A new energy automobile motor efficiency control method and system

Abstract

The application discloses a new energy automobile motor efficiency control method and system, relates to the new energy automobile motor control technical field, and comprises the following steps: acquiring the whole vehicle torque demand, the traction motor operation data, the inverter operation data and the electric drive system thermal state data of a control period; correcting the preset motor efficiency atlas according to the traction motor operation data and the thermal state data, and generating a dynamic motor efficiency evaluation result; correcting the preset inverter loss model according to the inverter operation data and the thermal state data, and generating inverter loss evaluation results of multiple preset modulation strategies; constructing a comprehensive loss evaluation function according to the motor dynamic efficiency evaluation result and the inverter loss evaluation result, solving the target current vector instruction and the target modulation strategy under the condition of meeting the torque, the current, the voltage and the thermal constraint, and generating the electric drive system efficiency control instruction. The application can consider the traction motor and the inverter loss, and improve the efficiency control stability under the high-temperature, high-load and high-speed working conditions.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle motor control technology, specifically to a method and system for controlling the efficiency of new energy vehicle motors. Background Technology

[0002] As new energy vehicles develop towards longer range, higher power density, and greater integration, the electric drive system has become a core component affecting the vehicle's energy consumption, power response, and thermal safety performance. Traction motors typically operate under complex conditions such as low-speed high torque, high-speed field weakening, frequent acceleration and deceleration, and prolonged high loads. Their efficiency control depends not only on the motor's speed, torque, and current vector distribution, but also on the inverter modulation strategy, DC bus voltage, and the thermal state of the electric drive system. Current new energy vehicles commonly employ methods such as efficiency graph lookup, maximum torque-to-current ratio control, field weakening control, and fixed modulation strategy switching to improve electric drive efficiency. While these methods offer some energy savings under standard operating conditions and stable temperatures, further optimization is still possible under actual vehicle dynamic operation.

[0003] Existing methods for controlling the efficiency of new energy vehicle motors typically rely on preset motor efficiency maps as the primary control basis. However, these preset efficiency maps are mostly derived from bench calibration, and their corresponding temperature conditions, motor parameters, and loss distributions differ from those in actual vehicle operation. When the traction motor stator temperature rises, the increased winding resistance leads to changes in copper losses; when the rotor temperature rises, the decay of permanent magnet flux linkages leads to changes in torque output capability; and when the motor enters the medium-to-high speed operating range, the proportion of iron losses increases, making it difficult for fixed efficiency maps to accurately reflect the true high-efficiency range under current thermal conditions. Furthermore, existing technologies often treat inverter-side losses relatively independently, frequently estimating inverter losses based on fixed loss models, current modulation strategies, or offline calibration rules, failing to fully consider the impact of power semiconductor device junction temperature, switching frequency, modulation ratio, and DC bus voltage on conduction losses, switching losses, and modulation-related losses.

[0004] Therefore, existing methods are prone to situations where the traction motor side has high efficiency but the inverter side has increased losses, or the inverter modulation strategy has low losses but requires the traction motor to pay a higher current cost, resulting in the overall efficiency of the electric drive system not reaching its optimum. In addition, existing control methods often handle motor current vector control and inverter modulation strategy selection separately, lacking a technical mechanism for unified optimization of the target current vector command and the target modulation strategy under the combined effects of vehicle torque demand, current constraints, voltage constraints, and thermal constraints, making it difficult to achieve dynamic and coordinated optimization of the overall losses of the traction motor and inverter. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by this invention is: existing new energy vehicle motor efficiency control methods have problems such as the inability of preset motor efficiency maps to adapt to changes in the actual vehicle thermal state, the inverter loss evaluation not fully taking into account the differences in device junction temperature and modulation strategy, the disconnect between motor current vector control and inverter modulation strategy selection, and how to achieve coordinated optimization control of the comprehensive loss of traction motor and inverter under the conditions of meeting the vehicle torque requirements, current constraints, voltage constraints and thermal constraints.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a method for controlling the efficiency of a new energy vehicle motor, comprising the following steps: S1: Obtain the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle; S2: Based on the traction motor operating data and the electric drive system thermal state data, the preset motor efficiency spectrum is thermally corrected to obtain a dynamic motor efficiency spectrum, and a motor dynamic efficiency evaluation result is generated based on the dynamic motor efficiency spectrum. S3: Based on the inverter operating data and the electric drive system thermal state data, perform thermal state correction on the preset inverter loss model, determine the inverter loss corresponding to each of the multiple preset modulation strategies, and generate inverter loss evaluation results. S4: Based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, construct a comprehensive loss evaluation function for the traction motor and the inverter; S5: Under the conditions of satisfying the vehicle torque demand, current constraint, voltage constraint and thermal constraint of the current control cycle, solve for the target current vector command and target modulation strategy that minimize the value of the comprehensive loss evaluation function; S6: Generate an electric drive system efficiency control command according to the target current vector command and the target modulation strategy, and control the traction motor and the inverter according to the electric drive system efficiency control command.

[0008] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S1 specifically includes: The vehicle torque requirement is the target torque value for the current control cycle; The traction motor operating data includes the actual speed, actual output torque, and three-phase current of the traction motor; The inverter operating data includes the current modulation strategy identifier, switching frequency, modulation ratio, and DC bus voltage. The thermal state data of the electric drive system includes the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter. The vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data are all data corresponding to the current control cycle.

[0009] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S2 specifically includes: Based on the stator temperature of the traction motor in the thermal state data of the electric drive system, determine the winding resistance temperature correction coefficient under the current control cycle; Based on the estimated rotor temperature of the traction motor in the thermal state data of the electric drive system, determine the permanent magnet flux linkage temperature correction coefficient under the current control cycle. Based on the actual speed of the traction motor, the stator temperature of the traction motor, and the estimated rotor temperature of the traction motor, determine the iron loss temperature correction coefficient under the current control cycle; The copper loss component in the preset motor efficiency spectrum is corrected using the winding resistance temperature correction coefficient, the torque output capability in the preset motor efficiency spectrum is corrected using the permanent magnet flux linkage temperature correction coefficient, and the iron loss component in the preset motor efficiency spectrum is corrected using the iron loss temperature correction coefficient, thus obtaining the dynamic motor efficiency spectrum.

[0010] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S2 further includes: Based on the actual speed of the traction motor and the vehicle torque requirement of the current control cycle, the motor efficiency value corresponding to the current operating point is determined in the dynamic motor efficiency graph. Based on the motor efficiency value corresponding to the current operating point, the actual speed of the traction motor, and the vehicle torque requirement of the current control cycle, determine the motor power loss value corresponding to the current operating point. The motor efficiency offset is determined based on the motor efficiency value corresponding to the current operating point and the benchmark efficiency value of the corresponding operating point in the preset motor efficiency map. The thermal constraint margin of the motor is determined based on the estimated values ​​of the stator temperature and the rotor temperature of the traction motor. Based on the motor power loss value corresponding to the current operating point, the motor efficiency offset, and the motor thermal constraint margin, the motor dynamic efficiency evaluation result is generated.

[0011] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S3 specifically includes: Based on the estimated junction temperature of the power semiconductor devices in the inverter, determine the conduction loss temperature correction coefficient and the switching loss temperature correction coefficient under the current control cycle. Based on the estimated junction temperature of the power semiconductor devices in the inverter, the DC bus voltage, the modulation ratio, and the switching frequency, determine the modulation additional loss correction coefficient under the current control cycle; The conduction loss calculation parameters in the preset inverter loss model are corrected using the conduction loss temperature correction coefficient, the switching loss calculation parameters in the preset inverter loss model are corrected using the switching loss temperature correction coefficient, and the modulation additional loss calculation parameters in the preset inverter loss model are corrected using the modulation additional loss correction coefficient, thus obtaining the inverter loss model after thermal state correction.

[0012] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S3 further includes: Establish a set of preset modulation strategies corresponding to the current control cycle, wherein each preset modulation strategy in the set of preset modulation strategies has a corresponding modulation strategy identifier; Based on the modulation rules corresponding to each preset modulation strategy in the preset modulation strategy set, determine the candidate switching frequency and candidate modulation ratio corresponding to each preset modulation strategy; The DC bus voltage, the estimated junction temperature of the power semiconductor devices in the inverter, the candidate switching frequency and the candidate modulation ratio corresponding to each preset modulation strategy are input into the thermally corrected inverter loss model to obtain the conduction loss value, switching loss value and modulation additional loss value corresponding to each preset modulation strategy. Based on the conduction loss value, the switching loss value, and the modulation additional loss value corresponding to each preset modulation strategy, the total inverter loss value corresponding to each preset modulation strategy is determined. The inverter loss evaluation result is generated based on the total inverter loss value corresponding to each preset modulation strategy and the corresponding modulation strategy identifier.

[0013] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S4 specifically includes: Extract the motor power loss value, motor efficiency offset, and motor thermal constraint margin corresponding to the current operating point from the motor dynamic efficiency evaluation results. Extract the total inverter loss value and the corresponding modulation strategy identifier for each preset modulation strategy from the inverter loss evaluation results; For each preset modulation strategy, the motor power loss value and the corresponding total inverter loss value are added together to obtain the basic loss value of the electric drive system corresponding to each preset modulation strategy. The efficiency deviation penalty value is determined based on the motor efficiency deviation, and the thermal margin penalty value is determined based on the motor thermal constraint margin. For each preset modulation strategy, a comprehensive loss evaluation value corresponding to each preset modulation strategy is obtained based on the corresponding basic loss value of the electric drive system, the efficiency deviation penalty value, and the thermal margin penalty value. Based on the comprehensive loss evaluation value corresponding to each preset modulation strategy, the corresponding modulation strategy identifier, and the evaluation result of the candidate current vector command by the dynamic motor efficiency spectrum, a comprehensive loss evaluation function for the traction motor and the inverter is constructed that can output the corresponding comprehensive loss evaluation value according to the candidate current vector command and the preset modulation strategy.

[0014] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S5 specifically includes: Based on the vehicle torque demand of the current control cycle, an initial current vector command set is generated. Each initial current vector command in the initial current vector command set includes an initial d-axis current command and an initial q-axis current command. The current constraint boundary is determined based on the preset maximum current limit value of the traction motor, and the voltage constraint boundary is determined based on the DC bus voltage; Based on the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter, the current limit value corresponding to the thermal constraint is determined. Based on the current constraint boundary, the voltage constraint boundary and the current limit value corresponding to the thermal constraint, the initial current vector instruction set is filtered to obtain a feasible current vector instruction set. Based on the set of feasible current vector commands and the set of preset modulation strategies, multiple candidate control combinations are formed, each candidate control combination including a feasible current vector command and a preset modulation strategy; Each candidate control combination is input into the comprehensive loss evaluation function to obtain the comprehensive loss evaluation value corresponding to each candidate control combination; The candidate control combination with the minimum comprehensive loss evaluation value is determined as the target control combination, the feasible current vector command in the target control combination is determined as the target current vector command, and the preset modulation strategy in the target control combination is determined as the target modulation strategy.

[0015] As a preferred embodiment of the new energy vehicle motor efficiency control method of the present invention, step S6 specifically includes: Based on the target d-axis current command and target q-axis current command in the target current vector command, generate the three-phase current control signal for the traction motor; According to the target modulation strategy, the target switching frequency, target modulation ratio, and target switching sequence are determined, and an inverter switching control signal is generated based on the target switching frequency, the target modulation ratio, and the target switching sequence. The three-phase current control signal of the traction motor and the switching control signal of the inverter are used as the efficiency control command of the electric drive system. The current vector of the traction motor is controlled according to the efficiency control command of the electric drive system, and the modulation process of the inverter is controlled. The execution feedback data of the traction motor and the inverter after executing the efficiency control command of the electric drive system is obtained. The execution feedback data includes the actual three-phase current of the traction motor, the actual output torque of the traction motor, the stator temperature feedback value of the traction motor, the rotor temperature feedback estimate of the traction motor, and the junction temperature feedback value of the power semiconductor devices in the inverter. Based on the execution feedback data, the dynamic motor efficiency graph and the preset inverter loss model are updated, and the updated dynamic motor efficiency graph and the updated preset inverter loss model are used in the next control cycle.

[0016] Secondly, embodiments of the present invention provide a new energy vehicle motor efficiency control system, comprising: Data acquisition module: Acquires the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle; The graph correction module corrects the preset motor efficiency graph based on the traction motor operating data and the electric drive system thermal state data to obtain a dynamic motor efficiency graph, and generates a motor dynamic efficiency evaluation result based on the dynamic motor efficiency graph. Loss evaluation module: Based on the inverter operating data and the electric drive system thermal state data, the preset inverter loss model is thermally corrected to determine the inverter loss corresponding to each of the multiple preset modulation strategies and generate inverter loss evaluation results. Function construction module: Based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, construct a comprehensive loss evaluation function for the traction motor and the inverter; Joint optimization module: Under the conditions of satisfying the vehicle torque demand, current constraint, voltage constraint and thermal constraint of the current control cycle, solve for the target current vector command and target modulation strategy that minimizes the value of the comprehensive loss evaluation function; Control execution module: Generates electric drive system efficiency control instructions according to the target current vector command and the target modulation strategy, and controls the traction motor and the inverter according to the electric drive system efficiency control instructions.

[0017] The beneficial effects of this invention are as follows: This invention generates a dynamic motor efficiency map that reflects the current stator temperature, rotor temperature estimate, and motor operating state by thermally correcting a preset motor efficiency map. Simultaneously, it thermally corrects a preset inverter loss model and evaluates the inverter losses corresponding to multiple preset modulation strategies. Based on this, a comprehensive loss evaluation function for the traction motor and inverter is constructed, and the target current vector command and target modulation strategy are jointly solved. This allows the efficiency control of the electric drive system to move beyond local optima on the motor or inverter side, achieving control decisions with lower overall system-level losses within the current control cycle. This improves the efficiency control stability of new energy vehicles under conditions of high temperature, high load, high speed operation, and multiple modulation strategy switching. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is an overall flowchart of a method for controlling the efficiency of a new energy vehicle motor, provided in the first embodiment of the present invention. Figure 2 This is a module connection diagram of a new energy vehicle motor efficiency control system provided in the third embodiment of the present invention. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0020] Example 1, referring to Figure 1 This invention provides a method for controlling the efficiency of a new energy vehicle motor, as one embodiment of the present invention.

[0021] S1: Obtain the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle.

