WO2009080993A2

WO2009080993A2 - Electrical energy storage system and management method

Info

Publication number: WO2009080993A2
Application number: PCT/FR2008/052273
Authority: WO
Inventors: Antoine Grivaux
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2007-12-14
Filing date: 2008-12-11
Publication date: 2009-07-02
Also published as: CN101904075B; FR2925237A1; FR2925237B1; CN101904075A; WO2009080993A3; EP2220742A2

Abstract

The invention relates to a method of managing the storage of electrical energy in a storage system comprising a first storage device (1) and a second storage device (2) which are connected by an energy converter device (3), the second device (2) being intended to power a motor vehicle electrical circuit, the method being characterized in that it comprises the following steps: - parameters representative of a vehicle mode of operation are determined, - a target charge for the second device (2) is determined on the basis of the vehicle mode of operation, and - the energy converter is operated in such a way as to allow energy to be transferred from one of the devices to the other so as to attain and maintain the level of charge of the second storage device at the target charge level. The invention also relates to an electrical energy storage system comprising all the means needed to implement this method.

Description

MANAGEMENT METHOD AND ENERGY STORAGE SYSTEM

ELECTRIC

The present invention is in the field of electric power supply of motor vehicles.

More specifically, this invention is in the field of management of the storage of electrical energy in motor vehicles whose traction system uses at least the electrical energy.

These motor vehicles are, for example, electric type vehicles, or hybrid type vehicles.

In the field of the supply of electrical energy for this type of motor vehicle, the use of electrochemical accumulator batteries for electrically powering the traction system and other electronic devices installed in the electrical system is known. vehicle. However, this type of battery has the major disadvantage of providing poor performance in terms of power capacity, storage, longevity, and cost.

Indeed, electrochemical accumulator batteries offer low power, both in charge and discharge, and have a limited life. As a result, it is necessary to regularly change the entire battery, which represents relatively high maintenance and maintenance costs. In order to overcome these drawbacks, it has been envisaged a coupled use of different electrical energy storage systems such as an electrochemical accumulator system coupled to a supercapacitor system. It is recalled here that a supercapacitor is a capacitor made in such a way that it makes it possible to obtain an intermediate power density and energy density between the batteries and the conventional electrolytic capacitors. Thus, these supercapacitors have a greater electrical energy storage capacity than conventional capacitors, while allowing a return of this energy faster than a conventional battery.

Thus, these two types of systems have complementary features, one to provide a high power but low energy, the other to provide a low power but high energy.

Generally, the two storage systems are interconnected by simple conductors, and do not implement any method of distribution of electrical energy between the two systems. In such coupled installations, the two systems are generally connected to each other in parallel, and the balancing of voltages, imposed by the laws of electricity, leads to natural energy exchanges, at any moment, between the systems. Consequently, the distribution of the electrical energy obtained is not always optimal with respect to the mode of operation of the vehicle, and therefore the energy requirements at each moment. Indeed, it may happen that the main power system is not fully recharged, while the vehicle is in an all-electric mode of operation, during which a large amount of electrical power is needed at the same time. The global energy storage system therefore has average performance, particularly in terms of the availability of electrical energy, and therefore the response time of the system to a solicitation.

The invention aims to remedy, at least in part, these drawbacks by providing a method for managing the storage of electrical energy in at least two electrical storage devices. So more precisely, the invention aims to provide a method for effectively distributing the electrical energy between different storage devices, in particular according to the characteristics of these devices, as well as a mode of operation of the vehicle.

Thus, the invention relates to a method for managing the storage of electrical energy in a storage system comprising a first and a second storage device connected by a power converter device, the second device being intended to supply an electrical circuit of motor vehicle.

The method is characterized in that it comprises the following steps:

- parameters representative of an operating mode of the vehicle are determined, - a charging objective of the second device is determined, according to the operating mode of the vehicle, and

the energy converter is piloted so as to allow a transfer of energy from one of the devices to the other, so as to reach and maintain the state of charge of the second storage device at the level of the charging goal.

It should be noted that throughout the description, the terms "energy transfer" and "energy exchange" have the same meaning.

In an advantageous embodiment of the invention, the method further comprises the step of determining, in addition to the parameters representative of a mode of operation of the vehicle, state parameters, representing the state of the storage devices, and driving the converter by providing a control signal dependent on these parameters.

