Device for controlling a terminal for the compensation of a voltage disturbance

Abstract

Disclosed is a device for controlling a terminal connected in a multi-terminal high-voltage direct current transmission facility, the terminal being able to provide or draw power on the DC part of the facility comprised between an upper power limit and a lower power limit, the device further comprising at least one regulation circuit configured to vary the power provided or drawn by the terminal on the DC part of the facility, as a function of a voltage variation on the DC part of the facility, the device further comprising a limitation circuit configured to limit the variation of the power provided or drawn by the terminal, for a given voltage variation, when the power difference between the power provided or drawn by said terminal and the upper power limit or the lower power limit becomes smaller than a determined value.

Claims

1. A device for controlling a terminal connected in a multi-terminal high-voltage direct current transmission facility, the terminal being connected between a first AC power supply network and a DC part of said facility, the terminal configured to provide or draw power on the DC part of the facility comprised between an upper power limit and a lower power limit, the device further comprising at least one regulation circuit configured to vary the power provided or drawn by the terminal on the DC part of the facility, as a function of a voltage variation on the DC part of the facility, the device further comprising a limitation circuit configured to limit the variation of the power provided or drawn by the terminal, for a given voltage variation, when the power difference between the power provided or drawn by said terminal and the upper power limit or the lower power limit becomes smaller than a determined value.

2. The control device according to claim 1, wherein the regulation circuit is configured to increase the power provided or to decrease the power drawn by the terminal on the DC part of the facility in the event of a voltage drop on the DC part of the facility.

3. The control device according to claim 2, wherein the limitation circuit is configured to limit the increase in the power provided or the decrease in the power drawn by the terminal on the DC part of the facility, for a given voltage drop, when the power difference between said power provided or drawn by the terminal and the upper power limit is smaller than the determined value.

4. The control device according to claim 1, wherein the regulation circuit is configured to decrease the power provided or to increase the power drawn by the terminal on the DC part of the facility in the event of a voltage increase on the DC part of the facility.

5. The control device according to claim 4, wherein the limitation circuit is configured to limit the decrease of the power provided or the increase of the power drawn by the terminal on the DC part of the facility, for a given voltage increase, when the power difference between said power provided or drawn by the terminal and the lower power limit becomes smaller than the determined value.

6. The control device according to claim 1, wherein the limitation circuit is configured to increase the variation of the power provided or drawn by the terminal on the DC part of the facility, for a given voltage variation, when the power difference between said power provided or drawn by the terminal and the upper power limit or the lower power limit becomes greater than an additional determined value.

7. The control device according to claim 1, wherein the limitation circuit comprises a management circuit configured to allocate to the terminal an upper power compensation limit P.sub.upper and a lower power compensation limit P.sub.lower from maximum and minimum power values provided by the first AC power supply network and from operating power setpoints of the terminal.

8. The control device according to claim 1, wherein the limitation circuit is configured to determine an overvoltage constant g.sup.+and an under-voltage constant g.sup.−, different from the overvoltage constant, associated with the terminal, and wherein the regulation circuit is configured to vary the power provided or drawn by the terminal on the DC part of the facility by application of the linear relation:
ΔP=−g.sup.+Δv.sub.dc if Δv.sub.dc>0 and
ΔP=−g.sup.−Δv.sub.dc if Δv.sub.dc<0 where ΔP is the variation of the power provided or drawn by the terminal, induced by the regulation circuit, Δv.sub.dc is the voltage variation on the DC part of the facility.

9. The control device according to claim 8, wherein the limitation circuit is configured to determine an under-voltage constant g.sup.−smaller than the overvoltage constant g.sup.+when the power difference between the power provided or drawn by the terminal on the DC part of the facility and the upper power limit is smaller than the determined value.

10. The control device according to claim 8, wherein the limitation circuit is configured to determine an overvoltage constant g.sup.+smaller than the under-voltage constant g.sup.−when the power difference between the power provided or drawn by the terminal on the DC part of the facility and the lower power limit is smaller than the determined value.