[0022] The vehicle torque requirement is the target torque value for the current control cycle; The traction motor operating data includes the actual speed, actual output torque, and three-phase current of the traction motor; The inverter operating data includes the current modulation strategy identifier, switching frequency, modulation ratio, and DC bus voltage. The thermal state data of the electric drive system includes the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter. The vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data are all data corresponding to the current control cycle.

[0023] In step S1, the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle are acquired. It should be noted that the current control cycle refers to the time period corresponding to the motor controller performing one efficiency evaluation, control parameter solution, and control command output. In one embodiment, the current control cycle can be set to 1 to 10 milliseconds; when the change in traction motor speed exceeds 0.5% of the rated speed of the traction motor within two adjacent control cycles, and the change in vehicle torque demand exceeds 5% of the rated torque of the traction motor, a control cycle of 1 to 5 milliseconds can be used; when the vehicle is in cruising mode, low-speed stable operation mode, or when the thermal status change does not exceed 2 degrees Celsius per second, a control cycle of 5 to 10 milliseconds can be used. By using the current control cycle as the time reference for data acquisition, subsequent dynamic motor efficiency map correction, inverter loss evaluation, and comprehensive loss optimization can all be based on vehicle demand and electric drive status within the same time range, avoiding inaccurate efficiency evaluation caused by mixing data from different time points.

[0024] The vehicle torque requirement is the target torque value for the current control cycle, and the unit can be Newton-meters (N·m). It should be noted that the target torque value characterizes the vehicle's demand for traction motor output torque within the current control cycle. It can be determined by the vehicle power control logic based on accelerator pedal opening, brake pedal state, vehicle driving mode, vehicle speed, and energy management strategy, and then sent to the motor controller. Alternatively, it can be directly provided by the integrated power domain controller within the current control cycle. The generation method of this target torque value is not limited; it only requires that it serve as the torque tracking target for traction motor efficiency control within this control cycle. In one embodiment, when the vehicle is in a driving state, the target torque value is the positive traction torque; when the vehicle is in an energy recovery state, the target torque value is the reverse braking recovery torque; when the vehicle is in a coasting state, the target torque value can be a near-zero sustaining torque. "Near-zero" can be understood as the absolute value of the target torque value not exceeding 2% of the traction motor's rated torque.

[0025] The traction motor operating data includes the actual speed, actual output torque, and three-phase current of the traction motor. It should be noted that the actual speed of the traction motor refers to the mechanical speed of the traction motor rotor within the current control cycle, measured in revolutions per minute (rpm). This speed can be obtained through a rotary transformer, encoder, and motor position observation algorithm, and converted to the motor speed for the current control cycle after acquiring the rotor position change. The actual output torque of the traction motor refers to the mechanical torque actually output to the transmission system by the traction motor within the current control cycle, measured in Newton-meters (N·m). This torque can be directly obtained from a torque sensor or estimated based on motor current, rotor position, motor parameters, and a torque observation model. The three-phase current refers to the instantaneous value of the current flowing through the three-phase windings of the traction motor, measured in amperes (Amperes). This current can be acquired by current sensors located on the inverter output side. Furthermore, to reduce the impact of current sampling noise on subsequent efficiency evaluation, the three-phase current can be limited, biased, and low-pass filtered within the current control cycle. Sampling points where the current mutation value exceeds the allowable current change value of adjacent control cycles can be identified as abnormal sampling points. The allowable current change value can be set to 5% to 15% of the rated phase current of the traction motor.

[0026] The inverter operating data includes the current modulation strategy identifier, switching frequency, modulation ratio, and DC bus voltage. It should be noted that the modulation strategy identifier distinguishes the modulation method used by the inverter in the current control cycle. In one implementation, different modulation strategies can be represented by numerical codes; for example, code 1 represents a continuous pulse width modulation (PWM) strategy, code 2 represents a first-type discontinuous PWM strategy, code 3 represents a second-type discontinuous PWM strategy, and code 4 represents an overmodulation strategy. The switching frequency refers to the number of switching actions performed by the power semiconductor devices in the inverter per unit time, and the unit can be Hertz (Hz). In one implementation, the switching frequency can be set to 2 kHz to 20 kHz. The modulation ratio characterizes the utilization of the inverter's output voltage; it can be understood as the ratio between the fundamental amplitude of the inverter's output phase voltage and half of the DC bus voltage. In one implementation, the modulation ratio can be between 0 and 1 under normal linear modulation, and greater than 1 but not greater than 1.15 under overmodulation. When the modulation ratio is greater than 0.9 but not greater than 1, the inverter output voltage utilization is considered to be high; when the modulation ratio is greater than 1 but not greater than 1.15, the inverter is considered to be in an overmodulation state. The DC bus voltage refers to the voltage across the DC-side support capacitor of the inverter, measured in volts. This voltage value can be acquired by a voltage sensor. In one implementation, the DC bus voltage of the electric drive system of a new energy vehicle can be in the range of 200 volts to 900 volts. The aforementioned inverter operating data is used to subsequently determine the conduction loss, switching loss, and modulation-related loss under different preset modulation strategies, thereby avoiding the neglect of inverter loss changes when selecting control parameters solely based on traction motor efficiency.

[0027] The thermal state data of the electric drive system includes the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter, all in degrees Celsius. It should be noted that the stator temperature of the traction motor can be obtained using temperature sensors placed near the stator windings and stator core, reflecting changes in winding resistance and copper losses. The estimated rotor temperature of the traction motor can be indirectly estimated using a thermal network model, a rotor thermal inertia model, and flux linkage observations. Since the rotor is rotating, it is difficult to reliably and directly place temperature sensors in mass-produced vehicles over a long period; therefore, using estimation to obtain the rotor temperature is beneficial for reflecting changes in permanent magnet flux linkage decay and torque output capability. The estimated junction temperature of the power semiconductor devices in the inverter can be obtained based on the inverter housing temperature, cooling conditions, device conduction state, switching state, and power loss estimation results, reflecting the changes in conduction and switching losses with temperature. In one implementation, when the stator temperature is above 120 degrees Celsius, the estimated rotor temperature is above 140 degrees Celsius, and the estimated junction temperature of the power semiconductor device is above 150 degrees Celsius, the electric drive system can be considered to be in a high thermal load state. Under the high thermal load state, the subsequent steps to correct the thermal state of the efficiency spectrum and the inverter loss model will have greater control significance, so as to reduce the probability of continuing to select high-heat control parameters. The high-heat control parameters can be understood as control parameters that make the estimated total loss of the current control cycle higher than the average candidate total loss under the current operating condition by 10%.

[0028] It should also be noted that the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data are all data corresponding to the current control cycle. Since the acquisition frequencies of different data may differ—for example, the acquisition frequencies of three-phase current and DC bus voltage are usually higher than those of temperature data—timestamps can be configured for each data item, and data whose timestamps fall within the current control cycle can be directly used as the data for the current cycle. For thermal status data with a sampling period longer than the current control cycle, the set of effective temperature data closest to the current control cycle can be used as the corresponding data for the current control cycle. The closest set of effective temperature data can be understood as data with a time interval of no more than 100 milliseconds; when the time interval exceeds 100 milliseconds, the thermal status data can be determined to be invalid, and compensation can be made using the previous effective temperature data combined with the temperature rise trend estimate. Through the above processing, it can be ensured that the thermal status correction in subsequent steps S2 and S3 has a unified time basis, enabling the dynamic motor efficiency spectrum and inverter loss evaluation results to truly reflect the electric drive system status of the current control cycle.

[0029] S2: Based on the traction motor operating data and the electric drive system thermal state data, the preset motor efficiency spectrum is thermally corrected to obtain a dynamic motor efficiency spectrum, and a motor dynamic efficiency evaluation result is generated based on the dynamic motor efficiency spectrum.

[0030] Based on the stator temperature of the traction motor in the thermal state data of the electric drive system, determine the winding resistance temperature correction coefficient under the current control cycle; Based on the estimated rotor temperature of the traction motor in the thermal state data of the electric drive system, determine the permanent magnet flux linkage temperature correction coefficient under the current control cycle. Based on the actual speed of the traction motor, the stator temperature of the traction motor, and the estimated rotor temperature of the traction motor, determine the iron loss temperature correction coefficient under the current control cycle; The copper loss component in the preset motor efficiency spectrum is corrected using the winding resistance temperature correction coefficient, the torque output capability in the preset motor efficiency spectrum is corrected using the permanent magnet flux linkage temperature correction coefficient, and the iron loss component in the preset motor efficiency spectrum is corrected using the iron loss temperature correction coefficient, thus obtaining the dynamic motor efficiency spectrum.

[0031] Based on the actual speed of the traction motor and the vehicle torque requirement of the current control cycle, the motor efficiency value corresponding to the current operating point is determined in the dynamic motor efficiency graph. Based on the motor efficiency value corresponding to the current operating point, the actual speed of the traction motor, and the vehicle torque requirement of the current control cycle, determine the motor power loss value corresponding to the current operating point. The motor efficiency offset is determined based on the motor efficiency value corresponding to the current operating point and the benchmark efficiency value of the corresponding operating point in the preset motor efficiency map. The thermal constraint margin of the motor is determined based on the estimated values ​​of the stator temperature and the rotor temperature of the traction motor. Based on the motor power loss value corresponding to the current operating point, the motor efficiency offset, and the motor thermal constraint margin, the motor dynamic efficiency evaluation result is generated.

[0032] In step S2, based on the traction motor operating data and the electric drive system thermal state data, the preset motor efficiency map is thermally corrected to obtain a dynamic motor efficiency map, and a dynamic efficiency evaluation result is generated based on the dynamic motor efficiency map. It should be noted that the preset motor efficiency map can be a basic efficiency map formed during the bench calibration stage of the traction motor. This preset motor efficiency map uses the traction motor speed and output torque as index conditions to record the baseline efficiency value, copper loss component, iron loss component, and torque output capability at different speed and torque operating points. Since the preset motor efficiency map is usually obtained under standard temperature conditions, such as a stator temperature of 20°C to 40°C and a rotor temperature of 20°C to 60°C under bench conditions, and new energy vehicles experience continuous acceleration, hill climbing, high-speed cruising, and frequent start-stop conditions during actual operation, the stator and rotor temperatures of the traction motor will deviate from the bench calibration temperature. This deviation can be understood as the difference between the current temperature and the corresponding bench calibration temperature exceeding 10 degrees Celsius. Therefore, directly using the preset motor efficiency chart for efficiency control can easily lead to underestimation of copper losses, misjudgment of flux linkage status, and deviation in iron loss evaluation. This step corrects the preset motor efficiency chart using thermal data from the current control cycle, ensuring that subsequent efficiency evaluations reflect the actual efficiency changes of the traction motor under the current thermal state. It should also be noted that after the dynamic motor efficiency chart is formed, the position of the highest efficiency point may shift with the thermal state. This shift can be manifested as a movement of the speed-torque region corresponding to the highest efficiency point relative to the preset motor efficiency chart. When the shift exceeds the range of two adjacent calibrated torque intervals, the highest efficiency point can be considered to have experienced a recognizable shift.

[0033] Based on the stator temperature of the traction motor in the thermal state data of the electric drive system, the winding resistance temperature correction coefficient for the current control cycle is determined. It should be noted that the resistance of the traction motor stator winding increases with temperature. Increased winding resistance leads to higher copper losses under the same current conditions. Therefore, the winding resistance temperature correction coefficient characterizes the degree of copper loss change caused by the current stator temperature relative to the reference calibration temperature. In one embodiment, a calibration mapping table between stator temperature and the winding resistance temperature correction coefficient can be pre-established. This calibration mapping table can be obtained through thermal steady-state testing on a motor bench. When the stator temperature is between 20°C and 60°C, the winding resistance temperature correction coefficient is considered to be in the low correction range; when the stator temperature is between 60°C and 120°C, it is considered to be in the normal correction range; and when the stator temperature is above 120°C, it is considered to be in the high correction range. The low correction range, normal correction range, and high correction range do not represent fixed values, but rather indicate a gradual increase in the copper loss correction intensity at different temperature ranges. In practice, the motor controller can look up the calibration mapping table based on the current stator temperature to obtain the winding resistance temperature correction coefficient corresponding to the current stator temperature.

[0034] Furthermore, based on the estimated rotor temperature of the traction motor in the thermal state data of the electric drive system, a permanent magnet flux linkage temperature correction coefficient is determined for the current control cycle. It should be noted that for new energy vehicles using permanent magnet synchronous traction motors, the permanent magnet flux linkage decays as the rotor temperature increases. This flux linkage decay alters the motor's torque output capability under the same current vector and affects the efficiency in the field weakening region and the medium-to-high speed region. Therefore, the permanent magnet flux linkage temperature correction coefficient is used to characterize the impact of the current rotor temperature estimate on the permanent magnet flux linkage and torque output capability. In one implementation, a correspondence between the rotor temperature estimate and the permanent magnet flux linkage temperature correction coefficient can be established based on the temperature demagnetization characteristics of the permanent magnet material. When the rotor temperature estimate is not higher than 80 degrees Celsius, the permanent magnet flux linkage attenuation is considered small, which can be understood as the change in flux linkage relative to the reference flux linkage not exceeding 3%. When the rotor temperature estimate is higher than 80 degrees Celsius but not higher than 140 degrees Celsius, the permanent magnet flux linkage is considered to be in a correctable attenuation state. When the rotor temperature estimate is higher than 140 degrees Celsius, the impact of permanent magnet flux linkage attenuation on torque output capability is considered significant, which can be understood as the torque output capability decreases by more than 5% under the same current conditions. By introducing the permanent magnet flux linkage temperature correction coefficient, the controller can avoid evaluating motor efficiency based on the low-temperature flux linkage state, thereby reducing the risk of target torque deviation and excessive current compensation due to flux linkage attenuation. It should also be noted that the target torque achievement deviation can be understood as the difference between the actual output torque of the traction motor and the vehicle torque demand in the current control cycle exceeding 3% of the rated torque of the traction motor; excessive current compensation can be understood as the required current amplitude increasing by more than 5% relative to the current amplitude at the reference temperature when maintaining the same vehicle torque demand.

