CN105844432A - VANET based electric automobile charge scheduling system and method - Google Patents

Abstract

The invention discloses a VANET (Vehicular Ad-hoc Network) based electric automobile charge scheduling system and method. The system includes an electric automobile intelligent electric meter system, a road side unit RSU, a server and a charge station intelligent electric meter system. The electric automobile intelligent electric meter system includes an intelligent electric meter, a vehicle GPS positioning device, an application unit AU and an onboard unit OBU. The charge station intelligent electric meter system includes an intelligent electric meter and a charge station control and management unit. The method includes that charge stations make charge prices according to geographic locations and lining conditions; a server calculates and obtains an optimal charge station strategy according to real time dynamic information of the charge stations and electric automobiles; and a user determines whether to charge or not according to the received optical strategy and stands in a line in an interface of a target charge station through an application unit.

Description

Electric vehicle charging scheduling system and method based on VANET

Technical Field

The invention belongs to the technical field of electric automobiles, and particularly relates to a VANET (vehicular ad-hoc network) based electric automobile charging scheduling system and method.

Background

With the rising cost of fossil fuels and the increasing awareness of human environmental protection, electric vehicles as a green vehicle help mitigate greenhouse gas emissions. With the large-scale introduction of new energy sources with intermittency and unpredictability, great fluctuation is brought, the safe and stable operation of a power grid is influenced, and the scheduling of the electric automobile helps to alleviate the problem. In addition, studies have shown that replacing fuel powered vehicles with electric vehicles will bring about a great economic return. Electric vehicles have received attention from all parties and are increasingly taking up a greater share of the market. And large-scale electric automobile can also cause harm to the electric wire netting if not controlled to merge into the electric wire netting, and the charging station that has the geographical advantage often can attract more charging demands, leads to the unbalance of demand, so also be the focus of research to electric automobile's scheduling problem.

VANET has emerged as a special mobile ad hoc network due to advances in wireless technology and the automotive industry and people's travel habits. The VANET can improve traffic safety factor, optimize traffic flow, reduce traffic jam, provide network access and entertainment application, share data and the like, and bring great convenience and benefit to life of people. The VANET can bring great convenience for the dispatching of the electric automobile, and is helpful for a user to master information more quickly.

Disclosure of Invention

Aiming at the problems, the invention aims to provide an electromobile charging scheduling system and method based on VANET (vehicular ad hoc network) to enable users to queue for requesting charging service more quickly and conveniently and balance charging requirements, so that the time is saved for the users and the stability of a power grid is improved.

The technical scheme adopted by the invention is as follows:

a VANET-based electric vehicle charging scheduling system comprises an electric vehicle intelligent electric meter system, a Road Side Unit (RSU), a server and a charging station intelligent electric meter system; the intelligent electric meter system of the electric vehicle comprises an intelligent electric meter SM (smart meter), a vehicle-mounted GPS (global positioning system) positioning device, an application unit AU (application unit), and a vehicle-mounted unit OBU (on board unit), wherein the intelligent electric meter system of the charging station comprises an intelligent electric meter and a charging station control management unit; the intelligent electric meter and the vehicle-mounted GPS positioning device of the electric vehicle intelligent electric meter system are respectively in wired connection with the vehicle-mounted unit, the application unit is in wired or wireless connection with the vehicle-mounted unit, wireless communication between the vehicle-mounted unit and the vehicle-mounted unit is achieved between the vehicle-mounted unit and the road side unit through V2V (vehicle-to-vehicle), V2R (vehicle-to-RSU, vehicle and base station), the road side unit and the road side unit are in wired connection, the road side unit and the charging station control management unit are respectively in wired connection with the server, and the intelligent electric meter and the charging station control management unit of the charging station intelligent electric meter system are in wired connection.

The intelligent ammeter of the electric automobile intelligent ammeter system has the functions of detecting the charge state SoC (state of charge) of the battery, judging the energy flow direction according to the phase difference of voltage and current waveforms, namely, feeding energy to a power grid or transmitting energy to the electric automobile by the power grid, calculating the charge and discharge habits of a user according to historical data and user input data, and pushing charge and discharge suggestions to the user through an application unit when a certain charge state is met and the charge and discharge habits of the user are met; the vehicle-mounted GPS positioning device is used for positioning the position of the electric automobile and providing shortest path navigation to a target charging station; the application unit is a mobile application of a mobile phone or an embedded unit integrated in a vehicle-mounted unit, when a user of the electric vehicle needs a charging service, the user can queue and take a number directly through the application unit, and the push service is provided, so that a certain time is saved for the user; the vehicle-mounted units are mounted on the electric automobile, and the electric automobile information is relayed and forwarded between the vehicle-mounted units through V2V wireless communication; the roadside units are uniformly deployed at two sides of a road, and electric vehicle information transmitted by the vehicle-mounted unit is collected through V2R wireless communication; the intelligent electric meter in the charging station intelligent electric meter system has the functions of collecting historical and real-time electric power price information of a power grid, detecting the charging amount conveyed to the electric automobile, calculating the real-time queuing condition and formulating the real-time charging price; the function of the charging station control management unit is to transmit real-time charging station information to the server, and to queue users queued on the application unit and users arriving at the charging station; the server calculates to obtain an optimal charging station strategy according to the information transmitted by the road side unit and the charging station control management unit; and after receiving the optimal strategy transmitted by the server, the road side unit transmits the optimal strategy to an electric vehicle user through R2V (RSU-to-vehicle) and V2V wireless communication.

