WO2022228925A1

WO2022228925A1 - Method for controlling a thermoelectric module, thermal actuator and control system

Info

Publication number: WO2022228925A1
Application number: PCT/EP2022/060196
Authority: WO
Inventors: Mohamed-Amine BOUBAKER; Georges De Pelsemaeker; William LAPIERRE
Original assignee: Valeo Systemes Thermiques
Priority date: 2021-04-26
Filing date: 2022-04-15
Publication date: 2022-11-03

Abstract

The present invention relates to a method for controlling a thermoelectric module (1) for a motor vehicle, comprising: - a first conduit (5) configured to receive a heat-transport liquid, - a second conduit (7) configured to receive air intended for an interior of the motor vehicle, - a plurality of thermoelectric elements (3) positioned between the first (5) and the second (7) conduits, the control method comprising: - a preliminary step (101) of determining a plurality of operating points combining a duty cycle and a pulse width modulation cycle frequency, said operating points corresponding, for each duty cycle value selected, to the cycle frequency that maximizes, on the one hand, the magnitude of the useful power produced and, on the other hand, the magnitude of a coefficient of performance, - a step (103) of selecting the operating point to be applied according to the target useful power on the basis of the results of the preliminary step (101), and - a step (104) of applying pulse width modulation in powering the thermoelectric elements (3) on the basis of a target useful power.

Description

METHOD FOR CONTROLLING A THERMOELECTRIC MODULE, THERMAL ACTUATOR AND MANAGEMENT SYSTEM

[1]The present invention relates to the field of thermoelectric modules

5 comprising thermoelectric elements making it possible in particular to create an electric current in the presence of a temperature gradient between two of their opposite faces according to the phenomenon known as the Seebeck effect.

[2]These thermoelectric modules can also be used in particular to cool when powered by the Peltier effect. 0 [3]Such thermoelectric modules can therefore be used as a substitute or in addition to an air conditioning and/or heating device in a motor vehicle.

[4]However, by applying a direct current to the thermoelectric elements, the sensation of cold or heat can be significant and5 therefore not very pleasant for the user and the electrical consumption can be significant.

[5] However, with the advent of electric vehicles, it is necessary to limit energy consumption as much as possible in order to maximize the autonomy of the vehicle. 0 [6] To this end, the present invention aims to provide a solution making it possible to provide optimum comfort to users while minimizing the electrical consumption of the thermoelectric modules.

[7]The subject of the invention is therefore a method for controlling a thermoelectric module for a motor vehicle comprising: 5 - a first conduit configured to receive a heat transfer liquid,

- a second duct configured to receive air intended for a passenger compartment of the motor vehicle,

-a plurality of thermoelectric elements arranged between the first and the second duct, 0 the control method comprising a step of applying pulse-width modulation to supply the thermoelectric elements as a function of a target useful power, the method also comprising: - a preliminary step of determining a plurality of operating points associating a duty cycle and a frequency of cycles of the pulse width modulation, said operating points corresponding, for each selected duty cycle value, to the frequency

5 cycles maximizing on the one hand the value of the useful power produced and on the other hand the value of a coefficient of performance,

- a step for selecting the operating point to be applied according to the target useful power based on the results of the preliminary step.

[8]According to another aspect of the present invention, the preliminary step of determining the operating points is carried out with given conditions of temperature and flow rate of the heat transfer liquid in the first conduit and of the air in the second conduit.

[9] According to another aspect of the present invention, the selected temperature of the heat transfer liquid in the first conduit is between 3°C and 20°C,5 for example 20°C, the selected flow rate of the heat transfer liquid in the first conduit is between 30 L/h and 200 L/h, for example 60 L/h, the temperature of the air in the second conduit is between 18°C and 40°C, for example 20°C, the flow rate of the air in the second conduit is between 1 kg / h and 10 kg / h, for example 7.5 kg / h. 0 [10]According to another aspect of the present invention, in the case where there does not exist an operating point maximizing both the useful power produced and the coefficient of performance during the preliminary stage, the operating point selected is the one maximizing the useful power produced.

[1 l] According to another aspect of the present invention, the selected duty cycles5 are distributed between 10% and 90%.

[12]According to another aspect of the present invention, the preliminary step comprises an extrapolation of the values of the intermediate operating points located between the selected duty cycles by applying a polynomial regression linking the various determined operating points. 0 Alternatively, the different operating points determined can be connected by straight line segments.