[0035] Furthermore, based on the actual speed of the traction motor, the stator temperature of the traction motor, and the estimated rotor temperature of the traction motor, the iron loss temperature correction coefficient for the current control cycle is determined. It should be noted that iron loss is typically related to the traction motor speed, magnetic flux state, and temperature state. Especially under medium- and high-speed operating conditions, the proportion of iron loss in the total loss increases. Therefore, this step cannot only correct copper loss while ignoring iron loss correction. Medium- and high-speed operating conditions can be understood as the actual speed of the traction motor being higher than 40% of its maximum rated speed; high-speed operating conditions can be understood as the actual speed of the traction motor being higher than 70% of its maximum rated speed. In one embodiment, an iron loss correction mapping relationship can be established with the actual speed, stator temperature, and estimated rotor temperature as inputs. When the actual speed is lower than 40% of the maximum rated speed of the traction motor, the iron loss temperature correction coefficient is mainly used to compensate for the influence of temperature changes on the core loss parameters; when the actual speed is higher than 40% of the maximum rated speed of the traction motor, the iron loss temperature correction coefficient is also used to compensate for iron loss offset caused by increased speed and changes in thermal state. This processing ensures that the dynamic motor efficiency graph remains well-applicable under medium- and high-speed operating conditions, avoiding the efficiency evaluation bias caused by only correcting copper losses while ignoring iron losses.

[0036] Furthermore, the copper loss component in the preset motor efficiency graph is corrected using the winding resistance temperature correction coefficient, the torque output capability in the preset motor efficiency graph is corrected using the permanent magnet flux linkage temperature correction coefficient, and the iron loss component in the preset motor efficiency graph is corrected using the iron loss temperature correction coefficient, thus obtaining the dynamic motor efficiency graph. It should be noted that the copper loss component refers to the loss portion in the preset motor efficiency graph related to winding current and winding resistance; the iron loss component refers to the loss portion in the preset motor efficiency graph related to the core magnetization state, speed state, and flux change; and the torque output capability refers to the output torque capability that the traction motor can achieve under corresponding speed and current conditions. In specific implementation, the motor controller can first locate the corresponding speed-torque operating point in the preset motor efficiency graph based on the actual speed and vehicle torque requirements of the current control cycle. If the actual operating point is located between two adjacent calibrated operating points, the reference efficiency value, copper loss component, iron loss component, and torque output capability corresponding to that actual operating point can be obtained using a neighboring operating point interpolation method. The adjacent calibration operating points can be understood as calibration points where the difference from the actual speed does not exceed 5% of the traction motor's maximum rated speed, and the difference from the actual torque does not exceed 5% of the traction motor's rated torque. Subsequently, the winding resistance temperature correction coefficient, permanent magnet flux linkage temperature correction coefficient, and iron loss temperature correction coefficient are applied to the corresponding spectral components to obtain the efficiency spectral data under the current thermal state. The resulting dynamic spectral data is no longer a fixed calibration result, but rather an efficiency evaluation basis that can change with the thermal state during the current control cycle.

[0037] It should also be noted that the dynamic motor efficiency graph does not necessarily require recalculation of all operating points in each control cycle. In one implementation, only the current operating point and its neighboring operating points can be locally corrected. The neighboring operating points can include the graph region within 5% above and below the actual speed and within 5% above and below the actual torque. In another implementation, operating points that may be accessed by candidate current vector commands in the current control cycle can also be locally corrected. By using local correction, the computational burden on the controller can be reduced, making this step suitable for real-time operation in the vehicle controller. If the vehicle is under high thermal load conditions, such as a stator temperature above 120 degrees Celsius and an estimated rotor temperature above 140 degrees Celsius, the local correction range can be expanded. Expanding the range can be understood as increasing the neighborhood range of the actual speed and actual torque from 5% above and below to 10% above and below, thereby improving the safety of efficiency evaluation under high thermal load conditions.

[0038] Furthermore, based on the actual speed of the traction motor and the vehicle torque demand of the current control cycle, the motor efficiency value corresponding to the current operating point is determined in the dynamic motor efficiency graph. It should be noted that the current operating point refers to the motor operating position determined jointly by the actual speed and vehicle torque demand of the current control cycle. The vehicle torque demand is used instead of only the actual output torque to determine the current operating point because the subsequent control objective of this invention is to generate control commands that meet the torque demand and have low overall losses for the current and subsequent control cycles. The vehicle torque demand can more directly characterize the target operating condition to be achieved. If there is a difference between the current vehicle torque demand and the actual output torque, for example, a difference greater than 3% of the traction motor's rated torque, it can be considered that there is a torque following deviation in the current operating condition. In this case, the motor efficiency value corresponding to the current operating point can be used to evaluate the efficiency state of the traction motor under the target torque state, rather than only evaluating the already output actual torque state.

[0039] Based on the motor efficiency value corresponding to the current operating point, the actual speed of the traction motor, and the vehicle torque demand of the current control cycle, the motor power loss value corresponding to the current operating point is determined. It should be noted that the motor power loss value characterizes the power loss of the traction motor at the current operating point in order to meet the vehicle torque demand; it can also be understood as the portion dissipated as heat during the conversion of input electrical power into output mechanical power. The motor power loss value can be determined based on the output power demand and motor efficiency value at the current operating point, or it can be obtained by summing the copper loss component, iron loss component, and other loss components in the dynamic motor efficiency graph. In one embodiment, if the motor efficiency value is low (low can be understood as being more than 5% lower than the average efficiency value of neighboring operating points at the same speed in the preset motor efficiency graph), the motor power loss value corresponding to the current operating point will be judged as high; high can be understood as being more than 10% higher than the average power loss value of neighboring operating points at the same speed. Through this judgment, situations where a previously efficient operating point becomes an inefficient operating point due to changes in thermal state can be identified.

[0040] Furthermore, the motor efficiency offset is determined based on the motor efficiency value corresponding to the current operating point and the baseline efficiency value of the corresponding operating point in the preset motor efficiency map. It should be noted that the motor efficiency offset characterizes the degree of change in the efficiency value after thermal correction relative to the baseline calibration efficiency value, that is, the degree of deviation of the motor efficiency under the current thermal state from the baseline efficiency. If the motor efficiency offset is small (meaning the efficiency change is less than 1 percentage point), it indicates that the current thermal state has a limited impact on the efficiency of this operating point. If the motor efficiency offset is in a medium range (meaning the efficiency change is greater than 1 percentage point but less than 3 percentage points), it indicates that the current thermal state has already had a perceptible impact on the efficiency evaluation. If the motor efficiency offset is large (meaning the efficiency change exceeds 3 percentage points), it indicates that the preset motor efficiency map can no longer directly reflect the true efficiency under the current thermal state. By setting the motor efficiency offset, the subsequent comprehensive loss evaluation function can consider not only the current loss magnitude but also the degree of efficiency drift caused by the thermal state, thereby avoiding the continued use of the optimal control point under a fixed efficiency map.

[0041] Furthermore, the motor thermal constraint margin is determined based on the estimated stator temperature and rotor temperature of the traction motor. It should be noted that the motor thermal constraint margin characterizes the remaining space between the current thermal state of the motor and the allowable thermal boundary. The allowable thermal boundary can be determined based on the insulation class of the traction motor stator windings, the temperature resistance of the permanent magnets, and the vehicle's thermal management strategy. In one embodiment, the difference between the stator temperature and the upper limit of the stator's allowable temperature, and the difference between the estimated rotor temperature and the upper limit of the rotor's allowable temperature, can be used together to determine the motor thermal constraint margin. A sufficient thermal constraint margin can be understood as both the estimated stator temperature and the estimated rotor temperature being more than 20 degrees Celsius below their respective upper limits of allowable temperature; an insufficient thermal constraint margin can be understood as either the estimated stator temperature or the estimated rotor temperature corresponding to an upper limit of allowable temperature not exceeding 10 degrees Celsius; a critical thermal constraint margin can be understood as either the estimated stator temperature or the estimated rotor temperature corresponding to an upper limit of allowable temperature not exceeding 5 degrees Celsius. By incorporating the motor's thermal constraint margin into the motor's dynamic efficiency evaluation results, subsequent control can avoid selecting the current vector that might lead to further temperature increases when the thermal margin is insufficient or the condition is critical.

[0042] Furthermore, based on the motor power loss value corresponding to the current operating point, the motor efficiency offset, and the motor thermal constraint margin, the motor dynamic efficiency evaluation result is generated. It should be noted that the motor dynamic efficiency evaluation result is not a single efficiency value, but a composite evaluation result that simultaneously includes the magnitude of loss, the degree of efficiency drift, and the thermal safety margin. The motor power loss value characterizes the energy loss level under the current operating condition, the motor efficiency offset characterizes the efficiency deviation caused by the thermal state relative to the baseline graph, and the motor thermal constraint margin characterizes the thermal safety margin for the motor to continue bearing the load. By using all three as the motor dynamic efficiency evaluation result, it can be comprehensively evaluated with the inverter loss evaluation result in subsequent step S4. This allows the present invention to avoid selecting control parameters that appear efficient but actually have high thermal loads based solely on a fixed efficiency graph under conditions of high temperature, ramping, high-speed cruising, and frequent acceleration and deceleration. The purpose of this process is to provide a motor-side evaluation basis that reflects the current thermal state for the subsequent comprehensive loss evaluation function, enabling the determination process of the target current vector command to have dynamic thermal adaptability.

[0043] S3: Based on the inverter operating data and the electric drive system thermal state data, perform thermal state correction on the preset inverter loss model, determine the inverter loss corresponding to each of the multiple preset modulation strategies, and generate inverter loss evaluation results.

[0044] Based on the estimated junction temperature of the power semiconductor devices in the inverter, determine the conduction loss temperature correction coefficient and the switching loss temperature correction coefficient under the current control cycle. Based on the estimated junction temperature of the power semiconductor devices in the inverter, the DC bus voltage, the modulation ratio, and the switching frequency, determine the modulation additional loss correction coefficient under the current control cycle; The conduction loss calculation parameters in the preset inverter loss model are corrected using the conduction loss temperature correction coefficient, the switching loss calculation parameters in the preset inverter loss model are corrected using the switching loss temperature correction coefficient, and the modulation additional loss calculation parameters in the preset inverter loss model are corrected using the modulation additional loss correction coefficient, thus obtaining the inverter loss model after thermal state correction.

[0045] Establish a set of preset modulation strategies corresponding to the current control cycle, wherein each preset modulation strategy in the set of preset modulation strategies has a corresponding modulation strategy identifier; Based on the modulation rules corresponding to each preset modulation strategy in the preset modulation strategy set, determine the candidate switching frequency and candidate modulation ratio corresponding to each preset modulation strategy; The DC bus voltage, the estimated junction temperature of the power semiconductor devices in the inverter, the candidate switching frequency and the candidate modulation ratio corresponding to each preset modulation strategy are input into the thermally corrected inverter loss model to obtain the conduction loss value, switching loss value and modulation additional loss value corresponding to each preset modulation strategy. Based on the conduction loss value, the switching loss value, and the modulation additional loss value corresponding to each preset modulation strategy, the total inverter loss value corresponding to each preset modulation strategy is determined. The inverter loss evaluation result is generated based on the total inverter loss value corresponding to each preset modulation strategy and the corresponding modulation strategy identifier.

[0046] In step S3, based on the inverter operating data and the electric drive system thermal state data, the preset inverter loss model is thermally corrected to determine the inverter losses corresponding to each of the multiple preset modulation strategies, generating inverter loss evaluation results. It should be noted that the preset inverter loss model can be an inverter loss calculation model established during the bench calibration phase, used to describe the loss variation relationship of the inverter under different DC bus voltages, different switching frequencies, different modulation ratios, different modulation strategies, and different device temperature states. The preset inverter loss model may include conduction loss calculation parameters, switching loss calculation parameters, and modulation-related loss calculation parameters. The conduction loss calculation parameters characterize the loss characteristics of the power semiconductor device due to current flow in the conduction state; the switching loss calculation parameters characterize the loss characteristics of the power semiconductor device during turn-on and turn-off processes; the modulation-related loss calculation parameters characterize the additional loss characteristics caused by changes in modulation strategy, switching sequence, voltage utilization, and current ripple. It should also be noted that in existing motor efficiency control, inverter-side losses are often treated as fixed additional losses or estimated based solely on the currently used single modulation strategy. This makes it difficult to reflect the impact of power semiconductor device junction temperature variations and modulation strategy differences on system efficiency. Since the conduction and switching characteristics of power semiconductor devices are affected by junction temperature, and different modulation strategies lead to different loss distributions at different switching frequencies and modulation ratios, using only a fixed inverter loss model to evaluate each modulation strategy can easily result in underestimated inverter losses at high temperatures and the selection of modulation strategies that lead to excessively high switching losses. This step corrects the preset inverter loss model by introducing estimated junction temperatures of power semiconductor devices, DC bus voltage, modulation ratio, and switching frequency, ensuring that the subsequent inverter loss evaluation results reflect the actual device temperature and modulation state during the current control cycle.

[0047] Furthermore, based on the estimated junction temperature of the power semiconductor devices in the inverter, the conduction loss temperature correction coefficient and the switching loss temperature correction coefficient under the current control cycle are determined. It should be noted that the power semiconductor devices can be silicon-based IGBTs, silicon-based MOSFETs, silicon carbide MOSFETs, and other power switching devices suitable for new energy vehicle electric drive inverters. The estimated junction temperature of the power semiconductor devices is used to characterize the temperature state of the chip junction region inside the device, and is closer to the actual location of conduction and switching losses than the inverter housing temperature. In one embodiment, a first mapping table between the estimated junction temperature and the conduction loss temperature correction coefficient can be established in advance, and a second mapping table between the estimated junction temperature and the switching loss temperature correction coefficient can be established. The first and second mapping tables can be obtained through inverter bench thermal steady-state tests, device switching characteristic calibration, and temperature characteristic data from the device datasheet. When the estimated junction temperature is no higher than 80 degrees Celsius, the power semiconductor device can be considered to be in a low thermal load state; when the estimated junction temperature is higher than 80 degrees Celsius but no higher than 150 degrees Celsius, the power semiconductor device can be considered to be in a normal thermal load state; when the estimated junction temperature is higher than 150 degrees Celsius, the power semiconductor device can be considered to be in a high thermal load state. The high thermal load state indicates that the deviation between the device loss parameters and the room temperature calibration parameters is no longer negligible. "No longer negligible" can be understood as a loss deviation exceeding 5% relative to the room temperature calibration state. Through the above segmented junction temperature mapping, the conduction loss temperature correction coefficient and the switching loss temperature correction coefficient can be adjusted accordingly as the junction temperature increases, thereby avoiding evaluating inverter losses based on low-temperature device parameters under high junction temperature conditions.

