Electric bus charging system cost analysis method, system, device and medium

Abstract

The present invention discloses a cost analysis method, system, device and medium for an electric bus charging system, wherein the method comprises: defining the life cycle cost of the electric bus charging system, defining the initial investment including the initial construction cost of the charging facilities, the initial bus vehicle purchase cost and the initial battery purchase cost, and determining the initial investment of three charging modes; defining the annual recurring investment including the operating cost and the greenhouse gas emission cost, and determining the annual recurring investment of the three charging modes; defining the future additional investment including the technology replacement cost, and determining the future additional investment of the three charging modes; designing the operation modes of the electric bus system under the three charging modes, and calculating the corresponding life cycle costs of the three charging modes. The present invention defines the life cycle cost from the economic and environmental aspects, analyzes the three charging modes according to the life cycle cost, makes the evaluation results fit the actual situation, and can be widely used in the field of charging cost optimization technology.

Description

Technical Field

[0001] The present invention relates to the technical field of charging cost optimization, and in particular to a method, system, device and medium for analyzing the cost of an electric bus charging system. Background Art

[0002] Electric bus systems incur huge capital costs associated with the deployment of charging facilities and the purchase of batteries, which is an unignorable obstacle to the large-scale realization of electric public transportation. The current popular charging technologies include static charging technology, battery swap charging technology, and dynamic wireless charging technology. Static charging technology refers to charging facilities that allow buses to be charged by plug-in or wirelessly when they are parked at depots or bus stations along the bus route. Another advanced static charging technology is called opportunity charging, which can be charged frequently at intermediate stations. Opportunity charging at charging stations can be further classified according to the specific charging method, such as whether the charging station deploys a pantograph charger or whether it supports static wireless power transmission (WPT). This opportunity charging technology can reduce the capacity of bus batteries, but needs to be integrated into the bus schedule. Battery swap charging technology requires a battery swap station and multiple batteries as spare rotation. WPT technology can also be used as an on-the-go charging mode. WPT technology uses charging infrastructure embedded in the road surface (such as power grid, magnetic coil) to transmit electrical energy to the inductive pickup element of the vehicle. This wireless charging technology can provide uninterrupted charging services, but it is expensive.

[0003] Currently, lithium batteries are widely used in modern electric vehicles due to their high capacity. Researchers have conducted multiple laboratory aging tests on battery cells to study the capacity decay mechanism of lithium batteries and proposed multiple prediction models. Although the model form and model parameters vary depending on the battery material and modeling method, similar conclusions can still be found for all types of lithium batteries embedded in electric buses: operating conditions are the main cause of battery aging, which is related to time, energy conversion amount, temperature, and especially the state of charge (SoC). Under the battery capacity decay mechanism that depends on SoC, the larger the range of SoC variation, the faster the battery capacity decays. Therefore, it is recommended that bus operators keep the SoC of the battery pack within the smallest possible range. These recommendations further increase the number of charging facilities required for electric bus systems. Therefore, it is necessary to determine how to balance the construction of charging facilities, battery replacement costs and emissions, and develop an optimal charging design plan.

[0004] Existing studies have shown that parameter values ​​have a significant impact on the results of cost competitiveness analysis. However, in the framework of the system's life cycle evolution, the selection of charging mode remains challenging due to the lack of multiple charging methods. Summary of the invention

[0005] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the purpose of the present invention is to disclose a cost analysis method, system, device and medium for an electric bus charging system.

[0006] The technical solution adopted by the present invention is:

[0007] A cost analysis method for an electric bus charging system comprises the following steps:

[0008] Define the life cycle cost of the electric bus charging system, which includes the initial investment, future additional investment and annual recurring investment;

[0009] The initial investment is defined as the initial construction cost of the charging facilities, the initial bus purchase cost and the initial battery purchase cost, and the initial investment of the three charging modes is determined;

[0010] Define annual recurring investment including operating costs and greenhouse gas emission costs, and determine the annual recurring investment for the three charging modes;

[0011] Define the future additional investment including technology replacement costs and determine the future additional investment for the three charging modes;

[0012] Design the operation modes of the electric bus system under three charging modes and calculate the corresponding life cycle costs of the three charging modes;

[0013] Among them, the three charging modes are static charging station mode, battery replacement station mode and dynamic wireless charging lane mode.

[0014] Furthermore, the formula for the life cycle cost is as follows:

[0015] F LCC =F CAP +F OP +F GHG +F REP

[0016] Among them, F LCC is the life cycle cost, F CAP is the initial investment, F OP is the operating cost, F GHG represents the greenhouse gas emission cost, F REP Represents the technology replacement cost.

[0017] Further, the formula for the initial investment is as follows:

[0018] F CAP =F CO +F BA +F BUS

[0019] Among them, F CO represents the initial construction cost, F BUS represents the initial bus purchase cost, F BA represents the initial battery purchase cost;

[0020] Initial construction cost F under three charging modes CO The calculation method is as follows:

[0021] In the static charging station mode SCS, the initial construction cost F CO Including the cost of building terminal charging stations and the cost of building opportunity charging stations, the expression is as follows:

[0022]

[0023] In the formula, x i Indicates whether to choose to build bus station i as an opportunity charging station; C end is the cost of building a terminal charging station, C c,o The unit construction cost of opportunity charging stations;

[0024] In the battery swap station mode BSS, the initial construction cost F CO is the fixed cost of building a charging exchange station C c,s ;

[0025] In the dynamic wireless charging lane mode DWCL, the initial construction cost F CO Including the cost of terminal charging stations and the construction cost of charging lanes; the construction cost of the charging lanes includes the construction cost of each network segment and the construction cost of deploying underground feeders and paving the road; the initial construction cost F CO The expression is as follows:

[0026]

[0027] In the formula, C end is the cost of building a terminal charging station, i Whether to set up a charging lane on the route between bus station i and bus station i+1, C c,t and C c,l They represent the construction cost of each network segment and the construction cost of each kilometer of charging lane, d i represents the length of the charging lane between bus stop i and bus stop i+1.

[0028] Furthermore, the expressions for the initial construction costs of the three charging modes are as follows:

[0029]

[0030] The expressions for battery purchase costs for the three charging modes are as follows:

[0031]

[0032] In the formula, C BA is the battery price, E is the battery capacity, n BA is the number of batteries. In the static charging station mode SCS and the dynamic wireless charging lane mode DWCL, the number of batteries is the same as the number of buses in the bus fleet Q;

[0033] The expression of initial bus purchase cost is as follows:

[0034] F BUS =C BUS Q

[0035] In the formula, C BUS It is the unit price of the bus.

[0036] Furthermore, the operating cost includes power consumption cost and maintenance cost, and the expression of the operating cost is as follows:

[0037]

[0038] In the formula, F energy,j is the electricity consumption cost, F maintenance,j is the maintenance cost, j represents the year; d rate represents the discount rate; the expressions for the electricity consumption cost under the three charging modes are as follows:

[0039]

[0040] In the above formula, for the static charging station mode SCS, the energy consumption includes terminal charging power consumption and opportunity charging power consumption; the annual energy cost is the result of multiplying the energy consumed to complete a single line by the total number of lines served throughout the year, expressed as fTN day Indicates; during the charging process at the terminal station, the amount of electricity used is SOC max -SOC I Multiply by the energy efficiency α end and the unit electricity cost C of the terminal station p,end The energy cost of an opportunity charging station can be calculated from the charging time t c,o and the corresponding charging power P c,o Get; α c,o and C p,o They represent the charging efficiency and unit electricity cost of the opportunity charging station respectively;

[0041] For the battery swap station mode BSS, let y k indicates whether the battery is replaced on route k; the energy consumed in year j is the sum of the energy consumed on route k multiplied by the size of the bus fleet and the total number of operating days in a year;

[0042] For the dynamic wireless charging lane mode DWCL, the power consumption cost includes two parts: the terminal station consumption and the cost of the charging channel; the terminal station consumption is: the power used is SOC max -SOC I Multiply by the energy efficiency α end and the unit electricity cost C of the terminal station p,end ; The cost of a charging channel is given by the sum of all the power consumed by the charging channel: Let variable z i and d i They respectively indicate whether the route from bus stop i to bus stop i+1 is constructed as a charging lane and the length of the charging lane;

[0043] The maintenance cost includes the maintenance cost of buses and the maintenance cost of facilities. The expression of the maintenance cost in the jth year is as follows:

[0044]

[0045] Because the maintenance cost of buses and facilities is constant, the maintenance cost in year j depends on the number of buses Q and the number of batteries n in the fleet. BA , and charging mode;

[0046] The monetary value of the cost of greenhouse gas emissions is expressed as follows:

[0047]

[0048] In the formula, C β is the monetary scalar used to convert emissions into capital costs, d rate is the annual discount rate; F GHG,facility is the greenhouse gas emissions, F GHG,e-bus Represents the life cycle greenhouse gas emission cost of electric buses.

