Method and system for electric vehicle charging, the system comprising a plurality of alternative electrical energy charging stations

Abstract

Method and system for electric vehicle charging, the system comprising a plurality of alternative electrical energy charging stations. The electric charging method is implemented by a system comprising a supervisory module, a plurality of charging stations, each charging station being configured to communicate with the supervisory module via a communication link, the method comprising obtaining (50), from each charging station, a spectral representation of the current consumed by the station, determining (52) an overall spectral representation (Sg) of the charging system from the spectral representations of the current consumed per charging station and per spectral rank, calculating (54) a degradation value of the power factor of the charging system as a function of the overall spectral representation of the charging system.A derating coefficient to be applied (60) by at least one of the charging stations is calculated (56, 57, 58) using the calculated power factor degradation value. Figure for the abbreviation: Figure 4.

Description

Title of the invention: Method and system for electric vehicle charging, the system comprising a plurality of alternative electrical energy charging stations

[0001] The present invention relates to an electric charging method for electric vehicles, and an associated electric vehicle charging system, the system comprising a plurality of alternative electrical energy charging stations.

[0002] The invention also relates to a charging station and a supervision module for an electric charging system for electric vehicles.

[0003] The invention is in the field of electric charging of electric vehicles.

[0004] As is known, electric vehicles are equipped with rechargeable batteries, which supply electrical energy to their traction motor. The batteries of electric vehicles must be recharged from an electrical energy source, providing either alternating or direct current. For example, when the electrical energy source is an electricity distribution network, the electrical energy supplied is alternating, providing alternating current and alternating voltage over a given number of phases, for example, three-phase. Each electric vehicle is equipped with a converter, called an on-board converter, which transforms alternating current into direct current, or an AC-DC converter (for "Alternating Current" and "Direct Current"), to allow the rechargeable battery to be recharged.

[0005] Electric vehicle charging systems exist that include one or more alternating current charging stations, or AC terminals, each terminal being capable of supplying alternating current to an electric vehicle that connects, by means of a suitable cable, to such a charging station. The converter on board the electric vehicle is then used to convert the alternating current into direct current and recharge the electric vehicle's battery.

[0006] One of the problems that can arise in such an electric vehicle charging system is the phenomenon of power factor degradation, encompassing reactive power consumption and the production of harmonic currents, producing a phenomenon known as harmonic pollution. Indeed, the converters embedded in electric vehicles can be of poor quality, and thus consume significant reactive and distortion power. The power factor can therefore be degraded relative to a threshold of predetermined degradation considered acceptable, and this can generate various problems such as the re-injection of electrical current harmonics into the distribution network, cable heating, untimely tripping of electrical protections, billing penalties etc.

[0007] To limit the occurrence of such harmonic pollution, or more generally a poor power factor (i.e., a power factor below a predetermined value), a known solution is to add a passive LC filter and / or a reactive current compensation bank upstream of each charging station. This solution is costly and has a significant footprint. Furthermore, the use of such filters may generate losses, and their implementation can cause side effects.

[0008] Another solution involves implementing an active filter that generates a reactive current and / or harmonic currents in opposite phase to the harmonic currents consumed by each polluting load. This solution is also expensive and bulky.

[0009] The aim of the invention is then to propose a system and a method of electric charging which remedies the disadvantages of the state of the art, while making it possible to improve the power factor, for example by reducing the harmonic pollution of the charging system.

[0010] To this end, the invention relates to an electric vehicle charging method, implemented by an electric vehicle charging system comprising a plurality of alternative energy charging stations and a supervisory module, each charging station being configured to charge an electric vehicle connected to said charging station and to communicate with the supervisory module via a communication link, the method comprising:

[0011] A) for each charging station, an acquisition, by a current sensor of said charging station, of measurements of a current consumed by the electric vehicle connected to said charging station, at successive time instants, and formation of a digitized signal of current consumed by said station, then transmission of a message including data relating to said digitized signal of current consumed to the supervision module.

[0012] This process comprises the following steps, implemented by the monitoring module:

[0013] -B) receive the messages sent by each charging station, and obtain, for each charging station, from the said data relating to the digitized signal of current consumed, a spectral representation of the current consumed, the spectral representation being calculated by applying a spectral transformation to the digitized signal of current consumed by said charging station, said spectral representation comprising a plurality of pairs of amplitude and phase values, each pair being associated with a spectral rank of the current consumed,

[0014] - C) determine a global spectral representation of the charging system from spectral representations of the current consumed per charging station and per spectral rank,

[0015] -D) calculate a degradation value, representative of a degradation of the factor of the charging system's power, according to a power factor degradation calculation metric, based on said overall spectral representation of the charging system,

[0016] -E) compare said degradation value to a degradation threshold, and in the event of exceeding the degradation threshold,

[0017] -F) calculate at least one downgrade coefficient to be applied by at least one charging stations depending on the level of deterioration,

[0018] -G) control at least one of the charging stations to apply the coefficient derating calculated to modify a parameter of electrical energy supplied by said charging station.

[0019] Advantageously, the proposed method uses the current sensors already present in the charging stations, therefore does not require structural modification of the charging stations, and allows dynamic adaptation of the electrical energy delivered by each charging station to control the total harmonic distortion.

