EP2686746B1 - Series voltage regulator with electronics protected against short-circuits by magnetic circuit-based decoupling using holes and windows - Google Patents

Description

GENERAL TECHNICAL FIELD

The present invention relates to a voltage regulator adapted to be connected in series between, on the one hand, an alternating source and, on the other hand, a load, comprising a magnetic circuit comprising a first core and a second core parallel to each other, at least one first inductive coil wound around the first core and connected on the one hand to the alternative source and on the other hand to the load, and at least one voltage converter having a second coil wound around the second core.

STATE OF THE ART

As shown in figure 1 there are known alternative electrical networks (for example of high voltage transport, medium and low voltage distribution, as well as the industrial internal supply networks of the factories) which comprise at least one voltage regulator 10, adapted to be connected in series between an alternative S source and a C load.

Indeed, the voltage of the networks is frequently degraded, especially as one moves away from the source (such as for example a mean voltage drop, a flicker, a generation of harmonics or voltage dips), and the known regulator 10 allows voltage regulation, in order to correct the voltage of the connected loads at the end of the network.

For this purpose, the known regulator 10 comprises a magnetic circuit 2 comprising a first core 21 and a second core 22, parallel to each other. It also comprises at least a first inductive coil 1 wound around the first core 21 and connected on the one hand to the source S and on the other hand to the load C. Finally, it comprises at least one electronic voltage converter 4 comprising a second coil 7 wound around the second core 22. Such a regulator is described in the document US 2003/0076202 A1 .

The converter 4 makes it possible to regulate the voltage at the terminals Bc of the load when it is coupled, via the second coil 7, to the first coil 1 which has an inductance L.

Under normal conditions, that is to say without faults in the network, the magnetic flux F _A of the first coil 1 closes in the circuit 2 on the first core 21 and the second core 22.

In this case, the assembly formed by the first coil 1, the circuit 2 and the second coil 7 constitutes a voltage transformer which couples the converter 4 with the first coil 1 in series and upstream of the load C.

The converter 4 can therefore regulate the voltage at the terminals Bc of the load C.

The aforementioned electrical networks are inevitably subject to defects D (accident, equipment failure, lightning ... and in general any overcurrent (short-circuit) that can cross the regulator), especially since a dozen years, the risks of default increase due to aging networks.

At the same time, the connection to the networks of new types of installations, such as decentralized energy production installations (eg wind farms), increases the power of the short circuits in the networks in the event of a fault. The amplitude of the short-circuit currents is thus of the order of a few kA up to several tens or hundreds of kA, depending on the types of networks. Currents of high amplitude can damage the networks, and in particular the converter 4.

A known solution consists in providing an electromechanical decoupling device for the converter 4 and the first coil 1.

This solution is not optimal, however. Indeed, in the case of a voltage converter connected in series using a known transformer, the full fault voltage appears very quickly at its terminals, in the event of a fault, which can damage it.

The converter must therefore be decoupled by switches.

Take, for example, a known three-phase network of 20 kV, with a single-phase voltage of the order of 11.5 kV. The nominal current corresponding to a three-phase load C of 1 MVA is of the order of 30A, while the amplitude of the short-circuit can reach several hundred amperes (10 times the rated current), or even several thousand amperes .

Or a voltage regulation of plus or minus 10% corresponds to a single-phase voltage variation of the order of 1 kV, a permanent power of the converter 4 of the order of 30kVA.

To be operational during the entire duration of a fault of the order of ten times the nominal current, the characteristics of the switches of the converter must be such that they can convey a single-phase power of the order 300kVA, or more in case of short circuits of several thousand amperes. Such switches are consequently very expensive.

PRESENTATION OF THE INVENTION

The invention proposes to overcome at least one of these disadvantages.

• au moins une paire de trous dans le troisième noyau de découplage, et
• un bobinage se bobinant entre les trous de chaque paire de trous, et relié à une source de courant continu,

le régulateur fonctionnant entre au moins deux états, à savoir :

• un premier état dans lequel l'entrefer virtuel est ouvert en saturant magnétiquement le troisième noyau de découplage, le flux magnétique dans le troisième noyau étant faible, et la deuxième bobine du convertisseur étant couplée à la première bobine, de sorte que le régulateur puisse réguler une tension dans la charge, et
• un deuxième état dans lequel l'entrefer virtuel est fermé, le flux magnétique dans l'entrefer virtuel du troisième noyau étant important, de sorte que le convertisseur soit découplé de la première bobine.

For this purpose, the invention proposes a voltage regulator adapted to be connected in series between an alternating source and a load, comprising
a magnetic circuit comprising a first core and a second core,
at least a first inductive coil wound at least partially around the first core and connected on the one hand to the alternative source and on the other hand to the load, and
at least one voltage converter having a second coil wound around the second core,
the regulator being characterized in that
the circuit comprises
a third decoupling core, and
a virtual gap, the virtual gap including

• at least one pair of holes in the third decoupling core, and
• a coil winding between the holes of each pair of holes, and connected to a direct current source,

the regulator operating between at least two states, namely:

• a first state in which the virtual gap is open by magnetically saturating the third decoupling core, the magnetic flux in the third core being low, and the second coil of the converter being coupled to the first coil, so that the regulator can regulate a voltage in the load, and
• a second state in which the virtual gap is closed, the magnetic flux in the virtual gap of the third core being important, so that the converter is decoupled from the first coil.

