EP3445962A1

EP3445962A1 - Method for determining an energy state of an electrical power supply system

Info

Publication number: EP3445962A1
Application number: EP17717776.3A
Authority: EP
Inventors: Yannick BOTCHON; Vincent ROUDOT
Original assignee: PSA Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2016-04-19
Filing date: 2017-03-15
Publication date: 2019-02-27
Also published as: CN109072797B; FR3050160A1; WO2017182722A1; FR3050160B1; CN109072797A

Abstract

Method for determining an energy state of an electrical power supply system linked to a heat engine (4), to electrical consumers (3) and comprising an electric machine (2) and electrical energy storage (1), in which the current level of charge of the storage (1) is determined, characterized in that it comprises the steps of: - determining the current electrical power generation capacity of the electric machine (2); - determining whether the electrical power supply system is in a current energy state referred to as the nominal state if the current level of charge of the storage (1) is higher than a determined level of charge for which the storage (1) is deemed to have sufficient reserves and the current electrical power generation capacity of the electric machine (2) is lower than a determined threshold for which the electric machine (2) is able to provide the supply of electrical power by itself.

Description

METHOD FOR DETERMINING AN ENERGY STATE OF AN ELECTRIC POWER SUPPLY SYSTEM

The present invention relates to the automotive field, in particular to the management of the production of electrical energy and the management of the speed of the engine of the vehicle.

The engine speed of a vehicle influences its emissions and consumption, but also its ability to produce the electrical energy necessary for the operation of different electrical consumers.

Reduce and intelligently control the vehicle's engine speed, reduce its polluting emissions, as well as its fuel consumption, which is a major challenge in the automotive sector. However, reducing the engine speed, to reduce emissions and consumption, also reduces the amount of electrical energy that can be generated by the vehicle, which can be problematic in case of high demand of the electrical consumers activated on the vehicle. vehicle. Document EP213871 1 discloses a system for stopping and automatically restarting the engine of a vehicle taking into account the state of charge of the battery to decide to stop or restart the engine of the vehicle. However, the only consideration of the state of charge of the battery is not enough to know if the vehicle is able to provide enough electrical power, to meet the needs of different electrical consumers activated.

The objective of this invention is thus to predict at any moment, if the vehicle will be able to supply enough electrical energy, to meet the needs of the various activated electrical consumers, in the case where the engine speed of the vehicle would come in particular to to be reduced.

To achieve this objective, the invention provides a method for determining an energy state of an electrical energy supply system connected to a heat engine and to electrical consumers, this system comprising:

an electric machine that can take mechanical energy from the heat engine to produce electrical energy,

a storer of electrical energy, the method comprising a step of determining the current load level of the storer, and furthermore the steps of:

-determination of the current electrical power generation capacity of the electric machine, representing the current fraction of electric power generation of the electric machine relative to its maximum capacity,

determining that the electrical energy supply system is in a so-called nominal current energy state guaranteeing a nominal supply of electrical energy to the activated electrical consumers if the current load level of the storer is greater than a determined load level for which it is it is judged that the storer has sufficient reserve to overcome an increase in the load on the electrical consumers and that the current electrical power generation capacity of the electrical machine is below a determined threshold for which the electrical machine can provide the nominal supply of electrical energy to activated electrical consumers.

Various additional features may be provided, alone or in combinations:

In a variant, the method further comprises the steps of:

-determination of a target engine speed,

-determination of the maximum electric energy that the electric machine can produce at the target engine speed,

-decision that the system is in a predicted operating state said nominal for the target engine speed guaranteeing a nominal supply of electrical energy to the activated electrical consumers if the electrical energy consumed by the activated consumers is less than the maximum determined electrical energy - Deciding that the system is in a state of electrical shortage, which is critical if the system is not in a nominal current operating state and / or not in a nominal predicted operating state.

The invention also relates to a method for controlling a vehicle comprising an electric power supply system connected to a heat engine and to electrical consumers, comprising the preceding method, and wherein if it is decided that the system is not in a state of critical electrical shortage, it allows the control of the engine at the target engine speed determined. In a variant, it is possible to control the heat engine at the determined target engine speed if the decision that the system is not in a state of so-called critical electrical shortage is continuous during a predetermined confirmation time window. Advantageously, the duration of the confirmation time window is between 1 and 10 seconds.