[0048] Based on the estimated junction temperature of the power semiconductor devices in the inverter, the DC bus voltage, the modulation ratio, and the switching frequency, a correction coefficient for modulation-related additional losses under the current control cycle is determined. It should be noted that modulation-related additional losses are not limited to single switching losses; they can include current ripple additional losses caused by changes in the modulation method, output voltage distortion additional losses caused by dead-time effects, additional switching losses caused by changes in the switching sequence, and voltage utilization boundary losses caused by high modulation ratio operation. In one embodiment, a modulation ratio of no more than 0.7 can be considered a low-voltage utilization state, a modulation ratio greater than 0.7 but no more than 0.9 can be considered a normal voltage utilization state, and a modulation ratio greater than 0.9 can be considered a high-voltage utilization state. When the modulation ratio is greater than 0.9 and the switching frequency is higher than 12 kHz, the impact of modulation-related additional losses on the total inverter losses can be considered enhanced, meaning that the proportion of modulation-related additional losses to the total inverter losses exceeds 10%. Therefore, this embodiment uses the junction temperature estimate, DC bus voltage, modulation ratio, and switching frequency as input conditions to determine the modulation additional loss correction coefficient, which can avoid evaluating the modulation strategy based solely on the switching frequency while ignoring the effects of voltage utilization and device thermal state.

[0049] Furthermore, the conduction loss calculation parameters in the preset inverter loss model are corrected using the conduction loss temperature correction coefficient, the switching loss calculation parameters are corrected using the switching loss temperature correction coefficient, and the modulation additional loss calculation parameters are corrected using the modulation additional loss correction coefficient, resulting in a thermally corrected inverter loss model. It should be noted that the thermally corrected inverter loss model is not a completely independent new model, but rather a correction of the loss calculation parameters related to the current junction temperature, DC bus voltage, modulation ratio, and switching frequency within the current control cycle, based on the preset inverter loss model. This approach allows the inverter loss model to be updated in response to changes in device temperature and modulation state without significantly increasing the computational burden on the vehicle controller. Compared to directly using a fixed model, this method reduces the risk of underestimating inverter losses during high-temperature operation; compared to retraining the loss model online, this method requires less computation and is more suitable for execution within the control cycle of the vehicle controller.

[0050] Furthermore, a set of preset modulation strategies corresponding to the current control cycle is established, and each preset modulation strategy in the set has a corresponding modulation strategy identifier. It should be noted that the set of preset modulation strategies represents the range of modulation strategies allowed to participate in loss evaluation and subsequent optimization within the current control cycle. In one embodiment, the set of preset modulation strategies may include continuous pulse width modulation strategies, first-type discontinuous pulse width modulation strategies, second-type discontinuous pulse width modulation strategies, overmodulation strategies, and low switching loss modulation strategies. Continuous pulse width modulation strategies typically have better current waveform continuity; discontinuous pulse width modulation strategies typically reduce some switching actions; overmodulation strategies are typically used to improve voltage utilization; and low switching loss modulation strategies are typically used to reduce the number of power device switching operations under high thermal loads. It should be noted that different preset modulation strategies do not necessarily participate in the evaluation under all operating conditions; they can be selected based on the modulation ratio, DC bus voltage, and thermal state of the current control cycle. For example, when the modulation ratio is no greater than 0.7, continuous pulse width modulation (CPLM) and low switching loss modulation strategies can be prioritized; when the modulation ratio is greater than 0.9, overmodulation strategies can be retained for evaluation; when the estimated junction temperature is higher than 150 degrees Celsius, low switching loss modulation strategies can be retained for evaluation. This approach ensures that the set of modulation strategies included in the evaluation matches the actual operating conditions of the current control cycle, avoiding invalid calculations for obviously inapplicable modulation strategies. "Obviously inapplicable" can be understood as the candidate modulation ratio corresponding to the modulation strategy exceeding its allowable modulation ratio range, or the candidate switching frequency corresponding to the modulation strategy exceeding the inverter's allowable switching frequency range.

[0051] Furthermore, based on the modulation rules corresponding to each preset modulation strategy in the preset modulation strategy set, the candidate switching frequency and candidate modulation ratio corresponding to each preset modulation strategy are determined. It should be noted that the modulation rules may include the switching sequence generation rules, switching frequency value rules, and modulation ratio adjustment rules corresponding to the modulation strategy. For continuous pulse width modulation strategies, the candidate switching frequency can remain at the current switching frequency, and the candidate modulation ratio can be determined based on the current voltage requirement and DC bus voltage; for discontinuous pulse width modulation strategies, the candidate switching frequency can be lower than the current switching frequency, which can be understood as a reduction of 5% to 30% relative to the current switching frequency; for overmodulation strategies, the candidate modulation ratio can be higher than the conventional linear modulation state, which can be understood as a candidate modulation ratio greater than 0.95 and not greater than 1.15; for low switching loss modulation strategies, the candidate switching frequency can be set in the range of 70% to 95% of the current switching frequency. By mapping each preset modulation strategy to its corresponding candidate switching frequency and candidate modulation ratio, the inverter loss model can output comparable loss values ​​for each specific modulation strategy, rather than making a rough judgment based solely on the modulation strategy name.

[0052] Furthermore, the DC bus voltage, the estimated junction temperature of the power semiconductor devices in the inverter, and the candidate switching frequency and candidate modulation ratio corresponding to each preset modulation strategy are input into the thermally corrected inverter loss model to obtain the conduction loss value, switching loss value, and modulation additional loss value corresponding to each preset modulation strategy. It should be noted that the conduction loss value characterizes the energy loss of the power semiconductor devices in the current current path due to the conduction state; the switching loss value characterizes the energy loss generated by the devices during turn-on and turn-off operations; and the modulation additional loss value characterizes the additional energy loss introduced by the modulation strategy. For the same current control cycle, different preset modulation strategies may have the same estimated DC bus voltage and junction temperature, but their candidate switching frequencies and candidate modulation ratios are different, thus resulting in different switching loss values ​​and modulation additional loss values. By inputting the data corresponding to each preset modulation strategy into the thermally corrected inverter loss model, inverter loss results that reflect the current thermal state and modulation differences can be obtained.

[0053] Furthermore, based on the conduction loss value, switching loss value, and modulation additional loss value corresponding to each preset modulation strategy, the total inverter loss value corresponding to each preset modulation strategy is determined. It should be noted that the total inverter loss value represents the total power loss generated by the inverter to achieve traction motor control under the current control cycle and the corresponding preset modulation strategy. The total inverter loss value can be obtained by summing the conduction loss value, switching loss value, and modulation additional loss value. In one embodiment, if the total inverter loss value corresponding to a certain preset modulation strategy is higher than 10% of the average total loss value of all strategies in the preset modulation strategy set, the preset modulation strategy can be considered to be in a high-loss state under the current control cycle; if the total inverter loss value corresponding to a certain preset modulation strategy is lower than 10% of the average level, the preset modulation strategy can be considered to be in a low-loss state under the current control cycle. The high-loss state and low-loss state are only used for relative evaluation under the current control cycle and do not indicate that the modulation strategy is high-loss or low-loss under all operating conditions. Therefore, it is possible to avoid the assumption that a certain modulation strategy is always more efficient, and to enable subsequent control to make judgments based on the current thermal state and the current voltage utilization level.

[0054] Furthermore, based on the total inverter loss value corresponding to each preset modulation strategy and the corresponding modulation strategy identifier, the inverter loss evaluation result is generated. It should be noted that the inverter loss evaluation result may include the modulation strategy identifier, candidate switching frequency, candidate modulation ratio, conduction loss value, switching loss value, modulation additional loss value, and total inverter loss value for each preset modulation strategy. This evaluation result does not directly determine the final target modulation strategy, but serves as the input basis for subsequent steps S4 and S5. That is, this step is only responsible for forming the inverter-side loss evaluation under the current thermal state, and does not solely use the minimum total inverter loss as the final control basis. The final target modulation strategy needs to be determined in the subsequent comprehensive loss evaluation function by combining the motor dynamic efficiency evaluation result, the vehicle torque demand of the current control cycle, current constraints, voltage constraints, and thermal constraints. Through the above method, the present invention can avoid the local optimum problem in existing control systems that only focus on motor efficiency or only on inverter losses, enabling the efficiency control of the electric drive system to have a collaborative evaluation basis on both the motor and inverter sides.

[0055] S4: Based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, construct a comprehensive loss evaluation function for the traction motor and the inverter.

[0056] Extract the motor power loss value, motor efficiency offset, and motor thermal constraint margin corresponding to the current operating point from the motor dynamic efficiency evaluation results. Extract the total inverter loss value and the corresponding modulation strategy identifier for each preset modulation strategy from the inverter loss evaluation results; For each preset modulation strategy, the motor power loss value and the corresponding total inverter loss value are added together to obtain the basic loss value of the electric drive system corresponding to each preset modulation strategy. The efficiency deviation penalty value is determined based on the motor efficiency deviation, and the thermal margin penalty value is determined based on the motor thermal constraint margin. For each preset modulation strategy, a comprehensive loss evaluation value corresponding to each preset modulation strategy is obtained based on the corresponding basic loss value of the electric drive system, the efficiency deviation penalty value, and the thermal margin penalty value. Based on the comprehensive loss evaluation value corresponding to each preset modulation strategy, the corresponding modulation strategy identifier, and the evaluation result of the candidate current vector command by the dynamic motor efficiency spectrum, a comprehensive loss evaluation function for the traction motor and the inverter is constructed that can output the corresponding comprehensive loss evaluation value according to the candidate current vector command and the preset modulation strategy.

[0057] In step S4, a comprehensive loss evaluation function for the traction motor and the inverter is constructed based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results. It should be noted that the purpose of this step is not to judge the efficiency of the traction motor alone, nor to judge the magnitude of the inverter loss alone, but to incorporate the dynamic efficiency evaluation results of the traction motor side and the dynamic loss evaluation results of the inverter side into the same evaluation logic, enabling subsequent steps to select the target current vector command and target modulation strategy under the same evaluation scale. In existing motor efficiency control, the motor efficiency spectrum is usually used as the main control basis, and inverter loss is treated as a fixed additional item. This approach easily leads to situations where the traction motor side efficiency is high, but the inverter side switching loss or modulation additional loss is significantly increased. A significant increase can be understood as the inverter side loss being more than 10% higher than the average inverter loss value of multiple candidate modulation strategies under the current operating condition. This step, by constructing a comprehensive loss evaluation function, allows motor-side loss, inverter-side loss, efficiency offset state, and thermal constraint state to participate in the control decision, thus avoiding the problem of localized high efficiency of the motor but overall inefficiency of the electric drive system.

[0058] Furthermore, the motor power loss value, motor efficiency deviation, and motor thermal constraint margin corresponding to the current operating point are extracted from the motor dynamic efficiency evaluation results. It should be noted that the motor power loss value represents the energy loss generated by the traction motor when meeting the vehicle torque requirements at the current operating point; the motor efficiency deviation represents the degree of deviation of the current efficiency value in the dynamic motor efficiency map from the benchmark efficiency value in the preset motor efficiency map; and the motor thermal constraint margin represents the remaining space between the current thermal state of the traction motor and the allowable thermal boundary. These three types of data characterize the comprehensive state of the traction motor in the current control cycle from three dimensions: absolute loss level, relative efficiency drift, and thermal safety boundary. Among them, the motor power loss value belongs to the basic loss quantity, while the motor efficiency deviation and motor thermal constraint margin belong to the constraint evaluation quantity. By extracting these three types of data simultaneously, it is possible to avoid ignoring the subsequent risks caused by thermal state deterioration by using only the current motor power loss value as the evaluation basis.

[0059] It should also be noted that when the differences in motor power loss values ​​corresponding to different candidate control schemes are small, the motor efficiency offset and the motor thermal constraint margin can further distinguish the merits of different candidate control schemes. "Small difference" can be understood as the maximum difference between the motor power loss values ​​corresponding to different candidate control schemes not exceeding 5% of the smaller motor power loss value. In this case, if the motor efficiency offset corresponding to a certain candidate control scheme is large (large can be understood as an efficiency change exceeding 3 percentage points), it indicates that the motor operating state corresponding to this scheme is more significantly affected by the thermal state. If the motor thermal constraint margin corresponding to a certain candidate control scheme is insufficient (insufficient can be understood as either the stator temperature or the rotor temperature estimate corresponding to an allowable temperature upper limit not exceeding 10 degrees Celsius), it indicates that this scheme is more likely to trigger thermal limits during subsequent continuous operation. Therefore, incorporating the motor efficiency offset and motor thermal constraint margin into the comprehensive loss evaluation function enables subsequent control to compare not only instantaneous losses but also efficiency drift risks and thermal safety risks.

[0060] Furthermore, the total inverter loss value and corresponding modulation strategy identifier for each preset modulation strategy are extracted from the inverter loss evaluation results. It should be noted that the total inverter loss value is obtained based on the inverter loss model after thermal state correction, and it already includes conduction loss, switching loss, and modulation-related loss. The modulation strategy identifier is used to distinguish different preset modulation strategies, enabling the subsequent comprehensive loss evaluation function to retain the correlation between each preset modulation strategy and its corresponding loss result. In one embodiment, if the preset modulation strategy set includes continuous pulse width modulation (PWM), first-type discontinuous PWM, second-type discontinuous PWM, overmodulation, and low-switching-loss modulation strategies, then each modulation strategy corresponds to a modulation strategy identifier and a total inverter loss value. In this way, the inverter loss evaluation results can be directly read by the subsequent comprehensive loss evaluation function without losing the modulation strategy dimension.

[0061] Furthermore, for each preset modulation strategy, the motor power loss value and the corresponding total inverter loss value are added together to obtain the basic loss value of the electric drive system corresponding to each preset modulation strategy. It should be noted that the basic loss value of the electric drive system is used to characterize the basic energy loss jointly generated by the traction motor and inverter under the current control cycle. Since the motor power loss value reflects the loss on the traction motor side and the total inverter loss value reflects the loss on the inverter side, and both have the same control cycle time basis, they can be combined for evaluation within the same control cycle. It should also be noted that the basic loss value of the electric drive system is an intermediate evaluation quantity for generating the subsequent comprehensive loss evaluation value; it is not directly used as the final control basis. That is, even if the basic loss value of the electric drive system corresponding to a certain preset modulation strategy is low (lower can be understood as more than 5% lower than the average level of the basic loss values ​​corresponding to each preset modulation strategy), it is still necessary to make a comprehensive judgment in conjunction with the efficiency deviation penalty value and the thermal margin penalty value.

