Self-adaptive equivalent fuel consumption minimization strategy for fusing thermal characteristics of planetary series-parallel system

Abstract

The invention provides a self-adaptive equivalent fuel consumption minimization strategy of a planetary hybrid system fused with thermal characteristics, and aims to solve the problem that fuel economy optimization is insufficient due to the fact that a hybrid power system only adjusts equivalent factors according to the SOC of a battery and neglects the temperature influence in the electric quantity maintaining stage, and the method comprises the following steps that firstly, a proper thermal management system is designed; feedback and control over the temperature of all parts of the power system are achieved, and the power of the thermal management system is coupled in the whole vehicle demand power. Secondly, optimizing a Hamilton function by applying an equivalent fuel consumption minimum strategy and considering the temperature influence; and finally carrying out adaptive adjustment of the equivalent factors by fusing the thermal characteristics of the system and the SOC of the battery.

Description

Technical Field

[0001] The present invention relates to a self-adaptive equivalent fuel consumption minimization strategy integrating thermal characteristics, and in particular to a self-adaptive equivalent fuel consumption minimization strategy integrating thermal characteristics of a planetary series-parallel hybrid power system. Background Art

[0002] In the face of increasingly severe environmental and energy problems, improving the energy efficiency of vehicles is of great significance to reducing global energy consumption. Due to the characteristics of multiple power sources, the energy management strategy of hybrid power systems in improving fuel economy is more complex. At present, in the application of equivalent fuel consumption minimum strategy, most studies are to adjust the equivalent factor in real time according to the battery SOC, but the fuel economy obtained by adjusting the equivalent factor only according to the battery SOC has limitations. The efficiency of power system components changes significantly with temperature when working, and the output power of power system components has a significant impact on their own heat generation and thus affects their own temperature. Therefore, different power distribution schemes will also have an indirect impact on vehicle economy in terms of component temperature. In summary, considering the thermal characteristics of each component of the power system in the strategy will help further tap the energy-saving potential of hybrid vehicles.

[0003] The invention patent with publication number CN116522626A proposes a method and system for optimizing vehicle fuel consumption. The core idea of ​​this method is to collect and refine feature data through data acquisition modules and cloud servers, use equivalent fuel consumption minimum control strategy and digital twin model for offline simulation optimization, and obtain the optimization parameter equivalent factor to achieve global optimization of vehicle fuel consumption. The application of this method still lacks consideration of the impact of thermal characteristics of components such as engines on work efficiency and thus on fuel consumption, and cannot solve the problem of insufficient optimization of fuel economy due to ignoring the influence of temperature on the equivalent factor. Therefore, it is necessary to propose an adaptive equivalent fuel consumption minimum strategy that integrates thermal characteristics.

[0004] The present invention proposes an adaptive equivalent fuel consumption minimization strategy for a planetary parallel-parallel hybrid power system integrating thermal characteristics. This method can solve the problem of insufficient fuel economy optimization caused by the hybrid power system only adjusting the equivalent factor based on the battery SOC during the power maintenance stage while ignoring the temperature influence. Summary of the invention

[0005] In order to solve the problem of insufficient optimization of fuel economy caused by hybrid system only adjusting the equivalent factor based on battery SOC and ignoring the temperature effect during the power maintenance stage, this study proposes an adaptive equivalent fuel consumption minimum strategy for planetary hybrid system integrating thermal characteristics. By analyzing the heat generation of powertrain components and the thermal management system feeding back and controlling the temperature of each component, the required power is optimized and the equivalent factor of the integrated thermal characteristics is adaptively adjusted, making the fuel saving strategy more complete and optimized. The specific steps include the following:

[0006] The first step is to design a suitable thermal management system to optimize the required power, which includes the following steps:

[0007] The designed thermal management system should include three major circuits: engine, power battery, and motor. By controlling each water pump, three-way valve, and PTC heater, a variety of heating and cooling modes can be realized. At the same time, a switching control strategy for the thermal management system mode should be formulated to meet the use of different modes under different working conditions, and the calculation algorithms such as component temperature and system energy consumption under each mode should be integrated in the system to realize feedback and control of the temperature of each component of the power system.