In a variant, in which the vehicle can move in a freewheel mode, the target engine speed is an idle engine speed associated with the displacement of the vehicle in freewheel mode.

In another variant, in which while the vehicle is in freewheel mode, the current capacity of electric power production of the electric machine is scanned,

the idle engine speed associated with the displacement of the vehicle in freewheel mode is increased by a determined value, if the maximum power generation capacity of the electric machine at the idle engine speed is reached.

Advantageously, the idle speed increase value associated with the displacement of the vehicle in freewheel mode is between 100 and 150 revolutions per minute.

The invention also relates to an electronic computer, characterized in that it comprises the acquisition means, software instructions processing stored in a memory and control means required for the implementation of a method of the invention.

The invention also relates to a vehicle comprising a system for supplying electrical energy connected to a heat engine and to electrical consumers, this system comprising:

an electric machine that can take mechanical energy from the engine to produce electrical energy,

a storer of electrical energy,

the vehicle further comprising an electronic computer according to the preceding claim. Other features and advantages will appear on reading the following description of a particular embodiment, not limiting of the invention, with reference to the figures in which: - Figure 1 is a schematic representation of a electrical architecture of a vehicle equipped with a heat engine for which the invention can be implemented.

- Figure 2 is a schematic representation of a predictor of shortage of electrical energy of the invention.

FIG. 3 is a diagrammatic representation of an adaptation of the electrical energy shortage predictor of the invention to free wheel running of a vehicle.

FIG. 1 shows an electrical vehicle architecture comprising an electrical energy storage unit 1, for example a battery, for example an electrochemical battery, an electric machine such as an alternator 2, an edge network 3 of the vehicle assembling the parts of the vehicle that consume electrical energy, these consumers of electrical energy can each be activated or deactivated as needed. The storer of electrical energy 1 is electrically connected to the electrical machine and to the on-board network and has a mass M. The edge network 3 is electrically connected to the electric machine 2 and to an electrical ground M.

The electric machine 2 is mechanically connected to a heat engine 4 so that it can take mechanical energy from the heat engine 4 to produce electrical energy. The assembly consisting of the electric machine 2 and the electrical energy storage unit 1 forms the electrical energy supply system of the vehicle edge network 4. Thus, the electrical energy supply system makes it possible to supply the electrical consumers, either from electrical energy previously stored in the electrical energy store 1, or by converting the mechanical energy produced by the heat engine 4 into electrical energy by means of the electric machine 2.

This invention can be broken down mainly into three modules described in Figure 2:

A first module 20 has the function of calculating the current energy state, that is to say at the present time of the operation of the vehicle. The electrical power supply system is considered to be in a "Nominal" state when both of the following conditions are met:

the electrical energy stored in the storer 1 is greater than a previously defined threshold. For example, the predetermined threshold may be a load level of the storer 1 greater than 80%.

the electrical energy supply system is capable of guaranteeing the supply of electrical energy to the various activated electrical consumers solely by converting mechanical energy into electrical energy.

In the opposite case, it is considered that the electrical energy supply system is in a "degraded" state, ie when: the stored electrical energy is below the previously defined threshold or when it is is not able to guarantee the supply of electrical energy to the various activated consumers, solely by converting mechanical energy into electrical energy.

This first module 20 uses as input:

-A representative information 20a of the current load level of the storer 1 of electrical energy of the vehicle. This information can be a state of charge of the storer 1, commonly designated SOC (acronym for the English expression State Of Charge). -A 20b information representative of the current power generation capacity of the electric machine 2 and its saturation. The current capacity represents the current fraction of electric power generation of the electric machine 2 relative to its maximum capacity. In the case where the electric machine 2 is an alternator, this information can be a Cyclic Ratio of Opening (RCO) of the excitation circuit of this alternator. This information makes it possible to determine the current generating capacity of the alternator as well as its saturation (for example a 70% RCO indicates that the generator's current electrical energy production capacity is at 70% of its maximum, that he therefore still has a reserve of 30% before saturation at 100%). This first module 20 decides and outputs an information 20c representative of the current energy state of the electrical energy supply system, for example in the form of a boolean, to translate the state either "Nominal" or "Degraded". In the case where the information 20a representative of the current load level of the storage device 1 of the electrical energy of the vehicle is a state of charge, SOC, of the vehicle battery and that the information 20b representative of the current production capacity d electrical energy of the electrical machine 2 and its saturation is a cyclic opening ratio, RCO, this module 20 therefore constantly checks that:

the current state of charge of the storer 1 is greater than a state of charge level previously defined, SOCJim. This threshold, SOCJim, state of charge, for example 80%, is a threshold for which it is judged that the battery has sufficient reserve power to overcome an unexpected increase in the demand of electrical consumers (new consumers switched on for example).