When the intelligent electric meter of the electric automobile intelligent electric meter system detects that the SoC is lower than a certain preset threshold value or accords with the charging habit of a user, the electric automobile considers the charging service; the operation mode of the application unit can be a key mode, a touch screen mode or a voice control mode; the real-time charging station information sent to the server by the charging station control management unit comprises position information, real-time charging price, additional cost and queuing condition, wherein the real-time charging price relates to regional difference and demand adjustment; the charging station control management unit function can also comprise pushing reminding information to the user, and the setting of the pushing information can be set according to the preference and the living habits of the user, and comprises a reminding time starting point and a reminding interval time. Similarly, when the smart meter of the electric vehicle smart meter system detects that SoC is higher than a certain preset threshold and conforms to the habit of a user feeding energy to the power grid, the electric vehicle will consider discharging to the power grid.

The present invention is discussed in terms of electric vehicle charging. Considering different user characteristics and different living habits of different users under actual conditions, sometimes the users are anxious to charge the electric vehicle and wish to seek a priority charging service at a higher price, and for humanization, priorities are introduced, so that the users seeking the priority service can enjoy a non-dominated priority service, but pay a certain amount, and therefore the electric vehicle users are divided into two categories: a. a VIP (guest) user seeking priority service; b. the general user.

The non-preemptive priority service means that when a VIP user with a higher priority arrives at a charging station (for a user who uses an application unit to queue, the charging station confirms a charging option), if the charging pile provides the charging service, the charging pile cannot be preemptive to the charging pile regardless of whether the VIP user or a common user receives the charging service.

A VANET-based electric vehicle charging scheduling method comprises the following steps:

s100, the intelligent electric meters of all charging stations are combined with the positions of the located sections and the electric power price information, real-time charging prices are formulated according to the current queuing conditions, and the charging station control management unit transmits the real-time charging station information to a server;

s200, when an intelligent electric meter in the electric automobile intelligent electric meter system detects that SoC is lower than a certain threshold or accords with the charging habit of a user, a vehicle-mounted unit sends a charging service requirement and electric automobile real-time information to a server;

s300, calculating by the server according to the received real-time information of the electric automobile and the charging station to obtain an optimal charging station strategy and a function utility value of the electric automobile;

s400, the vehicle-mounted unit pushes the received optimal charging station strategy, the function utility value and the charging station information to a user through the application unit;

s500, selecting whether to charge or not by a user according to the self requirement and the judgment on the function utility value, and directly queuing and taking a number on a target charging station interface through an application unit if the charging selection is confirmed;

s600, after receiving queuing information transmitted by the application unit, a charging station control management unit of the target charging station arranges a user into a charging queue;

s700, when a user wants to go to a target charging station, the user sends a decision to the vehicle-mounted GPS positioning device through the application unit, and the vehicle-mounted GPS positioning device provides shortest path navigation to the target charging station.

Step S600 may be followed by step S600A: judging whether the user needs to push the reminding service, if so, sending push information to the application unit at a specific time according to user setting; otherwise, step S700 is performed.

The specific steps of step S100 are:

s110, calculating average queuing waiting time, and averaging the queuing waiting length;

s120, setting the regional price f by the charging station j according to the district_j ⁽¹⁾Adjusting the price f according to the demand calculated by the queuing condition_j ⁽²⁾Weighted to obtain the charge price f_j。

And S130, transmitting real-time charging station information including charging price, additional cost, position information and queuing condition to the server.

In step S200, when the SoC is lower than a predetermined threshold or meets the charging habit of the user, the electric vehicle considers charging, and the threshold may be set by a manufacturer or may be customized by the user. Once the intelligent electric meter in the electric vehicle intelligent electric meter system detects that the SoC is lower than a set value, the vehicle-mounted unit sends a charging demand and electric vehicle real-time information to the server. The real-time information comprises real-time position, required electric quantity and user weight parameter.

The specific steps of step S300 are:

s310, determining each weight of the utility function and a user parameter value according to the user characteristics;

s320, calculating utility values of the charging stations to users according to the electric vehicles and the real-time information of the charging stations to obtain a target function;

and S330, optimizing the objective function to obtain an optimal charging station selection strategy.

The invention has the following remarkable advantages:

by means of the VANET environment, a certain amount of time is saved by allowing the user to queue the number directly under the target charging station interface through the application unit when the user needs to seek charging services.

The dispatching system can set reminding service, and send the push message of queuing situation to the user according to the user's setting, need not to stay at the charging station, provides an effective scheme on the problem of too long waiting charging time.

The user is allowed to seek priority service under the condition of paying extra additional cost, and a humanized scheduling method is provided for the user.

And a pricing mechanism is provided by considering the difference of the sections and the adjustment of the demand, so that the charging price is dynamically changed along with the queuing condition, the charging demand is favorably adjusted, and the stability of the power grid is improved.

Drawings

Fig. 1 is a schematic diagram of an electric vehicle charging scheduling system based on VANET according to the present invention.

FIG. 2 is a schematic diagram of an application unit interface without push function according to the present invention.

FIG. 3 is a schematic diagram of an interface of an application unit with a push function according to the present invention.

Fig. 4 is a flowchart of the VANET-based electric vehicle charging scheduling method without a push function according to the present invention.

Fig. 5 is a flowchart of the VANET-based electric vehicle charging scheduling method with a push function according to the present invention.

Fig. 6 is a detailed flowchart of step S100 in fig. 4 or 5.

Fig. 7 is a detailed flowchart of step S300 in fig. 4 or 5.

Detailed Description

The following describes in further detail specific embodiments of the present invention with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of an electric vehicle charging scheduling system based on VANET according to the present invention.

