Method for controlling the temperature of at least one capacitor suitable for an embedded charger

Abstract

The invention relates to a method for optimizing the lifespan of at least one capacitor of a capacitor module (400) of an electronic device (100), the electronic device (100) being suitable for charging a high-voltage battery (600) of an electric vehicle, the device comprising a power-factor-correction circuit (300), a DC / DC converter (500), a cooling device (700) suitable for cooling at least one capacitor of the capacitor module (400), and a second temperature sensor (910) placed on at least one capacitor of the capacitor module (400) and suitable for measuring an actual temperature of the at least one capacitor, the method comprising the following steps: - a first step a1) of activating the charger (100) with a view to charging the high-voltage battery (600), and - a second step a2) of charging the high-voltage battery (600) by means of the charger (100) with a first setpoint power (P1_cons).

Description

[0001] DESCRIPTION

[0002] METHOD FOR CONTROLLING THE TEMPERATURE OF AT LEAST ONE CAPACITY SUITABLE FOR AN ON-BOARD CHARGER.

[0003] [Technical field]

[0004] The invention relates to the field of electric vehicles and more specifically to a method for optimizing the lifespan of at least one capacity for an on-board charger of an electric vehicle.

[0005] [State of the prior art]

[0006] An electric vehicle comprises at least one high-voltage battery, for example a 400-volt or 800-volt battery, coupled to a high-voltage electrical network (internal network of the electric vehicle) and a low-voltage battery, for example 12 volts, coupled to a low-voltage electrical network (internal network of the electric vehicle). The high-voltage battery and the low-voltage battery are adapted to deliver electrical energy and to store electrical energy respectively on the high-voltage electrical network and on the low-voltage electrical network.

[0007] To do this, the electric vehicle includes an on-board charger, better known as an OBC for "On Board Charger" in English, connected to the high-voltage battery called "BHT" via the high-voltage electrical network. The on-board charger is suitable for, once connected to a power supply network, converting the alternating voltage supplied by an external electrical network into a high-voltage direct voltage capable of recharging the high-voltage battery.

[0008] Figure 1 represents a schematic diagram of a state-of-the-art on-board electric charger 10 adapted to charge the high-voltage battery 60 dedicated, for example, to the power supply of an electric machine for the propulsion of an electric or hybrid vehicle.

[0009] The on-board electrical charger 10 comprises an electromagnetic filtering circuit 20, and a power factor correction circuit 30 called “PFC” which can be bidirectional. Said power factor correction circuit 30 further comprises an AC-DC converter circuit adapted to receive, for example, an electric current from a domestic AC power supply network. The on-board electrical charger 10 also comprises a capacitor module 40 arranged between the power factor correction circuit 30 and a DC / DC converter 50 adapted to charge the high-voltage battery 60.

[0010] As is known to those skilled in the art, the charging of the low voltage power supply battery, not shown in FIG. 1, is carried out by the high voltage battery 60, by a second DC-DC converter, not shown in FIG. 1 connected between the high voltage battery 60 and the low voltage power supply battery.

[0011] The high voltage battery is charged using the on-board electric charger 10 once coupled to the electrical network 70.

[0012] The capacitor module 40 is composed of a determined number of electrochemical capacitors whose equivalent value is relatively large to accept a relatively large effective current value when charging the battery and to reduce, or sufficiently filter the ripples of the rectified voltage at the output of the power factor correction circuit 30 so that said ripples, once filtered, are compatible with the input characteristics of the DC / DC converter 50.

[0013] A solution well known to those skilled in the art for producing the capacitor module 40 is to implement a relatively large number of capacitors to obtain a large equivalent capacity value to be able to both control the ripples and accept large effective currents (or RMS currents for "Root Mean Square" in English) when charging the high voltage battery at full power.

[0014] A disadvantage of this solution is the need to increase the surface area of ​​the printed circuit board or PCB to accommodate said capacities, significantly increasing the cost of the on-board charger 10.

[0015] Furthermore, the effective current value and more precisely the maximum effective current value depends on the battery charge level and the charger power. For example, an on-board charger may have a nominal power of 7KW.

