CN104852401A - Hybrid direct-current transmission system, control method and power reversal control method - Google Patents
Hybrid direct-current transmission system, control method and power reversal control method Download PDFInfo
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- CN104852401A CN104852401A CN201510295735.6A CN201510295735A CN104852401A CN 104852401 A CN104852401 A CN 104852401A CN 201510295735 A CN201510295735 A CN 201510295735A CN 104852401 A CN104852401 A CN 104852401A
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Abstract
The invention discloses a hybrid direct-current transmission system. A first group of thyristor converter units and a second group of thyristor converter units are connected with the same sending end alternating-current power grid through a converter respectively, or connected with different sending end alternating-current power grids. An inversion converter station is composed of at least one group of voltage source converters, direct-current lines at the positive and negative ends of each voltage source converter are respectively equipped with a first switching element and a fourth switching element, and the direct-current lines at the positive and negative ends are wired in parallel and in a cross manner to the opposite-end direct-current lines through the first switching element and the fourth switching element respectively. Converter stations at the two ends are connected by two direct-current lines. The invention further discloses a hybrid direct-current transmission system control method and a hybrid direct-current transmission system power reversal control method. The hybrid direct-current transmission system of the invention has the advantages of low cost of traditional direct current, flexible control on flexible direct current, and the like.
Description
Technical field
The present invention relates to Hybrid HVDC field, particularly relate to a kind of Hybrid HVDC system, control method and trend reversion control method.
Background technology
HVDC (High Voltage Direct Current) transmission system can be divided into two types: based on the Traditional DC transmission system (LCC-HVDC) of thyristor technology; Based on the flexible direct current power transmission system (Flexible-HVDC) of all-controlling power electronics device technology.Traditional DC transmission system (LCC-HVDC) cost is low, loss is little, running technology is ripe, at present, the DC transmission system run in the world is nearly all LCC-HVDC system, but there is the easy commutation failure of inverter side in Traditional DC transmission system (LCC-HVDC), strong to the dependence of AC system; Absorb idle in a large number, the shortcomings such as current conversion station floor space is large.The flexible direct current power transmission system (Flexible-HVDC) of a new generation then can realize active power and reactive power uneoupled control, can power to passive network, compact conformation floor space is little, there is not the advantages such as commutation failure fault, but also exist with high costs, cannot effectively process the defects such as DC side fault.Therefore the Hybrid HVDC in conjunction with Traditional DC transmission of electricity and flexible DC power transmission will have future in engineering applications.The Hybrid HVDC system one end that the present invention relates to is the LCC-HVDC based on thyristor technology, one end is the voltage source converter that all-controlling power electronics device is formed, the topological structure of current mixing two-terminal direct current transmission system mainly contains the mixing two-terminal direct current transmission system of the mixing two-terminal direct current transmission system of symmetrical monopolar wiring as shown in Figure 1 and the bipolar wiring of symmetry shown in Fig. 2, and the voltage source converter in Fig. 1 or Fig. 2 and the position of LCC-HVDC can exchange.This system combines that Traditional DC transmission losses is little, running technology is ripe and flexible DC power transmission can be powered to passive network, the advantage of commutation failure can not occur, but also there is following shortcoming: can not converter be made full use of, realize the optimal control of trend, if a thyristor converter device fault in system as shown in Figure 1, then owing to lacking current path, whole system power delivery will be forced to interrupt.Because the converter of Traditional DC all adopts thyristor converter device, the sense of current can not change, polarity of voltage can only be changed during trend reversion, and direct current direction can only be changed, DC voltage polarity can not be changed during the reversion of voltage source converter trend, the trend therefore mixing two-terminal direct current transmission system generally can not change.When needing to exchange power by direct current in addition between multiple AC network, according to thyristor converter device access system as shown in Figure 1, form three end systems, then need additionally to increase by two thyristor converter devices, add additional investment.
Summary of the invention
Object of the present invention: be to provide a kind of Hybrid HVDC system, control method and trend reversion control method, combine the advantage based on thyristor converter device and the direct current transportation topology based on voltage source converter, the Optimum utilization that converter realizes trend can be made full use of.
