the starting point for parameter transfer. The motor's base speed is the highest speed before field weakening. The initial flux linkage value refers to the flux linkage parameters that simultaneously meet the requirements of torque accuracy and efficiency at the benchmark speed. This can be obtained through a multi-objective optimization algorithm and serves as a reference benchmark for subsequent calibration processes.

[0021] Specifically, this method first constructs a calibration parameter matrix through torque discretization, avoiding parameter redundancy in traditional full-domain calibration. At the base speed, the flux linkage value is dynamically adjusted for each torque point. By monitoring torque output error and system energy consumption data in real time, the flux linkage parameter that meets the accuracy threshold and has the lowest energy consumption is selected as the initial value. This initial value serves as the reference parameter for subsequent calibration and is extended to adjacent torque points through a parameter transfer mechanism, forming a continuous sequence of calibration parameters. Torque discretization ensures a uniform distribution of calibration points, dual-objective optimization at the base speed achieves accurate acquisition of core parameters, and the parameter transfer mechanism significantly reduces the number of repeated tests.

[0022] This invention transforms global calibration into a phased optimization process by establishing a benchmark parameter transfer system, thereby reducing the number of test points while ensuring parameter continuity. In particular, by employing dual-objective optimization at the base speed, it effectively resolves the conflict between efficiency and accuracy, avoiding the compromises made between the two in traditional methods.

[0023] Through the above technical solutions, this invention achieves simultaneous improvement in calibration efficiency and parameter quality. Torque discretization gives the calibration process a clear direction, reducing the number of invalid tests; dual-objective optimization at the base speed ensures the global optimality of core parameters; and the parameter transfer mechanism maintains the consistency of calibration parameters through inheritance. This enables the motor to maintain high-precision output and optimal energy efficiency over a wide torque range, making it particularly suitable for the complex operating conditions of electric vehicles with frequent load changes.

[0024] This invention further proposes to calibrate the optimal flux linkage for each torque based on an initial flux linkage value. This involves selecting multiple verification speeds, determining whether the torque accuracy and efficiency of the motor drive system at each verification speed meet the requirements based on the initial flux linkage value, and if so, determining the initial flux linkage value as the optimal flux linkage for that torque. If not, the flux linkage is fine-tuned based on the initial value, with the optimal flux linkage value being the one that meets the requirements for torque accuracy and efficiency at all verification speeds. After determining the optimal flux linkage, the system efficiency, bench torque, and flux linkage value for each torque are recorded, and the recorded data is entered into a calibration data table. Then, the optimal flux linkage table is automatically calculated using a formula.

[0025] Verification speed refers to multiple test speeds covering different operating conditions of the motor. This can be achieved by combining low-speed and high-speed ranges; for example, the low speed can be set to less than one-third of the motor's maximum base speed, and the high speed to more than two-thirds of the motor's maximum base speed. By covering a wide speed range, the adaptability of the flux linkage value under different operating conditions can be verified. Fine-tuning refers to making small adjustments to the flux linkage value with a preset step size. This can be achieved using the binary search method or gradient descent method, gradually approaching the optimal value to avoid over-adjustment leading to calibration divergence. Meeting the requirements for torque accuracy and efficiency means that the deviation between the measured torque and the target value is within the allowable range, and the system efficiency is not lower than a set threshold. This can be determined by real-time acquisition of current and voltage signals and calculation of power loss.

[0026] Specifically, after initial flux linkage calibration, multi-speed joint verification is performed for each torque point. At each torque, the initial flux linkage value is loaded into the motor controller, and the motor is run at all verification speeds, collecting torque output data and energy consumption data. The initial flux linkage value is considered valid when the torque error at all verification speeds does not exceed ±3% and the system efficiency is not less than 0.5 percentage points of the highest system efficiency. If any speed fails to meet the requirements, the flux linkage value is adjusted in 0.5% increments, and the full-speed verification is repeated until a flux linkage value that meets all speed requirements is found. This process avoids the computational burden of repeated calibration across the entire speed domain by inheriting the initial calibration results and limiting the adjustment range.

[0027] This invention achieves universality of the final flux linkage value across the speed domain by performing joint verification at multiple characteristic speeds and making limited adjustments based on the initial value, thus eliminating the need for repeated calibration at multiple speeds. Simultaneously, by setting upper and lower limits for the verification speed, it effectively covers the typical operating range of the motor, ensuring the reliability of the calibration results for practical application.

