FR3112436A1 - Device for protecting an electrical energy distribution circuit - Google Patents

Abstract

This protection device (6) of a distribution circuit (1) of electrical energy (VIN) coming from a power source (2) and intended to be delivered to at least one electrical load (10), comprises at least one semiconductor power controller (6a) coupled between the power source (2) and the electrical load (10) and comprising at least one electrically conductive channel (3, 5), acquisition means (50) capable of measuring the voltage at the terminals of each channel (3, 5) and switching means (6b) coupled to each channel (3, 5) and capable of dissipating electrical energy when the voltage measured by the means d acquisition (50) is greater than a threshold value. Figure for the abstract: Fig 1

Description

Device for protecting an electrical energy distribution circuit

The present invention relates to secondary distribution circuits of electrical energy, and more particularly, the means of protection of such circuits intended to be carried on board an aircraft.

Prior techniques

An aircraft generally comprises an electrical system comprising in particular a primary distribution circuit and a secondary electrical power distribution circuit.

These distribution circuits allow electrical power to be distributed from internal sources, such as generators or batteries, or from external sources, such as power units or a park group, to payloads such as an inverter or to other aircraft distribution channels.

Distribution circuits are increasingly equipped with electronic boards and connectors to electrically connect power sources to aircraft loads.

Electronic boards are typically electrically conductive multi-channel solid-state power controllers called SSPCs (Solid State Power Controllers), in which each channel of the SSPC board controls the power supply to an electrical load. of the aircraft.

More particularly, in the event of electrical short-circuits or overloads, the channels of the semiconductor power controllers are able to pass from an electrically on state to an electrically off state in order to isolate the load or a circuit from distribution of energy from the electrical energy generating source.

In other words, semiconductor power controllers are capable of conducting electrical energy and interrupting its flow on command or when an electrical overload, a short-circuit is detected or when it is desired to stop supplying the charge.

However, to implement each function optimally, it is advantageous to use electronic components with specific electrical and thermal characteristics, which is not always the case with conventional controllers.

More precisely, the same electronic components are used to implement the conduction and switching functions.

Moreover, with the growing increase in the electrical energy consumption of aircraft, it is necessary to increase the performance of protection devices against overloads and short circuits.

Moreover, at medium voltage, for example 540 volts or at high voltage, close to 3000 volts, the fault currents increase, which amplifies the problem of the implementation of the conduction and switching functions.

It is then necessary to quickly isolate the electrical power distribution circuit to minimize the risk of destruction of the electrical charges. However, this generates voltage peaks which can be of the order of several kilovolts and in particular cause the destruction by breakdown of the components implementing the switching, such as a switch.

One solution consists in limiting these overvoltages by slowing down the opening of the switches in order to dissipate the parasitic energy stored in the lines of the network by the Joule effect.

However, to implement this solution when it comes to medium and high voltages, the size and weight of the circuit are considerably increased.

The object of the invention is to overcome the aforementioned drawbacks and, in particular, to overcome the drawbacks associated with switching following the appearance of overload currents or short circuits in an electrical power distribution circuit of average or high voltage and to prevent the destruction or alteration of the cables, see components of the circuit to be powered.

In view of the foregoing, the subject of the invention is a device for protecting a distribution circuit for electrical energy coming from a power source and intended to be delivered to at least one electrical load, comprising:

- at least one semiconductor power controller coupled between the power source and the electrical load and comprising at least one electrically conductive path and,

- acquisition means capable of measuring the voltage at the terminals of each channel.

This device comprises switching means coupled to each channel and capable of dissipating electrical energy when the voltage measured by the acquisition means is greater than a threshold value.

By separating the components implementing the conduction function from the components providing the switching function, these components can be optimized for optimal operation, and the weight and size of each function can be reduced.

The conduction function is here performed by the semiconductor power controller and particularly by the electrically conductive paths, which also makes it possible to minimize conduction losses by using components with low electrical resistance.

Furthermore, the conductive paths are also dimensioned to minimize the rise in temperature, in particular by optimizing the thermal conduction and convection resistance.

The switching means are sized to dissipate the parasitic electrical energy stored in the lines of the distribution circuit.

More particularly, the switching means are configured to limit the voltage in the transmission lines and thus limit overvoltages, and this for a period of time comprised for example between 20 and 400 μs , as soon as the channels switch from an electrically on state to an electrically off state.

Advantageously, the device comprises an active clamping circuit capable of controlling the switching means, and a control unit capable of controlling the power controller, the clamping circuit being coupled between the power source and the electrical load and comprising a diode chain.

By "active clamping circuit", commonly called "active clamp", is meant any device capable of fixing a voltage at the terminals of the electrically conductive paths to a value greater than the network voltage to allow the dissipation of the energy contained in the distribution circuit by the switching means.