the electric machine 2 of the vehicle is capable of guaranteeing only the supply of electrical energy to the various consumers, solely by conversion of mechanical energy into electrical energy. This is verified if the current duty cycle, RCO, is less than a threshold value, RCO_alt_lim, for which the electric machine 2 can alone provide the nominal supply of electrical energy to the activated electrical consumers, that is to say without the recourse to the energy stored in the storer 1. This threshold value may be the saturation threshold of 100% or better, which takes a safety margin and therefore in this case may be 80%.

If these two conditions are fulfilled, then the electrical energy supply system of the vehicle will be considered to be in a current energetic state called "Nominal" (as already defined above), otherwise it will be said in a current state "Degraded".

A second module 21 has the function of calculating the energy state of the electrical energy supply system, for a target engine speed, that is to say for which one would like to operate the vehicle engine, in the optical reduction of CO2 emissions and / or reduction of fuel consumption. This module aims to predict whether, at this target engine speed, the electric power supply system will still be able to supply electrical consumers powered solely by conversion of mechanical energy into electrical energy supplied by the electric machine, without recourse to the energy stored in the electrical storage unit.

The purpose of this second module 21 is to determine whether the electrical energy supply system of the vehicle will be able to satisfy its various electrical energy needs, in the event of a transition to a life stage characterized by a decrease in the maximum energy potential. mechanical, available to be converted into electrical energy. This phase of life results in a decrease in the engine speed of the vehicle, which implies a reduction in the maximum mechanical energy that can be taken by the electric machine 2, an alternator for example.

This second module 21 calculates at each instant, the current electrical energy needed to power the various electrical consumers activated on the vehicle, at the time of calculation.

This second module 21 also predicts the maximum electrical energy that can be provided by the electrical energy supply system of the vehicle, for a given target engine speed, lower than the current engine speed of the vehicle. These two values of electrical energy are compared, to decide on the possibility for the vehicle's electrical energy supply system, to always guarantee the supply of electrical energy to the consumers, solely by conversion of available mechanical energy into electrical energy. in the event of a decrease in the engine speed of the vehicle, to the desired target engine speed.

This second module 21 uses as input:

a representative information 21a of the target engine speed for which we want to predict the maximum electrical energy that can be produced.

an information representative of the current electrical energy needed to power the various electrical consumers activated on the vehicle. This information can be obtained from an output voltage information 21 b of the electrical machine 2 and an information 21 c of current intensity provided by the electric machine 2. This second module 21 decides and outputs an information 21 d representative of the prediction of the energy state of the electric power supply system for the future target engine speed at which it is desired to operate the engine of the vehicle. The predicted energy state will be called "Nominal", when the maximum electrical energy that can be provided by the vehicle's electrical energy supply system at the desired target engine speed will be greater than the electrical energy required, to supply the various consumers. activated at the time of calculation. The predicted energy state will be said to be "Degraded" when the maximum electrical energy that can be supplied by the vehicle's electrical energy supply system at the desired engine speed will be less than the electrical energy required to power the various activated electrical consumers. at the time of calculation. This information 21c may be for example in the form of a boolean, to translate the state either "Nominal" or "Degraded".

