An energy management control method for range-extended electric vehicles based on energy prediction

Abstract

The present invention discloses an energy management control method for a range-extended electric vehicle based on energy prediction. When the electric vehicle starts, road information for the trip is first obtained through the electric vehicle navigation system. By coordinating control method 1 and control method 2 of the range extender, control method 1 can ensure that the battery power of the electric vehicle always remains above the lower limit value during driving. Before the electric vehicle enters the urban road, the power battery is pre-charged through control method 2 to ensure that the power of the power battery can meet the requirements of the remaining urban road, so that the electric vehicle can rely entirely on the power battery to provide energy for driving on the urban road, thereby further improving the fuel economy of the vehicle.

Description

Technical Field

[0001] The present invention belongs to the field of new energy electric vehicles, and particularly relates to an energy management control method for a range-extended electric vehicle. Background Art

[0002] With the continuous aggravation of global environmental problems and energy crises, and the proposal of the "carbon neutrality" and "carbon peak" policies, it has become extremely urgent to vigorously develop new energy electric vehicles. In view of a series of problems of current pure electric vehicles, such as short battery life, short cruising range, and long charging time, range-extended electric vehicles can fully combine the advantages of both. Therefore, vigorously promoting and researching range-extended electric vehicles has become a hot topic in the current research field of new energy electric vehicles.

[0003] As a hybrid vehicle model, the basic structure of a range-extended electric vehicle is a unique series hybrid electric vehicle. Its power system consists of a range extender (engine and generator), a power battery, a drive motor, a main reducer, a differential, etc., and the energy management method has an important impact on the power performance and economy of the whole range-extended electric vehicle. Therefore, in engineering practice, it is necessary to set a reasonable energy management method to maximize the economy of the whole vehicle on the premise of meeting the power performance of the whole vehicle.

[0004] The energy management methods of range-extended electric vehicles can generally be divided into rule-based and optimization control-based methods. Since the rule-based energy management method is simple and easy to implement in engineering applications, most of the research is carried out based on the rule-based energy management method. However, there is a problem with the existing rule-based energy management method, that is, the range extender works in the high-efficiency fuel consumption area on highways, but once the electric vehicle enters urban roads with large speed changes, it will cause the range extender to no longer work in the high-efficiency fuel consumption area of the engine, resulting in increased fuel consumption, decreased charging efficiency, and decreased economic performance of the whole vehicle. If the electric vehicle can be powered entirely by the power battery after entering urban roads after the highway section, and the range extender does not work, the above problems can be solved and the economic performance of the electric vehicle can be improved. Therefore, the present invention proposes an energy management control method for a range-extended electric vehicle based on energy prediction, which pre-estimates the energy required by the electric vehicle in the upcoming urban roads, so as to supplement energy in advance on highways, so that after the electric vehicle enters urban roads, the power reserve of its power battery can meet the energy demand in this urban road, avoiding the start of the range extender in urban roads, so as to further improve the economy of the whole vehicle. Summary of the Invention

[0005] Aiming at the problem that the current energy management strategy of range-extended electric vehicles does not fully consider the driving roads of electric vehicles, the present invention provides an energy management method for range-extended electric vehicles based on energy prediction. When the electric vehicle starts, the road information of the trip is first obtained through the electric vehicle navigation system. By coordinating control method 1 and control method 2 of the range extender, through control method 1, the battery power of the electric vehicle can always be maintained above the lower limit value during driving. Before the electric vehicle enters the urban road, the power battery is pre-charged through control method 2 to ensure that the battery power can meet the requirements of the remaining urban road, so that the electric vehicle can rely entirely on the power battery to provide energy for driving on the urban road, thereby further improving the fuel economy of the vehicle.

