FR3079083A1 - METHOD FOR CONTROLLING AN ELECTRICAL TRANSMISSION LINK INCLUDING A CONTINUOUS HIGH VOLTAGE LINE - Google Patents

Abstract

The invention relates to a method for controlling an electrical transmission link (3) between first and second AC voltage buses (11, 21) comprising a high-voltage direct line (320), first and second AC / DC converters. (321, 322) connected to the high-voltage direct line (320), comprising: -reclaiming an applied reference power value (Pdc0) on a converter (321, 322); the recovery of the instantaneous values V1 and V2 of the voltages on the first and second buses; the set active power of the first or second converter is modified by a value including a term APdc, so as to impose new dynamics on the first and second zones, with: ΔPdc = (M1 * M2) / (M1 + M2 ) * (((Pm1 - Pl1 - D1 * dδ1 / dt) / M1) - ((Pm2 - Pl2 - D2 * d2 / dt) / M2) - (λδ * (δref - δ) + λω * Δω))

Description

The invention relates to control strategies for electrical networks, in particular control strategies for ensuring the stability of electrical networks including at least one AC power line and one DC power line connecting buses between AC voltage areas.

The document 'Inelfe, Europe's first integrated Onshore HVDC interconnection', published by P. Labra Francos et al in 2012 by ΙΊΕΕΕ, describes the establishment and operation of a high voltage link including an alternative power line and a power line continuous, connected in parallel between France and Spain. The high voltage DC power line has a respective AC / DC converter at each of its ends. These converters are voltage controlled (designated by the term VSC converters in the literature), which allows independent control of the active power on the DC side and the reactive power on the AC side.

In normal operation, the high voltage direct current line is controlled by means of its converters, in order to emulate the behavior of an alternative transmission line by means of a virtual line reactance. The active setpoint power transmitted on the continuous transmission line is then fixed as a function of the phase shift between the nodes at the ends of this line and as a function of the voltages on these nodes.

A dysfunction at the terminals of such a link is sometimes manifested by a transient power imbalance, some generators accelerating and others decelerating. We then observe an evolution of the phase shift between the nodes of the network. If the system cannot return to equilibrium after a disturbance, it can become unstable because the power generators can rotate asynchronously and the exchange of power can no longer be ensured.

In the event of a malfunction detected on the alternative power line, the continuous transmission line is operated while maintaining a reactance of the fixed virtual line. Indeed, the manufacturer of the line having to guarantee its stability in the event of a malfunction, important feasibility studies must be carried out on the stability of the line during transient operation. Maintaining the reactance of the virtual fixed line greatly simplifies such a stability study.

However, such a system has further reduced stability. The time available to remove a malfunction on the network before causing desynchronization of the nodes at the ends of the line is thus

ICG011221 EN Depot Texte.docx still too small. Furthermore, such a system does not make it possible to impose new dynamics on the areas of alternating voltage on either side of the transmission link.

The invention aims to solve one or more of these drawbacks. The invention thus relates to a method for controlling an electrical transmission link between first and second alternating voltage buses connected respectively to first and second alternating voltage zones, the transmission link comprising a direct high voltage line, a first AC / DC converter connected on the one hand to the first bus and on the other hand to the DC high voltage line, a second AC / DC converter connected on the one hand to the second bus and on the other hand to the DC high voltage line , the process comprising:

-the recovery of a setpoint active power value applied to the first or to the second converter;

the recovery of the instantaneous values V1 and V2 of the voltages on the first and second bus respectively;

-in which the active reference power of the first or of the second converter is modified by a value including a term APdc, so as to impose new dynamics on the first and second zones, with: APdc = (Ml * M2) / (M1 + M2) * (((Pmi - PU - DI * d <51 / dt) / Ml) - ((Pm2

- P12 - D2 * dô2 / dt) / M2) - (λδ * (ôref - δ) + λω * Δω))

With M1 and D1 the electric inertia and damping of an electric machine equivalent to the first zone, M2 and D2 the electric inertia and damping of an electric machine equivalent to the second zone, δΐ the angle of the voltage on the first bus, δ2 the angle of the voltage on the second bus, ref an initial phase shift value between the voltages of the first and second bus, δ the phase shift between the voltages of the first and second bus for the instantaneous values recovered , λδ and λω of the amplification gains, Pm1 the mechanical power of the electric machine equivalent to the first zone, PU an electric charge equivalent to the first zone, Pm2 the mechanical power of the electric machine equivalent to the second zone, PI2 a electrical charge equivalent to the second zone.