1. In this embodiment, as shown in fig. 1, an electric vehicle charging scheduling system based on VANET includes an electric vehicle smart meter system 100, a roadside unit 200, a server 300, a charging station smart meter system 400; the electric vehicle smart electric meter system 100 comprises a smart electric meter 110, a vehicle-mounted GPS positioning device 120, an application unit 130 and a vehicle-mounted unit 140, wherein the charging station smart electric meter system 400 comprises a smart electric meter 410 and a charging station control management unit 420; the smart meter 110 and the vehicle-mounted GPS positioning device 120 are respectively connected with the vehicle-mounted unit 140 in a wired manner, the application unit 130 is connected with the vehicle-mounted unit 140 in a wired manner or in a wireless manner, the vehicle-mounted unit 140 and the road side unit 200 realize wireless communication via V2V and V2R between the vehicle-mounted unit 140 and the vehicle-mounted unit 140, the road side unit 200 and the road side unit 200 are connected in a wired manner, the road side unit 200 and the charging station control management unit 420 are respectively connected with the server 300 in a wired manner, and the smart meter 410 is connected with the charging station control management unit 420 in a wired manner.

The smart meter 110 in the electric vehicle smart meter system 100 is configured to detect a charge state of a battery, a speed of the electric vehicle, a charge/discharge amount of the electric vehicle, and determine a direction of energy flow according to a phase difference between voltage and current waveforms, that is, whether the electric vehicle feeds energy to a power grid or the power grid delivers energy to the electric vehicle, calculate a charge/discharge habit of a user according to historical data and user input data, and push a charge/discharge advice to the user through the application unit 130 when a certain charge state is satisfied and the charge/discharge habit of the user is satisfied; the vehicle-mounted GPS positioning device 120 is used for positioning the position of the electric vehicle and providing shortest path navigation to a target charging station when needed; the vehicle-mounted unit 140 is mounted on the electric vehicle and used for relaying and forwarding dynamic information of the electric vehicle through a V2V wireless communication technology; the roadside units 200 are uniformly deployed at two sides of a road, and are used for collecting the electric vehicle dynamic information transmitted by the vehicle-mounted unit 140 through a V2R wireless communication technology and transmitting the information to the server 300 through a wired connection; the smart meter 410 in the charging station smart meter system 400 is configured to collect history of a power grid and power price information, detect a charging amount input to the electric vehicle, calculate a real-time queuing condition, and formulate a real-time charging price; the function of the charging station control management unit 420 includes transmitting real-time charging station information to the server 300, queuing users queued on the application unit 130 and users arriving at the charging station; the server 300 calculates an optimal charging station policy according to the real-time information transmitted from the roadside unit 200 and the charging station control management unit 420. After receiving the optimal strategy transmitted from the server 300, the roadside unit 200 transmits the optimal strategy to the electric vehicle user through R2V and V2V wireless communication technologies.

The real-time charging station information transmitted by the charging station control management unit 420 to the server 300 includes location information, a real-time charging price, an additional charge for seeking a priority service, and queuing conditions, wherein the real-time charging price relates to regional differences and demand adjustment.

When the smart meter 110 in the electric vehicle smart meter system 100 detects that the battery charge state is lower than a predetermined threshold or meets the charging habit of the user, the electric vehicle considers the charging service, and the threshold may be set as a fixed value or may be set according to the living habit and the actual demand of the user.

Fig. 2 is a schematic diagram of an interface of the application unit 130 without a push function.

In this embodiment, as shown in fig. 2, the application unit 130 may be a mobile app (application) or an embedded unit integrated in the vehicle-mounted unit 140, and when the user of the electric vehicle needs a charging service, the user can queue and take a number directly through the application unit 130 and has a push service, which saves a certain time for the user; the operation mode of the application unit 130 may be a key mode, a touch screen mode or a voice control mode.

Considering different user characteristics and different living habits of different users under actual conditions, sometimes the users are anxious to charge the electric vehicle and wish to seek a priority charging service at a higher price, and for humanization, priorities are introduced, so that the users seeking the priority service can enjoy a non-dominated priority service, but pay a certain amount, and therefore the electric vehicle users are divided into two categories: a. VIP users seeking priority service; b. the general user. It is not excluded that some users choose to queue to take their numbers directly to the charging station for reasons of habit or proximity, but the invention relates to the scheduling of users queuing to take numbers using the application unit 130, with only the users queuing to take numbers directly to the charging station as an influencing factor.

When a non-preemptive priority service, that is, when a VIP user with a higher priority arrives at a charging station (for a user who is queued using the application unit 130, the charging station confirms a charging option), if the charging pile is providing a charging service, the charging pile cannot be preemptively occupied by either a VIP user or a general user who receives the charging service. The average queuing latency for VIP users is the sum of two fractions of time: the average charging time sum of the VIP users who are arranged in front and the average waiting time for charging piles to be idle; the average queuing latency of a normal user is the sum of three parts: the average sum of charging time of the VIP users and general users who are ranked in front, the average waiting time for charging piles to be idle, and the average sum of delay time caused by priority service of VIP users who arrive during waiting.

Assuming that the VIP user and the general user respectively arrive at charging station j in mutually independent poisson flows, the user arrival rate of charging station j is:

λ_j＝λ_v,j+λ_u,j，

in the formula, λ_jArrival rates for all users to reach charging station j; lambda [ alpha ]_v,jThe arrival rate of VIP users at charging station j; lambda [ alpha ]_u,jThe arrival rate of the general user at charging station j.

Then at any moment in time the probability of the user arriving at charging station j being a VIP user and a regular user is λ respectively_v,j/λ_jAnd λ_u,j/λ_j。

And assuming that charging of each charging pile of the charging station j is mutually independent, service time is distributed according to negative indexes, and assuming that average charging time of the VIP user is equal to average charging time of the common user, average charging time of all users in the charging station j is as follows:

$\stackrel{\‾}{{\mathrm{ct}}_j}=E\left({\mathrm{ct}}_j\right)=({\mathrm{\λ}}_{v,j}/{\mathrm{\λ}}_j)*(1/{\mathrm{\μ}}_j)+({\mathrm{\λ}}_{u,j}/{\mathrm{\λ}}_j)*(1/{\mathrm{\μ}}_j)=1/{\mathrm{\μ}}_j,$

in the formula,average charging time for all users in charging station j; ct_jCharging time for all users in charging station j; mu.s_jThe average service rate of the individual charging poles for charging station j.

