WO2012085459A1

WO2012085459A1 - Device and method for dc/dc conversion in the onboard network of a vehicle

Info

Publication number: WO2012085459A1
Application number: PCT/FR2011/053125
Authority: WO
Inventors: Aurélien BATTELIER
Original assignee: Valeo Systemes De Controle Moteur
Priority date: 2010-12-23
Filing date: 2011-12-21
Publication date: 2012-06-28
Also published as: CN103444064A; FR2969849B1; FR2969849A1; CN103444064B; EP2656494A1

Abstract

The invention relates to a conversion device in the onboard network of a vehicle linked on the one hand to a stop-start module (11) comprising a starter-alternator and to a set of super-capacitors (12) and on the other hand to the 14 volt onboard network of the vehicle (13) and to a battery (14). This device comprises at least two differentiated DC/DC converters (20, 21), identical from a hardware and software point of view and disposed in parallel and linked to a supervisor by a communication system, with symmetric wiring at input and output, and means for learning the imbalance in wiring impedance over a predetermined period. The invention also relates to a method for conversion implementing this device.

Description

DC / DC CONVERSION DEVICE AND METHOD IN

THE ON-BOARD NETWORK OF A VEHICLE

DESCRIPTION

TECHNICAL AREA

The invention relates to a device and a conversion method in the on-board network of a vehicle, for example an automobile.

STATE OF THE PRIOR ART

There is a set of solutions that are easy to implement and that can be quickly introduced on the market for the various stages of hybridization of vehicles. Such solutions allow a significant reduction in consumption and CO ₂ emissions.

There are two complementary "Stop-Start" (or "stop-start") solutions, starting from either a reinforced starter or an alternator-starter. The Stop-Start function stops the engine when the vehicle is stopped and then restarts it instantly and quietly. The reinforced starter makes it possible to perform the Stop-Start function with a reduction of consumption of 4 to 6% on the European cycle NEDC ("New European Driving Cycle"). Due to the non-intrusiveness of the system on the architecture of the vehicle, it can be installed in a very short time. The Stop-Start function performed from a starter-alternator offers different levels of hybridization and, consequently, gains in consumption and emission reductions. This alternator-starter allows to obtain an improved efficiency since it cuts the engine as soon as the vehicle rolls below a certain speed, the consumption being able to be reduced from 6 to 8% in European cycle NEDC and up to 25 % in busy urban traffic, where vehicles spend 35% of their time at a standstill. Installed in place of a conventional alternator, this alternator-starter requires little modification of the vehicle architecture.

There is also an embodiment comprising ultra-capacitors for recovering the kinetic energy during braking and assist the engine if necessary. Thus, as illustrated in FIG. 1, in one embodiment of the known art, a DC / DC converter 10 is connected at the input to a Stop-Start module 11 and to an energy storage module 12, based on ultra-capacitors, and output to the 14 volts onboard network 13, and a battery 14 via a switch 15. Such a solution has a power doubled by its ability to handle higher electrical voltages. During periods of slowing down of the vehicle, it acts as an electric brake on the engine and transforms the energy thus recovered into electricity which is stored in ultra-capacitors 12 adapted to frequent cycles of loading / unloading. This electricity can be restored to the 14 volts onboard network 13 via the DC / DC converter 10 or reused by 1 alternator-starter of the Stop-Start 11 module in order to restart the engine during the Stop-Start function, or help him with a strong demand for power. It makes it possible to significantly reduce the consumption of the heat engine, the gain obtained being estimated to be between 10 and 12% in the European NEDC cycle.

The DC / DC converter 10 thus manages energy exchanges between a floating network, for example a nominal voltage of 24 volts and the 14 volts vehicle network. But this DC / DC converter 10 is provided for a power of 2.4 kW. It does not meet power requirements between 2.4 kW and 4.8 kW for new types of vehicle in development.

The purpose of the invention is to propose a solution that makes it possible to meet such needs in a case where development time constraints do not make it possible to provide a new design of the DC / DC converter.

