Energy management method for diesel-electric hybrid power system in low-temperature environment

Abstract

The invention discloses a diesel-electric hybrid power system energy management method in a low-temperature environment, and belongs to the field of hybrid power system energy management. The implementation method comprises the following steps: for a battery, introducing part of cooling liquid in a diesel engine cooling system into a battery cooling system, constructing a battery low-temperature preheating loop, preheating the battery through the battery low-temperature preheating loop, and fully utilizing the waste heat of the cooling liquid of the diesel engine. For the diesel engine, when the temperature of the cooling liquid of the diesel engine does not reach the preset suitable working temperature, the intake air of the diesel engine is preheated in the mode that flame preheating and positive temperature coefficient material preheating are combined. By combining the two preheating measures, on the basis of an equivalent fuel consumption minimum strategy, a self-adaptive equivalent fuel consumption minimum strategy is constructed, and the battery charge state, the power unit temperature and the diesel engine air inlet preheating power are comprehensively considered to conduct self-adaptive adjustment on equivalent factors; and related parameters of the adaptive equivalent factors are optimized based on an improved genetic algorithm, so that the temperature rise time of the power unit is shortened, and the fuel economy is improved.

Description

Technical Field

[0001] The invention relates to an energy management method for a diesel-electric hybrid power system in a low-temperature environment, and belongs to the field of energy management of hybrid power systems. Background Art

[0002] As an important subsystem of hybrid electric vehicles, the thermal management system can absorb the heat generated by the power unit to gradually increase the coolant temperature and maintain the power unit at an appropriate operating temperature through heat dissipation. The working performance of the vehicle power system is significantly affected by temperature, and the quality of the thermal management system's operation has an impact on the vehicle's power and economy. The energy management strategy can put the power unit at the optimal working point by reasonably allocating the required power. However, in a low-temperature environment, the power unit is in a low-temperature and inefficient state before it is fully preheated. It is necessary to add preheating measures to the power unit and incorporate temperature factors into the consideration scope of the energy management strategy, thereby accelerating the temperature rise rate of the power unit, further improving performance including power output and energy consumption, and improving the performance of the entire vehicle. Therefore, it is of great significance to design different preheating schemes for different power units in a low-temperature environment, incorporate the performance of the power unit thermal management system and the preheating scheme into the consideration scope of the energy management strategy, and optimize the power and economy goals. Summary of the invention

[0003] The purpose of the present invention is to provide an energy management method for a diesel-electric hybrid system in a low-temperature environment. For the battery, part of the coolant in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating circuit; for the diesel engine, when the diesel engine coolant temperature does not reach the preset suitable operating temperature, the diesel engine intake air is preheated by combining flame preheating and positive temperature coefficient material preheating. Combining the above two preheating measures, on the basis of the equivalent fuel consumption minimum strategy, an adaptive equivalent fuel consumption minimum strategy is constructed, which comprehensively considers the battery charge state, power unit temperature and diesel engine intake preheating power to adaptively adjust the equivalent factor, and optimizes the relevant parameters of the adaptive equivalent factor based on the improved genetic algorithm, thereby shortening the power unit temperature rise time and improving fuel economy.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] The present invention discloses a method for managing energy of a diesel-electric hybrid power system in a low-temperature environment, comprising the following steps:

[0006] Step 1: For the battery of the diesel-electric hybrid system in a low-temperature environment, part of the coolant in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating circuit. The battery is preheated through the battery low-temperature preheating circuit until the battery coolant is heated to a preset suitable temperature for the battery to operate.

[0007] When the diesel engine coolant temperature reaches the logic threshold value for opening the battery low temperature preheating circuit, the battery low temperature preheating circuit is opened, part of the diesel engine coolant flows through the battery cooling system circuit to preheat the battery, the battery cooling water pump is closed, the battery cooling water pump bypass valve is opened, and the diesel engine cooling water pump provides the power required for the diesel engine and battery coolant circulation. When the diesel engine coolant temperature does not reach the logic threshold value for opening the battery low temperature preheating circuit, or the battery coolant has been heated to the preset suitable temperature for the battery to work, the battery low temperature preheating circuit is closed, the diesel engine coolant does not flow through the battery cooling system circuit, the battery cooling water pump is opened, the battery cooling water pump bypass valve is closed, and the battery cooling water pump provides the power required for the battery coolant circulation.