[0049] Furthermore, the technology replacement cost F REP It is to calculate the capital costs incurred during the life cycle operation;

[0050] The technology replacement cost F REP Including battery replacement cost and bus replacement cost, technology replacement cost F REP The formula expression is as follows:

[0051]

[0052]

[0053] Qτ L / τ BUS is the natural life span; jIndicates whether the battery is replaced in the jth year. The low health state EoH of the battery in the jth year is calculated by formula (22), where SoH0 = 100%;

[0054]

[0055] In the above formula, ξ day Represents the daily capacity decay rate, N day Indicates the number of days per year of operation;

[0056] The EoL of the battery is a constant threshold, ranging from 70% to 80% of the new battery capacity; the replaced battery can then be used for static applications; when the SoH in the jth year reaches the threshold, replacement is performed according to equation (23), and constraints are imposed on the replacement process;

[0057] Mω j +SoH j ≥0 (23)

[0058] In the above formula, M represents a large given number, and the variable ω j Indicates whether the battery is replaced in year j;

[0059] In equation (24), another constraint is set to ensure that the battery is replaced no later than the natural life of the battery,

[0060] Mω j +J calendar -j>0 (24)

[0061] In the above formula, J calendar Indicates the maximum number of years a battery can operate based on its natural degradation;

[0062] Daily capacity decay rateξ day Calculated according to the charging method, as shown in formula (25):

[0063]

[0064] In the above formula, ξ SCS,cycle and DWCL.cycle represents the degradation of an operating cycle, and the daily degradation is obtained by multiplying the cycle degradation by the frequency f operating hours T and dividing by the fleet size Q; ξ BSS,day represents the daily degradation of the BSS mode;

[0065] For the static charging station mode SCS, Equation (26) shows the degradation model and its calculation process; each charging and discharging process includes a terminal station charging time, Number of times of charging and discharging:

[0066]

[0067] in,

[0068]

[0069]

[0070]

[0071] In the above formula, E d Indicates the energy consumption per kilometer, l i represents the distance from site i-1 to site i, Ah i,d Indicates the final charge during the discharge period, Ah i,c Indicates the final charge of an opportunity charging activity, Ah end Indicates the final amount of electricity charged by the terminal station;

[0072] For the battery swap station mode BSS, each charge and discharge process includes no more than one battery replacement and one discharge; the discharge process is ideally symmetrical with the charging process;

[0073]

[0074] in,

[0075]

[0076] In the above formula, Ah sc,k represents the final amount of electricity in line k;

[0077] For the dynamic wireless charging lane mode DWCL, each cycle of the DWCL charging and discharging process, including a terminal station charging time, is calculated using formula (32):

[0078]

[0079] In the above formula, is the number of wireless charging times in transit, and I is the number of discharge times; the amount of electricity transferred during charging and discharging can be calculated by (34) to (36);

[0080]

[0081]

[0082]

[0083] In the above formula, Ah i,d Indicates the final charge during the discharge period, Ah i,cl Indicates the final power of the wireless charging activity i, Ah end Indicates the final charge of the terminal station.

[0084] Furthermore, the design of the operation modes of the electric bus system under the three charging modes and the calculation of the life cycle costs corresponding to the three charging modes include:

[0085] The static charging station mode SCS includes a fixed terminal charging station and some opportunity charging stations deployed at intermediate bus stops. The bus is fully charged at the terminal station, and the battery power is:

[0086]

[0087] Discharge occurs during service, and the unit power consumption per kilometer is E d , then the SoC reduction per kilometer is E d / E, multiplied by the distance l i ; For bus stop i, the SoC reached can be obtained by the recursive formula As shown in formula (38):

[0088]

[0089] If you select bus stop x i , i∈I is an opportunity charging station, then the binary variable x i is 1; if charging facilities are available, the electric bus can be charged when it stops at the i bus station; when charging, SoC Increase to The amount of electricity that the battery can obtain at bus stop i can be obtained by converting the electric power P c,o Multiply by the stop time t stop Divide by the battery capacity E to calculate; P c,o t stop x i / E contains two variables x i and E, and is therefore nonlinear; the resulting recursive formula is shown in (39):

[0090]

[0091] To ensure that the battery SoC is always higher than the lower limit SoC min , set formula (40) as the constraint:

[0092]

[0093] The terminal station can provide an increase of SoC by P c,end t end / E, and formula (41) ensures that the electric bus is fully charged at the terminal;

[0094]

[0095] In addition, formula (42) ensures that there are enough buses to provide service at the service frequency f during the operating hours;

[0096]

[0097] This optimization problem has four variables, x i is a binary variable indicating whether bus stop i is constructed as an opportunity charging station; for the bus fleet size, E represents the initial battery capacity, Q represents the bus fleet size, and formulas (43)-(46) describe the variable domain of the variables;

[0098] x i ∈{0,1} (43)

[0099] ω j ∈{0,1} (44)

[0100]

[0101]

[0102] Solve the minimum cost F of the static charging station mode SCS LC :

[0103]

[0104] For the battery swap station mode BSS, represents the number of cycles that the battery undergoes before replacement; the total number of cycles K can be calculated by multiplying the frequency f by the number of operating hours T and dividing by the fleet size Q, and then rounding the total number of cycles per day to an integer, as shown in formula (48):

[0105]

[0106] According to the total number of cycles K, set the decision variable y k ,y k is a binary variable indicating whether the battery is in the circuit Since the running distance in a day is consistent, we can introduce a new decision variable n k To further simplify the exchange activity, this variable represents the number of cycles the electric bus has gone through before the exchange; y k From n in (49) k Obtained:

[0107]

[0108] The bus is at full SoC (i.e. battery charge SoC) in the first service in the morning (line k = 0). max ), as follows:

[0109]

[0110] For a unit cycle, the distance is Power consumption is Then, the SoC can be reduced For loop k, we reach SoC (i.e. ) can be obtained by subtracting E from loop k-1 d l i The recursive formula of / E is obtained as shown in formula (51):

[0111]

[0112] If circuit k involves battery swapping, y k =1, that is, 1-y k =0, so Otherwise k =0,1-y k =1, in this case, the recursive formula Applicable; This process can be summarized in formula (52);

[0113]

[0114] To ensure that the battery SoC is always higher than the lower limit SoC min , set formula (53) as a constraint;

[0115]

[0116] If the battery SoC is higher than the SoC min , and also ensure that the battery can provide enough energy to complete this journey; here, the SoC is introduced safe As a lower threshold, the lower threshold always enables the electric bus to return to its departure station as follows:

[0117] My k ≤SoC safe -SoC k (54)

[0118]

[0119] In addition, formula (56) ensures that there are enough buses operating in the bus system;

[0120]