[0020] According to other advantageous aspects of the invention, the electric charging method for electric vehicles comprises one or more of the following characteristics, taken individually or in all technically possible combinations.

[0021] The calculation of at least one derating coefficient to be applied by at least one of the charging stations is carried out according to the degradation threshold and said degradation value.

[0022] The process includes an iteration of steps A) to G) until the degradation value is below the degradation threshold.

[0023] The degradation value is chosen from a reactive power of the charging system, a total harmonic distortion, a partial harmonic distortion according to one or more predetermined harmonic ranks.

[0024] The calculation of at least one derating coefficient implements a calculation of derating coefficients of the same value for each charging station.

[0025] The calculation of at least one derating coefficient implements a calculation of differentiated derating coefficients per charging station, the derating coefficient being all the more penalizing as the charging station induces a high amount of degradation of the power factor according to said power factor degradation calculation metric.

[0026] Steps A) to G) are applied successively for a plurality of power factor degradation calculation metrics.

[0027] The derating coefficients vary between 0 and 1, each derating coefficient being applied, by a charging station, as a multiplicative factor of an electrical energy parameter delivered by said charging station.

[0028] The process includes, when said degradation value is less than the degradation threshold, an adjustment by increasing at least one downgrade coefficient.

[0029] According to another aspect, the invention also relates to an electric vehicle charging system comprising a plurality of alternative electric power charging stations, a supervisory module, each charging station being configured to charge an electric vehicle connected to said charging station and to communicate with the supervisory module via a communication link, each charging station comprising a current sensor configured to measure, at successive time instants, a current consumed by an electric vehicle connected to said charging station, and to form a digitized signal of current consumed by said station, and then to transmit a message comprising data relating to said digitized signal of current consumed to the supervisory module.

[0030] This charging system is such that the monitoring module is configured to run modules for:

[0031] - receive messages sent by each charging station,

[0032] - to obtain, from each charging station, a spectral representation of the current consumed calculated by applying a spectral transformation to the digitized signal of current consumed on said charging station, said spectral representation comprising a plurality of pairs of amplitude and phase values, each pair being associated with a spectral rank of the current consumed,

[0033] - determine a global spectral representation of the charging system from spectral representations of the current consumed per charging station and per spectral rank,

[0034] -calculate a degradation value, representative of a degradation of the power factor of the charging system, according to a power factor degradation calculation metric, as a function of said global spectral representation of the charging system,

[0035] - compare said degradation value to a degradation threshold, and in the event of exceeding the degradation threshold,

[0036] - calculate at least one downgrade coefficient to be applied by at least one of the charging stations depending on the level of deterioration,

[0037] - to order at least one of the charging stations to apply the calculated derating coefficient to reduce a parameter of electrical energy supplied by said charging station.

[0038] According to a particular aspect, each charging station includes a module configured to apply the spectral transformation to calculate the spectral representation of the current consumed by said charging station, and transmit the spectral representation to the supervisory module.

[0039] According to a particular aspect of the charging system, each charging station is configured to transmit the digitized signal of current consumed to the supervisory module, the supervisory module being configured to apply the spectral transformation on each digitized signal of current consumed to obtain the spectral representation of the current consumed by charging station.

[0040] According to another aspect, the invention relates to a monitoring module for an electric vehicle charging system, the electric vehicle charging system comprising a plurality of alternative energy charging stations, each charging station being configured to charge an electric vehicle connected to said charging station and to communicate with the monitoring module via a communication link, each charging station comprising a current sensor configured to measure, at successive time instants, the current consumed by an electric vehicle connected to said charging station, and to form a digitized signal of the current consumed by said station, and then transmit a message comprising data relating to said digitized signal of current consumed to the monitoring module, the monitoring module being configured to implement:

[0041] - a module for receiving messages sent by each charging station,

[0042] - a module for obtaining, from each charging station, a representation spectral of the current consumed calculated by applying a spectral transformation to the digitized signal of current consumed on said charging station, said representation comprising a plurality of pairs of amplitude and phase values, each pair being associated with a spectral rank of the current consumed,

[0043] - a module for determining a global spectral representation of the system of charging based on spectral representations of the current consumed per charging station and per spectral rank,

[0044] -a calculation module for a degradation value, representative of a degradation of the power factor of the charging system, according to a power factor degradation calculation metric, as a function of said overall spectral representation of the charging system,

[0045] - a module for comparing said degradation value to a threshold of degradation, and in the event of exceeding the degradation threshold,

[0046] - a calculation module for at least one downgrade coefficient to be applied by the minus one of the charging stations depending on the degradation threshold,

[0047] -a control module for at least one of the charging stations to apply the calculated derating coefficient to reduce a parameter of electrical energy supplied.

[0048] According to another aspect, the invention relates to a charging station of an electric vehicle charging system, the electric vehicle charging system comprising a supervisory module, the charging station being configured to charge an electric vehicle connected to said charging station and to communicate with the supervisory module via a communication link, and comprising a current sensor configured to measure, at successive time instants, a current consumed by an electric vehicle connected to said charging station, and to form a digitized signal of current consumed by said station, and then transmit a message comprising data relating to said digitized signal of current consumed to the supervisory module, the charging station being further configured to receive from said supervisory module a command to apply a derating coefficient calculated to reduce a parameter of electrical energy supplied,and apply said downgrading coefficient for the supply of electrical energy to said electric vehicle.