[0028] Through the above technical solution, the present invention reduces the number of calibrations by more than 60% while ensuring calibration accuracy through a multi-speed joint verification mechanism. At the same time, it ensures that the calibrated flux linkage value can maintain high system efficiency across the entire speed range, avoiding performance degradation caused by speed changes.

[0029] The present invention further proposes that the first basic speed is in the range of 1 / 3 to 2 / 3 of the highest basic speed of the motor. The given first basic speed is the basic speed for setting the dynamometer test bench, such as 3000 rpm.

[0030] The first base speed is the reference speed range selected during the index calibration process. Specifically, after obtaining the motor's highest base speed using a test bench, the 1 / 3 and 2 / 3 quantiles of this speed are determined numerically to define the speed range. The motor's highest base speed refers to the maximum speed at which the motor is allowed to operate under test conditions, usually determined by the motor's rated parameters or the limitations of the test equipment. The selection of this speed range can balance the differences in dynamic characteristics of the motor in different speed ranges, providing stable reference conditions for subsequent flux linkage calibration.

[0031] Specifically, during the calibration process, the first base speed is set to a medium speed range. This ensures that the motor's operating state is both away from the nonlinear effects caused by magnetic saturation and rotor resistance changes in the low-speed region, and avoids efficiency measurement errors caused by increased iron losses and significant temperature rise in the high-speed region. Within this speed range, the correspondence between the motor's output torque and flux linkage exhibits good smoothness, accurately reflecting the dynamic characteristics under typical operating conditions. By adjusting the flux linkage value within this range and selecting initial flux linkage values ​​that meet the torque accuracy and efficiency requirements, the reliability of the base data in subsequent multi-speed verification stages can be ensured, thereby reducing repeated calibration operations caused by deviations in the reference value.

[0032] This invention establishes a calibration benchmark that matches the dynamic characteristics of the motor by limiting the basic speed range, thus avoiding systematic errors caused by improper speed selection.

[0033] Through the above technical solution, this invention can effectively solve the problem of calibration result deviation caused by unreasonable selection of the base speed, ensuring the applicability of the initial flux linkage value under different speed conditions. This solution, by scientifically defining the speed range, reduces the number of repeated verifications caused by insufficient adjustment of the reference value, thus improving the overall efficiency of the calibration process.

[0034] This invention further proposes multiple verification speeds, including low verification speeds and high verification speeds, where the low verification speed is less than 1 / 3×n. max High-performance verification speed is greater than 2 / 3×n max n max This is the motor's maximum base speed.

[0035] The low verification speed refers to the speed range below one-third of the motor's maximum base speed. This can be achieved using a fixed percentage division method, such as defining 10%-30% of the maximum base speed as the low verification speed range. The high verification speed refers to the speed range above two-thirds of the motor's maximum base speed. This can be achieved using a stepped test point selection method, such as defining 70%-90% of the maximum base speed as the high verification speed range.

[0036] This invention constructs a verification system covering the entire operating range of the motor by dividing it into two boundary speed ranges: low and high. This eliminates the problem of calibration error accumulation caused by the segmentation of speed ranges. Through the above technical solution, this invention achieves synchronous optimization of motor flux linkage parameters under two extreme operating conditions: low-speed strong magnetic field and high-speed weak magnetic field. It solves the parameter adaptability contradiction that occurs in traditional calibration methods when the speed coverage is incomplete, and ensures a balance between torque control accuracy and energy conversion efficiency of the drive system across the entire speed range.

[0037] The present invention further proposes that the torque accuracy and efficiency of the motor drive system meet the requirements at all verification speeds, which means that the torque accuracy and efficiency of the motor drive system are within the set range at each verification speed.

[0038] The set range refers to the predefined allowable range for torque accuracy deviation and the minimum efficiency threshold. This can be set as a percentage or absolute value, for example, a torque accuracy deviation not exceeding ±3% and an efficiency not less than 0.5 percentage points of the highest system efficiency. This range ensures that the calibration results are within a controllable performance range by defining parameter boundaries. Verification speed refers to multiple test points covering the motor's operating speed range. For example, selecting low-speed points below one-third of the maximum base speed and high-speed points above two-thirds of the maximum base speed avoids localized validity in the calibration results by covering the entire speed range.