The invention also relates to the following variants. Those skilled in the art will understand that each of the characteristics of the following variants can be combined independently with the above characteristics, without however constituting an intermediate generalization.

According to a variant, the method comprises:

-the determination that the first zone operates as a generator;

ICG011221 EN Text Depot.docx with λ _δ = Ml * Κδ and λ _ω = Ml * Κω, with Κδ = ωη ² and λω = 2 * ξ * ωη, with ωη a frequency between 0.3 and 0.7 Hz and ξ a damping factor between 0.4 and 0.8, the second zone being assimilated to an infinite network.

According to another variant, the first or the second AC / DC converter is controlled so as to emulate a dynamic virtual admittance Y33 by transiently modifying its active target power value by a value including a term APdcl, with:

APdcl = Y33 | 71 || 72 | * Sin <5

Y33 being modified as a function of the values V1 and V2, as a function of the evolution of the phase difference δ, as a function of the pulsation differences between the voltages of the first and second bus, or as a function of a disturbance amplitude.

According to yet another variant, said first and second converters are voltage source converters.

According to yet another variant, the transmission link comprises an alternating high voltage line.

Other characteristics and advantages of the invention will emerge clearly from the description given below, by way of indication and in no way limitative, with reference to the appended drawings, in which:

FIG. 1 is an electrical diagram of a system including a high voltage link capable of implementing the invention;

FIGS. 2 to 4 illustrate the evolution of different parameters according to simulations carried out for the implementation of the invention, for a case of disconnection of the alternative line;

FIGS. 5 to 7 illustrate different parameters in the event of the AC line being disconnected until it is reconnected, with an example of implementation of the invention;

FIGS. 8 to 10 illustrate the evolution of different parameters according to simulations carried out for the implementation of the invention, for another case of fault;

FIG. 11 is a power-angle diagram illustrating the implementation of the invention when the alternative line is disconnected.

Figure 1 is an electrical diagram of a system including a high voltage electrical transmission link 1 capable of implementing the invention. By high voltage is meant here a voltage at least equal to 10kV in service on the link 3. The system here includes the high voltage link 3, a high voltage alternating current zone 1 and a high voltage alternating current zone 2. The zone 1 is connected to an AC node or bus (sometimes designated by the term busbar, for bus bar in English) 11 connected to a

ICG011221 EN Text Depot.docx end of link 3 and zone 2 is connected to a node or AC bus 21 connected to another end of link 3. For the sake of simplification, the system is represented here by assimilating zone 1 to an equivalent machine, and by assimilating zone 2 to a network of constant voltage and frequency (“infinite” network), for a particular case.

The link 3 includes a direct high voltage link 32 here and optionally an alternating high voltage line 31, connected in parallel between the buses 11 and 21. More specifically, the direct high voltage link 32 comprises a direct high voltage line 320, an AC converter / DC 321 connected to the bus 11 and at a first end of the line 320, and an AC / DC converter 322 connected to the bus 21 and at a second end of the line 320. The converters 321 and 322 advantageously have the same electrical characteristics.

The system also includes a control circuit 4, configured to control the converters 321 and 322. The converters 321 and 322 are advantageously voltage source converters. Such converters make it possible to independently regulate their active power and their reactive power. The active power management loop can be fixed to control either the active power injected into the AC network to which the converter is connected, or the DC voltage on line 320 to which it is connected. The reactive power loop can be fixed to regulate either the reactive power injected or absorbed at the connection point at a bus, or the voltage of the AC network to which the converter is connected.