STATEMENT OF THE INVENTION

The present invention relates to a conversion device in the on-board network of a vehicle connected on the one hand to a Stop-Start module comprising an alternator-starter and to a set of supercapacities and on the other hand to the 14-volt onboard network. of the vehicle and a battery, characterized in that it comprises at least two hardware-and-software-identical DC / DC converters arranged in parallel connected to a supervisor by a communication system, with symmetrical input wiring. and out and learning ways the imbalance of wiring impedance for a specified period.

Advantageously, the device of the invention further comprises reset means.

Advantageously, the device of the invention comprises two DC / DC converters, each converter comprising a software module receiving from the supervisor via a CAN bus an on / off conversion command, a voltage setpoint, a maximum current setpoint to be output and signals measuring voltage and current, followed by a hardware module which comprises two averaging modules, followed by one of a voltage control loop and the other of a current control loop, connected to a module setpoint calculation followed by a switching power supply, and wherein the software module comprises a voltage corrector and a current corrector.

In one embodiment, the device of the invention comprises a master supervisor and two slave converters receiving from it a common voltage setpoint and communicating with each other with adaptation of the voltage setpoint entering the converter providing the least current. . Each converter can include several modules:

a module for balancing the current as a function of the temperature and for performing the learning phase, connected to:

an evaluation module of the delta value U = f (delta Ohm), to a module for evaluating the desired voltage U_target for each of the converters, which receives an initial value of U_target delivered by a calculation module, and the value delta U delivered by the evaluation module of this value and in which one uses the following algorithm:

if "Boost" DC / DC 1

(U_target_2 = U_tar_init

A D

U_target_l = U_tar_init

+ Delta_U)

else if "Boost" DC / DC 2

(U_target_l = U_tar_init

A D

U_target_2 = U_tar_init

+ Delta_U)

Advantageously, it comprises means for applying a voltage offset to the voltage setpoint of the DC / DC converter providing the least current.

Advantageously, the device of the invention comprises means for processing degraded modes, and diagnostic redundancy means.

The present invention also relates to a DC / DC conversion method in the on-board network of a vehicle implementing the device described above which comprises the following steps:

a step of reception by each converter, from a control or supervisory unit, of a common voltage setpoint, for example via a communication system and a step of communication by each converter to the other internal information converter concerning the current and the internal temperature, and

a step of modifying the voltage setpoint applied to a DC / DC converter as a function of the temperature differences.

Advantageously, the method of the invention comprises a step of applying a voltage offset to the voltage setpoint of the DC / DC converter providing the least current.

Advantageously, the method of the invention comprises the following steps:

recording in each converter of the average current difference over one operating cycle by comparing its current with that delivered by the other converter and then saving this current difference at the end of the cycle, by carrying out this measurement during each cycle of the learning and by averaging the value previously recorded at the last recorded from the second cycle,

recording of the average temperature difference between the two converters over the same number of operating cycles, by effecting a "thermal coherence" which possibly makes it possible to inhibit the correction as a result of the learning phase,

applying a voltage offset to the voltage setpoint of the converter supplying the least current, this offset being deduced from the imbalance of wiring impedance from the learning phase.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a device of the prior art.

Figures 2 and 3 illustrate the device of the invention.

Figure 4 illustrates the current distribution between two DC / DC converters arranged in parallel. Figure 5 illustrates the corresponding temperature measurements.

FIG. 6 represents a Pareto diagram proposing the ratio of lifetime to temperature differences (AT ° C) between two DC / DC converters arranged in parallel.

Figure 7 illustrates the existing wiring impedances between the two converters arranged in parallel and a load.

FIG. 8 illustrates the current voltage regulation block diagram of a DC / DC converter.

Figure 9 illustrates the principle of software control of a DC / DC converter.

Figure 10 illustrates an embodiment of the device of the invention.

FIGS. 11 and 12 respectively illustrate a control without a thermal balancing strategy and with a thermal balancing strategy according to the invention.

FIGS. 13A and 13B illustrate two examples of compensation respectively of Delta U (AU) as a function of Delta I (ΔΙ), and delta U as a function of Delta Ohm.

FIG. 14 illustrates the implementation of the compensation of FIG. 13B in a DC / DC converter, in one embodiment of the device according to the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In the device of the invention, as illustrated in FIG. 2, it is considered a power architecture providing for the paralleling of at least two DC / DC converters (for example 12V / 24V) 20 and 21. In this FIG. 2 the references already used in FIG.