In order to reach above-mentioned purpose, solution of the present invention is: a kind of Hybrid HVDC system, comprises the sending end current conversion station for connecting sending end AC network, for connecting the receiving end current conversion station of receiving end AC network and the DC power transmission line for connecting sending end current conversion station and receiving end current conversion station; It is characterized in that: described sending end current conversion station is rectification current conversion station, receiving end current conversion station is inversion current conversion station; Described rectification current conversion station sends inversion current conversion station to by DC power transmission line after being used for that the three-phase alternating current of sending end AC network is converted to direct current; Described inversion current conversion station flows to receiving end AC network after being used for that direct current is converted to three-phase alternating current; Described rectification current conversion station comprises the first group of thyristor converter device unit and second group of thyristor converter device unit that are in series; First group of thyristor converter device unit is connected earth electrode with the series connection node of second group of thyristor converter device unit, or does not connect earth electrode; First group of thyristor converter device unit is connected sending end AC network with second group of thyristor converter device unit respectively by transformer.Same AC network, or connect an AC network respectively;
Inversion current conversion station connects receiving end AC network by transformer; Inversion current conversion station is made up of at least one group of voltage source converter, the first switch element S1 and the 4th switch element S4 is equipped with at the positive and negative two ends of voltage source converter respectively, simultaneously at positive and negative two-terminal DC transmission system circuit again respectively by second switch element S2 and the 3rd switch element S3 improved cross connect in parallel in the DC power transmission line of opposite end.
As further improved technical scheme of the present invention, first group of thyristor converter device unit is connected same sending end AC network with second group of thyristor converter device unit respectively by transformer, or connects different sending end AC network respectively.
As further improved technical scheme of the present invention, described thyristor converter device unit comprises thyristor controlled series compensation; Or comprise thyristor controlled series compensation and bypass cock is connected in parallel; Or comprise thyristor controlled series compensation and bypass cock and disconnecting link assembly, thyristor controlled series compensation and bypass cock are connected in parallel, and the unit two ends after parallel connection are connected with the one end being connected disconnecting link respectively, connect the other end bypass disconnecting link in parallel of disconnecting link.
As further improved technical scheme of the present invention, described thyristor controlled series compensation is six pulsation bridge circuits, or 12 pulsation bridge circuits, or two 12 pulsation bridge circuits; Described voltage source converter is two level converters, or diode-clamped three-level converter, or modularization multi-level converter MMC, or mixed multi-level converter HMC or tandem type two level converter CTL.
As further improved technical scheme of the present invention, when the described two groups of thyristor converter device unit be in series wherein one break down time, another can exit online, or off-line exits; After a thyristor converter device unit is out of service, the voltage source converter of inversion current conversion station keeps operational mode constant, or enters buck operating mode.
As further improved technical scheme of the present invention, described switch element refers to isolation switch, or DC circuit breaker, or the combination of isolation switch and DC circuit breaker.
As further improved technical scheme of the present invention, all smoothing reactor is installed at the positive and negative two ends of voltage source converter; The described switch element (S1, S4) being arranged on the same position of positive and negative two-terminal DC transmission system circuit both can be arranged between smoothing reactor and converter, also can be arranged between DC power transmission line and smoothing reactor.
For realizing above-mentioned technical purpose, the another kind of technical scheme that the present invention takes is: a kind of Hybrid HVDC system control method adopting above-mentioned Hybrid HVDC system, is characterized in that:
According to operation needs, operate the first switch element S1, second switch element S2 the 3rd switch element S3,4th switch element S4, form the first transmission system be made up of described first group of thyristor converter device unit and second group of thyristor converter device unit, and form the second transmission system be made up of described voltage source converter and at least one group of thyristor converter device unit;
First group of thyristor converter device unit is connected to different AC network from second group of thyristor converter device unit; Described first switch element S1 is closed to be closed with second switch element S2, and the 3rd switch element S3 disconnects and disconnects formation first current path with the 4th switch element S4; Or the first switch element S1 disconnects and disconnecting with second switch element S2, the 3rd switch element S3 is closed closes formation second current path with the 4th switch element S4;
Described first group of thyristor converter device unit is rectification unit or inversion unit;
Described second group of thyristor converter device unit is inversion unit or rectification unit; And
Active power from described first group of thyristor converter device unit connect AC network via described first group of thyristor converter device unit and described second group of thyristor converter device unit transfer to described second group of thyristor converter device unit connect AC network; Or active power from described second group of thyristor converter device unit connect AC network via described second group of thyristor converter device unit and described first group of thyristor converter device unit transfer to described first group of thyristor converter device unit connect AC network.
