An Electric Bus Scheduling Method Considering the Service Life of Power Batteries

Abstract

The present invention discloses an electric bus scheduling method considering the service life of power batteries, which fully considers meeting the demands of bus passengers on the line and can effectively reduce the permanent loss of the capacity of the power batteries of bus vehicles caused by charging behavior. Compared with the prior art, the method of the present invention, firstly, considers the scheduling problem of electric bus vehicles, which conforms to the development trend of future transportation; secondly, fully optimizes the operation behavior and charging behavior of electric bus vehicles, greatly alleviates the capacity loss rate of power batteries, and reduces the operation cost of the urban conventional bus system from the perspective of extending the service life of electric buses.

Description

Technical Field

[0001] The present invention belongs to the field of urban public transportation management, and particularly relates to an optimization method for the scheduling scheme of electric buses considering the service life of power batteries. Background Art

[0002] At present, according to the requirements of relevant national policies, in the future, conventional urban bus vehicles in China will mainly be electric vehicles. Compared with traditional fuel vehicles, electric buses have significant environmental friendliness. However, in the application of electric buses, there are two major problems that need to be solved urgently:

[0003] 1. The energy replenishment of traditional fuel vehicles, that is, refueling the vehicle (from zero to full tank), can be completed within a few minutes; however, the energy replenishment of electric buses, that is, charging the vehicle (from zero to full charge), takes 1 - 3 hours to complete. Therefore, in the application of electric buses, due to the charging requirements of the vehicles, it may cause the vehicles to be unavailable, resulting in insufficient transport capacity.

[0004] 2. The scrapping age of traditional fuel vehicles is more than 10 years. However, the power battery of an electric bus is restricted by the remaining available capacity, and the remaining available capacity of the power battery is affected by the charge-discharge behavior, that is, any charging behavior will cause a permanent loss of the battery capacity. Only the charging behavior of "small amount and multiple times, low current" can slow down the above permanent capacity loss. In the application of electric buses, if the charging behavior of the vehicles is not reasonably scheduled, it will lead to excessive loss of the power battery, resulting in early scrapping of the vehicle. Summary of the Invention

[0005] The purpose of the present invention is to provide a scheduling method for electric buses considering the service life of power batteries in view of the future traffic development trend. The scheduling method of the present invention is applicable to the situation where all urban bus vehicles are electric vehicles, and mainly considers meeting the following two aspects of requirements: First, it can reasonably schedule the charging behavior and operation behavior of bus vehicles to avoid insufficient transport capacity on the line due to charging; Second, since the service life of the power battery of an electric bus is related to the charging behavior, this method can rationalize the charging behavior, thereby increasing the service life of electric buses. The technical solution of the present invention is:

[0006] The operation mode of the bus line described in the present invention is that first, the bus vehicle departs from the bus hub station 1, passes through all the intermediate stations 4 in sequence along the operation direction 2, waits for a period of time after reaching the terminal station 3 and then turns back, passes through all the intermediate stations 4 in sequence again, and can be charged at the bus hub station according to needs after reaching the bus hub station 1. For the bus line, its length is denoted as l, and the round-trip operation duration including the waiting time at the terminal station 3 is denoted as T l, the total number of bus vehicles serving this route is M, and the bus numbers are m, where m ∈ {1, 2, 3, …, M}, and the nominal capacity of the power battery of each bus is C m , and its power at time t is denoted as SOC m (t), where SOC m (t) uses the percentage counting method, that is, the current power is the nominal capacity C m percentage.

[0007] The impact of the charging behavior described in the present invention on the life of the power battery of electric bus vehicles is represented by the following quantitative relationship: where ξ represents the loss value of the battery capacity caused by a single charging behavior, which is related to the charging behavior. SoC dev and SoC ave are the characterization indicators of the charging behavior, representing the power variance and power mean of a single charging behavior respectively, and their calculation methods are: where SoC(Ah) represents the mapping relationship between the battery power (Ah) and the battery percentage power, and Ah_ini and Ah_fin represent the battery power before and after the charging behavior respectively. Since the loss of the power battery capacity is directly related to the scrap quality of the power battery, the loss value of the power battery capacity is used to characterize the economic loss caused by the charging behavior.