[0039] Specifically, during the calibration process, torque accuracy and efficiency must be independently tested at each verification speed point. If the torque accuracy at a certain speed point exceeds the set deviation range or the efficiency falls below the threshold, the flux linkage value must be readjusted until the parameters at all speed points simultaneously meet the standards. For example, based on the initial flux linkage value, if the efficiency at high speed does not reach the threshold, the flux linkage needs to be fine-tuned and the parameters at all speed points re-verified to ensure that the adjusted flux linkage value can simultaneously meet the dual requirements of low-speed, medium-speed, and high-speed operating conditions.

[0040] This invention eliminates performance fluctuations caused by speed differences by forcing parameters at all verification speed points to meet standards, thus ensuring stable calibration results across the entire speed range. This invention ensures that the motor simultaneously meets torque control accuracy and system efficiency requirements under different speed conditions, avoiding the problem of performance degradation at other speeds due to optimization only at specific speeds during calibration, thereby improving the comprehensiveness and applicability of the calibration results.

[0041] This invention further proposes a method for correcting and calibrating the flux linkage of an induction motor, such as... Figure 2 As shown, the process includes dividing the torque into several equal parts based on the maximum output torque of the motor and increasing the torque sequentially, giving a second base speed and adjusting the flux linkage error value under each torque, taking the flux linkage error value corresponding to the highest torque accuracy of the motor drive system as the initial flux linkage error value, and completing the flux linkage correction calibration under each torque based on the initial flux linkage error value.

[0042] The flux linkage correction calibration refers to establishing a dynamic compensation mechanism for flux linkage parameters. This can be achieved through a combination of offline calibration and online compensation. By iteratively optimizing the flux linkage error under multiple speed conditions, compensation parameters adaptable to different operating conditions are formed. The second base speed refers to the typical speed within the stable operating range of the motor's medium speed. Specifically, it can be selected from 1 / 3 to 2 / 3 of the motor's highest base speed. This speed range reflects the dynamic characteristics of the motor under normal operating conditions. Flux linkage error value adjustment refers to correcting the parameters of the flux linkage observation model through a closed-loop control algorithm. Specifically, gradient descent or particle swarm optimization algorithms can be used to match the deviation between the actual torque output and the target value in real time.

[0043] Specifically, the equal division of torque ensures that the calibration process covers the entire operating range of the motor, avoiding control blind spots caused by uneven torque segmentation in traditional methods. The selection of a second base speed provides a stable test environment for the initial calibration of flux linkage error. Initial compensation values ​​are obtained through parameter optimization at this speed. Based on these initial values, multi-speed verification and correction are performed. By fine-tuning parameters in both low-speed and high-speed regions, a comprehensive compensation scheme that considers different speed characteristics is formed. During the correction process, torque accuracy is used as the core optimization indicator, directly calibrating the key performance parameters of the control system, effectively improving the practicality of the calibration results.

[0044] This invention overcomes the limitations of single-condition calibration by constructing a multi-speed verification mechanism and iteratively optimizing parameters across low, medium, and high speed ranges. A dynamic error compensation mechanism replaces fixed parameter compensation, significantly improving the adaptability of flux linkage parameters to changes in system operating conditions. This invention achieves improved torque output accuracy of the motor over a wide speed range, and the established dynamic flux linkage error compensation mechanism enhances the robustness of the control system to speed changes, enabling the motor to maintain precise torque control under different operating conditions. The multi-speed collaborative calibration method effectively eliminates parameter deviations caused by single-condition calibration, improving the engineering applicability of the flux linkage parameter calibration results.

[0045] This invention further proposes a method for completing flux linkage correction calibration under each torque based on an initial flux linkage error value. The method includes the following steps: selecting multiple correction speeds; under each torque, determining whether the torque accuracy of the motor drive system at the corresponding correction speed meets the requirements based on the initial flux linkage error value; if it does, determining the initial flux linkage error value as the flux linkage correction value under the corresponding torque; if it does not, fine-tuning the flux linkage error based on the initial flux linkage error value, and determining the flux linkage error value corresponding to when the torque accuracy of the motor drive system at each correction speed meets the requirements as the correction flux linkage error value; and taking the average of the initial flux linkage error value and multiple correction flux linkage error values ​​as the flux linkage correction value under the corresponding torque.