For realizing above-mentioned technical purpose, the another kind of technical scheme that the present invention takes is: a kind of Hybrid HVDC system load flow reversion control method adopting above-mentioned Hybrid HVDC system, is characterized in that:
Step one: the direct current power reducing direct current system;
Step 2: the direct current of direct current system is down to zero;
Step 3: disconnect the first switch element S1 in the DC line of positive and negative two ends, 4th switch element S4, closed improved cross connect in parallel is to the second switch element S2 in the DC line of opposite end simultaneously, 3rd switch element S3, or disconnect improved cross connect in parallel to the second switch element S2 in the DC line of opposite end, the 3rd switch element S3, the first switch element S1 simultaneously in the DC line of closed positive and negative two ends, 4th switch element S4, the DC voltage polarity of reversion direct current system;
Step 4: voltage source converter is rectification unit/inversion unit, first group of inverter unit forms inversion unit/rectification unit; Or second group of inverter unit forms inversion unit/rectification unit; Or first group of inverter unit and second group of inverter unit form inversion unit/rectification unit jointly.
As further improved technical scheme of the present invention, DC voltage polarity reversion before need off voltage source type converter connect transformer primary side AC circuit breaker; Or do not need off voltage source type converter connect transformer primary side AC circuit breaker.
Beneficial effect of the present invention:
1. topological structure of the present invention has the advantages such as traditional thyristors converter cost is low, loss is low, reliability is strong concurrently, and voltage source converter controls flexibly, active reactive power decoupled controls, to advantages such as AC system dependence are low; Wherein thyristor converter device can be implemented in line and off-line and throws and move back, and has higher reliability.
2. employing control method of the present invention can make full use of the trend conveying that existing converter realizes each electrical network, both saves investment, and also improves the safety of whole electrical network.
Accompanying drawing explanation
Fig. 1 is the mixing two-terminal direct current transmission system schematic diagram of symmetrical monopolar wiring.
Fig. 2 is the mixing two-terminal direct current transmission system schematic diagram of symmetrical bipolar wiring.
Fig. 3 is that a kind of sending end of the present invention is positioned at different electrical network, adopts thyristor converter device, the Hybrid HVDC system schematic that receiving end adopts voltage source converter to form.
Fig. 4 is that a kind of sending end of the present invention is positioned at identical electrical network, adopts thyristor converter device, the Hybrid HVDC system schematic that receiving end adopts voltage source converter to form.
Fig. 5 is a kind of sending end of the present invention is voltage source converter, and receiving end is positioned at identical electrical network, adopts the Hybrid HVDC system schematic that thyristor converter device is formed.
Fig. 6 is a kind of sending end of the present invention is voltage source converter, and receiving end is positioned at different electrical network, adopts the Hybrid HVDC system schematic that thyristor converter device is formed.
Fig. 7 is thyristor converter device cellular construction schematic diagram of the present invention.
Embodiment
Below with reference to accompanying drawing, technical scheme of the present invention and beneficial effect are described in detail.
The invention provides a kind of Hybrid HVDC system and control method, be applicable to Hybrid HVDC topological structure as shown in Figure 3 and Fig. 4 simultaneously, Fig. 5, topological structure shown in Fig. 6, the AC network G1 in each figure, AC network G2, AC network G3 represents different AC network respectively, the corresponding equiva lent impedance of each AC network is respectively: Zs1, Zs2, Zs3.Be described for Fig. 3 below.