[0121] At the exchange station, the exhausted battery is replaced with a fully charged battery; the replaced battery needs to be charged at the exchange station; this charging process takes less than t c,s; Then, in order to provide consistent service, redundant batteries are required, as shown in formula (57);

[0122]

[0123] This optimization problem has four variables, here, y k Is a binary variable indicating whether the battery is in the circuit exchange; E represents the initial battery capacity, Q represents the size of the bus fleet; there is a new variable n BA , which represents the number of batteries; Equations (58)-(60) describe the variable domain of the variables;

[0124] y k ∈{0,1} (58)

[0125]

[0126]

[0127] Find the minimum cost F of the battery swap station mode BSS LC :

[0128]

[0129] The dynamic wireless charging lane mode DWCL includes a fixed terminal charging station. Multiple dynamic charging lanes can be deployed between any bus station i and bus station i+1. The bus is fully charged at the terminal station (numbered 0), and the battery power is SoC max ;

[0130] SoC0=SoC max (62)

[0131] Discharge occurs during service, and the unit power consumption per kilometer is E c,l , then SoC along with (l i -d i ) increases and decreases. For the route from bus station i-1 to bus station i, the SoC (i.e. SoC i+1 ) can be expressed by the recursive formula Calculate, as shown in (63):

[0132]

[0133] To ensure that the battery SoC is always higher than the lower limit SoC min , set (64) as the constraint

[0134] SoC i ≥SoC min (64)

[0135] In addition, formula (65) ensures that there are enough buses to maintain the service frequency f during the operation time. To ensure the smooth operation process, we first calculate the total operation time of the bus, including the travel time ∑ i l i / v, boarding and alighting time at bus stops and charging time at terminal stations;

[0136]

[0137] End stations can provide charging for low SoC batteries and (66) ensuring that electric buses are fully charged at the terminal;

[0138]

[0139] Constraints (67)-(68) describe the variable domain:

[0140] z i ∈{0,1} (67)

[0141]

[0142] Solve the minimum cost F of the dynamic wireless charging lane mode DWCL LC :

[0143]

[0144] Another technical solution adopted by the present invention is:

[0145] A cost analysis system for an electric bus charging system, comprising:

[0146] A cost definition module, used to define the life cycle cost of the electric bus charging system, wherein the life cycle cost includes initial investment, future additional investment and annual recurring investment;

[0147] The initial investment calculation module is used to define the initial investment, including the initial construction cost of charging facilities, the initial bus purchase cost and the initial battery purchase cost, and determine the initial investment of the three charging modes;

[0148] An operating cost calculation module, which is used to define the annual recurring investment including operating costs and greenhouse gas emission costs, and determine the annual recurring investment of the three charging modes;

[0149] Future investment calculation module, used to define future additional investment including technology replacement cost, and determine future additional investment for three charging modes;

[0150] An operation mode determination module is used to design the operation modes of the electric bus system under three charging modes and calculate the life cycle costs corresponding to the three charging modes;

[0151] Among them, the three charging modes are static charging station mode, battery replacement station mode and dynamic wireless charging lane mode.

[0152] Another technical solution adopted by the present invention is:

[0153] A cost analysis device for an electric bus charging system, comprising:

[0154] at least one processor;

[0155] at least one memory for storing at least one program;

[0156] When the at least one program is executed by the at least one processor, the at least one processor implements the above method.

[0157] Another technical solution adopted by the present invention is:

[0158] A computer-readable storage medium stores a program executable by a processor, wherein the program executable by the processor is used to execute the method described above when executed by the processor.

[0159] The beneficial effects of the present invention are as follows: the present invention defines the life cycle cost from the economic and environmental aspects, analyzes the three charging modes according to the life cycle cost, and makes the evaluation result more in line with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0160] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0161] Figure 1 is a schematic diagram of a popular electric bus charging facility in an embodiment of the present invention;

[0162] Figure 2 is a schematic diagram of three charging modes in an embodiment of the present invention;

[0163] Figure 3 is a schematic diagram of experimental results based on a cost analysis method for an electric bus charging system in an embodiment of the present invention;

[0164] Figure 4It is a flow chart of a cost analysis method for an electric bus charging system in an embodiment of the present invention. DETAILED DESCRIPTION

[0165] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0166] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0167] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0168] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0169] This embodiment provides a cost analysis method for an electric bus charging system that takes both economy and environment into consideration. The method selects three electric bus charging models, proposes a unified life cycle cost analysis model for different charging models, and finally examines the competitiveness of different charging models relative to the investment cost of the bus system. Figure 1 This is a schematic diagram of popular electric bus charging facilities. Figure 1 (a) is a schematic diagram of a terminal charging station that allows parking and charging at night; Figure 1 (b) is a schematic diagram of a depot charging station with a plug-in charger; Figure 1 (c) Schematic diagram of an opportunity charging station equipped with a pantograph charger; Figure 1 (d) is a schematic diagram of charging using a static wireless charging pad; Figure 1 (e) Schematic diagram of a battery replacement charging station; Figure 1 (f) is a schematic diagram of the dynamic wireless charging channel. Figure 2 Schematic diagram of three charging modes used in the embodiment.

[0170] like Figure 4 As shown, a cost analysis method for an electric bus charging system includes the following steps:

[0171] S1. Definition: The life cycle cost (LCC) of an electric bus charging system is the sum of all expenditures over the entire life cycle of the system, including initial investment, future additional investment and annual recurring costs less any residual value, where the residual value is the residual value of replaced batteries, buses, etc.

[0172] Step S1 specifically includes S11-S12:

[0173] S11. In order to better formulate and evaluate the LCC model, the following assumptions are introduced in the research problem. All these assumptions are made to simplify the formula.

[0174] Assumption 1: All buses are electric, with the same battery size, and the batteries have the same initial state of health (SoH) at the beginning of use. A fully charged bus can provide at least one route service. This assumption is for calculating the state of charge (SoC) during charging and discharging and the SoH during battery replacement. The newly replaced battery is at the same initial SoH, which is usually 100% in electric buses.

[0175] Assumption 2: We assume that the electric bus is fully charged when it starts a route at the terminal charging station or the swap charging station to smooth charging and operation activities. In addition, it is assumed that the bus starts charging when it arrives at the opportunity charging station. The opportunity charging time is equal to the time the bus stays at each station minus the time the charger is connected and disconnected.

[0176] Assumption 3: During the charge and discharge process, the battery SoC is simplified to a linear function of the processed Ah. The battery operating temperature is constant.

[0177] S12. Unified the definitions of different charging modes for electric buses to avoid redundancy in parameter definitions of different charging facility design models. The following formula is given:

[0178] F LCC =F CAP +F OP +F GHG +F REP (1)

[0179] In the above formula, F LCC is the life cycle cost, F CAP is the initial capital cost, F OP is the operating cost, F GHG represents the greenhouse gas emission cost, F REP represents the technology substitution cost.

[0180] S2. The initial investment of LCC is defined as the initial construction cost of charging facilities, the initial bus purchase cost and the battery purchase cost. For the electric bus charging systems under three typical charging modes, the calculation formulas for their costs are given respectively.

[0181] Wherein step S2 specifically includes S21-S21:

[0182] S21, LCC initial capital cost is mainly generated before the system is put into operation, and its formula is shown in (2).

[0183] F CAP =F CO +F BA +F BUS (2)

[0184] In the above formula, F CAP It consists of three components, among which F CO represents the initial construction cost, F BUS represents the initial bus purchase cost, F BA Represents the initial battery purchase cost. These costs are closely related to the charging method, so the calculation method and value need to be discussed for each charging mode.

[0185] S22. Calculate the initial construction cost F of the LCC according to the formula given in step S21. CO , F CO It is the comprehensive cost during the construction process.