[0006] Among them, the working mode of the above-mentioned range extender control method 1 is as follows: the electric power output by the generator in the range extender is equal to the power required for the electric vehicle to drive, and there is no extra power to supplement the power battery with additional energy. Therefore, on the premise of meeting the energy required for the electric vehicle to drive, it can maintain the battery power at a certain value. The working mode of control method 2 is as follows: the engine in the range extender works at the maximum power point in the best fuel consumption area. After the power generated by the generator meets the power required for the current electric vehicle to drive, there is still extra power to supplement the battery with electric energy.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] An energy management control method for a range-extended electric vehicle based on energy prediction provided by the present invention is characterized in that the method includes the following steps:

[0009] Step S11: Calculate the mileage S of the urban road in the travel route 市 ;

[0010] Step S12: Calculate the required battery power Q under the urban road mileage;

[0011] Step S13: Calculate the required mileage L when charging to the required battery power Q on the highway.

[0012] In step S14, to avoid over-discharging the power battery and affecting the battery life, the battery usually has a lower limit value. If it does not drive until the battery power reaches the lower limit value, repeat the judgment.

[0013] In step S15, when the electric vehicle drives until the battery power reaches the lower limit value, the range extender starts and first provides energy for the electric vehicle to drive with control method 1.

[0014] In step S16, judge whether it has driven to a distance L from the highway exit. If not, repeat the judgment.

[0015] Step S17: When the electric vehicle travels to a distance L from the highway exit, it is necessary to switch to Control Method 2 to pre-charge the battery at this time.

[0016] Step S18: When the battery is charged to the required pre-charge amount Q, that is, when the electric vehicle just drives off the highway and enters the urban road, the range extender enters the off state, and the electric vehicle travels purely electrically on the above urban road with the remaining power Q.

[0017] The technical solution of the present invention has the following remarkable advantages:

[0018] 1. By combining the driving road conditions of the electric vehicle, the present invention switches between the two control methods when the switching conditions are met, which not only avoids the engine not being able to work in the best fuel area when the range extender is always in Control Method 1 after being turned on, but also avoids frequent charging of the battery when the range extender always works in Control Method 2, which affects the battery life, and effectively improves the fuel economy of the electric vehicle and the life of the power battery.

[0019] 2. The energy management control method designed in the present invention based on energy estimation pre-estimates the required power under urban roads in advance, so that the electric vehicle travels in pure electric mode when entering urban roads with large speed changes, avoiding the noise generated when the range extender works, and improving the comfort of the driver under urban roads. Brief Description of the Drawings

[0020] Figure 1 It is a flowchart of the solution when the road condition is unobstructed during the pre-charging process of the present invention.

[0021] Figure 2 It is a flowchart of the solution when the road condition is congested during the pre-charging process of the present invention. Detailed Embodiment

[0022] In order to make the invention purpose, technical solution and advantages of the present solution clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0023] The present invention provides an energy management control method for a range-extended electric vehicle based on energy prediction. When the electric vehicle enters the highway for operation after departure and the battery power drops to the set lower limit value, the range extender is turned on, and at this time, the range extender operates according to Control Method 1. After the control unit calculates the required power for the urban road in advance, when the electric vehicle travels to the control method switching position, the range extender switches to Control Method 2 for operation to pre-charge the battery with the required power for the urban road. And when the electric vehicle reaches the end point of the highway, the range extender is turned off. At this time, the battery power can meet the required electric energy for the remaining urban road. On the remaining urban road, the motor of the electric vehicle operates entirely with the energy provided by the battery, achieving true "zero emissions" and "zero pollution". The flowchart of this method is as shown in Figure 1 shown, and includes the following steps:

[0024] Step S11: Calculate the mileage of the urban road in the travel route: The urban mileage specified in this solution includes the remaining mileage after removing the highway mileage in the travel route obtained through the in-vehicle navigation system. When the total mileage of the travel route of the electric vehicle is S 总 , the mileage of the highway is S 高 , then the remaining mileage of the urban road is denoted as S 市 , where S 市 = S 总 - S 高 (1)