• le régulateur est en outre adapté pour fonctionner selon un troisième état dans lequel l'entrefer virtuel est partiellement ouvert en désaturant partiellement le troisième noyau, de sorte que le convertisseur soit partiellement découplé de la première bobine ;
• il comporte une commande passive ou active ou intelligente de l'ouverture, totale ou partielle, ou de la fermeture, totale ou partielle, de l'entrefer virtuel ;
• la commande passive comporte une liaison permanente entre la source de courant continu et le bobinage ;
• la commande active comporte un interrupteur commandé par un détecteur entre la source de courant continu et le bobinage ;
• la commande intelligente commande une source de courant continu comportant un variateur relié au bobinage ;
• le premier noyau comporte
  • une réduction de section, ou
  • un noyau complémentaire relié par un entrefer mécanique au circuit magnétique ;
• la première bobine se compose d'une première partie, s'enroulant autour du premier noyau, et d'une deuxième partie, s'enroulant autour d'une partie du circuit comprise entre le premier noyau et le troisième noyau, le régulateur présentant ainsi également une fonction de limiteur de courant ;
• le circuit comporte un circuit magnétique auxiliaire comportant un cadre comportant au moins un noyau et un entrefer mécanique, la première bobine s'enroulant autour du premier noyau et du noyau du cadre, le régulateur présentant ainsi également une fonction de limiteur de courant,
• le régulateur est adapté pour être mis en série avec une bobine limitatrice de courant.

The invention is advantageously completed by the following features, taken alone or in any of their technically possible combination:

• the regulator is further adapted to operate in a third state in which the virtual gap is partially open by partially desaturating the third core, so that the converter is partially decoupled from the first coil;
• it comprises a passive or active or intelligent control of the opening, total or partial, or the closure, total or partial, of the virtual gap;
• the passive control comprises a permanent connection between the DC power source and the winding;
• the active control comprises a switch controlled by a detector between the DC power source and the winding;
• the intelligent control controls a DC power source having a dimmer connected to the winding;
• the first core comprises
  • a section reduction, or
  • a complementary core connected by a mechanical gap to the magnetic circuit;
• the first coil consists of a first part, wrapping around the first core, and a second part, wrapping around a part the circuit between the first core and the third core, the controller thus also having a current limiting function;
• the circuit comprises an auxiliary magnetic circuit comprising a frame comprising at least one core and a mechanical air gap, the first coil winding around the first core and the core of the frame, the regulator thus also having a current limiting function,
• the regulator is adapted to be put in series with a current limiting coil.

The invention has many advantages.

The invention provides a voltage regulator for regulating a voltage across a load on the grid in normal operation, and for decoupling a regulator converter from the mains and a control source of the regulator, to protect them from voltage currents. short circuit in the event of a fault. The regulator of the invention, however, finds its voltage regulation function, without any maintenance, while network returns to its normal regime.

In the case where it also comprises a fault current limiting function, the high performance of the regulator of the invention makes it possible to reduce correspondingly the performance of the cut-off devices associated with it in the network. The invention therefore makes it possible to provide an inexpensive network protection device, especially since it may not comprise superconducting material.

The controller can include a passive or active control, even intelligent, depending on the type of network, the type of protection device and the amplitude of the normal, transient and fault currents. This control is performed from a direct current injected into a specific winding for magnetically saturating, locally, the magnetic circuit.

The invention is such that the continuous ampere-turns supplying the saturation coil of the magnetic circuit of the regulator are small, since the local saturation of the magnetic circuit (to form a virtual gap V E) is obtained easily (the perimeter of the holes on which the winding is coiled is weak). In this respect, a superconducting material may be used for the auxiliary winding, but it is not essential.

The saturation auxiliary winding time constant may be low to quickly shut off the DC current and change the state of the Virtual Gap quickly.

The advantage of the invention is that the voltage converter and the DC source of the air gap EV are magnetically decoupled, as long as the fault lasts.

When the Virtual Airlock is in its intermediate state, all the windings are coupled.

PRESENTATION OF FIGURES

• la figure 1, déjà commentée, représente schématiquement un réseau connu comportant un régulateur de tension ;
• les figures 2A, 2B et 2C représentent schématiquement un mode de réalisation possible d'un régulateur selon l'invention, dans un réseau, avec les flux magnétiques correspondants aux différents états de l'entrefer EV ;
• les figures 3A et 3B représentent schématiquement les principes de couplage d'un mode de réalisation possible d'un régulateur selon l'invention, dans un réseau ;
• la figure 4 représente schématiquement une commande active d'un régulateur selon l'invention ;
• la figure 5 représente schématiquement une commande intelligente d'un régulateur selon l'invention ;
• la figure 6A représente l'évolution de la tension efficace du réseau côté source en fonction du temps ;
• la figure 6B représente l'évolution de la tension efficace du réseau côté charge en fonction du courant efficace de réseau ;
• la figure 7 représente schématiquement une commande d'un régulateur selon l'invention ;
• les figures 8A à 8C représentent schématiquement différents cas de variation du courant instantané en fonction du temps ;
• les figures 9A et 9B représentent schématiquement des circuits magnétiques selon l'invention ;
• les figures 10A à 10D représentent schématiquement des schémas équivalents d'un régulateur selon l'invention, en fonction du courant dans le réseau ;
• la figure 11 représente schématiquement un circuit selon l'invention composé par une superposition de tôles magnétiques ;
• la figure 12 représente schématiquement une première variante d'un mode de réalisation d'un régulateur selon l'invention, présentant ainsi une fonction de limitation du courant ;
• la figure 13 représente schématiquement une deuxième variante d'un mode de réalisation d'un régulateur selon l'invention, présentant ainsi une fonction de limitation du courant ;
• la figure 14 représente schématiquement un régulateur de tension comportant également un limiteur de courant ; et
• la figure 15 représente la limitation du courant sur une courbe de l'évolution de la tension efficace du réseau côté charge en fonction du courant efficace de réseau.

Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended drawings in which:

• the figure 1 , already commented, schematically shows a known network comprising a voltage regulator;
• the Figures 2A, 2B and 2C schematically represent a possible embodiment of a regulator according to the invention, in a network, with the magnetic flux corresponding to the different states of the air gap EV;
• the Figures 3A and 3B schematically represent the coupling principles of a possible embodiment of a regulator according to the invention, in a network;
• the figure 4 schematically represents an active control of a regulator according to the invention;
• the figure 5 schematically represents an intelligent control of a regulator according to the invention;
• the Figure 6A represents the evolution of the effective voltage of the source-side network as a function of time;
• the Figure 6B represents the evolution of the RMS voltage on the load side as a function of the RMS current;
• the figure 7 schematically represents a control of a regulator according to the invention;
• the Figures 8A to 8C schematically represent different cases of variation of the instantaneous current as a function of time;
• the Figures 9A and 9B schematically represent magnetic circuits according to the invention;
• the Figures 10A to 10D schematically represent equivalent diagrams of a regulator according to the invention, as a function of the current in the network;
• the figure 11 schematically represents a circuit according to the invention composed by a superposition of magnetic sheets;
• the figure 12 schematically represents a first variant of an embodiment of a regulator according to the invention, thus having a function of limiting the current;
• the figure 13 schematically represents a second variant of an embodiment of a regulator according to the invention, thus having a function of limiting the current;
• the figure 14 schematically represents a voltage regulator also comprising a current limiter; and
• the figure 15 represents the limitation of the current on a curve of the evolution of the effective voltage of the network on the load side as a function of the network rms current.

In all the figures, similar elements bear identical reference numerals.

DETAILED DESCRIPTION

The Figures 2A, 2B , 2C , 3A and 3B schematically represent a possible embodiment of a voltage regulator 10 according to the invention.

The regulator 10 is adapted to be connected in series between, on the one hand, an alternating source S and, on the other hand, a load C.

The assembly formed by the source S, the regulator 10 and the load C thus forms an electrical network. The return of the current (normal or fault) to the source S is not shown in the simplified diagrams. The present invention thus relates to an alternating network, powered by a source S of voltage regulated power.

The voltage regulator 10, adapted to be connected in series, makes it possible to correct the voltage of the load C connected at the end of the network.

In the following developments, for the sake of clarity and simplicity of explanation, the regulator 10 which is the subject of the invention is located between an upstream network which comprises the source S of power (and which may comprise charges not represented on the figures) and a downstream network that includes charge C.

The regulator 10 serves to regulate the voltage downstream, that is to say and for simplicity, at the terminals Bc of a load C.

It will be understood that the invention naturally applies to real networks, and in particular three-phase networks, where the faults (any over-current or short-circuit that can cross the regulator) occur between phases and / or between phase and earth.

In a conventional manner, the regulator 10 comprises a magnetic circuit 2 embodied by a plate. The plate may be one-piece, or may comprise a superposition of magnetic sheets 28.

The plate has external peripheral outlines, and includes a first window 23 defining internal peripheral contours 26 of the plate, and a second window 24 defining internal peripheral contours 27 of the plate.

The circuit 2 also comprises a first core 21, delimited by the contours 26 and 27 of the plate, and a second core 22, delimited by the contours 25 and 26 of the plate, the first core 21 and the second core 22 being preferentially but not limitatively parallel to each other.

It also comprises at least a first inductive coil 1 wound around the first core 21 and connected on the one hand to the source S and on the other hand to the load C.

Finally, it comprises at least one electronic voltage converter 4 comprising a second coil 7 wound around the second core 22.

The converter 4 is known to those skilled in the art and is not described in detail later in this description.

It is specified however that the converter 4 is preferably an electronic switching converter, with components supporting a large power (including insulated gate bipolar transistors or "IGBT insulated gate bipolar transistors" in the terminology of the art) and switching frequencies greater than 1 kHz.

The circuit 2 comprises a third decoupling core 3.

In a particular but nonlimiting embodiment, the third core 3 extends at least partially on a side opposite to the second core 22 relative to the first core 21. Thus, the first core 21 is located between the second core 22 and the second core 22. the third decoupling core 3.

The third core 3 may however be located in any way with respect to the first core 21 and the second core 22.

Circuit 2 also has a virtual gap EV.

• au moins une paire 50 de trous 5 dans le troisième noyau 3 de découplage, et
• un bobinage 6 auxiliaire se bobinant entre les trous 5 de chaque paire 50 de trous 5, et relié à une source 8 de courant continu.