[0049] According to a particular aspect, the charging station includes a spectral transformation module, configured to perform said spectral transformation to calculate the spectral representation of the current consumed by said charging station, the charging station being configured to transmit the spectral representation to the supervisory module.

[0050] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0051] [Fig-1] [Fig.1] is a schematic representation of a charging system electric vehicles and connected electric vehicles;

[0052] [Fig.2] [Fig.2] is a synoptic diagram of the main functional blocks of a charging station and the supervision module;

[0053] [Fig.3] [Fig.3] is an example of current consumed and associated spectral representation;

[0054] [Fig.4] [Fig.4] is a flowchart of the main steps of a process for charging electric vehicles according to an embodiment.

[0055] Fig. 1 represents schematically, as a simplified example, an electric vehicle charging system 2 and electric vehicles, referenced 4i...4N on Fig. 1, each connected to a charging station 6i to 6N of the charging system 2.

[0056] In other words, the charging system shown as an example comprises N charging stations, N being an integer greater than or equal to 1.

[0057] Furthermore, the presence of an electric vehicle at each charging station is illustrated by way of example, in the case where the charging system 2 is used at its maximum capacity. It is clear that any number of electric vehicles, from 1 to N, can be connected simultaneously to recharge their batteries at any given time t.

[0058] Subsequently, the number N is considered to represent the number of charging stations requested for the supply of electrical energy.

[0059] The charging stations 6i to 6N of the charging system 2 are supplied with electrical energy by one or more electrical energy sources 10.

[0060] For example, the electrical energy source 10 is an alternative electrical energy distribution network. For example, the electrical energy distribution network is of the three-phase type (i.e., 3 current phases and a neutral) and more generally multi-phase.

[0061] For example, each charging station 6i to 6N is connected to the electrical power source 10 by current conductors 8i to 8N.

[0062] The 6i to 6N charging stations are alternative electrical energy charging stations, also called AC stations, configured to provide electric vehicles with alternative electrical energy.

[0063] Each charging station 6j supplies electrical energy according to an associated power profile, the profile comprising a maximum current value (or RMS value) Imaxj, a maximum power value PmaxJ, and a derating coefficient Oj to be applied. The alternating voltage supplied by each charging station is the alternating voltage supplied by the electrical energy source 10, with an RMS voltage U.

[0064] The derating coefficient is a real value, varying between a lower value, for example 0, and an upper value, for example 1. The derating coefficient is applied as a multiplicative factor to a parameter of electrical energy delivered by the charging station, for example, to the current value ImaxJ supplied by the charging station 6j. In other words, the current setpoint supplied by the charging station 6j is then OjX ImaxJ. Thus, each charging station 6j is configured to supply electrical energy whose electrical energy parameter is multiplied by the derating coefficient a.

[0065] By default, the derating coefficient Oj is equal to 1, in other words, the charging station is configured to provide the maximum electrical energy of setpoint current ImaxJ, which is the maximum current value that the station 6j provides to the electric vehicle 4j.

[0066] The calculation and updating of the derating coefficient a, associated with each power profile associated with a charging station, will be described in more detail below.

[0067] Each of the charging stations 6i to 6N, designated by the general reference 6, comprises similar functional blocks, described with reference to [Fig.2].

[0068] The charging station 6 includes a communication interface designated by the general reference numeral 12 (shown in [Fig. 2]), configured to communicate, in transmission and reception, according to a given communication protocol. For example, the communication interface 12 is configured to communicate according to a wireless communication protocol, for example according to the 4G, 5G, etc. protocol.

[0069] Alternatively, the communication interface 12 is configured to communicate according to a wired communication protocol.

[0070] When an electric vehicle 4j connects to a charging station 6j via a suitable connector, an alternative electrical power supply is implemented to recharge the electric vehicle's battery. As explained, the electric vehicle has an onboard AC-DC converter (not shown) that transforms the alternating current into direct current for battery charging. The electrical current used by the electric vehicle is hereafter referred to as the current consumed. Each charging station 6i to 6N has one or more current sensors 14i to 14N, designated by the general reference numeral 14, configured to measure the current consumed by an electric vehicle connected to the charging station.The measured current consumption is digitized, this digitization involving sampling at a sampling frequency F, the sampling frequency F being advantageously chosen according to the maximum harmonic that one wishes to measure. A series of current consumption samples over a sampling period forms a digitized current consumption signal, the sampling period being at least equal to one period of the electrical signal, i.e. at least equal to 20ms for a 50Hz distribution network.

[0071] The charging station 6 also includes an electronic controller 16, which comprises a module 18 for managing the supply of electrical power to a connected electric vehicle. In addition to electrical power management functionalities based on the type of electric vehicle, which are performed in a conventional manner and not described in further detail here, the module 18 is configured to apply the derating coefficient associated with the power profile supplied by the charging station 6.

[0072] Optionally, in one embodiment, the electronic controller 16 includes a spectral transformation module 19, configured to apply a transformation to a digitized signal of current consumption and obtain a spectral representation of the current consumed. For example, the module 19 puts into works a Fourier transform, and more specifically a fast Fourier transform or FFT (for "Fast Fourier Transform"). According to one variant, the spectral transformation module 19 is integrated into the current sensor 14.