[0046] The initial flux linkage error value refers to the baseline parameter obtained after adjusting the flux linkage error value using a second base speed. Specifically, it can be obtained by optimizing torque accuracy at a specific speed, providing a basic correction reference for different torque conditions. Multiple correction speeds refer to test points covering both low and high speed ranges. For example, multiple values ​​can be set below one-third and above two-thirds of the maximum base speed to verify the adaptability of the flux linkage correction value at different speeds. Fine-tuning refers to incrementally adjusting the flux linkage error value with a preset step size. For example, each adjustment can be controlled within 0.5% to 1% of the rated flux linkage value, eliminating deviations caused by single-speed calibration. Average value calculation involves arithmetically averaging the initial value with multiple correction values, such as using a weighted average or simple average algorithm. This balances parameter differences under different speed conditions, improving the global applicability of the correction value.

[0047] Specifically, after calibrating the initial flux linkage error value, cross-validation is performed at multiple correction speeds. If the torque accuracy meets the requirements at all correction speeds, the initial value is directly used as the final correction parameter. When there are speed points that do not meet the accuracy requirements, the flux linkage error value is gradually adjusted until all speed points meet the requirements, and the correction value corresponding to each speed is recorded. Finally, the initial value and each correction value are averaged to form a comprehensive correction parameter that takes into account different speed conditions. This method ensures the effectiveness of the correction parameter across the entire speed range through a multi-speed verification mechanism, while using an averaging algorithm to suppress local over-adjustment or under-adjustment, achieving global optimization of flux linkage correction.

[0048] This invention effectively covers the characteristic differences between low-speed and high-speed regions through multi-speed cross-validation and dynamic compensation mechanisms. Furthermore, using an average value algorithm instead of a single correction value reduces the impact of extreme operating conditions on calibration results and avoids parameter inaccuracies caused by abnormalities at individual speed points.

[0049] Through the above technical solution, this invention solves the problem of insufficient flux linkage correction accuracy in traditional calibration methods at different speeds, significantly improving torque control stability across the entire speed range. This method combines multi-dimensional verification with dynamic compensation to ensure that the flux linkage correction parameters maintain high accuracy under different speed conditions, thereby enhancing the control robustness of the motor drive system.

[0050] This invention further proposes that after determining the flux linkage correction value under the corresponding torque, the corresponding q-axis current is recorded simultaneously, the recorded data is filled into the calibration data table, and the flux linkage error-q-axis current curve is fitted based on the recorded data to obtain the flux linkage correction table.

[0051] The flux linkage correction value refers to the parameter used to adjust the flux linkage error so that the torque accuracy of the motor drive system meets the requirements. Specifically, it can be achieved by iteratively optimizing the flux linkage error using gradient descent or least squares methods, compensating for the impact of flux linkage error on torque accuracy under different operating conditions. The q-axis current refers to the current component in the motor control system that is directly related to torque. It can be acquired in real time using a current sensor or observer, reflecting the dynamic characteristics of the motor's output torque. The flux linkage error-q-axis current curve is a functional relationship between flux linkage error and q-axis current established through data fitting. This can be achieved using polynomial fitting or neural network modeling methods, describing the variation of flux linkage error with q-axis current. The flux linkage correction table is a lookup table storing the correspondence between flux linkage error and q-axis current. It can be implemented by discretizing the curve data and storing it as a two-dimensional array, used for quickly matching the flux linkage correction parameters under the current operating condition.

[0052] Specifically, during the calibration of the flux linkage correction value for each torque, the q-axis current value corresponding to the current torque is recorded simultaneously, and the correlation data between the flux linkage error and the q-axis current is used as input samples. A continuous function model of the flux linkage error as a function of the q-axis current is established through a fitting algorithm, generating a flux linkage correction table covering different current ranges. During actual motor operation, the correction table is consulted based on the real-time collected q-axis current value, and the flux linkage error compensation is dynamically adjusted to eliminate calibration errors caused by dynamic changes in current.

[0053] This invention introduces q-axis current as a correlated variable to establish a dynamic model of flux linkage error and current, enabling the correction parameters to be adaptively adjusted with changes in current, thus solving the problem that discrete calibration data cannot adapt to dynamic operating conditions.

[0054] Through the above technical solution, this invention achieves a systematic modeling of the dynamic relationship between flux linkage error and current, avoiding the problem of error accumulation caused by ignoring current changes, and improving the continuity and applicability of calibration data. The fast lookup mechanism of the flux linkage correction table reduces the number of repeated calibrations, improves calibration efficiency, and ensures torque control accuracy under different current conditions.

