Method for controlling the power of a high-voltage electrified vehicle network

Abstract

The present invention relates to a method for controlling the power of an electrical system (1) of an electrified vehicle comprising a first high-voltage electrical network (13) and a second low-voltage network (3), the method comprising the following steps of determining a first maximum power value consumed by a converter (4) for the electrical needs of the second network (3), determining a first voltage constraint value corresponding to a minimum voltage of the converter (4) required to meet the need for the first power value, determining a voltage operating limit range of the first high-voltage network (13) as a function of at least the first constraint value, calculating the power limit range of the first high-voltage network (13) from the voltage limit range and regulating the power of the first high-voltage network (13). Figure 1.

Description

Title of the invention: Method for controlling the power of a high-voltage network of an electrified vehicle

[0001] The field of the invention relates to a method for controlling the power of an electrified vehicle voltage network.

[0002] Conventionally, electrified vehicles with fully electric or hybrid engines comprise a high-voltage traction battery and a prime mover electrically connected through a high-voltage network. Other electrical systems, such as a heater or air conditioner, may be connected to it. In addition, these vehicles are equipped with a low-voltage on-board network intended to power the vehicle's critical computers and electrical systems, such as the electric brake system or the vehicle's steering system. The low-voltage network is powered by a DCDC power converter connected to the high-voltage network and a service battery. The electrical supply of this network is a critical function for a motor vehicle because it must constantly guarantee the correct operation and reliability of the vehicle's safety systems.

[0003] Known from the state of the art is patent document US11318855B2 describing an electrical architecture of a motor vehicle comprising a DCDC power converter comprising at least two power conversion modules capable of operating independently for the charging needs of a battery and for driving modes of the vehicle. This document further proposes a method for controlling the DCDC converter where at least one of the conversion modules is selected according to a power requirement of the low voltage network. This architecture aims to improve the energy efficiency of the voltage converter.

[0004] Document US8742615B2 is also known describing a solution for controlling a DCDC power converter dependent on the temperature and the state of charge of the service battery. Furthermore, this document teaches adapting the voltage control of the DCDC when the headlights are on to avoid flashing of the headlights or DCDC voltage cuts to protect the electrical systems. Furthermore, when the load of the low voltage network is greater than a threshold and the speed of the vehicle is lower than another threshold, the voltage control is operated at a minimum voltage value.

[0005] There is therefore a need to protect the electrical management of an electrified vehicle against a failure event of a DCDC power converter supplying the low voltage on-board network.

[0006] One objective of the invention is to propose a solution for controlling the electrical system of an electrified vehicle that makes it possible to protect the high-voltage network against a voltage drop that could affect the operability of the power converter. Another objective of the invention is to permanently guarantee the power required for the power supply needs of the low-voltage on-board network.

[0007] More specifically, the invention relates to a method for controlling the power of an electrified vehicle electrical system comprising a first high-voltage DC network comprising a DCDC voltage converter electrically connecting the first network and a second low-voltage DC network and in which the first network further comprises at least one traction battery. The method comprises the following steps of determining a first maximum power value consumed by the converter for the electrical needs of the second network, of regulating the power of the first high-voltage network consisting of allocating at least the charging and discharging power of the traction battery and the supply power of the converter within a limit power range.

[0008] According to the invention, the method further comprises the following steps, for determining the limit power range, of determining a first voltage constraint value corresponding to a minimum converter voltage required to meet the need for the first power value, of determining a limit operating voltage range of the first high voltage network as a function of at least the first constraint value and of calculating the limit power range of the first high voltage network from the limit voltage range.

[0009] The method according to the invention may include the following additional characteristics, alone or in combination:

[0010] - The determination of the maximum instantaneous power consumed by the second network during a sliding operating period of the converter for the determination of the first maximum power value.

[0011] - The first maximum power value is determined by the selection of the minimum value between the maximum instantaneous power and a theoretical maximum power deliverable by the converter for the needs of the second network.

[0012] - The first value of stress in tension is delivered by a mapping of the predetermined converter taking as input the first maximum power value and an instantaneous temperature value of the electrical system.

[0013] - The method further comprises determining at least one second value of voltage constraint of the first high voltage network for the operation of at least one high voltage device electrically connected to the first network, and wherein the voltage operating limit range is determined based on at least the first value and the second constraint value.