Fig. 3 is a schematic diagram of an interface of the application unit 130 with a push function.

In this embodiment, as shown in fig. 3, the charging station control management unit 420 functions may further include pushing a reminder message to the user, where the setting of the push message may be set according to the preference and the living habit of the user, including a reminder time start point and a reminder interval time.

Fig. 4 and 5 are flow charts of VANET-based electric vehicle charging scheduling methods without a push function and with a push function according to the present invention, respectively.

In this embodiment, as shown in fig. 4 and 5, the VANET-based electric vehicle charging scheduling method includes the following steps:

s100, the intelligent electric meters 410 of all charging stations combine the location of the place and the electric power price information, real-time charging prices are set according to the current queuing condition, and the charging station control management unit 420 transmits the real-time charging station information to the server 300;

s200, when the intelligent electric meter 110 in the electric automobile intelligent electric meter system 100 detects that the SoC is lower than a certain threshold or accords with the charging habit of a user, the vehicle-mounted unit 140 sends the charging service requirement and the electric automobile real-time information to the server 300;

s300, the server 300 calculates to obtain an optimal charging station strategy and a function utility value of the electric automobile according to the received real-time information of the electric automobile and the charging station;

s400, the vehicle-mounted unit 140 pushes the received optimal charging station strategy, the function utility value and the charging station information to a user through the application unit 130;

s500, selecting whether to charge or not by a user according to the self requirement and the judgment on the function utility value, and directly queuing and taking a number on a target charging station interface through the application unit 130 if the charging selection is confirmed;

s600, after receiving the queuing information transmitted from the application unit 130, the charging station control management unit 420 of the target charging station queues the user in a charging queue;

s700, when the user wants to go to the target charging station, the application unit 130 sends a decision to the vehicle-mounted GPS positioning device 120, and the vehicle-mounted GPS positioning device 120 provides the shortest path navigation to the target charging station.

Step S600 may be followed by step S600A: judging whether the user needs a reminding service, if so, sending push reminding information to the application unit 130 at a specific time according to user setting; otherwise, step S700 is performed.

Fig. 6 is a detailed flowchart of step S100 in fig. 4 or 5.

In this embodiment, as shown in fig. 6, the specific steps of step S100 are:

s110, calculating average queuing waiting time, wherein the average queuing waiting queue length:

when all charging piles are providing services, no matter whether a VIP user or a common user arrives at the charging station, the charging piles need to wait for the charging piles to be idle. The occupation of the charging piles is irrelevant to the user types, so the average time of waiting for the charging piles to be idle is calculated according to the service time distribution of the charging stations, the average charging time of the VIP users is equal to that of the common users, and therefore the average waiting time of waiting for the charging piles to be idle is irrelevant to the queuing sequence of the users and the user types do not need to be considered when the average waiting time of the charging piles to be idle is calculated.

The probability that each charging pile of the charging station provides the charging service after the user arrives at the charging station j is obtained by an Ireland delay formula as follows:

$\underset{n_j=N_j}{\overset{\mathrm{\∞}}{\Σ}}{p}_{n_j}=\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j},$

wherein,

ρ_j＝λ_j/(μ_j*N_j)＝ρ_1j/N_j，ρ_1j＝ρ_v,j+ρ_u,j＝λ_v,j/μ_j+λ_u,j/μ_j＝λ_j/μ_j，

ρ_v,j＝λ_v,j/μ_j，ρ_u,j＝λ_u,j/μ_j，

in the formula, n_jThe number of all users in the charging station j is set; n is a radical of_jThe number of charging piles for charging station j; p is a radical of_njFor charging station j all users number n_jThe probability of (d);the number of all users at charging station j is N_jThe probability of (d); rho_jIntensity of service for charging station j; p is a radical of_0jThe probability that the number of all users in the charging station j is 0 is obtained; rho_1jThe charging service intensity of all users for a single charging pile in the charging station j is obtained; rho_v,jCharging service intensity of a single charging pile in a charging station j to the VIP user; rho_u,jThe charging service intensity of a single charging pile in the charging station j to a common user is achieved.

The average time for any user to wait for the charging pile to be idle is as follows:

$\underset{n_j=N_j}{\overset{\mathrm{\∞}}{\Σ}}{p}_{n_j}*E\left({\mathrm{et}}_j\right)=\underset{n_j=N_j}{\overset{\mathrm{\∞}}{\Σ}}{p}_{n_j}*\stackrel{\‾}{{\mathrm{et}}_j}=\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\stackrel{\‾}{{\mathrm{et}}_j},$

in the formula, et_jRemaining service time for charging station j, i.e. when the user arrives at charging station j, if N_jIf all the charging piles are occupied, the charging piles still need to experience et_jOnly one charging pile can be vacated to provide charging service for the next user;the average remaining service time for charging station j.

Because the user types are not distinguished when the average waiting time of the idle charging piles is calculated, the queuing waiting time of the users is the sum of two parts of time: the average charging time sum of the users who are arranged in the front and the average waiting time for leaving the charging pile are as follows:

the sum of the average charging times of the users who are ranked ahead is:

$\stackrel{\‾}{{\mathrm{ct}}_j}*{\mathrm{lq}}_j={\mathrm{lq}}_j/{\mathrm{\μ}}_j={\mathrm{\ρ}}_{1j}*{\mathrm{wq}}_j,$

wherein lq is_j＝λ_j*wq_j，

In the formula, lq_jThe average number of all users in charge station j who are queued for charging service.