[0008] Due to the introduction of the thermal management system, the required power needs to be optimized. First, the required driving power of the vehicle is calculated according to the cycle conditions, and then the thermal management system power is coupled on this basis to form the required power of the vehicle. The optimized required power P req The calculation is as follows:

[0009] P req =P eng / η DC / DC +P MG1 +P MG2 +P VTM (1)

[0010] Where η DC / DC is the DC / DC converter efficiency, P VTM is the power of the thermal management system.

[0011] The power of the thermal management system is obtained as follows: first, the initial power allocation plan is determined (that is, the temperature control of the thermal management system is not considered). After the power allocation plan is determined, the heat generation model of each power component is used to calculate the heat. Then, the thermal management system control strategy controls the operating status of each component of the thermal management system according to variables such as heat generation and ambient temperature. Finally, the thermal management system feeds back the coolant temperature of each object to the energy management strategy. At the same time, the thermal management system control strategy outputs the thermal management system power to calculate the required power of the entire vehicle.

[0012] The second step is to consider the influence of temperature and optimize the Hamiltonian function, which includes the following steps:

[0013] Since only the power split mode in the planetary hybrid system involves the power distribution of the power source, the equivalent fuel consumption minimum strategy algorithm is applied in this mode. First, the traditional equivalent fuel consumption minimum strategy is used to set the boundary conditions for the torque and speed of the engine and motor, the power and current of the battery, and the battery SOC as follows:

[0014]

[0015] The Hamiltonian function can be constructed:

[0016]

[0017] Where P bat is the power of the battery.

[0018] Define the equivalence factor s:

[0019]

[0020] Substitute the equivalent factor s into equation (3) to replace the covariate λ:

[0021]

[0022] The first term on the right side of the equation is the engine fuel consumption, and the second term is the equivalent fuel consumption of the power battery. In order to maximize fuel economy, the calculation of engine fuel consumption can be combined with the engine's optimal operating curve and the universal characteristic diagram. First, the optimal torque and speed of the engine under each fuel consumption are determined, and then the engine power at this time is calculated to obtain the relationship between the engine's optimal fuel consumption and engine power. The optimal fuel consumption obtained by fitting is substituted into equation (5). Since the engine speed and torque are dually decoupled in the power split drive mode, the power distribution of the two motors follows the engine's optimal principle.

[0023] For the calculation of the equivalent factor s, it is difficult to accurately predict the global working conditions during actual driving, so it is impossible to predetermine the optimal equivalent factor value. In the real-time adjustment method of the equivalent factor, most studies only adjust it according to the battery SOC, ignoring that the efficiency of the power system components changes with temperature during operation. The adaptive equivalent fuel consumption minimization strategy that integrates thermal characteristics proposed in this patent not only considers the battery SOC but also the influence of temperature. The optimized Hamiltonian function is as follows:

[0024]

[0025] In the formula, θ eng is the engine temperature, that is, the battery SOC and the engine temperature are considered simultaneously when obtaining the equivalent factor.

[0026] The third step is to adaptively adjust the equivalent factor, which specifically includes the following steps

[0027] The selection scheme of the equivalent factor requires the selection of the initial value first, and then the adaptive equivalent factor optimization adjustment of the fusion system thermal characteristics. The selection of the initial equivalent factor is solved by binary search iteration. First, the upper and lower limits of the equivalent factor are set, and the initial value is selected to calculate the SOC trajectory. Then, it is determined whether the difference between the initial and final SOC values ​​meets the preset allowable deviation. If so, the current equivalent factor is considered to be the optimal initial value. Otherwise, the factor range is adjusted by binary search and the iteration continues until the conditions are met.

[0028] The adaptive equivalent factor optimization adjustment method integrating the thermal characteristics of the system is divided into two steps: first, an adjustment scheme based on battery SOC feedback is established, and second, a temperature penalty coefficient is introduced to perform real-time correction of the equivalent factor.