[0062] Furthermore, an efficiency deviation penalty value is determined based on the motor efficiency offset. It should be noted that the efficiency deviation penalty value characterizes the evaluation cost imposed on control selection when the dynamic motor efficiency map deviates from the preset motor efficiency map. If the motor efficiency offset is less than 1 percentage point, it can be considered a low offset, and the efficiency deviation penalty value can be set to a low level, which can be understood as not exceeding 2% of the current electric drive system's base loss value. If the motor efficiency offset is greater than 1 percentage point but not more than 3 percentage points, it can be considered a medium offset, and the efficiency deviation penalty value can be set to 2% to 6% of the current electric drive system's base loss value. If the motor efficiency offset exceeds 3 percentage points, it can be considered a high offset, and the efficiency deviation penalty value can be set to 6% to 12% of the current electric drive system's base loss value. By setting the efficiency deviation penalty value, subsequent control can reduce the probability of continuing to select the original baseline high-efficiency region when facing a significant shift in the efficiency map due to thermal conditions, thereby avoiding control misjudgments caused by a fixed efficiency map.

[0063] Furthermore, a thermal margin penalty value is determined based on the aforementioned motor thermal constraint margin. It should be noted that the thermal margin penalty value characterizes the evaluation cost imposed on control selection when the current motor thermal state approaches the thermal boundary. If the motor thermal constraint margin is greater than 20 degrees Celsius, the thermal margin can be considered sufficient, and the thermal margin penalty value can be set at a lower level, which can be understood as not exceeding 2% of the current electric drive system's base loss value. If the motor thermal constraint margin is greater than 10 degrees Celsius but not greater than 20 degrees Celsius, the thermal margin can be considered normal, and the thermal margin penalty value can be set to 2% to 5% of the current electric drive system's base loss value. If the motor thermal constraint margin is greater than 5 degrees Celsius but not greater than 10 degrees Celsius, the thermal margin can be considered insufficient, and the thermal margin penalty value can be set to 5% to 10% of the current electric drive system's base loss value. If the motor thermal constraint margin is not greater than 5 degrees Celsius, the thermal margin can be considered critical, and the thermal margin penalty value can be set to 10% to 20% of the current electric drive system's base loss value. Through this process, the comprehensive loss evaluation function not only reflects the current energy loss, but also the thermal safety risks that may result from continued operation, making the controller more inclined to select current vector and modulation strategies with lower heat generation risk when the thermal margin is insufficient.

[0064] Furthermore, for each preset modulation strategy, a comprehensive loss evaluation value is obtained based on the corresponding basic loss value of the electric drive system, the efficiency deviation penalty value, and the thermal margin penalty value. It should be noted that the comprehensive loss evaluation value can be understood as the evaluation cost obtained by comprehensively considering motor-side losses, inverter-side losses, efficiency deviation, and thermal safety margin under the corresponding preset modulation strategy. The comprehensive loss evaluation value can be jointly determined based on the basic loss value of the electric drive system, the efficiency deviation penalty value, and the thermal margin penalty value, and is not limited to a single linear superposition method. In one embodiment, a lookup table mapping method can be used to determine the comprehensive loss evaluation value; in another embodiment, a piecewise mapping method can be used; and in yet another embodiment, an interpolation mapping method can be used. This evaluation method avoids using the lowest total inverter loss or the lowest motor power loss as the sole control criterion, reducing system efficiency mismatch caused by local optima.

[0065] Furthermore, based on the comprehensive loss evaluation value corresponding to each preset modulation strategy and the corresponding modulation strategy identifier, a comprehensive loss evaluation function for the traction motor and the inverter is constructed, capable of outputting the corresponding comprehensive loss evaluation value according to the candidate current vector command and the preset modulation strategy. It should be noted that the comprehensive loss evaluation function can be implemented using lookup table mapping, piecewise mapping, interpolation mapping, and the controller's built-in evaluation rules. Its input can include the candidate current vector command and the preset modulation strategy, and its output is the comprehensive loss evaluation value corresponding to the candidate current vector command and the preset modulation strategy. The candidate current vector command is used to influence the motor power loss value, motor efficiency offset, and motor thermal constraint margin on the traction motor side, while the preset modulation strategy is used to influence the inverter total loss value, candidate switching frequency, and candidate modulation ratio on the inverter side. By using both the candidate current vector command and the preset modulation strategy as inputs to the comprehensive loss evaluation function, an evaluation basis can be provided for the joint optimization in the subsequent step S5, so that the target current vector command and the target modulation strategy are no longer determined independently, but are jointly determined under the same comprehensive loss evaluation logic.

[0066] It should also be noted that, in one embodiment, the comprehensive loss evaluation function can be implemented using a lookup table. Specifically, for multiple candidate current vector commands and multiple preset modulation strategies in the current control cycle, corresponding comprehensive loss evaluation values ​​can be generated respectively, and the correspondence between the candidate current vector commands, preset modulation strategies, and comprehensive loss evaluation values ​​can be stored as a local evaluation table. During the subsequent joint optimization in step S5, the comprehensive loss evaluation value corresponding to the candidate control combination can be obtained by reading the local evaluation table. This lookup table format does not mean that the comprehensive loss evaluation function can only be implemented using a lookup table; in other embodiments, it can also be implemented using piecewise mapping, interpolation mapping, and built-in evaluation rules of the controller. By supplementing the lookup table implementation method, those skilled in the art can clearly understand one possible implementation method of the comprehensive loss evaluation function in the vehicle controller.

[0067] It should also be noted that the comprehensive loss evaluation function does not require the complete global function to be regenerated in each control cycle. In one implementation, a local comprehensive loss evaluation function can be constructed only for the vehicle torque demand, the neighborhood of the current operating point, and the preset modulation strategy set for the current control cycle. The neighborhood of the current operating point can be understood as the candidate operating region within 5% above and below the actual speed of the traction motor and within 5% above and below the vehicle torque demand. When the motor thermal constraint margin is no greater than 10 degrees Celsius, the neighborhood of the current operating point can be expanded to the candidate operating region within 10% above and below the actual speed of the traction motor and within 10% above and below the vehicle torque demand, so as to improve the evaluation coverage near the thermal boundary. By constructing the function locally, the computational burden of the on-board controller can be reduced, making this step compatible with the real-time control task within the current control cycle.

[0068] Through the above steps, the comprehensive loss evaluation function can unify the motor dynamic efficiency evaluation result obtained in step S2 and the inverter loss evaluation result obtained in step S3 into the same evaluation framework. The beneficial effects of this process are: when a candidate control scheme is better evaluated on the motor side but leads to increased inverter-side losses, the comprehensive loss evaluation value will reflect this increase; when a candidate control scheme has low base losses at the current moment but insufficient motor thermal constraint margin, the comprehensive loss evaluation value will reflect its thermal risk through the thermal margin penalty value; when the base losses of multiple candidate control schemes are close, the comprehensive loss evaluation function can further distinguish their long-term operational adaptability using efficiency deviation penalty values ​​and thermal margin penalty values. The closeness of base losses can be understood as the maximum difference between the base loss values ​​of the electric drive system corresponding to multiple candidate control schemes not exceeding 5% of the smaller base loss value. Therefore, this step can provide an evaluation basis that is closer to the actual operating state of the electric drive system for the subsequent selection of target control combinations, thereby improving the adaptability of the motor efficiency control method under high temperature, high load, and multi-modulation strategy switching conditions.

[0069] S5: Under the conditions of satisfying the vehicle torque demand, current constraint, voltage constraint and thermal constraint of the current control cycle, solve for the target current vector command and target modulation strategy that minimize the value of the comprehensive loss evaluation function.

[0070] Based on the vehicle torque demand of the current control cycle, an initial current vector command set is generated. Each initial current vector command in the initial current vector command set includes an initial d-axis current command and an initial q-axis current command. The current constraint boundary is determined based on the preset maximum current limit value of the traction motor, and the voltage constraint boundary is determined based on the DC bus voltage; Based on the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter, the current limit value corresponding to the thermal constraint is determined. Based on the current constraint boundary, the voltage constraint boundary and the current limit value corresponding to the thermal constraint, the initial current vector instruction set is filtered to obtain a feasible current vector instruction set. Based on the set of feasible current vector commands and the set of preset modulation strategies, multiple candidate control combinations are formed, each candidate control combination including a feasible current vector command and a preset modulation strategy. Each candidate control combination is input into the comprehensive loss evaluation function to obtain the comprehensive loss evaluation value corresponding to each candidate control combination; The candidate control combination with the smallest comprehensive loss evaluation value is determined as the target control combination, the feasible current vector command in the target control combination is determined as the target current vector command, and the preset modulation strategy in the target control combination is determined as the target modulation strategy.

[0071] In step S5, under the conditions of satisfying the vehicle torque demand, current constraints, voltage constraints, and thermal constraints of the current control cycle, the target current vector command and target modulation strategy that minimize the value of the comprehensive loss evaluation function are solved. It should be noted that the purpose of this step is not to separately determine the high-efficiency current point on the traction motor side, nor to separately select the modulation strategy with the lowest inverter side loss, but rather to simultaneously consider the current vector command and modulation strategy within the same candidate control combination, so that the traction motor and inverter jointly meet the requirements for torque output, device current, voltage utilization, and thermal safety under the current control cycle. In the prior art, the current vector command is usually determined independently based on a fixed motor efficiency spectrum, the maximum torque-to-current ratio control curve, and the field weakening control rule, while the modulation strategy is usually selected independently based on a fixed modulation rule or offline calibration results. The lack of a unified evaluation process for both can easily lead to situations where the motor-side current vector is optimal but the inverter-side loss increases, or the inverter modulation strategy is optimal but the motor side requires higher current compensation. This step follows the comprehensive loss evaluation function obtained in step S4. The candidate current vector command and the preset modulation strategy are input into the comprehensive loss evaluation function for evaluation, thereby determining the target control combination at the electric drive system level.

[0072] Furthermore, based on the vehicle torque demand of the current control cycle, an initial current vector command set is generated. Each initial current vector command in the initial current vector command set includes an initial d-axis current command and an initial q-axis current command. It should be noted that the d-axis current command is used to adjust the traction motor flux linkage state, and the q-axis current command is used to adjust the traction motor torque output capability. The initial current vector command set can be generated based on the traction motor's torque-current mapping table, speed-current mapping table, and the vehicle torque demand of the current control cycle. In one embodiment, the motor controller can first determine a reference current vector command in a preset torque-current mapping table based on the vehicle torque demand, and then generate multiple initial current vector commands around this reference current vector command. "Around" can be understood as generating candidate points within a 5% rated current range above and below the reference d-axis current command, and within a 5% rated current range above and below the reference q-axis current command. When the change in vehicle torque demand exceeds 10% of the traction motor's rated torque, the range can be expanded to 10% of the rated current above and below, to improve the candidate coverage range under conditions of rapid acceleration, hill climbing, and rapid torque changes.

[0073] It should also be noted that the initial current vector command set can be generated by combining the maximum torque-to-current ratio control curve, the constant torque control curve, and the field weakening control region. The maximum torque-to-current ratio control curve is used to provide candidate current points with higher torque output efficiency under low- and medium-speed conditions; the constant torque control curve is used to generate different d-axis and q-axis current combinations while maintaining the current vehicle torque requirements; the field weakening control region is used to generate candidate current points with voltage constraint adaptability under high-speed and insufficient bus voltage margin conditions. The low- and medium-speed conditions can be understood as the actual speed of the traction motor not exceeding 40% of the maximum rated speed of the traction motor; the high-speed conditions can be understood as the actual speed of the traction motor exceeding 70% of the maximum rated speed of the traction motor; the insufficient bus voltage margin can be understood as the current DC bus voltage being lower than 90% of the rated DC bus voltage. By simultaneously introducing the above candidate generation criteria, the initial current vector command set can include both conventional high-efficiency current points and current points adapted to field weakening and voltage-constrained conditions, avoiding insufficient optimization range caused by the candidate set being generated only around a single control curve.

[0074] It should also be noted that the number of candidates for the initial current vector command set can be determined based on the computing power of the on-board controller. In one implementation, it can be set to 9 to 81 candidate current vector commands; when the control cycle is short, for example, no more than 2 milliseconds, 9 to 25 candidate current vector commands can be used; when the control cycle is long, for example, more than 5 milliseconds, 25 to 81 candidate current vector commands can be used. The number of candidates is not a fixed limit, but is used to achieve a balance between real-time computing power and optimization accuracy.

[0075] Furthermore, a current constraint boundary is determined based on a preset maximum current limit value for the traction motor, and a voltage constraint boundary is determined based on the DC bus voltage. It should be noted that the current constraint boundary is used to limit the current amplitude corresponding to the candidate current vector command from exceeding the current capacity allowed by the traction motor and inverter. The preset maximum current limit value for the traction motor can be determined jointly based on the rated current of the traction motor, the short-time peak current, the inverter's allowable output current, and the battery's discharge capacity. In one embodiment, the maximum current limit value under continuous operation conditions can be set to 80% to 100% of the rated current of the traction motor; the maximum current limit value under short-time acceleration conditions can be set to 100% to 150% of the rated current of the traction motor, where "short-time" can be understood as a duration not exceeding 10 seconds. The voltage constraint boundary is used to limit the output voltage required by the candidate current vector command at the current speed and current DC bus voltage from exceeding the voltage capacity provided by the inverter. It should be noted that the lower the DC bus voltage, the smaller the voltage margin that the inverter can provide, and the stricter the voltage constraint boundary. When the DC bus voltage is lower than 90% of the rated DC bus voltage, the voltage margin can be considered insufficient, and candidate current vector commands that are prone to voltage saturation should be reduced. The rated DC bus voltage can be the DC bus voltage reference value preset in the electric drive system calibration document.

[0076] Furthermore, based on the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter, a current limit value corresponding to the thermal constraint is determined. It should be noted that the current limit value corresponding to the thermal constraint is used to limit the current amplitude of the candidate current vector command when the traction motor or inverter approaches the thermal safety boundary, thereby reducing the risk of further temperature increases. In one implementation, when the stator temperature of the traction motor is more than 20 degrees Celsius below the upper limit of the stator allowable temperature, the estimated rotor temperature of the traction motor is more than 20 degrees Celsius below the upper limit of the rotor allowable temperature, and the estimated junction temperature of the power semiconductor device is more than 20 degrees Celsius below the upper limit of the junction temperature, the thermal margin can be considered sufficient. In this case, the current limit value corresponding to the thermal constraint can be close to the current constraint boundary, which can be understood as not less than 95% of the current constraint boundary. When the upper limit of the allowable temperature corresponding to any of the above-mentioned temperature distances does not exceed 10 degrees Celsius, the thermal margin can be considered insufficient. In this case, the current limit value corresponding to the thermal constraint can be set to 70% to 90% of the current constraint boundary. When the upper limit of the allowable temperature corresponding to any of the above-mentioned temperature distances does not exceed 5 degrees Celsius, the thermal margin can be considered critical. In this case, the current limit value corresponding to the thermal constraint can be set to 50% to 70% of the current constraint boundary. In this way, the thermal constraint can directly participate in the candidate current vector command screening, instead of passively derating after the temperature reaches the protection threshold.