[0186] In the static charging station (SCS) model, the construction cost has two components: building a terminal charging station and building an opportunity charging station. The initial construction cost of the SCS is calculated by the formula Calculate. Where x i Indicates whether to choose to build bus station i as an opportunity charging station; C end and C c,o are the unit construction costs of terminal charging stations and opportunity charging stations, respectively. The cost is linearly proportional to the number of opportunity charging stations.

[0187] The initial construction cost of a battery swapping station (BSS) is the fixed cost C of building a swap charging station. c,s .

[0188] The initial construction cost of dynamic wireless charging lanes (DWCL) includes the terminal charging station (i.e., C end The construction cost of the charging lane can be divided into two parts. One is the construction cost of each segment (such as inverters, power transmitters, radio lanes and other power facilities), which is related to the length of the construction segment. Define the binary variable z i Whether to set up a charging lane for the route between bus station i and bus station i+1. Another cost is the construction cost of deploying underground feeders and paving the road. Let the variable d i represents the length of the charging lane between bus stop i and bus stop i+1. c,t and C c,l They represent the construction cost of each network segment and the construction cost of each kilometer of charging lane. Then, the initial construction cost of DWCL can be calculated by the formula Calculation. As shown in formula (3), the summarized initial construction cost formula is the overall charging facility construction cost. The initial capital cost of LCC for the three charging modes is shown in formula (3)(3).

[0189]

[0190] The initial battery purchase cost can be calculated based on the price of multiple batteries C BA , battery capacity E and number of batteries n BA Calculate as shown in formula (4). In SCS and DWCL modes, the number of batteries is the same as the number of buses in the bus fleet (i.e., Q). The BSS mode requires many batteries to rotate, so the number of batteries is greater than the number of buses. Battery capacity and battery number are decision variables in the model.

[0191]

[0192] The initial bus purchase cost is shown in formula (5).

[0193] F BUS =C BUS Q (5)

[0194] In the above formula, C BUS It is the unit price of the bus.

[0195] S3. Define the annual recurring cost of LCC, including operating cost and greenhouse gas emission cost. For the electric bus charging system under three typical charging modes, the calculation formulas for their costs are given respectively.

[0196] Step S3 specifically includes S31-S32:

[0197] S31. The annual recurring cost of LCC includes operating cost and greenhouse gas emission cost. Equation (6) calculates the operating cost of LCC. The operating cost consists of two parts: electricity consumption cost F energy,j (j represents year) and maintenance cost F maintenance,j .

[0198]

[0199] In the above formula, d rate Indicates the discount rate.

[0200] The energy consumption cost in kilowatt-hours (kWh) fluctuates depending on the energy used by the electric bus. The energy consumption cost F in year j can be calculated based on the charging pattern: energy,j , as described in formula (7).

[0201]

[0202] In the above formula, for the SCS mode, energy consumption includes terminal charging power consumption and opportunity charging power consumption. The annual energy cost is the result of multiplying the energy consumed to complete a single line by the total number of lines served throughout the year, which can be expressed as fTN day Indicates. During the charging process at the terminal station, the amount of electricity used is SOC max -SOC I Multiply by the energy efficiency α end and the unit electricity cost C of the terminal station p,end The energy cost of an opportunity charging station can be derived from the charging time t c,o and the corresponding charging power P c,o Similarly, α c,o and C p,o Denote the charging efficiency and unit electricity cost of the opportunity charging station, respectively. Unit charging cost and power transmission efficiency may vary depending on the selected charging facilities and their technologies. For the BSS mode, let y k Indicates whether the battery is replaced on route k. Then, the energy consumed in year j is the sum of the energy consumed on route k multiplied by the size of the bus fleet and the total number of operating days in a year. For the DWCL mode, the energy calculation also includes two parts: terminal station and charging channel. The energy consumed by the terminal station is the same as that of the SCS. The cost of the charging channel is obtained by the sum of all the electricity consumed by the charging channel. Let the variable z i and d iThey respectively indicate whether the route from bus stop i to bus stop i+1 is constructed as a charging lane and the length of the charging lane.

[0203] The maintenance cost in year j (i.e., F maintenance,j ) can be calculated using formula (8), which includes two main components: buses and facilities. The annual maintenance cost of buses or some facilities is constant, so the maintenance cost in year j depends on the variable number of buses in the fleet (i.e., Q or n BA ) and the charging mode we choose.

[0204]

[0205] S32. The annual recurring costs of LCC include operating costs and greenhouse gas emission costs. Equation (9) can calculate the monetary value of the greenhouse gas emission costs of LCC.

[0206]

[0207] In the above formula, C β is the monetary scalar used to convert emissions into capital costs, d rate is the annual discount rate.

[0208] In order to calculate the life cycle greenhouse gas emissions of the three charging facility models, we listed the components that produce greenhouse gas emissions. The greenhouse gas costs of charging facilities include the construction materials of supporting facilities, grid transmission infrastructure (such as wires), electrical equipment (such as inverters, transformers and coils) or road modifications (such as pavement), as shown in Table 1.

[0209] Table 1 Components that generate greenhouse gas emissions

[0210]

[0211] The greenhouse gas emissions of different charging modes can be obtained according to formula (10).

[0212]

[0213] In the above formula, F GHG,end 、F GHG,opp 、F GHG,bss and F GHG,chargingline They represent the greenhouse gas emissions in terminal charging stations, opportunity charging stations, battery swap stations, and dynamic charging lanes, respectively. More specifically, the different greenhouse gas emission costs of charging facilities can be calculated based on the components they contain, as shown in formulas (11) to (14).

[0214]

[0215]

[0216] F GHG,bss =a con S floor +a char n char +a wire l length +a trans +a inv (13)

[0217]

[0218] The life cycle emissions of electric buses include four parts: the well-to-pump (WTT) stage, the pump-to-wheel (TTW) stage, the recycling stage, and the powertrain stage. Due to the emission-free nature of charging pure electric buses from the grid, the TTW stage can be omitted. In addition, the recycling and powertrain stages can be merged into the equipment lifecycle (ELC) emissions. Table 2 details the life cycle emissions of electric buses.

[0219] Table 2 Emissions of electric buses throughout their life cycle

[0220]

[0221] Due to the characteristics of electric buses, the relevant life cycle emissions can be calculated from two aspects: WTT cost and ELC cost. The WTT stage represents the power delivery from the power source to the bus energy storage system. ELC includes the recovery stage emissions (e.g., bus production, maintenance and recycling process) and the powertrain stage emissions (e.g., motor, battery and electronics production). The full life cycle greenhouse gas emission cost (F GHG,e-bus ) is calculated in formula (15),

[0222] F GHG,e-bus =a WTT l year,j +a ELC Q (15)

[0223] In the above formula, a ELC The impact of electric buses on global warming over 100 years, WTT Indicates the impact of charging facilities on global warming in 100 years, l year,j represents the total travel distance j of all buses in that year, calculated by formula (16).

[0224]

[0225] In the above formula, N day,j Number of operating days in year j, represents the length of the service line, f and T represent the service frequency and operating hours respectively.

[0226] S4. Define the future additional investment of LCC as the technology replacement cost, and give the cost calculation formulas for the electric bus charging systems under three typical charging modes.

[0227] Lithium batteries experience capacity decay during use and storage, corresponding to cycle aging and natural aging, respectively. Since the natural aging of lithium batteries is very small and its impact on capacity decay is negligible compared to cycle loss, this embodiment uses a uniform maximum natural life for all batteries, which means that batteries are replaced after a certain number of years, even if they have not degraded to the replacement threshold in terms of cycle aging. A practical battery degradation model can calculate the capacity loss within each charge and discharge cycle. For charging process i, the capacity decay rate can be obtained by formula (17).