Embodiment 1:
See Fig. 3, this kind of Hybrid HVDC system, comprises the sending end current conversion station for connecting sending end AC network, for connecting the receiving end current conversion station of receiving end AC network and the DC power transmission line for connecting sending end current conversion station and receiving end current conversion station; It is characterized in that: described sending end current conversion station is rectification current conversion station, receiving end current conversion station is inversion current conversion station; Described rectification current conversion station sends inversion current conversion station to by DC power transmission line after being used for that the three-phase alternating current of sending end AC network is converted to direct current; Described inversion current conversion station flows to receiving end AC network after being used for that direct current is converted to three-phase alternating current; Described rectification current conversion station comprises the first group of thyristor converter device unit and second group of thyristor converter device unit that are in series; First group of thyristor converter device unit is connected earth electrode with the series connection node of second group of thyristor converter device unit, or does not connect earth electrode; First group of thyristor converter device unit is connected sending end AC network with second group of thyristor converter device unit respectively by transformer.Same AC network, or connect an AC network respectively;
Inversion current conversion station connects receiving end AC network by transformer; Inversion current conversion station is made up of at least one group of voltage source converter, the first switch element S1 and the 4th switch element S4 is equipped with at the positive and negative two ends of voltage source converter respectively, simultaneously at positive and negative two-terminal DC transmission system circuit again respectively by second switch element S2 and the 3rd switch element S3 improved cross connect in parallel in the DC power transmission line of opposite end.
Preferably, first group of thyristor converter device unit is connected same sending end AC network with second group of thyristor converter device unit respectively by transformer, connects different sending end AC network respectively.Described thyristor converter device unit comprises thyristor controlled series compensation; Or comprise thyristor controlled series compensation and bypass cock is connected in parallel; Or comprise thyristor controlled series compensation and bypass cock and disconnecting link assembly, thyristor controlled series compensation and bypass cock are connected in parallel, and the unit two ends after parallel connection are connected with the one end being connected disconnecting link respectively, connect the other end bypass disconnecting link in parallel of disconnecting link.Described thyristor controlled series compensation is six pulsation bridge circuits, or 12 pulsation bridge circuits, or two 12 pulsation bridge circuits; Described voltage source converter is two level converters, or diode-clamped three-level converter, or modularization multi-level converter MMC, or mixed multi-level converter HMC or tandem type two level converter CTL.When the described two groups of thyristor converter device unit be in series wherein one break down time, another can exit online, or off-line exits; After a thyristor converter device unit is out of service, the voltage source converter of inversion current conversion station keeps operational mode constant, or enters buck operating mode.Described switch element refers to isolation switch, or DC circuit breaker, or the combination of isolation switch and DC circuit breaker.All smoothing reactor is installed at the positive and negative two ends of voltage source converter; The described switch element (S1, S4) being arranged on the same position of positive and negative two-terminal DC transmission system circuit both can be arranged between smoothing reactor and converter, also can be arranged between DC power transmission line and smoothing reactor.
In the present embodiment 1, Hybrid HVDC topological structure as shown in Figure 3 comprises: rectification current conversion station and inversion current conversion station, and both are connected by two DC power transmission line; Wherein: rectification current conversion station sends inversion current conversion station to by DC power transmission line after being used for that the three-phase alternating current of sending end AC network is converted to direct current; The bus that sending end AC network enters the station may be connected with passive filter, may not have, need determine according to system engineering condition, when converter is made up of thyristor converter device yet, generally need to install passive filter, sometimes also need to install reactive-load compensation capacitor.