[0029] ① Adaptive adjustment scheme of equivalent factor based on battery SOC feedback

[0030] In order to ensure the battery SOC balance in the power maintenance stage, the adaptive adjustment of the equivalent factor can be based on the error between the current SOC and the initial SOC in the power maintenance stage, and its discrete form is:

[0031]

[0032] Among them, s(k+1) and s(k) are the equivalent factor values ​​of the k+1th and kth times respectively; W SOC is the correction factor; It is the absolute value of the difference between the battery SOC and the reference value at time T. When the battery SOC is at a low level, the power consumption should be reduced as much as possible. At this time, the vehicle should rely more on the engine to drive, which means that the current power consumption is more expensive, the battery equivalent fuel consumption per unit time is higher, and the equivalent factor s should be larger; when the battery SOC is at a high level, in order to maximize fuel saving, the power consumption should be increased as much as possible. At this time, the vehicle requires more motor drive, which means that the current power consumption is cheaper, the battery equivalent fuel consumption per unit time is lower, and the equivalent factor s should be smaller. The balance of the battery SOC can be achieved by adjusting the battery SOC balance control coefficient.

[0033] ②Introduce temperature penalty coefficient to correct the equivalent factor in real time

[0034] Based on the above method, an equivalent factor adjustment scheme that integrates the thermal characteristics of the system and the battery SOC can be obtained: when the engine temperature exceeds a certain range, its working efficiency will decrease. Therefore, the engine temperature factor should also be considered when allocating power, and the engine should be operated in the inefficient range as little as possible. The specific implementation method is to introduce the engine temperature penalty coefficient α in the equivalent factor. Teng :

[0035] s(SOC,θ eng)=s(SOC)·α Teng (8)

[0036] Where s(SOC) is the equivalent factor obtained based on battery SOC feedback regulation, which is obtained by formula (7).

[0037] The fuel consumption rate of the engine is higher and the emission performance is worse at lower temperatures. Therefore, in order to improve the economy and emission performance, the power distribution to the engine should be reduced when the engine is at a lower temperature, and the equivalent factor should be appropriately reduced. At this time, the engine temperature penalty coefficient α Teng Should be less than 1. When calculating engine fuel consumption in the traditional way, the normal operating temperature of the engine is often used, that is, 85-95°C. Studies have shown that when the engine temperature reaches 80°C, the impact of temperature on fuel consumption can be ignored. In addition, since the engine thermal management system controls the engine temperature, the engine temperature can be maintained in the optimal operating range, and the fuel consumption change when the temperature exceeds the limit is not considered. Therefore, when the engine reaches 80°C, the temperature penalty coefficient α Teng Take 1. When the engine temperature is lower than 80℃, different α Teng The value will affect the calculation of the equivalent factor, and thus affect the engine working state, so it is necessary to adjust α Teng Taking the -25℃ ambient temperature condition as an example, the α Teng The value of α is explored. Teng The larger the value, the more power the strategy will tend to allocate to the engine, and the more energy the engine will output. At this time, on the one hand, the engine is in a low-temperature state and has low efficiency. The increased power output of the engine in an inefficient state will lead to a decrease in the average thermal efficiency of the entire operating condition. On the other hand, since the engine works more actively, it will generate more heat. Under this effect, the engine will heat up more quickly to get out of the low-temperature and inefficient working state as soon as possible. This effect will increase the average thermal efficiency of the engine in the entire operating condition. Under the combined influence of the above two factors, there may be an α that makes the engine thermally most efficient at a certain temperature. Teng This value can be used as the optimal α at this temperature Teng Get the value.

[0038] To verify the above analysis, Teng The average thermal efficiency of the engine under the condition of The calculation is as follows:

[0039]

[0040] Where E eng is the total output energy of the engine, h u is the calorific value of diesel, It can be obtained from step 2. Then we can get the α that makes the average thermal efficiency of the engine the highest at each temperature. Teng Then the best α at each temperature Teng The value points are drawn in the coordinate system, and the α obtained by fitting is Teng and engine temperature θ eng Finally, the working states of various components of the power system and the transmission mechanism are controlled according to the comprehensive power allocation scheme of the energy management strategy to realize the adaptive equivalent fuel consumption minimum strategy integrating thermal characteristics.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The adaptive equivalent fuel consumption minimum strategy of the planetary hybrid system integrating thermal characteristics described in the present invention realizes coupling the thermal management system power with the vehicle demand power and optimizes it as part of the demand power;