In the case where the information representative of the current electrical energy required to supply the different electrical consumers activated on the vehicle is obtained from an information 21 b of output voltage of the electric machine 2 and information 21 c current intensity provided by the electric machine 2, this second module determines:

-the current electrical power consumed by the various activated electrical consumers, Pelec_conso:

Pelec_conso = | u_Prod ^* i_Prod | ^* factor_correction_P_conso

With:

u_Prod: the output voltage of the electric machine 2,

i_Prod: The current intensity supplied by the electric machine 2,

factor_correction_P_conso: an adjustment factor taking into account the uncertainties on u_Prod and i_Prod. This factor can be a constant chosen to compensate for the maximum uncertainty or to be calibrated and determined by mapping. the maximum electrical power that can be supplied by the electric power supply system by the electric machine 2 to the target engine speed to which the engine of the vehicle is to be changed, Pelec_Max_dispo: Pelec_Max_dispo = | Rend_Alt_Max_rate_rate ^* Torque_Alt_Max_rate ^* 2ττ / 60 ^* Alt_Delivery_Ratio ^* Target_Not | ^* factor_correction_P_max

With:

Target_mot: the target engine speed at which the vehicle is to be driven, ie the information 21a,

Rend_Alt_bit_Max: the efficiency of the electric machine 2, associated with the maximum current that it can provide at the given target regime, N_mot_cible,

Torque_Alt_Fax_Max: the torque taken by the electric machine 2, associated with the maximum current that it can supply at the given target speed, N_mot_cible,

Report_Demul_Alt: the gear ratio for calculating the speed of the electric machine 2 according to the given target speed, N_mot_cible,

factor_correction_P_max: a factor of adjustment of the computation taking into account the uncertainties of the aforementioned parameters. This factor can be a constant chosen to compensate for the maximum uncertainty or to be calibrated and determined by mapping.

For this step, it is possible to provide the use of operating mappings of the electric machine 2 in which the current intensity, the torque and its efficiency are given as a function of the engine speed. These two values of electrical power are then compared, and the predicted energy state of the electrical energy supply system, for the target regime considered, will be called "Nominal" if:

Pelec_conso <Pelec_Max_dispo

In the opposite case, the predicted energy state of the electrical energy supply system, for the target regime considered, will be called "Gradient".

In the case where we would like to control the engine speed of the vehicle, in particular to reduce it, in particular to reduce the consumption and the C02 emissions of the vehicle, it is necessary to anticipate the impacts of this reduction in speed, on the capacity of the vehicle. of the vehicle's electrical energy production system, to always produce enough electrical power for the power supply of the various electrical consumers activated.

A third module 22 therefore has the function of determining if a risk of electrical shortage of the electrical power supply system is possible. This third module 22 uses for this input the information 20c and 21d respectively provided by the first and the second module 20 and 21.

This third module 22 decides and outputs:

an information 22a representative of the occurrence of a shortage of electrical energy of the electrical energy supply system of the vehicle. This information is the image of its ability to guarantee the supply of electrical energy to electrical consumers, both at the current engine speed of the vehicle, and at a future target engine speed, at which one wants to operate the vehicle.

The occurrence of a shortage of electrical energy will be said to be "Critical", if the electrical energy supply system of the vehicle can not meet the needs of the activated electrical consumers, for the current engine speed and / or for the target engine speed. , to which we want to evolve the vehicle, that is to say if the electrical power supply system is in a current operating state called "Degraded" AND / OR in a predicted operating state said "Degraded".

In the opposite case, if the electrical energy supply system is in a current operating state called "Nominal" AND in a predicted operating state called "Nominal", ie if the energy supply system electric vehicle is able to meet the needs of activated electric consumers, both for the current engine speed, for the target engine speed, which we want to change the vehicle, the occurrence of a shortage of electrical energy will be said " Not critical.

This information 22a may be for example in the form of a boolean, to translate the state is "Critical" or "Not Critical".

This information 22a determined in real time can then be used to make engine speed control decisions, as part of a strategy for reducing CO2 emissions and reducing the fuel consumption of the vehicle. For example, during a coasting phase the clutch of the vehicle is open, which allows to decouple the engine of the wheels, and it is desired to keep the engine at an idle speed, for example around 800 at 900 rpm for a motor vehicle. This has the effect of making it possible to take better advantage of the kinetic energy of the vehicle and to reduce its fuel consumption. Indeed, during this phase, the vehicle consumes little fuel because the engine is idling and it advances with the kinetic energy accumulated until then. This is favored by the decoupling engine / wheels, which decreases the motor resistances that oppose the movement of the vehicle.

Driving such a regime, however, involves a decrease in the capacity of the electric machine 2 to produce electrical energy, which can be problematic if electric consumers consuming more energy than can provide the vehicle at this engine speed, are activated, including consumers related to vehicle safety. In addition, a decrease in the production of electrical energy can lead to a decrease in the level of charge of the battery, which will have an impact on the availability of functions such as shutdown and automatic restart of the engine.