The converters 321 and 322 have the following functions in particular in steady state (the steady state will then correspond to operation in the absence of an electrical fault in link 3): check the voltage on line 320, control the bidirectional flow of power active on line 320, and control the reactive power injected or absorbed at the connection point. In steady state, the control circuit 4 is for example configured to control the converter 322 as a master by controlling the voltage level on the line 320, the converter 321 then operating as a slave by controlling the active power transmitted on the line 320. The master converter will drain the active power controlled by the slave.

By its commands, the control circuit 4 is advantageously configured to emulate virtual parallel admittance 33, in parallel with line 31 and link 32.

Initially, the control circuit 4 is configured to transmit a command of active power of reference on the first or the second

ICG011221 EN Depot Texte.docx converter, whose value is retrieved. The power PdcO is transmitted in the regime established by the link 32. The instantaneous values V1 and V2 of the voltages on the first and second bus are recovered.

According to a first aspect of the invention, the control circuit 4 is configured to then transmit an active reference power Pref (typically, Pref is the power setpoint applied to the control of the converter operating in slave mode in the example cited previously) defined as follows:

Pref = + Pdc0 APdc1

APdcl is a term included in the active power transmitted via virtual parallel admittance 33 during a transient phase, for example to impose a new dynamic on zones 1 and 2. APdcl can be defined as follows:

VI * V2

APdcl = * sin <5 = Y33 | V1 || V2 | * sin <5

X 3 3

With X33 the line reactance emulated by the control circuit 4, Y33 the line admittance emulated by the control circuit 4 for the admittance 33, V1 the voltage on the bus 11, V2 the voltage on the bus 21, and δ the phase shift between the voltages of buses 11 and 21.

The control circuit 4 is for example configured to recover the following information, for example by means of measurement devices at the level of buses 11 and 21:

the instantaneous values V1 and V2 of the voltages on the first and second bus;

the instantaneous value δ of the phase shift between the voltages of the buses 11 and 21;

-the last value ôref of the phase shift between the voltages of buses 11 and 21 in the absence of a malfunction on the system (in the absence of a malfunction, δ = ôref);

-detection of a malfunction on the system;

-electric pulsation ω on each bus.

In the event of an electrical fault, disturbance (for example short circuit, change of mechanical power references for electrical machines, temporary loss of one pole of link 32) either on transmission link 3, or on bus 11, or on bus 21, the control circuit 4 is configured to automatically modulate the active reference power of the first or of the second converter.

The control circuit 4 can be configured to communicate with the buses 11 and 21 to recover the values of phase angles, and the values of

ICG011221 EN Text Depot.docx voltage on these buses. The pulsation of a bus can be determined either by averaging the pulses of the machines connected to this bus, or by measuring the pulsation on this bus.

For example following an electrical fault, the control circuit 4 modulates the active power setpoint applied to the converters 321 and 322. The variation in active setpoint power is notably fixed:

-as a function of the evolution of the phase difference between the voltages of buses 11 and 21. The evolution of the phase difference can for example be measured by the value (<5- <5re /), representative the evolution of the phase difference after the electrical fault. Such taking into account the evolution of the phase difference makes it possible to define the oscillation frequencies between the nodes 11 and 21;

either according to the electrical pulsation of the voltage at the level of the bus 11, here assimilated to an electrical machine. Such taking into account the pulsation on the bus 11 makes it possible to take account of the frequency variation between the buses 11 and 21, in order to dampen the oscillations between the two zones 1 and 2 (in accordance with Figure 1);

- or as a function of a pert disturbance of a certain amplitude. A disturbance is a variation in power, for example a variation in mechanical power of the machine equivalent to zone 1, or a variation in load in this zone.

The line admittance control law Yv emulated by the control circuit 4 for admittance 33 for example to follow an electrical fault (or a network disturbance), can for example take the following form for the particular case previously presented:

171 * 177

APdc = Pm - PI - PdcO - * sin δ + λ _δ * (ôref - δ) + λ _ω * Δω

X31

71 * 72. "

- * sin δ

X31 being a first term which makes it possible to quickly compensate for network disturbances such as for example a load variation inside an area;

- λ _δ * (ôref - δ) being a second term which makes it possible to provide synchronization power in the two zones and to define the frequency of the inter-zone oscillations;

- λ _ω * Δω being a third term which makes it possible to provide a damping power as a function of Δω and to control the damping of inter-zone oscillations.