Rectification current conversion station is made up of two groups of thyristor converter device units in series, and its series connection node connects earth electrode, and the positive and negative two ends after series connection are all connected with DC power transmission line by smoothing reactor; Between DC line and earth electrode, be parallel with DC filter simultaneously, be that the two groups of thyristor converter device unit be in series in Fig. 3 are positioned at different current conversion station from the topological structure difference shown in Fig. 1, and this two current conversion station is positioned at two different AC network G1 and AC network G2.Wherein the structure of thyristor converter device unit as shown in Figure 7, and in figure, 1 is thyristor controlled series compensation, and 3 is bypass cock, and 4 is series connection isolation switch, and 5 is isolation switch in parallel.Thyristor converter device unit may be thyristor controlled series compensation, as Fig. 7 (a); Or for thyristor controlled series compensation and bypass cock are connected in parallel, as Fig. 7 (b); Or be thyristor controlled series compensation and bypass cock and disconnecting link assembly, thyristor controlled series compensation and bypass cock are connected in parallel, unit two ends after parallel connection are connected with the one end being connected disconnecting link respectively, connect the other end bypass disconnecting link in parallel of disconnecting link, as Fig. 7 (c), bypass cock in parallel with thyristor controlled series compensation in figure 3 or bypass cock and disconnecting link component equivalent are Sy1, Sy2.
Thyristor controlled series compensation adopts 12 pulsation bridge circuits; Wherein, each brachium pontis is formed by several Thyristors in series; Thyristor converter device adopts the strategy determined direct current power and control.The three-winding transformer that thyristor converter device is respectively Y0/Y/ Δ by a mode of connection is connected with sending end AC network.Transformer can carry out electric pressure conversion to the three-phase alternating current of sending end AC system, to adapt to required DC voltage level, two the six pulse conversion bridges not up and down being all 12 pulsation bridge-type thyristor controlled series compensation of the transformer secondary mode of connection provide phase angle difference to be the three-phase alternating current of 30 °, are then equiped with AC circuit breaker Sa and Sb respectively at positive and negative polarities transformer primary side.
Inversion current conversion station flows to receiving end AC network G3 after being used for that direct current is converted to three-phase alternating current, and its equiva lent impedance is Zs3; Inversion current conversion station is made up of a voltage source converter, the same position of its positive and negative two ends DC line is equipped with a switch element S1 respectively, S4, simultaneously at positive and negative two ends DC line same position again respectively by switch element S2, S3 improved cross connect in parallel in the DC line of opposite end; Switch element S1, S4 both can be arranged between smoothing reactor and converter, also can be arranged between DC line and smoothing reactor, and switch element S2, S3 also need corresponding with it.The two winding transformer that voltage source converter is Y0/ Δ by a mode of connection is connected with receiving end AC network S2, then be equiped with AC circuit breaker Sc respectively at positive and negative polarities transformer primary side, voltage source converter adopts to be determined direct voltage and determines Reactive Power Control policy control.
When forward transmission power works, rectification side thyristor converter device adjusts the size of direct current power by the size controlling IGBT group angle, simultaneously by controlling the gear of converter transformer, making Trigger Angle in certain limit, changing three-phase alternating current into direct current by rectification current conversion station; Simultaneous Switching element S1 and S4 is in co-bit, and S1 and S4 may be isolation switch, also may be DC circuit breaker, also may be the combination of DC circuit breaker and isolation switch.Direct current energy will be converted into threephase AC electric energy and inject receiving end AC system under the effect of inverter side voltage source converter, and it can realize decoupled active and reactive and control, and flexible control inputs is to the active power of AC network and reactive power.
In power transmission process, be connected to two thyristor converter device unit of AC network G1 and AC network G2, if one of them breaks down, then it can pass through phase shift locking immediately, its by-pass switch element in parallel closed realizes exiting online simultaneously, and do not affect another thyristor converter device unit normally run, continue holding power transmission.The thyristor converter device such as, being connected to AC network G1 in Fig. 3 breaks down, can be closed after protection act bypass cock Sy1 online, the thyristor converter device being connected to AC network G1 is exited in locking simultaneously, and the thyristor converter device unit being connected to AC network G2 can continue to maintain operation, accordingly, if the thyristor converter device being connected to AC network G2 breaks down, can be closed after protection act bypass cock Sy2 online, the thyristor converter device being connected to AC network G2 is exited in locking simultaneously, and the thyristor converter device unit being connected to AC network G1 can continue to maintain operation.Now the voltage source converter of Inverter Station keeps operational mode constant, or enters buck operating mode, and whole system can continue to run.
