FR3068789A1 - DEVICE FOR PROTECTING AGAINST A SHORT CIRCUIT IN AN ELECTRICITY NETWORK OF A SYSTEM DURING RAPID RECHARGING OF A BATTERY - Google Patents

Abstract

A protection device (DP) equips a system (S) comprising a battery (BR) rechargeable and connected, via first switching means (MC1) can be placed in first and second states in which respectively they allow and prevent the circulation current to an electrical network (RE) to which is connected a charging connector (CR) coupled to a station (SR) fast charging DC. This protection device (DP) comprises control means (MCT) which, during a fast charging of the battery (BR) when a charging current entering the battery (BR) is followed by a discharge current leaving the battery (BR) and representative of a short-circuit in the electrical network (RE), trigger the placement of the first switching means (MC1) in their second state and the transmission of a message requiring immediate stoppage fast charging to the station (SR).

Description

PROTECTION AGAINST A SHORT-CIRCUIT IN A

ELECTRICAL NETWORK OF A SYSTEM DURING A RECHARGE

QUICK BATTERY

The invention relates to systems which include an electrical network to which are connected a charging connector, suitable for being coupled to a rapid DC charging station, and at least one rechargeable battery, possibly with cell group (s). ) electric energy storage.

Certain systems include at least one rechargeable battery supplying an electrical network and which can be subject to rapid DC charging when this electrical network is coupled to a rapid DC charging station. This is for example the case of certain vehicles, of the all-electric or hybrid type and possibly of the automobile type.

It is recalled that during rapid recharging, the charging station, external to the system, is directly connected to the on-board electrical network (for example at high direct voltage (or HV DC ("high voltage direct current") according to English terminology) in order to recharge the battery and possibly to operate at least one on-board electrical equipment The charging station adapts the electrical charging power as a function of the instructions it receives from the system, and more particularly from the battery control means.

When the electrical network is subject to a short circuit, for example due to aggression (shocks, friction, corrosion) undergone by the insulation of a live conductor or the presence of a conductive part detached or forgotten in a casing of an equipment (such as for example a metal screw), a high current is called by the low value electrical resistance represented by this short circuit, which locally induces a strong heat (or hot spot). There is a risk of fire if this hot spot spreads. This risk is increased during a rapid recharge, generally called "mode 4 recharge" in the standards. Indeed, the electrical balance is then strongly unbalanced between the electric power which is supplied by the charging station and the current which is consumed by the battery, because the majority of the short-circuit current is supplied by the battery, and not by the charging station, when its electrochemistry has a capacity to provide much more instantaneous power than this charging station. The means of protection of the charging station not knowing how to distinguish a short-circuit current from a charging current of the battery, the charging station does not necessarily react or not quickly enough to avoid the hot spot.

In order to protect the electrical network in the presence of a short circuit, several solutions have been proposed.

A first solution, called preventive, consists in providing physical protections, such as, for example, reinforced insulation of the electrical conductors or an implantation of the components of the electrical network in zones little exposed to shocks.

This first solution proves to be expensive (both in hardware adaptation and in architectural adaptation) and may be impossible to implement in certain systems of small dimensions and / or with a high rate of congestion.

A second solution, called curative, consists of installing fuses in the electrical network or implementing electrical diagnostics which detect short circuits and cut the power supply to electrical equipment connected to the electrical network.

Protection by means of fuses has several disadvantages. Indeed, these fuses are bulky (and therefore bulky) and expensive, and must be accessible in order to be replaced. In addition, these fuses require a short-circuit current (or "fault current") to melt, which is significant in relation to their rating. However, in the case of an impedant short circuit or one having a high resistance, the fault current (or short circuit) may be insufficiently high to blow a fuse or be detected by the charging station, but sufficient to create a dangerous hot spot.

It has also been proposed in patent document FR 2831272 to measure in a two-voltage electrical network of a vehicle three currents (11, I2, I3) passing through three branches of this electrical network and a ground current (I4) of electrical equipment consumers, and to consider that there is a short circuit when the sum of the four currents 11 + 12 + 13 + 14 is zero. This solution can detect a short circuit, but it does not protect the electrical network against this short circuit, in particular during rapid recharging.

One of the object of the invention is to improve the situation.

It proposes in particular for this purpose a protection device intended to equip a system comprising a rechargeable and connected battery, via first switching means which can be placed in first and second states in which respectively they allow and prevent a flow of current, an electrical network to which is connected a charging connector which is suitable for being coupled to a fast DC charging station.