ICG011221 EN Text Depot.docx

It can be expected that the control law takes into account only one or more of the first to third terms according to a first aspect of the invention.

The control law of the control circuit 4 thus makes it possible to increase the stability of the system during the appearance of an electrical fault or a disturbance, by dynamically modifying the admittance of line emulated during such an electrical fault. . The control law makes it possible in particular to reduce the increase in the kinetic energy of the generator (s) during a fault, and increases the deceleration energy available for the generator after the fault has been eliminated. This translates into an increase in the transient stability margin. The control law makes it possible to control any electromechanical oscillations of the generator occurring after the fault has been rectified.

Advantageously, the control circuit 4 can control the converters 321 and 322, so as to temporarily absorb the oscillations in the event of detection of a malfunction.

The link 32 has a very high dynamic compared to the alternative network. Furthermore, the link 32 provided with the converters 321 and 322 makes it possible to carry out independent control of the active and reactive powers transmitted on the line 320. Each converter 321 and 322 can therefore behave like the equivalent of a current source with a control independent of active and reactive power compared to the alternative network. Assuming that the losses are negligible on line 320, we can use the injection model, according to which an active power injected on line 320 by the converter 321 is equal to an active power drawn by the converter 322 on this line 320 .

We can then deduce the following equation in steady state:

do ^{2 do}

M - = ~ + D —— = Pm - PI - PdcO - Pac d ² t dt

With M the equivalent inertia of the system, D the equivalent damping of the system, Pm the mechanical power applied to the equivalent machine assimilated to zone 1, PI the electric power taken by an equivalent load from zone 1 in Figure 1, PdcO the active power initially transmitted by link 32 in steady state, and Pac the active power initially transmitted by line 31 in steady state.

If the control circuit 4 controls the transmission of an active power APdc via the virtual parallel admittance 13, the previous relationship becomes the following dynamic equation:

dô ² dô VI * V2 + D —— = Pm - PI - PdcO - Pac - sinô d ² t dt X33

ICG011221 EN Text Depot.docx

X31 corresponds to the reactance of line 31, X33 corresponds to the reactance of virtual line 33.

The dynamic equation can be reformulated as follows:

(dô \ - = Δω) dt) c / Δω dô VI * V2

I M -; - 1- D —— = Pm - PI - PdcO --——— sinô - Yv * VI * V2 * sinô

V dt dt X31

The control parameter corresponds to the power value passing through the virtual admittance 33. To control the system via the virtual admittance value, it is possible for example to use a feedback technique by linearization can be adopted: the goal is to transform the dynamics of the nonlinear system from a partially linear system, through feedback. The power passing through the virtual admittance 33 can be formulated as follows:

F1 * F2

Yv | VI | | F21 * sinô = Pm - PI - PdcO --——— sinô + M * Kô * (ôref-δ) + (Μ * Κω - D) * Δω

A 31

Κδ and Κω being gains, making the system comparable to a damped oscillating system. By combining this equation with the previous dynamic equation, the dynamics of the closed loop system can be defined as follows:

fdô - = Δω) dt) c / Δω

Vdt ^{- =} ~ λδ ( ^δΓβ ί ~ ^δ ) ~ ^ ω ^Δω

We thus obtain a linear system.

By carrying out the change of variable x1 = (ôref-ô) and χ2 = Δω, we can formulate the system as follows:

xll 10 11 fold x'2-l L-K5 -KùJ tx2J

The dynamics of the closed loop system can thus be chosen by selecting the values Κδ and Κω. The characteristic polynomial of this state matrix can be identified by a second order system:

s ² + Kco * s + Κδ = λ ² + 2 * ξ * ωη * λ + ωη ²

We can then calculate the gains Κδ and Κω to define the desired natural frequency ωη and the desired damping coefficient for the system:

Κδ = ωη ² Κω = 2ξ * ωη

ICG011221 EN Text Depot.docx

Advantageously, ωη is a frequency between 0.3 and 0.7 Hz, preferably between 0.4 and 0.6 Hz. Advantageously, ξ is a damping factor between 0.4 and 0.8, preferably between 0.5 and 0.7.