[0073] In one embodiment, each of the modules 18, 19 of the electronic controller 16 is implemented as a programmable logic component, such as an FPGA (Field Programmable Gate Array), or an integrated circuit, such as an ASIC (Application-Specific Integrated Circuit), a PLC, one or more processors, or any other computing circuit.

[0074] The charging system 2 further includes a supervision module 20, equipped with a communication interface 22, configured to communicate with the charging stations 6.

[0075] Thus, in the charging system 2, the charging stations 6i to 6N are configured to communicate with the supervision module 20 via a communication link 25, this communication link being bidirectional, according to a wired or wireless communication protocol, depending on the circumstances.

[0076] Each charging station is configured to transmit to the supervisory module 20, via the communication link 25, in a dedicated message, data relating to the digitized signal of current consumed by the electric vehicle connected to the charging station.

[0077] In one embodiment, the data relating to the digitized signal of current consumed is the spectral representation of the current consumed obtained by spectral transformation of the digitized signal of current consumed on the charging station.

[0078] According to an alternative embodiment, the data relating to the digitized current consumption signal are the successive measurements of current consumption forming the digitized current consumption signal. In this embodiment, the spectral transformation on each digitized current consumption signal is performed by the monitoring module, as explained in more detail below.

[0079] The monitoring module further comprises a computing processor 24 and an electronic memory 26, configured to communicate with each other and with the communication interface 22 via an internal communication bus.

[0080] The processing unit 24 is configured to implement a module 28 for obtaining a spectral representation of the current consumed for each charging station, following the reception of messages containing data relating to the digitized signal of current consumed at each charging station. For a given charging station, the spectral representation is calculated by applying a spectral transformation to the digitized signal of current consumed at the charging station. The spectral representation comprises a plurality of pairs of values of amplitude and phase, each pair being associated with a spectral rank of the current consumed. The spectral ranks s, for s strictly greater than 1, are also called harmonic ranks, the spectral rank s=l being called the fundamental rank.

[0081] In the case where the charging station 6 has a spectral transformation module 19, each charging station transmits to the supervisory module a spectral representation of the current consumed, in a message, the supervisory module receives, via the communication interface 22, the message containing the spectral representation of the current consumed and the module 28 retrieves and temporarily stores the spectral representations of the current consumed received respectively from each charging station.

[0082] Alternatively, module 28 is configured to apply a spectral transformation, for example a fast Fourier transform or FFT. In this variant, module 28 is configured to retrieve, from each charging station, the digitized signal of current consumed, and apply the spectral transformation to obtain the corresponding spectral representation.

[0083] The computing processor 24 is configured to implement a module 30 for determining an overall spectral representation of the charging system from the spectral representations of the current consumed per charging station and per spectral rank.

[0084] In addition, the computing processor 24 is configured to implement:

[0085] - a calculation module 32 for at least one degradation value, representative of a degradation of the power factor of the charging system, depending on the overall spectral representation of the charging system;

[0086] - a modulus 34 for comparing at least one degradation value, representative of a degradation of the power factor of the charging system, to at least a degradation threshold;

[0087] - a module 36 for calculating at least one downgrade coefficient, implemented in In the event of exceeding at least one degradation threshold by an exceedance value, at least one downgrade coefficient must be applied by at least one of the charging stations depending on the exceedance value, and

[0088] - a control module 38 for at least one of the charging stations for apply at least one calculated derating coefficient to reduce a parameter of electrical energy supplied, the electrical parameter defining for example a power, a current or a voltage supplied to the electric vehicle connected to the terminal.

[0089] Module 38 is configured to cooperate with communication interface 22 for the transmission of an application command, via one or more charging terminals 6j, with a derating coefficient a, to be applied. The management module 18j the electrical energy supply from terminal 6j applies the derating coefficient ttj.

[0090] In one embodiment, modules 28, 30, 32, 34, 36 and 38 are each implemented as a programmable logic component, such as an FPGA (Field Programmable Gate Array) or as a dedicated integrated circuit, such as an ASIC (Application Specified Integrated Circuit).

[0091] In another embodiment, modules 28, 30, 32, 34, 36 and 38 are implemented as a logic program executable by one or more processors.

[0092] Advantageously, the charging system 2 is configured to improve the power factor, without the addition of additional hardware components, such as additional filters, thanks to the charging process implemented.

[0093] Fig. 3 illustrates a profile 15 of current consumed by an electric vehicle 4, as a function of time, provided from successive current consumption measurements provided by the current sensor 14, and a graph 17 of spectral amplitude values ​​obtained from the profile 15. The current consumption profile 15 is represented by instantaneous current measurements, in Amperes (ordinate axis), as a function of time (abscissa axis) expressed in seconds.

[0094] Graph 17 represents spectral amplitude values ​​in Amperes on the ordinate as a function of spectral ranks on the abscissa.

[0095] Fig. 4 is a synoptic diagram of the main steps of an electric vehicle charging process, implemented by an electric vehicle charging system as described above, in one embodiment.

[0096] The method comprises a set of 40 steps implemented by each respective charging station 6b.., 6j,..., 6N and steps 50 to 60 implemented by the supervision module.

[0097] Each 6j charging station, and more particularly the 14j sensor of the 6j charging station, implements a step 42j of acquiring instantaneous electric current intensity measurements consumed by an electric vehicle connected to the 6j charging station, and of forming a digitized signal of current consumed.