[0008] Step 2: For a diesel engine of a diesel-electric hybrid system in a low-temperature environment, when the diesel engine coolant temperature has not reached a preset suitable operating temperature, the diesel engine intake air is preheated using a combination of flame preheating and positive temperature coefficient (PTC) material preheating until the diesel engine coolant temperature reaches a preset suitable operating temperature.

[0009] When the diesel engine coolant temperature has not reached the preset suitable operating temperature, the diesel engine intake air is first preheated using flame preheating, which is powered by the battery and has a fixed working duration. After flame preheating, the diesel engine intake air is preheated using PTC, which is powered by the power battery, until the diesel engine coolant temperature reaches the preset suitable temperature.

[0010] Preferably, flame preheating has lower energy consumption than PTC preheating, but long-term use of the preheat plug of flame preheating will reduce its service life or cause damage, and PTC preheating has higher energy consumption than flame preheating. Therefore, the fixed working time of flame preheating in the warm-up stage is set to 180s to avoid long-term heating of the preheat plug during flame preheating and large energy consumption caused by using only PTC preheating.

[0011] Step 3: Based on the equivalent fuel consumption minimization strategy ECMS (Equivalent Consumption Minimization Strategy), the electric energy consumption is converted into fuel consumption through the equivalent factor. Under the constraint of meeting the boundary conditions, the minimum value of the Hamiltonian function is solved to obtain the instantaneous optimal diesel engine and battery output power.

[0012] The equivalent fuel consumption minimum strategy converts the electric energy consumption into fuel consumption through the equivalent factor, and adds it to the actual fuel consumption to get the equivalent fuel consumption. The instantaneous optimal value is solved with the minimum equivalent fuel consumption at a certain moment as the optimization goal, which improves the fuel economy of the whole vehicle while reducing the amount of calculation. The size of the equivalent factor in the equivalent fuel consumption minimum strategy reflects the proportion of the battery energy consumption cost in the total energy consumption cost and affects the energy distribution of the power unit. The equivalent fuel consumption is calculated according to the following formula:

[0013]

[0014] In the formula, is the instantaneous equivalent fuel consumption; u(t) is the control variable; Instantaneous fuel consumption of diesel engine; s(t) is the equivalent factor of converting electric energy consumption into fuel consumption; P bat (u(t),t) is the battery power; Q LHV The fuel has a low calorific value; The fuel consumption converted from the instantaneous electric energy consumption.

[0015] According to the working characteristics of the power unit, the following boundary constraints are met:

[0016]

[0017] Where P dem (t) is the total required power; P e (t) is the diesel engine power; P m (t) is the motor power; n e (t) is the speed of the diesel engine; P e_max (n e (t)) is the maximum power of the diesel engine at this speed; n m (t) is the motor speed; P m_max (n m (t)) is the maximum power of the motor at this speed; n e_min is the minimum speed of the diesel engine; n e_max is the maximum speed of the diesel engine; n m_max is the maximum speed of the motor; SOC min is the lower limit of battery SOC; SOC max is the upper limit of battery SOC; T e is the diesel engine coolant temperature; T e max is the upper limit of diesel engine coolant temperature; T b is the battery coolant temperature; T b max is the upper limit of battery coolant temperature; P heat P is the diesel engine intake preheating power; b_max The maximum power of the battery.

[0018] The state variable of the hybrid system is the battery SOC, the control variables are the diesel engine power and the battery power, and the Hamiltonian function is expressed as:

[0019]

[0020] Under the premise of meeting the boundary constraints of the hybrid power system, the minimum value of the Hamiltonian function is solved to obtain the optimal output power of the diesel engine and battery.