These calculations were based on the assumption that bus 21 is connected to an infinite network. By carrying out similar calculations for the case where zone 2 corresponds to an equivalent machine, it can easily be demonstrated that the gains can be defined identically to the previous case.

For a more generic case, the active target power of the first or of the second converter is temporarily changed by a term including an APdc term, so as to impose new dynamics on the first and second zones, with:

APdc = (Ml * M2) / (M1 + M2) * (((Pmi - Pli - DI * dôl / dt) / Ml) - ((Pm2 - P12 - D2 * dô2 / dt) / M2) - (λδ * (ôref - δ) + λω * Δω))

With M1 and D1 the electric inertia and damping of an electric machine equivalent to zone 1, M2 and D2 the electric inertia and damping of an electric machine equivalent to zone 2, <51 the angle of the voltage on the bus 11, <52 the angle of the voltage on the bus 21, λδ and λω the amplification gains defined previously, Pm1 the mechanical power of the electric machine equivalent to zone 1, PU an electric charge equivalent to zone 1, Pm2 the mechanical power of the electric machine equivalent to zone 2, PI2 an electrical charge equivalent to zone 2.

The active setpoint power of the first or second converter can also be temporarily changed by a term including an APdcl term, with:

APdcl = Y33 | V1 || V2 | * Sin <5

Y33 being modified as a function of the values V1 and V2, as a function of the evolution of the phase difference <5, as a function of the pulsation differences between the voltages of the first and second bus, or as a function of a disturbance amplitude .

The diagrams in FIGS. 2 to 4 illustrate the evolution of different parameters according to simulations carried out for the implementation of the invention, for a first case of fault.

The following assumptions have been taken into account:

-a generator receiving a mechanical power of 500MW, and an electrical charge of 100MW connected to the bus 11. The generator connected to the bus 11 has an inertia of 3.5 s;

ICG011221 EN Text Depot.docx

-a generator receiving a mechanical power of 100MW, and an electrical load of 500MW connected to the bus 21. The generator connected to the bus 21 has an inertia of 3 s;

In steady state, the power transmitted between buses 11 and 21 is distributed at 200MW for line 31, and 200MW for link 32. We will assume a phase shift of 30 ° between the voltages of buses 11 and 21 in steady state, and a line 320 with a length of 200km.

For the implementation of the invention, values of natural frequency ωη of 0.5 Hz and of damping factor ξ of 0.6 were chosen.

The electrical fault studied here is a three-phase fault on line 31, with a duration of 300 ms. This fault occurs at time t = 1 s on the diagrams. The dotted curves correspond to a link according to the state of the art, without dynamic management of a virtual admittance 33 after the electrical fault, with maintenance of the active power on line 320 at the same setpoint as before default. The dashed-point curves correspond to an implementation of the invention with management of virtual admittance 33 by limiting the power on the line 320 to 300MVA. The solid line curves correspond to an implementation of the invention with management of virtual admittance 33 by limiting the power on the line 320 to 600MVA.

The diagram in FIG. 2 illustrates the phase shift (in °) between the voltages of buses 11 and 21. The diagram in FIG. 3 illustrates the difference in pulsation (per unit) between buses 11 and 21 of the network. The diagram in Figure 4 illustrates the active power transmitted on line 320.

It can be seen that in the absence of dynamic virtual admittance during an electrical fault, by maintaining just a constant active power on the link 320, the phase shift between the buses 11 and 21 reaches a very high amplitude and presents significant oscillations after the fault has been eliminated, resulting in desynchronization between buses 11 and 21. The pulse difference between buses 11 and 21 is also very high in this configuration, this pulse difference also having poorly damped oscillations after the cancellation electrical fault.