This circuit controls the passage of the switching means from an electrically off state to an electrically on state when the voltage measured, at the terminals of the electrically conductive channel, is greater than the threshold voltage, for example 900 volts when the lines of the network have a voltage more or less equal to 270 volts.

As for the power controller, each electrically conductive channel is controlled by a control unit such as a microcontroller or any other device capable of executing machine instructions.

Preferably, the switching means are also controlled by the control unit.

In other words, the chain of diodes of the active clamping circuit and the control unit are coupled so that the switching means, for example transistors, can also deliver electrical energy to the load.

The control unit and the active clamping circuit therefore control the switching means.

Preferably, the switching means comprise at least one field-effect transistor or one insulated-gate bipolar transistor.

As switching means, it is particularly advantageous to use transistors having a high resistance to short-circuits in saturated regime to dissipate the parasitic electrical energy. These are transistors with an enlarged operating area (“Safe Operating Area”).

As for the electrically conductive paths, it is advantageous to use transistors having in the on state a low resistance between the drain and the source (Rdson for “Drain-Source on Resistance”). They are controlled in saturated or blocked mode and used mainly to deliver the current to the load.

Advantageously, the supply current of the device is direct and the transistor is coupled in series to a first resistor and/or coupled in series to an assembly comprising a second resistor and a capacitor coupled in shunt.

When the electric current to be delivered is continuous, the switching means may further comprise a first resistor having a value between 0.5 ohm and 5 ohms and coupled in series with a field-effect or insulated-gate bipolar transistor so that it can contribute to the dissipation of parasitic energy, which makes it possible to reduce the dimensions of the transistor.

The switching means may comprise a capacitor coupled in shunt to a second resistor, the assembly being coupled to the first resistor and/or to the transistor, which makes it possible, after opening of the electrically conductive path, to dissipate the heat from the transistor and to discharging the accumulated parasitic electrical energy from the capacitor to the second resistor.

Preferably, the supply current is alternating or direct, the device being capable of protecting the electrical power distribution circuit when the supply current flows in one or two directions.

For conduction of electrical energy in a single direction, the chain of diodes comprises, without limitation, at least two diodes connected in opposite conducting directions. The electrical energy thus flows in a single direction towards the switching means.

Furthermore, those skilled in the art will know how to make the couplings necessary for the circulation of electrical energy in one or two directions.

Advantageously, the device is capable of separating the power source from the electrical load.

Preferably, the switching means are coupled in parallel between said at least one channel of the power controller.

In other words, the switching means and an electrically conductive channel are coupled in series, the switching means being arranged on either side of said channel, which has the advantage of making the semiconductor power controller less sensitive to a potential failure of a plurality of transistors.

Moreover, by thus arranging the switching means in parallel, the switching means are pooled. In other words, since fewer components are used, the power controller is less prone to failure.

A circuit for distributing electrical energy coming from a power source and intended to be delivered to at least one electrical load is also proposed.

The distribution circuit includes a protection device as defined above.

Another subject of the invention is an aircraft comprising an electrical power distribution circuit as defined above.

Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the indexed drawings on which:

schematically illustrates an electrical power distribution circuit capable of delivering direct or alternating current and comprising a protection device;

schematically represents the switching means of the DC electric power distribution circuit, according to a first embodiment of the invention;

illustrates a second embodiment of the switching means;

And

show in detail the switching means of the direct current electric power distribution circuit according to a third and a fourth embodiment of the invention;

schematically illustrates a first embodiment of the AC electrical power distribution circuit;

And

represent in detail the electrically conductive paths and the switching means capable of cutting off the electric current in its two directions of circulation;

illustrates an example of a direct or alternating current electric power distribution circuit comprising switching means able to cut off the current when it flows in a defined direction and,

represents the DC or AC electrical power distribution circuit in which the switching means are coupled in series to an electrically conductive path.

Reference is made to FIG. 1 which illustrates an electrical power distribution circuit intended to be carried on board an aircraft and designated by the general numerical reference 1.

The electrical power distribution circuit 1 comprises a source 2 generating AC or DC voltage V _IN capable of being delivered to an electrical load 10, an inverter or a rectifier for example.

It further comprises a protection device 6 intended to prevent any propagation of electrical overloads in the electrical circuit 1 by isolating the load 10 from the source 2, and this once the fault has appeared.

To do this, the protection device 6 comprises a semiconductor power controller 6a coupled between the voltage generating source 2 and the electrical load 10 to deliver the electrical energy V _OUT to said load and protect it as well as the cables against overloads or short circuits.

More particularly, the power controller 6a here comprises an electrically conductive channel 3, such as a switch, capable of passing from an electrically on state to an electrically off state as soon as an overload or a short-circuit is detected. .