Du fait de son bobinage autour du premier noyau 21 et du fait qu'elle peut être parcourue par un courant alternatif, la bobine 1 peut créer dans le circuit 2 une force magnétomotrice référencée par FAt_a correspondant à des ampères-tours alternatifs. La force magnétomotrice FAt_a est d'une intensité égale au produit du nombre de spires de la bobine 1 par le courant alternatif en ampères qui les traverse.The virtual airgap EV has

• at least one pair 50 of holes 5 in the third decoupling core 3, and
• an auxiliary winding 6 wound between the holes 5 of each pair 50 of holes 5, and connected to a source 8 of direct current.

Due to its winding around the first core 21 and the fact that it can be traversed by an alternating current, the coil 1 can create in the circuit 2 a magnetomotive force referenced by FAt _a corresponding to alternating ampere-turns. The magnetomotive force FAt _a is of an intensity equal to the product of the number of turns of the coil 1 by the alternating current in amperes which passes through them.

Similarly, because of its winding around the third core 3 between the holes 5 and because it can be traversed by a direct current, the auxiliary winding 6 can create a magnetomotive force FAt _c corresponding to continuous ampere-turns. The magnetomotive force FAt _c is equal to the product of the number of turns of the winding 6 by the continuous current in amperes which passes through them. The magnetomotive force FAt _c thus created by the winding 6 can magnetically saturate the third core 3, locally at the air gap EV.

The continuous ampere-turns (At) supplying the winding 6 are relatively small. They are between 500 At and several thousand At, depending on the diameter of the holes 5 and according to the characteristic of variation of the magnetic induction B as a function of the magnetic field H in the circuit 2.

There are therefore losses and relatively low temperatures in the winding 6. If much larger currents are desired, the winding 6 may be of superconductive material, but this is not essential.

The virtual dimension of the air gap EV increases with the value of ampere-turns.

In general, it is possible to modify the number of pairs 50 on the core 3 (the core 3 may in particular comprise a plurality of virtual gaps EV), and, within each pair 50, to modify the shape, the diameter, and the position of the holes 5.

The increase in the number of holes does not significantly modify the impedance values of the coil 1 or the coil 6, nor the order of magnitude of the total number of At necessary to saturate the air gap EV during normal operation. The preference may respond to manufacturing facilities of circuit 2 or coil 1 or winding 6 or control functions of source 8.

Rectangular shapes of holes tend to increase harmonic currents. Here again, preference will be able to respond to manufacturing facilities.

The regulator 10 according to the invention operates between at least two states.

A first state is schematically represented on the Figures 2A and 3A , and is a state in which the virtual air gap EV is open and magnetically opens the magnetic circuit 2 by magnetically saturating the third decoupling core 3 locally.

As shown in Figure 2A , the magnetic flux in the third core 3 is low (leak flow) because it is interrupted by the virtual gap EV.

To achieve local saturation, the auxiliary winding 6 is supplied with direct current to saturate the periphery of the holes 5 arranged inside the third core 3. This local saturation is equivalent to the opening of the core 3 by a mechanical gap.

On the contrary, the magnetic flux F _A in the second core 22 is important: the converter 4 is then magnetically coupled to the first coil 1, via the second coil 7, so that the regulator 10 can regulate a voltage in the load C.

In the first state, we have: $$\mathit{FATC}>\mathit{Fata}\mathrm{.}$$

A second state is schematically represented on the Figures 2B and 3B , and is a state in which the virtual gap EV is closed and magnetically closes the magnetic circuit 2 at the third decoupling core 3.

As shown in Figure 2B , the magnetic flux Fc in the third core 3 is important because the virtual gap EV is closed, while the flux embraced by the coil 6 is negligible, due to the symmetrical arrangement of the holes 5.

On the contrary, the magnetic flux (leakage flux) in the second core 22 is small: as shown in FIG. figure 3B the converter 4 is then decoupled from the first coil 1, so that the regulator 10 no longer regulates the voltage in the load C, but is not damaged by a fault in the network. Preferably, the second coil 7 is short-circuited to obtain equivalence to the opening 70 of the core 22.

In the second state, we have: $$\mathit{FATC}<<\mathit{Fata}$$

• qu'il y ait un courant de court-circuit de grande amplitude dans le réseau (FAt_a est donc très importante), et/ou
• que le courant traversant le bobinage 6 soit nul (on a alors FAt_c égale à 0).

Après l'élimination du défaut sur le réseau et la fin du régime transitoire électrique (c'est-à-dire les oscillations de la tension transitoire de rétablissement sur les organes de coupure), l'entrefer EV est de nouveau ouvert, sans maintenance particulière, et le régulateur 10 peut de nouveau réguler la tension sur le réseau. Et en cas de nouveau de court-circuit de défaut, le circuit 2 est de nouveau fermé magnétiquement par la fermeture rapide de l'entrefer EV, et ainsi de suite.To have this situation, you have to

• there is a short-circuit current of great amplitude in the network (FAt _a is therefore very important), and / or
• that the current flowing through the winding 6 is zero (then FAt _{c is} equal to 0).