11. The control device according to claim 8, wherein the limitation circuit comprises a management circuit configured to allocate to the terminal an upper power compensation limit P.sub.upper and a lower power compensation limit P.sub.lower from maximum and minimum power values provided by the first AC power supply network and from operating power setpoints of the terminal, and wherein the limitation circuit comprises a calculator configured to determine an under-voltage constant g.sup.−satisfying the relation: $g^{-}=-\frac{P_{\mathrm{upper}}-P_0}{V_{\mathrm{dc}}^{\lim -}-V_{\mathrm{dc}0}}$ where V.sub.dc.sup.lim−is the set lower voltage limit of the DC part of the facility, V.sub.dc0 is the nominal voltage of the DC part of the facility in the absence of disturbance and P.sub.0 is the power provided or drawn by the terminal in the absence of disturbance.

12. The control device according to claim 8, wherein the limitation circuit comprises a management circuit configured to allocate to the terminal an upper power compensation limit P.sub.upper and a lower power compensation limit P.sub.lower from maximum and minimum power values provided by the first AC power supply network and from operating power setpoints of the terminal, and wherein the limitation circuit comprises a calculator configured to determine an overvoltage constant g.sup.+satisfying the relation: $g^{+}=-\frac{P_0-P_{\mathrm{lower}}}{V_{\mathrm{dc}0}-V_{\mathrm{dc}}^{\lim +}}$ where V.sub.dc.sup.lim+is the set upper voltage limit of the DC part of the facility, V.sub.dc0 is the nominal voltage of the DC part of the facility in the absence of disturbance and P.sub.0 is the power provided or drawn by the terminal in the absence of disturbance.

13. The control device according to claim 1, wherein the facility comprises a plurality of terminals each connected between an AC power supply network and the DC part of said facility, each of the terminals configured to provide or draw power on the DC part of the facility comprised between an upper power limit and a lower power limit that are specific thereto, the regulation circuit being configured to vary the power provided or drawn by each of the terminals on the DC part of the facility, as a function of a voltage variation on the DC part of the facility, the limitation circuit being configured to limit the variation of the power provided or drawn by each of the terminals, for a given voltage variation, when the power difference between the power provided or drawn by said terminals and the upper power limit or the lower power limit that are specific thereto is smaller than a determined value.

14. A multi-terminal high-voltage direct current transmission facility, comprising at least one terminal connected between a first AC power supply network and a DC part of said facility, the terminal configured to provide or draw power on the DC part of the facility comprised between an upper power limit and a lower power limit, the facility comprising a device for controlling the terminal further comprising at least one regulation circuit configured to vary the power provided or drawn by the terminal on the DC part of the facility, as a function of a voltage variation on the DC part of the facility, the regulation circuit comprising a limitation circuit configured to limit the variation of the power provided or drawn by the terminal, for a given voltage variation, when the power difference between the power provided or drawn by said terminal and the upper power limit or the lower power limit becomes smaller than a determined value.

15. A method for controlling a terminal connected in a multi-terminal high-voltage direct current transmission facility, the terminal being connected between a first AC power supply network and a DC part of said facility, the terminal configured to provide or draw power on the DC part of the facility comprised between an upper power limit and a lower power limit, the method comprising: varying the power provided or drawn by the terminal on the DC part of the facility, as a function of a voltage variation on the DC part of the facility; and limiting the variation of the power provided or drawn by the terminal, for a given voltage variation, when the power difference between the power provided or drawn by said terminal and the upper power limit or the lower power limit becomes smaller than a determined value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure will be better understood upon reading the following description of one embodiment of the disclosure given by way of non-limiting example, with reference to the appended drawings, in which:

(2) FIG. 1 illustrates an HVDC facility according to the prior art;

(3) FIG. 2 illustrates the change in the voltage of the DC part of the facility of FIG. 1, in response to the failure of the fourth terminal;

(4) FIG. 3 illustrates the change in the power of the terminals of FIG. 1, in response to the failure of the second terminal;

