A new energy pure electric vehicle power system over-temperature control method and system

Abstract

The application discloses a kind of new energy pure electric vehicle power system's over-temperature control method and system, method includes: obtaining the speed of motor and the temperature data of motor, according to temperature and speed calculation maximum allowable output torque of motor and maximum allowable output torque based on motor output torque limit;According to temperature and speed to the output power of motor is limited.The application has the advantages that: by high speed high temperature limit motor power, low speed high temperature limit motor torque mode, the maximum allowable output power of vehicle and the maximum allowable output torque of motor are reduced when user uses, under the premise that guaranteeing that motor temperature does not exceed threshold, as far as possible to give consideration to the safety of user, the durability quality of vehicle and the driving performance of user.

Description

Technical Field

[0001] This invention relates to the field of temperature control for new energy vehicles, and in particular to an over-temperature control method and system for the power system of a new energy pure electric vehicle. Background Technology

[0002] The electric drive system of new energy pure electric commercial vehicles mainly consists of: on-board power supply, motor drive and control system, and mechanical systems such as drive force transmission. Existing electric commercial vehicles often use small motors, and these vehicles frequently experience motor overheating issues due to prolonged operation exceeding the rated power. Motor overheating is often controlled using liquid cooling and / or overheat alarms. These strategies involve limiting power through alarms, providing frequent warnings, and ultimately reducing voltage once the temperature reaches a certain level.

[0003] Existing temperature control strategies often result in users noticing motor overheating and subsequent Ampere failures, and the lifespan of the motor is affected when it operates at high temperatures. Pure power limiting strategies are ineffective for low-speed, high-torque applications, failing to protect the motor or prevent Ampere failures. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an over-temperature control method and system for the power system of a new energy pure electric vehicle. This method limits the motor power at high speed and high temperature and limits the motor torque at low speed and high temperature, thereby subtly reducing the maximum allowable output power of the vehicle and the maximum allowable output torque of the motor when the user is using the vehicle. This ensures that the motor temperature does not exceed the threshold while taking into account the user's safety, the vehicle's durability and the user's driving performance as much as possible.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for over-temperature control of a power system for a new energy pure electric vehicle includes: acquiring motor speed and motor temperature data; calculating the maximum allowable output torque of the motor based on the temperature and speed; limiting the output torque of the motor based on the maximum allowable output torque; and limiting the output power of the motor based on the temperature and speed.

[0007] The maximum permissible output torque and maximum permissible output power of a motor are negatively correlated with motor temperature. When the motor temperature rises, both the maximum permissible output torque and maximum permissible output power decrease.

[0008] Multi-level alarm temperature thresholds are preset, and alarms are divided into multiple levels according to the temperature alarm thresholds. Corresponding motor output power and output torque limiting strategies are triggered according to the alarm level.

[0009] When multiple alarm levels are defined based on temperature alarm thresholds, a temperature alarm threshold T-max is set. When the detected motor temperature exceeds the temperature alarm threshold T-max, the motor output power is limited to below the rated power, and a level three fault alarm is issued.

[0010] When dividing alarms into multiple levels according to temperature alarm thresholds, temperature alarm thresholds T1 and T2 are set.

[0011] When the real-time temperature is lower than the temperature alarm threshold T1, no alarm is triggered, and the motor temperature data is continuously monitored.

[0012] Otherwise, when the motor temperature is between the temperature alarm thresholds T1 and T2, the warning intervention stage is entered; if the motor temperature threshold is between the temperature alarm thresholds T2 and T-max, the constant torque power reduction stage is entered.

[0013] During the early warning and intervention phase, the maximum allowable output torque of the motor is reduced proportionally based on the temperature rise.

[0014] During the early warning and intervention phase, the maximum allowable output torque is reduced proportionally according to the temperature rise. The maximum allowable output torque of the motor is T_qallow = ((T_max - T_m) / (T_max - T2) * (P_max - P_based) + P_based) / ω; where the rated power P_based, the temperature thresholds are T1, T2 and T_max; ω is the real-time speed of the motor; and Tm is the real-time motor temperature.

[0015] After entering the constant torque power reduction stage, it is determined whether the motor speed ω is greater than the rated speed ω_base; if so, the motor is in the constant power region and the constant power region derating strategy is executed; if not, the motor is in the constant torque region and the constant torque region limiting strategy is executed.

[0016] The constant power derating strategy includes: when the motor is running in the constant power region, the maximum allowable torque is gradually reduced according to the temperature data, where the maximum allowable torque is T_max_allowed = T_base × (ω_base / ω) × k(t);

[0017] Where k(t) is the temperature-related derating factor; when the motor temperature reaches T_max, the maximum power is forcibly limited to T_alllow = ((T_maxT_m) / (T_max-T2)*(P_max-P_based)*w+P_based) / ω.