[0014] Furthermore, according to the invention there is provided an electrical system for an electrified vehicle comprising a first high-voltage DC network comprising a DCDC voltage converter electrically connecting the first network and a second low-voltage DC network and in which the first network further comprises at least one traction battery, the system comprising a control unit configured to implement the power control method according to any one of the preceding embodiments of the method according to the invention.

[0015] According to a variant of the electrical system, the first high-voltage network further comprises at least one high-voltage device and in which the control unit is configured to implement the method according to the invention further comprising the determination of at least a second voltage constraint value of the first high-voltage network for the operation of at least the high-voltage device electrically connected to the first network, and in which the voltage operating limit range is determined as a function of at least the first value and the second constraint value.

[0016] According to a variant of the electrical system, the high voltage device is a water heater or a compressor.

[0017] Further provided is an electrified vehicle comprising a system according to any one of the preceding embodiments.

[0018] The invention further provides a computer program comprising instructions which, when the program is executed by a control unit of an electrical system of an electrified vehicle, cause the latter to implement the power control method according to any one of the preceding embodiments.

[0019] A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to implement the power control method according to any of the preceding embodiments.

[0020] The invention proposes a power regulation function making it possible to guarantee the voltage operation of the high voltage network in a voltage operating range making it possible to meet the electrical needs of the on-board network of an electrified vehicle.

[0021] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0022] [Fig. 1] schematically represents an embodiment of an architecture of an electrical system according to the invention for an electrified vehicle.

[0023] [Fig.2] is a diagram schematically representing the control method of power of an electrical system.

[0024] [Fig.3] is a schematic example of mapping implemented by the power control method to determine a minimum voltage to be respected for the needs of a voltage converter.

[0025] [Fig.4] is an example of a method of calculating a limit power range for implementing the power control method according to the invention.

[0026] The invention applies to electrical systems of electrified vehicles comprising an electric motor machine and power electronics, with fully electric or hybrid motorization, preferably motor vehicles, but not only such as aircraft, tractors, bicycles, ships. The method for controlling the power of the electrical system makes it possible to regulate the power of a high voltage network to maintain the operating voltage of a DCDC power converter within a nominal range.

[0027] In [Fig.l], a preferred embodiment of the electrical system 1 according to the invention is shown and comprises a first high-voltage DC network 13 comprising a DCDC voltage converter 4 electrically connecting the first network 13 and a second low-voltage DC network 3 and in which the first network 13 further comprises at least one high-voltage traction battery 2. By electrical network is meant a set of systems electrically connected to a voltage bus operating in a voltage range adapted to said systems.

[0028] The traction battery 2 may have a nominal voltage of between 48 volts and 1000 volts and comprises a plurality of electrochemical cells for energy storage determining the operating voltage. An electrochemical cell is an electrical energy accumulator having two terminals and having a voltage of a few volts, most often between 2.3V and 4.2V, approximately. The cells may be of the Lithium-ion type (a lithium Nickel Manganese Cobalt oxide NMC or a lithium iron phosphate LFP may be cited as examples of positive electrode active materials), Nickel Cadmium (Ni-cd), Nickel-Metal-Hydride (Ni-MH) for example. For example, the traction battery has a nominal voltage of between 300 volts and 450 volts. Alternatively, the voltage may be of the 800 volt type.

[0029] The voltage converter 4 transforms the voltage of the first network of a first electrical interface into a so-called low voltage voltage suitable for the second network 3, also called the on-board network or low voltage network, typically operating at values ​​between 12 volts and 14 volts. The voltage converter is an electrical power system comprising at least one voltage converter module. The converter 4 may comprise several voltage conversion modules to deliver several supply voltages. Ultimately, it comprises at least one conversion module.

[0030] The first network 13 is provided for the high-voltage electrical supply of the electrified vehicle. The first network 13 comprises at least one high-voltage electrical device 9, for example the nominal voltage is between 200 volts and 500 volts. The high-voltage device is for example a water heater or a compressor. The first network 13 further comprises an electrical motor machine 8 which can be connected to the direct voltage network by an inverter 10. In a variant, the first network 13 further comprises an on-board charger 14 allowing the recharging of the traction battery and the power supply of the converter 4 when the charger is electrically connected to an energy source 12 external to the vehicle through a charging interface 11. The charger 14 is not mandatory.

