The present patent application claims the priority benefit of French patent application FR13/61350 which is herein incorporated by reference.
The present application relates to a device and to a method for recharging rechargeable electric or hybrid vehicles.
The number of rechargeable electric vehicles and hybrid vehicles used continuously increases. As an example, the French Electricity Union (UFE: Union Française de l'Electricité) estimates that by 2030, nearly six million rechargeable electric or hybrid vehicles will be in circulation in France.
Such vehicles have batteries which should be regularly recharged by the electric power grid. The recharge of rechargeable electric and hybrid vehicles will have, with no specific measures being taken, a significant impact on the French national power consumption curve. Indeed, one million rechargeable electric or hybrid vehicles in slow simultaneous recharge draw from 3,000 to 6,000 MW.
It is desirable to control the electric power demand for the recharge of rechargeable electric and hybrid vehicles in order to avoid consumption peaks and thus to limit the modifications to be made to the current electric power grid, like the reinforcement of power lines. It is further desirable that the largest possible part of the electric energy used for the recharge of rechargeable electric or hybrid vehicles originates from renewable energy sources, such as photovoltaic power plants, wind power stations, hydraulic power plants, etc.
There exist methods for recharging rechargeable electric or hybrid vehicles which enable to control the electric power supplied to the vehicles. However, such methods generally require communicating, to a management module, a number of parameters relative to the electric or hybrid vehicles to be recharged, for example, the vehicle type, the capacity of the battery of each vehicle, the recharge profile of the battery of each vehicle, etc. It may be difficult to collect a large number of data to transmit them to the management module. Further, such methods may require controlling the number of vehicles to be recharged while this number is in practice variable and/or controlling the times of beginning or of end of recharge while these times can in practice not be controlled. Further, when the recharge is performed from the electric energy provided by a renewable energy electric power plant, recharge methods may require knowing an estimate of the energy which will be supplied by this power plant. However, such an estimate may be unavailable or be different from the real production of electric energy by the electric power plant.
An object of an embodiment is to overcome all or part of the disadvantages of previously-described methods and devices for recharging rechargeable electric and hybrid vehicles.
Another object of an embodiment is to limit the number of data relative to the vehicles to be recharged necessary for the implementation of the recharge method.
Another object of an embodiment is that the recharge method can be implemented in real time.
Another object of an embodiment is that it enables to favor the use of renewable energies for the recharge of vehicles.
Thus, an embodiment provides a method of recharging electric or hybrid vehicles by means of charging stations connected to an electric power grid, the method comprising the steps of:
supplying, for each vehicle to be recharged, a control module built into said vehicle or into the charging station of said vehicle with data representative of a total electric power required for recharging the vehicles;
measuring the total electric power supplied by the electric power grid for recharging the vehicles and supplying data representative of the measured total electric power to said control module for each vehicle to be recharged; and
determining, by means of said control module for each vehicle to be recharged, a setting of the electric charge power of said vehicle based on the difference between the required total electric power and the measured total electric power.
According to an embodiment, the setting for the electric charge power of said vehicle is further determined based on the state of charge of the vehicle, on the recharge time of the vehicle.
According to an embodiment, the data representative of the required total electric power are supplied by the power grid manager and/or by at least one electric power plant selected from the group comprising a photovoltaic power plant, a wind power station, a hydraulic power plant, or a tidal power station.
According to an embodiment, the method comprises determining, by means of said control module for each vehicle to be recharged, a first coefficient by fuzzy logic based on the state of charge of the vehicle and the recharge time of the vehicle and determining the setting for the electric charge power of said vehicle based on the first coefficient.
According to an embodiment, the method further comprises the step of multiplying the maximum electric charge power of said vehicle by a second coefficient obtained from the first coefficient and from the measured total electric power.
According to an embodiment, the method comprises the steps of:
According to an embodiment, the second coefficient is equal to the integral of the product between the first coefficient and said difference.
According to an embodiment, the determination of the first coefficient by fuzzy logic comprises determining first values of first membership functions of first fuzzy sets associated with the state of charge of the vehicle and of second values of second membership functions of second fuzzy sets associated with the vehicle recharge time.
According to an embodiment, the determination of the first coefficient by fuzzy logic comprises using a first inference table and a third membership function for the first coefficient on decrease of the required total electric power, and a second inference table, different from the first inference table, and a fourth membership function for the first coefficient different from the third membership function, on increase of the required total electric power.