[0018] When the motor is operating in the constant torque region and the temperature T_m > T2, the output torque of the motor is forcibly limited to be less than the rated torque T_base. The output torque of the motor is limited to T_max_allowed = T_base × k(t).

[0019] Where k(t) is the temperature-related derating factor; at the same time, the power limit warning light is illuminated to remind the driver that the vehicle has entered the power limit state.

[0020] An over-temperature control system for a power system of a new energy pure electric vehicle, the system comprising a temperature sensor, a speed sensor, a control unit (MCU), and a motor controller;

[0021] The temperature sensor is used to collect the temperature data of the motor, and the speed sensor is used to collect the speed of the motor. Both the temperature sensor and the speed sensor are connected to the control unit MCU. The control unit MCU calculates the maximum allowable output torque of the motor based on the temperature and speed and limits the output torque of the motor based on the maximum allowable output torque. The control unit MCU limits the output power of the motor based on the temperature and speed.

[0022] The advantages of this invention are: by limiting motor power at high speed and high temperature, and limiting motor torque at low speed and high temperature, the maximum permissible output power of the vehicle and the maximum permissible output torque of the motor during user operation are subtly reduced. This approach ensures that the motor temperature does not exceed the threshold while balancing user safety, vehicle durability, and driving performance as much as possible. This solution addresses the problems of inflexible control methods, unsatisfactory effects, low control precision, and potential hazards inherent in traditional motor temperature control strategies. Attached Figure Description

[0023] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0024] Figure 1 This is a schematic flowchart illustrating the temperature control strategy logic of the present invention. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments.

[0026] This embodiment subtly reduces the maximum permissible output power of the vehicle and the maximum permissible output torque of the motor during user operation by limiting motor power at high speed and high temperature, and limiting motor torque at low speed and high temperature. This approach balances user safety, vehicle durability, and driving performance while ensuring that the motor temperature does not exceed the threshold. It addresses the problems of inflexible control methods, unsatisfactory effects, low control precision, and potential hazards in traditional motor temperature control strategies.

[0027] like Figure 1As shown in this embodiment, an over-temperature control method for a power system of a new energy pure electric vehicle includes: acquiring motor speed and motor temperature data; calculating the maximum allowable output torque of the motor based on the temperature and speed; and limiting the motor output torque based on the maximum allowable output torque; simultaneously limiting the motor output power based on the temperature and speed. In this embodiment, the maximum allowable output torque and motor output power are calculated and limited using temperature and speed, thereby reducing the occurrence of over-temperature and achieving accurate motor control that conforms to temperature control. In this embodiment, when controlling based on motor speed and temperature data, a corresponding power limiting mode for the motor is set. By entering different limiting modes, the occurrence of over-temperature is reduced, avoiding or reducing situations such as accidents caused by over-temperature. In the specific execution process, the motor speed and motor stator temperature are acquired based on the motor resolver and temperature sensor; the maximum allowable output torque of the motor is acquired; the motor power limiting mode is determined comprehensively based on the motor speed and motor temperature; and the motor temperature is further fed back to the specific power limiting or torque limiting, thereby achieving the purpose of motor temperature control.

[0028] In this embodiment, the maximum permissible output torque and maximum permissible output power of the motor are negatively correlated with the motor temperature. When the motor temperature rises, both the maximum permissible output torque and / or maximum permissible output power decrease. Power or torque output is limited according to temperature-based restrictions.

[0029] In this embodiment, the current warning level is determined based on the temperature. An alarm is triggered accordingly, and the corresponding limiting strategy is activated. Specifically, multiple alarm temperature thresholds are pre-set. Alarms are categorized into different levels based on these thresholds, and corresponding motor output power and torque limiting strategies are activated based on the alarm level. Different alarm alerts and corresponding motor control strategies are achieved by setting different temperature thresholds.

[0030] When multiple alarm levels are defined based on temperature alarm thresholds, a temperature alarm threshold T-max is set. When the real-time motor temperature is detected to be higher than the temperature alarm threshold T-max, the motor output power is limited to below the rated power, and a level three fault alarm is issued. For example, if the motor temperature is set to 160℃, and the temperature exceeds 160℃, the system forcibly limits the output power to no more than 100kW of rated power. This ensures that at 3000rpm, the maximum permissible torque T = 1000000 / 3000 ≈ 333N•m, far below the normal peak torque at that speed. Through this tiered control, the vehicle can still maintain its trajectory to the top of the hill without completely losing power, while effectively protecting the electric drive system from overheating damage.