Embodiment 2:
As shown in Figure 3, the first group of thyristor converter device unit be in series and second group of thyristor converter device unit are connected to AC network G1, AC network G2; When Inverter Station voltage source converter breaks down out of service, and AC network G1 has excess power, there is power shortage in AC network G2 simultaneously, now can by closed first switch element S1, closed second switch element S2, disconnect the 3rd switch element S3, disconnect the 4th switch element S4 and form the first current path, power realizes being transmitted to AC network G2 by AC network G1; Now first group of thyristor converter device unit is rectification unit; Second group of thyristor converter device unit is inversion unit, active power from first group of thyristor converter device unit connect AC network G1 via described first group of thyristor converter device unit, first switch element S1, second switch element S2 and described second group of thyristor converter device unit transfer to second group of connected AC network G2 of thyristor converter device unit; Also disconnection first switch element S1 can be passed through, disconnect second switch element S2, closed 3rd switch element S3, closed 4th switch element S4 forms the second current path, now active power from first group of thyristor converter device unit connect AC network G1 via described first group of thyristor converter device unit, 3rd switch element S3, the 4th switch element S4 and described second group of thyristor converter device unit transfer to second group of connected AC network G2 of thyristor converter device unit
On the contrary, if power need be transmitted to AC network G1 by AC network G2, then now first group of thyristor converter device unit is inversion unit, and second group of thyristor converter device unit is rectification unit; Active power via the first current path namely from second group of thyristor converter device unit connect AC network G2 via described second group of thyristor converter device unit, first switch element S1, second switch element S2 and described first group of thyristor converter device unit transfer to described first group of thyristor converter device unit connect AC network G1.Also can via the second current path; Now active power from described second group of thyristor converter device unit connect AC network G2 via described second group of thyristor converter device unit, 3rd switch element S3, the 4th switch element S4 and described first group of thyristor converter device unit transfer to described first group of thyristor converter device unit connect AC network G1.
By adopting above topology structure, when HVDC Transmission system one end current conversion station breaks down, converter can be reused to build new DC transmission system, realizing active power and still can transmit between two AC network.In shortage of power situation, the safety of whole electrical network can be improved.Topological structure shown in Fig. 1 then can not build new DC transmission system, thus can not realize power support.
Embodiment 3
This Hybrid HVDC system control method, comprises the following steps:
According to operation needs, operate the first switch element S1, second switch element S2 the 3rd switch element S3,4th switch element (S4), form the first transmission system be made up of described first group of thyristor converter device unit and second group of thyristor converter device unit, and form the second transmission system be made up of described voltage source converter and at least one group of thyristor converter device unit;
First group of thyristor converter device unit is connected to different AC network from second group of thyristor converter device unit; Described first switch element S1 is closed to be closed with second switch element S2, and the 3rd switch element S3 disconnects and disconnects formation first current path with the 4th switch element S4; Or the first switch element S1 disconnects and disconnecting with second switch element S2, the 3rd switch element S3 is closed closes formation second current path with the 4th switch element S4;
Described first group of thyristor converter device unit is rectification unit or inversion unit;
Described second group of thyristor converter device unit is inversion unit or rectification unit; And
Active power from described first group of thyristor converter device unit connect AC network via described first group of thyristor converter device unit and described second group of thyristor converter device unit transfer to described second group of thyristor converter device unit connect AC network; Or active power from described second group of thyristor converter device unit connect AC network via described second group of thyristor converter device unit and described first group of thyristor converter device unit transfer to described first group of thyristor converter device unit connect AC network.
Embodiment 4
This Hybrid HVDC system load flow reversion control method, comprises the following steps:
Step one: the direct current power reducing direct current system;
Step 2: the direct current of direct current system is down to zero;
Step 3: disconnect the first switch element S1 in the DC line of positive and negative two ends, 4th switch element S4, closed improved cross connect in parallel is to the second switch element S2 in the DC line of opposite end simultaneously, 3rd switch element S3, or disconnect improved cross connect in parallel to the second switch element S2 in the DC line of opposite end, the 3rd switch element S3, the first switch element S1 simultaneously in the DC line of closed positive and negative two ends, 4th switch unit S4, the DC voltage polarity of reversion direct current system;
Step 4: voltage source converter is rectification unit/inversion unit, first group of inverter unit forms inversion unit/rectification unit; Or second group of inverter unit forms inversion unit/rectification unit; Or first group of inverter unit and second group of inverter unit form inversion unit/rectification unit jointly.