[0021] Step 4: Based on step 3, the equivalent factor of the equivalent fuel consumption minimum strategy is adaptively adjusted. Combined with the diesel engine intake preheating in step 2, the battery SOC, power unit temperature and diesel engine intake preheating power are comprehensively considered to construct an adaptive equivalent fuel consumption minimum strategy, further optimize the power distribution of the diesel engine and the battery, and improve the adaptability of the energy management strategy in low temperature environments. The equivalent factor formula of the equivalent fuel consumption minimum strategy includes the SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat .

[0022] The equivalent factor of the adaptive equivalent fuel consumption minimum strategy is as follows:

[0023] s(t+1)=s0+K p (SOC target -SOC(t))+K T (T E -T(t)) (4)

[0024] In the formula, s(t+1) is the value of the equivalent factor at the next moment; s0 is the initial value of the equivalent factor; K p is the adjustment coefficient based on SOC feedback; SOC target is the battery SOC target value; SOC(t) is the battery SOC value at the current moment; K T is the adjustment coefficient based on the power unit temperature feedback; T E is the suitable operating temperature of the diesel engine; T(t) is the temperature of the diesel engine coolant at time t.

[0025] Step 5: Within the boundary constraints, with the goal of minimizing the equivalent fuel consumption of the hybrid system in the entire operating condition under low temperature environment, based on the improved genetic algorithm, the SOC adjustment coefficient K in step 4 is p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat Perform optimization and solve to obtain the optimal SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat.

[0026] The improved genetic algorithm uses a larger crossover probability in the early stage of population iteration and a smaller crossover probability in the later stage of iteration to balance the optimization speed and accuracy of the algorithm. In view of the fact that the population diversity is larger in the early stage of iterative calculation and smaller in the later stage, it is easy to fall into the disadvantages of local optimum and poor convergence quality. The improved genetic algorithm uses a smaller mutation probability in the early stage of iterative calculation and a larger mutation probability in the later stage of iterative calculation. The values ​​of the crossover probability and mutation probability of the improved genetic algorithm are as follows:

[0027]

[0028]

[0029] Where P c is the crossover probability of the population; n is the genetic generation number; n t is the genetic generation corresponding to the crossover probability switching; P v is the mutation probability of the population.

[0030] The objective function of the optimization solution is as follows:

[0031]

[0032] The boundary conditions of the control variables are as follows:

[0033]

[0034] Solve to obtain the optimal SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat .

[0035] Step 6: Optimal SOC adjustment coefficient K obtained based on step 5 p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat , adjust the equivalent factor and diesel engine intake preheating power to achieve the effect of comprehensively considering the battery SOC, power unit temperature and diesel engine intake preheating, thereby improving economy while shortening the power unit temperature rise time.

[0036] Beneficial effects:

[0037] 1. The present invention discloses an energy management method for a diesel-electric hybrid power system in a low-temperature environment. For a battery of a diesel-electric hybrid power system in a low-temperature environment, part of the coolant in a diesel engine cooling system is introduced into a battery cooling system to construct a battery low-temperature preheating circuit. The battery is preheated by the battery low-temperature preheating circuit, thereby making full use of the waste heat of the diesel engine coolant, achieving efficient operation of the thermal management system and effective improvement of the performance of the entire vehicle.

[0038] 2. The present invention discloses an energy management method for a diesel-electric hybrid power system in a low-temperature environment. For a diesel engine in a diesel-electric hybrid power system in a low-temperature environment, when the coolant temperature of the diesel engine does not reach a preset suitable operating temperature, a combination of flame preheating and positive temperature coefficient (PTC) material preheating is used to preheat the intake air of the diesel engine, thereby avoiding long-term heating of the preheat plug during flame preheating and a large amount of energy consumption caused by using only PTC preheating.