[0031] When dividing the alarm into multiple levels according to the temperature alarm threshold, temperature alarm thresholds T1 and T2 are set. When the real-time temperature of the motor is lower than the temperature alarm threshold T1, no alarm is triggered, and the motor temperature data is continuously monitored. Since the temperature is lower than the threshold T1, it means that the motor temperature is in a normal state and there is no overheating. Therefore, only real-time monitoring is required, and no operation is necessary.

[0032] When the motor temperature is between the temperature alarm thresholds T1 and T2, the warning intervention phase begins; if the motor temperature threshold is between the temperature alarm thresholds T2 and T-max, the constant torque power reduction phase begins. The warning intervention phase and the constant torque power reduction phase represent two motor control strategies. The execution of these two strategies can achieve over-temperature control. Specific control strategies include:

[0033] During the early warning and intervention phase, the maximum allowable output torque of the motor is reduced proportionally to the temperature rise. The maximum allowable output torque of the motor is calculated as follows: T_qallow = ((T_max - T_m) / (T_max - T2) * (P_max - P_based) + P_based) / ω; where the rated power P_based, the temperature thresholds are T1, T2, and T_max; ω is the real-time motor speed; and Tm is the real-time motor temperature.

[0034] After entering the constant torque power reduction stage, it is determined whether the motor speed ω is greater than the rated speed ω_base; if so, the motor is in the constant power region and the constant power region derating strategy is executed; if not, the motor is in the constant torque region and the constant torque region limiting strategy is executed.

[0035] The constant power derating strategy includes: when the motor is running in the constant power region, the maximum allowable torque is gradually reduced according to the temperature data, where the maximum allowable torque is T_max_allowed = T_base × (ω_base / ω) × k(t);

[0036] Where k(t) is the temperature-related derating factor; when the motor temperature reaches T_max, the maximum power is forcibly limited to T_alllow = ((T_maxT_m) / (T_max-T2)*(P_max-P_based)*w+P_based) / ω.

[0037] When the motor is operating in the constant torque region and the temperature T_m > T2, the output torque of the motor is forcibly limited to be less than the rated torque T_base. The output torque of the motor is limited to T_max_allowed = T_base × k(t).

[0038] Where k(t) is the temperature-related derating factor; at the same time, the power limit warning light is illuminated to remind the driver that the vehicle has entered the power limit state.

[0039] The above solution achieves a way to subtly reduce the maximum allowable output power of the vehicle and the maximum allowable output torque of the motor when the user is using it by limiting the motor power at high speed and high temperature and limiting the motor torque at low speed and high temperature. This ensures that the motor temperature does not exceed the threshold while taking into account the user's safety, the vehicle's durability and the user's driving performance as much as possible.

[0040] This solution abandons the traditional "one-size-fits-all" global power derating method. Instead, it adopts differentiated limit adjustment methods based on the motor's current speed range: High-speed range (usually corresponding to high-speed cruising conditions): When the motor is at high speed and the temperature exceeds the threshold, the maximum output power is limited first. This is because the proportion of iron loss and windage loss in the motor increases significantly at high speeds. Limiting torque (i.e., limiting acceleration capability) has limited effect on temperature suppression, while reducing power directly reduces the total heat generation. By finely adjusting the upper limit of power, both overheating and aging of the winding insulation layer are prevented, while most of the high-speed cruising capability is preserved, avoiding sudden "stalling" of the vehicle. Low-speed range (usually corresponding to starting, climbing, and heavy-load conditions): When the motor is at low speed and the temperature exceeds the limit, the maximum output torque is limited first. At low speeds, copper loss (proportional to the square of the current) is the main heat source. Directly limiting the peak torque current can curb the temperature rise most quickly. Meanwhile, users are more sensitive to torque changes at low speeds, but this solution uses non-linear mapping (e.g., reducing the torque request slope with a smaller step size) to make users almost unaware of power loss, only manifesting as "smoother start-up" rather than "power interruption".

[0041] In this embodiment, by monitoring the rate of temperature change in real time, the power / torque limit curve is dynamically adjusted so that the maximum allowable value decreases continuously and gradually with increasing temperature, rather than with a step-like jump. For example, when the motor heats up due to prolonged uphill climbing, the system gradually reduces the torque limit on a millisecond timescale. The user will only feel a slight softening of the throttle response, without perceiving a noticeable power step. This "soft limit" ensures both safety and maintains driving quality.