[0016] Thus, depending on said maximum value of the effective current flowing through said capacitors of the capacitor module 40, the latter heat up and can sometimes reach temperatures equal to or greater than a critical capacity threshold temperature Tcritcap which is given by the manufacturer of the capacitors. For example, the critical capacity threshold temperature Tcritcap is 85°C. Thus, in the case where, during charging of the high-voltage battery by the charger, the temperature of the capacitors reaches or exceeds the critical capacity threshold temperature Tcritcap, then the lifetime of said capacitors is reduced compared to use of said capacitors at temperatures below the critical capacity threshold temperature Tcritcap.

[0017] To limit the temperature increase of the capacitors of the capacitor module 40, it is common to use a cooling device arranged for example on said capacitor module 40. The cooling device is suitable for cooling the capacitors through the capacitor module 40, but also for cooling electronic components arranged on the printed circuit of the on-board charger 10. Such a solution can use air cooling. However, since the quantities of calories to be evacuated are relatively large, the cooling device can also be based on a principle of cooling by a liquid, i.e. water or glycol. Thus, it is possible to improve the elimination of the calories generated by the electronic components and the capacitors.

[0018] As mentioned above, it is necessary to check the lifetime of the capacities of the on-board charger 10 because the latter is given for a minimum usage duration by the vehicle manufacturer, for example 20,000 hours, under typical usage and recharging conditions.

[0019] However, sometimes, said charger 10 and therefore the capacities of the capacity module 40 of said charger 10 are used in extreme conditions, for example when recharging the electric vehicle on a charging station in full sun in summer in a supermarket parking lot which causes abnormal heating of the capacities and therefore overheating of said charger which can reduce its duration of use.

[0020] There is therefore a real need to ensure temperature control of the capacities to avoid exceeding the critical temperature in order to avoid premature deterioration of the said capacities.

[0021] [Statement of the invention]

[0022] The invention relates to a method for optimizing the lifetime of at least one capacitor of a capacitor module of an electronic device, said electronic device being suitable for charging a high-voltage battery of an electric vehicle, said device comprising a power factor correction circuit, a DC / DC direct-direct converter, a cooling device suitable for cooling at least one capacitor of the capacitor module, a second temperature sensor arranged on at least one capacitor of the capacitor module and suitable for measuring an actual temperature of said at least one capacitor, the method comprising the following steps:

[0023] • a first step a1) consisting of activating the charger to charge the high voltage battery,

[0024] • a second step a2), consisting of charging the high voltage battery by the charger with a first set power,

[0025] • a third step a3), consisting of measuring the temperature of at least one capacity representative of the temperature of all the capacities of the capacity module using the second temperature sensor and storing in a memory area a first real temperature representative of the temperature of all the capacities of the capacity module,

[0026] • a fourth step a4), consisting of waiting for a first determined duration before moving on to a fifth step a5),

[0027] • the fifth step a5), consisting of recording a second real temperature of at least one capacity representative of the temperature of all the capacities of the capacity module, and storing the value of the second real temperature in a memory zone,

[0028] • a sixth step a6) consisting of waiting a second determined duration before moving on to a seventh step a7),

[0029] • the seventh step a7), consisting of recording a third actual temperature of at least one capacity representative of the temperature of all the capacities of the capacity module, and storing the third actual temperature in a memory zone,

[0030] • an eighth step a8), consisting of calculating a final temperature value of at least one capacity representative of the temperature of all the capacities of the capacity module using a first Equation: o Equation 1: Trelcap2 = Trelcapl + (Tfinalcap-Trelcap1)*exp(-tp1 / tau), and a second Equation: o Equation 2: Trelcap3 = Trelcapl + (Tfinalcap-Trelcap1)*exp((-tp1-tp2) / tau), the two unknowns being Tfinalcap and tau, the eighth step a8) further consisting of calculating a power setpoint reduction coefficient using a third equation: o Equation 3: Rcons= Tfinalcap / 85°C, and applying a new first setpoint power value to the charger,

[0031] • a ninth step a9), consisting of calculating using Equation 1, the temperature corresponding to the temperature of the capacity module after the duration of the time, and comparing the calculated value to a critical temperature value, and in the case where the value is higher then go to the third step a3) otherwise go to a tenth step a10),

[0032] • the tenth step a10), consisting of waiting for a waiting time equal to the duration of tau before moving on to the third step a3).