[13] The present invention also relates to a thermal actuator for a motor vehicle comprising at least one thermoelectric module and a control unit of said thermoelectric module, [14]said thermoelectric module comprising:

[15]- a first conduit configured to receive a heat transfer liquid,

5 [16]- a plurality of thermoelectric elements arranged between the first conduit and the second conduit,

[17]said control unit being configured to apply a pulse-width modulation to the thermoelectric elements of the at least one thermoelectric module as a function of a target useful power, a duty cycle and a frequency of cycles of said modulation with pulse width being determined as a function of the desired useful power from a curve connecting a plurality of operating points associating a duty cycle and a frequency of cycles of the pulse width modulation, said operating points corresponding, for each selected duty cycle value, at the frequency of the cycles maximizing on the one hand the value of the useful power produced and on the other hand the value of a coefficient of performance.

[18]According to another aspect of the present invention, the thermoelectric elements are Peltier elements. 0 [19] According to another aspect of the present invention, in normal operation, the temperature of the heat transfer liquid in the first conduit is between 3°C and 20°C, for example 20°C and the flow rate of the heat transfer liquid in the first pipe is between 30 L/h and 200 L/h, for example 60 L/h.

[20] According to another aspect of the present invention, in normal operation, the temperature of the air in the second duct is between 18°C and

40°C, for example 20°C, the air flow in the second duct is between 1 kg/h and 10 kg/h, for example 7.5 kg/h.

[21] The present invention also relates to a passenger comfort management system in a motor vehicle interior comprising a secondary thermal loop forming the first conduit and comprising at least one thermal actuator as described above, said secondary thermal loop being arranged to transport the heat transfer liquid which is configured to exchange calories and/or cold temperatures with a main air conditioning _unit [22] According to another aspect of the present invention, the secondary thermal loop comprises several thermal actuators arranged in series or in parallel, a single control unit being configured to apply a pulse width modulation to the thermoelectric elements of

5 all the thermal actuators.

[23]Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawings, including:

[24] Figure 1 shows a diagram of a thermoelectric module; 0 [25]Figure 2 shows a diagram of a thermal actuator;

[26] Figure 3 shows a diagram of a thermal management system according to a first embodiment;

[27] Figure 4 shows a diagram of a thermal management system according to a second embodiment; 5 [28] Figure 5 shows a graph representing the optimum cycle frequency as a function of the duty cycle value;

[29] FIG. 6 represents a graph of the curves of electrical power consumed, useful power supplied and power coefficient for different operating points; 0 [30] FIG. 7 represents a flowchart of the steps of a method for controlling a thermoelectric module according to the present invention;

[31] FIG. 8 represents a graph of the curves of electrical power consumed, useful power supplied and power coefficient as a function of the frequency of cycles for a given duty cycle; 5 [32] In these figures, identical elements bear the same references.

[33]The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference is to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined or interchanged to provide other realizations.

[34]In the present description, certain elements or parameters can be indexed, such as for example first element or second element as well as first parameter and second parameter or even first criterion and second criterion, etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria that are close, but not identical. This indexing does not imply a priority of one element, parameter or criterion with respect to another and such denominations can easily be interchanged without departing from the scope of the present description. This indexation does not imply an order in time either, for example to assess such and such a criterion.

[35] The present invention relates to a thermal actuator 10 for a motor vehicle, in particular an electric vehicle, said thermal actuator 100 comprising a thermoelectric module 1 configured to produce a temperature gradient when it is powered by an electric current. FIG. 1 represents an embodiment of a thermoelectric module 1 comprising a plurality of thermoelectric elements 3, eight thermoelectric elements 3 in the present case. 5 [36] The thermoelectric elements 3 are for example Peltier elements. The number of thermoelectric elements 3 can be adapted according to the application and the power sought for the thermoelectric module 1. It is also possible to arrange several thermoelectric modules 1 adjacently. 0 [37]The thermoelectric elements 3 are arranged between a first conduit 5 and a second conduit 7. The first conduit 5 is configured to receive a heat transfer liquid, for example glycol water. The heat transfer liquid is, for example, configured to circulate through a thermal regulation loop of the motor vehicle comprising in particular the first conduit 5 5 . The thermal regulation loop comprises for example a pump configured to circulate the heat transfer liquid in the regulation loop and in particular in the first duct 5.

[38] FIG. 3 represents an example of a thermal management system 1000 of a motor vehicle comprising a main air conditioning assembly 100 and a secondary thermal regulation loop 200 comprising a thermoelectric module 1. The main assembly 100 comprises a evaporator 21, a condenser 22, a compressor 23, expansion valves 24 and 25 arranged respectively upstream of G evaporator 21 and of a heat exchanger 26, for example a chiller. The evaporator 21 and the exchanger thermal 26 are here arranged in parallel. The compressor 23 is configured to circulate a heat transfer fluid, for example a fluid from among the references R1234YF, 134a, 1234yf or C02, in the various elements of the main assembly 100.