[0042] The technical advantages of adopting the above solution include:

[0043] (1) Enhanced safety: Precise temperature threshold management completely avoids dangerous conditions such as winding short circuits, magnet demagnetization, or controller burnout caused by overheating. Compared with traditional methods (such as temperature control switches with delayed action or simple proportional derating), this solution can initiate smooth intervention before the temperature approaches the threshold, eliminating the risk of thermal runaway caused by overshoot.

[0044] (2) Durability and quality assurance: By avoiding prolonged operation of the motor at the edge of high temperature limits (traditional strategies often lead to instantaneous overheating due to slow response), the thermal aging rate of the insulation layer and the risk of irreversible demagnetization of the permanent magnet are significantly reduced. Bench tests show that this solution can extend the life of the motor under continuous high load cycles by more than 30%.

[0045] (3) Driving performance maintenance: Since the downgrade is precisely allocated to two independent dimensions, namely "high speed power limit and low speed torque limit", and sufficient power redundancy is always maintained (for example, when power is limited, more than 70% of the rated power is still guaranteed, and when torque is limited, more than 50% of the starting torque is retained), the vehicle can still provide acceleration and top speed performance that meet the user's expectations in most daily scenarios.

[0046] This embodiment also provides an over-temperature control system for the power system of a new energy pure electric vehicle, the system including a temperature sensor, a speed sensor, a control unit MCU, and a motor controller;

[0047] The temperature sensor is used to collect the temperature data of the motor, and the speed sensor is used to collect the speed of the motor. Both the temperature sensor and the speed sensor are connected to the control unit MCU. The control unit MCU calculates the maximum allowable output torque of the motor based on the temperature and speed and limits the output torque of the motor based on the maximum allowable output torque. The control unit MCU limits the output power of the motor based on the temperature and speed.

[0048] In this embodiment, the speed sensor and temperature sensor serve as the data acquisition layer, primarily used to collect the motor's speed and temperature data. The control unit (MCU) executes the temperature control strategy, mainly achieving motor limitation control through strategy control. It sends the control commands corresponding to the control strategy to the motor controller, which executes these commands, including limiting torque and power. Specifically: the maximum allowable output torque of the motor is calculated based on the temperature and speed, and the motor's output torque is limited based on this maximum allowable output torque; simultaneously, the motor's output power is limited based on the temperature and speed.

[0049] Temperature sensors for motors can employ thermocouples, RTD (Resistance Temperature Detector), thermistors, and IC (Integrated Circuit) temperature sensors to detect motor temperature. Thermocouples, based on the Seebeck effect, are made of two different metal conductors welded together. When the measuring junction (hot junction) and the reference junction (cold junction) have different temperatures, a potential difference (thermoelectric potential) is generated in the circuit. By measuring this potential difference and compensating for the cold junction temperature, the temperature can be obtained. RTDs utilize the characteristic that the resistance of pure metals (such as platinum, nickel, and copper) increases systematically with increasing temperature (positive temperature coefficient). Thermistors are made of semiconductor ceramic materials, and their resistance is extremely sensitive to temperature changes. They are mainly divided into NTC (negative temperature coefficient), whose resistance decreases with increasing temperature, and PTC (positive temperature coefficient), whose resistance increases sharply after a specific temperature point. IC (Integrated Circuit) temperature sensors utilize the temperature characteristics of semiconductor PN junctions, integrating temperature sensing, signal conditioning, and analog-to-digital conversion functions onto a single chip. Considering the operating environment of the motor, using thermistors or RTD sensors can provide stable temperature acquisition.

[0050] Speed ​​sensors, based on principles such as electromagnetic induction and photoelectric effect, convert rotational motion into measurable electrical pulse signals. Encoders, for example, are precision sensors that convert rotational displacement into digital pulse signals. Incremental encoders output pulses with a 90° phase difference between phases A and B. The speed and direction can be determined by counting the pulses and calculating the phase difference. They are commonly used for cost-sensitive speed feedback where only relative position information is needed. Absolute encoders have multiple binary coding tracks on the code disk, with each axis position corresponding to a unique code. They are commonly used in precise control applications such as robots and CNC machine tools where position retention after power failure is required. Encoders accurately identify speed signals.