An embodiment also provides a device for recharging electric and hybrid vehicles, comprising charging stations connected to an electric power grid, each charging station being connected to one of the vehicles to be recharged, the device further comprising, for each vehicle to be recharged, a control module built into said vehicle or into the charging station of said vehicle, the device comprising means for transmitting, to the control module for each vehicle to be recharged, data representative of a total electric power required for recharging the vehicles, the device further comprising a sensor capable of measuring the total electric power supplied by the electric power grid for recharging said vehicles and means for transmitting data representative of the measured total electric power to said control module for each vehicle to be recharged, said control module for each vehicle to be recharged being capable of determining a setting for the electric power for recharging said vehicle based on the state of charge of the vehicle, on the recharge time of the vehicle, and on the difference between the required total electric power and the measured total electric power.
The foregoing and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, among which:
For clarity, the same elements have been designated with the same reference numerals in the different drawings.
Device 10 is connected to a main electric power grid 12. Device 10 comprises a local electric power grid 14 connected to main system 12 by a connection module 16. Local electric power grid 14 is capable of transmitting electric energy to N charging stations Bi, with i varying from 1 to N. Connection module 16 may comprise a transformer, for example, capable of supplying an electric power which may vary from 200 kW to 2,000 kW. Connection module 16 further comprises a sensor capable of measuring the total electric power Ps supplied by main electric power grid 12 to local electric power grid 14.
A rechargeable electric or hybrid vehicle VEi may be connected to one of charging stations Bi to be recharged by an electric power transmission link LPi. As an example, link LPi corresponds to a power transmission cable. As a variation, the electric power transmission to electric vehicle VEi may be performed remotely, for example, by induction. In the present embodiment, each electric VEi comprises a control module Mi capable of controlling an operation of recharge of electric vehicle VEi. Each control module Mi may comprise a dedicated processor and/or electronic circuit.
Device 10 comprises a local management module 17 which is capable of receiving data representative of the measured total electric power Ps supplied by connection module 16 and is capable of transmitting to control module Mi of each vehicle VEi the data representative of the measured total electric power Ps over a data transmission link LDi, with i varying from 1 to N. It may be a wire link or a wireless link. Link LDi may correspond to a RS-232 link or to a RS-485 link having data transmitted thereover according to a communication protocol, for example, the Modbus protocol. The transmission of the data representative of the measured total electric power Ps of local management module 17 to control modules Mi may be performed at regular intervals.
A grid management module 18 is capable of transmitting to local management module 17 data representative of an electric power Ps*, called reference electric power, and corresponding to the required total electric power to be used for the recharge of vehicles VEi. Local management module 17 is capable of transmitting the data representative of an electric power Ps* to control module Mi of each vehicle VEi over the corresponding communication link LDi. A new value of reference power Ps* may be transmitted only when this power varies. According to an example, reference power Ps* may vary in stages and a new value of reference power Ps* is transmitted by local management module 17 to control modules Mi only at the beginning of each new stage. According to another example, reference power Ps* varies continuously.
When a vehicle VEi is connected to station Bi, control module Mi is supplied with the expected end time tstopi. According to an example, the user of vehicle VEi enters this information on an interface module of vehicle VEi for example comprising a keyboard, a touch screen, a microphone, etc. The time at the beginning of the recharge istarti of vehicle VEi is automatically identified by control module Mi.
Control module Mi internally recovers once, at the beginning of the recharge, the maximum power PMAX_EVi to which the battery of vehicle VEi can be recharged.
During the recharge of vehicle VEi, data representative of state of charge SOCi of the vehicle are regularly transmitted to control module Mi of vehicle VEi. As a variation, data representative of state of charge SOCi of the vehicle are transmitted to control module Mi only at the beginning of the recharge, the control module determining the variation of state of charge SOCi of vehicle VEi based on the electric power supplied to recharge vehicle VEi. Such data relative to state of charge SOCi and to maximum power PMAX_EVi are transmitted to control module Mi with no intervention of the user.
According to an embodiment, control module Mi may operate according to a basic operating mode where it performs no regulation of the electric power to be supplied to recharge vehicle VEi. In this case, the power supplied to each vehicle is for example equal to maximum power PMAX_EVi.