[0039] 3. The present invention discloses an energy management method for a diesel-electric hybrid power system in a low-temperature environment. On the basis of an equivalent fuel consumption minimum strategy, the present invention comprehensively considers the battery SOC, the power unit temperature and the diesel engine intake preheating power, constructs an adaptive equivalent fuel consumption minimum strategy, adaptively adjusts the equivalent factors, further optimizes the power distribution of the diesel engine and the battery, and improves the adaptability of the energy management strategy in a low-temperature environment, thereby shortening the power unit temperature rise time and improving fuel economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of a method for managing energy of a diesel-electric hybrid power system in a low temperature environment according to a first embodiment of the present invention;

[0041] Figure 2 is a coupling relationship diagram of a diesel engine cooling system and a battery cooling system according to a first embodiment of the present invention, Figure 2 (a) The battery low temperature preheating circuit is turned on. Figure 2 (b) The battery low temperature preheating circuit is closed;

[0042] Figure 3 is a comparison diagram of system performance before and after preheating of the first embodiment of the present invention;

[0043] Figure 4 is a flow chart of ECMS strategy solution according to the first embodiment of the present invention;

[0044] Figure 5 is a comparison diagram of the coolant temperature change of the power unit of the adaptive ECMS strategy according to the first embodiment of the present invention;

[0045] Figure 6 It is a comparison diagram of the output power changes of the diesel engine and the battery according to the adaptive ECMS strategy of the first embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0047] Embodiment 1:

[0048] like Figure 1 As shown, the present embodiment discloses a method for energy management of a diesel-electric hybrid system under a low temperature environment, and the process is as follows: First, low-temperature preheating measures are respectively constructed for the diesel engine and the battery in the hybrid system. For the battery, part of the coolant in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating circuit; for the diesel engine, the diesel engine intake air is preheated by combining flame preheating and positive temperature coefficient material preheating. Secondly, combining the above two preheating measures, on the basis of the equivalent fuel consumption minimum strategy, an adaptive equivalent fuel consumption minimum strategy is constructed, and the equivalent factor is adaptively adjusted by comprehensively considering the battery charge state, the power unit temperature and the diesel engine intake preheating power, and the relevant parameters of the adaptive equivalent factor are optimized based on the improved genetic algorithm. Finally, under the boundary condition constraints of the working characteristics of the hybrid system, the minimum value of the objective function is obtained according to the minimum principle, and the optimal diesel engine and battery output power is obtained, thereby shortening the power unit temperature rise time and improving fuel economy.

[0049] The specific implementation steps are as follows:

[0050] Step 1: For the battery of the diesel-electric hybrid system in a low-temperature environment, part of the coolant in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating circuit. The battery is preheated through the battery low-temperature preheating circuit until the battery coolant is heated to a preset suitable temperature for the battery to operate.

[0051] When the diesel engine coolant temperature reaches the logic threshold value for opening the battery low temperature preheating circuit, such as Figure 2 As shown in (a), the battery low temperature preheating circuit is turned on, part of the diesel engine coolant flows through the battery cooling system circuit to preheat the battery, the battery cooling water pump is turned off, and the battery cooling water pump bypass valve is opened. The diesel engine cooling water pump provides the power required for the diesel engine and battery coolant circulation. When the diesel engine coolant temperature does not reach the logic threshold value for opening the battery low temperature preheating circuit, or the battery coolant has been heated to the preset suitable temperature for battery operation, such as Figure 2 As shown in (b), the battery low-temperature preheating circuit is closed, the diesel engine coolant does not flow through the battery cooling system circuit, the battery cooling water pump is turned on, the battery cooling water pump bypass valve is closed, and the battery cooling water pump provides the power required for the battery coolant circulation.

[0052] Step 2: For a diesel engine of a diesel-electric hybrid system in a low-temperature environment, when the diesel engine coolant temperature has not reached a preset suitable operating temperature, the diesel engine intake air is preheated using a combination of flame preheating and positive temperature coefficient (PTC) material preheating until the diesel engine coolant temperature reaches a preset suitable operating temperature.