[0008] The electric bus scheduling method considering the life of the power battery includes:

[0009] S1. At the beginning of a certain day (denoted as t = 0), the available power of vehicle m at this time is denoted as SOC m (t), m ∈ {1, 2, 3, …, M}. At the same time, referring to the historical data of bus demand along the route, calculate the bus departure intervals and departure time nodes within the future time period, denoted as t1, t2, t3, …….

[0010] S2. Assign a bus for t = t1. The bus vehicle starting to execute the task at t = t1 will return to the bus hub station 1 at t = t1 + T l moment. At this time, the set of available vehicles is Γ = {1, 2, 3, …, M}. Calculate the cost of each bus in the set Γ for executing the task starting at t = t1, that is, calculate the economic loss caused by charging vehicle m to full power after returning. The remaining power of vehicle m after the task is completed (i.e., the initial power of vehicle charging) is SOC m (0) - 2lγ, where γ is the power consumption of the vehicle per unit mileage; the power of vehicle m after the charging behavior is that is, the upper limit of the power battery capacity of vehicle m. Based on this, calculate the loss of the power battery capacity caused by different vehicles when executing the task starting at t = t1, and select the vehicle with the lowest economic cost to execute the task at t = t1.

[0011] S3. Remove the dispatched vehicles from the set Γ of available vehicles and update the set Γ according to the method described in step S2.

[0012] S4. Calculate whether there are in - transit vehicles returning to the bus hub station 1 before the next moment. If so, judge whether its remaining power is greater than 2lγ. If so, add the returned vehicle to the set Γ. If not, arrange for the returned vehicle to be charged and update the set Γ. Calculate whether there are vehicles with charging completed. If so, add the vehicles with charging completed to the set Γ, otherwise do not update the set Γ.

[0013] S5. Assign the bus vehicle to perform tasks at the next moment, calculate the economic cost of all vehicles in the set Γ of available vehicles to perform tasks, and thus select the vehicle with the lowest economic cost to perform the task at this moment.

[0014] S6. Execute S3 - S5 until all the vehicle dispatching tasks for the day are completed.

[0015] Appendix Figure 2 It shows the electric bus dispatching method considering the service life of power batteries according to the present invention. Compared with the prior art, the advantages and effects of the present invention are as follows:

[0016] First, the present invention considers the dispatching problem of electric bus vehicles, conforms to the development trend of future transportation, and can also ensure that the bus demand on the line is fully met.

[0017] Second, the present invention fully optimizes the operation behavior and charging behavior of electric bus vehicles, greatly alleviates the capacity loss rate of power batteries, and reduces the operation cost of the urban conventional bus system from the perspective of extending the service life of electric buses. Brief Description of the Drawings

[0018] Figure 1 It represents the schematic diagram of the bus line involved in the present invention.

[0019] Figure 2 It represents the flow chart of the electric bus dispatching method considering the service life of power batteries involved in the present invention. Detailed Embodiment

[0020] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the embodiments of the drawings, so that those skilled in the art can better understand the present invention.

[0021] The present invention proposes an electric bus dispatching method considering the service life of power batteries, in order to Figure 1Taking the bus line shown as an example, the buses on this bus line depart from bus hub station 1, follow the running direction 2 and pass through all intermediate stations 4 in sequence, wait for a period of time after reaching the terminal station 3 and then turn back, pass through all intermediate stations 4 in sequence again, and can be charged at the bus hub station according to needs after reaching the bus hub station 1.

[0022] The length of the above bus line is denoted as l. The total time from when the bus departs from bus hub station 1, reaches the terminal station 3, waits for a period of time and then turns back until it finally returns to bus hub station 1 is denoted as T. l , the total number of buses serving the above line is M, the bus number is m, where m ∈ {1, 2, 3, …, M}, and the nominal capacity of the power battery of each bus is C. m , and the battery power at time t is denoted as SOC m (t), where SOC m (t) uses the percentage counting method, that is, the current power is the percentage of the nominal capacity C. m Percentage.