[0228]

[0229] in,

[0230]

[0231]

[0232] In the above formula, k s1 , k s2 , k s3 and k s4 is a constant model parameter; Ah m-1 It is SoC avg Determine the initial charge of the pre-treatment; Ah m is the final amount for the predefined period; and ΔAh m Yes Ah m -Ah m-1 According to Assumption 3, the SoC of the battery is idealized as a linear function of the processed Ah, and the operating temperature is constant. SoC avg and SoC dev Can be further simplified to SoC max and SoC min function, because in our model, and

[0233] Set the technology substitution cost F REP It is to calculate the capital cost incurred during the life cycle operation. As described in formula (20), F REP It consists of two parts: battery replacement cost and bus replacement cost. Both buses and batteries have a maximum natural lifespan. Bus replacement cost is calculated based on the recommended natural lifespan QτL / τ BUS Calculation. Assuming that the battery degrades to a low state of health (EoH) after thousands of charge / discharge cycles, when the battery reaches a certain state of health (SoH), the battery will no longer be used for electric buses. Here, we introduce the end of battery life (EoL) to calculate the optimal battery replacement point. When the battery degrades to a certain SoH, it will be replaced according to its residual value C SV SoH j Typically, a battery reaches EoL when its capacity falls below a certain percentage of its initial rated capacity.

[0234]

[0235]

[0236] Then, the EoH of the battery in year j can be calculated by equation (22), where SoH0 = 100%.

[0237]

[0238] In the above formula, ξ day Represents the daily capacity decay rate, N day Indicates the number of days per year to run.

[0239] The EoL of the battery is a constant threshold ranging from 70% to 80% of the new battery capacity. The replaced battery can then be used for static applications such as apartment power storage and emergency lighting. When the SoH in year j reaches the threshold, replacement is performed according to equation (23), and constraints are imposed on the replacement process.

[0240] Mω j +SoH j ≥0 (23)

[0241] In the above formula, M represents a large given number. The variable ω j Indicates whether the battery is replaced in the jth year. Then, in equation (24), we set another constraint to ensure that the battery is replaced no later than the natural life of the battery.

[0242] Mω j +J calendar -j>0 (24)

[0243] In the above formula, J calendar Indicates the maximum number of years a battery can operate based on its natural degradation.

[0244] The daily capacity decay rate ξ_day can be calculated according to the charging method, as shown in formula (25):

[0245]

[0246] In the above formula, ξ SCS,cycle and DWCL.cycle Represents the degradation of an operating cycle. The daily degradation can be obtained by multiplying the cycle degradation by the frequency f and the number of operating hours T and dividing it by the fleet size Q. BSS,day represents the daily degradation of the BSS mode. The degradation rate is related to the working environment temperature, and the temperature change of the battery is difficult to obtain. Therefore, we uniformly use the degradation model with a temperature of 25°C.

[0247] For the SCS mode, Equation (26) shows the degradation model and its calculation process. Each SCS charging and discharging process includes a terminal station charging time, The number of times the opportunity is charged and the number of times it is discharged.

[0248]

[0249] in,

[0250]

[0251]

[0252]

[0253] In the above formula, E d Indicates the energy consumption per kilometer, l i represents the distance from site i-1 to site i, Ah i,d Indicates the final charge during the discharge period, Ah i,c Indicates the final charge of an opportunity charging activity, Ah end Indicates the final charge of the terminal station.

[0254] For the BSS mode, each charge and discharge process includes no more than one battery replacement and one discharge. The discharge process can be ideally symmetrical with the charging process.

[0255]

[0256] in,

[0257]

[0258] In the above formula, Ah sc,k Represents the final charge in line k.

[0259] For the DWCL mode, each cycle of the DWCL charging and discharging process, including a terminal station charging time, can be calculated using equation (32):

[0260]

[0261] In the above formula, is the number of wireless charging times on the way, and I is the number of discharge times. The amount of electricity transferred during charging and discharging can be calculated by (34) to (36).

[0262]

[0263]

[0264]

[0265] In the above formula, Ah i,d Indicates the final charge during the discharge period, Ah i,cl Indicates the final power of the wireless charging activity i, Ah end Indicates the final charge of the terminal station.

[0266] S5. Design three different specific operation modes of electric bus systems and calculate their respective life cycle costs.

[0267] Step S5 specifically includes S51-S53:

[0268] S51, SCS charging mode includes a fixed terminal charging station and some opportunistic charging stations deployed at intermediate bus stops. According to Assumption 2, the bus is fully charged at the terminal station (numbered 0), and the battery power is:

[0269]

[0270] Discharge occurs during service. The unit power consumption per kilometer is E d , then the SoC reduction per kilometer is E d / E, multiplied by the distance l i For bus stop i, the SoC (i.e. ) can be expressed by the recursive formula We get:

[0271]

[0272] If you select bus stop x i , i∈I is an opportunity charging station, then the binary variable x i is 1. If charging facilities are available, the electric bus can be charged while parked at the i bus station. When charging, SoC Increase to The amount of electricity that the battery can obtain at bus stop i can be obtained by converting the electric power P c,o Multiply by the stop time t stop Divide it by the battery capacity E to calculate. c,ot stop x i / E contains two variables x i and E, and is therefore nonlinear. The resulting recursive formula is shown in (39).

[0273]

[0274] To ensure that the battery SoC is always higher than the lower limit SoC min , set formula (40) as a constraint.

[0275]

[0276] The terminal station can provide an increase of SoC by P c,end t end / E, and (41) ensures that the electric bus is fully charged at the terminal.

[0277]

[0278] In addition, formula (42) can ensure that there are enough buses to provide service at the service frequency f during the operating hours.

[0279]

[0280] This optimization problem has four variables. i is a binary variable indicating whether bus stop i is built as an opportunity charging station. For bus fleet size, E represents the initial battery capacity and Q represents the bus fleet size. Formulas (43)-(46) describe the variable domains of the variables.

[0281] x i ∈{0,1} (43)

[0282] ω j ∈{0,1} (44)

[0283]

[0284]

[0285] In the SCS model, the F of LCC LC , as described in (47), includes the following four parts: capital cost, operating cost, GHG emission cost and technology substitution cost. The cost composition can be calculated by (16)-(46).

[0286]

[0287] st(2)-(14)and(16)-(46)

[0288] S52. For BSS mode, represents the number of cycles that the battery undergoes before replacement. The total number of cycles K can be calculated by multiplying the frequency f by the number of operating hours T and dividing by the fleet size Q. Then, the total number of cycles per day is rounded to an integer, as shown in formula (48).

[0289]

[0290] According to the total number of cycles K, we set the decision variable y k , which is a binary variable indicating whether the battery is in the circuit Since the running distance in a day is consistent, we can introduce a new decision variable n k To further simplify the exchange activity, this variable represents the number of cycles the electric bus has gone through before the exchange; y k is n from (49) k Obtained.

[0291] According to Assumption 2, the bus is at full SoC (i.e., battery charge SoC) in the first service in the morning (line k = 0). max ), as shown below.

[0292]

[0293] For a unit cycle, the distance is Power consumption is Then, we can get SoC reduction For loop k, we reach SoC (i.e. ) can be obtained by subtracting E from loop k-1 d l i The recursive formula of / E is obtained, as shown in formula (51).

[0294]

[0295] If circuit k involves battery swapping, y k =1, that is, 1-y k =0, so Otherwise k =0,1-y k =1, in this case, the recursive formula Applicable. This process can be summarized in formula (52).

[0296]

[0297] To ensure that the battery SoC is always higher than the lower limit SoC min , set formula (53) as a constraint.

[0298]

[0299] If the battery SoC is higher than the SoC min , and also ensure that the battery can provide enough energy to complete this journey. Here, we introduce SoC safe As a lower threshold, it can always enable the electric bus to return to its departure station as shown below.

[0300] My k ≤SoC safe -SoC k (54)

[0301]

[0302] In addition, formula (56) ensures that there are enough buses operating in the bus system.