[0053] When the diesel engine coolant temperature has not reached the preset suitable operating temperature, the diesel engine intake air is first preheated using flame preheating, which is powered by the battery and has a fixed working duration. After flame preheating, the diesel engine intake air is preheated using PTC, which is powered by the power battery, until the diesel engine coolant temperature reaches the preset suitable temperature.

[0054] Preferably, flame preheating has lower energy consumption than PTC preheating, but long-term use of the preheat plug of flame preheating will reduce its service life or cause damage, and PTC preheating has higher energy consumption than flame preheating. Therefore, the fixed working time of flame preheating in the warm-up stage is set to 180s to avoid long-term heating of the preheat plug during flame preheating and large energy consumption caused by using only PTC preheating.

[0055] After taking the preheating measures described in step 1 and step 2, the temperature changes of the diesel engine coolant and battery coolant are as follows: Figure 3 As shown in (a), the preheating measures have a significant effect on the power unit coolant temperature. The diesel engine coolant temperature reaches the appropriate temperature in 532s, and the warm-up time increases by 3.3% compared with 515s without preheating. The battery coolant temperature reaches the appropriate temperature in 417s, while the maximum battery temperature without preheating is -6°C, which does not reach the appropriate temperature. Therefore, taking preheating measures can help shorten the temperature rise time of the battery. Figure 3 (b) shows the change in vehicle acceleration performance before and after preheating. It can be seen that after taking preheating measures into account, the vehicle accelerates to the target speed in 354s. Compared with 496s without preheating, the acceleration time is reduced by 28.6%. The preheating measures improve the vehicle's dynamics in low temperature environments.

[0056] Step 3: Based on the equivalent fuel consumption minimization strategy ECMS (Equivalent Consumption Minimization Strategy), the electric energy consumption is converted into fuel consumption through the equivalent factor. Under the constraint of meeting the boundary conditions, the minimum value of the Hamiltonian function is solved to obtain the instantaneous optimal diesel engine and battery output power.

[0057] The solution process of the equivalent fuel consumption minimum strategy is as follows: Figure 4As shown, firstly, the signals of the hybrid powertrain are collected, including battery coolant temperature, diesel engine coolant temperature, battery power, engine power, engine speed, motor speed, battery SOC and other signals. Secondly, the equivalent fuel consumption of the whole vehicle is calculated according to ECMS, and the boundary condition constraints are set according to the working characteristics of the hybrid system. Finally, the Hamiltonian equation is constructed, and the minimum value of the instantaneous equivalent fuel consumption is solved according to the minimum principle to obtain the instantaneous optimal diesel engine and battery output power.

[0058] The equivalent fuel consumption minimum strategy converts the electric energy consumption into fuel consumption through the equivalent factor, and adds it to the actual fuel consumption to get the equivalent fuel consumption. The instantaneous optimal value is solved with the minimum equivalent fuel consumption at a certain moment as the optimization goal, which improves the fuel economy of the whole vehicle while reducing the amount of calculation. The size of the equivalent factor in the equivalent fuel consumption minimum strategy reflects the proportion of the battery energy consumption cost in the total energy consumption cost and affects the energy distribution of the power unit. The equivalent fuel consumption is calculated according to the following formula:

[0059]

[0060] In the formula, is the instantaneous equivalent fuel consumption; u(t) is the control variable; Instantaneous fuel consumption of diesel engine; s(t) is the equivalent factor of converting electric energy consumption into fuel consumption; P bat (u(t),t) is the battery power; Q LHV The fuel has a low calorific value; The fuel consumption converted from the instantaneous electric energy consumption.

[0061] According to the working characteristics of the power unit, the following boundary constraints are met:

[0062]

[0063] Where P dem (t) is the total required power; P e (t) is the diesel engine power; P m (t) is the motor power; n e (t) is the speed of the diesel engine; P e_max (n e (t)) is the maximum power of the diesel engine at this speed; n m (t) is the motor speed; P m_max (n m (t)) is the maximum power of the motor at this speed; n e_min is the minimum speed of the diesel engine; n e_max is the maximum speed of the diesel engine; n m_max is the maximum speed of the motor; SOC min is the lower limit of battery SOC; SOC max is the upper limit of battery SOC; Te is the diesel engine coolant temperature; T e_max is the upper limit of diesel engine coolant temperature; T b is the battery coolant temperature; T b_max is the upper limit of battery coolant temperature; P heat P is the diesel engine intake preheating power; b_max The maximum power of the battery.