The electrically conductive channel 3 is thus dimensioned to minimize the conduction losses by using components having a low electrical resistance. It is also dimensioned to minimize the rise in temperature, in particular by having a cooling system having a low thermal conduction and/or convection resistance.

The protection device 6 further comprises switching means 6b here comprising a switch 12 capable of dissipating the parasitic energy stored in said circuit 1 for a duration of the order of one millisecond.

Furthermore, the switching means 6b are coupled in parallel between the terminals of the electrically conductive channel 3. They are sized so as to dissipate the parasitic energy contained in the inductance of the electrical power distribution circuit 1.

An active wedging circuit not visible in the figure is able to control the switching means 6b and more particularly the switch 12.

More specifically, the active clamping circuit is configured to limit the voltage when the switch 12 passes from an electrically on state to an electrically off state as soon as a voltage threshold value at the terminals of the channel is exceeded. electrically conductive 3.

For example, the threshold value is greater than 900 volts when the voltage is continuous on a network of plus or minus 270 volts.

Reference is made to FIG. 2 which schematically represents a first embodiment of the switching means 6b when the electrical energy generated by the source 2 is continuous.

In this case, the generating source 2 is able to generate a medium or high voltage current of the “HVDC” type (for “High Voltage Direct Current” in English), of the order of 270 volts per power supply bus.

The protection device 6 is here coupled on either side of the transmission lines 4 and 8, respectively upstream and downstream of the protection device 6.

More precisely, the transmission lines 4 are coupled to the terminals of the source 2 of the distribution circuit 1 and the transmission lines 8 are coupled to the electrical load 10.

These transmission lines 4 and 8 are represented by inductors, each having for example a typical value of around 1 μH per meter of transmission cable.

In this example, there are two electrically conductive paths 3 and 5, path 3 being coupled between terminals A+ and A- of the positive bus and path 5 between terminals B+ and B- of the negative bus of distribution circuit 1.

Each channel is coupled in parallel to switching means 6b and more particularly to switch 12, for example one or more field-effect transistors or insulated-gate bipolar transistors in parallel.

In FIG. 3, the switch 12 is also coupled in series to an assembly comprising a resistor R1 coupled in shunt to a capacitor C1, which makes it possible to store parasitic electrical energy during the opening of the electrically conductive paths 3 and 5 and limit the voltage between terminals A+ and A- and between terminals B+ and B-.

More precisely, before the opening of electrically conductive paths 3 and 5, the differential voltage between terminals A and B is lower than the threshold voltage value, resistor R1 maintaining capacitor C1 discharged.

After the opening of the electrically conductive channels 3 and 5, the drop in current in these channels causes an overvoltage at the terminals of the inductors 4 and 8 which is proportional to the current variation.

The current variation being negative and the voltage being of fixed value at the terminals of the source 2, the voltage varies between the terminals A+/A- and B+/B-.

When the differential voltage between terminals A+ and A- or between B+ and B- becomes greater than the threshold value, the active clamping circuit closes switch 12 between terminals A+ and A- or B+ and B-.

Capacitor C1 then begins to charge rapidly, which allows parasitic energy to be transferred from inductors 4 to capacitor C1 which then discharges into resistor R1.

By way of example, capacitor C1 has a capacitance comprised for example between 5 and 20 μF and can be made of metallized polypropylene.

In the embodiments illustrated in Figures 4A and 4B, the switching means 6b as well as the active clamping circuit 14 are coupled between the positive and negative poles A+ and B+ of the supply bus of the source 2.

In this case, when the differential voltage between A and B becomes higher than the threshold value of the active clamping circuit 14, the active clamping circuit 14 closes the switch 12.

The coupling shown in Figures 4A and 4B has the advantage of halving the voltage limitation start threshold compared to an assembly of the Figure 3 type: a single active 900V clamping circuit in parallel with the load Figure 4A and 4B , against two 900V active clamping circuits in series with the load figure 3 (hence a total voltage limitation start threshold at 1800V).

It also makes it possible to pool the switching function implemented by the switching means 6b if several loads are coupled thereto through the power controllers 6a.

In these examples, the capacitor C1 is coupled in series with a resistor R2 which contributes to the dissipation of the parasitic electrical energy.

The active clamping circuit 14 here comprises a chain of diodes 50 of the Zener or Transil type voltage stabilizer diode type.

Diode chain 50 may also comprise 1 to 8 diodes coupled in series, each capable of achieving a voltage limitation of 150 volts at its terminals to trigger a passage of current through the active clamping circuit from 900 volts for example.

The clamping circuit 14 further comprises a capacitor C2 coupled in parallel to a resistor R4, to a resistor R3 in series and to a Zener diode Z1 in parallel.

Capacitor C2 has a capacity suitable for rapid charges and discharges of the order, for example, of a hundred nanofarads and makes it possible to drive switch 12.