This protection device is characterized by the fact that it includes control means which, during a rapid recharging of the battery when a recharging current entering the battery is followed by a discharging current leaving the battery. and representative of a short circuit in the electrical network, trigger:

placing the first switching means in their second state, and

- the transmission of a message requesting the immediate cessation of rapid recharging bound for the station.

Thus, the presence of a short circuit in the electrical network can be very quickly detected, and in this case the electrical network can be immediately "isolated" from any current source (battery and station).

The protective device according to the invention may include other characteristics which can be taken separately or in combination, and in particular:

- its control means can trigger when the recharge current is followed by a discharge current which is higher than a current threshold;

its control means can trigger when the recharging current is followed by the discharging current for a duration which is greater than a time threshold;

- It can include measuring means responsible for measuring the charging current and the discharging current;

> the measurement means can be installed in the battery.

The invention also provides a rechargeable battery, on the one hand, suitable for equipping a system and for being connected, via first switching means which can be placed in first and second states in which respectively they allow and prevent a flow of current. , to an electrical network to which is connected a charging connector suitable for being coupled to a rapid charging station for direct current, and, on the other hand, comprising a protection device of the type of that presented above.

For example, this rechargeable battery can comprise at least one group of electrical energy storage cell (s).

The invention also provides a system comprising an electrical network to which are connected a charging connector suitable for being coupled to a rapid DC charging station, and at least one rechargeable battery of the type presented above and supplying this network. electric.

The invention also proposes a system comprising, on the one hand, an electrical network to which are connected a recharging connector suitable for being coupled to a fast DC charging station, and at least one rechargeable battery supplying this electrical network, and , on the other hand, a protection device of the type presented above.

Each of these systems can, for example, constitute a vehicle of the all-electric or hybrid type, and possibly of the automobile type.

The invention also provides a vehicle, possibly of the automobile type, and comprising one of the systems presented above.

Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawing, in which the single figure schematically and functionally illustrates an example of a vehicle of the all-electric type and comprising a battery. rechargeable equipped with an exemplary embodiment of a protection device according to the invention.

The object of the invention is in particular to propose a protection device DP intended to equip a system S in order to protect its electrical network RE when it is the subject of a short circuit during a rapid recharging phase in direct current d '' at least one BR rechargeable battery.

In what follows, it is considered by way of nonlimiting example that the system S is a motor vehicle, such as for example a car. However, the invention is not limited to this type of system. It relates in fact to any type of system comprising at least one rechargeable battery and connected to an electrical network to which is also connected a charging connector suitable for being coupled to a rapid DC charging station. Consequently, the system could be a vehicle (land (and in particular a tram powered by a catenary), sea (or river) or air), an installation, possibly of industrial type, or a building, for example. Alternatively, an S system may be part of a vehicle, possibly of the automotive type.

Furthermore, it is considered in what follows, by way of nonlimiting example, that vehicle S comprises a powertrain (or GMP) of the all-electric type. But the GMP could also be of the hybrid type (thermal / electric).

In addition, it is considered in the following, by way of nonlimiting example, that the rechargeable battery BR comprises an assembly EG of at least one group of electrical energy storage cell (s). For example, each cell can be of the Li-ion, or Ni-MH, or lead, or Sodium-ion, or even Lithium-Metal-Polymer (or LMP) type. But the invention is not limited to this type of rechargeable battery. It relates to any type of rechargeable battery that can be recharged during rapid DC charging phases ("mode 4 recharges").

There is schematically shown in the single figure a system S, here a motor vehicle, comprising a transmission chain, a supervision computer CS, a protection device DP according to the invention, and an electrical network RE to which a battery is connected (rechargeable) BR, a first set E1 of electrical equipment consuming electrical energy, a second set E2 of electrical equipment producing electrical energy and a charging connector CR.

The transmission chain includes a powertrain (or GMP), here of the all-electric type.

The CS supervision computer is suitable for supervising (or managing) the operation of the GMP.

The GMP includes in particular an electrical equipment MM defining a driving machine and forming part of the first set E1, and a coupling means MCP.

The motive machine MM is an electric (and therefore non-thermal) machine or motor intended to supply torque for at least one TV train of the vehicle V via the coupling means MCP. It will be noted that in the exemplary embodiment illustrated without limitation, the motor machine MM supplies torque for the front axle TV via the coupling means MCP. But in an alternative embodiment it could provide torque to the rear axle only TR or to the front axle TV and rear axle TR. Here, the motor machine MM supplies its torque to a transmission shaft AT which is coupled to the front axle TV, via the coupling means MCP.