After the elimination of the fault on the network and the end of the electrical transient regime (that is to say the oscillations of the transient recovery voltage on the breaking devices), the air gap EV is again open, maintenance-free particular, and the regulator 10 can again regulate the voltage on the network. And in case of new fault short circuit, the circuit 2 is again closed magnetically by the rapid closing of the air gap EV, and so on.

• de mettre en sécurité le convertisseur 4 et la source 8 de l'entrefer EV (découplage magnétique),
• de réduire l'énergie des courants transitoires de commutation du convertisseur et des dispositifs de commande et de protection,
• de revenir rapidement en mode de régulation normal, si la variation de courant est due à un transitoire comme, par exemple, une impulsion haute fréquence.

Il est souvent préférable de ne pas découpler le régulateur 10 de tension lors des régimes transitoires, dits normaux, du courant de charge sur le réseau (sauf bien entendu si leur durée excessive est un signe de défaut sur le réseau). Les régimes transitoires normaux sont en effet dus par exemple :

• à l'enclenchement sur le réseau de transformateurs,
• au démarrage de moteurs sur le réseau,
• etc.

In an optimal design of the regulator, the decoupling of the converter 4 and the coil 1 can take place in a time of the order of 1 ms, which allows:

• to secure the converter 4 and the source 8 of the air gap EV (magnetic decoupling),
• to reduce the energy of the transient switching currents of the converter and the control and protection devices,
• to return quickly to normal regulation mode, if the current variation is due to a transient such as, for example, a high frequency pulse.

It is often preferable not to decouple the voltage regulator 10 during transient, so-called normal, load current on the network (except of course if their excessive duration is a sign of fault on the network). Normal transient regimes are indeed due for example:

• when switching on the transformer network,
• when starting engines on the network,
• etc.

The regulator 10 is then adapted to the needs of the network (transmission network, distribution network or industrial network) and the variety of power ranges (normal and short-circuit power).

It is for this reason that there is a third state of operation, as an optional variant.

The third state corresponds to an intermediate regime of the network, in which the alternating current is slightly greater than the current nominal load. In the intermediate regime, we therefore have the following condition: $${\mathrm{Has}}_{\mathrm{at}}>{\mathrm{Has}}_{\mathrm{vs}}\mathrm{.}$$

As shown in Figure 2C in the third state, which can be established and permanent (i.e. non-transient), the circuit 2 is then partially desaturated at the gap VE of the third core 3, and a part of the alternating magnetic flux F _A (imposed by FAt _a ) flows in the third core 3 in combination with the continuous flow Fc (imposed by FAt _c ). All the windings are then magnetically coupled.
The opening of the air gap EV in normal network or the closing of the air gap EV during a fault on the network can be passive or active or so-called intelligent.

Initially described a passive control of the opening and closing of the air gap EV.

In this case, the limiter 10 comprises a passive control 60 of the opening and closing of the air gap EV.

The passive control 60 comprises a permanent connection between the source 8 and the winding 6, in accordance with the Figures 2A, 2B and 2C .

The passive control 60 uses the closing of the air gap EV, by desaturation of the circuit 2 at the air gap EV due to the fact that the force FAt _a is very high compared to the force FAt _c , because of the defect at the the network and the strong current flowing through the coil 1.

This is a passive operation, without the need for control of the passive control 60. The intensity of the direct current flowing through the coil 6, fixed prior to the fault, is the only parameter for adjusting the level of desaturation of the third core 3 .

The source 8 is in a manner known to those skilled in the art protected against overcurrents and overvoltages that develop during transient network conditions and during defects.

Secondly, an active command 60 for opening and closing the air gap EV, shown in FIG. figure 4 .

In this case, the regulator 10 comprises an active control 60 of the opening and closing of the air gap EV.

The active control 60 comprises a switch 61 between the source 8 and the coil 6.

• jouer le rôle d'une liaison entre la source 8 et le bobinage 6 (on est alors dans premier état de fonctionnement du régulateur), ou
• annuler le courant continu dans le bobinage 6 (FAt_c est alors d'intensité nulle, et on est alors dans le deuxième état de fonctionnement du régulateur par exemple).

La commande 60 comporte un détecteur 62 qui définit le critère d'ouverture de l'interrupteur 61.The switch 61 can

• acting as a link between the source 8 and the winding 6 (it is then in the first operating state of the regulator), or
• cancel the DC current in the winding 6 (FAt _c is then zero intensity, and it is then in the second operating state of the regulator for example).

The control 60 comprises a detector 62 which defines the opening criterion of the switch 61.

The detector 62 compares the amplitude of the fault current with that of a setting threshold.

It is thus possible to operate the regulator 10 in the third state, in a range of fault current slightly higher than the current in normal mode, but below the threshold. Beyond the threshold, the switch 61 opens and the regulator 10 passes in a few milliseconds in its second state (closed EV).

When the fault is eliminated, the detector 62 closes the switch 61.

The active control 60 advantageously comprises an inductive current cutout overvoltage limiter 63, connected in parallel with the source 8, for example a zinc oxide arrester (ZnO), and / or a freewheeling diode in series with a resistor both known to those skilled in the art.

Thirdly, an intelligent control is described, schematically represented on the figure 5 , in which the control 60 is connected to a source 8 comprising a variator 81 of the intensity of the current in the winding 6.