The average waiting time for the charging pile to be idle is

So as to obtain the compound with the characteristics of,

${\mathrm{wq}}_j=\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\stackrel{\‾}{{\mathrm{et}}_j}+{\mathrm{\ρ}}_{1j}*{\mathrm{wq}}_j,$

so as to obtain the compound with the characteristics of,

$\stackrel{\‾}{{\mathrm{et}}_j}=\frac{(1-{\mathrm{\ρ}}_j)*(1-{\mathrm{\ρ}}_{1j})}{p_{N_j}}*{\mathrm{wq}}_j,$

in the formula, wq_jThe average queue wait time for all users in station j.

From M/M/N_jThe derivation conclusion of the waiting queuing model is as follows:

${\mathrm{wq}}_j=\frac{{({\mathrm{\ρ}}_j*N_j)}^{N_j}*p_{0j}}{{\mathrm{\μ}}_j*N_j*N_j!*{(1-{\mathrm{\ρ}}_j)}^2},$

so as to obtain the compound with the characteristics of,

$\stackrel{\‾}{{\mathrm{et}}_j}=\frac{(1-{\mathrm{\ρ}}_j)*(1-{\mathrm{\ρ}}_{1j})}{p_{N_j}}*\frac{{({\mathrm{\ρ}}_j*N_j)}^{N_j}*p_{0j}}{{\mathrm{\μ}}_j*N_j*N_j!*{(1-{\mathrm{\ρ}}_j)}^2}=\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)},$

then the average waiting time for the charging pile to be idle is as follows:

$\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\stackrel{\‾}{{\mathrm{et}}_j}=\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)},$

A. calculating the average queuing waiting time when the VIP user is queued in the queue of charging station j, the average queuing waiting queue length:

the VIP user cannot forcibly occupy the charging pile providing the charging service, and can only arrange in front of the ordinary user, and the average queuing waiting time of the VIP user consists of two parts:

1) average sum of charging times of preceding VIP users:

$\stackrel{\‾}{{\mathrm{ct}}_{v,j}}*{\mathrm{lq}}_{v,j}=\stackrel{\‾}{{\mathrm{ct}}_j}*{\mathrm{lq}}_{v,j}={\mathrm{lq}}_{v,j}/{\mathrm{\μ}}_j={\mathrm{\ρ}}_{v,j}*{\mathrm{wq}}_{v,j},$

wherein lq is_v,j＝λ_v,j*wq_v,j，

In the formula,average charging time for VIP users in charging station j; lq of_v,jAveragely queuing for VIP users in the charging station j to wait for the queue length; wq of_v,jThe average queuing wait time for VIP users in charging station j.

2) The average waiting time for the charging pile to be idle is

Obtaining:

${\mathrm{wq}}_{v,j}={\mathrm{\ρ}}_{v,j}*{\mathrm{wq}}_{v,j}+\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\stackrel{\‾}{{\mathrm{et}}_j}={\mathrm{\ρ}}_{v,j}*{\mathrm{wq}}_{v,j}+\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)},$

the average queuing waiting time and the average queuing waiting queue length of the VIP user at charging station j are respectively as follows:

${\mathrm{wq}}_{v,j}=\frac{p_{N_j}}{1-{\mathrm{\ρ}}_{v,j}}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*{(1-{\mathrm{\ρ}}_j)}^2},$

${\mathrm{lq}}_{v,j}={\mathrm{\λ}}_{v,j}*{\mathrm{wq}}_{v,j}={\mathrm{\λ}}_{v,j}*\frac{p_{N_j}}{1-{\mathrm{\ρ}}_{v,j}}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*{(1-{\mathrm{\ρ}}_j)}^2},$

wherein:

ρ_j＝λ_j/(μ_j*N_j)，ρ_v,j＝λ_v,j/μ_j，λ_j＝λ_v,j+λ_u,j，

B. calculating the average queuing waiting time when the common users are arranged in the queue of the charging station j, wherein the average queuing waiting queue length is as follows:

the average queuing waiting time of the ordinary users is composed of three parts:

1) the sum of the average charging times of the VIP users and the general users ranked ahead is:

$\stackrel{\‾}{{\mathrm{ct}}_{v,j}}*{\mathrm{lq}}_{v,j}=\stackrel{\‾}{{\mathrm{ct}}_j}*{\mathrm{lq}}_{v,j}={\mathrm{lq}}_{v,j}/{\mathrm{\μ}}_j={\mathrm{\ρ}}_{v,j}*{\mathrm{wq}}_{v,j},$

$\stackrel{\‾}{{\mathrm{ct}}_{u,j}}*{\mathrm{lq}}_{u,j}=\stackrel{\‾}{{\mathrm{ct}}_j}*{\mathrm{lq}}_{u,j}={\mathrm{lq}}_{u,j}/{\mathrm{\μ}}_j={\mathrm{\ρ}}_{u,j}*{\mathrm{wq}}_{u,j},$

wherein lq is_v,j＝λ_v,j*wq_v,j，lq_u,j＝λ_u,j*wq_u,j，

In the formula,average charging time for a common user in charging station j; lq of_u,jAverage queuing waiting queue length for common users in the charging station j; wq of_u,jThe average queue waiting time of the average user in charging station j.