[0098] The digitized signal of current consumption is formed from samples {Ijb.. .Ij Q], Q being a predetermined number of samples, Q being chosen according to the predetermined sampling frequency F and the chosen sampling duration. The sampling duration is advantageously chosen to be greater than or equal to one period of the electrical signal supplied by the distribution network, and preferably equal to a multiple of the periods of the electrical signal supplied by the distribution network, for example from 10 to 20 periods. According to some embodiments, an averaging of the current values ​​consumed over several successive periods of the electrical signal supplied by the distribution network are applied.

[0099] According to one embodiment, the spectral transformation module 19 of each charging station performs a spectral transformation at the spectral transformation step 44j on the digitized signal of current consumed, to obtain a spectral representation of the current consumed by the electric vehicle connected to the charging station 6j.

[0100] The spectral transformation is, for example, a discrete Fourier transform.

[0101] Preferably, a fast spectral transformation FFT (for "Fast Fourier") Transform") is performed, and allows us to obtain a representation of the electric current consumed, hereafter called spectral representation of the current consumed, and more simply spectral representation.

[0102] For the 6j limit, the spectral representation Sj=[(bji,Cji);(bj2,Cj2); - -.(bj Q, Cj Q)] includes pairs (bjk, cjk) of amplitude values ​​bjk and phase cjk, k being the associated spectral rank.

[0103] Each 6j charging station transmits a message, via its communication interface, to the supervision module, the message including the spectral representation Sj associated with the 6j charging station, or at least a part corresponding to the first P spectral ranks, with P an integer for example equal to 25.

[0104] Indeed, in practice, it can be considered that only the first P spectral ranks are of interest for characterizing the observed electrical phenomena.

[0105] The supervision module 20 implements a step 50 of obtaining the spectral representations Si to SN associated with each charging station 6i to 6N, following the reception, via its communication interface 22, of the messages transmitted by each charging station.

[0106] According to one embodiment, the charging stations 6i to 6N each transmit the digitized signal of current consumption, and the supervisory module 20 performs a spectral transformation to obtain the spectral representation of each received digitized current consumption signal. In other words, in this embodiment, step 50 of obtaining the spectral representations Si to SN associated with each charging station 6i to 6n involves receiving the digitized current consumption signal from each charging station and applying the spectral transformation. The spectral transformation is, for example, a discrete Fourier transform, and preferably an FFT.

[0107] The supervision module 20 then implements a step 52 of determining a global spectral representation Sg of the charging system from the spectral representations per charging station, for the spectral ranks P.

[0108] The determination step 52 implements, for each spectral rank k between 1 and P, a vector summation of the vectors defined by the pairs (bjk,cjk) of the spectral representations per charging terminal, for j ranging from 1 to N, the vector summation allowing to obtain a resultant vector for the spectral rank k. The respective values ​​of amplitude sk and phase tk of the global spectral representation are then the amplitude and phase of the resultant vector for the spectral rank k.

[0109] The global spectral representation Sg={(si,ti);... (Sj,tj);... .(sP,tP)}, comprising pairs (s;, f) of amplitude values ​​s; and phase L i being the associated spectral rank, is obtained at the end of the determination step 52.

[0110] The process then includes a step 54 of calculating a value representative of a degradation of the power factor, also called degradation value hereafter, V(Sg), as a function of the overall spectral representation of the system.

[0111] Preferably, the value representing a degradation of the power factor V(Sg) is one or a combination of:

[0112] -the reactive power of the charging system, calculated from (si,ti), Pr

[0113] -total harmonic distortion, THD

[0114] -a partial harmonic distortion, DHP(ki ...,¼) according to one or more predetermined harmonic ranks (or spectral ranks strictly greater than 1), kb... ,¼ , ...

[0115] The reactive power Pr of the charging system is calculated by the formula:

[0116] [Math.l] P r = ]3xUxs i x sin^j

[0117] in the case where the current is three-phase, where U is the effective voltage supplied by the charging system, (si,ti) the amplitude and phase values ​​of the spectral representation of current consumed of spectral rank 1.

[0118] The total harmonic distortion, expressed in Amperes (A), THD is calculated using the formula:

[0119] [Math.2] DHT = 2 + ... + ... + 4

[0120] The partial harmonic distortion, expressed in Amperes, DHP(ki,...,¼) according to one or more predetermined harmonic ranks kb.. .,¼, each kj being between 2 and P, is calculated by the formula:

[0121] [Math.3] DHP(kl, k2, kl) = + ... +s^

[0122] For example, if we consider the 5th and 7th harmonic ranks, the corresponding partial harmonic distortion is obtained by:

[0123] [Math.4] DHP(5j) = \lsZ + s^

[0124] The respective formulas for calculating the degradation value are also called power factor degradation calculation metrics.

[0125] In other words, the degradation value is calculated according to a power factor degradation calculation metric.

[0126] For example, when the degradation value considered is the reactive power of the charging system, the power factor degradation calculation metric of formula [MATH 1] is applied in step 54, and V(Sg)=Pr.

[0127] Alternatively, when the degradation value considered is the total harmonic distortion THD, formula [MATH 2] is applied in step 54, and V(Sg)=THD.