(5) FIG. 4 illustrates an HVDC facility whose terminals are controlled by a control device according to the disclosure;

(6) FIG. 5 illustrates a control device according to the disclosure;

(7) FIG. 6 illustrates the change in the power of the terminals of FIG. 4 as a function of the voltage of the DC part;

(8) FIG. 7 illustrates the power variations in the terminals of the facility of FIG. 1, controlled by a device according to the prior art;

(9) FIG. 8 illustrates the voltage variation in the DC part of the facility of FIG. 1, whose terminals are controlled by a device according to the prior art;

(10) FIG. 9 illustrates the power variations in the terminals of the facility of FIG. 4, controlled by a device according to the disclosure; and

(11) FIG. 10 illustrates the voltage variation in the DC part of the facility of FIG. 4, whose terminals are controlled by a device according to the disclosure.

DETAILED DESCRIPTION

(12) The disclosure relates to a device 10 for controlling a terminal 100 connected to a multi-terminal high-voltage direct current HVDC transmission facility 14.

(13) FIG. 4 illustrates a facility 14 comprising first 100, second 200, third 300 and fourth 400 terminals as well as a control device 10 according to the disclosure. In this example, the control device 10 is configured to control the first 100, second 200, third 300 and fourth 400 terminals.

(14) The first 100, second 200, third 300 and fourth 400 terminals are connected respectively to first 102, second 202, third 302 and fourth 402 AC power supply networks. It can be observed that the fourth terminal 400 is connected to a wind farm. These four terminals are also connected to a DC part 16 of the facility 14 via direct current lines. The terminals are voltage converters, configured to convert an AC voltage into a DC voltage and vice versa

(15) An example of a control device 10 according to the disclosure, for controlling the first 100, second 200, third 300 and fourth 400 terminals of the facility 14 is given in FIG. 5. This control device 10 comprises a regulation circuit 20, a power distribution circuit 22, a limitation circuit 24 and a synchronization circuit 23. The limitation circuit 24 comprises a management circuit 26 and a calculator 28.

(16) In this non-limiting example, the regulation circuit 20 is disposed centrally. As a variant, the regulation circuit 20 may include a plurality of regulation sub-circuits, each being disposed locally in the vicinity of a terminal specific thereto and from which it regulates the power provided or drawn on the DC part of the facility.

(17) The power distribution circuit 22 receives as input measured voltage values V.sub.dc1 . . . Nst on the DC part 16 of the facility 14 as well as measured values P.sub.1 . . . Nst and power setpoints P*.sub.1 . . . Nst provided or drawn by the terminals of the facility. It outputs power setpoints provided or drawn P*.sub.1 . . . Nst by the terminals as well as voltage setpoints V*.sub.dc1 . . . Nst of the DC part. The power distribution circuit 22 is configured to restore the power of the facility following a disturbance. The management circuit 26 receives as input maximum P.sup.ACmax.sub.1 . . . Nst and minimum P.sup.ACmin.sub.1 . . . Nst power values which can be provided by the AC power supply networks to the terminals of the facility 14, as well as power setpoints provided or drawn P*.sub.1 . . . Nst by the terminals, provided by the power distribution circuit 22.

(18) The management circuit 26 of the limitation circuit 24 is configured to output upper P.sub.upper1 . . . Nst and lower P.sub.lower1 . . . Nst power compensation limits allocated to each of the terminals.

(19) The calculator 28 receives in input the power compensation limits P.sub.upper1 . . . Nst and P.sub.lower1 . . . Nst delivered by the management circuit 26 and is configured to determine and output over-voltage constants g.sub.1 . . . Nst.sup.+ and under-voltage constants g.sub.1 . . . Nst.sup.− associated with each of the terminals.

(20) The synchronization circuit 23 receives as input the power setpoints provided or drawn P*.sub.1 . . . Nst* by the terminals as well as the voltage setpoints v*.sub.dc1 . . . Nst of the DC part, delivered by the power distribution circuit 22. This synchronization circuit 23 ensures the temporal coherence between these setpoints.