For this purpose, Figure 3 presents a complement to the modules presented in Figure 2. This complement presents two additional modules.

A fourth module 30 has the function of determining the authorization for the vehicle to coast, which ensures that at constant power consumption before and during the coasting phase, the activated electrical consumers will always be correctly powered.

This fourth module 30 uses as input:

-Information 22a representative of the occurrence of a shortage of electrical energy of the electrical energy supply system of the vehicle.

This fourth module 30 decides and outputs:

an information 30a, for example in the form of a boolean, to translate the authorization or not to the vehicle to coast. This authorization is thus based on the information 22a representative of the occurrence of a shortage of electrical energy of the electrical energy supply system of the vehicle, calculated for the engine speed associated with coasting. This target mode is usually a motor idle speed.

Thus for the target engine speed associated with running the vehicle coasting, the information 22a representative of the occurrence of a shortage of electrical energy of the electrical energy supply system of the vehicle is calculated and can take one or the other states already explained: "Critical" or "Not Critical".

Then, the third module 30 verifies that the information 22a is continuously in a "Not Critical" state during a confirmation time window. The duration of this confirmation window is advantageously between 1 and 10 seconds. The minimum duration is chosen so as to filter a transient "not critical" state, so as to ensure that at the current state, that is to say at the engine speed at the time of calculation, the vehicle is well able to provide enough electrical power to activated consumers. The maximum duration of the confirmation time window is chosen to be greater than the durations of the respective transient phases of the parameters used by the method.

If the information 22a remains in the "Not critical" state during the entire duration of the confirmation time window, then the third module 30 gives, via the information 30a, the authorization to the vehicle to be able to enter a phase of coasting at the associated target engine speed. This authorization remains valid as long as the information 22a remains in the "Not critical" state. If the information 22a goes to the "Critical" state before the end of the duration of the confirmation time window, then the third module 30 does not give, via the information 30a, the authorization to the vehicle to be able to enter a coasting phase.

In the case of life where the authorization has been granted, the engine is decoupled from the wheels, via the gearbox, thus reducing the friction resistance on the wheels linked to the engine. This reduces the fuel consumption and polluting emissions of the vehicle. When the vehicle is coasting, the engine speed is also reduced to the target engine speed associated with this phase of life (idle speed). The end of this phase of life is only signified by the will of the driver, for example, the will to accelerate or slow down.

This means that once the authorization to the vehicle to roll free is given and the vehicle is actually in freewheeling, it is not possible to directly end this phase of life.

The problem that may then arise is that of a change in the consumption of electrical energy of the consumers after the authorization of freewheeling. For example, new electrical consumers can be activated by the driver, after the freewheeling authorization, thus risking to impact the overall energy balance (constant production / higher electrical demand).

A fifth module 31 has the function of determining, when the vehicle is in coasting mode if it is necessary to provide an increase in the engine speed associated with this mode of driving.

This fifth module 31 uses as input:

-Information 20b representative of the current power generation capacity of the electric machine 2 and its saturation. In the case where the electric machine 2 is an alternator, this information can be a Cyclic Ratio of Opening (RCO) of the excitation circuit of this alternator. This fifth module 31 decides and outputs:

- A 31a information, representative of a need or not to increase the speed of the engine, associated with the running mode of the vehicle coasting.

In the case where the information 20b representative of the current electrical power generation capacity of the electrical machine 2 and its saturation is an opening duty ratio, RCO, this module 31 examines whether the electric machine 2 becomes saturated, that is, the RCO = 100%, for the engine speed (idle speed) at which the engine 4 operates during coasting. In the event of detection of a saturation of the electric machine 2 during the freewheeling phase, due to an increase in the electrical energy demand of the consumers (new activated electrical consumers for example), this means that the vehicle is no longer able to provide enough electrical energy to the various electrical consumers activated. The fifth module 31 transmits, via the information 31 has a value of increase of the idling speed of the engine 4, so as to increase the production of electrical energy of the electric machine 2, while remaining in the driving phase. freewheel. This increase value of the idle speed of the engine 4 associated with the displacement of the vehicle in freewheel mode is preferably between 100 and 150 rpm, which limits the feeling by the driver.