2) The average waiting time for the charging pile to be idle is

3) The average delay time due to priority service of VIP users arriving during the waiting period is summed up:

the VIP users have priority service privileges, and if any VIP user arrives at charging station j during the time that the common user is queued to receive charging service, the VIP user will be prioritized in front of the common user. Due to the waiting time wq of queuing required by the ordinary users_u,jDuring this period, the average number of VIP users arriving is wq_u,j*λ_v,jThen the sum of the average charging times it requires is:

${\mathrm{wq}}_{u,j}*{\mathrm{\λ}}_{v,j}*\stackrel{\‾}{{\mathrm{ct}}_{v,j}}={\mathrm{wq}}_{u,j}*{\mathrm{\ρ}}_{v,j},$

so as to obtain the compound with the characteristics of,

${\mathrm{wq}}_{u,j}={\mathrm{\ρ}}_{v,j}*{\mathrm{wq}}_{v,j}+{\mathrm{\ρ}}_{u,j}*{\mathrm{wq}}_{u,j}+\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)}+{\mathrm{wq}}_{u,j}*{\mathrm{\ρ}}_{v,j},$

the average queuing waiting time and the average queuing waiting queue length of the ordinary user at the charging station j are respectively as follows:

$\begin{array}{c}{\mathrm{wq}}_{u,j}=\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)}*\frac{1}{1-{\mathrm{\ρ}}_{u,j}-{\mathrm{\ρ}}_{v,j}}+\frac{{\mathrm{\ρ}}_{v,j}}{1-{\mathrm{\ρ}}_{u,j}-{\mathrm{\ρ}}_{v,j}}*{\mathrm{wq}}_{v,j}\\ =\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)}+\frac{p_{N_j}}{1-{\mathrm{\ρ}}_{v,j}}*\frac{{\mathrm{\ρ}}_{v,j}}{{\mathrm{\μ}}_j*N_j*{(1-{\mathrm{\ρ}}_j)}^2}\end{array},$

${\mathrm{lq}}_{u,j}={\mathrm{\λ}}_{u,j}*{\mathrm{wq}}_{u,j}={\mathrm{\λ}}_{u,j}*(\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)}+\frac{p_{N_j}}{1-{\mathrm{\ρ}}_{v,j}}*\frac{{\mathrm{\ρ}}_{v,j}}{{\mathrm{\μ}}_j*N_j*{(1-{\mathrm{\ρ}}_j)}^2}),$

wherein,

ρ_j＝λ_j/(μ_j*N_j)，ρ_u,j＝λ_u,j/μ_j，ρ_v,j＝λ_v,j/μ_j，λ_j＝λ_v,j+λ_u,j，

from the above calculation process, the average number of all users in the charging station j waiting for the charging service in queue is:

$\begin{array}{c}{\mathrm{lq}}_j={\mathrm{lq}}_{v,j}+{\mathrm{lq}}_{u,j}={\mathrm{\λ}}_{v,j}*{\mathrm{wq}}_{v,j}+{\mathrm{\λ}}_{u,j}*{\mathrm{wq}}_{u,j}\\ ={\mathrm{\λ}}_{v,j}*\frac{p_{N_j}}{1-{\mathrm{\ρ}}_{v,j}}*\frac{1-N_j*{\mathrm{\ρ}}_j}{{\mathrm{\μ}}_j*N_j*{(1-{\mathrm{\ρ}}_j)}^2}+{\mathrm{\λ}}_{u,j}*(\frac{p_{N_j}}{1-{\mathrm{\ρ}}_j}*\frac{1}{{\mathrm{\μ}}_j*N_j*(1-{\mathrm{\ρ}}_j)}+\frac{p_{N_j}}{1-{\mathrm{\ρ}}_{v,j}}*\frac{{\mathrm{\ρ}}_{v,j}}{{\mathrm{\μ}}_j*N_j*{(1-{\mathrm{\ρ}}_j)}^2})\end{array}.$

s120, setting the regional price f by the charging station j according to the district_j ⁽¹⁾Adjusting the price f according to the demand calculated by the queuing condition_j ⁽²⁾Weighted to obtain the charge price f_j：

Ground is favorableThe charging station can attract more customers, and the charging price can be set higher, therefore, the invention divides the area into z areas according to a certain criterion, and the area price f of the charging station in the same area_j ⁽¹⁾Are equal. The division criteria are, for example, traffic volume, distance from the city center, whether it is a residential area, a commercial area or an industrial area, etc.

According to defined criteria, the area price f of the charging station_j ⁽¹⁾Comprises the following steps:

f_j ⁽¹⁾＝f_z

in the formula (f)_zIs the zone price of the charging station in zone z.

In order to adjust the charging requirement, the user arrival rate of each charging station is close to the optimal value, the charging price dynamically changes along with the queuing condition, namely the actual queuing waiting queue length is larger than the corresponding queuing waiting queue length under the optimal value, and the charging price is raised; and if the actual queue waiting length is smaller than the corresponding queue waiting length under the optimal value, the charging price is reduced. The optimal arrival rate can be set according to the number of charging piles, the service strength, the power grid load and the like of the charging station.

Adjusting the price f according to the demand calculated by the queuing situation_j ⁽²⁾Comprises the following steps:

${f_j}^{\left(2\right)}={f_j}^{\left(2\right)}\frac{{\mathrm{lq}}_j({\mathrm{\λ}}_{v,j},{\mathrm{\λ}}_{u,j})-{{\mathrm{lq}}_j}^{*}({{\mathrm{\λ}}_{v,j}}^{*},{{\mathrm{\λ}}_{u,j}}^{*})}{{{\mathrm{lq}}_j}^{*}({{\mathrm{\λ}}_{v,j}}^{*},{{\mathrm{\λ}}_{u,j}}^{*})},$

in the formula, lq_j(λ_v,j,λ_u,j) Waiting for the actual average queue length; lq of_j ^*(λ_v,j ^*,λ_u,j ^*) Waiting for the queue length for average queuing at the optimal arrival rate.