[0064] The state variable of the hybrid system is the battery SOC, the control variables are the diesel engine power and the battery power, and the Hamiltonian function is expressed as:

[0065]

[0066] Under the premise of meeting the boundary constraints of the hybrid power system, the minimum value of the Hamiltonian function is solved to obtain the optimal output power of the diesel engine and battery.

[0067] Step 4: Based on step 3, the equivalent factor of the equivalent fuel consumption minimum strategy is adaptively adjusted. Combined with the diesel engine intake preheating in step 2, the battery SOC, power unit temperature and diesel engine intake preheating power are comprehensively considered to construct an adaptive equivalent fuel consumption minimum strategy, further optimize the power distribution of the diesel engine and the battery, and improve the adaptability of the energy management strategy in low temperature environments. The equivalent factor formula of the equivalent fuel consumption minimum strategy includes the SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat .

[0068] The equivalent factor of the adaptive equivalent fuel consumption minimum strategy is as follows:

[0069] s(t+1)=s0+K p (SOC target -SOC(t))+K T (T E -T(t)) (4)

[0070] In the formula, s(t+1) is the value of the equivalent factor at the next moment; s0 is the initial value of the equivalent factor; K p is the adjustment coefficient based on SOC feedback; SOC target is the battery SOC target value; SOC(t) is the battery SOC value at the current moment; K T is the adjustment coefficient based on the power unit temperature feedback; T E is the suitable operating temperature of the diesel engine; T(t) is the temperature of the diesel engine coolant at time t.

[0071] Step 5: Within the boundary constraints, with the goal of minimizing the equivalent fuel consumption of the hybrid system in the entire operating condition under low temperature environment, based on the improved genetic algorithm, the SOC adjustment coefficient K in step 4 is p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat Perform optimization and solve to obtain the optimal SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat .

[0072] The improved genetic algorithm uses a larger crossover probability in the early stage of population iteration and a smaller crossover probability in the later stage of iteration to balance the optimization speed and accuracy of the algorithm. In view of the fact that the population diversity is larger in the early stage of iterative calculation and smaller in the later stage, it is easy to fall into the disadvantages of local optimum and poor convergence quality. The improved genetic algorithm uses a smaller mutation probability in the early stage of iterative calculation and a larger mutation probability in the later stage of iterative calculation. The values ​​of the crossover probability and mutation probability of the improved genetic algorithm are as follows:

[0073]

[0074]

[0075] Where P c is the crossover probability of the population; n is the genetic generation number; n t is the genetic generation corresponding to the crossover probability switching; P v is the mutation probability of the population.

[0076] The objective function of the optimization solution is as follows:

[0077]

[0078] The boundary conditions of the control variables are as follows:

[0079]

[0080] Solve to obtain the optimal SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat .

[0081] Step 6: Optimal SOC adjustment coefficient K obtained based on step 5 p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat, the equivalent factor and the diesel engine intake preheating power are adjusted to achieve the effect of comprehensively considering the battery SOC, power unit temperature and diesel engine intake preheating, while shortening the power unit temperature rise time and having better economy.

[0082] like Figure 5 As shown in the figure, under the adaptive ECMS strategy, the temperature rise rates of the power unit coolant temperature, diesel engine coolant temperature and battery coolant temperature are faster than those of the ECMS strategy. The battery preheating time and diesel engine warm-up time are reduced by 40.9% and 37.8% respectively. This is because the adaptive ECMS strategy has both the equivalent factor adjustment of temperature feedback and the diesel engine intake preheating, which greatly shortens the diesel engine warm-up time. Due to the existence of the battery preheating circuit, the battery preheating time is also shortened accordingly, which effectively accelerates the temperature rise rate of the power unit.