[0025] Step S12: Calculate the required power for the urban road mileage: Obtain the speed limit conditions of different road sections included in the urban road in the travel route through the in-vehicle navigation system, and calculate the power consumption per kilometer of the electric vehicle in different speed limit sections. The specific method is as follows: Measure in advance through experiments the power consumption per kilometer of the electric vehicle at 4 different average vehicle speeds, and calculate the driving mileage per Kwh, that is, the driving mileage per degree of electricity, and store this data in the vehicle storage unit in advance; by retrieving the stored driving mileage per degree of electricity a i (Km) (i takes 1, 2... n), calculate the total required power for all the road sections that the electric vehicle is about to enter on the urban road, that is, calculate the power that needs to be reserved in the power battery before the electric vehicle enters the city, denoted as Q: In the formula: Q is the power value of the power battery when the electric vehicle enters the urban road, S 1 , S 2 ... S n are the mileages of different speed limit sections on the urban driving road in the city that the vehicle enters, a 1 , a 2 ,... a nFor the urban driving conditions stored in step S3, it is the driving mileage per degree of electricity when driving at average vehicle speeds of 30, 40, 60, and 80 km / h respectively.

[0026] Step S13: Calculate the mileage L required to charge the battery to the required power Q under highway conditions: First, determine the mathematical expression for the position where the range extender switches to control method 2 to pre-charge the battery: In this solution, through prior experiments, it is obtained that when the range extender is operating under control method 2 at an average vehicle speed of 100 km / h, the driving mileage b required for the power battery to supplement each degree of electricity. Combining with the required power value Q obtained in step S3 for urban roads, the driving mileage L required for the electric vehicle to charge the power battery to the power Q under highway conditions with the range extender operating under control method 2 is then determined, L = Q * b. In equation (3): L is the driving mileage required for the electric vehicle when the battery is supplemented with power Q under control method 2, that is, the distance of the electric vehicle from the highway exit; b is the driving mileage required for the power battery to supplement each degree of electricity under highway conditions and control method 2. Among them, the reason why the present invention first operates the range extender under control method 1 instead of control method 2 after the range extender is started is that control method 1 can avoid frequent charging and discharging of the battery, which affects the battery life. And when energy pre-storage is required later, control method 2 is adopted because the engine has been operating in a high fuel efficiency region, supplementing electrical energy to the battery, with higher charging efficiency and lower engine fuel consumption.

[0027] Step S14: To avoid over-discharging the power battery and affecting the battery life, the battery usually has a lower limit value. If it does not drive until the battery power reaches the lower limit value, repeat the judgment.

[0028] Step S15: When the electric vehicle drives until the battery power reaches the lower limit value, the range extender starts and first provides energy for the electric vehicle to drive under control method 1.

[0029] Step S16: Judge whether it has driven to the distance L from the highway exit. If not, repeat the judgment.

[0030] Step S17: When the electric vehicle drives to the distance L from the highway exit, at this time, it is necessary to switch to control method 2 to pre-charge the battery.

[0031] Step S18: When the battery is charged to the required pre-charge amount Q, that is, when the electric vehicle just drives out of the highway and enters urban roads, the range extender enters the off state, and the electric vehicle drives purely on electricity with the remaining power Q under the above urban roads.

[0032] Among them, if it is impossible to charge the battery to the required power when the highway ends due to other influencing factors, after the electric vehicle enters the urban road, when the battery power drops to the lower limit value but the journey has not ended, the range extender will be turned on again, and control method 1 will be used to ensure that the electric vehicle can drive to the destination. At this time, control method 1 is adopted because the electric vehicle will stop soon. By adopting control method 1, the battery power is maintained at the lower limit value unchanged. After parking, the external power grid can be fully utilized for charging to reasonably utilize the grid energy.

[0033] The present invention also provides an energy management control method for a range-extended electric vehicle based on energy prediction. When the electric vehicle encounters a traffic jam during the pre-charging process, this method is implemented as follows. The flowchart is as Figure 2 shown and includes the following steps:

[0034] Step S21: Calculate the mileage of the urban road in the travel route: The urban mileage specified in this solution includes the remaining mileage after removing the highway mileage in the travel route obtained through the in-vehicle navigation system. When the total mileage of the travel route of the electric vehicle is S 总 , the mileage of the highway is S 高 , then the remaining mileage of the urban road is denoted as S 市 , where S 市 = S 总 - S 高 (1)