[0051] When limiting the output power and torque of a motor, the current warning level is determined based on the temperature. An alarm is triggered according to the warning level, and the corresponding limiting strategy is activated. Specifically, multiple alarm temperature thresholds are preset, and alarms are divided into multiple levels according to these thresholds. The corresponding motor output power and torque limiting strategies are triggered based on the alarm level. Different temperature thresholds are used to implement different alarm alerts and corresponding motor control strategies. When dividing alarms into multiple levels based on temperature thresholds, a temperature alarm threshold T-max is set. When the real-time motor temperature is detected to be higher than the temperature alarm threshold T-max, the motor output power is limited to below the rated power, and a level three fault alarm is issued. For example, if the motor temperature is higher than the maximum temperature threshold T-max (e.g., T-max is set to 160℃), when the temperature exceeds 160℃, the system forcibly limits the output power to no more than 100kW of the rated power. This ensures that at a speed of 3000rpm, the maximum allowable torque T = 1000000 / 3000 ≈ 333N•m, which is far lower than the normal peak torque at that speed. Through this tiered control, the vehicle can still maintain its position at the top of the hill without completely losing power, while effectively protecting the electric drive system from overheating damage.

[0052] When dividing the alarm into multiple levels according to the temperature alarm threshold, temperature alarm thresholds T1 and T2 are set. When the real-time temperature of the motor is lower than the temperature alarm threshold T1, no alarm is triggered, and the motor temperature data is continuously monitored. Since the temperature is lower than the threshold T1, it means that the motor temperature is in a normal state and there is no overheating. Therefore, only real-time monitoring is required, and no operation is necessary.

[0053] When the motor temperature is between the temperature alarm thresholds T1 and T2, the warning intervention phase begins; if the motor temperature threshold is between the temperature alarm thresholds T2 and T-max, the constant torque power reduction phase begins. The warning intervention phase and the constant torque power reduction phase represent two motor control strategies. The execution of these two strategies can achieve over-temperature control. Specific control strategies include:

[0054] During the early warning and intervention phase, the maximum allowable output torque of the motor is reduced proportionally to the temperature rise. The maximum allowable output torque of the motor is calculated as follows: T_qallow = ((T_max - T_m) / (T_max - T2) * (P_max - P_based) + P_based) / ω; where the rated power P_based, the temperature thresholds are T1, T2, and T_max; ω is the real-time motor speed; and Tm is the real-time motor temperature.

[0055] After entering the constant torque power reduction stage, it is determined whether the motor speed ω is greater than the rated speed ω_base; if so, the motor is in the constant power region and the constant power region derating strategy is executed; if not, the motor is in the constant torque region and the constant torque region limiting strategy is executed.

[0056] The constant power derating strategy includes: when the motor is running in the constant power region, the maximum allowable torque is gradually reduced according to the temperature data, where the maximum allowable torque is T_max_allowed = T_base × (ω_base / ω) × k(t);

[0057] Where k(t) is the temperature-related derating factor; when the motor temperature reaches T_max, the maximum power is forcibly limited to T_alllow = ((T_maxT_m) / (T_max-T2)*(P_max-P_based)*w+P_based) / ω.

[0058] When the motor is operating in the constant torque region and the temperature T_m > T2, the output torque of the motor is forcibly limited to be less than the rated torque T_base. The output torque of the motor is limited to T_max_allowed = T_base × k(t).

[0059] Where k(t) is the temperature-related derating factor; at the same time, the power limit warning light is illuminated to remind the driver that the vehicle has entered the power limit state.

[0060] Once the motor temperature exceeds T1, components such as winding insulation, permanent magnets, and bearings are approaching safety limits. Continuing to output high torque will lead to a surge in current (and a sharp increase in copper losses), triggering thermal runaway. Torque must be limited in advance, but abrupt changes should be avoided to prevent users from perceiving a sudden drop in power. A linear proportional torque converter is chosen because it is simple, smooth, and easy to calibrate. As the temperature rises from T2 (the warning endpoint) to Tmax (the absolute upper limit), the limiting coefficient decreases linearly from 1 to 0. When Tm = T2, the coefficient = 1, allowing full torque output (the warning has just begun, with slight limitation); when Tm = Tmax, the coefficient = 0, and the torque drops to zero (the theoretical limit, but in practice, the minimum torque will be retained). At high speeds, the limiting torque has a more significant effect on power limitation; at low speeds, the limiting torque directly suppresses current. Therefore, this stage essentially limits heat generation while limiting torque, a "soft limiting" strategy. When the temperature continues to rise and the warning intervention is insufficient to suppress the temperature rise, a constant torque power reduction stage begins. This stage is based on the relationship between the motor's current speed and its rated speed ωbase. When ω > ω base When the motor is in the constant power region (weak magnetic field region), the voltage is close to its limit, the output power is basically constant, and the torque naturally decreases as the speed increases (T=P / ω). When ω≤ω baseWhen the motor is in the constant torque region (below base speed), it can output rated or maximum torque, and torque is decoupled from speed. In the constant power region derating strategy, the motor mainly suffers from iron losses, eddy current losses, and windage losses, which are related to high powers of speed. Reducing torque (essentially reducing current) can effectively reduce copper losses. Simultaneously, since P=T*ω, reducing torque reduces power, thus lowering total heat generation. Using Tmax_allowed for limitation can effectively reduce torque, reduce power, and reduce heat generation. The engineering effect is that if the motor overheats during high-speed cruising, this strategy will "quietly" reduce acceleration (maximum torque decreases), but the cruising power remains basically maintained, preventing stalling. The driver's perception of "weaker acceleration at high speeds" is within a safe and acceptable range.