[0077] Furthermore, based on the current constraint boundary, the voltage constraint boundary, and the current limit value corresponding to the thermal constraint, the initial current vector command set is filtered to obtain a feasible current vector command set. It should be noted that the filtering process can be performed sequentially according to current constraints, voltage constraints, and thermal constraints, or all three types of constraints can be used simultaneously to determine the feasibility of candidate current vector commands. For any initial current vector command, if its corresponding current amplitude exceeds the current constraint boundary, the initial current vector command is determined to be current infeasible; if its required output voltage under the current DC bus voltage and the current actual speed of the traction motor exceeds the voltage constraint boundary, it is determined to be voltage infeasible; if its corresponding current amplitude exceeds the current limit value corresponding to the thermal constraint, it is determined to be thermal infeasible. The initial current vector commands retained after the above filtering constitute the feasible current vector command set.

[0078] It should also be noted that when the number of candidates in the feasible current vector command set is lower than a preset number, the candidate point density can be increased, and the initial current vector command set can be regenerated within the range jointly defined by the current constraint boundary, the voltage constraint boundary, and the current limit value corresponding to the thermal constraint. The preset number can be set to 3 to 5; increasing the candidate point density can be understood as reducing the current interval between candidate current vector commands to 50% to 80% of the original current interval. Through this process, it is possible to avoid the loss of a comparison basis for comprehensive optimization due to too few candidates, while ensuring that the regenerated candidate current vector commands still meet the safety constraints of the current control cycle.

[0079] Furthermore, based on the feasible current vector command set and the preset modulation strategy set, multiple candidate control combinations are formed, each candidate control combination including a feasible current vector command and a preset modulation strategy. It should be noted that the candidate control combination represents a complete control scheme available within the current control cycle, where the feasible current vector command corresponds to the traction motor-side control variable, and the preset modulation strategy corresponds to the inverter-side control variable. In one embodiment, if the feasible current vector command set contains 20 feasible current vector commands and the preset modulation strategy set contains 4 preset modulation strategies, then 80 candidate control combinations can be formed. By evaluating the two in combination, the separate control methods of fixing the current vector first and then selecting the modulation strategy, or fixing the modulation strategy first and then selecting the current vector, can be avoided. This process places the target current vector command and the target modulation strategy in the same optimization space, embodying the joint efficiency control concept of this invention.

[0080] Furthermore, each candidate control combination is input into the comprehensive loss evaluation function to obtain the comprehensive loss evaluation value corresponding to each candidate control combination. It should be noted that for any candidate control combination, the comprehensive loss evaluation function determines the corresponding motor power loss, motor efficiency offset, and motor thermal constraint state based on the feasible current vector command, and determines the corresponding inverter total loss, candidate switching frequency, and candidate modulation ratio based on the preset modulation strategy, thereby outputting the comprehensive loss evaluation value of that candidate control combination. The smaller the comprehensive loss evaluation value, the lower the system-level loss and constraint cost of the candidate control combination within the current control cycle; the larger the comprehensive loss evaluation value, the higher the energy loss, efficiency offset, or thermal risk of the candidate control combination. "Higher" can be understood as the comprehensive loss evaluation value of the candidate control combination being more than 10% higher than the average comprehensive loss evaluation value of all candidate control combinations. By evaluating candidate control combinations one by one, the controller can obtain a complete ranking of candidate schemes, rather than only obtaining a partial evaluation result of a single strategy.

[0081] It should also be noted that if the comprehensive loss evaluation function in step S4 is implemented using a local evaluation table, then this step can use the feasible current vector command and preset modulation strategy in each candidate control combination as index conditions to directly read the comprehensive loss evaluation value corresponding to that candidate control combination. The local evaluation table can be an evaluation table formed within the current control cycle based on the neighborhood of the current operating point, the set of feasible current vector commands, and the set of preset modulation strategies. By reading the local evaluation table, the computational workload of repeatedly calculating the comprehensive loss evaluation value can be reduced, making this step more suitable for execution in vehicle controllers with shorter control cycles.

[0082] Furthermore, the candidate control combination with the minimum comprehensive loss evaluation value is determined as the target control combination, the feasible current vector command in the target control combination is determined as the target current vector command, and the preset modulation strategy in the target control combination is determined as the target modulation strategy. It should be noted that the target control combination is the candidate control combination that minimizes the comprehensive loss evaluation function value while satisfying the vehicle torque requirement, current constraint, voltage constraint, and thermal constraint. If two or more candidate control combinations have relatively small differences in their comprehensive loss evaluation values, a secondary selection can be made based on torque following deviation, thermal constraint margin, and modulation strategy switching cost. "Relatively small difference" can be understood as the difference between the comprehensive loss evaluation values ​​not exceeding 2% of the smaller comprehensive loss evaluation value; "torque following deviation" can be understood as the difference between the expected output torque corresponding to the candidate control combination and the vehicle torque requirement in the current control cycle; "modulation strategy switching cost" can be understood as the current fluctuation, switching sequence change, and control smoothness cost incurred when switching from the currently used modulation strategy to the candidate modulation strategy. In one implementation, when the difference in the comprehensive loss evaluation value is small, the candidate control combination with a torque following deviation not exceeding 2% of the rated torque of the traction motor and a larger thermal constraint margin can be selected first; if the difference in thermal constraint margin between the two candidate control combinations does not exceed 2 degrees Celsius, the candidate control combination that is consistent with the current modulation strategy can be selected first to reduce frequent modulation strategy switching.

[0083] It should also be noted that the joint optimization in this step does not require the use of complex global online optimization algorithms. In one implementation, a candidate set traversal approach can be used, where the comprehensive loss evaluation value is calculated for each candidate control combination, and the candidate control combination with the smallest evaluation value is selected. In another implementation, a hierarchical screening approach can be used, where the candidate current vector command set is first narrowed down using current constraints, voltage constraints, and thermal constraints, and then the comprehensive loss evaluation is performed on the remaining candidate control combinations. In yet another implementation, a local lookup table approach can be used, where the comprehensive loss evaluation value corresponding to the candidate control combination is directly read using the local comprehensive loss evaluation table constructed in step S4. All of the above methods can be implemented in the vehicle controller. The candidate set traversal approach is suitable for operating conditions with a small number of candidates, where the number of candidates can be understood as no more than 100 candidate control combinations. The local lookup table approach is suitable for operating conditions with a large number of candidates, where the number of candidates can be understood as more than 100 but no more than 500 candidate control combinations.

[0084] Through the above steps, this invention simultaneously considers the vehicle's torque requirements, current carrying capacity, voltage output capacity, and thermal safety boundary during the determination of the target current vector command and target modulation strategy. This ensures that the final control result is neither simply the optimal efficiency on the motor side nor simply the minimum loss on the inverter side. The beneficial effect of this approach is that when a certain current vector can reduce motor losses but leads to higher switching losses in the inverter under the corresponding modulation strategy, the overall loss evaluation value of the candidate control combination will increase. Similarly, when a certain modulation strategy can reduce inverter losses but requires a larger current vector from the motor to meet torque requirements, the candidate control combination will also be constrained by the overall loss evaluation function. Therefore, this step can achieve unified optimization between the motor and inverter sides, reducing the system efficiency decline caused by single-sided optimization and improving the efficiency control stability of new energy vehicles under conditions of high temperature, low bus voltage, high-speed cruising, and frequent torque changes.

[0085] S6: Generate an electric drive system efficiency control command according to the target current vector command and the target modulation strategy, and control the traction motor and the inverter according to the electric drive system efficiency control command.

[0086] Based on the target d-axis current command and target q-axis current command in the target current vector command, generate the three-phase current control signal for the traction motor; According to the target modulation strategy, the target switching frequency, target modulation ratio, and target switching sequence are determined, and an inverter switching control signal is generated based on the target switching frequency, the target modulation ratio, and the target switching sequence. The three-phase current control signal of the traction motor and the switching control signal of the inverter are used as the efficiency control command of the electric drive system. The current vector of the traction motor is controlled according to the efficiency control command of the electric drive system, and the modulation process of the inverter is controlled. The execution feedback data of the traction motor and the inverter after executing the efficiency control command of the electric drive system is obtained. The execution feedback data includes the actual three-phase current of the traction motor, the actual output torque of the traction motor, the stator temperature feedback value of the traction motor, the rotor temperature feedback estimate of the traction motor, and the junction temperature feedback value of the power semiconductor devices in the inverter. Based on the execution feedback data, the dynamic motor efficiency graph and the preset inverter loss model are updated, and the updated dynamic motor efficiency graph and the updated preset inverter loss model are used in the next control cycle.

[0087] In step S6, an electric drive system efficiency control command is generated according to the target current vector command and the target modulation strategy, and the traction motor and the inverter are controlled according to the electric drive system efficiency control command. It should be noted that this step is used to convert the target control combination determined in step S5 into specific control signals that the traction motor and the inverter can execute. The target current vector command and target modulation strategy output in step S5 are control decision results, which the traction motor and the inverter cannot directly execute. Therefore, in this step, the target current vector command needs to be converted into a three-phase current control signal for the traction motor, and the target modulation strategy needs to be converted into a switching control signal for the inverter. Through this processing, the comprehensive efficiency optimization result obtained in the preceding steps can be transformed into the actual control action of the electric drive system.

[0088] Furthermore, based on the target d-axis current command and target q-axis current command in the target current vector command, a three-phase current control signal for the traction motor is generated. It should be noted that the target d-axis current command is used to determine the flux linkage control component of the traction motor, and the target q-axis current command is used to determine the torque control component of the traction motor. The motor controller can convert the target d-axis current command and target q-axis current command into corresponding three-phase current target values ​​according to the current rotor position, and generate the three-phase current control signal for the traction motor based on the three-phase current target values. In one embodiment, the target d-axis current command and target q-axis current command can be converted into a three-phase current control signal for the traction motor through current closed-loop regulation, coordinate transformation, and voltage feedforward compensation. The current closed-loop regulation is used to correct the deviation between the actual current and the target current; the coordinate transformation is used to realize the conversion between the target d-axis current command, the target q-axis current command, and the three-phase current control signal; the voltage feedforward compensation is used to reduce the influence of speed changes and back EMF changes on current tracking. The above method is only one feasible example; in other embodiments, other current closed-loop control methods suitable for traction motor vector control can also be used.

[0089] It should also be noted that the three-phase current control signal of the traction motor may include a three-phase current reference value, a current closed-loop regulation amount, and a voltage command amount. The three-phase current reference value is used to indicate the target current that the three-phase windings of the traction motor need to track in the current control cycle. The current closed-loop regulation amount is used to correct the deviation between the actual three-phase current and the three-phase current reference value. The voltage command amount is used to drive the inverter to output the corresponding voltage to achieve current tracking. In one embodiment, when the deviation between the actual three-phase current and the three-phase current reference value does not exceed 3% of the rated phase current of the traction motor, the current tracking can be considered to be in a stable state. When the deviation exceeds 8% of the rated phase current of the traction motor, the current tracking deviation can be considered to be large. A large deviation can be understood as needing to increase the intensity of the current closed-loop regulation or reduce the slope of the target current change in the next control cycle. Reducing the slope of the target current change can be understood as limiting the change in the target phase current between adjacent control cycles to 3% to 8% of the rated phase current of the traction motor to reduce the impact of sudden current changes on torque smoothness.

[0090] Furthermore, based on the target modulation strategy, a target switching frequency, a target modulation ratio, and a target switching sequence are determined, and an inverter switching control signal is generated based on the target switching frequency, the target modulation ratio, and the target switching sequence. It should be noted that the target modulation strategy is used to determine the modulation method adopted by the inverter in the current control cycle, the target switching frequency is used to determine the switching frequency of the power semiconductor devices, the target modulation ratio is used to determine the utilization level of the inverter output voltage, and the target switching sequence is used to determine the turn-on and turn-off sequence of the power semiconductor devices in each arm of the inverter. In one implementation, when the target modulation strategy is a continuous pulse width modulation (PWM) strategy, the target switching sequence can ensure that all three phase arms participate in switching operations within the current modulation cycle; when the target modulation strategy is a discontinuous pulse width modulation (DMCM) strategy, the target switching sequence can ensure that one phase arm remains in a fixed switching state for a portion of the time, thereby reducing the number of switching operations; when the target modulation strategy is an overmodulation strategy, the target modulation ratio can be higher than the conventional linear modulation region, where "higher" can be understood as a target modulation ratio greater than 0.95 and not greater than 1.15; when the target modulation strategy is a low switching loss modulation strategy, the target switching frequency can be reduced by 5% to 30% relative to the current switching frequency. By refining the target modulation strategy into target switching frequency, target modulation ratio, and target switching sequence, the loss optimization results on the inverter side can be transformed into executable switching control signals.

[0091] Furthermore, the traction motor three-phase current control signal and the inverter switching control signal are used as the efficiency control command for the electric drive system. It should be noted that the efficiency control command for the electric drive system is not a single control quantity, but a combined command that simultaneously includes the traction motor-side current control content and the inverter-side modulation control content. The traction motor three-phase current control signal is used to implement the target current vector command determined in step S5, and the inverter switching control signal is used to implement the target modulation strategy determined in step S5. By using both as the efficiency control command for the electric drive system, it can be ensured that the motor-side control and the inverter-side control are executed in a coordinated manner within the same control cycle, avoiding situations where the motor current command has been updated but the inverter modulation strategy still uses the strategy from the previous control cycle. This coordinated execution can be understood as the traction motor three-phase current control signal and the inverter switching control signal being generated within the same control cycle and sent to the corresponding control execution stage within a time difference of no more than one control cycle.