[0303]

[0304] At the exchange station, the depleted battery is replaced with a fully charged battery. The replaced battery needs to be charged at the exchange station. This charging process takes less than t c,s . Then, in order to provide consistent service, redundant batteries are required, as shown in equation (57).

[0305]

[0306] This optimization problem has four variables. Here, y k Is a binary variable indicating whether the battery is in the circuit E represents the initial battery capacity, Q represents the size of the bus fleet. There is a new variable n BA , which represents the number of batteries. Equations (58)-(60) describe the variable domains of the variables.

[0307] y k ∈{0,1} (58)

[0308]

[0309]

[0310] In the BSS model, the F of LCC LC , as described in formula (61), includes the following four parts, which have been defined in the preceding claims.

[0311]

[0312] st(2)-(14),(35)-(36),and(48)-(60)

[0313] S53, DWCL charging mode includes a fixed terminal charging station, and several dynamic charging lanes can be deployed between any bus station i and bus station i+1. According to assumption 2, the bus is fully charged at the terminal station (numbered 0), and the battery power is SoC max .

[0314] SoC0=SoC max (62)

[0315] Discharge occurs during service. The unit power consumption per kilometer is E c,l , then SoC along with (l i -d i ) increases. For the route from bus stop i-1 to bus stop i, the SoC (i.e. SoC i+1 ) can be expressed by the recursive formula Calculate as shown in (63).

[0316]

[0317] To ensure that the battery SoC is always higher than the lower limit SoC min , set (64) as the constraint.

[0318] SoC i ≥SoC min (64)

[0319] In addition, formula (65) ensures that there are enough buses to maintain the service frequency f during the operation time. To ensure the smooth operation process, we first calculated the total operation time of the bus, including the travel time ∑ i l i / v, boarding and alighting times at bus stops and charging times at terminal stations.

[0320]

[0321] The terminal station can provide charging (P_(c, end)t_end) / E for the low SoC battery, and (66) ensures that the electric bus is fully charged at the terminal station.

[0322]

[0323] Constraints (67)-(68) describe the variable domain:

[0324] z i ∈{0,1} (67)

[0325]

[0326] In the DWCL model, the F of LCC LC , as described in formula (69), includes capital cost, operating cost, greenhouse gas emission cost and technology substitution cost. This optimization problem has four variables. Among them, z i is a binary variable, indicating whether the link i-1 to i is constructed as a charging link, d i Represents the construction length of the charging lane. Similarly, the model also contains variables such as initial battery size E and bus fleet size Q.

[0327]

[0328] st(2)-(14),(35)-(37),and(63)-(68)

[0329] The above method is explained in detail below in conjunction with specific embodiments.

[0330] This embodiment provides a cost analysis method for an electric bus charging system that takes both economic and environmental considerations into account. The method is based on the following assumptions:

[0331] Assumption 1: All buses are electric, with the same battery size, and the batteries have the same initial state of health (SoH) at the beginning of use. A fully charged bus can provide at least one route service. This assumption is for calculating the state of charge (SoC) during charging and discharging and the SoH during battery replacement. The newly replaced battery is at the same initial SoH, which is usually 100% in electric buses.

[0332] Assumption 2: We assume that the electric bus is fully charged when it starts a route at the terminal charging station or the swap charging station to smooth charging and operation activities. In addition, it is assumed that the bus starts charging when it arrives at the opportunity charging station. The opportunity charging time is equal to the time the bus stays at each station minus the time the charger is connected and disconnected.

[0333] Assumption 3: During the charge and discharge process, the battery SoC is simplified to a linear function of the processed Ah. The battery operating temperature is constant.

[0334] The default values ​​of the parameters adopted in this case are shown in Table 3. We assume that all facilities involve fixed building areas and costs related to the capital cost of the charging facilities. The fixed building area of ​​a terminal charging station contains a fixed building area and multiple buses. Then, it is assumed that it costs $500,000 to build a terminal charging station. In addition, the total construction cost of the electric bus transfer station is about $562,400. Again, we assume that the fixed cost of building a charging road section is $321,800 per kilometer and the unit inverter cost is $20,000. In this case, the bus purchase price is $300,000, they have different battery capacities (e.g., 50, 100, 150, 200, 250 kWh), and the unit battery purchase cost is $200 per kWh. Mature and advanced battery technology can reduce the battery unit price, significantly affecting the cost competitiveness results.

[0335] The charging efficiency of plug-in chargers in charging stations and battery swap stations is assumed to be 90%. The charging efficiency of charging lanes is assumed to be 85%. Moreover, wireless charging requires long-distance charging, and long-distance transmission wastes energy. The average unit electricity cost per kilowatt-hour varies slightly in different charging modes and cities because each energy supplier sets its own rates. With additional battery technology research and development, battery price decline is a worldwide trend. In addition, the unit manufacturing cost of batteries for electric buses (i.e., C_BA) ranges from $200 / kWh to $550 / kWh. We conservatively use $200 / kWh as the default value in this article. The parameter values ​​of the capacity fading model (e.g., k s1 ,k s2 ,k s3 and k s4 ) are shown in Table 1. Table 3 shows all parameters and their values.

[0336] Table 3 Parameter definitions and values

[0337]

[0338]

[0339] In this embodiment, the nonlinear component caused by the battery degradation model and its related technology substitution formula (17) is a mixed integer nonlinear programming (MINLP) problem. Here, we use BNB20 from MATLAB as an optimization tool. BNB2 is a branch and bound algorithm solver (branch and bound algorithm) designed to solve the MINLP model. The solutions and discussions in the following sections are based on the default values.

[0340] This section uses the case line B1 in Guangzhou, China as a representative scenario to examine the cost competitiveness of different types of charging facilities based on their corresponding optimal charging modes. Electric buses have been operating on the B1 line of the Bus Rapid Transit (BRT) corridor since June 2014. The round trip route is 55 km and has 20 bus stops. The peak service frequency f is 12Veh / h and the average speed v along the BRT corridor is 30km / h. The normal operating hours of the line are from 06:00 to 24:00, equivalent to 18 operating hours (T).

[0341] Figure 3 The cost structure, battery replacement cycle, battery size, fleet size, and average replacement cycle of different charging modes are shown. The results show that the LCC of the SCS mode is lower than that of the BSS and DWCL modes, such as Figure 3 More specifically, the LCC of the SCS model is $21.49 million, which is 29% and 51% lower than the cost of the BSS and DWCL models, respectively. Figure 3 (a) also shows the values ​​of capital cost, operating cost, emission cost, and replacement cost. Capital cost accounts for a large proportion of the total cost in the three charging modes. The capital costs of the SCS and BSS modes are similar, at $7.46 million and $7.38 million, respectively. In contrast, the capital cost of the DWCL mode is $29.86 million, about four times that of the SCS mode. These high initial capital costs hinder the widespread application of the DWCL mode.

[0342] However, the BSS model has the lowest capital cost but the highest replacement cost, which is about twice that of the SCS model. The higher replacement cost is due to the large battery capacity and short replacement cycle, such as Figure 3 (c) and (d). Due to the rapid degradation of the battery, the replacement cycle of the BSS mode is very short. The battery life can be extended by keeping the battery charge within a narrow range. This mode adopts single-point charging, in which the SoC (19) avg and SoC dev The values ​​of are greater than those of the SCS and DWCL modes, which involve charging at intermediate bus stops (opportunity charging stations) or en route (with wireless charging lanes). As a result, the batteries are more likely to reach the replacement threshold during cycle aging, leading to higher replacement costs.