[0033] [Description of the drawings]

[0034] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This description is purely illustrative and must be read in conjunction with the appended drawings in which:

[0035] Figure 1 is a structural illustration of a prior art charger,

[0036] Figure 2 shows a structural diagram of the charger according to the invention,

[0037] Figure 3 is an illustration of the method according to the invention.

[0038] [Description of embodiments]

[0039] The invention will be presented in the case of an implementation in an electric vehicle comprising at least one electrical machine capable of converting electrical energy into mechanical energy in order to drive at least one wheel of the electric vehicle in rotation.

[0040] With reference to Figure 2, there is shown a block diagram of an electronic device 100 which is for example an on-board electric charger 100 according to the invention. Said on-board electric charger 100 is adapted to charge the high voltage battery 600 dedicated for example to the power supply of a three-phase machine for the propulsion of an electric or hybrid vehicle.

[0041] The on-board electrical charger 100 may be unidirectional or bidirectional. The latter comprises an electromagnetic filtering circuit 200 and a power factor correction circuit 300 called “PFC” which may be bidirectional, said power factor correction circuit 300 comprising an AC-DC converter circuit adapted to receive an electric current from a domestic AC power supply network for example.

[0042] A capacity module 400 arranged between the power factor correction circuit 300 and a DC / DC converter 500 adapted to charge the high voltage battery 600. The capacity module 400 is also called by those skilled in the art “DC LINK” module.

[0043] As is known to those skilled in the art, the charging of the low voltage power supply battery, not shown in FIG. 2, is carried out by the high voltage battery 600, by a second DC-DC converter connected between the high voltage battery 600 and the low voltage power supply battery.

[0044] The high voltage battery is charged using the on-board electric charger 100 once coupled to the electrical network.

[0045] Cleverly, the capacitor module 400 is composed of a determined number of capacitors, for example electrochemical capacitors, adapted to accept a relatively high effective current value when charging the battery and to sufficiently filter the ripples of the rectified voltage at the output of the power factor correction circuit 300 so that said ripples, once filtered, are compatible with the input characteristics of the DC / DC converter 500. Cleverly, the device of the invention proposes to control an actual temperature of at least one capacitor called Trelcap.

[0046] The on-board charger 100 cleverly comprises a cooling device 800 arranged for example on the capacity module 400 but also on the power factor correction circuit 300 and on the DC / DC converter 500. The cooling device 800 comprises for example at least one pipe adapted to allow a cooling liquid to circulate. The cooling liquid is adapted to absorb calories originating from the heating of the electronic components of the power factor correction circuit 300 and the DC / DC converter 500 but also adapted to absorb the calories generated by the capacities of the capacity module 400. The mechanical fixing and the thermal coupling between the different elements are obvious to those skilled in the art.Advantageously, a first temperature sensor 900 is arranged at the level of the pipe of the cooling device 800 allowing measurements of the temperature of the coolant Tliq. In a variant, the temperature of the liquid is given by measuring means arranged on the cooling circuit of the electric vehicle.

[0047] Advantageously, a second temperature sensor 910 is arranged on at least one capacitor of the capacitor module 400. Alternatively, the second temperature sensor 910 is arranged on packaging of the capacitor module 400. The second temperature sensor 910 is adapted to measure the actual Trelcap temperature of at least one capacitor representative of the temperature of all the capacitors of the capacitor module 400. Thus, thanks to the device of the invention, it is possible to know the temperature in real time of the capacitor module 400 and, depending on this, to activate or not the on-board charger 100.

[0048] The first temperature sensor 900 and the second temperature sensor 910 may use thermistor technology or alternatively semiconductor technology.

[0049] The invention proposes a method for controlling the temperature of at least one capacitor controlling the power delivered by an electronic device 100 as a function of an actual temperature of at least one capacitor of said electronic device 100.

[0050] To do this, the method of the invention comprises and as illustrated in FIG. 3 in the case where the electric vehicle is coupled to an external voltage outlet and recharging of the high voltage battery 600 is necessary, a first step a1) consisting of activating the charger 100 to charge the high voltage battery 600.