Wherein the demand adjust price function should satisfy:

1) function value with lq_j(λ_v,j,λ_u,j) Is increased by an increase in;

2)

by way of example only, it is possible to illustrate,

${f_j}^{\left(2\right)}=k_j*\frac{{\mathrm{lq}}_j({\mathrm{\λ}}_{v,j},{\mathrm{\λ}}_{u,j})-{{\mathrm{lq}}_j}^{*}({{\mathrm{\λ}}_{v,j}}^{*},{{\mathrm{\λ}}_{u,j}}^{*})}{{{\mathrm{lq}}_j}^{*}({{\mathrm{\λ}}_{v,j}}^{*},{{\mathrm{\λ}}_{u,j}}^{*})},$

in the formula, k_jThe slope of the price function is adjusted for demand.

The charge price function is then:

$f_j={{\mathrm{\β}}_j}^{\left(1\right)}*f_z+{{\mathrm{\β}}_j}^{\left(2\right)}*{f_j}^{\left(2\right)}\left(\frac{{\mathrm{lq}}_j({\mathrm{\λ}}_{v,j},{\mathrm{\λ}}_{u,j})-{{\mathrm{lq}}_j}^{*}({{\mathrm{\λ}}_{v,j}}^{*},{{\mathrm{\λ}}_{u,j}}^{*})}{{{\mathrm{lq}}_j}^{*}({{\mathrm{\λ}}_{v,j}}^{*},{{\mathrm{\λ}}_{u,j}}^{*})}\right).$

wherein β is satisfied_j ⁽¹⁾+β_j ⁽²⁾＝1，β_j ⁽¹⁾≥0，β_j ⁽²⁾≥0，

In the formula, β_j ⁽¹⁾，β_j ⁽²⁾Is the weight coefficient of charging station j.

S130, transmitting the real-time charging station information including charging price, additional charge, location information, queuing condition to the server 300.

Fig. 7 is a detailed flowchart of step S300 in fig. 4 or 5.

In this embodiment, as shown in fig. 7, the specific steps of step S300 are:

s310, determining each weight of the utility function and a user parameter value according to the user characteristics:

the utility function for user i to select charging station j is:

U_i,j＝z_i-α_i ⁽¹⁾*l_i,j-α_i ⁽²⁾*(b_i,j*wq_v,j+(1-b_i,j)*wq_u,j)-α_i ⁽³⁾*(f_j+b_i,j*c_j)，

wherein, z is satisfied_i≥0，α_i ⁽¹⁾+α_i ⁽²⁾+α_i ⁽³⁾＝1，α_i ⁽¹⁾≥0，α_i ⁽²⁾≥0，α_i ⁽³⁾≥0，b_i,j∈{0,1}，

In the formula, z_iCharge willingness parameter for user i α_i ⁽¹⁾，α_i ⁽²⁾，α_i ⁽³⁾The weight parameter is the user i; l_i,jThe distance from the position of the user i to the charging station j is obtained; b_i,jWhether or not to choose to seek priority service for user i, i.e. to become a VIP user, b_i,j1 is VIP user, b_i,jIf 0, the user is a common user; wq of_v,jAverage queuing latency for VIP users; wq of_u,jAverage queuing waiting time for ordinary users; f. of_jA charge price for charge station j; c. C_jAn additional charge is required to seek priority service at charging station j.

Wherein z is_i，α_i ⁽¹⁾，α_i ⁽²⁾，α_i ⁽³⁾The user can set the interface of the application unit 130, and the evaluation can be carried out according to the historical data of the user; c. C_jSet by the charging station; b_i,jObtained by optimization calculation.

S320, calculating utility values of the charging stations to users according to the electric vehicles and the real-time information of the charging stations to obtain a target function:

the objective function is:

$\max U_i=max\underset{j=1}{\overset{J}{\Σ}}{U}_{i,j}*x_{i,j},$

wherein, satisfy

In the formula, J is the number of charging stations; x is the number of_i,jSelecting a variable, x, for the binary_i,jIf 1, user i selects charging station j, x_i,jIf 0, the user i does not select charging station j.

S330, optimizing a target function to obtain an optimal charging station selection strategy:

by means of an optimization algorithm, an optimal solution is obtained, comprising the user's choice of charging stations and whether priority service is sought, i.e. x_i,jAnd b_i,jThe value of (a). If it isThe optimal strategy is not to select any charging station.

Therefore, the invention has the following advantages:

1) by means of the VANET environment, the user is allowed to queue for a number by means of the application unit 130, saving a certain amount of time, i.e. the charging time of the arriving user during the arrival at the charging station. In this embodiment, for VIP users, the time savings isFor the ordinary user, the time saved is

In the formula, v_iThe average speed of the electric vehicle i.

2) The arrangement of the push reminding service enables the user not to stay at the charging station, and an effective scheme is provided for the problem of too long waiting time for charging.

3) Allowing the user to seek priority service at a premium.

4) The provided pricing mechanism enables the charging price to dynamically change along with the queuing condition by considering the section difference and the requirement adjustment, so that the charging requirement is favorably adjusted, and the stability of the power grid is improved.

Claims (9)

1. The electric vehicle charging scheduling system based on the VANET is characterized by comprising an electric vehicle intelligent electric meter system (100), a road side unit (200), a server (300) and a charging station intelligent electric meter system (400); the electric vehicle intelligent electric meter system (100) comprises an intelligent electric meter (110), a vehicle-mounted GPS positioning device (120), an application unit (130) and a vehicle-mounted unit (140), wherein the charging station intelligent electric meter system (400) comprises an intelligent electric meter (410) and a charging station control management unit (420); the intelligent electric meter (110) and the vehicle-mounted GPS positioning device (120) are respectively in wired connection with the vehicle-mounted unit (140), the application unit (130) is in wired or wireless connection with the vehicle-mounted unit (140), the vehicle-mounted unit (140) and the road side unit (200) are in wireless communication through V2V and V2R respectively, the road side unit (200) is in wired connection with the road side unit (200), the road side unit (200) and the charging station control management unit (420) are respectively in wired connection with the server (300), and the intelligent electric meter (410) is in wired connection with the charging station control management unit (420).