5 [39] The secondary thermal loop 200 is configured to transport heat and/or cold to a thermal actuator 10 comprising a thermoelectric module 1 as described previously. The thermal actuator 10 is configured to act on the thermal comfort of a passenger in the passenger compartment and/or to provide calories and/or cold temperatures to a comfort accessory of the passenger compartment, for example a refrigerated compartment for food . The secondary thermal loop 200 comprises a compressor 32 configured to circulate a heat transfer fluid, for example glycol water in the various elements of the secondary thermal loop 200. 5 [40]The main assembly 100 and the secondary thermal loop 200 are configured to exchange calories and/or cold temperatures via the heat exchanger 26.

[41] Alternatively, as shown in Figure 4, the secondary thermal loop 200 may include a plurality of thermal actuators 100 which may be arranged in parallel or in series. The temperature of the glycol water is for example between 15°C and 3°C and its flow rate is for example between 500 and 2000L/h.

[42] Regarding the thermoelectric module 1, as shown in Figure 1, the first conduit 5 may be a bidirectional conduit comprising a central wall5 separating a first half-duct 5a in which the heat transfer liquid circulates in a first direction and a second half -conduit 5b in which the heat transfer liquid circulates in a second direction opposite to the first direction. The two half-ducts 5a and 5b can be fluidically connected to one of the ends of the thermoelectric module 1. 0 [43]The second duct 7 is configured to receive air intended for a passenger compartment of the motor vehicle. The thermoelectric module 1 is for example configured to cool the air from the second duct 7 to the passenger compartment, the heat then being dissipated via the heat transfer liquid circulating in the first duct 5. [44] Alternatively, the thermoelectric module 1 can be configured to heat the air from the second duct 7 to the passenger compartment. In the latter case, the circulation of the heat transfer liquid in the first pipe 5 can be stopped.

5 [45] The air in the second duct 7 is for example circulated to the passenger compartment by a fan 9. The air in the second duct 7 is for example received from the passenger compartment or from outside the vehicle automobile.

[46] In addition, the first 5 and the second 7 ducts are arranged as close as possible to the thermoelectric elements so as to limit thermal losses. The thermal contact between the first and second ducts 5, 7 and the thermoelectric elements 3 can be ensured by a thermal paste. The thermal paste has for example a thermal conductivity of 3W/m.K.

[47] As shown in Figure 2, the thermal actuator 10 also comprises a control unit 11 of the thermoelectric module 15 configured to supply the thermoelectric elements 3 of the thermoelectric module 1 with an electric current. In the case of a device comprising a plurality of thermoelectric modules 1, a single control unit 11 can be used to control the power supply to the thermoelectric elements 3 of the various thermoelectric modules 1. 0 [48]The control unit 11 comprises in particular a battery 13 supplying direct current, a switch 14, for example a transistor whose opening and closing are controlled for example by a microcontroller or a microprocessor 16.

[49] The control unit 11 can also include a resistor 155 allowing the measurement of the electric current applied to the thermoelectric module 1. Alternatively, the battery 13 can be external to the control unit 10, for example a battery of the motor vehicle .

[50] The control unit 11 is more particularly configured to apply a pulse-width modulation (PWM) in English) via the transistor 14 according to a target useful power. The control unit 10 is more particularly configured to determine the parameters of the pulse width modulation, in particular the duty cycle and the frequency of the modulation cycles, making it possible to obtain the target power while optimizing the electrical consumption. [51]For this, optimal operating points associating a duty cycle and a cycle frequency of the pulse width modulation are determined beforehand. Thus, as shown in the graph of Figure 5, for different duty cycle values distributed between 0%

5 and 100%, in particular between 10% and 90%, in the present case between 20% and

80% (20%, 40%, 50%, 60% and 80%), the associated cycle frequency allowing to maximize both the useful power produced and the coefficient of performance (coefficient of performance "COP") is determined. 0 [52]If there is no operating point maximizing both the useful power produced and the coefficient of performance during the preliminary stage, the operating point selected is the one maximizing the useful power produced.

[53] This determination is carried out with given conditions of temperature5 and flow rate of the heat transfer liquid in the first conduit 5 and of the air in the second conduit 7. The conditions chosen are for example conditions encountered in normal operation. The temperature of the heat transfer liquid in the first conduit 5 is for example between 3° C. and 20° C. so that the chosen temperature can be 20° C., the flow rate of the heat transfer liquid 0 in the first conduit 5 is between 30 L/h and 200 L/h so that the chosen flow rate is for example 60 L/h, the temperature of the air in the second pipe 7 is for example between 18° C. and 40° C. so that the temperature of the chosen air can be 20° C., the air flow in the second duct 7 is between 1 kg/h and 10 kg/h so that the chosen air flow5 can be 7.5 kg /h.