[0051] In a second step a2), the high-voltage battery 600 is charged by the charger 100 with a first setpoint power P1_cons. For example, the first setpoint power P1_cons is that determined by the vehicle manufacturer in the case of optimal charging of the battery 600. For example, in the case of an 11 kW charger, the first setpoint power P1_cons has a value of 11 kW.

[0052] In a third step a3), the method according to the invention proposes measuring the temperature of at least one capacitor representative of the temperature of all the capacitors of the capacitor module 400. To do this, in the third step a3), the temperature of at least one capacitor is measured using the second temperature sensor 910. Thus, a first actual temperature Trelcapl of at least one capacitor representative of the temperature of all the capacitors of the capacitor module 400 is recorded. The method also proposes, in this third step a3), storing the first actual temperature Trelcapl in a memory area. Alternatively, n temperature values ​​of at least one capacitor are measured using the second temperature sensor, and an average calculation of the measured values ​​is then performed before storing the averaged value in a memory.

[0053] The method then proposes, in a fourth step a4), to wait for a first determined duration tp1. In an exemplary embodiment, the first determined duration tp1 has a value of 30 seconds.

[0054] The method proposes, after the elapse of the time of the first determined duration tp1, the transition to a fifth step a5).

[0055] The fifth step a5) consists of measuring the temperature of at least one capacitance using the second temperature sensor 910. Thus, a second actual temperature Trelcap2 of at least one capacitance is recorded, representative of the temperature of all the capacitances of the capacitance module 400. The method also proposes, during this fifth step a5), to store the second actual temperature Trelcap2 in a memory area. Alternatively, n temperature values ​​of at least one capacitance are measured using the second temperature sensor, and an average calculation of the measured values ​​is then carried out before storing the averaged value in a memory.

[0056] The method then proposes, in a sixth step a6), to wait for a second determined duration tp2. In an exemplary embodiment, the second determined duration tp2 has a value of 30 seconds.

[0057] The method proposes, after the second determined duration tp2 has elapsed, the transition to a seventh step a7).

[0058] The seventh step a7) consists of measuring the temperature of at least one capacitance using the second temperature sensor 910. Thus, a third actual temperature Trelcap3 of at least one capacitance is recorded, representative of the temperature of all the capacitances of the capacitance module 400. The method also proposes, during this seventh step a7), to store the third actual temperature Trelcap3 in a memory area. Alternatively, n temperature values ​​of at least one capacitance are measured using the second temperature sensor, and an average calculation of the measured values ​​is then carried out before storing the averaged value in a memory. During an eighth step a8), the final temperature Tfinalcap of at least one capacitance is calculated, representative of the temperature of all the capacitances of the capacitance module 400.The final temperature Tfinalcap represents the final stabilized temperature of at least one capacity representative of the temperature of all the capacities of the capacity module 400 following the constant application of the first setpoint power P1_cons.

[0059] As is known to those skilled in the art, the evolution of the temperature of a capacity under constant power is in the form of a first-order increasing exponential.

[0060] Advantageously, and thanks to the following measurement values, first actual temperature Trelcapl, first determined duration tp1, second actual temperature Trelcap2, second determined duration tp2, third actual temperature Trelcap3, it is possible to solve the following system of two equations with two unknowns:

[0061] Equation 1: Trelcap2 = Trelcapl + (Tfinalcap-Trelcap1)*exp(-tp1 / tau)

[0062] Equation 2: Trelcap3 = Trelcapl + (Tfinalcap-Trelcap1)*exp((-tp1-tp2) / tau)

[0063] The two unknowns are Tfinalcap and tau, tau represents the thermal time constant of the capacitance module 400. The resolution of such a system of equations with 2 unknowns is trivial for those skilled in the art and cleverly to simplify the resolution, it is proposed that the value of the second determined duration tp2 is an integer multiple of the value of the first determined duration tp1; for example, tp1=tp2.

[0064] Then in the same eighth step a8) a power setpoint reduction coefficient called Rcons in the rest of the description is calculated. It is equal to the following equation: Rcons= Tfinalcap / 85°C.

[0065] In the context of the invention, 85°C is selected as the critical temperature value not to be exceeded for the capacitors of the capacitor module 400 so as not to damage them.