All the modules of the invention may be housed in an electronic computer comprising the acquisition means, software instructions processing stored in a memory and control means required for the implementation of the invention.

This invention makes it possible to predict, depending on the engine speed, whether the electrical energy production of the vehicle, will ensure the power supply of all activated electrical consumers, when the vehicle will reduce its engine speed. It is based on a current energy state of the vehicle, which depends on its ability to provide the electrical energy required by consumers at each moment on the one hand and on a prediction of the evolution of this energy state, for a new target engine speed, to reach the other.

This invention makes it possible to determine, if the vehicle is exposed to a state of shortage of electrical energy, in the case where a reduction of its engine speed is desirable, for reasons of reduction of CO ₂ emissions for example.

It therefore allows to intelligently control the engine speed of the vehicle, so as to reduce its consumption and its emissions, safely from a point of view of the supply of electrical energy.

Claims

claims

A method for determining an energy state of an electric power supply system connected to a heat engine (4) and to electrical consumers (3), which system comprises:

an electric machine (2) able to take mechanical energy from the heat engine (4) to produce electrical energy,

a storer of electrical energy (1),

the method comprising a step of determining the current load level (20a) of the storer (1),

characterized in that it further comprises the steps of:

-determination of the current electrical power generation capacity of the electric machine (2), representing the current fraction of electric power generation of the electric machine (2) relative to its maximum capacity,

-determining (20) that the electrical power supply system is in a so-called nominal current state guaranteeing a nominal supply of electrical energy to the activated electrical consumers if the current load level (20a) of the storage unit (1) is greater than at a specified load level for which it is judged that the storer

(1) has sufficient reserve to overcome an increase in the load on electrical consumers and the current electrical power generation capacity of the electric machine (2) is below a certain threshold for which the electric machine (2) can alone provide the nominal supply of electrical energy to the activated electrical consumers.

2. Method according to claim 1, characterized in that it further comprises the steps of:

-determination of a target engine speed (21 a),

-determination of the maximum electrical energy (21b, 21c) as the electric machine

(2) can produce at the target engine speed (21 a),

-decision (21) that the system is in a so-called nominal operating state for the target engine speed ensuring a nominal supply of electrical energy to the activated electrical consumers if the electrical energy consumed by the activated consumers is less than the energy maximum electrical determined,

-decision (22) that the system is in a state of critical power shortage if the system is not in a nominal current operating state and / or not in a nominal predicted operating state.

3. A method of controlling a vehicle comprising an electrical energy supply system connected to a heat engine (4) and to electrical consumers (3), characterized in that it comprises a method according to claim 2, and in which if it is decided that the system is not in a state of critical electrical shortage, it allows (30) the control of the engine (4) at the target engine speed (21 a) determined.

4. Method according to the preceding claim, characterized in that authorizes the control of the engine (4) at target engine speed (21 a) determined if the decision that the system is not in a state of electrical shortage said critical is continuous during a predetermined confirmation time window.

5. Method according to claim 4, characterized in that the duration of the confirmation time window is between 1 and 10 seconds.

6. Method according to one of claims 3 to 5, characterized in that the vehicle can move in a freewheel mode, the target engine speed is a slow engine speed associated with the displacement of the vehicle in freewheel mode.

7. Method according to claim 6, characterized in that while the vehicle is in freewheel mode,

the current electrical power generation capacity of the electric machine (2) is scrutinized,

the idle engine speed associated with the displacement of the vehicle in freewheel mode is increased by a determined value, if the maximum power generation capacity of the electric machine (2) at the idle engine speed is reached.

8. A method according to claim 7, characterized in that the value of increase of the engine idle speed associated with the displacement of the vehicle in freewheel mode is between 100 and 150 revolutions per minute.

9. Electronic computer, characterized in that it comprises the acquisition means, processing by software instructions stored in a memory and control means required for the implementation of a method according to one of the preceding claims.

10. Vehicle comprising an electrical energy supply system connected to a heat engine (4) and to electric consumers (3), this system comprising:

an electric machine (2) able to take mechanical energy from the engine to produce electrical energy, a storer (1) of electrical energy,

the vehicle further comprising an electronic computer according to the preceding claim.