[0128] Alternatively, when the degradation value considered is a partial harmonic distortion DHP(ki,..ki), formula [MATH 3] is applied at step 54, and V(Sg)=DHP(k1,..k1).

[0129] According to another variant, described in more detail below, several metrics for calculating power factor degradation values ​​are applied.

[0130] The degradation value calculated in step 54 is compared to a degradation threshold (S_DH) corresponding to comparison step 56.

[0131] For example, when the degradation of the power factor is due to the presence of reactive power, the degradation value considered is the reactive power of the charging system, the degradation threshold S_DH is a maximum permissible reactive power Prmax, expressed in kVAR (kilovolt-amperes reactive).

[0132] For example, the maximum permissible reactive power is 60kVAR for a system sized at 1000 kVA.

[0133] When the power factor degradation is due to the presence of harmonics, the degradation threshold S_DH is chosen to be equal to a maximum value of the total harmonic distortion (THD) or the partial harmonic distortion. This maximum value can be expressed in Amperes (i.e., defining a maximum absolute value of the harmonic current) or as a percentage of the fundamental current (i.e., of spectral rank 1).

[0134] For example, when the degradation value considered is the total harmonic distortion THD, the corresponding degradation threshold S_DH is a maximum permissible total harmonic distortion value, for example equal to 20A, and more generally between 20A and 100A for a system sized at 1000A.

[0135] For example, when the degradation value considered is the partial harmonic distortion DHP(kl,kl), the corresponding degradation threshold S_DH is a Maximum value of partial harmonic distortion allowed for the ranks kb.. .,¼ considered, in Amperes.

[0136] When the power factor degradation is due to both reactive power and harmonics, several degradation thresholds similar to the previously described S_DH threshold can be defined. Alternatively, a single degradation threshold encompassing both types of degradation can be defined, for example, by considering the maximum permissible reactive power Prmax to correspond to a maximum permissible reactive current, and by defining the degradation threshold as a function of the maximum permissible reactive current and the maximum permissible harmonic current. In one embodiment, the S_DH threshold may correspond to the quadratic sum of the maximum permissible reactive current and the maximum permissible harmonic current.

[0137] When the degradation value considered exceeds the corresponding degradation threshold, the comparison step 56 is followed by a step 58 of calculation of at least one derating coefficient ak to be applied by at least one of the 6k charging stations.

[0138] Several embodiments of step 58 of calculating at least one downgrade coefficient aksont envisaged.

[0139] According to one embodiment, a derating coefficient of the same value a is applied to each of the charging stations. In other words, ai=a2=...=aN=a and the value a is, for example, calculated based on the permitted degradation threshold, as well as the calculated degradation value.

[0140] According to one embodiment, the ratio between the degradation threshold and the degradation value is taken into account. For example, the common value of the downgrading coefficient is calculated by:

[0141] [Math.5] _ SDH a ~ Efe)

[0142] According to another embodiment, the exceedance in relation to this degradation threshold, in other words the difference (V(Sg) - S_DH), is taken into consideration.

[0143] According to one variant, differentiated derating coefficients are calculated based on the actual amount of pollution (or power factor degradation) induced by the corresponding 6j charging station, according to the power factor degradation metric considered. For example, a "polluter pays" principle is applied: the greater the actual amount of power factor degradation induced by the 6j charging station, the more the charging station is penalized, and therefore the corresponding derating coefficient is close to zero, resulting in a high derating.

[0144] As an example, consider 3 charging stations, the calculation metric for a degradation of the power factor being in this example the reactive power of the current consumed.

[0145] Charging station 6i consumes a reactive power of Prl=3kVAR, charging station 62 consumes a reactive power of Pr2=2kVAR and charging station 63 consumes a reactive power of Pr3=lkVAR.

[0146] The reactive power of the system is Pr=Prl+Pr2+Pr3=6kVAR.

[0147] If the corresponding degradation threshold is 3kVAR, the exceedance is 3kVAR.

[0148] To limit the overall reactive power to S_DH=3kVAR, the following equality must be verified:

[0149] [Math.6] a3Pr 1 + a2Pr2 + a3Pr3 = S_DH

[0150] According to the "polluter pays" principle, charging station 6i consuming more reactive power than the other two stations, and charging station 63 consuming less reactive power than the other two stations, we must respect: < a2 < H3.

[0151] Thus, for example, we can choose a2 and a3 such that:

[0152] [Math.7] aA = a, a2 = 2a, a3 = 3a

[0153] By combining these formulas [MATH 6] and [MATH 7], we obtain:

[0154] [Math. 8] aPr 1 + 2aPr2 + 3aPr3 = S_DH

[0155] With the numerical values ​​given here as a simplified example, we finally obtain:

[0156] a1=3 / 14; a2=6 / 14 and a3=9 / 14.

[0157] Of course the above calculations are given as a non-limiting example, other formulas being of course conceivable.

[0158] According to one variant, only the most polluting charging stations are penalized, for example when the amount of pollution induced by each one exceeds a percentage of the degradation threshold considered.

[0159] Other rules for calculating one or more derating coefficients are applicable, preferably respecting the principle of a higher penalty for charging stations inducing a higher degradation of the power factor.