[0066] Cleverly, the Rcons coefficient is used to calculate the new first Picons setpoint power which will allow not to exceed the critical temperature with an optimal setpoint power to obtain an optimal charging time.

[0067] In the case where the new calculated first Picons setpoint power exceeds the value of the maximum power of the charger, which in our example is 11kW, the value of the maximum power of the charger, i.e. 11kW, is selected as the new first Picons setpoint power. During this eighth step a8), the new first Picons setpoint power is applied to the charger. Then, the transition to a ninth step a9) is proposed.

[0068] In the ninth step a9), it is calculated using the previous equation 1, the temperature Ttau corresponding to the temperature of the capacity module 400 after the duration of the time tau.

[0069] Cleverly, the calculated value of Ttau is compared to a critical temperature value Tcapcrit. For example, the value Tcapcrit is equal to 85°C. In the case where the value of Ttau is greater than Tcapcrit, then it is proposed to move on to the third step a3), otherwise it is proposed to move on to a tenth step a10). At the tenth step a10), it is proposed to wait for a waiting time equal to the duration of tau before moving on to the third step a3). This waiting time makes it possible to avoid measurements and calculations of the new first setpoint power Picons too frequently because the final temperature Tfinalcap will not reach 85°C.

[0070] Thanks to this clever invention, the battery recharge time is optimized because it is possible to estimate the optimal set power without exceeding the critical temperature of the capacities.

Claims

Claims

1. Method for optimizing the lifetime of at least one capacitor of a capacitor module (400) of an electronic device (100), said electronic device (100) being adapted to charge a high voltage battery (600) of an electric vehicle, said device comprising a power factor correction circuit (300), a DC / DC converter (500), a cooling device (700) adapted to cool at least one capacitor of the capacitor module (400), a second temperature sensor (910) arranged on at least one capacitor of the capacitor module (400) and adapted to measure an actual temperature of said at least one capacitor, the method comprising the following steps: • a first step a1) consisting of activating the charger (100) to charge the high voltage battery (600), • a second step a2), consisting of charging the high voltage battery (600) by the charger (100) with a first set power (P1_cons), • a third step a3), consisting of measuring the temperature of at least one capacity representative of the temperature of all the capacities of the capacity module (400) using the second temperature sensor (910) and storing in a memory area a first real temperature (Trelcapl) representative of the temperature of all the capacities of the capacity module (400), • a fourth step a4), consisting of waiting for a first determined duration (tp1) before moving on to a fifth step a5), • the fifth step a5), consisting of recording a second real temperature (Trelcap2) of at least one capacity representative of the temperature of all the capacities of the capacity module (400), and storing the value of the second real temperature (Trelcap2) in a memory zone, • a sixth step a6) consisting of waiting a second determined duration (tp2) before moving on to a seventh step a7), • the seventh step a7), consisting of recording a third real temperature (Trelcap3) of at least one capacity representative of the temperature of all the capacities of the capacity module (400), and storing the third real temperature (Trelcap3) in a memory area, • an eighth step a8), consisting of calculating a final temperature value (Tfinalcap) of at least one capacity representative of the temperature of all the capacities of the capacity module (400) using a first equation: o Equation 1: Trelcap2 = Trelcapl + (Tfinalcap-Trelcap1)*exp(-tp1 / tau), and a second equation: o Equation 2: Trelcap3 = Trelcapl + (Tfinalcap-Trelcap1)*exp((-tp1-tp2) / tau), the two unknowns being Tfinalcap and tau, the eighth step a8) further consisting of calculating a power setpoint reduction coefficient (Rcons) using a third equation: o Equation 3: Rcons= Tfinalcap / 85°C, and applying a new first setpoint power value (Picons) to the charger (100), • a ninth step a9), consisting of calculating using Equation 1, the temperature (Ttau) corresponding to the temperature of the capacity module (400) after the duration of time (tau), and comparing the value of (Ttau) calculated with a critical temperature value (Tcapcrit), and in the case where the value (Ttau) is greater than (Tcapcrit) then moving on to the third step a3) otherwise moving on to a tenth step a10), • the tenth step a10), consisting of waiting for a waiting time equal to the duration of tau before moving on to the third step a3).

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