Taking into account the type of vehicle S described, the front undercarriages TV and rear undercarriage TR comprise wheels.

The operation of the motive machine MM is controlled by the supervision computer CS.

The battery BR is for example installed in the base of the vehicle V. It here comprises an assembly EG of at least one group of cell (s) which is connected to the electrical network RE via first switching means MC1.

These first switching means MC1 can be placed in at least one first state (closed), in which they allow current to flow from the electrical network RE to the battery BR or from the battery BR to the electrical network RE, and a second state (open) in which they prevent the flow of current between the electrical network RE and the battery BR. They therefore provide at least one switch function. It will be noted that in the case of “mode 4”, two other states are provided in order to avoid having high voltage at the level of the charging connector CR when the vehicle is traveling, and therefore so that the part of the electrical network RE located between the BR rechargeable battery and the CR charging connector is not energized during driving.

For example, and as illustrated without limitation in the single figure, the first switching means MC1 can comprise first R1 and second R2 switching relays installed respectively on the two inputs / outputs of the group of cell group (s) (s) EG. Each of these first R1 and second R2 switching relays can, for example, include at least one power switch, the first and second states of which can be controlled by voltage commands. Each power switch can, for example, be of the IGBT (Insulated Gâte Bipolar Transistor >>) type, or MOSFET, or relay.

The CR charging connector is connected to the electrical network RE and is suitable for being coupled to a fast DC charging station SR, via a CL charging cable.

The SR station is connected to an electrical power supply network. It includes second switching means MC2 and a charging supervision module MSR.

The second switching means MC2 can be placed in a first state (closed), in which they allow current to flow from the station SR to the electrical network RE of the vehicle S, and a second state (open) in which they prevent the current flow from station SR to the electrical network RE of vehicle S.

For example, and as illustrated without limitation in the single figure, the second switching means MC2 can comprise third R3 and fourth R4 switching relays installed respectively on the two power outputs of the station SR. Each of these third R3 and fourth R4 switching relays can, for example, include at least one power transistor (possibly of MOSFET type), the first and second states of which can be controlled by voltage commands supplied by the supervisory module. MSR refill.

This MSR recharging supervision module is responsible for controlling the electric recharging power which supplies the electrical network RE during a rapid recharging phase, according to instructions and information transmitted by the vehicle S via the recharging connector CR and the CL charging cable, and supplied by the BR battery control means, which may be part of the latter (BR).

The protection device DP comprises at least MCT control means which are responsible for acting upon rapid recharging of the battery BR when a recharging current entering the battery BR is followed by a discharging current exiting from the battery BR and representative of a short circuit in the electrical network RE. Whenever this situation is present, the control means MCT trigger a placement of the first switching means MC1 in their second state (open) and the transmission of a message requesting the immediate stopping of rapid recharging bound for the station. SR (and more precisely its MSR recharge supervision module).

It will indeed be understood that the placement of the first switching means MC1 in their second state (open) prevents any circulation of current (outgoing) from the battery BR to the electrical network RE, and that on receipt of the request the supervision module charging station MSR places the second switching means MC2 in their second state (open), for example by means of at least one voltage control, which prevents any circulation of current (leaving) from the station SR to the electrical network RE .

Thus, by monitoring the current flowing between the battery BR and the electrical network RE during rapid recharging, it is very quickly possible to detect the presence of a short circuit in this electrical network RE and to “isolate” the latter. (RE), and therefore all the electrical equipment which is connected to it, from any current source (BR battery and SR station). This certainly results in an interruption in the operation of the electrical equipment, but above all an immediate stop in the production of high heat (or hot spot) at the short circuit, and therefore an prevention of the propagation of this hot spot.

It will be noted that the triggering of the placement of the first switching means MC1 in their second (open) state can, for example, be done by means of a voltage command (and therefore of analog type). But in a variant it could be done by means of a command or instruction of the numerical type.

It will also be noted that the recharging current and the discharging current are measured (or estimated) by means of measurement MM, for example on an input / output of the group of cell group (s) EG, such as illustrated without limitation. Preferably, a current measurement means MM is used on each power rail. These measurement means MM can be part of the protection device DP. But it is not compulsory. Indeed, they can possibly be part of the BR battery or of another device monitoring the operation of the latter (BR). Furthermore, these measurement means MM can, as shown without limitation, be installed inside the battery BR. But it is not compulsory.