[54]From the determined operating points, a curve C can be extrapolated for the intermediate values as shown in Figure 5. This extrapolation of the value of the operating points located between the chosen duty cycles can be obtained by applying a regression0 polynomial linking the different operating points determined or by any other type of appropriate regression. Alternatively, straight segments can be used to connect the various determined operating points. [55] Figure 6 shows the curves associated respectively with the electrical power consumed (curve Cl), with the useful power also called cold power in the case where one wants to cool the air of the second conduit 7 (curve C2) and the coefficient of performance (curve C3) for the different

5 operating points previously determined in FIG. 5. Thus, depending on the desired useful power, the control unit 11 is configured to select the optimal operating point associated with this useful power.

[56] Furthermore, one of the parameters of the pulse width modulation, for example the duty cycle, can be imposed and fixed for the application of the pulse width modulation. In this case, the useful power and the coefficient of performance obtained for different cycle frequencies can be determined as represented on the respective curves C4 (useful power) and C5 (coefficient of performance) of FIG. 8 for a duty cycle of 80% (Curve C6 represents the electrical power consumed).

[57] Thus the frequency can be determined according to the desired useful power or the frequency maximizing this useful power, here the 90Hz frequency corresponding to the optimal operating point of curve C for a duty cycle of 80% (figure 8 corresponds at a duty cycle of

80%).

[58] In the same way, if the frequency of cycles is imposed, the duty cycle can be chosen from curve C of figure 5 so as to maximize the useful power produced. 5 [59] Thus, the control unit 11 is configured to determine the optimal parameters of a pulse width modulation according to the desired useful power and/or the constraints imposed by the equipment and to apply this modulation pulse width on the thermoelectric elements 3 of the thermoelectric module 1. 0 [60] The application of such a pulse width modulation makes it possible to limit the electrical consumption while obtaining the desired useful power and therefore the cooling, or the heating, desired which makes it possible, in the case of an electric vehicle, to increase the autonomy of the vehicle without reducing the comfort of the passengers. [61] The present invention also relates to a method for controlling the thermoelectric module 1 described above. FIG. 7 represents a flowchart of the different steps of this method.

[62]The first step 101 is a preliminary step of determining a

5 plurality of optimal operating points associating a duty cycle and a cycle frequency of the pulse width modulation. For each chosen duty cycle value, the frequency of the cycles maximizing on the one hand the value of the useful power produced and on the other hand the value of a performance coefficient is selected to provide an operating point.

[63] A plurality of operating points are selected from a range of 10% to 90%. FIG. 5 represents 5 operating points associated respectively with the duty cycles 20%, 40%, 50%, 60% and 80%. The corresponding frequencies are respectively 50Hz, 240Hz, 300Hz, 200Hz5 and 90Hz.

[64]These operating points are obtained for given values of temperature and flow rate of the heat transfer liquid in the first conduit 5 and of air in the second conduit 7 but can be used for the entire range of use of these parameters. Alternatively, different operating points can be determined for different temperatures and/or flow rates.

[65] In the present case, the chosen temperature of the heat transfer liquid in the first pipe is 20°C, the chosen flow rate of the heat transfer liquid in the first pipe is 60 L/h, the chosen temperature of the air in the second5 duct is 20°C, the selected air flow rate in the second duct 7 is

7.5 kg/h but other values of the normal use range can be chosen.

[66] From the determined operating points, a curve can be extrapolated for intermediate values like curve C in figure 5. 0 Curve C can be saved in a memory of the control unit 11.

[67] The second step 102 is also a preliminary step and concerns the determination of the useful power and/or the performance coefficient obtained for the various operating points determined as represented in FIG. 6. In the same way, from the values obtained, curves such as curves C2 (useful power) and C3 (coefficient of performance) of FIG. 6 can be obtained by extrapolation for the intermediate values. The curves C2 and C3 can be saved in a memory of the control unit 11.

[68] The third step 103 concerns the selection of an operating point according to a thermal regulation command. This command is for example sent to the control unit 11 by a central controller of the motor vehicle, for example according to a regulation temperature 0 selected by a user. This command corresponds to a useful power to be supplied by the thermoelectric module(s) 1. Thus, from the curve C2 of FIG. 6, the control unit determines the operating point making it possible to obtain the desired output power.