The drive 81 is an electronic power converter, known to those skilled in the art, which delivers a current comprising a component continuous, but may also include alternative components, especially at twice the network frequency.

Depending on the value of the mains current measured by the command 60 (normal speed, or intensity of the current slightly higher than the current in normal mode, or finally short circuit), the command 60 controls the drive 81 which then makes the regulator 10 pass through. the magnetic operating state 1, 2 or 3 most adapted to the context.

The command 60 can also be remotely controlled to take into account the operation of the protection devices of the network, or even modify its adjustment thresholds as needed.

The drive 81 is advantageously provided with protection devices, known to those skilled in the art, against overcurrents and overvoltages.
The Figures 6A and 6B schematically represent functions of a regulator according to the invention, with reference to the three magnetic states of the airgap EV.

For extreme amplitude faults (here very high, typically 5 to 10 times the rated current in the network, referenced by I _n ), it is necessary to decouple the voltage converter 4 quickly by magnetically closing the air gap EV. The flow generated by the fault current is closed mainly by the third core 3 at the air gap EV.

The winding 7 of the converter 4 can remain open for the duration of the fault or, preferably, be short-circuited to help push the magnetic flux to the air gap EV. This short-circuiting is equivalent to an opening of the magnetic circuit 70, as shown in FIG. figure 3B . It can be provided by the converter 4 itself or by complementary components, including converter protections known to those skilled in the art.

• découpler totalement et rapidement le convertisseur 4 comme dans le cas des courants de court-circuit, référencés par I_cc, extrêmes,
• maintenir l'entrefer EV dans un état intermédiaire.

For normal transient conditions (with a current slightly greater than a nominal current, typically 2 to 3 times the rated current In in the network) two options are possible:

• completely and quickly decoupling the converter 4 as in the case of short-circuit currents, referenced by I _cc , extremes,
• maintain the air gap EV in an intermediate state.

The flux generated by the transient current then closes partly on the side of the air gap EV (proportion X%) and for the other part (proportion 100-X%) on the side of the converter 4.

This requires significantly higher performance for the converter 4 and for the source 8, but the regulation then has the advantage of responding to normal transients without sudden voltage jumps. The converter 4 is also in an intermediate state of partial decoupling during the normal transient period.

Table 1 below summarizes the magnetic states of the air gap EV and those of the voltage converter 4. Table 1 Amplitude of the alternating current of the network Normal diet (In) Normal transient regime (2 to 3 In) Default (5 to 10 In or more) Two operating modes, with the EV air gap in active order Regulated voltage Open air gap EV Totally decoupled converter Air gap EV closed Two operating modes, with the EV air gap in passive control Regulated voltage Open air gap EV Partially regulated voltage, according to converter design and control Partially decoupled converter VE gap in intermediate state Three operating regimes, with the EV gap in three possible magnetic states Regulated voltage Open air gap EV Partially regulated voltage, according to the design and control of the converter Partially decoupled converter VE gap in intermediate state Totally decoupled converter Air gap EV closed

The choice of embodiment of a regulator with two or three operating regimes depends on the context.

Thus, for a network affected by normal transient regimes that are very frequent and whose load is sensitive to voltage variations, the three-speed device is desirable.

Conversely, if the transient regimes are rare, the additional design cost of the regulator is not justified.

Similarly, in the case where the extreme defects do not exist, because of the weakness of the network, a passive command 60 of the air gap EV can be interesting.

Preferably, the control 60 controls the DC source 8 and the voltage converter 4 in a coordinated manner.

As schematically shows figure 7 the command 60 sends a voltage regulation setpoint 601 to the electronic converter 4, and a regulation setpoint 602 to the source 8.

The control of the intermediate state of the air gap EV is done by the current variation in the winding 6, the current comprising a DC component and harmonic components. The source 8 may also advantageously comprise a current converter.

The case of the embodiment of the device by an assembly having three operating speeds can therefore be done with an intelligent control 60 which manages the operations of a voltage converter and a current converter.

In any case, the converter 4 must be decoupled quickly from the network when a fault arises.

As shown in figure 8A all protection devices are faced with the same difficulty of predicting the evolution of the current, from a current variation di / dt significant in a relatively short time, typically of the order of 1 ms. It is necessary to decouple the voltage converter in 1 ms, otherwise it is destroyed by the short circuit.

The Figure 8B shows indeed that it can be a normal transient regime (network operation, load variation, etc.), and in this case there is a return to a normal regime in a time typically of the order of a few milliseconds.

On the contrary, Figure 8C shows that the intensity can be extreme (from 5 to 10 In or more) and alternative with a period corresponding to the period of the network voltage, for example 20ms, and therefore correspond to a defect.

One of the advantages of a regulator 10 according to the invention is to size the power of the voltage converter for the purpose of regulation only, whatever the amplitude and the duration of the defects, in particular to reduce the fluctuations of voltages, the distortions harmonics, the effects of "flicker", and even offset all or part of the voltage dips.

The source 8 is sized to provide the permanent ohmic losses of the winding 6 and to hold the transient fast switching of the air gap EV transient situation which is also represented on the Figure 2C .

The choice of the ratio of the number of turns of the first coil 1 to the number of turns of the second coil 7 makes it possible to optimize the cost of the voltage converter 4 by adapting to the performance of the electronic equipment on the market, but also by benefiting from advances in switching speed (> kHz), withstand voltage (> kV) and withstand current (> kA).