Preferably, DC voltage polarity reversion before need off voltage source type converter connect transformer primary side AC circuit breaker; Or do not need off voltage source type converter connect transformer primary side AC circuit breaker.
Along with the development of electrical network or the needs that control due to urgent power, system need change reverse transmission power into by forward transmission power, and in the present embodiment, the further preferred version of trend Umklapp process comprises the steps:
(1) automatic trend reversion enabling signal is obtained;
(2) direct current power is reduced, until direct current is down to minimum current with given pace;
(3) when direct current is down to minimum current, stoppage in transit direct current;
(4) after direct current is stopped transport, by voltage source converter connect transformer primary side AC circuit breaker Sc disconnect, after AC circuit breaker Sc disconnects, disconnect the switch element S1 in the DC line of positive and negative two ends, S4, at switch element S1, after S4 all disconnects, wait for 0 ~ 60 minute, close a switch element S2, S3, finally close AC circuit breaker Sc again; , DC voltage polarity oppositely and start direct current;
(5) after direct current starts, when direct current power rises to setting power value, power reverses process completes.
In above-mentioned trend inversion scheme: trend reverse function enabling signal refers to and operates by operations staff the startup that trend reverse function triggers; Or the startup caused by dispatcher's remote operation trend reverse function; Or by other Control protection functions trigger startup.
In above-mentioned trend inversion scheme: in the auto-reverse process of trend, trend automatic reverse rotation function can be terminated, trend automatic reverse rotation function is terminated rear direct current system by constant for the running status kept before end time.
In above-mentioned trend inversion scheme: in the auto-reverse process of trend, alternating current filter both can according to the idle control logic switching of the normal start and stop of direct current, also the running status of the filter dropped into can be kept constant, do not carry out switching operation, operations staff moves back function pressing plate to adjust selection by throwing.
Above embodiment is only and technological thought of the present invention is described, can not limit protection scope of the present invention with this, and every technological thought proposed according to the present invention, any change that technical scheme basis is done, all falls within scope.
Claims (9)
1. a Hybrid HVDC system, comprises the sending end current conversion station for connecting sending end AC network, for connecting the receiving end current conversion station of receiving end AC network and the DC power transmission line for connecting sending end current conversion station and receiving end current conversion station; It is characterized in that: described sending end current conversion station is rectification current conversion station, receiving end current conversion station is inversion current conversion station; Described rectification current conversion station sends inversion current conversion station to by DC power transmission line after being used for that the three-phase alternating current of sending end AC network is converted to direct current; Described inversion current conversion station flows to receiving end AC network after being used for that direct current is converted to three-phase alternating current; Described rectification current conversion station comprises the first group of thyristor converter device unit and second group of thyristor converter device unit that are in series; First group of thyristor converter device unit is connected earth electrode with the series connection node of second group of thyristor converter device unit, or does not connect earth electrode; First group of thyristor converter device unit is connected same sending end AC network with second group of thyristor converter device unit respectively by transformer, or connects different sending end AC network respectively;
Inversion current conversion station connects receiving end AC network by transformer; Inversion current conversion station is made up of at least one group of voltage source converter, the positive and negative two ends of voltage source converter are equipped with the first switch element (S1) and the 4th switch element (S4) respectively, simultaneously at positive and negative two-terminal DC transmission system circuit again respectively by second switch element (S2) and the 3rd switch element (S3) improved cross connect in parallel in the DC power transmission line of opposite end.
2. a kind of Hybrid HVDC system as claimed in claim 1, is characterized in that:
Described thyristor converter device unit comprises thyristor controlled series compensation; Or comprise thyristor controlled series compensation and bypass cock is connected in parallel; Or comprise thyristor controlled series compensation and bypass cock and disconnecting link assembly, thyristor controlled series compensation and bypass cock are connected in parallel, and the unit two ends after parallel connection are connected with the one end being connected disconnecting link respectively, connect the other end bypass disconnecting link in parallel of disconnecting link.