Even by limiting the active power on the line 320 to 300MVA, the amplitude of the phase shift between the voltages of buses 11 and 21 and the amplitude of the pulse difference between buses 11 and 21 are greatly reduced. The oscillations of the phase shift and of the pulse difference are moreover very quickly absorbed, even after the fault has been eliminated. The active power on line 31 is also limited to 450MW during the electrical fault.

ICG011221 EN Text Depot.docx

By limiting the active power on line 320 to 600MVA, the amplitude of the phase shift between the voltages of buses 11 and 21 and the amplitude of the pulse difference between buses 11 and 21 are even more greatly reduced. The oscillations of the phase shift and of the pulse difference are damped even faster, even after the fault has been eliminated. The active power on line 31 is also limited to 350MW during the electrical fault.

It is noted that with the implementation of the invention for such a defect, the line 320 makes it possible to ensure synchronism between the zones 1 and 2, despite the cut on the line 31.

Maintaining stability and phase shift is best illustrated by the diagrams in FIGS. 5 to 7, corresponding to the implementation of the invention with a limitation of active power to 600MVA on line 320. Line 31 is disconnected very quickly at t = 1 s, then reconnected at t = 8s.

Figure 5 illustrates the active power on line 320 in solid lines and the broken line represents active power on line 31. Figure 6 illustrates the phase difference (in °) between the voltages of buses 11 and 21 on the same time interval. FIG. 7 illustrates the difference in electrical pulsation (per unit) between the buses 11 and 21 over the same time interval.

The diagram in FIG. 6 illustrates that fairly quickly after the electrical fault, the phase difference between the voltages of buses 11 and 21 stabilizes at a value fairly close to that preceding the fault, despite the disconnection of line 31. The diagram of FIG. 7 illustrates that fairly quickly after the electrical fault, the pulse difference between the buses 11 and 21 converges to 0, despite the disconnection of line 31. The two zones 1 and 2 therefore remain synchronous despite the disconnection of the line 31.

FIG. 11 is a power-angle diagram illustrating the implementation of the invention during the first case of malfunction. X31 corresponds to the reactance of line 31, X33 corresponds to the reactance of virtual line 33. At point 1, the system is initially in equilibrium, with a phase shift δθ between zones 1 and 2. During the appearance from the electrical fault, the power transmitted on line 31 becomes zero. Upon detection of the electrical fault, virtual admittance 33 is activated, so as to transmit more power on line 320. Thus, we go to point 2 of the diagram, keeping the phase shift δθ. The rotor of the generator assimilated to zone 1 sees its speed increasing until reaching a phase angle angle eclosed at point 5. The kinetic energy acquired by the rotor is however limited, due to the

ICG011221 EN Depot Texte.docx electric power transmitted by virtual admittance 33, which increases the stability of the system.

The electrical fault is then eliminated. With the power again supplied by line 31, we then go to point 8 on the diagram, corresponding to the cumulation of a power on line 31 and by virtual admittance 33. From point 8, the rotor corresponding to the generator in zone 1 slows down, with an increase in the phase shift angle between zones 1 and 2.

Point 10 corresponds to the phase shift limit guaranteeing the stability of the system. It can be seen that the limit phase shift angle uu ’is greater than the limit phase shift angle ôu (point 9 of the diagram) in the absence of implementation of the invention.

The diagrams in FIGS. 8 to 10 illustrate the evolution of different parameters according to simulations carried out for the implementation of the invention, for a second case of fault.

The assumptions are identical to those of the first fault. The electrical fault here is a short circuit in zone 2, inducing a multiplication of the electrical charge by a factor of 3 for a period of 150ms.

This fault occurs at time t = 1 s on the diagrams. The dotted curves correspond to a link according to the state of the art, without dynamic management of a virtual admittance 33 after the electrical fault, with maintenance of the active power on line 320 at the same setpoint as before default. The dashed-point curves correspond to an implementation of the invention with management of virtual admittance 33 by limiting the power on the line 320 to 300MVA. The solid line curves correspond to an implementation of the invention with management of virtual admittance 33 by limiting the power on the line 320 to 600MVA.

