A method for energy management of a diesel-electric hybrid power system in a low temperature environment

Abstract

The application discloses a low-temperature environment diesel-electric hybrid power system energy management method, and belongs to the field of hybrid power system energy management. The application realizes the method as follows: for the battery, part of the cooling liquid in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating loop, the battery is preheated through the battery low-temperature preheating loop, and the waste heat of the diesel engine cooling liquid is fully utilized. For the diesel engine, when the temperature of the diesel engine cooling liquid does not reach a preset suitable working temperature, the intake air of the diesel engine is preheated in a form combining flame preheating and positive temperature coefficient material preheating. In combination with the above two preheating measures, on the basis of the minimum equivalent fuel consumption strategy, an adaptive minimum equivalent fuel consumption strategy is constructed, the state of charge of the battery, the temperature of the power unit and the intake air preheating power of the diesel engine are comprehensively considered to adaptively adjust the equivalent factor, and related parameters of the adaptive equivalent factor are optimized based on an improved genetic algorithm, so that the temperature rising time of the power unit is shortened and the fuel economy is improved.

Description

TECHNICAL FIELD

[0001] The application relates to a diesel-electric hybrid power system energy management method under a low-temperature environment and belongs to the field of hybrid power system energy management. BACKGROUND

[0002] As an important subsystem of a hybrid electric vehicle, a thermal management system can absorb heat generated by a power unit, gradually increase the temperature of coolant, and maintain the power unit to work at an appropriate temperature through heat dissipation. The working performance of a vehicle power system is obviously affected by temperature, and the pros and cons of the operation of the thermal management system have an impact on the power performance and economy of the vehicle. An energy management strategy can make the power unit be at an optimal working point by reasonably allocating demand power. However, under a low-temperature environment, the power unit is in a low-temperature and low-efficiency state before being completely preheated, and it is necessary to add a preheating measure to the power unit and consider the temperature factor in the energy management strategy, so as to accelerate the temperature rising speed of the power unit and further improve the performance including power output and energy consumption, and improve the performance of the whole vehicle. Therefore, it is of great significance to design different preheating schemes for different power units under a low-temperature environment, and to consider the performance of the power unit thermal management system and the preheating scheme in the energy management strategy and optimize the power performance and economy targets. SUMMARY

[0003] The application aims to provide a diesel-electric hybrid power system energy management method under a low-temperature environment. For a battery, 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. For a diesel engine, when the temperature of the diesel engine coolant does not reach a preset appropriate working temperature, the intake air of the diesel engine is preheated by using a combination of flame preheating and positive temperature coefficient material preheating. On the basis of the minimum equivalent fuel consumption strategy, an adaptive minimum equivalent fuel consumption strategy is constructed by combining the above two preheating measures, the state of charge of the battery, the temperature of the power unit and the preheating power of the diesel engine intake air are comprehensively considered to adaptively adjust the equivalent factor, and the related parameters of the adaptive equivalent factor are optimized based on an improved genetic algorithm, so as to shorten the temperature rising time of the power unit and improve the fuel economy.

[0004] The application aims to achieve the above-mentioned purpose by the following technical scheme.

[0005] The application discloses a diesel-electric hybrid power system energy management method under a low-temperature environment, which comprises the following steps.

[0006] Step one, for the battery of the diesel-electric hybrid power system under 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, and the battery coolant is heated until the battery works at a preset appropriate temperature.

[0007] When the diesel engine coolant temperature reaches the logical threshold value of the battery low temperature preheating circuit opening, the battery low temperature preheating circuit is opened, the diesel engine part of the 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 and battery coolant circulation power is provided by the diesel engine cooling water pump. When the diesel engine coolant temperature does not reach the logical threshold value of the battery low temperature preheating circuit opening, or the battery coolant has warmed up to the preset suitable temperature for battery operation, 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 coolant circulation power is provided by the battery cooling water pump.

[0008] Step two, for the diesel engine of the diesel-electric hybrid system in a low temperature environment, when the diesel engine coolant temperature does not reach the preset suitable working temperature, the intake air of the diesel engine is preheated using a combination of flame preheating and positive temperature coefficient (PTC) material preheating until the diesel engine coolant temperature reaches the preset suitable working temperature.