[0043] 2. The adaptive equivalent fuel consumption minimum strategy of the planetary hybrid system integrating thermal characteristics described in the present invention takes the system temperature into consideration when allocating power, which helps to improve work efficiency and further taps the fuel saving potential of the equivalent fuel consumption minimum strategy;

[0044] 3. The adaptive equivalent fuel consumption minimization strategy of a planetary hybrid system integrating thermal characteristics described in the present invention proposes an adaptive adjustment method for an optimized equivalent factor that combines system thermal characteristics with battery SOC error feedback. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further described below in conjunction with the accompanying drawings:

[0046] Figure 1 This is a diagram of the architecture of a strategy for minimizing the equivalent fuel consumption of a planetary hybrid system integrating thermal characteristics according to the present invention;

[0047] Figure 2 It is a thermal management system architecture diagram of a planetary hybrid system in an adaptive equivalent fuel consumption minimum strategy integrating thermal characteristics according to the present invention;

[0048] Figure 3 A flow chart of motor power allocation in a self-adaptive equivalent fuel consumption minimization strategy for a planetary hybrid system integrating thermal characteristics according to the present invention; DETAILED DESCRIPTION

[0049] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings.

[0050] See also Figure 1 The overall architecture of the adaptive equivalent fuel consumption minimum energy management strategy integrating the thermal characteristics of the system is described as follows:

[0051] (1) The energy management strategy calculates the required driving power of the vehicle based on the cycle conditions, and on this basis, couples the thermal management system power to form the required power of the vehicle;

[0052] (2) Power is allocated to each component of the power system. In addition to considering the battery SOC, the temperature is also taken into account when allocating power. The temperature is obtained as follows: first, the initial power allocation plan is determined. After the power allocation plan is determined, the heat generation model calculates the heat generation of each component. Then, the thermal management system control strategy controls the operating status of each component of the thermal management system based on variables such as heat generation and ambient temperature. Finally, the thermal management system feeds back the coolant temperature of each object to the energy management strategy. At the same time, the thermal management system control strategy outputs the thermal management system power to calculate the required power of the entire vehicle.

[0053] (3) Control the working status of each component of the power system and the transmission mechanism according to the comprehensive power allocation plan of the energy management strategy.

[0054] The first step is to design a suitable thermal management system to optimize the required power, which includes the following steps:

[0055] See also Figure 2 The designed thermal management system should include three major circuits: engine, power battery, and motor. The engine circuit and the power battery circuit are coupled with each other, and the coolant can be interconnected. The components in each circuit are as follows:

[0056] (1) Engine-battery circuit: water pump 1, engine water jacket, engine radiator, water pump 2, battery water jacket, PTC heater, battery radiator, three-way valve 1, three-way valve 2, three-way valve 3, three-way valve 4, three-way valve 5, engine-battery circuit water tank;

[0057] (2) Motor circuit: water pump 3, MG1 water jacket, MG2 water jacket, motor radiator, motor circuit water tank.

[0058] In addition to the above components, a water tank is also set in each circuit to store coolant, and a cooling fan is arranged in front of the radiator to enhance heat dissipation.

[0059] By controlling the water pumps, three-way valves and PTC heaters, the thermal management system can achieve a variety of heating and cooling modes. At the same time, a switching control strategy for the thermal management system mode is formulated to meet the use of different modes under different working conditions, and the calculation algorithms such as component temperature and system energy consumption under each mode are integrated in the system to achieve feedback and control of the temperature of each component of the power system.

[0060] Due to the introduction of the thermal management system, the required power needs to be optimized. First, the required driving power of the vehicle is calculated according to the cycle conditions, and then the thermal management system power is coupled on this basis to form the required power of the vehicle. The optimized required power P req The calculation is as follows:

[0061] P req =P eng / η DC / DC +P MG1 +P MG2 +P VTM (1)

[0062] Where η DC / DC is the DC / DC converter efficiency, P VTM is the power of the thermal management system.