[0061] Using the above embodiments, different alarms are triggered based on temperature data, and different temperature protection strategies are implemented based on temperature, thereby achieving motor over-temperature protection.

[0062] In this embodiment, to verify the effectiveness of the proposed solution, relevant parameters for clicking were set for experimental verification. The control strategy of the above solution was integrated into the controller. Specifically, the electric drive system includes a drive motor, a motor controller (MCU), a temperature sensor, and a vehicle instrument alarm device. The drive motor is a permanent magnet synchronous motor, and its optimal operating temperature does not exceed 160℃. Exceeding this limit may cause demagnetization of the permanent magnets. The MCU is responsible for executing the torque control algorithm, calculating and limiting the motor output torque based on the received temperature and speed signals. The temperature sensor is embedded in the motor stator winding to monitor the motor temperature in real time. The alarm device includes a warning indicator light and a power limit alarm light on the instrument panel. During system initialization, key parameters need to be set: motor rated speed ω_base, rated torque T_base, rated power P_base, and temperature thresholds T1 (warning temperature, usually set to 135℃), T2 (temperature at which power reduction begins, usually set to 140℃), and T_max (maximum allowable temperature, 160℃).

[0063] In implementation, the method for controlling the motor output power / output torque based on the motor temperature in an electric drive system according to this embodiment is summarized as follows:

[0064] The motor speed and stator temperature are obtained from the motor's resolver and temperature sensor.

[0065] Obtain the maximum allowable output torque of the motor, and determine the motor's power limiting mode based on a comprehensive assessment of motor speed and motor temperature;

[0066] The temperature of the motor is further fed back to the specific power / torque limits;

[0067] The specific alarm level of the vehicle was determined based on the feedback motor temperature. Ultimately, in the case of a serious motor failure causing the motor temperature to soar (exceeding 160°C), the high voltage was forcibly shut off, triggering a level three fault.

[0068] The hardware system involved in the over-temperature protection strategy in this embodiment is initialized with parameters. The hardware system includes an electric drive system, comprising a drive motor, a motor controller (MCU), a temperature sensor, a motor speed sensor (resolver), and a vehicle instrument panel alarm device. The drive motor is a permanent magnet synchronous motor, whose optimal operating temperature does not exceed 160°C. Exceeding this limit may cause demagnetization of the permanent magnets. The MCU is responsible for executing the torque control algorithm, calculating and limiting the motor's output torque based on the received temperature and speed signals. The temperature sensor is embedded in the motor stator windings to monitor the motor temperature in real time. The alarm device includes a warning indicator light and a power limit alarm light on the instrument panel. During system initialization, key parameters need to be set: motor rated speed ω_base, rated torque T_base, rated power P_base, and temperature thresholds T1 (warning temperature, typically set to 135°C), T2 (temperature at which power reduction begins, typically set to 140°C), and T_max (maximum allowable temperature, 160°C).

[0069] After initializing parameters, the over-temperature protection process was executed, such as... Figure 1 As shown, the execution flow of the over-temperature protection strategy of the present invention includes the following steps:

[0070] Step S101: Power on and initialize the system, read the motor parameters and temperature threshold, and read the motor temperature T_m, motor speed ω and output torque T_q;

[0071] Step S102: Monitor the motor temperature T_m, motor speed ω, and output torque T_q in real time.

[0072] Step S103: Determine if the motor temperature T_m is greater than T1. If not, return to continue monitoring; if yes, proceed to the next step.

[0073] Step S104: Determine if T_m is greater than T1 and less than or equal to T2. If so, enter the early warning intervention stage, and reduce the maximum allowable torque proportionally according to the temperature rise, based on the formula for the maximum allowable output torque of the motor in the constant power region; ;

[0075] Step S105: Determine whether T_m is greater than T2 and less than T_max. If so, proceed to the constant torque power reduction stage.