[0009] When the diesel engine coolant temperature does not reach the preset suitable working temperature, the intake air of the diesel engine is first preheated using flame preheating, the flame preheating is powered by the battery, and the flame preheating has a fixed working time, after the flame preheating, the intake air of the diesel engine is preheated using PTC, the PTC preheating is powered by the power battery, until the diesel engine coolant temperature reaches the preset suitable temperature.

[0010] As a preferred embodiment, the energy consumption of flame preheating is lower than that of PTC preheating, but the long-term use of the preheating plug in flame preheating can lead to reduced service life or damage, while the energy consumption of PTC preheating is higher than that of 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 preheating plug in flame preheating and the large amount of energy consumption brought by only using PTC preheating.

[0011] Step three, based on the equivalent fuel consumption minimization strategy (ECMS), the electric energy consumption is converted into fuel consumption through an equivalent factor, the minimum value of the Hamilton function is solved under the constraint of meeting the boundary condition, and the instantaneous optimal diesel engine and battery output power is obtained.

[0012] The equivalent fuel consumption minimum strategy converts the electric energy consumption into fuel consumption by equivalent factor and adds it to the actual fuel consumption to get the equivalent fuel consumption. The instantaneous optimal value is solved by taking the minimum equivalent fuel consumption at a certain moment, which reduces the calculation amount and improves the fuel economy of the 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:

[0013]

[0014] In the formula, is the instantaneous equivalent fuel consumption; u(t) is the control variable; is the instantaneous fuel consumption of the diesel engine; s(t) is the equivalent factor of the electric energy consumption converted into fuel consumption; P bat (u(t),t) is the battery power; Q LHV is the low heat value of fuel; is 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] In the formula, P dem (t) is the total demand power; P e (t) is the diesel engine power; P m (t) is the motor power; n e (t) is the diesel engine speed; 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 value of the battery SOC; SOC max is the upper limit value of the battery SOC; T e is the diesel engine coolant temperature; T e max is the upper limit value of the diesel engine coolant temperature; T b is the battery coolant temperature; T b max is the upper limit value of the battery coolant temperature; P heat is the preheating power of the diesel engine intake air; P b_max is 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 Hamilton function is expressed as:

[0019]

[0020] The minimum value of the Hamilton function is solved to obtain the optimal diesel engine and battery output power under the premise of satisfying the boundary constraints of the hybrid system.

[0021] Step four: based on the equivalent factor of the equivalent fuel consumption minimum strategy in step three, the equivalent factor is adaptively adjusted, combined with the diesel engine intake preheating in step two, the battery SOC, the power unit temperature and the diesel engine intake preheating power are comprehensively considered, and an adaptive equivalent fuel consumption minimum strategy is constructed to further optimize the power distribution of the diesel engine and the battery and improve the adaptability of the energy management strategy in low temperature environment. The equivalent factor formula of the equivalent fuel consumption minimum strategy includes the SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake 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 time; 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 value of the battery SOC at the current time; K T is the adjustment coefficient based on power unit temperature feedback; T E is the appropriate working temperature of the diesel engine; and T(t) is the temperature of the diesel engine coolant at time t.

[0025] Step five: within the boundary constraint range, the minimum equivalent fuel consumption of the hybrid system in the whole operating condition under low temperature environment is taken as the target, and based on the improved genetic algorithm, the SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heat in step four are optimized and solved to obtain the optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heat.

[0026] The improved genetic algorithm uses a larger crossover probability before the population iteration, and a smaller crossover probability in the later iteration, so as to balance the optimization speed and accuracy of the algorithm. Since the population diversity is large at the beginning of the iteration calculation and small at the later stage, it is easy to fall into local optimum and poor convergence quality. Therefore, the improved genetic algorithm uses a smaller mutation probability at the beginning of the iteration calculation, and a larger mutation probability at the later stage. The values of the crossover probability and the mutation probability of the improved genetic algorithm are as follows:

[0027]

[0028]

[0029] In the formula, P c is the crossover probability of the population; n is the genetic generation number; n t is the corresponding genetic generation number of 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] The optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T , and the intake preheating power P heat are obtained.

[0035] Step six: based on the optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T , and the intake preheating power P heat obtained in step five, the equivalent factor and the diesel engine intake preheating power are adjusted, so as to achieve the effect of comprehensively considering the battery SOC, the power unit temperature and the diesel engine intake preheating, shorten the power unit temperature rise time and improve the economy.