[0083] like Figure 6 As shown in the figure, in the early stage of driving condition, due to the low temperature of the power unit, the equivalent factor based on temperature feedback is high in the early stage of driving condition, and the diesel engine bears more output power. In the later stage of driving condition, the temperature of the power unit coolant gradually rises, the equivalent factor adjustment effect of temperature feedback weakens, and the equivalent factor adjustment effect of battery SOC feedback gradually increases. The power distribution of the diesel engine and the battery also changes accordingly with the change of the equivalent factor.

[0084] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for energy management of a diesel-electric hybrid power system in a low temperature environment, characterized in that: The following steps are included: Step 1: For the battery of the diesel-electric hybrid system in a low-temperature environment, part of the coolant in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating circuit, and the battery is preheated through the battery low-temperature preheating circuit until the battery coolant is heated to a preset suitable temperature for the battery to work; Step 2: For a diesel engine of a diesel-electric hybrid system in a low temperature environment, when the diesel engine coolant temperature does not reach a preset suitable working temperature, the intake air of the diesel engine is preheated by combining flame preheating and positive temperature coefficient PTC material preheating until the diesel engine coolant temperature reaches a preset suitable working temperature; Step 3: Based on the equivalent fuel consumption minimum strategy ECMS, the electric energy consumption is converted into fuel consumption through the equivalent factor. Under the constraint of satisfying the boundary conditions, the minimum value of the Hamiltonian function is solved to obtain the instantaneous optimal diesel engine and battery output power; Step 4: Based on step 3, the equivalent factor of the equivalent fuel consumption minimum strategy is adaptively adjusted. Combined with the diesel engine intake preheating in step 2, the battery SOC, power unit temperature and diesel engine intake preheating power are comprehensively considered to construct an adaptive equivalent fuel consumption minimum strategy, further optimize the power distribution of the diesel engine and the battery, and improve the adaptability of the energy management strategy in a low temperature environment; the equivalent factor formula of the equivalent fuel consumption minimum strategy includes the SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat ; Step 5: Within the boundary constraints, with the goal of minimizing the equivalent fuel consumption of the hybrid system in the entire operating condition under low temperature environment, based on the improved genetic algorithm, the SOC adjustment coefficient K in step 4 is p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat Perform optimization and solve to obtain the optimal SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat ; Step 6: Optimal SOC adjustment coefficient K obtained based on step 5 p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat , adjust the equivalent factor and diesel engine intake preheating power to achieve the effect of comprehensively considering the battery SOC, power unit temperature and diesel engine intake preheating, thereby improving economy while shortening the power unit temperature rise time.

2. The method for energy management of a diesel-electric hybrid power system in a low temperature environment as claimed in claim 1, characterized in that: The implementation method of step one is: When the diesel engine coolant temperature reaches the logic threshold value for opening the battery low-temperature preheating circuit, the battery low-temperature preheating circuit is opened, and part of the diesel engine coolant flows through the battery cooling system circuit to preheat the battery, the battery cooling water pump is closed, and the battery cooling water pump bypass valve is opened, and the diesel engine cooling water pump provides the power required for the diesel engine and battery coolant circulation; when the diesel engine coolant temperature does not reach the logic threshold value for opening the battery low-temperature preheating circuit, or the battery coolant has been heated to the preset suitable temperature for the battery to work, the battery low-temperature preheating circuit is closed, the diesel engine coolant does not flow through the battery cooling system circuit, the battery cooling water pump is opened, the battery cooling water pump bypass valve is closed, and the battery cooling water pump provides the power required for the battery coolant circulation.

3. The method for energy management of a diesel-electric hybrid power system in a low temperature environment as claimed in claim 2, characterized in that: In step 2, When the diesel engine coolant temperature has not reached the preset suitable operating temperature, the diesel engine intake air is first preheated using flame preheating, which is powered by the battery and has a fixed working duration. After flame preheating, the diesel engine intake air is preheated using PTC, which is powered by the power battery, until the diesel engine coolant temperature reaches the preset suitable temperature.