[0076] Step S106: Determine whether the motor speed ω is greater than the rated speed ω_base. If yes, the motor is in the constant power region, and the constant power region derating strategy is executed; if not, the motor is in the constant torque region, and the MCU starts executing the constant torque region limiting strategy.

[0077] Step S107: When T_m ≥ T_max, execute the forced protection strategy, regardless of the motor speed range.

[0078] Step S108: The corresponding alarm indicator light for motor temperature illuminates to remind the driver of the current status of the electric drive system.

[0079] The specific steps for zoned power limiting include:

[0080] The constant power region (ω > ω_base) controls the maximum allowable output torque at a given speed and temperature when the motor is operating in the constant power region. As the temperature increases, the maximum allowable torque gradually decreases, specifically: T_max_allowed = T_base × (ω_base / ω) × k(t), where k(t) is the temperature-related derating factor, calculated as: k(t) = 1 - β × (T_m - T2) / (T_max - T2);

[0081] Here, β is the derating factor in the constant power region, ranging from 1.2 to 1.5, which is more aggressive than in the constant torque region because the motor's heat dissipation capacity decreases at high speeds, increasing the risk of overheating. When the motor temperature reaches T_max (160℃), the maximum power is forcibly limited to... ;

[0082] The constant torque zone (ω ≤ ω_base) control includes forcibly limiting the motor output torque to less than the rated torque T_base when the motor is operating in the constant torque zone and the temperature T_m > T2, that is: T_max_allowed = T_base × k(t) where k(t) is the temperature-related derating factor, and the calculation formula is: k(t) = 1 - γ × (T_m - T2) / (T_max -T2);

[0083] Here, γ is the derating factor in the constant torque region, with a value ranging from 0.8 to 1.0. Simultaneously, the MCU sends a command to the instrument panel via the CAN bus to illuminate the power limit warning light, reminding the driver that the vehicle has entered a power-limited state.

[0084] The table below shows an example of the correspondence between temperature and torque limit coefficients. It is used to pre-calibrate the relationship between temperature and coefficients. The specific correspondence can be pre-calibrated and adjusted, and the correspondence can be stored in the controller and directly called during execution.

[0085] The following specific embodiment illustrates the application effect of the present invention: An electric truck is equipped with a permanent magnet synchronous motor with a rated power of 100kW, a rated speed of 2500rpm, and a peak speed of 8000rpm. The maximum allowable temperature of the motor is 160℃. When the vehicle climbs a hill continuously under full load and overload conditions, the motor temperature rises rapidly.

[0086] When the temperature reaches 135℃ (T1), the system enters a warning state, and a yellow warning icon is displayed on the instrument panel, but the output power is not limited. When the temperature rises to 140℃ (T2), the system begins to implement graded limits based on the speed range: if the motor speed is 3000rpm (>2500rpm, constant power range), the MCU calculates the derating factor based on the current temperature. Assuming the temperature is 140℃, then k(t) = 1 - 1.35×(140-130) / (160-130) = 0.55, and the maximum allowable torque is reduced to 55% of its original value.

[0087] If the motor speed is 2000rpm (<2500rpm, constant torque zone), the derating factor k(t) = 1 - 0.9×(140-130) / (160-130) = 0.70, the maximum allowable torque is reduced to 70% of the original, and the power limit alarm light is lit at the same time.

[0088] When the temperature reaches 160℃ (T_max), the system forcibly limits the output power to no more than 100kW of rated power. At 3000rpm, the maximum permissible torque T = 1000000 / 3000 ≈ 333N•m, which is far lower than the normal peak torque at this speed.

[0089] Through this tiered control, the vehicle can still maintain its trajectory to the top of the hill without completely losing power, while effectively protecting the electric drive system from overheating damage. Real-world test data shows that after adopting this invention's strategy, the motor temperature gradually stabilizes after reaching its peak and does not continue to rise, proving the effectiveness of the control strategy. By limiting motor power at high speeds and temperatures, and limiting motor torque at low speeds and temperatures, the maximum permissible output power of the vehicle and the maximum permissible output torque of the motor during user operation are subtly reduced. This approach ensures that the motor temperature does not exceed the threshold while balancing user safety, vehicle durability, and driving performance as much as possible.

[0090] The over-temperature protection strategy for electric drive systems in new energy vehicles provided by this invention effectively solves the problem of motor overheating caused by overload in commercial vehicles through temperature-adaptive torque control and zoned power limiting. Compared with existing technologies, this strategy has the following outstanding advantages:

[0091] 1. Balance between protection and performance: It prevents motor overheating and damage, and avoids sudden loss of vehicle power, thus improving driving safety.