The diagram in FIG. 8 illustrates the phase shift (in °) between the voltages of buses 11 and 21. The diagram in FIG. 9 illustrates the difference in pulsation (per unit) between buses 11 and 21 of the network. The diagram in Figure 10 illustrates the active power transmitted on line 320.

It can be seen that in the absence of dynamic virtual admittance during an electrical fault, by maintaining just a constant active power on the link 320, the phase shift between the tenions of the buses 11 and 21 increases very rapidly and is not limit. The pulse difference between buses 11 and 21 also increases rapidly and without limitation. This leads to a desynchronization between zones 1 and 2.

Even by limiting the active power on the line 320 to 300MVA, the amplitude of the phase shift between the voltages of buses 11 and 21 and the amplitude of the pulse difference between buses 11 and 21 are limited. Oscillations of the

ICG011221 EN Depot Texte.docx phase shift and the pulse difference are also very quickly amortized.

By limiting the active power on the line 320 to 600MVA, the amplitude of the phase shift between the voltages of buses 11 and 21 and the amplitude of the difference in pulsation between buses 11 and 21 are even more greatly reduced. The oscillations of the phase shift and the pulse difference are damped even faster.

For such a type of fault, the implementation of the invention makes it possible to benefit from a power reserve to avoid stalling the network in 10 cases of fault.

Claims (5)

1. Method for controlling an electrical transmission link (3) between first and second alternating voltage buses (11, 21) respectively connected to first and second alternating voltage zones, the transmission link comprising a high voltage line DC (320), a first AC / DC converter (321) connected on the one hand to the first bus (11) and on the other hand to the DC high voltage line (320), a second AC / DC converter (322) connected on the one hand to the second bus (21) and on the other hand to the direct high voltage line, the method comprising: -recovery of an active power value of setpoint applied (PdcO) on the first or on the second converter (321, 322); the recovery of the instantaneous values V1 and V2 of the voltages on the first and second bus respectively; -in which the active reference power of the first or of the second converter is modified by a value including a term APdc, so as to impose new dynamics on the first and second zones, with: APdc = (Ml * M2) / (M1 + M2) * (((Pmi - Pli - Dl * δδ1 / δί) / Μ1) - ((Pm2 - ΡΓ2 - D2 * dô2 / dt) / M2) - (Λδ * (ôref - δ) + λω * Δω)) With M1 and D1 the electric inertia and damping of an electric machine equivalent to the first zone, M2 and D2 the electric inertia and damping of an electric machine equivalent to the second zone, δΐ the angle of the voltage on the first bus, δ2 the angle of the voltage on the second bus, dref an initial value of phase shift between the voltages of the first and second bus, δ the phase difference between the voltages of the first and second bus for the instantaneous values recovered , λδ and λω of the amplification gains, Pm1 the mechanical power of the electric machine equivalent to the first zone, PU an electric charge equivalent to the first zone, Pm2 the mechanical power of the electric machine equivalent to the second zone, PI2 a electrical charge equivalent to the second zone. 2. Control method according to claim 1, comprising: -the determination that the first zone operates as a generator; With λ _δ = Ml * Κδ and λ _ω = Ml * Κω, with Κδ = ωη ² and Αω = 2 * ξ * ωη, with ωη a frequency between 0.3 and 0.7 Hz and ξ a damping factor between 0.4 and 0.8, the second zone being assimilated to an infinite network. 3. The control method according to claim 1 or 2, wherein the first or the second AC / DC converter is controlled so as to emulate a dynamic virtual admittance Y33 by transiently modifying ICG011221 EN Depot Texte.docx its active power target value of a value including an APdcl term, with: APdcl = Y33 | V1 || V2 | * Sin <5 Y33 being modified as a function of the values V1 and V2, as a function of the evolution 5 of the phase difference δ, as a function of the pulsation differences between the voltages of the first and second bus, or as a function of a disturbance amplitude . 4. Control method according to any one of the preceding claims, in which said first and second converters (321, 10 322) are voltage source converters. 5. Control method according to any one of the preceding claims, in which the transmission link comprises a high voltage alternating line (31).