[0092] Furthermore, the current vector of the traction motor is controlled according to the efficiency control command of the electric drive system, and the modulation process of the inverter is controlled. It should be noted that controlling the current vector of the traction motor means making the actual three-phase current of the traction motor follow the three-phase current reference value obtained by converting the target d-axis current command and the target q-axis current command; controlling the modulation process of the inverter means making the inverter perform switching actions according to the target switching frequency, target modulation ratio, and target switching sequence. In one embodiment, the motor controller can use current closed-loop control to gradually bring the actual three-phase current closer to the three-phase current reference value, and generate corresponding bridge arm switching signals through modulation control. It should also be noted that, to avoid torque fluctuations caused by modulation strategy switching, a smooth switching process can be performed when the target modulation strategy is inconsistent with the currently used modulation strategy. The smooth switching process may include limiting the rate of change of the target switching frequency, limiting the rate of change of the target modulation ratio, and gradually adjusting the switching sequence within adjacent control cycles. The target switching frequency change rate can be limited to a change of no more than 10% of the current switching frequency between two adjacent control cycles; the target modulation ratio change rate can be limited to a change of no more than 0.05 between two adjacent control cycles. This process can reduce current ripple and torque fluctuations caused by abrupt changes in the modulation strategy.

[0093] Furthermore, the execution feedback data of the traction motor and the inverter after executing the efficiency control command of the electric drive system is obtained. This execution feedback data includes the actual three-phase current of the traction motor, the actual output torque of the traction motor, the stator temperature feedback value of the traction motor, the estimated rotor temperature feedback value of the traction motor, and the junction temperature feedback value of the power semiconductor devices in the inverter. It should be noted that the execution feedback data reflects the actual operating and thermal states of the electric drive system after executing the efficiency control command. The actual three-phase current of the traction motor is used to determine the execution deviation of the target current vector command; the actual output torque of the traction motor is used to determine the tracking effect of the vehicle's torque demand; the stator temperature feedback value of the traction motor is used to determine whether the stator-side thermal state correction in the dynamic motor efficiency graph is consistent with the actual temperature rise trend; the estimated rotor temperature feedback value of the traction motor is used to determine whether the rotor-side thermal state correction in the dynamic motor efficiency graph is consistent with the rotor thermal state change trend; and the junction temperature feedback value of the power semiconductor devices in the inverter is used to determine whether the preset inverter loss model accurately represents the actual device thermal state. The rotor temperature feedback estimate of the traction motor can be obtained based on the stator temperature feedback value, the actual three-phase current of the traction motor, the actual output torque of the traction motor, and the motor thermal network model.

[0094] It should also be noted that the execution feedback data can be obtained within a preset sampling delay after the issuance of the electric drive system efficiency control command, and the preset sampling delay can not exceed 20% of the current control cycle. By obtaining the feedback data after the control command is issued, the feedback data can be closer to the actual result after the execution of the control command in the current control cycle, avoiding premature sampling that would cause the feedback data to still reflect the state of the previous control cycle. In one embodiment, if the deviation between the actual output torque of the traction motor and the vehicle torque demand in the current control cycle does not exceed 2% of the rated torque of the traction motor, the torque tracking requirement can be considered met; if the deviation exceeds 5% of the rated torque of the traction motor, the torque tracking deviation can be considered large, and the target current vector command generation process needs to be corrected in the next control cycle. If the junction temperature feedback value of the power semiconductor device in the inverter deviates from the estimated junction temperature value by more than 5 degrees Celsius, the preset inverter loss model's estimation of the device's thermal state can be considered to have a significant deviation, which can be understood as being sufficient to affect the inverter loss evaluation result in the next control cycle.

[0095] Furthermore, based on the execution feedback data, the dynamic motor efficiency map and the preset inverter loss model are updated, and the updated dynamic motor efficiency map and the updated preset inverter loss model are used in the next control cycle. It should be noted that updating the dynamic motor efficiency map may include correcting the motor efficiency value, motor power loss value, motor efficiency offset, and motor thermal constraint margin corresponding to the current operating point and its neighboring operating points based on the actual three-phase current of the traction motor, the actual output torque of the traction motor, and the traction motor temperature feedback value. The neighboring operating points can be understood as the map region within 5% above and below the actual speed of the traction motor and within 5% above and below the actual output torque. When the traction motor temperature feedback value is close to the upper limit of the allowable temperature (close can be understood as being no more than 10 degrees Celsius away from the upper limit of the allowable temperature), the range of the neighboring operating points can be expanded to within 10% above and below the actual speed of the traction motor and within 10% above and below the actual output torque to improve the coverage of the map update near the thermal boundary.

[0096] It should also be noted that updating the preset inverter loss model may include correcting the calculation parameters for conduction loss, switching loss, and modulation additional loss based on the junction temperature feedback value of the power semiconductor devices in the inverter, the target switching frequency, the target modulation ratio, and the inverter's operating state after execution. This update does not mean abandoning the preset inverter loss model and rebuilding a new model, but rather correcting the local parameters related to the current operating condition based on the execution feedback data, so that it more accurately reflects the actual device loss state in the next control cycle. In one implementation, when the deviation between the junction temperature feedback value and the estimated junction temperature value does not exceed 3 degrees Celsius, the preset inverter loss model can remain unchanged. When the deviation is greater than 3 degrees Celsius but not more than 8 degrees Celsius, the loss calculation parameters corresponding to the current operating point can be slightly updated, where a slight update means that the magnitude of a single update does not exceed 5% of the original parameter value. When the deviation exceeds 8 degrees Celsius, the loss calculation parameters corresponding to the current operating point and its adjacent modulation strategies can be enhanced, where an enhanced update means that the magnitude of a single update is 5% to 10% of the original parameter value. The specific value of the update magnitude can be calibrated according to the model stability and the vehicle thermal management strategy to avoid excessive fluctuations in model parameters caused by a single feedback anomaly.

[0097] Furthermore, the updated dynamic motor efficiency graph and the updated preset inverter loss model are used in the next control cycle. It should be noted that the feedback update in this step does not involve resolving the target current vector command and target modulation strategy for the current control cycle, but rather provides a corrected evaluation basis for steps S2 and S3 in the next control cycle. Through this process, a cycle-by-cycle adaptive control closed loop can be formed, enabling the dynamic motor efficiency graph to be updated according to the actual thermal state of the traction motor, and enabling the preset inverter loss model to be updated according to the junction temperature feedback of the power semiconductor devices and the modulation execution state. Therefore, this invention can reduce efficiency evaluation deviations caused by initial model calibration errors, device aging, changes in cooling conditions, and changes in ambient temperature. Device aging can be understood as a shift in the conduction or switching characteristics of the power semiconductor devices relative to their factory calibration state after long-term operation; changes in cooling conditions can be understood as a change in cooling medium temperature exceeding 10 degrees Celsius or a change in cooling flow rate exceeding 10% of the rated cooling flow rate. By using the execution feedback data for the next control cycle, this invention enables the efficiency control process on both the motor and inverter sides to have continuous correction capabilities, thereby improving the stability of the electric drive system efficiency control under long-term operation and complex conditions.

[0098] Through the above steps, this invention completes a full closed-loop control process, from data acquisition, dynamic efficiency evaluation on the motor side, multi-strategy loss evaluation on the inverter side, construction of a comprehensive loss evaluation function, joint optimization of current vector and modulation strategies, control command generation and execution, to graph and model feedback updates. This control process uses the control cycle as the basic execution unit, enabling the efficiency control of the electric drive system to continuously adjust in response to changes in vehicle operating conditions and thermal states, thereby improving the overall efficiency control stability of the traction motor and inverter in new energy vehicles under different operating conditions.

[0099] Example 2 is the second embodiment of the present invention, which differs from the previous embodiment in that: If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art or the current technical solution, can be embodied in the form of a software product. This current computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0100] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0101] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0102] Example 3, referring to Figure 2 As an embodiment of the present invention, a new energy vehicle motor efficiency control system is provided, which includes a data acquisition module, a spectrum correction module, a loss evaluation module, a function construction module, a joint optimization module, and a control execution module.

[0103] Data acquisition module: Acquires the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle; The graph correction module corrects the preset motor efficiency graph based on the traction motor operating data and the electric drive system thermal state data to obtain a dynamic motor efficiency graph, and generates a motor dynamic efficiency evaluation result based on the dynamic motor efficiency graph. Loss evaluation module: Based on the inverter operating data and the electric drive system thermal state data, the preset inverter loss model is thermally corrected to determine the inverter loss corresponding to each of the multiple preset modulation strategies and generate inverter loss evaluation results. Function construction module: Based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, construct a comprehensive loss evaluation function for the traction motor and the inverter; Joint optimization module: Under the conditions of satisfying the vehicle torque demand, current constraint, voltage constraint and thermal constraint of the current control cycle, solve for the target current vector command and target modulation strategy that minimizes the value of the comprehensive loss evaluation function; Control execution module: Generates electric drive system efficiency control instructions according to the target current vector command and the target modulation strategy, and controls the traction motor and the inverter according to the electric drive system efficiency control instructions.

[0104] Example 4 is an embodiment of the present invention, which provides a method for controlling the efficiency of a new energy vehicle motor. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation / comparative experiments.

[0105] To verify the effectiveness of the new energy vehicle motor efficiency control method of this invention under actual vehicle dynamic conditions, an electric drive system test platform was built, comprising a permanent magnet synchronous traction motor, a silicon carbide power module inverter, a dynamometer load simulation system, a power battery simulator, a cooling system, and a real-time controller. Before the test, the traction motor was bench-calibrated under reference temperature conditions to generate a preset motor efficiency spectrum. This preset motor efficiency spectrum records the reference efficiency value, copper loss component, iron loss component, and torque output capability corresponding to different speed and torque operating points. Simultaneously, under the inverter's reference junction temperature conditions, a preset inverter loss model was established through dual-pulse testing and thermal steady-state testing. This preset inverter loss model includes calculation parameters for conduction losses, switching losses, and modulation additional losses. Before the test, the electric drive system under test was preheated to an initial thermal state with a stator temperature of approximately 60°C, an estimated rotor temperature of approximately 55°C, and an estimated junction temperature of approximately 50°C for the inverter's power semiconductor devices, to avoid excessive data fluctuations caused by a completely cold state. Subsequently, the real-time controller sends operating condition commands to the motor controller in the order of low-speed climbing, medium-speed acceleration, high-speed initial stage, high-speed cruising, high-speed high heat and deceleration recovery, simulating the typical load changes and thermal accumulation process of new energy vehicles during continuous operation.

[0106] Within each 5-millisecond control cycle, step S1 is first executed to obtain the vehicle torque demand, actual traction motor speed, actual output torque, three-phase current, inverter modulation strategy identifier, switching frequency, modulation ratio, DC bus voltage, traction motor stator temperature, estimated traction motor rotor temperature, and estimated junction temperature of inverter power semiconductor devices for the current control cycle. Then, step S2 is executed to determine the winding resistance temperature correction coefficient based on the stator temperature, the permanent magnet flux linkage temperature correction coefficient based on the estimated rotor temperature, and the iron loss temperature correction coefficient based on the actual speed, stator temperature, and estimated rotor temperature. This performs thermal state correction on the copper loss component, torque output capability, and iron loss component in the preset motor efficiency spectrum, resulting in the dynamic motor efficiency spectrum for the current control cycle. Furthermore, the motor power loss value, motor efficiency offset, and motor thermal constraint margin are obtained. Next, step S3 is executed. Based on the inverter junction temperature estimate, DC bus voltage, modulation ratio, and switching frequency, the preset inverter loss model is thermally corrected, and the total inverter loss value corresponding to preset modulation strategies such as continuous pulse width modulation, first type discontinuous pulse width modulation, second type discontinuous pulse width modulation, and low switching loss modulation is calculated. Then, step S4 is executed, and the motor dynamic efficiency evaluation result and the inverter loss evaluation result are uniformly incorporated into the comprehensive loss evaluation function, so that motor power loss, total inverter loss, efficiency offset, and thermal margin status participate in the evaluation together. Then, step S5 is executed, and under the conditions of meeting the vehicle torque demand, current constraint, voltage constraint, and thermal constraint of the current control cycle, the candidate control combination formed by the candidate current vector command and the preset modulation strategy is evaluated, and the target current vector command and target modulation strategy with the minimum comprehensive loss evaluation value are determined. Finally, step S6 is executed to convert the target current vector command into a three-phase current control signal for the traction motor, convert the target modulation strategy into an inverter switching control signal, and record the actual three-phase current, actual output torque, stator temperature feedback value, rotor temperature feedback estimate, and junction temperature feedback value after execution. These are used to update the dynamic motor efficiency spectrum and the preset inverter loss model in the next control cycle.

[0107] To demonstrate the advantages of this invention over existing technologies, a conventional fixed scheme was used as a comparative example under the same test platform, operating condition sequence, and initial thermal state. The conventional fixed scheme uses a fixed motor efficiency graph at a reference temperature and a fixed modulation strategy for control, without thermal state correction of the motor efficiency graph or dynamic comparison of inverter losses corresponding to multiple modulation strategies. The experimental example employs the dynamic efficiency graph correction, multi-modulation strategy inverter loss evaluation, and comprehensive loss joint optimization control method of this invention. After the experiment, six representative operating points were selected for data processing, and the results are shown in Table 1.

[0108] Table 1. Experimental Data Reference Table

[0109] The data above shows that the present invention reduces the total system loss at all six typical operating conditions, and its advantages over the fixed solution become more pronounced as the thermal condition worsens. At operating condition 1, during the low-speed ramp-up phase, the stator temperature is 62.4℃, the estimated rotor temperature is 57.2℃, and the estimated inverter junction temperature is 52.5℃. The electric drive system is still under relatively low thermal load, and the difference between the fixed solution and the present invention is relatively small. At this time, the total system loss of the fixed solution is 1002W, while the total system loss of the present invention is 970W, a reduction of 3.2%. This result indicates that when the thermal condition is not significant, the present invention does not incur additional losses due to the introduction of comprehensive evaluation. Instead, it can select a continuous pulse width modulation strategy that matches the current operating condition, maintaining a relatively balanced loss state between the motor side and the inverter side.

[0110] After entering the medium-speed acceleration phase of operating point 2, the target torque rises to 171.8 Nm, the stator temperature rises to 78.1℃, and the estimated rotor temperature rises to 73.4℃. In this state, the fixed-mode scheme still selects the current vector based on the motor efficiency spectrum at the reference temperature, without fully considering the impact of increased winding resistance and changes in permanent magnet flux linkage on motor efficiency. Therefore, the motor power loss reaches 936 W. This invention corrects the copper loss component and torque output capability in thermal state through step S2, reducing the motor power loss to 901 W. Simultaneously, through step S3, it compares the inverter losses under different modulation strategies and selects the first type of discontinuous pulse width modulation strategy, reducing the total inverter loss from 586 W to 524 W, ultimately reducing the total system loss by 6.4%. This result shows that this invention does not simply correct the motor spectrum, but simultaneously involves the inverter modulation strategy in loss evaluation, thereby avoiding the disconnect between motor-side and inverter-side control.