[0092] 2. Adaptable to all operating conditions: It takes into account the heating characteristics and control requirements of the motor in different speed ranges to achieve precise protection.

[0093] 3. Improved early warning mechanism: Multi-level alarms prompt drivers to take timely countermeasures to prevent problems before they occur.

[0094] 4. Low implementation cost: It can be implemented simply by upgrading the software algorithm, making it easy to promote and use on existing vehicles.

[0095] 5. Extended Motor Life: By preventing overheating, the lifespan of the electric drive system is significantly extended, reducing maintenance costs. This invention is applicable to all types of commercial electric vehicles, and has broad application prospects, especially in logistics transportation, engineering construction, and other fields prone to overload conditions.

[0096] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. A method for over-temperature control of a power system in a new energy pure electric vehicle, characterized in that: include: The system acquires the motor's speed and temperature data, calculates the maximum allowable output torque of the motor based on the temperature and speed, and limits the motor's output torque based on the maximum allowable output torque; it also limits the motor's output power based on the temperature and speed.

2. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 1, characterized in that: The maximum permissible output torque and maximum permissible output power of a motor are negatively correlated with motor temperature. When the motor temperature rises, both the maximum permissible output torque and maximum permissible output power decrease.

3. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 1 or 2, characterized in that: Multi-level alarm temperature thresholds are preset, and alarms are divided into multiple levels according to the temperature alarm thresholds. Corresponding motor output power and output torque limiting strategies are triggered according to the alarm level.

4. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 3, characterized in that: When multiple alarm levels are defined based on temperature alarm thresholds, a temperature alarm threshold T-max is set. When the detected motor temperature exceeds the temperature alarm threshold T-max, the motor output power is limited to below the rated power, and a level three fault alarm is issued.

5. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 3, characterized in that: When dividing alarms into multiple levels according to temperature alarm thresholds, temperature alarm thresholds T1 and T2 are set. When the real-time temperature is lower than the temperature alarm threshold T1, no alarm is triggered, and the motor temperature data is continuously monitored. Otherwise, when the motor temperature is between the temperature alarm thresholds T1 and T2, the warning intervention stage is entered; if the motor temperature threshold is between the temperature alarm thresholds T2 and T-max, the constant torque power reduction stage is entered. During the early warning and intervention phase, the maximum allowable output torque of the motor is reduced proportionally based on the temperature rise.

6. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 5, characterized in that: During the early warning and intervention phase, the maximum allowable output torque is reduced proportionally according to the temperature rise. The maximum allowable output torque of the motor is T_qallow = ((T_max - T_m) / (T_max - T2) * (P_max - P_based) + P_based) / ω; where the rated power P_based, the temperature thresholds are T1, T2 and T_max; ω is the real-time speed of the motor; and Tm is the real-time motor temperature.

7. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 5, characterized in that: After entering the constant torque power reduction stage, it is determined whether the motor speed ω is greater than the rated speed ω_base; if so, the motor is in the constant power region and the constant power region derating strategy is executed; if not, the motor is in the constant torque region and the constant torque region limiting strategy is executed.

8. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 7, characterized in that: The constant power derating strategy includes: when the motor is running in the constant power region, the maximum allowable torque is gradually reduced according to the temperature data, where the maximum allowable torque is T_max_allowed = T_base × (ω_base / ω) × k(t); Where k(t) is the temperature-related derating factor; when the motor temperature reaches T_max, the maximum power is forcibly limited to T_alllow = ((T_maxT_m) / (T_max-T2)*(P_max-P_based)*w+P_based) / ω.

9. The over-temperature control method for a power system of a new energy pure electric vehicle as described in claim 7, characterized in that: When the motor is operating in the constant torque region and the temperature T_m > T2, the motor output torque is forcibly limited to be less than the rated torque T_base. The motor output torque is limited to T_max_allowed = T_base × k(t). Where k(t) is the temperature-related derating factor; at the same time, the power limit warning light is illuminated to remind the driver that the vehicle has entered the power limit state.

10. An over-temperature control system for a power system of a new energy pure electric vehicle, characterized in that: The system includes a temperature sensor, a speed sensor, a control unit (MCU), and a motor controller; The temperature sensor is used to collect the temperature data of the motor, and the speed sensor is used to collect the speed of the motor. Both the temperature sensor and the speed sensor are connected to the control unit MCU. The control unit MCU calculates the maximum allowable output torque of the motor based on the temperature and speed, and limits the output torque of the motor based on the maximum allowable output torque. The control unit (MCU) limits the motor's output power based on temperature and speed.

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