According to the embodiments, the state parameters of a storage device are included in the group comprising: the electrical charge of a device, the voltage at the terminals of this device, the operating temperature of this device, and the values circulating electric currents in the conductors connecting the devices to the electrical converter, or connecting the second device to the circuit to be powered.

The circuit to be powered, meanwhile, comprises the traction system of the vehicle and possibly, in some embodiments, any other secondary electrical circuit, in particular for the supply of various electrical and / or electronic devices, or consumers installed in the vehicle.

Depending on the vehicle operating mode, the traction system uses electrical energy, or on the contrary product. Indeed, the operating principle of a hybrid vehicle is such that, in certain driving phases, for example a high speed driving phase with few accelerations and decelerations, the traction system is powered by the engine. which produces electrical energy. In the context of the implementation of the invention in such a vehicle, the possibility is provided during the deceleration phases of recovering the electrical energy produced by the heat engine for future use. In this case, it is necessary to be able to store this produced energy, if necessary, and it is therefore useful to keep the second storage device in a very light state, in order to allow recovery and storage of energy. a large amount of energy produced.

On the other hand, when a hybrid vehicle is in a purely electric mode of operation, no electrical energy is produced by the traction system, and so there is no need to leave free storage space in the second. energy storage device.

It therefore appears that, during the energy exchanges controlled between the two storage devices, it is necessary to take into account the mode of operation of the vehicle. This consideration is made by setting a charging objective of the second device that depends on the operating mode, as previously mentioned.

The parameters representative of the operating state of the vehicle may be of different types, depending on the embodiments: it may be motor parameters, for example the engine speed, - It may be electrical parameters, such as the operating mode of the vehicle electrical system, or the forecast of future energy demands, it may be vehicle parameters, resulting from the combination of two or more elements among : motor parameters, driving constraints, and user instructions; an example of a vehicle parameter is the speed of the vehicle.

The modes of operation of the vehicle are, in one embodiment, determined according to the driving conditions, for example an urban mode and an extra-urban mode. In another embodiment, they are determined according to the characteristics of the vehicle, for example all electric or hybrid.

Furthermore, in one embodiment, the method comprises the step of determining, in addition to the parameters representative of a mode of operation of the vehicle, state parameters, representing the state of the storage devices, and of controlling the converter by providing a control signal dependent on these parameters.

The charging objective is determined so as to guarantee a margin of charge or discharge of the second storage device, compatible with the requirements of consumption or production of the electrical system of the vehicle. Indeed, the operating principle of a hybrid vehicle is such that, when the vehicle is in a rolling phase at high speed, and with small variations, typically a highway travel, the vehicle traction system produces electrical energy. During the deceleration phases, the possibility is provided of recovering the electrical energy produced by the heat engine for future use. Consequently, in such rolling situations, it is useful for the second storage device, connected to the traction system, not to be in a fully charged state, in order to be able to store the energy produced as it goes along. . Thus, to take account of these constraints, in one embodiment, the charging objective is determined as follows:

- when the vehicle operates in an urban mode, during which accelerations and decelerations are frequent, the charging objective is set at approximately half of the maximum load of the second device, when the vehicle is in purely electric operation mode, the load objective is set at 100% of the maximum load of the second device, and

- when the vehicle is operating in an extra-urban mode, where the speed is relatively high and varies little, the charging objective is set to 0.

In an advantageous implementation of the invention, in urban mode, the load objective is set at a value between 45% and 55% of the maximum load.

In an even more advantageous implementation, the charging objective is set at a value of between 49% and 51%, typically at 50% of the maximum charge of the second storage device.

However, the power converter used during the implementation of a method according to the invention has a limited maximum power, which depends on the type of converter. Thus, in some embodiments, it is possible for the second storage device to reach a load level of 0% while the load objective is not set at this value. Such a situation occurs, in particular, when the flow of electrical energy supplied to the traction system by the second storage device is greater than the rate that can provide the converter.

In the same way, it is possible for the second storage device to reach a load level of 100%, for example when the operating conditions of the vehicle are such that the electrical energy is produced too quickly or in too large a quantity.

Such a situation, of full load or total depletion, may also occur for the first storage device. In all cases, these extreme situations require an adaptation of the operation of the vehicle to prevent malfunction or breakdown.

For this purpose, in one embodiment, the method comprises the following steps: the state of charge of the first and / or second storage device is determined, if this state is a state of full charge or total depletion, or a state very close to one of these states, it transmits an information message to one or more electronic computer (s) installed (s) in the vehicle.