[0343] The operating costs of the three charging modes are SCS, DWCL and BSS (US$59,700, US$55,700 and US$3.51 million respectively). The total operating cost during the life cycle includes the electricity consumption cost (i.e., F energy,j ) and maintenance costs. Since the power transfer efficiency of the BSS mode is higher than that of the opportunity charging station (a component of the SCS mode) and the wireless charging channel (a component of the DWC mode), the F energy,jThe maintenance cost of the three charging modes is the lowest among the three modes. As shown in formula (6), the maintenance cost of each bus and some facilities is constant, so the maintenance cost depends on the variable number of buses in the fleet (i.e., Q or n BA ) and the charging mode we choose. In this case, the results show that although the number of buses in BSS mode is greater than that in other charging modes, maintaining battery swap stations can significantly reduce the number of buses.

[0344] The environmental analysis of the charging modes shows that the DWCL mode is the most expensive of the three charging modes (US$30.27 million). This cost is more than five times the emission cost of the SCS mode. The emission cost includes both bus emissions and facility emissions. Figure 3 (e) As shown; Due to the limitation of fixed charging time, the fleet in BSS mode is smaller than that in SCS and DWCL modes. Therefore, the emission cost of the bus fleet in BSS mode is the lowest. The charging facility cost of DWCL mode is the highest because of the large construction workload, namely underground facilities and road surface, which will lead to a large amount of greenhouse gas emissions compared with other charging facilities. Then, the emission cost of SCS and BSS modes is lower, involving the trade-off results of buses and facilities. The replacement of these three charging modes and their battery capacity and replacement cycle are shown in Figure 3 (c) and (d). The battery capacity of the BSS mode is the largest among the three because it exchanges and charges at fixed exchange stations after several rounds of service. In addition, the SCS and DWCL modes can provide charging services between bus stations. This on-the-way service can effectively reduce the need for larger battery capacity, but requires more frequent battery replacement. Among them, Figure 3 (a) Schematic diagram of the LCC component and its performance under different charging modes; Figure 3 (b) is a schematic diagram of the number of batteries in three charging modes; Figure 3 (c) is a schematic diagram of the replacement period in the three charging modes; Figure 3 (d) is a schematic diagram of the battery capacity in three charging modes; Figure 3 (e) is the fleet size in the three charging modes; Figure 3 (f) Schematic diagram of the replacement cost in three charging modes.

[0345] In summary, compared with the prior art, this embodiment has the following beneficial effects:

[0346] (1) The method of this embodiment incorporates battery capacity degradation into the life cycle cost framework, making the life cycle cost analysis of the electric bus charging system by the method of this embodiment more practical.

[0347] (2) The method of this embodiment analyzes the life cycle cost from the economic and environmental aspects, which meets the requirements of sustainable development.

[0348] (3) The model of this embodiment analyzes the advantages, disadvantages and applicability of three typical electric bus charging modes, and the empirical analysis is based on real-world data, which further proves the effectiveness of the model. The evaluation results of the model can be customized in different cities and have strong generalizability.

[0349] This embodiment also provides an electric bus charging system cost analysis system, including:

[0350] A cost definition module, used to define the life cycle cost of the electric bus charging system, wherein the life cycle cost includes initial investment, future additional investment and annual recurring investment;

[0351] The initial investment calculation module is used to define the initial investment, including the initial construction cost of charging facilities, the initial bus purchase cost and the initial battery purchase cost, and determine the initial investment of the three charging modes;

[0352] An operating cost calculation module, which is used to define the annual recurring investment including operating costs and greenhouse gas emission costs, and determine the annual recurring investment of the three charging modes;

[0353] Future investment calculation module, used to define future additional investment including technology replacement cost, and determine future additional investment for three charging modes;

[0354] An operation mode determination module is used to design the operation modes of the electric bus system under three charging modes and calculate the life cycle costs corresponding to the three charging modes;

[0355] Among them, the three charging modes are static charging station mode, battery replacement station mode and dynamic wireless charging lane mode.

[0356] An electric bus charging system cost analysis system of this embodiment can execute an electric bus charging system cost analysis method provided by the method embodiment of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0357] This embodiment also provides a cost analysis device for an electric bus charging system, comprising:

[0358] at least one processor;

[0359] at least one memory for storing at least one program;

[0360] When the at least one program is executed by the at least one processor, the at least one processor implements the following Figure 4 The method shown.

[0361] An electric bus charging system cost analysis device of this embodiment can execute an electric bus charging system cost analysis method provided by the method embodiment of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0362] This embodiment also provides a storage medium, which stores instructions or programs that can execute an electric bus charging system cost analysis method provided by the method embodiment of the present invention. When the instructions or programs are run, any combination of implementation steps of the method embodiment can be executed, and the corresponding functions and beneficial effects of the method can be obtained.