[0036] Beneficial effects:

[0037] 1. The application discloses a low-temperature environment diesel-electric hybrid power system energy management method, for the battery of the low-temperature environment diesel-electric hybrid power system, part of the cooling liquid in the diesel engine cooling system is introduced into the battery cooling system to construct a battery low-temperature preheating loop, and the battery is preheated through the battery low-temperature preheating loop, so that the waste heat of the diesel engine cooling liquid is fully utilized, and efficient operation of the thermal management system and effective improvement of the vehicle performance are realized.

[0038] 2. The application discloses a low-temperature environment diesel-electric hybrid power system energy management method, for the diesel engine of the low-temperature environment diesel-electric hybrid power system, when the temperature of the diesel engine cooling liquid does not reach a preset suitable working temperature, the diesel engine intake is preheated in a form combining flame preheating and positive temperature coefficient (PTC) material preheating, so that long-time heating of the preheating plug in the flame preheating and a large amount of energy consumption caused by only using PTC preheating are avoided.

[0039] 3. The application discloses a low-temperature environment diesel-electric hybrid power system energy management method, on the basis of the minimum equivalent fuel consumption strategy, the battery SOC, the power unit temperature and the diesel engine intake preheating power are comprehensively considered to construct a self-adaptive minimum equivalent fuel consumption strategy, the equivalent factor is adaptively adjusted, the power distribution of the diesel engine and the battery is further optimized, the adaptability of the energy management strategy in the low-temperature environment is improved, so that the power unit temperature rise time is shortened and the fuel economy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a low-temperature environment diesel-electric hybrid power system energy management method flow chart of the first embodiment of the application,

[0041] Figure 2 It is a coupling relationship diagram of the diesel engine cooling system and the battery cooling system of the first embodiment of the application, Figure 2 (a) is the opening of the battery low-temperature preheating loop, Figure 2 (b) is the closing of the battery low-temperature preheating loop;

[0042] Figure 3 It is a system performance comparison chart before and after preheating of the first embodiment of the application;

[0043] Figure 4 It is an ECMS strategy solving flow chart of the first embodiment of the application;

[0044] Figure 5 It is a power unit cooling liquid temperature change comparison chart of the adaptive ECMS strategy of the first embodiment of the application;

[0045] Figure 6 It is a diesel engine and battery output power change comparison chart of the adaptive ECMS strategy of the first embodiment of the application. DETAILED DESCRIPTION

[0046] To better illustrate the purpose and advantages of the present application, the summary will be further described below in conjunction with the drawings and examples.

[0047] Example 1:

[0048] As Figure 1 shown, the low-temperature environment diesel-electric hybrid power system energy management method disclosed in this embodiment has the following process: first, for the diesel engine and the battery in the hybrid power system, low-temperature preheating measures are respectively constructed. For the battery, part of the cooling liquid 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 is preheated in the form of combination of flame preheating and positive temperature coefficient material preheating. Secondly, on the basis of the minimum equivalent fuel consumption strategy, an adaptive minimum equivalent fuel consumption strategy is constructed in combination with the above two preheating measures, the state of charge of the battery, the temperature of the power unit and the diesel engine intake preheating power are comprehensively considered to adaptively adjust the equivalent factor, and the related 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 power system, the minimum value of the objective function is obtained according to the minimum value principle, and the optimal diesel engine and battery output power is obtained, so as to shorten the power unit temperature rise time and improve the fuel economy.

[0049] The specific implementation steps are as follows:

[0050] Step one, for the battery of the diesel-electric hybrid power system in low-temperature environment, part of the cooling liquid 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, and the battery cooling liquid is heated to the preset suitable temperature for the battery to work.

[0051] When the diesel engine cooling liquid temperature reaches the logical threshold value for opening the battery low-temperature preheating circuit, as Figure 2 (a) shown, the battery low-temperature preheating circuit is opened, part of the cooling liquid of the diesel engine 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 circulation of the diesel engine and battery cooling liquid. When the diesel engine cooling liquid temperature does not reach the logical threshold value for opening the battery low-temperature preheating circuit, or the battery cooling liquid has been heated to the preset suitable temperature for the battery to work, as Figure 2 (b) shown, the battery low-temperature preheating circuit is closed, the diesel engine cooling liquid does not flow through the battery cooling system circuit, the battery cooling water pump is opened, and the battery cooling water pump bypass valve is closed, and the battery cooling water pump provides the power required for the circulation of the battery cooling liquid.