[0055] The present invention further proposes that the second base speed is in the range of 1 / 3 to 2 / 3 of the highest base speed of the motor. The given second base speed is the base speed for setting the dynamometer test bench, such as 3000 rpm.

[0056] The second base speed is the reference speed range selected during the index calibration process. Specifically, after obtaining the motor's highest base speed using a test bench, the 1 / 3 and 2 / 3 quantiles of this speed are determined through numerical calculation, thus defining the speed range. The selection of this speed range balances the differences in dynamic characteristics across different speed ranges of the motor, providing stable reference conditions for subsequent flux linkage calibration.

[0057] This invention further proposes multiple correction speeds, including low correction speeds and high correction speeds, where the low correction speed is less than 1 / 3×n. max High correction speed is greater than 2 / 3×n max n max This is the motor's maximum base speed.

[0058] Here, low correction speed refers to the speed range below one-third of the motor's maximum base speed. This can be achieved by setting a speed threshold, for example, setting n... max 30% is used as the upper limit of the low-correction speed. This speed range corresponds to motor starting or high torque output conditions, where rotor resistance changes significantly affect flux linkage observation errors and require targeted correction. The high-correction speed refers to the speed range higher than two-thirds of the motor's highest base speed. This can be achieved by setting a speed threshold, for example, setting n...max 70% is used as the lower limit of the high-correction speed. This speed range corresponds to the field weakening speed boundary. At this point, the iron loss increases, leading to a decrease in system efficiency. It is necessary to use flux error correction to balance torque accuracy and losses.

[0059] In some specific implementations, the low correction speed can be set to n. max 10%-30%, high correction speed can be set to n max The accuracy ranges from 70% to 90%. During the calibration process, flux linkage error data corresponding to low and high correction speeds can be collected at each torque, and the final correction value can be generated by weighted averaging or curve fitting.

[0060] This invention overcomes the limitations of single-range calibration by adding verification points at low and high correction speeds, achieving dynamic error compensation across the entire speed range. Through this technical solution, the invention addresses the problem of insufficient flux linkage correction calibration accuracy under extreme low and high speed conditions using traditional methods, enabling the motor drive system to simultaneously meet torque accuracy requirements and efficiency optimization needs across a wide speed range. Specifically, it effectively suppresses torque fluctuations caused by rotor resistance changes in the low correction speed range and reduces efficiency decline due to iron losses in the high correction speed range, thereby improving the motor's operational stability and economy under all operating conditions.

[0061] This invention also provides a method for calibrating the stator resistance of an induction motor, which involves measuring the resistance values ​​Ruv, Rvw, and Rwu between two phases at the motor connection point using a milliohm meter or a bridge. The average of the three resistance values ​​is taken as the stator resistance R = (Ruv + Rvw + Rwu) / 3.

[0062] This invention also provides a method for calibrating the rotor resistance and leakage inductance of an induction motor, which obtains the rotor resistance and leakage inductance calibration through a stall test. Specifically, the low-voltage power supply is set to 12V, the high-voltage power supply is set to 650V, the water cooling equipment is turned on, the flux linkage calibration is turned off, and the controller is turned on. The dynamometer stand is set to 0rpm to ensure that the motor rotor is stationary. The current is divided into several equal parts according to the maximum current of the motor, and the current is increased sequentially. The average effective value of the line voltage, the average effective value of the line current, the average power factor, and the stator temperature in the report are recorded on the power analyzer at each current. The recorded data are filled into a calibration data table, and then the rotor resistance and leakage inductance are automatically calculated according to the formula.

[0063] This invention also provides a method for calibrating the main inductance of an induction motor, which obtains the main inductance through a no-load test. Specifically, the low-voltage power supply is set to 12V, the high-voltage power supply to 650V, the water cooling equipment is turned on, the flux linkage correction is turned off, and the controller is turned on. The dynamometer test bench is set to 1000rpm. The current is increased sequentially, and the average effective value of the line voltage, the average effective value of the line current, and the average power factor on the power analyzer are recorded at each current. The recorded data are entered into a calibration data table, and then the main inductance is automatically calculated according to the formula.