Figure 3 illustrates the wiring diagram of several DC / DC converters arranged in parallel. These converters 30 are connected on the one hand to a supervisor (ECU) 31 via a CAN bus 32, for example, and on the other hand to a power supply 33 and to a load 34 via wiring modules 35. and 36.

During such a paralleling of several up / down DC / DC converters receiving the same setpoint and regulating in voltage, the current supplied by each DC / DC converter depends on the impedance of the output cables.

In the case where the voltage withstand stresses require such precision that it is not possible to limit the current in one or other of the converters without the risk of collapsing the voltage, or to deregulate without a strategy balancing internal currents to the supervisor or to each DC / DC converter, it is impossible to ensure a balance of the currents supplied by the different converters.

In the hypothesis of identical cooling for each of the DC / DC converters arranged in parallel, an imbalance in current results in a thermal imbalance between each converter. Given that the positioning of these converters, their thermal environment and their cooling mode are not known and are very unlikely to be identical, it is therefore necessary to provide a control strategy of these converters.

In the following, to simplify the description, a set of two DC / DC1 and DC / DC2 converters in parallel and means for communicating these converters with each other and with a supervisor (ECU) is considered as a nonlimiting example. using CAN bus.

The curves illustrated in FIGS.

5 show the temperature differences measured as a function of the current imbalances between the first and the second DC / DC converter (DC / DC1 and DC / DC2) cooled in an identical manner. As a function of time, each current difference of an ampere corresponds to a temperature difference of about one degree Celsius. However, the temperature difference (or delta) between these two converters, during their life cycles, strongly influences their respective lifetimes.

The Pareto diagram shown in Figure 6 assesses the lifetimes of these two converters according to their temperature differences (successively for a control card, for a power card and for the complete converter). It can be deduced from this diagram that the lifetime of the first DC / DC1 converter operating at temperatures 30 ° C higher than those of the second DC / DC2 converter is approximately five times shorter. The operating constraints of such DC / DC converters arranged in parallel must therefore include algorithms to ensure their thermal equilibrium in order to optimize and harmonize their lifetimes.

In the case of a similar cooling of the two converters, the temperature difference is logically proportional to the measured current difference or it directly depends on the difference in wiring impedance between the load and each DC / DC converter. FIG. 7 thus illustrates the wiring impedances R1, R2, and R3 between the two converters and the load.

To achieve thermal balancing of the two DC / DC converters, the invention defines a strategy for managing the distribution of the respective currents of these two DC / DC converters according to their internal temperature, knowing that the temperature of a converter is directly related to the current it provides. The objective is to achieve a temperature difference that is below a certain value, for example 10 ° C.

To do this, the invention proposes to use a current balancing strategy in performing training in the impedance imbalance of the wiring between the load and each DC / DC converter during a learning period, thus managing the current balance between each converter in order to harmonize their lifetimes.

The invention also makes it possible to envisage a reinitialization of the training of the imbalance of impedance of the wiring during the life of the converters.

In the device of the invention consider two DC / DC converters (DC / DC1 and DC / DC2) identical from a hardware and software point of view connected to a communication system, for example a CAN bus ("Controller Area Network"). ") Private or public, and commissioned by an external supervisor (ECU). A keying makes it possible to define the configuration of each converter: they therefore have two different identifiers after recognition of the keying and are differentiated on the communication network. They are controlled via two different frames.

Each DC / DC1 and DC / DC2 converter receives the following instructions:

* an ON / OF conversion order,

a U_target voltage setpoint,

* a maximum current setpoint to be debited I_max_target.

The synoptic of the hardware / software interface of a DC / DC converter 39, connected to a load 48, is illustrated in FIG. 8. A software module 40 receives the ON / OFF, U_target, instructions. I_max_target and the voltage measurement signals U_meas and I_meas current, and delivers PWM_U and PWM_I pulse width modulation signals. A hardware module 41, which receives these signals PWM_U and PWM_I, comprises two averaging modules 42 and 43, followed by one of a voltage control loop 44 and the other of a current control loop 45, connected to each other. to a setpoint calculation module 46 followed by a switching power supply 47.