[0063] The power of the thermal management system is obtained as follows: first, the initial power allocation plan is determined (that is, the temperature control of the thermal management system is not considered). After the power allocation plan is determined, the heat generation model of each power component is used to calculate the heat. Then, the thermal management system control strategy controls the operating status of each component of the thermal management system according to variables such as heat generation and ambient temperature. Finally, the thermal management system feeds back the coolant temperature of each object to the energy management strategy. At the same time, the thermal management system control strategy outputs the thermal management system power to calculate the required power of the entire vehicle.

[0064] The second step is to consider the influence of temperature and optimize the Hamiltonian function, which includes the following steps:

[0065] Since only the power split mode in the planetary hybrid system involves the power distribution of the power source, the equivalent fuel consumption minimum strategy algorithm is applied in this mode. First, the traditional equivalent fuel consumption minimum strategy is used to set the boundary conditions for the torque and speed of the engine and motor, the power and current of the battery, and the battery SOC as follows:

[0066]

[0067] The Hamiltonian function can be constructed:

[0068]

[0069] Where P bat is the power of the battery.

[0070] Define the equivalence factor s:

[0071]

[0072] Substitute the equivalent factor s into equation (3) to replace the covariate λ:

[0073]

[0074] The first term on the right side of the equation is the engine fuel consumption, and the second term is the equivalent fuel consumption of the power battery. In order to maximize fuel economy, the calculation of engine fuel consumption can be combined with the engine's optimal operating curve and the universal characteristic diagram. First, the engine's optimal torque and speed under various fuel consumptions are determined, and then the engine power at this time is calculated to obtain the relationship between the engine's optimal fuel consumption and engine power. The optimal fuel consumption obtained by fitting is substituted into equation (5).

[0075] See also Figure 3 The specific distribution of motor power. Since the engine speed and torque are decoupled in the power split drive mode, the power distribution of the two motors follows the engine optimal principle. The optimal working curve of the engine can be used to decouple the power allocated to the engine to obtain the optimal torque and speed under this power. Since the MG2 motor directly drives the wheels, the MG2 motor speed can be obtained from the current vehicle speed, and then the torque and speed of the MG1 motor can be obtained from the connection relationship between the various components of the power system and the planetary gear, and then the power can be calculated.

[0076] For the calculation of the equivalent factor s, it is difficult to accurately predict the global working conditions during actual driving, so it is impossible to predetermine the optimal equivalent factor value. In the real-time adjustment method of the equivalent factor, most studies only adjust it according to the battery SOC, ignoring that the efficiency of the power system components changes with temperature during operation. The adaptive equivalent fuel consumption minimization strategy that integrates thermal characteristics proposed in this patent not only considers the battery SOC but also the influence of temperature. The optimized Hamiltonian function is as follows:

[0077]

[0078] In the formula, θ eng is the engine temperature, that is, the battery SOC and the engine temperature are considered simultaneously when obtaining the equivalent factor.

[0079] The third step is to adaptively adjust the equivalent factor, which specifically includes the following steps

[0080] The selection scheme of the equivalent factor requires the selection of the initial value first, and then the adaptive equivalent factor optimization adjustment of the fusion system thermal characteristics. The selection of the initial equivalent factor is solved by binary search iteration. First, the upper and lower limits of the equivalent factor are set, and the initial value is selected to calculate the SOC trajectory. Then, it is determined whether the difference between the initial and final SOC values ​​meets the preset allowable deviation. If so, the current equivalent factor is considered to be the optimal initial value. Otherwise, the factor range is adjusted by binary search and the iteration continues until the conditions are met.

[0081] The adaptive equivalent factor optimization adjustment method integrating the thermal characteristics of the system is divided into two steps: first, an adjustment scheme based on battery SOC feedback is established, and second, a temperature penalty coefficient is introduced to perform real-time correction of the equivalent factor.