[0052] Step two, for the diesel engine of the diesel-electric hybrid system in low temperature environment, when the diesel engine coolant temperature does not reach the preset suitable working temperature, the intake air of the diesel engine is preheated by using the combination of flame preheating and PTC (positive temperature coefficient) material preheating until the diesel engine coolant temperature reaches the preset suitable working temperature.

[0053] When the diesel engine coolant temperature does not reach the preset suitable working temperature, the intake air of the diesel engine is preheated by using the flame preheating first, the flame preheating is powered by the battery, and the flame preheating has a fixed working time, and then the intake air of the diesel engine is preheated by using the PTC, the PTC preheating is powered by the power battery, until the diesel engine coolant temperature reaches the preset suitable temperature.

[0054] As preferred, the energy consumption of the flame preheating is lower than that of the PTC preheating, but the preheating plug of the flame preheating will be damaged or have a reduced service life after a long time of use, and the energy consumption of the PTC preheating is higher than that of the flame preheating, therefore, the fixed working time of the flame preheating in the warm-up stage is set to 180s to avoid the long time heating of the preheating plug in the flame preheating and the large energy consumption caused by using only the PTC preheating.

[0055] After taking the preheating measures described in steps one and two, the temperature changes of the diesel engine coolant and the battery coolant are as shown in Figure 3 (a), the preheating measures have a significant effect on the temperature of the power unit coolant, the diesel engine coolant temperature reaches the suitable temperature at 532s, compared with 515s without preheating, the warm-up time is increased by 3.3%, and the battery coolant temperature reaches the suitable temperature at 417s, while the battery temperature is maximum of -6℃ without preheating, which does not reach the suitable temperature, therefore, taking the preheating measures helps to shorten the temperature rise time of the battery. Figure 3 (b) is the change of the vehicle acceleration performance before and after the preheating, it can be seen that after considering the preheating measures, the vehicle accelerates to the target speed at 354s, compared with 496s without preheating, the acceleration time is reduced by 28.6%, and the preheating measures improve the power performance of the vehicle in low temperature environment.

[0056] Step three, based on the ECMS (Equivalent Consumption Minimization Strategy), the electric energy consumption is converted into fuel consumption by using the equivalent factor, the minimum value of the Hamilton function is solved under the constraint of meeting the boundary condition, and the instantaneous optimal diesel engine and battery output power is obtained.

[0057] The solving process of the ECMS is as shown in Figure 4As shown, first, the signals of the hybrid power assembly are collected, including battery coolant temperature, diesel engine coolant temperature, battery power, engine power, engine speed, motor speed, battery SOC, etc. Secondly, the equivalent fuel consumption of the vehicle is calculated according to ECMS, and the boundary condition constraints are set according to the working characteristics of the hybrid power system. Finally, the Hamilton equation is constructed, and the minimum value of the instantaneous equivalent fuel consumption is solved according to the minimum value 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 an equivalent factor, adds it to the actual fuel consumption to obtain the equivalent fuel consumption, and solves the instantaneous optimal value with the optimization goal of minimum equivalent fuel consumption at a certain moment, thereby reducing the calculation amount and improving the fuel economy of the 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:

[0059]

[0060] In the formula, is the instantaneous equivalent fuel consumption; u(t) is the control variable; is the instantaneous diesel engine fuel consumption; s(t) is the equivalent factor for converting electric energy consumption into fuel consumption; P bat (u(t),t) is the battery power; Q LHV is the low heat value of fuel; is 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] In the formula, P dem (t) is the total demand power; P e (t) is the diesel engine power; P m (t) is the motor power; n e (t) is the diesel engine speed; 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 diesel engine speed; n e_max is the maximum diesel engine speed; n m_max is the maximum motor speed; SOC min is the lower limit of the battery SOC; SOC max is the upper limit of the battery SOC; Te T is the temperature of the diesel engine coolant; T e_max T is the upper limit of the temperature of the diesel engine coolant; T b T is the temperature of the battery coolant; T b_max T is the upper limit of the temperature of the battery coolant; T heat P is the preheating power of the diesel engine intake air; P b_max P is the maximum power of the battery.

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

[0065]

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

[0067] Step four: based on the adaptive adjustment of the equivalent factor of the equivalent minimum fuel consumption strategy in step three, combined with the diesel engine intake air preheating in step two, the battery SOC, the power unit temperature and the diesel engine intake air preheating power are comprehensively considered to construct an adaptive equivalent minimum fuel consumption 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 environment. The equivalent factor formula of the equivalent minimum fuel consumption strategy includes the SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake air preheating power P heat .