Resistor R4 is sized so as to discharge capacitor C2 in less, for example, half a second.

Active clamp circuit 14 further includes a diode D2 coupled in series with capacitor C2 to block any current flowing in the reverse direction in clamp circuit 14.

More particularly, as illustrated in FIG. 4A, switch 12 is made in the form of two transistors T1 and T2.

Alternatively, as illustrated in FIG. 4B, switch 12 comprises a diode D1 in place of transistor T2 serving as anti-return current in switching means 6b.

Figure 5 schematically illustrates a first embodiment of the protection circuit 6.

In this example, the semiconductor power controller 6a comprises at least two field-effect transistors TR ₁ and TR ₂ , the transistor TR ₁ being coupled at its source to the source of the transistor TR ₂ .

The gate of each transistor TR ₁ and TR ₂ is controlled by control unit 21.

As for the switching means 6b, they also comprise at least two field-effect or insulated-gate bipolar transistors TR ₃ and TR ₄ , the transistor TR ₃ having its source coupled to the source of the transistor TR ₄ .

The gate of each transistor TR3 and TR4 is controlled by active clamping circuit 14.

Alternatively, as illustrated in Figure 6A, the semiconductor power controller 6a comprises at least two rows 100 and 200 comprising field effect transistors.

The first row 100 includes transistors TR ₁ and TR ₂ and the second row 200 field effect transistors TR ₅ and TR ₆ .

The sources of transistors TR ₅ and TR ₆ are connected to the sources of transistors TR ₁ and TR ₂ .

Similarly, as illustrated in FIG. 6B, the switching means 6b comprise at least two rows 300 and 400 of field-effect or bipolar transistors with an insulated gate.

The row 300 here comprises the two transistors TR ₃ and TR ₄ and the second row 400 comprises the transistors TR ₇ and TR ₈ .

The sources of transistors TR ₇ and TR ₈ are connected to the sources of transistors TR ₃ and TR ₄ .

This configuration allows current to be blocked or conducted in both directions.

In order to cut off the current in a defined direction, the switching means 6b comprise, as illustrated in FIG. 7, the transistor TR ₃ and the transistor TR ₄ coupled by their source and their drain.

Furthermore, it is possible to have a plurality of transistors comprising a plurality of drain-sources coupled in parallel.

As for the semiconductor power controller 6a, it comprises the transistor TR ₁ and TR ₂ also coupled by their source and their drain.

In the embodiment of Figure 8 the switching means 6b are coupled on either side of the conduction means 6a.

In other words, by putting the switching means 6b and the electrically conductive path 3 of the power controller 6a in series, the power controller 6a becomes less sensitive to any failures of a plurality of switches, for example transistors.

Claims (10)

Protection device (6) for a distribution circuit (1) of electrical energy (V _IN ) coming from a power source (2) and intended to be delivered to at least one electrical load (10), including:
- conduction means (6a) such as at least one semiconductor power controller (6a) coupled between the power source (2) and the electrical load (10) and comprising at least one electrically conductive channel (3 , 5);
- acquisition means (50) capable of measuring the voltage at the terminals of each channel (3, 5) and,
characterized in that the device (6) comprises switching means (6b) coupled to each channel (3, 5) and capable of dissipating electrical energy when the voltage measured by the acquisition means (50) is greater than a threshold value. Device according to Claim 1, comprising an active clamping circuit (14) capable of controlling the switching means (6b), and a control unit (21) capable of controlling the at least one power controller (6a), the circuit clamp (14) being coupled between the power source (2) and the electrical load (10) and comprising a chain of diodes (50). Device according to Claim 2, in which the switching means (6b) are further controlled by the control unit (21). Device according to any one of the preceding claims, in which the switching means (6b) comprise at least one field effect transistor (12) or an insulated gate bipolar transistor. Device according to Claim 4, in which the supply current is direct, the transistor (12) being coupled in series to a first resistor (R2) and/or coupled in series to an assembly comprising a second resistor (R1) and a capacitor (C1) connected in parallel. Device according to any one of Claims 1 to 4, in which the supply current is alternating or direct, the device being able to protect the electrical energy distribution circuit (1) when the supply current propagates in a or two senses. Device according to Claim 6, in which the device (6) is able to separate the power source (2) from the electrical load (10). Device according to Claim 6 or 7, in which the switching means (6b) are coupled in parallel on either side of the said at least one channel of the power controller (3). Distribution circuit (1) of electrical energy (V _IN ) coming from a power source (2) and intended to be delivered to at least one electrical load (10), characterized in that it comprises a device protection (6) according to any one of the preceding claims. Aircraft comprising at least one circuit (1) for distributing electrical energy (V _IN ) according to claim 9.