Thus, in a configuration, an information message is transmitted to one or more electronic computer (s) installed in the vehicle, since the charge level of one of the storage devices is greater than 95% of its maximum load, or less than 5%.

The consequences of a state of full load or total depletion are somewhat different, depending on whether it is a state of the first or second storage device.

Indeed, if the second storage device, which is directly connected to the circuit to be powered, is in one of these extreme situations, it results in the unavailability of the entire storage system, both to provide information. electrical energy than to receive it. It is therefore necessary to inform all computers and other electronic devices of the vehicle that they can no longer use or supply electrical power for a certain period. On the other hand, if it is the first device, the consequences are less troublesome for the operation of the vehicle, since this device is not used to feed directly to any body of the vehicle, but only to exchange energy with the second device, so as to optimally distribute the electrical energy between these two devices. In this case, however, it is necessary to inform the different calculators of the vehicle of this situation, in order to avoid any operation which could result in an increase in demand or production and thus lead to a situation of full load or total depletion of the second device. The invention also relates to an electrical energy storage system, intended to be installed in a motor vehicle. This system is characterized in that it comprises: a first and a second device for storing electrical energy, - a power converter connecting the storage devices, and allowing energy transfers from one to the other ,

a module for monitoring the energy exchanges, making it possible to determine a charging objective of the second storage device and to control the power converter according to this objective, via a control channel, and

information tracking channels for connecting the supervision module to the two storage devices.

In order to allow energy transfers, from the first device to the second or the second to the first, it is necessary that the power converter is reversible.

In one embodiment, the system further comprises a communication channel for connecting the supervision module to at least one computer installed on the vehicle, so as to receive information relating to the operating state of the vehicle.

In one embodiment, the first storage device has a low power and a high energy, and the second storage device has a large power and a low energy.

In one embodiment, the first storage device comprises a battery of electrochemical accumulators.

In one embodiment, the second storage device comprises a battery of supercapacitors.

Other features and advantages of the invention will become apparent with the description of some of its particular embodiments, this description being given by way of nonlimiting example using FIG. 1, which shows a system according to the invention, allowing the implementation of a method according to the invention. The system shown in Figure 1 comprises a first electrical energy storage device 1, capable of storing a large amount of electrical energy, and a second storage device 2, capable of exchanging a large electrical power. In a preferred configuration, the first storage device 1 is a battery of electrochemical accumulators, and the second storage device 2 is a battery of supercapacitors.

Between these two storage devices is installed a voltage converter 3, connected to the two storage devices 1 and 2, respectively via electrical conductors 5 and 6. This voltage converter makes it possible to perform electrical exchanges between the two devices 1 and 2, via the electrical conductors.

The second storage device 2 is connected, via conductors 4, to the electrical circuit 7 to be powered. As mentioned above, this electrical circuit comprises the traction system of an electric or hybrid vehicle and, optionally, any other secondary electrical circuit, in particular allowing the supply of various electronic devices installed in the vehicle.

The system further comprises a supervision module 8 for all the elements of the storage system. This module comprises, in particular, a processor for receiving and processing a set of data corresponding to vehicle operating parameters, or parameters relating to the state of the storage devices 1 and 2. The parameters relating to the state storage devices are measured by means of sensors located near or inside the storage devices 1 and 2; the measurements are transmitted to the supervision module 8 via information path channels 10 and 11.

The supervision module 8 controls the operation of the converter via a control channel 9. This channel makes it possible to send the converter control signals indicating whether it should allow a transfer of energy of a device. from storage to storage and, if so, in what sense and to what extent this transfer is to be made. In addition, in certain configurations, the system is provided with a communication channel 12 and a connector 13, enabling the supervision module 8 to exchange information with other elements installed in the vehicle, notably computers controlling the electronic components of the on-board circuit.

Such a communication channel is, for example, particularly useful for informing the different computers of the state of full load or the state of total depletion of one of the storage devices.

Moreover, this communication channel 12 enables the supervision module 8 to receive data representative of the state of the various electronic components of the vehicle, data which make it possible, in particular, to predict the upcoming loads in terms of the amount of electrical energy. .