[69] The fourth step 104 concerns the application of a pulse width modulation5 whose parameters correspond to the operating points determined in step 103.

Claims

[Claim 1] Method of controlling a thermoelectric module (1) for a motor vehicle comprising:

- a first conduit (5) configured to receive a liquid

5 coolant,

- a second duct (7) configured to receive air intended for a passenger compartment of the motor vehicle,

- a plurality of thermoelectric elements (3) arranged between the first (5) and the second conduit (7), 0 the control method comprising a step (104) of applying a pulse width modulation to supply the thermoelectric elements (3) as a function of a target useful power, characterized in that the method also comprises: 5 - a preliminary step (101) of determining a plurality of operating points associating a duty cycle and a frequency of cycles of the pulse-width modulation, said operating points corresponding, for each selected duty cycle value, to the frequency of the cycles0 maximizing on the one hand the value of the useful power produced and on the other hand the value of a coefficient of performance,

- a step (103) for selecting the operating point to be applied as a function of the target useful power from the results of the preliminary step (101). 5

[Claim 2] Control method according to the preceding claim, in which the preliminary step (101) of determining the operating points is carried out with given conditions of temperature and flow rate of the heat transfer liquid in the first conduit (5) and of the air in the second duct (7). 0

[Claim 3] Control method according to the preceding claim, in which the chosen temperature of the heat transfer liquid in the first conduit (5) is between 3°C and 20°C, for example 20°C, the chosen flow rate of the heat transfer liquid in the first pipe (5) is between 30 L/h and 200 L/h, for example 60L/h, the temperature of the air in the second pipe (7) is between 18°C and 40°C, for example 20°C, the air flow in the second duct (7) is between 1 kg/h and 10 kg/h, for example 7.5 kg /h.

[Claim 4] Control method according to one of the preceding claims wherein, in the case where there is no operating point maximizing both the useful power produced and the coefficient of performance during the preliminary step, the operating point selected is that which maximizes the useful power produced.

[Claim 5] Control method according to one of the preceding claims, in which the selected duty ratios are distributed between 10% and 90%.

[Claim 6] Control method according to one of the preceding claims, in which the preliminary step (101) comprises an extrapolation of the values of the intermediate operating points located between the selected duty cycles by applying a polynomial regression linking the different operating points determined.

[Claim 7] Thermal actuator (10) for a motor vehicle comprising at least one thermoelectric module (1) and a control unit (11) of said thermoelectric module (1),5 said thermoelectric module (1) comprising:

- a first conduit (5) configured to receive a heat transfer liquid,

- a second duct (7) configured to receive air intended for a passenger compartment of the motor vehicle, 0 - a plurality of thermoelectric elements (3) arranged between the first duct (5) and the second duct (7) , said control unit (11) being configured to apply a pulse width modulation to the thermoelectric elements (3) of the at least one module thermoelectric (1) as a function of a target useful power, a duty cycle and a cycle frequency of said pulse width modulation being determined as a function of the desired useful power from a curve (C)

5 connecting a plurality of operating points associating a duty cycle and a frequency of cycles of the pulse width modulation, said operating points corresponding, for each selected duty cycle value, to the frequency of cycles maximizing on the one hand the value of the useful power produced and on the other hand the value of a coefficient of performance.

[Claim 8] Thermal actuator (10) according to the preceding claim, in which the thermoelectric elements (3) are Peltier elements. 5

[Claim 9] Thermal actuator (10) according to Claim 7 or 8, in which, in normal operation, the temperature of the heat transfer liquid in the first conduit (5) is between 3°C and 20°C, for example 20°C and the flow rate of the heat transfer liquid in the first pipe (5) is between 30 L/h and 2000 L/h, for example 60 L/h.

[Claim 10] Thermal actuator (10) according to one of Claims 7 to 9, in which, in normal operation, the temperature of the air in the second duct (7) is between 18°C and 40°C, for example 20° C., the flow rate of the air in the second duct (7) is between 1 kg/h and 10 kg/h, for example 7.5 kg/h.

[Claim 11] Passenger comfort management system (1000) in a motor vehicle interior comprising a secondary thermal loop (200) forming the first conduit (5) and0 comprising at least one thermal actuator (10) according to one of claims 7 to 10, said secondary thermal loop (200) being arranged to transport the heat transfer liquid which is configured to exchange calories and/or cold with a main air conditioning assembly (100). [Claim 12] Comfort management system (1000) according to the preceding claim, in which the secondary thermal loop (200) comprises several thermal actuators (10) arranged in series or in parallel, a single control unit (11) being configured to apply a pulse width modulation to the thermoelectric elements (3) of the set of thermal actuators (10).