(21) The regulation circuit 20 receives as input the power setpoints provided or drawn P*.sub.1 . . . Nst by the terminals as well as the voltage setpoints V*.sub.dc1 . . . Nst of the DC part as well as the over-voltage g.sub.1 . . . Nst.sup.+ and under-voltage g.sub.1 . . . Nst.sup.− constants provided by the synchronization circuit 23.

(22) The regulation circuit 20 varies the power provided or drawn by the terminals 100, 200, 300, 400 of the facility as a function of said provided or drawn power setpoints, said voltage setpoints as well as over-voltage and under-voltage constants. In the variant where the regulation circuit comprises a plurality of sub-circuits located locally in the vicinity of the terminals, each of the sub-circuits varies the power provided or drawn by the terminal with which it is associated, as a function of said setpoints and constants.

(23) FIG. 6 is a graph illustrating the change of the powers provided or drawn by the first 100, second 200, third 300 and fourth 400 terminals of the facility of FIG. 4, as a function of the voltage variation in the DC part 16 of the facility 14, these terminals being controlled by a control device 10 according to the disclosure.

(24) It can be observed that, in this example, the fourth terminal 400 provides the DC part 16 of the facility with a constant power P.sub.4 equal to 500 MW. The first and second terminals 100, 200 operate in inverter mode, so that they draw power on the DC part of the facility. In this example, the drawn power P.sub.1 by the first terminal has an initial value P.sub.01 equal to −900 MW while the power P.sub.2 drawn by the second terminal has an initial value P.sub.02 equal to −400 MW. The third terminal operates in rectifier mode, so that it provides the DC part 16 with a power P.sub.3 having an initial value P.sub.03 equal to 800 MW. In this non-limiting example, the nominal power of the terminals is 1000 MW. Also, the powers P.sub.1,2,3 drawn or provided by the first, second and third terminals can vary between an upper power limit P.sub.max equal to 1000 MW and a lower power limit P.sub.min equal to −1000 MW.

(25) The voltage of the DC part 16 of the facility 14 is initially V.sub.dc0, which is equivalent in this graph to 1 voltage unit, for reasons of simplification. The voltage variation in the DC part 16 is limited by an upper voltage limit V.sub.dc.sup.lim+ and a lower voltage limit V.sub.dc.sup.lim−. In the example of FIG. 6, these upper and lower voltage limits represent a variation of 10% relative to the initial voltage V.sub.dc0.

(26) The curves P.sub.1 and P.sub.2 represent respectively the change in the power drawn by the first terminal 100 and by the second terminal 200 in response to a voltage variation on the DC part 16. The curve P.sub.3 represents the change in the power provided by the third terminal 300 to the DC part.

(27) Firstly, the management circuit 26 of the limitation circuit 24 determines the upper P.sub.upper1 . . . Nst and lower P.sub.lower1 . . . Nst power compensation limits allocated to each of the terminals 100, 200, 300. These limits define higher UVCR and lower OVCR power ranges in which the power provided or drawn by each of the terminals can vary. The ranges allocated by the limitation circuit 24 to each of the terminals are darkened in FIG. 6. The upper and lower ranges of the third terminal are denoted UVCR (Under Voltage Containment Reserve) and OVCR (Over Voltage Containment Reserve).

(28) In this example, the lower compensation limit P.sub.lower1 allocated to the first terminal 100 is set to −1000 MW, so as to correspond to the lower power limit P.sub.min of the terminals. The power P.sub.01 initially drawn by the first terminal 100 being −900 MW, it is understood that the first terminal can draw up to additional 100 MW on the DC part 16 of the facility 14. The upper compensation limit P.sub.upper1 allocated to the first terminal is set to −600 MW. The lower compensation limit P.sub.lower2 allocated to the second terminal 200 is set to 800 MW and its upper compensation limit P.sub.upper2 is set to 100 MW. The lower compensation limit P.sub.lower3 allocated to the third terminal 300 is set to 300 MW. The upper compensation limit P.sub.upper3 allocated to the third terminal 300 is set to 1000 MW so as to correspond to the upper power limit P.sub.max of the terminals. The initial power P.sub.03 provided by the third terminal 300 being 800 MW, it is understood that the power it provides to the DC part can increase by 200 MW at most.