[0082] ① Adaptive adjustment scheme of equivalent factor based on battery SOC feedback

[0083] In order to ensure the battery SOC balance in the power maintenance stage, the adaptive adjustment of the equivalent factor can be based on the error between the current SOC and the initial SOC in the power maintenance stage, and its discrete form is:

[0084]

[0085] Among them, s(k+1) and s(k) are the equivalent factor values ​​of the k+1th and kth times respectively; W SOC is the correction factor; It is the absolute value of the difference between the battery SOC and the reference value at time T. When the battery SOC is at a low level, the power consumption should be reduced as much as possible. At this time, the vehicle should rely more on the engine to drive, which means that the current power consumption is more expensive, the battery equivalent fuel consumption per unit time is higher, and the equivalent factor s should be larger; when the battery SOC is at a high level, in order to maximize fuel saving, the power consumption should be increased as much as possible. At this time, the vehicle requires more motor drive, which means that the current power consumption is cheaper, the battery equivalent fuel consumption per unit time is lower, and the equivalent factor s should be smaller. The balance of the battery SOC can be achieved by adjusting the battery SOC balance control coefficient.

[0086] ②Introduce temperature penalty coefficient to correct the equivalent factor in real time

[0087] Based on the above method, an equivalent factor adjustment scheme that integrates the thermal characteristics of the system and the battery SOC can be obtained: when the engine temperature exceeds a certain range, its working efficiency will decrease. Therefore, the engine temperature factor should also be considered when allocating power, and the engine should be operated in the inefficient range as little as possible. The specific implementation method is to introduce the engine temperature penalty coefficient α in the equivalent factor. Teng :

[0088] s(SOC,θ eng )=s(SOC)·α Teng (8)

[0089] Where s(SOC) is the equivalent factor obtained based on battery SOC feedback regulation, which is obtained by formula (7).

[0090] The fuel consumption rate of the engine is higher and the emission performance is worse at lower temperatures. Therefore, in order to improve the economy and emission performance, the power distribution to the engine should be reduced when the engine is at a lower temperature, and the equivalent factor should be appropriately reduced. At this time, the engine temperature penalty coefficient αTeng Should be less than 1. When calculating engine fuel consumption in the traditional way, the normal operating temperature of the engine is often used, that is, 85-95°C. Studies have shown that when the engine temperature reaches 80°C, the impact of temperature on fuel consumption can be ignored. In addition, since the engine thermal management system controls the engine temperature, the engine temperature can be maintained in the optimal operating range, and the fuel consumption change when the temperature exceeds the limit is not considered. Therefore, when the engine reaches 80°C, the temperature penalty coefficient α Teng Take 1. When the engine temperature is lower than 80℃, different α Teng The value will affect the calculation of the equivalent factor, and thus affect the engine working state, so it is necessary to adjust α Teng Taking the -25℃ ambient temperature condition as an example, the α Teng The value of α is explored. Teng The larger the value, the more power the strategy will tend to allocate to the engine, and the more energy the engine will output. At this time, on the one hand, the engine is in a low-temperature state and has low efficiency. The increased power output of the engine in an inefficient state will lead to a decrease in the average thermal efficiency of the entire operating condition. On the other hand, since the engine works more actively, it will generate more heat. Under this effect, the engine will heat up more quickly to get out of the low-temperature and inefficient working state as soon as possible. This effect will increase the average thermal efficiency of the engine in the entire operating condition. Under the combined influence of the above two factors, there may be an α that makes the engine thermally most efficient at a certain temperature. Teng This value can be used as the optimal α at this temperature Teng Get the value.

[0091] To verify the above analysis, Teng The average thermal efficiency of the engine under the condition of The calculation is as follows:

[0092]

[0093] Where E eng is the total output energy of the engine, h u is the calorific value of diesel, It can be obtained from step 2. Then we can get the α that makes the average thermal efficiency of the engine the highest at each temperature. Teng Then the best α at each temperature Teng The value points are drawn in the coordinate system, and the α obtained by fitting is Teng and engine temperature θ eng Finally, the working states of various components of the power system and the transmission mechanism are controlled according to the comprehensive power allocation scheme of the energy management strategy to realize the adaptive equivalent fuel consumption minimum strategy integrating thermal characteristics.