[0068] The equivalent factor of the adaptive equivalent minimum fuel consumption 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 time; s0 is the initial value of the equivalent factor; K p is the adjustment coefficient based on SOC feedback; SOC target is the target value of the battery SOC; SOC(t) is the value of the battery SOC at the current time; K T is the adjustment coefficient based on power unit temperature feedback; T E is the appropriate working temperature of the diesel engine; T(t) is the temperature of the diesel engine coolant at time t.

[0071] Step five, in the boundary constraint range, with the minimum equivalent fuel consumption of the hybrid power system in the whole operating condition as the target, based on the improved genetic algorithm, the SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heat are solved and optimized to obtain the optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake 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 larger population diversity in the early stage of iteration and the smaller population diversity in the later stage of iteration, the improved genetic algorithm uses a smaller mutation probability in the early stage of iteration and a larger mutation probability in the later stage of iteration to avoid falling into local optimum and poor convergence quality. The values of the crossover probability and the mutation probability of the improved genetic algorithm are as follows:

[0073]

[0074]

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

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

[0077]

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

[0079]

[0080] The optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heat are obtained.

[0081] Step six: based on the optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heatAdjust the equivalent factor and the diesel engine intake preheating power to achieve the effect of comprehensively considering the battery SOC, power unit temperature and diesel engine intake preheating, shorten the power unit temperature rise time and have better economy.

[0082] As shown in Figure 5 The temperature rise speed of the diesel engine coolant temperature and the battery coolant temperature under the adaptive ECMS strategy is faster than that under the ECMS strategy, the battery preheating time and the diesel engine warm-up time are reduced by 40.9% and 37.8% respectively, because the adaptive ECMS strategy has the equivalent factor adjustment of temperature feedback and considers the diesel engine intake preheating, so that the diesel engine warm-up time is greatly shortened, and due to the existence of the battery preheating circuit, the battery preheating time is also shortened, which effectively accelerates the temperature rise speed of the power unit.

[0083] As shown in Figure 6 At the initial stage of the driving cycle, the equivalent factor based on temperature feedback is high at the initial stage of the driving cycle because the power unit temperature is low, and the diesel engine bears more output power. In the later stage of the driving cycle, the power unit coolant temperature gradually rises, the temperature feedback equivalent factor adjustment effect is weakened, and the battery SOC feedback equivalent factor adjustment effect is gradually enhanced, and the power distribution of the diesel engine and the battery also changes accordingly with the change of the equivalent factor.

[0084] The above specific description further details the purpose, technical scheme and beneficial effects of the application. It should be understood that the above description is only a specific embodiment of the application and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A method for energy management of a diesel-electric hybrid system in a cryogenic environment, the method comprising: The method comprises the following steps, Step one, for the battery of the diesel-electric hybrid system in a low temperature environment, part of the cooling liquid 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 cooling liquid is heated to a preset suitable temperature for the battery to work; Step two, for the diesel engine of the diesel-electric hybrid system in a low temperature environment, when the temperature of the diesel engine cooling liquid does not reach a preset suitable working temperature, the intake air of the diesel engine is preheated in a combination of flame preheating and positive temperature coefficient (PTC) material preheating until the temperature of the diesel engine cooling liquid reaches the preset suitable working temperature; Step three, based on the equivalent fuel consumption minimum strategy (ECMS), the electric energy consumption is converted into fuel consumption through an equivalent factor, the minimum value of the Hamilton function is solved under the constraint of meeting the boundary condition to obtain the instantaneous optimal diesel engine and battery output power; Step four: based on the adaptive adjustment of the equivalent factor of the equivalent fuel consumption minimum strategy in step three, combined with the diesel engine intake preheating in step two, considering the battery SOC, power unit temperature and diesel engine intake preheating power, an adaptive equivalent fuel consumption minimum strategy is constructed to further optimize the power distribution of the diesel engine and the battery and improve the adaptability of the energy management strategy in low temperature environment; the equivalent factor formula of the equivalent fuel consumption minimum strategy includes SOC adjustment coefficient K p , power unit temperature adjustment coefficient K T and intake preheating power P heat ; Step five, in the boundary constraint range, taking the minimum equivalent fuel consumption of the hybrid power system in the whole operating condition under low temperature environment as the target, based on the improved genetic algorithm, the SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heat in step four are solved and optimized, and the optimal SOC adjustment coefficient K p , the power unit temperature adjustment coefficient K T and the intake preheating power P heat are obtained; Step six: based on the optimal SOC adjustment coefficient K obtained in step five p , power unit temperature adjustment coefficient K T and intake 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 improving the economy.