The supervision module 8 thus makes it possible to implement a method for managing the storage of electrical energy comprising, in a particular embodiment, the following steps:

firstly, the supervision module 8 receives, via the channels 10 and 11, data relating to the storage devices 1 and 2, such as the electric charge, the electrical voltage or the internal temperature of these devices. , or data relating to the electrical conductors 4, 5 and 6, such as the value of the electric currents flowing in these conductors,

the supervision module 8 also receives, via the channel 12, data relating to the operating state of the electric system of the vehicle, such as the quantity of electrical energy available in the storage system, a mode of operation of the electrical system of the vehicle, or a prediction of the energy demands of the storage system, and

- As a function of all these parameters, the supervision module 8 determines at any time a charging objective of the second storage device 2, and the electrical power to be exchanged between the storage devices 1 and 2 by means of the converter 3 , in order to control the maintenance of this objective, to guarantee at all times the availability of the control system. - From this determination, the supervision module transmits a control signal towards the converter 3, via the control channel 9.

By the use of one or more of the elements previously described, it is thus possible to provide a method for managing the storage of electrical energy such that the second storage device, directly connected to the vehicle circuit, is never fully charged. Such a situation allows the second storage device 2 to accept, via the connectors 7, a quantity of energy produced by the drive train, for example during a deceleration of the vehicle. In addition, the maintenance in a non-empty state of charge makes it possible to permanently ensure the possibility, for the second device 2, of supplying electrical power to the circuit to be powered, for example during an acceleration of the vehicle during from which the traction system requires the input of a large amount of energy over a short period.

The present invention is not limited to systems having only two electrical energy storage devices. It can also be applied to any energy storage system comprising several storage devices of different types.

The invention presented here thus makes it possible to provide a method and a system enabling active management of the power distribution between different energy storage devices installed in a vehicle. Such a system allows relatively substantial energy savings compared to known storage devices of comparable cost since, due to the distribution of energy according to the operating mode of the vehicle, there is no loss of energy. energy, since all the energy produced during rolling phases is stored for later use.

In addition, by virtue of the complementary characteristics of the various storage devices, this invention makes it possible to provide a storage device capable of supplying and accepting both a large amount of power and electrical energy.

Claims

1. A method of managing the storage of electrical energy in a storage system comprising a first (1) and a second (2) storage device connected by a device (3) energy converter, the second device

(2) being intended to supply an electric circuit (7) of a motor vehicle, the method being characterized in that it comprises the following steps:

parameters representing a mode of operation of the vehicle are determined,

a load objective of the second device (2) is determined according to the operating mode of the vehicle, and the energy converter is piloted so as to allow a transfer of energy from one of the devices to the another, so as to achieve and maintain the state of charge of the second storage device at the charging objective.

The method according to claim 1, comprising the step of determining, in addition to the parameters representative of a vehicle operating mode, state parameters, representing the state of the storage devices (1, 2), and driving the converter (3) by providing a control signal dependent on these parameters.

3. The method of claim 2 wherein:

- when the vehicle operates in an urban mode, during which accelerations and decelerations are frequent, the load objective is set at approximately half of the maximum load of the second device, - when the vehicle is a hybrid vehicle in pure operation the charging objective is set at 100% of the maximum load of the first device, and

The method of claim 3, further comprising the steps of: the state of charge of the first (1) and / or second (2) storage device (s) is determined,

if this state is a state of full charge or total depletion, an information message is transmitted to all the electronic computers installed in the vehicle.

5. An electrical energy storage system, intended to be installed in a motor vehicle, characterized in that it comprises:

a first (1) and a second (2) electrical energy storage device,

a power converter (3) connecting the storage devices (1, 2) and allowing energy transfers from one to the other,

a module (8) for monitoring energy exchanges, making it possible to determine a charging objective of the second storage device and to control the power converter (3) as a function of this objective, via a channel; control (9), and

information routing channels (10, 11) for connecting the supervision module (8) to the two storage devices,

6. System according to claim 5, further comprising a communication channel (12) for connecting the supervision module (8) to at least one computer installed on the vehicle, so as to be able to receive information relating to the state. of operation of the vehicle.

7. System according to claim 5 or 6, wherein the first storage device (1) has a low power and a high energy, and the second storage device (2) has a large power and power. 'a weak energy.

8. System according to one of claims 5 to 7, wherein the first storage device (1) comprises a battery of electrochemical accumulators.

9. System according to one of claims 5 to 8, wherein the second storage device (2) comprises a battery of supercapacitors.