[0111] Operating points 3 and 4 further demonstrate the technical value of this invention under medium-to-high speed conditions. At operating point 3, the motor speed reaches 5236 rpm, and at operating point 4, the motor speed reaches 6118 rpm, with a significant increase in the proportion of iron loss and modulation-related losses in the total system loss. The fixed scheme, due to the lack of thermal state correction for the iron loss component and the failure to dynamically evaluate different modulation strategies based on junction temperature, modulation ratio, and switching frequency, resulted in total system losses of 1421W and 1395W, respectively. This invention employs a second type of discontinuous pulse width modulation strategy at operating point 3 and a low-switching-loss modulation strategy at operating point 4, reducing the total system loss to 1292W and 1233W, respectively, representing reductions of 9.1% and 11.6%. This result proves that the iron loss temperature correction, modulation-related loss correction, and multi-modulation strategy evaluation in this invention are not merely ordinary parameter replacements, but rather work together under high-speed, high-modulation-ratio conditions, enabling the controller to identify system loss migrations that cannot be reflected by fixed patterns and fixed modulation strategies.

[0112] Operating condition 5 is a high-speed, high-heat condition, with a stator temperature reaching 124.2℃, an estimated rotor temperature of 126.3℃, and an estimated inverter junction temperature of 119.4℃. This is the most thermally demanding condition in this embodiment. Under this condition, the fixed scheme has a motor power loss of 836W, a total inverter loss of 925W, and a total system loss of 1761W. This is because the fixed scheme still follows a single modulation strategy and cannot reselect the modulation method based on the changes in switching losses and modulation-related losses under high junction temperatures. This invention, through the thermal margin evaluation mechanism in the comprehensive loss evaluation function, ensures that the control result no longer simply pursues local high efficiency on the motor side, but instead selects a low-switching-loss modulation strategy that can reduce total system losses and thermal risks. Ultimately, this invention reduces motor power loss to 721W, total inverter losses to 732W, and total system losses to 1453W, a reduction of 17.5%. This operating point best demonstrates the inventiveness of the invention: when the thermal margin is insufficient, the controller does not mechanically follow the fixed efficiency spectrum and fixed modulation strategy, but performs system-level joint optimization based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, thereby avoiding the problem of "local high efficiency of the motor but severe overall heat generation of the electric drive system" in the prior art.

[0113] During the deceleration and regeneration phase at operating point 6, the target torque is negative, indicating that the traction motor is in an energy recovery state. The total system loss of the fixed scheme is 675W, while the total system loss of this invention is 623W, a reduction of 7.7%. This result demonstrates that this invention is applicable not only to drive conditions but also to regenerative braking conditions. In the recovery state, both the motor operating point and the inverter modulation state change. If a fixed efficiency chart and fixed modulation strategy are still used, it is easy to cause inaccurate evaluation of motor and inverter losses during the recovery process. This invention, through a dynamic motor efficiency chart and a thermally corrected inverter loss model, allows the control strategy under recovery conditions to still be adjusted according to the current thermal and modulation states.

[0114] Based on data from six operating conditions, the total system loss of the proposed solution is lower than that of the fixed solution, with an average reduction of approximately 9.3%, and a reduction of 17.5% under high-heat conditions. These results demonstrate that the beneficial effects of the proposed solution do not stem from single-parameter optimization, but rather from the following synergistic mechanisms: First, step S2 ensures that motor efficiency evaluation no longer relies on a fixed efficiency profile at a reference temperature, reflecting efficiency drift caused by changes in winding resistance, permanent magnet flux linkage, and iron losses with thermal conditions. Second, step S3 ensures that inverter loss evaluation is no longer limited to a single fixed modulation strategy, but allows comparison of loss differences between multiple preset modulation strategies under current junction temperature, DC bus voltage, modulation ratio, and switching frequency. Third, steps S4 and S5 unify the motor-side evaluation results with the inverter-side evaluation results into a comprehensive loss evaluation function, enabling the target current vector command and the target modulation strategy to be jointly determined within the same constraint framework. Therefore, this invention can overcome the problems of separation between motor efficiency control and inverter modulation control in the prior art, difficulty in adapting fixed efficiency graphs to changes in thermal state, and difficulty in taking into account changes in high temperature loss with fixed modulation strategies. It has strong engineering feasibility and system-level energy-saving effect.

[0115] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for controlling the efficiency of a new energy vehicle motor, characterized in that, include: S1: Obtain the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle; S2: Based on the traction motor operating data and the electric drive system thermal state data, the preset motor efficiency spectrum is thermally corrected to obtain a dynamic motor efficiency spectrum, and a motor dynamic efficiency evaluation result is generated based on the dynamic motor efficiency spectrum. S3: Based on the inverter operating data and the electric drive system thermal state data, perform thermal state correction on the preset inverter loss model, determine the inverter loss corresponding to each of the multiple preset modulation strategies, and generate inverter loss evaluation results. S4: Based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, construct a comprehensive loss evaluation function for the traction motor and the inverter; S5: Under the conditions of satisfying the vehicle torque demand, current constraint, voltage constraint and thermal constraint of the current control cycle, solve for the target current vector command and target modulation strategy that minimize the value of the comprehensive loss evaluation function; S6: Generate an electric drive system efficiency control command according to the target current vector command and the target modulation strategy, and control the traction motor and the inverter according to the electric drive system efficiency control command.

2. The method for controlling the efficiency of a new energy vehicle motor as described in claim 1, characterized in that, Step S1 specifically includes: The vehicle torque requirement is the target torque value for the current control cycle; The traction motor operating data includes the actual speed, actual output torque, and three-phase current of the traction motor; The inverter operating data includes the current modulation strategy identifier, switching frequency, modulation ratio, and DC bus voltage. The thermal state data of the electric drive system includes the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter. The vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data are all data corresponding to the current control cycle.

3. The method for controlling the efficiency of a new energy vehicle motor as described in claim 2, characterized in that, Step S2 specifically includes: Based on the stator temperature of the traction motor in the thermal state data of the electric drive system, determine the winding resistance temperature correction coefficient under the current control cycle; Based on the estimated rotor temperature of the traction motor in the thermal state data of the electric drive system, determine the permanent magnet flux linkage temperature correction coefficient under the current control cycle. Based on the actual speed of the traction motor, the stator temperature of the traction motor, and the estimated rotor temperature of the traction motor, determine the iron loss temperature correction coefficient under the current control cycle; The copper loss component in the preset motor efficiency spectrum is corrected using the winding resistance temperature correction coefficient, the torque output capability in the preset motor efficiency spectrum is corrected using the permanent magnet flux linkage temperature correction coefficient, and the iron loss component in the preset motor efficiency spectrum is corrected using the iron loss temperature correction coefficient, thus obtaining the dynamic motor efficiency spectrum.

4. The method for controlling the efficiency of a new energy vehicle motor as described in claim 3, characterized in that, Step S2 also includes: Based on the actual speed of the traction motor and the vehicle torque requirement of the current control cycle, the motor efficiency value corresponding to the current operating point is determined in the dynamic motor efficiency graph. Based on the motor efficiency value corresponding to the current operating point, the actual speed of the traction motor, and the vehicle torque requirement of the current control cycle, determine the motor power loss value corresponding to the current operating point. The motor efficiency offset is determined based on the motor efficiency value corresponding to the current operating point and the benchmark efficiency value of the corresponding operating point in the preset motor efficiency map. The thermal constraint margin of the motor is determined based on the estimated values ​​of the stator temperature and the rotor temperature of the traction motor. Based on the motor power loss value corresponding to the current operating point, the motor efficiency offset, and the motor thermal constraint margin, the motor dynamic efficiency evaluation result is generated.

5. The method for controlling the efficiency of a new energy vehicle motor as described in claim 4, characterized in that, Step S3 specifically includes: Based on the estimated junction temperature of the power semiconductor devices in the inverter, determine the conduction loss temperature correction coefficient and the switching loss temperature correction coefficient under the current control cycle. Based on the estimated junction temperature of the power semiconductor devices in the inverter, the DC bus voltage, the modulation ratio, and the switching frequency, determine the modulation additional loss correction coefficient under the current control cycle; The conduction loss calculation parameters in the preset inverter loss model are corrected using the conduction loss temperature correction coefficient, the switching loss calculation parameters in the preset inverter loss model are corrected using the switching loss temperature correction coefficient, and the modulation additional loss calculation parameters in the preset inverter loss model are corrected using the modulation additional loss correction coefficient, thus obtaining the inverter loss model after thermal state correction.

6. The method for controlling the efficiency of a new energy vehicle motor as described in claim 5, characterized in that, Step S3 also includes: Establish a set of preset modulation strategies corresponding to the current control cycle, wherein each preset modulation strategy in the set of preset modulation strategies has a corresponding modulation strategy identifier; Based on the modulation rules corresponding to each preset modulation strategy in the preset modulation strategy set, determine the candidate switching frequency and candidate modulation ratio corresponding to each preset modulation strategy; The DC bus voltage, the estimated junction temperature of the power semiconductor devices in the inverter, the candidate switching frequency and the candidate modulation ratio corresponding to each preset modulation strategy are input into the thermally corrected inverter loss model to obtain the conduction loss value, switching loss value and modulation additional loss value corresponding to each preset modulation strategy. Based on the conduction loss value, the switching loss value, and the modulation additional loss value corresponding to each preset modulation strategy, the total inverter loss value corresponding to each preset modulation strategy is determined. The inverter loss evaluation result is generated based on the total inverter loss value corresponding to each preset modulation strategy and the corresponding modulation strategy identifier.

7. The method for controlling the efficiency of a new energy vehicle motor as described in claim 6, characterized in that, Step S4 specifically includes: Extract the motor power loss value, motor efficiency offset, and motor thermal constraint margin corresponding to the current operating point from the motor dynamic efficiency evaluation results. Extract the total inverter loss value and the corresponding modulation strategy identifier for each preset modulation strategy from the inverter loss evaluation results; For each preset modulation strategy, the motor power loss value and the corresponding total inverter loss value are added together to obtain the basic loss value of the electric drive system corresponding to each preset modulation strategy. The efficiency deviation penalty value is determined based on the motor efficiency deviation, and the thermal margin penalty value is determined based on the motor thermal constraint margin. For each preset modulation strategy, a comprehensive loss evaluation value corresponding to each preset modulation strategy is obtained based on the corresponding basic loss value of the electric drive system, the efficiency deviation penalty value, and the thermal margin penalty value. Based on the comprehensive loss evaluation value corresponding to each preset modulation strategy, the corresponding modulation strategy identifier, and the evaluation result of the candidate current vector command by the dynamic motor efficiency spectrum, a comprehensive loss evaluation function for the traction motor and the inverter is constructed that can output the corresponding comprehensive loss evaluation value according to the candidate current vector command and the preset modulation strategy.

8. The method for controlling the efficiency of a new energy vehicle motor as described in claim 7, characterized in that, Step S5 specifically includes: Based on the vehicle torque demand of the current control cycle, an initial current vector command set is generated. Each initial current vector command in the initial current vector command set includes an initial d-axis current command and an initial q-axis current command. The current constraint boundary is determined based on the preset maximum current limit value of the traction motor, and the voltage constraint boundary is determined based on the DC bus voltage; Based on the stator temperature of the traction motor, the estimated rotor temperature of the traction motor, and the estimated junction temperature of the power semiconductor devices in the inverter, the current limit value corresponding to the thermal constraint is determined. Based on the current constraint boundary, the voltage constraint boundary and the current limit value corresponding to the thermal constraint, the initial current vector instruction set is filtered to obtain a feasible current vector instruction set. Based on the set of feasible current vector commands and the set of preset modulation strategies, multiple candidate control combinations are formed, each candidate control combination including a feasible current vector command and a preset modulation strategy; Each candidate control combination is input into the comprehensive loss evaluation function to obtain the comprehensive loss evaluation value corresponding to each candidate control combination; The candidate control combination with the minimum comprehensive loss evaluation value is determined as the target control combination, the feasible current vector command in the target control combination is determined as the target current vector command, and the preset modulation strategy in the target control combination is determined as the target modulation strategy.

9. The method for controlling the efficiency of a new energy vehicle motor as described in claim 8, characterized in that, Step S6 specifically includes: Based on the target d-axis current command and target q-axis current command in the target current vector command, generate the three-phase current control signal for the traction motor; According to the target modulation strategy, the target switching frequency, target modulation ratio, and target switching sequence are determined, and an inverter switching control signal is generated based on the target switching frequency, the target modulation ratio, and the target switching sequence. The three-phase current control signal of the traction motor and the switching control signal of the inverter are used as the efficiency control command of the electric drive system. The current vector of the traction motor is controlled according to the efficiency control command of the electric drive system, and the modulation process of the inverter is controlled. The execution feedback data of the traction motor and the inverter after executing the efficiency control command of the electric drive system is obtained. The execution feedback data includes the actual three-phase current of the traction motor, the actual output torque of the traction motor, the stator temperature feedback value of the traction motor, the rotor temperature feedback estimate of the traction motor, and the junction temperature feedback value of the power semiconductor devices in the inverter. Based on the execution feedback data, the dynamic motor efficiency graph and the preset inverter loss model are updated, and the updated dynamic motor efficiency graph and the updated preset inverter loss model are used in the next control cycle.

10. A new energy vehicle motor efficiency control system, used to implement the new energy vehicle motor efficiency control method as described in any one of claims 1 to 9, characterized in that, include: Data acquisition module: Acquires the vehicle torque demand, traction motor operating data, inverter operating data, and electric drive system thermal status data for the current control cycle; The graph correction module corrects the preset motor efficiency graph based on the traction motor operating data and the electric drive system thermal state data to obtain a dynamic motor efficiency graph, and generates a motor dynamic efficiency evaluation result based on the dynamic motor efficiency graph. Loss evaluation module: Based on the inverter operating data and the electric drive system thermal state data, the preset inverter loss model is thermally corrected to determine the inverter loss corresponding to each of the multiple preset modulation strategies and generate inverter loss evaluation results. Function construction module: Based on the motor dynamic efficiency evaluation results and the inverter loss evaluation results, construct a comprehensive loss evaluation function for the traction motor and the inverter; Joint optimization module: Under the conditions of satisfying the vehicle torque demand, current constraint, voltage constraint and thermal constraint of the current control cycle, solve for the target current vector command and target modulation strategy that minimizes the value of the comprehensive loss evaluation function; Control execution module: Generates electric drive system efficiency control instructions according to the target current vector command and the target modulation strategy, and controls the traction motor and the inverter according to the electric drive system efficiency control instructions.

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