[0023] The permanent loss of the capacity of the power battery caused by the charging behavior in the present invention is represented by the following quantitative relationship:

[0024]

[0025] Among them, ξ represents the loss value of the battery capacity caused by a single charging behavior, which is related to the charging behavior. SoC dev and SoC ave are the characterization indicators of the charging behavior, representing the variance and mean value of the battery power of a single charging behavior respectively, and their calculation methods are as follows:

[0026]

[0027]

[0028] Among them, SoC(Ah) represents the mapping relationship between the battery power (Ah) and the battery percentage power. Ah_ini and Ah_fin represent the battery power before and after the charging behavior respectively. Since the loss of the power battery capacity is directly related to the quality of the power battery at the end of its life, the loss value of the power battery capacity is used to characterize the economic loss caused by the charging behavior.

[0029] For the buses on the above bus line, the operation behavior scheduling and charging behavior scheduling within a day are carried out according to the Figure 2 shown scheduling method flowchart until all the vehicle dispatching tasks for the day are completed.

Claims

1. An electric bus scheduling method considering the battery life of power batteries defines the operation mode of an electric bus as follows: First, the electric bus departs from the bus hub station (1), travels along the set route and operation direction (2), passes through all intermediate stations (4) in sequence, arrives at the terminal station (3), waits for a set time interval, then turns back, passes through all intermediate stations (4) again in sequence, and returns to the bus hub station (1). After that, it charges at the bus hub station as needed (5); the total length of the route from the bus hub station (1) to the return of the bus hub station (1) is denoted as l, and the total operation duration including the waiting time at the terminal station (3) is set as T l , the total number of electric buses serving this route is M, the electric bus number is m, where m ∈ {1, 2, 3,..., M}, and the nominal capacity of the power battery of each electric bus is C m , and the power level at time t is denoted as SOC m (t), where SOC m (t) adopts the percentage counting method, that is, the current power level is the percentage of the nominal capacity C m percentage; It is characterized in that The electric bus scheduling method includes: S1. Define the initial moment as t = 0, and the available electric energy of vehicle m at the initial moment is denoted as SOC m (t), where m ∈ {1, 2, 3, …, M}. At the same time, according to the historical data of the bus demand along the specified route collected, the bus departure intervals and departure time nodes within the specified future time period are designated, denoted as t1, t2, t3, ……; S2. Assign a bus to perform a task at time t = t1. The bus that starts to perform the task at time t = t1 will return to the bus terminal station (1) at time t = t1 + T. At this time, the set of available vehicles is Γ = {1, 2, 3, …, M}. Calculate the cost of each bus in the set Γ to perform the task starting at time t = t1, that is, calculate the economic loss caused by charging each vehicle m to full charge after it returns. Specifically: the remaining battery level of vehicle m after the task is completed is SOC l (0) - 2lγ, where γ is the power consumption of the vehicle per unit mileage; the battery level of vehicle m after charging is m Accordingly, calculate the loss of the power battery capacity caused by different vehicles when performing the task starting at time t = t1, and select the vehicle with the lowest economic cost to perform the task at time t = t1; ​ S3. According to the method described in step S2, remove the dispatched vehicles from the set Γ of available vehicles and update the set Γ; S4. Calculate whether there are in-transit vehicles returning to the bus hub station (1) before the next moment. If so, judge whether its remaining power is greater than 2lγ. If so, add the returned vehicles to the set Γ. Otherwise, arrange for the returned vehicles to be charged and update the set Γ; Calculate whether there are vehicles with charging completed. If so, add the vehicles with charging completed to the set Γ. Otherwise, do not update the set Γ; S5. Assign the bus vehicle to perform tasks at the next moment. Use the method in S2 to calculate the economic cost of all vehicles in the set Γ of available vehicles to perform tasks, so as to select the vehicle with the lowest economic cost to perform the tasks at this moment; S6. Repeat S3 - S5 until all the vehicle dispatching tasks for the day are completed.

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