4. The method for energy management of a diesel-electric hybrid power system in a low temperature environment as claimed in claim 3, characterized in that: The implementation method of step three is: The equivalent fuel consumption minimum strategy converts the electric energy consumption into fuel consumption through the equivalent factor, and adds it to the actual fuel consumption to obtain the equivalent fuel consumption. The instantaneous optimal value is solved with the minimum equivalent fuel consumption at a certain moment as the optimization goal, which reduces the amount of calculation and improves the fuel economy of the whole vehicle. The size of the equivalent factor in the equivalent fuel consumption minimum strategy reflects the proportion of the battery energy consumption cost in the total energy consumption cost and affects the energy distribution of the power unit. The equivalent fuel consumption is calculated according to the following formula: In the formula, is the instantaneous equivalent fuel consumption; u(t) is the control variable; Instantaneous fuel consumption of diesel engine; s(t) is the equivalent factor of converting electric energy consumption into fuel consumption; P bat (u(t),t) is the battery power; Q LHV The fuel has a low calorific value; The fuel consumption converted from the instantaneous electric energy consumption; According to the working characteristics of the power unit, the following boundary constraints are met: Where P dem (t) is the total required power; P e (t) is the diesel engine power; P m (t) is the motor power; n e (t) is the speed of the diesel engine; P e_max (n e (t)) is the maximum power of the diesel engine at this speed; n m (t) is the motor speed; P m_max (n m (t)) is the maximum power of the motor at this speed; n e_min is the minimum speed of the diesel engine; n e_max is the maximum speed of the diesel engine; n m_max is the maximum speed of the motor; SOC min is the lower limit of battery SOC; SOC max is the upper limit of battery SOC; T e is the diesel engine coolant temperature; T e_max T is the upper limit of diesel engine coolant temperature; b is the battery coolant temperature; T b_max is the upper limit of battery coolant temperature; P heat P is the diesel engine intake preheating power; b_max is the maximum power of the battery; The state variable of the hybrid system is the battery SOC, the control variables are the diesel engine power and the battery power, and the Hamiltonian function is expressed as: Under the premise of satisfying the boundary conditions of the hybrid system, the minimum value of the Hamiltonian function is solved to obtain the optimal output power of the diesel engine and battery.

5. The method for energy management of a diesel-electric hybrid power system in a low temperature environment as claimed in claim 4, characterized in that: In step four, The equivalent factor of the adaptive equivalent fuel consumption minimum strategy is as follows: s(t+1)=s0+K p (SOC target -SOC(t))+K T (T E -T(t)) (4) In the formula, s(t+1) is the value of the equivalent factor at the next moment; s0 is the initial value of the equivalent factor; K p is the adjustment coefficient based on SOC feedback; SOC target is the battery SOC target value; SOC (t) is the battery SOC value at the current moment; K T is the adjustment coefficient based on the power unit temperature feedback; T E is the suitable operating temperature of the diesel engine; T(t) is the temperature of the diesel engine coolant at time t.

6. The method for energy management of a diesel-electric hybrid power system in a low temperature environment as claimed in claim 5, characterized in that: The implementation method of step five is: The improved genetic algorithm uses a smaller mutation probability in the early stage of iterative calculation and a larger mutation probability in the later stage of iterative calculation; the values ​​of the crossover probability and mutation probability of the improved genetic algorithm are as follows: Where P c is the crossover probability of the population; n is the genetic generation number; n t is the genetic generation corresponding to the crossover probability switching; P v is the mutation probability of the population; The objective function of the optimization solution is as follows: The boundary conditions of the control variables are as follows: Solve to obtain the optimal SOC adjustment coefficient K p , Power unit temperature adjustment coefficient K T And intake air preheating power P heat .

7. A method for managing energy of a diesel-electric hybrid power system in a low temperature environment as claimed in claim 3, 4, 5 or 6, characterized in that: Set the fixed working time of flame preheating in the warm-up phase to 180s.

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