The number of turns of the winding 6 is related to the characteristics of the circuit 2 to obtain a speed of control of the air gap EV of the order of one millisecond for a 50 Hz or 60 Hz industrial network.

For exemple :

Performance of the single-phase regulator

Single-phase network voltage 11,5kV Serial voltage regulation + or - 10% Rated current 30A Three-phase equivalent power 1MVA

Electronic converters

Characteristic of IGBT switches 1200A, 2500V EV command time constant 1ms

Examples of regulator sizing

Hole diameter 5 10 to 25cm Number of winding turns 6 5 to 20 Number of turns of the first coil (alternative) 1 150 to 200 Number of turns of the second coil (converter) 7 20 to 40 Thickness of the third core 3 10 to 30cm As the size of the magnetic circuit 2 increases, the area of a hole 5 increases faster than its perimeter. This results in the advantage of being able to choose a current density in the winding 6 sufficiently small to reduce the permanent ohmic losses, when the airgap EV is open.
The Figure 9A and the Figure 9B specify some characteristics of the first core 21 (also referenced by N _R ), the second core 22 (also referenced by N _U ) and the third core 3 (also referenced by N _EV ).

As shown in Figure 9A in the normal control regime, the first core 21, a possible section reduction 210 and the second core 22 must not be magnetically saturated.

The magnetic circuit 2 must be closed to ensure good coupling between the second coil 7 of the converter 4 and the first coil 1. It is therefore necessary to avoid the mechanical gaps along the flow path F _A (as also represented on the Figure 2A ).

In transient conditions, and especially during extreme faults, it is essential to avoid mechanical gaps along the flow path F _C (as shown in FIG. Figure 2B ), to protect the voltage converter 4. The third core 3 must never be saturated during these defects.

However, under transient conditions, and even more so during extreme faults, the first core 21 may be saturated in order to limit the magnetic flux. For this purpose, the first core 21 may include a section reduction 210.

In another embodiment shown in the Figure 9B , the excess flow following the transient or fault can be channeled by a complementary core 220 connected by at least one gap 221 to the magnetic circuit 2. The first coil 1 then surrounds the cores 21 and 220.
The figure 10A represents an equivalent circuit diagram of the regulator 10, with impedances L _NEV , L _NU and L _NR respectively representative of the nuclei N _EV (3), N _U (22) and N _R (21) of the Figure 9A .

As shown in figure 10B in normal operation, the air gap EV is open, the inductance L _NEV of the third core 3 is of low value. The voltage converter 4 regulates the voltage U by compensating for the voltage drop in the inductance L _NEV .

As shown in Figure 10C in intermediate mode, the air gap EV is not completely closed. The current of the network (of intensity between 1 to 3 In) flows partly by the saturable inductance L _NR and partly in the branch composed of the inductance L _NEV (controlled by the source 8 of direct current I ), in series with the converter 4 delivering the voltage U (for an intensity of 0 to 2 In, depending on the performance of the source 8 and the converter 4).

As shown in figure 10D in fault mode (the intensity of the current in the network is between 3 to 10 In for example), the air gap EV is closed and the inductance L _NEV limits the current in the voltage converter 4. This current is then lower than In, or very low, depending on the sizing and operating choices of the regulator. Preferably, the second coil is short-circuited to contribute to the opening 70 of the core 22 (as shown schematically on the figure 3B ): the voltage U represented on the figure 10D is then zero.

As shown in figure 11 for the regimes where the first core 21 is saturated, and to prevent the short-circuit voltage drop ΔVcc from being too great and / or too non-linear, it is possible to reduce the section 21 of the first core 21 in a manner which favors eddy current losses, i.e. currents induced by magnetic induction variations, by fabricating the circuit board 2 by a superposition of magnetic sheets 28. In another embodiment, the plate can also ensure this dissipative energy function by electromagnetic losses using suitable materials. Conversely, it may be desired to increase the voltage drop ΔVcc, since the increase of ΔVcc makes it possible to limit the fault current. The regulator 10 thus comprises a function for limiting the fault current.

Two embodiments are presented here to obtain this result.

The figure 12 shows that according to a first embodiment, the first coil 1 consists of a first part 1a, wrapping around the first core 21, and a second part 1b, winding in the same winding direction, around a part of the circuit 2, called the yoke, between the first core 21 and the third core 3, for example in the vicinity of the holes 5.

In normal operation, the third core 3 is opened by the air gap EV, and the inductance L1b of the second part 1b of the first coil 1 is of low value. It introduces a low voltage drop ΔVcc which can be compensated by the voltage converter 4.

In the fault regime, the inductances L1a and L1b of the parts 1a and 1b of the coil 1 are traversed by the same flux F _C which closes by the third core 3. The voltage drops ΔVcc depend on the number of turns of the parts 1a and 1b of the first coil 1 and are added in parts 1a and 1b according to the square of the numbers N1a and N1b of turns, namely $${\left(\mathrm{NOT}\mathrm{1}\mathrm{at}+\mathrm{NOT}\mathrm{1}\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">b</figure-callout>}\right)}^{\mathrm{2}}\mathrm{.}$$

The figure 13 , showing a longitudinal section, seen from above, of the circuit 2, shows that according to a second embodiment, to increase the voltage drop ΔVcc without changing the number of turns, it is necessary to increase the flow F _C , in particular by increasing the section of the first core 21.