Preferably, the MCT control means can trigger (following the detection of the short circuit) when the recharging current is followed by a discharging current which is higher than a current threshold. For example, when the system S is a vehicle, this current threshold can be between 10 A and 30 A. For example, this current threshold can be equal to 20 A.

This option is intended to avoid stopping a rapid recharge when the discharge current leaving the BR battery is low and therefore that the risk of a hot spot in the electrical network RE at the short circuit is very weak. There are indeed transient life phases where the BR battery can deliver current without there being a short circuit.

Also preferably, the MCT control means can trigger (consecutive to the detection of the short circuit) when the recharge current is followed by a discharge current for a duration which is greater than a time threshold. For example, when the system S is a vehicle, this time threshold can be between 500 ms and 2 s. As an example, this time threshold can be equal to 1 s.

This other option, which can be optionally but advantageously combined with the previous one, is intended to avoid stopping a rapid recharging in the presence of an error in current measurement by the measurement means MM or else a measurement of current just but very brief and therefore not significant.

It will also be noted, as illustrated without limitation in the single figure, that the MCT control means can be part of the battery BR. But it is not compulsory. Indeed, they can possibly be part of a computer, such as for example the supervisory computer CS, or even constitute part of the control means of the battery BR. Consequently, the MCT control means can be produced in the form of software modules (or computer or even "software"), or else of a combination of electronic circuits (or "hardware") and software modules.

It will also be noted that the invention can also be considered from the angle of a protection method which can in particular be implemented by means of a DP protection device of the type of that presented above. The functionalities offered by the implementation of the method according to the invention being identical to those offered by the protection device DP presented above, only the combination of main functionalities offered by the method is presented below.

This protection method comprises a step in which, during a rapid recharging of the battery BR when a recharging current entering the battery BR is followed by a discharge current leaving the battery BR and representative of a short -circuit in the electrical network RE, the first switching means MC1 are placed in their second state and a message requesting the immediate stopping of the rapid recharging is sent to the station SR.

The invention offers several advantages, including:

- it makes it possible to very significantly improve electrical safety during rapid recharges,

- it is very easy to implement,

- it is very inexpensive.

Claims (10)

1. Protection device (DP) for a system (S) comprising a rechargeable and connected battery (BR), via first switching means (MC1) which can be placed in first and second states in which respectively they allow and prevent a current flow, to an electrical network (RE) to which is connected a charging connector (CR) suitable for being coupled to a station (SR) for rapid DC charging, characterized in that it comprises control means ( MCT) which, during rapid recharging of said battery (BR) when a recharging current entering said battery (BR) is followed by a discharge current leaving said battery (BR) and representative of a short -circuit in said electrical network (RE), trigger a placement of said first switching means (MC1) in their second state and the transmission of a message requesting the immediate stopping of said rapid recharging for destination n of said station (SR). 2. Device according to claim 1, characterized in that said control means (MCT) effect said triggering when said recharging current is followed by a discharge current greater than a current threshold. 3. Device according to claim 1 or 2, characterized in that said control means (MCT) effect said triggering when said recharging current is followed by said discharging current for a duration greater than a time threshold. 4. Device according to one of claims 1 to 3, characterized in that it comprises measurement means (MM) measuring said recharging current and said discharging current. 5. Device according to claim 4, characterized in that said measuring means (MM) are located in said battery (BR). 6. Rechargeable battery (BR) suitable for equipping a system (S) and for being connected, via first switching means (MC1) which can be placed in first and second states in which respectively they allow and prevent a flow of current, to an electrical network (RE) to which is connected a charging connector (CR) suitable for being coupled to a station (SR) for rapid DC charging, characterized in that it comprises a protection device (DP) according to the 'one of the 5 preceding claims. 7. Rechargeable battery (BR) according to claim 6, characterized in that it comprises at least one group of cell (s) for storing electrical energy. 8. System (S) comprising an electrical network (RE) to which is connected a charging connector (CR) suitable for being coupled to a station (SR) for rapid DC charging, characterized in that it further comprises at least one rechargeable battery (BR) according to claim 6 or 7, connected to said electrical network (RE), or a protection device (DP) according to one of claims 1 to 5. 15 9. System according to claim 8, characterized in that it constitutes an all-electric or hybrid type vehicle. 10. System according to claim 9, characterized in that said vehicle is of automobile type.