(29) The limitation circuit calculator then determines first g.sub.1.sup.+ second g.sub.2.sup.+ and third g.sub.3.sup.+ over-voltage constants and the first g.sub.1.sup.−, second g.sub.2.sup.− and third g.sub.3.sup.− under-voltage constants associated respectively with first 100, second 200 and third 300 terminals. These constants are determined to verify:

(30) $g_{1,2,3}^{-}=-\frac{P_{\mathrm{upper}1,2,3}-P_{01,02,03}}{V_{\mathrm{dc}}^{\lim -}-V_{\mathrm{dc}0}}=-\frac{{\mathrm{UVCR}}_{1,2,3}}{V_{\mathrm{dc}}^{\lim -}-V_{\mathrm{dc}0}}\mathrm{and}$$g_{1,2,3}^{+}=-\frac{P_{01,02,03}-P_{\mathrm{lower}1,2,3}}{V_{\mathrm{dc}0}-V_{\mathrm{dc}}^{\lim +}}=\frac{{\mathrm{OVCR}}_{1,2,3}}{V_{\mathrm{dc}0}-V_{\mathrm{dc}}^{\lim +}}$

(31) According to the disclosure, the limitation circuit 24 determines an under-voltage constant g.sub.3.sup.− of the third terminal 300 less than its over-voltage constant g.sub.3.sup.+, insofar as the power difference between the initial power P.sub.03 of the third terminal and the upper power limit P.sub.max of the third terminal 300 is low, and more particularly smaller than a determined value, for example 300 MW. Similarly, the over-voltage constant g.sub.1.sup.+ of the first terminal 100 is smaller than its over-voltage constant g.sub.1.sup.−, insofar as the power difference between the initial power P.sub.01 of the first terminal 100 and the lower power limit P.sub.lower of the first terminal is low, and more particularly smaller than a determined value, for example 300 MW.

(32) The regulation circuit 20 is then configured to vary the power provided or drawn by each of the terminals on the DC part of the facility by application of the linear relation:
ΔP.sub.1,2,3=−g.sub.1,2,3.sup.+Δv.sub.dc if Δv.sub.dc>0 and
ΔP.sub.1,2,3=−g.sub.1,2,3.sup.−Δv.sub.dc if Δv.sub.dc<0

(33) In response to a positive or negative voltage variation on the DC part of the facility, the regulation circuit 20 therefore varies linearly the power P.sub.1,2,3 provided or drawn by each of the terminals 100, 200, 300 on the DC part 16, the over-voltage g.sub.1,2,3.sup.+ and under-voltage g.sub.1,2,3.sup.− constants constituting the slope coefficients of the power variation lines as a function of the voltage variation on the DC part.

(34) The over-voltage g.sub.1,2,3.sup.+ and under-voltage g.sub.1,2,3.sup.− constants are determined so that the powers P.sub.1,2,3 provided or drawn by the terminals reach the lower power compensation limits P.sub.lower1,2,3 when the voltage of the DC part reaches the upper voltage limit V.sub.dc.sup.lim+ and so that the powers P.sub.1,2,3 provided or drawn by the terminals reach the upper power compensation limits P.sub.upper1,2,3 when the voltage of the DC part reaches the lower voltage limit V.sub.dc.sup.lim−. The operating constraints of the terminals are therefore better met.

(35) It is observed that, thanks to the disclosure, the increase of the power provided to the DC part of the third terminal 300, whose power P.sub.03 initially provided to the DC part 16 is close to its upper power limit P.sub.max, is reduced for a given voltage drop. The under-voltage constant g.sub.3.sup.− associated thereto by the limitation circuit 24 is low. The contribution of this third terminal 300 to the compensation for the voltage drop is therefore reduced.