FIG. 9 illustrates the principle of regulation of the software module 50 of a DC / DC converter. A software voltage corrector 51 receives a difference signal U _ta rget ^~ U _me as and delivers the signal PWM_U. A software current corrector 52 receives a difference signal I _max _target-Imeas and delivers the signal PWM_I. If voltage is regulated, ie no current limitation is applied, the signal PWM_I is equal to 100% and it is the signal PWM_U which regulates the output voltage.

In the following, we consider the case of current balancing, no current limitation being applied: I_max_target> Imeas.

In other words, in the following examples the current of a converter remains below the maximum current setpoint to be output I_max_target.

In one embodiment of the device of the invention illustrated in FIG. 10, the current / thermal balancing strategy is implemented in the two DC / DC converters. The master ECU does not handle the thermal balancing of both converters. It sends a single voltage target U target to both converters that self-balance at the end of the learning period. He does not limit them while running. The strategy of thermal balancing by learning is implemented symmetrically in each DC / DC converter. But the adaptation of the voltage setpoint as a function of the measured wiring impedance difference can be antisymmetrically in both converters in the converter that provides the least current and that one must "boost", c that is, increase the output current.

Degraded mode processing (operation at X% of the total power) and redundancy of the diagnostics are also possible by the processing of information passing between the DC / DC converters and the master ECU and between the two DC / DC converters.

FIGS. 11 and 12 make it possible to highlight the characteristics of this embodiment in view of controlling two DC / DC converters in parallel respectively without and with a thermal balancing strategy. In the absence of thermal balancing, as illustrated in FIG. 11, the currents II and 12 (Itotal = Il + 12) depend on the differences in cable length between each DC / DC1 and DC / DC2 converter and the load. An asymmetry of the wiring automatically leads to a current imbalance.

When the stress is the voltage withstand and the accuracy of the load side regulation, before any strategy application current balancing, it is necessary to determine the converter providing the least current which must "boost" the operation to ensure balancing current without clamping the other converter.

To avoid such a current imbalance, the invention proposes to perform the wiring impedance unbalance learning, as illustrated in FIG. 12. It is therefore implemented internally of each DC / DC converter a learning phase. over a predetermined number of operating cycles in order to deduce the voltage difference to be applied to the voltage setpoint of one of the DC / DC converters (or anti-symmetrically to both) according to the measurement of the difference in average current and that of the average temperature difference between the converters during these learning cycles.

In the case of two converters connected in parallel, each of the converters records, for example, the average current difference over one operating cycle by comparison between its current and that delivered by the second converter and then saves this current difference I at the end of the cycle. This measurement is made during each cycle of learning and the previously recorded value is averaged over the last recorded from the second cycle.

The same is done for the average temperature difference between the two converters on the same number of operating cycles, a "thermal coherence" is carried out which eventually allows to inhibit the correction as a result of the learning phase.

Finally, a voltage offset is applied to the voltage setpoint of the converter providing the least current. This offset is deduced from the impedance imbalance of wiring taken from the learning phase.

In order to reduce the delta I, a compensation offset on the voltage setpoint is applied, as illustrated in FIGS. 13A and 13B, and is proportional (gain G) to the difference in impedance or depends on a table of dots. support defined after characterization of the paralleling of the converters: Delta U compensation = f (Delta Ω).

FIG. 13A shows an example in which the Delta U voltage compensation offset is proportional to the delta current difference I. FIG. 13B shows an example of a "lookup table" consisting of a mapping which, at a difference in impedance delta Ω, associates a compensation offset Delta U to be applied to the converter.