[0160] Step 58 of calculating at least one derating coefficient is followed by step 60 of commanding the application of the derating coefficient(s) by the charging stations. In other words, each 6k charging station will multiply its Power consumed is determined by the derating coefficient ak provided by the monitoring module. The derating coefficient ak is updated at each iteration of step 58, and possibly of step 57 described below.

[0161] During step 60, the derating coefficient(s) are transmitted to the charging stations for application by their respective electrical power supply management modules.

[0162] If, during comparison step 56, the degradation value is lower than the corresponding degradation threshold, then step 56 is optionally followed by a step 57 for upward adjustment of the derating coefficients. In other words, during step 57, each derating coefficient ak can be updated by increasing its value by a predetermined value or percentage, which allows each derating coefficient ak to approach the value of 1 if the power factor degradation becomes acceptable (i.e., lower than the predefined S_DH threshold).

[0163] Advantageously, this allows the values ​​of the downgrade coefficients to be updated to take into account any changes in circumstances dynamically.

[0164] For example, if at least some of the downgrade coefficients are strictly less than 1, they are increased by a given percentage increase, for example 1%, while verifying that none of the coefficients is greater than 1 after increase.

[0165] In other words, for each downgrade coefficient ak strictly less than 1, and more generally less than the upper value of the downgrade coefficient, we apply:

[0166] [Math.9] aft = max(l; 1,01 xaj

[0167] Of course, the percentage of 1% is given as an example, other percentage values ​​being applicable.

[0168] Alternatively, other types of increase in the values ​​of the downgrade coefficients are conceivable, for example an increase of a predetermined fixed value.

[0169] Step 57 is followed by step 60 as previously described.

[0170] The steps of the process are iterated at a frequency chosen to limit the degradation of the power factor of the charging system.

[0171] Advantageously, in one embodiment, the steps of the process are iterated, for the same calculation metric of a power factor degradation, until the degradation value according to this power factor degradation metric is less than the corresponding degradation threshold.

[0172] Advantageously, according to one embodiment, the method described above is applied successively to several power factor degradation calculation metrics and corresponding degradation thresholds, according to a chosen order of priority. Thus, potential pollution according to several power factor degradation metrics is controlled.

[0173] For example, the method is first applied iteratively to a first metric for calculating a power factor degradation, for example the reactive power of the charging system. Then, the method is applied iteratively to a second metric for calculating a power factor degradation, for example the total harmonic distortion, and so on.

[0174] Advantageously, it is possible to consider successively, as calculation metrics for a degradation of the power factor, partial harmonic distortions on several distinct harmonic ranks.

[0175] Advantageously, the invention makes it possible to achieve a management of the charging stations of the charging system for electric vehicles, optimized to improve the power factor of this charging system.

Claims

1. Demands A method for charging electric vehicles (4b, 4n), implemented by an electric vehicle charging system (2) comprising a plurality of alternative energy charging stations (6, 6b, ..., 6N) and a supervisory module (20), each charging station (6b, ..., 6N) being configured to charge an electric vehicle (4b, ..., 4N) connected to said charging station and to communicate with the supervisory module (20) via a communication link, the method comprising the steps of: A) for each charging station, an acquisition (42b..,42N), by a current sensor of said charging station, of measurements of a current consumed by the electric vehicle connected to said charging station, at successive time instants, and formation of a digitized signal of current consumed by said station, then transmission (46i,..., 46n) of a message comprising data relating to said digitized signal of current consumed to the supervisory module (20), the method being characterized in that it comprises the following steps, implemented by the supervisory module (20): -B) receive the messages sent by each charging station, and obtain (50), for each charging station, from said data relating to the digitized signal of current consumed, a spectral representation of the current consumed, the spectral representation being calculated by applying a spectral transformation to the digitized signal of current consumed by said charging station, said spectral representation comprising a plurality of pairs of amplitude and phase values, each pair being associated with a spectral rank of the current consumed, - C) determine (52) a global spectral representation of the charging system from the spectral representations of the current consumed per charging station and per spectral rank, -D) calculate (54) a degradation value (V(Sg)), representative of a degradation of the power factor of the charging system, according to a power factor degradation calculation metric, based on said global spectral representation (Sg) of the charging system, -E) compare (56) said degradation value (V(Sg)) to a degradation threshold (S_DH), and in case of exceeding the degradation threshold, -F) calculate (58) at least one derating coefficient to be applied by at least one of the charging stations based on the degradation threshold, G) -command (60) at least one of the charging stations to apply the calculated derating coefficient to modify a parameter of electrical energy supplied by said charging station.

2. Method according to claim 1, wherein the calculation (58) of at least one derating coefficient to be applied by at least one of the charging stations is carried out as a function of the degradation threshold (S_DH) and said degradation value (V(Sg)).

3. A method according to any one of claims 1 to 2, comprising an iteration of steps A) to G) until the degradation value (V(Sg)) is less than the degradation threshold (S_DH).

4. A method according to any one of claims 1 to 3, wherein the degradation value is chosen from a reactive power of the charging system, a total harmonic distortion, a partial harmonic distortion according to one or more predetermined harmonic ranks.

5. A method according to any one of claims 1 to 4, wherein the calculation (58) of at least one derating coefficient implements a calculation of derating coefficients of the same value for each charging station.