[0031] The second network 3 is provided for the electrical supply of the on-board network, and comprises a traction battery 5, computers as well as electrical systems of the powertrain. The second network 3 supplies at least the supervision control unit 6 of the vehicle and the computers 7 specific to the electrical systems including an electric brake system, an electric steering system or a driving assistance system, in particular. The power control method aims to guarantee sufficient power for the electrical needs of the second network 3.

[0032] The EVCU control unit 6 is provided with an integrated circuit computer and electronic memories and are configured to execute the control method according to the invention. But this is not obligatory. Indeed, the computer could be external to the EVCU control unit 6, while being coupled to the latter 6. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Consequently, the control unit, according to the invention, can be produced in the form of software modules (or computer modules (or even "software")), or electronic circuits (or "hardware"), or even a combination of electronic circuits and software modules.

[0033] Furthermore, the electrical system comprises communication means enabling the exchange of data between the vehicle's computers for the collection of data and parameters from sensors and on-board functions. The communication means are, for example, a CAN bus ("Control Area Network"). The communication means enable the control unit to collect, in particular, temperature, voltage, current and power values ​​for the supervision of the electrical system 1.

[0034] In [Fig.2], an embodiment of the method according to the invention is shown schematically. The method preferably comprises a first step of determining SI of the maximum instantaneous power PMAXt consumed by the second network during a sliding operating period of the converter. Observing the sliding operating period has the advantage of avoiding fluctuations in the consumption of the second on-board network during the power control process and makes it possible to estimate the maximum consumption of the second network. The sliding operating period lasts several seconds, for example 10 seconds, and provides for sampling of the instantaneous power values ​​Pdcdc every millisecond. The SI step is not mandatory and in this case the SI determination consists of transmitting the last maximum power value.

[0035] Furthermore, the method comprises a second step S2 of determining a first value P1Dcdc of maximum power consumed by the converter for the electrical needs of the second network. More precisely, the first value PI DcDcest is obtained by comparing the instantaneous power PMAXt and a theoretical maximum power PMAXTH deliverable by the converter for the needs of the second network. The power PMAXTH can be determined by calculation as a function of the theoretical power of the converter on the side of the electrical interface of the second network and the electrical efficiency of the converter in energy transfer mode from the first network to the second network, according to the following relationship:

[0036] PMAXTH = P12V / RDcdc, where P12V is the power on the second network side expressed in watts and RDcdc is the efficiency in energy transfer mode.

[0037] Following the comparison, the minimum value is selected, either the instantaneous power PMAXt or the theoretical maximum power PMAXTH.

[0038] This step makes it possible to reliably estimate the power consumed by the converter on the interface side of the first high-voltage network. Furthermore, the estimated value has a stability allowing effective correction of the power regulators downstream of the processing chain. Data processing means may also be provided to avoid fluctuation in the power values.

[0039] The method further comprises a third step S3 of determining a first voltage constraint value V 1Dcdc corresponding to a minimum voltage of the converter required to meet the need of the first power value PIdcdc- More precisely, this value is delivered by a predetermined converter map, recorded in the memory of the vehicle control unit, and taking as input the first power value, obtained by step S2, and an instantaneous temperature value TDCdc of the electrical system. The temperature may be the measured temperature of the DCDC converter or the temperature of the traction battery.

[0040] In [Fig.3], a map representing on the ordinate axis the minimum voltage of the DCDC converter on the side of the interface of the first high voltage network, expressed in volts, and on the abscissa the power PlocDc of the converter expressed in watts. Two curves represent the bijection of the minimum power and voltage for two distinct temperature value ranges, Templ above 20°C and Temp2 below 20°C. This mapping is recorded in the memory of the electrical system control unit.

[0041] Then, the method comprises a fourth S4 whose function is the processing of a synthesis of the constraint voltages of the first high voltage network. More precisely, step S4 determines a limit operating range in voltage LimV, delimited by a low limit and a high limit in voltage, of the first high voltage network as a function of at least the first constraint value V1DCdc corresponding to a minimum voltage of the converter required to meet the need of the first power value P1Dcdc-

[0042] Furthermore, if the first network comprises one or more additional electrical devices, it is envisaged that the control method further comprises a step S7 of determining at least a second voltage constraint value V2WH of the first high voltage network, and where the voltage operating limit range is determined as a function of at least the first value V1Dcdc and the second constraint value V2WH.