The learning phase is carried out in each converter which, as illustrated in FIG. 14, comprises several modules, namely:

a module 61 for balancing the current as a function of temperature and for performing the learning phase, connected to:

to a delta evaluation module U = f (delta Ohm), a module 63 for evaluating the desired voltage (U target) for each of the converters, which receives an initial value of U target delivered by a module 64 and a value Delta U delivered by the module 62, and in which one uses the following algorithm:

if "Boost" DC / DC 1

(U_target_2 = U_tar_init

A D

U_target_l = U_tar_init

+ Delta_U)

else if "Boost" DC / DC 2

(U_target_l = U_tar_init

A D

U_target_2 = U_tar_init

+ Delta_U)

In other words, when the temperature T ° C 1 of the DC / DC converter 1 is lower than that T ° C 2 of the DC / DC converter 2, the offset offset delta U is added to the voltage setpoint U_target_l of the DC converter / DC 1. When the temperature T ° C 2 of the DC / DC converter 2 is lower than that T ° C 1 of the DC / DC converter 1, the offset offset delta U is added to the voltage set point U_target_2 of the DC converter / DC 2.

We "boost", indeed the converter

DC / DC1 or DC / DC2 coldest.

If the wiring configuration is known in advance, the delta U can be saturated by a maximum value that can be calibrated after tests that make it possible to prevent such a phenomenon from occurring. One can also possibly provide a predefined delta U value to be applied at the end of the learning phase. Thus, after the learning phase, this delta value U is applied to the setpoint of one or the other of the DC / DC converters according to their wiring configuration.

We can provide a reinitialization of learning during the life of the module: after X wake cycles for example, in anticipation of a rise / disassemble of the converters and / or their inversion in the wiring circuit along of their life .

Claims

1. Device for conversion in the on-board network of a vehicle connected on the one hand to a Stop-Start module (11) comprising an alternator-starter and to a set of supercapacities (12) and on the other hand to the network of edge 14 volts of the vehicle (13) and a battery (14), characterized in that it comprises at least two DC / DC converters (20, 21) differentiated, identical from a hardware and software point of view arranged in parallel connected to a supervisor by a communication system with balanced input and output wirings and means for learning the wiring impedance imbalance for a determined period of time.

2. Device according to claim 1, which comprises reset means.

3. Device according to claim 1, which comprises two DC / DC converters, each converter (30) comprising a software module (40) receiving from the supervisor (31) via a CAN bus an on / off conversion command, a voltage setpoint a maximum current setpoint to be output and voltage and current measurement signals, followed by a hardware module (41) which comprises two averaging modules (42 and 43), followed by one of a control loop voltage (44) and the other of a current control loop (45), connected to a setpoint calculation module (46) followed by a switching power supply (47), and wherein the software module (50) comprises a voltage corrector and a current corrector (52).

4. Device according to claim 2, comprising a master supervisor and two slave converters receiving from it a common voltage setpoint, and communicating with each other with adaptation of the voltage setpoint entering the converter providing the least current.

5. Device according to claim 1, wherein each converter comprises several modules:

a module (61) for balancing the current as a function of the temperature and for performing the learning phase, connected to:

a module (62) for evaluating the delta value U = f (delta Ohm),

to a module (63) for evaluating the desired voltage (U_target) for each of the converters, which receives an initial value of U_target delivered by a calculation module (64) and the delta value U delivered by the module (64) evaluation of this value, and in which the following algorithm is used:

if "Boost" DC / DC 1

(U_target_2 = U_tar_init

A D

U_target_l = U_tar_init

+ Delta_U)

else if "Boost" DC / DC 2 (U_target_l = U_tar_init

A D

U_target_2 = U_tar_init

+ delta_U).

6. Device according to claim 5, which comprises means for applying a voltage offset to the voltage setpoint of the DC / DC converter providing the least current.

7. Device according to claim 3, which comprises means for processing degraded modes.

8. Device according to claim 3, which comprises diagnostic redundancy means.

9. A DC / DC conversion method in the on-board network of a vehicle implementing the device according to claim 2, which comprises the following steps:

a step of receiving in each converter, from the supervisor, a common voltage setpoint,

a step of communication by each converter to the other internal information converter concerning the current and the internal temperature, and

10. The method of claim 9, comprising a step of applying a voltage offset to the voltage setpoint of the DC / DC converter providing the least current.

The method of claim 10, comprising the steps of:

recording of the average temperature difference between the two converters over the same number of operating cycles, by effecting a thermal coherence which possibly makes it possible to inhibit the correction as a result of the learning phase,

applying a voltage offset to the voltage setpoint of the converter providing the least current, this offset being deduced from the wiring impedance imbalance derived from the learning phase.