3. as a kind of Hybrid HVDC system that claim 1 or 2 is stated, it is characterized in that: described thyristor controlled series compensation is six pulsation bridge circuits, or 12 pulsation bridge circuits, or two 12 pulsation bridge circuits; Described voltage source converter is two level converters, or diode-clamped three-level converter, or modularization multi-level converter MMC, or mixed multi-level converter HMC or tandem type two level converter CTL.
4. a kind of Hybrid HVDC system as claimed in claim 1 or 2, is characterized in that:
When the described two groups of thyristor converter device unit be in series wherein one break down time, another can exit online, or off-line exits; After a thyristor converter device unit is out of service, the voltage source converter of inversion current conversion station keeps operational mode constant, or enters buck operating mode.
5. a kind of Hybrid HVDC system as described in claim 1 and 2, is characterized in that:
Described switch element refers to isolation switch, or DC circuit breaker, or the combination of isolation switch and DC circuit breaker.
6. a kind of Hybrid HVDC system as described in claim 1 and 2, is characterized in that:
All smoothing reactor is installed at the positive and negative two ends of voltage source converter; The described switch element (S1, S4) being arranged on the same position of positive and negative two-terminal DC transmission system circuit both can be arranged between smoothing reactor and converter, also can be arranged between DC power transmission line and smoothing reactor.
7. adopt a Hybrid HVDC system control method for the Hybrid HVDC system according to any one of claim 1-6, it is characterized in that:
According to operation needs, operate the first switch element (S1), second switch element (S2) the 3rd switch element (S3), 4th switch element (S4), form the first transmission system be made up of described first group of thyristor converter device unit and second group of thyristor converter device unit, and form the second transmission system be made up of described voltage source converter and at least one group of thyristor converter device unit;
First group of thyristor converter device unit is connected to different AC network from second group of thyristor converter device unit; Described first switch element (S1) is closed to be closed with second switch element (S2), and the 3rd switch element (S3) disconnects and disconnects formation first current path with the 4th switch element (S4); Or the first switch element (S1) disconnects and disconnecting with second switch element (S2), closed formation second current path closed with the 4th switch element (S4) of the 3rd switch element (S3);
Described first group of thyristor converter device unit is rectification unit or inversion unit;
Described second group of thyristor converter device unit is inversion unit or rectification unit; And
Active power from described first group of thyristor converter device unit connect AC network via described first group of thyristor converter device unit and described second group of thyristor converter device unit transfer to described second group of thyristor converter device unit connect AC network; Or active power from described second group of thyristor converter device unit connect AC network via described second group of thyristor converter device unit and described first group of thyristor converter device unit transfer to described first group of thyristor converter device unit connect AC network.
8. adopt a Hybrid HVDC system load flow reversion control method for the Hybrid HVDC system according to any one of claim 1-6, it is characterized in that:
Step one: the direct current power reducing direct current system;
Step 2: the direct current of direct current system is down to zero;
Step 3: disconnect the first switch element (S1) in the DC line of positive and negative two ends, 4th switch element (S4), closed improved cross connect in parallel is to the second switch element (S2) in the DC line of opposite end simultaneously, 3rd switch element (S3), or disconnect improved cross connect in parallel to the second switch element (S2) in the DC line of opposite end, 3rd switch element (S3), the first switch element (S1) simultaneously in the DC line of closed positive and negative two ends, 4th switch element (S4), the DC voltage polarity of reversion direct current system;
Step 4: voltage source converter is rectification unit/inversion unit, first group of inverter unit forms inversion unit/rectification unit; Or second group of inverter unit forms inversion unit/rectification unit; Or first group of inverter unit and second group of inverter unit form inversion unit/rectification unit jointly.
9. a kind of Hybrid HVDC system load flow reversion control method as claimed in claim 8, is characterized in that: need before DC voltage polarity reversion off voltage source type converter connect transformer primary side AC circuit breaker; Or do not need off voltage source type converter connect transformer primary side AC circuit breaker.
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