6. A method according to any one of claims 1 to 4, wherein the calculation (58) of at least one derating coefficient implements a calculation of differentiated derating coefficients per charging station, the derating coefficient being more penalizing as the charging station induces a high amount of power factor degradation according to said power factor degradation calculation metric.

7. A method according to any one of the preceding claims, wherein steps A) to G) are applied successively for a plurality of power factor degradation calculation metrics.

8. A method according to any one of the preceding claims, wherein the derating coefficients vary between 0 and 1, each derating coefficient being applied, by a charging station, as a multiplicative factor of an electrical energy parameter delivered by said charging station.

9. A method according to any one of claims 1 to 8, comprising, when said degradation value (V(Sg)) is less than the degradation threshold (S_DH), an adjustment (57) by increasing at least one downgrade coefficient.

10. Electric vehicle charging system (2) comprising a plurality of alternative electrical charging stations (6, 6b, ..., 6N), a supervisory module (20), each charging station (6, 6i, ..., 6N) being configured to charge an electric vehicle (4b, ..., 4N) connected to said charging station and to communicate with the supervisory module (20) via a communication link, each charging station comprising a current sensor (14) configured to measure, at successive time instants, a current consumed by an electric vehicle connected to said charging station, and to form a digitized signal of current consumed by said station, and then transmit a message comprising data relating to said digitized signal of current consumed to the supervisory module,the charging system (2) being characterized in that the supervisory module is configured (20) to execute modules to: - receive messages sent by each charging station, - obtain (28), from each charging station, a spectral representation of the current consumed calculated by applying a spectral transformation to the digitized signal of the current consumed at said charging station, said spectral representation comprising a plurality of pairs of amplitude and phase values, each pair being associated with a spectral rank of the current consumed, - determine (30) an overall spectral representation of the charging system from the spectral representations of the current consumed per charging station and per spectral rank, - calculate (32) a degradation value, representative of a degradation of the power factor of the charging system, according to, a power factor degradation calculation metric, based on said global spectral representation of the charging system, - compare (34) said degradation value to a degradation threshold, and in case of exceeding the degradation threshold, - calculate (36) at least one derating coefficient to be applied by at least one of the charging stations based on the degradation threshold, - order (38) at least one of the charging stations to apply the calculated derating coefficient to reduce a parameter of electrical energy supplied by said charging station.

11. Electric vehicle charging system according to claim 10, wherein each charging station (6) includes a module (19) configured to apply spectral transformation to calculate the spectral representation of the current consumed by said charging station (6), and transmit the spectral representation to the supervisory module (20).

12. Electric vehicle charging system according to claim 11, wherein each charging station (6b.. .,6 N) is configured to transmit the digitized signal of current consumed to the supervisory module, the supervisory module (20) being configured to apply the spectral transformation on each digitized signal of current consumed to obtain the spectral representation of the current consumed per charging station.

13. Supervisory module (20) of an electric vehicle charging system (2) (4b..4N), the electric vehicle charging system comprising a plurality of alternative electrical charging stations (6, 61,...,6N), each charging station (6, 6b ...,6N) being configured to charge an electric vehicle (4b ...,4N) connected to said charging station and to communicate with the supervisory module (20) via a communication link, each charging station comprising a current sensor (14) configured to measure, at successive time instants, the current consumed by an electric vehicle connected to said charging station, and to form a digitized signal of the current consumed by said station, and then transmit a message comprising data relating to said digitized signal of current consumed to The monitoring module, the monitoring module being configured to implement: - a module (22) for receiving messages sent by each charging station, - a module (28) for obtaining, from each charging station, a spectral representation of the current consumed calculated by applying a spectral transformation to the digitized signal of current consumed on said charging station, said representation comprising a plurality of pairs of amplitude and phase values, each pair being associated with a spectral rank of the current consumed, - a module (30) for determining an overall spectral representation of the charging system from the spectral representations of the current consumed per charging station and per spectral rank, - a module (32) for calculating a degradation value, representative of a degradation of the power factor of the charging system, according to a power factor degradation calculation metric,based on said overall spectral representation of the charging system, - a module (34) for comparing said degradation value to a degradation threshold, and in the event of exceeding the degradation threshold, - a module (36) for calculating at least one derating coefficient to be applied by at least one of the charging stations based on the degradation threshold, - a module (38) for controlling at least one of the charging stations to apply the calculated derating coefficient to reduce a parameter of electrical energy supplied.

14. A charging station of an electric vehicle charging system according to claims 10 to 12, said electric vehicle charging system comprising a supervisory module (20), the charging station (6) being configured to charge an electric vehicle (4) connected to said charging station and to communicate with the supervisory module (20) via a communication link, and comprising a current sensor (14) configured to measure, at successive time instants, the current consumed by an electric vehicle (4) connected to said charging station (6), and to form a digitized signal of the current consumed by said terminal, then transmit (12) a message including data relating to said digitized signal of current consumed to the supervisory module (20), the charging terminal (6) being further configured to receive from said supervisory module a command to apply a calculated derating coefficient to reduce a parameter of electrical energy supplied, and apply (18) said derating coefficient for the supply of electrical energy to said electric vehicle.

15. Charging station according to claim 14, comprising a spectral transformation module (19), configured to perform said spectral transformation to calculate the spectral representation of the current consumed by said charging station, the charging station being configured to transmit the spectral representation to the supervisory module (20).

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