[0064] This invention also provides a method for calibrating the maximum driving torque and maximum generating torque of an induction motor, i.e., calibrating the motor's external characteristic limiting parameters. Specifically, the low-voltage power supply is set to 12V, the high-voltage power supply is set to 650V, and the water-cooling equipment is turned on. Magnetic flux correction is activated, and the controller is turned on. The dynamometer test bench is sequentially set from 1000rpm to its maximum speed, and the torque values ​​fed back by the test bench are recorded under different given torques. The maximum driving torque and maximum generating torque for each speed range are entered into tables, resulting in the external characteristic table for the driving mode and the external characteristic table for the generating mode, respectively.

[0065] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Contents not described in detail in this specification belong to prior art known to those skilled in the art.

Claims

1. A calibration method for an induction motor, characterized in that, Including optimal flux linkage calibration: Divide the torque into several equal parts based on the motor's maximum output torque, and increase the torque in sequence. Given a first base speed, the flux linkage value is adjusted under each torque, and the initial flux linkage value is the one that corresponds to the highest torque accuracy of the motor drive system and the highest efficiency of the motor drive system. Optimal flux linkage calibration is performed for each torque, using the initial flux linkage value as a reference. The process of calibrating the optimal flux linkage under each torque based on the initial flux linkage value includes: Multiple verification speeds were selected. At each torque, using the initial flux linkage value as a reference, it was determined whether the torque accuracy and efficiency of the motor drive system at the corresponding verification speed met the requirements. If satisfied, the initial flux linkage value is determined to be the optimal flux linkage under the corresponding torque. If the initial flux linkage value is not met, the flux linkage is fine-tuned based on the initial flux linkage value. The flux linkage value corresponding to the condition that the torque accuracy and efficiency of the motor drive system meet the requirements at all verified speeds is the optimal flux linkage for the corresponding torque.

2. The calibration method for an induction motor according to claim 1, characterized in that: The first basic speed is 1 / 3×nmax ~ 2 / 3×nmax, where nmax is the highest basic speed of the motor.

3. The calibration method for an induction motor according to claim 1, characterized in that: The multiple verification speeds include low verification speeds and high verification speeds. The low verification speed is less than 1 / 3×nmax, and the high verification speed is greater than 2 / 3×nmax, where nmax is the highest base speed of the motor.

4. The calibration method for an induction motor according to claim 1, characterized in that, The requirement that the torque accuracy and efficiency of the motor drive system meet the requirements at all verified speeds means that the torque accuracy and efficiency of the motor drive system are within the set range at each verified speed.

5. The calibration method for an induction motor according to claim 1, characterized in that, It also includes flux linkage correction calibration: Divide the torque into several equal parts based on the motor's maximum output torque, and increase the torque in sequence. Given a second base speed, the flux linkage error value is adjusted for each torque, and the flux linkage error value corresponding to the highest torque accuracy of the motor drive system is used as the initial flux linkage error value. The flux linkage correction calibration is performed for each torque based on the initial flux linkage error value.

6. The calibration method for an induction motor according to claim 5, characterized in that, The flux correction calibration under each torque, based on the initial flux error value, includes: Multiple corrected speeds are selected, and at each torque, the torque accuracy of the motor drive system at the corresponding corrected speed is determined based on the initial flux linkage error value to see if it meets the requirements. If satisfied, the initial flux error value is determined to be the flux correction value under the corresponding torque; If not, the flux error is fine-tuned based on the initial flux error value, and the flux error value corresponding to the torque accuracy of the motor drive system at each corrected speed is determined as the corrected flux error value. The average of the initial flux linkage error value and multiple corrected flux linkage error values ​​is taken as the flux linkage correction value under the corresponding torque.

7. The calibration method for an induction motor according to claim 6, characterized in that: The second basic speed is 1 / 3×nmax ~ 2 / 3×nmax, where nmax is the highest basic speed of the motor.

8. The calibration method for an induction motor according to claim 6, characterized in that, The multiple corrected speeds include low corrected speeds and high corrected speeds. The low corrected speed is less than 1 / 3×nmax, and the high corrected speed is greater than 2 / 3×nmax, where nmax is the highest base speed of the motor.

9. The calibration method for an induction motor according to claim 6, characterized in that: After determining the flux linkage correction value under the corresponding torque, the corresponding q-axis current is recorded. Based on the determined data, the flux linkage error-q-axis current curve is fitted to obtain the flux linkage correction table.

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