According to an embodiment, control module Mi may operate according to a regulation operating mode where it determines in real time a setting PEVi, for example, for battery control system 24, of the electric power to be supplied to recharge vehicle VEi.
A weighting coefficient Coeffi is determined from coefficient ki and from difference ΔPS. As an example, the regulation is of integral type, where difference ΔPS is multiplied by coefficient ki and is integrated. As a variation, it may be a correction of proportional-integral-derivative type.
Power setting PEVi corresponds to the product of the value of maximum power PMAX_EVi and of coefficient Coeffi.
The control method may be implemented by the execution of a sequence of instructions by a processor. As a variation, it may be implemented by a dedicated electronic circuit.
According to an embodiment, for each control module Mi, coefficient ki is determined by fuzzy logic. For this purpose, the variables used by control module Mi are the state of charge, SOC, the recharge time, T, and the correction coefficient, k.
The “state of charge” variable, SOC, is associated with a plurality of fuzzy sets, for example, five in the present embodiment, corresponding to a plurality of state of charge levels of the battery of vehicle VEi.
The “recharge time” variable, T, is associated with a plurality of fuzzy sets, for example, five in the present embodiment, corresponding to a plurality of ranges of values of the recharge time.
The “correction coefficient” variable, k, is associated with a plurality of fuzzy sets, for example, five in the present embodiment, corresponding to a plurality of ranges of values of the correction coefficient.
According to an embodiment, coefficient ki is determined differently in case of a decrease or of an increase of the reference total electric power Ps*.
The membership functions of the fuzzy sets of the “state of charge”, “recharge time”, and “correction coefficient” variables may be stored in memories of each control module Mi.
In
An example of a detection array, or inference table, in the case of a decrease in power Ps* is given by the following table (1):
In the case of a decrease in power Ps*, the membership function of variable k shown in
The reading of the fuzzy rule corresponding, for example, to the first box at the top left of inference table (1) is the following: if the state of charge is low (socP) and if the recharge time is short (tP), then coefficient k is low (P). This means that variable k belongs to fuzzy set P at a degree which depends on the degree of validity of the premises, in other words on the degree of membership of variable SOC to fuzzy set socP and on the degree of membership of variable T to fuzzy set tP.
Table (1) is not symmetrical. This illustrates the fact that coefficient ki is low as a priority as soon as the state of charge is low. Indeed, the object is that the state of charge is at 100% at the time where the electric vehicle is disconnected from the associated charging station.
An example of the inference table in the case of an increase in power Ps* is given by the following table (2):
In the case of an increase in power Ps*, the membership function of variable k shown in
The reading of the fuzzy rule corresponding, for example, to the first box at the top left of inference table (2) is the following: if the state of charge is low (socP) and if the recharge time is short (tP), then coefficient k is high (G). This means that variable k belongs to fuzzy set G at a degree which depends on the degree of validity of the premises, in other words on the degree of membership of variable SOC to fuzzy set socP and on the degree of membership of variable T to fuzzy set tP.
Table (2) is not symmetrical. This illustrates the fact that coefficient ki is high as a priority as soon as the state of charge is low. Indeed, the object is for the state of charge to be at 100% at the time where the electric vehicle is disconnected from the charging station.
In fuzzy logic, coordinating conjunction “and” which connects the premises translates as a fuzzy operator and linker “then” connecting the conclusion to the premises translates as a fuzzy implication.
As an example, the Zadeh fuzzy operators may be used. Intersection operator AND connecting two fuzzy sets then returns the minimum of the membership functions of the two fuzzy sets.
Generally, the fuzzy implication defines how to delimit, according to the specific values of variables SOC and T of the premises of the fuzzy rule, a portion of the surface under the curve of the membership function of the fuzzy set of the conclusion of the fuzzy rule, that is, the obtaining of a subset.
As an example, the fuzzy implication used may be the Mamdani implication or the Larsen implication.
For specific values SOCi and Ti of variables SOC and T, each fuzzy rule of the inference table results in the obtaining of a subset, possibly zero, for variable k. the subsets are aggregated by using, for example, operator MAX. The determination of the final value of coefficient ki from the aggregated subsets is called defuzzification. As an example, the defuzzification step implements the mean-of-maxima method or the center-of-gravity method.