Claims

1. An adaptive equivalent fuel consumption minimization strategy for a planetary hybrid system integrating thermal characteristics, characterized by: It breaks through the limitation of hybrid system that only adjusts the equivalent factor according to the battery SOC to obtain fuel economy during the power maintenance stage, and fully considers the impact of the operating temperature of power system components on efficiency and fuel economy, including the following: The first step is to design a suitable thermal management system to optimize the required power, which includes the following steps: The designed thermal management system should include three major circuits: engine, power battery, and motor. By controlling each water pump, three-way valve, and PTC heater, a variety of heating and cooling modes can be realized. At the same time, a switching control strategy for the thermal management system mode should be formulated to meet the use of different modes under different working conditions. The component temperature and system energy consumption calculation algorithms under each mode should be integrated in the system to realize feedback and control of the temperature of each component of the power system. Due to the introduction of the thermal management system, the required power needs to be optimized. First, the required driving power of the vehicle is calculated according to the cycle conditions, and then the thermal management system power is coupled on this basis to form the required power of the vehicle. The optimized required power P req The calculation is as follows: P req =P eng / η DC / DC +P MG1 +P MG2 +P VTM (1) Where η DC / DC is the DC / DC converter efficiency, P VTM is the power of the thermal management system; The power of the thermal management system is obtained as follows: first, the initial power allocation scheme is determined (i.e., the temperature control of the thermal management system is not considered). After the power allocation scheme is determined, the heat generation model of each power component calculates the heat. Then, the thermal management system control strategy controls the operating state of each component of the thermal management system according to the heat generation and the ambient temperature variable. Finally, the thermal management system feeds back the coolant temperature of each object to the energy management strategy. At the same time, the thermal management system control strategy outputs the thermal management system power to calculate the required power of the whole vehicle. The second step is to consider the temperature effect and optimize the Hamiltonian function, which includes the following steps: Since only the power split mode in the planetary hybrid configuration system involves the power distribution of the power source, the equivalent fuel consumption minimum strategy algorithm is applied in this mode; first, the traditional equivalent fuel consumption minimum strategy is used to set the boundary conditions for the torque and speed of the engine and motor, the power and current of the battery, and the battery SOC as follows: The Hamiltonian function can be constructed: Where P bat is the power of the battery; Define the equivalence factor s: Substitute the equivalent factor s into equation (3) to replace the covariate λ: The first term on the right side of the equation is the engine fuel consumption, and the second term is the equivalent fuel consumption of the power battery; in order to maximize fuel economy, the calculation of engine fuel consumption can be combined with the engine's optimal working curve and the universal characteristic diagram. First, the engine's optimal torque and speed under each fuel consumption are determined, and then the engine power at this time is calculated to obtain the relationship between the engine's optimal fuel consumption and the engine power. The optimal fuel consumption obtained by fitting is substituted into formula (5); since the engine speed and torque are dually decoupled in the power split drive mode, the power distribution of the two motors follows the engine's optimal principle; For the calculation of the equivalent factor s, it is difficult to accurately predict the global working conditions during actual driving, so it is impossible to determine the optimal equivalent factor value in advance; and in the real-time adjustment method of the equivalent factor, most studies only adjust it according to the battery SOC, ignoring the change of efficiency of the power system components with temperature during operation; the adaptive equivalent fuel consumption minimum strategy integrating thermal characteristics proposed in this patent not only considers the battery SOC but also takes into account the influence of temperature; the optimized Hamiltonian function is as follows: In the formula, θ eng is the engine temperature, that is, the battery SOC and the engine temperature are considered simultaneously when obtaining the equivalent factor; The third step is adaptive adjustment of the equivalent factor, which specifically includes the following steps: The selection scheme of the equivalent factor requires the selection of the initial value first, and then the adaptive equivalent factor optimization adjustment of the fusion system thermal characteristics; the selection of the initial equivalent factor is solved by binary search iteratively; first, the upper and lower limits of the equivalent factor are set, and the initial value is selected to calculate the SOC trajectory; then, it is determined whether the difference between the initial and final SOC values ​​meets the preset allowable deviation. If so, the current equivalent factor is considered to be the optimal initial value, otherwise, the