2. The energy management method for a diesel-electric hybrid power system in a cryogenic environment as claimed in claim 1, wherein: The implementation method of step one is that When the temperature of the diesel engine cooling liquid reaches the logical threshold value for opening the battery low temperature preheating circuit, the battery low temperature preheating circuit is opened, part of the cooling liquid of the diesel engine 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 circulation of the diesel engine and battery cooling liquid; when the temperature of the diesel engine cooling liquid does not reach the logical threshold value for opening the battery low temperature preheating circuit, or the battery cooling liquid has been heated to the preset suitable temperature for the battery to work, the battery low temperature preheating circuit is closed, the diesel engine cooling liquid 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 circulation of the battery cooling liquid.

3. The method of claim 2, wherein: In step two, When the temperature of the diesel engine cooling liquid does not reach the preset suitable working temperature, the intake air of the diesel engine is first preheated by flame preheating, the flame preheating is powered by a storage battery, and the flame preheating has a fixed working time; after the flame preheating, the intake air of the diesel engine is preheated by PTC, the PTC preheating is powered by a power battery, until the temperature of the diesel engine cooling liquid reaches the preset suitable temperature.

4. The energy management method for a diesel-electric hybrid power system in a cryogenic environment according to claim 3, wherein: The implementation method of step three is that The equivalent fuel consumption minimum strategy converts the electric energy consumption into fuel consumption through an equivalent factor, and adds the actual fuel consumption to obtain the equivalent fuel consumption, so as to solve the instantaneous optimal value with the optimization target of minimizing the equivalent fuel consumption at a certain moment, thereby reducing the calculation amount and improving the fuel economy of the 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: wherein is the instantaneous equivalent fuel consumption; u(t) is the control variable; is the diesel instantaneous fuel consumption; s(t) is the equivalent factor of the electric energy consumption converted into fuel consumption; P bat (u(t),t) is the battery power; Q LHV is the fuel lower heating value; is the instantaneous 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 demand power; P e (t) is the diesel engine power; P m (t) is the electric motor power; n e (t) is the diesel engine speed; P e_max (n e (t)) is the maximum power of the diesel engine at this speed; n m (t) is the electric motor speed; P m_max (n m (t)) is the maximum power of the electric motor at this speed; n e_min is the minimum diesel engine speed; n e_max is the maximum diesel engine speed; n m_max is the maximum electric motor speed; SOC min is the lower limit value of the battery SOC; SOC max is the upper limit value of the battery SOC; T e is the diesel engine coolant temperature; T e_max is the upper limit value of the diesel engine coolant temperature; T b is the battery coolant temperature; T b_max is the upper limit value of the battery coolant temperature; P heat is the diesel engine intake air preheating power; P b_max is the maximum battery power; The state variable of the hybrid power system is the battery SOC, the control variable is the diesel engine power and the battery power, and the Hamilton function is expressed as: Under the premise of meeting the boundary condition constraints of the hybrid power system, the minimum value of the Hamilton function is solved to obtain the optimal diesel engine and battery output power.

5. The method of claim 4, wherein: 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 time; s0 is the initial value of the equivalent factor; K p is the adjustment coefficient based on SOC feedback; SOC target is the target value of the battery SOC; SOC (t) is the value of the battery SOC at the current time; K T is the adjustment coefficient based on the temperature feedback of the power unit; T E is the suitable working temperature of the diesel engine; T(t) is the temperature of the diesel engine coolant at time t.

6. The method of claim 5, wherein: The implementation method of step five is that The improved genetic algorithm uses smaller mutation probability in the initial iteration calculation and larger mutation probability in the later iteration calculation; the values of the crossover probability and the mutation probability of the improved genetic algorithm are as follows: In the formula, P c is the crossover probability of the population; n is the genetic generation; n t is the genetic generation corresponding to the crossover probability switching time; 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: Solving the optimal SOC adjustment coefficient K p , power unit temperature adjustment coefficient K T and intake preheating power P heat .

7. The method of claim 3, 4, 5 or 6, wherein: The fixed working time of the flame preheating in the warm-up stage is set to 180 s.

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