[0043] A set of voltages, presented in the form of a vector of constraint voltages, can therefore be used to determine the limit range, such as the low and high limit voltages of each high-voltage electrical device electrically connected to the voltage of the first network, water heater or compressor, in particular. All of the values ​​of the constraint voltages are classified in a vector for scheduling the limit values ​​in order of priority. For example, according to a control strategy of the electrical system, because the converter supplies the critical systems of the vehicle, the electrical needs are classified as having priority over the water heater or compressor. The limit operating range in voltage LimV is delimited for example by the minimum voltage value obtained in step S3 and by a maximum voltage value. Furthermore, margins can be assigned to these limits.

[0044] Furthermore, the voltage operating limit range LimV makes it possible, during a fifth step S5 of the method, to calculate a limit power range LimP of the first high-voltage network and of the traction battery. The power range which is obtained from the voltage limits makes it possible to control the power regulation of the first network and to ensure that the operating voltage will not drop below the minimum voltage of the DCDC voltage converter when implementing the power regulation and that it will also not exceed the maximum voltage. This step makes it possible to limit the power regulation to values ​​which have been established at regarding the voltage operating range.

[0045] In [Fig.4], a block diagram describes an embodiment of the principle for calculating the power range LimP. According to this embodiment, the method comprises a first sub-step S51 for calculating first charging current and discharge current limits, as well as power limits of the traction battery. These first current and power limits make it possible to regulate the first network and the traction battery in the voltage operating range LimV. In one embodiment, these first current limits are calculated from the parameters of the voltage operating limit range LimV, the internal resistance limit in charge and discharge of the traction battery and the no-load voltage of the traction battery according to the following relationship:

[0046] ILimc= (Uocv- LirnVmax) / Rintc, and ILimd= (Uocv - LimVmin) / Rintd,

[0047] where ILimc and ILimd are the first limits of currents at constant voltage under load and discharge respectively expressed in amperes, Uocv the no-load voltage of the battery, Rintc and Rintd are the internal limit resistances in charge and discharge respectively of the traction battery, expressed in ohms, and finally, LimVmax and LimVmin are the values ​​of the maximum voltage in charge and the minimum voltage in discharge respectively of the operating range in voltage LimV, expressed in volts.

[0048] It is then provided that the power range LimP is calculated from at least the first current limits ILimc and ILimd resulting from the synthesis of the voltage operating range. It will be noted that these first current limits can therefore be one of the limits among other current limits.

[0049] In one embodiment, it is therefore envisaged that the calculation of the power range LimP also takes into account second current limits ILimSE resulting from a protection function of the electrical system, as well as third limits ILimBAT resulting from a function specific to the protection of the traction battery. A second sub-step S52 of a current limit synthesis processing can therefore also be provided, delivering a current limit range operating the synthesis of all the first, second and third current limits. The synthesis processing consists of choosing the maximum value from among the charging and discharging limits and delivering a value IsyntLimc during charging and a value IsyntLimden during discharging.

[0050] Then, from the synthesis of the current limits, step S5 further comprises a third sub-step S53 of calculating voltage limits UmaxLim and UminLim at the traction battery level according to the following relationships: UmaXLim=Uocv+ LyntLimc*Rintc, and U minLim= Uocv + IsyntLimd*Rintd, where Uocv is the no-load voltage of the battery, Rintc and Rintd are the internal limit resistances in charge and discharge respectively of the traction battery, expressed in ohms.

[0051] Finally, the power range LimP is determined by a fourth sub-step S54 power synthesis processing, delimited by the limit PsyntLimc and PsyntLimd in charge and discharge respectively and depending on the limit values ​​of the charge power PLimbatc and discharge P, imh],tride the traction battery and a charge and discharge power at the traction battery level determined from the voltage limits UmaxLim and UminLim calculated previously.

[0052] According to this embodiment, the processing of power syntheses consists of selecting the maximum value from among the power limit values ​​according to the following relationship:

[0053]

[0054] PsyntLimc max( UmaxLim IsyntLimc 5 PLimbatc) 5 PsyntLimd — max( Umm|im:' ISyntLimd ,PLimbatd)-

[0055] Furthermore, the method comprises a sixth step S6 of regulating the power of the first high-voltage network consisting of allocating at least the charging power P Limbatc and discharging power PLimbatd of the traction battery and the charging power P <ynt| imr, cette dernière contrôlant la puissance d’alimentation du convertisseur DCDC, de sorte à respecter la plage de fonctionnement en tension LimV.