[0035] Step S22: Calculate the required power for the urban road mileage: Obtain the speed limit conditions of different sections included in the urban road in the travel route through the in-vehicle navigation system, and calculate the power consumption per kilometer of the electric vehicle in different speed limit sections. The specific method is as follows: Measure in advance through experiments the power consumption per kilometer of the electric vehicle at 4 different average vehicle speeds, and calculate the driving mileage per Kwh, that is, the driving mileage per degree of electricity, and store this data in the vehicle storage unit in advance; by retrieving the stored driving mileage a i (Km) (i takes 1, 2...n) of each degree of electricity in different speed limit sections, calculate the total power required for all sections that the electric vehicle is about to drive into on the urban road, that is, calculate the power that needs to be reserved in the power battery before the electric vehicle enters the city, denoted as Q: In the formula: Q is the power value of the power battery when the electric vehicle enters the urban road, S 1 , S 2 ...S n are the mileage of different speed limit sections on the urban driving road in the city that the vehicle drives into, a 1 , a 2 ,...a nFor the urban driving conditions stored in step S3, it is the driving mileage per kilowatt-hour when driving at average vehicle speeds of 30, 40, 60, and 80 km / h respectively.

[0036] Step S23: Calculate the mileage L required to charge the battery to the required power Q under highway conditions: First, determine the mathematical expression for the position where the range extender switches to control method 2 to pre-charge the battery: In this solution, through prior experiments, it is obtained that when the range extender is operating under control method 2 at an average vehicle speed of 100 km / h, the driving mileage b required to supplement each kilowatt-hour of the power battery. Combining with the required power value Q obtained in step S3 for urban roads, the driving mileage L required for the electric vehicle to charge the power battery to the power Q under highway conditions with the range extender operating under control method 2 is then determined, L = Q * b. In equation (3): L is the driving mileage required for the electric vehicle when the battery is supplemented with power Q under control method 2, that is, the distance of the electric vehicle from the highway exit; b is the driving mileage required to supplement each kilowatt-hour of the power battery under highway conditions and control method 2. Among them, the reason why the present invention first operates in control method 1 rather than control method 2 after the range extender is started is that control method 1 can avoid frequent charging and discharging of the battery, which affects the battery life. And when energy pre-storage is required later, control method 2 is adopted because the engine always operates in a high fuel efficiency region, supplementing electrical energy to the battery, with higher charging efficiency and lower engine fuel consumption.

[0037] Step S24: To avoid over-discharging the power battery and affecting the battery life, the battery usually has a lower limit value. If it has not traveled until the battery power reaches the lower limit value, repeat the judgment.

[0038] Step S25: When the electric vehicle travels until the battery power reaches the lower limit value, the range extender starts and first provides energy for the electric vehicle to travel with control method 1.

[0039] Step S26: Judge whether it has traveled to the distance L from the highway exit. If not, repeat the judgment.

[0040] Step S27: When the electric vehicle travels to the distance L from the highway exit, at this time, it is necessary to switch to control method 2 to pre-charge the battery.

[0041] Step S28: When the electric vehicle performs pre-charging with control method 2, if the pre-charging process is completed in advance due to encountering a congested section, the range extender will not be turned off during the remaining highway mileage, but will switch to control method 1 to maintain the current battery power at the current value, so as to ensure that the pre-charged power of the electric vehicle will not be consumed before driving out of the highway exit.

[0042] Step S29: Determine whether the electric vehicle enters the urban road. If not, the electric vehicle continues to operate using Control Method 1.

[0043] Step S210: When the electric vehicle enters the urban road, i.e., just exits the highway exit, the range extender is turned off, and the electric vehicle runs in pure electric mode.

[0044] Among them, if due to other influencing factors, the battery cannot be charged to the required power at the end of the highway. After the electric vehicle enters the urban road, when the battery power drops to the lower limit but the journey has not ended, the range extender will be turned on again and operate using Control Method 1 to ensure that the electric vehicle can reach the destination. At this time, Control Method 1 is adopted because the electric vehicle will stop soon. By using Control Method 1 to keep the battery power at the lower limit unchanged, the external power grid can be fully utilized for charging after parking to reasonably utilize the grid energy.