factor range is adjusted by binary search and the iteration is continued until the conditions are met; The adaptive optimization adjustment method of equivalent factor integrating system thermal characteristics is divided into two steps: first, an adjustment scheme based on battery SOC feedback is established, and second, a temperature penalty coefficient is introduced to correct the equivalent factor in real time; ① Adaptive adjustment scheme of equivalent factor based on battery SOC feedback In order to ensure the battery SOC balance in the power maintenance stage, the adaptive adjustment of the equivalent factor can be based on the error between the current SOC and the initial SOC in the power maintenance stage, and its discrete form is: Among them, s(k+1) and s(k) are the equivalent factor values ​​of the k+1th and kth times respectively; W SOC is the correction factor; It is the absolute value of the difference between the battery SOC and the reference value at time T; when the battery SOC is at a low level, the power consumption should be reduced as much as possible. At this time, the vehicle should rely more on the engine to drive, which means that the current power consumption is more expensive, the battery equivalent fuel consumption per unit time is higher, and the equivalent factor s should be larger; when the battery SOC is at a high level, in order to maximize fuel saving, the power consumption should be increased as much as possible. At this time, the vehicle requires more motor drive, which means that the current power consumption is cheaper, the battery equivalent fuel consumption per unit time is lower, and the equivalent factor s should be smaller; the battery SOC balance can be achieved by adjusting the battery SOC balance control coefficient; ②Introduce temperature penalty coefficient to correct the equivalent factor in real time Based on the above method, an equivalent factor adjustment scheme that integrates the thermal characteristics of the system and the battery SOC can be obtained: when the engine temperature exceeds a certain range, its working efficiency will decrease. Therefore, the engine temperature factor should also be considered when allocating power, and the engine should be operated in the inefficient range as little as possible. The specific implementation method is to introduce the engine temperature penalty coefficient α in the equivalent factor. Teng : s(SOC,θ eng )=s(SOC)·α Teng (8) Where s(SOC) is the equivalent factor based on battery SOC feedback regulation, which is obtained by formula (7); The fuel consumption rate of the engine is higher and the emission performance is worse at lower temperatures. Therefore, in order to improve the economy and emission performance, the power distribution to the engine should be reduced when the engine is at a lower temperature, and the equivalent factor should be appropriately reduced. At this time, the engine temperature penalty coefficient α Teng Should be less than 1; the traditional method of calculating engine fuel consumption often takes the normal operating temperature of the engine, that is, 85-95°C. Studies have shown that when the engine temperature reaches 80°C, the impact of temperature on fuel consumption can be ignored. In addition, since the engine thermal management system controls the engine temperature, the engine temperature can be maintained in the optimal operating range, and the fuel consumption change when the temperature exceeds the limit is not considered. Therefore, when the engine reaches 80°C, the temperature penalty coefficient α Teng Take 1; when the engine temperature is lower than 80℃, different α Teng The value will affect the calculation of the equivalent factor, and thus affect the engine working state, so it is necessary to adjust α Teng How to select the value is explored; taking the -25℃ ambient temperature condition as an example, the α Teng The value of α was explored; Teng The larger the value, the more power the strategy will tend to allocate to the engine, and the more energy the engine will output. At this time, on the one hand, the engine is in a low-temperature state and has low efficiency. The increased power output of the engine in an inefficient state will lead to a decrease in the average thermal efficiency of the entire operating condition. On the other hand, since the engine works more actively, it will generate more heat. Under this effect, the engine will heat up more quickly to get out of the low-temperature and inefficient working state as soon as possible. This effect will increase the average thermal efficiency of the engine in the entire operating condition. Under the combined influence of the above two factors, there may be an α that makes the engine thermally most efficient at a certain temperature. Teng This value can be used as the optimal α at this temperature Teng Get value; To verify the above analysis, Teng The average thermal efficiency of the engine under the condition of The calculation is as follows: Where E eng is the total output energy of the engine, h u is the calorific value of diesel, It can be obtained from step 2; then we can get the α that makes the average thermal efficiency of the engine the highest at each temperature Teng Then the best α at each temperature Teng The value points are drawn in the coordinate system, and the α obtained by fitting is Teng and engine temperature θ eng relationship; finally, the working states of various components of the power system and the transmission mechanism are controlled according to the comprehensive power allocation scheme of the energy management strategy to realize the adaptive equivalent fuel consumption minimum strategy integrating thermal characteristics.

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