[0363] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0364] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0365] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A cost analysis method for an electric bus charging system, characterized in that: The following steps are involved: Define the life cycle cost of the electric bus charging system, which includes the initial investment, future additional investment and annual recurring investment; The initial investment is defined as the initial construction cost of the charging facilities, the initial bus purchase cost and the initial battery purchase cost, and the initial investment of the three charging modes is determined; Define annual recurring investment including operating costs and greenhouse gas emission costs, and determine the annual recurring investment for the three charging modes; Define the future additional investment including technology replacement costs and determine the future additional investment for the three charging modes; Design the operation modes of the electric bus system under three charging modes and calculate the corresponding life cycle costs of the three charging modes; Among them, the three charging modes are static charging station mode, battery swap station mode and dynamic wireless charging lane mode; The formula for the life cycle cost is as follows: F LCC =F CAP +F OP +F GHG +F REP Among them, F LCC is the life cycle cost, F CAP is the initial investment, F OP is the operating cost, F GHG represents the greenhouse gas emission cost, F REP represents the technology replacement cost; The formula for the initial investment is as follows: F CAP =F CO +F BA +F BUS Among them, F CO represents the initial construction cost, F BUS represents the initial bus purchase cost, F BA represents the initial battery purchase cost; Initial construction cost F under three charging modes CO The calculation method is as follows: In the static charging station mode SCS, the initial construction cost F CO Including the cost of building terminal charging stations and the cost of building opportunity charging stations, the expression is as follows: In the formula, x i Indicates whether to choose to build bus station i as an opportunity charging station; C end is the cost of building a terminal charging station, C c,o The unit construction cost of opportunity charging stations; In the battery swap station mode BSS, the initial construction cost F CO is the fixed cost of building a charging exchange station C c,s ; In the dynamic wireless charging lane mode DWCL, the initial construction cost F CO Including the cost of terminal charging stations and the construction cost of charging lanes; the construction cost of the charging lanes includes the construction cost of each network segment and the construction cost of deploying underground feeders and paving the road; the initial construction cost F CO The expression is as follows: In the formula, C end is the cost of building a terminal charging station, i Whether to set up a charging lane on the route between bus station i and bus station i+1, C c,t and C c,l They represent the construction cost of each network segment and the construction cost of each kilometer of charging lane, d i represents the length of the charging lane between bus stop i and bus stop i+1; The expressions for the initial construction costs of the three charging modes are as follows: The expressions for battery purchase costs for the three charging modes are as follows: In the formula, C BA is the battery price, E is the battery capacity, n BA is the number of batteries. In the static charging station mode SCS and the dynamic wireless charging lane mode DWCL, the number of batteries is the same as the number of buses in the bus fleet Q; The expression of initial bus purchase cost is as follows: F BUS =C BUS Q In the formula, C BUS is the unit price of the bus; The operating cost includes power consumption cost and maintenance cost. The expression of the operating cost is as follows: In the formula, F energy,j is the electricity consumption cost, F maintenance,j is the maintenance cost, j represents the year; d rate represents the discount rate; the expressions for the electricity consumption cost under the three charging modes are as follows: In the above formula, for the static charging station mode SCS, the energy consumption includes terminal charging power consumption and opportunity charging power consumption; the annual energy cost is the result of multiplying the energy consumed to complete a single line by the total number of lines served throughout the year, expressed as fTN day Indicates; during the charging process at the terminal station, the amount of electricity used is SOC max -SOC I Multiply by the energy efficiency α end and the unit electricity cost C of the terminal station p,end The energy cost of an opportunity charging station can be calculated from the charging time t c,o and the corresponding charging power P c,o Get; α c,o and C p,o They represent the charging efficiency and unit electricity cost of the opportunity charging station respectively; For the battery swap station mode BSS, let y k indicates whether the battery is replaced on route k; the energy consumed in year j is the sum of the energy consumed on route k multiplied by the size of the bus fleet and the total number of operating days in a year; For the dynamic wireless charging lane mode DWCL, the power consumption cost includes two parts: the terminal station consumption and the cost of the charging channel; the terminal station consumption is: the power used is SOC max -SOC I Multiply by the energy efficiency α end and the unit electricity cost C of the terminal station p,end ; The cost of a charging channel is given by the sum of all the power consumed by the charging channel: Let variable z i and d i They respectively indicate whether the route from bus stop i to bus stop i+1 is constructed as a charging lane and the length of the charging lane; The maintenance cost includes the maintenance cost of buses and the maintenance cost of facilities. The expression of the maintenance cost in the jth year is as follows: Because the maintenance cost of buses and facilities is constant, the maintenance cost in year j depends on the number of buses Q and the number of batteries n in the fleet. BA , and charging mode; The monetary value of the cost of greenhouse gas emissions is expressed as follows: In the formula, C β is the monetary scalar used to convert emissions into capital costs, d rate is the discount rate; F GHG,facility is the greenhouse gas emissions, F GHG,e-bus represents the life cycle greenhouse gas emission costs of electric buses; The technology replacement cost F REP It is to calculate the capital costs incurred during the life cycle operation; The technology replacement cost F REP Including battery replacement cost and bus replacement cost, technology replacement cost F REP The formula expression is as follows: s.t.C REPj =(C BA -C SV SoH j )Eω j (21) Qτ L / τ BUS is the natural lifespan; the battery's low state of health SoH in year j j By calculating according to formula (22), where SoH0 = 100%; In the above formula, ξ day Represents the daily capacity decay rate, N day represents the number of operating days per year; EoL is a constant threshold; the operation modes of the electric bus system under the three charging modes are designed, and the life cycle costs corresponding to the three charging modes are calculated, including: The static charging station mode SCS includes a fixed terminal charging station and some opportunity charging stations deployed at intermediate bus stops. The bus is fully charged at the terminal station, and the battery power is: Discharge occurs during service, and the unit power consumption per kilometer is E d , then the SoC reduction per kilometer is E d / E, multiplied by the distance l i ; For bus stop i, the SoC reached is given by the recursive formula As shown in formula (38): If you select bus stop x i , i∈I is an opportunity charging station, then the binary variable x i is 1; if charging facilities are available, the electric bus can be charged when it stops at the i bus station; when charging, SoC Increase to The amount of electricity that the battery can obtain at bus stop i can be obtained by converting the electric power P c,o Multiply by the stop time t stop Divide it by the battery capacity E to calculate; P c,o t stop x i / E contains two variables x i and E, and is therefore nonlinear; the resulting recursive formula is shown in (39): To ensure that the battery SoC is always higher than the lower limit SoC min , set formula (40) as the constraint: The terminal station can provide an increase of SoC by P c,end t end / E, and formula (41) ensures that the electric bus is fully charged at the terminal; In addition, formula (42) ensures that there are enough buses to provide service at the service frequency f during the operating hours; This optimization problem has four variables, x i is a binary variable indicating whether bus stop i is constructed as an opportunity charging station; for bus fleet size, E represents the initial battery capacity and Q represents the number of buses; Solve the minimum cost F of the static charging station mode SCS LC : For the battery swap station mode BSS, represents the number of cycles that the battery undergoes before replacement; the total number of cycles K can be calculated by multiplying the frequency f by the number of operating hours T and dividing by the fleet size Q, and then rounding the total number of cycles per day to an integer, as shown in formula (48): According to the total number of cycles K, set the decision variable y k ,y k Is a binary variable indicating whether the battery is in the circuit Since the running distance in a day is consistent, we can introduce a new decision variable n k To further simplify the exchange activity, this variable represents the number of cycles the electric bus has gone through before the exchange; y k From n in (49) k Obtained: The bus is at full SoC (i.e. battery charge SoC) in the first service in the morning (line k = 0). max ), as follows: For a unit cycle, the distance is Power consumption is Then, we can get SoC minus For loop k, we reach By subtracting E based on loop k-1 d l i The recursive formula of / E is obtained as shown in formula (51): If line k involves battery swapping, y k =1, that is, 1-y k =0, so Otherwise k =0,1-y k =1, in this case, the recursive formula Applicable; This process can be summarized in formula (52); To ensure that the battery SoC is always higher than the lower limit SoC min , set formula (53) as a constraint; If the battery SoC is higher than the SoC min , and also ensure that the battery can provide enough energy to complete this journey; here, the SoC is introduced safe As a lower threshold, the lower threshold always enables the electric bus to return to its departure station as follows: My k ≤SoC safe -SoC k (54) In addition, formula (56) ensures that there are enough buses operating in the bus system; At the exchange station, the exhausted battery is replaced with a fully charged battery; the replaced battery needs to be charged at the exchange station; this charging process takes less than t c,s ; Then, in order to provide consistent service, redundant batteries are required, as shown in formula (57); This optimization problem has four variables, here, y k Is a binary variable indicating whether the battery is in the circuit exchange; E represents the initial battery capacity, Q represents the number of buses; there is a new variable n BA , which indicates the number of batteries; Find the minimum cost F of the battery swap station mode BSS LC : The dynamic wireless charging lane mode DWCL includes a fixed terminal charging station. Multiple dynamic charging lanes can be deployed between any bus station i and bus station i+1. The bus is fully charged at the terminal station (numbered 0), and the battery power is SoC max ; SoC0=SoC max (62) Discharge occurs during service, and the unit power consumption per kilometer is E c,l , then SoC along with (l i -d i ) increases and decreases. For the route from bus stop i-1 to bus stop i, the SoC i+1 Through the recursive formula Calculate, as shown in (63): To ensure that the battery SoC is always higher than the lower limit SoC min , set (64) as the constraint SoC i ≥SoC min (64) In addition, formula (65) ensures that there are enough buses to maintain the service frequency f during the operation time. To ensure the smooth operation process, we first calculate the total operation time of the bus, including the travel time ∑ i l i / v, boarding and alighting time at bus stops and charging time at terminal stations; End stations can provide charging for low SoC batteries and (66) ensuring that electric buses are fully charged at the terminal; Solve the minimum cost F of the dynamic wireless charging lane mode DWCL LC :

2. An electric bus charging system cost analysis system, applied to the electric bus charging system cost analysis method according to claim 1, characterized in that: include: A cost definition module, used to define the life cycle cost of the electric bus charging system, wherein the life cycle cost includes initial investment, future additional investment and annual recurring investment; The initial investment calculation module is used to define the initial investment, including the initial construction cost of charging facilities, the initial bus purchase cost and the initial battery purchase cost, and determine the initial investment of the three charging modes; An operating cost calculation module, which is used to define the annual recurring investment including operating costs and greenhouse gas emission costs, and determine the annual recurring investment of the three charging modes; Future investment calculation module, used to define future additional investment including technology replacement cost, and determine future additional investment for three charging modes; An operation mode determination module is used to design the operation modes of the electric bus system under three charging modes and calculate the life cycle costs corresponding to the three charging modes; Among them, the three charging modes are static charging station mode, battery replacement station mode and dynamic wireless charging lane mode.

3. A cost analysis device for an electric bus charging system, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method of claim 1.

4. A computer-readable storage medium storing a program executable by a processor, characterized in that: The processor-executable program is used to perform the method according to claim 1 when being executed by the processor.

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