As an illustration, two vehicles VE1 and VE2 are considered. State of charge SOC1 of vehicle VE1 is higher than state of charge SOC2 of vehicle VE2 and charge time T1 of vehicle VE1 is longer than charge time T2 of vehicle VE2.
An advantage of the present embodiment is that it is essentially formed locally by each control module of the electric vehicle and only requires the remote transmission of a small number of data.
Another advantage of the present embodiment is that it requires no information which may be difficult to obtain, for example, the type of vehicle to be recharged.
Another advantage of the present embodiment is that it does not require knowing in advance the number of vehicles to be recharged or the times of arrival of the vehicles to be recharged.
Another advantage of the present embodiment is that it may be implemented in real time.
Another advantage of the present embodiment is that the electric power setting PVEi supplied by control module Mi of each vehicle VEi may be determined continuously so that the total electric power Ps supplied to all the electric vehicles may continuously follow reference power Ps*.
Another advantage of the present embodiment is that reference power Ps* does not have to be determined in advance. Thereby, reference power Ps* may follow the electric power supplied by an electric power plant, particularly a photovoltaic power plant, a wind power station, a hydraulic power plant, or a tidal power plant.
Simulations have been performed by the inventors. For all these simulations, twenty electric vehicles each having a battery having a 24-KWh capacity with a maximum charge power of 3 kW have been considered.
For the first simulation, initial state of charge SOCini of the electric vehicles was between 40% and 60% and has been obtained by a random selection according to a uniform distribution. Time tstart of beginning of the recharge was 7 am for all vehicles and end time tstop of the recharge was between 4:30 pm and 7 pm and has been obtained by random selection. These values are gathered in the following table (3):
For the first simulation, there is no determination of a charge power setting, each vehicle being recharged to the maximum charge power.
As appears in the drawings, each vehicle has been recharged with the maximum 3-kW charge power during the entire recharge period. Total electric power PS1 was thus as high as 60 kW as long as all vehicles were recharging and then decreased down to 0 kW as the state of charge of each vehicle reached 100%.
A second simulation has been carried out with the same conditions as the first simulation, with the difference that the total reference power starting from 7 am was 25 kW.
A third simulation has been performed with the same conditions as the second simulation, with the difference that the time of beginning of the recharge tstart was between 7 am and 12 am and has been obtained by random selection and that total reference power P*S3 was successively 25 kW from 12 am to 9 am, 15 kW from 9 am to 11 am, 20 kW from 11 am to 2 pm, and 40 kW from 2 pm to midnight. A new value of total reference power P*S3 was thus transmitted to each charging station at 12 am, 9 am, 11 am, and 2 pm.
A fourth simulation has been carried out in the case where the electric vehicles are further capable of supplying electric energy to the main power grid. The fourth simulation has been performed with the same conditions as the third simulation, with the difference that total reference power P*S4 was successively 25 kW from midnight to 9 am, −15 kW from 9 am to 11 am, 20 kW from 11 am to 2 pm, and 40 kW from 2 pm to midnight. A new value of total reference power P*S4 was thus transmitted to each charging station at midnight, 9 am, 11 am, and 2 pm.
A fifth simulation has been carried out in the absence of a control. For the fifth simulation, initial state of charge SOCini of the electric vehicles was between 20% and 80% and has been obtained by a random selection according to a uniform distribution. The time tstart of beginning of the recharge was in the range from 7 am to midnight and has been obtained by random selection and end time tstop of the recharge was between 7 pm and 9 pm and has been obtained by a random selection. These values are gathered in the following table (4):
For the fifth simulation, there is no determination of a charge power setting, each vehicle being recharged to the maximum charge power.
For the fifth simulation, the solar coverage is 55.62%, that is, 55.62% of the total electric power Ps supplied to the vehicles to be recharged has been provided by the photovoltaic power plant.
A sixth simulation has been performed with the same conditions as the fifth simulation, with the difference that the setting for total available power P*S corresponds to the electric power PPV shown in
For the sixth simulation, the solar coverage is 97.88%, that is, 97.88% of the total electric power PS6 supplied to the vehicles to be recharged has been provided by the photovoltaic power plant.
Specific embodiments have been described. Various alterations and modifications will readily occur to those skilled in the art.
Number | Date | Country | Kind |
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1361350 | Nov 2013 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2014/052805 | 11/4/2014 | WO | 00 |