[0056] According to one embodiment, the power regulation is controlled by a PID (“Proportional Integral Derivative”) regulator. When discharging the traction battery, this regulator controls the battery discharge limit power P, imhatd and the discharge limit power PSyntLimd to respect the minimum voltage defined by the voltage range LimV. When charging, the regulation controls the battery charge limit power PLimbatc and the charge limit power PsyntLimc to respect the maximum voltage defined by the voltage range LimV. The regulator is designed to regulate each power of the electrical device supplied by the first network.

[0057] Finally, the control method compares the power consumed or delivered by the traction battery with the power range LimP and the power regulation is controlled so as to respect this power range. If the power exceeds the expected limits for at least a predetermined time delay, for example from 50 milliseconds to a few hundred milliseconds, a protection triggers the opening of contactors for cutting off the current line connecting the battery to the first network.

[0058] The method of calculating the power limit range described in [Fig.4] is given as a non-limiting example. Other variants can be envisaged by those skilled in the art depending on the electrical architecture of the high-voltage network and criteria for prioritizing electrical power constraints. The essential feature of the control method according to the invention is to take into account a limit determined from at least the minimum voltage constraint to ensure the electrical needs of the second low-voltage network.

[0059] The invention is described in the foregoing by way of example. It is understood that the A person skilled in the art is able to produce different variant embodiments of the invention by combining, for example, the different characteristics above taken alone or in combination, without departing from the scope of the invention.

Claims

Claims

1. Method for controlling the power of an electrical system (1) of an electrified vehicle comprising a first high-voltage DC network (13) comprising a DCDC voltage converter (4) electrically connecting the first network (13) and a second low-voltage DC network (3) and in which the first network (13) further comprises at least one traction battery (2), the method comprising the following steps: - determining (S2) a first value (PIdcdc) of maximum power consumed by the converter (4) for the electrical needs of the second network (3), - regulating (S6) the power of the first high-voltage network (13) consisting of allocating at least the charging and discharging power of the traction battery (2) and the supply power of the converter (4) within a limit power range (LimP),the method being characterized in that it further comprises the following steps for determining the limit power range (LimP): - determining (S3) a first constraint value (V1DCdc) in voltage corresponding to a minimum voltage of the converter (4) required to meet the need of the first power value (PI DCDC), - determining (S4) a limit operating range in voltage (LimV) of the first high voltage network (13) as a function of at least the first constraint value (V Idcdc), - calculating (S5) the limit power range (LimP) of the first high voltage network (13) from the limit voltage range (LimV).,

2. Method according to claim 1, further comprising the determination (SI) of the maximum instantaneous power (PMAXt) consumed by the second network (3) during a sliding operating period of the converter (4) for the determination (S2) of the first maximum power value (PIdcdc).

3. Method according to claim 2, in which the first maximum power value (PIdcdc) is determined by selecting the minimum value between the maximum instantaneous power (PMAXt) and a theoretical maximum power (PMAXTH) deliverable by the converter (4) for the needs of the second network (3).

4. A method according to any one of claims 1 to 3, wherein the first stress value (V 1Dcdc) in voltage is delivered by a predetermined converter map taking as input the first maximum power value (P1Dcdc) and an instantaneous temperature value of the electrical system (1).

5. A method according to any one of claims 1 to 4, further comprising determining (S7) at least one second voltage stress value (V2WH) of the first high voltage network (13) for the operation of at least one high voltage device (9) electrically connected to the first network (13), and wherein the voltage operating limit range (LimV) is determined as a function of at least the first value (V1DCdc) and the second stress value (V2WH).

6. An electrical system (1) of an electrified vehicle comprising a first high-voltage DC network (13) comprising a DCDC voltage converter (4) electrically connecting the first network (13) and a second low-voltage DC network (3) and in which the first network (13) further comprises at least one traction battery (2), the system comprising a control unit (6) configured to implement the power control method according to any one of claims 1 to 4.

7. Electrical system (1) according to claim 6 wherein the first high voltage network (13) further comprises at least one high voltage device (9) and wherein the control unit (6) is configured to implement the method according to claim 5.

8. An electrical system (1) according to claim 7 wherein the high voltage device (9) is a water heater or a compressor.

9. Electrified vehicle comprising a system (1) according to any one of claims 6 to 8.

10. A computer program comprising instructions which, when the program is executed by a control unit of an electrified vehicle electrical system, cause the latter to implement the power control method according to any one of claims 1 to 5.

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