For this purpose, the circuit 2 comprises an auxiliary magnetic circuit 200 comprising a frame comprising a core 212 and a core NF, parallel to each other and to the first core 21, and a mechanical air gap EM.

• du premier noyau 21, de section similaire au premier noyau 21 décrit jusqu'à présent, et
• du noyau 212.

The first reel 1 wraps around

• the first core 21, similar in section to the first core 21 described so far, and
• of the core 212.

The increase in flux F _C in the first coil 1 does not therefore require increasing the section of the first core.

Under normal conditions, the flow F _A is negligible in the circuit 200, because of the mechanical air gap EM.

In the fault mode, the flux F _C in excess of the saturation level of the first core 21 closes in the circuit 200.

The voltage drop ΔVcc1, due to the first core 21, is increased by ΔVcc2, due to the auxiliary circuit 200 (ΔVcc2 is adjustable by the mechanical gap EM).

Another embodiment also making it possible to limit the fault current consists in adding in series with the regulator a separate inductance of the latter.

As shown in figure 14 in normal operation, the voltage regulator can compensate for the voltage drop in this series inductance.

The figure 15 shows the relation between the effective voltage across the load and the effective current of the regulator, when a limiting function is provided by the regulator or by a separate inductance.
It is understood that to optimize the construction of the regulator, the skilled person may prefer another arrangement of the windows 23 and 24 made with the cores and yokes, to facilitate for example the connection to the output terminals, or to meet the requirement of resistance to dielectric tests (lightning shock).

Similarly, the choice of a dry insulation (for example by an epoxy resin) or of an oil insulation (by impregnated paper) can lead to arrange the windows 23 or 24 in a different way than that presented schematically in the FIGS.

Finally, it is understood that the realization of a multiphase regulator or regulator-limiter, and in particular three-phase, can be based on the grouping of several identical single-phase units or on the design of a multiphase magnetic circuit, in the rules of the art known to those skilled in the art. One of the aims of such an embodiment is to reduce the mass and bulk of the magnetic circuit. Another goal it may be to obtain different performances in direct mode and in zero sequence mode, especially when the sources of voltage disturbances and / or faults are different in these modes, in particular because of the types of grounding of the AC network.

Claims (10)

1. Voltage regulator (10) adapted to be connected in series between firstly an alternating source (S) and secondly a load (C) comprising
   a magnetic circuit (2) comprising a first core (21) and a second core (22),
   at least a first inductive coil (1) wound at least partially around the first core (21) and connected firstly to the alternating source (S) and secondly to the load (C), and
   at least one voltage converter (4) comprising a second coil (7) wound around the second core (22),
   the regulator (10) being characterised in that the circuit (2) comprises
   a third decoupling core (3) and
   a virtual air gap (EV), the virtual air gap (EV) comprising

   - at least one pair (50) of holes (5) in the third decoupling core (3), and

   - a winding (6) being wound between the holes (5) in each pair (50) of holes (5) and connected to a DC source (8),

   the regulator (10) operating between at least two states, namely:

   a first state in which the virtual air gap (EV) is open by magnetically saturating the third decoupling core (3), the magnetic flux in the third core (3) being low and the second coil (7) of the converter (4) being coupled to the first coil (1), such that the regulator can regulate a voltage in the load (C), and

   a second state in which the virtual air gap (EV) is closed, the magnetic flux in the virtual air gap (EV) of the third core (3) being high, such that the converter (4) is decoupled from the first coil (1).
2. Regulator according to claim 1, also being adapted to operate in a third state in which the virtual air gap (EV) is partially opened by partially desaturating the third core (3) such that the converter (4) is partially decoupled from the first coil (1).
3. Regulator according to one of claims 1 and 2, comprising a passive or active or smart control (60) of complete or partial opening or complete or partial closing of the virtual air gap (EV).
4. Regulator according to claim 3, in which the passive control (60) comprises a permanent connection between the DC current source (8) and the winding (6).
5. Regulator according to claim 3, in which the active control (60) comprises a switch (61) controlled by a detector (62) between the DC source (8) and the winding (6).
6. Regulator according to claim 3, in which the smart control (60) controls a DC current source (8) comprising a variator (81) connected to the winding (6).
7. Regulator according to one of claims 1 to 6, in which the first core (21) comprises

   - a cross-section reducer (210) or

   - a complementary core (220) connected by a mechanical air gap (221) to the magnetic circuit (2).
8. Regulator according to one of claims 1 to 7, in which the first coil (1) is composed of a first part (1a) being wound around the first core (21), and a second part (1b) being wound around a part of the circuit (2) between the first core (21) and the third core (3), the regulator thus performing a current limitation function.
9. Regulator according to one of claims 1 to 7, in which the circuit (2) comprises an auxiliary magnetic circuit (200) comprising a frame comprising at least one core (212) and a mechanical air gap (EM), the first coil (1) being wound around the first core (21) and the core (212) of the frame, the regulator thus performing a current limitation function.
10. Regulator according to one of claims 1 to 9, adapted to be put into series with a current limiting coil.

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