2. The VANET-based electric vehicle charging scheduling system of claim 1, wherein the smart meter (110) in the electric vehicle smart meter system (100) is used for detecting the charge state of a battery, the speed and the charge and discharge amount of an electric vehicle, judging the energy flowing direction according to the phase difference of voltage and current waveforms, calculating the charge and discharge habits of a user according to historical data and user input data, and pushing a charge and discharge suggestion to the user through the application unit (130) when a certain charge state is met and the charge and discharge habits of the user are met; the vehicle-mounted GPS positioning device (120) is used for positioning the position of the electric automobile and providing shortest path navigation to a target charging station; the application unit (130) is a mobile application of a mobile phone or an embedded unit integrated in the vehicle-mounted unit (140), and when an electric vehicle user needs a charging service, the electric vehicle user can directly queue for number fetching through the application unit (130) and has a push service, so that a certain time is saved for the user; the vehicle-mounted unit (140) is mounted on an electric vehicle, and electric vehicle information is relayed and forwarded between the vehicle-mounted units (140) through V2V wireless communication; the roadside units (200) are uniformly deployed at two sides of a road, and electric vehicle information transmitted by the vehicle-mounted unit (140) is collected through V2R wireless communication; the intelligent electric meter (410) in the charging station intelligent electric meter system (400) has the functions of collecting electric power price information of a power grid, detecting the charging amount input to the electric automobile, calculating the real-time queuing condition and formulating the real-time charging price; the function of the charging station control management unit (420) is to transmit real-time charging station information to the server (300), queuing users queued on the application unit (130) and users arriving at the charging station; the server (300) calculates an optimal charging station strategy according to the information transmitted by the road side unit (200) and the charging station control management unit (420); and after receiving the optimal strategy transmitted by the server (300), the road side unit (200) transmits the optimal strategy to the electric automobile user through R2V and V2V wireless communication.

3. The VANET-based electric vehicle charging scheduling system of claim 1 or 2, characterized in that V2V wireless relay forwarding between the vehicle-mounted unit (140) and the vehicle-mounted unit (140) is single hop or multi-hop.

4. The VANET-based electric vehicle charging scheduling system of claim 1 or 2, wherein the real-time charging station information transmitted by the charging station control management unit (420) to the server (300) comprises position information, real-time charging price, queuing condition; the system is also used for pushing reminding information to the user, and comprises a reminding time starting point and a reminding interval time according to the preference and the living habit setting of the user.

5. The VANET-based electric vehicle charging scheduling system of claim 4, wherein the real-time charging price established by the smart meters (410) in the charging station smart meter system (400) relates to the district difference and the demand adjustment.

6. A VANET-based electric vehicle charging scheduling method is characterized by comprising the following steps:

s100, the intelligent electric meters (410) of all charging stations are combined with the positions of the places where the intelligent electric meters are located and the electric power price information, real-time charging prices are formulated according to the current queuing conditions, and the charging station control management unit (420) transmits the real-time charging station information to the server (300);

s200, when the intelligent electric meter (110) in the electric automobile intelligent electric meter system (100) detects that the charge state of a battery is lower than a certain threshold value or accords with the charging habit of a user, the vehicle-mounted unit (140) sends a charging service demand and electric automobile real-time information to the server (300);

s300, calculating by the server (300) according to the received real-time information of the electric automobile and the charging station to obtain an optimal charging station strategy and a function utility value of the electric automobile;

s400, the vehicle-mounted unit (140) pushes the received optimal charging station strategy, the function utility value and the charging station information to a user through the application unit (130);

s500, selecting whether to charge or not by a user according to the self requirement and the judgment on the function utility value, and directly queuing and taking a number on a target charging station interface through an application unit (130) if the charging selection is confirmed;

s600, after receiving queuing information transmitted by the application unit (130), a charging station control management unit (420) of the target charging station arranges a user into a charging queue;

s700, when a user wants to go to a target charging station, the application unit (130) sends a decision to the vehicle-mounted GPS positioning device (120), and the vehicle-mounted GPS positioning device (120) provides shortest path navigation to the target charging station.

7. The VANET-based electric vehicle charging scheduling method according to claim 6, characterized in that after the step S600, the method further comprises the step S600A: judging whether the user needs to push the reminding service, if so, sending push information to the application unit (130) at a specific time according to the user setting; otherwise, step S700 is performed.

8. The VANET-based electric vehicle charging scheduling method according to claim 6, wherein the specific steps of the step S100 are as follows:

s110, calculating average queuing waiting time, and averaging the queuing waiting length;

s120, setting the regional price f by the charging station j according to the district_j ^{（1 ）}Adjusting the price f according to the demand calculated by the queuing condition_j ^{（2 ）}Weighted to obtain the charge price f_j；

S130, transmitting real-time charging station information including charging price, additional cost, position information and queuing condition to the server (300).

9. The VANET-based electric vehicle charging scheduling method according to claim 6, wherein the specific steps of the step S300 are as follows:

s310, determining each weight of the utility function and a user parameter value according to the user characteristics;

s320, calculating utility values of the charging stations to users according to the electric vehicles and the real-time information of the charging stations to obtain a target function;

and S330, optimizing the objective function to obtain an optimal charging station selection strategy.