(36) Similarly, the increase of the power drawn on the DC part of the first terminal 100, whose power P.sub.01 initially provided to the DC part 16 is close to its lower power limit P.sub.min, is reduced for a given voltage increase. The over-voltage constant g.sub.1.sup.+ associated therewith by the limitation circuit 24 is low. The contribution of this first terminal to the compensation for the voltage increase is therefore reduced.

(37) Thanks to the disclosure, the power P.sub.3 provided by the third terminal 300 reaches the upper power limit P.sub.max when the lower voltage limit V.sub.dc.sup.lim− is reached. Similarly, the power P.sub.1 drawn by the first terminal 100 reaches the lower power limit P.sub.min when the upper voltage limit V.sub.dc.sup.lim+ is reached. Also, the voltage of the DC part 16 of the facility 14 is maintained between the upper and lower voltage limits chosen.

(38) In the example of FIG. 6, the calculator 28 of the limitation circuit 24 determines the following over-voltage constants: g.sub.1.sup.+=1.563 MW/kV for the first terminal 100, g.sub.2.sup.+=6.250 MW/kV for the second terminal 200, g.sub.3.sup.+=7.813 MW/kV for the third terminal 300. The calculator 28 of the limitation circuit 24 also determines the following under-voltage constants: g.sub.1.sup.−=4.688 MW/kV for the first terminal 100, g.sub.2.sup.−=7.813 MW/kV for the second terminal 200, g.sub.3.sup.−=3.125 MW/kV for the third terminal 300. The limitation circuit can implement an algorithm for calculating over-voltage and under-voltage constants.

(39) FIG. 7 illustrates the results of simulation of the change in the power of the terminals 100, 200, 300, 400 of the facility 14 of FIG. 1 controlled by a device according to the prior art. At time t.sub.0, there is a simulation of the failure of the second terminal 200 of the facility 14, which then no longer draws power on the DC part 16 of the facility. The power P.sub.2 of the second terminal 200 becomes zero at time t.sub.0. It is observed that the power P.sub.1 of the first terminal 100 very quickly reaches the lower power limit P.sub.min=1000 MW, and the first terminal 100 enters into saturation. The control device according to the prior art does not take into account the upper P.sub.max and lower P.sub.min power limits of the terminals so that the variation of the power provided or drawn by these terminals is not adapted to the approach to these power limits. The power provided or drawn by these terminals may reach the upper P.sub.max and lower P.sub.min power limits and must be then put into saturation.

(40) From the moment when the first terminal 100 enters into saturation, the power P.sub.2 it draws can no longer increase to interrupt or compensate for the voltage increase. It can no longer contribute to the compensation for the voltage variation on the DC part 16 of the facility 14. Only the third terminal 300 therefore contributes to the voltage variation compensation, which is not sufficient. The voltage variation is no longer sufficiently compensated, which leads to an even greater voltage variation. Consequently, as can be seen in FIG. 8, the voltage of the DC part increases until it exceeds the upper voltage limit V.sub.dc.sup.lim+.

(41) FIG. 9 illustrates the results of simulation of the change in the power of the terminals 100, 200, 300, 400 of the facility 14 of FIG. 5 controlled by a device 10 according to the disclosure. At time t.sub.0, there is also a simulation of the failure of the second terminal 200 of the facility 14, which then no longer draws power on the DC part 16 of the facility. The power P.sub.2 of the second terminal 200 becomes zero at time t.sub.0. It is observed that the power P.sub.1 of the first reached terminal 100 tends gently towards the lower power limit P.sub.min=−1000 MW, in an asymptotic manner. The control device according to the disclosure takes into account the upper P.sub.max and lower P.sub.min power limits of the terminals so that the variation of the power provided or drawn by these terminals is adapted to the approach to these power limits, so as to avoid saturating the terminals.

(42) As observed in FIG. 10, the voltage of the DC part is maintained below the upper voltage limit V.sub.dc.sup.lim+ and tends towards this limit in an asymptotic manner. The terminals are not overloaded, and do not enter into saturation, regardless of the voltage variation. The device according to the disclosure allows a better distribution of the compensation powers.