Claims

1. An energy management control method for a range-extended electric vehicle based on energy prediction, characterized in that, it includes the following steps: Step S11: Calculate the mileage S of urban roads in the travel route 市 ; Step S12: Calculate the required power Q for urban road mileage; Step S13: Calculate the required mileage L when charging to the required power Q on the highway; Step S14: To avoid over-discharging the power battery and affecting the battery life, the battery usually has a lower limit value. If the vehicle does not drive until the battery power reaches the lower limit value, repeat the judgment; Step S15: When the electric vehicle drives until the battery power reaches the lower limit value, the range extender starts and first provides energy for the electric vehicle to drive with Control Method 1; Step S16: Judge whether the vehicle has driven to a distance of the required mileage L from the highway exit. If not, repeat the judgment; Step S17: When the electric vehicle drives to a distance of the required mileage L from the highway exit, it is necessary to switch to Control Method 2 to pre-charge the battery; Step S18: When the battery is charged to the required pre-charge amount Q that is, when the electric vehicle just drives off the highway and enters the urban road, the range extender enters the off state, and the electric vehicle runs purely on electricity with the remaining battery power Q on the above urban road; The specific content of Step S12 is as follows: Obtain the speed limit conditions of different road sections included in the urban road in the travel route through the in-vehicle navigation system, and calculate the power consumption per kilometer of the electric vehicle in different speed limit sections. The specific method is: Measure in advance through experiments the power consumption per kilometer of the electric vehicle at 4 different average vehicle speeds, and calculate the driving mileage per Kwh, that is, the driving mileage per degree of electricity, and store the driving mileage per degree of electricity in the vehicle storage unit in advance; By retrieving the stored driving mileage per degree of electricity under different speed limit sections, calculate the total power Q required for all road sections that the electric vehicle is about to drive into on the urban road; The working characteristic of Control Method 1 is that the electric power output by the range extender changes in real time, and its magnitude is equal to the magnitude of the power required for the electric vehicle to drive in real time, and there is no extra electric energy to supplement the battery; The working characteristic of Control Method 2 is that the electric power output by the range extender is constant. After ensuring the normal driving of the electric vehicle, there is still extra electric power to charge the battery; When the battery is charged to the required pre-charging amount in step S18 Q However, if due to other influencing factors, the battery cannot be charged to the required power at the end of the highway, then after the electric vehicle enters the urban road, when the battery power drops to the lower limit value but the journey has not ended, the range extender will be turned on again and the control method 1 will be used to ensure that the electric vehicle can travel to the destination; After switching to Control Method 2 to pre-charge the battery in Step S17, if the pre-charging process is completed in advance due to encountering a congested section, the range extender will not be turned off during the remaining highway mileage, but will switch to Control Method 1 to maintain the current battery power at the current value to ensure that the pre-charged power of the vehicle will not be consumed before driving out of the highway exit.

2. An energy management control method for a range-extended electric vehicle based on energy prediction according to Claim 1, characterized in that: The 4 different average vehicle speeds are 30 km / h, 40 km / h, 60 km / h, and 80 km / h respectively.

3. An energy management control method for a range-extended electric vehicle based on energy prediction according to Claim 1, characterized in that: The specific content of Step S13 is to determine the position when the range extender switches from Control Method 1 to Control Method 2 to pre-charge the battery, that is, the distance of the vehicle from the highway exit is the required mileage L.

4. An energy management control method for a range-extended electric vehicle based on energy prediction according to Claim 1, characterized in that: The lower limit value of the battery in step S14 is set to 20% of the total battery capacity.

5. A method for energy management and control of a range-extended electric vehicle based on energy prediction according to claim 1, characterized in that when the pre-charging process is completed in advance due to encountering a congested section, but if the battery cannot be charged to the required power at the end of the highway due to other influencing factors, then after the electric vehicle enters the urban road, when the battery power drops to the lower limit value but the journey has not ended, the range extender will be turned on again, and control method 1 is used to ensure that the electric vehicle travels to the destination.

Images